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  Subjects -> ENGINEERING (Total: 2167 journals)
    - CHEMICAL ENGINEERING (184 journals)
    - CIVIL ENGINEERING (168 journals)
    - ELECTRICAL ENGINEERING (94 journals)
    - ENGINEERING (1173 journals)
    - ENGINEERING MECHANICS AND MATERIALS (355 journals)
    - HYDRAULIC ENGINEERING (55 journals)
    - INDUSTRIAL ENGINEERING (57 journals)
    - MECHANICAL ENGINEERING (81 journals)

ENGINEERING (1173 journals)            First | 1 2 3 4 5 6 7 8 | Last

BER : Survey of Business Conditions in Retail : An Executive Summary     Full-text available via subscription   (Followers: 3)
Bharatiya Vaigyanik evam Audyogik Anusandhan Patrika (BVAAP)     Open Access  
Biointerphases     Open Access  
Biomaterials Science     Full-text available via subscription   (Followers: 4)
Biomedical Engineering     Hybrid Journal   (Followers: 10)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 13)
Biomedical Engineering Letters     Hybrid Journal   (Followers: 5)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 16)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 15)
Biomedical Engineering: Applications, Basis and Communications     Hybrid Journal   (Followers: 5)
Biomedical Microdevices     Hybrid Journal   (Followers: 7)
Biomedical Science and Engineering     Open Access   (Followers: 1)
Biomedizinische Technik - Biomedical Engineering     Hybrid Journal  
Biomicrofluidics     Open Access   (Followers: 3)
BioNanoMaterials     Hybrid Journal   (Followers: 1)
Biotechnology Progress     Hybrid Journal   (Followers: 21)
Boletin Cientifico Tecnico INIMET     Open Access  
Botswana Journal of Technology     Full-text available via subscription  
Boundary Value Problems     Open Access   (Followers: 1)
Brazilian Journal of Science and Technology     Open Access  
Broadcasting, IEEE Transactions on     Hybrid Journal   (Followers: 5)
Bubble Science, Engineering & Technology     Hybrid Journal   (Followers: 1)
Bulletin of Canadian Petroleum Geology     Full-text available via subscription   (Followers: 1)
Bulletin of Engineering Geology and the Environment     Hybrid Journal   (Followers: 3)
Bulletin of the Crimean Astrophysical Observatory     Hybrid Journal  
Calphad     Hybrid Journal  
Canadian Geotechnical Journal     Full-text available via subscription   (Followers: 15)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 13)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 4)
Case Studies in Thermal Engineering     Open Access   (Followers: 1)
Catalysis Communications     Hybrid Journal   (Followers: 5)
Catalysis Letters     Hybrid Journal   (Followers: 2)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 7)
Catalysis Science and Technology     Free   (Followers: 5)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 4)
Catalysis Today     Hybrid Journal   (Followers: 6)
CEAS Space Journal     Hybrid Journal   (Followers: 1)
Cellular and Molecular Neurobiology     Hybrid Journal   (Followers: 2)
Central European Journal of Engineering     Hybrid Journal   (Followers: 1)
CFD Letters     Open Access   (Followers: 2)
Chaos : An Interdisciplinary Journal of Nonlinear Science     Hybrid Journal   (Followers: 1)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 1)
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 1)
Chinese Journal of Engineering     Open Access  
Chinese Science Bulletin     Open Access  
Ciencia e Ingenieria Neogranadina     Open Access  
Ciencia en su PC     Open Access  
Ciencias Holguin     Open Access  
Cientifica     Open Access  
CIRP Annals - Manufacturing Technology     Full-text available via subscription   (Followers: 10)
CIRP Journal of Manufacturing Science and Technology     Full-text available via subscription   (Followers: 9)
City, Culture and Society     Hybrid Journal   (Followers: 20)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Clean Air Journal     Full-text available via subscription   (Followers: 2)
Clinical Science     Full-text available via subscription   (Followers: 8)
Coal Science and Technology     Full-text available via subscription   (Followers: 4)
Coastal Engineering     Hybrid Journal   (Followers: 8)
Coastal Engineering Journal     Hybrid Journal   (Followers: 2)
Coatings     Open Access   (Followers: 2)
Cogent Engineering     Open Access   (Followers: 1)
Cognitive Computation     Hybrid Journal   (Followers: 3)
Color Research & Application     Hybrid Journal   (Followers: 1)
COMBINATORICA     Hybrid Journal  
Combustion Theory and Modelling     Hybrid Journal   (Followers: 6)
Combustion, Explosion, and Shock Waves     Hybrid Journal   (Followers: 11)
Communications Engineer     Hybrid Journal  
Communications in Information Science and Management Engineering     Open Access   (Followers: 7)
Communications in Numerical Methods in Engineering     Hybrid Journal   (Followers: 3)
Components, Packaging and Manufacturing Technology, IEEE Transactions on     Hybrid Journal   (Followers: 14)
Composite Interfaces     Hybrid Journal   (Followers: 4)
Composite Structures     Hybrid Journal   (Followers: 145)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 108)
Composites Part B : Engineering     Hybrid Journal   (Followers: 138)
Composites Science and Technology     Hybrid Journal   (Followers: 105)
Comptes Rendus Mécanique     Full-text available via subscription   (Followers: 2)
Computation     Open Access   (Followers: 1)
Computational Geosciences     Hybrid Journal   (Followers: 13)
Computational Optimization and Applications     Hybrid Journal   (Followers: 6)
Computational Science and Discovery     Full-text available via subscription  
Computational Water, Energy, and Environmental Engineering     Open Access   (Followers: 2)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 7)
Computer Science and Engineering     Open Access   (Followers: 8)
Computers & Geosciences     Hybrid Journal   (Followers: 7)
Computers & Mathematics with Applications     Full-text available via subscription   (Followers: 4)
Computers and Electronics in Agriculture     Hybrid Journal   (Followers: 3)
Computers and Geotechnics     Hybrid Journal   (Followers: 7)
Computing and Visualization in Science     Hybrid Journal   (Followers: 3)
Computing in Science & Engineering     Full-text available via subscription   (Followers: 13)
Conciencia Tecnologica     Open Access   (Followers: 1)
Concurrent Engineering     Hybrid Journal   (Followers: 4)
Conference Proceedings - Lucian Blaga University Sibiu     Open Access  
Continuum Mechanics and Thermodynamics     Hybrid Journal   (Followers: 3)
Control and Dynamic Systems     Full-text available via subscription   (Followers: 4)
Control Engineering Practice     Hybrid Journal   (Followers: 32)
Control Theory and Informatics     Open Access   (Followers: 4)
Corrosion Science     Hybrid Journal   (Followers: 22)
Corrosion Series     Full-text available via subscription   (Followers: 7)
CT&F Ciencia, Tecnologia y Futuro     Open Access  
Current Applied Physics     Full-text available via subscription   (Followers: 4)
Dams and Reservoirs     Hybrid Journal   (Followers: 4)

  First | 1 2 3 4 5 6 7 8 | Last

Journal Cover   AIChE Journal
  [SJR: 1.098]   [H-I: 104]   [23 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0001-1541 - ISSN (Online) 1547-5905
   Published by John Wiley and Sons Homepage  [1597 journals]
  • New MINLP Formulation for the Multiperiod Pooling Problem
    • Authors: Pedro M. Castro
      Abstract: This paper addresses the modeling of blending tank operations in petroleum refineries for the most profitable production of liquid fuels in a context of time‐varying supply and demand. A new mixed‐integer nonlinear programming formulation is proposed that by using individual flows and split fractions as key model variables leads to a different set of non‐convex bilinear terms compared to the original work of Kolodziej et al. (Comput Chem Eng 2013;53:122‐142). Through the solution of a set of test problems from the literature, we show that these are better handled by decomposition algorithms that divide the problem into integer and nonlinear components as well as by commercial solvers. In fact, BARON and GloMIQO can solve to global optimality all problems resulting from the new formulation and literature data. A tailored global optimization algorithm working with a tight mixed‐integer linear relaxation from multiparametric disaggregation achieves a similar performance. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-29T10:41:53.89397-05:0
      DOI: 10.1002/aic.15018
       
  • Interaction dynamics of a spherical particle with a suspended liquid film
    • Authors: Subhasish Mitra; Elham Doroodchi, Geoffrey M. Evans, Vishnu Pareek, Jyeshtharaj B. Joshi
      Abstract: Hydrodynamics of collision interactions between a particle and gas‐liquid interface such as droplet/film is of keen interest in many engineering applications. This study reports on the collision interaction between a suspended liquid (water) film of thickness 3.41±0.04 mm and an impacting hydrophilic particle (glass ballotini) of different diameters (1.1‐3.0 mm) in low particle impact Weber number (We=ρlvp2dp/σ) range (1.4 – 33). Two distinct outcomes were observed – particle retention in the film at lower Weber number and complete penetration of the film towards higher Weber number cases. A collision parameter was defined based on energy balance approach to demarcate these two interaction regimes which agreed reasonably well with the experimental outcomes. It was shown that the liquid ligament forming in the complete penetration cases breaks up purely by “dripping/end pinch‐off” mechanism and not due to capillary wave instability. An analytical model based on energy balance approach was proposed to determine the liquid mass entrainment associated with the ligament which compared well with the experimental measurements. A good correlation between the % film mass entrained and the particle Bond number (Bo = ρlgdp2/σ) was obtained which indicated a dependency of Bo1.72. Computationally, a three dimensional CFD model was developed to simulate these interactions using different contact angle boundary conditions which in general showed reasonable agreement with experiment but also indicated deficiency of a constant contact angle value to depict the interaction physics in entirety. The computed force profiles from CFD model suggest dominance of the pressure force over the viscous force almost by an order of magnitude in all the Weber number cases studied. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-28T17:41:37.853681-05:
      DOI: 10.1002/aic.15027
       
  • Effect of channel size on liquid‐liquid plug flow in small channels
    • Authors: Dimitrios Tsaoulidis; Panagiota Angeli
      Abstract: The hydrodynamic properties of plug flow were investigated in small channels with 0.5, 1, and 2 mm ID, for an ionic liquid/aqueous two‐phase system with the aqueous phase forming the dispersed plugs. Bright field PIV combined with high speed imaging were used to obtain plug length, velocity and film thickness, and to acquire velocity profiles within the plugs. Plug length decreased with mixture velocity, while for constant mixture velocity it increased with channel size. Plug velocity increased with increasing mixture velocity and channel size. The film thickness was predicted reasonably well for Ca>0.08 by Taylor's1 model. A fully developed laminar profile was established in the central region of the plugs. Circulation times in the plugs decreased with increasing channel size. Pressure drop was predicted reasonably well by a modified literature model, using a new correlation for the film thickness derived from experimental values. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-28T17:40:54.687092-05:
      DOI: 10.1002/aic.15026
       
  • Chemical nature of active sites for defect‐mediated nucleation on
           silicon dioxide
    • Authors: Joseph M. McCrate; John G. Ekerdt
      Abstract: Germanium nanoparticle growth on SiO2 proceeds via defect‐mediated nucleation and particle density can be enhanced by chemically treating the SiO2 with SiHx. The influence of SiHx fragments on SiO2 surface sites is studied using a fluorescent probe‐based technique to understand the chemical nature of the inherent defect trapping sites and the chemical nature of the additional trapping sites formed by SiHx. We show oxygen‐vacancy sites on SiO2 are the inherent sites for defect‐mediated nucleation. SiHx fragments, generated by cracking disilane on a hot tungsten filament, are shown to react with strained siloxane sites, leading to a conversion of these strained siloxane sites into a different low density defect site that is shown to display reactive characteristics similar to the oxygen‐vacancy defect sites. Previous work demonstrating an increased density of Ge nuclei on SiO2 surfaces with increasing SiHx exposure is interpreted in the context of the current experimental results. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-28T03:31:02.610608-05:
      DOI: 10.1002/aic.15023
       
  • Adsorption of nitrogen and sulfur containing compounds on nimos for
           hydrotreating reactions: A DFT and vdW‐corrected study
    • Authors: Srinivas Rangarajan; Manos Mavrikakis
      Abstract: Adsorption of thirty five molecules, comprising of organonitrogen and organosulfur compounds and hydrocarbons relevant to hydrotreating, was studied on the nickel promoted metal edge of molybdenum sulfide catalysts using periodic DFT, accounting for van der Waal's interactions in several cases. Basic molecules tend to adsorb via their nitrogen atoms directly on top of nickel atoms while non‐basic molecules adsorb via carbon atoms relatively weakly. Molecular size, electron density, and alkyl substitution affects binding at the GGA‐PW91 level of theory. van der Waal's corrections influences adsorption geometry and leads to significant additional stabilization of adsorbates. The differential binding energy of nitrogen‐containing compounds decreases by 0.2 – 0.3 eV for each additional molecule added on the edge and their presence destabilizes the binding of organosulfur compounds by more than 0.2 eV. The inhibition of hydrodesulfurization is suggested to arise from site blocking and destabilization of reaction intermediates and transition states by organonitrogen compounds. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-28T03:30:28.032528-05:
      DOI: 10.1002/aic.15025
       
  • Effect of dead volumes on the performance of an industrial‐scale
           simulated moving‐bed parex unit for p‐xylene purification
    • Abstract: The cyclic steady state (CSS) of the industrial‐scale, seven‐zone, simulated moving‐bed unit for p‐xylene (p‐x) purification (Parex unit) with three types of dead volumes—bed lines, pusharound and pumparound circulation lines, and bed heads—is analysed. In particular, the effects of the size and level of hydrodynamic dispersion of each dead volume on process performance and on its CSS are studied in detail. The circulation lines change the CSS behaviour from t*‐periodic to Nt*‐periodic, where t* is the switching interval and N = 12 is the number of columns in each adsorbent chamber. A high level of axial dispersion in the bed lines, characterized by Péclet numbers smaller than 100, affects the p‐x purity. Moreover, the bed lines lower the average p‐x concentration in the extract, which reduces the p‐x recovery. If the small time lags introduced by the circulation lines are neglected, it is possible to develop a detailed process model that considers the operation of the Parex unit over a single switching interval as opposed to a full cycle, and whose CSS solution can be efficiently computed using a full‐discretization approach. Finally, it is shown that the volume of the bed heads influences significantly the performance of the Parex unit, and that its impact on the location of the operating point with respect to the boundaries of the separation region can be approximately taken into account using the standard TMB‐SMB equivalence rules if they are corrected for the presence of extra interparticle fluid. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-28T03:29:37.185235-05:
      DOI: 10.1002/aic.15022
       
  • Liquid‐liquid flow patterns in reduced dimension based on energy
           minimization approach
    • Authors: Aadithya Kannan; Subhabrata Ray, Gargi Das
      Abstract: Study of liquid‐liquid flow patterns in reduced dimensions is relevant under the current trends to miniaturize process equipment. The phase distribution results from interplay of surface (dominant in microchannels) and gravity forces (dominant in larger dimensions). The proposed analysis, based on minimization of total system energy comprising of kinetic, surface and potential energy, unravels the influence of wetting properties and predicts the range of existence of annular and plug flow as well as the onset of stratification with increasing conduit dimension. Unlike existing models marking abrupt transitions, the proposed methodology can predict zones of transition where interfacial distributions gradually evolve with change of operating conditions ‐ the predictions agreeing closely to experimental and literature data. The analysis illustrates the coupled effect of diameter, contact angle and inlet composition on flow distribution and defines the transition from macro to micro domain (millichannels) in terms of Bond number as 0.1
      PubDate: 2015-08-28T03:28:54.632234-05:
      DOI: 10.1002/aic.15024
       
  • CFD simulation of a transpiring‐wall SCWO reactor: Formation and
           optimization of the water film
    • Authors: Fengming Zhang; Chunyuan Ma
      Abstract: A 2‐dimentional axisymmetric computational fluid dynamics model of a transpiring wall reactor for supercritical water oxidation (SCWO) was developed using the commercial software Fluent 6.3. Numerical model was validated by comparisons with experimental temperature profiles and product properties (total organic carbon and CO). Compared with the transpiration intensity, the transpiring water temperature was found to have a more significant influence on the reaction zone. An assumption that an ideal corrosion and salt deposition inhibitive water film can be formed when the temperature of the inner surface of the porous tube is less than 374°C was made. It was observed that lowering transpiring water temperature is conducive to the formation of the water film at the expense of feed degradation. The appropriate mass flux ratio between the total transpiring flow and the core flow was determined at 0.05 based on the formation of the water film and feed degradation. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-27T18:41:28.582313-05:
      DOI: 10.1002/aic.15021
       
  • Kinetic study of 1‐butanol dehydration to di‐n‐butyl
           ether over Amberlyst 70
    • Abstract: Kinetics of the catalytic dehydration of 1‐butanol to di‐n‐butyl ether (DNBE) over Amberlyst‐70 was investigated. Experiments were performed in liquid phase at 4 MPa and 413‐463 K. Three elementary reaction mechanisms were considered: a Langmuir‐Hinselwood‐ Hougen‐Watson (LHHW) formulation; an Eley‐Rideal (ER) formulation in which DNBE remains adsorbed; an ER formulation in which water remains adsorbed. Two kinetic models explain satisfactorily the dehydration of 1‐butanol to DNBE: a LHHW formalism in which the surface reaction between two adjacent adsorbed molecules of 1‐butanol is the rate limiting step (RLS) and where the adsorption of water is negligible, and a mechanism in which the RLS is the desorption of water being the adsorption of DNBE negligible. In both models the strong inhibiting effect of water was successfully taken into account by means of a correction factor derived from a Freundlich adsorption isotherm. Both models present similar values of apparent activation energies (122±2 kJ/mol). This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-27T18:37:03.299048-05:
      DOI: 10.1002/aic.15020
       
