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  • Enhanced gas migration through permeable bubble networks within consolidated soft sediments
    AlChE J. (IF 3.326) Pub Date : 2018-07-19
    Michael Johnson; Jeffrey Peakall; Michael Fairweather; Simon Biggs; Xiaodong Jia; David Harbottle; Timothy N. Hunter

    Many consolidated sediments experience in situ gas generation from methanogenesis, corrosion or radiolysis reactions and can retain bubbles for long periods. Particular interest is motivated by the retention and acute release of flammable hydrogen from nuclear legacy waste sludge. X‐ray computed tomography was employed to observe 0.07‐10 mm bubble populations within 30‐1112 Pa yield strength Mg(OH)2 sediments. High rates of partial coalescence were observed amongst sub‐millimetre microvoids, forming extensive bubble networks which spanned the 32 mm field of view. Lattice Boltzmann and Monte Carlo modelling demonstrated these networks to be highly pervious to gas, with effective diffusivities for hydrogen of 3.7‐12.5 × 10−5m2s−1. Continuous vessel‐spanning bubble networks, dynamic conductivity between ganglia of coalesced bubbles, Haines jumps and composite diffusion through the gas and aqueous phase can account for enhanced gas migration over length‐scales of several metres, thus enabling chronic gas release from low‐intermediate strength sediments (10 Pa ≲ τ ≲ 1 kPa) too strong for buoyant bubble ebullition and too weak for vertical channel formation.

    更新日期:2018-07-20
  • 3D numerical simulation of upflow bubbling fluidized bed in opaque tube under high flux solar heating
    AlChE J. (IF 3.326) Pub Date : 2018-07-19
    Hadrien Benoit; Renaud Ansart; Hervé Neau; Pablo Garcia Triñanes; Gilles Flamant; Olivier Simonin

    Solid particles can be used as a heat transfer medium in concentrated solar power plants to operate at higher temperature and achieve higher heat conversion efficiency than using the current solar Heat Transfer Fluids (HTF) that only work below 600 °C. Among various particle circulation concepts, the Dense Particle Suspension (DPS) flow in tubes, also called Upflow Bubbling Fluidized Bed (UBFB), was studied in the frame of the CSP2 FP7 European project. The DPS capacity to extract heat from a tube absorber exposed to concentrated solar radiation was demonstrated and the first values of the tube wall‐to‐DPS heat transfer coefficient were measured. A stable outlet temperature of 750 °C was reached with a metallic tube, and a particle reflux in the near tube wall region was evidenced. In this paper, the UBFB behavior is studied using the multiphase flow code NEPTUNE CFD.

    更新日期:2018-07-20
  • Development of a kinetic model for the moderate temperature chemical vapor deposition of SiO2 films from TEOS and oxygen
    AlChE J. (IF 3.326) Pub Date : 2018-07-18
    Simon Ponton; Hugues Vergnes; Diane Samelor; Daniel Sadowski; Constantin Vahlas; Brigitte Caussat

    An apparent kinetic model for the CVD of SiO2 from TEOS and O2 was developed in a poorly investigated range of operating conditions, i.e. at atmospheric pressure and between 350 and 500°C, based on literature survey and experimental results obtained in a hot wall tubular reactor. The kinetic model was implemented into the CFD code Fluent and validated both in shape and value by comparison with experimental deposition rate profiles. It reveals that for the conditions tested, a possible mechanism of SiO2 deposition involves two intermediate species formed from TEOS homogeneous decomposition, the first one being active from 300°C and the second one contributing to deposition for temperatures higher than 370°C.

    更新日期:2018-07-19
  • Polyketide synthases as a platform for chemical product design
    AlChE J. (IF 3.326) Pub Date : 16 July 20
    Amin Zargar; Jesus F. Barajas; Ravi Lal; Jay D. Keasling

    To reduce the effects of greenhouse gas emissions on climate change, scientific efforts have sought to develop biofuels and bio‐based commodity chemicals as petrochemical replacements primarily for their environmental benefits. As the biological design space is far greater than chemical synthesis, there has been a drive to leverage this ability to create and replace fine and specialty chemicals. While polyketide synthases have traditionally been studied for their biosynthesis of pharmaceutical chemicals, the unique advantages of engineering polyketide synthases for the production of biofuels, commodity chemicals, and both pharmaceutical and nonpharmaceutical fine and specialty chemicals are discussed. With our increased understanding of polyketide biosynthetic logic, new computational tools for prospective polyketide synthesis pathways for the creation of existing and novel biochemicals are also outlined. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-18
  • Simulation of the granular flow of cylindrical particles in the rotating drum
    AlChE J. (IF 3.326) Pub Date : 2018-07-13
    Shiliang Yang; Yuhao Sun; Jia Wei Chew

    This study aims at unveiling the effect of particle shape on granular flow behavior. Discrete element method is used to simulate cylindrical particles with different aspect ratios in the rotating drum operating in the rolling regime. The results demonstrate that the cylindrical particles exhibit similar general flow patterns as the spherical particles. As the aspect ratio of the cylindrical particles increases, the active‐passive interfaces become steeper, and the number fraction, solid residence time, and collision force in the active region decreases. The mechanism underlying the difference is the preferential orientation, with particles of greater aspect ratios increasingly orientating their longitudinal axes perpendicular to the drum length. Also, particle alignment in the active region is more uniform than that in the passive region. The results obtained in this work provide new insights regarding the impact of particle shape on granular flow in the rotating drum. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-14
  • Borescopy in pressurized gas‐solid fluidized beds
    AlChE J. (IF 3.326) Pub Date : 2018-04-18
    Mohammad Banaei; Rik Dellaert; Niels G. Deen; Martin van Sint Annaland; Johannes A. M. Kuipers

    A borescopic technique was used for finding the effect of pressure on the hydrodynamics of gas‐solid fluidized beds. The results showed that solids radial distribution may become more or less uniform with increasing pressure depending on the superficial gas velocity. Moreover, it is found that the solids volume fraction of the emulsion phase may decrease at relatively high pressures, only in the central region of the bed. Additionally, it is observed that with increasing pressure the bubble size generally decreased in the central regions and increased near the wall regions. This trend was more complicated at low excess gas velocities. The number of bubbles increased for the central regions and near the walls for all the performed experiments. However, this parameter showed a different trend at other radial positions. © 2018 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-14
  • Modeling granular material blending in a rotating drum using a finite element method and advection‐diffusion equation multiscale model
    AlChE J. (IF 3.326) Pub Date : 2018-04-10
    Yu Liu; Marcial Gonzalez; Carl Wassgren

    A multiscale model is presented for predicting the magnitude and rate of powder blending in a rotating drum blender. The model combines particle diffusion coefficient correlations from the literature with advective flow field information from blender finite element method simulations. The multiscale model predictions for overall mixing and local concentration variance closely match results from discrete element method (DEM) simulations for a rotating drum, but take only hours to compute as opposed to taking days of computation time for the DEM simulations. Parametric studies were performed using the multiscale model to investigate the influence of various parameters on mixing behavior. The multiscale model is expected to be more amenable to predicting mixing in complex geometries and scale more efficiently to industrial‐scale blenders than DEM simulations or analytical solutions. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-14
  • Co‐doped ZnO thin films grown by pulsed electron beam ablation as model nano‐catalysts in fischer‐tropsch synthesis
    AlChE J. (IF 3.326) Pub Date : 2018-04-06
    Asghar Ali; Redhouane Henda; James Aluha; Nicolas Abatzoglou

    A single‐step deposition of cobalt‐doped zinc oxide (Co‐ZnO) thin film nano‐composites on three different crystalline substrates, viz., Al2O3 (c‐sapphire), silicon (100) (Si), and SiO2 (quartz) is reported, using pulsed electron beam ablation (PEBA). The results indicate that the type of substrate has no effect on Co‐ZnO films stoichiometry, morphology, microstructure, and film thickness. The findings show the presence of hexagonal close‐packed metallic Co whose content increases in the films deposited on Al2O3 and Si substrates relatively to SiO2 substrate. The potential of the films as model nano‐catalysts has been evaluated in the context of the Fischer‐Tropsch (FT) process. Fuel fractions, which have been observed in FT liquid products, are rich in diesel and waxes. Specifically, Co‐ZnO/Al2O3 nano‐catalyst shows a selectivity of ∼4%, 31%, and 65% towards gasoline, diesel, and waxes, respectively, while Co‐ZnO/SiO2 nano‐catalyst shows a selectivity of ∼12%, 51%, and 37%, for gasoline, diesel, and waxes, respectively. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-14
  • Residual film thickness following immiscible fluid displacement in noncircular microchannels at large capillary number
    AlChE J. (IF 3.326) Pub Date : 2018-04-06
    Yu Lu; Nina M. Kovalchuk; Mark J. H. Simmons

