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ENGINEERING (1180 journals)            First | 1 2 3 4 5 6 7 8 | Last

Bharatiya Vaigyanik evam Audyogik Anusandhan Patrika (BVAAP)     Open Access  
Biointerphases     Open Access   (Followers: 1)
Biomaterials Science     Full-text available via subscription   (Followers: 4)
Biomedical Engineering     Hybrid Journal   (Followers: 11)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 14)
Biomedical Engineering Letters     Hybrid Journal   (Followers: 5)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 17)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 15)
Biomedical Engineering: Applications, Basis and Communications     Hybrid Journal   (Followers: 6)
Biomedical Microdevices     Hybrid Journal   (Followers: 7)
Biomedical Science and Engineering     Open Access   (Followers: 2)
Biomedizinische Technik - Biomedical Engineering     Hybrid Journal  
Biomicrofluidics     Open Access   (Followers: 5)
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: 2)
Bulletin of Engineering Geology and the Environment     Hybrid Journal   (Followers: 3)
Bulletin of the Crimean Astrophysical Observatory     Hybrid Journal  
Cahiers, Droit, Sciences et Technologies     Open Access  
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: 2)
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: 11)
CIRP Journal of Manufacturing Science and Technology     Full-text available via subscription   (Followers: 10)
City, Culture and Society     Hybrid Journal   (Followers: 19)
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: 6)
Coastal Engineering     Hybrid Journal   (Followers: 9)
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 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: 188)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 160)
Composites Part B : Engineering     Hybrid Journal   (Followers: 172)
Composites Science and Technology     Hybrid Journal   (Followers: 136)
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: 3)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 7)
Computer Science and Engineering     Open Access   (Followers: 8)
Computers & Geosciences     Hybrid Journal   (Followers: 8)
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: 8)
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: 5)
Control Engineering Practice     Hybrid Journal   (Followers: 34)
Control Theory and Informatics     Open Access   (Followers: 4)
Corrosion Science     Hybrid Journal   (Followers: 23)
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)
Data Handling in Science and Technology     Full-text available via subscription   (Followers: 3)
Design Journal : An International Journal for All Aspects of Design     Hybrid Journal   (Followers: 23)

  First | 1 2 3 4 5 6 7 8 | Last

Journal Cover   AIChE Journal
  [SJR: 1.098]   [H-I: 104]   [24 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]
  • Optimization of Grade Transitions in Polyethylene Solution Polymerization
    • Authors: Jun Shi; Lorenz T. Biegler, Intan Hamdan
      Abstract: This study considers the development of optimization models for grade transition of polyethylene solution polymerization processes. A detailed mathematical model is developed to capture the dynamics of the solution polymerization process. This includes time delay models for vapor and liquid recycle streams as well as a reduced, yet accurate, vapor‐liquid equilibrium (VLE) model derived from rigorous VLE calculations. Simultaneous dynamic optimization approach is applied to solve the optimization problem to reduce off‐spec production time and transition time. Two optimization formulations, single stage and multistage, are developed to deal with single‐value target and specification bands of product properties, respectively. The results show significant reductions in grade transition time and off‐spec production time. In addition, the multistage formulation designed for problems with specification bands is developed and demonstrated. The mutistage formulation outperforms its single stage counterpart. It minimizes transition time and off‐spec production directly, and leads to higher performance control profiles. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-20T17:50:08.558568-05:
      DOI: 10.1002/aic.15113
  • Kinetic Modeling of Pt/C Catalyzed Aqueous Phase Glycerol Conversion with
           In Situ Formed Hydrogen
    • Authors: Xin Jin; Prem S. Thapa, Bala Subramaniam, Raghunath V. Chaudhari
      Abstract: Detailed kinetic modeling of Pt/C catalyzed conversion of glycerol to lactic acid, glycols and alcohols with in‐situ formed hydrogen is reported. Experimental concentration‐time profiles were obtained in a batch slurry reactor at different glycerol concentrations, nitrogen partial pressures, and NaOH concentrations in a temperature range of 130 ‐ 160 oC. Six different kinetic models, were evaluated to describe the competing dehydrogenation, hydrogenolysis, dehydration and C‐C cleavage reactions, and discriminated to fit the experimental data. It is found that a “dual‐similar‐site” mechanism involving alkali promoted dehydrogenation, on two adjacent Pt sites to affect C‐C and C‐O cleavage best describes the experimental data. The dehydrogenation reaction proceeds with a significantly lower activation barrier (Ea = 53 kJ/mol) compared to the non‐catalytic hydrothermal conversion (Ea = 128 kJ/mol). The activation energy for glycerol hydrogenolysis on Pt/C catalyst without adding hydrogen is estimated to be 64 kJ/mol. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-20T17:49:41.540332-05:
      DOI: 10.1002/aic.15114
  • Ceramic Tubular MOF Hybrid Membrane Fabricated through In Situ
           Layer‐by‐Layer Self‐Assembly for Nanofiltration
    • Abstract: Nanofiltration has been playing an important role in water purification, in which the developments of novel membrane materials and modules are among significant. Herein, a metal‐organic framework (MOFs) hybrid membrane, ZIF‐8/PSS was fabricated on a tubular alumina substrate through a layer‐by‐layer self‐assembly technique. ZIF‐8 particles in situ grow into PSS layers to improve their compatibility and dispersion, thereby getting high quality membrane, which was loaded into a steel tubular module for nano‐filtrating dyes from water. Under optimized conditions, it shows outstanding nanofiltration properties towards methyl blue, with the flux of 210 Lm−2 h−1 MPa−1 and the rejection of 98.6%. Furthermore, the good pressure resistance ability and running stability of the membrane were revealed, which can be attributed to use the ceramic substrate and the inherent stability of ZIF‐8. This work thus illustrates a simple approach for fabricating MOFs hybrid membranes on tubular ceramic substrates, having great potential for industrial applications. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-20T17:48:32.332626-05:
      DOI: 10.1002/aic.15115
  • Simulation of biomass char gasification in a downdraft reactor for syngas
    • Authors: Augustina Ephraim; Victor Pozzobon, Olivier Louisnard, Doan Pham Minh, Ange Nzihou, Patrick Sharrock
      Abstract: A steady‐state, one‐dimensional computational fluid dynamics model of wood char gasification in a downdraft reactor is presented. The model is not only based on reaction kinetics and fluid flow in the porous char bed but also on equations of heat and mass conservation. An original OpenFOAM solver is used to simulate the model and the results are found to be in good agreement with published experimental data. Next, a sensitivity analysis is performed to study the influence of reactor inlet temperature and gas composition on char conversion, bed temperature profile and syngas composition. In addition, the evolution of the complex reaction mechanisms involved in mixed atmosphere gasification is investigated, and the most suitable operating parameters for controlling syngas composition are evaluated. Our simulation results provide essential knowledge for optimizing the design and operation of downdraft gasifiers in order to produce syngas that meets the requirements of various biofuel applications. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-18T18:44:36.733649-05:
      DOI: 10.1002/aic.15111
  • Natural convection in shear‐thinning yield stress fluids in a square
    • Abstract: The influence of viscoplastic rheological features on the Rayleigh‐Bénard convection is investigated by numerical means in order to compare with first experimental results given by Darbouli et al, (Phys. Fluids 2013;25). The fluid is modelled by a regularized Herschel‐Bulkley law which is often used to fit numerous pasty fluids. We consider natural convection in a 2D square cavity heated from below. Critical values of Oldroyd number Od and yield number Y are provided. Numerical results highlight a stabilizing effect of the yield stress as well as a destabilizing effect of increasing shear‐thinning coefficient n since the increase in n enhances the heat transfer in the range of our calculations. Unyielded regions are located in the square corners of the cavity and in the cavity where convection occurs. The unyielded zones size increases with the increase in Od and can invade all the cavity for sufficiently large values of Od. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-18T18:44:08.673039-05:
      DOI: 10.1002/aic.15112
  • Osmotic power production from seawater brine by hollow fiber membrane
           modules: Net power output and optimum operating conditions
    • Abstract: This study analyzes the net energy output and optimum operating conditions for osmotic power generation from seawater brine based on the currently available hollow fiber membranes in the module scale. Factors that are influential on membrane performances, such as external concentration polarization, internal concentration polarization, salt reverse diffusion and dilution have been taken into account. Net power density is defined and applied to characterize the efficiency of the PRO system, in terms of power production minus pumping energy, pre‐treatment cost and energy consumption by pressure drop in the membranes. When using 1M NaCl as the draw solution and 10 mM NaCl as the feed, it is found that up to 7 W m−2 net power density can be harvested by the PRO system depending on the water sources. Coupling with the existing RO plant is highly beneficial in terms of readily available high pressure source, high salinity and less or negligible pre‐treatment costs for the draw solution. Sources with higher salt concentrations are preferred. The optimum hydraulic pressure, module length, flow rate to membrane area ratio and feed to draw flow rate ratio have also been analyzed to maximize the net power output. In addition, implications on hollow fiber development are discussed. Fibers with high water permeability, lower structural parameter, good mechanical stability, better fouling resistance and outer‐selective configurations are recommended for further studies. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-17T18:18:24.29555-05:0
      DOI: 10.1002/aic.15109
  • Impact of ownership structure along the value chain in the manufacturing
    • Authors: Jan H Scholtz
      Abstract: In the chemical and petrochemical industry it is quite common that the manufacturing of a final product is the result of several consecutive steps which can be owned and operate by one or many participants. Although not always practical, equal ownership among all partners along the value chain is often recommended as a way to simplify business structure, ensuring all partners share equally in the ups and downs of an uncertain market. In contrast to this approach, there are instances where more benefit can be derived from having different owners and operators along the value chain. Examples which are common practise in the industry are the supply of utilities (e.g. electricity), feedstock and services. In these cases the non‐integrated approach offers value as: It provides the operator of the upstream or utility plants the opportunity to specialize, for example, by operating very similar plants around the world. Such specialization enables the use of regional operating centres, minimum onsite cash costs, optimized operating conditions, minimized energy consumption and the optimal use of other variable cost parameters. This paper shows that if outsourcing results in a cash cost saving by an upstream operator, the benefit to the downstream owner will (in financial reward) be proportional to the cash cost saving achieved. In absolute terms, the magnitude of the benefit is moderated by the size of the downstream capital investment. (The bigger the downstream investment relative to the upstream investment, the smaller the impact of the saving on the economics of the downstream company.) As a “utility provider” an upstream operator benefits from lower risk in terms of offtake and market price uncertainties. Such owners benefit from a lower cost of capital, and as such also have lower return expectations than players further along in the value chain (who are exposed to all the uncertainties in volatile markets). This paper shows that the positive impact of such benefits to the return of the downstream partner is directly proportional the difference in return expectations between the upstream and downstream company. Once again, the absolute magnitude of the saving becomes more substantial as the ratio of upstream capital investment increases relative to the downstream capital investment. Economy of learning may also enable a specialized upstream company to obtain an asset at a lower capital than a less specialized downstream operator. This paper shows that the positive impact of such a benefit is very similar to that of a lower return expectation by the upstream company. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-17T18:17:35.390268-05:
      DOI: 10.1002/aic.15108
  • Understanding hydrotropism: A chemical engineering perspective
    • Authors: Qian Gao; Jie Xiao, Xiao Dong Chen
      Abstract: The mechanism of root hydrotropism has been a mystery for many years, due to the complexity of the interactions between the external environment and plants themselves. In order to gain an engineering perspective, the time‐dependent hydrotropism of a single root has been modeled, initially using a two‐dimensional model. Based on the water and nutrient distribution in rhizosphere as computed with the conservation equations, together with a basic reaction‐kinetics‐type growth model and an intuitive root bending model, it has been found that the root already possesses the property of hydrotropism. For the first time, hydrotropism could be tracked by a process engineering model, which is a new idea based upon chemical engineering concept, suggesting an alternative mechanism of hydrotropism. The effects of different initial root widths, lengths and other growth/transport coefficients on root hydrotropism have then been explored in this study. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-17T18:17:10.182728-05:
