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  Subjects -> ENGINEERING (Total: 2169 journals)
    - CHEMICAL ENGINEERING (186 journals)
    - CIVIL ENGINEERING (168 journals)
    - ELECTRICAL ENGINEERING (92 journals)
    - ENGINEERING (1176 journals)
    - ENGINEERING MECHANICS AND MATERIALS (356 journals)
    - HYDRAULIC ENGINEERING (56 journals)
    - INDUSTRIAL ENGINEERING (54 journals)
    - MECHANICAL ENGINEERING (81 journals)

ENGINEERING (1176 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: 14)
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  
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: 6)
Catalysis Science and Technology     Free   (Followers: 4)
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: 11)
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: 11)
Clean Air Journal     Full-text available via subscription   (Followers: 2)
Clinical Science     Full-text available via subscription   (Followers: 7)
Coal Science and Technology     Full-text available via subscription   (Followers: 4)
Coastal Engineering     Hybrid Journal   (Followers: 9)
Coastal Engineering Journal     Hybrid Journal   (Followers: 2)
Coatings     Open Access   (Followers: 2)
Cogent Engineering     Open Access   (Followers: 1)
Cognitive Computation     Hybrid Journal   (Followers: 3)
Color Research & Application     Hybrid Journal   (Followers: 1)
COMBINATORICA     Hybrid Journal  
Combustion Theory and Modelling     Hybrid Journal   (Followers: 5)
Combustion, Explosion, and Shock Waves     Hybrid Journal   (Followers: 10)
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: 3)
Composite Structures     Hybrid Journal   (Followers: 103)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 83)
Composites Part B : Engineering     Hybrid Journal   (Followers: 105)
Composites Science and Technology     Hybrid Journal   (Followers: 77)
Comptes Rendus Mécanique     Full-text available via subscription   (Followers: 1)
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: 6)
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: 21)
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: 3)

  First | 1 2 3 4 5 6 7 8 | Last

Journal Cover   AIChE Journal
  [SJR: 1.098]   [H-I: 104]   [20 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  [1607 journals]
  • Issue information
    • Abstract: Cover illustration. Created by Jeffrey Mathison from Abdalla C, Drohan J, Rahm B, et al. Water's journey through the shale gas drilling and production processes in the Mid‐Atlantic region. Penn State Extension, 2011. Available at: http://extension.psu.edu/natural‐resources/water/marcellus‐shale/regulations/waters‐journeythrough‐the‐shale‐gasdrilling‐and‐productionprocesses‐in‐the‐midatlantic‐region. 10.1002/aic.14804
      PubDate: 2015-05-23T22:25:35.557138-05:
      DOI: 10.1002/aic.14585
       
  • 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
       
  • Erratum
    • PubDate: 2015-05-18T11:58:11.527804-05:
      DOI: 10.1002/aic.14862
       
  • Semi‐analytical solution for power‐law polymer solution flow
           in a converging annular spinneret
    • Authors: Yi‐Rui Chen; Liang‐Hsun Chen, Kuo‐Lun Tung, Yu‐Ling Li, Yu‐Shao Chen, Che‐Chia Hu, Ching‐Jung Chuang
      Abstract: A semi‐analytical solution for a power‐law fluid flowing through a conical annulus was derived to estimate the velocity profile in the axial direction, the shear rate and the elongation rate within a spinneret during the spinning of hollow fiber membranes. The angle coefficient was introduced as a new parameter to account for the effect of radial flow and to modify the governing equation, which initially neglected the effect of radial flow. The results estimated from this semi‐analytical solution agreed more closely with computational fluid dynamics simulation results than those obtained from the approximate analytical solution in our previous study. By accurately predicting the velocity profile in the axial direction and the shear and elongation rates in a conical annulus, the solution derived in this study is expected to provide a reliable criterion for spinneret design to achieve a specified membrane morphology with a desired performance. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-14T17:30:00.250842-05:
      DOI: 10.1002/aic.14875
       
  • 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
       
  • A Numerical Comparison of Precipitating Turbulent Flows Between
           Large‐Eddy Simulation and One‐Dimensional Turbulence
    • Authors: Alex W. Abboud; Ben B. Schroeder, Tony Saad, Sean T. Smith, Derek D. Harris, David O. Lignell
      Abstract: This study presents the results of computational fluid dynamics (CFD) simulations of a multiphase, reacting, turbulent mixing layer in an idealized geometry. The purpose is to compare Large‐Eddy Simulation (LES) to One‐Dimensional Turbulence (ODT) and examine the trends of the flow under differing mixing conditions. Aqueous streams are mixed together to precipitate polymorphs of calcium carbonate. The polymorphs of calcium carbonate are tracked numerically using population balance equations (PBE). Each PBE contains all of the relevant physical models to track the particle evolution including nucleation, growth and aggregation. A simple subgrid mixing model that is convenient for use with PBEs was implemented in the LES code. The higher spatial resolution achievable with ODT allowed an investigation on the effect of resolution on the mixing‐model error. The Reynolds number of the flow is varied and is shown to cause a decrease in average particle sizes with higher mixing rates. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-14T00:22:16.738484-05:
      DOI: 10.1002/aic.14870
       
  • Salting‐Out of Acetone, 1‐Butanol, and Ethanol from Dilute
           Aqueous Solutions
    • Authors: Shaoqu Xie; Conghua Yi, Xueqing Qiu
      Abstract: The salting‐out phase equilibria for acetone, 1‐butanol, and ethanol (ABE) from dilute aqueous solutions by using potassium carbonate (K2CO3) and dipotassium hydrogen phosphate trihydrate (K2HPO4·3H2O) as outstanding salting‐out agents were investigated. Increasing the salt concentration strengthened the salting‐out effects and improved the distribution coefficients of all three solvents (ABE) significantly. Temperature had a slight effect on the phase equilibria. The K2HPO4 solution (69 wt %) showed a stronger salting‐out effect than the K2CO3 solution (56 wt %) on recovering ABE from dilute aqueous solutions. Dilute aqueous solutions containing more solvents increased the recoveries of acetone and 1‐butanol, while the results showed a negligible effect on the solubility of ABE. The solubility of ABE was also correlated well with the molar number of salt per gram of water in the aqueous phase. A new equation demonstrated this satisfactorily. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-14T00:13:51.733817-05:
      DOI: 10.1002/aic.14872
       
  • Influence of Impeller Type in Hydrodynamics and Gas‐Liquid Mass
           Transfer Characteristics in Stirred Airlift Bioreactor
    • Authors: Sérgio S. de Jesus; João Moreira Neto, Aline Santana, Rubens Maciel Filho
      Abstract: The influence of impeller type in a mechanically stirred airlift bioreactor was analyzed in relation to the non‐Newtonian viscous fluids. The agitation was carried out through a marine impeller (axial impeller) and a paddle impeller (radial impeller) located along with the gas sparger in the region comprised by the riser. The bioreactor was sparged with air under different velocities (0.036 to 0.060 ms−1). Carboxymethylcellulose 1.94% and xanthan 1.80% were used as a fluid model. The gas holdup and volumetric mass transfer coefficient increased in up to five and three times, respectively, when compared to a conventional airlift bioreactor; however, better results were obtained when the straight paddle impeller type was used. The results suggest that the studied bioreactor can be used successfully in viscous fluid, and it can be more efficient than conventional airlift bioreactors. Based on the results, we suggest the use of radial impellers. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-13T23:48:43.863347-05:
      DOI: 10.1002/aic.14871
       
  • Intensification and Kinetics of Methane Hydrate Formation under Heat
           Removal by Phase Change of n‐Tetradecane
    • Authors: Xiaofei Song; Feng Xin, Hongchao Yan, Xingang Li, Hongri Jia
      Abstract: A method of direct heat removal resulting from the phase change of n‐tetradecane was employed to intensify the heat transfer during hydrate formation. The growth rates of methane hydrate in aqueous slurries containing 25–45 wt% of solid n‐tetradecane were investigated at pressures between 4.70 and 6.46 MPa (gauge) and near the fusion point of solid n‐tetradecane. Methane hydrate growth started at a practically constant rate, which became variable after a sudden increase. Two rate laws were established to correlate with the experimental data for the constant and variable rate stages. The methane hydrate growth rates achieved with solid n‐tetradecane were significantly enhanced compared with those obtained under indirect heat removal. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-11T21:33:40.345431-05:
      DOI: 10.1002/aic.14867
       
  • 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
       
  • Bayesian method for simultaneous gross error detection and data
           reconciliation
    • Authors: Yuan Yuan; Shima Khatibisepehr, Biao Huang, Zukui Li
      Abstract: Process measurements collected from daily industrial plant operations are essential for process monitoring, control and optimization. However, those measurements are generally corrupted by errors, which include gross errors and random errors. Conventionally, those two types of errors were addressed separately by gross error detection and data reconciliation. This work focuses on solving the simultaneous gross error detection and data reconciliation problem using the hierarchical Bayesian inference technique. The proposed approach solves the following problems in a unified framework. First, it detects which measurements contain gross errors. Second, the magnitudes of the gross errors are estimated. Third, the covariance matrix of the random errors is estimated. Finally, data reconciliation is performed using the maximum a posteriori estimation. The proposed algorithm is applicable to both linear and nonlinear systems. For nonlinear case, the algorithm does not involve any linearization or approximation steps. Numerical case studies are provided to demonstrate the effectiveness of the proposed method. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-08T02:31:59.506735-05:
      DOI: 10.1002/aic.14864
       
