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Table of Content
28 March 2017, Volume 25 Issue 3
    Fluid Dynamics and Transport Phenomena
    Eulerian-Lagrangian simulation of bubble coalescence in bubbly flow using the spring-dashpot model
    Jing Xue, Feiguo Chen, Ning Yang, Wei Ge
    2017, 25(3):  249-256.  doi:10.1016/j.cjche.2016.08.006
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    The Eulerian-Lagrangian simulation of bubbly flow has the advantage of tracking the motion of bubbles in continuous fluid, and hence the position and velocity of each bubble could be accurately acquired. Previous simulation usually used the hard-sphere model for bubble-bubble interactions, assuming that bubbles are rigid spheres and the collisions between bubbles are instantaneous. The bubble contact time during collision processes is not directly taken into account in the collision model. However, the contact time is physically a prerequisite for bubbles to coalesce, and should be long enough for liquid film drainage. In thiswork we applied the spring-dashpot model to model the bubble collisions and the bubble contact time, and then integrated the spring-dashpot model with the film drainage model for coalescence and a bubble breakage model. The bubble contact time is therefore accurately recorded during the collisions. We investigated the performance of the spring-dashpot model and the effect of the normal stiffness coefficient on bubble coalescence in the simulation. The results indicate that the spring-dashpot model together with the bubble coalescence and breakage model could reasonably reproduce the two-phase flow field, bubble coalescence and bubble size distribution. The influence of normal stiffness coefficient on simulation is also discussed.
    Diffusion of chemically reactive species in third grade fluid flow over an exponentially stretching sheet considering magnetic field effects
    T. Hayat, M. Ijaz Khan, M. Waqas, A. Alsaedi, T. Yasmeen
    2017, 25(3):  257-263.  doi:10.1016/j.cjche.2016.06.008
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    This article addresses the magnetohydrodynamics (MHD) flow of a third grade fluid over an exponentially stretching sheet. Analysis is carried out in the presence of first order chemical reaction. Both cases of constructive and destructive chemical reactions are reported. Convergent solutions of the resulting differential systems are presented in series forms. Characteristics of various sundry parameters on the velocity, concentration, skin friction and local Sherwood number are analyzed and discussed.
    An improved CFD model of gas flow and particle interception in a fiber material
    Zhiwei Sun, JianhuiWen, Xiao Luo, Wen Du, Zhiwu Liang, Kaiyun Fu
    2017, 25(3):  264-273.  doi:10.1016/j.cjche.2016.08.026
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    An improved CFDmodel of gas flow and particle interception in a fiber material which fiber size is Y-shape was developed in this work. The porousmedium model was used to build the model of the whole size of fiber filter medium. Mixture modelwas adopted. The algorithm of particle interception in the whole size of fiber filter medium was derived and UDF (User Defined Function) that described kinds of particle filtering mechanisms in filter fibrous media was added to the Fluent default conservation equation as source term for simulation. The inertial resistance of the filter was taken into consideration, which provided a more precise measurement of the smoke flow and the particle interception in the filter under higher smoke speed conditions. The commercial software, Fluent 6.3, was used to simulate the smoke flow and particle interception in the filter in a single suction. The velocity and pressure profiles of smoke or nicotine particle in the filter, as well as nicotine particle volume fraction profile were well simulated. Finally, the comparisons of nicotine particle filtration efficiency between Fluent simulation results in this work and experimental results, as well as the model prediction in the literature were made to validate the simulation model. The comparisons showed that the particle entrapment model from simulation results was in good agreement with that from the experimental results. In addition, the Fluent simulation results are closer to reality both at the beginning and the end of the smoke process comparing with the model predicted results in the literature.
    Separation Science and Engineering
    Separation process of butanol-butyl acetate-methyl isobutyl ketone system by the analysis to residual curve and the double effect pressure-swing distillation
    Chunli Li, Yuanyuan Song, Jing Fang, Yang Liu, Weiyi Su, Yuqi Hu
    2017, 25(3):  274-277.  doi:10.1016/j.cjche.2016.08.011
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    The separation of ternary mixture of butanol, butyl acetate, andmethyl isobutyl ketone (MIBK)was initially analyzed by the residual curve. In this process, MIBK was chosen as the azeotropic agent during the first step of separation. The optimum mass ratio of extra MIBK was 1.6 in the modified feed stream according to the residual curve. Thus on this condition the top product was butanol-MIBK azeotrope while the bottom product was butyl acetate in the preliminary separation of the mixture. Then the butanol and MIBK azeotrope was separated by the double effect pressures wing distillation with the low pressure column performing at 30 kPa and the atmospheric pressure column at 101 kPa. The optimal operating conditions were then obtained by using Aspen Plus to simulate and optimize the process. The results showed that the mass purities of butanol, butyl acetate, and MIBK were all more than 99% and reached the design requirements. Additionally, compared with the traditional distillation with outside heating, the double effect pressure swing distillation saved the reboiler duty by 48.6% and the condenser duty by 44.6%.
