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  • Particle Dynamics Investigation by means of Shadow Imaging inside an Air Separator
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-21
    Christoph Roloff, Eduard Lukas, Berend van Wachem, Dominique Thévenin

    A multicamera shadow imaging (shadowgraphy) system is developed to simultaneously capture particle dynamics at multiple locations inside a so called zigzag air separator which is used for separating fine from coarse particle fractions. The adaption of the shadowgraphy system to the specific requirements of the separator apparatus to measure particle sizes and velocities including calibration and particle size correction strategies is described. Measurements reveal the behaviour of glass beads ranging from 1 to 4 mm in diameter with variable particle mass loadings and air flow rates inside the zigzag channel. From the processing of the shadow data, particle flow morphologies and characteristic particle trajectories inside the channel stages are obtained. Furthermore, it is shown that particle mean velocities and particle fluctuation energies depend on the particle mass loading, the air flow rate and the location inside the zigzag channel. The results reveal novel quantitative insights into particle velocities in such an air separator which can be used to better understand the underlying particle mechanisms and foster the development of refined process models.

    更新日期:2018-09-22
  • Joint Mass Transfer of Two Components Associated with the Spontaneous Interfacial Convection in the Liquid-Liquid Extraction System
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-21
    Ekaterina A. Shevchenko, Shirsendu Mitra, Sergei A. Ermakov, Anatolii G. Titov, Anatolii A. Ermakov, Partho Sarathi Gooh Pattader
    更新日期:2018-09-21
  • A simple and reliable procedure to accurately estimate NRTL interaction parameters from liquid-liquid equilibrium data
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-21
    Ismael Díaz, Manuel Rodríguez, Emilio J. González, María González-Miquel

    Fitting liquid-liquid equilibrium (LLE) data to common thermodynamic models (NRTL, UNIQUAC…) has been proved in the past to be a non trivial task. Many times it leads to inconsistent solutions where the Gibbs stability criteria is not satisfied. In this work, a simplified parameter estimation problem is formulated where the Gibbs stability criteria and the minimization of experimental and calculated phase composition distances, are simultaneously applied. This formulation is intended to be implemented in general mathematical computing software. Five isothermal ternary systems are studied and the obtained NRTL binary interaction parameters are compared with both existing published parameters and those obtained from commercial data regression tools. Results show that the combination of the proposed problem formulation with commercial non-linear programming solvers improves the quality of the ternary fittings obtained.

    更新日期:2018-09-21
  • Quality Variable Prediction for Chemical Processes Based on Semisupervised Dirichlet Process Mixture of Gaussians
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-20
    Weiming Shao, Zhiqiang Ge, Zhihuan Song

    Data driven soft sensors have found widespread applications in chemical processes for predicting those important yet difficult-to-measure quality variables. In the vast majority of chemical processes, relationships among primary and secondary variables are nonlinear, and process data inherently contain uncertainties and present strongly non-Gaussian characteristics. In addition, labeled samples are often scarce due to certain technical or economical difficulties. These process and data characteristics impose challenges on high-accuracy soft sensors. To deal with these issues, this paper proposes a soft sensing approach referred to as the semisupervised Dirichlet process mixture of Gaussians (SsDPMG). In the SsDPMG, a fully Bayesian model structure is first designed to enable semisupervised tasks that are suitable for regression applications. Subsequently, a Bayesian learning procedure for the SsDPMG is developed based on variational inference framework, where information contained in both labeled and unlabeled samples are extracted. Case studies are carried out on one numerical example and two real-life chemical processes to evaluate the performance of the proposed approach. The results demonstrate that the SsDPMG is an effective soft sensing approach with promising application foreground.

    更新日期:2018-09-21
  • Experimental implementation of a Quality-by-Control (QbC) framework using a mechanistic PBM-based nonlinear model predictive control involving chord length distribution measurement for the batch cooling crystallization of L-ascorbic acid
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-20
    Botond Szilágyi, Ákos Borsos, Kanjakha Pal, Zoltán K. Nagy

    L-ascorbic acid is synthetized in large industrial scale from glucose and marketed as an immune system strengthening agent and anti-oxidant ingredient. The overall yield of conversion of the precursor glucose to L-ascorbic acid is limited, therefore the crystallization is a critically important step of the L-ascorbic acid production from economic point of view. It is widely accepted that the crystal size distribution (CSD) influences numerous relevant macroscopic properties of the final crystalline product and it also significantly affects the downstream operations. The present paper discusses the chord length distribution (CLD, which is directly related to the CSD) control, during the crystallization of L-ascorbic acid from aqueous solution. Batch crystallization process is employed, which is the classical, and still dominant, operation in fine chemical and pharmaceutical industries. A comparative experimental study of two state-of-the-art Quality-by-Control (QbC) based crystallization design approaches are presented: (1) a model-free QbC based on direct nucleation control (DNC) and (2) a model-based QbC using a novel nonlinear model predicative control (NMPC) framework. In the first investigation, the DNC, a process analytical technology based state-of-the-art model free control strategy, is applied. Although, DNC requires minimal preliminary system information and often provides robust process control, due to the unusual crystallization behavior of L-ascorbic acid, it leads to long batch times and oscillatory operation. In a second study the benefits of model-based QbC approach are demonstrated, based on using a NMPC approach. A population balance based crystallization process model is built and calibrated by estimating the nucleation and growth kinetics from concentration and CLD measurements. A projection based CSD to CLD forward transformation is used in the estimation of nucleation and growth kinetics. For robustness and adaptive behavior, the NMPC is coupled with a growing horizon state estimator, which is aimed to continuously improve the model by re-adjusting the kinetic constants. The study demonstrates that the model-based QbC framework can lead to rapid and robust crystallization process development with the NMPC system presenting good control behavior under significant plant model mismatch (PMM) conditions.

    更新日期:2018-09-20
  • Improving lycopene production in Saccharomyces cerevisiae through optimizing pathway and chassis metabolism
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-19
    Xia Li, Zhaoxia Wang, Genlin Zhang, Lijuan Yi
    更新日期:2018-09-20
  • A fast adhesive discrete element method for random packings of fine particles
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-18
    Sheng Chen, Wenwei Liu, Shuiqing Li

    Introducing a reduced particle stiffness in discrete element method (DEM) allows for bigger time steps and therefore fewer total iterations in a simulation. Although this approach works well for dry non-adhesive particles, it has been shown that for fine particles with adhesion, system behaviors are drastically sensitive to the particle stiffness. Besides, a simple and applicable principle to set the parameters in adhesive DEM is also lacking. To solve these two problems, we first propose a fast DEM based on scaling laws to reduce particle Young’s modulus, surface energy and to modify rolling and sliding resistances simultaneously in the framework of Johnson-Kendall-Roberts (JKR)-based contact theory. A novel inversion method is then presented to help users to quickly determine the damping coefficient, particle stiffness and surface energy to reproduce a prescribed experimental result. After validating this inversion method, we apply the fast adhesive DEM to packing problems of microparticles. Measures of packing fraction, averaged coordination number and distributions of local packing fraction and contact number of each particle are in good agreement with results simulated using original value of particle properties. The new method should be helpful to accelerate DEM simulations for systems associated with aggregates or agglomerates.