  • Higher energy saving with new heat integration arrangement in heat
           integrated distillation column (HIDiC)
    • Authors: Toshihiro Wakabayashi; Shinji Hasebe
      Abstract: In conventional heat integrated distillation columns (HIDiC), the internal heat exchange is executed between the pressurized rectifying section and the stripping section, which are located at the same elevation. In such a structure, the amount of heat exchanged between two sections depends on the temperature profile of both sections. The resulting enthalpy profile inside the column departs from that in reversible distillation, which is the ideal distillation operation in view of energy conservation. More energy saving may be achieved by providing appropriate arrangement of heat exchanges between sections. We developed the interactive graphical design method to determine the appropriate heat exchange arrangement in a previous paper for a binary system. In this paper, the design method was extended and applied to a multi‐component system by adopting the idea of a quasi‐binary system. Also, a new HIDiC structure that can realize the outcomes of the proposed design method was developed. The economics of the proposed structure was precisely evaluated through a case study of a commercial scale column. It demonstrated that the proposed structure has attractive economics. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-08T02:31:40.279242-05:
      DOI: 10.1002/aic.14865
       
  • Erratum
    • PubDate: 2015-05-07T08:22:58.209457-05:
      DOI: 10.1002/aic.14845
       
  • Determination of the Trichloroethylene diffusion coefficient in water
    • Authors: Federico Rossi; Raffaele Cucciniello, Adriano Intiso, Oriana Motta, Nadia Marchettini, Antonio Proto
      Abstract: Trichloroethylene (TCE) is a halogenated aliphatic organic compound frequently detected as pollutant in soils and ground water. In order to study the fate of TCE in water and to devise effective remediation strategies, a series of advection‐diffusion (dispersion) models, where the diffusion coefficient of TCE (DTCE) is an important parameter, have been developed. However, DTCE in water has never been experimentally determined and only theoretical values (≃ 1 × 10−5 cm2,s−1 at 25°C) are present in the literature. In this paper we present a new method based on the Taylor dispersion technique, which allows to measure DTCE in a broad range of temperature and, in principle, in any solvent. We found that at 25°C DTCE = 8.16±0.06 × 10−6 cm2 s−1 and the value increases almost linearly with the temperature, while, in the limit of the experimental error, is independent from [TCE] for dilute solutions. From the temperature dependence of DTCE it was possible to calculate the specific TCE fitting constant in the well known Wilke & Chang theoretical relation and the activation energy of the diffusion process through the Arrhenius plot. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-04T23:54:15.018708-05:
      DOI: 10.1002/aic.14861
       
  • A numerical‐indicator‐based method for design of distributed
           wastewater treatment systems with multiple contaminants
    • Authors: Ai‐Hong Li; Yu‐Zhen Yang, Zhi‐Yong Liu
      Abstract: In design of distributed wastewater treatment systems with multiple contaminants, it is very important to minimize un‐necessary stream mixing to reduce total treatment flow rate as much as possible. In this paper, we will introduce a new numerical indicator, Total Mixing Influence Potential (TMIP), to reflect the influence of the stream mixing caused by performing a process on the total treatment flow rate of a distributed wastewater system. In design procedure, the TMIP value is calculated based on pinch principle. The process with the smallest TMIP value will be performed first. The results of a few literature examples show that designs with very low (even minimum) total treatment flow rates can be obtained with the method proposed. In addition, the method proposed is simple and of clear engineering insight. The calculation effort does not increase significantly when the number of streams, contaminants and/or treatment units increases. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-04T17:57:26.155681-05:
      DOI: 10.1002/aic.14863
       
  • A probabilistic model for correcting the directional sensitivity of
           optical probe measurements
    • Authors: Boung Wook Lee; Milorad P. Dudukovic
      Abstract: A probabilistic model is introduced for correcting the directional sensitivity of the optical probe technique routinely used to determine gas holdup and bubble dynamics in gas‐liquid systems. Measurements from optical probes oriented at various angles were collected from the tapered end of optical probes in regions where approximately unidirectional and bubbly flow conditions were observed. Based on logical assumptions, constitutive equations for a probabilistic model were formulated, and contributions to the overall local gas phase holdup from bubbles traveling in two opposite directions were quantified. The results demonstrate a novel and useful way to interpret optical probe measurements. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-29T15:12:58.890389-05:
      DOI: 10.1002/aic.14860
       
  • Rapid prediction of solvation free energy and vapor pressure of liquid and
           solid from molecular dynamics simulation
    • Authors: Li Yang; Shiang‐Tai Lin
      Abstract: We show that the solvation free energy and vapor pressure are important thermodynamic properties of pure substances in liquid or solid states can be obtained from short, about 20 ps, molecular dynamics simulations. The method combines the determination of free energy of a chemical in vacuum using the normal‐mode analysis (energy minimization), and in the condensed phase using the two‐phase thermodynamic (2PT) model. We have examined the calculation results for common liquids and solids, including water, alcohol, acid, aromatics, and alkanes. The results, referred to as 2PT‐NMA, is comparable to those calculated from thermodynamic integration (TI) for liquids, and is readily applicable to solids, where simple TI is not applicable. Furthermore, the free energy from 2PT‐NMA converges (20 ps) much faster than that from TI (1 ns). The new method could be a very useful tool for fast screening of condensed phase pressure from the trajectory of MD simulations. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-29T15:12:20.408523-05:
      DOI: 10.1002/aic.14859
       
  • Gas‐Solid Catalytic Reactions with an Extended DSMC Model
    • Authors: Georg R. Pesch; Norbert Riefler, Udo Fritsching, Lucio Colombi Ciacchi, Lutz Mädler
      Abstract: An algorithm of diffusive gas transport in porous solids based on random collisions of molecules (DSMC) is extended to include basic heterogeneous reaction mechanisms (adsorption, coadsorption, desorption, and reaction of gas species on the surface of the solid). With this model we study the catalytic oxidation of CO inside highly porous nanoparticle layers in the transition regime using kinetic parameters from Pd(111) surfaces at UHV conditions. Investigation of the reaction at different temperatures reveals a clear transition between a kinetic limit (low temperatures) and a diffusion limit (high temperatures). At high temperatures and under steady‐state conditions, the porous layer shows three distinct regions with different reaction rates (reactor poisoning, an effective reaction region, and a region with CO depletion), whose extends are determined by CO concentration and mass‐transport limitation. We expect that similar investigations help optimizing the structure of gas sensor elements based on nanoparticle layers fabricated with flame spray pyrolysis. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-28T21:50:45.002738-05:
      DOI: 10.1002/aic.14856
       
  • 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
       
  • A multi‐objective optimization framework for design of integrated
           biorefineries under uncertainty
    • Authors: A. Geraili; J.A. Romagnoli
      Abstract: A systematic approach for development of a reliable optimization framework to address the optimal design of integrated biorefineries in the face of uncertainty is presented. In the current formulation, we apply a distributed strategy which is composed of different layers including strategic optimization, risk management, detailed mechanistic modeling and operational level optimization. In the strategic model, a multi‐objective stochastic optimization approach is utilized to incorporate the tradeoffs between the cost and the financial risk. Then, Aspen Plus models are built to provide detailed simulation of biorefineries. In the final layer, an evolutionary algorithm is employed to optimize the operating condition. To demonstrate the effectiveness of the framework, a hypothetical case study referring to a multi‐product lignocellulosic biorefinery is utilized. The numerical results reveal the efficacy of the proposed approach; it provides decision makers with a quantitative analysis to determine the optimum capacity plan and operating conditions of the biorefinery. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-22T17:32:09.313775-05:
      DOI: 10.1002/aic.14849
       
  • Thermal conductivity of nanofluids: Effect of brownian motion of
           nanoparticles
    • Authors: Rachid Chebbi
      Abstract: We discuss the model of Xuan et al. (2003) for the thermal conductivity of nanofluids in which Brownian motion effect is added to the classical Maxwell's equation. The model is revised. Also a different model is given and found to yield the same expression for the effective thermal conductivity after amending Xuan et al.'s model. The findings do not support the claim that Brownian motion of nanoparticles has a significant impact on thermal conductivity. Also nanoparticles clustering is found to have a very minor effect on the effective thermal conductivity of nanofluids; however the analysis may not be appropriate to draw conclusions about the impact of clustering. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-22T17:31:46.779486-05:
      DOI: 10.1002/aic.14847
       
  • A letter to the editor
    • Authors: Yimin Xuan
      PubDate: 2015-04-22T17:31:27.819205-05:
      DOI: 10.1002/aic.14848
       
  • 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
       
  • Aggregation of silica nanoparticles in an aqueous suspension
    • Authors: Lande Liu
      Abstract: Aggregation affects the stability of the nanoparticles in fluids. For hydrophilic particles in aqueous suspensions, zeta potential becomes a common measure to control the stability of the particles. However, it is not clear how zeta potential impacts on the interaction of the particles during their close range contact when the hydration repulsion arises strongly. This paper demonstrates a method that uses the kinetic theory of aggregation for an aggregation system of changing zeta potential to determine the hydration repulsion and the aggregation efficiency. It was found that the hydration repulsion has an equivalent electrical potential of 30 mV on the stem surface of the particles and an exponential decay length of 2.77 Å. This hydration potential is equivalent to 12 mV zeta potential and contributes 29% to the aggregation coefficient that is 5.5 × 10−6 for a 30 mV zeta potential stabilised silica particle suspension. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-09T16:14:21.241866-05:
      DOI: 10.1002/aic.14839
       
