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Table of Content
28 March 2020, Volume 28 Issue 3
    Fluid Dynamics and Transport Phenomena
    CFD simulation of flow field and resistance in a 19-core tandem ceramic membrane module
    Yujia Tong, Lukuan Huang, Weixing Li
    2020, 28(3):  625-635.  doi:10.1016/j.cjche.2019.11.006
    Abstract ( 286 )   PDF (5794KB) ( 50 )  
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    CFD simulation of the permeation process of a 19-core tandem ceramic membrane module was established to investigate flow field and resistance and its change in permeate flux to the membrane element position and the channel of each membrane element. The results show that when the volume flow rate changes from 26 m3·h-1 to 89 m3·h-1, the resistance of each part of the membrane module increases gradually. The increase in resistance loss in the membrane element is faster than the plates and the bell mouths. In a single ceramic membrane module, the maximum difference in flow rate of each membrane tube is 7.23%. In a single membrane tube, the outer ring channels 3-5, 3-6, 3-7, 3-8 are relatively slow. The maximum mass flow deviation from the mean is 2.7%. This work helps to clarify the flow mechanism within the modules, optimize the structure of the equipment and provide a reliable basis for the improvement of industrial ceramic membrane modules.
    Surface wettability and flow properties of non-metallic pipes in laminar flow
    Hongyuan Qi, Aiguo Liang, Huayi Jiang, Jianying Shi, Nana Sun, Yulong Wang
    2020, 28(3):  636-642.  doi:10.1016/j.cjche.2019.11.005
    Abstract ( 233 )   PDF (1066KB) ( 53 )  
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    In this paper, three liquids flowing in five pipes with the same inner diameter of 14 mm were studied to determine the relationship between the surface wettability and flow properties in laminar flow (Re < 2000). This was motivated by oilfield observations of increased pressure drops in non-metallic pipes compared to those in metal pipes, which was contrary to expectations. A new expression for the frictional coefficient that considers the Reynolds number and contact angle θ in laminar flow for non-metallic pipes was proposed based on the experimental results of single-phase flow using dimension and regression analyses. The solutions of the anomalous phenomenon were proposed from the perspectives of the pipe diameter, contact-angle difference, and the compatibility between flexible composite pipe and JLHW105 oil according to the new formula. The surprising finding was that the surface wettability could control the frictional resistance by the critical contact angle (39.9°) obtained at the same Reynolds number. If 0° < θ ≤ 39.9°, the frictional coefficient increased as the contact angle increased. In contrast, if 39.9° < θ < 180°, the frictional coefficient decreased with increasing contact angle. The influences of the pipe diameter and contactangle difference on the pressure drop difference of JLHW105 oil showed an inversely proportional relation. A series of materials and liquids were tested. The selection of pipe material for transporting a given fluid can be based on the contact angle, surface tension, and critical limit of the contact angle obtained. The research results are expected to provide some guidelines for the selection of the appropriate pipe material for a given set of fluids.
    Natural convection heat transfer enhancement of different nanofluids by adding dimple fins on a vertical channel wall
    Milad Gholami, Mohammad Reza Nazari, Mohammad Hossien Talebi, Farzad Pourfattah, Omid Ali Akbari, Davood Toghraie
    2020, 28(3):  643-659.  doi:10.1016/j.cjche.2019.11.001
    Abstract ( 181 )   PDF (11603KB) ( 26 )  
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    In this numerical study, natural flow and heat transfer of nanofluids with Al2O3, TiO2, Cu and CNT nanoparticles in a vertical channel with dimpled fins at Rayleigh number (Ra) of Ra = 3.25×107 to Ra = 1×108 are investigated by using the finite volume method. The obtained results revealed that, using CNT in volume fractions of 2% and 4% leads to significant heat transfer and at φ = 6%, using TiO2 nanoparticles has a great effect on Nu number enhancement. Also, using solid nanoparticles in base fluid causes more uniform heat transfer distribution, especially in areas close to heated surface and by adding more volume fraction in base fluid, temperature level reduces. In general, according to temperature contours, reduction of wall temperature depends on the increase of Ra and volume fraction and the type of solid nanoparticles.
    Enhanced heat transfer in rectangular duct with punched winglets
    Pongjet Promvonge, Sompol Skullong
    2020, 28(3):  660-671.  doi:10.1016/j.cjche.2019.09.012
    Abstract ( 259 )   PDF (5071KB) ( 83 )  
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    Thermal performance of a heat exchanger duct with punched winglets (PWs) mounted on the upper duct wall has been examined for Reynolds number (Re) ranging from 4100 to 25,500. In the present experiment, two types of PWs: punched delta- and elliptical-winglets (P-DW and P-EW) with four punched-hole sizes were tested at a fixed attack angle, optimal relative pitch and height. Also, data of solid delta- and elliptical-winglets (DW and EW) were included for comparison. The investigation has shown that the P-DW yields higher thermal-performance enhancement factor (η) than the P-EW. Although the solid DW and EW with no punch have the highest heat transfer and friction loss, the PWs yield better η than the solid ones. For PWs, the P-DW with smaller hole size has the peak heat transfer and friction loss around 5.7 and 40 times over the smooth duct, respectively but the optimum η of 2.17 is seen for the one with a certain hole size. The PWs provide η at about 5%-8% above the solid winglets.
    Comparative analysis of different static mixers performance by CFD technique: An innovative mixer
    M. M. Haddadi, S. H. Hosseini, D. Rashtchian, Martin Olazar
    2020, 28(3):  672-684.  doi:10.1016/j.cjche.2019.09.004
    Abstract ( 268 )   PDF (4917KB) ( 195 )  
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    The flow and mixing behavior of two miscible liquids has been studied in an innovative static mixer by using CFD, with Reynolds numbers ranging from 20 to 160. The performance of the new mixer is compared with those of Kenics, SMX, and Komax static mixers. The pressure drop ratio (Z-factor), coefficient of variation (CoV), and extensional efficiency (α) features have been used to evaluate power consumption, distributive mixing, and dispersive mixing performances, respectively, in all mixers. The model is firstly validated based on experimental data measured for the pressure drop ratio and the coefficient of variation. CFD results are consistent with measured data and those obtained by available correlations in the literature. The new mixer shows a superior mixing performance compared to the other mixers.