    An experimental study of the displacement of one immiscible fluid by another was performed in microchannels with circular, square and near‐semicircular cross‐sections, with hydraulic diameters from 100 to 200 μm. Experiments were performed over a range of capillary number, Ca, from 0.02 < Ca < 80, with viscosity ratios between the two fluids ranging from 20 to 100. The liquid film left on the channel wall following the advance of the displacing fluid was obtained from visual measurements and a method for the estimation of mean film thickness was shown to be in good agreement with existing correlations. The addition of a surfactant (Sodium Dodecyl Sulfate, SDS) dissolved in the displacing fluid led to a reduction in the thickness of the residual film. © 2018 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-14
  • Liquid‐bridge flow in the channel of helical string and its application to gas–liquid contacting process
    AlChE J. (IF 3.326) Pub Date : 2018-04-06
    Haifeng Cong; Zhenyu Zhao; Xingang Li; Hong Li; Xin Gao

    To solve the problems of the traditional packings, such as high pressure drop, mal‐distribution and short liquid residence time, a helical flow structured packings was proposed. Two different flow patterns, liquid‐bridge flow and liquid‐drop flow were identified when the width of the channel of the helical string was adjusted. Moreover, the characteristics of the helical liquid‐bridge flow including maximum liquid loading, mean thickness of liquid film, mean residence time and effective specific surface area, were examined. And the separation efficiency was studied by the lab‐scale distillation column. In comparison, the effective specific surface area of the helical flow type packings is almost as large as the traditional B1‐350Y structured packings, but with thinner liquid film, longer liquid residence time and finally higher separation efficiency. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-14
  • A trimethylamine–carbon dioxide draw solution for osmotic engines
    AlChE J. (IF 3.326) Pub Date : 19 April 2
    Lingling Xia; Jason T. Arena; Jian Ren; Kevin K. Reimund; Amy Holland; Aaron D. Wilson; Jeffrey R. McCutcheon

    This study evaluates the pressure retarded osmosis performance of TMA–CO2 for potential use in osmotic heat engines. Power densities up to 18.6 W m−2 were achievable at relatively low pressure (10 bar) using 5 M TMA–CO2 draw solutions. Compared to NaCl control tests, the TMA–CO2 exhibited 20% lower water flux due in large part to its larger molecular size and associated higher solution viscosity and lower diffusion coefficient. Compared to the ammonia‐carbon dioxide draw solution, water flux was comparable but reverse solute flux of TMA–CO2 was nearly one order of magnitude lower. Larger solute size was found to create a performance tradeoff as reduced reverse solute flux improved water flux while higher viscosity and lower diffusion coefficient worsened water flux. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-14
  • Manganese‐containing redox catalysts for selective hydrogen combustion under a cyclic redox scheme
    AlChE J. (IF 3.326) Pub Date : 16 April 2
    Ryan B. Dudek; Yunfei Gao; Junshe Zhang; Fanxing Li

    Selective hydrogen combustion (SHC) in the presence of light hydrocarbons was demonstrated with a series of Mn‐containing mixed oxide redox catalysts in the context of a chemical looping‐oxidative dehydrogenation scheme. Unpromoted and 20 wt % Na2WO4‐promoted Mg6MnO8, SrMnO3, and CaMnO3 exhibited varying SHC capabilities at temperatures between 550 and 850°C. Reduction temperature of unpromoted redox catalysts increased in the order Mg6MnO8 < SrMnO3 < CaMnO3. Promotion with 20 wt % Na2WO4 resulted in more selective redox catalysts capable of high‐temperature SHC. XPS analysis revealed a correlation between suppression of near‐surface Mn and SHC selectivity. Na2WO4/CaMnO3 showed steady SHC performance (89% H2 conversion, 88% selectivity) at 850°C over 50 redox cycles. In series with a Cr2O3/Al2O3 ethane dehydrogenation catalyst, Na2WO4/CaMnO3 combusted 84% of H2 produced while limiting COx yield below 2%. The redox catalysts reported can be suitable for SHC in a cyclic redox scheme for the production of light olefins from alkanes. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-14
  • Towards scale‐up of graphene production via nonoxidizing liquid exfoliation methods
    AlChE J. (IF 3.326) Pub Date : 2018-03-31
    Jason Stafford; Andrius Patapas; Nwachukwu Uzo; Omar K. Matar; Camille Petit

    Graphene, the two‐dimensional form of carbon, has received a great deal of attention across academia and industry due to its extraordinary electrical, mechanical, thermal, chemical, and optical properties. In view of the potential impact of graphene on numerous and diverse applications in electronics, novel materials, energy, transport, and healthcare, large‐scale graphene production is a challenge that must be addressed. In the past decade, top–down production has demonstrated high potential for scale‐up. This review features the recent progress made in top–down production methods that have been proposed for the manufacturing of graphene‐based products. Fabrication methods such as liquid‐phase mechanical, chemical and electrochemical exfoliation of graphite are outlined, with a particular focus on nonoxidizing routes for graphene production. Analysis of exfoliation mechanisms, solvent considerations, key advantages and issues, and important production characteristics including production rate and yield, where applicable, are outlined. Future challenges and opportunities in graphene production are also highlighted. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-14
  • On the steady‐state drop size distribution in stirred vessels. Part I: Effect of dispersed phase viscosity
    AlChE J. (IF 3.326) Pub Date : 2018-03-30
    Sergio Carrillo De Hert; Thomas L. Rodgers

    Previous studies on emulsification have used the maximum drop size (dmax) or Sauter mean diameter ( ) to investigate the effect of viscosity on the drop size distribution (DSD), however, these parameters fall short for highly polydispersed emulsions. In this investigation (Part I), the steady‐state DSD of dilute emulsions is studied using of silicon oils with viscosities varying across six orders of magnitude at different stirring speeds. Different emulsification regimes were identified; our modeling and analysis is centered on the intermediate viscosity range where interfacial cohesive stresses can be considered negligible and drop size increases with viscosity. The bimodal frequency distributions by volume were well described using two log‐normal density functions. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-14
  • Effect of fuel composition on NOx formation in high‐pressure syngas/air combustion
    AlChE J. (IF 3.326) Pub Date : 11 April 2
    Nazli Asgari; Bihter Padak

    In this study, an experimental investigation of lean premixed syngas/air flames with H2/CO ratio of 1.0 and equivalence ratio of 0.5 has been conducted in a high‐pressure burner facility to investigate the effects of pressure and the presence of hydrocarbons on NOx speciation. Detailed NOx speciation measurements in the post‐flame region were conducted for various pressures up to 1.5 MPa (15 bar) using Fourier transform infrared (FTIR) spectroscopy. When the pressure is increased, NO concentration decreases while NO2 increases due to pressure dependence of NO to NO2 conversion. For a given pressure, the presence of hydrocarbons in syngas leads to an increase in NOx concentrations possibly due to prompt NO formation. Comparison of NO concentrations in presence of CH4 at different pressures shows that the effect of CH4 due to prompt NO formation is more dominant than the effect of pressure on NO. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-14
  • Near‐UV activated, photostable nanophosphors for in vitro dosimetry and dynamic bioimaging
    AlChE J. (IF 3.326) Pub Date : 2018-03-23
    Anastasia Spyrogianni; Peter Tiefenboeck; Fabian H. L. Starsich; Kerda Keevend; Frank Krumeich; Inge K. Herrmann; Jean‐Christophe Leroux; Georgios A. Sotiriou

