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  Subjects -> ENGINEERING (Total: 2156 journals)
    - CHEMICAL ENGINEERING (186 journals)
    - CIVIL ENGINEERING (168 journals)
    - ELECTRICAL ENGINEERING (93 journals)
    - ENGINEERING (1164 journals)
    - ENGINEERING MECHANICS AND MATERIALS (355 journals)
    - HYDRAULIC ENGINEERING (55 journals)
    - INDUSTRIAL ENGINEERING (54 journals)
    - MECHANICAL ENGINEERING (81 journals)

ENGINEERING (1164 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: 7)
Catalysis Science and Technology     Free   (Followers: 5)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 4)
Catalysis Today     Hybrid Journal   (Followers: 6)
CEAS Space Journal     Hybrid Journal   (Followers: 1)
Cellular and Molecular Neurobiology     Hybrid Journal   (Followers: 2)
Central European Journal of Engineering     Hybrid Journal   (Followers: 1)
CFD Letters     Open Access   (Followers: 2)
Chaos : An Interdisciplinary Journal of Nonlinear Science     Hybrid Journal   (Followers: 1)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 1)
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 1)
Chinese Journal of Engineering     Open Access  
Chinese Science Bulletin     Open Access  
Ciencia e Ingenieria Neogranadina     Open Access  
Ciencia en su PC     Open Access  
Ciencias Holguin     Open Access  
Cientifica     Open Access  
CIRP Annals - Manufacturing Technology     Full-text available via subscription   (Followers: 10)
CIRP Journal of Manufacturing Science and Technology     Full-text available via subscription   (Followers: 9)
City, Culture and Society     Hybrid Journal   (Followers: 20)
Clay Minerals     Full-text available via subscription   (Followers: 11)
Clean Air Journal     Full-text available via subscription   (Followers: 2)
Clinical Science     Full-text available via subscription   (Followers: 8)
Coal Science and Technology     Full-text available via subscription   (Followers: 4)
Coastal Engineering     Hybrid Journal   (Followers: 9)
Coastal Engineering Journal     Hybrid Journal   (Followers: 2)
Coatings     Open Access   (Followers: 3)
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: 4)
Composite Structures     Hybrid Journal   (Followers: 130)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 101)
Composites Part B : Engineering     Hybrid Journal   (Followers: 124)
Composites Science and Technology     Hybrid Journal   (Followers: 89)
Comptes Rendus Mécanique     Full-text available via subscription   (Followers: 2)
Computation     Open Access   (Followers: 1)
Computational Geosciences     Hybrid Journal   (Followers: 12)
Computational Optimization and Applications     Hybrid Journal   (Followers: 6)
Computational Science and Discovery     Full-text available via subscription  
Computational Water, Energy, and Environmental Engineering     Open Access   (Followers: 2)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 7)
Computer Science and Engineering     Open Access   (Followers: 8)
Computers & Geosciences     Hybrid Journal   (Followers: 7)
Computers & Mathematics with Applications     Full-text available via subscription   (Followers: 4)
Computers and Electronics in Agriculture     Hybrid Journal   (Followers: 3)
Computers and Geotechnics     Hybrid Journal   (Followers: 7)
Computing and Visualization in Science     Hybrid Journal   (Followers: 3)
Computing in Science & Engineering     Full-text available via subscription   (Followers: 13)
Conciencia Tecnologica     Open Access   (Followers: 1)
Concurrent Engineering     Hybrid Journal   (Followers: 4)
Conference Proceedings - Lucian Blaga University Sibiu     Open Access  
Continuum Mechanics and Thermodynamics     Hybrid Journal   (Followers: 3)
Control and Dynamic Systems     Full-text available via subscription   (Followers: 4)
Control Engineering Practice     Hybrid Journal   (Followers: 32)
Control Theory and Informatics     Open Access   (Followers: 4)
Corrosion Science     Hybrid Journal   (Followers: 22)
Corrosion Series     Full-text available via subscription   (Followers: 7)
CT&F Ciencia, Tecnologia y Futuro     Open Access  
Current Applied Physics     Full-text available via subscription   (Followers: 4)
Dams and Reservoirs     Hybrid Journal   (Followers: 4)

  First | 1 2 3 4 5 6 7 8 | Last

Journal Cover   AIChE Journal
  [SJR: 1.098]   [H-I: 104]   [21 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  [1610 journals]
  • Hybrid PIV/PTV measurements of velocity and position distributions of
           gas‐conveyed particles in small, narrow channels
    • Authors: M.W. Korevaar; J.T. Padding, N.G. Deen, J. Wang, M. de Wit, M.A.I. Schutyser, J.A.M. Kuipers
      Abstract: Pneumatic conveying of particles is generally applied in large ducts. However, new applications are emerging which benefit from millimeter sized ducts; e.g.\triboelectric separators where intensive wall‐particle contact is desirable. In this paper an optical method is proposed to measure the distribution of the position and velocity of 100‐1000 μm particles in such narrow ducts. Images of the system are captured using a digital camera on which a Hough transform is applied to detect the particles and their positions. The velocities are acquired by applying a hybrid particle tracking and particle image velocimetry approach. This made it is possible to overcome challenges caused by suboptimal lighting, non‐smooth background and a large ratio between particle and duct diameter (>O(0.1)). It is shown that the algorithm is subpixel accurate when sufficient particles can be sampled. Finally, typical results are shown to illustrate the method's capabilities. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-02T11:59:48.029563-05:
      DOI: 10.1002/aic.14928
       
  • Classical density functional theory for methane adsorption in
           metal‐organic framework materials
    • Authors: Jia Fu; Yun Tian, Jianzhong Wu
      Abstract: Natural gas is considered as a promising alternative to petroleum as the next generation of primary transportation fuel owing to relatively smaller carbon footprint and lower SOx/NOx emissions and to fast developments of shale gas in recent years. Since the volumetric energy density of methane amounts to only about 1% of that of gasoline at ambient conditions, natural gas storage represents one of the key challenges for prevalent deployment of natural gas vehicles. In this work, we present a molecular thermodynamic model potentially useful for high‐throughput screening of nanoporous materials for natural gas storage. We investigate methane adsorption in a large library of metal‐organic frameworks (MOFs) using four versions of classical density functional theory (DFT) and calibrate the theoretical predictions with extensive simulation data for total gas uptake and delivery capacity. In combination with an extended excess entropy scaling method, the classical DFT is also used to predict the self‐diffusion coefficients of the confined gas in several top‐ranked MOFs. The molecular thermodynamic model has been used to identify promising MOF materials and possible variations of operation parameters to meet the Advanced Research Projects Agency‐Energy (ARPA‐E) target set by the U.S. Department of Energy for natural gas storage. © 2015 The
      Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 2015
      PubDate: 2015-07-02T11:52:52.906265-05:
      DOI: 10.1002/aic.14877
       
  • An effective rate approach (ERA) to modelling single‐stage spray
           drying
    • Authors: Oluwafemi Ayodele George; Jie Xiao, Mengwai Woo, Liming Che, Xiao Dong Chen
      Abstract: An effective rate approach (ERA) is proposed in this work to achieve a fast and reliable prediction of dryer outlet conditions for a given single‐stage spray drying system operated under a range of scenarios. This approach is improved from existing methods based on simple mass and energy balances due to the incorporation of a reliable drying rate model, which is the reaction engineering approach for the material of interest. It allows quick solution procedure without the need to solve the partial differential equations that govern the heat and mass transfer in the spray drying process. By following a generic procedure, this technique has been exercised upon the experimental results from running a mono‐disperse droplet spray dryer, i.e., a well‐established experimental platform for model validation. The proposed ERA has been shown to be rather promising. It could become a powerful approach for proactive control and optimization for existing spray drying facilities. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-02T03:30:00.194032-05:
      DOI: 10.1002/aic.14940
       
  • Probabilistic slow feature analysis‐based representation learning
           from massive process data for soft sensor modeling
    • Authors: Chao Shang; Biao Huang, Fan Yang, Dexian Huang
      Abstract: Latent variable (LV) models provide explicit representations of underlying driving forces of process variations and retain the dominant information of process data. In this study, slow features as temporally correlated LVs are derived using probabilistic slow feature analysis. Slow features evolving in a state‐space form effectively represent nominal variations of processes, some of which are potentially correlated to quality variables and hence help improving the prediction performance of soft sensors. An efficient EM algorithm is proposed to estimate parameters of the probabilistic model, which turns out to be suitable for analyzing massive process data. Two criteria are also proposed to select quality‐relevant slow features. The validity and advantages of the proposed method are demonstrated via two case studies. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-02T03:27:50.906688-05:
      DOI: 10.1002/aic.14937
       