      DOI: 10.1002/aic.15110
  • Fast Pyrolysis of Glucose‐Based Carbohydrates with Added NaCl Part
           1: Experiments and Development of a Mechanistic Model‡
    • Authors: Xiaowei Zhou; Michael W. Nolte, Heather B. Mayes, Brent H. Shanks, Linda J. Broadbelt
      Abstract: Sodium ions, one of the natural inorganic constituents in lignocellulosic biomass, significantly alter pyrolysis behavior and resulting chemical speciation. Here, experiments were conducted using a micropyrolyzer to investigate the catalytic effects of NaCl on fast pyrolysis of glucose‐based carbohydrates (glucose, cellobiose, maltohexaose and cellulose), and on a major product of cellulose pyrolysis, levoglucosan. A mechanistic model that addressed the significant catalytic effects of NaCl on the product distribution was developed. The model incorporated interactions of Na+ with cellulosic chains and low molecular weight species, reactions mediated by Na+ including dehydration, cyclic/Grob fragmentation, ring‐opening/closing, isomerization, and char formation, and a degradation network of levoglucosan in the presence of Na+. Rate coefficients of elementary steps were specified based on Arrhenius parameters. The mechanistic model for cellulose included 768 reactions of 222 species, which included 252 reactions of 150 species comprising the mechanistic model of glucose decomposition in the presence of NaCl. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-17T08:20:41.400962-05:
      DOI: 10.1002/aic.15106
  • Fast Pyrolysis of Glucose‐Based Carbohydrates with Added NaCl Part
           2: Validation and Evaluation of the Mechanistic Model‡
    • Authors: Xiaowei Zhou; Michael W. Nolte, Heather B. Mayes, Brent H. Shanks, Linda J. Broadbelt
      Abstract: A mechanistic model considering the significant catalytic effects of Na+ on fast pyrolysis of glucose‐based carbohydrates was developed in Part 1 of this study. A computational framework based on continuous distribution kinetics and mass action kinetics was constructed to solve the mechanistic model. Agreement between model yields of various pyrolysis products with experimental data from fast pyrolysis of glucose‐based carbohydrates dosed with NaCl ranging from 0 − 0.34 mmol/g at 500°C validated the model and demonstrated the robustness and extendibility of the mechanistic model. The model was able to capture the yields of major and minor products as well as their trends across NaCl concentrations. Modeling results showed that Na+ accelerated the rate of decomposition and reduced the time for complete thermoconversion of carbohydrates. The sharp reduction in the yield of levoglucosan from fast pyrolysis of cellulose in the presence of NaCl was mainly caused by reduced decomposition of cellulose chains via endchain initiation and depropagation due to Na+ favoring competing dehydration reactions. Analysis of the contributions of reaction pathways showed that the decomposition of levoglucosan made a minor contribution to its yield reduction and contributed less than 0.5% to the final yield of glycolaldehyde from fast pyrolysis of glucose‐based carbohydrates in the presence of NaCl. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-17T08:16:05.658271-05:
      DOI: 10.1002/aic.15107
  • Facile Growth of 1‐D Nanowire‐based WO3 Thin Films with
           Enhanced Photoelectrochemical Performance
    • Abstract: We developed a flame reactor embedded with a constant tungsten wire feeding system to prepare 1‐D nanostructured tungsten oxide thin film for photoelectrochemical water splitting. Photoactive vertically‐aligned nanowire‐based WO3 thin films could be obtained with a controlled thickness via a flame vapor deposition process followed by air‐annealing. The photoelectrochemical performances of WO3 photoelectrodes for different thin film thicknesses were examined. The optimum thickness of WO3 thin film was found to be about 7.2 μm for PEC water splitting based on IPCE plots and I‐V curves. The WO3 prepared with optimum thickness showed better PEC performance than those of recently reported nanostructured WO3 photoanodes. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-17T05:19:44.421123-05:
      DOI: 10.1002/aic.15105
  • The dissipation rate of news in online mass media evaluated by chemical
           engineering and process control tools
    • Authors: Robert N. Grass; Wendelin J. Stark
      Abstract: Basic chemical engineering and processes control tools were utilized to describe the flow of news information in the Internet. Data on the news coverage of scientific articles provided by Altmetric were analyzed for six chemistry journals. The timecourse of the news was modeled using linear system dynamics, resulting in an interpretable description of the timescales involved. The model was additionally tested by applying it to the flow of non‐scientific news information. An investigation on the distribution of news items per scientific article further identified online news generation as a preferential growth process. The model results allowed a discussion on scientific impact in public media and an analysis on how this impact can be influenced by authors and journals. In respect to the field of engineering the work shows that traditional ChemE and process control tools developed for the abstraction of physical and chemical systems can also be utilized to describe social and information related processes. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-13T23:36:28.348331-05:
      DOI: 10.1002/aic.15103
  • Gas‐liquid mass transfer behavior in a surface‐aerated vessel
           stirred by a novel long‐short blades agitator
    • Authors: Peicheng Luo; Jun Wu, Xiang Pan, Yueqiao Zhang, Hua Wu
      Abstract: For a recently developed long‐short blades (LSB) agitator, we have investigated its critical rotational speed for the onset of gas entrainment, power number and gas‐liquid mass transfer behavior, in the case of surface aeration. The effect of the LSB configurations and the liquid level on the agitator performance has been studied in details. The obtained results clearly show several advantages of the LSB agitator in gas‐liquid mass transfer with respect to the agitators in the literature. It is found that its gas‐liquid volumetric mass transfer coefficient at a given specific power can be several times larger than those shown in the literature. It can also avoid decrease in the gas‐liquid mass transfer rate as the liquid level increases. In addition, the bubble distribution in the system is more uniform with respect to conventional agitators, resulting from better distribution of the dissipated energy for the LSB agitator. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-13T23:32:47.937379-05:
      DOI: 10.1002/aic.15104
  • Synthesis, characterization, and tunable adsorption and diffusion
           properties of hybrid ZIF‐7‐90 frameworks
    • Authors: Fereshteh Rashidi; Catherine R. Blad, Christopher W. Jones, Sankar Nair
      Abstract: Hybrid zeolitic imidazolate frameworks (ZIFs), containing more than one type of imidazolate linker, can allow highly tunable molecular sieving and adsorption. Their crystallization becomes more challenging when the end‐member (single‐linker) ZIFs crystallize in different crystal systems. We demonstrate the controlled synthesis and detailed characterization of hybrid ZIF‐7‐90 frameworks containing linkers of ZIF‐7 (rhombohedral) and ZIF‐90 (cubic). ZIF‐7‐90 materials with SOD‐type topology are obtained in three crystalline phases depending on the linker composition and synthesis technique. The effect of synthesis conditions on the activation‐induced phase transition from rhombohedral to other topologies is studied. Nitrogen physisorption at 77 K and CO2 physisorption at 273 K shows the tunability of the pore size distribution and the framework flexibility as a function of framework composition. Measurements of water adsorption and butane isomer diffusion illustrate the tunability of diffusivity over seven orders of magnitude and control of hydrophobic to hydrophilic adsorption behavior. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-11T18:39:56.729568-05:
      DOI: 10.1002/aic.15102
  • The Effect of Inter-particle Cohesion on Powder Mixing in a Ribbon Mixer
    • Authors: H. Musha; G. R. Chandratilleke, K.J. Dong, A.B. Yu
      Abstract: The effect of inter-particle cohesion on powder mixing in a ribbon mixer was studied by means of the discrete element method. It is shown that with an increase in the cohesion, the mixing rate and uniformity of mixing deteriorate, the coordination number increases indicating the loss of the ability of particles to be engaged in free flowing motion, and a majority of particles have a stronger tangential velocity allowing bulk angular motion of particles. Conversely, with a decrease in the cohesion, more particles have larger axial velocities, which will increase convective motion in the axial direction. When the cohesion is reduced, the number of particles having large radial stresses increases, and normal stress in the axial direction remains mostly unchanged. The ribbon mixer can mix cohesive particles in a wide range of the Bond numbers without causing large stresses. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-04T21:44:40.907281-05:
      DOI: 10.1002/aic.15101
  • Multi-Cycle Investigation of a Sol-Gel-Derived Fe2O3/ATP Oxygen Carrier
           for Coal Chemical Looping Combustion
    • Authors: Qingjie Guo; Mingming Yang, Yongzhuo Liu, Qinqin Yang, Yunpeng Zhang
      Abstract: Fe-based oxygen-carrier (OC) particles with attapulgite (ATP) as a support material for coal chemical looping combustion (CLC) have been prepared using a sol-gel approach. The multi-redox characteristics of the prepared Fe4ATP6 (Fe2O3 to ATP mass ratio of 40:60) were experimentally examined in a batch fluidized bed reactor at 900°C. The experimental results indicated that the synergistic reactions between ATP and Fe2O3 increased the coal conversion. Fe4ATP6 exhibited high reactivity, particularly for low-rank coals, in the CLC process. The improved pore structure and surface area were responsible for the high reactivity of Fe4ATP6. In 60 redox cycles, H2 was mainly generated in the outlet gas as the carbon conversion efficiency had reached 95%, and both the coal combustion efficiency and CO2 capture efficiency were greater than 95%. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-04T21:44:16.117854-05:
      DOI: 10.1002/aic.15100
  • Performance of a Medical Oxygen Concentrator Using Rapid Pressure Swing
           Adsorption Process: Effect of Feed Air Pressure
    • Authors: Rama Rao Vemula; Mayuresh V. Kothare, Shivaji Sircar
      Abstract: The effects of feed air pressure on the steady state performance of a medical oxygen concentrator (MOC) was experimentally evaluated using a novel design of a MOC unit which produced a continuous stream of ∼ 90% O2 employing a rapid pressure swing adsorption (RPSA) process scheme. Dry, CO2 free air containing ∼ 1% Ar at different feed gas pressures was used in the tests in conjunction with a commercial sample of LiLSX zeolite as the N2 selective adsorbent in the process. The study showed that the bed size factor (BSF) can be systematically reduced by increasing the feed air pressure for any given total cycle time. The effect of feed air pressure on the oxygen recovery (R) is, however, more complex; it increases with increasing feed pressure only at longer cycle times while the effect is marginal at shorter cycle times. The study also shows that the BSF cannot be indefinitely reduced by lowering total process cycle time at any pressure – a minimum is exhibited in the BSF-cycle time plot. The minimum value of the BSF decreases as the feed pressure is increased. The cycle time for the minimum BSF is, however, not significantly altered by the feed pressure in the data range of this work. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-04T21:41:06.825359-05:
      DOI: 10.1002/aic.15099
  • Internal Fluid Motion and Particle Transport in Externally Heated Sessile
    • Authors: Ashish Kumar Thokchom; Subrata Kumar Majumder, Anugrah Singh
      Abstract: Experiments and numerical simulations were carried out for an evaporating sessile droplet. The droplet was confined in the narrow gap between two glass plates, making it a ‘Hele-Shaw' droplet and particle image velocimetry (PIV) technique was used. In case of the evaporating droplet with pinned contact line and exposed to ambient condition, two symmetric but counter rotating convection cells were observed. After complete evaporation the particles deposited on the substrate near the contact line. The direction of the flow was reversed for a droplet placed on uniformly heated substrate, and the final deposition pattern was a large spot at the center with a thin line at the periphery. For asymmetrically heated substrate a single convection cell appeared, and the final deposition was also asymmetric. When the liquid was subjected to localized heating, the contact line no longer remains pinned and a relatively uniform deposition was obtained after complete drying. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-03T17:51:41.652213-05:
      DOI: 10.1002/aic.15098
  • Mean-Squared-Error-Based Method for Parameter Ranking and Selection with
           Non-Invertible Fisher Information Matrix
    • Authors: Zahra Eghtesadi; Kimberley B. McAuley
      Abstract: Two approaches are developed to rank and select model parameters for estimation in complex models when data are limited, the Fisher information matrix (FIM) is non-invertible, and accurate predictions are desired at key operating conditions. These approaches are evaluated using synthetic data sets in a linear regression example to examine the influence of several factors including: the quality of initial parameter guesses, uncertainty ranges for initial parameter values, noise variances, and the operating region of interest. It is shown that using a reduced FIM with full rank leads to more reliable model predictions for a variety of cases than the alternative approach using the pseudo-inverse of the FIM. The proposed reduced-FIM methodology also provides better predictions than related techniques that do not consider the operating region where reliable predictions are required. The methodology is illustrated using a nonlinear differential equation model of a polymer film casting process. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-03T17:50:30.605706-05:
      DOI: 10.1002/aic.15096
  • Separation of azeotropic mixtures using air microbubbles generated by
           fluidic oscillation
    • Authors: Nada Abdulrazzaq; Baseem Al-Sabbagh, Julia M. Rees, William B. Zimmerman