    Luminescent rare earth nanoparticles exhibit superior optical stability over commonly‐used organic dyes and higher biocompatibility over quantum dots, rendering them advantageous as bioimaging nanoprobes. However, their typical excitation inhibits their broad employment with conventional fluorescence microscopes and, thus, solutions are sought to shift their activation in the long‐wavelength (near‐UV) spectral region. Here, we synthesize YVO4:Eu3+ nanophosphors by flame aerosol technology to systematically study the effect of Bi3+ codoping on their luminescence. That way, we identify an optimal Bi‐content for sufficient near‐UV activation. These nanophosphors are highly crystalline and appeared bright red under a conventional fluorescence microscope, facilitating bioimaging with HeLa cells and in vitro dosimetry correlations in the presence and absence of serum. The nanophosphor superiority over organic‐dye‐labeled silica nanoparticles is shown during dynamic imaging for 4 h without photobleaching for the former. These YVO4:Eu3+/Bi3+ nanophosphors can provide a non‐photobleaching tool for further dynamic nanoparticle‐cell interaction studies with conventional fluorescence microscopes. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-14
  • Economic model predictive control of stochastic nonlinear systems
    AlChE J. (IF 3.326) Pub Date : 2018-03-23
    Zhe Wu; Junfeng Zhang; Zhihao Zhang; Fahad Albalawi; Helen Durand; Maaz Mahmood; Prashant Mhaskar; Panagiotis D. Christofides

    This work focuses on the design of stochastic Lyapunov‐based economic model predictive control (SLEMPC) systems for a broad class of stochastic nonlinear systems with input constraints. Under the assumption of stabilizability of the origin of the stochastic nonlinear system via a stochastic Lyapunov‐based control law, an economic model predictive controller is proposed that utilizes suitable constraints based on the stochastic Lyapunov‐based controller to ensure economic optimality, feasibility and stability in probability in a well‐characterized region of the state‐space surrounding the origin. A chemical process example is used to illustrate the application of the approach and demonstrate its economic benefits with respect to an EMPC scheme that treats the disturbances in a deterministic, bounded manner. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-14
  • Convex relaxations for global optimization under uncertainty described by continuous random variables
    AlChE J. (IF 3.326) Pub Date : 10 January
    Yuanxun Shao; Joseph K. Scott

    This article considers nonconvex global optimization problems subject to uncertainties described by continuous random variables. Such problems arise in chemical process design, renewable energy systems, stochastic model predictive control, and many other applications. Here, we restrict our attention to problems with expected‐value objectives and no recourse decisions. In principle, such problems can be solved globally using spatial branch‐and‐bound. However, branch‐and‐bound requires the ability to bound the optimal objective value on subintervals of the search space, and existing techniques are not generally applicable because expected‐value objectives often cannot be written in closed‐form. To address this, this article presents a new method for computing convex and concave relaxations of nonconvex expected‐value functions, which can be used to obtain rigorous bounds for use in branch‐and‐bound. Furthermore, these relaxations obey a second‐order pointwise convergence property, which is sufficient for finite termination of branch‐and‐bound under standard assumptions. Empirical results are shown for three simple examples. © 2017 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-14
  • Dynamics and scaling of explosion cratering in granular media
    AlChE J. (IF 3.326) Pub Date : 09 January
    Ming Gao; Xiao Liu; Luana Pasetti Vanin; Ting‐Pi Sun; Xiang Cheng; Leonardo Gordillo

    Granular cratering is a ubiquitous phenomenon occurring in various natural and industrial contexts. Although impact‐induced granular cratering has been extensively studied, fewer experiments have been conducted on granular cratering via low‐energy explosions. Here, we study the dynamics and scaling of explosion granular cratering by injecting short pulses of pressurized air in quasi‐two‐dimensional granular media. Through an analysis of the dynamics of explosion processes at different explosion pressures, explosion durations, and burial depths, we identify two regimes, the bubbling and the eruption regimes, in explosion granular cratering. Our experiments explore the distinctive dynamics and crater morphologies of these regimes and show the energy scaling of the size of explosion craters. We compare high‐energy and low‐energy explosion cratering as well as explosion and impact cratering in terms of their energy scalings. Our work illustrates complex granular flows in explosion cratering and provides new insights into the general scaling of granular cratering processes. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2018-07-14
  • Rheological properties and structure of step‐ and chain‐growth gels concentrated above the overlap concentration
    AlChE J. (IF 3.326) Pub Date : 05 January
    Matthew D. Wehrman; Andrew Leduc; Holly E. Callahan; Michelle S. Mazzeo; Mark Schumm; Kelly M. Schultz

    Cross‐linked polymeric gels are widely used in applications ranging from biomaterial scaffolds to additives in enhanced oil recovery. Despite this, fundamental understanding of the effect of polymer concentration and reaction mechanism on the scaffold structure is lacking. We measure scaffold properties and structure during gelation using multiple particle tracking microrheology. To determine the effect of concentration, we measure gelation as polymer interactions are increased in the backbone precursor solution: below, at and above the overlap concentration, . To determine structural changes due to the gelation mechanism, we measure gelation between the same polymers undergoing both step‐ and chain‐growth reactions using self‐assembling maleimide:thiol and photo‐initiated acrylate:thiol chemistries, respectively. We determine the critical relaxation exponent, n, a measure of structure. n decreases with increasing concentration, indicating a change from a percolated ( ) to a tightly cross‐linked network ( ). The gelation mechanism does not have a measurable effect on the scaffold structure. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2018-07-14
  • Stem cell biomanufacturing under uncertainty: A case study in optimizing red blood cell production
    AlChE J. (IF 3.326) Pub Date : 07 Decembe
    Ruth Misener; Mark C. Allenby; María Fuentes‐Garí; Karan Gupta; Thomas Wiggins; Nicki Panoskaltsis; Efstratios N. Pistikopoulos; Athanasios Mantalaris

    As breakthrough cellular therapy discoveries are translated into reliable, commercializable applications, effective stem cell biomanufacturing requires systematically developing and optimizing bioprocess design and operation. This article proposes a rigorous computational framework for stem cell biomanufacturing under uncertainty. Our mathematical tool kit incorporates: high‐fidelity modeling, single variate and multivariate sensitivity analysis, global topological superstructure optimization, and robust optimization. The advantages of the proposed bioprocess optimization framework using, as a case study, a dual hollow fiber bioreactor producing red blood cells from progenitor cells were quantitatively demonstrated. The optimization phase reduces the cost by a factor of 4, and the price of insuring process performance against uncertainty is approximately 15% over the nominal optimal solution. Mathematical modeling and optimization can guide decision making; the possible commercial impact of this cellular therapy using the disruptive technology paradigm was quantitatively evaluated. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2018-07-14
  • Magnetic resonance imaging of gas–solid fluidization with liquid bridging
    AlChE J. (IF 3.326) Pub Date : 05 Decembe
    C. M. Boyce; A. Penn; K. P. Pruessmann; C. R. Müller

    Magnetic resonance imaging is used to generate snapshots of particle concentration and velocity fields in gas–solid fluidized beds into which small amounts of liquid are injected. Three regimes of bed behavior (stationary, channeling, and bubbling) are mapped based on superficial velocity and liquid loading. Images are analyzed to determine quantitatively the number of bubbles, the bubble diameter, bed height, and the distribution of particle speeds under different wetting conditions. The cohesion and dissipation provided by liquid bridges cause an increase in the minimum fluidization velocity and a decrease in the number of bubbles and fast particles in the bed. Changes in liquid loading alter hydrodynamics to a greater extent than changes in surface tension or viscosity. Keeping U/Umf at a constant value of 1.5 produced fairly similar hydrodynamics across different wetting conditions. The detailed results presented provide an important dataset for assessment of the validity of assumptions in computational models. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2018-07-14
  • Control of viscous fingering and mixing in miscible displacements with time‐dependent rates
    AlChE J. (IF 3.326) Pub Date : 2018-07-13
    Qingwang Yuan; Xiang Zhou; Jinjie Wang; Fanhua Zeng; Kelvin D. Knorr; Muhammad Imran

    In miscible displacements encountered in enhanced oil recovery processes, the unfavorable viscosity contrast between injected solvent and oil usually leads to viscous fingering (VF), a hydrodynamic instability which may result in a lower sweep efficiency and oil recovery. This phenomenon can be observed in a wide range of flows in subsurface porous media. The present study examined a simple cyclic time‐dependent displacement rate and its effects on the onset and longer development of VF. It is found that such varying displacement rate can either stabilize or destabilize VF, depending on the cycle period, amplitude, and displacement scenarios. The most important mechanism is that such time‐dependent rate can effectively change the competition between convection (destabilizing effect) and dispersion (stabilizing effect). This is different from the widely used constant injection rate where the flow instability is actually determined by the Peclet number and mobility contrast for a given scenario. This study therefore provided a new aspect to control VF, either enhance or reduce, with low additional costs. It is therefore both scientifically and practically important for a wide range of flows in subsurface porous media.