  • Multivariate statistical process monitoring of batch‐to‐batch
           startups
    • Authors: Zhengbing Yan; Bi‐Ling Huang, Yuan Yao
      Abstract: In batch processes, multivariate statistical process monitoring (MSPM) plays an important role for ensuring process safety. However, despite many methods proposed, few of them can be applied to batch‐to‐batch startups. The reason is that, during the startup stage, process data are usually non‐stationary and non‐identically distributed from batch to batch. In this paper, the trajectory signal of each process variable is decomposed into a series of components corresponding to different frequencies, by adopting a nonparametric signal decomposition technique named ensemble empirical mode decomposition (EEMD). Then, through instantaneous frequency calculation, these components can be divided into two groups. The first group reflects the long‐term trend between batches, which extracts the batch‐wise non‐stationary drift information. The second group corresponds to the short‐term intra‐batch variations. The variable trajectory signals reconstructed from the latter fulfills the requirements of conventional MSPM. The feasibility of the proposed method is illustrated using an injection molding process. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-01T10:46:55.370645-05:
      DOI: 10.1002/aic.14939
       
  • Trajectory Modeling of Gas‐Liquid Flow in Microchannels with
           Stochastic Differential Equation and Optical Measurement
    • Authors: Lexiang Zhang; Feng Xin, Dongyue Peng, Weihua Zhang, Yuexing Wang, Xiaodong Chen, Yi Wang
      Abstract: The numbering up of microchannel reactors definitely faces great challenge in uniformly distributing fluid flow in every channel, especially for multiphase systems. A model of stochastic differential equations (SDEs) is proposed based on the experimental data recorded by a long term optical measurement to well quantify the stochastic trajectories of gas bubbles and liquid slugs in parallel microchannels interconnected with two dichotomic distributors. The expectation and variance of each sub flow rate are derived explicitly from the SDEs associated with the Fokker‐Planck equation and solved numerically. A bifurcation in the trajectory is found by using the original model, then a modification on interactions of feedback and crosstalk is introduced, the evolutions of sub flow rates calculated by the modified model match well with experimental results. The established methodology is helpful for characterizing the flow uniformity and numbering up the microchannel reactors of multiphase system. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-01T10:46:24.439242-05:
      DOI: 10.1002/aic.14938
       
  • Hybrid Mixture Theory Based Modeling of Transport Mechanisms and Expansion
           ‐ Thermomechanics of Starch During Extrusion
    • Authors: Srivikorn Ditudompo; Pawan S. Takhar
      Abstract: Water, vapor and heat transport mechanisms and thermomechanical changes occurring inside the expanding extrudate were described using hybrid mixture theory based unsaturated transport equations. Transport equations were transformed from the Eulerian coordinates to the Lagrangian coordinates. Good agreements between the predicted and experimental values of surface temperature, moisture content and expansion ratio of the extrudates were obtained. The model was also used to calculate temperature, moisture content, pore‐pressure and viscoelastic‐stress distribution in the extrudate. Matrix collapse and glassy crust formation under the surface was calculated as a function of extrusion conditions. Expansion behavior of the extrudate was described using the difference between stress due to pore pressure and viscoelastic stress. The modeling results can serve as a guide for predictably modifying the extrusion parameters for obtaining specific textural attributes of expanded starch for various food, feed and biomedical applications. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-01T10:34:38.724043-05:
      DOI: 10.1002/aic.14936
       
  • Ni‐Al2O3/Ni‐foam catalyst with enhanced heat transfer for
           hydrogenation of CO2 to methane
    • Authors: Yakun Li; Qiaofei Zhang, Ruijuan Chai, Guofeng Zhao, Fahai Cao, Ye Liu, Yong Lu
      Abstract: Monolithic Ni‐Al2O3/Ni‐foam catalyst is developed by modified wet chemical etching of Ni‐foam, being highly active/selective and stable in strongly exothermic CO2 methanation process. The as‐prepared catalysts are characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma atomic emission spectrometry (ICP‐AES) and H2‐temperature programmed reduction‐mass spectrometry (H2‐TPR‐MS). The results indicate that modified wet chemical etching method is working efficiently for one‐step creating and firmly embedding NiO‐Al2O3 composite catalyst layer (∼2 μm) into the Ni‐foam struts. High CO2 conversion of 90% and high CH4 selectivity of >99.9% can be obtained and maintained for a feed of H2/CO2 (molar ratio of 4/1) at 320 oC and 0.1 MPa with a gas hourly space velocity (GHSV) of 5000 h−1, throughout entire 1200 h test over 10.2 mL such monolithic catalysts. Computational fluid dynamics (CFD) calculation and experimental measurement consistently confirm a dramatic reduction of ‘hotspot' temperature due to enhanced heat transfer. This article is protected by copyright. All rights reserved.
      PubDate: 2015-07-01T10:33:58.221705-05:
      DOI: 10.1002/aic.14935
       
  • Experimental investigation of electrostatic effect on particle motions in
           gas‐solid fluidized beds
    • Authors: Kezeng Dong; Qing Zhang, Zhengliang Huang, Zuwei Liao, Jingdai Wang, Yongrong Yang, Fang Wang
      Abstract: The excess accumulation of charges in the fluidized bed has a severe impact on hydrodynamics. Due to lack of effective experimental methods, electrostatic effects on hydrodynamics have mostly been studied using numerical simulation. By injecting a trace of liquid antistatic agents (LAA) into a fluidized bed, charges were controlled and electrostatic influences on particle motions were investigated. The average particle‐wall impact angles are acquired by developing multi‐scales wavelet decomposition of acoustic emission (AE) signals. The impact angles are significantly influenced by both charge levels and gas velocities. If the electric force is reduced and/or fluid drag is increased, friction dominates the particle‐wall interactions. Under a larger gas velocity where fluid drag dominates, charges elimination causes no significant variation in particle impact angles, but particle velocities increase as well as at lower gas velocities. In addition, existence of electrostatic charges influences the ranges of bubble growing zone and jet impacting zone. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-30T17:58:47.589711-05:
      DOI: 10.1002/aic.14933
       
  • Mass transfer rate enhancement for CO2 separation by ionic liquids:
           theoretical study on the mechanism
    • Authors: Wenlong Xie; Xiaoyan Ji, Xin Feng, Xiaohua Lu
      Abstract: To promote the development of ionic liquid (IL) immobilized sorbents and supported IL membranes (SILMs) for CO2 separation, in this work, the kinetics of CO2 absorption/desorption in IL immobilized sorbents was studied using a novel method based on non‐equilibrium thermodynamics. It shows that the apparent chemical‐potential‐based mass‐transfer coefficients of CO2 were in three regions with 3‐order difference in magnitude for the IL‐film thicknesses in micro‐scale, 100 nm‐scale and 10 nm‐scale. Using a diffusion‐reaction theory, it is found that by tailoring the IL‐film thickness from micro‐scale to nano‐scale, the process was altered from diffusion‐control to reaction‐control, revealing the inherent mechanism for the dramatic rate enhancement. The extension to SILMs shows that the significant improvement of CO2 flux can be obtained theoretically for the membranes with nano‐scale IL‐films, which makes it feasible to implement CO2 separation by ILs with low investment cost. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-30T17:58:22.166741-05:
      DOI: 10.1002/aic.14932
       
  • Process to Planet: A Multiscale Modeling Framework for Sustainable
           Engineering
    • Authors: Rebecca J. Hanes; Bhavik R. Bakshi
      Abstract: To prevent the chance of unintended environmental harm, engineering decisions need to consider an expanded boundary that captures all relevant connected systems. Comprehensive models for sustainable engineering may be developed by combining models at multiple scales. Models at the finest “equipment” scale are engineering models based on fundamental knowledge. At the intermediate “value chain” scale, empirical models represent average production technologies, and at the coarsest “economy” scale, models represent monetary and environmental exchanges for industrial sectors in a national or global economy. However, existing methods for sustainable engineering design ignore the economy scale, while existing methods for life cycle assessment do not consider the equipment scale. This work proposes an integrated, multi‐scale modeling framework for connecting models from process to planet (P2P) and using them for sustainable engineering applications. The proposed framework is demonstrated with a toy problem, and potential applications of the framework including current and future work are discussed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-30T06:02:43.832912-05:
      DOI: 10.1002/aic.14919
       
  • Future Feedstocks For the Chemical Industry—Where Will the Carbon
           Come From?
    • Authors: Scott F. Mitchell; Daniel F. Shantz
      PubDate: 2015-06-30T05:45:39.901615-05:
      DOI: 10.1002/aic.14910
       