      Abstract: The feasibility of separating the azeotropic mixture of ethanol-water using microbubble-mediated batch distillation is presented. The effects of the depth of the liquid mixture in the bubble tank and of the inlet air microbubble temperature on the process efficiency were investigated. The enrichment of ethanol in the vapor phase was higher than that achieved at equilibrium conditions for all liquid ethanol mole fractions considered, including the azeotrope. Upon decreasing the depth of the liquid mixture and increasing the temperature of the air microbubbles, the separation efficiency of ethanol was improved. Ethanol with purity of about 98.2%vol. was obtained using the lowest liquid level (3 mm) in conjunction with the highest air microbubble temperature (90°C). Separation was achieved with a small rise in the temperature of the liquid mixture (4°C) at a depth of 3 mm and evaporation time of 90 min making this system suitable for treating thermally sensitive mixtures. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-03T17:50:06.094306-05:
      DOI: 10.1002/aic.15097
  • Probing Pore Blocking Effects on Multiphase Reactions within Porous
           Catalyst Particles Using a Discrete Model
    • Abstract: A discrete model coupling mass transfer, reaction, and phase change in porous catalyst particles is proposed to probe pore blocking effects on multiphase reactions. This discrete model is validated by comparing the results with experiments and those obtained using a continuum model, for the hydrogenation of benzene to cyclohexane in Pd/γ‐alumina catalyst particles. The results show that pore blocking has a significant effect on the effectiveness factor and can contribute to up to 50% of the hysteresis loop area for multiphase reactions in porous catalysts, indicating that pore blocking must be accounted for. Moreover, the pore blocking effects are significantly enhanced when the pore network is poorly connected and the pore size distribution is wide, while the pore blocking effects are insensitive to the volume‐averaged pore size. Multiphase catalyst material characterization and design should account for this effect. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-31T09:50:00.184894-05:
      DOI: 10.1002/aic.15095
  • Measurement of Ultra‐low Permeability
    • Authors: T. S. Ramakrishnan; M. G. Supp
      Abstract: We formulate a permeability measurement method based on perturbed pressure decay between a source and a sink communicating through a porous medium. Nonideality of gas, as well as corrections due to adsorption are considered. The method allows us to infer permeability at a given rock and fluid state. The accuracy of the method may be evaluated through comparison with theoretical decay characteristics and its modal amplitudes. A quantitative evaluation of the experimental inference is therefore possible. Based on the pressure decay theory, we present an apparatus built in our laboratory for measuring permeability. As a secondary output, data analysis also provides porosity. The lowest permeability that the present apparatus is capable of characterizing is about 0.3\,nm$^2$, and with additional improvements, we anticipate capability down to 0.05\,nm$^2$. Where a steady‐state permeameter is pragmatic, we show excellent agreement between the two measurements, validating the method. Measurements in synthetic samples also show that the method is accurate. Porosity data from a standard helium pycnometer confirm the porosity obtained from the decay method. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-30T17:58:23.865866-05:
      DOI: 10.1002/aic.15094
  • Highly Porous Ti4O7 Reactive Electrochemical Water Filtration Membranes
           Fabricated via Electrospinning/Electrospraying
    • Authors: Melissa C. Santos; Yin Jing, Lei Fang, Brian P. Chaplin, Yossef A. Elabd
      Abstract: Porous, flexible, reactive electrochemical membranes (REMs) for water purification were synthesized by a novel simultaneous electrospinning/electrospraying (E/E) technique, which produced a network of poly(sulfone) fibers and Ti4O7 particles as evidenced by scanning electron microscopy. Cyclic voltammetry indicated that the kinetics for water electrolysis reactions and the Fe(CN)64‐/3‐ redox couple were enhanced by Ti4O7 deposition using the E/E technique. Membrane filtration experiments using phenol as a model contaminant showed a 2.6‐fold enhancement in the observed first‐order rate constant for phenol oxidation (kobs,phenol) in filtration mode relative to cross‐flow operation. Phenol oxidation in filtration mode was approaching the pore diffusion mass transfer limit, and was 6 to 8 times higher than measured in a previous study that utilized a ceramic Ti4O7 REM operated in filtration mode and is comparable to rate constants obtained with carbon nanotube flow‐through reactors, which are among the highest reported in the literature to date. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-30T17:56:53.330876-05:
      DOI: 10.1002/aic.15093
  • Ensemble locally‐weighted partial least squares as a
           just‐in‐time modeling method
    • Authors: Hiromasa Kaneko; Kimito Funatsu
      Abstract: The predictive ability of soft sensors, which estimate values of an objective variable y online, decreases due to process changes in chemical plants. To reduce the decrease of predictive ability, adaptive soft sensors have been developed. We focused on just‐in‐time (JIT) soft sensors, especially locally‐weighted partial least squares (LWPLS) regression. Since a set of hyperparameters in an LWPLS model has to be set beforehand and there is only one data set, a traditional LWPLS model is difficult to accurately predict y‐values in multiple process states. In this study, we propose to combine LWPLS and ensemble learning, and predict y‐values with multiple LWPLS models, whose datasets and sets of hyperparameters are different. The weights of LWPLS models are determined based on Bayes' theorem, considering their predictive ability. We confirmed that the proposed model has higher predictive accuracy than traditional models through numerical simulation data and two industrial data analyses. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-29T18:50:31.600901-05:
      DOI: 10.1002/aic.15090
  • Hydrodynamics and mass transfer of oscillating gas‐liquid flow in
           ultrasonic microreactors
    • Authors: Zhengya Dong; Chaoqun Yao, Yuchao Zhang, Guangwen Chen, Jie Xu, Quan Yuan
      Abstract: In this paper, ultrasonic microreactors were used to intensify gas‐liquid mass transfer process and study the intensification mechanism. Fierce surface wave oscillation with different modes was excited on the bubble. It was found that for slug bubbles confined in smaller microchannel, surface wave oscillations require more ultrasound energy to excite due to the confinement effect. Cavitation microstreaming with two toroidal vortices was observed near the oscillating bubble by a streak photography experiment. Surface wave oscillation at the gas‐liquid interface increases the specific surface area, while cavitation microstreaming accelerates the interface renewal and thus improves the individual mass transfer coefficient. With these two reasons, the overall mass transfer coefficient was enhanced by 3‐20 times under utlrasonication. As for gas‐liquid flow hydrodynamics, ultrasound oscillation disturbs the bubble formation process, and changes the initial bubble length and pressure drop. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-29T18:50:08.005407-05:
      DOI: 10.1002/aic.15091
  • Synergetic effect of graphene sheet and 3‐dimensional crumpled
           graphene on the performance of dye‐sensitized solar cells
    • Abstract: Herein, we demonstrate an improved structure of the dye‐sensitized solar cell (DSSC) which is composed of surface modified fluorine‐doped tin oxide (FTO) glass with graphene (GR) sheets and TiO2 films incorporated with 3‐dimensional crumped graphene (3D CGR)/GR sheets. The morphologies of the as‐prepared GR sheets on FTO glasses and 3D CGR/GR sheets/TiO2 films were observed by field‐emission scanning electron microscopy (FESEM). Light harvesting and charge recombination kinetics were investigated with a solar simulator and electrochemical impedance spectroscopy (EIS) analysis. In addition to the reduced charge resistance by the GR modified FTO, the enhanced dye loading capability of the 3D CGR, and the rapid charge transport by the 2D GR sheets, the power conversion efficiency (PCE) was 7.2%, which was an increase of 56% compared to a “conventional” structured DSSC. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-29T18:49:41.213425-05:
      DOI: 10.1002/aic.15089
  • A theoretical unsteady‐state model for kL of bubbles based on the
           framework of wide energy spectrum
    • Authors: Luchang Han; Jin Fu, Ming Li, Shenggao Gong, Ningning Gao, Chi Zhang, He'an Luo
      Abstract: An unsteady‐state model for predicting mass transfer coefficient kL of bubbles with mobile surface was developed for turbulent gas‐liquid dispersions. This model was derived from an unsteady‐state convection and diffusion equation through a characteristics method. Unlike the previous work, this model considered the contributions of the amount of fluid structures of different scales (i.e. eddies) existing in the turbulent flows, the frequency of eddies arriving at the surface, the deformation and oscillation of bubbles to mass transfer. This model was based on the framework of wide energy spectrum and can account for the role of eddies of different sizes in mass transfer. Thus the assumption adopted by the previous models that mass transfer was controlled by eddies of certain sizes is no more needed. The overall kL predicted by the proposed model showed a better agreement with the reported experimental data. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-29T18:49:15.382865-05:
      DOI: 10.1002/aic.15092
  • Hybrid model for optimization of crude oil distillation units
    • Authors: Gang Fu; Yoel Sanchez, Vladimir Mahalec
      Abstract: Planning, scheduling and real time optimization (RTO) are currently implemented by using different types of models, which causes discrepancies between their results. This work presents a single model of a crude distillation unit (preflash, atmospheric, and vacuum towers) suitable for all of these applications, thereby eliminating discrepancies between models used in these decision processes. Product true boiling point (TBP) curves are predicted via partial least squares model from the feed TBP curve and operating conditions (flows, pumparound heat duties, furnace coil outlet temperatures). Combined with volumetric and energy balances, this enables prediction of crude distillation on par with a rigorous distillation model, with 0.5% RMSE over a wide range of conditions. Associated properties (e.g. gravity, sulfur) are computed for each product based on its distillation curve and corresponding property distribution in the feed. Model structure makes it particularly amenable for development from plant data. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-28T18:48:57.133376-05:
      DOI: 10.1002/aic.15086
  • Mass transfer into/from nanofluid drops in a spray liquid–liquid
           extraction column
    • Abstract: The performance of a spray liquid‐liquid extraction column at two mass transfer directions was experimentally studied in the presence of silica nanoparticles. Toluene‐based nanofluid drops containing 0.0005‐0.01 volume percent silica nanoparticles were dispersed in aqueous phase and acetic acid (AA) transfer between phases was investigated. The experiments were performed at fixed volumetric flow rates of dispersed and continuous phases. Maximum enhancement of 47.4% and 107.5% in overall mass transfer coefficient respectively for mass transfer direction of dispersed to continuous phase and vice versa were achieved for drops with 0.001 vol% silica nanoparticles. These enhancements can be referred to Brownian motion of nanoparticles and induced microconvection. The results showed that nanoparticles are more effective in augmenting AA transfer from continuous to dispersed phase. Probable reason is that smaller diameter and lower internal turbulence of drops in this transfer direction increase dispersed phase resistance potential to be manipulated by Brownian motion of nanoparticles. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-28T18:35:29.123477-05:
      DOI: 10.1002/aic.15084
  • Impact of a binary size distribution on particle erosion due to an
           impinging gas plume
    • Authors: Kyle J. Berger; Christine M. Hrenya
      Abstract: Solid particles of non‐uniform sizes exhibit behaviors not seen in monodisperse distributions. Following a previous study of monodisperse particles, the goal of this study is to investigate effects of a binary size distribution on erosion of lunar soil from a rocket landing. The discrete element method is used to examine near‐field (near impingement) and far‐field behavior. For near‐field simulations, small particles preferentially collide with large particles from below, due to a difference in velocity caused by gas forces, which is analogous to behavior for entrainment in gas‐solid fluidized beds. These collisions cause vertical momentum transfer from small to large particles that affects species and total erosion flux. For far‐field simulations, collisions result in an increase in vertical dispersion (binary) and a reduction in maximum horizontal velocity (binary and monodisperse). These results have implications on the most appropriate modeling framework to use for predictions over large distances utilizing wide size distributions. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-28T18:35:01.382173-05:
      DOI: 10.1002/aic.15087
  • Identification and characterization of three‐dimensional turbulent
           flow structures
    • Authors: Farideh Ghasempour; Ronnie Andersson, Bengt Andersson
      Abstract: Many phenomena in chemical processes e.g. fast mixing, coalescence and break‐up of bubbles and drops are not correctly described using average turbulence properties since the outcome is governed by the interaction with individual vortices. In this study, an efficient vortex‐tracking algorithm has been developed to identify thousands of vortices and quantify properties of the individual vortices. The traditional algorithms identifying vortex‐cores only capture a fraction of the total turbulent kinetic energy, which is often not sufficient for modeling of coalescence and break‐up phenomena. In the present algorithm, turbulent vortex‐cores are identified using normalized Q‐criterion, and allowed to grow using morphological methods. The growth is constrained by estimating the influence from all neighboring vortices using the Biot‐Sawart law. This new algorithm allows 82% of the total turbulent kinetic to be captured, at the same time the individual vortices can be tracked in time. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-28T18:34:35.05866-05:0
      DOI: 10.1002/aic.15085
  • The effect of different porous media on moisture loss and oil absorption
           profiles during frying using glass micromodels