  • 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
       
  • Co‐gasification of woody biomass and sewage sludge in a
           fixed‐bed downdraft gasifier
    • Authors: Zhehan Ong; Yongpan Cheng, Thawatchai Maneerung, Zhiyi Yao, Yanjun Dai, Yen Wah Tong, Chi‐Hwa Wang
      Abstract: In this work, experimental and numerical studies of co‐gasification 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 (CGE). The deviation between the numerical and experimental results obtained in this study was lower than 10%. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-09T16:12:30.486522-05:
      DOI: 10.1002/aic.14836
       
  • Erratum
    • PubDate: 2015-04-09T10:21:34.009885-05:
      DOI: 10.1002/aic.14811
       
  • 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
       
  • Simulation study of the effect of wall roughness on the dynamics of
           granular flows in rotating semi‐cylindrical chutes
    • Authors: S.S. Shirsath; J.T. Padding, H.J.H. Clercx, J.A.M. Kuipers
      Abstract: A discrete element model (DEM) is used to investigate the behavior of spherical particles flowing down a semi‐cylindrical rotating chute. The DEM simulations are validated by comparing with Particle Tracking Velocimetry (PTV) results of spherical glass particles flowing through a smooth semi‐cylindrical chute at different rotation rates of the chute. The DEM model predictions agree well with experimental results of surface velocity and particle bed height evolution. The validated DEM model is used to investigate the influence of chute roughness on the flow behaviour of monodisperse granular particles in rotating chutes. To emulate different base roughnesses, a rough base is constructed out of a square close packing of fixed spherical particles with a diameter equal to, smaller, or larger than the flowing particles. Finally, the DEM model is used to study segregation in a binary density mixture for different degrees of roughness of the chute. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-07T17:43:42.997403-05:
      DOI: 10.1002/aic.14828
       
  • Consideration of low viscous droplet breakage in the framework of the wide
           energy spectrum and the multiple fragments
    • Authors: Luchang Han; Shenggao Gong, Yaowen Ding, Jin Fu, Ningning Gao, He'an Luo
      Abstract: An improved model for low viscous droplet breakage has been developed. Unlike the previous work that considered the inertia subrange and adopted the assumption of binary breakage, this work considered the breakage of droplets in the framework of the multiple fragments and the wide energy spectrum (i.e. including the dissipation range, the inertia subrange and the energy containing range simultaneously). The previous interactions between the droplet and the surrounding fluid have been considered through introducing the interaction forces. The effect of the surface deformation and oscillation resulting from these interactions on the constraints of multiple breakages has been accounted for. These factors have been neglected in the existing models. The wide energy spectrum distribution was found to have an important effect on the non‐monotone evolution of breakage frequency with increasing parent droplet size. The cumulative volume fractions predicted by this work showed a better agreement with the experimental data. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-07T17:42:51.464663-05:
      DOI: 10.1002/aic.14830
       
  • 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
       
  • Experimental Studies and Modeling of CO2 Solubility in High Temperature
           Aqueous CaCl2, MgCl2, Na2SO4, and KCl Solutions
    • Authors: Haining Zhao; Robert M. Dilmore, Serguei N. Lvov
      Abstract: The phase equilibria of CO2 and aqueous electrolyte solutions are important to various chemical‐, petroleum‐ and environmental‐related technical applications. In this study, we measured CO2 solubility in aqueous CaCl2, MgCl2, Na2SO4 and KCl solutions at a pressure of 15 MPa, the temperatures from 323 to 423 K, and the ionic strength from 1 to 6 mol kg−1. Based on the measured experimental CO2 solubility, the previous developed fugacity‐activity thermodynamic model for the CO2‐NaCl‐H2O system was extended to account for the effects of different salt specieson CO2 solubility in aqueous solutions at temperatures up to 523 K, pressures up to 150 MPa, and salt concentrations up to saturation. Comparisons of different models against literature data reveal a clear improvement of the proposed PSUCO2 model in predicting CO2 solubility in aqueous salt solutions. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-04T03:21:25.36965-05:0
      DOI: 10.1002/aic.14825
       
  • A low‐disturbance nonequilibrium molecular dynamics algorithm
           applied to the determination of thermal conductivities
    • Authors: Filipe A. Furtado; Charlles R. A. Abreu, Frederico W. Tavares
      Abstract: A new nonequilibrium molecular dynamics algorithm is proposed for the determination of thermal conductivity and other transport properties. The proposed algorithm aims at diminishing the energy drift problem observed in this type of method while conserving linear momentum and being compatible with constrained molecules. The features of the proposed algorithm are evaluated by determining thermal conductivities of water at 323 K, n‐octane at 300 K, and argon close to its triple point, and by comparing these results with those obtained using established methods. The analysis of systems presenting diverse molecular characteristics allowed us to assess the usefulness of the proposed algorithm. The energy drift and temperature variation were reduced in the range of 10–80%, depending on the parameters of the proposed algorithm and the characteristics of the system. The determined thermal conductivities showed good agreement when compared to experimental and simulation data. © 2015 American Institute of Chemical Engineers AIChE J, 2015
      PubDate: 2015-04-03T10:17:58.709766-05:
      DOI: 10.1002/aic.14803
       
  • Thermodynamics of protein aqueous solutions: From the structure factor to
           the osmotic pressure
    • Authors: Luís Fernando Mercier Franco; Cristiano Luis Pinto de Oliveira, Pedro de Alcântara Pessôa Filho
      Abstract: An analytical expression for the structure factor for globular proteins in aqueous solution is presented in this work. This expression was obtained considering a potential given by the sum of a hard core, a van der Waals attractive and a screened Coulomb contribution. Experimental data of Small Angle X‐Ray Scattering for bovine serum albumin in aqueous solutions containing sodium salts at different protein concentrations and pH values are also presented. The developed expression for the structure factor describes accurately these experimental data provided a dependence of the attractive parameter on protein concentration is established. An expression for the osmotic pressure was derived from the structure factor. With attractive parameters adjusted from X‐ray scattering data, the osmotic pressure of bovine serum albumin aqueous solutions could be predicted with very good agreement with experimental data. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-03T06:21:32.372128-05:
      DOI: 10.1002/aic.14802
       
  • 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
       
  • Simultaneous integration of water and energy in heat‐integrated
           water allocation networks
    • Authors: Zuming Liu; Yiqing Luo, Xigang Yuan
      Abstract: This article proposes a new methodology for simultaneous integration of water and energy in heat‐integrated water allocation networks (WAHEN). A novel disjunctive model is first developed to determine an optimal water allocation network (WAN) where water and energy are integrated in one step. Based on the optimal WAN, a detailed heat exchanger network (HEN) to satisfy the utility target is then synthesized. Although the final network structure is obtained through two steps, the targets of freshwater and utility are optimized simultaneously. The proposed method has specific advantages. First of all, it can capture a trade‐off among freshwater usage, utility consumption and direct heat transfer by non‐isothermal mixing. Second, it can greatly reduce the complexity of subsequent HEN design. Finally, it is effective for simultaneous water and energy integration in large‐scale WAHEN systems. The advantages and applicability of this new method are illustrated by three examples from literature. This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-02T18:46:09.148186-05:
      DOI: 10.1002/aic.14823
       
  • 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
       
  • Enhanced gravimetric CO2 capacity and viscosity for ionic liquids with
           cyanopyrrolide anion
    • Authors: Paul Brown; Burcu E. Gurkan, T. Alan Hatton
      Abstract: “Ionic Liquids are considered as alternative solvents for the separation of CO2 from flue gas due mainly to their CO2 affinity and thermal stability. This paper systematically investigates the cation architecture in a matrix of ammonium and mostly phosphonium‐based ionic liquids with 2‐cyanopyrrolide as the anion to evaluate its impact on gravimetric CO2 absorption capacity, viscosity and thermal stability; the three fundamental properties vital for application realization. Among the investigated ILs, [P2,2,2,8][2‐CNpyr] demonstrated the lowest viscosity, 95 cP at 40 ºC, and highest CO2 uptake, 114 mg CO2/g IL at 40 ºC. Combined effects of asymmetry and the optimized chain lengths also resulted in improved thermal stability for [P2,2,2,8][2‐CNpyr], with a mass loss rate of 1.35 x 10−6 g h−1 (0.0067 mass % h−1) at 80 ºC.” This article is protected by copyright. All rights reserved.
      PubDate: 2015-04-01T15:23:17.597522-05:
      DOI: 10.1002/aic.14819
       
  • 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
       
  • Delignification of intact biomass and cellulosic coproduct of
           acid‐catalyzed hydrolysis
    • Authors: Majid Soleimani; Lope G. Tabil, Catherine Niu
      Abstract: The kinetics of acid‐catalyzed hemicellulose removal and also alkaline delignification of oat hull biomass were investigated. All three operational parameters namely, catalyst concentration (0.10–0.55 N H2SO4), temperature (110–130°C), and residence time (up to 150 min) affected the efficiency of hemicellulose removal, with 100% of hemicellulose removed by appropriate selection of process parameters. Analysis of delignification kinetics (in the temperature range of 30–100°C) indicated that it can be expressed very well by a two‐phase model for the crude biomass and also for the hemicellulose‐prehydrolyzed material. The application of acid‐catalyzed prehydrolysis improved the capacity of lignin dissolution especially at lower temperatures (30 and 65°C) and accelerated the dissolution of lignin. This acceleration of delignification by prehydrolysis was possible at all levels of temperature in the bulk phase; however, results were more significant at the lower temperatures in the terminal phase. © 2015 American Institute of Chemical Engineers AIChE J, 2015
      PubDate: 2015-04-01T08:53:25.220682-05:
      DOI: 10.1002/aic.14794
       
