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  • The solubility of gases in ionic liquids
    AlChE J. (IF 2.836) Pub Date : 2017-09-21
    Mark B. Shiflett, Edward J. Maginn

    In this Perspective, we provide a detailed discussion of the techniques and methods used for determining the solubility of gases in ionic liquids (ILs). This includes various experimental measurement techniques, equation of state (EOS) modeling, and predictive molecular-based modeling. Many of the key papers from the past 15 years are discussed and put into the context of the latest advances in the field. Limitations of these methods plus future developments and new research opportunities are discussed. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-21
  • Multiscale modeling of methane catalytic partial oxidation: From the mesopore to the full-scale reactor operation
    AlChE J. (IF 2.836) Pub Date : 2017-09-21
    Jorge E. P. Navalho, José M. C. Pereira, José C. F. Pereira

    A multiscale methodology combining three different reactor length-scales is presented to investigate the role of the catalyst internal pore structure and metal loading and dispersion on the catalyst layer and full-scale reactor performances. At the catalyst level, the methodology involves pore-scale simulations in the three-dimensional mesopore and macropore space. The information gathered at the catalyst level is delivered to the full-scale reactor model. The methodology is applied to a honeycomb reactor performing methane partial oxidation considering reaction kinetics described through a detailed multistep reaction mechanism. Realistic mesopore and macropore structures were reconstructed and combined to form specific bidisperse porous washcoat layers. The study shows that species effective diffusivities vary significantly but not in the same proportion for different structures. For structures featuring poor transport characteristics, the integral methane conversion and hydrogen selectivity are strongly affected while the reactor temperatures increase substantially. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-21
  • Flow field design and optimization of high power density vanadium flow batteries: A novel trapezoid flow battery
    AlChE J. (IF 2.836) Pub Date : 2017-09-20
    Meng Yue, Qiong Zheng, Huamin Zhang, Xianfeng Li, Xiangkun Ma

    Vanadium flow battery (VFB) is one of the preferred techniques for efficient large-scale energy storage applications. The key issue for its commercialization is cost reduction, which can be achieved by developing high power density VFB stacks. One of the effective strategies for developing high power density stacks is to enhance the mass transport by performing flow field design. Based on the maldistribution characteristics of concentration polarization inside a conventional rectangular flow battery (RFB), a novel trapezoid flow battery (TFB) was first proposed. Furthermore, a practical and general strategy, consisting of a stepping optimization method and an arithmetic progression model, has been developed for the TFB's structure optimization. By combining numerical simulation with charge-discharge test of the magnified stacks, it was verified that mass transport enhancement and performance improvement of the optimized TFB, with significant increments in voltage efficiency and electrolyte utilization, allowed it to possess great superiority over the RFB. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-20
  • Flow of viscoelastic surfactants through porous media
    AlChE J. (IF 2.836) Pub Date : 2017-09-19
    S. De, S. P. Koesen, R. V. Maitri, M. Golombok, J. T. Padding, J. F. M. van Santvoort

    We compare the flow behavior of viscoelastic surfactant (VES) solutions and Newtonian fluids through two different model porous media having similar permeability: (a) a 3D random packed bed and (b) a microchannel with a periodically spaced pillars. The former provides much larger flow resistance at the same apparent shear rate compared to the latter. The flow profile in the 3D packed bed cannot be observed since it is a closed system. However, visualization of the flow profile in the microchannel shows strong spatial and temporal flow instabilities in VES fluids appear above a critical shear rate. The onset of such elastic instabilities correlates to the flow rate where increased flow resistance is observed. The elastic instabilities are attributed to the formation of transient shear induced structures. The experiments provide a detailed insight into the complex interplay between the pore scale geometry and rheology of VES in the creeping flow regime. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-19
  • Verification of Eulerian–Eulerian and Eulerian–Lagrangian simulations for turbulent fluid–particle flows
    AlChE J. (IF 2.836) Pub Date : 2017-09-18
    Ravi G. Patel, Olivier Desjardins, Bo Kong, Jesse Capecelatro, Rodney O. Fox

    We present a verification study of three simulation techniques for fluid–particle flows, including an Euler–Lagrange approach (EL) inspired by Jackson's seminal work on fluidized particles, a quadrature–based moment method based on the anisotropic Gaussian closure (AG), and the traditional two-fluid model. We perform simulations of two problems: particles in frozen homogeneous isotropic turbulence (HIT) and cluster-induced turbulence (CIT). For verification, we evaluate various techniques for extracting statistics from EL and study the convergence properties of the three methods under grid refinement. The convergence is found to depend on the simulation method and on the problem, with CIT simulations posing fewer difficulties than HIT. Specifically, EL converges under refinement for both HIT and CIT, but statistics exhibit dependence on the postprocessing parameters. For CIT, AG produces similar results to EL. For HIT, converging both TFM and AG poses challenges. Overall, extracting converged, parameter-independent Eulerian statistics remains a challenge for all methods. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-18
  • Modular methanol manufacturing from shale gas: Techno-economic and environmental analyses of conventional large-scale production versus small-scale distributed, modular processing
    AlChE J. (IF 2.836) Pub Date : 2017-09-17
    Minbo Yang, Fengqi You

    This article presents comparative techno-economic and environmental analyses of four representative shale gas monetization options, namely, conventional shale gas processing, large-scale methanol manufacturing, modular methanol manufacturing with shale gas supplied by pipelines, and modular methanol manufacturing with consideration of plant relocation. We first present shale gas supply models for the four gas monetization options. Next, the process designs for shale gas processing and methanol manufacturing from shale gas are described. We develop detailed process simulation models for shale gas processing and methanol manufacturing with different scales using raw shale gas extracted from the Marcellus, Eagle Ford, and Bakken shale plays. On this basis, techno-economic analyses and environmental impact analyses are conducted for the four shale gas monetization options to systematically compare their economic and environmental performances based on the same conditions. The results show that modular methanol manufacturing is more economically competitive than conventional shale gas processing, although it leads to higher environmental impacts. Besides, modular methanol manufacturing is better than large-scale methanol manufacturing for raw shale gas produced from distributed, remote wells from both economic and environmental perspectives. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-18
  • Settling and re-entrainment of wax particles in near-gelling systems
    AlChE J. (IF 2.836) Pub Date : 2017-09-14
    Seetharaman Navaneetha Kannan, Nagu Daraboina, Rama Venkatesan, Cem Sarica

    Under near-gelling conditions, the precipitated wax particles can settle down due to gravity and form a bed at the bottom of the pipeline. During restart, the settled waxy bed can increase the pressure drop significantly, and the necessity for pigging and/or addition of chemicals has to be determined to re-entrain settled wax particles. A laboratory-scale flow loop, first of its kind, has been built and used to understand the settling and re-entrainment behavior. The experimental results confirmed the settling of precipitated wax in a pipe under quiescent conditions when the oil temperature falls between wax appearance temperature and pour point. During restart, complete re-entrainment was attained after reaching a critical flow rate. Solid transport models were able to predict reasonably good results in agreement with experiments. This work emphasizes the importance of understanding the behavior of waxy crude oil during production shutdown and design appropriate startup strategies. © 2017 American Institute of Chemical Engineers AIChE J, 00: 000–000, 2017

    更新日期:2017-09-14
  • Adsorption separation of R134a, R125, and R143a fluorocarbon mixtures using 13X and surface modified 5A zeolites
    AlChE J. (IF 2.836) Pub Date : 2017-09-14
    Darshika K. J. A. Wanigarathna, Bin Liu, Jiajian Gao