    • Abstract: Microstructure plays a key role in oil absorption during frying. The aim of this work was to improve our understanding of the relationship between microstructure and oil absorption, through the use of glass micromodels to obtain evidence of transport phenomena in three porous networks. Micromodels were saturated with water and partially immersed in oil at 190oC. Moisture and oil profiles were imaged to get water and oil saturation maps. Image and fractal analyses were performed to describe the morphology of the evaporation and oil fronts. Results showed that higher porosity facilitated the moisture removal and promoted greater oil absorption during cooling. The fractal dimension showed that microstructures with a relatively high number of fine capillaries were less stable and propitiated fingering during the advance of the evaporation front. In all matrices, the disruption of the surface oil film due to air penetration was a critical factor to stop oil imbibition. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-28T18:34:07.617955-05:
      DOI: 10.1002/aic.15088
  • Fault Detection and Isolation Analysis and Design For Solution
           Copolymerization of MMA and VAc Process
    • Authors: Hadi Shahnazari; Prashant Mhaskar
      Abstract: In this work, we consider the problem of detecting and isolating distinguishable actuator and sensor faults in the solution copolymerization of Methyl Methacrylate (MMA) and Vinyl Acetate (VAc) monomers. To this end, first state estimates are generated using a bank of high‐gain observers, and nonlinear fault detection and isolation (FDI) residuals are defined. The process dynamics are further analyzed to categorize fault scenarios as distinguishable and indistinguishable, and the necessary and sufficient conditions for the classification are presented. Subsequently, filters are designed that enable FDI for the distinguishable fault scenarios, with the advantage of detecting and confining possible locations for indistinguishable faults. The FDI filters are implemented on the copolymerization process, and the results compared with a linear model based filter design. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-28T18:31:48.257548-05:
      DOI: 10.1002/aic.15083
  • Evaluation of mixing profiles for a new micromixer design strategy
    • Authors: Shusaku Asano; Taisuke Maki, Kazuhiro Mae
      Abstract: The relationship between mixing history and reaction performance in microreactors using computational fluid dynamics (CFD) simulations is identified. In the idealized, simplified mixing model, mixing proceeds linearly and only the mixing time determined the reaction performance. However, in the case of realistic models where mixing proceeds unequally, the partial rapid progression of mixing, more than the mixing time, significantly impacts the reaction. The use of the fluid segment size distribution to capture this effect is proposed. The effective Damköhler number derived from the fluid segment size distribution predicted the reaction yield well. To demonstrate the utility of the mixing profile design strategy, we fabricated a novel micromixer with multiple partial rapid mixing zones. This micromixer achieved excellent results both in a CFD simulation and an experiment. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-27T18:22:38.193259-05:
      DOI: 10.1002/aic.15082
  • Issue information
    • Abstract: Cover illustration. Understanding nitrogen inhibition of hydrodesulfurization at the atomic scale. Image courtesy: Srinivas Rangarajan and Manos Mavrikakis 10.1002/aic.15025
      PubDate: 2015-10-27T10:11:36.727338-05:
      DOI: 10.1002/aic.14591
  • Testing of a new Dynamic Ergun Equation for Transport with Positron
           Emission Particle Tracking
    • Authors: G. B. Tupper; I. Govender, D. N. De Klerk, M. C. Richter, A. N. Mainza
      Abstract: The issue of formulating an Ergun‐like equation that applies to dynamic beds previously considered in Tupper et al. (2013) [Minerals Engineering 43‐44: 102‐104] is revisited. Using new high quality Positron Emission Particle Tracking data we compute the volume and time averaged kinematic distributions of the granular (glass beads) and slurry (silica sand and water) mixture. Incorporating these measured ingredients into the model then reveals that turbulence is not described by the usual effective viscosity, but nonetheless is negligible such that the new “Inertial Cell Equation” is first order in spatial derivatives. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-27T08:35:22.304755-05:
      DOI: 10.1002/aic.15081
  • Temperature Dependence of Interaction Parameters in Electrolyte NRTL Model
    • Abstract: The electrolyte NRTL model captures the electrolyte solution nonideality over the entire concentration range with two binary interaction parameters. Here the temperature dependence of the binary parameters is formulated with a Gibbs‐Helmholtz expression containing three temperature coefficients associated with Gibbs energy, enthalpy, and heat capacity contributions. We show the Gibbs energy term is correlated to the excess Gibbs energy of aqueous single electrolyte systems at 298.15 K. With the Gibbs energy term identified, the enthalpy term is correlated to the excess enthalpy at 298.15 K. With the Gibbs energy term and the enthalpy term identified, the heat capacity term is correlated to the excess heat capacity at 298.15 K. Once the temperature coefficients are properly quantified by regressing data of mean ionic activity coefficient, excess enthalpy, and heat capacity at 298.15 K or the equivalents, the model provides a comprehensive thermodynamic framework to represent all thermodynamic properties of electrolyte solutions. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-27T08:17:58.208808-05:
      DOI: 10.1002/aic.15080
  • Pervaporation removal of volatile organic compounds from aqueous solutions
           using the highly permeable PIM‐1 membrane
    • Authors: Xin Mei Wu; Qiu Gen Zhang, Faizal Soyekwo, Qing Lin Liu, Ai Mei Zhu
      Abstract: Wastewater containing volatile organic compounds (VOCs) is generated in various industrial processes and is seriously harmful to the natural environment and human health. Its treatment has become extremely important due to increasing environment concerns. Here we report a high permeable membrane for fast and high‐efficient VOCs removal from aqueous solutions by pervaporation. The as‐prepared PIM‐1 membrane, allows ultrafast permeation of VOCs and exhibits excellent VOCs selectivity, particularly for ethyl acetate, dimethyl ether and acetonitrile. Typically, the PIM‐1 membrane exhibits an ultrahigh flux and separation factor of 39.5 kg µm m−2 h−1 and 189 respectively in the pervaporation of 1.0 mol% aqueous ethyl acetate solution. Furthermore, the solubility‐diffusion mechanism is revealed in the pervaporation of ten kinds of 1.0 mol% VOCs solutions. It is found that the pervaporation performance is affected directly by physicochemical properties of VOCs. Moreover, effects of feed composition and temperature on the pervaporation are studied in details. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-26T10:36:04.909808-05:
      DOI: 10.1002/aic.15077
  • Investigation on UWS Evaporation for Vehicle SCR Applications
    • Authors: Wei Lin; Youtong Zhang, Asif Muhammad
      Abstract: Urea Water Solution (UWS) droplet evaporation characteristics directly affect the conversion and distribution of NH3 in Urea based Selective Catalytic Reduction (SCR) system. The UWS droplet temperature is very difficult to be measured directly. Whereas, this piece of research work involves the measurement of droplet temperature by an Omega‐K type thermocouple of 127 μm diameter. According to the temperature changes of the droplet, the evaporation process can be divided into four steps. Droplets heat and mass transfer processes are derived theoretically at high exhaust temperature. The UWS droplet has been placed in a continuous observation test system in order to investigate its diameter and temperature variations in the aforementioned four steps. The results shown that, this unique method of four steps analysis has more explicitly and better described the UWS evaporation process, hence establishing the basis for the subsequent detailed simulation and monitoring. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-26T10:35:38.236947-05:
      DOI: 10.1002/aic.15078
  • Thermally‐induced Phase Separation (TIPS) and Electrospinning
           Methods for Emerging Membrane Applications: a Review
    • Authors: Jeong F. Kim; Ji Hoon Kim, Young Moo Lee, Enrico Drioli
      Abstract: In this review, the thermally‐induced phase separation (TIPS) and electrospinning methods for preparation of fluoropolymer membranes are assessed, particularly for the polyvinylidene fluoride (PVDF) and polyethylene chlorotrifluoroethylene (ECTFE) membranes. This review focuses on controlling the membrane morphology from the thermodynamic and kinetic perspectives in order to understand the relationship between the membrane morphology and fabrication parameters. In addition, the current status of the nonsolvent induced phase separation (NIPS) method and the combined NIPS‐TIPS (N‐TIPS) method, which is a new emerging fabrication method, are discussed. The past literature data are compiled and an upperbound curve (permeability vs tensile strength) is proposed for the TIPS‐prepared PVDF membranes. Furthermore, the key parameters that control and determine the membrane morphology when using the electrospinning method are reviewed. Exploiting the unique advantages of the electrospinning method, our current understanding in controlling and fine‐tuning the PVDF crystal polymorphism (i.e. β‐phase) is critically assessed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-26T10:35:14.728374-05:
      DOI: 10.1002/aic.15076
  • Reduced‐order modeling for the control of selective
           non‐catalytic reduction (SNCR) of nitrogen monoxide
    • Authors: Benjamin Farcy; Luc Vervisch, Pascale Domingo, Nicolas Perret
      Abstract: The design of a reduced‐order model is discussed to help in the control of selective non‐catalytic reduction (SNCR) of nitrogen monoxide. Instead of relying on a look‐up table of nominal operating points, it is proposed to solve for the time evolution of a set of stochastic particles interacting through a model for turbulent mixing and a reduced chemistry. Each particle is representative of a fraction of the mass flowing in the system in gaseous or liquid form. To calibrate and validate the reduced‐order model, which runs in a few minutes on a desktop computer, reference three‐dimensional and unsteady Large Eddy Simulation is performed in the complex geometry of a real incinerator. This is done solving the full set of conservation equations of mass, momentum and energy over a 162 million cells mesh. The results confirm the possibility of real‐time SNCR optimization from the solving of partial differential equations. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-26T10:33:54.276976-05:
      DOI: 10.1002/aic.15079
  • A concept of reactive compatibilizer‐tracer for studying reactive
           polymer blending processes
    • Abstract: A concept called reactive compatibilizer‐tracer is proposed. The latter bears reactive groups capable of reacting with its counterpart upon forming a copolymer for in‐situ compatibilization, and fluorescent labels allowing determining very small amounts of the in‐situ formed compatibilizer and formation of micelles when it occurs. Owing to this concept, it is shown that a reactive compatibilizer may be very efficient at the beginning of a reactive blending process and may suddenly become completely inefficient, resulting in an abrupt and drastic increase in size of the dispersed phase domains. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-21T03:33:30.312546-05:
      DOI: 10.1002/aic.15074
  • Integrated crude selection and refinery optimization under uncertainty
    • Authors: Yu Yang; Paul I. Barton
      Abstract: Crude oil selection and procurement is the most important step in the refining process and impacts the profit margin of the refinery significantly. Due to uncertain quality of the crudes, conventional deterministic modeling and optimization methods are not suitable for refinery profitability enhancement. Therefore, a novel optimization scheme for crude oil procurement integrated with refinery operations in the face of uncertainties is presented. The decision process comprises two stages and is solved using a scenario‐based stochastic programming formulation. In Stage I, the optimal crude selections and purchase amounts are determined by maximizing the expected profit across all scenarios. In Stage II, the uncertainties are realized and optimal operations for the refinery are determined according to this realization. The resulting large‐scale mixed‐integer nonlinear programming (MINLP) formulation incorporates integer variables for crude selection and continuous variables for refinery operations, as well as bilinear terms for pooling processes. Non‐convex generalized Benders decomposition (NGBD) is employed to solve this problem to obtain an ε‐global optimum efficiently. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-21T03:32:29.40367-05:0
      DOI: 10.1002/aic.15075
  • Carbon capture from natural gas combined cycle (NGCC) power plants:
           Solvent performance comparison at an industrial scale
    • Authors: Mahdi Sharifzadeh; Nilay Shah
      Abstract: Natural gas is an important source of energy. This paper addresses the problem of integrating an existing natural gas combined cycle (NGCC) power plant with a carbon capture process using various solvents. The power plant and capture process have mutual interactions in terms of the flue gas flowrate and composition versus the extracted steam required for solvent regeneration. Therefore, evaluating solvent performance at a single (nominal) operating point is not indicative and solvent performance should be considered subject to the overall process operability and over a wide range of operating conditions. In the present research, a novel optimization framework was developed in which design and operation of the capture process are optimized simultaneously and their interactions with the upstream power plant are fully captured. The developed framework was applied for solvent comparison which demonstrated that GCCmax, a newly developed solvent, features superior performances compared to the MEA baseline solvents. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-13T03:25:32.454712-05:
      DOI: 10.1002/aic.15072
  • Experimental Study on the Solvent Regeneration of a CO2‐Loaded MEA
           Solution using Single and Hybrid Solid Acid Catalysts
    • Authors: Zhiwu Liang; Fanghui Yu, Helei Liu, Wichitpan Rongwong, Raphael Idem, Paitoon Tontiwachwuthikul
