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  Subjects -> ENGINEERING (Total: 2160 journals)
    - CHEMICAL ENGINEERING (186 journals)
    - CIVIL ENGINEERING (168 journals)
    - ELECTRICAL ENGINEERING (93 journals)
    - ENGINEERING (1165 journals)
    - ENGINEERING MECHANICS AND MATERIALS (355 journals)
    - HYDRAULIC ENGINEERING (55 journals)
    - INDUSTRIAL ENGINEERING (57 journals)
    - MECHANICAL ENGINEERING (81 journals)

ENGINEERING (1165 journals)            First | 1 2 3 4 5 6 7 8 | Last

BER : Survey of Business Conditions in Retail : An Executive Summary     Full-text available via subscription   (Followers: 3)
Bharatiya Vaigyanik evam Audyogik Anusandhan Patrika (BVAAP)     Open Access  
Biointerphases     Open Access  
Biomaterials Science     Full-text available via subscription   (Followers: 4)
Biomedical Engineering     Hybrid Journal   (Followers: 10)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 13)
Biomedical Engineering Letters     Hybrid Journal   (Followers: 5)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 16)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 15)
Biomedical Engineering: Applications, Basis and Communications     Hybrid Journal   (Followers: 5)
Biomedical Microdevices     Hybrid Journal   (Followers: 7)
Biomedical Science and Engineering     Open Access   (Followers: 1)
Biomedizinische Technik - Biomedical Engineering     Hybrid Journal  
Biomicrofluidics     Open Access   (Followers: 3)
BioNanoMaterials     Hybrid Journal   (Followers: 1)
Biotechnology Progress     Hybrid Journal   (Followers: 21)
Boletin Cientifico Tecnico INIMET     Open Access  
Botswana Journal of Technology     Full-text available via subscription  
Boundary Value Problems     Open Access   (Followers: 1)
Brazilian Journal of Science and Technology     Open Access  
Broadcasting, IEEE Transactions on     Hybrid Journal   (Followers: 5)
Bubble Science, Engineering & Technology     Hybrid Journal   (Followers: 1)
Bulletin of Canadian Petroleum Geology     Full-text available via subscription   (Followers: 1)
Bulletin of Engineering Geology and the Environment     Hybrid Journal   (Followers: 3)
Bulletin of the Crimean Astrophysical Observatory     Hybrid Journal  
Calphad     Hybrid Journal  
Canadian Geotechnical Journal     Full-text available via subscription   (Followers: 15)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 13)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 4)
Case Studies in Thermal Engineering     Open Access   (Followers: 1)
Catalysis Communications     Hybrid Journal   (Followers: 5)
Catalysis Letters     Hybrid Journal   (Followers: 2)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 7)
Catalysis Science and Technology     Free   (Followers: 5)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 4)
Catalysis Today     Hybrid Journal   (Followers: 6)
CEAS Space Journal     Hybrid Journal   (Followers: 1)
Cellular and Molecular Neurobiology     Hybrid Journal   (Followers: 2)
Central European Journal of Engineering     Hybrid Journal   (Followers: 1)
CFD Letters     Open Access   (Followers: 2)
Chaos : An Interdisciplinary Journal of Nonlinear Science     Hybrid Journal   (Followers: 1)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 1)
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 1)
Chinese Journal of Engineering     Open Access  
Chinese Science Bulletin     Open Access  
Ciencia e Ingenieria Neogranadina     Open Access  
Ciencia en su PC     Open Access  
Ciencias Holguin     Open Access  
Cientifica     Open Access  
CIRP Annals - Manufacturing Technology     Full-text available via subscription   (Followers: 10)
CIRP Journal of Manufacturing Science and Technology     Full-text available via subscription   (Followers: 9)
City, Culture and Society     Hybrid Journal   (Followers: 20)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Clean Air Journal     Full-text available via subscription   (Followers: 2)
Clinical Science     Full-text available via subscription   (Followers: 8)
Coal Science and Technology     Full-text available via subscription   (Followers: 4)
Coastal Engineering     Hybrid Journal   (Followers: 8)
Coastal Engineering Journal     Hybrid Journal   (Followers: 2)
Coatings     Open Access   (Followers: 2)
Cogent Engineering     Open Access   (Followers: 1)
Cognitive Computation     Hybrid Journal   (Followers: 3)
Color Research & Application     Hybrid Journal   (Followers: 1)
COMBINATORICA     Hybrid Journal  
Combustion Theory and Modelling     Hybrid Journal   (Followers: 5)
Combustion, Explosion, and Shock Waves     Hybrid Journal   (Followers: 11)
Communications Engineer     Hybrid Journal  
Communications in Information Science and Management Engineering     Open Access   (Followers: 7)
Communications in Numerical Methods in Engineering     Hybrid Journal   (Followers: 3)
Components, Packaging and Manufacturing Technology, IEEE Transactions on     Hybrid Journal   (Followers: 13)
Composite Interfaces     Hybrid Journal   (Followers: 4)
Composite Structures     Hybrid Journal   (Followers: 136)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 107)
Composites Part B : Engineering     Hybrid Journal   (Followers: 135)
Composites Science and Technology     Hybrid Journal   (Followers: 99)
Comptes Rendus Mécanique     Full-text available via subscription   (Followers: 2)
Computation     Open Access   (Followers: 1)
Computational Geosciences     Hybrid Journal   (Followers: 12)
Computational Optimization and Applications     Hybrid Journal   (Followers: 6)
Computational Science and Discovery     Full-text available via subscription  
Computational Water, Energy, and Environmental Engineering     Open Access   (Followers: 2)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 7)
Computer Science and Engineering     Open Access   (Followers: 8)
Computers & Geosciences     Hybrid Journal   (Followers: 7)
Computers & Mathematics with Applications     Full-text available via subscription   (Followers: 4)
Computers and Electronics in Agriculture     Hybrid Journal   (Followers: 3)
Computers and Geotechnics     Hybrid Journal   (Followers: 7)
Computing and Visualization in Science     Hybrid Journal   (Followers: 3)
Computing in Science & Engineering     Full-text available via subscription   (Followers: 13)
Conciencia Tecnologica     Open Access   (Followers: 1)
Concurrent Engineering     Hybrid Journal   (Followers: 4)
Conference Proceedings - Lucian Blaga University Sibiu     Open Access  
Continuum Mechanics and Thermodynamics     Hybrid Journal   (Followers: 3)
Control and Dynamic Systems     Full-text available via subscription   (Followers: 4)
Control Engineering Practice     Hybrid Journal   (Followers: 32)
Control Theory and Informatics     Open Access   (Followers: 4)
Corrosion Science     Hybrid Journal   (Followers: 22)
Corrosion Series     Full-text available via subscription   (Followers: 7)
CT&F Ciencia, Tecnologia y Futuro     Open Access  
Current Applied Physics     Full-text available via subscription   (Followers: 4)
Dams and Reservoirs     Hybrid Journal   (Followers: 4)

  First | 1 2 3 4 5 6 7 8 | Last

Journal Cover   AIChE Journal
  [SJR: 1.098]   [H-I: 104]   [23 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0001-1541 - ISSN (Online) 1547-5905
   Published by John Wiley and Sons Homepage  [1609 journals]
  • Computational study of spout collapse and impact of partition plate in a
           double slot‐rectangular spouted bed
    • Authors: Shiliang Yang; Ke Zhang, Jia Wei Chew
      Abstract: Gas‐solid hydrodynamics in a three‐dimensional slot‐rectangular double‐spouted bed was numerically investigated by a combined approach of discrete element method (DEM) and computational fluid dynamics (CFD), and the knowledge gained was extended to understand the mechanisms leading to operational instability due to the collapse of a spout, along with the beneficial impact of inserting a vertical partition plate. The setup investigated has two diverging bases and contains up to 2,590,000 particles. The computational results show different behaviors of pressure drop, in terms of average value, fluctuations and power spectral trends, in the five distinct flow regimes corresponding to various superficial gas velocities. Two types of spout shapes are observed under stable spouting conditions, and the spout sizes are quantified. When one of the spouts chokes then collapses, complex interactions between the chambers are identified. Furthermore, the insertion of a vertical partition plate between two chambers appears to be an effective way to prevent the interactions between adjacent fountains, which is advantageous for improving the operational stability of such systems upon scale‐up. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-27T13:55:41.362616-05:
      DOI: 10.1002/aic.14973
       
  • Determination of kinetics of CO2 absorption in solutions of
           2‐amino‐2‐methyl‐1‐propanol using a
           microfluidic technique
    • Authors: C. Zheng; B.C. Zhao, K. Wang, G.S. Luo
      Abstract: The kinetics for the reactions of carbon dioxide with 2‐amine‐2‐methyl‐1‐propanol (AMP) and carbon dioxide (CO2) in both aqueous and nonaqueous solutions were measured using a microfluidic method at a temperature range of 298‐318 K. The mixtures of AMP‐water and AMP‐ethylene glycol (EG) were applied for the working systems. Gas‐liquid bubbly mciroflows were formed through a micro‐sieve device and used to determine the reaction characteristics by online observation of the volume change of microbubbles at the initial flow stage. In this condition, a mathematical model according to zwitterion mechanism has been developed to predict the reaction kinetics. The predicted kinetics of CO2 absorption in the AMP aqueous solution verified the reliability of the method by comparing with literatures' results. Furthermore, the reaction rate parameters for the reaction of CO2 with AMP in both solutions were determined. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-27T13:54:30.669493-05:
      DOI: 10.1002/aic.14972
       
  • Flexibility Assessment and Risk Management in Supply Chains
    • Authors: Nihar Sahay; Marianthi Ierapetritou
      Abstract: Increased uncertainty in recent years has led the supply chains to incorporate measures to be more flexible in order to perform well in the face of the uncertain events. It has been shown that these measures improve the performance of supply chains by mitigating the risks associated with uncertainties. However, it is also important to assess the uncertainty under which a supply chain network can perform well and manage risk. In this work, flexibility is defined in terms of the bounds of uncertain parameters within which supply chain operation is feasible. A hybrid simulation based optimization framework that uses two‐stage stochastic programming in a rolling horizon framework is proposed. The framework enables taking optimum planning decisions considering demand uncertainty while managing risk. The framework is used to study the trade‐offs between flexibility, economic performance and risk associated with supply chain operation. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-24T10:27:05.028984-05:
      DOI: 10.1002/aic.14971
       
  • Modeling and Analysis of Conventional and Heat‐Integrated
           Distillation Columns
    • Authors: Thomas Bisgaard; Jakob Kjøbsted Huusom, Jens Abildskov
      Abstract: A generic model that can cover diabatic and adiabatic distillation column configurations is presented, with the aim of providing a consistent basis for comparison of alternative distillation column technologies. Both a static and a dynamic formulation of the model, together with a model catalogue consisting of the conventional, the heat‐integrated and the mechanical vapor recompression distillation columns are presented. The solution procedure of the model is outlined and illustrated in three case studies. One case study being a benchmark study demonstrating the size of the model and the static properties of two different HIDiC schemes and the MVRC. The second case study exemplifies the difference between a HIDiC and a CDiC in the composition profiles within a multicomponent separation, whereas the last case study demonstrates the difference in available dynamic models for the HIDiC and the proposed model. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-24T10:02:47.212608-05:
      DOI: 10.1002/aic.14970
       
  • Kinetic Insight into Electrochemically Mediated ATRP Gained through
           Modeling
    • Authors: Jun‐Kang Guo; Yin‐Ning Zhou, Zheng‐Hong Luo
      Abstract: A detailed kinetic model was constructed using the method of moments to elucidate the electrochemically mediated atom transfer radical polymerization (eATRP). Combined with electrochemical theory, the reducing rate coefficient relevant to the overpotential in eATRP was coupled into the kinetic model. The rate coefficients for eATRP equilibrium and the reducing rate coefficient were fitted to match the experimental data. The effects of catalyst loading, overpotential, and application of programmable electrolysis on the eATRP behavior were investigated based on the tested kinetic model. Results showed that the apparent polymerization rate exhibited a square root dependence on catalyst loading. In addition, a more negative potential accelerated the polymerization rate before the mass transport limitation was reached. This phenomenon indicated that the polymerization rate could be artificially controlled by the designed program (i.e., stepwise and intermittent electrolysis programs). What's more, the normal ATRP, photo‐ATRP, and eATRP were compared to obtain a deeper understanding of these ATRP systems. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-23T18:23:57.072058-05:
      DOI: 10.1002/aic.14969
       
  • Integrating expanders into heat exchanger networks above ambient
           temperature
    • Authors: Chao Fu; Truls Gundersen
      Abstract: The integration of expanders into heat exchanger networks (HENs) is a complex task since both heat and work are involved. In addition, the role of streams (as hot or cold), the utility demand, and the location of pinch points may change. With certain well‐defined conditions, four theorems are proposed for the integration of expanders into HENs above ambient temperature with the objective of minimizing exergy consumption. A straightforward graphical methodology for above ambient HENs design including expanders is developed on the basis of Grand Composite Curves (GCCs). It is concluded that in order to achieve a design with minimum exergy consumption, stream splitting may be applied and expansion should be done at pinch temperatures, hot utility temperature or ambient temperature. In the majority of cases, however, and in line with the concept of Appropriate Placement from Pinch Analysis, expansion at pinch temperatures gives the minimum exergy consumption. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-23T18:19:51.364947-05:
      DOI: 10.1002/aic.14968
       
  • Nanocolloid cake properties determined from step‐up pressure
           filtration with single‐stage reduction in filtration area
    • Authors: Eiji Iritani; Nobuyuki Katagiri, Ryota Nakajima, Kuo‐Jen Hwang, Tung‐Wen Cheng
      Abstract: A sophisticated method was developed for evaluating simultaneously and accurately both the average specific resistance and average porosity of the filter cake formed in unstirred dead‐end ultrafiltration of nanocolloids such as protein solution and nano silica sol. In the method, a step‐up pressure filtration test was conducted by using a filter with a single‐stage reduction in the effective filtration area. The influence of the pressure drop across the cake on not only the average specific cake resistance but also on the average cake porosity of highly compressible filter cake was evaluated using only flux decline data in one dead‐end filtration test, taking advantage of the decrease in the cake thickness caused by the pressure increase. As a result, the cake properties were easily determined for a variety of nanocolloids. Constant pressure dead‐end ultrafiltration data obtained under various pressures and concentrations were well evaluated based on the method proposed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-22T17:28:54.712045-05:
      DOI: 10.1002/aic.14967
       
  • Multistream heat exchanger modeling and design
    • Authors: Harry A. J. Watson; Kamil A. Khan, Paul I. Barton
      Abstract: A new model formulation and solution strategy for the design and simulation of processes involving multistream heat exchangers (MHEXs) is presented. The approach combines an extension of pinch analysis with an explicit dependence on the heat exchange area in a nonsmooth equation system to create a model which solves for up to three unknown variables in an MHEX. Recent advances in automatic generation of derivative‐like information for nonsmooth equations make the method tractable, and the use of nonsmooth equation solving methods make the method very precise. Several illustrative examples and a case study featuring an offshore liquefied natural gas production concept are presented which highlight the flexibility and strengths of the formulation. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-21T10:54:11.414921-05:
      DOI: 10.1002/aic.14965
       
  • Retrofit design of a pharmaceutical batch process considering “green
           chemistry and engineering” principles
    • Authors: Alireza Banimostafa; Stavros Papadokonstantakis, Konrad Hungerbühler
      Abstract: Considering the capital intensive nature of the chemical industry, redesign of existing production plants is a strategic decision. In this study, retrofitting is performed by using a systematic path flow decomposition method, enriching it with hazard assessment and life cycle analysis path flow indicators and proposing a classification scheme for coupling these new path flow indicators with relevant heuristics for process alternative generation. The developed methodology is applied in a batch production plant from the pharmaceutical industry. The method highlights solvent recovery or substitution as importanECt retrofitting actions, generates diverse process layout structures to achieve this task and evaluates them from cost, hazard and life cycle assessment point of view. Extractive distillation using glycol as an entrainer is identified as the multiobjective optimal option for separating the THF/Water azeotrope with improvement up to 40% for the various objectives compared to a base case where the waste solvent is incinerated. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-21T10:53:40.529575-05:
      DOI: 10.1002/aic.14966
       