    We report a facile method for the adsorption separation of fluorocarbon blends containing tetrafluoroethane (R134a), pentafluoroethane (R125) and trifluoroethane (R143a) refrigerants into their pure components using commercial 13X zeolite and pore-size modified 5A zeolite under ambient condition. Based on the measured R134a, R125, and R143a pure gas equilibrium adsorption isotherms, the adsorption capacity varies in the order of R134a > R143a > R125 on 13X zeolite. The mixed gas breakthrough experiments reveal that 13X zeolite selectively adsorbs R134a over R125 and R143a. By running two adsorption cycles, it is possible to obtain R134a with ultrahigh purity. Furthermore, through chemical modification of tetraethyl orthosilicate (TEOS), the pore size of 5A zeolite could be successfully narrowed to the extent to just adsorb R125 while excluding R143a. The modified 5A zeolite was utilized to separate refrigerant mixtures containing R125 and R143a into their pure components. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-14
  • The effect of liquid bridge model details on the dynamics of wet fluidized beds
    AlChE J. (IF 2.836) Pub Date : 2017-09-13
    Mingqiu Wu, Johannes G. Khinast, Stefan Radl

    Wet fluidized beds of particles in small periodic domains are simulated using the CFD-DEM approach. A liquid bridge is formed upon particle-particle collisions, which then ruptures when the particle separation exceeds a critical distance. The simulations take into account both surface tension and viscous forces due to the liquid bridge. We perform a series of simulations based on different liquid bridge formation models: (1) the static bridge model of Shi and McCarthy, (2) a simple static version of the model of Wu et al., as well as (3) the full dynamic bridge model of Wu et al. We systematically compare the differences caused by different liquid bridge formation models, as well as their sensitivity to system parameters. Finally, we provide recommendations for which systems a dynamic liquid bridge model must be used, and for which application this appears to be less important. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-13
  • Model of inertial spreading and imbibition of a liquid drop on a capillary plate
    AlChE J. (IF 2.836) Pub Date : 2017-09-13
    Michel Y. Louge, Shilpa Sahoo

    We outline a low-order Lagrangian model for the inertial dynamics of spreading and imbibition of a spherical liquid cap on a plane featuring independent cylindrical capillaries without gravity. The analysis predicts the relative roles of radial and axial kinetic energy, reveals the critical Laplace number beyond which the drop oscillates, and attributes the exponent of the initial power-law for contact patch radius vs. time to the form of capillary potential energy just after the liquid sphere touches the plate. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-13
  • Nonlinear robust optimization for process design
    AlChE J. (IF 2.836) Pub Date : 2017-09-12
    Yuan Yuan, Zukui Li, Biao Huang

    A novel robust optimization framework is proposed to address general nonlinear problems in process design. Local linearization is taken with respect to the uncertain parameters around multiple realizations of the uncertainty, and an iterative algorithm is implemented to solve the problem. Furthermore, the proposed methodology can handle different categories of problems according to the complexity of the problems. First, inequality-only constrained optimization problem as studied in most existing robust optimization methods can be addressed. Second, the proposed framework can deal with problems with equality constraint associated with uncertain parameters. In the final case, we investigate problems with operation variables which can be adjusted according to the realizations of uncertainty. A local affinely adjustable decision rule is adopted for the operation variables (i.e., an affine function of the uncertain parameter). Different applications corresponding to different classes of problems are used to demonstrate the effectiveness of the proposed nonlinear robust optimization framework. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-12
  • Chemical solvent in chemical solvent: A class of hybrid materials for effective capture of CO2
    AlChE J. (IF 2.836) Pub Date : 2017-09-12
    Feng-Feng Chen, Kuan Huang, Jie-Ping Fan, Duan-Jian Tao

    Amino acid ionic liquids (AAILs) are chemical solvents with high reactivity to CO2. However, they suffer from drastic increase in viscosity on the reaction with CO2, which significantly limits their application in the industrial capture of CO2. In this work, 1-ethyl-3-methylimidazolium acetate ([emim][Ac]) which also exhibits chemical affinity to CO2 but low viscosity, and its viscosity does not increase drastically after CO2 absorption, was proposed as the diluent for AAILs to fabricate hybrid materials. The AAIL+[emim][Ac] hybrids were found to display enhanced kinetics for CO2 absorption, and their viscosity increase after CO2 absorption are much less significant than pure AAILs. More importantly, owing to the fact that [emim][Ac] itself can absorb large amount of CO2, the AAIL+[emim][Ac] hybrids still have high absolute capacities of CO2. Such hybrid materials consisting of a chemical solvent plus another chemical solvent are believed to be a class of effective absorbents for CO2 capture. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-12
  • Gravitational discharge of fine dry powders with asperities from a conical hopper
    AlChE J. (IF 2.836) Pub Date : 2017-09-12
    Hui Lu, Jia Zhong, Gui-Ping Cao, Hai-Feng Liu

    The effects of particle properties, especially the surface roughness and particle type, on the gravity discharge rate and flow behavior of fine dry powders from a conical hopper are studied in detail. The van der Waals force is considered to dominate the discharge of small particles, while the empty annulus effect dominates the discharge of large particles. To predict the van der Waals force between two rough spherical particles, a model based on Rumpf theory is adopted. The effect of surface roughness can be reflected by Bond number Bog which is correlated with discharge rate. By modifying the powder bed porosity and Beverloo constant, the discharge rates of fine dry powders can be well predicted by an empirical correlation. Finally, not only the ratio of hopper outlet size to particle size D0/dp but also the Bond number Bog is found to be an important indicator to determine the powder flowability. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-12
  • Organocatalyzed Beckmann rearrangement of cyclohexanone oxime in a microreactor: Kinetic model and product inhibition
    AlChE J. (IF 2.836) Pub Date : 2017-09-12
    Chencan Du, Jisong Zhang, Guangsheng Luo

    The kinetic study of Beckmann rearrangement of cyclohexanone oxime catalyzed by trifluoroacetic acid and acetonitrile in a microreactor is presented in this article. Parametric studies are conducted varying temperature, ratio of trifluoroacetic acid to acetonitrile, and concentration of cyclohexanone oxime. The inhibition effect of ɛ-caprolactam in this reaction system is firstly reported. A comprehensive mathematic kinetic model considering the product inhibition effect of caprolactam has been developed in the temperature range of 368–391 K, which agrees well with the experimental results across a broad experimental parameter space. In addition, kinetic study indicates that the esterification of cyclohexanone oxime and transposition reaction of the intermediate are both supposed to be the rate-determining steps, and in this catalyst system, the ratio of trifluoroacetic acid and acetonitrile mainly influences the reaction rate and the activation energy of the transposition step. The developed model could provide much reliable knowledge for industrial application. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-12
  • Sorption enhanced reaction for high purity products in reversible reactions
    AlChE J. (IF 2.836) Pub Date : 2017-09-12
    Fan Ni, Hugo S. Caram

    Reversible reactions (A + B = C + D) can be performed to near completion using an admixture of catalyst and sorbent that will selectively adsorb one of the reaction products. For an initially clean sorbent and a favorable adsorption isotherm and a long reactor, the adsorbed product, C, will propagate as a sharp, shock-like front. While the adsorbed product will not move faster than this front, the second, nonadsorbed product, D, will, in principle, leave the reactor, uncontaminated. However, a parametric analysis of the two examples presented in this work, the water gas shift and the cracking of hydrogen sulfide, reveals an unexpectedly complex behavior. While assuming adsorption equilibrium the effect of the equilibrium constant, the reaction kinetics and adsorption isotherm on the reactant and product concentration profiles are simulated. It is found that desired behavior is favored by large equilibrium constants, rapid kinetics, and strong nonlinear adsorption. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-12
  • Novel semi-interpenetrating network structural phase change composites with high phase change enthalpy
    AlChE J. (IF 2.836) Pub Date : 2017-09-12
    Yuang Zhang, Jinghai Xiu, Bingtao Tang, Rongwen Lu, Shufen Zhang

    High phase change enthalpy, controllable temperature, and stable shape can expand the application of phase change materials (PCMs) in energy storage. In this study, a series of novel form-stable PCMs with high phase change enthalpy (169–195 J/g) and controllable temperature (45.3–61.4°C) were prepared. The PCMs exhibited a semi-interpenetrating polymer network (semi-IPN) structure resulting from the combination of polyethylene glycol (PEG) and a three-dimensional (3-D) network gel. The gel itself featured an inherent phase change characteristic and a 3-D network structure. Thus, it improved the phase transition enthalpy of the materials and facilitated the formation of a semi-IPN that endowed the materials with excellent form-stable properties. In addition, the latent heat of the composites (169–195 J/g) is much higher than most of the previously reported composites using PEG as phase change component (68–132 J/g). © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-12
  • Confinement of a polymer chain: An entropic study by Monte Carlo method
    AlChE J. (IF 2.836) Pub Date : 2017-09-08
    Flavia Ruggiero, Rosaria Aruta, Paolo Antonio Netti, Enza Torino