      Abstract: The performance of a hybrid solid acid catalyst consisting of a physical mixture of γ‐Al2O3 and H‐ZSM‐5 in terms of the rate and heat duty for solvent regeneration (i.e. CO2 stripping) of a CO2‐rich MEA solution was compared with the individual performance of γ‐Al2O3, H‐ZSM‐5 and H‐Y solid acid catalysts using MEA (2 ‐ 7 mol/L), with initial CO2 loading of 0.5 mol CO2/mol MEA at 378 K. It was observed that any catalyst significantly decreased the energy required for CO2 regeneration. The performance of the catalysts investigated ranked as follows: γ‐Al2O3/H‐ZSM‐5 = 2/1 > γ‐Al2O3 > H‐ZSM‐5 > H‐Y if the process is in the lean CO2 loading region whereas it was H‐ZSM‐5 > γ‐Al2O3/H‐ZSM‐5 = 2/1 > γ‐Al2O3 > H‐Y if the process is in the rich CO2 loading region. These results highlight the joint dependence on Brønsted/Lewis acidity and mesopore surface area of heat duty for solvent regeneration. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-13T03:25:09.3401-05:00
      DOI: 10.1002/aic.15073
  • Three‐dimensional simulations of gas‐liquid cocurrent downflow
           in vertical, inclined and oscillating packed beds
    • Abstract: The hydrodynamic behavior of gas‐liquid downflow in vertical, inclined and oscillating packed beds related to offshore floating applications was analyzed by means of three‐dimensional unsteady‐state two‐fluid simulations. Angular oscillations of the column between two angled symmetrical positions and between vertical and inclined position were considered while bed non‐uniformity was described using radial porosity distributions. For vertical and slightly inclined columns, two‐phase flow was concentrated in the core area of the bed. However, the two‐phase flow was predicted to deviate significantly from axial symmetry at higher inclinations with prominent liquid accumulation in the bottommost reactor cross‐sectional area. Oscillating packed beds unveiled complex reverse secondary flows radially and circumferentially resulting in oscillatory patterns of liquid holdup and pressure drop whose amplitude and propagation frequency were affected by column inclination angle and travel time between vertical and angled positions. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-12T17:53:40.058439-05:
      DOI: 10.1002/aic.15071
  • In Situ ETEM Study of Composition Redistribution in Pt‐Ni Octahedral
           Catalysts for Electrochemical Reduction of Oxygen
    • Abstract: Dynamics of thermally‐induced composition redistribution of sandwich‐like Pt‐Ni octahedral (Oh) electrocatalysts was studied in situ using a variable‐temperature environmental transmission electron microscope (ETEM). Dislocations were observed and upon heating treatment moved towards the surface over time, resulting in an alloy nanoparticle with significant increase Ni content on the surface, which was confirmed by X‐ray photoelectron (XPS) spectroscopy. The thermally‐treated Pt‐Ni octahedral catalysts showed significant improvement in catalyzing oxygen reduction reaction (ORR) over the as‐made nanoparticles, reaching values of 1.4 A/mgPt in mass activity and 4.8 mA/cm2Pt in area specific activity. Our study shows the important effect of post‐synthesis treatment on the optimization of Pt and Ni atomic distribution, thus the catalytic activity and stability; and the power of in situ ETEM in understanding the structural origin of enhanced catalytic performance with atomic level of details. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-09T17:36:01.333307-05:
      DOI: 10.1002/aic.15070
  • A computational framework and solution algorithms for two‐stage
           adaptive robust scheduling of batch manufacturing processes under
    • Authors: Hanyu Shi; Fengqi You
      Abstract: This paper proposes a novel two‐stage adaptive robust optimization approach to production scheduling of batch processes under uncertainty. We first reformulate the deterministic mixed‐integer linear programming (MILP) model of batch scheduling into a two‐stage optimization problem. Symmetric uncertainty sets are then introduced to confine the uncertain parameters, and budgets of uncertainty are used to adjust the degree of conservatism. We then apply both the Benders decomposition algorithm and the column‐and‐constraint generation (C&CG) algorithm to efficiently solve the resulting two‐stage adaptive robust optimization (ARO) problem, which cannot be tackled directly by any existing optimization solvers. Two case studies are considered to demonstrate the applicability of the proposed modeling framework and solution algorithms. The results show that the C&CG algorithm is more computationally efficient than the Benders decomposition algorithm, and the proposed two‐stage ARO approach returns 9% higher profits than the conventional robust optimization approach for batch scheduling. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-08T03:17:53.701665-05:
      DOI: 10.1002/aic.15067
  • Analysis of non‐Brownian particle deposition from turbulent
    • Abstract: We numerically analyse the deposition of non‐Brownian particles from turbulent liquid‐flow onto channel walls. Our approach combines Lagrangian particle tracking with a kinematic model of the near‐wall shear layer. For nonbuoyant particles, direct interception is the main deposition mechanism and the deposition velocity scales as the particle diameter (in wall units) to the power of 1.7. When wall/particle hydrodynamic interactions are taken into account, the deposition velocity is significantly reduced and the correction factor scales as the cubic root of the wall roughness to particle diameter ratio. For buoyant particles, sedimentation is usually the predominant deposition mechanism and the hydrodynamic interactions significantly affect the deposition velocity when the drainage characteristic time driven by buoyancy is of the order of the particle residence time close to the wall. Last, we propose a wall‐function for the suspended particles. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-08T03:17:27.475318-05:
      DOI: 10.1002/aic.15068
  • Membrane assisted cooling crystallization: process model, nucleation,
           metastable zone and crystal size distribution
    • Authors: Xiaobin Jiang; Dapeng Lu, Xiao Wu, Xuehua Ruan, Jian Fang, Gaohong He
      Abstract: The membrane assisted cooling crystallization was proposed and investigated by the simulation and experiments. The developed process model concerned the supersaturation evolution on the membrane interface, the combined nucleation rate in the crystallizer. The impact of different membrane on reducing the nucleation barrier was investigated by introducing the metastable zone width theory. The influence of membrane distillation conditions on the crystal nucleation and growth kinetic was uncovered based on the simulation and experiments results. The experimental results indicated that membrane assisted cooling mode with optimized profiles did improve the crystal size distribution and crystal habit comparing with conventional cooling mode. Terminal C.V. decreased from 55.4 to 33.9 under similar mean crystal growth rate, 2.27 × 10−7 m s−1 (conventional cooling) and 1.98 × 10−7 m s−1 (membrane assisted cooling). Finally, the brief summary on the advantages and key issues of this propose membrane assisted crystallization operation were concluded. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-08T03:16:58.460358-05:
      DOI: 10.1002/aic.15069
  • Toward transformational carbon capture systems
    • Authors: David C. Miller; John T. Litynski, Lynn A. Brickett, Bryan D. Morreale
      PubDate: 2015-10-07T03:28:54.751195-05:
      DOI: 10.1002/aic.15066
  • Prediction of gas–liquid interfacial area in valve trays
    • Authors: Jun Wang; Yixin Leng, Hui Shao, Weiming Li, Chunxiang Huang
      Abstract: An accurate prediction of gas–liquid interfacial area is very important for the design and optimization of column trays. However, the difference of the gas–liquid flow regimes operating at different scale trays significantly affect the interfacial area calculation. Therefore, in this study, an interfacial area model operating at small column was established using the Kolmogorov's isotropic turbulence hypothesis. According to the analyses of the gas–liquid flow phenomena of different scale columns, an assumption that the similarity principle of flow characteristics of gas–liquid in full contact was proposed. Moreover, a new model that can be used to predict the gas–liquid interfacial area of a large column with exiting the non‐ideal flow was obtained through the extension of the small tray interfacial area model based on this principle. Finally, the new model was tested by comparisons with the experimental results of references. The prediction accuracy significantly improved with the maximum deviation of approximately 40%. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-06T03:29:26.20916-05:0
      DOI: 10.1002/aic.15065
  • Calculation of the phase envelope of multicomponent mixtures with the bead
           spring method
    • Authors: Ilias K. Nikolaidis; Georgios C. Boulougouris, Loukas D. Peristeras, Ioannis G. Economou
      Abstract: In this work, we propose a robust numerical scheme for the calculation of constant composition (isoplethic) phase diagrams of complex multicomponent mixtures. The scheme refers to the sequential calculation of the phase envelope of a mixture by guiding the estimation for the equilibrium curve via the introduction of a “spring” that sets the slope value of the modified tangent plane distance with respect to either temperature or pressure. A simple variation of the proposed method allows direct estimation of the Cricondentherm and/or Cricondenbar points, thus avoiding the calculation of the entire phase diagram. We provide extensive tests of the proposed scheme for different types of phase diagrams, using both cubic and higher order equations of state. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-30T19:44:42.432655-05:
      DOI: 10.1002/aic.15064
  • A systematic comparison of PCA‐based statistical process monitoring
           methods for high‐dimensional, time‐dependent processes
    • Authors: Tiago Rato; Eric Schmitt, Bart De Ketelaere, Mia Hubert, Marco Reis
      Abstract: High‐dimensional and time‐dependent data pose significant challenges to Statistical Process Monitoring (SPM). Most of the high‐dimensional methodologies to cope with these challenges rely on some form of Principal Component Analysis (PCA) model, usually classified as non‐adaptive and adaptive. Non‐adaptive methods include the static PCA approach and Dynamic PCA for data with autocorrelation. Methods, such as Dynamic PCA with Decorrelated Residuals, extend Dynamic PCA to further reduce the effects of autocorrelation and cross‐correlation on the monitoring statistics. Recursive PCA and Moving Window PCA, developed for non‐stationary data, are adaptive. These fundamental methods will be systematically compared on high‐dimensional, time‐dependent processes (including the Tennessee Eastman benchmark process) to provide practitioners with guidelines for appropriate monitoring strategies and a sense of how they can be expected to perform. The selection of parameter values for the different methods is also discussed. Finally, the relevant challenges of modeling time‐dependent data are discussed, and areas of possible further research are highlighted. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-30T18:42:10.034627-05:
      DOI: 10.1002/aic.15062
  • Engineering uniform nanocrystals: Mechanism of formation and
           self‐assembly into bimetallic nanocrystal superlattices
    • Abstract: The preparation of metal nanocrystals with precise and tunable size is of great interest for many applications. Following previous reports on the synthesis of monodisperse Ni, Pd and Pt nanocrystals, we here show that the narrow size distributions are the result of an optimized combination of surfactants that play a dynamic, synergistic role in stabilizing the particles at different stages (nucleation, growth) of their preparation. This dynamical process allows the temporal separation of nucleation and growth responsible for the narrow size distributions achievable with this heat‐up method. Finally, the uniform nanocrystals are exploited in the preparation of binary nanocrystals superlattices (BNSLs) entirely based on metal components, with promising applicability in the fields of catalysis, sensing and optics. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-30T18:41:13.903542-05:
      DOI: 10.1002/aic.15063
  • Microstructured Al‐fiber@meso‐Al2O3@Fe‐Mn‐K
           Fischer‐Tropsch Catalyst for Lower Olefins
    • Authors: Lupeng Han; Chunzheng Wang, Guofeng Zhao, Ye Liu, Yong Lu
      Abstract: A thin‐sheet Al‐fiber@meso‐Al2O3@Fe‐Mn‐K catalyst is developed for the mass/heat‐transfer limited Fischer‐Tropsch synthesis to lower olefins (FTO), delivering a high FTY of 206.9 μmolCO gFe−1 s−1 at 90% CO conversion with 40% selectivity to C2‐C4 olefins under optimal reaction conditions (350°C, 4.0 MPa, 10000 mL/(g·h)). A microfibrous structure consisting of 10 vol% 60‐μm Al‐fiber and 90 vol% voidage undergoes a steam‐only‐oxidation and calcination to create 0.6 μm mesoporous γ‐Al2O3 shell along with the Al‐fiber core. Active components of Fe and Mn as well as additives (K, Mg, or Zr) are then placed into the pore surface of γ‐Al2O3 shell of the Al‐fiber@meso‐Al2O3 composite by incipient wetness impregnation method. Neither Mg‐modified nor Zr‐modified structured catalyst yields better FTO results than K‐modified one, because of their lower reducibility, poorer carbonization property and fewer basicity. The favorable heat/mass transfer characteristics of this new approach are also discussed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-30T18:39:05.60909-05:0
      DOI: 10.1002/aic.15061
  • Equation‐oriented optimization of process flowsheets with
           dividing‐wall columns
    • Authors: Richard C. Pattison; Akash M. Gupta, Michael Baldea
      Abstract: We present a new modeling approach for dividing‐wall columns (DWCs) that is amenable to equation‐oriented flowsheet simulation and optimization. The material, equilibrium, summation, and heat (MESH) equations describing a DWC are highly coupled and nonlinear, making DWC‐based process flowsheets challenging to simulate. Design optimization poses further challenges, typically requiring integer variables to select the number of column stages. To address these difficulties, we represent DWCs as networks of pseudo‐transient (differential‐algebraic) sub‐unit models. We show that these networks have the same steady state solution as the original (algebraic) MESH equations, but present significant numerical benefits. We then embed these models in a previously developed pseudo‐transient flowsheet modeling and optimization framework. We further reformulate the models to require only continuous decision variables when selecting the optimal number of stages during design optimization. To illustrate these concepts, we discuss the DWC‐based intensification of the dimethyl ether process. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-30T18:38:25.445688-05:
      DOI: 10.1002/aic.15060