  • Sustainable Process Design by the Process to Planet Framework
    • Authors: Rebecca J. Hanes; Bhavik R. Bakshi
      Abstract: Sustainable process design (SPD) problems combine a process design problem with life cycle assessment (LCA) to optimize process economics and life cycle environmental impacts. While SPD makes use of recent advances in process systems engineering and optimization, its use of LCA has stagnated. Currently, only process LCA is utilized in SPD, resulting in designs based on incomplete and potentially inaccurate life cycle information. To address these shortcomings, the multi‐scale process to planet (P2P) modeling framework is applied to formulate and solve the SPD problem. The P2P framework offers a more comprehensive analysis boundary than conventional SPD and greater modeling detail than advanced LCA methodologies. Benefits of applying this framework to SPD are demonstrated with an ethanol process design case study. Results show that current methods shift emissions outside the analysis boundary, while applying the P2P modeling framework results in environmentally superior process designs. Future extensions of the P2P framework are discussed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-30T05:28:25.579045-05:
      DOI: 10.1002/aic.14918
       
  • Assessing the performance of an industrial SBCR for fischer‐tropsch
           synthesis: Experimental and modeling
    • Authors: Laurent Sehabiague; Omar M. Basha, Zhansheng Shi, Haolin Jia, Yemin Hong, Li Weng, Zhuowu Men, Yi Cheng, Ke Liu, Badie Morsi
      Abstract: The main objective of this study is to predict the performance of an industrial‐scale (ID = 5.8 m) slurry bubble column reactor (SBCR) operating with iron‐based catalyst for Fischer‐Tropsch (FT) synthesis, with emphasis on catalyst deactivation. In order to achieve this objective, a comprehensive reactor model, incorporating the hydrodynamic and mass transfer parameters (gas holdup, εG, Sauter‐mean diameter of gas bubbles, d32, and volumetric liquid‐side mass transfer coefficients, kLa), and FT as well as water gas shift (WGS) reaction kinetics, was developed. The hydrodynamic and mass transfer parameters for He/N2 gaseous mixtures, as surrogates for H2/CO, were obtained in an actual molten FT reactor wax produced from the same reactor. The data were measured in a pilot‐scale (0.29 m) SBCR under different pressures (4‐31 bar), temperatures (380‐500 K), superficial gas velocities (0.1‐0.3 m/s) and iron‐based catalyst concentrations (0‐45 wt%). The data were modeled and predictive correlations were incorporated into the reactor model. The reactor model was then used to study the effects of catalyst concentration and reactor length‐to‐diameter ratio (L/D) on the water partial pressure, which is mainly responsible for iron catalyst deactivation, the H2 and CO conversions and the C5+ product yields. The modeling results of the industrial SBCR investigated in this study showed that (1) the water partial pressure should be maintained under 3 bars in order to minimize deactivation of the iron‐based catalyst used; (2) the catalyst concentration has much more impact on the gas holdup and reactor performance than the reactor height; and (3) the reactor should be operated in the kinetically‐controlled regime with an L/D of 4.48 and a catalyst concentration of 22 wt% in order to maximize C5+ products yield, while minimizing the iron catalyst deactivation. Under such conditions, the H2 and CO conversions were 49.4% and 69.3%, respectively and the C5+ products yield was 435.6 ton/day. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-27T10:36:26.930008-05:
      DOI: 10.1002/aic.14931
       
  • Droplets sliding over shearing surfaces studied by molecular dynamics
    • Authors: J.J. Derksen
      Abstract: We study, through molecular dynamics, the sliding motion of a liquid drop embedded in another liquid over a substrate as a result of a shear flow. The two immiscible Lennard‐Jones liquids have the same density and viscosity. The system is isothermal. Viscosity, surface tension, and static contact angles follow from calibration simulations. Sliding speeds and drop deformations (in terms of dynamic contact angles) are determined as a function of the shear rate. The latter is non‐dimensionalized as a capillary number (Ca) that has been varied in the range 0.02 to 0.64. For Ca up to 0.32, sliding speeds are approximately linear in Ca. For larger Ca, very strong droplet deformations are observed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-27T10:36:01.14552-05:0
      DOI: 10.1002/aic.14930
       
  • Evaluation of pure‐component adsorption properties of silicalite
           based on the langmuir and sips models
    • Authors: Alessio Caravella; Pasquale F. Zito, Adele Brunetti, Enrico Drioli, Giuseppe Barbieri
      Abstract: In this work, the adsorption parameters of several light gases and hydrocarbons (H2, CH4, CO2, CO, N2, C2H6, C3H8, n‐C4H10) in Silicalite are estimated along with and their functionality with temperature using both Langmuir and Sips models. This is a scientific attempt to resume and reconcile the number of available experimental data and supply scientists and other operators with the adsorption properties of silicalite within a wider range of temperature and pressure. Furthermore, to provide readers with more detailed information on where each of the two models work better, the analysis is divided into three temperature ranges: low‐temperature, high‐temperature and whole temperature range. As a result, it is found that the Langmuir model works well in the whole temperature range for the light gases considered but not for the other hydrocarbons, for which it is better to use the Sips model by splitting calculation over low‐ and high‐temperature range. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-27T10:34:34.560883-05:
      DOI: 10.1002/aic.14925
       
  • Pure H2 production through hollow fiber hydrogen‐selective MFI
           zeolite membranes using steam as sweep gas
    • Authors: Yuting Zhang; Qi Sun, Xuehong Gu
      Abstract: Hollow fiber MFI zeolite membranes were modified by catalytic cracking deposition of methyldiethoxysilane (MDES) to enhance their H2/CO2 separation performance and further employed in high temperature water gas shift membrane reactor (MR). Steam was used as the sweep gas in the MR for the production of pure H2. Extensive investigations were conducted on MR performance by variations of temperature, feed pressure, sweep steam flow rate and steam‐to‐CO ratio. CO conversion was obviously enhanced in the MR as compared with conventional packed‐bed reactor (PBR) due to the coupled effects of H2 removal as well as counter‐diffusion of sweep steam. Significant increment in CO conversion for MR vs. PBR was obtained at relatively low temperature and steam‐to‐CO ratio. A high H2 permeate purity of 98.2% could be achieved in the MR swept by steam. Moreover, the MR exhibited an excellent long‐term operating stability for 100 h in despite of the membrane quality. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-27T10:34:08.318729-05:
      DOI: 10.1002/aic.14924
       
  • High activity and wide temperature window of
           Fe‐Cu‐SSZ‐13 in the selective catalytic reduction of NO
           with ammonia
    • Authors: Tao Zhang; Jianmei Li, Jian Liu, Daxi Wang, Zhen Zhao, Junhua Li, Kai Cheng
      Abstract: Fe‐Cu‐SSZ‐13 catalysts were prepared by aqueous solution ion‐exchange method based on the one‐pot synthesized Cu‐SSZ‐13. The catalysts were applied to the selective catalytic reduction of NO with NH3 and characterized by the means of XRD, UV‐Vis, EPR, XPS, NH3‐TPD, and so on. The selected Fe‐Cu‐SSZ‐13‐1 catalyst exhibited the high NO conversion (> 90%) in the wide temperature range (225‐625 oC), which also showed good N2 selectivity and excellent hydrothermal stability. The results of XPS showed that the Cu and Fe species were in the internal and outer parts of the SSZ‐13 crystals, respectively. The results of UV‐Vis and EPR indicated that the monomeric Cu2+ ions coordinated to three oxygen atoms on the six‐ring sites and Fe monomers are the real active species in the NH3‐SCR reaction. Furthermore, the influence of intra‐crystalline mass‐transfer limitations on the Fe‐Cu‐SSZ‐13 catalysts is related to the location of active species in the SSZ‐13 crystals. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-27T10:33:49.597788-05:
      DOI: 10.1002/aic.14923
       
  • NMR imaging of low pressure, gas‐phase transport in packed beds
           using hyperpolarised xenon‐129
    • Authors: Galina Pavlovskaya; Navin Gopinathan, Joseph Six, Thomas Meersman, Sean P. Rigby
      Abstract: Gas‐phase MRI has been used to investigate heterogeneity in mass transport in a packed bed of commercial, alumina, catalyst supports. Hyperpolarised 129Xe MRI enables study of transient diffusion for microscopic porous systems using xenon chemical shift to selectively image gas within the pores, and, thence, permits study of low‐density, gas‐phase mass‐transport, such that diffusion can be studied in the Knudsen regime, and not just the molecular regime, which is the limitation with other current techniques. Knudsen‐regime diffusion is common in many industrial, catalytic processes. Significantly larger spatial variability in mass transport rates across the packed bed was found compared to techniques using only molecular diffusion. It has thus been found that that these heterogeneities arise over length‐scales much larger than ∼100 microns This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-27T10:33:48.259054-05:
      DOI: 10.1002/aic.14929
       