  • Economic model predictive control of nonlinear time‐delay systems:
           Closed‐loop stability and delay compensation
    • Authors: Matthew Ellis; Panagiotis D. Christofides
      Abstract: Closed‐loop stability of nonlinear time‐delay systems under Lyapunov‐based economic model predictive control (LEMPC) is considered. LEMPC is formulated with an ordinary differential equation model and is designed on the basis of an explicit stabilizing control law. To address closed‐loop stability under LEMPC, first, we establish that the steady‐state of the closed‐loop sampled‐data system resulting from the nonlinear continuous‐time delay system with state and input delays under a sample‐and‐hold implementation of the explicit stabilizing control law is practically stable. Second, conditions such that closed‐loop stability, in the sense of boundedness of the closed‐loop state, under LEMPC are derived. A chemical process example is used to demonstrate that indeed closed‐loop stability is maintained under LEMPC for sufficiently small time‐delays. To cope with performance degradation owing to the effect of input delay, a predictor feedback LEMPC methodology is also proposed. The predictor feedback LEMPC design employs a predictor to compute a prediction of the state after the input delay period and an LEMPC scheme that is formulated with a differential difference model (DDE) model, which describes the time‐delay system, initialized with the predicted state. The predictor feedback LEMPC is applied to the chemical process example and yields improved closed‐loop stability and economic performance properties. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-21T10:48:49.689961-05:
      DOI: 10.1002/aic.14964
       
  • Effect of ship tilting and motion on amine absorber with
           structured‐packing for CO2 removal from natural gas
    • Authors: Dung A. Pham; Young‐Il Lim, Hyunwoo Jee, Euisub Ahn, Yongwon Jung
      Abstract: A gas‐liquid Eulerian porous media computational fluid dynamics (CFD) model was developed for an absorber with structured packing to remove CO2 from natural gas by mono‐ethanol‐amine (MEA). The three dimensional geometry of the amine absorber with Mellapak 500.X was constructed to investigate the effect of the tilting and motion experienced on ships and barges for offshore plants. The momentum equation included porous resistance, gas‐liquid momentum exchange and liquid dispersion to replace structured‐packing by porous media. The mass equation involved mass transfer of CO2 gas into MEA solution, and one chemical reaction. Parameters of the CFD model were adjusted to fit experimental data measured in the CO2‐MEA system. As the tilting angle increased, the liquid holdup and effective interfacial area decreased and CO2 removal efficiency was lowered. The uniformity of liquid holdup deteriorated by 10% for a 3° static tilting, and a rolling motion with 4.5° amplitude and 12s period, respectively. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-20T18:32:05.561834-05:
      DOI: 10.1002/aic.14962
       
  • Real‐time preventive sensor maintenance using robust moving horizon
           estimation and economic model predictive control
    • Authors: Liangfeng Lao; Matthew Ellis, Helen Durand, Panagiotis D. Christofides
      Abstract: Conducting preventive maintenance of measurement sensors in real‐time during process operation under feedback control while ensuring the reliability and improving the economic performance of a process is a central problem of the research area focusing on closed‐loop preventive maintenance of sensors and actuators. To address this problem, a robust moving horizon estimation (RMHE) scheme and an economic model predictive control (EMPC) system are combined to simultaneously achieve preventive sensor maintenance and optimal process economic performance with closed‐loop stability. Specifically, given a preventive sensor maintenance schedule, a robust moving horizon estimation scheme is developed that accommodates varying numbers of sensors to continuously supply accurate state estimates to a Lyapunov‐based economic model predictive control (LEMPC) system. Closed‐loop stability for this control approach can be proven under fairly general observability and stabilizability assumptions to be made precise in the manuscript. Subsequently, a chemical process example incorporating this RMHE‐based LEMPC scheme demonstrates its ability to maintain process stability and achieve optimal process economic performance as scheduled preventive maintenance is performed on the sensors. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-17T00:01:49.18498-05:0
      DOI: 10.1002/aic.14960
       
  • Density segregation of dry and wet granular mixtures in gas fluidized beds
    • Authors: Stella Lin Li SEAH; Eldin Wee Chuan LIM
      Abstract: The Discrete Element Method combined with Computational Fluid Dynamics was coupled to a capillary liquid bridge force model for computational studies of mixing and segregation behaviors in gas fluidized beds containing dry or wet mixtures of granular materials with different densities. The tendency for density segregation decreased with increasing fluidizing velocity, coefficient of restitution and amount of liquid present. Due to the presence of strong capillary forces between wet particles, there was a high tendency for particles to form agglomerates during the fluidization process, resulting in lower segregation efficiency in comparison with fluidization of dry particles. Particle‐particle collision forces were on average stronger than both fluid drag forces and capillary forces. The magnitudes of drag forces and particle‐particle collision forces increased with increasing fluidizing velocity and this led to higher mixing or segregation efficiencies observed in dry particles as well as in wet particles at higher fluidizing velocities. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-16T23:58:44.084632-05:
      DOI: 10.1002/aic.14959
       
  • Ockham's razor for paring microkinetic mechanisms: Electrical analogy vs.
           Campbell's degree of rate control
    • Authors: Patrick D. O'Malley; Saurabh A. Vilekar, Ravindra Datta
      Abstract: Elucidation of the key molecular steps and pathways in an overall reaction is of central importance in developing a better understanding of catalysis. Campbell's degree of rate control (DRC) is the leading methodology currently available for identifying the germane steps and key intermediates in a catalytic mechanism. We contrast Campbell's DRC to our alternate new approach involving an analysis and comparison of the “resistance” and de Donder “affinity,” i.e., the driving force, of the various steps and pathways in a mechanism, in a direct analogy to electrical networks. We show that our approach is as just rigorous and more insightful than Campbell's DRC. It clearly illuminates the bottleneck steps within a pathway and allows one to readily discriminate among competing pathways. The example used for a comparison of these two methodologies is a DFT study of the water‐gas shift (WGS) reaction on Pt‐Re catalyst published recently. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-15T18:21:30.586835-05:
      DOI: 10.1002/aic.14956
       
  • Depletion of cross‐stream diffusion in the presence of
           viscoelasticity
    • Authors: Arman Sadeghi
      Abstract: This work presents an effort to analyze the viscoelasticity effects on transverse transport of neutral solutes between two miscible streams in an electrokinetic T‐sensor. The analysis is based on an approximate analytical solution for the depthwise averaged concentration, assuming a channel of large width to depth ratio for which a 1‐D profile is sufficient for describing the velocity field. We show that the solution derived is surprisingly accurate even for very small channel aspect ratios and the maximum error reduces to only about 1% when the aspect ratio is 5. The developed model reveals that the mixing length for a viscoelastic fluid may be by far larger than that for a Newtonian fluid. Moreover, the Taylor dispersion coefficient for electroosmotic flow of viscoelastic fluids, which its determination is a main part of the analysis, is found to be an increasing function of both the elasticity level and the EDL thickness. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-15T18:21:05.310829-05:
      DOI: 10.1002/aic.14955
       
  • Dynamic modeling and validation of a biomass hydrothermal pretreatment
           process ‐ A demonstration scale study
    • Authors: Remus Mihail Prunescu; Mogens Blanke, Jon Geest Jakobsen, Gürkan Sin
      Abstract: Hydrothermal pretreatment of lignocellulosic biomass is a cost effective technology for second generation biorefineries. The process occurs in large horizontal and pressurized thermal reactors where the biomatrix is opened under the action of steam pressure and temperature to expose cellulose for the enzymatic hydrolysis process. Several by‐products are also formed, which disturb and act as inhibitors downstream. The objective of this study is to formulate and validate a large scale hydrothermal pretreatment dynamic model based on mass and energy balances, together with a complex conversion mechanism and kinetics. The study includes a comprehensive sensitivity and uncertainty analysis, with parameter estimation from real‐data in the 178‐185° range. To highlight the application utility of the model, a state estimator for biomass composition is developed. The predictions capture well the dynamic trends of the process, outlining the value of the model for simulation, control design, and optimization for full‐scale applications. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-15T18:20:40.575318-05:
      DOI: 10.1002/aic.14954
       
  • Three‐dimensional hydrogel encapsulated embryonic stem and carcinoma
           cells as culture platforms for cytotoxicity studies
    • Authors: Sneha Oberai; Kalpith Ramamoorthi, Jared Hara, Ailing Teo, Mayasari Lim, Prashanth Asuri
      Abstract: Our study describes the utility of alginate hydrogels for 3D culture of mouse embryonic stem cells (mESCs) and future development of 3D stem cell culture‐based in vitro screens of toxicity. Using alginate hydrogels of various stiffness, we first evaluated the impact of substrate modulus on mESC viability, proliferation, as well as expression of pluripotency and germ‐layer markers and observed that low concentration alginate hydrogels (0.5% and 1% alginate) were most suitable for long‐term culture of mESCs. These results were not unique to mESCs; long‐term viability and proliferation of mouse embryonic carcinoma cells (mECCs) was also best supported by similar conditions. Finally, we determined cytotoxic responses of alginate encapsulated cells to commercially available chemicals and interestingly observed similar responses for mESCs and mECCs, thereby suggesting that mECCs can predict stem cell responses to chemicals. These studies will facilitate future design of optimal stem cell‐based platforms of organ‐specific and developmental toxicity. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-15T18:20:17.058032-05:
      DOI: 10.1002/aic.14957
       
  • Scaling inline static mixers for flocculation of oil sand mature fine
           tailings
    • Authors: Alebachew Demoz
      Abstract: Operations to reclaim mature fine tailings (MFT) ponds involve flocculation using high‐molecular‐weight polymers, for which inline static mixers are suited. Three different commercial static mixers were utilized to determine mixing parameters corresponding to optimal dewatering performance of flocculated MFT. MFT was treated with polymer solution under different mixing conditions. The dewatering rates passed through a peak with increasing mean velocity, V and Reynolds number, Re of the fluid. The greater the number of mixer elements, the lower the V and Re at which the peak dewatering rate occurred. Mixing parameters such as G‐value, residence time, and mixing energy dissipation rate of the most rapidly dewatering flocculated MFT were dependent on mixer type and setup. In contrast, peak dewatering rates converged when scaled with respect to specific mixing energy, E, demonstrating that E is a suitable scale‐up parameter for inline static mixing to produce optimally dewatering MFT. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-15T18:19:50.52966-05:0
      DOI: 10.1002/aic.14958
       
  • Microkinetic model for the pyrolysis of methyl esters: From model compound
           to industrial biodiesel
    • Authors: Ruben De Bruycker; Steven Pyl, Marie‐Françoise Reyniers, Kevin M. Van Geem, Guy B. Marin
      Abstract: A tool for the generation of decomposition schemes of large molecules has been developed. These decomposition schemes contain radicals which can be eliminated from the model equations if both the μ‐hypothesis and the pseudo‐steady‐state approximation are valid. The reaction rate coefficients and thermodynamic parameters have been calculated by incorporating a comprehensive group additive framework. A microkinetic model for the pyrolysis of methyl esters with a carbon number of up to 19 has been generated using this tool. It is validated by comparing calculated and experimental yields of the pyrolysis of methyl decanoate and novel rapeseed methyl ester pyrolysis data in the temperature range from 800 to 1100K and methyl ester partial pressure range from 1 10−3 to 1 10−2 MPa. This modeling frame work allows to not only assess the use of methyl ester mixtures as potential feedstock for olefin production but also their effect as blend‐in or trace impurity. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-15T01:53:36.607321-05:
      DOI: 10.1002/aic.14953
       
  • Refactoring β‐amyrin synthesis in Saccharomyces cerevisiae
    • Authors: Genlin Zhang; Qian Cao, Jingzhu Liu, Baiyang Liu, Jun Li, Chun Li
      Abstract: Triterpenoids are a highly diverse group of natural products and used particularly as medicine. Here, a strategy combining stepwise metabolic engineering and transcriptional control was developed to strengthen triterpenoid biosynthesis in Saccharomyces cerevisiae. Consequently, an efficient biosynthetic pathway for producing β‐amyrin, a commercially valuable compound and precursor of triterpenoids, was constructed through expressing a plant‐derived β‐amyrin synthase. Introducing a heterologous squalene monooxygenase greatly dragged intermediate metabolite squalene toward β‐amyrin. Increasing squalene pool by overexpressing IPP isomerase, FPP and squalene synthase further enhanced β‐amyrin synthesis of 49 folds. Through reconstructing the promoters with the binding site of transcription factor UPC2, directed transcriptional regulation on engineered pathway was availably achieved, resulting in β‐amyrin titer increased by 65 folds. Using ethanol fed‐batch fermentation, β‐amyrin titer was finally improved up to 138.80 mg/L with a yield of 16.30 mg/g dry cell, almost 185 and 232 and folds of the initially engineered strain respectively. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-15T01:52:31.035708-05:
      DOI: 10.1002/aic.14950
       
  • Impact of the fluid flow conditions on the formation rate of carbon
           dioxide hydrates in a semi‐batch stirred tank reactor
    • Authors: S. Douïeb; L. Fradette, F. Bertrand, B. Haut
      Abstract: CO2 hydrate formation experiments are performed in a 20 L semi‐batch stirred tank reactor using three different impellers (a down‐pumping pitched blade turbine, a Maxblend™, and a Dispersimax™) at various rotational speeds to examine the impact of the flow conditions on the CO2 hydrate formation rate. An original mathematical model of the CO2 hydrate formation process that assigns a resistance to each of its constitutive steps is established. For each experimental condition, the formation rate is measured and the rate‐limiting step is determined on the basis of the respective values of the resistances. The efficiencies of the three considered impellers are compared and, for each impeller, the influence of the rotational speed on the rate‐limiting step is discussed. For instance, it is shown that a formation rate limitation due to heat transfer can occur at the relatively small scale used to perform our experiments. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-15T01:52:05.397182-05:
      DOI: 10.1002/aic.14952
       
  • Integrated production scheduling and model predictive control of
           continuous processes
    • Authors: Michael Baldea; Juan Du, Jungup Park, Iiro Harjunkoski
      Abstract: The integration of production management and process control decisions is critical for improving economic performance of the chemical supply chain. In this paper, we propose a novel framework for integrating production scheduling and model predictive control (MPC) for continuous processes. Our framework is predicated on using a low‐dimensional time scale‐bridging model (SBM) that captures the closed‐loop process dynamics over the longer time scales that are relevant to scheduling calculations. The SBM is used as a constraint in a mixed‐integer dynamic formulation of the scheduling problem. To synchronize the scheduling and MPC calculations, we propose a novel scheduling‐oriented MPC concept, whereby the SBM is incorporated in the expression of the controller as a (soft) dynamic constraint and allows for obtaining an explicit description of the closed‐loop process dynamics. Our framework scales favorably with system size and provides desirable closed‐loop stability and performance properties for the resulting integrated scheduling and control problem. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-15T01:51:41.366151-05:
      DOI: 10.1002/aic.14951
       
  • Microstructure of room temperature ionic liquids at stepped graphite
           electrodes
    • Authors: Guang Feng; Song Li, Wei Zhao, Peter T. Cummings
      Abstract: Molecular dynamics simulations of room temperature ionic liquid (RTIL) [emim][TFSI] at stepped graphite electrodes were performed to investigate the influence of the thickness of the electrode surface step on the microstructure of interfacial RTILs. A strong correlation was observed between the interfacial RTIL structure and the step thickness in electrode surface as well as the ion size. Specifically, when the step thickness is commensurate with ion size, the interfacial layering of cation/anion is more evident; whereas, the layering tends to be less defined when the step thickness is close to the half of ion size. Furthermore, two‐dimensional microstructure of ion layers exhibits different patterns and alignments of counterion/co‐ion lattice at neutral and charged electrodes. As the cation/anion layering could impose considerable effects on ion diffusion, the detailed information of interfacial RTILs at stepped graphite presented here would help to understand the molecular mechanism of RTIL‐electrode interfaces in supercapacitors. © 2015 American Institute of Chemical Engineers AIChE J, 2015
      PubDate: 2015-07-14T09:16:27.448864-05:
      DOI: 10.1002/aic.14927
       