  • Trends and Challenges in Process Safety
    • PubDate: 2015-08-27T18:27:33.00836-05:0
      DOI: 10.1002/aic.15019
       
  • New frames of reference for mapping drugs in the four classes of the BCS
           and BDDCS into regions with clear boundaries
    • Authors: Kalliopi Chatzizacharia; Dimitris Hatziavramidis
      Abstract: The Biopharmaceutics Classification System (BCS), adopted by drug regulatory agencies for oral drug products approval, classify drug substances into four classes according to their aqueous solubility and epithelial membrane permeability. In a solubility‐permeability frame of reference, drugs on the boundaries of the four regions depicting the four drug classes are problematic to classify. To remove the fuzziness in the boundaries of the solubility‐permeability frame of reference, a data set of 85 oral drugs from all four classes of BCS are mapped into new frames of references in which the coordinate axes are based on the rates of dissolution, systemic elimination (metabolism) and membrane permeation. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-20T01:54:07.96739-05:0
      DOI: 10.1002/aic.15017
       
  • A Thermodynamic Approach Towards Defining the Limits of Biogas Production
    • Authors: Ralph Farai Muvhiiwa; Diane Hildebrandt, David Glasser, Tonderayi Matambo, Craig Sheridan
      Abstract: In this paper the authors present theoretical thermodynamic targets for producing biogas. The research shows the relationship between the mass of substrate used versus the methane produced from a feedstock of glucose and an estimate for that of cellulose. Calculations based on material and energy balances are used to determine the performance target (material and energy limits) of an anaerobic digestion system. These limits cannot be exceeded even if one genetically engineer organisms to increase yield. The results show that all processes that produce methane are feasible from a Gibbs Free Energy point of view but do not conserve the chemical potential of the feed material. The thermodynamics show that methane production is material and energy limited. The maximum amount of methane that can be formed sustainably is 3 moles per mole of glucose, producing 142 kJ of heat per mole of glucose which needs to be rejected. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-19T11:11:20.635909-05:
      DOI: 10.1002/aic.15016
       
  • Experimental Investigation of Solid Particles Flow in a Conical Spouted
           Bed Using Radioactive Particle Tracking
    • Authors: L. Spreutels; B. Haut, R. Legros, F. Bertrand, J. Chaouki
      Abstract: Solid particles flow in a conical spouted bed is characterized by radioactive particle tracking (RPT). The influence of operating conditions on key parameters of this flow is evaluated and discussed: the morphology of the solid bed is not strongly influenced by the forces exerted by the gas on the solid particles, but rather by geometrical considerations; the particles spend approximately eight percent of their time in the spout in all experiments; it is the force exerted on the solid particles by the gas that directly controls the volumetric flow rate between adjacent regions, and not the amount of particles in the bed; as U/Ums increases, the volume of solid particles in the annulus decreases, the volume of solid particles in the fountain increases and the volume of solid particles in the spout remains constant. Correlations to predict key flow parameters as functions of operating conditions are also established and discussed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-19T01:12:01.503479-05:
      DOI: 10.1002/aic.15014
       
  • Thermodynamics and Separation Process for Quaternary Acrylic Systems
    • Authors: Cuncun Zuo; Yaping Li, Chunshan Li, Shasha Cao, Haoyu Yao, Suojiang Zhang
      Abstract: Vapor‐liquid equilibrium (VLE) and liquid‐liquid equilibrium (LLE) data of binary and ternary acrylic systems were systematically measured. Subsequently, VLLE phase diagrams of binary systems, tridimensional VLE phase diagrams of methyl acrylate (MA)‐methanol (Me)‐H2O ternary system, and quaternary LLE phase diagrams of MA‐Me‐H2O‐methyl acetate (MeOAc) system were constructed. These diagrams clearly demonstrated the effects of temperature on phase equilibrium. The experimental data was fitted by the NRTL and UNIQUAC models, and the best‐fitted parameters were used to predict interaction properties of ternary and quaternary mixture. Therefore, the phase equilibrium data were provided as reference for the design of acrylic systems rectification or extraction process. Residue curve was mapped out for MA‐Me‐H2O system through Aspen plus software. Finally, using thermodynamics and residue curve as theoretical basis, two novel separation processes were proposed and applied to the quaternary acrylic systems. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-19T01:10:59.36514-05:0
      DOI: 10.1002/aic.15015
       
  • Advanced technologies for water treatment and reuse
    • Authors: Inmaculada Ortiz Uribe; Anuska Mosquera Corral, Juan Lema Rodicio, Santiago Esplugas
      PubDate: 2015-08-17T18:43:07.814198-05:
      DOI: 10.1002/aic.15013
       
  • Engineering Design of Outer‐Selective Tri‐bore Hollow Fiber
           Membranes for Forward Osmosis and Oil‐Water Separation
    • Abstract: Outer‐selective thin‐film composite (TFC) hollow fiber membranes offer advantages like less fiber blockage in the feed stream and high packing density for industrial applications. However, outer‐selective TFC hollow fiber membranes are rarely commercially available due to the lack of effective ways to remove residual reactants from fiber's outer surface during interfacial polymerization and form a defect‐free polyamide film. This study reports a new simplified method to fabricate outer‐selective TFC membranes on tri‐bore hollow fiber substrates. Mechanically robust tri‐bore hollow fiber substrates containing 3 circular‐sector channels were first prepared by spinning a P84/ethylene glycol mixed dope solution with delayed demixing at the fiber lumen. The thin wall tri‐bore hollow fibers have a large pure water permeability up to 300 L m−2 h−1 bar−1. Outer‐selective TFC tri‐bore hollow fiber membranes were then fabricated by interfacial polymerization with the aid of vacuum sucking to ensure the TFC layer well‐attached to the substrate. Under forward osmosis studies, the TFC tri‐bore hollow fiber membrane exhibits a good water flux and a small flux difference between active‐to‐draw (i.e., the active layer facing the draw solution) and active‐to‐feed (i.e., the active layer facing the feed solution) modes due to the small internal concentration polarization. A hyper‐branched polyglycerol was further grafted on top of the newly developed TFC tri‐bore hollow fiber membranes for oily wastewater treatment. The membrane displays low fouling propensity and can fully recover its water flux after a simple 20‐min water wash at 0.5 bar from its lumen side, which makes the membrane preferentially suitable for oil‐water separation. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-13T18:21:26.997763-05:
      DOI: 10.1002/aic.15012
       
  • First‐Principles Based Group Additivity Values for Thermochemical
           Properties of Substituted Aromatic Compounds
    • Abstract: A set of 7 Benson group additive values (GAV) together with 15 correction terms for non‐nearest neighbor interactions (NNI) is developed to calculate the gas phase standard enthalpies of formation, entropies and heat capacities of monocyclic aromatic compounds containing methyl, ethyl, vinyl, formyl, hydroxyl and methoxy substituents. These GAVs are obtained through least squares regression of a database of thermodynamic properties of 143 molecules, calculated at the post‐Hartree–Fock G4 composite method. Out of the 15 NNIs, which account for several well‐known substituent effects in aromatic molecules, 13 have been determined for the first time. All but two group additively calculated standard enthalpies of formation agree within 4 kJ mol‐1. The entropies and the heat capacities generally deviate less than 4 J mol‐1 K‐1 from the ab initio results. Natural bond orbital (NBO) analysis is utilized to identify the underlying causes of the observed NNIs. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-12T18:16:20.308654-05:
      DOI: 10.1002/aic.15008
       
  • Process Intensification on the Separation of Benzene and Thiophene by
           Extractive Distillation
    • Authors: Jingli Han; Zhigang Lei, Yichun Dong, Chengna Dai, Biaohua Chen
      Abstract: The separation of benzene and trace thiophene by extractive distillation was intensified in two aspects, i.e., selection of a suitable entrainer and improvement of the process. The mixture of dimethylformamide (DMF) and an ionic liquid (IL) was chosen as the entrainer. Vapor‐liquid equilibrium (VLE) experiments using pure DMF and a mixed entrainer were conducted, and UNIFAC model for ILs was extended to the benzene‐thiophene‐DMF‐IL system. The results demonstrated that volatilization loss of DMF in the vapor phase was significantly reduced by adding IL. Moreover, an improved process with only four columns using a mixed entrainer was proposed. The results indicated that the improved process is more promising for decreasing energy consumption and equipment investment compared with the conventional six‐column process. The total heat duties of reboilers and condensers was decreased by 6.47% and 6.41%, respectively. The process intensification strategy may be directly extended to separate trace components of other systems. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-12T18:13:09.013163-05:
      DOI: 10.1002/aic.15009
       
  • Mixed matrix membranes based on 6FDA polyimide with silica and zeolite
           microsphere dispersed phases
    • Abstract: Mixed matrix membranes (MMMs) prepared with 6FDA‐DAM polymer using ordered mesoporous silica MCM‐41 spheres (MSSs), Grignard surface functionalized MSSs (Mg‐MSSs) and hollow zeolite spheres (HZSs) are studied to evaluate the effects of surface modification on performance. Performance near or above the so‐called permeability‐selectivity trade‐off curve was achieved for the H2/CH4, CO2/N2, CO2/CH4 and O2/N2 systems. Two loadings (8 and 16 wt%) of MSSs were tested using both constant volume and Wicke‐Kallenbach sweep gas permeation systems. Besides single gas H2, CO2, O2, N2 and CH4 tests, mixed gas (50/50 vol%) selectivities were obtained for H2/CH4, CO2/N2, CO2/CH4 and O2/N2 and found to show enhancements vs. single gases for CO2 including cases. Mg‐MSS/6FDA‐DAM was the best performing MMM with H2/CH4, CO2/N2, CO2/CH4 and O2/N2 separation selectivities of 21.8 (794 Barrer of H2), 24.4 (1214 Barrer of CO2), 31.5 (1245 Barrer of CO2) and 4.3 (178 Barrer of O2), respectively. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-12T18:09:52.783452-05:
      DOI: 10.1002/aic.15011
       
  • PtZn‐ETS‐2: A Novel Catalyst for Ethane Dehydrogenation
    • Authors: Zhengnan Yu; James A. Sawada, Weizhu An, Steven M. Kuznicki
      Abstract: Catalysts having unprecedented selectivity toward ethane dehydrogentation were prepared by combining platinum and zinc on the surface of the titanate ETS‐2. This high surface area, sodium titanate ion exchanger affords high metal dispersion, presents many active sites to the gas stream, and is free of any pore structure that can influence mass transfer to and away from the active sites. It was determined that the addition of zinc to platinum‐loaded ETS‐2 changes the electronic properties of the metals and significantly improves the specificity of the catalyst. By changing the zinc‐to‐platinum ratio, and by manipulating the space velocity of the gas, the production of side products and coke can be suppressed or eliminated. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-12T18:09:22.531979-05:
      DOI: 10.1002/aic.15010
       
  • Effect of Liquid Addition on the Bulk and Flow Properties of Fine and
           Coarse Glass Beads
    • Authors: James V. Scicolone; Matthew Metzger, Sara Koynov, Kellie Anderson, Paul Takhistov, Benjamin J. Glasser, Fernando J. Muzzio
      Abstract: The effect of water on the packing and flow properties of fine and coarse particles was experimentally investigated. Four different particle sizes of glass beads, from 5 to 275μm, were studied with increasing water weight‐percentages. Using a FT4 Powder Rheometer, changes in bulk properties were collected as a function of water content and particle size. The results show that water content plays a significant role on the packing and flow of the particles. Small amounts of water created porous aggregates due to liquid bridging. Greater amounts of water resulted in the filling of the void‐spaces. This was indicated by an increase in basic flow energy, density, and pressure drop, with a decrease in porosity. A greater understanding of bulk properties of wetted material is useful to develop standard systems that can be used to examine the behavior of more complex situations, and implement changes to improve materials handling and processing. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-11T19:41:41.407228-05:
      DOI: 10.1002/aic.15004
       
  • A model for supersaturation and aspect ratio for growth dominated
           crystallization from solution
    • Authors: L. Derdour; E.J. Chan
      Abstract: A model for predicting supersaturation, crystal growth rate, crystal size distribution and aspect ratio is presented. The model applies to isothermal anti‐solvent crystallization where crystal growth is the dominant phenomena and for systems where crystal habit can be characterized by two dimensional variables. A parameter estimation algorithm was derived to extract solute integration coefficients in the two growth directions from experimental data about temporal evolution of concentration during crystallization, the final aspect ratio and the aspect ratio at the end of the seed age period. Model's predictions for supersaturation and aspect ratio were in good agreement with experimental data obtained on an investigational drug that crystallizes in the parallelepipedic shape. Finally, model simulations predict that for a given initial seed size, the seed loading is the main factor impacting the final aspect ratio and thus identified the range of seed loading that would result in undesired powder flow. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-11T19:31:21.088942-05:
      DOI: 10.1002/aic.15007
       
  • Ultra‐thin Carbon Molecular Sieve Membrane for Propylene/Propane
           Separation
    • Authors: Xiaoli Ma; Y.S. Lin, Xiaotong Wei, Jay Kniep
      Abstract: Ultra‐thin (down to 300 nm), high quality carbon molecular sieve (CMS) membranes were synthesized on mesoporous γ‐alumina support by pyrolysis of defect free polymer films. The effect of membrane thickness on the micropore structure and gas transport properties of CMS membranes was studied with the feed of He/N2 and C3H6/C3H8 mixtures. Gas permeance increases with constant selectivity as the membrane thickness decreases to 520 nm. The 520 nm CMS membrane exhibits C3H6/C3H8 mixture selectivity of ∼31 and C3H6 permeance of ∼1.0 × 10−8 mol m−2 s−1 Pa−1. Both C3H8 permeance and He/N2 selectivity increase, but the permeance of He, N2 and C3H6 and the selectivity of C3H6/C3H8 decrease with further decrease in membrane thickness from 520 nm to 300 nm. These results can be explained by the thickness‐dependent chain mobility of the polymer film which yields thinner final CMS membranes with reduction in pore size and possible closure of C3H6‐accessible micropores. The authors would like to acknowledge the support of the National Science Foundation (IIP‐1127395) for this project, and Belle K. Lin for assistance in some experiments. We also acknowledge the use of facilities with the LeRoy Eyring Center for Solid State Science at Arizona State University. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-11T19:30:44.538053-05:
      DOI: 10.1002/aic.15005
       
  • Efficient recovery of high‐purity aniline from aqueous solutions
           using pervaporation‐fractional condensation system
    • Authors: Chuncheng Li; Xinru Zhang, Xiaogang Hao, Minmin Wang, Chuan Ding, Zhongde Wang, Yinan Wang, Guoqing Guan, Abuliti Abudula
      Abstract: Selective recovery of valuable minor component with high‐purity form from dilute aqueous solution is an interesting issue in the area of organophilic pervaporation. In this study, high‐purity aniline was recovered with a high production rate from dilute aqueous solution by a pervaporation‐fractional condensation (PVFC) coupling system. The effects of downstream pressure and temperature (the first condenser) on the performance of PVFC system were investigated based on experimental measurements and Aspen simulations. Sorption and desorption experiments demonstrated that the sorption selectivity of PEBA‐2533 membrane to aniline was extremely high, indicating excellent pervaporation performance for aniline/water solutions. The perfect integration of high‐performance PEBA‐2533 membrane with the fractional condensation process yielded high production rate of 1222.5 g/(m2·h) as well as high recovery efficiency (86.5%) for recovering high‐purity aniline in the first condenser when feed concentration and temperature were 1 wt% and 80 ˚C, respectively. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-11T19:30:06.365446-05:
      DOI: 10.1002/aic.15006
       
  • Issue information
    • Abstract: Cover illustration. Surrounding John Prausnitz are symbols of his bridges among abstractions and reality. The lower left image shows fundamental formulae relating thermodynamic properties, taken from his 1959 paper “Fugacities in High‐Pressure Equilibria and in Rate Processes”, AIChE Journal. 5(1), pp.3‐9. The lower right image shows how “Chemical Thermodynamics Provides A Methodology Toward Answering Two Questions” redrawn with permission from the author from Figure 5 of his 1986 paper “ion and Reality. The Two Sources of Chemical Thermodynamics”, J. Non‐Equilib. Thermodyn., 11(1/2), pp. 49‐66, published by de Gruyter, Berlin. The top image illustrates disparate elements of life connected by bridges that people may cross alone or together, taken from his paper “Rediscovering the Relevance of Chemical Engineering”, (Reprinted with permission from CHEMTECH, December 1993, 23(12), pp. 12‐15). Copyright 1993 American Chemical Society.) 10.1002/aic.14961
      PubDate: 2015-08-07T09:38:27.197022-05:
      DOI: 10.1002/aic.14588
       