  • Numerical study of laminar core‐annular flow in a torus and in a
           90° pipe bend
    • Authors: Gijs Ooms; Mathieu J. B. M. Pourquie, Jerry Westerweel
      Abstract: A numerical study has been made of laminar core‐annular through a torus. It is a follow‐up of the study by Picardo and Pushpavanam, AIChE J. 2013;59(12):4871–4886, who obtained an analytical solution for the case that the core is concentric and circular. In our study, we investigated the possibility of eccentric core‐annular flow and the deformation of the core‐annular interface. We found that a stable eccentric core position is possible, which is shifted in the direction of the inner or outer side of the torus depending on the balance of the normal stresses at the core‐annular interface. When these stresses are too far off from those for concentric and circular core‐annular flow, fouling of the wall occurs. We compared the results of core‐annular flow in a torus with those for a 90° pipe bend and found that the flow pattern in the torus is representative for the flow pattern in the bend. © 2015 American Institute of Chemical Engineers AIChE J, 2015
      PubDate: 2015-03-31T11:13:57.672037-05:
      DOI: 10.1002/aic.14796
       
  • A consecutive microreactor system for the synthesis of caprolactam with
           high selectivity
    • Authors: Kai Wang; Jisong Zhang, Chen Zheng, Chen Dong, Yangcheng Lu, Guangsheng Luo
      Abstract: A microreactor system containing two consecutive microreactors and a stirred vessel was developed for the improvement of selectivity of caprolactam (CPL) synthesis. The first microreactor was used to conduct the reaction of cyclohexanecarboxylic acid and oleum, and 97% selectivity for the intermediate product, named mixed anhydride, was obtained. The mixed anhydride then quickly reacted with nitroso‐sulfuric acid in the second microreactor, and the reaction was completed in the vessel, where CPL selectivity reached 93.9%, a much higher value than that achieved either in a control experiment with a batch reactor or in industrial process. The advantage of microreactors is that they can provide high‐quality mixed anhydride and can mix it quickly with the nitroso‐sulfuric acid prior to reaction in the vessel reactor, which, from an engineering standpoint, gives better performance than the traditional syringe‐fed method that is common in chemical synthesis. © 2015 American Institute of Chemical Engineers AIChE J, 2015
      PubDate: 2015-03-31T11:13:31.418275-05:
      DOI: 10.1002/aic.14797
       
  • Pore‐size evaluation and gas transport behaviors of microporous
           membranes: An experimental and theoretical study
    • Authors: Gang Li; Hye Ryeon Lee, Hiroki Nagasawa, Masakoto Kanezashi, Tomohisa Yoshioka, Toshinori Tsuru
      Abstract: A modified gas‐translation (GT) model based on a GT mechanism was successfully applied to the pore‐size evaluation and gas transport‐behavior analysis of microporous membranes with different pore‐size distributions. Based on the gas permeation results of three microporous membranes derived from different alkoxides, the effects of activation energy and the selection of a standard gas on the pore‐size evaluation were discussed in a comparative study. The presence of nano‐sized defects had an important influence on the gas permeation performance of microporous membranes, depending largely on the original pore size of the membrane in question. Moreover, the gas‐separation effect of the pore‐size distribution in a silica membrane was theoretically studied, and revealed a significant increase in gas permeance for relatively large gas species but not for small ones. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-30T17:39:19.505342-05:
      DOI: 10.1002/aic.14812
       
  • A compact photomicroreactor design for kinetic studies of gas‐liquid
           photocatalytic transformations
    • Authors: Yuanhai Su; Volker Hessel, Timothy Noël
      Abstract: A compact photomicroreactor assembly consisting of a capillary microreactor and small‐scale LEDs was developed for the study of reaction kinetics in the gas‐liquid photocatalytic oxidation of thiophenol to phenyl disulfide within Taylor flow. The importance of photons was convincingly shown by a suction phenomenon due to the fast consumption of oxygen. Mass transfer limitations were evaluated and an operational zone without mass transfer effects was chosen to study reaction kinetics. Effects of photocatalyst loading and light sources on the reaction performance were investigated. Reaction kinetic analysis was performed to obtain reaction orders with respect to both thiophenol and oxygen based on heterogeneous and homogeneous experimental results, respectively. The Hatta number further indicated elimination of mass transfer limitations. Reaction rate constants at different photocatalyst loadings and different photon flux were calculated. Furthermore, the advantages of this photomicroreactor assembly for studying gas‐liquid photocatalytic reaction kinetics were demonstrated as compared with batch reactors. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-30T17:33:46.117974-05:
      DOI: 10.1002/aic.14813
       
  • Emulation of gas‐liquid flow in packed beds for offshore floating
           applications using a swell simulation hexapod
    • Authors: Gnouyaro P. Assima; Amir Motamed‐Dashliborun, Faïçal Larachi
      Abstract: A laboratory‐scale packed column was positioned on a 6‐degree‐of‐freedom swell simulation hexapod to emulate the hydrodynamics of packed bed scrubbers/reactors onboard offshore floating systems. The bed was instrumented with wire mesh capacitance sensors to measure liquid saturation and velocity fields, flow regime transition, liquid maldistribution, and tracer radial and axial dispersion patterns while robot was subject to sinusoidal translation (sway, heave) and rotation (roll, roll + pitch, yaw) motions at different frequencies. Three metrics were defined to analyze the deviations induced by the various column motions, namely, coefficient of variation and degree of uniformity for liquid saturation fluctuating fields, and effective Péclet number. Non‐tilting oscillations led to frequency‐independent maldistribution while tilting motions induced swirl/zigzag secondary circulation and prompted non‐uniform maldistribution oscillations that deteriorated with decreasing frequencies. Regardless of excited degree of freedom, a qualitative loss of plug‐flow character was observed compared to static vertical beds which worsened as frequencies decreased. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-30T17:31:09.083555-05:
      DOI: 10.1002/aic.14816
       
  • 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
       
  • On‐line control of crystal properties in non‐isothermal
           antisolvent crystallization
    • Authors: Navid Ghadipasha; Jose A. Romagnoli, Stefania Tronci, Roberto Baratti
      Abstract: This paper deals with the issues regarding the design and implementation of on‐line optimal control strategies of crystal properties in non‐isothermal antisolvent crystallization processes to control particles' mean size and standard deviation. The one‐dimensional Fokker‐Planck equation (FPE) is used to represent the dynamic characteristics of the crystal growth and generate iso‐mean and iso‐standard deviation curves. Using controllability tools it is demonstrated that the system is ill conditioned in the whole operational range, posing limitations on the achievable control performance. To circumvent the problem, a control strategy is formulated by pairing crystals' mean size with antisolvent feed rate and manipulating temperature to control the standard deviation. A novel digital image texturing analysis approach is discussed and implemented to track crystals' size distribution along the experiment and providing the on‐line information for further feedback control action. Subsequently, alternative control strategies are implemented and tested to achieve a desired crystal size distribution (CSD). This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-30T17:27:59.122586-05:
      DOI: 10.1002/aic.14815
       
  • Aldol condensation of n‐butyraldehyde in a biphasic stirred tank
           reactor: Experiments and models
    • Authors: Shinbeom Lee; Arvind Varma
      Abstract: To model a biphasic stirred tank reactor, intrinsic reaction kinetics and interfacial area are required. In this study, reactor modeling for n‐butyraldehyde aldol condensation was investigated under industrially relevent conditions. The interfacial area in the reactor was directly measured using a borescope system under appropriate temperature, NaOH concentration and rpm conditions. To estimate the interfacial area, a semi‐empirical correlation was developed, which provides good estimates within ±15% error. The reactor model based on two‐film theory was developed, combining the interfacial area and intrinsic reaction kinetics reported in our prior work. The model was verified by reaction experiments in the range 0.05‐1.9M NaOH, 80‐130 oC and 600‐1000 rpm. The prediction errors using the interfacial area from direct measurements and the correlation were ±8% and ±15%, respectively, suggesting that the model accuracy may be improved with better interfacial area estimation. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-30T17:25:03.729629-05:
      DOI: 10.1002/aic.14817
       
  • Model‐based analysis of a gas/vapor–liquid microchannel
           membrane contactor
    • Authors: Anna Lautenschleger; Eugeny Y. Kenig, Andreas Voigt, Kai Sundmacher
      Abstract: A comprehensive numerical investigation on membrane distillation of methanol and water in a microseparator was carried out. The focus was to investigate the impact of the apparatus geometry on the separation performance and to develop alternative designs for process intensification. To describe the process, a computational fluid dynamics‐based model was developed and validated against experimental data from literature. Based on this model, parametric studies were performed to gain a deeper understanding of the microchannel geometry influence. Furthermore, two geometry modifications were suggested and analyzed, a miniaturization of the channel and an implementation of baffles. The modification with baffles was chosen for a new separator design which was studied experimentally, and the obtained experimental data were used for another model validation, this time for the baffle arrangement. Subsequent comprehensive simulations were performed to investigate mass‐transfer enhancement by the modified geometry. Generally, the baffles reveal a considerable potential for the process intensification. © 2015 American Institute of Chemical Engineers AIChE J, 2015
      PubDate: 2015-03-30T11:02:58.267045-05:
      DOI: 10.1002/aic.14784
       