  • Determination and comparison of rotational velocity in a pseudo 2D
           fluidized bed using Magnetic Particle Tracking and Discrete Particle
           Modelling
    • Authors: K.A. Buist; T.W. van Erdewijk, N.G. Deen, J.A.M. Kuipers
      Abstract: Modelling of dense granular flow has been subject to a large amount of research. Particularly discrete particle modelling has been of great importance because of the ability to describe the strongly coupled dynamics of the fluid and the solids in dense suspensions. Many studies have been reported on the validation of the translational particle velocities predicted by employing these models. The rotational motion however has received far less attention, mainly because of the spherical nature of the particles under investigation and the lack of techniques with the capability to study the rotational behaviour of the solid phase. In this study we will for the first time present experimental data on the rotational behaviour of particles in a pseudo 2D fluidized bed setup using Magnetic Particle Tracking (MPT). In addition the experimental results are compared to data obtained from discrete particle simulations. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-14T08:28:17.538249-05:
      DOI: 10.1002/aic.14949
       
  • Issue information
    • Abstract: Cover illustration. The chemical industry will need to identify new feedstock sources to meet increasing global demand. This perspectives article identifies possible future carbon sources beyond petroleum. Images available in the public domain and obtained from http://images.google.com/ 10.1002/aic.14910
      PubDate: 2015-07-14T08:07:26.808048-05:
      DOI: 10.1002/aic.14587
       
  • Effect of interfacial mass transfer on the dispersion in segmented flow in
           straight capillaries
    • Authors: Jaydeep B. Deshpande; Amol A. Kulkarni
      Abstract: The effect of interfacial mass transfer on the extent of dispersion in liquid‐liquid segmented flow in straight capillaries is studied. In the absence of interfacial mass transfer dispersion coefficient was seen to go through a minimum with increasing flow rates. In the presence of mass transfer, physicochemical properties of both the phases and slug lengths were seen to vary along the capillary length. The extent of dispersion was always higher in the presence of interfacial mass transfer. The predictions using axial dispersion model deviated noticeably for larger capillaries as the model does not account for varying buoyancy, dynamic contacting and Marangoni convection. Simulations of a 1st order interfacial reaction considering varying slug lengths showed a significant change in optimum operating parameters than the conventional approach. A special case of ‘drop‐on‐demand' type of controlled two‐phase flow in capillaries was also studied. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-07T10:17:10.591772-05:
      DOI: 10.1002/aic.14945
       
  • Mechanism and analytical models for the gas distribution on the SiC foam
           monolithic tray
    • Authors: Hong Li; Long Fu, Xingang Li, Xin Gao
      Abstract: SiC foam material has been applied as monolithic tray for distillation column in our previous study. A systematic understanding of the gas distribution process on the foam tray should help to the design of commercial application. In this article, local gas hold up distribution and bubble size distribution are used to measure the gas distribution. The local gas holdup is tested by the conductive probe and the number of test point is counted in different local gas hold up. The bubbles are captured by the high speed camera to measure the bubble size. Bubble size is calculated as ellipsoidal bubble and counted with different pore sizes. Furthermore, a three stage process model is put forward to explain the uneven distribution of gas phase, and verified by the experimental values. The results show that the structure and the thickness of SiC foam is the decisive factor for the gas distribution performance. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-07T10:16:46.60193-05:0
      DOI: 10.1002/aic.14944
       
  • Morphology of polystyrene/poly(methyl methacrylate) blends: Effects of
           carbon nanotubes aspect ratio and surface modification
    • Authors: Jiaxi Guo; Nicholas Briggs, Steven Crossley, Brian P. Grady
      Abstract: MWCNTs with aspect ratios (ARs) ranging from 94 to 474 were incorporated into polystyrene (PS)/poly(methyl methacrylate) (PMMA) blends using solution mixing and melt mixing. Also, two functionalized MWCNTs were prepared from the nanotubes having AR 94: one was oxidized by nitric acid while the other was further modified with amine‐terminated PS attached to carboxyl groups to form amides. The two functionalized MWCNTs (1 wt.%) were used to show that which phase the CNTs were located in could be controlled with nanotube surface chemistry. When nanotubes were confined to the minor phase, the size of the minor domain first decreased with adding low aspect ratio CNT as expected due to the increased viscosity of the minor phase. However, at higher aspect ratios the size increased beyond the size for the minor domain with no nanotubes, and finally the shape of the minor domain changed from spherical to an elongated irregular shape. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-06T03:08:31.518384-05:
      DOI: 10.1002/aic.14943
       
  • On identification of well‐conditioned nonlinear systems: Application
           to economic model predictive control of nonlinear processes
    • Authors: Anas Alanqar; Helen Durand, Panagiotis D. Christofides
      Abstract: This work focuses on economic model predictive control (EMPC) that utilizes well‐conditioned polynomial nonlinear state‐space models for processes with nonlinear dynamics. Specifically, the article initially addresses the development of a nonlinear system identification technique for a broad class of nonlinear processes which leads to the construction of polynomial nonlinear state‐space dynamic models which are well‐conditioned over a broad region of process operation in the sense that they can be correctly integrated in real‐time using explicit numerical integration methods via time steps that are significantly larger than the ones required by nonlinear state‐space models identified via existing techniques. Working within the framework of polynomial nonlinear state‐space (PNLSS) models, additional constraints are imposed in the identification procedure to ensure well‐conditioning of the identified nonlinear dynamic models. This development is key because it enables the design of Lyapunov‐based EMPC (LEMPC) systems for nonlinear processes using the well‐conditioned nonlinear models that can be readily implemented in real‐time since the computational burden required to compute the control actions within the process sampling period is reduced. A stability analysis for this LEMPC design is provided that guarantees closed‐loop stability of a process under certain conditions when an LEMPC based on a nonlinear empirical model is used. Finally, a classical chemical engineering reactor example demonstrates both the system identification and LEMPC design techniques, and the significant advantages in terms of computation time reduction in LEMPC calculations when using the nonlinear empirical model. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-03T00:50:43.244084-05:
      DOI: 10.1002/aic.14942
       
  • Hybrid PIV/PTV measurements of velocity and position distributions of
           gas‐conveyed particles in small, narrow channels
    • Authors: M.W. Korevaar; J.T. Padding, N.G. Deen, J. Wang, M. de Wit, M.A.I. Schutyser, J.A.M. Kuipers
      Abstract: Pneumatic conveying of particles is generally applied in large ducts. However, new applications are emerging which benefit from millimeter sized ducts; e.g.\triboelectric separators where intensive wall‐particle contact is desirable. In this paper an optical method is proposed to measure the distribution of the position and velocity of 100‐1000 μm particles in such narrow ducts. Images of the system are captured using a digital camera on which a Hough transform is applied to detect the particles and their positions. The velocities are acquired by applying a hybrid particle tracking and particle image velocimetry approach. This made it is possible to overcome challenges caused by suboptimal lighting, non‐smooth background and a large ratio between particle and duct diameter (>O(0.1)). It is shown that the algorithm is subpixel accurate when sufficient particles can be sampled. Finally, typical results are shown to illustrate the method's capabilities. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-02T11:59:48.029563-05:
      DOI: 10.1002/aic.14928
       
  • Classical density functional theory for methane adsorption in
           metal‐organic framework materials
    • Authors: Jia Fu; Yun Tian, Jianzhong Wu
      Abstract: Natural gas is considered as a promising alternative to petroleum as the next generation of primary transportation fuel owing to relatively smaller carbon footprint and lower SOx/NOx emissions and to fast developments of shale gas in recent years. Since the volumetric energy density of methane amounts to only about 1% of that of gasoline at ambient conditions, natural gas storage represents one of the key challenges for prevalent deployment of natural gas vehicles. In this work, we present a molecular thermodynamic model potentially useful for high‐throughput screening of nanoporous materials for natural gas storage. We investigate methane adsorption in a large library of metal‐organic frameworks (MOFs) using four versions of classical density functional theory (DFT) and calibrate the theoretical predictions with extensive simulation data for total gas uptake and delivery capacity. In combination with an extended excess entropy scaling method, the classical DFT is also used to predict the self‐diffusion coefficients of the confined gas in several top‐ranked MOFs. The molecular thermodynamic model has been used to identify promising MOF materials and possible variations of operation parameters to meet the Advanced Research Projects Agency‐Energy (ARPA‐E) target set by the U.S. Department of Energy for natural gas storage. © 2015 The
      Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 2015
      PubDate: 2015-07-02T11:52:52.906265-05:
      DOI: 10.1002/aic.14877
       
  • An effective rate approach (ERA) to modelling single‐stage spray
           drying
    • Authors: Oluwafemi Ayodele George; Jie Xiao, Mengwai Woo, Liming Che, Xiao Dong Chen
      Abstract: An effective rate approach (ERA) is proposed in this work to achieve a fast and reliable prediction of dryer outlet conditions for a given single‐stage spray drying system operated under a range of scenarios. This approach is improved from existing methods based on simple mass and energy balances due to the incorporation of a reliable drying rate model, which is the reaction engineering approach for the material of interest. It allows quick solution procedure without the need to solve the partial differential equations that govern the heat and mass transfer in the spray drying process. By following a generic procedure, this technique has been exercised upon the experimental results from running a mono‐disperse droplet spray dryer, i.e., a well‐established experimental platform for model validation. The proposed ERA has been shown to be rather promising. It could become a powerful approach for proactive control and optimization for existing spray drying facilities. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-02T03:30:00.194032-05:
      DOI: 10.1002/aic.14940
       
  • Probabilistic slow feature analysis‐based representation learning
           from massive process data for soft sensor modeling
    • Authors: Chao Shang; Biao Huang, Fan Yang, Dexian Huang
      Abstract: Latent variable (LV) models provide explicit representations of underlying driving forces of process variations and retain the dominant information of process data. In this study, slow features as temporally correlated LVs are derived using probabilistic slow feature analysis. Slow features evolving in a state‐space form effectively represent nominal variations of processes, some of which are potentially correlated to quality variables and hence help improving the prediction performance of soft sensors. An efficient EM algorithm is proposed to estimate parameters of the probabilistic model, which turns out to be suitable for analyzing massive process data. Two criteria are also proposed to select quality‐relevant slow features. The validity and advantages of the proposed method are demonstrated via two case studies. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-02T03:27:50.906688-05:
      DOI: 10.1002/aic.14937
       
  • Multivariate statistical process monitoring of batch‐to‐batch
           startups
    • Authors: Zhengbing Yan; Bi‐Ling Huang, Yuan Yao
      Abstract: In batch processes, multivariate statistical process monitoring (MSPM) plays an important role for ensuring process safety. However, despite many methods proposed, few of them can be applied to batch‐to‐batch startups. The reason is that, during the startup stage, process data are usually non‐stationary and non‐identically distributed from batch to batch. In this paper, the trajectory signal of each process variable is decomposed into a series of components corresponding to different frequencies, by adopting a nonparametric signal decomposition technique named ensemble empirical mode decomposition (EEMD). Then, through instantaneous frequency calculation, these components can be divided into two groups. The first group reflects the long‐term trend between batches, which extracts the batch‐wise non‐stationary drift information. The second group corresponds to the short‐term intra‐batch variations. The variable trajectory signals reconstructed from the latter fulfills the requirements of conventional MSPM. The feasibility of the proposed method is illustrated using an injection molding process. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-01T10:46:55.370645-05:
      DOI: 10.1002/aic.14939
       
  • Trajectory Modeling of Gas‐Liquid Flow in Microchannels with
           Stochastic Differential Equation and Optical Measurement
    • Authors: Lexiang Zhang; Feng Xin, Dongyue Peng, Weihua Zhang, Yuexing Wang, Xiaodong Chen, Yi Wang
      Abstract: The numbering up of microchannel reactors definitely faces great challenge in uniformly distributing fluid flow in every channel, especially for multiphase systems. A model of stochastic differential equations (SDEs) is proposed based on the experimental data recorded by a long term optical measurement to well quantify the stochastic trajectories of gas bubbles and liquid slugs in parallel microchannels interconnected with two dichotomic distributors. The expectation and variance of each sub flow rate are derived explicitly from the SDEs associated with the Fokker‐Planck equation and solved numerically. A bifurcation in the trajectory is found by using the original model, then a modification on interactions of feedback and crosstalk is introduced, the evolutions of sub flow rates calculated by the modified model match well with experimental results. The established methodology is helpful for characterizing the flow uniformity and numbering up the microchannel reactors of multiphase system. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-01T10:46:24.439242-05:
      DOI: 10.1002/aic.14938
       
  • Hybrid Mixture Theory Based Modeling of Transport Mechanisms and Expansion
           ‐ Thermomechanics of Starch During Extrusion
    • Authors: Srivikorn Ditudompo; Pawan S. Takhar
      Abstract: Water, vapor and heat transport mechanisms and thermomechanical changes occurring inside the expanding extrudate were described using hybrid mixture theory based unsaturated transport equations. Transport equations were transformed from the Eulerian coordinates to the Lagrangian coordinates. Good agreements between the predicted and experimental values of surface temperature, moisture content and expansion ratio of the extrudates were obtained. The model was also used to calculate temperature, moisture content, pore‐pressure and viscoelastic‐stress distribution in the extrudate. Matrix collapse and glassy crust formation under the surface was calculated as a function of extrusion conditions. Expansion behavior of the extrudate was described using the difference between stress due to pore pressure and viscoelastic stress. The modeling results can serve as a guide for predictably modifying the extrusion parameters for obtaining specific textural attributes of expanded starch for various food, feed and biomedical applications. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-01T10:34:38.724043-05:
      DOI: 10.1002/aic.14936
       
  • Ni‐Al2O3/Ni‐foam catalyst with enhanced heat transfer for
           hydrogenation of CO2 to methane
    • Authors: Yakun Li; Qiaofei Zhang, Ruijuan Chai, Guofeng Zhao, Fahai Cao, Ye Liu, Yong Lu
      Abstract: Monolithic Ni‐Al2O3/Ni‐foam catalyst is developed by modified wet chemical etching of Ni‐foam, being highly active/selective and stable in strongly exothermic CO2 methanation process. The as‐prepared catalysts are characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma atomic emission spectrometry (ICP‐AES) and H2‐temperature programmed reduction‐mass spectrometry (H2‐TPR‐MS). The results indicate that modified wet chemical etching method is working efficiently for one‐step creating and firmly embedding NiO‐Al2O3 composite catalyst layer (∼2 μm) into the Ni‐foam struts. High CO2 conversion of 90% and high CH4 selectivity of >99.9% can be obtained and maintained for a feed of H2/CO2 (molar ratio of 4/1) at 320 oC and 0.1 MPa with a gas hourly space velocity (GHSV) of 5000 h−1, throughout entire 1200 h test over 10.2 mL such monolithic catalysts. Computational fluid dynamics (CFD) calculation and experimental measurement consistently confirm a dramatic reduction of ‘hotspot' temperature due to enhanced heat transfer. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-01T10:33:58.221705-05:
      DOI: 10.1002/aic.14935
       
  • Experimental investigation of electrostatic effect on particle motions in
           gas‐solid fluidized beds
    • Authors: Kezeng Dong; Qing Zhang, Zhengliang Huang, Zuwei Liao, Jingdai Wang, Yongrong Yang, Fang Wang
      Abstract: The excess accumulation of charges in the fluidized bed has a severe impact on hydrodynamics. Due to lack of effective experimental methods, electrostatic effects on hydrodynamics have mostly been studied using numerical simulation. By injecting a trace of liquid antistatic agents (LAA) into a fluidized bed, charges were controlled and electrostatic influences on particle motions were investigated. The average particle‐wall impact angles are acquired by developing multi‐scales wavelet decomposition of acoustic emission (AE) signals. The impact angles are significantly influenced by both charge levels and gas velocities. If the electric force is reduced and/or fluid drag is increased, friction dominates the particle‐wall interactions. Under a larger gas velocity where fluid drag dominates, charges elimination causes no significant variation in particle impact angles, but particle velocities increase as well as at lower gas velocities. In addition, existence of electrostatic charges influences the ranges of bubble growing zone and jet impacting zone. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-30T17:58:47.589711-05:
      DOI: 10.1002/aic.14933
       
  • Mass transfer rate enhancement for CO2 separation by ionic liquids:
           theoretical study on the mechanism
    • Authors: Wenlong Xie; Xiaoyan Ji, Xin Feng, Xiaohua Lu
      Abstract: To promote the development of ionic liquid (IL) immobilized sorbents and supported IL membranes (SILMs) for CO2 separation, in this work, the kinetics of CO2 absorption/desorption in IL immobilized sorbents was studied using a novel method based on non‐equilibrium thermodynamics. It shows that the apparent chemical‐potential‐based mass‐transfer coefficients of CO2 were in three regions with 3‐order difference in magnitude for the IL‐film thicknesses in micro‐scale, 100 nm‐scale and 10 nm‐scale. Using a diffusion‐reaction theory, it is found that by tailoring the IL‐film thickness from micro‐scale to nano‐scale, the process was altered from diffusion‐control to reaction‐control, revealing the inherent mechanism for the dramatic rate enhancement. The extension to SILMs shows that the significant improvement of CO2 flux can be obtained theoretically for the membranes with nano‐scale IL‐films, which makes it feasible to implement CO2 separation by ILs with low investment cost. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-30T17:58:22.166741-05:
      DOI: 10.1002/aic.14932
       