    更新日期:2018-07-14
  • An interfacial curvature distribution model and phase inversion
    AlChE J. (IF 3.326) Pub Date : 2017-10-06
    A. Vikhansky

    The state of the two‐phase system is described by the interfacial curvature distribution. A phenomenological closure model is proposed for the exact (unclosed) equations. Parameters of the model are related to the existing correlations for drop size in stirred flows. If water is dispersed in oil, the curvature has a uni‐modal distribution with a positive mode. When a control parameter, e.g., water volume fraction is increasing, the distribution becomes bi‐modal with both negative and positive values. After a while, the phase inversion occurs, and the distribution becomes uni‐modal with a negative mode. Going in the other direction the phase inversion happens at lower volume fraction of water, i.e., there is an ambivalent region, where both phases might be in the dispersed state. The model implies, that even if the conditions for phase inversion are met, there might be a significant delay before the new morphology is established. This article is protected by copyright. All rights reserved.

    更新日期:2018-07-14
  • Retraction
    AlChE J. (IF 3.326) Pub Date : 2017-09-01

    Modeling and Prediction of Protein Solubility Using the Second Osmotic Virial Coefficient by Marcel Herhut, Christoph Brandenbusch, Gabriele Sadowski,

    更新日期:2018-07-14
  • Monte Carlo modeling of binder‐Less spray agglomeration in fluidized beds
    AlChE J. (IF 3.326) Pub Date : 2018-06-27
    Christian Rieck; Martin Schmidt; Andreas Bück; Evangelos Tsotsas

    Fluidized bed spray agglomeration is used in the industry to increase the particle size and to improve several properties, for example, bulk density, flowability, and dissolution behavior of particulate products. Usually, a binder liquid is sprayed on a particle bed. If amorphous materials are used, spraying of pure water may cause agglomeration due to glass transition at wet spots on the particle surface. As no process models covering binder‐less spray agglomeration currently exist, a model based on a Monte Carlo method is presented. In this method, the process is described by events and processes on the single particle scale. Additionally, agglomeration experiments in a lab‐scale fluidized bed using three different maltodextrins are presented. For each experiment, a simulation was performed. The simulation results are compared with the obtained experimental data. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-12
  • Modeling of thermodynamics of substituted toluene derivatives and benzylic radicals via group additivity
    AlChE J. (IF 3.326) Pub Date : 2018-06-25
    Alper Ince; Hans‐Heinrich Carstensen; Maarten Sabbe; Marie‐Françoise Reyniers; Guy B. Marin

    The thermodynamic properties of unsubstituted, mono‐, and di‐substituted toluene derivatives and benzylic radicals with hydroxy, methoxy, formyl, vinyl, methyl, and ethyl substituents are calculated with the bond additivity corrected (BAC) post‐Hartree‐Fock CBS‐QB3 method. Benson's group additivity (GA) scheme is extended to toluene derivatives by determining six group additive value (GAV) and five non‐nearest neighbor interaction (NNI) parameters through least‐squares regression to a database of thermodynamic properties of 168 compounds and to benzylic radicals by defining 6 GAV and 14 NNI parameters based on a set of 168 radicals. Comparison between CBS‐QB3/BAC and GA‐calculated thermodynamic values shows that the standard enthalpies of formation generally agree within 4 kJ mol−1, whereas the entropies and the heat capacities generally deviate <4 J mol−1 K−1. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-12
  • Metal‐organic gels of simple chemicals and their high efficacy in removing arsenic(V) in water
    AlChE J. (IF 3.326) Pub Date : 2018-06-23
    Zhiliang Gao; Jianfei Sui; Xiaolin Xie; Xiaoyu Li; Shuo Song; Hongshu Zhang; Yuanyuan Hu; Yue Hong; Xiaolin Wang; Jiwei Cui; Jingcheng Hao

    Metal‐organic gels (MOGs) have emerged as a class of functional materials that show great potential applications in the field of catalysis, energy storage, template synthesis, and environmental technology. The construction of functional MOGs and the control of functionality are still challenging due to complicated chemicals or routes involved in previous works. Here we report a series of tunable multifunctional MOGs by directly gelating between Fe3+ and simple chemicals, propanedioic acid (H2PA), succinic acid (H2SA), glutaric acid (H2GA), and fumaric acid (H2FA) in ethanol. The obtained MOGs exhibit self‐healing property and good conductivity, and were used for high efficacy removal of arsenic (As) in water. The ease, low cost, and scalability of the assembly process combined with multifunctionality make these MOGs be potentially applied in the fields of energy storage and sewage disposal. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-12
  • Detection and quantification of vitamins in microliter volumes of biological samples by LC‐MS for clinical screening
    AlChE J. (IF 3.326) Pub Date : 2018-06-23
    Maryam Khaksari; Lynn R. Mazzoleni; Chunhai Ruan; Peng Song; Neil D. Hershey; Robert T. Kennedy; Mark A. Burns; Adrienne R. Minerick

    A method for simultaneous determination of water‐soluble vitamins B1, B2, B3 (nicotinamide), B5, B6 (pyridoxamine), B9 and fat‐soluble vitamins E (α‐tocopherol) and K1 in tears, and B1, B2, B3, B5, B6, B9, A (retinol), and E in blood serum is described. Liquid chromatography‐mass spectrometry (LC‐MS) was used with a ternary mobile phase of water and acetonitrile containing 0.1% formic acid and methanol containing 5 mM ammonium formate. Vitamins were quantified using an internal standard method. Using 25 μL injection volumes, the limits of detection were in the range of 0.066‐5.3 ng in tear, and 0.087‐1.1 ng in serum with linear responses for all vitamins. Intra‐ and inter‐day precision and recoveries were satisfactory. This is the first study to demonstrate simultaneous vitamin detections in microliters of biological samples which has distinct advantages in many diagnostic applications with limited available fluids (e.g., tears; elderly anemic blood) or sampling small subjects (e.g., rodents). © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-12
  • Predictions of flow instabilities in the shear‐thickening regime with an improved bautista–manero–puig model
    AlChE J. (IF 3.326) Pub Date : 2018-06-14
    J. E. Puig; F. Bautista; E. Hernández; F. López‐Serrano

    The trajectories of chaotic fluctuations in dilute micellar solutions, which typically occur during the creation and destruction of shear‐induced structures in the flow inception of a 0.4 wt % cetyltrimethylammonium tosilate aqueous solution and an aqueous solution of 3 mM cetyyltrimethylammonium bromide‐sodium salicylate, are predicted here with an improved Bautista–Manero–Puig model. To determine the constancy of the model parameters with time, we applied successfully an integro‐differential approach. This methodology revealed that all the model parameters, but the elastic modulus is constant. The nature of the predicted fluctuations was analyzed by employing the exponent of Lyapunov. This analysis demonstrates that the fluctuations are chaotic deterministic in Regimes I and IV, whereas they are random in Region II. We found that the predictions of the modified model follow the experimental data and reveal that these fluctuations are related to the creation of elastic structures at the inception of shear flow. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-12
  • Turbulent flow field in a stirred vessel agitated by an impeller with flexible blades
    AlChE J. (IF 3.326) Pub Date : 2018-07-11
    Yangyang Liang; Daien Shi; Bohang Xu; Ziqi Cai; Zhengming Gao

    In order to reveal the effect of the blades normal vibration on flow turbulence in the stirred vessel, we designed three kinds of blades: the flexible, flat‐rigid and curved‐rigid blades. The flow fields produced by the impellers with these three kinds of blades were measured by two‐dimensional particle image velocimetry. The results showed that the calculated turbulent kinetic energy (TKE) based on the pseudo‐isotropic assumption is slightly higher than that by the three fluctuating velocities for the flexible and curved‐rigid impellers, and the difference between above two calculations is smaller for the former impeller. For the flexible blades, the trailing vortices slightly move outwards in radial direction than those for the curved‐rigid blades, enhancing TKE transport from the blade to the bulk region of the vessel. For the flexible impeller, the phase‐averaged TKE differs slightly from that for the flat‐rigid impeller, but is higher than that for the curved‐rigid impeller.