    更新日期:2018-09-19
  • Self-assembly of DCPD-loaded cross-linked micelle from triblock copolymers and its pH-responsive behavior: A dissipative particle dynamics study
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-17
    Jianbang Gao, Pei Wang, Zhikun Wang, Chunling Li, Shuangqing Sun, Songqing Hu

    Dissipative particle dynamics (DPD) simulations were applied to investigate the solution self-assembly and pH-responsive behavior of hydrophobic DCPD (dicyclopentadiene)-loaded microcapsules from triblock copolymers poly (1,2-ethanediol, homopolymer-b-2-Diethylaminoethylmethacrylate-b-methyl methacrylate) (PEG-b-PDMAEMA-b-PMMA). Results indicate that micelles with longer hydrophilic PEG blocks and shorter hydrophobic PMMA blocks were in favor of encapsulating hydrophobic DCPD. Cross-linking at the core/shell interface generates a chemically bonded network structure in the micelle and leads to a significant decrease of their thermodynamic mobility (i.e., the increase of stability). Both non cross-linked and cross-linked micelles show a good pH-responsive behavior. In particular, cross-linked micelles still have the ability to carry DCPD due to the incomplete dispersion even completely protonation of PDMAEMA, which indicates that the cross-linked micelles could be expected to realize the slow release of encapsulated DCPD agent.

    更新日期:2018-09-18
  • Interactions Between Colliding Oil Drops Coated with Non-ionic Surfactant Determined Using Optical Tweezers
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-17
    An Chen, Shao-Wei Li, Dian Jing, Jian-Hong Xu
    更新日期:2018-09-18
  • Gallium-Promoted HZSM-5 Zeolites as Efficient Catalysts for the Aromatization of Biomass-derived Furans
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-17
    Evgeny A. Uslamin, Beatriz Luna-Murillo, Nikolay Kosinov, Pieter C.A. Bruijnincx, Evgeny A. Pidko, Bert M. Weckhuysen, Emiel J.M. Hensen
    更新日期:2018-09-18
  • Penetration time of hydrophilic micron particles impacting into an unconfined planar gas-liquid interface
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-17
    Shi-Jie Zhu, Run-Zhe Liu, Tian Wang, Yong-Jian Niu, Hai-Feng Lu, Xue-Li Chen

    The penetration time of hydrophilic micron particles during the submergence process is experimentally studied by using a high-speed camera. The effects of impact velocity (0.5m/s ≤ up0 ≤ 1.48m/s), surface tension (44.3mN/m ≤ γ ≤ 73.9mN/m) and dynamic viscosity (1.31mPa·s ≤ μ ≤ 2.13mPa·s) on the penetration time have been investigated. The penetration time for different fluids can be expressed as two different functions with the increase of impact velocity, which are in a good accordance with the experimental results. The results show that the penetration time exhibits a power function with particle size at lower impact velocity (up0 ≤ 0.5m/s), which increases with the surface tension decreasing and dynamic viscosity increasing. As the impact velocity increases, the penetration time can be expressed as a linear function of particle size. When the impact velocity exceeds the transition velocity (up0 ≈ 0.74m/s), the penetration time decreases at first and then increases with the decreasing surface tension, while changing little with the increase of dynamic viscosity. The confinement effect of cavity induced by the Marangoni stress and viscous stress has been analyzed in the different surface tension and dynamic viscosity solutions, respectively. The competitive motion of the three-phase contact line (TPCL) width and interfacial deformation width is the key factor that controls the capillary force, further influencing the penetration time.

    更新日期:2018-09-18
  • 更新日期:2018-09-18
  • Numerical simulation of dynamic behavior of compound droplets on solid surface in shear flow by front-tracing method
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-17
    Xinglong Shang, Zhengyuan Luo, Bofeng Bai

    The dynamic behavior of compound droplets on the wall of a rectangle channel by the action of an imposed shear flow is simulated using our developed three-dimensional front-tracking method combined with generalized Navier boundary condition. The validity of the present method was confirmed by comparing results of the compound droplet spreading under gravity force with analytical solutions. To determine the physical condition required for detaching/pinching-off the compound droplet, we have performed a large number of simulations with varying capillary numbers of two interfaces and obtained a phase diagram of compound droplets on solid surface in shear flow. The deformation and motion of the compound droplet including its contact line motion are investigated. It is found that the behavior of the compound droplet is controlled by two dimensionless parameters, the capillary numbers of the outer interface and the inner interface. Moreover, we also analyze the deformation and migration of the inner droplet and discuss its effect on the compound droplet. The simulation demonstrate that the lateral migration of the small inner droplet could accelerates the pinch-off process and the large inner droplet could promote the detachment for a moderate capillary number of the outer interface.

    更新日期:2018-09-17
  • Compact Coiled Flow Inverter for Process Intensification
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-13
    Surbhi Soni, Loveleen Sharma, Priya Meena, Shantanu Roy, K.D.P. Nigam

    The present study focuses on the intensification of flow and mixing in coiled flow inverter (CFI) geometries in order to achieve higher mixing efficiency with a lower base footprint. For this, two processes intensified designs of “compact coiled flow inverter (CCFI)”, namely, symmetrical compact coiled flow inverter and asymmetrical compact coiled flow inverter, are proposed within the same floor area as covered by a standard design of a conventional CFI. The design of the symmetrical CCFI is based on incorporating as maximum as possible 90° bends, whereas the asymmetrical CCFI is based on incorporating as maximum as possible mixing volume.In order to quantify the improvements caused by proposed designs, all three geometries (two CCFIs and one standard CFI) are compared (experimentally and numerically) with each other in terms of dimensionless dispersion number (D/UL) and mixing efficiency (that measures induced radial mixing by incorporating pressure drop penalty), over laminar flow regime (10⩽NRe⩽145). After validation of the numerical model (CFD) with experimental data, the RTD at various interior localized cross-sectional planes (throughout the length of coiled tube of the geometries) is investigated. Such a study provides the relative contribution of helical turns and 90°bends in reducing axial dispersion, and also provides an insight of the required length of coiled tube that is sufficient to achieve a desired reduction in the axial dispersion. The present study reveals that the symmetrical compact coiled flow inverter has the highest mixing efficiency per unit occupied floor area, and requires the least length of coiled tube in order to reduce the axial dispersion at same extent. Thus, the symmetrical CCFI has potential to save significant material and operational energy cost in the Industry.