  • Process to Planet: A Multiscale Modeling Framework for Sustainable
           Engineering
    • Authors: Rebecca J. Hanes; Bhavik R. Bakshi
      Abstract: To prevent the chance of unintended environmental harm, engineering decisions need to consider an expanded boundary that captures all relevant connected systems. Comprehensive models for sustainable engineering may be developed by combining models at multiple scales. Models at the finest “equipment” scale are engineering models based on fundamental knowledge. At the intermediate “value chain” scale, empirical models represent average production technologies, and at the coarsest “economy” scale, models represent monetary and environmental exchanges for industrial sectors in a national or global economy. However, existing methods for sustainable engineering design ignore the economy scale, while existing methods for life cycle assessment do not consider the equipment scale. This work proposes an integrated, multi‐scale modeling framework for connecting models from process to planet (P2P) and using them for sustainable engineering applications. The proposed framework is demonstrated with a toy problem, and potential applications of the framework including current and future work are discussed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-30T06:02:43.832912-05:
      DOI: 10.1002/aic.14919
       
  • Future Feedstocks For the Chemical Industry—Where Will the Carbon
           Come From?
    • Authors: Scott F. Mitchell; Daniel F. Shantz
      PubDate: 2015-06-30T05:45:39.901615-05:
      DOI: 10.1002/aic.14910
       
  • Sustainable Process Design by the Process to Planet Framework
    • Authors: Rebecca J. Hanes; Bhavik R. Bakshi
      Abstract: Sustainable process design (SPD) problems combine a process design problem with life cycle assessment (LCA) to optimize process economics and life cycle environmental impacts. While SPD makes use of recent advances in process systems engineering and optimization, its use of LCA has stagnated. Currently, only process LCA is utilized in SPD, resulting in designs based on incomplete and potentially inaccurate life cycle information. To address these shortcomings, the multi‐scale process to planet (P2P) modeling framework is applied to formulate and solve the SPD problem. The P2P framework offers a more comprehensive analysis boundary than conventional SPD and greater modeling detail than advanced LCA methodologies. Benefits of applying this framework to SPD are demonstrated with an ethanol process design case study. Results show that current methods shift emissions outside the analysis boundary, while applying the P2P modeling framework results in environmentally superior process designs. Future extensions of the P2P framework are discussed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-30T05:28:25.579045-05:
      DOI: 10.1002/aic.14918
       
  • Assessing the performance of an industrial SBCR for fischer‐tropsch
           synthesis: Experimental and modeling
    • Authors: Laurent Sehabiague; Omar M. Basha, Zhansheng Shi, Haolin Jia, Yemin Hong, Li Weng, Zhuowu Men, Yi Cheng, Ke Liu, Badie Morsi
      Abstract: The main objective of this study is to predict the performance of an industrial‐scale (ID = 5.8 m) slurry bubble column reactor (SBCR) operating with iron‐based catalyst for Fischer‐Tropsch (FT) synthesis, with emphasis on catalyst deactivation. In order to achieve this objective, a comprehensive reactor model, incorporating the hydrodynamic and mass transfer parameters (gas holdup, εG, Sauter‐mean diameter of gas bubbles, d32, and volumetric liquid‐side mass transfer coefficients, kLa), and FT as well as water gas shift (WGS) reaction kinetics, was developed. The hydrodynamic and mass transfer parameters for He/N2 gaseous mixtures, as surrogates for H2/CO, were obtained in an actual molten FT reactor wax produced from the same reactor. The data were measured in a pilot‐scale (0.29 m) SBCR under different pressures (4‐31 bar), temperatures (380‐500 K), superficial gas velocities (0.1‐0.3 m/s) and iron‐based catalyst concentrations (0‐45 wt%). The data were modeled and predictive correlations were incorporated into the reactor model. The reactor model was then used to study the effects of catalyst concentration and reactor length‐to‐diameter ratio (L/D) on the water partial pressure, which is mainly responsible for iron catalyst deactivation, the H2 and CO conversions and the C5+ product yields. The modeling results of the industrial SBCR investigated in this study showed that (1) the water partial pressure should be maintained under 3 bars in order to minimize deactivation of the iron‐based catalyst used; (2) the catalyst concentration has much more impact on the gas holdup and reactor performance than the reactor height; and (3) the reactor should be operated in the kinetically‐controlled regime with an L/D of 4.48 and a catalyst concentration of 22 wt% in order to maximize C5+ products yield, while minimizing the iron catalyst deactivation. Under such conditions, the H2 and CO conversions were 49.4% and 69.3%, respectively and the C5+ products yield was 435.6 ton/day. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-27T10:36:26.930008-05:
      DOI: 10.1002/aic.14931
       
  • Droplets sliding over shearing surfaces studied by molecular dynamics
    • Authors: J.J. Derksen
      Abstract: We study, through molecular dynamics, the sliding motion of a liquid drop embedded in another liquid over a substrate as a result of a shear flow. The two immiscible Lennard‐Jones liquids have the same density and viscosity. The system is isothermal. Viscosity, surface tension, and static contact angles follow from calibration simulations. Sliding speeds and drop deformations (in terms of dynamic contact angles) are determined as a function of the shear rate. The latter is non‐dimensionalized as a capillary number (Ca) that has been varied in the range 0.02 to 0.64. For Ca up to 0.32, sliding speeds are approximately linear in Ca. For larger Ca, very strong droplet deformations are observed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-27T10:36:01.14552-05:0
      DOI: 10.1002/aic.14930
       
  • Evaluation of pure‐component adsorption properties of silicalite
           based on the langmuir and sips models
    • Authors: Alessio Caravella; Pasquale F. Zito, Adele Brunetti, Enrico Drioli, Giuseppe Barbieri
      Abstract: In this work, the adsorption parameters of several light gases and hydrocarbons (H2, CH4, CO2, CO, N2, C2H6, C3H8, n‐C4H10) in Silicalite are estimated along with and their functionality with temperature using both Langmuir and Sips models. This is a scientific attempt to resume and reconcile the number of available experimental data and supply scientists and other operators with the adsorption properties of silicalite within a wider range of temperature and pressure. Furthermore, to provide readers with more detailed information on where each of the two models work better, the analysis is divided into three temperature ranges: low‐temperature, high‐temperature and whole temperature range. As a result, it is found that the Langmuir model works well in the whole temperature range for the light gases considered but not for the other hydrocarbons, for which it is better to use the Sips model by splitting calculation over low‐ and high‐temperature range. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-27T10:34:34.560883-05:
      DOI: 10.1002/aic.14925
       
  • Pure H2 production through hollow fiber hydrogen‐selective MFI
           zeolite membranes using steam as sweep gas
    • Authors: Yuting Zhang; Qi Sun, Xuehong Gu
      Abstract: Hollow fiber MFI zeolite membranes were modified by catalytic cracking deposition of methyldiethoxysilane (MDES) to enhance their H2/CO2 separation performance and further employed in high temperature water gas shift membrane reactor (MR). Steam was used as the sweep gas in the MR for the production of pure H2. Extensive investigations were conducted on MR performance by variations of temperature, feed pressure, sweep steam flow rate and steam‐to‐CO ratio. CO conversion was obviously enhanced in the MR as compared with conventional packed‐bed reactor (PBR) due to the coupled effects of H2 removal as well as counter‐diffusion of sweep steam. Significant increment in CO conversion for MR vs. PBR was obtained at relatively low temperature and steam‐to‐CO ratio. A high H2 permeate purity of 98.2% could be achieved in the MR swept by steam. Moreover, the MR exhibited an excellent long‐term operating stability for 100 h in despite of the membrane quality. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-27T10:34:08.318729-05:
      DOI: 10.1002/aic.14924
       
  • High activity and wide temperature window of
           Fe‐Cu‐SSZ‐13 in the selective catalytic reduction of NO
           with ammonia
    • Authors: Tao Zhang; Jianmei Li, Jian Liu, Daxi Wang, Zhen Zhao, Junhua Li, Kai Cheng
      Abstract: Fe‐Cu‐SSZ‐13 catalysts were prepared by aqueous solution ion‐exchange method based on the one‐pot synthesized Cu‐SSZ‐13. The catalysts were applied to the selective catalytic reduction of NO with NH3 and characterized by the means of XRD, UV‐Vis, EPR, XPS, NH3‐TPD, and so on. The selected Fe‐Cu‐SSZ‐13‐1 catalyst exhibited the high NO conversion (> 90%) in the wide temperature range (225‐625 oC), which also showed good N2 selectivity and excellent hydrothermal stability. The results of XPS showed that the Cu and Fe species were in the internal and outer parts of the SSZ‐13 crystals, respectively. The results of UV‐Vis and EPR indicated that the monomeric Cu2+ ions coordinated to three oxygen atoms on the six‐ring sites and Fe monomers are the real active species in the NH3‐SCR reaction. Furthermore, the influence of intra‐crystalline mass‐transfer limitations on the Fe‐Cu‐SSZ‐13 catalysts is related to the location of active species in the SSZ‐13 crystals. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-27T10:33:49.597788-05:
      DOI: 10.1002/aic.14923
       
  • NMR imaging of low pressure, gas‐phase transport in packed beds
           using hyperpolarised xenon‐129
    • Authors: Galina Pavlovskaya; Navin Gopinathan, Joseph Six, Thomas Meersman, Sean P. Rigby
      Abstract: Gas‐phase MRI has been used to investigate heterogeneity in mass transport in a packed bed of commercial, alumina, catalyst supports. Hyperpolarised 129Xe MRI enables study of transient diffusion for microscopic porous systems using xenon chemical shift to selectively image gas within the pores, and, thence, permits study of low‐density, gas‐phase mass‐transport, such that diffusion can be studied in the Knudsen regime, and not just the molecular regime, which is the limitation with other current techniques. Knudsen‐regime diffusion is common in many industrial, catalytic processes. Significantly larger spatial variability in mass transport rates across the packed bed was found compared to techniques using only molecular diffusion. It has thus been found that that these heterogeneities arise over length‐scales much larger than ∼100 microns This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-27T10:33:48.259054-05:
      DOI: 10.1002/aic.14929
       
  • Phthalic anhydride production from hemicellulose solutions: Technoeconomic
           analysis and life cycle assessment
    • Authors: Zhaojia Lin; Vladimiros Nikolakis, Marianthi Ierapetritou
      Abstract: This work presents the process synthesis, technoeconomic analysis and life cycle assessment of a novel route for phthalic anhydride (PAN) production from hemicellulose solutions. The production contains six steps including dehydration of xylose to furfural, reductive decarbonylation of furfural to furan, oxidation of furfural to maleic anhydride (MA), Diels‐Alder cycloaddition of furan and MA to exo‐4,10‐dioxa‐tricyclo[5.2.1.0]dec‐8‐ene‐3,5‐dione followed by dehydration to PAN in the presence of mixture of methanesulfonic acid and acetic anhydride (AAN) which is converted to acetyl methanesulfonate and acetic acid (AAD), and dehydration of AAD to AAN. The minimum selling price of PAN is determined to be $810/metric ton about half of oil‐based PAN. The coproduction of high‐value products is essential to improve the economics. Biomass feedstock contributes to the majority of cost. LCA results shows that biomass‐based PAN has advantages over oil‐based PAN to reduce climate change and fossil depletion however requires more water usage. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-25T02:08:41.867446-05:
      DOI: 10.1002/aic.14921
       
  • Jamming of cellulose ether solutions in porous medium
    • Authors: C. Marliere; D. Vlassopoulos, P. Faure, A. Larsen, B. Loppinet, P. Coussot
      Abstract: We investigate the flow of aqueous cellulose ether solutions through a bead packing using MRI (Magnetic Resonance Imaging) and filtration measurements. We observe a rather complex behaviour dominated by jamming (clogging) and unjamming phenomena in time. With the help of several characterization techniques (laser grain sizing, dynamic light scattering, optical microscopy, rheometry) we confirm that the particular methyl(hydroxyethyl) cellulose prepared with a specific protocol, tends to form aggregates in water, even at the lowest achievable concentration. These aggregates are highly polydisperse, ranging from hundred nanometers to hundred microns in size, and are deformable. Their origin appears to be the hydrophobic links among molecules and the related local crystallization. It is suggested that these features play a key role in the observed jamming/unjamming during filtration tests. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-25T02:07:34.49213-05:0
      DOI: 10.1002/aic.14920
       
  • Breakage and Adhesion Maps for the Normal Impact of Loose Agglomerates
           with a Spherical Target
    • Authors: Duy Nguyen; Anders Rasmuson, Kyrre Thalberg, Ingela Niklasson Björn
      Abstract: DEM‐based analysis is conducted to investigate the effects of interface energy between particles on the breakage and adhesion of loose agglomerates upon impact with a spherical target. A mechanistic approach is tested to find a relationship between particle properties and the agglomerate structure after the impact, which resulted in a new dimensionless number, i.e. the ratio of the two interface energies. In combination with Δ ‐ a dimensionless number relating incident kinetic energy to agglomerate strength 1, a good description of the agglomerate impact is obtained. The agglomerate structure after impact is mapped using the two dimensionless numbers and is in good agreement with experimental observations. The constructed regime map can serve as a guide for selecting preliminary process parameters in adhesive particle mixing. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-25T02:06:50.915939-05:
      DOI: 10.1002/aic.14922
       
  • Radial pressure profiles in a cold‐flow Gas‐Solid Vortex
           Reactor
    • Authors: M.N. Pantzali; J.Z. Kovacevic, V.N. Shtern, G.J. Heynderickx, G.B. Marin
      Abstract: A unique normalized radial pressure profile characterizes the bed of a Gas‐Solid Vortex Reactor (GSVR) over a range of particle densities and sizes, solid capacities and gas flow rates: 950‐1240 kg/m3, 1‐2 mm, 2 kg to maximum solids capacity and 0.4‐0.8 Nm3/s (corresponding to gas injection velocities of 55‐110 m/s) respectively. The combined momentum conservation equations of both gas and solid phases predict this pressure profile when accounting for the corresponding measured particle velocities. The pressure profiles for a given type of particles and a given solids loading but for different gas injection velocities merge into a single curve when normalizing the pressures with the pressure value downstream of the bed. The normalized ‐with respect to the overall pressure drop‐ pressure profiles for different gas injection velocities in particle‐free flow merge in a unique profile. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-24T02:26:22.259474-05:
      DOI: 10.1002/aic.14912
       
  • An integrated Framework for Scheduling and Control Using Fast Model
           Predictive Control
    • Authors: Jinjun Zhuge; Marianthi G. Ierapetritou
      Abstract: Integration of scheduling and control involves extensive information exchange and simultaneous decision making in industrial practice 1,2. Modeling the integration of scheduling and dynamic optimization at control level using mathematical programming results in a Mixed Integer Dynamic Optimization (MIDO) which is computationally expensive 3. In this study, we propose a framework for the integration of scheduling and control to reduce the model complexity and computation time. We identify a piece‐wise affine (PWA) model from the first principle model and integrate it with the scheduling level leading to a new integration. At the control level we employ fast Model Predictive Control (fast MPC) to track a dynamic reference. Fast MPC also overcomes the increasing dimensionality of multi‐parametric MPC in our previous study.4 Results of CSTR case studies prove that the proposed approach reduces the computing time by at least two orders of magnitude compared to the integrated solution using mp‐MPC. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-24T02:25:42.950339-05:
      DOI: 10.1002/aic.14914
       