  • Phthalic anhydride production from hemicellulose solutions: Technoeconomic
           analysis and life cycle assessment
    • Authors: Zhaojia Lin; Vladimiros Nikolakis, Marianthi Ierapetritou
      Abstract: This work presents the process synthesis, technoeconomic analysis and life cycle assessment of a novel route for phthalic anhydride (PAN) production from hemicellulose solutions. The production contains six steps including dehydration of xylose to furfural, reductive decarbonylation of furfural to furan, oxidation of furfural to maleic anhydride (MA), Diels‐Alder cycloaddition of furan and MA to exo‐4,10‐dioxa‐tricyclo[5.2.1.0]dec‐8‐ene‐3,5‐dione followed by dehydration to PAN in the presence of mixture of methanesulfonic acid and acetic anhydride (AAN) which is converted to acetyl methanesulfonate and acetic acid (AAD), and dehydration of AAD to AAN. The minimum selling price of PAN is determined to be $810/metric ton about half of oil‐based PAN. The coproduction of high‐value products is essential to improve the economics. Biomass feedstock contributes to the majority of cost. LCA results shows that biomass‐based PAN has advantages over oil‐based PAN to reduce climate change and fossil depletion however requires more water usage. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-25T02:08:41.867446-05:
      DOI: 10.1002/aic.14921
       
  • Jamming of cellulose ether solutions in porous medium
    • Authors: C. Marliere; D. Vlassopoulos, P. Faure, A. Larsen, B. Loppinet, P. Coussot
      Abstract: We investigate the flow of aqueous cellulose ether solutions through a bead packing using MRI (Magnetic Resonance Imaging) and filtration measurements. We observe a rather complex behaviour dominated by jamming (clogging) and unjamming phenomena in time. With the help of several characterization techniques (laser grain sizing, dynamic light scattering, optical microscopy, rheometry) we confirm that the particular methyl(hydroxyethyl) cellulose prepared with a specific protocol, tends to form aggregates in water, even at the lowest achievable concentration. These aggregates are highly polydisperse, ranging from hundred nanometers to hundred microns in size, and are deformable. Their origin appears to be the hydrophobic links among molecules and the related local crystallization. It is suggested that these features play a key role in the observed jamming/unjamming during filtration tests. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-25T02:07:34.49213-05:0
      DOI: 10.1002/aic.14920
       
  • Breakage and Adhesion Maps for the Normal Impact of Loose Agglomerates
           with a Spherical Target
    • Authors: Duy Nguyen; Anders Rasmuson, Kyrre Thalberg, Ingela Niklasson Björn
      Abstract: DEM‐based analysis is conducted to investigate the effects of interface energy between particles on the breakage and adhesion of loose agglomerates upon impact with a spherical target. A mechanistic approach is tested to find a relationship between particle properties and the agglomerate structure after the impact, which resulted in a new dimensionless number, i.e. the ratio of the two interface energies. In combination with Δ ‐ a dimensionless number relating incident kinetic energy to agglomerate strength 1, a good description of the agglomerate impact is obtained. The agglomerate structure after impact is mapped using the two dimensionless numbers and is in good agreement with experimental observations. The constructed regime map can serve as a guide for selecting preliminary process parameters in adhesive particle mixing. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-25T02:06:50.915939-05:
      DOI: 10.1002/aic.14922
       
  • Radial pressure profiles in a cold‐flow Gas‐Solid Vortex
           Reactor
    • Authors: M.N. Pantzali; J.Z. Kovacevic, V.N. Shtern, G.J. Heynderickx, G.B. Marin
      Abstract: A unique normalized radial pressure profile characterizes the bed of a Gas‐Solid Vortex Reactor (GSVR) over a range of particle densities and sizes, solid capacities and gas flow rates: 950‐1240 kg/m3, 1‐2 mm, 2 kg to maximum solids capacity and 0.4‐0.8 Nm3/s (corresponding to gas injection velocities of 55‐110 m/s) respectively. The combined momentum conservation equations of both gas and solid phases predict this pressure profile when accounting for the corresponding measured particle velocities. The pressure profiles for a given type of particles and a given solids loading but for different gas injection velocities merge into a single curve when normalizing the pressures with the pressure value downstream of the bed. The normalized ‐with respect to the overall pressure drop‐ pressure profiles for different gas injection velocities in particle‐free flow merge in a unique profile. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-24T02:26:22.259474-05:
      DOI: 10.1002/aic.14912
       
  • An integrated Framework for Scheduling and Control Using Fast Model
           Predictive Control
    • Authors: Jinjun Zhuge; Marianthi G. Ierapetritou
      Abstract: Integration of scheduling and control involves extensive information exchange and simultaneous decision making in industrial practice 1,2. Modeling the integration of scheduling and dynamic optimization at control level using mathematical programming results in a Mixed Integer Dynamic Optimization (MIDO) which is computationally expensive 3. In this study, we propose a framework for the integration of scheduling and control to reduce the model complexity and computation time. We identify a piece‐wise affine (PWA) model from the first principle model and integrate it with the scheduling level leading to a new integration. At the control level we employ fast Model Predictive Control (fast MPC) to track a dynamic reference. Fast MPC also overcomes the increasing dimensionality of multi‐parametric MPC in our previous study.4 Results of CSTR case studies prove that the proposed approach reduces the computing time by at least two orders of magnitude compared to the integrated solution using mp‐MPC. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-24T02:25:42.950339-05:
      DOI: 10.1002/aic.14914
       
  • Impact of Water Film Thickness on Kinetic Rate of Mixed Hydrate Formation
           During Injection of CO2 Into CH4 Hydrate
    • Authors: Khuram Baig; Bjørn Kvamme, Tatiana Kuznetsova, Jordan Bauman
      Abstract: In this work non‐equilibrium thermodynamics and phase field theory (PFT) has been applied studies of the kinetics of phase transitions associated with CO2 injection into systems containing CH4 hydrate, free CH4 gas, and varying amounts of liquid water. The CH4 hydrate was converted into either pure CO2 or mixed CO2‐CH4 hydrate to investigate the impact of two primary mechanisms governing the relevant phase transitions: solid‐state mass transport through hydrate and heat transfer away from the newly formed CO2 hydrate. Experimentally‐proven dependence of kinetic conversion rate on the amount of available free pore water was investigated and successfully reproduced in our model systems. We found that rate of conversion was directly proportional to the amount of liquid water initially surrounding the hydrate. When all of the liquid has been converted into either CO2 or mixed CO2‐CH4 hydrate, a much slower solid‐state mass transport becomes the dominant mechanism. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-24T02:25:08.74865-05:0
      DOI: 10.1002/aic.14913
       
  • An Energy‐Efficient Cost‐Effective Transient Batch Rectifier
           with Bottom Flashing: Process Dynamics and Control
    • Authors: Amiya K. Jana
      Abstract: Exploring an internal heat source through bottom flashing route, this work introduces a dynamic batch column configuration within the framework of mechanical heat pump system. This batch rectifier with bottom flashing (BRBF) scheme attempts to employ the reboiler liquid as a heat exchanging medium in the overhead condenser, thereby avoiding the use of any external coolant stream and reducing the consumption of hot utility in the reboiler. Aiming to operate the proposed transient process unit at an optimal state of energy use, we formulate an online open‐loop control policy that estimates the multiple control actions simultaneously. Furthermore, in order to achieve constant product purity, a gain‐scheduled closed‐loop control system is synthesized with keeping the stability margin constant. Simulating a multicomponent reactive system, the novel BRBF arrangement is evaluated in the aspects of energy savings and cost under both the open‐loop and closed‐loop control modes. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-24T02:24:41.556754-05:
      DOI: 10.1002/aic.14915
       
  • Systematic design of an extractive distillation for maximum‐boiling
           azeotropes with heavy entrainers
    • Authors: Weifeng Shen; Jie Li, Hassiba Benyounes, Lichun Dong, Shun'an Wei, Xinqiang You, Vincent Gerbaud
      Abstract: Extractive distillation is one of the most attractive approaches for separating azeotropic mixtures. Few contributions have been reported to design an extractive distillation for separating maximum‐boiling azeotropes and no systematic approaches for entrainer screening have been presented. In this paper, we propose a systematic approach to design of two‐column extractive distillation for separating azeotropes with heavy entrainers. We first conduct a thermodynamic feasibility analysis for azeotropes with potential heavy entrainers. Then, five important properties are selected for entrainer evaluation. We employ fuzzy logic and develop membership functions to calculate attribute values of selected properties. An overall indicator for entrainer evaluation is proposed and a ranking list is generated. Finally, we select the top five entrainers from the ranking list and use process optimization techniques to further evaluate selected entrainers and generate an optimal design. The capability of the proposed method is illustrated using the separation of acetone‐chloroform azeotropes with five potential entrainers. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-18T17:59:17.666074-05:
      DOI: 10.1002/aic.14908
       