    更新日期:2018-09-13
  • Effect of Capillary Pressure on Three-Phase Equilibria in a Confined Pore Space
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-12
    Hao Sun, Huazhou Andy Li

    Tight/shale reservoirs are extensively containing nanopores, and the confined space in nanopores can greatly alter the phase behavior of reservoir fluids due to the strong capillarity effect. Many researches have been recently conducted to investigate the effect of capillary pressure in nanopores on altering the oleic-vapor two-phase equilibria. Few attempts have been made to describe the effect of capillarity on the aqueous-oleic-vapor three-phase equilibria. This work proposes a new algorithm for performing three-phase pressure-temperature (P-T) flash coupled with capillary effect. This algorithm considers two capillary pressures that exist across the two interfaces dividing the three phases in a nanopore. When describing the three-phase equilibria, two types of reservoir wettability are considered: water-wet formation and oil-wet formation. In each case, distribution of the three phases in a nanopore is determined based on the spreading coefficient which refers to the spreading ability of an oleic phase over the spreading ability of an aqueous phase. Example calculations are conducted to show the robustness of the new algorithm as well as to study the effect of capillarity on the three-phase equilibria. Computation results show that the three-phase P-T envelope for a given hydrocarbons/water mixture in a nanopore can be significantly altered by capillary pressure, but how the envelope moves will depend on the wettability of the nanopore and the spreading coefficient. The general trend is that both the upper branch (i.e., the oleic-aqueous/vapor-oleic-aqueous boundary) and the lower branch (i.e., the liquid-vapor/liquid-liquid-vapor boundary) of the three-phase envelope tend to move downward. Compared to the water-wet case, the oil-wet nanopore will shift the three-phase boundaries in a much larger degree. In addition to the alteration of the three-phase envelope, the presence of capillarity will also lead to the alteration of the phase fractions and phase compositions in the nanopore.

    更新日期:2018-09-12
  • The exact regulation of temperature evolutions for droplet impact on ultrathin cold films at superhydrophilic surface
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-12
    Yun Li, Yi Zheng, Yansong Chen, Zhong Lan, Xuehu Ma

    The present study reports a study of water droplets impacting on cold thin water films on a superhydrophilic surface. A thermal infrared imager was used to record the surface temperature distribution after the droplet impact on the liquid films. A ring-shaped high temperature zone was found after impact with the temperature first increasing and then gradually decreasing in the radial direction. Numerical simulations were then used to study the velocity distribution and the droplet motion inside the liquid film. The droplet spreading motion was restricted by liquid in the film for lower We which then reduces the heat transfer in that area and causes the formation of a ring-shaped high temperature distribution. The ring structure shape then changes with the increasing of We. This hot ring becomes wider and the temperature difference between the ring and the impact center decrease with the increasing of We. As We continues to increase, the ring-shaped temperature distribution disappears with the highest temperature at the center and the temperature in radial direction monotonically decreasing from the center to the edge. The initial film thickness also affects the temperature distribution after droplet impact. A thicker film causes the ring-shaped hot region to gradually move inward until it reaches the center and forms a hottest region in the impact center. Thus, the ring-shaped temperature distribution only occurs for lower We and thinner films. The shape and position of the temperature distribution after droplet impact on the cold, thin liquid films can then be precisely controlled by regulating the impact We and the initial film thickness. These results will greatly facilitate the design of precision spraying processes.

    更新日期:2018-09-12
  • 更新日期:2018-09-11
  • Propyl gallate: A novel collector for flotation separation of fluorite from calcite
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-11
    Jiande Gao, Wei Sun, Yuehua Hu, Li Wang, Runqing liu, Zhiyong Gao, Pan Chen, Honghu Tang, Wei Jiang, Fei Lyu

    In real flotation systems, the flotation separation of fluorite from calcite is a challenge due to the similar surface properties of these two minerals. The purpose of this paper is to develop a highly selective flotation collector for calcium-containing minerals. Propyl gallate (PG) was introduced as a collector for selective flotation separation of fluorite from calcite. The separation of fluorite from calcite without using any depressant can be achieved by using PG as the collector. The flotation mechanism of fluorite and calcite was studied by zeta potential measurements, adsorption, FT-IR and XPS analysis. The results indicated that phenolic hydroxyls were the functional groups of PG, and the adsorption amount of PG on the surface of fluorite was larger than on calcite.

    更新日期:2018-09-11
  • The rheology of slurries of athermal cohesive micro-particles immersed in fluid: a computational and experimental comparison
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-11
    Eric Murphy, Gilson Lomboy, Kejin Wang, Sriram Sundararajan, Shankar Subramaniam

    Immersed cohesive particles that aggregate under shear are commonly encountered in chemical engineering contexts. This work concerns the rheology of a particular set of systems, cement pastes, that have been difficult to treat from first-principles. In practice, these pastes exhibit large polydispersity with micron to millimeter sized particles, complicated particle shapes, and non-trivial surface morphology and surface chemistry. Simulations utilize the discrete element model, informed by microscale atomic force microscopy measurements of surface topography, surface energy, and friction, and a simplified version of Stokesian Dynamics. Using these simulations, we study simple shear of two cementitious slurries composed of Portland cement and fly ash particles. These computations are then compared with steady-state vane rheometer experiments. This first-principles approach to comparing simulation and experiment allows us to explore how the microscale and macroscale physics are linked. Both computations and experiments agree qualitatively and are well modeled as Bingham plastics. Computations also show the emergence of percolating clusters, responsible for the rheology. Finally, including the mechanisms that are responsible for frustrated particle motions, such as effects of friction and rough walls at experimental scales, are shown to help give quantitatively better comparisons between simulation and experiment.

    更新日期:2018-09-11
  • Intensification of the Liquid Side Mass Transfer in Double-side Falling Film Microchannels by Micro-mixing Structures
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-11
    Siyuan Chen, Tao Zhang, Li Lv, Yanxiao Chen, Yongchang Yang, Shengwei Tang
    更新日期:2018-09-11
  • 更新日期:2018-09-11
  • Heat transfer and particulate flow analysis of a 30 kW directly irradiated solar fluidized bed reactor for thermochemical cycling
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-11
    Selvan Bellan, Tatsuya Kodama, Koji Matsubara, Nobuyuki Gokon, Hyun Seok Cho, Kousuke Inoue

    To perform thermochemical cycles using non-volatile metal oxides to split water and produce hydrogen, a directly irradiated fluidized bed reactor is designed and fabricated for beam-down configuration. As the main aim of this investigation is to analyze the heat transfer and particulate flow of the reactor, chemically inert particles are used. A transient 3D heat and mass transfer model is formulated by the combined approach of discrete element method and computational fluid dynamics. The radiative transfer is solved using the discrete ordinate radiation model. Experimental validation is accomplished by the measured temperatures, obtained with the fluidized bed reactor prototype tested under 30 kWth high-flux solar simulator. The model is applied to analyze the granular flow characteristics and efficiency of the reactor for various superficial gas velocities and bed masses. The results indicate that higher gas flow rate increases the velocity and convection loss of the bed and decreases the bed temperature and efficiency of the reactor.