    The properties of macromolecules in presence of an interface could be considerably modified due to confinement effects. When phase separations are performed in nanoconfined domains, the concurrent presence of high-energy interfaces and conformational entropy constraints of the macromolecules causes profound differences in polymer aggregation behavior. Here, thermodynamics of a polymer chain in solution, confined by a three-dimensional cubic interface, is studied by means of Monte Carlo method, focusing on the chain conformational entropy penalty arising from the excluded volume effects. The presented method might become a general tool for a preliminary evaluation of the thermodynamic effects due to the confinement of a polymer system. Further, the interface effects on Thermally Induced Phase Separation (TIPS) of polymer solutions, confined by High-Pressure Homogenization, are experimentally studied, regarding final morphologies. It is confirmed how peculiar polymer morphologies are obtained only when the TIPS develops under nanoconfinement degrees above a threshold one. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-08
  • Nanoparticles@rGO membrane enabling highly enhanced water permeability and structural stability with preserved selectivity
    AlChE J. (IF 2.836) Pub Date : 2017-09-06
    Mengchen Zhang, Kecheng Guan, Jie Shen, Gongping Liu, Yiqun Fan, Wanqin Jin

    Developing advanced membranes with high separation performance and robust mechanical properties is critical to the current water crisis. Herein, a general and scalable fabrication of nanoparticles (NPs)@reduced graphene oxide (rGO) membranes with significantly expanded nanochannels meanwhile ordered laminar structures using in situ synthesized NPs@rGO nanosheets as building blocks is reported. Size- and density-controllable NPs were uniformly grown on the regularly stacked rGO nanosheets through coordination, followed by filtration-deposition on inner surface of porous ceramic tubes. The NPs bonded rGO building blocks enabled the as-prepared membranes 1–2 orders of magnitudes higher water permeance than the counterparts while keeping excellent rejections for various organic matters and ions. Moreover, the industrially preferred GO-based tubular membrane exhibited an extraordinary structural stability under high-pressure and cross-flow process of water purification, which is considered as a notable step toward realizing scalable GO-based membranes. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-07
  • Dynamic modeling and simulations of the behavior of a fixed-bed reactor-exchanger used for CO2 methanation
    AlChE J. (IF 2.836) Pub Date : 2017-09-05
    Rasmey Try, Alain Bengaouer, Pierre Baurens, Christian Jallut

    A multidimensional heterogeneous and dynamic model of a fixed-bed heat exchanger reactor used for CO2 methanation has been developed in this work that is based on mass, energy and momentum balances in the gas phase and mass and energy balances for the catalyst phase. The dynamic behavior of this reactor is simulated for transient variations in inlet gas temperature, cooling temperature, gas inlet flow rate, and outlet pressure. Simulation results showed that wrong-way behaviors can occur for any abrupt temperature changes. Conversely, temperature ramp changes enable to attenuate and even fade the wrong-way behavior. Traveling hot spots appear only when the change of an operating condition shifts the reactor from an ignited steady state to a non-ignited one. Inlet gas flow rate variations reveal overshoots and undershoots of the reactor maximum temperature. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-05
  • Automated measurements of gas-liquid mass transfer in micropacked bed reactors
    AlChE J. (IF 2.836) Pub Date : 2017-09-05
    Jisong Zhang, Andrew R. Teixeira, Klavs F. Jensen

    Gas-liquid mass transfer in micropacked bed reactors is characterized with an automated platform integrated with in-line Fourier transform infrared spectroscopy. This setup enables screening of a multidimensional parameter space underlying absorption with chemical reaction. Volumetric gas-liquid mass-transfer coefficients (kLa) are determined for the model reaction of CO2 absorption in a methyl diethanolamine/water solution. Parametric studies are conducted varying gas and liquid superficial velocities, packed bed dimensions and packing particle sizes. The results show that kLa values are in the range of 0.12∼0.39 s−1, which is about one-to-two orders of magnitude larger than those of conventional trickle beds. An empirical correlation predicts kLa in micropacked bed reactors in good agreement with experimental data. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-05
  • On the use of a powder rheometer to characterize the powder flowability at low consolidation with torque resistances
    AlChE J. (IF 2.836) Pub Date : 2017-09-02
    Hamid Salehi, Diego Barletta, Massimo Poletto, Denis Schütz, Richard Romirer

    The Anton Paar Powder Cell was used to measure the torque necessary to rotate an impeller in beds of glass beads, sand and alumina powders aerated between no aeration to the minimum for fluidization. Measured torque values depend on the material tested, on the air flow rate applied, on the impeller depth and on the height of the impeller blade. The effect of the impeller depth is linear for low impeller depth and is less than linear at high depth values. A model was developed for the interpretation of the experimental results based on the idea that the material is shearing on the surface described by the impeller rotation. The model allows to estimate an effectiveness of the impeller in the torque determination and also to predict the torque for the impeller at the at deepest positions at which the wall effects have to be considered. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-04
  • La-hexaaluminate for synthesis gas generation by Chemical Looping Partial Oxidation of Methane Using CO2 as Sole Oxidant
    AlChE J. (IF 2.836) Pub Date : 2017-09-01
    Yanyan Zhu, Weiwei Liu, Xueyan Sun, Xiaoxun Ma, Yu Kang, Xiaodong Wang, Junhu Wang

    Chemical looping partial oxidation of methane using a sole CO2 oxidant (CL-POM-CO2) is an emerging technology for synthesis gas generation and CO2 utilization, which is highly dependent on an oxygen carrier (OC). In this work, Fe-substituted La-hexaaluminate as the OC was found to exhibit good reactivity and stability during 50 periodic CH4/CO2 redox cycles due to the formation of magnetoplumbite La-hexaaluminate structure with the introduction of La. Deeper reduction for synthesis gas generation did not destroy the La-hexaaluminate structure via a charge compensation mechanism, which increased CH4 reactivity and further improved CO2 utilization under subsequent re-oxidation. In the La-hexaaluminate structure, O6-Fe3+(Oh) was highly active for the total oxidation of methane, while O5-Fe3+(Tr) and O4-Fe3+(Th) selectively oxidized CH4 to synthesis gas. The sole CO2 oxidant only selectively recovered O5-Fe3+(Tr) and O4-Fe3+(Th), and thus is more favorable for improving synthesis gas selectivity than O2/air, which offers an attractive opportunity for CO2 utilization. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-04
  • Effects of compositional variations on CO2 foam under miscible conditions
    AlChE J. (IF 2.836) Pub Date : 2017-08-31
    Siavash Kahrobaei, Kai Li, Sebastien Vincent-Bonnieu, Rouhollah Farajzadeh

    Foam can mitigate the associated problems with the gas injection by reducing the mobility of the injected gas. The presence of an immiscible oleic phase can adversely affect the foam stability. Nevertheless, under miscible conditions gas and oil mix in different proportions forming a phase with a varying composition at the proximity of the displacement front. Therefore, it is important to understand how the compositional variations of the front affect the foam behavior. In this study through several core-flood experiments under miscible condition, three different regimes were identified based on the effects of the mixed-phase composition on CO2 foam-flow behavior: In Regime 1 the apparent viscosity of the in-situ fluid was the highest and increased with increasing xCO2. In Regime 2 the apparent viscosity increased with decreasing xCO2. In Regime 3 the apparent viscosity of the fluid remained relatively low and insensitive to the value of xCO2. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-04
  • Fenton-like degradation of rhodamine B over highly durable Cu-embedded alumina: Kinetics and mechanism
    AlChE J. (IF 2.836) Pub Date : 2017-08-31
    Yiyi Sheng, Yang Sun, Jing Xu, Jie Zhang, Yi-Fan Han