  • Drop printing of pharmaceuticals: Effect of molecular weight on PEG
           coated‐naproxen/PEG3350 solid dispersions
    • Abstract: Solid dispersions have been used to enhance the bioavailability of poorly water‐soluble active pharmaceutical ingredients (APIs). However, the solid state phase, compositional uniformity, and scale‐up problems are issues that need to be addressed. To allow for highly controllable products, the Drop Printing (DP) technique can provide precise dosages and predictable compositional uniformity of APIs in two/three dimensional structures. In this study, DP was used to prepare naproxen (NAP)/polyethylene glycol 3350 (PEG3350) solid dispersions with PEG coatings of different molecular weights (MW). A comparison of moisture‐accelerated crystallization inhibition by different PEG coatings was assessed. Scanning electron microscopy (SEM), second harmonic generation (SHG) microscopy, and differential scanning calorimetry (DSC) analysis were performed to characterize the morphology and quantify the apparent crystallinity of NAP within the solid dispersions. Thermogravimetric analysis (TGA) was employed to measure the water content within each sample. The results suggest that the moisture‐accelerated crystallization inhibition capability of the PEG coatings increased with increasing MW of the PEG coating. Besides, to demonstrate the flexibility of DP technology on manufacturing formulation, multilayer tablets with different PEG serving as barrier layers were also constructed, and their dissolution behavior was examined. By applying DP and appropriate materials, it is possible to design various carrier devices used to control the release dynamics of the API. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-06T18:37:55.283444-05:
      DOI: 10.1002/aic.14979
       
  • Lumped reaction kinetic models for pyrolysis of heavy oil in the presence
           of supercritical water
    • Abstract: The reaction kinetics of the pyrolysis of heavy oil in the presence of supercritical water (SCW) and high pressure N2 were measured. At any reaction temperature applied, the pyrolysis under SCW environments is faster than that under N2 environments. Meanwhile, at lower temperatures the pyrolysis under both environments is accelerated by the introduction of coke into the feedstock. On the basis of a first‐order four‐lump reaction network consisting of the sequential condensation of maltenes and asphaltenes, the pyrolysis in whichever medium can be preferably described either by the lumped reaction kinetic model modified with autocatalysis and pseudo‐equilibrium or by the model modified solely with pseudo‐equilibrium. Benefited from the reduced limitation of diffusion to reaction kinetics, the pyrolysis in the SCW phase is more sensitive to the increase in reaction temperature than that in the oil phase, disengaging readily from the dependence on autocatalysis at a lower temperature. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-06T18:37:27.567937-05:
      DOI: 10.1002/aic.14978
       
  • The separation of two different sized particles in an evaporating droplet
    • Authors: Nicole Raley Devlin; Katherine Loehr, Michael T. Harris
      Abstract: The separation of two different sized particles during evaporation of a dilute droplet is examined both computationally and experimentally. A transport model of the evaporating droplet system was solved using the finite element method to determine the fluid velocity, pressure, vapor concentration surrounding the droplet, temperature, and both particle concentrations. Experimentally, 1 μm and 3 μm polystyrene particles were used during the evaporation of a sessile water droplet. It was determined that to accurately model particle deposition, thermal effects need to be considered. The Marangoni currents in evaporating droplets keep particles suspended in the droplet until the end of the evaporation. Previous models of particle deposition during droplet evaporation have rapid accumulation of particles at the contact line. Our experiments and the experiments of others demonstrate that this is not accurate physically. In addition, to model the separation of two different sized particles the consideration of thermal effects is essential. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-06T11:03:56.646128-05:
      DOI: 10.1002/aic.14977
       
  • On the Accuracy of Landweber and Tikhonov Reconstruction Techniques in
           Gas‐Solid Fluidized Bed Applications
    • Authors: M. Banaei; M. van Sint Annaland, J.A.M Kuipers, N.G. Deen
      Abstract: As electrical capacitance tomography (ECT) technique needs a sophisticated reconstruction, the accuracy of two of the most widely used reconstruction techniques (Landweber and Tikhonov) for gas‐fluidized bed applications were assessed. For this purpose, the results of two‐fluid model (TFM) simulations were used as an input of reconstruction. After finding the optimum reconstruction parameters for the studied system, it is found that both techniques were able to obtain the radial profile and overall value of average volume fraction very well. Conversely, both methods were incapable to determine bubble sizes accurately especially small bubble sizes, unless the Landweber technique with inverted Maxwell concentration model is applied. The probability distribution of the reconstructed results were also smoother in transition between the emulsion and bubble phases compared to the reality. Finally, no significant differences in noise immunity of these two techniques was observed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-03T03:04:48.503616-05:
      DOI: 10.1002/aic.14976
       
  • Using short‐term resource scheduling for assessing effectiveness of
           CCS within electricity generation sub‐sector
    • Authors: Colin Alie; Ali Elkamel, Eric Croiset, Peter L. Douglas
      Abstract: A new methodology for assessing the effectiveness of CCS (Carbon Capture and Storage) that does explicitly consider the detailed operation of the target electricity system is proposed in this paper. The electricity system simulation consists of three phases, each one using a modified version of an economic dispatch problem that seeks to maximize the producers' and consumers' surplus while satisfying the technical constraints of the system. The economic dispatch is formulated as a dynamic MINLP (Mixed‐Integer Non‐Linear Programming) problem and implemented in GAMS (General Algebraic Modelling System). The generating unit with CCS is designed and simulated using Aspen Plus®. In the first case study, the operation of the IEEE RTS '96 (Institute of Electrical and Electronics Engineers One‐Area Reliability Test System ‐ 1996)) is simulated with GHG regulation implemented in the form of CO2 permits that generators need to acquire for every unit of CO2 that it is emitted. In the second case study, CCS is added at one of the buses and the operation of the modified IEEE RTS '96 is again simulated with and without GHG regulation. The results suggest that the detailed operation of the target electricity system should be considered in future assessments of CCS and a general procedure for undertaking this for any GHG mitigation option is proposed. Future work will use the novel methodology for assessing the effectiveness of generating units with flexible CO2 capture. This article is protected by copyright. All rights reserved.
      PubDate: 2015-08-01T03:51:45.396917-05:
      DOI: 10.1002/aic.14975
       
  • A novel adaptive surrogate modeling based algorithm for simultaneous
           optimization of sequential batch process scheduling and dynamic operations
           
    • Authors: Hanyu Shi; Fengqi You
      Abstract: We propose a novel adaptive surrogate modeling based algorithm to solve the integrated scheduling and dynamic optimization problem for sequential batch processes. The integrated optimization problem is formulated as a large scale mixed integer nonlinear programming (MINLP) problem. In order to overcome the computational challenge of solving the integrated MINLP problem, we propose an efficient solution algorithm based on the bilevel structure of the integrated problem. Because processing times and costs of each batch are the only linking variables between the scheduling and dynamic optimization problems, surrogate models based on piece‐wise linear functions are built for the dynamic optimization problems of each batch. These surrogate models are then updated adaptively, either by adding a new sampling point based on the solution of the previous iteration, or by doubling the upper bound of total processing time for the current surrogate model. The performance of our proposed method is demonstrated through the optimization of a multi‐product sequential batch process with seven units and up to five tasks. The results show that the proposed algorithm leads to a 31% higher profit than the sequential method. The proposed method also outperforms the full space simultaneous method by reducing the computational time by more than four orders of magnitude and returning a 9.59% higher profit. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-30T17:50:08.993106-05:
      DOI: 10.1002/aic.14974
       
  • Computational study of spout collapse and impact of partition plate in a
           double slot‐rectangular spouted bed
    • Authors: Shiliang Yang; Ke Zhang, Jia Wei Chew
      Abstract: Gas‐solid hydrodynamics in a three‐dimensional slot‐rectangular double‐spouted bed was numerically investigated by a combined approach of discrete element method (DEM) and computational fluid dynamics (CFD), and the knowledge gained was extended to understand the mechanisms leading to operational instability due to the collapse of a spout, along with the beneficial impact of inserting a vertical partition plate. The setup investigated has two diverging bases and contains up to 2,590,000 particles. The computational results show different behaviors of pressure drop, in terms of average value, fluctuations and power spectral trends, in the five distinct flow regimes corresponding to various superficial gas velocities. Two types of spout shapes are observed under stable spouting conditions, and the spout sizes are quantified. When one of the spouts chokes then collapses, complex interactions between the chambers are identified. Furthermore, the insertion of a vertical partition plate between two chambers appears to be an effective way to prevent the interactions between adjacent fountains, which is advantageous for improving the operational stability of such systems upon scale‐up. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-27T13:55:41.362616-05:
      DOI: 10.1002/aic.14973
       
  • Determination of kinetics of CO2 absorption in solutions of
           2‐amino‐2‐methyl‐1‐propanol using a
           microfluidic technique
    • Authors: C. Zheng; B.C. Zhao, K. Wang, G.S. Luo
      Abstract: The kinetics for the reactions of carbon dioxide with 2‐amine‐2‐methyl‐1‐propanol (AMP) and carbon dioxide (CO2) in both aqueous and nonaqueous solutions were measured using a microfluidic method at a temperature range of 298‐318 K. The mixtures of AMP‐water and AMP‐ethylene glycol (EG) were applied for the working systems. Gas‐liquid bubbly mciroflows were formed through a micro‐sieve device and used to determine the reaction characteristics by online observation of the volume change of microbubbles at the initial flow stage. In this condition, a mathematical model according to zwitterion mechanism has been developed to predict the reaction kinetics. The predicted kinetics of CO2 absorption in the AMP aqueous solution verified the reliability of the method by comparing with literatures' results. Furthermore, the reaction rate parameters for the reaction of CO2 with AMP in both solutions were determined. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-27T13:54:30.669493-05:
      DOI: 10.1002/aic.14972
       
  • Flexibility Assessment and Risk Management in Supply Chains
    • Authors: Nihar Sahay; Marianthi Ierapetritou
      Abstract: Increased uncertainty in recent years has led the supply chains to incorporate measures to be more flexible in order to perform well in the face of the uncertain events. It has been shown that these measures improve the performance of supply chains by mitigating the risks associated with uncertainties. However, it is also important to assess the uncertainty under which a supply chain network can perform well and manage risk. In this work, flexibility is defined in terms of the bounds of uncertain parameters within which supply chain operation is feasible. A hybrid simulation based optimization framework that uses two‐stage stochastic programming in a rolling horizon framework is proposed. The framework enables taking optimum planning decisions considering demand uncertainty while managing risk. The framework is used to study the trade‐offs between flexibility, economic performance and risk associated with supply chain operation. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-24T10:27:05.028984-05:
      DOI: 10.1002/aic.14971
       
  • Modeling and Analysis of Conventional and Heat‐Integrated
           Distillation Columns
    • Abstract: A generic model that can cover diabatic and adiabatic distillation column configurations is presented, with the aim of providing a consistent basis for comparison of alternative distillation column technologies. Both a static and a dynamic formulation of the model, together with a model catalogue consisting of the conventional, the heat‐integrated and the mechanical vapor recompression distillation columns are presented. The solution procedure of the model is outlined and illustrated in three case studies. One case study being a benchmark study demonstrating the size of the model and the static properties of two different HIDiC schemes and the MVRC. The second case study exemplifies the difference between a HIDiC and a CDiC in the composition profiles within a multicomponent separation, whereas the last case study demonstrates the difference in available dynamic models for the HIDiC and the proposed model. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-24T10:02:47.212608-05:
      DOI: 10.1002/aic.14970
       
  • Kinetic Insight into Electrochemically Mediated ATRP Gained through
           Modeling
    • Abstract: A detailed kinetic model was constructed using the method of moments to elucidate the electrochemically mediated atom transfer radical polymerization (eATRP). Combined with electrochemical theory, the reducing rate coefficient relevant to the overpotential in eATRP was coupled into the kinetic model. The rate coefficients for eATRP equilibrium and the reducing rate coefficient were fitted to match the experimental data. The effects of catalyst loading, overpotential, and application of programmable electrolysis on the eATRP behavior were investigated based on the tested kinetic model. Results showed that the apparent polymerization rate exhibited a square root dependence on catalyst loading. In addition, a more negative potential accelerated the polymerization rate before the mass transport limitation was reached. This phenomenon indicated that the polymerization rate could be artificially controlled by the designed program (i.e., stepwise and intermittent electrolysis programs). What's more, the normal ATRP, photo‐ATRP, and eATRP were compared to obtain a deeper understanding of these ATRP systems. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-23T18:23:57.072058-05:
      DOI: 10.1002/aic.14969
       
  • Integrating expanders into heat exchanger networks above ambient
           temperature
    • Authors: Chao Fu; Truls Gundersen
      Abstract: The integration of expanders into heat exchanger networks (HENs) is a complex task since both heat and work are involved. In addition, the role of streams (as hot or cold), the utility demand, and the location of pinch points may change. With certain well‐defined conditions, four theorems are proposed for the integration of expanders into HENs above ambient temperature with the objective of minimizing exergy consumption. A straightforward graphical methodology for above ambient HENs design including expanders is developed on the basis of Grand Composite Curves (GCCs). It is concluded that in order to achieve a design with minimum exergy consumption, stream splitting may be applied and expansion should be done at pinch temperatures, hot utility temperature or ambient temperature. In the majority of cases, however, and in line with the concept of Appropriate Placement from Pinch Analysis, expansion at pinch temperatures gives the minimum exergy consumption. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-23T18:19:51.364947-05:
      DOI: 10.1002/aic.14968
       
  • Nanocolloid cake properties determined from step‐up pressure
           filtration with single‐stage reduction in filtration area
    • Abstract: A sophisticated method was developed for evaluating simultaneously and accurately both the average specific resistance and average porosity of the filter cake formed in unstirred dead‐end ultrafiltration of nanocolloids such as protein solution and nano silica sol. In the method, a step‐up pressure filtration test was conducted by using a filter with a single‐stage reduction in the effective filtration area. The influence of the pressure drop across the cake on not only the average specific cake resistance but also on the average cake porosity of highly compressible filter cake was evaluated using only flux decline data in one dead‐end filtration test, taking advantage of the decrease in the cake thickness caused by the pressure increase. As a result, the cake properties were easily determined for a variety of nanocolloids. Constant pressure dead‐end ultrafiltration data obtained under various pressures and concentrations were well evaluated based on the method proposed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-22T17:28:54.712045-05:
      DOI: 10.1002/aic.14967
       
  • Multistream heat exchanger modeling and design
    • Authors: Harry A. J. Watson; Kamil A. Khan, Paul I. Barton
      Abstract: A new model formulation and solution strategy for the design and simulation of processes involving multistream heat exchangers (MHEXs) is presented. The approach combines an extension of pinch analysis with an explicit dependence on the heat exchange area in a nonsmooth equation system to create a model which solves for up to three unknown variables in an MHEX. Recent advances in automatic generation of derivative‐like information for nonsmooth equations make the method tractable, and the use of nonsmooth equation solving methods make the method very precise. Several illustrative examples and a case study featuring an offshore liquefied natural gas production concept are presented which highlight the flexibility and strengths of the formulation. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-21T10:54:11.414921-05:
      DOI: 10.1002/aic.14965
       
  • Retrofit design of a pharmaceutical batch process considering “green
           chemistry and engineering” principles
    • Abstract: Considering the capital intensive nature of the chemical industry, redesign of existing production plants is a strategic decision. In this study, retrofitting is performed by using a systematic path flow decomposition method, enriching it with hazard assessment and life cycle analysis path flow indicators and proposing a classification scheme for coupling these new path flow indicators with relevant heuristics for process alternative generation. The developed methodology is applied in a batch production plant from the pharmaceutical industry. The method highlights solvent recovery or substitution as importanECt retrofitting actions, generates diverse process layout structures to achieve this task and evaluates them from cost, hazard and life cycle assessment point of view. Extractive distillation using glycol as an entrainer is identified as the multiobjective optimal option for separating the THF/Water azeotrope with improvement up to 40% for the various objectives compared to a base case where the waste solvent is incinerated. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-21T10:53:40.529575-05:
      DOI: 10.1002/aic.14966
       
  • Economic model predictive control of nonlinear time‐delay systems:
           Closed‐loop stability and delay compensation
    • Authors: Matthew Ellis; Panagiotis D. Christofides
      Abstract: Closed‐loop stability of nonlinear time‐delay systems under Lyapunov‐based economic model predictive control (LEMPC) is considered. LEMPC is formulated with an ordinary differential equation model and is designed on the basis of an explicit stabilizing control law. To address closed‐loop stability under LEMPC, first, we establish that the steady‐state of the closed‐loop sampled‐data system resulting from the nonlinear continuous‐time delay system with state and input delays under a sample‐and‐hold implementation of the explicit stabilizing control law is practically stable. Second, conditions such that closed‐loop stability, in the sense of boundedness of the closed‐loop state, under LEMPC are derived. A chemical process example is used to demonstrate that indeed closed‐loop stability is maintained under LEMPC for sufficiently small time‐delays. To cope with performance degradation owing to the effect of input delay, a predictor feedback LEMPC methodology is also proposed. The predictor feedback LEMPC design employs a predictor to compute a prediction of the state after the input delay period and an LEMPC scheme that is formulated with a differential difference model (DDE) model, which describes the time‐delay system, initialized with the predicted state. The predictor feedback LEMPC is applied to the chemical process example and yields improved closed‐loop stability and economic performance properties. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-21T10:48:49.689961-05:
      DOI: 10.1002/aic.14964
       