    更新日期:2018-09-11
  • eTailored mesoporosity and acidity of shape-selective fibrous silica beta zeolite for enhanced toluene co-reaction with methanol
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-08
    N.N.M. Ghani, A.A. Jalil, S. Triwahyono, M.A.A. Aziz, A.F.A. Rahman, M.Y.S. Hamid, S.M. Izan, M.G.M. Nawawi
    更新日期:2018-09-09
  • Catalyst ignition and extinction: a microkinetics-based bifurcation study of adiabatic reactors for oxidative coupling of methane
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-04
    Laurien A. Vandewalle, Istvan Lengyel, David H. West, Kevin M. Van Geem, Guy B. Marin

    Understanding ignition and extinction behavior is of crucial importance for oxidative coupling of methane (OCM). Therefore, for the first time the bifurcation behavior of OCM has been investigated while considering both homogeneous gas phase reactions and heterogeneous reactions using a detailed microkinetic model. Three different adiabatic reactor models are considered: a plug flow reactor (PFR), a continuously stirred tank reactor (CSTR) and a lumped thermal reactor (LTR) model. The latter represents the limiting case with zero backmixing (cf. PFR behavior) for species and perfect thermal backmixing (cf. CSTR behavior). For homogeneous processes this reactor type could for example be realized by adding a high thermal conductivity inert to the reactor tubes, for catalytic processes a high thermal conductivity catalyst could be used.The bifurcation behavior in these reactor types is compared with a focus on methane conversion, C2 yields and their dependence on operating conditions such as inlet composition, inlet temperature and space time. Steady state multiplicity is observed for adiabatic CSTR and LTR models. This multiplicity of steady states is not observed for isothermal reactor models, indicating that it is caused solely by thermal backmixing and is not related to chemical feedback features such as autocatalysis. The start-up procedures or initial conditions determine the actual steady state that is obtained. Among the three investigated reactor types, a LTR shows the highest product yields and the lowest extinction temperatures, which allows autothermal operation at a much lower inlet temperature compared to a PFR and CSTR. For OCM without catalyst, autothermal operation on the ignited branch at ambient inlet temperatures and reasonable space times is only possible by using methane-to-oxygen ratios below 3 leading to low selectivities. For catalytic OCM compared to OCM without catalyst, the range for autothermal operation is much broader and it is much easier to find feasible operating conditions allowing autothermal operation at ambient inlet temperatures.By operating a LTR on the ignited branch at ambient inlet temperature of 300 K, methane-to-oxygen ratio CH4:O2 = 6, space time V/FCH4,0 = 0.02 s, bulk density of Sn-Li/MgO = 1000 kgcat/m3 and pressure P = 1 bar, overall C2 selectivities (i.e. sum of ethane, ethylene and acetylene selectivity) of 80% can be obtained at methane conversions as high as 30%.

    更新日期:2018-09-05
  • A comprehensive CFD study on the effect of dense vertical internals on the hydrodynamics and population balance model in bubble columns
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-05
    Siamak Agahzamin, Leila Pakzad

    In this paper, the effects of dense vertical internals (rods) on gas holdup and local gas and liquid velocities were investigated by using the Eulerian-Eulerian model coupled with the population balance model. The inclusion of lift and wall lubrication forces was studied by applying different models. The results indicated that just by choosing the appropriate interfacial forces, the numerical model agrees well with the experimental data. A sharper gas holdup, a stronger gas velocity gradient, and a more intense liquid recirculation were observed as the important impacts of the internals. Moreover, three circular internals’ arrangements were considered to study the effect of wall and core clearance distances on the bubble column hydrodynamics. The results revealed that by increasing the wall clearance distance, flatter gas holdup and velocity distributions could be achieved. Also, the turbulence parameters were used to evaluate the capability of the model in the prediction of the bubble size distribution. A modification factor for the breakage and coalescence kernels was proposed; the factor enabled the model to reach equilibrium mean diameters for bubbles. The comparison of the probability distribution function (PDF) of bubble sizes in the bubble column with and without internals showed a narrower bubble size distribution with a smaller mean diameter in the presence of internals.

    更新日期:2018-09-05
  • Continuum modeling of granular segregation during hopper discharge
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-05
    Hongyi Xiao, Yi Fan, Karl V. Jacob, Paul B. Umbanhowar, Madhusudhan Kodam, James F. Koch, Richard M. Lueptow

    Modeling segregation of size disperse granular materials during hopper discharge is important as hoppers are widely used in various industries. However, due to the complexity of segregation and hopper discharge flows, accurately modeling this process has been challenging. In this study, we apply a continuum transport model to predict segregation of size bidisperse granular material during the discharge of quasi-2D hoppers. We apply Discrete Element Method (DEM) simulations to reveal that segregation occurs mainly in a surface layer where particles are transported from the sidewalls to the hopper center. Velocity profiles are also developed based on a kinematic model and DEM data. The continuum model, which captures the interplay of advection, diffusion, and segregation, is then applied to predict the particle concentration distribution in the surface layer and the bulk. The continuum model accurately predicts the segregation pattern inside the hopper during discharge and the concentration profile of the discharged materials, in agreement with DEM simulations and experiments.

    更新日期:2018-09-05
  • Questioning the catalytic effect of Ni nanoparticles on CO2 hydration and the very need of such catalysis for CO2 capture by mineralization from aqueous solution - Response to Letter
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-04
    Danish J. Malik, Ilya J. Sokolov, Jeremy J. Ramsden

    Thank you for giving us the opportunity to formally respond to the comments by Bhaduri and Siller on our published paper. I have consulted with all the co-authors of our paper and our response is provided in the attached correspondence letter.