    Cu-embedded mesoporous alumina, as a Fenton-like catalyst prepared via a sol-gel method, showed excellent activity and durability for the degradation of refectory compounds. The origin of active sites for the generation of hydroxyl radicals (•OH) were thoroughly studied using multitechniques. Cu, as the only active element, could be penetrated into the bulk of alumina and some Cu atoms were embedded into the framework. The dynamic structure of surface Cu species (the variety of Cu+/Cu2+ ratio) during the reaction were determined as well. Furthermore, the structure plasticity of catalyst has proved by optimizing preparation and reaction conditions. A 98.53% degradation of RhB was recorded within 30 min, following a pseudo-first-order reaction rate expression. Electron spin resonance spectra and •OH scavenging experiments have confirmed that •OH is the main reactive oxidant for the elimination of RhB. By the surface-enhanced Raman spectroscopy and gas chromatography-mass spectrometer results, plausible pathways of RhB degradation were elaborated. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-04
  • Plasma assisted nitrogen oxide production from air: Using pulsed powered gliding arc reactor for a containerized plant
    AlChE J. (IF 2.836) Pub Date : 2017-08-31
    Bhaskar S. Patil, F. J. J. Peeters, Gerard J. van Rooij, J. A. Medrano, Fausto Gallucci, J. Lang, Qi Wang, Volker Hessel

    The production of NOx from air and air + O2 is investigated in a pulsed powered milli-scale gliding arc (GA) reactor, aiming at a containerized process for fertilizer production. Influence of feed mixture, flow rate, temperature, and Ar and O2 content are investigated at varying specific energy input. The findings are correlated with high-speed imaging of the GA dynamics. An O2 content of 40–48% was optimum, with an enhancement of 11% in NOx production. Addition of Ar and preheating of the feed resulted in lower NOx production. Lower flow rates produced higher NOx concentrations due to longer residence time in the GA. The volume covered by GA depends strongly on the gas flow rate, emphasizing that the gas flow rate has a major impact on the GA dynamics and the reaction kinetics. For 0.5 L/min, 1.4 vol % of NOx concentration was realized, which is promising for a containerized process plant to produce fertilizer in remote locations. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-04
  • Economic assessment of carbon capture by minichannel absorbers
    AlChE J. (IF 2.836) Pub Date : 2017-08-31
    Ziqiang Yang, Tariq S. Khan, Mohamed Alshehhi, Yasser F. AlWahedi

    In this work, a physio-economic model supported by lab-scale experiments assessing the economic viability of minichannel based carbon capture units is presented. The net present value of (capital and operating) costs (NPVC) ensued throughout the plant life is selected as the benchmarking parameter. An optimization problem is formulated and solved with the objective of minimizing the NPVC of the unit subject to constraints imposed by the physics of absorption and pressure drop limits; both of which are captured via experimentally deduced empirical correlations. The results show that the minichannel absorbers are economically competitive to conventional systems for low capacity CO2 capture achieving savings ranging from ∼50% to 3% for plant capacities ranging from 5 to 50 MMSCFD, respectively, primarily due to their lower capital costs. At higher plant capacities, the higher operating costs of the minichannel units dominate their NPVC and as such lead them to lose their competitiveness. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-04
  • Experiments on breakup of bubbles in a turbulent flow
    AlChE J. (IF 2.836) Pub Date : 2017-08-31
    Jiří Vejražka, Mária Zedníková, Petr Stanovský

    The breakup of air bubbles in a turbulent water flow is studied experimentally. Water flows from a nozzle array, generating intense turbulence, and then flows downward through a cell. The velocity field is measured by PIV, and the local dissipation rate is estimated using a large-eddy PIV technique. Bubbles (1.8 to 5 mm) are injected in the bottom of the cell and rise toward the region of intense turbulence, where they break. The time spent by bubbles in various zones without breaking and the number of breakups are evaluated, providing information about the breakup frequency. The number of daughter bubbles and their size distribution are determined. The number of daughters depends on a Weber number , where ϵ is the turbulent energy dissipation rate, D′ is the mother particle size, ρ and σ are the liquid density and surface tension. The daughter size distribution is a function of their number. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-09-04
  • Issue information
    AlChE J. (IF 2.836) Pub Date : 2017-09-04
    更新日期:2017-09-04
  • Ultrasound–assisted synthesis and characterization of polymethyl methacrylate/reduced graphene oxide nanocomposites
    AlChE J. (IF 2.836) Pub Date : 2017-08-30
    Maneesh Kumar Poddar, Sushobhan Pradhan, Vijayanand S. Moholkar, Mohammad Arjmand, Uttandaraman Sundararaj

    This article reports ultrasound–assisted synthesis of polymethyl methacrylate (PMMA)/reduced graphene oxide (RGO) nanocomposites by in situ emulsion polymerization coupled with in situ reduction of graphene oxide. The thermal degradation kinetics of the nanocomposites was also assessed with Criado and Coats-Redfern methods. Intense microconvection generated by ultrasound and cavitation results in uniform dispersion of RGO in the polymer matrix, which imparts markedly higher physical properties to resulting nanocomposites at low (≤1.0 wt %) RGO loadings, as compared to nanocomposites synthesized with mechanical stirring. Some important properties of the PMMA/RGO nanocomposites synthesized with sonication (with various RGO loadings) are: glass transition temperature (0.4 wt %) = 124.5°C, tensile strength (0.4 wt %) = 40.4 MPa, electrical conductivity (1.0 wt %) = 2 × 10−7 S/cm, electromagnetic interference shielding effectiveness (1.0 wt %) = 3.3 dB. Predominant thermal degradation mechanism of nanocomposites (1.0 wt % RGO) is 1D diffusion with activation energy of 111.3 kJ/mol. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-30
  • Using the discrete element method to develop collisional dissipation rate models that incorporate particle shape
    AlChE J. (IF 2.836) Pub Date : 2017-08-29
    Kevin E. Buettner, Yu Guo, Jennifer S. Curtis

    Discrete Element Method simulations of Homogeneous Cooling Systems (HCS) are used to develop a collisional dissipation rate model for non-spherical particle systems that can be incorporated in a two-fluid multiphase flow framework. Two types of frictionless, elongated particle models are compared in the HCS simulations: glued-sphere and true cylinder. Simulation results show that the ratio of translational to rotational granular temperatures is equal to one for the true cylindrical particles with particle aspect ratios (AR) greater than one and glued-sphere particles with AR >1.5, while the temperature ratio is less than one for glued-sphere particles with 1 < AR <1.5. The total collisional dissipation rate, which is associated with both translational and rotational granular temperature change rates, increases linearly with the particle aspect ratio. Thus, a collisional dissipation rate model for the elongated cylinders is developed by a simple modification of the existing spherical particle model. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-29
  • CFD simulation of the effect of rain on the performance of horizontal wind turbines
    AlChE J. (IF 2.836) Pub Date : 2017-08-29
    Hamid Arastoopour, Aiden Cohan

    Wind turbine power output is influenced by environmental conditions, including rain. Therefore, a better understanding of the effect of rain on the performance of wind turbines is necessary. Our coupled Lagrangian-Eulerian multiphase computational fluid dynamics model was modified to more accurately simulate the momentum transfer during water film formation on the airfoils of a horizontal-axis turbine and the performance loss caused by the rainwater film on the National Renewable Energy Laboratory (NREL) turbine performance. To obtain three-dimensional numerical simulation of the wind turbine in manageable computational time, simplifying assumptions were made and the validity of these assumptions was verified by simulating the flow over the S809 airfoil of the NREL turbine. In a dry environment, simulation of turbine power output agreed well with NREL experimental data. Our multiphase model showed that the rain film accumulation and flow on the surface of the turbine airfoil reduces the power output of the turbine. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-29
  • Gas drying with ionic liquids
    AlChE J. (IF 2.836) Pub Date : 2017-08-29
    Jingli Han, Chengna Dai, Zhigang Lei, Biaohua Chen