    Effect of wall temperature modulation on the heat transfer characteristics of droplet-train flow inside a rectangular microchannel
    Vivekanand S. V. B., Raju V. R. K.
    2020, 28(3):  685-697.  doi:10.1016/j.cjche.2019.04.022
    Abstract ( 127 )   PDF (8732KB) ( 22 )  
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    The numerical studies of water-oil two-phase slug flow inside a two-dimensional vertical microchannel subjected to modulated wall temperature boundary conditions have been discussed in the present paper. Many researchers have contributed their efforts in exploring the characteristics of Taylor flows inside microchannel under constant wall heat flux or isothermal wall conditions. However, there is no study available in the literature which discusses the impact of modulated thermal wall boundary conditions on the heat transfer behavior of slug flows inside microchannels. Hence, to bridge this gap, an effort has been made to understand the heat transfer characteristics of the flow under sinusoidal wall temperature conditions. Initially, a single phase flow and heat transfer study was performed in microchannels, and the results of the fully developed velocity profile and heat transfer rate were validated with benchmark analytical results. Then an optimal selection of the combination of sinusoidal thermal wall boundary conditions has been made for the two-phase slug flow study. Later, the effects of amplitude (0 < ε < 0.03) and frequency (0 < ω < 750π rad·s-1) of the sinusoidal wall temperature profile on the heat transfer have been studied using the optimal combination of the wall boundary conditions. The results of the numerical study using modulated temperature conditions on channel walls showed a significant improvement in the heat transfer over liquid-only flow by approximately 50% as well as over two-phase flow without wall temperature modulation. The non-dimensional temperature contours obtained for different cases of temperature modulation clearly explain the root cause of such improvement in the heat transfer. Besides, the results based on the hydrodynamics of the flow have also been reported in terms of variation of droplet shapes and film thickness. The influence of Capillary number on the film thickness as well as heat transfer rates has also been discussed. In addition, the measured film thickness has also been compared with that calculated using standard empirical and analytical models available in the literature. The heat transfer rate obtained from the numerical study for the case of unmodulated wall temperature was found to be in a close match with a phenomenological model to evaluate slug flow heat transfer having a mean absolute deviation of 7.56%.
    Prediction of curved oil-water interface in horizontal pipes using modified model with dynamic contact angle
    Hongxin Zhang, Lusheng Zhai, Ruoyu Liu, Cong Yan, Ningde Jin
    2020, 28(3):  698-711.  doi:10.1016/j.cjche.2019.08.008
    Abstract ( 229 )   PDF (5359KB) ( 52 )  
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    In this study, interface shapes of horizontal oil-water two-phase flow are predicted by using Young-Laplace equation model and minimum energy model. Meanwhile, the interface shapes of horizontal oil-water twophase flow in a 20 mm inner diameter pipe are measured by a novel conductance parallel-wire array probe (CPAP). It is found that, for flow conditions with low water holdup, there is a large deviation between the model-predicted interface shape and the experimentally measured one. Since the variation of pipe wetting characteristics in the process of fluid flow can lead to the changes of the contact angle between the fluid and the pipe wall, the models mentioned above are modified by considering dynamic contact angle. The results indicate that the interface shapes predicted by the modified models present a good consistence with the ones measured by CPAP.
    Experimental study on fusion and break-up motion after droplet collision
    Yi Li, Zhi Ning, Ming Lü
    2020, 28(3):  712-720.  doi:10.1016/j.cjche.2019.09.002
    Abstract ( 180 )   PDF (2190KB) ( 34 )  
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    The interactions between droplets have an important influence on the atomization of liquid fuel, the combustion efficiency, and the reduction of particulate matter emissions for an engine. For this reason, this paper presents results from an experimental study on the coalescence and break-up of droplets after collision. According to the shape and parameters of the droplets at different times after the collision of the droplets was captured by a high speed camera, analysis was done for the following effects of droplet collisions: the collision-coalescence motion for the collision between the droplets, the change history of the dimensionless length-to-width ratio of the oscillation motion, the critical size ratio of the breakup motion, and the liquid physical properties of the particles. The results show that the droplets collide and exhibit two forms of coalescence oscillation and break-up: for oscillating motion, at higher droplet collision velocities and dimensionless size ratios, there will be a larger dimensionless length-to-width ratio for the droplet oscillation; for the break-up motion, at higher collision velocities, there will be lower dimensionless size ratios, and lower liquid surface tension, shorter times over which the droplet breaks, and facilitated droplet break-up. The research results presented here can be used for atomization in engine cylinder, increasing the gas/liquid contact area and enhancing the combustion efficiency of gas/liquid heat transfer to improve the combustion efficiency of the engine.