  • A System‐Size Independent Validation of CFD‐DEM for
           Non‐Cohesive Particles
    • Authors: Casey Q. LaMarche; Peiyuan Liu, Kevin M. Kellogg, Alan Weimer, Christine M. Hrenya
      Abstract: For the first time, CFD‐DEM simulations of small‐scale fluidized beds are quantitatively validated against large‐scale experiments. Such validation is possible via the identification of a measurement independent of system size, namely defluidization. CFD‐DEM inputs (particle properties and operating conditions) are measured directly. Sphericity is found to be critical, even for highly‐spherical particles. This size‐independent method of validation is valuable since it allows for validation of CFD‐DEM models without restrictions on system sizes or particle sizes. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-29T09:36:23.304287-05:
      DOI: 10.1002/aic.15057
  • Morphology‐Dependent Electrocatalytic Activity of Nanostructured
           Pt/C Particles from Hybrid Aerosol–Colloid Process
    • Authors: Ratna Balgis; Aditya F. Arif, Takahiro Mori, Takashi Ogi, Kikuo Okuyama, Gopinathan M. Anilkumar
      Abstract: An optimum nanostructure and pore size of catalyst supports is very important in achieving high catalytic performances. In this instance, we evaluated the effects of various carbon nanostructures on the catalytic performances of carbon‐supported platinum (Pt/C) electrocatalysts experimentally and numerically. The Pt/C catalysts were prepared using a hybrid method involving the preparation of dense, hollow, and porous nanostructured carbon particle via aerosol spray pyrolysis followed by microwave‐assisted Pt deposition. Electrochemical characterization of the catalysts showed that the porous Pt/C catalyst gave the best performance; its electrochemical surface area was much higher, more than twice than those of hollow or dense Pt/C. The effects of pore size on electrocatalysis were also studied. The results showed the importance of a balance between meso‐ and macro‐pores for effective catalysis with a high charge transfer rate. A fluid flow model showed that good oxygen transport contributed to the catalytic activity. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-24T18:52:46.434568-05:
      DOI: 10.1002/aic.15059
  • Formation and Stability of String Phase in Polyamide 6/Polystyrene Blends
           in Confined Flow: Effects of Nanoparticles and Blend Ratio
    • Authors: Miqiu Kong; Yajiang Huang, Yadong Lv, Qi Yang, Guangxian Li
      Abstract: Influences of silica nanoparticles on the microstructural evolution of polyamide 6 (PA6)/polystyrene (PS) blends with varying blend ratios was investigated in confined shear flow. Hydrophilic silica nanoparticles were found to promote the formation of PA6 strings with excellent shape stability during shearing. It was ascribed to the promoted coalescence of PA6 droplets induced both by the significantly increased droplet viscoelasticity and confinement, and the reduced interfacial tension by adding silica nanoparticles. Additionally, the width and aspect ratio of droplets obtained by experiments were compared to the predictions of MM, M, SH, MMSH and mM models. Good agreements were found in the droplet width in blends with low nanoparticle concentrations, whereas the experimental aspect ratio showed a negative deviation to model predictions, which was attributed to the enhanced droplet viscoelasticity and the omitted droplet orientation angle in these models. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-24T18:51:22.427122-05:
      DOI: 10.1002/aic.15058
  • Thermal Coupling Links to Liquid‐only Transfer Streams: An
           Enumeration Method for New FTC Dividing Wall Columns
    • Authors: Gautham Madenoor Ramapriya; Mohit Tawarmalani, Rakesh Agrawal
      Abstract: Novel dividing wall columns (DWCs) can be obtained by converting thermal couplings to liquid‐only transfer streams. Here, we develop a simple four‐step method to generate a complete set of DWCs containing n‐2 dividing walls, for a given n‐component fully thermally coupled (FTC) distillation. Among the novel DWCs, some easy‐to‐operate DWCs possess the property that the vapor flow in every section of the DWC can be controlled during operation by means that are external to the column. We develop a simple method to enumerate all such easy‐to‐operate DWCs. We expect that the easy‐to‐operate DWCs can be operated close‐to‐optimality; leading to a successful industrial implementation of the n‐component (n≥3) FTC distillation in the form of a DWC. As an illustration, we show figures of all easy‐to‐operate DWCs with two dividing walls for the four‐component FTC distillation. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-24T12:26:21.956674-05:
      DOI: 10.1002/aic.15053
  • The role of microexplosions in flame spray synthesis for homogeneous
           nanopowders from low‐cost metal precursors
    • Abstract: One of the most versatile and rapid manufacturing processes for a variety of nanopowders is flame‐spray‐pyrolysis (FSP). The production costs of this scalable process are largely controlled by the raw materials, pushing for the utilization of low‐cost metal precursors. These, however, typically yield inhomogeneous products containing large particles up to micrometer size along with fine nanoparticles. Here we investigate the release mechanism of nitrate and carboxylate precursors from spray droplets by single droplet combustion experiments and thermogravimetric analysis. The results show that neither precursor evaporation nor choice of solvents are prerequisites for homogeneous nanopowders but droplet microexplosions with continuing combustion. It is shown that even low‐cost metal nitrates yield homogeneous nanopowders if precursors are formulated such that droplet microexplosions occur by internal superheating. The proposed precursor release mechanisms are verified with lab‐ and pilot‐scale FSP, demonstrating that single droplet combustion experiments can be employed to predict the product quality. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-19T10:47:47.176765-05:
      DOI: 10.1002/aic.15056
  • Process Fault Detection Using Time‐Explicit Kiviat Diagrams
    • Authors: Ray Wang; Thomas F. Edgara, Michael Baldeaa, Mark Nixon, Willy Wojsznis, Ricardo Dunia
      Abstract: Significant amounts of data are collected and stored during chemical process operations. The corresponding data sets are typically difficult to represent and analyze using traditional visualization methods. This paper introduces time‐explicit Kiviat diagrams as means to visualize the multi‐dimensional time series data acquired from plant operations. We then use this framework to build multivariate control charts for large scale time series data sets, and to develop a fault detection mechanism that lends itself to real‐time implementation. The proposed methodology is applied to an industrial case study as well as to data obtained from the Tennessee Eastman process simulator, showing very good performance. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-18T18:38:24.679205-05:
      DOI: 10.1002/aic.15054
  • Development of a Hybrid Shrinking‐Core Shrinking‐Particle
           Model for Entrained‐Flow Gasifiers
    • Authors: Pratik Pednekar; Debangsu Bhattacharyya, Job S. Kasule, Richard Turton, Raghunathan Rengaswamy
      Abstract: The slagging entrained‐flow gasifiers operate above the melting temperature of the ash. Since slag is highly non‐wetting on the surface of char (carbon) particles, it is likely that it will agglomerate into one or several slag droplets and some of these droplets can detach from the char particles. If the slag exists in the form of droplets on the char surface rather than as a solid shell around the unreacted char particle, a shrinking particle model (SPM) would be more physically realistic representation in comparison to the widely‐used shrinking core model (SCM). In the early section of the gasifier, the temperature remains below the ash melting temperature and therefore, the SCM is more appropriate in this region. With this motivation, a novel hybrid shrinking‐core shrinking‐particle (HSCSP) model has been developed. The model provides spatial profile of a number of important variables that are not available from the traditional SCM. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-18T18:37:43.015802-05:
      DOI: 10.1002/aic.15055
  • CFD‐DEM Modelling of Gas Fluidization of Fine Ellipsoidal Particles
    • Authors: J.Q. Gan; Z.Y. Zhou, A.B. Yu
      Abstract: Particle characteristics are important factors affecting gas fluidization. In this work, the effects of both particle size and shape on fluidization in different flow regimes are studied using the combined CFD‐DEM approach. The results are first analysed in terms of flow patterns and fluidization parameters such as pressure drop, minimum fluidization and bubbling velocities. The results show that with particle size decreasing, agglomerates can be formed for fine ellipsoidal particles. In particular, “chain phenomenon”, a special agglomerate, exists in expanded and fluidized beds for fine prolate particles, which is caused by the van der Waals force. The minimum fluidization velocity increases exponentially with the increase of particle size, and for a given size, it shows a “W” shape with aspect ratio. A correlation is established to describe the dependence of minimum fluidization velocity on particle size and shape. Ellipsoids have much higher minimum bubbling velocities and fluidization index than spheres. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-17T17:42:53.0607-05:00
      DOI: 10.1002/aic.15050
  • Quantitative Assessment of Fine‐Grid
           Kinetic‐Theory‐Based Predictions of Mean‐Slip in
           Unbounded Fluidization
    • Authors: W.D. Fullmer; C.M. Hrenya
      Abstract: The quantitative ability of a kinetic‐theory‐based, two‐fluid model is demonstrated in a clustering (unstable) gas‐solid system via highly‐resolved simulations. Unlike previous works, this assessment is validated against ideal CFD‐DEM data to minimize sources of discrepancy. Overall, good agreement in mean slip velocities is observed with relative errors less than 20% over a mean solids concentration range of 0.02–0.25. Local concentration gradient distributions are also studied, showing a distinct shift towards higher gradients at higher mean solids concentrations which is proposed as the bottleneck in obtaining grid‐independence rather than the cluster length scale. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-17T17:42:14.058854-05:
      DOI: 10.1002/aic.15052
  • Analysis of particle cloud height dynamics in a stirred tank
    • Authors: Matthias Eng; Rasmus Jonsson, Anders Rasmuson
      Abstract: Local and temporal variations of the particle cloud formed in a cylindrical mixing vessel were investigated experimentally. Different particle sizes (0.5mm, 1mm, 2mm) and volumetric concentration up to 20%vol were evaluated at different impeller speeds. The time‐averaged cloud height was linear with impeller frequency and with volume concentration. Suspensions with larger particles had a lower average cloud height, while the standard deviation for the temporal cloud height variation was larger. Two strong periodic phenomena were identified to be dominating the particle cloud height variations. The frequencies were linear with impeller speed, resulting in dimensionless frequencies of S1=0.02 – 0.03 and S2=0.05 – 0.06. The frequencies were affected by neither the particle size, nor the volumetric concentration. The amplitude showed no dependency on the particle size, but the S2 amplitude significantly decreases and S1 increases with increasing solid concentration. The results were compared to LES/DEM simulations and showed a fair agreement. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-17T17:41:39.352336-05:
      DOI: 10.1002/aic.15051
  • Novel graphical tool for the design of the heat integrated water
           allocation networks
    • Authors: Zuwei liao; Xiaodong Hong, Binbo Jiang, Jingdai Wang, Yongrong Yang
      Abstract: A new graphical tool has been developed for the HEN design of WAHEN. An ΔH‐F diagram is proposed to deal with the heat exchange matches. Non‐isothermal stream mixing and splitting can be achieved by the transformation of stream composite curve in the ΔH‐F diagram. A matching composite curve is proposed for the design of HEN with parallel structure. The structure of HEN can be simplified by adjusting the shape of the matching composite curve. Both small scale and large scale examples are illustrated. Results show that the proposed method is as good as the previous methods for small scale problem, while it gets a better result for large scale problem. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-16T11:21:45.399841-05:
      DOI: 10.1002/aic.15049
  • In Situ Metal Doping during Modified Anodization Synthesis of Nb2O5 with
           Enhanced Photoelectrochemical Water Splitting
    • Authors: Chenyan Hu; Wey Yang Teoh, Shulin Ji, Changhui Ye, Akihide Iwase
      Abstract: A new technique of in situ doping of alkali metal (Li+, Na+, K+, Rb+, and Cs+) in Nb2O5 was showcased by the modified anodization of Nb foils at high frequency, negative‐to‐positive pulsed voltage. At the optimized dopant concentration and synthesis condition, the doped‐Nb2O5 shows 2‐fold enhancement in photoelectrochemical water splitting efficiencies compared to the undoped Nb2O5 electrode, as a result of improved charge carrier density and enhanced surface charge transfer. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-16T11:05:37.49991-05:0
      DOI: 10.1002/aic.15048
  • Long‐term testing of a high temperature polymer electrolyte membrane
           fuel cell: The effect of reactant gases
    • Authors: F. Javier Pinar; Nadine Pilinski, Peter Wagner
      Abstract: The investigations have been conducted with different oxidants and fuels with the aim of determining the state‐of‐the‐art of commercially available HT‐PEMFC based on PBI for its application in CHP systems. The fuel cell test carried out with synthetic reformate (‐63 μV/h) showed an increase of anode charge and mass transfer resistances. This behaviour has suggested that CO may be generated from the CO2 included in the synthetic reformate via reverse water gas shift reaction. The fuel cell test carried out with pure O2 developed the highest degradation rates (‐70 μV/h) due to fast oxidative degradation of MEA materials such as cathode catalyst and membrane. Fuel cell operation with H2/air exhibited the lowest degradation rates (‐57 μV/h) and it requires longer investigating times to identify the different degradation mechanisms. Moreover, fuel cell tests carried out with air suggested longer break‐in procedures to complete catalyst activation and redistribution of electrolyte. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-15T16:25:02.126177-05:
      DOI: 10.1002/aic.15044
  • On the length to diameter ratio of extrudates in catalyst technology I.