    The gas drying technology with ionic liquids (ILs) was systematically studied ranging from the molecular level to industrial scale. The COSMO-RS model was first used to screen the suitable IL and provide theoretical insights at the molecular level. Toward CO2 gas dehydration, we measured the CO2 solubility in single [EMIM][Tf2N] and in the [EMIM][Tf2N] + H2O mixture, as well as the vapor-liquid equilibrium (VLE) of [EMIM][Tf2N] + H2O system, to justify the applicability of UNIFAC model. Based on the thermodynamic study, the rigorous equilibrium (EQ) stage mathematical model was established for process simulation. The gas drying experiment with IL was also performed and the water content in gas product can be reduced to 375 ppm. It was confirmed that a less flow rate of absorbent, a higher CO2 recovery ratio and a much lower energy consumption can be achieved with IL than with the conventional triethylene glycol (TEG). © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-29
  • Bubble splitting under gas–liquid–liquid three-phase flow in a double T-junction microchannel
    AlChE J. (IF 2.836) Pub Date : 2017-08-25
    Yanyan Liu, Jun Yue, Shuainan Zhao, Chaoqun Yao, Guangwen Chen

    Gas–aqueous liquid–oil three-phase flow was generated in a microchannel with a double T-junction. Under the squeezing of the dispersed aqueous phase at the second T-junction (T2), the splitting of bubbles generated from the first T-junction (T1) was investigated. During the bubble splitting process, the upstream gas–oil two-phase flow and the aqueous phase flow at T2 fluctuate in opposite phases, resulting in either independent or synchronous relationship between the instantaneous downstream and upstream bubble velocities depending on the operating conditions. Compared with two-phase flow, the modified capillary number and the ratio of the upstream velocity to the aqueous phase velocity were introduced to predict the bubble breakup time. The critical bubble breakup length and size laws of daughter bubbles/slugs were thereby proposed. These results provide an important guideline for designing microchannel structures for a precise manipulation of gas–liquid–liquid three-phase flow which finds potential applications among others in chemical synthesis. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-28
  • Protic ionic liquid as excellent shuttle of MDEA for fast capture of CO2
    AlChE J. (IF 2.836) Pub Date : 2017-08-25
    Wen-Tao Zheng, Kuan Huang, You-Ting Wu, Xing-Bang Hu

    A cheap protic ionic liquid (PIL), 3-(Dimethylamino)-1-propylamine acetate (abbreviated as [DMAPAH][Ac]), is investigated in this work as the activator of N-methyldiethanolamine (MDEA) for fast capture of CO2. The PIL-activated MDEA solutions show excellent performance in absorption rate and capacity (≥2.5 mol·kg−1). A novel absorption mechanism is proposed to account for the phenomenon, where the shuttling role of the PIL is described in detail. Additionally, the enthalpy change ΔHSOL (−45 to −52 kJ·mol−1), the turnover number of the PIL and the regeneration efficiency (>92%) are also measured. All these data show that the PIL-mediated MDEA solutions may be used as a kind of promising absorbents for fast capture of CO2. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-28
  • Particle-resolved PIV experiments of solid-liquid mixing in a turbulent stirred tank
    AlChE J. (IF 2.836) Pub Date : 2017-08-25
    Genghong Li, Zhengming Gao, Zhipeng Li, Jiawei Wang, J. J. Derksen

    Particle Image Velocimetry (PIV) experiments on turbulent solid-liquid stirred tank flow with careful refractive index matching of the two phases have been performed. The spatial resolution of the PIV data is finer than the size of the spherical, uniformly sized solid particles, thereby providing insight in the flow around individual particles. The impeller is a down-pumping pitch-blade turbine. The impeller-based Reynolds number has been fixed to Re = 104. Overall solids volume fractions up to 8% have been investigated. The PIV experiments are impeller-angle resolved, that is, conditioned on the angular position of the impeller. The two-phase systems are in partially suspended states with an inhomogeneous distribution of solids: high solids loadings near the bottom and near the outer walls of the tank, much less solids in the bulk of the tank. The liquid velocity fields show very strong phase coupling effects with the particles increasingly attenuating the overall circulation patterns as well as the liquid velocity fluctuation levels when the solids volume fraction is increased. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-28
  • Adiabatic time to maximum rate evaluation using an analytical approach
    AlChE J. (IF 2.836) Pub Date : 2017-08-25
    Roberto Sanchirico

    This article presents an analytical method for the calculation of the adiabatic time to maximum rate. The procedure is developed considering a thermal decomposition process described by a simple n-order kinetic and is based on the introduction of a special function that is possible by integrating analytically. The application of the method requires the knowledge of the thermokinetic parameters of the process under study and allows the calculation of the adiabatic time to maximum rate without the numerical integration of the heat and mass balance equations or the use of relationships based on particular simplifying hypotheses. Its validity has been demonstrated considering numerical and real experiments (thermal decomposition of trityl azide) providing in both cases times to maximum rate values which are very close to the real ones. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-28
  • Quantitative and qualitative studies of microorganisms involved in full-scale autotrophic nitrogen removal performance
    AlChE J. (IF 2.836) Pub Date : 2017-08-25
    Barbara Muñoz-Palazon, Alejandro Rodriguez-Sanchez, Antonio Castellano-Hinojosa, Jesus Gonzalez-Lopez, Mark C. M. van Loosdrecth, Riku Vahala, Alejandro Gonzalez-Martinez

    Autotrophic nitrogen removal systems have been implemented at full-scale and provide an efficient way for nitrogen removal from industrial and urban wastewaters. Our study present qualitative and quantitative analysis of archaeal and bacterial amoA genes and Candidatus Brocadiales bacteria analyzed in six full-scale autotrophic nitrogen removal bioreactors. The results showed that ammonium oxidizing bacteria (AOB) were detected in all bioreactors. However, ammonium oxidizing archaea (AOA) were detected only in the non-aerated technologies. Conversely, different Candidatus Brocadiales phylotypes appeared due to differences in influent wastewater composition and hydraulic retention time (HRT). In the same terms multivariate redundancy analysis confirmed that AOA was positively correlated with temperature, ammonium concentration and low HRT. However, AOB population was positively correlated with pH, temperature, and dissolved oxygen concentration. Our data suggested a correlation between the microorganisms involved in the nitrogen removal performance and the operational conditions in the different full-scale bioreactors. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-28
  • Model for the outer cavity of a dual-cavity die with parameters determined by two-dimensional finite-element analysis
    AlChE J. (IF 2.836) Pub Date : 2017-08-25
    Kenneth J. Ruschak, Steven J. Weinstein

    A coating die forms liquid layers of uniform thickness for application to a substrate. In a dual-cavity coating die an outer cavity and slot improves flow distribution from an inner cavity and slot. A model for axial flow in the outer cavity must consider the ever-present cross flow. A 1-D equation for the pressure gradient for a power-law liquid is obtained as a small departure from a uniform flow distribution and no axial flow. The equation contains a shape factor dependent on cavity shape, Reynolds number, and power-law index. The shape factor for five triangular cavity shapes is obtained by finite-element analysis and correlated for application to die design up to the onset of flow recirculation which arises at the junction of the cavity and outer slot. The performance of the combined cavity and slot is considered and the most effective design determined. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-28
  • Chaotic mixing in a barrier-embedded partitioned pipe mixer
    AlChE J. (IF 2.836) Pub Date : 2017-08-25
    Seon Yeop Jung, Kyung Hyun Ahn, Tae Gon Kang, Gi Taek Park, Sang Ug Kim