    Separation Science and Engineering
    New process development and process evaluation for capturing CO2 in flue gas from power plants using ionic liquid [emim][Tf2N]
    Lan Li, Xiaoting Huang, Quanda Jiang, Luyue Xia, Jiawei Wang, Ning Ai
    2020, 28(3):  721-732.  doi:10.1016/j.cjche.2019.08.005
    Abstract ( 190 )   PDF (9842KB) ( 22 )  
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    Using the ionic liquid [emim][Tf2N] as a physical solvent, it was found by Aspen Plus simulation that it was possible to attempt to capture CO2 from the flue gas discharged from the coal-fired unit of the power plant. Using the combination of model calculation and experimental determination, the density, isostatic heat capacity, viscosity, vapor pressure, thermal conductivity, surface tension and solubility of [emim][Tf2N] were obtained. Based on the NRTL model, the Henry coefficient and NRTL binary interaction parameters of CO2 dissolved in [emim][Tf2N] were obtained by correlating [emim][Tf2N] with the gas-liquid equilibrium data of CO2. Firstly, the calculated relevant data is imported into Aspen Plus, and the whole process model of the ionic liquid absorption process is established. Then the absorption process is optimized according to the temperature distribution in the absorption tower to obtain a new absorption process. Finally, the density, constant pressure heat capacity, surface tension, thermal conductivity, and viscosity of [emim][Tf2N] were changed to investigate the effect of ionic liquid properties on process energy consumption, solvent circulation and heat exchanger design. The results showed that based on the composition of the inlet gas stream to the absorbers, CO2 with a capture rate of 90% and a mass purity higher than 99.5% was captured. These results indicate that the [emim][Tf2N] could be used as a physical solvent for CO2 capture from coal-fired units. In addition, the results will provide a theoretical basis for the design of new ionic liquids for CO2 capture.
    Study of reverse osmosis membranes fouling by inorganic salts and colloidal particles during seawater desalination
    Santiago Gutiérrez Ruiz, Juan Antonio López-Ramírez, Mohammed Hassani Zerrouk, Agata Egea-Corbacho Lopera, José María Quiroga Alonso
    2020, 28(3):  733-742.  doi:10.1016/j.cjche.2019.10.004
    Abstract ( 159 )   PDF (3425KB) ( 70 )  
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    Fouling phenomenon is considered among the major reasons that cause significant increase of operating cost of desalination plants equipped with reverse osmosis (RO) membranes. This phenomenon is studied in the present work in the case of RO polyamide aromatic membranes using model seawater containing inorganic salts and colloidal compounds. Different solubility conditions of CaCO3 and CaSO4 were applied to study RO performances with and without colloid presence. During experiments, the membrane permeate fluxes were continuously monitored. Moreover, studies of chemical composition, structure, and morphology of the materials deposited on the membrane surface were conducted using energy dispersive microanalysis (EDS) X-ray diffraction and scanning electronic microscopy (SEM). Results show that in conditions of calcium carbonate oversaturation there is a reduction in the permeate flow of 11.2% due to fouling of the membrane by the precipitation of this compound. While in the same conditions of calcium sulphate oversaturation the reduction of the flow is 5%, so we can conclude that in conditions of oversaturation of both salts, calcium carbonate produces a greater fouling of the membrane that in its view causes greater decrease in the flow of permeate. All this based on the results of the test with both salts in oversaturated conditions. Resulting in the formation of calcite and gypsum crystals onto the membranes as XRD analyses stated. Additional presence of colloidal silica in those conditions intensifies strongly the fouling, leading until to 24.1% of permeate flux decrease.
    Mechanochemical sulfidization of a mixed oxide-sulphide copper ore by co-grinding with sulfur and its effect on the flotation efficiency
    Mojtaba Masdarian, Asghar Azizi, Zahra Bahri
    2020, 28(3):  743-748.  doi:10.1016/j.cjche.2019.10.005
    Abstract ( 202 )   PDF (3282KB) ( 63 )  
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    Mechanochemical sulfidization of a mixed sulfide/oxide copper ore by co-grinding with sulfur and additives including Mg(NO3)2 and Fe(NO3)3 salts and iron, aluminum and magnesium powders was investigated for the first time. Also, the influence of sulfidization during the wet-milling process was examined on the separation efficiency and recovery of copper in detail. The results demonstrated that co-grinding with sulfur solely had the best flotation performance at the value of 0.5 wt.% and it was attributed to the possible existence of S-O bonding on copper oxides surfaces. In addition, adding magnesium nitrate salt, magnesium powder, iron nitrate salt and aluminum powder as additive associated with 0.5 wt% sulfur into ball milling caused the flotation improvement at the amounts of 0.2 wt%, 0.2 wt%, 0.5 wt% and 0.5 wt%, respectively. Also, the effect of grinding time and sulfidization pH with 0.5 wt% sulfur solely was determined and pHs of 7.5 to 8.5 gave the best results. The highest recovery (75.76%) and separation efficiency (63.44%) were achieved at pH of 7.5 and 8.5, respectively.
    Negatively charged organic-inorganic hybrid silica nanofiltration membranes for lithium extraction
    Xiaoxian Wu, Haoyue Liu, Yibin Wei, Ying Fei, Hong Qi
    2020, 28(3):  749-757.  doi:10.1016/j.cjche.2019.11.004
    Abstract ( 180 )   PDF (2331KB) ( 44 )  
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    Effective extraction of lithium from high Mg2+/Li+ ratio brine lakes is of great challenge. In this work, organic- inorganic hybrid silica nanofiltration (NF) membranes were prepared by dip-coating a 1,2-bis(triethoxysilyl)ethane (BTESE)-derived separation layer on tubular TiO2 support, for efficient separation of LiCl and MgCl2 salt solutions. We found that the membrane calcinated at 400 ℃ (M1-400) could exhibit a narrow pore size distribution (0.63-1.66 nm) owing to the dehydroxylation and the thermal degradation of the organic bridge groups. All as-prepared membranes exhibited higher rejections to LiCl than to MgCl2, which was attributed to the negative charge of the membrane surfaces. The rejection for LiCl and MgCl2 followed the order: LiCl N MgCl2, revealing that Donnan exclusion effect dominated the salt rejection mechanism. In addition, the triplecoated membrane calcined at 400 ℃ (M3-400) exhibited a permeability of about 9.5 L·m-2·h-1·bar-1 for LiCl or MgCl2 solutions, with rejections of 74.7% and 20.3% to LiCl and MgCl2, respectively, under the transmembrane pressure at 6 bar. Compared with the previously reported performance of NF membranes for Mg2+/Li+ separation, the overall performance of M3-400 is highly competitive. Therefore, this work may provide new insight into designing robust silica-based ceramic NF membranes with negative charge for efficient lithium extraction from salt lakes.