  • Effect of ship tilting and motion on amine absorber with
           structured‐packing for CO2 removal from natural gas
    • Abstract: A gas‐liquid Eulerian porous media computational fluid dynamics (CFD) model was developed for an absorber with structured packing to remove CO2 from natural gas by mono‐ethanol‐amine (MEA). The three dimensional geometry of the amine absorber with Mellapak 500.X was constructed to investigate the effect of the tilting and motion experienced on ships and barges for offshore plants. The momentum equation included porous resistance, gas‐liquid momentum exchange and liquid dispersion to replace structured‐packing by porous media. The mass equation involved mass transfer of CO2 gas into MEA solution, and one chemical reaction. Parameters of the CFD model were adjusted to fit experimental data measured in the CO2‐MEA system. As the tilting angle increased, the liquid holdup and effective interfacial area decreased and CO2 removal efficiency was lowered. The uniformity of liquid holdup deteriorated by 10% for a 3° static tilting, and a rolling motion with 4.5° amplitude and 12s period, respectively. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-20T18:32:05.561834-05:
      DOI: 10.1002/aic.14962
       
  • Real‐time preventive sensor maintenance using robust moving horizon
           estimation and economic model predictive control
    • Authors: Liangfeng Lao; Matthew Ellis, Helen Durand, Panagiotis D. Christofides
      Abstract: Conducting preventive maintenance of measurement sensors in real‐time during process operation under feedback control while ensuring the reliability and improving the economic performance of a process is a central problem of the research area focusing on closed‐loop preventive maintenance of sensors and actuators. To address this problem, a robust moving horizon estimation (RMHE) scheme and an economic model predictive control (EMPC) system are combined to simultaneously achieve preventive sensor maintenance and optimal process economic performance with closed‐loop stability. Specifically, given a preventive sensor maintenance schedule, a robust moving horizon estimation scheme is developed that accommodates varying numbers of sensors to continuously supply accurate state estimates to a Lyapunov‐based economic model predictive control (LEMPC) system. Closed‐loop stability for this control approach can be proven under fairly general observability and stabilizability assumptions to be made precise in the manuscript. Subsequently, a chemical process example incorporating this RMHE‐based LEMPC scheme demonstrates its ability to maintain process stability and achieve optimal process economic performance as scheduled preventive maintenance is performed on the sensors. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-17T00:01:49.18498-05:0
      DOI: 10.1002/aic.14960
       
  • Density segregation of dry and wet granular mixtures in gas fluidized beds
    • Authors: Stella Lin Li SEAH; Eldin Wee Chuan LIM
      Abstract: The Discrete Element Method combined with Computational Fluid Dynamics was coupled to a capillary liquid bridge force model for computational studies of mixing and segregation behaviors in gas fluidized beds containing dry or wet mixtures of granular materials with different densities. The tendency for density segregation decreased with increasing fluidizing velocity, coefficient of restitution and amount of liquid present. Due to the presence of strong capillary forces between wet particles, there was a high tendency for particles to form agglomerates during the fluidization process, resulting in lower segregation efficiency in comparison with fluidization of dry particles. Particle‐particle collision forces were on average stronger than both fluid drag forces and capillary forces. The magnitudes of drag forces and particle‐particle collision forces increased with increasing fluidizing velocity and this led to higher mixing or segregation efficiencies observed in dry particles as well as in wet particles at higher fluidizing velocities. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-16T23:58:44.084632-05:
      DOI: 10.1002/aic.14959
       
  • Ockham's razor for paring microkinetic mechanisms: Electrical analogy vs.
           Campbell's degree of rate control
    • Authors: Patrick D. O'Malley; Saurabh A. Vilekar, Ravindra Datta
      Abstract: Elucidation of the key molecular steps and pathways in an overall reaction is of central importance in developing a better understanding of catalysis. Campbell's degree of rate control (DRC) is the leading methodology currently available for identifying the germane steps and key intermediates in a catalytic mechanism. We contrast Campbell's DRC to our alternate new approach involving an analysis and comparison of the “resistance” and de Donder “affinity,” i.e., the driving force, of the various steps and pathways in a mechanism, in a direct analogy to electrical networks. We show that our approach is as just rigorous and more insightful than Campbell's DRC. It clearly illuminates the bottleneck steps within a pathway and allows one to readily discriminate among competing pathways. The example used for a comparison of these two methodologies is a DFT study of the water‐gas shift (WGS) reaction on Pt‐Re catalyst published recently. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-15T18:21:30.586835-05:
      DOI: 10.1002/aic.14956
       
  • Depletion of cross‐stream diffusion in the presence of
           viscoelasticity
    • Authors: Arman Sadeghi
      Abstract: This work presents an effort to analyze the viscoelasticity effects on transverse transport of neutral solutes between two miscible streams in an electrokinetic T‐sensor. The analysis is based on an approximate analytical solution for the depthwise averaged concentration, assuming a channel of large width to depth ratio for which a 1‐D profile is sufficient for describing the velocity field. We show that the solution derived is surprisingly accurate even for very small channel aspect ratios and the maximum error reduces to only about 1% when the aspect ratio is 5. The developed model reveals that the mixing length for a viscoelastic fluid may be by far larger than that for a Newtonian fluid. Moreover, the Taylor dispersion coefficient for electroosmotic flow of viscoelastic fluids, which its determination is a main part of the analysis, is found to be an increasing function of both the elasticity level and the EDL thickness. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-15T18:21:05.310829-05:
      DOI: 10.1002/aic.14955
       
  • Dynamic modeling and validation of a biomass hydrothermal pretreatment
           process ‐ A demonstration scale study
    • Abstract: Hydrothermal pretreatment of lignocellulosic biomass is a cost effective technology for second generation biorefineries. The process occurs in large horizontal and pressurized thermal reactors where the biomatrix is opened under the action of steam pressure and temperature to expose cellulose for the enzymatic hydrolysis process. Several by‐products are also formed, which disturb and act as inhibitors downstream. The objective of this study is to formulate and validate a large scale hydrothermal pretreatment dynamic model based on mass and energy balances, together with a complex conversion mechanism and kinetics. The study includes a comprehensive sensitivity and uncertainty analysis, with parameter estimation from real‐data in the 178‐185° range. To highlight the application utility of the model, a state estimator for biomass composition is developed. The predictions capture well the dynamic trends of the process, outlining the value of the model for simulation, control design, and optimization for full‐scale applications. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-15T18:20:40.575318-05:
      DOI: 10.1002/aic.14954
       
  • Three‐dimensional hydrogel encapsulated embryonic stem and carcinoma
           cells as culture platforms for cytotoxicity studies
    • Authors: Sneha Oberai; Kalpith Ramamoorthi, Jared Hara, Ailing Teo, Mayasari Lim, Prashanth Asuri
      Abstract: Our study describes the utility of alginate hydrogels for 3D culture of mouse embryonic stem cells (mESCs) and future development of 3D stem cell culture‐based in vitro screens of toxicity. Using alginate hydrogels of various stiffness, we first evaluated the impact of substrate modulus on mESC viability, proliferation, as well as expression of pluripotency and germ‐layer markers and observed that low concentration alginate hydrogels (0.5% and 1% alginate) were most suitable for long‐term culture of mESCs. These results were not unique to mESCs; long‐term viability and proliferation of mouse embryonic carcinoma cells (mECCs) was also best supported by similar conditions. Finally, we determined cytotoxic responses of alginate encapsulated cells to commercially available chemicals and interestingly observed similar responses for mESCs and mECCs, thereby suggesting that mECCs can predict stem cell responses to chemicals. These studies will facilitate future design of optimal stem cell‐based platforms of organ‐specific and developmental toxicity. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-15T18:20:17.058032-05:
      DOI: 10.1002/aic.14957
       
  • Scaling inline static mixers for flocculation of oil sand mature fine
           tailings
    • Authors: Alebachew Demoz
      Abstract: Operations to reclaim mature fine tailings (MFT) ponds involve flocculation using high‐molecular‐weight polymers, for which inline static mixers are suited. Three different commercial static mixers were utilized to determine mixing parameters corresponding to optimal dewatering performance of flocculated MFT. MFT was treated with polymer solution under different mixing conditions. The dewatering rates passed through a peak with increasing mean velocity, V and Reynolds number, Re of the fluid. The greater the number of mixer elements, the lower the V and Re at which the peak dewatering rate occurred. Mixing parameters such as G‐value, residence time, and mixing energy dissipation rate of the most rapidly dewatering flocculated MFT were dependent on mixer type and setup. In contrast, peak dewatering rates converged when scaled with respect to specific mixing energy, E, demonstrating that E is a suitable scale‐up parameter for inline static mixing to produce optimally dewatering MFT. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-15T18:19:50.52966-05:0
      DOI: 10.1002/aic.14958
       
  • Microkinetic model for the pyrolysis of methyl esters: From model compound
           to industrial biodiesel
    • Abstract: A tool for the generation of decomposition schemes of large molecules has been developed. These decomposition schemes contain radicals which can be eliminated from the model equations if both the μ‐hypothesis and the pseudo‐steady‐state approximation are valid. The reaction rate coefficients and thermodynamic parameters have been calculated by incorporating a comprehensive group additive framework. A microkinetic model for the pyrolysis of methyl esters with a carbon number of up to 19 has been generated using this tool. It is validated by comparing calculated and experimental yields of the pyrolysis of methyl decanoate and novel rapeseed methyl ester pyrolysis data in the temperature range from 800 to 1100K and methyl ester partial pressure range from 1 10−3 to 1 10−2 MPa. This modeling frame work allows to not only assess the use of methyl ester mixtures as potential feedstock for olefin production but also their effect as blend‐in or trace impurity. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-15T01:53:36.607321-05:
      DOI: 10.1002/aic.14953
       
  • Refactoring β‐amyrin synthesis in Saccharomyces cerevisiae
    • Authors: Genlin Zhang; Qian Cao, Jingzhu Liu, Baiyang Liu, Jun Li, Chun Li
      Abstract: Triterpenoids are a highly diverse group of natural products and used particularly as medicine. Here, a strategy combining stepwise metabolic engineering and transcriptional control was developed to strengthen triterpenoid biosynthesis in Saccharomyces cerevisiae. Consequently, an efficient biosynthetic pathway for producing β‐amyrin, a commercially valuable compound and precursor of triterpenoids, was constructed through expressing a plant‐derived β‐amyrin synthase. Introducing a heterologous squalene monooxygenase greatly dragged intermediate metabolite squalene toward β‐amyrin. Increasing squalene pool by overexpressing IPP isomerase, FPP and squalene synthase further enhanced β‐amyrin synthesis of 49 folds. Through reconstructing the promoters with the binding site of transcription factor UPC2, directed transcriptional regulation on engineered pathway was availably achieved, resulting in β‐amyrin titer increased by 65 folds. Using ethanol fed‐batch fermentation, β‐amyrin titer was finally improved up to 138.80 mg/L with a yield of 16.30 mg/g dry cell, almost 185 and 232 and folds of the initially engineered strain respectively. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-15T01:52:31.035708-05:
      DOI: 10.1002/aic.14950
       
  • Impact of the fluid flow conditions on the formation rate of carbon
           dioxide hydrates in a semi‐batch stirred tank reactor
    • Abstract: CO2 hydrate formation experiments are performed in a 20 L semi‐batch stirred tank reactor using three different impellers (a down‐pumping pitched blade turbine, a Maxblend™, and a Dispersimax™) at various rotational speeds to examine the impact of the flow conditions on the CO2 hydrate formation rate. An original mathematical model of the CO2 hydrate formation process that assigns a resistance to each of its constitutive steps is established. For each experimental condition, the formation rate is measured and the rate‐limiting step is determined on the basis of the respective values of the resistances. The efficiencies of the three considered impellers are compared and, for each impeller, the influence of the rotational speed on the rate‐limiting step is discussed. For instance, it is shown that a formation rate limitation due to heat transfer can occur at the relatively small scale used to perform our experiments. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-15T01:52:05.397182-05:
      DOI: 10.1002/aic.14952
       
  • Integrated production scheduling and model predictive control of
           continuous processes
    • Authors: Michael Baldea; Juan Du, Jungup Park, Iiro Harjunkoski
      Abstract: The integration of production management and process control decisions is critical for improving economic performance of the chemical supply chain. In this paper, we propose a novel framework for integrating production scheduling and model predictive control (MPC) for continuous processes. Our framework is predicated on using a low‐dimensional time scale‐bridging model (SBM) that captures the closed‐loop process dynamics over the longer time scales that are relevant to scheduling calculations. The SBM is used as a constraint in a mixed‐integer dynamic formulation of the scheduling problem. To synchronize the scheduling and MPC calculations, we propose a novel scheduling‐oriented MPC concept, whereby the SBM is incorporated in the expression of the controller as a (soft) dynamic constraint and allows for obtaining an explicit description of the closed‐loop process dynamics. Our framework scales favorably with system size and provides desirable closed‐loop stability and performance properties for the resulting integrated scheduling and control problem. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-15T01:51:41.366151-05:
      DOI: 10.1002/aic.14951
       
  • Microstructure of room temperature ionic liquids at stepped graphite
           electrodes
    • Authors: Guang Feng; Song Li, Wei Zhao, Peter T. Cummings
      Abstract: Molecular dynamics simulations of room temperature ionic liquid (RTIL) [emim][TFSI] at stepped graphite electrodes were performed to investigate the influence of the thickness of the electrode surface step on the microstructure of interfacial RTILs. A strong correlation was observed between the interfacial RTIL structure and the step thickness in electrode surface as well as the ion size. Specifically, when the step thickness is commensurate with ion size, the interfacial layering of cation/anion is more evident; whereas, the layering tends to be less defined when the step thickness is close to the half of ion size. Furthermore, two‐dimensional microstructure of ion layers exhibits different patterns and alignments of counterion/co‐ion lattice at neutral and charged electrodes. As the cation/anion layering could impose considerable effects on ion diffusion, the detailed information of interfacial RTILs at stepped graphite presented here would help to understand the molecular mechanism of RTIL‐electrode interfaces in supercapacitors. © 2015 American Institute of Chemical Engineers AIChE J, 2015
      PubDate: 2015-07-14T09:16:27.448864-05:
      DOI: 10.1002/aic.14927
       
  • Determination and comparison of rotational velocity in a pseudo 2D
           fluidized bed using Magnetic Particle Tracking and Discrete Particle
           Modelling
    • Authors: K.A. Buist; T.W. van Erdewijk, N.G. Deen, J.A.M. Kuipers
      Abstract: Modelling of dense granular flow has been subject to a large amount of research. Particularly discrete particle modelling has been of great importance because of the ability to describe the strongly coupled dynamics of the fluid and the solids in dense suspensions. Many studies have been reported on the validation of the translational particle velocities predicted by employing these models. The rotational motion however has received far less attention, mainly because of the spherical nature of the particles under investigation and the lack of techniques with the capability to study the rotational behaviour of the solid phase. In this study we will for the first time present experimental data on the rotational behaviour of particles in a pseudo 2D fluidized bed setup using Magnetic Particle Tracking (MPT). In addition the experimental results are compared to data obtained from discrete particle simulations. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-14T08:28:17.538249-05:
      DOI: 10.1002/aic.14949
       
  • Effect of interfacial mass transfer on the dispersion in segmented flow in
           straight capillaries
    • Authors: Jaydeep B. Deshpande; Amol A. Kulkarni
      Abstract: The effect of interfacial mass transfer on the extent of dispersion in liquid‐liquid segmented flow in straight capillaries is studied. In the absence of interfacial mass transfer dispersion coefficient was seen to go through a minimum with increasing flow rates. In the presence of mass transfer, physicochemical properties of both the phases and slug lengths were seen to vary along the capillary length. The extent of dispersion was always higher in the presence of interfacial mass transfer. The predictions using axial dispersion model deviated noticeably for larger capillaries as the model does not account for varying buoyancy, dynamic contacting and Marangoni convection. Simulations of a 1st order interfacial reaction considering varying slug lengths showed a significant change in optimum operating parameters than the conventional approach. A special case of ‘drop‐on‐demand' type of controlled two‐phase flow in capillaries was also studied. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-07T10:17:10.591772-05:
      DOI: 10.1002/aic.14945
       
  • Mechanism and analytical models for the gas distribution on the SiC foam
           monolithic tray
    • Authors: Hong Li; Long Fu, Xingang Li, Xin Gao
      Abstract: SiC foam material has been applied as monolithic tray for distillation column in our previous study. A systematic understanding of the gas distribution process on the foam tray should help to the design of commercial application. In this article, local gas hold up distribution and bubble size distribution are used to measure the gas distribution. The local gas holdup is tested by the conductive probe and the number of test point is counted in different local gas hold up. The bubbles are captured by the high speed camera to measure the bubble size. Bubble size is calculated as ellipsoidal bubble and counted with different pore sizes. Furthermore, a three stage process model is put forward to explain the uneven distribution of gas phase, and verified by the experimental values. The results show that the structure and the thickness of SiC foam is the decisive factor for the gas distribution performance. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-07T10:16:46.60193-05:0
      DOI: 10.1002/aic.14944
       
  • Morphology of polystyrene/poly(methyl methacrylate) blends: Effects of
           carbon nanotubes aspect ratio and surface modification
    • Authors: Jiaxi Guo; Nicholas Briggs, Steven Crossley, Brian P. Grady
      Abstract: MWCNTs with aspect ratios (ARs) ranging from 94 to 474 were incorporated into polystyrene (PS)/poly(methyl methacrylate) (PMMA) blends using solution mixing and melt mixing. Also, two functionalized MWCNTs were prepared from the nanotubes having AR 94: one was oxidized by nitric acid while the other was further modified with amine‐terminated PS attached to carboxyl groups to form amides. The two functionalized MWCNTs (1 wt.%) were used to show that which phase the CNTs were located in could be controlled with nanotube surface chemistry. When nanotubes were confined to the minor phase, the size of the minor domain first decreased with adding low aspect ratio CNT as expected due to the increased viscosity of the minor phase. However, at higher aspect ratios the size increased beyond the size for the minor domain with no nanotubes, and finally the shape of the minor domain changed from spherical to an elongated irregular shape. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-06T03:08:31.518384-05:
      DOI: 10.1002/aic.14943
       