    更新日期:2018-07-12
  • Novel multi‐domain, multi‐functional glycoside hydrolases from highly lignocellulolytic Caldicellulosiruptor species
    AlChE J. (IF 3.326) Pub Date : 2018-07-11
    Jonathan M. Conway; James R. Crosby; Andrew P. Hren; Robert T. Southerland; Laura L. Lee; Vladimir V. Lunin; Petri Alahuhta; Michael E. Himmel; Yannick J. Bomble; Michael W.W. Adams; Robert M. Kelly

    Biological hydrolysis of microcrystalline cellulose is an uncommon feature in the microbial world, especially among bacteria and archaea growing optimally above 70°C (the so‐called extreme thermophiles). In fact, among this group only certain species in the genus Caldicellulosiruptor are capable of rapid and extensive cellulose degradation. Four novel multi‐domain glycoside hydrolases (GHs) from Caldicellulosiruptor morganii and Caldicellulosiruptor danielii were produced recombinantly in Caldicellulosiruptor bescii and characterized. These GHs are structurally organized with two or three catalytic domains flanking carbohydrate binding modules from Family 3 (CBM3). Collectively, these enzymes represent GH families 5, 9, 10, 12, 44, 48, and 74, and hydrolyze crystalline cellulose, glucan, xylan, and mannan, the primary carbohydrates in plant biomass. Degradation of microcrystalline cellulose by cocktails of GHs from three Caldicellulosiruptor species demonstrated that synergistic interactions enable mixtures of multiple enzymes to outperform single enzymes, suggesting a community mode of action for lignocellulose utilization in thermal environments.

    更新日期:2018-07-12
  • Probing the acyl carrier protein‐enzyme interactions within terminal alkyne biosynthetic machinery
    AlChE J. (IF 3.326) Pub Date : 2018-07-11
    Michael Su; Xuejun Zhu; Wenjun Zhang

    The alkyne functionality has attracted much interest due to its diverse chemical and biological applications. We recently elucidated an acyl carrier protein (ACP)‐dependent alkyne biosynthetic pathway, however, little is known about ACP interactions with the alkyne biosynthetic enzymes, an acyl‐ACP ligase (JamA) and a membrane‐bound bi‐functional desaturase/acetylenase (JamB). Here, we showed that JamB has a more stringent interaction with ACP than JamA. In addition, site directed mutagenesis of a non‐cognate ACP significantly improved its compatibility with JamB, suggesting a possible electrostatic interaction at the ACP‐JamB interface. Finally, error‐prone PCR and screening of a second non‐cognate ACP identified hot spots on the ACP that are important for interacting with JamB and yielded mutants which were better recognized by JamB. Our data thus not only provide insights into the ACP interactions in alkyne biosynthesis, but it also potentially aids in future combinatorial biosynthesis of alkyne‐tagged metabolites for chemical and biological applications.

    更新日期:2018-07-12
  • Controllability and flexibility in particle‐manufacturing of a segmented microfluidic device with passive picoinjection
    AlChE J. (IF 3.326) Pub Date : 2018-07-11
    Le Du; Yang Li; Ruomei Gao; Jiabin Yin; Chun Shen; Yujun Wang; Guangsheng Luo

    Segmented flow microfluidics has attracted considerable attention owing to the excellent controllability of reaction environment. However, the accurate and stepwise addition of other reactants into the formed droplets/slugs in segmented flow is extraordinarily challenging to achieve, especially for performing particle growth and crystallization processes. Herein, we employed a segmented flow microchannel with passive picoinjection to realize the accurate addition of reactants and continuous particle‐manufacturing. A Venturi junction was integrated into the microchannel to control the injection volume without external power. Rapid mixing for the preparation of BaSO4 nanoparticles with an average size of 30−40 nm, multiple injection for the growth of Au nanoparticles from 32 to 91 nm, and continuous crystallization of vaterite CaCO3 with a high crystal purity were all successfully performed in this microchannel. The feasibility of long‐term operation and large‐scale production of particles by combining with droplet splitting was also experimentally verified.

    更新日期:2018-07-12
  • Hierarchical N‐doped carbons from designed N‐rich polymer: Adsorbents with a record‐high capacity for desulfurization
    AlChE J. (IF 3.326) Pub Date : 2018-07-11
    Peng Tan; Ding‐Ming Xue; Jing Zhu; Yao Jiang; Qiu‐Xia He; ZhuFeng Hou; Xiao‐Qin Liu; Lin‐Bing Sun

    The removal of 4,6‐dimethyldibenzothiophene is quite challenging in petroleum refining process. Adsorptive desulfurization is an efficient technique but the capacities and/or poor stability of current adsorbents need to be improved. Here we report the fabrication of hierarchical N‐doped carbons (NCs) derived from carbonizing the polymerization of 2,4,6‐tris(chloromethyl)mesitylene and p‐phenylenediamine. The results show that the NCs have developed micropores (0.34–0.93 cm3 g–1) and mesopores (0.15–0.47 cm3 g–1), and their surfaces have abundant pyrrole‐like/graphitic N and topological defects and vacancies, and high cycle stability (6 cycles). The typical adsorbent NC‐700 shows a record‐high capacity of 2.91 mmol g–1 under ambient conditions. The computational results show that the doped N is capable of promoting adsorptive strength by 0.055–0.178 eV. In conclusion, the obtained materials exhibit excellent performance for deep desulfurization, and this work may open up new avenues for the development of efficient adsorbents.

    更新日期:2018-07-12
  • Scale formation on the wall of a mechanically stirred vessel – experimental assessment and interpretation using CFD
    AlChE J. (IF 3.326) Pub Date : 2018-07-11
    Meysam Davoody; Graeme Lane; Lachlan J.W. Graham; Jie Wu; Srinivasan Madapusi; Rajarathinam Parthasarathy

    Accelerated growth of scale was studied in a baffled agitated reactor, which could be disassembled into nine sections, allowing quantitative determination of scale thickness. A coordinate measuring machine was used to determine the scale thickness on individual wall segments. The growth pattern of the scale was found to be non‐uniform due to the variation of fluid velocity near the wall at various heights. Computational fluid dynamics (CFD) simulation showed that fluid flow is time‐dependent and has two distinct flow zones, one involving recirculation through the impeller in the lower part of the vessel and the other involving lower velocities due to the flow separation at the wall in the upper part. CFD simulation also showed the presence of macroinstabilities, which manifest as asymmetrical and chaotic flow structures with relatively long‐time scales. Scale growth is found to be prominent in regions where the fluid velocity and wall shear stresses are low.

    更新日期:2018-07-12
  • Production of ethylene glycol from xylose by metabolically engineered Escherichia coli
    AlChE J. (IF 3.326) Pub Date : 2018-06-19
    Tong Un Chae; So Young Choi; Jae Yong Ryu; Sang Yup Lee

    Ethylene glycol (EG) is an important chemical used for several industrial applications including poly(ethylene terephthalate) synthesis. In this study, Escherichia coli was metabolically engineered to efficiently produce EG from xylose. To biosynthesize EG, the Dahms pathway was introduced by expressing xylBC genes from Caulobacter crescentus (xylBCccs). Various E. coli strains and glycolaldehyde reductases were screened to find E. coli W3110 strain and glycolaldehyde reductase (yqhD) as optimal combination for EG production. In silico genome‐scale metabolic simulation suggested that increasing the native xylose pathway flux, in the presence of the overexpressed Dahms pathway, is beneficial for EG production. This was achieved by reducing the Dahms pathway flux by employing a synthetic small regulatory RNA targeting xylBccs. Fed‐batch culture of the final engineered E. coli strain produced 108.2 g/L of EG in a xylose minimal medium. The yield on xylose and EG productivity were 0.36 g/g (0.87 mol/mol) and 2.25 g/L/h, respectively. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-09
  • Process synthesis using block superstructure with automated flowsheet generation and optimization
    AlChE J. (IF 3.326) Pub Date : 05 July 20
    Jianping Li; Salih Emre Demirel; M. M. Faruque Hasan