    Salt transport in polymeric pervaporation membrane
    Dihua Wu, Aoran Gao, Xianshe Feng
    2020, 28(3):  758-765.  doi:10.1016/j.cjche.2019.11.009
    Abstract ( 106 )   PDF (1380KB) ( 38 )  
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    The salt transport in a PEBA membrane used in pervaporative desalination was studied. The concentration profile of salt in the membrane during pervaporation was investigated experimentally using a multilayer membrane. The salt was found to be sorbed in the membrane but was not removed during the pervaporative desalination process, and the salt concentration in the membrane varied linearly with position. High purity water was obtained as the permeate as long as the permeate side was kept dry under vacuum. The accumulated salt uptake in the membrane follows the order of MgCl2 > NaCl > Na2SO4. The solubility of salt in the membrane follows the order of MgCl2 > NaCl > Na2SO4. Both the permeability and diffusivity of salt in the membrane follow the order of NaCl > MgCl2 > Na2SO4. The permeability of salt in the membrane is not influenced by the feed salt concentration. It is mainly determined by the diffusion coefficients.
    Effects of imidazolium-based ionic liquids on the isobaric vapor-liquid equilibria of methanol + dimethyl carbonate azeotropic systems
    Songsong Chen, Li Dong, Junping Zhang, Weiguo Cheng, Feng Huo, Qian Su, Wei Hua
    2020, 28(3):  766-776.  doi:10.1016/j.cjche.2019.12.001
    Abstract ( 247 )   PDF (4009KB) ( 48 )  
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    The separation of methanol (MeOH) and dimethyl carbonate (DMC) is important but difficult due to the formation of an azeotropic mixture. In this work, isobaric vapor-liquid equilibrium (VLE) data for the ternary systems containing different imidazolium-based ionic liquids (ILs), i.e. MeOH + DMC + 1-butyl-3-methy-limidazolium bis[(trifluoromethyl)sulfonyl]imide ([Bmim][Tf2N]), MeOH + DMC + 1-ethyl-3-methyl-imidazolium bis [(trifluoromethyl)sulfonyl]imide ([Emim][Tf2N]), and MeOH + DMC + 1-ethyl-3-methylimidazolium hexafluorophosphate ([Emim][PF6])) were measured at 101.3 kPa. The mole fraction of IL was varied from 0.05 to 0.20. The experimental data were correlated with the NRTL and Wilson equations, respectively. The results show that imidazolium-based ILs were beneficial to improve the relative volatility of MeOH to DMC, and [Bmim][Tf2N] showed a much more excellent performance on the activity coefficient of MeOH. The interaction energies of system components were calculated using Gaussian program, and the effects of cation and anion on the separation coefficient of the azeotropic system were discussed.
    Classification performance of model coal mill classifiers with swirling and non-swirling inlets
    Lele Feng, Hai Zhang, Lilin Hu, Yang Zhang, Yuxin Wu, Yuzhao Wang, Hairui Yang
    2020, 28(3):  777-784.  doi:10.1016/j.cjche.2019.12.002
    Abstract ( 173 )   PDF (3659KB) ( 58 )  
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    The classification performance of model coal mill classifiers with different bottom incoming flow inlets was experimentally and numerically studied. The flow field adjacent to two neighboring impeller blades was measured using the particle image velocimetry technique. The results showed that the flow field adjacent to two neighboring blades with the swirling inlet was significantly different from that with the non-swirling inlet. With the swirling inlet, there was a vortex located between two neighboring blades, while with the nonswirling inlet, the vortex was attached to the blade tip. The vorticity of the vortex with the non-swirling inlet was much lower than that with the swirling inlet. The classifier with the non-swirling inlet demonstrated a larger cut size than that with the swirling inlet when the impeller was stationary (~0 r·min-1). As the impeller rotational speed increased, the cut size of the cases with non-swirling and swirling inlets both decreased, and the one with the non-swirling inlet decreased more dramatically. The values of the cut size of the two classifiers were close to each other at a high impeller rotational speed (≥120 r·min-1). The overall separation efficiency of the classifier with the non-swirling inlet was lower than that with the swirling inlet, and monotonically increased as the impeller rotational speed increased. With the swirling inlet, the overall separation efficiency first increased with the impeller rotational speed and then decreased when the rotational speed was above 120 r·min-1, and the variation trend of the separation efficiency was more moderate. As the initial particle concentration increased, the cut sizes of both swirling and non-swirling inlet cases decreased first and then barely changed. At a low initial particle concentration (<0.04 kg·m-3), the classifier with the swirling inlet had a larger cut size than that with the non-swirling inlet.
    Development of separation sharpness model for hydrocyclone
    Pakpoom Supachart, Thanit Swasdisevi, Pratarn Wongsarivej, Mana Amornkitbamrung, Naris Pratinthong
    2020, 28(3):  785-792.  doi:10.1016/j.cjche.2019.12.014
    Abstract ( 150 )   PDF (1308KB) ( 48 )  
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    Hydrocyclones are mechanical devices used in classifying and separating many different types of materials. A classification function of the hydrocyclone has been continually developed for solid-liquid separation. In the classification process of solids from liquids, it is desirable to reduce the amount of misplaced material; therefore, the separation sharpness, α (alpha), is a parameter that helps in evaluating misplaced material and has been developed as a model to help the designer predict the performance of the classification. However, the problem with the separation sharpness model is that it cannot be used outside the range of conditions under which it was developed. Therefore, this research aimed to develop the separation sharpness model to predict more accurately and cover a wide range of conditions using the multiple linear regression method. The new regression model of separation sharpness was based on a wide range of both experimental and industrial data-sets of 431 tests collaborating with the additional experiments of 117 tests that were obtained from a total of 548 tests. The new model of separation sharpness can be used in the range of 30-762 mm hydrocyclone body diameters and feed solid concentrations in the range of 0.5wt%-80 wt%. When compared with the experimental separation sharpness, the accuracy of the separation sharpness model prediction has an error of 4.53% and R2 of 0.973.