  • Intensification of convective heat transfer in a
           stator–rotor–stator spinning disc reactor
    • Authors: Michiel M. de Beer; Jos T.F. Keurentjes, Jaap C. Schouten, John van der Schaaf
      Abstract: A stator–rotor–stator spinning disc reactor is presented, which aims at intensification of convective heat‐transfer rates for chemical conversion processes. Single phase fluid‐rotor heat‐transfer coefficients hr are presented for rotor angular velocities ω=0−157 rad s−1 and volumetric throughflow rates ϕv=15−20·10−6 m3s−1. The values of hr are independent of ϕv and increase from 0.95 kWm−2K−1 at ω = 0 rad s−1 to 34 kWm−2K−1 at ω = 157 rad s−1. This is a factor 2–3 higher than values achievable in passively enhanced reactor‐heat exchangers, due to the 1–2 orders of magnitude larger specific energy input achievable in the stator–rotor–stator spinning disc reactor. Moreover, as hr is independent of ϕv, the heat‐transfer rates are independent of residence time. Together with the high mass‐transfer rates reported for rotor–stator spinning disc reactors, this makes the stator–rotor–stator spinning disc reactor a promising tool to intensify heat‐transfer rates for highly exothermal chemical reactions. © 2015 American Institute of Chemical Engineers AIChE J, 2015
      PubDate: 2015-03-30T10:58:40.862975-05:
      DOI: 10.1002/aic.14788
       
  • Modelling of a membrane reactor system for crude palm oil
           transesterification. Part I: Chemical and phase equilibrium
    • Authors: Pin Pin Oh; Mei Fong Chong, Harrison Lik Nang Lau, Junghui Chen, Yuen May Choo
      Abstract: Using a membrane reactor for reversible transesterification reaction involves reaction and product separation within a single unit. However, a pseudo‐homogeneous reaction and heterogeneous separation must be maintained for successful membrane reactor operation. Present research is aimed to develop an integrated model of chemical and phase equilibrium (CPE) and modified Maxwell‐Stefan equation that describes the simultaneous CPE and mass transport phenomena of biodiesel production from crude palm oil (CPO) by using a membrane reactor. In the first part of this work, a systematic approach describing simultaneous CPE of CPO transesterification in the membrane reactor was developed with the reconciliation of transesterification reaction and phase equilibrium that involves six‐component. The results revealed that regressed apparent equilibrium constant, Keq value of 17.557±1.51% was higher than the literatures. This indicates that forward reaction of the reversible CPO transesterification is much favored in the membrane reactor than the conventional reactor. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-27T00:19:34.541869-05:
      DOI: 10.1002/aic.14806
       
  • 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
       
  • Investment optimization model for freshwater acquisition and wastewater
           handling in shale gas production
    • Authors: Linlin Yang; Meagan Mauter, Robert Dilmore, Ignacio E. Grossmann
      Abstract: Major challenges of water use in the drilling and fracturing process in shale gas production are large volumes required in a short‐period of time and the nonsteady nature of wastewater treatment. We present a new mixed‐integer linear programming (MILP) model for optimizing capital investment decisions for water use for shale gas production through a discrete‐time representation of the State‐Task Network. The objective is to minimize the capital cost of impoundment, piping, and treatment facility, and operating cost including freshwater, pumping, and treatment. The goal is to determine the location and capacity of impoundment, the type of piping, treatment facility locations and removal capability, freshwater sources, as well as the frac schedule. In addition, we examine the impact of several factors such as limiting truck hauling and increasing flowback volume on the solution. A case study is optimized to illustrate the application of the proposed formulation. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-27T00:18:47.000691-05:
      DOI: 10.1002/aic.14804
       
  • Mesoscopic coarse‐grained simulations of hydrophobic charge
           induction chromatography (HCIC) for protein purification
    • Authors: Gaobo Yu; Jie Liu, Jian Zhou
      Abstract: Mesoscopic coarse‐grained simulations are adopted to investigate interfacial mechanisms of hydrophobic charged induction chromatography for protein purification by regulating pH. Simulations results indicate that: (i) lysozyme can be adsorbed mainly with “top end‐on” and “bottom end‐on” orientation on hydrophobic surfaces, dominated by the two hydrophobic regions located at both ends of lysozyme's long axis. Elution from the “top end‐on” orientation is more difficult than that from the “bottom end‐on” orientation; (ii) a higher ligand density can get a faster adsorption rate and stronger adsorption. Interestingly, the effect of ligand density on the desorption is mainly determined by the distribution probability of the positively charged groups of ligands; (iii) a higher ionic strength can lead to a wider orientation distribution, a stronger adsorption and a lower elution rate. This work might provide an efficient way to optimize the operating conditions and designing novel ligands. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-27T00:18:25.392627-05:
      DOI: 10.1002/aic.14805
       
  • A model‐based precipitation study of copper‐based catalysts
    • Authors: Martin A. J. Hartig; Nikolas Jacobsen, Alexander Leuthold, Wolfgang Peukert
      Abstract: Numerical methods of particle technology are used to model the formation of catalyst precursors with the purpose to control disperse properties. A multi‐component and multi‐phase population balance model is applied to the precipitation of catalyst precursors in a T‐mixer. Copper precursors are chosen to be investigated in detail as a basis for catalysts with a broad range of applications such as in methanol synthesis, water‐gas‐shift and hydrogenation reactions. The simulations results could be validated by ex‐situ measurements such as the pH of the suspension, the solid dry weight of the precipitate and the yield. Simulations show that dissociation reactions of copper and carbonate species in water control significantly the formation of Georgeite. Consumption of the copper component by solid formation can be controlled in a range of 20% to 100% by the adjustment of the pH of the copper nitrate reactant solution. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-27T00:13:56.500006-05:
      DOI: 10.1002/aic.14810
       
  • Solvent evaluation for desulfurization and denitrification of gas oil
           using performance and industrial usability indices
    • Authors: Sunil Kumar; Vimal Chandra Srivastava, S.M. Nanoti, Abhishek Kumar
      Abstract: In this paper, a new strategy for screening of solvents for sulfur, nitrogen and aromatic compounds removal from gas oil is presented. This ranking is based on comparative assessment of solvents' capacity, selectivity, performance and newly defined industrial usability index. Twenty eight solvents comprising of six most widely used industrially proven conventional solvents and twenty two imidazolium based ionic liquids solvents were selected to illustrate the strategy. The solvents were ranked for removal of benzothiophene, dibenzothiophene and their alkylated derivatives sulfur compounds, quinoline, indole and carbazole nitrogen compounds from gas oil. Performance index (PI) which combines the effect of both capacity and selectivity seems to be better index than individual capacity and selectivity indexes to rank the solvents. Industrial usability index (SIUI) of solvents which includes PI and process complexity factor of solvent recovery seems more practical and realistic criteria to be used for solvents assessment for a given separation. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-27T00:13:36.150343-05:
      DOI: 10.1002/aic.14809
       
  • Rigorous design of distillation columns using surrogate models based on
           kriging interpolation
    • Authors: Natalia Quirante; Juan Javaloyes, José A. Caballero
      Abstract: The economic design of a distillation column or distillation sequences is a challenging problem that has been addressed by superstructure approaches. However, these methods have not been widely used because they lead to mixed‐integer nonlinear programs that are hard to solve, and require complex initialization procedures. In this paper, we propose to address this challenging problem by substituting the distillation columns by kriging‐based surrogate models generated via state of the art distillation models. We study different columns with increasing difficulty, and show that it is possible to get accurate kriging based surrogate models. The optimization strategy ensures that convergence to a local optimum is guaranteed for numerical noise‐free models. For distillation columns (slightly noisy systems), Karush‐Kuhn‐Tucker optimality conditions cannot be tested directly on the actual model, but still we can guarantee a local minimum in a trust region of the surrogate model that contains the actual local minimum. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-21T09:25:13.669651-05:
      DOI: 10.1002/aic.14798
       
  • Thermodynamic mechanism of free heme action on sickle cell hemoglobin
           polymerization
    • Authors: Anupam Aich; Weichun Pan, Peter G. Vekilov
      Abstract: For insights into the mechanisms of heme action on the rate of sickle cell hemoglobin polymerization, we determine the erythrocytic concentration of free heme by employing a novel method based on enzymatic catalysis and luminescence. We find in sickle cell patients 44±10 μM, in sickle trait individuals, 33±4 μM, and in healthy adults, 21±2 μM. We test the applicability of two mechanisms of heme action: a kinetic one, whereby heme aggregates serve as heterogeneous nucleation centers, and a thermodynamic pathway, in which free heme enhances the attraction between HbS molecules in solution. We show that the latter mechanism exclusively operates. The enhanced attraction leads to increase of the total volume of a population of dense liquid clusters by about two orders of magnitude. Since the dense liquid clusters serve as locations and precursors to the formation of the HbS polymer nuclei, their increased volume directly leads to faster polymer nucleation. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-21T09:25:12.125809-05:
      DOI: 10.1002/aic.14800
       