    An alternative method for chemical process synthesis using a block‐based superstructure representation is proposed. The block‐based superstructure is a collection of blocks arranged in a two‐dimensional grid. The assignment of different equipment on blocks and the determination of their connectivity are performed using a mixed‐integer nonlinear formulation for automated flowsheet generation and optimization‐based process synthesis. Based on the special structure of the block representation, an efficient strategy is proposed to generate and successively refine feasible and optimized process flowsheets. Our approach is demonstrated using two process synthesis case studies adapted from the literature and one new process synthesis problem for methanol production from biogas © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-08
  • Utilizing yield‐stress fluids to suppress chaining during magnetic alignment of microdisks via rotating fields
    AlChE J. (IF 3.326) Pub Date : 05 July 20
    Mingyang Tan; Adam L. Lambert; Britany M. Swann; Han Song; Pallavi Dhagat; Albrecht Jander; Travis W. Walker

    Inkjet printing can be used to deposit photopolymerizable magnetic inks for the creation of functionalized composites. Anisotropic properties in the composites can be achieved when inkjet printing is combined with external magnetic fields to align magnetically orientable particles (MOPs). When a MOP is induced by an external magnetic field, it will create its own magnetic field that can attract neighboring particles. The coarsening of particles into higher‐order structures like chains and sheets is unwanted in certain areas, such as high‐frequency applications. We show that this particle–particle attraction and subsequent particle migration can be inhibited with the introduction of a yield stress into the suspending medium, while still allowing the alignment of the particle to proceed. For magnetically induced rotational and translational motions for oblate spheroids in a rotating magnetic field, theoretical scalings are presented for the characteristic timescales in a linear fluid and for the characteristic stresses in a yield‐stress fluid. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-08
  • Assessment of mesoscale solid stress in coarse‐grid TFM simulation of Geldart A particles in all fluidization regimes
    AlChE J. (IF 3.326) Pub Date : 06 July 20
    Xi Gao; Tingwen Li; William A. Rogers

    This study focused on assessing the effect of mesoscale solid stress in the coarse grid two‐fluid model (TFM) simulation of gas–solid fluidized beds of Geldart Group A particles over a broad range of flow regimes, including bubbling, turbulent, fast, and pneumatic transport fluidization regimes. Particularly, the impact of mesoscale solid pressure, mesoscale solid viscosity, and mesoscale solid stress anisotropy were investigated by comparing six different coarse‐grid TFM settings. Compared with the available experimental data, it is found that both the kinetic theory‐based TFM with only drag correction and the filtered TFM can predict the flow behavior in all fluidization regimes. Mesoscale solid pressure and viscosity have the opposite impact on flow hydrodynamics; they compete and offset each other, which confirms the assumption employed in many previous studies that the mesoscale solid stress could be neglected in coarse‐grid TFM simulation. Published 2018. This article is a U.S. Government work and is in the public domain in the USA. AIChE J, 2018

    更新日期:2018-07-08
  • Understanding the preferential oxidation of carbon monoxide (PrOx) using size‐controlled Au nanocrystal catalyst
    AlChE J. (IF 3.326) Pub Date : 2018-05-12
    Arik Beck; An‐Chih Yang; Amelia R. Leland; Andrew R. Riscoe; Francisco A. Lopez; Emmett D. Goodman; Matteo Cargnello

    Removing CO from hydrogen streams is an important industrial process. The catalytic preferential oxidation of CO (PrOx) is a promising method for CO removal, leaving the hydrogen concentration unchanged. Here, the effect of size and support on the gold‐catalyzed PrOx reaction using size‐controlled Au nanocrystals (NCs) is investigated. For all supports, Au NC sizes of 2–5 nm show the highest rates, whereas for larger sizes rates drop. Ceria‐supported Au shows by far the best performance. By analyzing the dependency of the reaction rate on the NC diameter, the most active centers for CO oxidation on Au/CeO2 are Au+ corner atoms at the interface with the support, resulting in 2.1 nm Au NCs supported on ceria reaching full O2 conversion and CO selectivity of about 50%. Therefore, it is suggested that increasing the fraction of Au‐ceria interface sites would lead to the best performing materials for this reaction. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-08
  • Investigation of hydrodynamic performance and effective mass transfer area for Sulzer DX structured packing
    AlChE J. (IF 3.326) Pub Date : 2018-06-21
    Hongxia Gao; Sen Liu; Xiao Luo; Haiyan Zhang; Zhiwu Liang

    The hydrodynamic performance in terms of pressure drop (▵P) and liquid holdup (hL), and tshe effective mass transfer area (ae) of Sulzer DX structured packing were investigated at 293.15 K and 101.3 kPa. In addition, the flooding velocity (uF) was also calculated based on the experimental results of liquid holdup, and the effective voidage correction factor (ς) was obtained by combining the Billet model and the experimental effective fraction. The liquid volume method and pressure difference from just below to above the column packing approach are used to describe the hydrodynamic performance in a structured packing column. Experimental results showed that the operational conditions in terms of gas flow rate, liquid flow rate, viscosity, and liquid systems strongly affect the hydrodynamic performance. The experimental comparison between the pressure drop profiles in air‐water (polyethylene oxide [PEO]) and MEA‐H2O‐CO2 systems indicated that both the reacting MEA and CO2 partial pressure can enhance the pressure drop value. In addition, the Bain‐Haugen correlation model was developed to predict the flooding velocity data with an acceptable AARD of 8.1%, and a model was also successfully proposed to predict the values of liquid holdup with an AARD of 11.8%, which is lower than 14.7% in Billet model. Furthermore, the effective mass transfer area was found to be increased by increasing both the liquid and gas flow rate by using NaOH‐H2O‐CO2 system. A model was also proposed to calculate the experimental ae with an acceptable AARD% of 19.52, and this built model (Eq. 39) can reasonably explain the experimental phenomenon. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-05
  • Prediction of gas density effects on bubbly flow hydrodynamics: New insights through an approach combining population balance models and computational fluid dynamics
    AlChE J. (IF 3.326) Pub Date : 2018-06-19
    K. J. Hecht; U. Krause; J. Hofinger; O. Bey; M. Nilles; P. Renze

    Detailed measurements and computational fluid dynamics (CFD) investigation of the hydrodynamics in a bubble column containing internal features causing flow disturbances are presented for both air and helium gases. An optical needle probe has been used to measure profiles of bubble size, bubble velocity, and gas holdup at different locations across the cross section of the column. An approach combining CFD with population balances is able to represent observed multiphase flow phenomena such as the effect of the pipes to remix and redistribute the gas as well as the tendency of the gas to channel through a slit in the pipes rather than go around the pipes. The comparison of CFD simulation to experimental measurements reveal that the overall decrease in gas holdup observed when switching from air to helium gas can be explained by swarm effects, whereas the steeper decrease in the gas holdup profile across the column is due to coalescence effects. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-05
  • Demand side management and operational mode switching in chlorine production
    AlChE J. (IF 3.326) Pub Date : 2018-07-04
    Luisa C. Brée; Karen Perrey; Andreas Bulan; Alexander Mitsos

    Demand side management gains importance due to penetration of renewable energy in energy provision. A promising candidate is the chlor‐alkali process since it is an energy‐intensive process with a high installed capacity and high penetration worldwide. In this article, we consider demand side management for the purpose of membrane electrolysis. We allow for switching between two different operational modes with different respective electrical power demands on a per ton of produced chlorine basis and different modulation of production rate. Switching necessitates a cleaning procedure leading to downtimes of the chlorine production, while a constant provision of chlorine for downstream processes is necessary. The optimal operation of a variable and switchable chlor‐alkali process under aforementioned constraints is determined by formulation as a mixed integer linear program. The results demonstrate that oversizing, in combination with switching, leads to substantial savings, especially in future scenarios for the electricity price.