    更新日期:2018-09-04
  • Thermodynamic stability and formation kinetics of CHClF2 hydrates in the presence of NiCl2
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-04
    Yesol Woo, Jae Hak Jeong, Jong-Won Lee, Jeasung Park, Minjun Cha, Dongseon Kim, Kyoungkeun Yoo, Ji-Ho Yoon

    A hydrate-based technology is suggested for the desalination of industrial effluents, especially electroplating effluents including NiCl2. To decrease the required energy for operating a hydrate-based desalination (HBD) process, chlorodifluoromethane (CHClF2) was used as a guest for hydrate formation at relatively mild conditions. The phase equilibria of CHClF2 hydrates formed in aqueous NiCl2 solutions were investigated to identify the effect of NiCl2 on the thermodynamic stability of CHClF2 hydrates. The dissociation phase boundary of CHClF2 hydrates in the presence of NiCl2 was shifted to higher pressures and lower temperatures as the salinity of aqueous solutions increased. To confirm the feasibility of NiCl2 separation from wastewaters via the HBD process, X-ray diffraction and Raman spectroscopic measurements were performed. The results showed that the Ni2+ and Cl− ions did not participate in the hydrate framework, which revealed that the HBD process could be used to remove NiCl2 from effluents. The formation kinetics of CHClF2 hydrates were analyzed by a new kinetic model adopting transient time-dependent apparent rate constants, which significantly depends on the sub-cooling temperature and the concentration of NiCl2 in the aqueous solutions. Thermodynamic approximations regarding the Ni2+ and Cl− ion exclusion from the clathrate framework and the full occupancy of CHClF2 molecules in the large cages of structure I clathrate hydrate were confirmed by comparing the calculated Ni2+ concentrations in the liquid phase in equilibrium with CHClF2 clathrate hydrates with the experimental measurements. These results provide good information for separating metal ions from wastewater streams by HBD processes.

    更新日期:2018-09-04
  • Scaling up of extractor-free electrosprays in linear arrays
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-04
    Nikolas Sochorakis, Jordi Grifoll, Joan Rosell-Llompart

    Electrospray offers unique atomization of liquids, whereby micro- or nano-droplets with very narrow size distributions are generated from electrified Taylor cones. To scale up this process, many electrospray emitters must be operated simultaneously, while the flow rate per emitter must remain low to preserve stability. To cope with the electrostatic repulsion between the various elements in the system, it is common to position the emitters very near a counter-electrode. Instead, we have studied the conditions leading to robust scalable spraying by using linear arrays of electrosprays in which the counter-electrode is far compared to the inter-emitter separation. In our design, a row of emitter tubes protrudes out of a backplate, and the counter-electrode is a flat collector plate set at a high negative electric potential. In addition, electrodes at both ends of the array enable uniform electrical field conditions, while preventing electrical gaseous discharges. Strong electrostatic interactions are expected between the spray plumes and the Taylor cones. Nonetheless, we show that this geometry is scalable without bound, both by electric field computations, as by experiments performed under different geometrical configurations, liquid flow rates per emitter, and electrical conductivities of the liquid (mainly, NaCl/MEG solutions). The onset voltage required to stabilize the spraying at all emitter positions approaches a plateau as the number of operated emitters increases. Eventually, at high enough potential difference, the cones and sprays misalign, pointing in directions in consonance with minute zig-zag misalignments of the emitters, revealing the importance of small imbalances in the electrostatic forces at the Taylor cones.

    更新日期:2018-09-04
  • Evaluation of carrier size and surface morphology in carrier-based dry powder inhalation by surrogate modeling
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-03
    Amir Abbas Kazemzadeh Farizhandi, Adam Pacłaawski, Jakub Szlęk, Aleksander Mendyk, Yu-Hsuan Shao, Raymond Lau

    In this work, design parameters of carrier-based dry powder inhalation were studied using surrogate modeling technique. The surrogate models constructed were then used to evaluate the key design parameters independently, which were otherwise difficult to determine based on experimental studies alone. Artificial neural network (ANN) was chosen as the surrogate modeling technique and models were constructed based on experimental data obtained from the literature. Twenty eight variables describing the carrier size distribution, density, surface characteristics and operating conditions of dry powder inhaler were used as the input variables and emitted dose (ED) and fine particle fraction (FPF) were used as the output variables. Carrier surface characteristics were evaluated by applying image analysis on carrier SEM images. Genetic algorithm (GA) was used for the selection of important variables to be included in the surrogate models. Sensitivity analysis was also performed to determine the key variables affecting ED and FPF. Key design criteria for carrier-based dry powder inhalation were proposed based on the surrogate models constructed.

    更新日期:2018-09-04
  • Characteristics of Energy Production and Dissipation around a Bubble Rising in Water
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-01
    M. Gumulya, J.B. Joshi, R.P. Utikar, G.M. Evans, V. Pareek

    A numerical simulation on the rise behaviour of a bubble rising in stagnant water at Re ≈ 800-1300 has been conducted. It is found that vorticity generated at the side of the bubble is transferred to the wake region, forming chains of hairpin vortices that are regularly shed and transported downstream. The resulting fluctuations in shape, trajectory, and rise velocity were found to conform well to experimental observations. The fluctuations in velocity resulting from the unsteady wakes were analysed through a fixed-frame approach about the centre of mass of the bubble. The average turbulent kinetic energy in the near wake region was found to be ≈ 1.4 - 4.8% with respect to the average kinetic energy of the bubble. The production of the turbulent kinetic energy was found to occur predominantly at the near wake region of the bubble, mostly as a result of normal and tangential gradients of the mean streamwise velocity. Interestingly, several regions of negative rate of energy production were identified, namely at the top and side interfaces of the bubble. Overall, the ratio of positive-to-negative production rate was found to be ≈ 2.4-3.1, resulting in a net conversion towards smaller-scale fluctuations from the mean flow. Small–scale dissipation was found to occur throughout the wake of the bubble.

    更新日期:2018-09-03
  • 更新日期:2018-09-03
  • A mass-conserving Lattice Boltzmann method for bubble behavior estimation
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-09-01
    Xue Li, Deyang Gao, Baolin Hou, Xiaodong Wang

    The Lattice Boltzmann Method (LBM) has been known as a promising approach for simulating the deformable moving interface of multiphase fluid phenomena due to its mesoscopic nature in organizing and executing distribution functions. However, LBMs are limited in simulating real gas-liquid bubbly flows, where the numerical inaccuracy and instability may significantly increase due to the high surface tension force and the large density ratio. In this paper, a mass-conserving LBM model is developed. The proposed model introduces a conserving correction step and an effective surface tension formula to improve physical accuracy, and utilizes a Multiple-Relaxation-Time (MRT) D3Q19 (three-dimensional and 19 discrete direction) operator to increase numerical stability. The proposed model was applied to estimate bubble behaviors, dimensionless parameter correlations, and drag force coefficient. The results were compared with analytical results, existing numerical results, and experimental data in literature and performed. The good agreement indicates that the proposed mass-conserving LBM model has the ability to predict bubble behaviors in the gas-liquid system.