  • On identification of well‐conditioned nonlinear systems: Application
           to economic model predictive control of nonlinear processes
    • Authors: Anas Alanqar; Helen Durand, Panagiotis D. Christofides
      Abstract: This work focuses on economic model predictive control (EMPC) that utilizes well‐conditioned polynomial nonlinear state‐space models for processes with nonlinear dynamics. Specifically, the article initially addresses the development of a nonlinear system identification technique for a broad class of nonlinear processes which leads to the construction of polynomial nonlinear state‐space dynamic models which are well‐conditioned over a broad region of process operation in the sense that they can be correctly integrated in real‐time using explicit numerical integration methods via time steps that are significantly larger than the ones required by nonlinear state‐space models identified via existing techniques. Working within the framework of polynomial nonlinear state‐space (PNLSS) models, additional constraints are imposed in the identification procedure to ensure well‐conditioning of the identified nonlinear dynamic models. This development is key because it enables the design of Lyapunov‐based EMPC (LEMPC) systems for nonlinear processes using the well‐conditioned nonlinear models that can be readily implemented in real‐time since the computational burden required to compute the control actions within the process sampling period is reduced. A stability analysis for this LEMPC design is provided that guarantees closed‐loop stability of a process under certain conditions when an LEMPC based on a nonlinear empirical model is used. Finally, a classical chemical engineering reactor example demonstrates both the system identification and LEMPC design techniques, and the significant advantages in terms of computation time reduction in LEMPC calculations when using the nonlinear empirical model. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-03T00:50:43.244084-05:
      DOI: 10.1002/aic.14942
       
  • Hybrid PIV/PTV measurements of velocity and position distributions of
           gas‐conveyed particles in small, narrow channels
    • Authors: M.W. Korevaar; J.T. Padding, N.G. Deen, J. Wang, M. de Wit, M.A.I. Schutyser, J.A.M. Kuipers
      Abstract: Pneumatic conveying of particles is generally applied in large ducts. However, new applications are emerging which benefit from millimeter sized ducts; e.g.\triboelectric separators where intensive wall‐particle contact is desirable. In this paper an optical method is proposed to measure the distribution of the position and velocity of 100‐1000 μm particles in such narrow ducts. Images of the system are captured using a digital camera on which a Hough transform is applied to detect the particles and their positions. The velocities are acquired by applying a hybrid particle tracking and particle image velocimetry approach. This made it is possible to overcome challenges caused by suboptimal lighting, non‐smooth background and a large ratio between particle and duct diameter (>O(0.1)). It is shown that the algorithm is subpixel accurate when sufficient particles can be sampled. Finally, typical results are shown to illustrate the method's capabilities. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-02T11:59:48.029563-05:
      DOI: 10.1002/aic.14928
       
  • Classical density functional theory for methane adsorption in
           metal‐organic framework materials
    • Authors: Jia Fu; Yun Tian, Jianzhong Wu
      Abstract: Natural gas is considered as a promising alternative to petroleum as the next generation of primary transportation fuel owing to relatively smaller carbon footprint and lower SOx/NOx emissions and to fast developments of shale gas in recent years. Since the volumetric energy density of methane amounts to only about 1% of that of gasoline at ambient conditions, natural gas storage represents one of the key challenges for prevalent deployment of natural gas vehicles. In this work, we present a molecular thermodynamic model potentially useful for high‐throughput screening of nanoporous materials for natural gas storage. We investigate methane adsorption in a large library of metal‐organic frameworks (MOFs) using four versions of classical density functional theory (DFT) and calibrate the theoretical predictions with extensive simulation data for total gas uptake and delivery capacity. In combination with an extended excess entropy scaling method, the classical DFT is also used to predict the self‐diffusion coefficients of the confined gas in several top‐ranked MOFs. The molecular thermodynamic model has been used to identify promising MOF materials and possible variations of operation parameters to meet the Advanced Research Projects Agency‐Energy (ARPA‐E) target set by the U.S. Department of Energy for natural gas storage. © 2015 The
      Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 2015
      PubDate: 2015-07-02T11:52:52.906265-05:
      DOI: 10.1002/aic.14877
       
  • An effective rate approach (ERA) to modelling single‐stage spray
           drying
    • Authors: Oluwafemi Ayodele George; Jie Xiao, Mengwai Woo, Liming Che, Xiao Dong Chen
      Abstract: An effective rate approach (ERA) is proposed in this work to achieve a fast and reliable prediction of dryer outlet conditions for a given single‐stage spray drying system operated under a range of scenarios. This approach is improved from existing methods based on simple mass and energy balances due to the incorporation of a reliable drying rate model, which is the reaction engineering approach for the material of interest. It allows quick solution procedure without the need to solve the partial differential equations that govern the heat and mass transfer in the spray drying process. By following a generic procedure, this technique has been exercised upon the experimental results from running a mono‐disperse droplet spray dryer, i.e., a well‐established experimental platform for model validation. The proposed ERA has been shown to be rather promising. It could become a powerful approach for proactive control and optimization for existing spray drying facilities. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-02T03:30:00.194032-05:
      DOI: 10.1002/aic.14940
       
  • Probabilistic slow feature analysis‐based representation learning
           from massive process data for soft sensor modeling
    • Authors: Chao Shang; Biao Huang, Fan Yang, Dexian Huang
      Abstract: Latent variable (LV) models provide explicit representations of underlying driving forces of process variations and retain the dominant information of process data. In this study, slow features as temporally correlated LVs are derived using probabilistic slow feature analysis. Slow features evolving in a state‐space form effectively represent nominal variations of processes, some of which are potentially correlated to quality variables and hence help improving the prediction performance of soft sensors. An efficient EM algorithm is proposed to estimate parameters of the probabilistic model, which turns out to be suitable for analyzing massive process data. Two criteria are also proposed to select quality‐relevant slow features. The validity and advantages of the proposed method are demonstrated via two case studies. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-02T03:27:50.906688-05:
      DOI: 10.1002/aic.14937
       
  • Multivariate statistical process monitoring of batch‐to‐batch
           startups
    • Abstract: In batch processes, multivariate statistical process monitoring (MSPM) plays an important role for ensuring process safety. However, despite many methods proposed, few of them can be applied to batch‐to‐batch startups. The reason is that, during the startup stage, process data are usually non‐stationary and non‐identically distributed from batch to batch. In this paper, the trajectory signal of each process variable is decomposed into a series of components corresponding to different frequencies, by adopting a nonparametric signal decomposition technique named ensemble empirical mode decomposition (EEMD). Then, through instantaneous frequency calculation, these components can be divided into two groups. The first group reflects the long‐term trend between batches, which extracts the batch‐wise non‐stationary drift information. The second group corresponds to the short‐term intra‐batch variations. The variable trajectory signals reconstructed from the latter fulfills the requirements of conventional MSPM. The feasibility of the proposed method is illustrated using an injection molding process. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-01T10:46:55.370645-05:
      DOI: 10.1002/aic.14939
       
  • Trajectory Modeling of Gas‐Liquid Flow in Microchannels with
           Stochastic Differential Equation and Optical Measurement
    • Authors: Lexiang Zhang; Feng Xin, Dongyue Peng, Weihua Zhang, Yuexing Wang, Xiaodong Chen, Yi Wang
      Abstract: The numbering up of microchannel reactors definitely faces great challenge in uniformly distributing fluid flow in every channel, especially for multiphase systems. A model of stochastic differential equations (SDEs) is proposed based on the experimental data recorded by a long term optical measurement to well quantify the stochastic trajectories of gas bubbles and liquid slugs in parallel microchannels interconnected with two dichotomic distributors. The expectation and variance of each sub flow rate are derived explicitly from the SDEs associated with the Fokker‐Planck equation and solved numerically. A bifurcation in the trajectory is found by using the original model, then a modification on interactions of feedback and crosstalk is introduced, the evolutions of sub flow rates calculated by the modified model match well with experimental results. The established methodology is helpful for characterizing the flow uniformity and numbering up the microchannel reactors of multiphase system. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-01T10:46:24.439242-05:
      DOI: 10.1002/aic.14938
       
  • Hybrid Mixture Theory Based Modeling of Transport Mechanisms and Expansion
           ‐ Thermomechanics of Starch During Extrusion
    • Authors: Srivikorn Ditudompo; Pawan S. Takhar
      Abstract: Water, vapor and heat transport mechanisms and thermomechanical changes occurring inside the expanding extrudate were described using hybrid mixture theory based unsaturated transport equations. Transport equations were transformed from the Eulerian coordinates to the Lagrangian coordinates. Good agreements between the predicted and experimental values of surface temperature, moisture content and expansion ratio of the extrudates were obtained. The model was also used to calculate temperature, moisture content, pore‐pressure and viscoelastic‐stress distribution in the extrudate. Matrix collapse and glassy crust formation under the surface was calculated as a function of extrusion conditions. Expansion behavior of the extrudate was described using the difference between stress due to pore pressure and viscoelastic stress. The modeling results can serve as a guide for predictably modifying the extrusion parameters for obtaining specific textural attributes of expanded starch for various food, feed and biomedical applications. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-01T10:34:38.724043-05:
      DOI: 10.1002/aic.14936
       
  • Ni‐Al2O3/Ni‐foam catalyst with enhanced heat transfer for
           hydrogenation of CO2 to methane
    • Authors: Yakun Li; Qiaofei Zhang, Ruijuan Chai, Guofeng Zhao, Fahai Cao, Ye Liu, Yong Lu
      Abstract: Monolithic Ni‐Al2O3/Ni‐foam catalyst is developed by modified wet chemical etching of Ni‐foam, being highly active/selective and stable in strongly exothermic CO2 methanation process. The as‐prepared catalysts are characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma atomic emission spectrometry (ICP‐AES) and H2‐temperature programmed reduction‐mass spectrometry (H2‐TPR‐MS). The results indicate that modified wet chemical etching method is working efficiently for one‐step creating and firmly embedding NiO‐Al2O3 composite catalyst layer (∼2 μm) into the Ni‐foam struts. High CO2 conversion of 90% and high CH4 selectivity of >99.9% can be obtained and maintained for a feed of H2/CO2 (molar ratio of 4/1) at 320 oC and 0.1 MPa with a gas hourly space velocity (GHSV) of 5000 h−1, throughout entire 1200 h test over 10.2 mL such monolithic catalysts. Computational fluid dynamics (CFD) calculation and experimental measurement consistently confirm a dramatic reduction of ‘hotspot' temperature due to enhanced heat transfer. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-01T10:33:58.221705-05:
      DOI: 10.1002/aic.14935
       
  • Mass transfer rate enhancement for CO2 separation by ionic liquids:
           theoretical study on the mechanism
    • Authors: Wenlong Xie; Xiaoyan Ji, Xin Feng, Xiaohua Lu
      Abstract: To promote the development of ionic liquid (IL) immobilized sorbents and supported IL membranes (SILMs) for CO2 separation, in this work, the kinetics of CO2 absorption/desorption in IL immobilized sorbents was studied using a novel method based on non‐equilibrium thermodynamics. It shows that the apparent chemical‐potential‐based mass‐transfer coefficients of CO2 were in three regions with 3‐order difference in magnitude for the IL‐film thicknesses in micro‐scale, 100 nm‐scale and 10 nm‐scale. Using a diffusion‐reaction theory, it is found that by tailoring the IL‐film thickness from micro‐scale to nano‐scale, the process was altered from diffusion‐control to reaction‐control, revealing the inherent mechanism for the dramatic rate enhancement. The extension to SILMs shows that the significant improvement of CO2 flux can be obtained theoretically for the membranes with nano‐scale IL‐films, which makes it feasible to implement CO2 separation by ILs with low investment cost. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-30T17:58:22.166741-05:
      DOI: 10.1002/aic.14932
       
  • Process to Planet: A Multiscale Modeling Framework for Sustainable
           Engineering
    • Authors: Rebecca J. Hanes; Bhavik R. Bakshi
      Abstract: To prevent the chance of unintended environmental harm, engineering decisions need to consider an expanded boundary that captures all relevant connected systems. Comprehensive models for sustainable engineering may be developed by combining models at multiple scales. Models at the finest “equipment” scale are engineering models based on fundamental knowledge. At the intermediate “value chain” scale, empirical models represent average production technologies, and at the coarsest “economy” scale, models represent monetary and environmental exchanges for industrial sectors in a national or global economy. However, existing methods for sustainable engineering design ignore the economy scale, while existing methods for life cycle assessment do not consider the equipment scale. This work proposes an integrated, multi‐scale modeling framework for connecting models from process to planet (P2P) and using them for sustainable engineering applications. The proposed framework is demonstrated with a toy problem, and potential applications of the framework including current and future work are discussed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-30T06:02:43.832912-05:
      DOI: 10.1002/aic.14919
       
  • Sustainable Process Design by the Process to Planet Framework
    • Authors: Rebecca J. Hanes; Bhavik R. Bakshi
      Abstract: Sustainable process design (SPD) problems combine a process design problem with life cycle assessment (LCA) to optimize process economics and life cycle environmental impacts. While SPD makes use of recent advances in process systems engineering and optimization, its use of LCA has stagnated. Currently, only process LCA is utilized in SPD, resulting in designs based on incomplete and potentially inaccurate life cycle information. To address these shortcomings, the multi‐scale process to planet (P2P) modeling framework is applied to formulate and solve the SPD problem. The P2P framework offers a more comprehensive analysis boundary than conventional SPD and greater modeling detail than advanced LCA methodologies. Benefits of applying this framework to SPD are demonstrated with an ethanol process design case study. Results show that current methods shift emissions outside the analysis boundary, while applying the P2P modeling framework results in environmentally superior process designs. Future extensions of the P2P framework are discussed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-30T05:28:25.579045-05:
      DOI: 10.1002/aic.14918
       
  • Assessing the performance of an industrial SBCR for fischer‐tropsch
           synthesis: Experimental and modeling
    • Authors: Laurent Sehabiague; Omar M. Basha, Zhansheng Shi, Haolin Jia, Yemin Hong, Li Weng, Zhuowu Men, Yi Cheng, Ke Liu, Badie Morsi
      Abstract: The main objective of this study is to predict the performance of an industrial‐scale (ID = 5.8 m) slurry bubble column reactor (SBCR) operating with iron‐based catalyst for Fischer‐Tropsch (FT) synthesis, with emphasis on catalyst deactivation. In order to achieve this objective, a comprehensive reactor model, incorporating the hydrodynamic and mass transfer parameters (gas holdup, εG, Sauter‐mean diameter of gas bubbles, d32, and volumetric liquid‐side mass transfer coefficients, kLa), and FT as well as water gas shift (WGS) reaction kinetics, was developed. The hydrodynamic and mass transfer parameters for He/N2 gaseous mixtures, as surrogates for H2/CO, were obtained in an actual molten FT reactor wax produced from the same reactor. The data were measured in a pilot‐scale (0.29 m) SBCR under different pressures (4‐31 bar), temperatures (380‐500 K), superficial gas velocities (0.1‐0.3 m/s) and iron‐based catalyst concentrations (0‐45 wt%). The data were modeled and predictive correlations were incorporated into the reactor model. The reactor model was then used to study the effects of catalyst concentration and reactor length‐to‐diameter ratio (L/D) on the water partial pressure, which is mainly responsible for iron catalyst deactivation, the H2 and CO conversions and the C5+ product yields. The modeling results of the industrial SBCR investigated in this study showed that (1) the water partial pressure should be maintained under 3 bars in order to minimize deactivation of the iron‐based catalyst used; (2) the catalyst concentration has much more impact on the gas holdup and reactor performance than the reactor height; and (3) the reactor should be operated in the kinetically‐controlled regime with an L/D of 4.48 and a catalyst concentration of 22 wt% in order to maximize C5+ products yield, while minimizing the iron catalyst deactivation. Under such conditions, the H2 and CO conversions were 49.4% and 69.3%, respectively and the C5+ products yield was 435.6 ton/day. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-27T10:36:26.930008-05:
      DOI: 10.1002/aic.14931
       
  • Droplets sliding over shearing surfaces studied by molecular dynamics
    • Authors: J.J. Derksen
      Abstract: We study, through molecular dynamics, the sliding motion of a liquid drop embedded in another liquid over a substrate as a result of a shear flow. The two immiscible Lennard‐Jones liquids have the same density and viscosity. The system is isothermal. Viscosity, surface tension, and static contact angles follow from calibration simulations. Sliding speeds and drop deformations (in terms of dynamic contact angles) are determined as a function of the shear rate. The latter is non‐dimensionalized as a capillary number (Ca) that has been varied in the range 0.02 to 0.64. For Ca up to 0.32, sliding speeds are approximately linear in Ca. For larger Ca, very strong droplet deformations are observed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-27T10:36:01.14552-05:0
      DOI: 10.1002/aic.14930
       