    更新日期:2018-07-05
  • Three‐dimensionally printed bioinspired superhydrophobic PLA membrane for oil‐water separation
    AlChE J. (IF 3.326) Pub Date : 2018-06-21
    Ruizhe Xing; Renliang Huang; Wei Qi; Rongxin Su; Zhimin He

    A novel lotus‐leaf‐inspired superhydrophobic poly(lactic acid) (PLA) porous membrane was fabricated for oil‐water separation based on fused deposition modeling three‐dimensional printing and subsequent chemical etching and the decoration of polystyrene nanospheres. A superhydrophobic PLA fractal surface with a water contact angle of 151.7° and low water adhesion force of 21.8 μN was achieved. The membrane pore size could be easily adjusted from 40 to 600 μm via a computer‐aided design program to optimize separation performance. The maximal oil‐water separation efficiency of 99.4% was achieved with a pore size of 250 μm, which also exhibited a high flux of 60 kL m−2 h−1. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-07-04
  • Oxygen mass transfer in a gas/membrane/liquid system surrogate of membrane blood oxygenators
    AlChE J. (IF 3.326) Pub Date : 2018-06-11
    Mónica Faria; Cíntia Moreira; Tiago Mendonça Eusébio; Maria Norberta de Pinho; Pedro Brogueira; Viriato Semião

    Oxygen mass transfer in a membrane blood oxygenator (MBO) surrogate system has been addressed in this work. It consists of a slit for water circulation as a surrogate blood flow channel and a constant pressure oxygen chamber separated by an integral asymmetric hemocompatible polyurethane‐based membrane. The oxygenated stream enters a well‐mixed reservoir of constant volume, V, for the oxygen average concentration, , measurement as a function of time, t. In a range of short times, the linearity of vs. t allows the direct determination of the permeation fluxes , with no recourse to dimensionless correlations for the determination of mass‐transfer coefficients. The experimental fluxes are in very good agreement with the predictions based in unidimensional axial convection and unidimensional transversal diffusion. This custom‐made benchmark system allows the optimization of the flow and oxygen mass transfer for the design of a novel flat‐sheet MBO. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-06-30
  • Process intensification of distillation using a microwick technology to demonstrate separation of propane and propylene
    AlChE J. (IF 3.326) Pub Date : 29 June 20
    Danny Bottenus; Dustin Caldwell; Christopher Fischer; Paul Humble; Michael Powell; Richard Lucke; Ward TeGrotenhuis

    Process intensification (PI) of distillation using a microchannel distillation (MCD) device successfully reduced the height of a theoretical plate (HETP) in separating propane and propylene to 1.2 cm, representing 10 theoretical stages. Mass transfer is enhanced using thin wicking structures that are 0.17 mm thick in counterflow with vapor. Liquid is segregated in the wicks by applying a siphon relative to the vapor phase, which also enables the device to operate horizontally. A scalable device containing 11 wicks was operated cryogenically in total reflux. The HETP varied between 1.2 and 4.5 cm, representing a dramatic reduction over commercial structured packings and comparable to other PI approaches. Significant improvements are expected with further development. Potential application for intensified distillation processes include distributed manufacturing and difficult separations involving close boiling compounds and meeting high purity specifications. The ultimate application is isotopic enrichment, where the number of stages required is typically multiple thousands. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-06-30
  • Product design: Nanoparticle‐Loaded polyvinyl butyral interlayer for solar control
    AlChE J. (IF 3.326) Pub Date : 2018-06-11
    Shaqi Ge; Neng Wang; Ka Yip Fung; Ka Wai Wong; Che Ting Chan; Ka Ming Ng

    A systematic procedure for the design of nanoparticle‐loaded polyvinyl butyral (PVB) interlayer for solar control applications is developed. Desirable product attributes—transparency, energy savings, pleasant color, and so on and the related product specifications—transmittance of visible light, solar heat gain coefficient, color coordinates, and so on are met by properly selecting the type(s) of nanoparticles, their volume fraction in the PVB interlayer, and so on. The selection is based on the Maxwell Garnett relation to account for the localized surface plasmon resonance of the nanoparticles, Beer–Lambert's law, various international standards, and a database of transmittance and reflectance developed in our laboratory. The final product that meets all the product specifications as verified by prototypes is obtained by iterating between predictions and experiments. A causal table is provided to guide the verification step. Two examples of preparing solar control PVB interlayers with different specifications are provided to illustrate this design procedure. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-06-30
  • Identification of the pyranonigrin A biosynthetic gene cluster by genome mining in Penicillium thymicola IBT 5891
    AlChE J. (IF 3.326) Pub Date : 27 June 20
    Man‐Cheng Tang; Yi Zou; Danielle Yee; Yi Tang

    A polyketide synthase and nonribosomal peptide synthetase hybrid gene cluster from the genome of Penicillium thymicola was identified through genome mining. Heterologous expression of this cluster leads to the production of pyranonigrin A. A series of experiments established that only four genes are sufficient to biosynthesize pyranonigrin A. Based on the results from the current study, a biosynthetic pathway of pyranonigrin A is proposed. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-06-28
  • Highly efficient separation of methane from nitrogen on a squarate‐based metal‐organic framework
    AlChE J. (IF 3.326) Pub Date : 2018-06-11
    Liangying Li; Lifeng Yang; Jiawei Wang; Zhiguo Zhang; Qiwei Yang; Yiwen Yang; Qilong Ren; Zongbi Bao

    Highly selective capture of methane from nitrogen is considered to be a feasible approach to improve the heating value of methane and mitigate the effects of global warming. In this work, an ultramicroporous squarate‐based metal‐organic framework (MOF), [Co3(C4O4)2(OH)2] (C4O42− = squarate), with enhanced negative oxygen binding sites was synthesized for the first time and used as adsorbent for efficient separation of methane and nitrogen. Adsorption performance of this material was evaluated by single‐component adsorption isotherms and breakthrough experiments. Furthermore, density functional theory calculation was performed to gain the deep insight into the adsorption binding sites. Compared with the other state‐of‐the‐art materials, this material exhibited the highest adsorption selectivity (8.5–12.5) of methane over nitrogen as well as the moderate volumetric uptake of methane (19.81 cm3/cm3) under ambient condition. The unprecedented selectivity and chemical stability guaranteed this MOF as a candidate adsorbent to capture CH4 from N2, especially for the unconventional natural gas upgrading. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-06-28
  • Modeling flow distribution and pressure drop in redox flow batteries
    AlChE J. (IF 3.326) Pub Date : 2018-06-25
    Malcolm MacDonald; Robert M. Darling

    The combination of interdigitated flow fields (IDFF) with porous electrodes offers lower pressure drop and better performance than conventional flow‐through porous electrodes in redox flow batteries. Comprehensive three‐dimensional and simplified one‐dimensional + two‐dimensional models describing flow uniformity and pressure losses within flow through, parallel, and interdigitated flow fields were developed and used to demonstrate the benefits of IDFF. Analytical solutions for IDFF that compare favorably with computational fluid dynamics quantify the trade between pressure loss and velocity maldistribution both along the channels and within the electrode. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-06-27
  • Kinetic parameter estimation based on spectroscopic data with unknown absorbing species
    AlChE J. (IF 3.326) Pub Date : 2018-06-11
    Weifeng Chen; Lorenz T. Biegler; Salvador García Muñoz

    In many studies, kinetic parameter estimation from spectroscopic data is performed with the absorbing species known beforehand, as this provides a straightforward link between the reaction models to the spectroscopic data. In practice, however, the absorbing species are generally unknown and they are only estimated based on professional experience and prior knowledge of the kinetic reaction. In this work, we propose an optimization strategy with both continuous and discrete decision variables in order to estimate kinetic parameters from spectroscopic data with unknown absorbing species. Also included in our approach is an estimability analysis for kinetic parameters based on the Gram‐Schmidt orthogonalization procedure, along with covariance estimation. Four case studies were considered, which demonstrate the effectiveness of our approach. The first and second have simulated data and illustrate our approach with known solutions. The third and fourth are based on actual experiments from spectroscopy data sets. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-06-27
  • Design of metallic nickel hollow fiber membrane modules for pure hydrogen separation
    AlChE J. (IF 3.326) Pub Date : 2018-06-11
    Yuan Li; Mingzhi Zhang; Yuanyuan Chu; Xiaoyao Tan; Jun Gao; Shaobin Wang; Shaomin Liu

    Cost‐effective and robust nickel (Ni) membrane for H2 separation is a promising technology to upgrade the conventional H2 industries with improved economics and environmental benignity. In this work, Ni hollow fibers (HFs) with one closed end were fabricated and assembled into a membrane module for pure H2 separation by applying vacuum to the permeate side. The separation behavior of the HF module was investigated both experimentally and theoretically. Results indicate that H2 recovery can be improved significantly by changing the operation conditions (temperature or feed pressure). Ni HF is a promising membrane geometry, but the negative effect of pressure drop when H2 passes through the lumen cannot be ignored. Under the vacuum operation mode, there is little difference in term of H2 recovery efficiency whether the feed gas flow is controlled in countercurrent or recurrent operation. This work provides important insight to the development of superior membrane H2 separation system. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-06-27
  • Promoted adsorption of CO2 on amine‐impregnated adsorbents by functionalized ionic liquids
    AlChE J. (IF 3.326) Pub Date : 2018-06-11
    Fujian Liu; Kuan Huang; Lilong Jiang