  • Impact of Water Film Thickness on Kinetic Rate of Mixed Hydrate Formation
           During Injection of CO2 Into CH4 Hydrate
    • Authors: Khuram Baig; Bjørn Kvamme, Tatiana Kuznetsova, Jordan Bauman
      Abstract: In this work non‐equilibrium thermodynamics and phase field theory (PFT) has been applied studies of the kinetics of phase transitions associated with CO2 injection into systems containing CH4 hydrate, free CH4 gas, and varying amounts of liquid water. The CH4 hydrate was converted into either pure CO2 or mixed CO2‐CH4 hydrate to investigate the impact of two primary mechanisms governing the relevant phase transitions: solid‐state mass transport through hydrate and heat transfer away from the newly formed CO2 hydrate. Experimentally‐proven dependence of kinetic conversion rate on the amount of available free pore water was investigated and successfully reproduced in our model systems. We found that rate of conversion was directly proportional to the amount of liquid water initially surrounding the hydrate. When all of the liquid has been converted into either CO2 or mixed CO2‐CH4 hydrate, a much slower solid‐state mass transport becomes the dominant mechanism. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-24T02:25:08.74865-05:0
      DOI: 10.1002/aic.14913
       
  • An Energy‐Efficient Cost‐Effective Transient Batch Rectifier
           with Bottom Flashing: Process Dynamics and Control
    • Authors: Amiya K. Jana
      Abstract: Exploring an internal heat source through bottom flashing route, this work introduces a dynamic batch column configuration within the framework of mechanical heat pump system. This batch rectifier with bottom flashing (BRBF) scheme attempts to employ the reboiler liquid as a heat exchanging medium in the overhead condenser, thereby avoiding the use of any external coolant stream and reducing the consumption of hot utility in the reboiler. Aiming to operate the proposed transient process unit at an optimal state of energy use, we formulate an online open‐loop control policy that estimates the multiple control actions simultaneously. Furthermore, in order to achieve constant product purity, a gain‐scheduled closed‐loop control system is synthesized with keeping the stability margin constant. Simulating a multicomponent reactive system, the novel BRBF arrangement is evaluated in the aspects of energy savings and cost under both the open‐loop and closed‐loop control modes. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-24T02:24:41.556754-05:
      DOI: 10.1002/aic.14915
       
  • Systematic design of an extractive distillation for maximum‐boiling
           azeotropes with heavy entrainers
    • Authors: Weifeng Shen; Jie Li, Hassiba Benyounes, Lichun Dong, Shun'an Wei, Xinqiang You, Vincent Gerbaud
      Abstract: Extractive distillation is one of the most attractive approaches for separating azeotropic mixtures. Few contributions have been reported to design an extractive distillation for separating maximum‐boiling azeotropes and no systematic approaches for entrainer screening have been presented. In this paper, we propose a systematic approach to design of two‐column extractive distillation for separating azeotropes with heavy entrainers. We first conduct a thermodynamic feasibility analysis for azeotropes with potential heavy entrainers. Then, five important properties are selected for entrainer evaluation. We employ fuzzy logic and develop membership functions to calculate attribute values of selected properties. An overall indicator for entrainer evaluation is proposed and a ranking list is generated. Finally, we select the top five entrainers from the ranking list and use process optimization techniques to further evaluate selected entrainers and generate an optimal design. The capability of the proposed method is illustrated using the separation of acetone‐chloroform azeotropes with five potential entrainers. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-18T17:59:17.666074-05:
      DOI: 10.1002/aic.14908
       
  • A filtration model for prediction of local flux distribution and
           optimization of submerged hollow fiber membrane module
    • Authors: Xianhui Li; Jianxin Li, Hong Wang, Xiaoxu Huang, Benqiao He, Yonghong Yao, Jie Wang, Hongwei Zhang, Huu Hao Ngo, Wenshan Guo
      Abstract: A filtration mathematical model was developed on the basis of complete mass balance and momentum balance for the local flux distribution prediction and optimization of submerged hollow fiber membrane module. In this model, the effect of radial permeate flow on internal flow resistance was considered through a slip parameter obtained from the local flux experiments. The effects of fiber length, inside diameter and average operating flux on local flux distribution were investigated using this model. The predicted results were in good agreement with the experimental data obtained from literature. It was also found that the asymmetry distribution of local flux could be intensified with the increase of average operating flux and fiber length, but slowed down with the increase of fiber inside diameter. Furthermore, the simulation coupled with energy consumption analysis could efficiently predict and illustrate the relationship between fiber geometry and water production efficiency. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-18T17:55:21.740497-05:
      DOI: 10.1002/aic.14906
       
  • Nonlinear PI Controllers with Output Transformations
    • Authors: Jietae Lee; Thomas F. Edgar
      Abstract: Well‐designed nonlinear proportional‐integral (PI) controllers are successful for nonlinear dynamical processes like linear PI controllers are for linear processes. Two nonlinear blocks representing proportional and integral terms can be designed so that the linearized controllers perform the same as linear PI controllers for linearized processes at the given operating points. For some nonlinear processes, nonlinear blocks for nonlinear PI controllers can be singular at some operating points, and control performances can be poor for set points near those points. To mitigate such disadvantages, new nonlinear PI controllers that introduce output transformations are proposed. Several examples are given, showing the performance of the proposed nonlinear PI controllers. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-17T17:54:55.625143-05:
      DOI: 10.1002/aic.14907
       
  • Filtration model for polydisperse aerosols in gas‐solid flow using
           granule‐resolved direct numerical simulation
    • Authors: R. Kolakaluri; E. Murphy, R. C. Brown, R. O. Fox, S. Subramaniam
      Abstract: An analytical framework for calculating the filtration efficiency of polydisperse aerosols in a granular bed is developed for cases where inertial impaction and interception are the principal filtration mechanisms. This framework is used to develop a model for the polydisperse single‐collector efficiency from monodisperse single‐collector efficiency correlations. Conceptually, the polydisperse model is developed by transforming the probability density of particle radius into a probability density of particle Stokes number that is then used to weight the monodisperse single‐collector efficiency at a given Stokes number. An extension of this polydisperse filtration concept results in an analytical solution for the axial variation of polydisperse particle flux in a random three‐dimensional (3D) granule configuration. In order to verify the analytical results for polydisperse particle filtration, a granule–resolved Direct Numerical Simulation (DNS) approach is coupled with Lagrangian Particle Tracking (LPT) to simulate filtration of polydisperse aerosols in a granular bed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-15T02:25:43.8892-05:00
      DOI: 10.1002/aic.14901
       
  • Scanning curves in wedge pore with the wide end closed: Effects of
           temperature
    • Authors: Nikom Klomkliang; D.D. Do, D. Nicholson
      Abstract: The desorption scanning curves within the hysteresis loop of argon adsorbed in a wedge shaped pore with its wide end closed, have been studied in the temperature range between 60 and 87K, using grand canonical Monte Carlo simulation. The distinct features are: (1) adsorbate packing follows a sequence of commensurate regions (zones) and incommensurateregions (junctions); (2) the mechanism forevaporationswitches from cavitation‐like pore blocking to cavitation when the temperature is increased; as typically observed for ink‐bottle pores. When cavitation is the operating mechanism, the descending scanning curve spans across the loop in two stages: a gradual decrease in density in azonefollowed by a sharp evaporation froma junction, and then terminates at the lowest point on the vertical cavitation boundary. The adsorption scanning curve proceeds across the loop in two stages complementary to the desorption scanning‐curve:a gradual change in density ata junction followed by a sharp change througha zone. On the other hand, when cavitation‐like pore blocking is operating, the descending curve leaves the adsorption boundary, spans across the hysteresis loop and returns to a different point on the same boundary, rather than to the desorption boundary or to the lower closure point. This feature does not seem to have been recognized in earlier literature, and should be considered in the classification of scanning curves. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-12T11:12:37.864639-05:
      DOI: 10.1002/aic.14905
       
  • Degradation mechanism analysis of Ba0.5Sr0.5Co0.8Fe0.2O3‐δ
           membranes at intermediate‐low temperatures
    • Authors: Yan Liu; Xuefeng Zhu, Weishen Yang
      Abstract: The degradation of the permeation flux of Ba0.5Sr0.5Co0.8Fe0.2O3‐δ membranes has typically been attributed to the phase transformation of the material at intermediate temperatures. In this study, the effect of the interfacial oxygen exchange steps was considered to give an overall view of the degradation mechanism. The changes in the interfacial exchange resistances, bulk resistance, and morphologies of the membranes were investigated via physical characterizations and a permeation model. The interfacial oxygen exchange resistances increased more quickly with time than bulk resistance. Meanwhile, BaSO4 particles were detected on both surfaces of the membranes, and their contents reached maximum at 650°C. However, after the membrane surfaces were coated by Sm0.5Sr0.5CoO3‐δ porous layers, the interfacial oxygen exchange resistances kept constant and the degradation rates were slowed down. The degradation was predominated by the increase of interfacial oxygen exchange resistances induced by the enrichment of BaSO4 particles on membrane surfaces. © 2015 American Institute of Chemical Engineers AIChE J, 2015
      PubDate: 2015-06-11T13:26:29.951524-05:
      DOI: 10.1002/aic.14900
       
  • A new bubbling extraction tower: Towards liquid‐liquid solvent
           extraction at large aqueous‐to‐oil phase ratios
    • Authors: Jie Liu; Kun Huang, Huaizhi Wu, Huizhou Liu
      Abstract: Enrichment and recovery of valuable components in industrial waste waters by traditional liquid‐liquid solvent extraction is not economic due to extremely low concentrations of those targets. Large‐phase‐ratio extraction exhibits potential advantages for recovery of small quantities of target components from large volume of aqueous solutions. In present work, a novel bubbling extraction tower is proposed towards performing solvent extraction at large aqueous‐to‐oil phase ratios. Organic extractants were covered onto surface of gas bubbles to form a layer of organic liquid membrane and the dispersed organic phase in tower could be small enough. The target components are extracted from aqueous feed solution onto the surface of the bubbles, and the enrichment ratios could be extremely high. We develop a feasible methodology to calculate tower height and operation phase ratios of the bubbling extraction tower, which is essential for future industrial scale‐up. Experimental results in pilot test are highly consistent with calculations. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-11T00:53:25.001099-05:
      DOI: 10.1002/aic.14904
       
  • Dynamic Modeling of a Multiple Hearth Furnace for Kaolin Calcination
    • Authors: Aleksi Eskelinen; Alexey Zakharov, Jonathan Hearle, Sirkka‐Liisa Jämsä‐Jounela
      Abstract: A dynamic model of a multiple hearth kaolin calciner has been developed and is presented in this paper. This model describes the physical‐chemical phenomena taking place in the six furnace parts: the solid phase, gas phase, walls, cooling air, rabble arms and the central shaft. The solid phase movement, in particular, is described by a novel mixing model. The mixing model divides the solid bed in a hearth into volumes and the distribution of their contents, after one full central shaft rotation, is identified by the pilot experiments. First, the model is validated by the industrial data, and then the dynamics of the multiple hearth furnace (MHF) is studied by introducing step changes to the three manipulated variables: the feed rate, and the gas and air flows supplied. The responses of the gas phase temperature and solid bed component profiles are analysed and the results are discussed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-09T00:16:52.578066-05:
      DOI: 10.1002/aic.14903
       
  • Mechanistic insights into the structure dependent selectivity of catalytic
           furfural conversion on platinum catalysts
    • Authors: Qiu‐Xia Cai; Jian‐Guo Wang, Yang‐gang Wang, Donghai Mei
      Abstract: The effects of surface structures on the selectivity of catalytic furfural conversion over platinum (Pt) catalysts in the presence of hydrogen have been studied using first principles density functional theory (DFT) calculations and microkinetic modeling. Three Pt model surface structures, i.e., flat Pt(111), stepped Pt(211) and Pt55 cluster are chosen to represent the terrace, step, and corner sites of Pt nanoparticle. DFT results show that the dominant reaction route (hydrogenation or decarbonylation) in furfural conversion depends strongly on the structures (or reactive sites). Using the size‐dependent site distribution rule, our microkinetic modeling results indicate the decarbonylation route prevails over smaller Pt particles less than 1.4 nm while the hydrogenation is the dominant reaction route over larger Pt catalyst particles at T = 473 K and PH2 = 93 kPa. This is in good agreement with the reported experimental observations. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-06T02:47:37.214882-05:
      DOI: 10.1002/aic.14902
       
  • Bubble formation and dynamics in a quiescent high‐density liquid
    • Authors: I. Chakraborty; Gautam Biswas, P. Satyamurthy, P.S. Ghoshdastidar
      Abstract: Gas bubble formation from a submerged orifice under constant‐flow conditions in a quiescent high‐density liquid metal, lead–bismuth eutectic (LBE), at high Reynolds numbers was investigated numerically. The numerical simulation was carried out using a coupled level‐set and volume‐of‐fluid (CLSVOF) method governed by axisymmetric Navier–Stokes equations. The ratio of liquid density to gas density for the system of interest was about 15261. The bubble formation regimes varied from quasi‐static to inertia‐dominated and the different bubbling regimes such as period‐1 and period‐2 with pairing and coalescence were described. The volume of the detached bubble was evaluated for various Weber numbers, We, at a given Bond number, Bo, with Reynolds number Re≫1. It was found that at high values of the Weber number, the computed detached bubble volumes approached a 3/5 power law. The different bubbling regimes were identified quantitatively from the time evolution of the growing bubble volume at the orifice. It was shown that the growing volume of two consecutive bubbles in the period‐2 bubbling regime was not the same whereas it was the same for the period‐1 bubbling regime. The influence of grid resolution on the transition from period‐1 to period‐2 with pairing and coalescence bubbling regimes was investigated. It was observed that the transition is extremely sensitive to the grid size. The transition of period‐1 and period‐2 with pairing and coalescence is shown on a Weber–Bond numbers map. The critical value of Weber number signalling the transition from period‐1 to period‐2 with pairing and coalescence decreases with Bond number as We ∼ Bo−1, which is shown to be consistent with the scaling arguments. Furthermore, comparisons of the dynamics of bubble formation and bubble coalescence in LBE and water systems are discussed. It was found that in a high Reynolds number bubble formation regime, a difference exists in the transition from period‐1 to period‐2 with pairing and coalescence between the bubbles formed in water and the bubbles formed in LBE. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-03T02:53:16.819545-05:
      DOI: 10.1002/aic.14896
       
  • Shear dispersion in combined pressure‐driven and
           electro‐osmotic flows in a capillary tube with a porous wall
    • Authors: Morteza Dejam; Hassan Hassanzadeh, Zhangxin Chen
      Abstract: An analytical expression is derived for the shear dispersion during transport of a neutral non‐reacting solute within a coupled system comprised of a capillary tube and a porous medium under the combined effects of pressure‐driven and electro‐osmotic flows. We use the Reynolds decomposition technique to obtain a dispersion coefficient by considering a sufficiently low wall or zeta potential that accounts for the combined flows. The coupled dispersion coefficient depends on the Debye‐Hückel parameter, Poiseuille contribution fraction, and Péclet number. The developed model also provides a shear dispersion coefficient for an impervious capillary tube (non‐coupled system). The ratio of the coupled (porous wall) and non‐coupled (impervious) dispersion coefficients reveals that it is essential to include the transport of chemical species from the tube to the porous medium in several important physical situations. These findings have implications for design of chemical species transport in porous microfluidic networks and separation of emulsions in microchannel‐membrane systems. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-03T02:52:26.847773-05:
      DOI: 10.1002/aic.14897
       
  • Dissipativity‐based distributed model predictive control with low
           rate communication
    • Authors: Chaoxu Zheng; Michael James Tippett, Jie Bao, Jinfeng Liu
      Abstract: Distributed or networked model predictive control can provide a computationally efficient approach that achieves high levels of performance for plantwide control, where the interactions between processes can be determined from the information exchanged among controllers. Distributed controllers may exchange information at a lower rate to reduce the communication burden. In this work, a dissipativity‐based analysis is developed to study the effects of low communication rates on plantwide control performance and stability. A distributed dissipativity‐based model predictive control design approach is also developed to guarantee the plantwide stability and minimum plantwide performance with low communication rates. These results are illustrated by a case study of a reactor‐distillation column network. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-03T02:51:55.749042-05:
      DOI: 10.1002/aic.14899
       
  • Nucleation curves of model natural gas hydrates on a quasi‐free
           water droplet
    • Authors: Nobuo Maeda
      Abstract: We studied heterogeneous nucleation probability distributions of gas hydrates on a water droplet that was supported by inert and immiscible perfluorocarbon oil, perfluorodecalin. The guest gas used was a mixture of 90 mol% methane and 10 mol% propane. The probability distribution was measured using a High Pressure Automated Lag Time Apparatus (HP‐ALTA) under the guest gas pressure range of 6.7 to 12.5 MPa and the cooling rate range of 0.002K/sec to 0.02K/sec. Nucleation curves were derived for unit area of water surface. We also derived the nucleation rate per unit area of water surface that was contained in a glass sample cell, which differed significantly from that on a quasi‐free water droplet. It is concluded that the nucleation curves in the presence of a solid wall should be normalized to the unit length of the three‐phase line at which water, guest gas and the solid wall meet. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-03T02:51:30.077497-05:
      DOI: 10.1002/aic.14898
       