  • Pure H2 production through hollow fiber hydrogen‐selective MFI
           zeolite membranes using steam as sweep gas
    • Authors: Yuting Zhang; Qi Sun, Xuehong Gu
      Abstract: Hollow fiber MFI zeolite membranes were modified by catalytic cracking deposition of methyldiethoxysilane (MDES) to enhance their H2/CO2 separation performance and further employed in high temperature water gas shift membrane reactor (MR). Steam was used as the sweep gas in the MR for the production of pure H2. Extensive investigations were conducted on MR performance by variations of temperature, feed pressure, sweep steam flow rate and steam‐to‐CO ratio. CO conversion was obviously enhanced in the MR as compared with conventional packed‐bed reactor (PBR) due to the coupled effects of H2 removal as well as counter‐diffusion of sweep steam. Significant increment in CO conversion for MR vs. PBR was obtained at relatively low temperature and steam‐to‐CO ratio. A high H2 permeate purity of 98.2% could be achieved in the MR swept by steam. Moreover, the MR exhibited an excellent long‐term operating stability for 100 h in despite of the membrane quality. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-27T10:34:08.318729-05:
      DOI: 10.1002/aic.14924
       
  • Jamming of cellulose ether solutions in porous medium
    • Authors: C. Marliere; D. Vlassopoulos, P. Faure, A. Larsen, B. Loppinet, P. Coussot
      Abstract: We investigate the flow of aqueous cellulose ether solutions through a bead packing using MRI (Magnetic Resonance Imaging) and filtration measurements. We observe a rather complex behaviour dominated by jamming (clogging) and unjamming phenomena in time. With the help of several characterization techniques (laser grain sizing, dynamic light scattering, optical microscopy, rheometry) we confirm that the particular methyl(hydroxyethyl) cellulose prepared with a specific protocol, tends to form aggregates in water, even at the lowest achievable concentration. These aggregates are highly polydisperse, ranging from hundred nanometers to hundred microns in size, and are deformable. Their origin appears to be the hydrophobic links among molecules and the related local crystallization. It is suggested that these features play a key role in the observed jamming/unjamming during filtration tests. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-25T02:07:34.49213-05:0
      DOI: 10.1002/aic.14920
       
  • Breakage and Adhesion Maps for the Normal Impact of Loose Agglomerates
           with a Spherical Target
    • Abstract: DEM‐based analysis is conducted to investigate the effects of interface energy between particles on the breakage and adhesion of loose agglomerates upon impact with a spherical target. A mechanistic approach is tested to find a relationship between particle properties and the agglomerate structure after the impact, which resulted in a new dimensionless number, i.e. the ratio of the two interface energies. In combination with Δ ‐ a dimensionless number relating incident kinetic energy to agglomerate strength 1, a good description of the agglomerate impact is obtained. The agglomerate structure after impact is mapped using the two dimensionless numbers and is in good agreement with experimental observations. The constructed regime map can serve as a guide for selecting preliminary process parameters in adhesive particle mixing. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-25T02:06:50.915939-05:
      DOI: 10.1002/aic.14922
       
  • Radial pressure profiles in a cold‐flow Gas‐Solid Vortex
           Reactor
    • Authors: M.N. Pantzali; J.Z. Kovacevic, V.N. Shtern, G.J. Heynderickx, G.B. Marin
      Abstract: A unique normalized radial pressure profile characterizes the bed of a Gas‐Solid Vortex Reactor (GSVR) over a range of particle densities and sizes, solid capacities and gas flow rates: 950‐1240 kg/m3, 1‐2 mm, 2 kg to maximum solids capacity and 0.4‐0.8 Nm3/s (corresponding to gas injection velocities of 55‐110 m/s) respectively. The combined momentum conservation equations of both gas and solid phases predict this pressure profile when accounting for the corresponding measured particle velocities. The pressure profiles for a given type of particles and a given solids loading but for different gas injection velocities merge into a single curve when normalizing the pressures with the pressure value downstream of the bed. The normalized ‐with respect to the overall pressure drop‐ pressure profiles for different gas injection velocities in particle‐free flow merge in a unique profile. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-24T02:26:22.259474-05:
      DOI: 10.1002/aic.14912
       
  • An integrated Framework for Scheduling and Control Using Fast Model
           Predictive Control
    • Authors: Jinjun Zhuge; Marianthi G. Ierapetritou
      Abstract: Integration of scheduling and control involves extensive information exchange and simultaneous decision making in industrial practice 1,2. Modeling the integration of scheduling and dynamic optimization at control level using mathematical programming results in a Mixed Integer Dynamic Optimization (MIDO) which is computationally expensive 3. In this study, we propose a framework for the integration of scheduling and control to reduce the model complexity and computation time. We identify a piece‐wise affine (PWA) model from the first principle model and integrate it with the scheduling level leading to a new integration. At the control level we employ fast Model Predictive Control (fast MPC) to track a dynamic reference. Fast MPC also overcomes the increasing dimensionality of multi‐parametric MPC in our previous study.4 Results of CSTR case studies prove that the proposed approach reduces the computing time by at least two orders of magnitude compared to the integrated solution using mp‐MPC. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-24T02:25:42.950339-05:
      DOI: 10.1002/aic.14914
       
  • A filtration model for prediction of local flux distribution and
           optimization of submerged hollow fiber membrane module
    • Authors: Xianhui Li; Jianxin Li, Hong Wang, Xiaoxu Huang, Benqiao He, Yonghong Yao, Jie Wang, Hongwei Zhang, Huu Hao Ngo, Wenshan Guo
      Abstract: A filtration mathematical model was developed on the basis of complete mass balance and momentum balance for the local flux distribution prediction and optimization of submerged hollow fiber membrane module. In this model, the effect of radial permeate flow on internal flow resistance was considered through a slip parameter obtained from the local flux experiments. The effects of fiber length, inside diameter and average operating flux on local flux distribution were investigated using this model. The predicted results were in good agreement with the experimental data obtained from literature. It was also found that the asymmetry distribution of local flux could be intensified with the increase of average operating flux and fiber length, but slowed down with the increase of fiber inside diameter. Furthermore, the simulation coupled with energy consumption analysis could efficiently predict and illustrate the relationship between fiber geometry and water production efficiency. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-18T17:55:21.740497-05:
      DOI: 10.1002/aic.14906
       
  • Nonlinear PI Controllers with Output Transformations
    • Authors: Jietae Lee; Thomas F. Edgar
      Abstract: Well‐designed nonlinear proportional‐integral (PI) controllers are successful for nonlinear dynamical processes like linear PI controllers are for linear processes. Two nonlinear blocks representing proportional and integral terms can be designed so that the linearized controllers perform the same as linear PI controllers for linearized processes at the given operating points. For some nonlinear processes, nonlinear blocks for nonlinear PI controllers can be singular at some operating points, and control performances can be poor for set points near those points. To mitigate such disadvantages, new nonlinear PI controllers that introduce output transformations are proposed. Several examples are given, showing the performance of the proposed nonlinear PI controllers. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-17T17:54:55.625143-05:
      DOI: 10.1002/aic.14907
       
  • Modeling permporometry of mesoporous membranes using dynamic mean field
           theory
    • Authors: A. Rathi; J. R. Edison, D. M. Ford, P. A. Monson
      Abstract: Mesoporous inorganic membranes have significant potential for important small‐molecule separations like carbon dioxide recovery from stack emissions. However, tailoring materials for a given separation remains an outstanding problem. Preferential adsorption, layering and capillary effects, and surface flow are key mechanisms that determine permeation rates and are ultimately linked to the mesopore characteristics. To further the understanding of these systems we propose a modeling approach based on dynamic mean field theory, which has previously been used to study the dynamics of adsorption in mesoporous materials. This theory describes both relaxation dynamics and non equilibrium steady states in membranes and is fully consistent with a mean field density functional theory of the thermodynamics. We demonstrate the capabilities and promise of the approach by modeling a permporometry experiment, in which a light gas permeates through a mesopore in the presence of a condensable vapor at a controlled relative pressure. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-21T00:43:28.411103-05:
      DOI: 10.1002/aic.14846
       
  • High‐throughput and comprehensive prediction of H2 adsorption in
           metal‐organic frameworks under various conditions
    • Authors: Yu Liu; Shuangliang Zhao, Honglai Liu, Ying Hu
      Abstract: High‐throughput prediction of H2 adsorption in MOF materials has been extended from a few specific conditions to the whole T, p space. The prediction is based on a classical density functional theory and has been implemented over 712 MOFs in 441 different conditions covering a wide range. Some testing materials show excellent behavior at low temperatures and obvious improvement at high temperatures compared to conventional MOFs. The structures of the best MOFs at high and low temperatures are totally different. Linear and nonlinear correlations between the two Langmuir parameters have been found at high and low temperatures, respectively. According to the analysis of the excess uptake, we found that the saturated pressure increases along with temperature in the low temperature region but decreases in the high temperature region. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-17T16:09:51.556324-05:
      DOI: 10.1002/aic.14842
       
  • An electrolyte CPA equation of state for mixed solvent electrolytes
    • Abstract: Despite great efforts over the past decades, thermodynamic modeling of electrolytes in mixed solvents is still a challenge today. The existing modeling frameworks based on activity coefficient models are data‐driven and require expert knowledge to be parameterized. It has been suggested that the predictive capabilities could be improved through the development of an electrolyte equation of state. In this work, the Cubic Plus Association (CPA) Equation of State is extended to handle mixtures containing electrolytes by including the electrostatic contributions from the Debye‐Hückel and Born terms using a self‐consistent model for the static permittivity. A simple scheme for parameterization of salts with a limited number of parameters is proposed and model parameters for a range of salts are determined from experimental data of activity and osmotic coefficients as well as freezing point depression. Finally, the model is applied to predict VLE, LLE, and SLE in aqueous salt mixtures as well as in mixed solvents. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-07T17:42:34.244232-05:
      DOI: 10.1002/aic.14829
       
  • On the simultaneous description of h‐bonding and dipolar
           interactions with point charges in force field models
    • Authors: Kai Langenbach; Cemal Engin, Steffen Reiser, Martin Horsch, Hans Hasse
      Abstract: H‐bonding and polar interactions occur together in real fluids, but are of different nature and have different effects on macroscopic properties. Nevertheless, both are usually described by point charges in force field models. We show that, despite this, the two effects can be separated. We study a simple model fluid: a single Lennard‐Jones site with two opposing point charges q placed in the center of the Lennard‐Jones site and at a distance d. By suitably varying both d and q the dipole moment μ is kept constant. Both μ and d are systematically varied to study the properties of the resulting models, including H‐bonding, which is determined using a geometric criterion from literature. We show that d can be used for tuning the H‐bonding strength and, thus, polarity and H‐bonding can be adjusted individually. The study of a second related model with symmetrically positioned point charges does not reveal this separation. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-02T18:45:17.356024-05:
      DOI: 10.1002/aic.14820
       
  • Dew‐point measurements for water in compressed carbon dioxide
    • Authors: Christopher W. Meyer; Allan H. Harvey
      Abstract: When transporting CO2 for sequestration, it is important to know the water dew point in order to avoid condensation that can lead to corrosion. We have constructed a flow apparatus to measure the water content at saturation in a compressed gas. A saturator humidifies the flowing gas by equilibrating it with liquid water. Then, a gravimetric hygrometer measures the water mole fraction of the humid gas. We report dew‐point data for H2O in CO2 on six isotherms between 10 °C and 80 °C at pressures from 0.5 MPa to 5 MPa. Our uncertainties in water content at the dew point (expanded uncertainty with coverage factor k=2) are on average 0.3%, significantly smaller than in any previous work. The data have been analyzed to extract the interaction second virial coefficient; our values are consistent with the theoretical estimates of Wheatley and Harvey but have a much smaller uncertainty. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-01T15:19:24.165662-05:
      DOI: 10.1002/aic.14818
       
  • A tribute to John M. Prausnitz
    • Authors: Michael P. Harold; Manos Mavrikakis, Ignacio E. Grossmann
      Pages: 2674 - 2674
      PubDate: 2015-08-07T09:38:44.005994-05:
      DOI: 10.1002/aic.14961
       
  • John M. Prausnitz: Bridging abstractions and realities
    • Authors: John P. O'Connell
      Pages: 2675 - 2688
      Abstract: This Founders Tribute issue honors John Prausnitz as an exceptional intellectual leader, scholar, and educator and summarizes his impact on chemical engineering. John's early vision of connecting fundamental molecular theory to practical thermodynamic applications with Molecular Thermodynamics was an essential element in our profession's paradigm shift from empiricism to engineering science. John's writings and lectures have transformed our core knowledge and guided its utilization into areas well outside traditional engineering bounds. Further, he has vigorously advocated for technology to be considered in the context of all of life and as a human enterprise. Finally, John's personal interactions across generations and disciplines have inspired the personal and professional development of a vast community of students, coworkers, and colleagues. In countless ways, John Prausnitz has influenced the contemporary foundation and functioning of chemical engineering and of realms beyond. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2675–2688, 2015
      PubDate: 2015-03-17T15:08:20.495039-05:
      DOI: 10.1002/aic.14761
       
  • Renewable fuels from biomass: Technical hurdles and economic assessment of
           biological routes
    • Pages: 2689 - 2701
      Abstract: Lignocellulosic biomass is an abundant, renewable source of polysaccharides that could be available in amounts sufficient to provide a source of sugars for carbon neutral biofuel production. We review the background to biofuels production in the US from corn sugars and subsequent R and D efforts to saccharify plant biomass to provide an alternative sugar source. Research efforts and programs have generally not addressed the key technical hurdles in providing a commodity‐scale supply of biomass and in developing biological routes to saccharify it at high yields. Techno‐economic analyses of proposed processes highlight the importance of biomass cost, the role of pretreatment on both inhibitor generation, and the contribution of enzyme costs to saccharification. Alternatives, such as the production of fatty acids by microalgae, have comparable technical hurdles. Although there is a regulatory framework for biofuels, which is discussed, a credible biological process for large‐scale, cost‐effective production of lignocellulosic biofuels remains elusive. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2689–2701, 2015
      PubDate: 2015-02-23T13:56:43.888917-05:
      DOI: 10.1002/aic.14755
       
  • Population balance modeling of a microalgal culture in photobioreactors:
           Comparison between experiments and simulations
    • Authors: Alberto Bertucco; Eleonora Sforza, Valentina Fiorenzato, Matteo Strumendo
      Pages: 2702 - 2710
      Abstract: The growth of Scenedesmus obliquus in photobioreactors was both experimentally investigated and numerically simulated by solving a population balance equation (PBE), accounting for cell growth and division. The PBE is solved using the Finite size domain Complete set of trial functions Method Of Moments (FCMOM) and a wide range of operative conditions, namely both a batch and a continuous reactor under different light intensities, were considered in the experiments and in the numerical simulations. A thorough validation of the mathematical model was performed by comparing the experimental temporal profiles and steady‐state values of the cell density, wet weight, cell average mass, and mass distributions of the microalgal culture with the corresponding simulation results. The parameters of the distribution of division mass were identified to fit the experimental data; specifically, from the continuous reactor data, the dependence of the mean division mass from the cell average mass was obtained. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2702–2710, 2015
      PubDate: 2015-08-07T09:38:38.435281-05:
      DOI: 10.1002/aic.14893
       
  • Molecular thermodynamics of LNA:LNA base pairs and the hyperstabilizing
           effect of 5′‐proximal LNA:DNA base pairs
    • Pages: 2711 - 2731
      Abstract: Locked nucleic acids (LNAs) can greatly enhance duplex DNA stability, and are therefore creating opportunities to improve therapeutics, as well as PCR‐based disease and pathogen diagnostics. Realizing the full potential of LNAs will require better understanding of their contributions to duplex stability, and the ability to predict their hydridization thermodynamics. Melting thermodynamics data for a large set of diverse duplexes containing LNAs in one or both strands are presented. Those data reveal that LNAs, when present on both strands, can stabilize a duplex not only through direct interaction with their base‐pair partner, but also through nonlocal hyperstablization effects created by LNA:LNA base pairs and/or specific patterns of oppositely oriented LNA:DNA base pairs. The data are, therefore, used to extend a thermodynamic model previously developed in our lab to permit accurate prediction of melting temperatures for duplexes bearing LNA substitutions within both strands using a classic group‐contribution approach. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2711–2731, 2015
      PubDate: 2015-08-07T09:38:18.852655-05:
      DOI: 10.1002/aic.14916
       
  • Lidocaine‐ibuprofen ionic liquid for dermal anesthesia
    • Authors: Han Jung Park; Mark R. Prausnitz
      Pages: 2732 - 2738
      Abstract: Local anesthesia in the skin occurs approximately 1 h after application of a commercial topical formulation of lidocaine and prilocaine prepared as a eutectic mixture. A number of lidocaine salts was screened and lidocaine‐ibuprofen was found to form a room‐temperature ionic liquid. When applied to the skin of rats, local anesthesia of skin was achieved within 10–20 min in the rats’ paws and tails with no apparent adverse effects to the skin as determined by histological analysis. We believe that the lidocaine‐ibuprofen ionic liquid increased lidocaine absorption into the skin due to the high lidocaine concentration in the ionic liquid and due to possible interactions between the ionic liquid and the skin to increase skin permeability. These findings suggest that lidocaine‐ibuprofen ionic liquid may provide a more rapid method of drug delivery to the skin for local anesthesia. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2732–2738, 2015
      PubDate: 2015-08-07T09:38:35.88126-05:0
      DOI: 10.1002/aic.14941
       