  • A filtration model for prediction of local flux distribution and
           optimization of submerged hollow fiber membrane module
    • Authors: Xianhui Li; Jianxin Li, Hong Wang, Xiaoxu Huang, Benqiao He, Yonghong Yao, Jie Wang, Hongwei Zhang, Huu Hao Ngo, Wenshan Guo
      Abstract: A filtration mathematical model was developed on the basis of complete mass balance and momentum balance for the local flux distribution prediction and optimization of submerged hollow fiber membrane module. In this model, the effect of radial permeate flow on internal flow resistance was considered through a slip parameter obtained from the local flux experiments. The effects of fiber length, inside diameter and average operating flux on local flux distribution were investigated using this model. The predicted results were in good agreement with the experimental data obtained from literature. It was also found that the asymmetry distribution of local flux could be intensified with the increase of average operating flux and fiber length, but slowed down with the increase of fiber inside diameter. Furthermore, the simulation coupled with energy consumption analysis could efficiently predict and illustrate the relationship between fiber geometry and water production efficiency. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-18T17:55:21.740497-05:
      DOI: 10.1002/aic.14906
       
  • Nonlinear PI Controllers with Output Transformations
    • Authors: Jietae Lee; Thomas F. Edgar
      Abstract: Well‐designed nonlinear proportional‐integral (PI) controllers are successful for nonlinear dynamical processes like linear PI controllers are for linear processes. Two nonlinear blocks representing proportional and integral terms can be designed so that the linearized controllers perform the same as linear PI controllers for linearized processes at the given operating points. For some nonlinear processes, nonlinear blocks for nonlinear PI controllers can be singular at some operating points, and control performances can be poor for set points near those points. To mitigate such disadvantages, new nonlinear PI controllers that introduce output transformations are proposed. Several examples are given, showing the performance of the proposed nonlinear PI controllers. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-17T17:54:55.625143-05:
      DOI: 10.1002/aic.14907
       
  • Issue information
    • Abstract: Cover illustration. Algorithm for diffusive gas transport and surface reactions in porous solids based on random collisions of molecules (DSMC). Image courtesy of Georg Pesch and Lutz Mädler, University of Bremen. 10.1002/aic.14856
      PubDate: 2015-06-16T10:35:26.810513-05:
      DOI: 10.1002/aic.14586
       
  • Filtration model for polydisperse aerosols in gas‐solid flow using
           granule‐resolved direct numerical simulation
    • Authors: R. Kolakaluri; E. Murphy, R. C. Brown, R. O. Fox, S. Subramaniam
      Abstract: An analytical framework for calculating the filtration efficiency of polydisperse aerosols in a granular bed is developed for cases where inertial impaction and interception are the principal filtration mechanisms. This framework is used to develop a model for the polydisperse single‐collector efficiency from monodisperse single‐collector efficiency correlations. Conceptually, the polydisperse model is developed by transforming the probability density of particle radius into a probability density of particle Stokes number that is then used to weight the monodisperse single‐collector efficiency at a given Stokes number. An extension of this polydisperse filtration concept results in an analytical solution for the axial variation of polydisperse particle flux in a random three‐dimensional (3D) granule configuration. In order to verify the analytical results for polydisperse particle filtration, a granule–resolved Direct Numerical Simulation (DNS) approach is coupled with Lagrangian Particle Tracking (LPT) to simulate filtration of polydisperse aerosols in a granular bed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-15T02:25:43.8892-05:00
      DOI: 10.1002/aic.14901
       
  • Scanning curves in wedge pore with the wide end closed: Effects of
           temperature
    • Authors: Nikom Klomkliang; D.D. Do, D. Nicholson
      Abstract: The desorption scanning curves within the hysteresis loop of argon adsorbed in a wedge shaped pore with its wide end closed, have been studied in the temperature range between 60 and 87K, using grand canonical Monte Carlo simulation. The distinct features are: (1) adsorbate packing follows a sequence of commensurate regions (zones) and incommensurateregions (junctions); (2) the mechanism forevaporationswitches from cavitation‐like pore blocking to cavitation when the temperature is increased; as typically observed for ink‐bottle pores. When cavitation is the operating mechanism, the descending scanning curve spans across the loop in two stages: a gradual decrease in density in azonefollowed by a sharp evaporation froma junction, and then terminates at the lowest point on the vertical cavitation boundary. The adsorption scanning curve proceeds across the loop in two stages complementary to the desorption scanning‐curve:a gradual change in density ata junction followed by a sharp change througha zone. On the other hand, when cavitation‐like pore blocking is operating, the descending curve leaves the adsorption boundary, spans across the hysteresis loop and returns to a different point on the same boundary, rather than to the desorption boundary or to the lower closure point. This feature does not seem to have been recognized in earlier literature, and should be considered in the classification of scanning curves. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-12T11:12:37.864639-05:
      DOI: 10.1002/aic.14905
       
  • Degradation mechanism analysis of Ba0.5Sr0.5Co0.8Fe0.2O3‐δ
           membranes at intermediate‐low temperatures
    • Authors: Yan Liu; Xuefeng Zhu, Weishen Yang
      Abstract: The degradation of the permeation flux of Ba0.5Sr0.5Co0.8Fe0.2O3‐δ membranes has typically been attributed to the phase transformation of the material at intermediate temperatures. In this study, the effect of the interfacial oxygen exchange steps was considered to give an overall view of the degradation mechanism. The changes in the interfacial exchange resistances, bulk resistance, and morphologies of the membranes were investigated via physical characterizations and a permeation model. The interfacial oxygen exchange resistances increased more quickly with time than bulk resistance. Meanwhile, BaSO4 particles were detected on both surfaces of the membranes, and their contents reached maximum at 650°C. However, after the membrane surfaces were coated by Sm0.5Sr0.5CoO3‐δ porous layers, the interfacial oxygen exchange resistances kept constant and the degradation rates were slowed down. The degradation was predominated by the increase of interfacial oxygen exchange resistances induced by the enrichment of BaSO4 particles on membrane surfaces. © 2015 American Institute of Chemical Engineers AIChE J, 2015
      PubDate: 2015-06-11T13:26:29.951524-05:
      DOI: 10.1002/aic.14900
       
  • A new bubbling extraction tower: Towards liquid‐liquid solvent
           extraction at large aqueous‐to‐oil phase ratios
    • Authors: Jie Liu; Kun Huang, Huaizhi Wu, Huizhou Liu
      Abstract: Enrichment and recovery of valuable components in industrial waste waters by traditional liquid‐liquid solvent extraction is not economic due to extremely low concentrations of those targets. Large‐phase‐ratio extraction exhibits potential advantages for recovery of small quantities of target components from large volume of aqueous solutions. In present work, a novel bubbling extraction tower is proposed towards performing solvent extraction at large aqueous‐to‐oil phase ratios. Organic extractants were covered onto surface of gas bubbles to form a layer of organic liquid membrane and the dispersed organic phase in tower could be small enough. The target components are extracted from aqueous feed solution onto the surface of the bubbles, and the enrichment ratios could be extremely high. We develop a feasible methodology to calculate tower height and operation phase ratios of the bubbling extraction tower, which is essential for future industrial scale‐up. Experimental results in pilot test are highly consistent with calculations. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-11T00:53:25.001099-05:
      DOI: 10.1002/aic.14904
       
  • Dynamic Modeling of a Multiple Hearth Furnace for Kaolin Calcination
    • Authors: Aleksi Eskelinen; Alexey Zakharov, Jonathan Hearle, Sirkka‐Liisa Jämsä‐Jounela
      Abstract: A dynamic model of a multiple hearth kaolin calciner has been developed and is presented in this paper. This model describes the physical‐chemical phenomena taking place in the six furnace parts: the solid phase, gas phase, walls, cooling air, rabble arms and the central shaft. The solid phase movement, in particular, is described by a novel mixing model. The mixing model divides the solid bed in a hearth into volumes and the distribution of their contents, after one full central shaft rotation, is identified by the pilot experiments. First, the model is validated by the industrial data, and then the dynamics of the multiple hearth furnace (MHF) is studied by introducing step changes to the three manipulated variables: the feed rate, and the gas and air flows supplied. The responses of the gas phase temperature and solid bed component profiles are analysed and the results are discussed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-09T00:16:52.578066-05:
      DOI: 10.1002/aic.14903
       