    更新日期:2018-09-03
  • 更新日期:2018-09-03
  • A new method for voidage correlation of gas-liquid mixture based on differential pressure fluctuation
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-30
    Weiwei Wang, Xiao Liang, Mingzhu Zhang, Khellil Sefiane

    Differential pressure of gas-liquid mixture contains abundant information about fluid flow and its nature. In this paper, a differential pressure across a Venturi tube is measured for a gas-liquid mixture. Trend component and fluctuation components of the differential pressure are extracted using Extreme-Point Symmetric Mode Decomposition. The analysis shows that the mean of the trend component is related to liquid flowrate, and the amplitude of the fluctuation components is correlated to voidage and flow pattern. Hence, a fluctuation coefficient based approach to access voidage is proposed. This is based on the trend and fluctuation components. Since there exists an influence of gas/liquid flowrate, fluid density and voidage on fluctuation coefficient, their qualitative relationships are analyzed to find the appropriate variables to modify the fluctuation coefficient. Experimental data are used to determine the appropriate specific modification parameters. The modified fluctuation coefficient is found to be flow pattern dependent, and hence fuzzy pattern recognition is adopted to identify flow patterns combining statistics from differential pressure. Finally, a flow pattern-based correlation is proposed to estimate the voidage. Verifications through confrontation with experimental results show that the proposed correlation is effective in estimating voidage of mixtures.

    更新日期:2018-08-31
  • Nature inspired fractal tree-like photobioreactor via 3D printing for CO2 capture by microaglae
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-30
    Luhaibo Zhao, Gaofeng Zeng, Yu Gu, Zhiyong Tang, Gang Wang, Tao Tang, Ying Shan, Yuhan Sun

    Based on the bionic fractal theory, a fractal tree-like photobioreactor (PBR) with high surface area to volume ratio is designed on the basis of bifurcation tree algorithm and manufactured via 3D printing technology. Numerical simulation and experimental results show that the fractal structure has a good flow performance and can lead to secondary flow, which is beneficial to enhance the turbulence and produce smaller bubble sizes. Chlorella culture in the fractal tree-like PBR has a higher Fv/Fm (Chlorophyll fluorescence parameter), close to 0.767, and higher efficiency of photosynthetic growth as well as CO2 capture, compared with multitubular PBR and conventional acrylic column reactors. Therefore, the fractal tree-like PBR can improve the efficiency of light energy utilization and bioreaction. Combined with 3D printing technology, fractal PBR blazes a new trail for process intensification on the microalgae cultivation.

    更新日期:2018-08-31
  • Permeability measurements of quartz sands with methane hydrate
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-30
    Gang Li, Xiao-Sen Li, Qiu-Nan Lv, Yu Zhang

    The permeability of porous media is one of the critical parameters that determines gas recovery from natural gas hydrate reservoirs. We measured the permeability of quartz sands by injecting water at a certain flow rate. In hydrate-bearing sands, the larger the hydrate saturation, the smaller the shape factor in the presence of hydrate. A kr - SH relationship with the hydrate saturation both lower and higher than 10% was obtained. Based on the experimental results, the saturation exponent n varied from 6.0 to 1.0.

    更新日期:2018-08-31
  • Transferring bioelectrochemical processes from H-cells to a scalable bubble column reactor
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-30
    Franziska Enzmann, Florian Mayer, Markus Stöckl, Klaus-Michael Mangold, Rolf Hommel, Dirk Holtmann
    更新日期:2018-08-31
  • Drop Impact on Small Targets With Different Target-to-Drop Diameters Ratio
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-30
    M. Arogeti, E. Sher, T. Bar-Kohany
    更新日期:2018-08-31
  • Effect of Microwave Heating on the Performance of Catalytic Oxidation of n-Butane in a Gas-Solid Fluidized Bed Reactor
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-29
    Sepehr Hamzehlouia, Jaber Shabanian, Mohammad Latifi, Jamal Chaouki
    更新日期:2018-08-29
  • Mesoscale modeling of emulsification in rotor-stator devices. Part II: A model framework integrating emulsifier adsorption
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-28
    Chao Chen, Xiaoping Guan, Ying Ren, Ning Yang, Jinghai Li, Christian Kunkelmann, Eduard Schreiner, Christian Holtze, Kerstin Mülheims, Bernd Sachweh

    Precise and rational control of droplet size distribution (DSD) is important in emulsification for target-oriented product design. To develop a complete DSD model, crossing the two mesoscales of two different levels is of great significance, viz., the emulsifier adsorption at interfacial level (Mesoscale 1) and the droplet breakage and coalescence in turbulence in rotor-stator device level (Mesoscale 2). While the first mesoscale can be simulated by coarse-grained molecular dynamic (CGMD), the second has been investigated in computational fluid dynamics and population balance model (CFD-PBM) simulation through the Energy-Minimization Multi-Scale (EMMS) approach in Part I. We then developed a model framework in Part II, coupling CGMD and CFD-PBM simulation through surfactant transport equations in bulk phase and interface, with source terms taking account of emulsifier adsorption parameters. The parameters including maximal adsorption amount, diffusion coefficient and adsorption/desorption kinetic constants are acquired from CGMD. The coalescence efficiency is then corrected by the interfacial area fraction not occupied by surfactant and fed into the coalescence kernel functions in PBM. Compared to traditional CFD-PBM simulation, the coupled model can greatly improve the simulation of DSD, Sauter mean diameter, median diameter and span for high dispersed phase amount (DPA), and correctly reflect the influence of DPA, surfactant concentration and rotational speed of rotor-stator (RS) devices. While the simulation cases validate and demonstrate the advantage of this new model framework, it is also promising to incorporate different types of surfactant in future.

    更新日期:2018-08-29
  • Mesoscale modeling of emulsification in rotor-stator devices. Part I: A population balance model based on EMMS concept
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-27
    Chao Chen, Xiaoping Guan, Ying Ren, Ning Yang, Jinghai Li, Christian Kunkelmann, Eduard Schreiner, Christian Holtze, Kerstin Mülheims, Bernd Sachweh

    Droplet size distribution represents one of the key parameters of emulsification products and emulsification efficiency. While there is a large number of computational fluid dynamics and population balance model (CFD-PBM) simulation for droplet size distribution in various emulsification devices, fitting parameters or empirical correlations were always involved to generate the reasonable simulation. In this study, we applied the Energy-Minimization Multi-scale (EMMS) approach for the liquid-liquid flow in rotor-stator (RS) mixing devices. The so-called mesoscale energy dissipation for droplet breakage was derived to close the population balance equations through a breakage rate corrector. The correction factor was then integrated into the fully-coupled CFD-PBM simulation for a surfactant-free MCT-oil/water system. Compared to the original Alopaeus breakage model or the combination of Alopaeus model and Prince coalescence model, this new model could greatly improve the prediction of droplet size distribution, Sauter mean diameter, median diameter and span of size distribution for both the dilute and the dense systems of dispersed oil phase.