  • Modeling the permittivity of electrolyte solutions
    • Authors: Jørgen M. Mollerup; Martin P. Breil
      Abstract: Solution of a strong electrolyte in a high‐density polar fluid gives rise to a dielectric saturation that decreases the orientation polarizability of the solvent molecules in close proximity to the ions wherefore the relative permittivity in this region is determined solely by the atomic and electronic polarization. This causes a substantial decrease in the static permittivity of the solution. By considering the dielectric saturation, we have developed a model for the permittivity of an electrolyte solution and determined the parameters, the relative permittivities at dielectric saturation in close proximity to the ions, for 17 ions in water at 298.15K. By scaling these relative permittivities in proportion to the permittivity of the solvent, we were able to extend the model to calculate the permittivity of solutions of electrolytes in methanol and admixtures of water and ethanol. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-21T09:25:10.682099-05:
      DOI: 10.1002/aic.14799
       
  • Multiscale modeling of oil uptake in fried products
    • Authors: Jean‐Michaël Vauvre; Anna Patsioura, Régis Kesteloot, Olivier Vitrac
      Abstract: Oil‐air biphasic flow has been simulated at the scale of an entire potato tuber tissue using a Kinetic Monte‐Carlo (KMC) formulation parameterized on microscopic observations. Extrapolations to more general configurations are proposed by combining the proposed KMC framework with oil momentum equations integrated at microscopic scale. Branched percolation routes in 3D honeycomb arrangement of cells are explored using a first‐passage algorithm. Three major applications are presented. KMC simulations are first considered to homogenize sparse dynamic observations at the scale of isolated cells up to the scale of a full tissue. The second application investigates the effect of cell damages on oil uptake. Finally, our general KMC formulation was successfully compared with a diffusive model of oil uptake. Comprehensive rules to set the distribution parameters of all quantities (kinetic and structure parameters) from scarce observations or general assumptions are discussed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-21T09:12:35.302834-05:
      DOI: 10.1002/aic.14801
       
  • Liquid li structure and dynamics: A comparison between OFDFT and second
           nearest‐neighbor embedded‐atom method
    • Authors: Mohan Chen; Joseph R. Vella, Frank H. Stillinger, Emily A. Carter, Athanassios Z. Panagiotopoulos, Pablo G. Debenedetti
      Abstract: The structure and dynamics of liquid lithium are studied using two simulation methods: orbital‐free first‐principles molecular dynamics, which employs orbital‐free density functional theory, and classical molecular dynamics utilizing a second nearest‐neighbor embedded‐atom method potential. The properties studied include the dynamic structure factor, the self‐diffusion coefficient, the dispersion relation, the viscosity, and the bond angle distribution function. We compare simulation results to available experimental data when possible. We find that each method has distinct advantages and disadvantages. For example, orbital‐free density functional theory gives better agreement with experimental dynamic structure factors, yet is more computationally demanding than classical simulations. Classical simulations can access a broader temperature range and longer time scales. We conclude that the combination of first‐principles and classical simulations is a powerful tool for studying properties of liquid lithium. This article is protected by copyright. All rights reserved.
      PubDate: 2015-03-21T09:12:32.212563-05:
      DOI: 10.1002/aic.14795
       
  • DEM‐CFD modeling of particle systems with long‐range
           electrostatic interactions
    • Authors: Chunlei Pei; Chuan‐Yu Wu, David England, Stephen Byard, Harald Berchtold, Michael Adams
      Pages: 1792 - 1803
      Abstract: To investigate dynamic behaviors of monocharged particle systems, a direct truncation (DT) method and a hybrid particle‐cell (HPC) method are implemented into the discrete element method coupled with computational fluid dynamics (DEM‐CFD) with defined cutoff distances. The DT method only considers electrostatic interactions between particles within the cutoff distance while the HPC method computes electrostatic interactions in the entire computational domain. The deposition process of monocharged particles in a container in air was simulated using the developed DEM‐CFD. It was found that using the DT method, the macrostructure, evolution of granular temperature, and radial distribution function of the particle system were sensitive to the specified cutoff distance. In contrast, using the HPC method, these results were independent of the specified cutoff distance, as expected. This implies that, although electrostatic interactions between particles with large separation distances are weak, they should be considered in DEM‐CFD for accurate modeling of charged particle systems. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1792–1803, 2015
      PubDate: 2015-03-26T13:02:01.327721-05:
      DOI: 10.1002/aic.14768
       
  • The role of wall deposition and re‐entrainment in swirl spray dryers
    • Authors: Víctor Francia; Luis Martín, Andrew E. Bayly, Mark J. H. Simmons
      Pages: 1804 - 1821
      Abstract: A new experimental method is outlined to study fouling in spray dryers and similar devices. In essence, it makes the deposits traceable so that one can quantify the material that comes off the walls, how long it remains there and how the deposits agglomerate with particles in the air. This paper investigates a countercurrent swirl spray dryer of detergent and provides sound evidence that fouling is a dynamic process: clusters form and break at the walls renewing an active layer of deposits. Remarkably, the wall generates >20% of the product and most of the large granules, and increases drastically the residence time of the powder. The assumptions of current numerical models are clearly invalid (i.e. particles rebound at the wall or deposit indefinitely). Several re‐entrainment mechanisms and their times scales are identified in this work, and accordingly, a new general framework to describe fouling in spray dryers is proposed. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1804–1821, 2015
      PubDate: 2015-03-29T17:40:33.802972-05:
      DOI: 10.1002/aic.14767
       
  • Uncertainty quantification of property models: Methodology and its
           application to CO2‐loaded aqueous MEA solutions
    • Authors: Joshua C. Morgan; Debangsu Bhattacharyya, Charles Tong, David C. Miller
      Pages: 1822 - 1839
      Abstract: Uncertainties in property models can significantly affect the results obtained from process simulations. If these uncertainties are not quantified, optimal plant designs based on such models can be misleading. With this incentive, a systematic, generalized uncertainty quantification (UQ) methodology for property models is developed. Starting with prior beliefs about parametric uncertainties, a Bayesian method is used to derive informed posteriors using the experimental data. To reduce the computational expense, surrogate response surface models are developed. For downselecting the parameter space, a sensitivity matrix‐based approach is developed. The methodology is then deployed to the property models for an MEA‐CO2‐H2O system. The UQ analysis is found to provide interesting information about uncertainties in the parameter space. The sensitivity matrix approach is also found to be a valuable tool for reducing computational expense. Finally, the effect of the estimated parametric uncertainty on CO2 absorption and monoethanolamine (MEA) regeneration is analyzed. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1822–1839, 2015
      PubDate: 2015-03-09T11:11:54.153726-05:
      DOI: 10.1002/aic.14762
       
  • Practical improvements to autocovariance least‐squares
    • Authors: Megan A. Zagrobelny; James B. Rawlings
      Pages: 1840 - 1855
      Abstract: Identifying disturbance covariances from data is a critical step in estimator design and controller performance monitoring. Here, the autocovariance least‐squares (ALS) method for this identification is examined. For large industrial models with poorly observable states, the process noise covariance is high dimensional and the optimization problem is poorly conditioned. Also, weighting the least‐squares problem with the identity matrix does not provide minimum variance estimates. Here, ALS method to resolve these two challenges is modified. Poorly observable states using the singular value decomposition (SVD) of the observability matrix is identified and removed, thus decreasing the computational time. Using a new feasible‐generalized least‐squares estimator that approximates the optimal weighting from data, the variance of the estimates is significantly reduced. The new approach on industrial data sets provided by Praxair is successfully demonstrated. The disturbance model identified by the ALS method produces an estimator that performs optimally over a year‐long period. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1840–1855, 2015
      PubDate: 2015-03-11T09:05:33.249009-05:
      DOI: 10.1002/aic.14771
       
  • Multistream heat exchangers: Equation‐oriented modeling and
           flowsheet optimization
    • Authors: Richard C. Pattison; Michael Baldea
      Pages: 1856 - 1866
      Abstract: Multistream heat exchangers (MHEXs), typically of the plate‐fin or spiral‐wound type, are a key enabler of heat integration in cryogenic processes. Equation‐oriented modeling of MHEXs for flowsheet optimization purposes is challenging, especially when streams undergo phase transformations. Boolean variables are typically used to capture the effect of phase changes, adding considerable difficulty to solving the flowsheet optimization problem. A novel optimization‐oriented MHEX modeling approach that uses a pseudo‐transient approach to rapidly compute stream temperatures without requiring Boolean variables is presented. The model also computes an approximate required heat exchange area to determine the optimal tradeoff between operating and capital expenses. Subsequently, this model is seamlessly integrated in a previously‐introduced pseudo‐transient process modeling and flowsheet optimization framework. Our developments are illustrated with two optimal design case studies, an MHEX representative of air separation operation and a natural gas liquefaction process. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1856–1866, 2015
      PubDate: 2015-03-21T10:30:25.419206-05:
      DOI: 10.1002/aic.14766
       
  • Adaptive model predictive inventory controller for multiproduct batch
           plant
    • Authors: Gyeongbeom Yi; Gintaras V. Reklaitis
      Pages: 1867 - 1880
      Abstract: An inventory control system was developed for multiproduct batch plants with an arbitrary number of batch processes and storage units. Customer orders are received by the plant at order intervals and in order quantities that are subject to random fluctuations. The objective of the plant operation is to minimize the total cost while maintaining inventory levels within the storage or warehouse capacity by adjusting the startup times, the quantities of raw material orders, and production batch sizes. An adaptive model predictive control algorithm was developed that uses a periodic square wave model to represent the flows of the material between the processes and the storage units. The boundedness of the control output and the convergence of the estimated parameters in implementations of the proposed algorithm were mathematically proven under the assumption that disturbances in the orders are bounded. The effectiveness of this approach was demonstrated by performing simulations. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1867–1880, 2015
      PubDate: 2015-03-25T08:42:55.242493-05:
      DOI: 10.1002/aic.14783
       