  • Environmental aspects of metals removal from waters and gold recovery
    • Pages: 2739 - 2748
      Abstract: Mining and metals processing are not invisible activities and are heavy industries, which require energy, water, chemicals, and land area. Recently more emphasis is given to environmental and societal aspects in mining and processing. Development of good practices with improved resource efficiency, new recovery methods and sustainability thinking are increasingly required. This work shows pH titration method for acid mine drainage (AMD) water incorporated with aqueous thermodynamic model for selective metals precipitation from complex solution. Also two examples on gold recovery methods from aqueous streams are shown: biosorption using fungal matter and solvent extraction using a task‐specific ionic liquid. By understanding chemical thermodynamics and natural phenomena, there is a better chance of developing solutions for environmental problems and new industrial processes. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2739–2748, 2015
      PubDate: 2015-08-07T09:38:14.827581-05:
      DOI: 10.1002/aic.14917
       
  • Effects of cell construction parameters on the performance of
           lithium/sulfur cells
    • Pages: 2749 - 2756
      Abstract: Current lithium‐ion batteries are predicted to be unable to provide the specific energy required to meet the ever‐increasing demands of rapidly emerging technologies. Due to a high theoretical specific capacity of 1675 mAh/g, sulfur has gained much attention as a promising positive electrode material for high specific energy rechargeable batteries. Although the lithium/sulfur cell has been studied for many years and continues to receive much attention today as an alternative power source for zero‐emission vehicles and advanced electronic devices, the realization of this novel cell's promise as a commercial product has yet to be successful. The major problems with sulfur electrodes involve: (1) the dissolution of sulfur (as polysulfides) and the resulting diffusion of dissolved polysulfides and (2) the deposition of insulating products (including Li2S) on both the negative and the positive electrodes. These solid deposits can physically block the electrode reaction sites, thus passivating the electrode surfaces. Another important problem is the large volume change that occurs with the conversion of S to Li2S. It is important to understand that the performance of Li/S cells is hampered by linked chemical and mechanical degradations and both degradation mechanisms must be correctly alleviated in order to markedly improve current‐technology Li/S cells. In this study, improved cycling performance via the reactive functional groups on graphene oxide to successfully immobilize sulfur and lithium polysulfides during operation has been demonstrated. The use of a new electrolyte and binder leads to improved cell performance in terms of high‐rate capability (up to at least 2 C) and good reversibility (S ↔ Li2S), yielding at least 800 cycles have also been demonstrated. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2749–2756, 2015
      PubDate: 2015-08-07T09:38:21.480233-05:
      DOI: 10.1002/aic.14947
       
  • Predicting multicomponent adsorption: 50 years of the ideal adsorbed
           solution theory
    • Authors: Krista S. Walton; David S. Sholl
      Pages: 2757 - 2762
      Abstract: Describing multi‐component adsorption is fundamental to using sorption in any chemical separation. 50 years ago, Myers and Prausnitz made a seminal contribution to characterization and prediction of multi‐component adsorption by introducing Ideal Adsorbed Solution Theory (IAST). Here, we give an overview of IAST, highlighting its continued role as a benchmark method in describing adsorption using illustrative examples from a variety of experimental and molecular modeling studies. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2757–2762, 2015
      PubDate: 2015-08-07T09:38:24.532293-05:
      DOI: 10.1002/aic.14878
       
  • Biofuel purification in GME zeolitic–imidazolate frameworks: From ab
           initio calculations to molecular simulations
    • Authors: Kang Zhang; Krishna M. Gupta, Yifei Chen, Jianwen Jiang
      Pages: 2763 - 2775
      Abstract: A multiscale modeling study is reported on the adsorption of ethanol/water in five zeolitic–imidazolate frameworks (ZIFs) for biofuel purification. The ZIFs (ZIF‐68, −69, −78, −79, and −81) have isoreticular Gmelinite topology but differ in organic linkers. The simulated adsorption isotherms of ethanol and water in ZIF‐68 agree fairly well with experimental data. At a low pressure, ZIF‐78 exhibits the highest uptake due to strong hydrogen‐bonding between NO2 groups and adsorbates. The heats of adsorption at infinite dilution largely follow the trend of binding energies estimated from ab initio calculations. At a high pressure, the uptake is governed primarily by free volume but also affected by hydrogen‐bonding. Among the five ZIFs, ZIF‐79 with hydrophobic CH3 groups shows the highest adsorptive selectivity for ethanol/water mixtures. This study provides microscopic insights into the adsorption and separation of ethanol/water in ZIFs, and would facilitate the development of new ZIFs for biofuel purification. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2763–2775, 2015
      PubDate: 2015-03-17T15:09:00.471826-05:
      DOI: 10.1002/aic.14787
       
  • Thermodynamic model for the permeability of light gases in glassy polymers
    • Authors: Matteo Minelli; Giulio C. Sarti
      Pages: 2776 - 2788
      Abstract: The permeability of light gases in a series of different glassy polymers is analyzed through a thermodynamic‐based approach for solubility and diffusivity. The nonequilibrium thermodynamic model for glassy polymers describes the solubility of the different penetrants; diffusivity is given as the product of a mobility factor and a thermodynamic factor. The latter is predicted by the nonequilibrium lattice fluid thermodynamic model, while the mobility coefficient is determined using the experimental permeability data. For rather soluble penetrants (e.g., CO2), a plasticization factor is also accounted for, considering the mobility to depend exponentially on penetrant concentration, as often observed experimentally. The model is able to describe accurately the experimental behavior in a simple and effective way, considering only two adjustable parameters. The mobility coefficient is found to depend on the penetrant size (critical volume) and on the fractional free volume of the polymer matrix, following rather general and reasonable correlations. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2776–2788, 2015
      PubDate: 2015-08-07T09:38:18.183315-05:
      DOI: 10.1002/aic.14858
       
  • Pervaporation of organic compounds from aqueous mixtures using
           polydimethylsiloxane‐containing block copolymer membranes
    • Authors: Douglas R. Greer; A. Evren Ozcam, Nitash P. Balsara
      Pages: 2789 - 2794
      Abstract: Pervaporation of aqueous mixtures of ethanol, acetone, butanol, isobutanol, and furfural through polystyrene‐b‐polydimethylsiloxane‐b‐polystyrene (SDS) triblock copolymer membranes is reported. These mixtures are important for biofuel production from lignocellulosic feedstocks. Feedstock depolymerization results in the formation of furfural which must be removed before fermentation. Ethanol, butanol, isobutanol, and acetone are important fermentation biofuels. The membrane selectivity of SDS is about unity over a wide range of concentrations of aqueous ethanol mixtures, similar to the membrane selectivity of crosslinked polydimethylsiloxane (PDMS). The permeabilities of butanol, isobutanol, and furfural are larger than those of ethanol and acetone. The volatile organic compound permeability through SDS is similar to or higher than that through PDMS across a broad range of temperatures and feed concentrations is found. More selective and permeable membranes are needed to lower the cost of biofuel purification. The SDS membranes developed are but one step toward improved membranes. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2789–2794, 2015
      PubDate: 2015-08-07T09:38:28.758409-05:
      DOI: 10.1002/aic.14876
       
  • Analysis of countercurrent membrane vapor extraction of a dilute aqueous
           biosolute
    • Authors: David E. Liu; Colin Cerretani, Rodrigo Tellez, Agnes P. Scheer, Steve Sciamanna, Paul F. Bryan, Clayton J. Radke, John M. Prausnitz
      Pages: 2795 - 2809
      Abstract: Removal of dilute bioproducts from fermenter broths is a major challenge both to avoid microbe inhibition and to recover solutes economically without water loss. We analyze a proposed new process, membrane vapor extraction (MVE), where semi‐volatile dilute aqueous solutes vaporize at the upstream side of an omniphobic, microporous membrane and dissolve into a nonpolar solvent highly favorable to the solutes but not to water. A new membrane‐process analysis is outlined and applied to the countercurrent recovery of 2 wt % aqueous butanol by a prototype solvent (dodecane) at 40°C. Thermodynamic phase equilibria, pioneered by the Prausnitz school, are crucial to MVE process design. Over 90% of the feed butanol is recovered with essentially no water loss giving a separation factor of over 1000. Energy requirements in MVE are low. Our design calculations demonstrate that MVE is a viable separation process to remove and recover dilute aqueous biosolutes. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2795–2809, 2015
      PubDate: 2015-08-07T09:38:37.375714-05:
      DOI: 10.1002/aic.14892
       
  • Separation of conglomerate forming enantiomers using a novel continuous
           preferential crystallization process
    • Authors: Thomas Vetter; Christopher L. Burcham, Michael F. Doherty
      Pages: 2810 - 2823
      Abstract: Providing enantiomerically pure products is of key importance in the fine chemicals, food, and pharmaceutical industries. A continuous preferential crystallization process is presented that allows the separation of conglomerate forming enantiomers in a stable, robust, and flexible way. This is achieved by coupling two continuous crystallizers by exchanging their clear liquid phases. Each crystallizer is connected to a suspension mill responsible for in situ seed generation through particle breakage. The dynamic and steady‐state behavior of this process is extensively analyzed for racemic feed streams through process simulations, and parameter regions, which yield pure enantiomers in both crystallizers, are identified. For enriched feed streams, it is further shown when this novel flow sheet is capable of outperforming an ideal batch process in terms of solvent consumption per unit mass of desired enantiopure product produced. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2810–2823, 2015
      PubDate: 2015-08-07T09:38:31.568776-05:
      DOI: 10.1002/aic.14934
       
  • Understanding cubic equations of state: A search for the hidden clues of
           their success
    • Pages: 2824 - 2831
      Abstract: This work investigates the hidden details that are responsible for the practical success of cubic equations of state (EOS) in phase equilibrium calculations. A detailed consideration of the van der Waals method for evaluating the pure compound EOS parameters sheds new light on the reasons why the elimination of the actual critical volume as parameter was also adopted in the Redlich–Kwong and the Peng–Robinson (PR) frameworks. It is shown that an interesting relationship for the critical compressibility factor arising from the Martin–Hou method opens a new door for future exploration of different frameworks. A consideration of the key steps of Soave's reasoning for determining the temperature dependence of the attractive parameter explains the larger success of the Stryjek–Vera modification of PR EOS over the PR EOSs. A reference to the extension of cubic EOS to calculate liquid densities and enthalpies and a ready to use algorithm for the evaluation of the roots of a cubic equation are included for instructional purposes. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2824–2831, 2015
      PubDate: 2015-03-04T12:08:13.689949-05:
      DOI: 10.1002/aic.14741
       
  • An experimental investigation on the influence of phenol on the solubility
           of CO2 in aqueous solutions of NaOH
    • Pages: 2832 - 2840
      Abstract: Experimental results are presented for the solubility of CO2 in an aqueous solution of phenol and NaOH (molalties in water: phenol: 0.5; NaOH: 1.0) at (314, 354, and 395) K and pressures up to 10 MPa. The experimental work extends recent investigations on the influence of phenol as well as of (phenol + NaCl) on the solubility of CO2 in water. In contrast to those previous investigations, the strong electrolyte reacts with carbon dioxide and also with phenol. The experimental results are compared with predictions from a thermodynamic model. That model combines a model for the “chemical” solubility of CO2 in aqueous solutions of NaOH with a model for the “physical” solubility of CO2 in aqueous solutions of phenol. An extension is introduced to account for the chemical reaction between the weak acid phenol and the strong base sodium hydroxide. The prediction results nicely agree with the new experimental data. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2832–2840, 2015
      PubDate: 2015-03-04T12:07:44.761681-05:
      DOI: 10.1002/aic.14742
       
  • Liquid li structure and dynamics: A comparison between OFDFT and second
           nearest‐neighbor embedded‐atom method
    • Authors: Mohan Chen; Joseph R. Vella, Athanassios Z. Panagiotopoulos, Pablo G. Debenedetti, Frank H. Stillinger, Emily A. Carter
      Pages: 2841 - 2853
      Abstract: The structure and dynamics of liquid lithium are studied using two simulation methods: orbital‐free (OF) first‐principles molecular dynamics (MD), which employs OF density functional theory (DFT), and classical MD utilizing a second nearest‐neighbor embedded‐atom method potential. The properties studied include the dynamic structure factor, the self‐diffusion coefficient, the dispersion relation, the viscosity, and the bond angle distribution function. Simulation results were compared to available experimental data when possible. Each method has distinct advantages and disadvantages. For example, OFDFT gives better agreement with experimental dynamic structure factors, yet is more computationally demanding than classical simulations. Classical simulations can access a broader temperature range and longer time scales. The combination of first‐principles and classical simulations is a powerful tool for studying properties of liquid lithium. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2841–2853, 2015
      PubDate: 2015-04-08T12:12:10.079387-05:
      DOI: 10.1002/aic.14795
       
  • Modeling the permittivity of electrolyte solutions
    • Pages: 2854 - 2860
      Abstract: Solution of a strong electrolyte in a high‐density polar fluid gives rise to a dielectric saturation that decreases the orientation polarizability of the solvent molecules in close proximity to the ions wherefore the relative permittivity in this region is determined solely by the atomic and electronic polarization. This causes a substantial decrease in the static permittivity of the solution. By considering the dielectric saturation, a model for the permittivity of an electrolyte solution have been developed and the parameters, the relative permittivities at dielectric saturation in close proximity to the ions, for 17 ions in water at 298.15 K were determined. By scaling these relative permittivities in proportion to the permittivity of the solvent, the model could be extended to calculate the permittivity of solutions of electrolytes in methanol and admixtures of water and ethanol. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2854–2860, 2015
      PubDate: 2015-04-08T11:08:59.64825-05:0
      DOI: 10.1002/aic.14799
       
  • Thermodynamic mechanism of free heme action on sickle cell hemoglobin
           polymerization
    • Authors: Anupam Aich; Weichun Pan, Peter G. Vekilov
      Pages: 2861 - 2870
      Abstract: For insights into the mechanisms of heme action on the rate of sickle cell hemoglobin polymerization, we determine the erythrocytic concentration of free heme using a novel method based on enzymatic catalysis and luminescence. We find in sickle cell patients 44 ± 10 µM, in sickle trait individuals, 33 ± 4 µM, and in healthy adults, 21 ± 2 µM. We test the applicability of two mechanisms of heme action: a kinetic one, whereby heme aggregates serve as heterogeneous nucleation centers, and a thermodynamic pathway, in which free heme enhances the attraction between sickle hemoglobin (HbS) molecules in solution. We show that the latter mechanism exclusively operates. The enhanced attraction leads to increase of the total volume of a population of dense liquid clusters by about two orders of magnitude. As the dense liquid clusters serve as locations and precursors to the formation of the HbS polymer nuclei, their increased volume directly leads to faster polymer nucleation. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2861–2870, 2015
      PubDate: 2015-04-08T12:11:26.311064-05:
      DOI: 10.1002/aic.14800
       
  • Thermodynamics of protein aqueous solutions: From the structure factor to
           the osmotic pressure
    • Pages: 2871 - 2880
      Abstract: An analytical expression for the structure factor for globular proteins in aqueous solution is presented. This expression was obtained considering a potential given by the sum of a hard core, a van der Waals attractive, and a screened Coulomb contribution. Experimental data of small angle x‐ray scattering for bovine serum albumin (BSA) in aqueous solutions containing sodium salts at different protein concentrations and pH values are also presented. The developed expression for the structure factor describes accurately these experimental data provided a dependence of the attractive parameter on protein concentration is established. An expression for the osmotic pressure was derived from the structure factor. With attractive parameters adjusted from x‐ray scattering data, the osmotic pressure of BSA aqueous solutions could be predicted with very good agreement with experimental data. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2871–2880, 2015
      PubDate: 2015-04-10T14:17:41.808567-05:
      DOI: 10.1002/aic.14802
       
  • A low‐disturbance nonequilibrium molecular dynamics algorithm
           applied to the determination of thermal conductivities
    • Authors: Filipe A. Furtado; Charlles R. A. Abreu, Frederico W. Tavares
      Pages: 2881 - 2890
      Abstract: A new nonequilibrium molecular dynamics algorithm is proposed for the determination of thermal conductivity and other transport properties. The proposed algorithm aims at diminishing the energy drift problem observed in this type of method while conserving linear momentum and being compatible with constrained molecules. The features of the proposed algorithm are evaluated by determining thermal conductivities of water at 323 K, n‐octane at 300 K, and argon close to its triple point, and by comparing these results with those obtained using established methods. The analysis of systems presenting diverse molecular characteristics allowed us to assess the usefulness of the proposed algorithm. The energy drift and temperature variation were reduced in the range of 10–80%, depending on the parameters of the proposed algorithm and the characteristics of the system. The determined thermal conductivities showed good agreement when compared to experimental and simulation data. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2881–2890, 2015
      PubDate: 2015-04-03T10:17:58.709766-05:
      DOI: 10.1002/aic.14803
       