    Inspired by the partitioned pipe mixer (PPM), a barrier-embedded partitioned pipe mixer (BPPM) is designed and analyzed using a numerical simulation scheme. The BPPM is a static mixer, composed of orthogonally connected rectangular plates with a pair of barriers, which divide, stretch, and fold fluid elements, leading to chaotic mixing via the baker's transformation. The aspect ratio of the plate (α) and the dimensionless height of the barrier (β) are chosen as design parameters to conduct a parameter study on the mixing performance. The flow characteristics and mixing performance are analyzed using the cross-sectional velocity vectors, Poincaré section, interface tracking, and the intensity of segregation. The results indicate that several designs of the BPPM significantly enhance the PPM's mixing performance. The best BPPMs are identified with regard to compactness and energy consumption. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-28
  • Kinetics of glycerol conversion to hydrocarbon fuels over Pd/H-ZSM-5 catalyst
    AlChE J. (IF 2.836) Pub Date : 2017-08-25
    Yang Xiao, Arvind Varma

    The utilization of glycerol, primary byproduct of biodiesel production, is important to enhance process economics. In our recent prior work, it was shown that glycerol can be converted to hydrocarbon fuels over bifunctional catalysts, containing a noble metal supported on H-ZSM-5. Over Pd/H-ZSM-5 catalyst, an optimal ∼60% yield of hydrocarbon fuels was obtained. In the present work, based on experimental data over Pd/H-ZSM-5 catalyst, a lumped reaction network and kinetic model are developed. Using differential kinetic experiments over the temperature range 300–450°C, the rate constants, reaction orders, and activation energies are obtained for each reaction step. The predicted values match well with experimental data for glycerol conversion up to ∼90%. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-25
  • Dynamic formation and scaling law of hollow droplet with gas/oil/water system in dual-coaxial microfluidic devices
    AlChE J. (IF 2.836) Pub Date : 2017-08-25
    Fu-Ning Sang, Zhuo Chen, Yun-Dong Wang, Jian-Hong Xu

    Based on the one-step microfluidic method of producing hollow droplet with thin film, this article studies the effect of water and oil flow rate, gas pressure, and viscosity of aqueous phase on the dynamic formation and size of hollow droplet by analyzing large amounts of data acquired automatically. The results show that the filling stage of hollow droplet is similar to that of microbubble formation, while the necking stage is similar to that of droplet formation process. Furthermore, based on the data and mathematical model describing droplet formation mechanism, a filling stage model including Capillary number of continuous phase is developed. Considering the dynamic interface breakup and displacement of droplet in necking stage, a necking stage model is developed. The results show that the model results considering filling and necking stage fit well with the experimental data, and the relative error is less than 5%. Finally, the same model with parameters is used to predict the size of hollow droplet with other systems and devices, and the model is proved to be relative precise in our experimental conditions. The results presented in this work provide a more in-depth understanding of the dynamic formation and scaling law of hollow droplet with G/L/L systems in microfluidic devices. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-25
  • Interface-shrinkage-driven breakup of droplets in microdevices with different dispersed fluid channel shape
    AlChE J. (IF 2.836) Pub Date : 2017-08-23
    Wenjie Lan, Zhihui Wang, Yinjie Du, Xuqiang Guo, Shaowei Li

    A new droplet breakup mechanism is previously proposed—interface-shrinkage-driven breakup. In coaxial microdevices, when the contact angle between the continuous phase and dispersed fluid channel (DFC) is sufficiently low, the new mechanism instead of the classic shear-driven mechanism dominates the breakup. The present study further investigated the new mechanism in microdevices with DFCs of different shape. Critical contact angles in different devices were determined by theoretical analysis and verified by experiments. It was found that the critical contact angle for the new mechanism depends on the shape of the DFC. The droplet size was measured for different devices when the new mechanism dominated the breakup. In contrast to the case for the shear-driven mechanism, the droplet size is little affected by the capillary number. Mathematical models were established to predict the droplet size in different devices and results were found to agree well with experimental results. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-24
  • Systematic analysis and optimization of power generation in pressure retarded osmosis: Effect of multistage design
    AlChE J. (IF 2.836) Pub Date : 2017-08-12
    Mingheng Li

    This work presents a systematic method for analysis and optimization of specific energy production (SEP) of pressure retarded osmosis (PRO) systems employing single-stage configuration as well as multistage design with interstage hydro-turbines. It is shown that the SEP normalized by the draw solution feed osmotic pressure increases with the number of stages as well as a dimensionless parameter . As compared to the single-stage PRO, the multistage arrangement not only increases flux and volume gain, but also allows a stage-dependent, progressively decreasing hydraulic pressure, both of which contribute to enhanced SEP and power density. At the thermodynamic limit where γtot goes to infinity, the theoretical maximum SEP by an N-stage PRO system is , where qtot is the ratio of the draw solution flow rate at the outlet to the inlet on the system level. For single-stage PRO, it is no more than π0. For infinite number of stages, the theoretical limit becomes . SEP under realistic conditions and practical constraints on multistage design are discussed. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-13
  • Tensile modulus of polymer/CNT nanocomposites containing networked and dispersed nanoparticles
    AlChE J. (IF 2.836) Pub Date : 2017-08-12
    Yasser Zare, Kyong Yop Rhee

    The properties of three-dimensional networks of nanoparticles in polymer/carbon nanotubes (CNT) nanocomposites (PCNT) are particularly interesting from fundamental and application views. In this article, a new model is suggested for predicting the tensile modulus of PCNT using the Ouali and Paul models. The Ouali model considers the network of CNT in a polymer matrix, while the Paul model predicts the tensile modulus of samples containing dispersed nanoparticles. The predictions of the suggested approach are compared with experimental data from several samples. Also, the roles of the main parameters in the tensile modulus of PCNT are evaluated. The predictions agree with the experimental results at different filler concentrations. The roles of these parameters on the tensile modulus of PCNT are discussed based on the properties of CNT networks. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-13
  • Intrusive probes in riser applications
    AlChE J. (IF 2.836) Pub Date : 2017-08-12
    Ray A. Cocco, S.B. Reddy Karri, Ted M. Knowlton, John Findlay, Thierry Gauthier, Jia Wei Chew, Christine M. Hrenya

    Many of the probes used to understand hydrodynamics in circulating fluidized bed risers intrude into the environment they are measuring, although assumptions are typically asserted that the intrusive probes do not affect the data collected. This could be a poor assumption in some cases and conditions. We found that intrusive fiber-optic probe measurements consistently mis-predicted the solids concentration compared to the nonintrusive pressure drop measurements outside the fully developed flow region of a riser containing fluid catalytic cracking catalyst or glass bead particles. The discrepancy was sensitive to superficial gas velocity, solid circulation rate, probe position, and flow direction. Barracuda VR™ computational fluid dynamics simulations confirmed this, and indicated that particle momentum was lost at the leading edge of the probe and particles were spilling over to the probe tip. Accordingly, new probe designs were proposed to mitigate the intrusiveness of a fiber-optic probe for more accurate characterization. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-13
  • Kinetic Monte Carlo simulation for homogeneous nucleation of metal nanoparticles during vapor phase synthesis
    AlChE J. (IF 2.836) Pub Date : 2017-08-12
    Seyyed Ali Davari, Dibyendu Mukherjee

    We present a free-energy driven kinetic Monte Carlo model to simulate homogeneous nucleation of metal nanoparticles (NPs) from vapor phase. The model accounts for monomer-cluster condensations, cluster–cluster collisions, and cluster evaporations simultaneously. Specifically, we investigate the homogeneous nucleation of Al NPs starting with different initial background temperatures. Our results indicate good agreement with earlier phenomenological studies using the Gibbs# free energy formulation from Classical Nucleation Theory (CNT). Furthermore, nucleation rates for various clusters are calculated through direct cluster observations. The steady-state nucleation rate estimated using two different approaches namely, the Yasuoka-Matsumoto (YM) and mean first passage time (MFPT) methods indicate excellent agreement with each other. Finally, our simulation results depict the expected increase in the entropy of mixing as clusters approach the nucleation barrier, followed by its subsequent drastic loss after the critical cluster formation resulting from first-order phase transitions. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-13
  • Kinetic and transport effects on enzymatic biocatalysis resulting from the PEGylation of cofactors
    AlChE J. (IF 2.836) Pub Date : 2017-08-09
    Harun F. Ozbakir, Scott Banta