  • On the leakage flow around gas bubbles in slug flow in a microchannel
    • Authors: Chaoqun Yao; Zhengya Dong, Yuchao Zhang, Yuan Mi, Yuchao Zhao, Guangwen Chen
      Abstract: The leakage flow is that liquid does not push gas bubbles and leaks through the channel corners. This leakage flow was confirmed by tracking particles moving in the liquid film with a double light path method and was quantified by tracking the gas‐liquid interface movement. The results show that leakage flow varies during bubble formation process. The average net leakage flow Qnet‐leak in a bubble formation cycle at T‐junction can be as large as 62.4% of the feeding liquid flow rate, depending on the liquid properties. Qnet‐leak for regular flow at main channel is much smaller, ranging from about 0 to 30% of the feeding liquid flow rate. The difference between the two leakage flows would lead to an increase in liquid slug length after generation. Finally, the effects of parameters such as phase flow rates, surface tension and viscosity were investigated. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-03T02:47:14.81168-05:0
      DOI: 10.1002/aic.14895
       
  • Azimuthally oscillating membrane emulsification for controlled droplet
           production
    • Authors: Pedro S. Silva; Mike Stillwell, Bruce Williams, Marijana Dragosavac, Goran T. Vladisavljević, Hemaka Bandulasena, Richard G. Holdich
      Abstract: A novel membrane emulsification system is reported consisting of a tubular metal membrane, periodically azimuthally (tangentially) oscillated with frequencies up to 50 Hz and 7 mm displacement in a gently cross flowing continuous phase. A CFD analysis showed consistent axial shear at the membrane surface, which became negligible at distances from the membrane surface greater than 0.5 mm. For comparison, CFD analysis of a fully rotating membrane emulsification system showed local vortices in the continuous phase leading to a variable shear along the axis of the membrane. Using an azimuthally oscillating membrane, oil‐in‐water emulsions were experimentally produced with a median diameter of 20‐120 µm, and a coefficient of variation of droplet size of 8%. The drop size was correlated with shear stress at the membrane surface using a force balance. In a single pass of continuous phase it was possible to achieve high dispersed phase concentrations of 40% v/v. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-03T02:42:23.172721-05:
      DOI: 10.1002/aic.14894
       
  • Kinetic Study of Reactions of Aniline and Benzoyl Chloride in a
           Microstructured Chemical System
    • Authors: Peijian Wang; Kai Wang, Jisong Zhang, Guangsheng Luo
      Abstract: The reaction between aniline and benzoyl chloride is well known for producing high performance polymers and chemicals. But the fast main reaction and reversible consecutive side reaction make process rather complicated and no thorough kinetics study has ever been reported before. A microstructured chemical system, consisting of a micromixer, pre‐heat exchange coiled capillaries, a delay loop and a microhydrolyzer, was designed to carry out this reaction in this study using NMP as the solvent. A kinetic model was established, and the values of kinetic constants, pre‐exponential factors and activation energies of each reaction as well as their confidence intervals were acquired. With this model each substance concentration versus residence time were obtained to help understand reaction process and further optimize operating conditions. Compared to earlier reports on this reaction, this microstructured chemical system provides more accurate parameters and can develop a reliable platform for kinetic study of similar chemical reactions. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-29T11:32:28.801191-05:
      DOI: 10.1002/aic.14891
       
  • Pressure Cycling for Purging of Dead Spaces in High‐Purity Gas
           Delivery Systems
    • Authors: Jivaan Kishore; Farhang Shadman, Roy Dittler, Carl Geisert
      Abstract: The purging of stagnant or dead volumes in gas distribution systems is an important method for removing impurities and maintaining cleanliness. A combination of experimental investigation and computational process modeling is used to study the dynamics of impurity removal under variety of purge conditions. The controlled cycling of pressure during purge is found to enhance the cleaning process significantly, particularly in dead spaces. The process simulator was used to develop and analyze a pressure‐cyclic purge (PCP) method and understand the conditions that would make PCP advantageous over steady‐state purge (SSP). In particular, the effect of geometric factors, impurity surface interactions, flow rate, and cycle characteristics on PCP and its comparison with SSP was studied. The advantage of the PCP method, in terms of both purge time and gas usage, becomes more pronounced in systems with larger number and size of dead spaces and impurities that interact strongly with the surfaces. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-29T11:28:52.597524-05:
      DOI: 10.1002/aic.14890
       
  • Droplet velocity, size, and local holdup measurements in an extraction
           column by tri‐sensor optical probe
    • Authors: Tingliang Xie; Yang Gao, Wei Liu
      Abstract: The tri‐sensor optical probe was applied to study the hydrodynamic characteristic in a pulsed sieve plate extraction column. Two immiscible liquids consisting of the dispersed phase (kerosene) and continuous phase (water) were introduced in countercurrent operation. Local parameters such as droplet velocity, drop size and holdup of the dispersed phase were obtained. It was found that the tri‐sensor optical probe could be used as an efficient and convenient technique for measuring local hydrodynamic parameters inside the pulsed sieve plate extraction column. Furthermore, the results indicated that pulsation intensity imposed more influence on these hydrodynamic parameters than two‐phase superficial flow rates in the investigated ranges. Experimental results were found to be in good agreement with the empirical correlations reported in literature. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-27T18:22:36.137888-05:
      DOI: 10.1002/aic.14889
       
  • Concurrent Monitoring of Operating Condition Deviations and Process
           Dynamics Anomalies with Slow Feature Analysis
    • Authors: Chao Shang; Fan Yang, Xinqing Gao, Xiaolin Huang, Johan A.K. Suykens, Dexian Huang
      Abstract: Latent variable (LV) models have been widely used in multivariate statistical process monitoring. However, whatever deviation from nominal operating condition is detected, an alarm is triggered based on classical monitoring methods. Therefore they fail to distinguish real faults incurring dynamics anomalies from normal deviations in operating conditions. In this article, a new process monitoring strategy based on slow feature analysis (SFA) is proposed for the concurrent monitoring of operating point deviations and process dynamics anomalies. Slow features as LVs are developed to describe slowly varying dynamics, yielding improved physical interpretation. In addition to classical statistics for monitoring deviation from design conditions, two novel indices are proposed to detect anomalies in process dynamics through the slowness of LVs. The proposed approach can distinguish whether the changes in operating conditions are normal or real faults occur. Two case studies show the validity of the SFA‐based process monitoring approach. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-23T10:06:03.420087-05:
      DOI: 10.1002/aic.14888
       
  • Experimental and Numerical Investigation of the Dynamics of Loop Seals in
           a Large‐Scale DFB System under Hot Conditions
    • Authors: Anton Larsson; Henrik Ström, Srdjan Sasic, Henrik Thunman
      Abstract: We investigate the dynamics of the loop seals in a large‐scale dual fluidized bed (DFB) system as a function of variations in the flux of the bed material through the seal and changes in the bed material density. These investigations are performed numerically with a computational fluid dynamics (CFD) model and experimentally for the loop seals of the Chalmers 2‐4 MWth DFB gasifier. Both experiments and simulations show that more of the aeration gas leaves the loop seal in the direction of the solids when a low‐density bed material (silica) is used rather than a high‐density one (bauxite). The simulations also reveal homogeneous fluidization in a vertical connection to the loop seal, whereas an inclined connection yields heterogeneous fluidization. The minor discrepancies between the experiments and simulations with silica are attributed to particle agglomeration, and it is proposed that CFD models applied to loop seals should account for this phenomenon. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-23T09:41:53.298603-05:
      DOI: 10.1002/aic.14887
       
  • Hydrodynamical particle containment in a rotor‐stator spinning disc
           device
    • Authors: K.M.P. van Eeten; D.H.J. Hülsman, J. van der Schaaf, J.C. Schouten
      Abstract: A novel type of rotor‐stator spinning disc device is proposed which allows for the entrapment of solid particles solely by hydrodynamic means. In this new configuration, the solid rotating disc is replaced with two conjoined rotors with a variable gap spacing. Liquid is fed through the top stator and can flow out again through the rotor‐rotor interior and the hollow rotation axis. Moreover, the volume between the two rotors is optionally filled with a highly porous reticulated carbon foam. It was found that particle containment was strongly improved by the presence of this reticulated foam as it hinders the buildup of centripetal boundary layer flow near the discs in the interior of the rotor‐rotor assembly. These centripetal boundary layers drag along particles resulting in a loss of containment. Experiments utilising glass beads showed that particles with a diameter down to 17.8 μm can be completely entrapped when a carbon foam is placed between the two conjoined discs at rotor speeds up to the maximum investigated value of 178 rad s−1. Additionally, the rotor‐rotor gap did not have an effect on the particle entrapment level when the reticulated carbon foam was omitted and can be ascribed to the build‐up of boundary layers, which is independent of rotor‐rotor distance. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-23T09:33:14.684942-05:
      DOI: 10.1002/aic.14886
       
  • More effective membrane chromatography
    • Authors: Yong‐Ming Wei; Yanxiang Li, Chuanfang Yang, E.L. Cussler
      Abstract: Adsorption in membranes with polydispersed pores gives a dispersed breakthrough curve even when mass transfer is so fast that it reaches saturation. Such a breakthrough is due to unequal flows in unequally sized pores. A theory of polydispersed pores can predict the breakthrough curves for the removal of lead ions from model solutions if the pore size distribution is known. Such predictions are in better agreement for lead adsorption than predictions based on mass transfer. The results suggest ways in which more effective membrane chromatography can be achieved. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-20T21:11:53.944611-05:
      DOI: 10.1002/aic.14884
       
  • Multiphase transport modeling for vacuum drying of pharmaceutical products
    • Authors: Aditya G. Dodda; Kostas Saranteas, Michael A. Henson
      Abstract: Vacuum drying of active pharmaceutical ingredients (API) is an energy‐intensive process that is often a manufacturing bottleneck. In this paper, we develop a multiphase transport model to predict drying performance under the assumption that boiling is the dominant mechanism. Laboratory scale drying experiments were performed over a range of temperatures and pressures using acetone as the solvent and glass beads of three different particle sizes to mimic APIs. We found that a two phase transport model with the vapor and solid considered as one phase and the liquid treated as the second phase was capable of qualitatively reproducing the drying dynamics. Adjustable model parameters estimated from experimental data collected over a range of operating conditions exhibited trends that provided further insight into drying behavior. We concluded that boiling is the dominant mechanism in vacuum drying and that our transport model captured the key physics of the process. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-19T18:26:59.05646-05:0
      DOI: 10.1002/aic.14879
       
  • Multi‐scale model for solid oxide fuel cell with electrode
           containing mixed conducting material
    • Authors: Daifen Chen; Hanzhi Wang, Shundong Zhang, Moses O. Tade, Huili Chen, Zongping Shao
      Abstract: Solid oxide fuel cells (SOFCs) with electrodes that contain mixed conducting materials usually show very different relationships among microstructure parameters, effective electrode characteristics and detailed working processes from conventional ones. A new multi‐scale model for SOFCs using mixed conducting materials, such as LSCF or BSCF, was developed. It consisted of a generalized percolation micro model to obtain the electrode properties from microstructure parameters and a multiphysics single cell model to relate these properties to performance details. Various constraint relationships between the activation overpotential expressions and electric boundaries for SOFC models were collected by analyzing the local electrochemical equilibrium. Finally, taking a typical LSCF‐SDC/SDC/Ni‐SDC intermediate temperature SOFC as an example, the application of the multi‐scale model was illustrated. The accuracy of the models was verified by fitting 25 experimental I‐V curves reported in literature with a few adjustable parameters; additionally, and several conclusions were drawn from the analysis of simulation results. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-19T18:26:36.019409-05:
      DOI: 10.1002/aic.14881
       
  • Micro‐Structured Bi1.5 Y0.3Sm0.2O3‐δ Catalysts for
           Oxidative Coupling of Methane
    • Authors: Nur Hidayati Othman; Zhentao Wu, K. Li
      Abstract: In this study, Bi1.5 Y0.3Sm0.2O3‐δ (BYS), a ceramic material showing great activity and selectivity to oxidative coupling of methane (OCM), has been fabricated into catalyst rings (i.e. capillary tubes) with a plurality of self‐organised radial microchannels. The unique micro‐channels inside such BYS catalyst rings allow easier access of reactants, as well as increased the surface area, which potentially contributes to higher reaction efficiencies due to improved mass transfer. The micro‐structured BYS catalyst rings were investigated systematically via two types of reactors; (1) randomly packed fixed bed reactor and (2) monolithic‐like structured reactor. These two reactor designs have different flow patterns of reactants, i.e. non‐ideal and ideal flows, which can significantly affect the final OCM performance. A remarkable improvement in C2+ yield (YC2+>20%) was obtained in the monolith‐like structured reactor, in contrast to randomly packed powder and micro‐structured rings (YC2+
      PubDate: 2015-05-19T18:26:16.59569-05:0
      DOI: 10.1002/aic.14883
       
  • Modeling heterogeneous bacterial populations exposed to antibiotics: The
           logistic‐dynamics case
    • Authors: Pratik R. Bhagunde; Vincent H. Tam, Michael Nikolaou
      Abstract: In typical in vitro tests for clinical use or development of antibiotics, samples from a bacterial population are exposed to an antibiotic at various concentrations. The resulting data can then be used to build a mathematical model suitable for dosing regimen design or for further development. For bacterial populations that include resistant subpopulations – an issue that has reached alarming proportions – building such a model is challenging. In prior work we developed a related modeling framework for such heterogeneous bacterial populations following linear dynamics when exposed to an antibiotic. We extend this framework to the case of logistic dynamics, common among strongly resistant bacterial strains. Explicit formulas are developed that can be easily used in parameter estimation and subsequent dosing regimen design under realistic pharmacokinetic conditions. A case study using experimental data from the effect of an antibiotic on a gram‐negative bacterial population exemplifies the usefulness of the proposed approach. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-19T18:25:59.450744-05:
      DOI: 10.1002/aic.14882
       
  • 3‐D numerical simulation of coalescence and interactions of multiple
           horizontal bubbles rising in shear‐thinning fluids
    • Authors: Jingru Liu; Chunying Zhu, Xiaoda Wang, Taotao Fu, Youguang Ma, Huaizhi Li
      Abstract: The dynamics of multiple horizontal bubbles rising from different orifice arrangements in shear‐thinning fluids was simulated numerically by 3‐D Volume of Fluid (VOF) method. The effects of bubble size, rheological properties of shear‐thinning fluids and orifice structure arrangements on multiple bubbles interaction and coalescence were analyzed, and the mechanisms of bubble coalescence and breakup were fully discussed and elucidated. The variation of bubble rising velocity during coalescence process and freely rising processes for different orifice arrangements was also deeply investigated. The critical initial horizontal intervals for coalescence of multiple horizontal bubbles with various orifice arrangements were attained by simulation, which could serve as the critical criterion of bubble coalescence or non‐coalescence. Furthermore, the critical bubble interval was predicted based on the film drainage model, the prediction accords well with the simulation result and is quite conducive for the design and optimization of perforated gas‐liquid contact equipment. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-14T17:28:59.932818-05:
      DOI: 10.1002/aic.14874
       
  • Nonlinear process identification in the presence of multiple correlated
           hidden scheduling variables with missing data
    • Authors: Lei Chen; Shima Khatibisepehr, Biao Huang, Fei Liu, Yongsheng Ding
      Abstract: This paper is concerned with identification of nonlinear processes in the presence of noise corrupted and correlated multiple scheduling variables with missing data. The dynamics of the hidden scheduling variables are represented by a state‐space model with unknown parameters. To assure generality, it is assumed that the multiple correlated scheduling variables are corrupted with unknown disturbances and the identification data‐set is incomplete with missing data. A multiple model approach is proposed to formulate the identification problem of nonlinear systems under the framework of the expectation‐maximization (EM) algorithm. The parameters of the local process models and scheduling variable models as well as the hyperparameters of the weighting function are simultaneously estimated. The particle smoothing technique is adopted to handle the computation of expectation functions. The efficiency of the proposed method is demonstrated through several simulated examples. Through an experimental study on a pilot‐scale multitank system, the practical advantages are further illustrated. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-08T02:32:18.156601-05:
      DOI: 10.1002/aic.14866
       