  • Developing intermolecular‐potential models for use with the
           SAFT‐VR Mie equation of state
    • Authors: Simon Dufal; Thomas Lafitte, Amparo Galindo, George Jackson, Andrew J. Haslam
      Pages: 2891 - 2912
      Abstract: A major advance in the statistical associating fluid theory (SAFT) for potentials of variable range (SAFT‐VR) has recently been made with the incorporation of the Mie (generalized Lennard–Jones [LJ]) interaction between the segments comprising the molecules in the fluid (Lafitte et al. J. Chem. Phys. 2013;139:154504). The Mie potential offers greater versatility in allowing one to describe the softness/hardness of the repulsive interactions and the range of the attractions, which govern fine details of the fluid‐phase equilibria and thermodynamic derivative properties of the system. In our current work, the SAFT‐VR Mie equation of state is employed to develop models for a number of prototypical fluids, including some of direct relevance to the oil and gas industry: methane, carbon dioxide and other light gases, alkanes, alkyl benzenes, and perfluorinated compounds. A complication with the use of more‐generic force fields such as the Mie potential is the additional number of parameters that have to be considered to specify the interactions between the model molecules, leading to a degree of degeneracy in the parameter space. A formal methodology to isolate intermolecular‐potential models and assess the adequacy of the description of the thermodynamic properties in terms of the complex parameter space is developed. Fluid‐phase equilibrium properties (the vapor pressure and saturated‐liquid density) are chosen as the target properties in the refinement of the force fields; the predictive capability for other properties such as the enthalpy of vaporization, single‐phase density, speed of sound, isobaric heat capacity, and Joule–Thomson coefficient, is appraised. It is found that an overall improvement of the representations of the thermophysical properties of the fluids is obtained using the more‐generic Mie form of interaction; in all but the simplest of fluids, one finds that the LJ interaction is not the most appropriate. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2891–2912, 2015
      PubDate: 2015-06-02T09:53:26.123456-05:
      DOI: 10.1002/aic.14808
       
  • Liquid‐liquid phase split in ionic liquid + toluene
           mixtures induced by CO2
    • Authors: Roberto I. Canales; Joan F. Brennecke
      Pages: 2968 - 2976
      Abstract: High pressure carbon dioxide was dissolved in ionic liquid + toluene mixtures to obtain the conditions of pressure and composition where a liquid‐liquid phase split occurs at constant temperature. Ionic liquids (ILs) with four different cations paired with the bis(trifluoromethylsulfonyl)imide ([Tf2N]−) anion were selected: 1‐hexyl‐3‐methylimidazolium ([hmim]+), 1‐hexyl‐3‐methylpyridinium ([hmpy]+), triethyloctylphosphonium ([P2228]+), and tetradecyltrihexylphosphonium ([P66614]+). The solubility of CO2 was measured in the liquid mixtures at temperatures between 298 and 333 K and at pressures up to 8 MPa, or until the second liquid phase appeared, for initial liquid phase compositions of 0.30, 0.50, and 0.70 mole fraction of IL. Ternary isotherms were compared with the binary solubility of CO2 in each IL and pure toluene. The lowest pressure for separating toluene in a second liquid phase was achieved by decreasing the temperature of the system, increasing the amount of toluene in the initial liquid mixture and using [hmim][Tf2N]. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2968–2976, 2015
      PubDate: 2015-08-07T09:38:39.007435-05:
      DOI: 10.1002/aic.14850
       
  • Binary and ternary mixtures of liquid crystals with CO2
    • Authors: M. de Groen; T. J. H. Vlugt, T. W. de Loos
      Pages: 2977 - 2984
      Abstract: Liquid crystals, elongated molecules with a structured liquid phase, may be used as new solvents for CO2 capture. However, no molecule has been found yet with optimal properties. Therefore, mixtures of two liquid crystals and CO2 are investigated. Also, the phase behavior of some binary subsystems of the investigated ternary systems is studied for comparison. In the mixtures investigated, 4,4′‐pentyloxycyanobiphenyl + 4,4′‐heptyloxycyanobiphenyl + CO2 and 4,4′‐propylcyclohexylbenzonitrile + 4,4′‐heptylcyclohexylbenzonitrile + CO2, the nematic phases form a nematic homogeneous solution and the solid phases form an eutectic system, leading to a material with improved properties for CO2 capture. Moreover, the ternary mixture of 4,4′‐propylcyclohexylbenzonitrile + 4,4′‐heptylcyclohexylbenzonitrile + CO2 showed an increased solubility of CO2 compared with the binary subsystems. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2977–2984, 2015
      PubDate: 2015-08-07T09:38:42.405374-05:
      DOI: 10.1002/aic.14857
       
  • Application of the functional renormalization group method to classical
           free energy models
    • Authors: Leo Lue
      Pages: 2985 - 2992
      Abstract: A simple functional renormalization group method is presented to correct the behavior of classical free energy models near the critical point. This approach is applied to the Soave–Redlich–Kwong equation of state to illustrate its ability to better reproduce the phase behavior of simple fluids and to understand the influence of its parameters on the shape of the vapor‐liquid phase diagram. The method is then extended to account for the correlations induced by intramolecular bonds. It is then applied to a first‐order thermodynamic perturbation theory for chain fluids to examine fluids composed of linearly bonded Lennard‐Jones atoms. Unlike previous approaches for applying renormalization group corrections to chain fluids, this is able to accurately reproduce the critical point without predicting an overly flat liquid‐vapor coexistence region. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2985–2992, 2015
      PubDate: 2015-08-07T09:38:41.84138-05:0
      DOI: 10.1002/aic.14868
       
  • Water and methane in shale rocks: Flow pattern effects on fluid transport
           and pore structure
    • Authors: Tuan A. Ho; Alberto Striolo
      Pages: 2993 - 2999
      Abstract: Using molecular dynamics simulations, the two‐phase flow of water and methane through slit‐shaped nanopores carved from muscovite is studied. The simulations are designed to investigate the effect of flow patterns on fluids transport and on pore structure. The results indicate that the Darcy's law, which describes a linear relation between flow rate and pressure drop, can be violated when the flow pattern is altered. This can happen when the driving force, that is, the pressure drop, increases above a pore‐size dependent threshold. Because the system considered here contains two phases, when the fluid structure changes, the movement of methane with respect to that of water changes, leading to the violation of the Darcy's law. Our results illustrate the importance of the capillary force, due to the formation of water bridges across the model pores, not only on the fluid flow, but also on the pore structure, in particular its width. When the water bridges are broken, perhaps because of fast fluid flow, the capillary force vanishes leading to significant pore expansion. Because muscovite is a model for illite, a clay often found in shale rocks, these results advance our understanding regarding the mechanism of water and gas transport in tight shale gas formations. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2993–2999, 2015
      PubDate: 2015-08-07T09:38:22.415834-05:
      DOI: 10.1002/aic.14869
       
  • Solvent effects on esterification equilibria
    • Authors: Ole Riechert; Maik Husham, Gabriele Sadowski, Tim Zeiner
      Pages: 3000 - 3011
      Abstract: Solvents are known to have strong impacts on the yields of equilibrium reactions. This work focuses on the thermodynamic investigation of these solvent effects on esterification reactions of acetic acid and propionic acid with ethanol. Esterification of acetic acid was performed in the solvents acetone, acetonitrile (ACN), dimethylformamide (DMF), and tetrahydrofurane as well as in mixtures thereof. ACN promotes the esterification of acetic acid, whereas it is strongly suppressed by DMF. The esterification of propionic acid was investigated with various reactant concentrations in acetone. The experimental equilibrium data in pure solvents and solvent mixtures were modeled using the thermodynamic equilibrium constant Ka and the reactant/product activity coefficients predicted by the perturbed chain‐statistical associating fluid theory (PC‐SAFT). For a given Ka, PC‐SAFT is able to predict the influence of the solvent and even solvent mixtures on the equilibrium concentrations of esterification in almost quantitative agreement with the experimental data. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3000–3011, 2015
      PubDate: 2015-08-07T09:38:14.074505-05:
      DOI: 10.1002/aic.14873
       
  • Molecular‐based virial coefficients of CO2‐H2O mixtures
    • Authors: Andrew J. Schultz; David A. Kofke, Allan H. Harvey
      Pages: 3029 - 3037
      Abstract: We report second and third virial coefficients for the system CO2‐H2O, calculated via cluster integrals using quantitative molecular models taken from the literature. Considered models include (1) fits to highly accurate ab initio calculations of the potential energy surfaces, and (2) semiempirical Gaussian Charge Polarizable Models (GCPM). Three‐body effects are found to be essential for obtaining quantitative results. Good agreement with experiment is obtained for the pure‐component coefficients, and for the cross second virial coefficient. For the two cross third virial coefficients, the few experimental data available do not agree well with the calculations; it is not clear whether this is due to problems with the data or deficiencies in the three‐body potentials. The uncertain state of the experimental data, and the relative mutual consistency of values computed from ab initio and GCPM models, suggest that calculated mixture third virial coefficients could be more accurate than values from experiment. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3029–3037, 2015
      PubDate: 2015-08-07T09:38:29.370502-05:
      DOI: 10.1002/aic.14880
       
  • High pressure measurements and molecular modeling of the water content of
           acid gas containing mixtures
    • Authors: Wael A. Fouad; Matt Yarrison, Kyoo Y. Song, Kenneth R. Cox, Walter G. Chapman
      Pages: 3038 - 3052
      Abstract: Water content of three carbon dioxide containing natural gas mixtures in equilibrium with an aqueous phase was measured using a dynamic saturation method. Measurements were performed up to high temperatures (477.6 K = 400°F) and pressures (103.4 MPa = 15,000 psia). The perturbed chain form of the statistical associating fluid theory was applied to predict water content of pure carbon dioxide (CO2), hydrogen sulfide (H2S), nitrous oxide (N2O), nitrogen (N2), and argon (Ar) systems. The theory application was also extended to model water content of acid gas mixtures containing methane (CH4). To model accurately the liquid‐liquid equilibrium at subcritical conditions, cross association between CO2, H2S, and water was included. The agreement between the model predictions and experimental data measured in this work was found to be good up to high temperatures and pressures. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3038–3052, 2015
      PubDate: 2015-08-07T09:38:30.036916-05:
      DOI: 10.1002/aic.14885
       
  • Predicting the thermodynamic properties and dielectric behavior of
           electrolyte solutions using the SAFT‐VR+DE equation of state
    • Authors: Gaurav Das; Stepan Hlushak, M. Carolina dos Ramos, Clare McCabe
      Pages: 3053 - 3072
      Abstract: We extend the SAFT‐VR+DE equation of state to describe 19 aqueous electrolyte solutions with both a fully dissociated and a partially dissociated model. The approach is found to predict thermodynamic properties such as the osmotic coefficient, water activity coefficient, and solution density, across different salt concentrations at room temperature and pressure in good agreement with experiment using only one or two fitted parameters. At higher temperatures and pressures, without any additional fitting, the theory is found to be in qualitative agreement with experimental mean ionic activities and osmotic coefficients. The behavior of the dielectric constant as a function of salt concentration is also reported for the first time using a statistical associating fluid theory (SAFT)‐based equation of state. At high salt concentrations, the stronger electrostatic interactions between the ionic species due to the dielectric decrement, is captured through the inclusion of ion association. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3053–3072, 2015
      PubDate: 2015-08-07T09:38:12.313476-05:
      DOI: 10.1002/aic.14909
       
  • Incorporating critical divergence of isochoric heat capacity into the
           soft‐SAFT equation of state
    • Pages: 3073 - 3080
      Abstract: In the critical region, widely used equations of state, including molecular‐based statistical associating fluid theory (SAFT) equations, fail to quantitatively describe the critical anomalies affected by the diverging fluctuations of density due to their classical mean‐field approximation. Description of some properties in the critical region, in particular vapor‐liquid coexistence and isothermal compressibility, can be improved by fitting (multi) parameters of an equation of state to the properties obtained in accurate computer simulations. However, some anomalies in the critical region, which are caused exclusively by critical fluctuations, cannot be readily generated by this procedure. An example of a critical anomaly, completely absent in the mean‐field approximation, is the divergence of the isochoric heat capacity. A simplified methodology for modifying the original soft‐SAFT equation of state to take into account these anomalies is explored. Possible procedures for further improvement are mentioned. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3073–3080, 2015
      PubDate: 2015-08-07T09:38:25.830703-05:
      DOI: 10.1002/aic.14911
       
  • An improved algorithm for the three‐fluid‐phase VLLE flash
           calculation
    • Pages: 3081 - 3093
      Abstract: The VLLE flash is important in water and hydrocarbons mixtures, hydrocarbon and CO2 rich mixtures, and hydrocarbon methane rich mixtures that are encountered in reservoir performance and recovery studies. A robust VLLE flash algorithm is proposed. The equilibrium and mass balance equations are solved as a constrained minimization problem. An inverse barrier function is used to handle the inequality constrains to solve for the phase fractions. It warrants always arriving to the solution. The challenging cases analyzed showed that the initialization procedure proposed, together with successive substitution iteration in the outer loop, is a good method for a stable VLLE flash algorithm, even near critical points. Whenever the result is in the region outside the three‐phase physical domain, the solution suggests that the system has fewer phases. In one of the cases analyzed, a region with three liquid phases was encountered and the algorithm found two different solutions with positive phase fractions. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3081–3093, 2015
      PubDate: 2015-08-07T09:38:22.80649-05:0
      DOI: 10.1002/aic.14946
       
  • A crossover‐UNIQUAC model for critical and noncritical LLE
           calculations
    • Authors: Khalil Parvaneh; Reza Haghbakhsh, Alireza Shariati, Cor J. Peters
      Pages: 3094 - 3103
      Abstract: A new model, named the crossover‐UNIQUAC model, has been proposed based on the crossover procedure for predicting constant‐pressure liquid–liquid equilibria (LLE). In this manner, critical fluctuations were incorporated into the classical UNIQUAC equation. Coexistence curves were estimated for systems having a diverse range of asymmetries. These systems included the LLE of five different mixtures, composed of nitrobenzene with one of the members of the alkane homologous family (either pentane, octane, decane, dodecane, or tetradecane), as well as an extra system having a different chemical nature, namely the mixture of n‐perfluorohexane and hexane, to further check the validity of the proposed approach. Using these nonideal mixtures, the validity of the new model was investigated within wide ranges, covering near‐critical to regions falling far away from the critical point. The graphical trends, as well as the quantitative comparison with experimental data indicated the good agreement of the proposed model results with the experimental data. A maximum AARD% value of 3.97% was obtained in calculating molar compositions by the proposed model for such challenging systems covering noncritical, as well as critical regions. In addition, to show the strength of the proposed crossover approach to describe properties other than LLE, molar heat capacities were investigated for the system of nitrobenzene + dodecane. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3094–3103, 2015
      PubDate: 2015-08-07T09:38:27.243975-05:
      DOI: 10.1002/aic.14948
       
  • Thermodynamics of flat thin liquid films
    • Authors: Philip C. Myint; Abbas Firoozabadi
      Pages: 3104 - 3115
      Abstract: The two main themes of this study aim to resolve conflicting results in the literature regarding the thermodynamics of flat (uniform thickness) thin liquid films. One of the themes concerns the augmented Young equation, which is a condition for mechanical equilibrium. Two different expressions for the augmented Young equation have appeared in the literature. It is shown that under certain assumptions, the two expressions can be made equivalent. The second main theme addresses thermodynamic functions describing systems with non‐pressure‐volume (non‐PV) work. In thin liquid films, the non‐PV work is the film tension work. Two different expressions that relate the film's Gibbs energy to its internal energy have appeared in the literature. This ambiguity is resolved by showing that only one of the Gibbs energies can be used to determine the equilibrium state via energy minimization. The analysis can be readily generalized to systems with other types of non‐PV work. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3104–3115, 2015
      PubDate: 2015-08-07T09:38:32.35973-05:0
      DOI: 10.1002/aic.14963
       
  • Viscosity and density of isobutane measured in wide ranges of temperature
           and pressure including the near‐critical region
    • Authors: Sebastian Herrmann; Egon Hassel, Eckhard Vogel
      Pages: 3116 - 3137
      Abstract: Accurate ηρpT data for isobutane were measured for nine isotherms between 298.15 and 498.15 K using simultaneously a vibrating‐wire viscometer and a single‐sinker densimeter. The maximum pressure was 93% of the saturated for subcritical isotherms and 30 MPa for supercritical isotherms. The density measurements are generally characterized by an uncertainty of ≤0.1%. Allocation errors for temperature and pressure influence significantly their uncertainty in the near‐critical region. A comparison with the equation of state by Bücker and Wagner shows agreement normally within ±0.1%. The near‐critical isotherm 410.15 K reveals differences to −3.7% exceeding the uncertainty of 1.9%. The uncertainty in viscosity is ≤0.3%. The comparison with the correlation of Vogel et al. yields deviations exceeding the uncertainty of the correlation (3%). The critical enhancement becomes evident for the near‐critical isotherm amounting to 1.4%. The new data will improve the viscosity surface correlation. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3116–3137, 2015
      PubDate: 2015-03-02T14:07:39.046257-05:
      DOI: 10.1002/aic.14759
       
  • Diffusion in fluids between Knudsen and Fickian limits: Departure from
           classical behavior
    • Authors: Gregory L. Aranovich; Marc D. Donohue
      Pages: 3138 - 3143
      Abstract: The finite‐difference equation of diffusion (consistent with Einstein's evolution equation of diffusion) without the assumption of small mean free path is discussed. This equation predicts significant deviations from classical behavior for the simplest geometry: fluid in a pipe with a large density gradient, such that one end is at the Fickian limit, the other end is at Knudsen limit and there can be a transition zone between them. This has not been considered in previous studies. The analysis indicates that significant deviations from classical (Fickian) behavior arise due to the large change in mean free path which is important in numerous situations, including vacuum technology and propulsion in space. Other examples of deviations from Fick's law include cases where the mean free path is not small compared to system size (nanoscale systems and low density systems) and cases where there are large gradients. These are important in a variety of practical applications, including vacuum distillation, vacuum pumps, and adsorption measurements. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3138–3143, 2015
      PubDate: 2015-08-07T09:38:39.501983-05:
      DOI: 10.1002/aic.14926
       
 
 
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