           modeling catalyst breakage by impulsive forces
    • Authors: Jean W. L. Beeckman; Natalie A. Fassbender, Theodore E. Datz
      Abstract: Natural or forced catalyst extrudate breakage is an important phenomenon during catalyst manufacture. Here we develop a two parameter model for predicting the reduction in the length to diameter ratio of catalyst extrudates due to breakage by impulsive forces as experienced in a laboratory drop test. In Part II we will show that both parameters can be correlated with the strength of the extrudates and the severity of the drop test. For breakage by impulsive forces, the model reveals that extrudates are reduced in length to diameter ratio according to a pseudo‐second order break law. Also, a tie‐in exists with the well‐known Golden Ratio that is famous for its inherent esthetic value. Applying the model to cases of “severity sequencing” and “severity conditioning” reveals the non‐linear behavior of the length to diameter ratio and yields results that are often non‐intuitive and hard to get without this engineering analysis. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-15T16:23:40.698545-05:
      DOI: 10.1002/aic.15046
  • Dispersion of feed spray in a new type of FCC feed injection scheme
    • Authors: Zihan Yan; Yiping Fan, Zhao Wang, Sheng Chen, Chunxi Lu
      Abstract: A new type of FCC feed injection scheme in which the feed is injected downwards into the riser to realize a countercurrent contact of feed oil with catalyst particles is put forward. The dispersion of feed spray and flow behaviors of particles in the new type of feed injection scheme are investigated via a large scale cold‐riser model. Experimental results show that the proposed scheme provides a better contact of feed oil with catalyst particles. Furthermore, the centerline equations of both the feed main flow and the secondary flow in the riser are given by introducing a density correction coefficient. The momentum‐ratio of the secondary flow to the main flow is then obtained and the trajectory of the feed main jets as well as the secondary flow is estimated by the centerline equation. The computed results give a reasonable agreement with the experimental data. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-15T16:23:07.545803-05:
      DOI: 10.1002/aic.15047
  • Stereo Imaging of Crystal Growth
    • Authors: Cai Y. Ma; Jing J. Liu, Xue Z. Wang
      Abstract: A methodology that directly images the full three‐dimensional shape of crystals within a crystalliser is reported. It is based on the mathematical principle that if the two‐dimensional images of an object are obtained from two or more different angles, the full three‐dimensional crystal shape could be reconstructed. A prototype instrument is built and proof of concept study carried out to demonstrate the potentials in using the system for three‐dimensional measurement of crystal shape and shape distribution. It is our belief that 3D measurement of crystal shape represents a significant step forward from existing work of 2D measurement of crystal morphology and is potentially of great significance to research towards closed‐loop control of crystal morphology. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-11T18:27:32.720601-05:
      DOI: 10.1002/aic.15041
  • A Novel Framework for Integrating Data Mining with Control Loop
           Performance Assessment
    • Authors: Laya Das; Babji Srinivasan, Raghunathan Rengaswamy
      Abstract: Data driven control loop performance assessment techniques assume that the data being analysed correspond to single plant‐controller configuration. However in an industrial setting where processes are affected due to the presence of feedstock variability and drifts, the plant‐controller configuration changes with time. Also, user‐defined benchmarking of control loops (common in industrial plants) requires that the data corresponding to optimal operation of the controller be known. However such information might not be available beforehand in which case it is necessary to extract the same from routine plant operating data. We propose a technique that addresses these fundamental requirements for ensuring reliable performance assessment. The proposed technique performs a recursive binary segmentation of the data and makes use of the fact that changes in controller settings translate to variations in plant output for identifying regions corresponding to single plant‐controller configurations. The statistical properties of the data in each such window are then compared with the theoretically expected behaviour to extract the data corresponding to optimal configuration. This approach has been applied on: (i) raw plant output (ii) Hurst exponent and (iii) minimum variance index of the process data. Simulation examples demonstrate the applicability of proposed approach in industrial settings. A comparison of the three routes is provided with regard to the amount of data needed and the efficacy achieved. Key results are emphasised and a framework for applying this technique is described. This tool is of significance to industries interested in an automated analysis of large scale control loop data for multiple process variables that is otherwise left un‐utilised. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-11T18:26:22.71426-05:0
      DOI: 10.1002/aic.15042
  • Breakup Dynamics for High‐viscosity Droplet Formation in a
           Flow‐Focusing Device: Symmetrical and Asymmetrical Ruptures
    • Authors: Wei Du; Taotao Fu, Chunying Zhu, Youguang Ma, Huai Z. Li
      Abstract: The breakup mechanism of high‐viscosity thread for droplet formation in a flow‐focusing device is investigated using a high‐speed digital camera. Aqueous solution of 89.5%‐glycerol is used as the dispersed phase, while silicone oil as the continuous phase. The breakup process of the dispersed thread presents two categories: symmetrical rupture and asymmetrical rupture. Furthermore, the rupture behavior could be divided into two stages: the squeezing stage controlled by the squeezing pressure and the pinch‐off stage controlled by viscous stresses of both phases and surface tension. Specifically, it suggests that the differences in the shape of the liquid‐liquid interface and the dynamics in the two breakup processes are caused by the disparity of the strain field at the point of detachment. Moreover, the thinning rate and the dynamics of the dispersed thread change with the viscosity of the continuous phase, but are less dependent of the flow rate of the continuous phase. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-11T18:25:20.920618-05:
      DOI: 10.1002/aic.15043
  • Optimal Flowsheet Configuration of a Polymerization Process with Embedded
           Molecular Weight Distributions
    • Authors: Chen Zhang; Zhijiang Shao, Xi Chen, Xueping Gu, Lianfang Feng, Lorenz T. Biegler
      Abstract: We consider the optimal reactor network synthesis of a polymerization process with detailed molecular weight distributions (MWDs). Based on an industrial high‐density polyethylene (HDPE) slurry process model including an embedded MWD, a fully connected process superstructure of continuous stirred tank reactors (CSTRs) is established through the introduction of splitters. Using this generalized superstructure as a basis, two nonlinear programming (NLP) problem formulations, which simultaneously maximize the monomer conversion and minimize the deviation between the calculated and target MWDs, are developed by applying multiobjective optimization (MO) methods. Different optimal flowsheet configurations are generated by systematically manipulating a set of continuous decision variables. Several case studies that consider different specifications on MWD are conducted to illustrate the effectiveness and efficiency of the proposed synthesis approach. Numerical results show that the optimal flowsheet configurations overcome the limitations of conventional reactor network structures and help to increase reactor productivity at the desired product quality. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-11T18:07:20.954002-05:
      DOI: 10.1002/aic.15040
  • Sustainability Decision Support Framework for Industrial System
    • Authors: Jingzheng Ren; Di Xu, Huan Cao, Shun'an Wei, Michael Evan Goodsite, Lichun Dong
      Abstract: This study proposed a multi‐criteria decision making methodology for the sustainability prioritization of industrial systems. The methodology incorporates a fuzzy Analytic Hierarchy Process method that allows the users to assess the soft criteria by using linguistic terms. A fuzzy Analytic Network Process method is used to calculate the weights of each criterion, which can tackle the interdependencies and interactions among the criteria. The Preference Ranking Organization Method for Enrichment Evaluation approach is used to prioritize the sustainability sequence of the alternative systems. Moreover, a sensitivity analysis method was developed to investigate the most critical and sensitive criteria. The developed methodology was illustrated by a case study to rank the sustainability of five alternative hydrogen production technologies. The advantages of the developed methodology over the previous approaches were demonstrated by comparing the results determined by the proposed framework with those determined by using the pervious approaches. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-09T17:49:53.722672-05:
      DOI: 10.1002/aic.15039
  • A new insight to validation of local composition models in binary mixtures
           using molecular dynamic simulation
    • Authors: Ali Haghtalab; Jaber Yousefi Seyf
      Abstract: A computational method based on molecular dynamics (MD) simulation is developed to predict the interaction parameters in local composition (LC) models such as Wilson, NRTL, and UNIQUAC applicable in vapor liquid equilibrium calculations so that LC models are validated. The five binary mixtures of water‐acetonitrile, water‐isopropanol, methanol‐chloroform, acetone‐cyclohexane, and meta xylene‐benzene were simulated. The MD simulations are carried out using the COMPASS force field and all ranges of radial distribution function (RDF) are considered. In addition, the interaction parameters are determined by optimization through experimental data and are compared with the MD results. The interaction parameters are calculated through RDF where the effective radius is investigated by experimental data. The present results demonstrate that interaction parameters are composition dependent which are best fitted by a third‐order polynomial relation. Based on the deviation in the activity coefficients, the results of the UNIQUAC model are more accurate than Wilson and NRTL models. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-09T17:48:59.087977-05:
      DOI: 10.1002/aic.15038
  • A new dynamic model of crude oil fouling deposits and its application to
           the simulation of fouling‐cleaning cycles
    • Abstract: Modelling of crude oil fouling in heat exchangers has been traditionally limited to a description of the deposit as a thermal resistance. However, consideration of the local change in thickness and the evolution of the properties of the deposit due to ageing or changes in foulant composition is important to capture the thermal and hydraulic impact of fouling. A dynamic, distributed, first‐principles model of the deposit is presented that considers it as a multi‐component varying‐thickness solid undergoing multiple reactions. For the first time, full cleaning, partial cleaning and fouling resumption after cleaning can be simulated in any order with a single deposit model. The new model, implemented within a single tube framework, is demonstrated in a case study where various cleaning actions are applied following a period of organic deposition. It is shown that complete mechanical cleaning and chemical cleaning of different extent, according to a condition‐based efficacy, can be seamlessly simulated. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-09T17:47:27.379576-05:
      DOI: 10.1002/aic.15036
  • Kinetic modeling strategy for an exothermic multiphase reactor system:
           application to vegetable oils epoxidation by using Prileschajew method
    • Abstract: Epoxidation of cottonseed oil by peroxyformic acid (PFA) was studied in a semi‐batch calorimeter. This liquid‐liquid reaction system is composed of different exothermic steps. Thus, a kinetic modeling strategy to diminish the number of parameters to estimate was developed by investigating each reaction system: PFA synthesis and decomposition, ring‐opening and epoxidation. A thermal study was conducted by determining heat capacity of the different organic species, and by analyzing the evolution of global heat transfer coefficient with the reaction extent. The epoxidation reaction was performed in a semi‐batch reactor under isoperibolic mode within an initial temperature range of 50‐70°C, an organic phase of 30‐34 wt.%, a formic acid molar flow rate of 0.02‐0.05 mol/min and an addition time of 25‐50 min. The interfacial mass transfer was supposed to be faster than the intrinsic reaction kinetics suppressing the use of mass transfer correlation. Non‐linear regression was used to estimate the kinetic and thermal parameters. The kinetic parameters of epoxidation of the three different fatty acids, namely oleic, linoleic and its intermediate were estimated. The reaction enthalpy of epoxidation was estimated to ‐230 ± 3.8 kJ/mol, and the reaction enthalpy of ring‐opening was measured to be ‐90 kJ/mol by Tian‐Calvet calorimeter. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-09T17:47:24.080801-05:
      DOI: 10.1002/aic.15037
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • Radial pressure profiles in a cold‐flow Gas‐Solid Vortex
    • 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
  • 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
  • A breakage and adhesion regime map for the normal impact of loose
           agglomerates with a spherical target
    • Pages: 4059 - 4068
      Abstract: Discrete element method‐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, kinetic energy, and the agglomerate structure after the impact, which resulted in a new dimensionless number, the ratio of the two interface energies. In combination with Δ, a dimensionless number relating incident kinetic energy to agglomerate strength (Moreno‐Atanasio and Ghadiri M, Chem Eng Sci. 2006;61(8):2476–2481), 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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4059–4068, 2015
      PubDate: 2015-07-16T07:54:38.807386-05:
      DOI: 10.1002/aic.14922
  • Density segregation of dry and wet granular mixtures in gas fluidized beds
    • Authors: Stella Lin Li Seah; Eldin Wee Chuan Lim
      Pages: 4069 - 4086
      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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4069–4086, 2015
      PubDate: 2015-08-01T19:21:32.446881-05:
      DOI: 10.1002/aic.14959
  • 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
      Pages: 4087 - 4101