  • Mechanistic insights into the structure dependent selectivity of catalytic
           furfural conversion on platinum catalysts
    • Authors: Qiu‐Xia Cai; Jian‐Guo Wang, Yang‐gang Wang, Donghai Mei
      Abstract: The effects of surface structures on the selectivity of catalytic furfural conversion over platinum (Pt) catalysts in the presence of hydrogen have been studied using first principles density functional theory (DFT) calculations and microkinetic modeling. Three Pt model surface structures, i.e., flat Pt(111), stepped Pt(211) and Pt55 cluster are chosen to represent the terrace, step, and corner sites of Pt nanoparticle. DFT results show that the dominant reaction route (hydrogenation or decarbonylation) in furfural conversion depends strongly on the structures (or reactive sites). Using the size‐dependent site distribution rule, our microkinetic modeling results indicate the decarbonylation route prevails over smaller Pt particles less than 1.4 nm while the hydrogenation is the dominant reaction route over larger Pt catalyst particles at T = 473 K and PH2 = 93 kPa. This is in good agreement with the reported experimental observations. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-06T02:47:37.214882-05:
      DOI: 10.1002/aic.14902
       
  • Bubble formation and dynamics in a quiescent high‐density liquid
    • Authors: I. Chakraborty; Gautam Biswas, P. Satyamurthy, P.S. Ghoshdastidar
      Abstract: Gas bubble formation from a submerged orifice under constant‐flow conditions in a quiescent high‐density liquid metal, lead–bismuth eutectic (LBE), at high Reynolds numbers was investigated numerically. The numerical simulation was carried out using a coupled level‐set and volume‐of‐fluid (CLSVOF) method governed by axisymmetric Navier–Stokes equations. The ratio of liquid density to gas density for the system of interest was about 15261. The bubble formation regimes varied from quasi‐static to inertia‐dominated and the different bubbling regimes such as period‐1 and period‐2 with pairing and coalescence were described. The volume of the detached bubble was evaluated for various Weber numbers, We, at a given Bond number, Bo, with Reynolds number Re≫1. It was found that at high values of the Weber number, the computed detached bubble volumes approached a 3/5 power law. The different bubbling regimes were identified quantitatively from the time evolution of the growing bubble volume at the orifice. It was shown that the growing volume of two consecutive bubbles in the period‐2 bubbling regime was not the same whereas it was the same for the period‐1 bubbling regime. The influence of grid resolution on the transition from period‐1 to period‐2 with pairing and coalescence bubbling regimes was investigated. It was observed that the transition is extremely sensitive to the grid size. The transition of period‐1 and period‐2 with pairing and coalescence is shown on a Weber–Bond numbers map. The critical value of Weber number signalling the transition from period‐1 to period‐2 with pairing and coalescence decreases with Bond number as We ∼ Bo−1, which is shown to be consistent with the scaling arguments. Furthermore, comparisons of the dynamics of bubble formation and bubble coalescence in LBE and water systems are discussed. It was found that in a high Reynolds number bubble formation regime, a difference exists in the transition from period‐1 to period‐2 with pairing and coalescence between the bubbles formed in water and the bubbles formed in LBE. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-03T02:53:16.819545-05:
      DOI: 10.1002/aic.14896
       
  • Shear dispersion in combined pressure‐driven and
           electro‐osmotic flows in a capillary tube with a porous wall
    • Authors: Morteza Dejam; Hassan Hassanzadeh, Zhangxin Chen
      Abstract: An analytical expression is derived for the shear dispersion during transport of a neutral non‐reacting solute within a coupled system comprised of a capillary tube and a porous medium under the combined effects of pressure‐driven and electro‐osmotic flows. We use the Reynolds decomposition technique to obtain a dispersion coefficient by considering a sufficiently low wall or zeta potential that accounts for the combined flows. The coupled dispersion coefficient depends on the Debye‐Hückel parameter, Poiseuille contribution fraction, and Péclet number. The developed model also provides a shear dispersion coefficient for an impervious capillary tube (non‐coupled system). The ratio of the coupled (porous wall) and non‐coupled (impervious) dispersion coefficients reveals that it is essential to include the transport of chemical species from the tube to the porous medium in several important physical situations. These findings have implications for design of chemical species transport in porous microfluidic networks and separation of emulsions in microchannel‐membrane systems. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-03T02:52:26.847773-05:
      DOI: 10.1002/aic.14897
       
  • Dissipativity‐based distributed model predictive control with low
           rate communication
    • Authors: Chaoxu Zheng; Michael James Tippett, Jie Bao, Jinfeng Liu
      Abstract: Distributed or networked model predictive control can provide a computationally efficient approach that achieves high levels of performance for plantwide control, where the interactions between processes can be determined from the information exchanged among controllers. Distributed controllers may exchange information at a lower rate to reduce the communication burden. In this work, a dissipativity‐based analysis is developed to study the effects of low communication rates on plantwide control performance and stability. A distributed dissipativity‐based model predictive control design approach is also developed to guarantee the plantwide stability and minimum plantwide performance with low communication rates. These results are illustrated by a case study of a reactor‐distillation column network. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-03T02:51:55.749042-05:
      DOI: 10.1002/aic.14899
       
  • Nucleation curves of model natural gas hydrates on a quasi‐free
           water droplet
    • Authors: Nobuo Maeda
      Abstract: We studied heterogeneous nucleation probability distributions of gas hydrates on a water droplet that was supported by inert and immiscible perfluorocarbon oil, perfluorodecalin. The guest gas used was a mixture of 90 mol% methane and 10 mol% propane. The probability distribution was measured using a High Pressure Automated Lag Time Apparatus (HP‐ALTA) under the guest gas pressure range of 6.7 to 12.5 MPa and the cooling rate range of 0.002K/sec to 0.02K/sec. Nucleation curves were derived for unit area of water surface. We also derived the nucleation rate per unit area of water surface that was contained in a glass sample cell, which differed significantly from that on a quasi‐free water droplet. It is concluded that the nucleation curves in the presence of a solid wall should be normalized to the unit length of the three‐phase line at which water, guest gas and the solid wall meet. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-03T02:51:30.077497-05:
      DOI: 10.1002/aic.14898
       
  • On the leakage flow around gas bubbles in slug flow in a microchannel
    • Authors: Chaoqun Yao; Zhengya Dong, Yuchao Zhang, Yuan Mi, Yuchao Zhao, Guangwen Chen
      Abstract: The leakage flow is that liquid does not push gas bubbles and leaks through the channel corners. This leakage flow was confirmed by tracking particles moving in the liquid film with a double light path method and was quantified by tracking the gas‐liquid interface movement. The results show that leakage flow varies during bubble formation process. The average net leakage flow Qnet‐leak in a bubble formation cycle at T‐junction can be as large as 62.4% of the feeding liquid flow rate, depending on the liquid properties. Qnet‐leak for regular flow at main channel is much smaller, ranging from about 0 to 30% of the feeding liquid flow rate. The difference between the two leakage flows would lead to an increase in liquid slug length after generation. Finally, the effects of parameters such as phase flow rates, surface tension and viscosity were investigated. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-03T02:47:14.81168-05:0
      DOI: 10.1002/aic.14895
       
  • Azimuthally oscillating membrane emulsification for controlled droplet
           production
    • Authors: Pedro S. Silva; Mike Stillwell, Bruce Williams, Marijana Dragosavac, Goran T. Vladisavljević, Hemaka Bandulasena, Richard G. Holdich
      Abstract: A novel membrane emulsification system is reported consisting of a tubular metal membrane, periodically azimuthally (tangentially) oscillated with frequencies up to 50 Hz and 7 mm displacement in a gently cross flowing continuous phase. A CFD analysis showed consistent axial shear at the membrane surface, which became negligible at distances from the membrane surface greater than 0.5 mm. For comparison, CFD analysis of a fully rotating membrane emulsification system showed local vortices in the continuous phase leading to a variable shear along the axis of the membrane. Using an azimuthally oscillating membrane, oil‐in‐water emulsions were experimentally produced with a median diameter of 20‐120 µm, and a coefficient of variation of droplet size of 8%. The drop size was correlated with shear stress at the membrane surface using a force balance. In a single pass of continuous phase it was possible to achieve high dispersed phase concentrations of 40% v/v. This article is protected by copyright. All rights reserved.
      PubDate: 2015-06-03T02:42:23.172721-05:
      DOI: 10.1002/aic.14894
       