  • Optimal planning for the reuse of municipal solid waste considering
           economic, environmental, and safety objectives
    • Authors: José Ezequiel Santibañez‐Aguilar; Juan Martinez‐Gomez, José María Ponce‐Ortega, Fabricio Nápoles‐Rivera, Medardo Serna‐González, Janett Betzabe González‐Campos, Mahmoud M. El‐Halwagi
      Pages: 1881 - 1899
      Abstract: A mathematical programming model is presente for the optimal planning of the reuse of municipal solid waste (MSW) to maximize the economic benefit while simultaneously considering sustainability and safety criteria. The proposed methodology considers several phases of the supply chain including waste separation, distribution to processing facilities, processing to obtain useful products, and distribution of products to consumers. Additionally, the safety criteria are based on the potential fatalities associated with waste management. The proposed optimization model is formulated as a multiobjective optimization problem, which considers three different objectives including the maximization of the net annual profit, the maximization of the amount of reused MSW, and the minimization of the social risk associated with the supply chain. The proposed model is applied to a case study in the central‐west region of Mexico. The results show the tradeoff between the social risk and the economic and environmental criteria. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1881–1899, 2015
      PubDate: 2015-03-25T08:54:07.725406-05:
      DOI: 10.1002/aic.14785
       
  • Mathematical modeling of polyethylene terephthalate pyrolysis in a spouted
           bed
    • Authors: Arezou Niksiar; Amir Hasan Faramarzi, Morteza Sohrabi
      Pages: 1900 - 1911
      Abstract: A model has been developed for pyrolysis of polyethylene terephthalate (PET) in a spouted bed reactor based on the conservation equations for heat, mass, and momentum transports. A spouted bed has been constructed and the kinetic parameters have been obtained within the temperature range of 723–833 K, using two particle size ranges, (0.1–1.0) × 10−3 and (1.0–3.0) × 10−3 m. The model' predictions for the radial distributions of temperature and concentration confirm the excellent mixing of particles. Thus, spouted beds are appropriate equipments for performing kinetic studies of PET pyrolysis. The inlet gas temperature and the mass of PET highly affect PET conversion. The amount of inert particles has a negligible effect on the conversion and it can be reduced as far as a stable spouting is preserved. The gas flow suffices to eliminate the external heat and mass‐transfer limitations. It can be reduced to the minimum value to decrease the energy consumption. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1900–1911, 2015
      PubDate: 2015-03-16T16:51:08.90381-05:0
      DOI: 10.1002/aic.14775
       
  • Shear‐rate‐dependent rheology effects on mass transport and
           surface reactions in biomicrofluidic devices
    • Authors: Arman Sadeghi; Younes Amini, Mohammad Hassan Saidi, Hadi Yavari
      Pages: 1912 - 1924
      Abstract: Consideration is given to shear‐rate‐dependent rheology effects on mass transport in a heterogeneous microreactor of rectangular cross section, utilizing both numerical and analytical approaches. The carrier liquid obeys the power‐law viscosity model and is actuated primarily by an electrokinetic pumping mechanism. It is discovered that, considering the shear‐thinning biofluids to be Newtonian fluids gives rise to an overestimation of the saturation time. The degree of overestimation is higher in the presence of large Damkohler numbers and electric double layer thicknesses. It is also increased by the application of a favorable pressure gradient, whereas the opposite is true when an opposed pressure gradient is applied. In addition, a channel of square cross section corresponds to the maximum fluid rheology effects. Finally, the numerical results indicate the existence of a concentration wave when using long channels. This is confirmed by analytical solutions, providing a closed form solution for wave propagation speed. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1912–1924, 2015
      PubDate: 2015-03-25T09:04:27.27197-05:0
      DOI: 10.1002/aic.14781
       
  • Thermodynamic and kinetic studies on alkoxylation of camphene over cation
           exchange resin catalysts
    • Authors: Huiqin Nie; Ruyin Xu, Feng Zhang, Zheng Zhou, Zhibing Zhang, Gaodong Yang
      Pages: 1925 - 1932
      Abstract: The alkoxylation of camphene with 2‐methyl‐1,3‐propanediol was studied using anhydrous macroporous and strong acid cation exchange resins as catalysts. The effects of various parameters, such as catalyst type, solvent, molar ratio of reactants, reaction temperature, and reusability of catalysts, were investigated in a 250 mL stirred tank reactor to optimize the reaction conditions. The UNIFAC group contribution method was used to correct liquid nonideality, giving the thermodynamic equilibrium constant at 333–370 K. The enthalpy changes calculated by three different methods (Gaussian 03, constant, and a function of temperature) were compared. The value (−74.6 ± 3.3 kJ/mol) calculated by the last method was closer to the theoretical value (−75.73 kJ/mol) than that given by the second method (−30.2 ±1.2 kJ/mol). A Langmuir–Hinshelwood–Hougen–Watson model based on activity was used to fit experimental data and the activation energy was 29.14 kJ/mol. The optimized reaction conditions were also verified in a 5 L reaction kettle. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1925–1932, 2015
      PubDate: 2015-03-25T08:58:49.692363-05:
      DOI: 10.1002/aic.14786
       
  • Thermodynamic and kinetic studies of the
           MgCl2‐NH4Cl‐NH3‐H2O system for the production of high
           purity MgO from calcined low‐grade magnesite
    • Authors: Junfeng Wang; Zhibao Li, Ah‐Hyung Alissa Park, Camille Petit
      Pages: 1933 - 1946
      Abstract: To improve the overall sustainability of MgO‐based refractory production, a novel process to produce high purity MgO from calcined low‐grade magnesite in ammonium chloride solution was developed. The process was designed on the basis of the phase equilibria of the NH4Cl‐MgCl2‐NH3‐H2O system obtained using the Mixed Solvent Electrolyte model embedded in OLI software. The optimum calcination temperature of low‐grade magnesite was determined to be 650°C in terms of the conversion ratio of magnesium and calcium in the leaching experiments. An apparent activation energy of Mg extraction was 30.98 kJ/mol, which is slightly lower than that of Ca leaching. An empirical kinetic model of magnesium extraction was also developed to describe the effects of NH4Cl concentration, particle size of calcined magnesite, and solid‐to‐liquid ratio on the extent of extraction of magnesium. At leaching time of 10 min, the leachate with high Mg/Ca molar ratio was obtained. Then, MgO with a purity of 99.09% was produced through the decomposition of intermediate 4MgCO3·Mg(OH)2·4H2O. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1933–1946, 2015
      PubDate: 2015-03-27T11:39:32.479334-05:
      DOI: 10.1002/aic.14789
       
  • An old kinetic method for a new polymerization mechanism: Toward
           photochemically mediated ATRP
    • Authors: Yin‐Ning Zhou; Zheng‐Hong Luo
      Pages: 1947 - 1958
      Abstract: With the idea of “an old method for a new mechanism,” a detailed kinetic insight into photochemically mediated atom‐transfer radical polymerization (photo ATRP) was presented through a validated comprehensive model. The simulation mimics the experimental results of the model system using optimized photochemically mediated radical generation rate coefficients. The activator and radical (re)generated from the photo mediated reactions endow the photo ATRP with unique features, such as rapid ATRP equilibrium and quick consumption of initiator with a small amount of residual. The effect of the reaction parameters on ATRP behaviors was also investigated. Results showed that the acceleration of polymerization rate follows the square root law in the following three cases: the overall photochemically mediated radical generation rate coefficients (kr), the free ligand concentration, and the initiator concentration. However, the independence of the apparent propagation rate coefficient ( kpapp) on the square root of catalyst concentration might be attributed to the result of the synergy between the activators regenerated by electron‐transfer ATRP and the initiators for continuous activator regeneration ATRP mechanism. The photo ATRP is able to design and prepare various polymers by carefully tuning the conditions using the model‐based optimization approach. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1947–1958, 2015
      PubDate: 2015-03-29T17:34:02.228949-05:
      DOI: 10.1002/aic.14792
       
  • Modeling of a membrane reactor system for crude palm oil
           transesterification. Part II: Transport phenomena
    • Authors: Pin Pin Oh; Mei Fong Chong, Harrison Lik Nang Lau, Yuen May Choo, Junghui Chen
      Pages: 1981 - 1996
      Abstract: The mechanistic modeling of biodiesel production process in membrane reactor with the consideration of chemical reaction, phase equilibrium, and ultrafiltration is important for the membrane reactor design. In part II of this work, the chemical and phase equilibrium (CPE) model for crude palm oil transesterification reaction in the membrane reactor developed in part I is extended to an integration of CPE with modified Maxwell–Stefan model, which considers multicomponent mass transport phenomena of concentration polarization and intramembrane. A good fit of simulated permeate fluxes and apparent solute rejection to the experimental data shows that the model has a good prediction capability. Reversible fouling was found to be the major fouling and no pore plugging was observed. Simulation results verified that micelles were retained by the membrane at CPO:MEOH molar ratio of 1:24 and catalyst concentration of 0.5 wt %. However, phase inversion happened when catalyst concentration of 0.05 and 0.1 wt % were used. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1981–1996, 2015
      PubDate: 2015-03-07T09:05:49.704481-05:
      DOI: 10.1002/aic.14763
       