      Abstract: Gas‐solid hydrodynamics in a three‐dimensional slot‐rectangular double‐spouted bed was numerically investigated by a combined approach of discrete element method and computational fluid dynamics, 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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4087–4101, 2015
      PubDate: 2015-08-04T16:35:51.955634-05:
      DOI: 10.1002/aic.14973
  • 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
      Pages: 4102 - 4113
      Abstract: As electrical capacitance tomography 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 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 was 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 were observed. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4102–4113, 2015
      PubDate: 2015-08-11T00:18:22.572034-05:
      DOI: 10.1002/aic.14976
  • Probabilistic slow feature analysis‐based representation learning
           from massive process data for soft sensor modeling
    • Authors: Chao Shang; Biao Huang, Fan Yang, Dexian Huang
      Pages: 4126 - 4139
      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 (SFs) as temporally correlated LVs are derived using probabilistic SF analysis. SFs 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 expectation maximum 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 SFs. The validity and advantages of the proposed method are demonstrated via two case studies. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4126–4139, 2015
      PubDate: 2015-07-18T23:28:06.286491-05:
      DOI: 10.1002/aic.14937
  • An effective rate approach to modeling single‐stage spray drying
    • Authors: Oluwafemi Ayodele George; Xiao Dong Chen, Jie Xiao, Mengwai Woo, Liming Che
      Pages: 4140 - 4151
      Abstract: An effective rate approach (ERA) is proposed 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 on the experimental results from running a monodisperse droplet spray dryer, that is, 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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4140–4151, 2015
      PubDate: 2015-07-18T23:27:22.992776-05:
      DOI: 10.1002/aic.14940
  • Economic model predictive control of nonlinear time‐delay systems:
           Closed‐loop stability and delay compensation
    • Authors: Matthew Ellis; Panagiotis D. Christofides
      Pages: 4152 - 4165
      Abstract: Closed‐loop stability of nonlinear time‐delay systems under Lyapunov‐based economic model predictive control (LEMPC) is considered. LEMPC is initially 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 consider the stability properties of the sampled‐data system resulting from the nonlinear continuous‐time delay system with state and input delay under a sample‐and‐hold implementation of the explicit controller. The steady‐state of this sampled‐data closed‐loop system is shown to be 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 equation (DDE) model, which describes the time‐delay system, initialized with the predicted state. The predictor feedback LEMPC is also applied to the chemical process example and yields improved closed‐loop stability and economic performance properties. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4152–4165, 2015
      PubDate: 2015-08-03T13:07:17.466208-05:
      DOI: 10.1002/aic.14964
  • Flexibility assessment and risk management in supply chains
    • Authors: Nihar Sahay; Marianthi Ierapetritou
      Pages: 4166 - 4178
      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. 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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4166–4178, 2015
      PubDate: 2015-08-06T14:37:22.285667-05:
      DOI: 10.1002/aic.14971
  • Integrated production scheduling and model predictive control of
           continuous processes
    • Authors: Michael Baldea; Juan Du, Jungup Park, Iiro Harjunkoski
      Pages: 4179 - 4190
      Abstract: The integration of production management and process control decisions is critical for improving economic performance of the chemical supply chain. A novel framework for integrating production scheduling and model predictive control (MPC) for continuous processes is proposed. 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, a novel scheduling‐oriented MPC concept is proposed, 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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4179–4190, 2015
      PubDate: 2015-08-12T21:32:03.324595-05:
      DOI: 10.1002/aic.14951
  • A novel adaptive surrogate modeling‐based algorithm for simultaneous
           optimization of sequential batch process scheduling and dynamic operations
    • Authors: Hanyu Shi; Fengqi You
      Pages: 4191 - 4209
      Abstract: A novel adaptive surrogate modeling‐based algorithm is proposed 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. To overcome the computational challenge of solving the integrated MINLP problem, an efficient solution algorithm based on the bilevel structure of the integrated problem is proposed. 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 the proposed method is demonstrated through the optimization of a multiproduct 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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4191–4209, 2015
      PubDate: 2015-08-12T21:43:58.618227-05:
      DOI: 10.1002/aic.14974
  • Using short‐term resource scheduling for assessing effectiveness of
           CCS within electricity generation subsector
    • Authors: Colin Alie; Ali Elkamel, Eric Croiset, Peter L. Douglas
      Pages: 4210 - 4234
      Abstract: A new methodology for assessing the effectiveness of carbon capture and storage (CCS) that does explicitly consider the detailed operation of the target electricity system is proposed. 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 mixed‐integer nonlinear programming problem and implemented in general algebraic modelling system (GAMS). 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 greenhouse gas (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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4210–4234, 2015
      PubDate: 2015-08-17T22:47:09.965746-05:
      DOI: 10.1002/aic.14975
  • Dynamic modeling and validation of a biomass hydrothermal pretreatment
           process—a demonstration scale study
    • Pages: 4235 - 4250
      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°C 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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4235–4250, 2015
      PubDate: 2015-08-19T16:16:48.040747-05:
      DOI: 10.1002/aic.14954
  • Modeling and analysis of conventional and heat‐integrated
           distillation columns
    • Pages: 4251 - 4263
      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 heat‐integrated distillation column (HIDiC) schemes and the mechanical vapor recompression column. The second case study exemplifies the difference between a HIDiC and a conventional distillation column 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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4251–4263, 2015
      PubDate: 2015-08-22T14:27:13.496007-05:
      DOI: 10.1002/aic.14970
  • Effect of interfacial mass transfer on the dispersion in segmented flow in
           straight capillaries
    • Authors: Jaydeep B. Deshpande; Amol A. Kulkarni
      Pages: 4294 - 4308
      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 first‐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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4294–4308, 2015
      PubDate: 2015-07-16T07:58:00.670394-05:
      DOI: 10.1002/aic.14945
  • Microkinetic model for the pyrolysis of methyl esters: From model compound
           to industrial biodiesel
    • Pages: 4309 - 4322
      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 pseudosteady‐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 1100 K 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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4309–4322, 2015
      PubDate: 2015-07-24T11:57:55.032218-05:
      DOI: 10.1002/aic.14953
  • Ni‐Al2O3/Ni‐foam catalyst with enhanced heat transfer for
           hydrogenation of CO2 to methane
    • Authors: Yakun Li; Qiaofei Zhang, Ruijuan Chai, Guofeng Zhao, Ye Liu, Yong Lu, Fahai Cao
      Pages: 4323 - 4331
      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 scanning electron microscopy, inductively coupled plasma atomic emission spectrometry, and H2‐temperature programmed reduction‐mass spectrometry. 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°C and 0.1 MPa with a gas hourly space velocity of 5000 h−1, throughout entire 1200 h test over 10.2 mL such monolithic catalysts. Computational fluid dynamics calculation and experimental measurement consistently confirm a dramatic reduction of “hotspot” temperature due to enhanced heat transfer. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4323–4331, 2015
      PubDate: 2015-07-26T17:51:55.596179-05:
      DOI: 10.1002/aic.14935
  • Ockham's razor for paring microkinetic mechanisms: Electrical analogy vs.
           Campbell's degree of rate control
    • Authors: Patrick D. O'Malley; Ravindra Datta, Saurabh A. Vilekar
      Pages: 4332 - 4346
      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,” that is, 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 reaction on Pt–Re catalyst published recently. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4332–4346, 2015
      PubDate: 2015-08-01T19:08:22.339023-05:
      DOI: 10.1002/aic.14956
  • Kinetic insight into electrochemically mediated ATRP gained through
    • Pages: 4347 - 4357
      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 is more, the normal ATRP, photo‐ATRP, and eATRP were compared to obtain a deeper understanding of these ATRP systems. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4347–4357, 2015
      PubDate: 2015-08-08T10:46:23.269973-05:
      DOI: 10.1002/aic.14969
  • 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
      Pages: 4377 - 4386
      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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4377–4386, 2015
      PubDate: 2015-07-26T18:01:58.605491-05:
      DOI: 10.1002/aic.14906
  • Impact of the fluid flow conditions on the formation rate of carbon
           dioxide hydrates in a semi‐batch stirred tank reactor
    • Pages: 4387 - 4401
      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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4387–4401, 2015
      PubDate: 2015-07-26T17:32:29.065806-05:
      DOI: 10.1002/aic.14952
  • Scaling inline static mixers for flocculation of oil sand mature fine
    • Authors: Alebachew Demoz
      Pages: 4402 - 4411
      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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4402–4411, 2015
      PubDate: 2015-07-27T13:36:02.865448-05:
      DOI: 10.1002/aic.14958
  • Effect of ship tilting and motion on amine absorber with
           structured‐packing for CO2 removal from natural gas
    • Pages: 4412 - 4425
      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 12 s period, respectively. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4412–4425, 2015
      PubDate: 2015-08-01T19:32:07.287028-05:
      DOI: 10.1002/aic.14962
  • Nanocolloid cake properties determined from step‐up pressure
           filtration with single‐stage reduction in filtration area
    • Pages: 4426 - 4436
      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 nanosilica 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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4426–4436, 2015
      PubDate: 2015-08-01T19:19:20.381418-05:
      DOI: 10.1002/aic.14967
  • Mass‐transfer rate enhancement for CO2 separation by ionic liquids:
           Theoretical study on the mechanism
    • Authors: Wenlong Xie; Xiaoyan Ji, Xin Feng, Xiaohua Lu
      Pages: 4437 - 4444
      Abstract: To promote the development of ionic liquid (IL) immobilized sorbents and supported IL membranes (SILMs) for CO2 separation, the kinetics of CO2 absorption/desorption in IL immobilized sorbents was studied using a novel method based on nonequilibrium thermodynamics. It shows that the apparent chemical‐potential‐based mass‐transfer coefficients of CO2 were in three regions with three‐order difference in magnitude for the IL‐film thicknesses in microscale, 100 nm‐scale, and 10 nm‐scale. Using a diffusion‐reaction theory, it is found that by tailoring the IL‐film thickness from microscale to nanoscale, 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 nanoscale IL‐films, which makes it feasible to implement CO2 separation by ILs with low investment cost. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4437–4444, 2015
      PubDate: 2015-08-19T16:15:24.842646-05:
      DOI: 10.1002/aic.14932
  • Drop printing of pharmaceuticals: Effect of molecular weight on PEG
           coated‐naproxen/PEG 3350 solid dispersions
    • Pages: 4502 - 4508
      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. DP was used to prepare naproxen (NAP)/polyethylene glycol 3350 (PEG 3350) solid dispersions with PEG coatings of different molecular weights (MWs). A comparison of moisture‐accelerated crystallization inhibition by different PEG coatings was assessed. Scanning electron microscopy, second harmonic generation microscopy, and differential scanning calorimetry analysis were performed to characterize the morphology and quantify the apparent crystallinity of NAP within the solid dispersions. Thermogravimetric analysis 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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4502–4508, 2015
      PubDate: 2015-08-14T14:49:11.481972-05:
      DOI: 10.1002/aic.14979
  • Mechanism and analytical models for the gas distribution on the SiC foam
           monolithic tray
    • Authors: Hong Li; Long Fu, Xingang Li, Xin Gao
      Pages: 4509 - 4516
      Abstract: Silicon carbide (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 holdup 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 holdup. 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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4509–4516, 2015
      PubDate: 2015-07-18T23:28:36.043091-05:
      DOI: 10.1002/aic.14944
  • Hybrid mixture theory based modeling of transport mechanisms and
           expansion‐thermomechanics of starch during extrusion
    • Authors: Srivikorn Ditudompo; Pawan S. Takhar
      Pages: 4517 - 4532
      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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4517–4532, 2015
      PubDate: 2015-07-22T09:18:19.202004-05:
      DOI: 10.1002/aic.14936
  • Depletion of cross‐stream diffusion in the presence of
    • Authors: Arman Sadeghi
      Pages: 4533 - 4541
      Abstract: An effort to analyze the viscoelasticity effects on transverse transport of neutral solutes between two miscible streams in an electrokinetic T‐sensor is presented. 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 one‐dimensional 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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4533–4541, 2015
      PubDate: 2015-08-03T13:07:42.040123-05:
      DOI: 10.1002/aic.14955
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