    Catalysis, Kinetics and Reaction Engineering
    Numerical investigation of complex chemistry performing in Ptcatalyzed oxidative dehydrogenation of ethane fixed-bed reactors
    Zhongfeng Geng, Hao Deng, Yonghui Li, Minhua Zhang
    2020, 28(3):  793-807.  doi:10.1016/j.cjche.2019.09.010
    Abstract ( 91 )   PDF (7452KB) ( 10 )  
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    Ethylene is one of the most important basic chemicals in the modern chemical industry. Thermal or catalytic cracking of hydrocarbons is the main industrial technologies nowadays, which suffer from equilibriumlimitation and rapid coke formation. The oxidative dehydrogenation of ethane (ODHE) is considered to be a promising alternative process since it overcomes equilibrium-limitations, avoids catalyst deactivation by coke formation, and decreases the number of side reactions. In this study, particle-resolved 2D CFD simulations of fixed-beds filled with eggshell catalysts coupled with micro-kinetics of Pt-catalyzed ODHE were performed to understand the effect of operation conditions and catalyst properties on ethylene selectivity. The catalyst bed was created by discrete element method (DEM) and the central longitudinal section of the reactor tube was defined as the 2D simulation region. Both of the homogeneous and catalytic heterogeneous chemical reactions were described by detailed micro-kinetics within the particle-resolved CFD simulation. At first, the established model of monolith reactors was verified by comparing the simulated results with experimental results reported in literature. Then, the effects of operation conditions and catalyst concentration on the ethylene selectivity in randomly packed beds were explored. The specific variation of certain operation conditions including inlet flow rate, inlet temperature, pressure, inlet C2H6/O2 ratio and N2 dilution ratio can effectively increase ethylene selectivity. And the reduction of ratio of catalytic active area to geometric area Fcat/geo representing catalyst properties from 140 to 30 increases the selectivity from 42.2% to 59.3%. This research can provide reference for the industrialization of ODHE process in the future.
    Oxidation of benzyl alcohols to ketones and aldehydes by O3 process enhanced using high-gravity technology
    Wenqiang Gao, Lei Du, Weizhou Jiao, Youzhi Liu
    2020, 28(3):  808-814.  doi:10.1016/j.cjche.2020.02.015
    Abstract ( 138 )   PDF (2158KB) ( 32 )  
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    In this study, a practical process for ozonization of benzyl alcohols to ketones and aldehydes in a rotating packed bed (RPB-O3) reactor has been developed. Using 1-phenylethanol as a model reactant, the performance of RPB-O3 process in different solvents has been compared with the commonly used stirred tank reactor (STR-O3). Ethyl acetate was the optimum solvent for the conversion of 1-phenylenthanol to acetophenone in RPB-O3 process, with 78% yield after 30 min. In a parallel STR-O3 experiment, the yield of acetophenone was 50%. Other experimental variables, i.e. O3 concentration, reaction time, high-gravity factor and liquid flow rate were also optimized. The highest yield of acetophenone was obtained using O3 concentration of 80 mg·L-1, reaction time of 30 min, high gravity factor of 40 and liquid flow rate of 120 L·h-1. Under the optimized reaction conditions, a series of structurally diverse primary and secondary alcohols was oxidized with (19%-92%) yield. The ozonization mechanism was studied by Electron Paramagnetic Resonance (EPR) spectroscopy, monitoring the radical species formed upon self-decomposition of O3. The characteristic quadruple peak with the 1:2:2:1 intensity ratio that corresponds to hydroxyl radicals (·OH) was observed in the electron paramagnetic resonance (EPR) spectrum, indicating an indirect oxidation mechanism of alcohols via ·OH radical.
    Process Systems Engineering and Process Safety
    Stochastic optimization based on a novel scenario generation method for midstream and downstream petrochemical supply chain
    Peixian Zang, Guoming Sun, Yongming Zhao, Yiqing Luo, Xigang Yuan
    2020, 28(3):  815-823.  doi:10.1016/j.cjche.2019.06.008
    Abstract ( 284 )   PDF (1885KB) ( 38 )  
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    A two-stage mixed integer linear programming model (MILP) incorporating a novel method of stochastic scenario generation was proposed in order to optimize the economic performance of the synergistic combination of midstream and downstream petrochemical supply chain. The uncertainty nature of the problem intrigued the parameter estimation, which was conducted through discretizing the assumed probability distribution of the stochastic parameters. The modeling framework was adapted into a real-world scale of petrochemical enterprise and fed into optimization computations. Comparisons between the deterministic model and stochastic model were discussed, and the influences of the cost components on the overall profit were analyzed. The computational results demonstrated the rationality of using reasonable numbers of scenarios to approximate the stochastic optimization problem.