  • Kinetic Study of Reactions of Aniline and Benzoyl Chloride in a
           Microstructured Chemical System
    • Authors: Peijian Wang; Kai Wang, Jisong Zhang, Guangsheng Luo
      Abstract: The reaction between aniline and benzoyl chloride is well known for producing high performance polymers and chemicals. But the fast main reaction and reversible consecutive side reaction make process rather complicated and no thorough kinetics study has ever been reported before. A microstructured chemical system, consisting of a micromixer, pre‐heat exchange coiled capillaries, a delay loop and a microhydrolyzer, was designed to carry out this reaction in this study using NMP as the solvent. A kinetic model was established, and the values of kinetic constants, pre‐exponential factors and activation energies of each reaction as well as their confidence intervals were acquired. With this model each substance concentration versus residence time were obtained to help understand reaction process and further optimize operating conditions. Compared to earlier reports on this reaction, this microstructured chemical system provides more accurate parameters and can develop a reliable platform for kinetic study of similar chemical reactions. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-29T11:32:28.801191-05:
      DOI: 10.1002/aic.14891
       
  • Pressure Cycling for Purging of Dead Spaces in High‐Purity Gas
           Delivery Systems
    • Authors: Jivaan Kishore; Farhang Shadman, Roy Dittler, Carl Geisert
      Abstract: The purging of stagnant or dead volumes in gas distribution systems is an important method for removing impurities and maintaining cleanliness. A combination of experimental investigation and computational process modeling is used to study the dynamics of impurity removal under variety of purge conditions. The controlled cycling of pressure during purge is found to enhance the cleaning process significantly, particularly in dead spaces. The process simulator was used to develop and analyze a pressure‐cyclic purge (PCP) method and understand the conditions that would make PCP advantageous over steady‐state purge (SSP). In particular, the effect of geometric factors, impurity surface interactions, flow rate, and cycle characteristics on PCP and its comparison with SSP was studied. The advantage of the PCP method, in terms of both purge time and gas usage, becomes more pronounced in systems with larger number and size of dead spaces and impurities that interact strongly with the surfaces. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-29T11:28:52.597524-05:
      DOI: 10.1002/aic.14890
       
  • Droplet velocity, size, and local holdup measurements in an extraction
           column by tri‐sensor optical probe
    • Authors: Tingliang Xie; Yang Gao, Wei Liu
      Abstract: The tri‐sensor optical probe was applied to study the hydrodynamic characteristic in a pulsed sieve plate extraction column. Two immiscible liquids consisting of the dispersed phase (kerosene) and continuous phase (water) were introduced in countercurrent operation. Local parameters such as droplet velocity, drop size and holdup of the dispersed phase were obtained. It was found that the tri‐sensor optical probe could be used as an efficient and convenient technique for measuring local hydrodynamic parameters inside the pulsed sieve plate extraction column. Furthermore, the results indicated that pulsation intensity imposed more influence on these hydrodynamic parameters than two‐phase superficial flow rates in the investigated ranges. Experimental results were found to be in good agreement with the empirical correlations reported in literature. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-27T18:22:36.137888-05:
      DOI: 10.1002/aic.14889
       
  • Concurrent Monitoring of Operating Condition Deviations and Process
           Dynamics Anomalies with Slow Feature Analysis
    • Authors: Chao Shang; Fan Yang, Xinqing Gao, Xiaolin Huang, Johan A.K. Suykens, Dexian Huang
      Abstract: Latent variable (LV) models have been widely used in multivariate statistical process monitoring. However, whatever deviation from nominal operating condition is detected, an alarm is triggered based on classical monitoring methods. Therefore they fail to distinguish real faults incurring dynamics anomalies from normal deviations in operating conditions. In this article, a new process monitoring strategy based on slow feature analysis (SFA) is proposed for the concurrent monitoring of operating point deviations and process dynamics anomalies. Slow features as LVs are developed to describe slowly varying dynamics, yielding improved physical interpretation. In addition to classical statistics for monitoring deviation from design conditions, two novel indices are proposed to detect anomalies in process dynamics through the slowness of LVs. The proposed approach can distinguish whether the changes in operating conditions are normal or real faults occur. Two case studies show the validity of the SFA‐based process monitoring approach. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-23T10:06:03.420087-05:
      DOI: 10.1002/aic.14888
       
  • Experimental and Numerical Investigation of the Dynamics of Loop Seals in
           a Large‐Scale DFB System under Hot Conditions
    • Authors: Anton Larsson; Henrik Ström, Srdjan Sasic, Henrik Thunman
      Abstract: We investigate the dynamics of the loop seals in a large‐scale dual fluidized bed (DFB) system as a function of variations in the flux of the bed material through the seal and changes in the bed material density. These investigations are performed numerically with a computational fluid dynamics (CFD) model and experimentally for the loop seals of the Chalmers 2‐4 MWth DFB gasifier. Both experiments and simulations show that more of the aeration gas leaves the loop seal in the direction of the solids when a low‐density bed material (silica) is used rather than a high‐density one (bauxite). The simulations also reveal homogeneous fluidization in a vertical connection to the loop seal, whereas an inclined connection yields heterogeneous fluidization. The minor discrepancies between the experiments and simulations with silica are attributed to particle agglomeration, and it is proposed that CFD models applied to loop seals should account for this phenomenon. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-23T09:41:53.298603-05:
      DOI: 10.1002/aic.14887
       
  • Hydrodynamical particle containment in a rotor‐stator spinning disc
           device
    • Authors: K.M.P. van Eeten; D.H.J. Hülsman, J. van der Schaaf, J.C. Schouten
      Abstract: A novel type of rotor‐stator spinning disc device is proposed which allows for the entrapment of solid particles solely by hydrodynamic means. In this new configuration, the solid rotating disc is replaced with two conjoined rotors with a variable gap spacing. Liquid is fed through the top stator and can flow out again through the rotor‐rotor interior and the hollow rotation axis. Moreover, the volume between the two rotors is optionally filled with a highly porous reticulated carbon foam. It was found that particle containment was strongly improved by the presence of this reticulated foam as it hinders the buildup of centripetal boundary layer flow near the discs in the interior of the rotor‐rotor assembly. These centripetal boundary layers drag along particles resulting in a loss of containment. Experiments utilising glass beads showed that particles with a diameter down to 17.8 μm can be completely entrapped when a carbon foam is placed between the two conjoined discs at rotor speeds up to the maximum investigated value of 178 rad s−1. Additionally, the rotor‐rotor gap did not have an effect on the particle entrapment level when the reticulated carbon foam was omitted and can be ascribed to the build‐up of boundary layers, which is independent of rotor‐rotor distance. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-23T09:33:14.684942-05:
      DOI: 10.1002/aic.14886
       
  • More effective membrane chromatography
    • Authors: Yong‐Ming Wei; Yanxiang Li, Chuanfang Yang, E.L. Cussler
      Abstract: Adsorption in membranes with polydispersed pores gives a dispersed breakthrough curve even when mass transfer is so fast that it reaches saturation. Such a breakthrough is due to unequal flows in unequally sized pores. A theory of polydispersed pores can predict the breakthrough curves for the removal of lead ions from model solutions if the pore size distribution is known. Such predictions are in better agreement for lead adsorption than predictions based on mass transfer. The results suggest ways in which more effective membrane chromatography can be achieved. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-20T21:11:53.944611-05:
      DOI: 10.1002/aic.14884
       
  • Multiphase transport modeling for vacuum drying of pharmaceutical products
    • Authors: Aditya G. Dodda; Kostas Saranteas, Michael A. Henson
      Abstract: Vacuum drying of active pharmaceutical ingredients (API) is an energy‐intensive process that is often a manufacturing bottleneck. In this paper, we develop a multiphase transport model to predict drying performance under the assumption that boiling is the dominant mechanism. Laboratory scale drying experiments were performed over a range of temperatures and pressures using acetone as the solvent and glass beads of three different particle sizes to mimic APIs. We found that a two phase transport model with the vapor and solid considered as one phase and the liquid treated as the second phase was capable of qualitatively reproducing the drying dynamics. Adjustable model parameters estimated from experimental data collected over a range of operating conditions exhibited trends that provided further insight into drying behavior. We concluded that boiling is the dominant mechanism in vacuum drying and that our transport model captured the key physics of the process. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-19T18:26:59.05646-05:0
      DOI: 10.1002/aic.14879
       
  • Multi‐scale model for solid oxide fuel cell with electrode
           containing mixed conducting material
    • Authors: Daifen Chen; Hanzhi Wang, Shundong Zhang, Moses O. Tade, Huili Chen, Zongping Shao
      Abstract: Solid oxide fuel cells (SOFCs) with electrodes that contain mixed conducting materials usually show very different relationships among microstructure parameters, effective electrode characteristics and detailed working processes from conventional ones. A new multi‐scale model for SOFCs using mixed conducting materials, such as LSCF or BSCF, was developed. It consisted of a generalized percolation micro model to obtain the electrode properties from microstructure parameters and a multiphysics single cell model to relate these properties to performance details. Various constraint relationships between the activation overpotential expressions and electric boundaries for SOFC models were collected by analyzing the local electrochemical equilibrium. Finally, taking a typical LSCF‐SDC/SDC/Ni‐SDC intermediate temperature SOFC as an example, the application of the multi‐scale model was illustrated. The accuracy of the models was verified by fitting 25 experimental I‐V curves reported in literature with a few adjustable parameters; additionally, and several conclusions were drawn from the analysis of simulation results. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-19T18:26:36.019409-05:
      DOI: 10.1002/aic.14881
       