    The utilization of cofactor-dependent redox enzymes in bioprocess technologies requires low cost cofactor regeneration methods. PEGylated NAD(H) (PEG-NAD(H)) has been utilized in enzyme membrane reactors as a means to recover the cofactor; however, there is a lack of understanding of the effect of PEGylation on enzymatic activity, especially on the relationship between biocatalysis and transport phenomena. To explore this further, two redox enzymes (formate dehydrogenase (FDH) from Saccharomyces cerevisiae and NAD(H)-dependent d-lactate dehydrogenase (nLDH) from Escherichia coli) have been chosen and the kinetic effects caused by cofactor modifications (with PEG of three different chain lengths) have been investigated. The PEGylation did not impact the cofactor dissociation constants and mass transfer was not the rate-limiting step in biocatalysis for either enzyme. However, the PEG chain length had different impacts on the formation of enzyme/cofactor and/or enzyme/cofactor/substrate ternary complexes for the enzymes. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-10
  • A rigorous method to evaluate the consistency of experimental data in phase equilibria. Application to VLE and VLLE
    AlChE J. (IF 2.836) Pub Date : 2017-08-09
    Luís J. Fernández, Juan Ortega, Jaime Wisniak

    This work forms part of a broader study that describes a methodology to validate experimental data of phase equilibria for multicomponent systems from a thermodynamic-mathematical perspective. The goal of this article is to present and justify this method and to study its application to vapor–liquid equilibria (VLE) and vapor–liquid–liquid equilibria (VLLE), obtained under isobaric/isothermal conditions. A procedure based on the Gibbs-Duhem equation is established which presents two independent calculation paths for its resolution: (a) an integral method and (b) a differential method. Functions are generated for both cases that establish the verification or consistency of data, δψ for the integral test and δζ for the differential approach, which are statistically evaluated by their corresponding average values [ , ], and the standard deviations [ , ]. The evaluation of these parameters for application to real cases is carried out using a set of hypothetical systems (with data generated artificially), for which the values are adequately changed to determine their influence on the method. In this way, the requirements of the proposed method for the data are evaluated and their behavior in response to any disruption in the canonical variables (p,T, phase compositions). The conditions for thermodynamic consistency of data are: , , , and . In systems with VLLE, in addition to the previous criteria, must occur that: and . The new proposed method has been tested with a set of 300 experimental binary systems, biphasic and triphasic, obtained from published bibliography, and the results are compared with those of other tests commonly used for testing thermodynamic consistency. The results show that the greater rigor of the proposed method is mainly due to the simultaneous verification of various independent variables. As a result, the conditions for the new test are verified for fewer systems than using other tests mentioned in the literature (i.e., Fredenslund-test and direct of Van Ness). Its unique application is sufficient to ensure the consistency of experimental data, without using other tests. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-10
  • Influence and CFD analysis of cooling air velocity on the purification of aqueous nickel sulfate solutions by freezing
    AlChE J. (IF 2.836) Pub Date : 2017-08-08
    Mehdi Hasan, Miia John, Roman Filimonov, Joonas Sorvari, Marjatta Louhi-Kultanen

    Finite energy resources and their rapidly waning imprint necessitate a sustainable wastewater treatment method. Nature could be exploited to freeze wastewater in locations which experience subzero temperatures during winter. The two most vital components that influence the efficiency of natural freezing are the ambient temperature and air velocity. The turbulent and unsteady air-cooled natural freezing is simulated for ice crystallization from 0.1 wt % and 1 wt % NiSO4 (aq) solutions. The efficiency of natural freezing is tested for different air velocities (2 ms−1, 5 ms−1) and levels of undercooling (ΔT = 0.5°C, 1°C) from the freezing temperature of the corresponding solution. The airflow in the winter simulator is modeled by computational fluid dynamics to investigate its behavior and to assess its effect on freezing. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-08
  • Steady microfluidic measurements of mutual diffusion coefficients of liquid binary mixtures
    AlChE J. (IF 2.836) Pub Date : 2017-08-08
    Anne Bouchaudy, Charles Loussert, Jean-Baptiste Salmon

    We present a microfluidic method leading to accurate measurements of the mutual diffusion coefficient of a liquid binary mixture over the whole solute concentration range in a single experiment. This method fully exploits solvent pervaporation through a poly(dimethylsiloxane) (PDMS) membrane to obtain a steady concentration gradient within a microfluidic channel. Our method is applicable for solutes which cannot permeate through PDMS, and requires the activity and the density over the full concentration range as input parameters. We demonstrate the accuracy of our methodology by measuring the mutual diffusion coefficient of the water (1) + glycerol (2) mixture, from measurements of the concentration gradient using Raman confocal spectroscopy and the pervaporation-induced flow using particle tracking velocimetry. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-08
  • A new superstructure optimization paradigm for process synthesis with product distribution optimization: Application to an integrated shale gas processing and chemical manufacturing process
    AlChE J. (IF 2.836) Pub Date : 2017-08-07
    Jian Gong, Fengqi You

    We propose a novel process synthesis framework that combines product distribution optimization of chemical reactions and superstructure optimization of the process flowsheet. A superstructure with a set of technology/process alternatives is first developed. Next, the product distributions of the involved chemical reactions are optimized to maximize the profits of the effluent products. Extensive process simulations are then performed to collect high-fidelity process data tailored to the optimal product distributions. Based on the simulation results, a superstructure optimization model is formulated as a mixed-integer nonlinear program (MINLP) to determine the optimal process design. A tailored global optimization algorithm is used to efficiently solve the large-scale nonconvex MINLP problem. The resulting optimal process design is further validated by a whole-process simulation. The proposed framework is applied to a comprehensive superstructure of an integrated shale gas processing and chemical manufacturing process, which involves steam cracking of ethane, propane, n-butane, and i-butane. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-07
  • Modular manufacturing processes: Status, challenges, and opportunities
    AlChE J. (IF 2.836) Pub Date : 2017-08-05
    Michael Baldea, Thomas F. Edgar, Bill L. Stanley, Anton A. Kiss

    Chemical companies are constantly seeking new, high-margin growth opportunities, the majority of which lie in high-grade, specialty chemicals, rather than in the bulk sector. To realize these opportunities, manufacturers are increasingly considering decentralized, flexible production facilities: large-scale production units are uneconomical for innovative products with a short lifespan and volatile markets. Small modular plants have low financial risks, are flexible and can respond rapidly to changes in demand. Logistics costs can be also reduced by moving production closer to customers and/or sources of raw materials. Moreover, stricter safety regulations can in many cases be more easily met using smaller distributed facilities. Modularization of chemical production can thus have potentially significant economic and safety benefits. In this article, several drivers for modular production are reviewed, and modular production architectures are evaluated based on a new metric, the value density of feedstock resources and markets for the products of a process. The links between modularization and process intensification are also discussed. Several industrial examples are provided and used to highlight challenges and future directions for this area. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-06
  • CFD as an approach to understand flammable dust 20 L standard test: Effect of the ignition time on the fluid flow
    AlChE J. (IF 2.836) Pub Date : 2017-08-05
    Daniel Vizcaya, Andrés Pinilla, Mariangel Amín, Nicolás Ratkovich, Felipe Munoz, Carlos Murillo, Nathalie Bardin-Monnier, Olivier Dufaud

    A computational study based on the Euler–Lagrange approach was developed for the characterization of flammable dusts in the 20 L sphere standard test. The aim of the study was to analyze some parameters that might affect the experimental data (e.g., cold turbulence and particle size). The turbulence of a wheat starch cloud was described with the Detached Eddy Simulation model. Both the pressure of the system and the RMS velocity were compared with the flow patterns established with a particle image velocimetry analysis. It was concluded that the rebound nozzle forms a cloud that is composed by clumps. This fact implies dissimilarities between the local concentrations and the nominal value. Finally, a granulometric analysis established that the mean diameter of the particle size distribution (PSD) decreased by 69% during the dispersion. Thus, it is suggested to consider the PSD at the ignition zone rather than the PSD of the sample. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-06
  • Considerations on film reactivity in the aqueous biphasic hydroformylation
    AlChE J. (IF 2.836) Pub Date : 2017-08-04
    H. Warmeling, A.-C. Schneider, A. J. Vorholt