    Energy, Resources and Environmental Technology
    Influence of bio-inspired flow channel designs on the performance of a PEM fuel cell
    Srinivasa Reddy Badduri, G. Naga Srinivasulu, S. Srinivasa Rao
    2020, 28(3):  824-831.  doi:10.1016/j.cjche.2019.07.010
    Abstract ( 151 )   PDF (6753KB) ( 119 )  
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    Performance of the proton exchange membrane fuel cell (PEMFC) is appreciably affected by the channel geometry. The branching structure of a plant leaf and human lung is an efficient network to distribute the nutrients in the respective systems. The same nutrient transport system can be mimicked in the flow channel design of a PEMFC, to aid even reactant distribution and better water management. In this work, the effect of bio-inspired flow field designs such as lung and leaf channel design bipolar plates, on the performance of a PEMFC was examined experimentally at various operating conditions. A PEMFC of 49 cm2 area, with a Nafion 212 membrane with a 40% catalyst loading of 0.4 mg·cm-2 on the anode side and also 0.6 mg·cm-2 on the cathode side is assembled by incorporating the bio-inspired channel bipolar plate, and was tested on a programmable fuel-cell test station. The impact of the working parameters like reactants' relative humidity (RH), back pressure and fuel cell temperature on the performance of the fuel cell was examined; the operating pressure remains constant at 0.1 MPa. It was observed that the best performance was attained at a back pressure of 0.3 MPa, 75 ℃ operating temperature and 100% RH. The three flow channels were also compared at different operating pressures ranging from 0.1 MPa to 0.3 MPa, and the other parameters such as operating temperature, RH and back pressure were set as 75 ℃, 100% and 0.3 MPa. The experimental outcomes of the PEMFC with bio-inspired channels were compared with the experimental results of a conventional triple serpentine flow field. It was observed that among the different flow channel designs considered, the leaf channel design gives the best output in terms of power density. Further, the experimental results of the leaf channel design were compared with those of the interdigitated leaf channel design. The PEMFC with the interdigitated leaf channel design was found to generate 6.72% more power density than the non-interdigitated leaf channel design. The fuel cell with interdigitated leaf channel design generated 5.58% more net power density than the fuel cell with non-interdigitated leaf channel design after considering the parasitic losses.
    Dynamic optimization oriented modeling and nonlinear model predictive control of the wet limestone FGD system
    Lukuan Yang, Wenqi Zhong, Li Sun, Xi Chen, Yingjuan Shao
    2020, 28(3):  832-845.  doi:10.1016/j.cjche.2019.07.017
    Abstract ( 195 )   PDF (2139KB) ( 44 )  
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    Nonlinear model predictive control (NMPC) scheme is an effective method of multi-objective optimization control in complex industrial systems. In this paper, a NMPC scheme for the wet limestone flue gas desulphurization (WFGD) system is proposed which provides a more flexible framework of optimal control and decision-making compared with PID scheme. At first, a mathematical model of the FGD process is deduced which is suitable for NMPC structure. To equipoise the model's accuracy and conciseness, the wet limestone FGD system is separated into several modules. Based on the conservation laws, a model with reasonable simplification is developed to describe dynamics of different modules for the purpose of controller design. Then, by addressing economic objectives directly into the NMPC scheme, the NMPC controller can minimize economic cost and track the set-point simultaneously. The accuracy of model is validated by the field data of a 1000 MW thermal power plant in Henan Province, China. The simulation results show that the NMPC strategy improves the economic performance and ensures the emission requirement at the same time. In the meantime, the control scheme satisfies the multiobjective control requirements under complex operation conditions (e.g., boiler load fluctuation and set point variation). The mathematical model and NMPC structure provides the basic work for the future development of advanced optimized control algorithms in the wet limestone FGD systems.
    Performance of anaerobic fluidized bed microbial fuel cell with different porous anodes
    Xiuli Zhang, Chunhu Li, Qingjie Guo, Kelei Huang
    2020, 28(3):  846-853.  doi:10.1016/j.cjche.2019.10.002
    Abstract ( 157 )   PDF (4341KB) ( 34 )  
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    Anode materials were used to construct microbial fuel cells (MFCs), and the characteristics of the anodes were important for successful applied performance of the MFCs. Via the cyclic voltammetry (CV) method, the experiments showed that 5 wt% multiwalled carbon nanotubes (MWNTs) were optimal for the PANI/MWNT film anodes prepared using 24 polymerization cycles. The maximum output voltage of the PANI/MWNT film anodes reached 967.7 mV with a power density of 286.63 mW·m-2. Stable output voltages of 860 mV, 850 mV, and 870 mV were achieved when the anaerobic fluidized bed microbial fuel cell (AFBMFC) anodes consisted of carbon cloth with carbon black on one side, copper foam and carbon brushes, respectively. Pretreatment of the anodes before starting the AFBMFC by immersion in a stirred bacterial fluid significantly shortened the AFBMFC startup time. After the AFBMFC was continuously run, the anode surfaces generated active microbial catalytic material.
    Electrodeposition of aluminum on needle cathode using AlCl3/urea molten salts at low-temperature and its application to hydrogen generation
    Samikannu Prabu, Hong-wen Wang
    2020, 28(3):  854-863.  doi:10.1016/j.cjche.2019.11.002
    Abstract ( 156 )   PDF (3636KB) ( 70 )  
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    The electrodeposition of aluminum (Al) was studied using two electrolyte solutions, such as anhydrous AlCl3-urea and hydrated AlCl3·6H2O-urea. A systematic examination using cell voltages 1.0-2.0 V was carried out at temperatures ((50-100)±2) ℃. A needle-shaped cathode was employed for the deposition of aluminum. A dendrite and particulate microstructure of Al were observed on the needle-shaped cathode. An improved condition for the manufacturing of small sizes and high purity of aluminum deposits was obtained. Pure Al with a current efficiency (yield) of 84%-99% was obtained from those of non-aqueous electrolytes and only of 8.6%-9.3% from those of hydrated electrolytes. The electrical conductivities of electrolytes remained considerable at ((50-100)±2) ℃. The improved aluminum powders were used for the reaction with water. The aluminum reacts with water at room temperature, producing pure H2 with 100% yield. The electrodeposited aluminum metal can be used as an excellent energy carrier.