    更新日期:2018-08-27
  • Understanding of Imidazolium Group Hydration and Polymer Structure for Hydroxide Anion Conduction in Hydrated Imidazolium-g-PPO Membrane by Molecular Dynamics Simulations
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-27
    Ning Zhang, Jun Huo, Boyun Yang, Xuehua Ruan, Xiaopeng Zhang, Junjiang Bao, Wenxu Qi, Gaohong He
    更新日期:2018-08-27
  • Effect of flow and fluid properties on the mobility of multiphase flows through porous media
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-27
    H.V. Patel, J.A.M. Kuipers, E.A.J.F. Peters

    In this paper we quantify the effect of capillary number ( Ca ) , contact angle ( θ ) and viscosity ratio ( M ) on the mobility of multiphase flow through porous media. The focus is mainly on oil-water flows through porous rocks observed during the water flooding process. Simulations are performed using a finite volume method employing a staggered grid formulation. Interactions between fluids and complex solid boundaries are resolved by a direct forcing, implicit and sharp interface immersed boundary method (IBM). The fluid-fluid interface is tracked by a mass conservative sharp interface volume of fluid (VOF) method. IBM and VOF are coupled by imposing the contact angle as a boundary condition at the three phase contact line. Our methodology has been verified/validated for several test cases including multiphase Poiseuille flow in a channel, a viscous finger in a channel and mesh convergence of the contact force. Two types of porous structures are considered: i) a repeated single pore and ii) a random multi-pore arrangement. Temporal evolution of phase pressure difference and oil saturation have been studied as viscous fingers penetrate the pores. We observed that the residual oil saturation for different capillary numbers shows exactly the opposite trend for the single and multi pore arrangement. The residual oil saturation for multi-pore shows a well defined linear trend with log Ca , θ and log M .

    更新日期:2018-08-27
  • Optimization of fixed-bed methanation reactors: Safe and efficient operation under transient and steady-state conditions
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-25
    Axel Fache, Frédéric Marias, Vincent Guerré, Stéphane Palmade
    更新日期:2018-08-26
  • Interaction between Binder and High Silica HZSM-5 Zeolite for Methanol to Olefins Reactions
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-25
    Xiao-Di Chen, Xue-Gang Li, Hu Li, Jia-Ji Han, Wen-De Xiao

    Aluminum phosphate (AlPO4) bound HZSM-5 extrudates were prepared with different Al/P ratios, and characterized with respect to the species chemical state, surface morphology, pore structure, and acidity, in comparison to conventional alumina bound and as-received HZSM-5 zeolite catalyst. The binder results in decrease in micropore volume implying blockage of micro channels within the zeolite crystal. AlPO4 binder forms dense amorphous matrix, while alumina forms a porous matrix with significant increase in mesopore volume and surface area. Moreover, both of the bound samples exhibit decreases in acidity strength and sites number, while the alumina bound one shows an increase in strong acidity strength which implies an enhancement of the acid stability of the strong acid sites. The reaction performance experiments on the simulated MTP operating conditions show that compared to alumina bound catalyst the AlPO4-bound type exhibits much lower paraffins and aromatics yields, and particularly that the polymer grade propylene may be easily obtained without C3 splitter, though the lifetime assessment reveals that alumina is much superior to AlPO4 as the binder.

    更新日期:2018-08-26
  • Hydrodynamics study of bubbly flow in a top-submerged lance vessel
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-24
    Yannan Wang, Maarten Vanierschot, Lingling Cao, Zhongfu Cheng, Bart Blanpain, Muxing Guo

    Free surfaces of large bubbles are involved in gas injection into liquid through a top-submerged lance. The Volume of Fluid (VOF) multiphase model is chosen to simulate these flows. However, the selection of an appropriate turbulence model remains a point of discussion. Therefore, three representative turbulence models, namely the Renormalization Group (RNG) k-ε model, the Reynolds Stress model (RSM) and the Large Eddy Simulation (LES) model, respectively coupled with VOF simulations, are studied. The results are compared with Particle Imaging Velocimetry (PIV) experiments. Afterwards, the selected turbulence model is used to study the two-phase flow characteristics. It has been found that the three turbulence models are able to capture the main averaged features of the flow such as the flow structures and average velocity field. However, the RNG and RSM models are not capable of estimating the fluctuating flow parameters such as the Reynolds stresses. In contrast, the LES model gives very good agreement with experimental data. The subsequent study on flow characteristics also showed that the 3D VOF-LES model can describe the bubble behavior and surface fluctuation. Resorting to Fast Fourier Transform (FFT) method, it has been proven that the bubble frequency is around 20 Hz and the turbulence in the bubbly region is between the single phase -5/3 and two-phase -10/3 power law in the inertial sub-range. Finally, the effect of the contact angle between the formed bubbles and outer lance wall on the flow has been estimated. The results showed that contact angle has limited influence on the flow.

    更新日期:2018-08-24
  • Moving from momentum transfer to heat transfer - a comparative study of an advanced Graetz-Nusselt problem using immersed boundary methods
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-24
    Jiangtao Lu, Xiaojue Zhu, E.A.J.F. Peters, Roberto Verzicco, Detlef Lohse, J.A.M. Kuipers
    更新日期:2018-08-24
  • Simple correlation for critical isotherm of pure compounds
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-23
    Sunil S. Bhagwat, Ashwin Kane, Sparsh Ganju, Praful P. Vora

    A volumetric equation of state (PVT behavior of a fluid) is often based on a critical isotherm. Soave-Redlich-Kwong and Peng-Robinson are by far the most popular cubic equations of state. These equations use the first and second differential conditions at the critical point to obtain the parameters but fail to reproduce the P-V-T behavior near the critical point. A new simple equation is proposed for the critical isotherm which matches experimental data for a variety of molecules in the entire range from critical point to ideal gas condition as well as the liquid region. The new proposed critical isotherm equation matches experimental data of a wide variety of compounds much better than these cubic equations of state employed commonly.

    更新日期:2018-08-23
  • 更新日期:2018-08-23
  • Non-spherical particles in a pseudo-2D fluidised bed: Modelling study
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-23
    Vinay V. Mahajan, Tim M.J. Nijssen, J.A.M. Kuipers, Johan T. Padding
    更新日期:2018-08-23
  • Parametric Study of Hydrogen Production via Sorption Enhanced Steam Methane Reforming in a Circulating Fluidized Bed Riser
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-22
    Kiattikhoon Phuakpunk, Benjapon Chalermsinsuwan, Sompong Putivisutisak, Suttichai Assabumrungrat

    Computational fluid dynamics was applied for sorption enhanced steam methane reforming (SESMR) operating in a circulating fluidized bed (CFB) riser. The solid mixtures consisted of Ni-based catalyst and CaO sorbent. The aim of study was to design a proper pilot-scale CFB riser which produced hydrogen (H2) with both high purity and high flux. The design parameters and the reaction parameters were examined with 2k full factorial design. The significances of each parameter were analyzed by analysis of variance. Using the optimum result, the highest H2 purity reached 98.58% in dry basis accompanied with the highest H2 flux of 0.301 kg/m2s. The hydrodynamics of this optimum case showed that SESMR was nearly completed since 5.0 m height because axial and radial distributions of solid were well developed without excessive segregation between catalyst and sorbent. Thus, the H2 purity and the H2 flux approached fully developed within the riser height.