    In experiments and kinetic models it was shown that the reaction rate of the biphasic aqueous hydroformylation of 1-octene is linear dependent on the created interfacial area. This phenomenon is directly linked to the question whether the reaction takes place in the bulk phase and is mass transfer limitation or at the surface which would mean an increase of reaction space. To evaluate the place of reaction a mass transfer analysis has been carried out. No mass transfer limitation for the gaseous components carbon monoxide and hydrogen as well as the olefin 1-octene was determined for the aqueous catalyst phase by calculating the Hatta numbers. With this observation it is possible to exclude the mass transfer as a potential influence and hence the aqueous bulk as the place of reaction. Thus the reaction is most probably surface active. This can be either explained the increase in film volume fraction where non-polar substrate as well as polar catalyst complex is present or through an increased catalyst concentration at the surface through dipole moment fluctuations. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-04
  • COSMO-based computer-aided molecular/mixture design: A focus on reaction solvents
    AlChE J. (IF 2.836) Pub Date : 2017-08-04
    Nick D. Austin, Nikolaos V. Sahinidis, Ivan A. Konstantinov, Daniel W. Trahan

    In this article, we investigate reaction solvent design using COSMO-RS thermodynamics in conjunction with computer-aided molecular design (CAMD) techniques. CAMD using COSMO-RS has the distinct advantage of being a method based in quantum chemistry, which allows for the incorporation of quantum-level information about transition states, reactive intermediates, and other important species directly into CAMD problems. This work encompasses three main additions to our previous framework for solvent design (Austin et al., Chem Eng Sci. 2017;159:93–105): (1) altering the group contribution method to estimate hydrogen-bonding and non-hydrogen-bonding σ-profiles; (2) ab initio modeling of strong solute/solvent interactions such as H-bonding or coordinate bonding; and (3) solving mixture design problems limited to common laboratory and industrial solvents. We apply this methodology to three diverse case studies: accelerating the reaction rate of a Menschutkin reaction, controlling the chemoselectivity of a lithiation reaction, and controlling the chemoselectivity of a nucleophilic aromatic substitution reaction. We report improved solvents/mixtures in all cases. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-04
  • Some mechanistic insights into the action of facilitating agents on gas permeation through glassy polymeric membranes
    AlChE J. (IF 2.836) Pub Date : 2017-08-04
    Md Oayes Midda, Akkihebbal K. Suresh

    Incorporation of facilitating agents is one of the promising strategies being researched in recent years to cross the Robeson bounds for gas separations using polymeric membranes. The ways in which such inclusions modify the performance of membranes are not always clear. Here, we study the performance of two glassy membranes, Polyfurfuryl alcohol and Polysulfone, in O2/N2 and CO2/N2 separations, with Cobalt phthalocyanine in insoluble and solubilized forms as the facilitating agent. The results show that in general, three effects are important: (1) a barrier effect, (2) a facilitation effect, and (3) morphological effects on the polymer matrix due to an incompatibility between the particles and the polymer. These results provide some insight into the action of facilitating agents in soluble and insoluble form, when used as membrane additives. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-04
  • Investigation of gas–solid bubbling fluidized beds using ECT with a modified Tikhonov regularization technique
    AlChE J. (IF 2.836) Pub Date : 2017-08-03
    Qiang Guo, Shuanghe Meng, Dehu Wang, Yinfeng Zhao, Mao Ye, Wuqiang Yang, Zhongmin Liu

    Electrical capacitance tomography (ECT) provides a non-intrusive means to visualize cross-sectional material distribution of gas–solid bubbling fluidized beds. Successful application of ECT strongly depends on the image reconstruction algorithm used. For on-line measurements of bubbling fluidized beds, employing an algorithm that can produce high-quality images without extensive computation is necessary. Using the conventional Tikhonov regularization algorithm, image quality in the central area is basically satisfied but suffers from artifacts in the near-wall region. To solve this problem, a similar division operation learned from linear back projection was introduced to modify the conventional Tikhonov algorithm. Both numerical simulations and experiments were performed to evaluate the modified technique. The results indicate that the artifacts can be effectively removed and the reconstructed image quality is similar to Landweber method with dozens of iterations. Furthermore, the modified Tikhonov technique shows high accuracy when obtaining important hydrodynamic parameters in gas–solid bubbling fluidized beds. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-04
  • Formation of liquid–liquid slug flow in a microfluidic T-junction: Effects of fluid properties and leakage flow
    AlChE J. (IF 2.836) Pub Date : 2017-08-03
    Chaoqun Yao, Yanyan Liu, Chao Xu, Shuainan Zhao, Guangwen Chen

    Characteristics of liquid–liquid slug flow are investigated in a microchannel with focus on the leakage flow that bypasses droplets through channel gutters. The results show that the leakage flow rate varies in a range of 10.7–53.5% and 8.3–30.9% of the feed flow rate, during the droplet formation (i.e., at T-junction) and downstream flow (i.e., in the main channel), respectively, which highly depends on Ca number and wetting condition. Empirical correlations are proposed to predict them for perfectly and partially wetting conditions. Leakage flow contribution is further used to improve the Garstecki model for size scaling in order to extend its suitability for both squeezing and shearing regimes. The instantaneous flow rates of the immiscible phases are found to fluctuate periodically with the formation cycles, but in opposite behavior. The effect of the presence of leakage flow on such fluctuation are investigated and compared with gas–liquid systems. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-04
  • Complete carbon analysis of sulfur-containing mixtures using postcolumn reaction and flame ionization detection
    AlChE J. (IF 2.836) Pub Date : 2017-08-03
    Connor A. Beach, Kristeen E. Joseph, Paul J. Dauenhauer, Charles S. Spanjers, Andrew J. Jones, Triantafillos J. Mountziaris

    Quantitative analysis of complex mixtures containing hundreds-to-thousands of organic compounds rich in heteroatoms, including oxygen, sulfur, and nitrogen, is a major challenge in the fuel, food, and chemical industries. In this work, a two-stage (oxidation and methanation) catalytic process in a 3-D–printed metal microreactor was evaluated for its capability to convert sulfur-containing organic compounds to methane. The microreactor was inserted into a gas chromatograph between the capillary column and flame ionization detector. Catalytic conversion of all sulfur-containing analytes to methane enabled carbon quantification without calibration, by the method identified as “quantitative carbon detection” or QCD. Quantification of tetrahydrothiophene, dimethyl sulfoxide, diethyl sulfide, and thiophene indicated complete conversion to methane at 450°C. Long-term performance of a commercial microreactor was evaluated for 2000 consecutive injections of sulfur-containing organic analytes. The sulfur processing capacity of the microreactor was identified experimentally, after which reduced conversion to methane was observed. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-04
  • Molecular simulation study of aluminum–noble gas interfacial thermal accommodation coefficients
    AlChE J. (IF 2.836) Pub Date : 2017-08-03
    Haoyan Sha, Roland Faller, Gulcin Tetiker, Peter Woytowitz

    Thermal accommodation coefficients (TAC) between aluminum and noble gases were studied with molecular dynamics (MD) simulations. Gases interacting with aluminum substrates were modeled by MD with gas velocities sampled from the Maxwell–Boltzmann distribution to give accumulated TAC results. Different implementations of the equation to calculate the TAC, which differ in the amount of information gleaned from MD and the corresponding simulation results, were carefully discussed. The best formula for MD modeling in finite simulation time was determined. Additionally, the influence of the combining rules applied on aluminum–noble gas interatomic potential was characterized with the well-known Lennard–Jones 12–6 potential combined with Lorentz–Berthelot and Fender–Halsey mixing rules. The results were compared with experimental values and previous analytical model. TACs simulated with Fender–Halsey rules present excellent agreement with the experimental values. Detailed TAC distributions and accumulated TAC convergence are also included. © 2017 American Institute of Chemical Engineers AIChE J, 2017

    更新日期:2017-08-04
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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