    Sulfur resource recovery based on electrolytic manganese residue calcination and manganese oxide ore desulfurization for the clean production of electrolytic manganese
    Dong Sun, Lin Yang, Ning Liu, Wenju Jiang, Xia Jiang, Jianjun Li, Zhengyou Yang, Zhengping Song
    2020, 28(3):  864-870.  doi:10.1016/j.cjche.2019.11.013
    Abstract ( 179 )   PDF (2151KB) ( 64 )  
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    An environmentally friendly and resource-conserving route to the clean production of electrolytic manganese was developed, in which the electrolytic manganese residue (EMR) was initially calcined for cement buffering; then the generated SO2-containing flue gas was managed using manganese oxide ore and anolyte (MOOA) desulfurization; at last, the desulfurized slurry was introduced to the electrolytic manganese production (EMP). Results showed that 4.0 wt% coke addition reduced the sulfur of calcined EMR to 0.9%, thereby satisfying the cement-buffer requirement. Pilot-scale desulfurization showed that about 7.5 vol% of high SO2 containing flue gas can be cleaned to less than 0.1 vol% through a five-stage countercurrent MOOA desulfurization. The desulfurized slurry had 42.44 g·L-1 Mn2+ and 1.92 g·L-1 S2O62-, which was suitable for electrowinning after purification, and the purity of manganese product was 99.93%, satisfy the National Standard of China YB/T051-2015. This new integrated technology fulfilled 99.7% of sulfur reutilization from the EMR and 94.1% was effectively used to the EMP. The MOOA desulfurization linked the EMP a closed cycle without any pollutant discharge, which promoted the cleaner production of EMP industry.
    Application of silver-based dihydric alcohol to the extraction of methyl linolenate with high extractability and stability replacing ionic liquids
    Qianxia Chen, Xianghong Lu, Jianbing Ji
    2020, 28(3):  871-880.  doi:10.1016/j.cjche.2019.12.012
    Abstract ( 160 )   PDF (1746KB) ( 20 )  
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    A novel silver-based dihydric alcohol extractant was substituted for ionic liquids to enrich methyl linolenate (C18-3) from tallow seed oil methyl ester in this study. The interactions among dihydric alcohol, Ag(I) and C18-3 were explored by FT-IR spectroscopy. The effects of dihydric alcohol structure, carrier Ag (I) concentration, temperature and initial feed concentration on extraction yield and selectivity were reported. The good extraction performance was achieved by 1,4-butanediol containing AgBF4. The complexation of Ag (I) with C18-3 was dominant in extraction operation rather than physical partition. Furthermore, a multi-step reverse extraction method was proposed to obtain C18-3 product and regenerate the extractant. 1-Hexene as the stripping phase can facilitate C18-3 reverse extraction. The content of C18-3 in the product was up to 93.36%, and the yield was 73.76%. This work opened a new route for the utilization of the dihydric alcohol properties to manipulate the carrier efficiency for extracting unsaturated fatty acid methyl esters at a lower cost.
    Evaluation on the natural gas hydrate formation process
    Shuqi Fang, Xinyue Zhang, Jingyi Zhang, Chun Chang, Pan Li, Jing Bai
    2020, 28(3):  881-888.  doi:10.1016/j.cjche.2019.12.021
    Abstract ( 139 )   PDF (666KB) ( 34 )  
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    Gas hydrates have endowed with great potential in gas storage, and rapid formation of gas hydrates is critical to use this novel technology. This work evaluated the natural gas hydrate formation process, which was compared from six parameters, including conversion of water to hydrate, storage capacity, the rate of hydrate formation, space velocity (SV) of hydrate reaction, energy consumption and hydrate removal. The literature was selected by analyzing and comparing these six parameters mentioned above, meanwhile placing emphasis on the three parameters of storage capacity, the rate of hydrate formation and space velocity of hydrate reaction. Through analysis and comparison, four conclusions could be obtained as follows. Firstly, the overall performance of the stirring process and the spraying process were better than other processes after analyzing the six parameters. Secondly, the additive types, the reactor structure and the reactor size had influence on the natural gas hydrate formation process. Thirdly, the energy consumption via reciprocating impact in the hydrate formation process was higher than that via stirring, spraying and static higee. Finally, it was one key for hydrate removal to realize the hydrate industrial production.
    Materials and Product Engineering
    Interfacial potassium induced enhanced Raman spectroscopy for single-crystal TiO2 nanowhisker
    Fan Pan, Guobing Zhou, Liangliang Huang, Wei Li, Mingshen Lin, Chang Liu
    2020, 28(3):  889-895.  doi:10.1016/j.cjche.2019.10.003
    Abstract ( 183 )   PDF (3538KB) ( 15 )  
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    Structural control and element doping are two popular strategies to produce semiconductors with surface enhanced Raman spectroscopy (SERS) properties. For TiO2 based SERS substrates, maintaining a good crystallinity is critical to achieve excellent Raman scattering. At elevated temperatures (>600 ℃), the phase transition from anatase to rutile TiO2 could result in a poor SERS performance. In this work, we report the successful synthesis of TiO2 nanowhiskers with excellent SERS properties. The enhancement factor, an index of SERS performance, is 4.96×106 for methylene blue molecule detecting, with a detection sensitivity around 10-7 mol·L-1. Characterizations, such as XRD, Raman, TEM, UV-vis and Zeta potential measurement, have been performed to decrypt structural and chemical characteristics of the newly synthesized TiO2 nanowhiskers. The photo absorption onset of MB adsorbed TiO2 nanowhiskers was similar to that of bare TiO2 nanowhiskers. In addition, no new band was observed from the UV-vis of MB modified TiO2 nanowhiskers. Both results suggest that the high enhancement factor cannot be explained by the charge-transfer mechanism. With the support of ab initio density functional theory calculations, we reveal that interfacial potassium is critical to maintain thermal stability of the anatase phase up to 900 ℃. In addition, the deposition of potassium results in a negatively charged TiO2 nanowhisker surface, which favors specific adsorption of methylene blue molecules and significantly improves SERS performance via the electrostatic adsorption effect.