  • Micro‐Structured Bi1.5 Y0.3Sm0.2O3‐δ Catalysts for
           Oxidative Coupling of Methane
    • Authors: Nur Hidayati Othman; Zhentao Wu, K. Li
      Abstract: In this study, Bi1.5 Y0.3Sm0.2O3‐δ (BYS), a ceramic material showing great activity and selectivity to oxidative coupling of methane (OCM), has been fabricated into catalyst rings (i.e. capillary tubes) with a plurality of self‐organised radial microchannels. The unique micro‐channels inside such BYS catalyst rings allow easier access of reactants, as well as increased the surface area, which potentially contributes to higher reaction efficiencies due to improved mass transfer. The micro‐structured BYS catalyst rings were investigated systematically via two types of reactors; (1) randomly packed fixed bed reactor and (2) monolithic‐like structured reactor. These two reactor designs have different flow patterns of reactants, i.e. non‐ideal and ideal flows, which can significantly affect the final OCM performance. A remarkable improvement in C2+ yield (YC2+>20%) was obtained in the monolith‐like structured reactor, in contrast to randomly packed powder and micro‐structured rings (YC2+
      PubDate: 2015-05-19T18:26:16.59569-05:0
      DOI: 10.1002/aic.14883
       
  • Modeling heterogeneous bacterial populations exposed to antibiotics: The
           logistic‐dynamics case
    • Authors: Pratik R. Bhagunde; Vincent H. Tam, Michael Nikolaou
      Abstract: In typical in vitro tests for clinical use or development of antibiotics, samples from a bacterial population are exposed to an antibiotic at various concentrations. The resulting data can then be used to build a mathematical model suitable for dosing regimen design or for further development. For bacterial populations that include resistant subpopulations – an issue that has reached alarming proportions – building such a model is challenging. In prior work we developed a related modeling framework for such heterogeneous bacterial populations following linear dynamics when exposed to an antibiotic. We extend this framework to the case of logistic dynamics, common among strongly resistant bacterial strains. Explicit formulas are developed that can be easily used in parameter estimation and subsequent dosing regimen design under realistic pharmacokinetic conditions. A case study using experimental data from the effect of an antibiotic on a gram‐negative bacterial population exemplifies the usefulness of the proposed approach. This article is protected by copyright. All rights reserved.
      PubDate: 2015-05-19T18:25:59.450744-05:
      DOI: 10.1002/aic.14882
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • A model‐based precipitation study of copper‐based catalysts
    • Authors: Martin A. J. Hartig; Wolfgang Peukert, Nikolas Jacobsen, Alexander Leuthold
      Pages: 2104 - 2116
      Abstract: Numerical methods of particle technology are used to model the formation of catalyst precursors with the purpose to control disperse properties. A multicomponent and multiphase 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 20–100% by the adjustment of the pH of the copper nitrate reactant solution. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2104–2116, 2015
      PubDate: 2015-04-13T14:31:50.357074-05:
      DOI: 10.1002/aic.14810
       
  • Rigorous design of distillation columns using surrogate models based on
           Kriging interpolation
    • Authors: Natalia Quirante; Juan Javaloyes, José A. Caballero
      Pages: 2169 - 2187
      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 article, 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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2169–2187, 2015
      PubDate: 2015-04-06T11:51:20.347956-05:
      DOI: 10.1002/aic.14798
       
  • On‐line control of crystal properties in nonisothermal antisolvent
           crystallization
    • Authors: Navid Ghadipasha; Jose A. Romagnoli, Stefania Tronci, Roberto Baratti
      Pages: 2188 - 2201
      Abstract: The issues regarding the design and implementation of on‐line optimal control strategies of crystal properties in nonisothermal antisolvent crystallization processes to control particles’ mean size and standard deviation are dealt. The one‐dimensional Fokker–Planck equation 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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2188–2201, 2015
      PubDate: 2015-04-13T14:32:12.4009-05:00
      DOI: 10.1002/aic.14815
       
  • A compact photomicroreactor design for kinetic studies of gas‐liquid
           photocatalytic transformations
    • Authors: Yuanhai Su; Volker Hessel, Timothy Noël
      Pages: 2215 - 2227
      Abstract: A compact photomicroreactor assembly consisting of a capillary microreactor and small‐scale light emitting diodes 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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2215–2227, 2015
      PubDate: 2015-04-09T09:05:37.996255-05:
      DOI: 10.1002/aic.14813
       
  • Model‐based analysis of a gas/vapor–liquid microchannel
           membrane contactor
    • Authors: Anna Lautenschleger; Eugeny Y. Kenig, Andreas Voigt, Kai Sundmacher
      Pages: 2240 - 2256
      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, 61: 2240–2256, 2015
      PubDate: 2015-03-30T11:02:58.267045-05:
      DOI: 10.1002/aic.14784
       
  • Solvent evaluation for desulfurization and denitrification of gas oil
           using performance and industrial usability indices
    • Authors: Sunil Kumar; Vimal Chandra Srivastava, Shrikant Madhusudan Nanoti, Abhishek Kumar
      Pages: 2257 - 2267
      Abstract: 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 indices. Twenty eight solvents comprising of six most widely used industrially proven conventional solvents and 22 imidazolium‐based ionic liquids solvents were selected to illustrate the strategy. The solvents were ranked for removal of sulfur compounds namely benzothiophene, dibenzothiophene and their alkylated derivatives, and nitrogenous compounds namely quinoline, indole and carbazole 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 indices to rank the solvents. Industrial usability index (SIUI) of solvents which includes PI and process complexity factor for solvent recovery section seems more practical and realistic criteria for solvent assessment. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2257–2267, 2015
      PubDate: 2015-04-08T12:26:05.727921-05:
      DOI: 10.1002/aic.14809
       
  • Enhanced gravimetric CO2 capacity and viscosity for ionic liquids with
           cyanopyrrolide anion
    • Authors: Paul Brown; Burcu E. Gurkan, T. Alan Hatton
      Pages: 2280 - 2285
      Abstract: Ionic Liquids (ILs) are considered as alternative solvents for the separation of CO2 from flue gas due mainly to their CO2 affinity and thermal stability. The cation architecture in a matrix of ammonium and mostly phosphonium‐based ILs with 2‐cyanopyrrolide as the anion to evaluate its impact on gravimetric CO2 absorption capacity, viscosity, and thermal stability and the three fundamental properties vital for application realization are systematically investigated. Among the investigated ILs, [P2,2,2,8][2‐CNpyr] demonstrated the lowest viscosity, 95 cP at 40°C, and highest CO2 uptake, 114 mg CO2 per g IL at 40°C. 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 × 10−6 g h−1 (0.0067 mass % h−1) at 80°C. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2280–2285, 2015
      PubDate: 2015-04-13T14:52:49.15386-05:0
      DOI: 10.1002/aic.14819
       
  • 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
      Pages: 2307 - 2318
      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, 61: 2307–2318, 2015
      PubDate: 2015-03-30T10:58:40.862975-05:
      DOI: 10.1002/aic.14788
       
  • 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
      Pages: 2319 - 2328
      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, 61: 2319–2328, 2015
      PubDate: 2015-03-31T11:13:57.672037-05:
      DOI: 10.1002/aic.14796
       
  • Multiscale modeling of oil uptake in fried products
    • Authors: Jean‐Michaël Vauvre; Anna Patsioura, Vitrac Olivier, Régis Kesteloot
      Pages: 2329 - 2353
      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 three‐dimensional 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. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2329–2353, 2015
      PubDate: 2015-04-08T12:43:08.991854-05:
      DOI: 10.1002/aic.14801
       
  • 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
      Pages: 2354 - 2367
      Abstract: A laboratory‐scale packed column was positioned on a six 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. Nontilting oscillations led to frequency‐independent maldistribution while tilting motions induced swirl/zigzag secondary circulation and prompted nonuniform maldistribution oscillations that deteriorated with decreasing frequencies. Regardless of excited degree of freedom, a qualitative loss of plug‐flow character was observed compared with static vertical beds which worsened as frequencies decreased. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2354–2367, 2015
      PubDate: 2015-04-13T14:30:42.585278-05:
      DOI: 10.1002/aic.14816
       
 
 
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