    更新日期:2018-08-22
  • Layered two-phase flows in microchannels with arbitrary interface-wall contact angles
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-22
    Rajat Dandekar, Jason R. Picardo, S. Pushpavanam

    In this work, we study unidirectional, fully developed, layered two-phase flows in microchannels, where the interface meets the wall at an arbitrary contact angle. Interfacial tension causes the interface to take the form of a circular arc, with a radius that depends on the contact angle. The momentum equations must therefore be solved on a domain with boundaries that are, in general, not iso-coordinate surfaces. We adopt the technique developed by Shankar [Proc. Roy. Soc. A., 2005: 2121-2133], which extends the use of eigenfunctions to arbitrary shaped domains, and apply it to layered flows for rectangular and circular cross-sections of the channel. This method is computationally efficient and allows us to analyze in detail the effect of the contact angle on flow properties. We focus on the case of a rectangular channel, which is commonly encountered in microfluidic applications, and consider two distinct cases: (a) free interface whose equilibrium contact angle is a function of fluid wetting properties, and (b) pinned interface whose apparent contact angle is determined by fluid flow rates. We calculate the relationship between the volume fractions (holdups) and flow rate fractions of the fluids and show that a non-zero contact angle can significantly restrict the range of permissible flow rates. This range is greater when the less viscous fluid has a greater affinity for the wall. For fixed flow rates, the residence time of a fluid is found to increase as its affinity for the wall increases. The pressure drop, which directly impacts operational costs, is found to be lower when the more viscous fluid is more wetting. This non-intuitive result is explained in terms of the corresponding variation in fluid volume fractions.

    更新日期:2018-08-22
  • On the reactivity of carbon formed from CO CVD over Ni(111)/TiO2
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-21
    Rui Zhou, Xinxiang Cao, Xinyu Jia, Jiajun Wang, Chang-jun Liu
    更新日期:2018-08-21
  • Producing carbon nanotubes from thermochemical conversion of waste plastics using Ni/ceramic based catalyst
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-18
    Xiaotong Liu, Boxiong Shen, Zhentao Wu, Christopher M. A. Parlett, Zhenan Han, Adwek George, Peng Yuan, Dipesh Patel, Chunfei Wu

    As the amount of waste plastic increases, thermo-chemical conversion of plastics provides an economic flexible and environmental friendly method to manage recycled plastics, and generate valuable materials, such as carbon nanotubes (CNTs). The choice of catalysts and reaction parameters are critical to improving the quantity and quality of CNTs production. In this study, a ceramic membrane catalyst (Ni/Al2O3) was studied to control the CNTs growth, with reaction parameters, including catalytic temperature and Ni content investigated. A fixed two-stage reactor was used for thermal pyrolysis of plastic waste, with the resulting CNTs characterized by various techniques including scanning electronic microscopy (SEM), transmitted electronic microscopy (TEM), temperature programmed oxidation (TPO), and X-ray diffraction (XRD). It is observed that different loadings of Ni resulted in the formation of metal particles with various sizes, which in turn governs CNTs production with varying degrees of quantity and quality, with an optimal catalytic temperature at 700 °C.

    更新日期:2018-08-20
  • Highly efficient nickel-niobia composite catalysts for hydrogenation of CO2 to methane
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-19
    Edwin S. Gnanakumar, Narendraraj Chandran, Ivan V. Kozhevnikov, Aida Grau-Atienza, Enrique V. Ramos Fernández, Antonio Sepulveda-Escribano, N. Raveendran Shiju
    更新日期:2018-08-20
  • Modeling the Transport and Retention of Polydispersed Colloidal Suspensions in Porous Media
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-18
    Scott A. Bradford, Feike J. Leij

    Colloid suspensions commonly exhibit a distribution of sizes, but most transport models only consider a single colloid size. A mathematical model was therefore developed to describe the advective and dispersive transport and first-order retention and release of a stable or aggregating polydispersed colloid suspension in porous media. The colloid size distribution was described using a unimodal or a bimodal lognormal probability density function (PDF), and Brownian aggregation was considered by making lognormal PDF parameters a function of time. Filtration theory was used to predict the retention rate coefficients for the various colloid sizes. The amount of retention for a stable polydispersed suspension was highly dependent on the colloid size distribution parameters, especially for a bimodal lognormal PDF. Increasing the distribution variance produced hyper-exponential retention profiles and an increase or a decrease in colloid retention depending on whether the medium colloid size was close to the optimum size for transport. Aggregation produced a similar decrease in the breakthrough concentrations with injection time as ripening, especially when the sticking efficiency was low. Aggregation effects were much more pronounced at higher input concentration levels, which also produced retention profiles that were increasingly hyper-exponential. Simulation results indicate that the colloid size distribution of stable and aggregating polydispersed suspensions always becomes more uniform and approaches the optimum transport size with increasing distance, suggesting that consideration of polydispersed suspensions is of primary importance near the injection surface.

    更新日期:2018-08-18
  • 更新日期:2018-08-18
  • Development of a drag force correlation for assemblies of cubic particles: The effect of solid volume fraction and Reynolds number
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-18
    Y. Chen, C.R. Müller

    The accurate prediction of the drag force exerted by a fluid on assemblies of particles is critical to simulate key characteristics of gas-solid systems such as the bed expansion in fluidized beds. To this end, a lattice Boltzmann method has been applied to compute the drag force acting on assemblies of cubes for a wide range of Reynolds numbers, Re V = 0 - 200 , and solid volume fractions, ϕ = 0.1 - 0.45 . The numerical data was used to propose a new drag force correlation for assemblies of cubes as a function of the Reynolds number and solid volume fraction. The new drag force correlation is expected to improve the accuracy of Euler-Euler and Euler-Lagrangian simulations of cubic particles.

    更新日期:2018-08-18
  • Homogenization of liquids inside a new soft elastic reactor: Revealing mixing behavior through dimensional analysis
    Chem. Eng. Sci. (IF 3.306) Pub Date : 2018-08-18
    Guillaume Delaplace, YingYing Gu, Minghui Liu, Romain Jeantet, Jie Xiao, Xiao Dong Chen
    更新日期:2018-08-18
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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