    Egg shell waste as an activation agent for the manufacture of porous carbon
    Yawei Shi, Guozhu Liu, Mingde Li, Liang Wang
    2020, 28(3):  896-900.  doi:10.1016/j.cjche.2019.09.014
    Abstract ( 127 )   PDF (3659KB) ( 46 )  
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    Egg shell waste was used as an activation agent directly for the manufacture of a biomass-derived porous carbon, which possessed a surface area of 626 m2·g-1 and was rich in nitrogen, sulfur and oxygen functionalities. The activation mechanism was proposed, and the carbon showed its potential to act as an adsorbent for the adsorptive removal of various contaminants from both aqueous and non-aqueous solutions, possessing maximum adsorption capacities of 195.9, 185.1, 125.5 and 44.6 mg·g-1 for sulfamethoxazole, methyl orange, diclofenac sodium and dibenzothiophene, respectively. Through the utilization of egg shell waste as a sustainable activation agent, this work may help to make the widely applied biomass-derived porous carbons more economical and ecological.
    Hydrophilic polymeric membrane supported on silver nanoparticle surface decorated polyester textile: Toward enhancement of water flux and dye removal
    Marziyeh Mofradi, Hajir Karimi, Mehrorang Ghaedi
    2020, 28(3):  901-912.  doi:10.1016/j.cjche.2019.09.011
    Abstract ( 139 )   PDF (4856KB) ( 48 )  
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    A novel mixed matrix nanofiltration membrane was constructed by coating a casting solution containing polyvinylidene fluoride (PVDF), polyethylene glycol (PEG) as hydrophilic agent, zeolitic like framework-67 (ZIF-67), ethylenediamine as cross-linking agent on Ag-nanoparticle-decorated polyester textile (PT) support (PT/AgNPs/PVDF-PEG/ZIF-67). PT/Ag-NPs/PVDF-PEG/ZIF-67 morphology, crystalline structure, surface chemical composition and hydrophilicity of PT/Ag-NPs/PVDF-PEG/ZIF-67 were fully characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and water contact angle technique, respectively. PT/Ag-NPs/PVDF-PEG/ZIF-67 was applied in cross module set-up for removal of contaminated water containing rose bengal (RB) dye. The effect of operational parameters such as dye concentration, solution pH and flow rate on performance of PT/Ag-NPs/PVDF-PEG/ZIF-67 were investigated and optimized by central composite design (CCD). Casting solution containing 0.5 wt.% ZIF-67 as optimum value showed the good wettability, high pure water flux (PWF; 35.8 L·m-2·h-1), flux recovery ratio (FRR;90%), dye removal efficiency (96.41%). The selectivity factor of 12.72 and 14.42 was found to be for RB in the presence of amido black and methylene blue as interferent dyes, respectively, which showed a good selective recognition ability for RB dye.
    Synthesis and characterization of hybrid graphene nanocoolant for heat transfer dissipation in microchannel heat sinks
    Sudha G., Parthiban R.
    2020, 28(3):  913-922.  doi:10.1016/j.cjche.2019.06.006
    Abstract ( 201 )   PDF (1273KB) ( 40 )  
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    An attempt is made to examine the effect of hybrid nanocoolant in microchannel heat sink for computer cooling. Two-hybrid coolants with graphene as one of the prime components are synthesized and images of the particles are shown using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Heat transfer properties like thermal conductivity of the hybrid fluid, specific heat, density, and viscosity are evaluated experimentally and theoretically. The heat transfer characteristics are also studied in heat sink channels of micro level in the processors of personal computers. The parameters like internal heat transfer coefficient, thermal resistances and base temperature representing the processor temperature are examined for the applied heater power of 325 W. The coolant dilution was varied in the range of 0.05 vol%, 0.075 vol% and 0.1 vol% and the base temperature is noted. The recorded lowest base temperature is 310.01 K for the concentration of 0.1 vol% graphene-iron oxide (GFO) system for 0.5 mm fin spacing for the graphene-iron oxide hybrid coolant and for graphene oxide-iron oxide (GOFO) hybrid coolant it is 311.24 K for the same operating conditions.
    Preparation of nano-sized tungsten carbide via fluidized bed
    Feng Pan, Zhan Du, Shaofu Li, Jun Li, Meiju Zhang, Maoqiao Xiang, Qingshan Zhu
    2020, 28(3):  923-932.  doi:10.1016/j.cjche.2019.10.001
    Abstract ( 113 )   PDF (6751KB) ( 37 )  
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    Ultrafine or nano-sized of tungsten carbide (WC) is the key material to prepare ultrafine grained cemented carbides. In this paper, nano-sized WC powders were directly prepared by using industrial nano-needle violet tungsten oxide (WO2.72) as the raw material, a fluidized bed as the reactor, and CO as the carbonization gas. The relationship between particle sizes and reaction temperatures, residence times, atmospheres has been investigated systematically. In addition, the physical-chemical indexes (such as residual oxygen, total carbon and free carbon) of the products were measured. The results indicated that the particle size of WC increased with the increase of temperature from 800 to 950 ℃. As the residence time increased, the particle size decreased gradually, and then increased due to slight sintering. The introduction of hydrogen reduced the carbonization rate, and is not beneficial to obtaining nano-sized WC. Products that satisfy the standard were obtained when WO2.72 reacted with CO at 850 ℃, 900 ℃ and 950 ℃ for 3.0 h, 2.5 h and 2.0 h, respectively. The particle sizes of the three samples calculated from the specific surface area were 46.4 nm, 53.2 nm and 52.1 nm, respectively.