    Amine‐impregnated adsorbents are promising alternatives to aqueous amines for CO2 capture. However, the diffusion‐controlled CO2 adsorption process is a significant issue associated with them, resulting in the insufficient utilization of amine groups. Herein, we propose the use of functionalized ionic liquids 1‐ethyl‐3‐methylimidazolium acetate ([emim][Ac]) with chemical reactivity to CO2 and low viscosity as the additive to amine‐impregnated adsorbents. The key is that [emim][Ac] does not show drastic increase in viscosity after reacting with CO2. Taking the polyethyleneimine (PEI)‐impregnated SBA‐15 as a model system, it is found that the CO2 capacities of PEI/SBA‐15 composites are improved by 86%, and the active site efficiencies are improved by 270%, after the addition of [emim][Ac]. The addition of [emim][Ac] to PEI/SBA‐15 composites also helps improve the CO2 adsorption rate and recycling stability of composites. Therefore, [emim][Ac] offers the opportunity to fabricate amine‐impregnated adsorbents with simultaneously improved CO2 capacities, adsorption kinetics, and recycling stability. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-06-27
  • Revisiting electrolyte thermodynamic models: Insights from molecular simulations
    AlChE J. (IF 3.326) Pub Date : 2018-06-23
    Nazir Hossain; Ashwin Ravichandran; Rajesh Khare; Chau‐Chyun Chen

    Pitzer and electrolyte nonrandom two‐liquid (eNRTL) models are the two most widely used electrolyte thermodynamic models. For aqueous sodium chloride (NaCl) solution, both models correlate the experimental mean ionic activity coefficient (γ±) data satisfactorily up to salt saturation concentration, that is, ionic strength around 6 m. However, beyond 6 m, the model extrapolations deviate significantly and diverge from each other. We examine this divergence by calculating the mean ionic activity coefficient over a wide range of concentration based on molecular simulations and Kirkwood–Buff theory. The asymptotic behavior of the activity coefficient predicted by the eNRTL model is consistent with the molecular simulation results and supersaturation experimental data. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-06-25
  • Effect of the CaO sintering on the calcination rate of CaCO3 under atmospheres containing CO2
    AlChE J. (IF 3.326) Pub Date : 2018-06-11
    Juan C. Maya; Farid Chejne; Carlos A. Gómez; Suresh K. Bhatia

    For the calcination of CaCO3 under CO2‐containing atmospheres, a mathematical model taking into account the CO2‐catalyzed sintering of the CaO product layer is developed. In this model, a modified shrinking core model is coupled with a population balance‐based sintering model. By comparing model predictions with experimental data, it is found that CO2 strongly affects the overall calcination rate both at high temperature and CO2 partial pressure, since under these conditions CaO densification considerably reduces the effective diffusivity of CO2 within product layer. It is observed that for large particles, the CO2‐catalyzed sintering of CaO can produce the “die off” phenomenon, which takes place when the reaction stops due to the blockage of pores within product layer. Finally, it was determined that limestone impurities do not significantly affect the calcination reaction under atmospheres containing CO2, because CO2 causes a much greater increase of the CaO sintering rate than limestone impurities do. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-06-25
  • Constraint‐based metabolic targets for the improved production of heterologous compounds across molecular classification
    AlChE J. (IF 3.326) Pub Date : 2018-06-20
    Nicholas Moscatello; Blaine A. Pfeifer

    The natural products 6‐deoxyerythronolide B (6dEB), erythromycin D, yersiniabactin (Ybt), and salicylate 2‐O‐β‐D‐glucoside (SAG), representing a range of primary and secondary metabolites generated through heterologous microbial biosynthesis, were analyzed using computational metabolic engineering for the purpose of predicting improved production. Specifically, flux balance analysis (FBA) allowed for the comprehensive screening of medium components and the determination of single gene deletions that resulted in improved product titers for the target compounds. Outcomes included the identification of amino acids and alternative carbon sources capable of culture medium supplementation for increased cellular production. Separately, Minimization of Metabolic Adjustment (MoMA) and OptForce were used to identify single gene deletion and over‐expression targets, respectively, for improvements to the aforementioned biosynthetic schemes. The computational engineering predictions thus provide a starting point for experimental implementation with the goal of improving metabolic carbon flow to the compounds presented in this study, each of which possesses valuable bioactivity.

    更新日期:2018-06-22
  • SbOx‐promoted Pt Nanoparticles Supported on CNTs as Catalysts for Base‐free Oxidation of Glycerol to Dihydroxyacetone
    AlChE J. (IF 3.326) Pub Date : 2018-06-19
    Xuezhi Duan; Yanfang Zhang; Minjian Pan; Hua Dong; Bingxu Chen; Yuanyuan Ma; Gang Qian; Xinggui Zhou; Jia Yang; De Chen

    Understanding of selective base‐free oxidation of glycerol to dihydroxyacetone (DHA) over Pt‐based catalysts is of paramount scientific and industrial importance. In this work, a comparative study between differently sized SbOx‐promoted and unpromoted Pt/CNTs catalysts is carried out to decouple the promoter effects from the metal size effects. The introduction of SbOx appears to enhance both the glycerol oxidation activity and the DHA selectivity, and the largely sized promoted Pt/CNTs catalysts afford a relatively high DHA yield and less C‐C bond cleavage. XPS measurements reveal that the Sb species are mainly in the form of SbOx, and the differently sized promoted catalysts show similar metal binding energies. Furthermore, theoretical studies on the promotional effects of SbOx are carried out by DFT calculations. It is found that the presence of the promoter on the catalyst surface favors the preferential activation of the secondary hydroxyl group. This article is protected by copyright. All rights reserved.

    更新日期:2018-06-20
  • Measurements and Correlations for Gas Liquid Surface Tension at High Pressure and High Temperature
    AlChE J. (IF 3.326) Pub Date : 2018-06-19
    C. Leonard; J‐H. Ferrasse; O. Boutin; S. Lefevre; A. Viand

    Surface tension of water/nitrogen and water‐phenol/nitrogen systems was successfully measured by the hanging drop method in a wide domain of temperature (from 100 to 300°C) and pressure (from 4 to 30MPa), conditions little explored literature. Results show that surface tension of water‐phenol mixtures decreases as phenol mass fraction increases. This decrease is observed under saturated and unsaturated conditions and is more pronounced at low temperatures and does not seem to depend on pressure. The effect of saturation on surface tension in the water/nitrogen system has been correlated with water vapor pressure by using experimental points with a great accuracy. For the water‐phenol/nitrogen system, experimental data obtained with different mass fraction of phenol were correlated using Macleod‐Sugden equation for mixtures. This article is protected by copyright. All rights reserved.

    更新日期:2018-06-20
  • Heterogeneous production of Cl2 from particulate chloride: Effects of composition and relative humidity
    AlChE J. (IF 3.326) Pub Date : 2018-05-07
    Cameron B. Faxon; Surya Venkatesh Dhulipala; David T. Allen; Lea Hildebrandt Ruiz

    Reactions initiated by chlorine atoms can enhance the formation of ozone (O3) and secondary organic aerosol (SOA) in the troposphere. Environmental chamber experiments were conducted to quantify heterogeneous Cl2 production from NH4Cl and NaCl particles exposed to O3 and hydroxyl radicals (•OH). Observations are inconsistent with models of Cl2 production resulting solely from surface‐mediated reactions of •OH and suggest that O3 plays a significant role. The production of Cl2 increased with relative humidity and decreased in the presence of SOA or nitric oxides (NOx). Heterogeneous reactive uptake coefficients for the production of Cl2 from O3 on pure NH4Cl ( ) averaged 1.4 ± 1.0 × 10−3. Cl2 production was six times more efficient on NH4Cl aerosol than on NaCl aerosol. Model calculations under atmospheric conditions suggest this heterogeneous Cl2 production could increase peak daily O3 concentrations by over 10%. © 2018 American Institute of Chemical Engineers AIChE J, 2018

    更新日期:2018-06-07
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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