  • Effects of Combustor Size and Filling Condition on Stability Limits of
           Premixed H2‐Air Flames in Planar Micro‐Combustors
    • Authors: Jun Li; Yuantao Wang, Jinxing Chen, Zhaoli Guo, Xueling Liu
      Abstract: An experimental study on stability limits of premixed hydrogen‐air flames in planar micro‐combustors (H=1 and 1.5 mm) partially filled with porous medium is carried out, focusing on the effects of combustor sizes and filling conditions. Critical conditions for blow‐offs, flashbacks, and breaking through the porous medium are experimentally measured. The blow‐off limits are nearly independent of combustor sizes and filling conditions, while the flashback limits are strongly influenced by the combustor size and the filling conditions. Critical values for breaking through are identified with two different methods, and it is shown that standing combustion waves are settled over a range of velocities, instead of a fixed value of filtration velocity, which is considered an important characteristic of micro‐combustion. Most results can be explained by the classic boundary velocity gradient theory by von Elbe and Lewis, and thus the validity of the theory to the present channel spacings is confirmed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-25T10:12:58.272869-05:
      DOI: 10.1002/aic.14855
       
  • High‐temperature molecular dynamics simulation of cellobiose and
           maltose
    • Authors: Jessica D. Murillo; Melissa Moffet, Joseph J. Biernacki, Scott Northrup
      Abstract: Thermochemical conversion of lignocellulosic biomass to renewable fuels and chemicals occurs through high temperature decomposition of the main structural components in plants, including cellulose, hemicellulose and lignin. Cellulose and hemicellulose comprise mostly carbohydrates. In this study, two disaccharides, maltose and cellobiose, are used as model compounds to explore differences in thermal stability due to the orientation of the glycosidic bond. First principles molecular dynamics (MD) and density functional theory (DFT) have been used to probe the decomposition of these disaccharides during pyrolysis at 700 K. The results suggest that maltose, the α‐disaccharide, is less thermally stable. Dynamic bond length analysis for maltose indicates that several C‐C bonds and the C‐O bonds on the pyranose ring demonstrate signs of weakening, whereas no such scissile bonds were identified for cellobiose. The higher stability of the cellobiose is believed to originate from the persistence of low‐energy hydroxymethyl conformers throughout the simulation which enable strong inter‐ring hydrogen bonding. Thermogravimtetric and mass spectroscopic experiments corroborate the enhanced thermal stability of cellobiose, wherein the onset of decomposition was observed at higher temperatures for cellobiose than for maltose. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-23T23:51:17.924462-05:
      DOI: 10.1002/aic.14854
       
  • Efficient tuning of microstructure and surface chemistry of nanocarbon
           catalysts for ethylbenzene direct dehydrogenation
    • Authors: Zhongkui Zhao; Yitao Dai, Guifang Ge, Guiru Wang
      Abstract: A facile and scalable approach to efficiently tune microstructure and surface chemical properties of N‐doped carbocatalysts through the controlled glucose hydrothermal treatment with diverse parameters and subsequent pyrolysis of pretreated carbonaceous materials with melamine (GHT‐PCM) was presented. Various characterization techniques including HRTEM, BET, XRD, XPS, Raman and FT‐IR were employed to investigate the effect of prior GHT on the microstructure and surface chemical properties of N‐doped carbocatalysts, as well as to reveal the relationship between catalyst nature and catalytic performance in oxidant‐ and steam‐free direct dehydrogenation of ethylbenzene (DDH) for styrene production. It was found that the GHT process and its conditions significantly affect microstructure and surface chemical properties of the N‐doped carbocatalysts, which subsequently influences their catalytic performance in DDH reaction dramatically. Interestingly, the prior GHT can remove the carbon nitride layer formed on parent nanocarbon in the process of melamine pyrolysis, produce structural defects and tune surface element component, through the “detonation” of polysaccharide coating on nanocarbon. The as‐prepared N‐doped CNT (M‐Glu‐CNT) by the established GHT‐PCM approach in this work demonstrates higher catalytic performance (4.6 mmol g−1 h−1 styrene rate with 98% selectivity) to the common N‐doped CNT (M‐CNT, 3.4 mmol g−1 h−1 styrene rate with 98.2% selectivity) as well as to pristine CNT (2.8 mmol g−1 h−1 styrene rate with 96.8% selectivity), mainly ascribed to increased structural defects, enriched surface ketonic C=O groups, and improved basic properties from N‐doping on the M‐Glu‐CNT, those strongly depend on GHT conditions. The excellent catalytic performance of the developed M‐Glu‐CNT catalyst endows it with great potential for future clean production of styrene via oxidant‐ and steam‐free conditions. Moreover, the directed GHT‐PCM strategy can be extended to the other N‐doped carbonaceous materials with enhanced catalytic performance in diverse reactions by tuning their microstructure and surface chemistry. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-22T17:40:02.013477-05:
      DOI: 10.1002/aic.14853
       
  • Control of spatially distributed processes with unknown
           transport‐reaction parameters via two layer system adaptations
    • Authors: Davood Babaei Pourkargar; Antonios Armaou
      Abstract: We consider the control problem of dissipative distributed parameter systems described by semilinear parabolic partial differential equations with unknown parameters and its application to transportreaction chemical processes. The infinite dimensional modal representation of such systems can be partitioned into finite dimensional slow and infinite dimensional fast and stable subsystems. A combination of a model order reduction approach and a Lyapunov‐based adaptive control technique is used to address the control issues in the presence of unknown parameters of the system. Galerkin's method is used to reduce the infinite dimensional description of the system where we apply adaptive proper orthogonal decomposition (APOD) to initiate and recursively revise the set of empirical basis functions needed in Galerkin's method to construct switching reduced order models. The effectiveness of the proposed APOD‐based adaptive control approach is successfully illustrated on temperature regulation in a catalytic chemical reactor in the presence of unknown transport and reaction parameters. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-22T17:39:37.56325-05:0
      DOI: 10.1002/aic.14852
       
  • Effect of ionic strength on bubble coalescence in inorganic salt and
           seawater solutions
    • Authors: J.M. Sovechles; K.E. Waters
      Abstract: Bubble size is of fundamental importance in the flotation process, as it provides the surface area for particle collection. Typically weak surfactants (frothers) are added to process water to reduce bubble coalescence. Certain inorganic electrolytes, which occur naturally in some flotation process water, have been shown to mimic the role of frothers. The concentration at which bubble coalescence is inhibited, the critical coalescence concentration, was determined in a 5.5 L mechanical flotation cell for a series of coalescence inhibiting inorganic salts. To mimic some industrial flotation process water, a synthetic sea salt solution was also tested. It was found that when the multi‐component sea salt solution was broken down into its constituent parts, the addition of the ionic strength of each ion correlated well with the overall ionic strength curve of all the salts tested. The critical coalescence ionic strength ranged from 0.22 to 0.35, with sea salt being 0.26. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-22T17:39:16.488239-05:
      DOI: 10.1002/aic.14851
       
  • Modeling permporometry of mesoporous membranes using dynamic mean field
           theory
    • Authors: A. Rathi; J. R. Edison, D. M. Ford, P. A. Monson
      Abstract: Mesoporous inorganic membranes have significant potential for important small‐molecule separations like carbon dioxide recovery from stack emissions. However, tailoring materials for a given separation remains an outstanding problem. Preferential adsorption, layering and capillary effects, and surface flow are key mechanisms that determine permeation rates and are ultimately linked to the mesopore characteristics. To further the understanding of these systems we propose a modeling approach based on dynamic mean field theory, which has previously been used to study the dynamics of adsorption in mesoporous materials. This theory describes both relaxation dynamics and non equilibrium steady states in membranes and is fully consistent with a mean field density functional theory of the thermodynamics. We demonstrate the capabilities and promise of the approach by modeling a permporometry experiment, in which a light gas permeates through a mesopore in the presence of a condensable vapor at a controlled relative pressure. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-21T00:43:28.411103-05:
      DOI: 10.1002/aic.14846
       
  • Process synthesis for cascade refrigeration system based on exergy
           analysis†
    • Authors: Ha Dinh; Jian Zhang, Qiang Xu
      Abstract: Refrigeration system holds an important role in chemical/petrochemical processes. The traditional cascade refrigeration system (CRS) used in ethylene plants contains multiple refrigerants working at multiple temperature/pressure levels. In this study, a general methodology is developed for the optimal process synthesis of a CRS based on exergy analysis. This procedure involves four stages: i) refrigeration system exergetic analysis; ii) optimization model development for simultaneous synthesis of refrigeration system and heat exchanger network (HEN); iii) HEN configuration; and iv) final solution validation. The exergy‐temperature chart is employed to comprehensively analyze a CRS. A mathematical model is presented to minimize total compressor shaft work of the HEN‐considered CRS, where multiple recycling loops satisfying all cooling/heating demands are simultaneously addressed. The optimal solution is examined by rigorous simulations to verify its feasibility and consistency. The efficacy of the developed methodology is demonstrated by a case study of a propylene CRS in an ethylene plant. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-17T16:10:47.092361-05:
      DOI: 10.1002/aic.14843
       
  • Numerical study of pipeline restart of weakly compressible irreversibly
           thixotropic waxy crude oils
    • Authors: Lalit Kumar; Chris Lawrence, Yansong Zhao, Kristofer Paso, Brian Grimes, Johan Sjöblom
      Abstract: A 3D axisymmetric model is developed to predict pressure wave propagation processes during gelled waxy oil pipeline restart operations. A finite volume method is implemented on a staggered grid. An iterative predictor‐corrector algorithm provides solutions to the combined parabolic‐hyperbolic set of governing equations. A new shear‐history‐dependent thixotropic rheology model is proposed for pressure wave propagation computations. Moderate Reynolds number flows within the laminar regime are computed, demonstrating the impact of inertial effects. The results clearly illustrate the important mechanisms of pipeline restart. The nature of pressure wave propagation is governed by gel strength as well as overall fluid compressibility. Three sequential pressure wave propagation regimes are dominated by inertial, viscous and gel degradation phenomena, respectively. The viscous and gel degradation regimes are effectively coupled by imposed deformation conditions. For initially homogenous thixotropic gels, strain tends to localize near the pipeline wall, playing a central role in assuring the pipeline restart. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-17T16:10:12.461041-05:
      DOI: 10.1002/aic.14844
       
  • High‐throughput and comprehensive prediction of H2 adsorption in
           metal‐organic frameworks under various conditions
    • Authors: Yu Liu; Shuangliang Zhao, Honglai Liu, Ying Hu
      Abstract: High‐throughput prediction of H2 adsorption in MOF materials has been extended from a few specific conditions to the whole T, p space. The prediction is based on a classical density functional theory and has been implemented over 712 MOFs in 441 different conditions covering a wide range. Some testing materials show excellent behavior at low temperatures and obvious improvement at high temperatures compared to conventional MOFs. The structures of the best MOFs at high and low temperatures are totally different. Linear and nonlinear correlations between the two Langmuir parameters have been found at high and low temperatures, respectively. According to the analysis of the excess uptake, we found that the saturated pressure increases along with temperature in the low temperature region but decreases in the high temperature region. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-17T16:09:51.556324-05:
      DOI: 10.1002/aic.14842
       
  • Thermal transport model of a sorbent particle undergoing
           calcination–carbonation cycling
    • Authors: Lindsey Yue; Wojciech Lipiński
      Abstract: A numerical model coupling transient radiative, convective, and conductive heat transfer, mass transfer, and chemical kinetics of heterogeneous solid–gas reactions has been developed for a semi‐transparent, non‐uniform, and non‐isothermal particle undergoing cyclic thermochemical transformations. The calcination–carbonation reaction pair for calcium oxide looping is selected as the model cycle because of its suitability for solar‐driven carbon dioxide capture. The analyzed system is a single, porous particle undergoing thermochemical cycling in an idealized, reactor‐like environment. The model is used to investigate two cases distinguished by the length of the calcination and carbonation periods. The calcination–carbonation process for a single particle is shown to become periodic after three cycles. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-16T04:27:19.167469-05:
      DOI: 10.1002/aic.14840
       
  • Investigation of the Heat Transfer Intensification Mechanism for a New
           Fluidized Catalyst Cooler
    • Authors: Xiuying Yao; Xiao Han, Yongmin Zhang, Chunxi Lu
      Abstract: A small cold model was employed to investigate the heat transfer mechanism for a new fluidized catalyst cooler. Local heat transfer coefficients (h) and tube surface hydrodynamics were systematically measured by a specially designed heat tube and an optical fiber probe. The higher total h further validated the feasibility of the heat transfer intensification method employed in the new catalyst cooler, which indicated that the induced higher packet renewal frequency due to the non‐uniform gas distribution played a dominant role in its increased hs. Strongest heat transfer intensification effect was located at r/Rw>0.8 below the heat transfer intensification height. The changes of the mean packet residence time in the radial and axial directions and with superficial gas velocity were all agreeable with the measured hs according to the packet renewal theory. This further demonstrated the feasibility of the experimental method for tube surface hydrodynamics. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-15T00:41:02.872059-05:
      DOI: 10.1002/aic.14841
       
  • A robust mixed‐conducting multichannel hollow fiber membrane reactor
    • Authors: Jiawei Zhu; Shaobin Guo, Gongping Liu, Zhengkun Liu, Zhicheng Zhang, Wanqin Jin
      Abstract: To accelerate the commercial application of mixed‐conducting membrane reactor for catalytic reaction processes, a robust mixed‐conducting multichannel hollow fiber (MCMHF) membrane reactor was constructed and characterized in this work. The MCMHF membrane based on reduction‐tolerant and CO2‐stable SrFe0.8Nb0.2O3‐δ (SFN) oxide not only possesses a good mechanical strength, but also has a high oxygen permeation flux under air/He gradient, which is about four times that of SFN disk membrane. When partial oxidation of methane (POM) was performed in the MCMHF membrane reactor, excellent reaction performance (oxygen flux of 19.2 ml·min−1·cm−2, hydrogen production rate of 54.7 ml·min−1·cm−2, methane conversion of 94.6% and the CO selectivity of 99%) was achieved at 1173 K. And also, the MCMHF membrane reactor for POM reaction was operated stably for 120 h without obvious degradation of reaction performance. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-09T16:14:01.577761-05:
      DOI: 10.1002/aic.14835
       
  • Accuracy and optimal sampling in monte carlo solution of population
           balance equations
    • Authors: Xi Yu; Michael J Hounslow, Gavin K Reynolds
      Abstract: Implementation of a Monte Carlo simulation for the solution of population balance equations requires choice of initial sample number (N0), number of replicates (M) and number of bins for probability distribution reconstruction (n). It is found that Squared Hellinger Distance, H2, is a useful measurement of the accuracy of MC simulation, and can be related directly to N0, M and n. Asymptotic approximations of H2 are deduced and tested for both 1D and 2D PBEs with coalescence. The CPU cost, C, is found in a power‐law relationship, C= aMN0b, with the CPU cost index, b, indicating the weighting of N0 in the total CPU cost. n must be chosen to balance accuracy and resolution. For fixed n, M×N0 determines the accuracy of MC prediction; if b>1, then the optimal solution strategy uses multiple replications and small sample size. Conversely if 0
      PubDate: 2015-04-09T16:13:41.436584-05:
      DOI: 10.1002/aic.14837
       
  • A hierarchical method to integrated solvent and process design of physical
           CO2 absorption using the SAFT‐γ mie approach
    • Authors: J. Burger; V. Papaioannou, S. Gopinath, G. Jackson, A. Galindo, C. S. Adjiman
      Abstract: Molecular‐level decisions are increasingly recognised as an integral part of process design. Finding the optimal process performance requires the integrated optimisation of process and solvent chemical structure, leading to a challenging mixed‐integer nonlinear programming (MINLP) problem. We present the formulation of such problems when using a group contribution version of the statistical associating fluid theory (SAFT‐ γ Mie) to predict the physical properties of the relevant mixtures reliably over process conditions. To solve the challenging MINLP, a novel hierarchical methodology for integrated process and solvent design (HiOpt) is presented. Reduced models of the process units are developed and used to generate a set of initial guesses for the MINLP solution. The methodology is applied to the design of a physical absorption process to separate carbon dioxide from methane, using a large selection of ethers as the molecular design space. The solvents with best process performance are found to be poly(oxymethylene)dimethylethers. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-09T16:13:22.051972-05:
      DOI: 10.1002/aic.14838
       