  • A CO2‐stable hollow‐fiber membrane with high hydrogen
           permeation flux
    • Authors: Yan Chen; Qing Liao, Zhong Li, Haihui Wang, Yanying Wei, Armin Feldhoff, Jürgen Caro
      Pages: 1997 - 2007
      Abstract: A Mo‐substituted lanthanum tungstate mixed proton‐electron conductor, La5.5W0.6Mo0.4O11.25−δ (LWM04), was synthesized using solid state reactions. Dense U‐shaped LWM04 hollow‐fiber membranes were successfully prepared using wet‐spinning phase‐inversion and sintering. The stability of LWM04 in a CO2‐containing atmosphere and the permeation of hydrogen through the LWM04 hollow‐fiber membrane were investigated in detail. A high hydrogen permeation flux of 1.36 mL/min cm2 was obtained for the U‐shaped LWM04 hollow‐fiber membranes at 975°C when a mixture of 80% H2−20% He was used as the feed gas and the sweep side was humidified. Moreover, the hydrogen permeation flux did not significantly decrease over 70 h of operation when fed with a mixture containing 25% CO2, 50% H2, and 25% He, indicating that the LWM04 hollow‐fiber membrane has good stability under a CO2‐containing atmosphere. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1997–2007, 2015
      PubDate: 2015-03-11T08:52:36.127633-05:
      DOI: 10.1002/aic.14772
       
  • Anatomy of a rapid pressure swing adsorption process performance
    • Authors: Rama Rao Vemula; Mayuresh V. Kothare, Shivaji Sircar
      Pages: 2008 - 2015
      Abstract: A detailed numerical study of the individual and cumulative effects of various mass, heat, and momentum transfer resistances, which are generally present inside a practical adiabatic adsorber, on the overall separation performance of a rapid pressure swing adsorption (RPSA) process is performed for production of nearly pure helium gas from an equimolar binary (N2 +He) gas mixture using 5 A zeolite. Column bed size factor (BSF) and helium recovery (R) from the feed gas are used to characterize the separation performances. All practical impediments like column pressure drop, finite gas‐solid mass and heat transfer resistances, mass and heat axial dispersions in the gas phase, and heats of ad(de)sorption causing nonisothermal operation have detrimental impacts on the overall process performance, which are significantly accentuated when the total cycle time of a RPSA process is small and the product gas helium purity is high. These impediments also prohibit indefinite lowering of BSF (desired performance) by decreasing process cycle time alone. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2008–2015, 2015
      PubDate: 2015-03-11T09:11:50.05939-05:0
      DOI: 10.1002/aic.14779
       
  • Design and screening of ionic liquids for C2H2/C2H4 separation by
           COSMO‐RS and experiments
    • Authors: Xu Zhao; Qiwei Yang, Dan Xu, Zongbi Bao, Yi Zhang, Baogen Su, Qilong Ren, Huabin Xing
      Pages: 2016 - 2027
      Abstract: Ionic liquids (ILs) have been proposed as promising solvents for separating C2H2 and C2H4, but screening an industrially attractive IL with high capacity from numerous available ILs remains challenging. In this work, a rapid screening method based on COSMO‐RS was developed. We also present an efficient strategy to improve the C2H2 capacity in ILs together with adequate C2H2/C2H4 selectivity with the aid of COSMO‐RS. The essence of this strategy is to increase molecular free volume of ILs and simultaneously enhance hydrogen‐bond basicity of anions by introducing flexible and highly asymmetric structures, which is validated by a new class of tetraalkylphosphonium ILs featuring long‐chain carboxylate anions. At 298.1 K and 1 bar, the solubility of C2H2 in ILs reaches 0.476 mol/mol IL, very high for a physical absorption, with a selectivity of up to 21.4. The separation performance of tetraalkylphosphonium ILs to the mixture of C2H2/C2H4 was also evaluated. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2016–2027, 2015
      PubDate: 2015-03-25T09:13:21.988982-05:
      DOI: 10.1002/aic.14782
       
  • Designing of anion‐functionalized ionic liquids for efficient
           capture of SO2 from flue gas
    • Authors: Kaihong Chen; Wenjun Lin, Xini Yu, Xiaoyan Luo, Fang Ding, Xi He, Haoran Li, Congmin Wang
      Pages: 2028 - 2034
      Abstract: Five kinds of anion‐functionalized ionic liquids (ILs) with different basicity and substituent were selected, prepared and applied in the capture of SO2 from flue gas, where the concentration of SO2 is only 2000 ppm. The effect of the anion on SO2 absorption capacity, desorption residue, and available absorption capacity under 2000 ppm was investigated. The relationship between available absorption capacity and absorption enthalpy was also studied. Through a combination of thermodynamic analysis and quantum calculation, the results indicated that the effect of the cation in the IL on absorption enthalpy was significant. However, the effect of chain length in the cation was weak. Hence, a new IL with low molecular weight, [P4442][Tetz], was further designed and applied for the capture of SO2, which shows the high absorption capacity of 0.18 g SO2 per g IL and excellent reversibility for 2000 ppm SO2. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2028–2034, 2015
      PubDate: 2015-03-27T10:19:11.562572-05:
      DOI: 10.1002/aic.14793
       
  • Freeze‐drying of aqueous solution frozen with prebuilt pores
    • Authors: Wei Wang; Dapeng Hu, Yanqiu Pan, Yanqiang Zhao, Guohua Chen
      Pages: 2048 - 2057
      Abstract: To save drying time and increase productivity, a novel idea was proposed for freeze‐drying of liquid materials by creating an initially unsaturated frozen structure. An experimental investigation was carried out aiming at verifying the idea using a multifunctional freeze‐drying apparatus. Mannitol was selected as the primary solute in aqueous solution. Liquid nitrogen ice‐cream making method was used to prepare the frozen materials with different initial porosities. Results show that freeze‐drying can be significantly enhanced with the initially unsaturated frozen material, and substantial drying time can be saved compared with conventional freeze‐drying of the initially saturated one. Drying time was found to decrease with the decrease in the initial saturation. The drying time for the initially unsaturated frozen sample (S0 = 0.28 or 0.69 of initial porosity) can be at best 32% shorter than that required for the saturated one (S0 = 1.00 or zero porosity). This unique technique is easy to implement and improves the freeze‐drying performance of liquid materials. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2048–2057, 2015
      PubDate: 2015-03-11T08:56:16.500241-05:
      DOI: 10.1002/aic.14769
       
  • Gas absorption into a wavy two‐layer falling film
    • Authors: G. Çekiç; G. M. Sisoev
      Pages: 2058 - 2069
      Abstract: Absorption of a weakly soluble gas into a two‐layer film flowing down a vertical wall is studied in the framework of an approximate long‐wave model. It is shown that wavy regimes in the film strongly affect the absorption rate. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2058–2069, 2015
      PubDate: 2015-03-11T08:43:42.38015-05:0
      DOI: 10.1002/aic.14778
       
  • Experimental and linear analysis for the instability of
           non‐Newtonian liquid jets issuing from a pressurized vibrating
           nozzle
    • Authors: Cristina Rodríguez‐Rivero; Eva M. M. Del Valle, Miguel A. Galán
      Pages: 2070 - 2078
      Abstract: The laminar capillary breakup of viscoelastic jets to produce polymeric microcapsules is analyzed experimentally and theoretically. The phenomenon is based on subjecting a capillary jet to controlled disturbances so that it eventually breaks up forming individual droplets. A dispersion relation from a temporal linear analysis to describe and predict the system behavior that includes the Oldroyd‐B constitutive equation to take into account the viscoelasticity of the liquid is obtained. Dispersion curves relating growth rate and wavenumber of the perturbed jets are compared with experimental conditions and the chosen mathematical approach is found that fairly describes the system. The obtained dispersion relation eases the study of the effect of viscosity, elasticity, through relaxation times, and flow rate in the system. The approach allows finding the best conditions to obtain homogeneous droplets and describes the system qualitatively. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2070–2078, 2015
      PubDate: 2015-03-27T11:32:23.054286-05:
      DOI: 10.1002/aic.14790
       
  • A model for gas transport in microfractures of shale and tight gas
           reservoirs
    • Authors: Keliu Wu; Xiangfang Li, Chenchen Wang, Zhangxin Chen, Wei Yu
      Pages: 2079 - 2088
      Abstract: A model for gas transport in microfractures of shale and tight gas reservoirs is established. Slip flow and Knudsen diffusion are coupled together to describe general gas transport mechanisms, which include continuous flow, slip flow, transitional flow, and Knudsen diffusion. The ratios of the intermolecular collision frequency and the molecule‐wall collision frequency to the total collision frequency are defined as the weight coefficients of slip flow and Knudsen diffusion, respectively. The model is validated by molecular simulation results. The results show that: (1) the model can reasonably describe the process of the mass transform of different gas transport mechanisms; (2) fracture geometry significantly impacts gas transport. Under the same fracture aperture, the higher the aspect ratio is, the stronger the gas transport capacity, and this phenomenon is more pronounced in the cases with higher gas pressure and larger fracture aperture. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2079–2088, 2015
      PubDate: 2015-03-27T10:22:30.588363-05:
      DOI: 10.1002/aic.14791
       
 
 
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