  • Modeling heterogeneous photocatalytic inactivation of E.coli using
           suspended and immobilized TiO2 reactors
    • Authors: M. Kacem; G. Plantard, N. Wery, V. Goetz
      Abstract: A study was carried out to develop a kinetic model of the photocatalytic inactivation of E. coli using different TiO2 catalysts. The model developed is based on a reaction scheme that involves effectively coupling mass transfer fluxes between bacteria and catalyst surface on one hand and bacterial degradation reaction on the other. The photocatalytic results were derived from experiments led in a batch reactor under both dark and UV irradiation conditions. Using a reference catalyst the robustness of the developed model was tested under solar conditions. The experimental data validated the model as successfully able to reproduce evolutions in the viable bacteria concentration in the range of parameters studied without any further adjustment of the kinetic parameters. The model was used to simulate the bacterial degradation kinetics under different working conditions in order to describe the partitioning of both bacterial adhesion and photocatlaytic reaction in the solution to be treated This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-09T16:13:03.077146-05:
      DOI: 10.1002/aic.14834
       
  • Optimal distribution of temperature driving forces in
           low‐temperature heat transfer
    • Authors: Bjørn Austbø; Truls Gundersen
      Abstract: This paper provides a fairly extensive review of research on optimal distribution of driving forces in heat transfer processes. Four different guidelines for specifying the temperature profiles in heat exchangers have been compared. Not surprisingly, the irreversibilities due to heat transfer were found to be minimized when the temperature difference is proportional to the absolute temperature. Comparing a design with an optimal temperature profile and a design with a uniform temperature difference throughout the heat exchanger, sensitivity analyses illustrated that savings in irreversibilities increase with decreasing temperature level and increasing temperature span for the cooling load. Heat exchanger size was found to be of negligible importance. The results indicated that optimal utilization of heat exchanger area is of little importance for processes operating above ambient temperature, while significant savings can be obtained by optimal distribution of temperature driving forces in processes below ambient temperature. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-07T17:44:18.558876-05:
      DOI: 10.1002/aic.14832
       
  • Integration of scheduling, design and control of multi‐product
           chemical processes under uncertainty
    • Authors: Bhushan P. Patil; Eduardo Maia, Luis A. Ricardez‐Sandoval
      Abstract: This study focuses on the development of a methodology that addresses the simultaneous design, scheduling and control of multiproduct processes. The proposed methodology takes into account the influence of disturbances by the identification of their critical frequency, which is used to quantify the worst‐case variability in the controlled variables via frequency response analysis. The uncertainty in the demands of products has also been addressed by creating critical demand scenarios with different probabilities of occurrence, while the nominal stability of the system has been ensured. Two case studies have been developed as applications of the methodology. The first case study focuses on the comparison of classical semi‐sequential approach against the simultaneous methodology developed in this work, while the second case study demonstrates the capability of the methodology in application to a large‐scale nonlinear system. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-07T17:44:00.242568-05:
      DOI: 10.1002/aic.14833
       
  • An electrolyte CPA equation of state for mixed solvent electrolytes
    • Authors: Bjørn Maribo‐Mogensen; Kaj Thomsen, Georgios M. Kontogeorgis
      Abstract: Despite great efforts over the past decades, thermodynamic modeling of electrolytes in mixed solvents is still a challenge today. The existing modeling frameworks based on activity coefficient models are data‐driven and require expert knowledge to be parameterized. It has been suggested that the predictive capabilities could be improved through the development of an electrolyte equation of state. In this work, the Cubic Plus Association (CPA) Equation of State is extended to handle mixtures containing electrolytes by including the electrostatic contributions from the Debye‐Hückel and Born terms using a self‐consistent model for the static permittivity. A simple scheme for parameterization of salts with a limited number of parameters is proposed and model parameters for a range of salts are determined from experimental data of activity and osmotic coefficients as well as freezing point depression. Finally, the model is applied to predict VLE, LLE, and SLE in aqueous salt mixtures as well as in mixed solvents. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-07T17:42:34.244232-05:
      DOI: 10.1002/aic.14829
       
  • Characterization of liquid‐liquid dispersions with variable
           
    • Authors: Michal Vonka; Miroslav Soos
      Abstract: Sustaining stable liquid‐liquid dispersion with the desired drop size still relies on experimental correlations, which do not reflect our understanding of the underlying physics and have limited prediction capability. The complex behaviour of liquid‐liquid dispersions inside a stirred tank, which is equipped with a Rushton turbine, was characterized by a combination of Computational Fluid Dynamics (CFD) and Population Balance Equations (PBE). PBE took into account both the drop coalescence and breakup. With increasing drop viscosity the resistance to drop breakage increases, which was introduced by the local criteria for drop breakup in the form of the local critical Webber number (). The dependency of on the drop viscosity was derived from the experimental data available in the literature. Predictions of Sauter mean diameter agree well with the experimentally measured values allowing prediction of mean drop size as a function of variable viscosity, interfacial tension and stirring speed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-07T17:42:21.164492-05:
      DOI: 10.1002/aic.14831
       
  • A generalized procedure for the prediction of multicomponent adsorption
           equilibria
    • Authors: Austin Ladshaw; Sotira Yiacoumi, Costas Tsouris
      Abstract: Prediction of multicomponent adsorption equilibria has been investigated for several decades. While there are theories available to predict the adsorption behavior of ideal mixtures, there are few purely predictive theories to account for non‐idealities in real systems. Most models available for dealing with non‐idealities contain interaction parameters that must be obtained through correlation with binary‐mixture data. However, as the number of components in a system grows, the number of parameters needed to be obtained increases exponentially. Here, a generalized procedure is proposed, as an extension of the Predictive Real Adsorbed Solution Theory, for determining the parameters of any activity model, for any number of components, without correlation. This procedure is then combined with the Adsorbed Solution Theory to predict the adsorption behavior of mixtures. As this method can be applied to any isotherm model and any activity model, it is referred to as the Generalized Predictive Adsorbed Solution Theory. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-07T11:11:06.966511-05:
      DOI: 10.1002/aic.14826
       
  • Pilot‐scale studies of process intensification by cyclic
           distillation
    • Authors: Bogdan V. Maleta; Alexander Shevchenko, Olesja Bedruk, Anton A. Kiss
      Abstract: Process intensification in distillation systems receives much attention with the aim of increasing both energy and separation efficiency. Several technologies have been investigated and developed, as for example: dividing‐wall column, HiGee distillation, or internal heat‐integrated distillation. Cyclic distillation is a different method based on separate phase movement – achievable with specific internals and a periodic operation mode – that leads to key advantages: increased column throughput, reduced energy requirements, and better separation performance. This article is the first to report the performance of a pilot‐scale distillation column for ethanol‐water separation, operated in a cyclic mode. A comparative study is made between a pilot‐scale cyclic distillation column and an existing industrial beer column used to concentrate ethanol. Using specially designed trays that truly allow separate phase movement, the practical operation confirmed that 2.6 times fewer trays and energy‐savings of about 30% are possible as compared to classic distillation. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-06T23:55:29.612385-05:
      DOI: 10.1002/aic.14827
       
  • Towards economical purification of styrene monomers: Eggshell Mo2C for
           front‐end hydrogenation of phenylacetylene
    • Authors: Min Pang; Zhengfeng Shao, Wei Xia, Xinkui Wang, Changhai Liang
      Abstract: We describe an eggshell Mo2C catalyst which is designed from the rapid combination of molybdate with melamine. In contrast to Pd‐based catalysts, the eggshell Mo2C operates effectively with a wide concentration window in high‐temperature gas phase hydrogenation of phenylacetylene thus an economical and energy‐efficient front‐end purification of styrene monomers might be possible. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-02T18:47:16.789707-05:
      DOI: 10.1002/aic.14822
       
  • A generalized model to predict minimum particle transport velocities in
           multiphase air‐water horizontal pipes
    • Authors: Kamyar Najmi; Alan L. Hill, Selen Cremaschi, Brenton S. McLaury, Siamack A. Shirazi
      Abstract: A new model is proposed to predict minimum flow rates required to constantly move particles in both intermittent and stratified flow regimes. The new model consists of a single‐phase flow model along with an appropriate length scale to be extended to multiphase flow regime. A comparison of the new model with experimental data in a multiphase air‐water flow shows that the new model is able to predict minimum flow rates well for a wide range of operating conditions. The new model can capture the effects of particle size, particle concentration and pipe size as confirmed by experimental data. A comparison of the new model with previously proposed models in the literature shows that the new model improves critical velocity predictions significantly. Moreover, the new model is the only model that takes into account the effect of particle concentration and can predict critical velocity in both intermittent and stratified flow regimes. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-02T18:46:35.130779-05:
      DOI: 10.1002/aic.14824
       
  • Numerical study of turbulent liquid‐liquid dispersions
    • Authors: A.E. Komrakova; D. Eskin, J.J. Derksen
      Abstract: A numerical approach is developed to gain fundamental insight in liquid‐liquid dispersion formation under well‐controlled turbulent conditions. The approach is based on a free energy lattice Boltzmann equation method, and relies on detailed resolution of the interaction of the dispersed and continuous phase at the microscopic level, including drop breakup and coalescence. The capability of the numerical technique to perform direct numerical simulations of turbulently agitated liquid‐liquid dispersions is assessed. Three‐dimensional simulations are carried out in fully‐periodic cubic domains with grids of size 1003‐10003. The liquids are of equal density. Viscosity ratios (dispersed phase over continuous phase) are in the range 0.3 to 1.0. The dispersed phase volume fraction varies from 0.001 to 0.2. The process of dispersion formation is followed and visualized. The size of each drop in the dispersion is measured in‐line with no disturbance of the flow. However, the numerical method is plagued by numerical dissolution of drops that are smaller than 10 times the lattice spacing. It is shown that to mitigate this effect it is necessary to increase the resolution of the Kolmogorov scales, such as to have a minimum drop size in the range 20‐30 lattice units [lu]. Four levels of Kolmogorov length scale resolution have been considered\eta_K=1, 2.5, 5 and 10 [lu]. In addition, the numerical dissolution reduces if the concentration of the dispersed phase is increased. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-02T18:45:43.104236-05:
      DOI: 10.1002/aic.14821
       
  • On the simultaneous description of h‐bonding and dipolar
           interactions with point charges in force field models
    • Authors: Kai Langenbach; Cemal Engin, Steffen Reiser, Martin Horsch, Hans Hasse
      Abstract: H‐bonding and polar interactions occur together in real fluids, but are of different nature and have different effects on macroscopic properties. Nevertheless, both are usually described by point charges in force field models. We show that, despite this, the two effects can be separated. We study a simple model fluid: a single Lennard‐Jones site with two opposing point charges q placed in the center of the Lennard‐Jones site and at a distance d. By suitably varying both d and q the dipole moment μ is kept constant. Both μ and d are systematically varied to study the properties of the resulting models, including H‐bonding, which is determined using a geometric criterion from literature. We show that d can be used for tuning the H‐bonding strength and, thus, polarity and H‐bonding can be adjusted individually. The study of a second related model with symmetrically positioned point charges does not reveal this separation. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-02T18:45:17.356024-05:
      DOI: 10.1002/aic.14820
       
  • Dew‐point measurements for water in compressed carbon dioxide
    • Authors: Christopher W. Meyer; Allan H. Harvey
      Abstract: When transporting CO2 for sequestration, it is important to know the water dew point in order to avoid condensation that can lead to corrosion. We have constructed a flow apparatus to measure the water content at saturation in a compressed gas. A saturator humidifies the flowing gas by equilibrating it with liquid water. Then, a gravimetric hygrometer measures the water mole fraction of the humid gas. We report dew‐point data for H2O in CO2 on six isotherms between 10 °C and 80 °C at pressures from 0.5 MPa to 5 MPa. Our uncertainties in water content at the dew point (expanded uncertainty with coverage factor k=2) are on average 0.3%, significantly smaller than in any previous work. The data have been analyzed to extract the interaction second virial coefficient; our values are consistent with the theoretical estimates of Wheatley and Harvey but have a much smaller uncertainty. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-01T15:19:24.165662-05:
      DOI: 10.1002/aic.14818
       
  • Multi‐objective optimization for designing and operating more
           sustainable water management systems for a city in Mexico
    • Authors: Ma. Guadalupe Rojas‐Torres; Gonzalo Guillén‐Gosálbez, Fabricio Nápoles‐Rivera, José María Ponce‐Ortega, Laureano Jiménez‐Esteller, Medardo Serna‐González
      Abstract: This paper proposes a multi‐objective optimization model for the design of a macroscopic water system of a Mexican city that solves simultaneously the planning and scheduling of water storage and distribution tasks. The model, which considers rainwater harvesting and reclaimed water reusing as alternative water sources, maximizes the revenues from water sales and minimizes simultaneously the water consumption and land use. A case study based on the city of Morelia in Mexico was solved. It was found that the use of alternative water sources (such as harvested rainwater) along with an appropriate planning and scheduling of storage and distribution tasks have the potential to reduce the pressure over natural reservoirs significantly. Our approach considers simultaneously economic and environmental concerns, thereby contributing to the implementation of more sustainable alternatives in urban water distribution. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-30T17:30:12.812187-05:
      DOI: 10.1002/aic.14814
       
  • Developing intermolecular‐potential models for use with the
           SAFT‐VR Mie Equation of State
    • Authors: Simon Dufal; Thomas Lafitte, Amparo Galindo, George Jackson, Andrew J. Haslam
      Abstract: A major advance in the statistical associating fluid theory for potentials of variable range (SAFT‐VR) has recently been made with the incorporation of the Mie (generalized Lennard‐Jones) interaction between the segments comprising the molecules in the fluid. [Lafitte et al. J. Chem. Phys. 2013;139:154504] The Mie potential offers greater versatility in allowing one to describe the softness/hardness of the repulsive interactions and the range of the attractions, which govern fine details of the fluid‐phase equilibria and thermodynamic derivative properties of the system. In our current work, the SAFT‐VR Mie equation of state is employed to develop models for a number of prototypical fluids, including some of direct relevance to the oil and gas industry: methane, carbon dioxide and other light gases, alkanes, alkyl benzenes, and perfluorinated compounds. A complication with the use of more‐generic force fields like the Mie potential is the additional number of parameters that have to be considered to specify the interactions between the molecules, leading to a degree of degeneracy in the parameter space. A formal methodology to isolate intermolecular‐potential models and assess the adequacy of the description of the thermodynamic properties in terms of the complex parameter space is developed. Fluid‐phase equilibrium properties (the vapour pressure and saturated‐liquid density) are chosen as the target properties in the refinement of the force fields; the predictive capability for other properties such as the enthalpy of vaporization, single‐phase density, speed of sound, isobaric heat capacity, and Joule‐Thomson coefficient, is appraised. It is found that an overall improvement of the representations of the thermophysical properties of the fluids is obtained by using the more‐generic Mie form of interaction; in all but the simplest of fluids, one finds that the Lennard‐Jones interaction is not the most appropriate. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-27T00:19:08.693497-05:
      DOI: 10.1002/aic.14808
       
  • Co‐gasification of woody biomass and sewage sludge in a
           fixed‐bed downdraft gasifier
    • Authors: Zhehan Ong; Yongpan Cheng, Thawatchai Maneerung, Zhiyi Yao, Yen Wah Tong, Chi‐Hwa Wang, Yanjun Dai
      Pages: 2508 - 2521
      Abstract: Experimental and numerical studies of cogasification of woody biomass and sewage sludge have been carried out. The gasification experiments were performed in a fixed‐bed downdraft gasifier and the experimental results show that 20 wt % dried sewage sludge in the feedstock was effectively gasified to generate producer gas comprising over 30 vol % of syngas with an average lower heating value of 4.5 MJ/Nm3. Further increasing sewage sludge content to 33 wt % leads to the blockage of gasifier, which is resulted from the formation of agglomerated ash. The numerical models were then developed to simulate the reactions taking place in four different zones of the gasifier (i.e., drying, pyrolysis, combustion, and reduction zones) and to predict the producer gas composition and cold gas efficiency. The deviation between the numerical and experimental results obtained was lower than 10%. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2508–2521, 2015
      PubDate: 2015-04-20T13:15:44.513876-05:
      DOI: 10.1002/aic.14836
       
 
 
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