    CO2/CH4 separation using inside coated thin film composite hollow fiber membranes prepared by interfacial polymerization
    Eun-Sung Jo, Xinghai An, Pravin G. Ingole, Won-Kil Choi, Yeong-Sung Park, Hyung-Keun Lee
    2017, 25(3):  278-287.  doi:10.1016/j.cjche.2016.07.010
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    Carbon dioxide (CO2) is greenhouse gas which originates primarily as a main combustion product of biogas and landfill gas. To separate this gas, an inside coated thin film composite (TFC) hollow fiber membrane was developed by inter facial polymerization between 1,3-cyclohexanebis-methylamine (CHMA) and trimesoyl chloride (TMC). ATR-FTIR, SEM and AFM were used to characterize the active thin layer formed inside the PSf hollow fiber. The separation behavior of the CHMA-TMC/PSf membrane was scrutinized by studying various effects like feed gas pressure and temperature. Furthermore, the influence of CHMA concentration and TMC concentration on membrane morphology and performance were investigated. As a result, it was found that mutually the CHMA concentration and TMC concentration play key roles in determining membrane morphology and performance. Moreover, the CHMA-TMC/PSf composite membrane showed good CO2/CH4 separation performance. For CO2/CH4 mixture gas (30/70 by volume) test, the membrane (PD1 prepared by CHMA 1.0% and TMC 0.5%) showed a CO2 permeance of 25 GPU and the best CO2/CH4 selectivity of 28 at stage cut of 0.1. The high CO2/CH4 separation performance of CHMA-TMC/PSf thin film composite membrane was mostly accredited to the thin film thickness and the properties of binary amino groups.
    Prediction of mass transfer coefficients in an asymmetric rotating disk contactor using effective diffusivity
    Meisam Torab-Mostaedi, Mehdi Asadollahzadeh, Jaber Safdari
    2017, 25(3):  288-293.  doi:10.1016/j.cjche.2016.08.021
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    Mass transfer characteristics have been investigated in a 113 mm diameter asymmetric rotating disk contactor of the pilot plant scale for two different liquid-liquid systems. The effects of operating parameters including rotor speed and continuous and dispersed phase velocities on the volumetric overall mass transfer coefficients are investigated. The results show that the mass transfer performance is strongly dependent on agitation rate and interfacial tension, but only slightly dependent on phase flow rates. In this study, effective diffusivity is used instead of molecular diffusivity in the Gröber equation for estimation of dispersed phase overall mass transfer coefficient. The enhancement factor is determined experimentally and there from an empirical expression is derived for prediction of the enhancement factor as a function of Reynolds number. The predicted results compared to the experimental data show that the proposed correlation can efficiently predict the overall mass transfer coefficients in asymmetric rotating disk contactors.
    Catalysis, Kinetics and Reaction Engineering
    Influence factors on activity of Ru-Zn catalysts in selective hydrogenation of benzene
    Qi Zhang, Xuhua Yan, Peng Zheng, Zhengbao Wang
    2017, 25(3):  294-300.  doi:10.1016/j.cjche.2016.08.004
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    Selective hydrogenation of benzene is an atom economic green route to produce cyclohexene. The control of Zn species is the key to the catalytic performance of Ru-Zn catalysts. The influences of ZnO crystals on selective hydrogenation of benzene were explored. A series of Ru-Zn catalysts with different Zn contents and ZnO morphologies were prepared by changing the amount of NaOH in the co-precipitation process. The catalysts were characterized by N2 physisorption, X-ray powder diffraction (XRD), inductively coupled plasma optical emission spectrometer (ICP-OES), scanning electron microscope (SEM), temperature-programmed reduction (H2-TPR) and Malvern laser particle size analyzer. It is found that with increasing the amount of NaOH, the Zn content first increased then decreased, and the ZnO crystals changed from relatively thicker pyramidal-shaped crystals to slimmer needle-shaped crystals. The catalyst had the highest Zn content (22.1%) and strongest interaction between ZnO crystals and Ru particles at pH 10.6 of the solution after reduction. As a result, it had the lowest activity. The activity of Ru-Zn catalysts is affected by both the Zn content and the interaction between ZnO crystals and Ru particles. The effect of reduction time was also investigated. Prolonging the reduction time caused no significant growth of ZnO crystals but the aggregation of catalyst particles and growth of Ru nanocrystals, thus resulting in the decrease of catalytic activity.
    Synthesis of epichlorohydrin from 1,3-dichloropropanol using solid base
    Yangcheng Lu, Tianyang Li, Rui Wang, Guangsheng Luo
    2017, 25(3):  301-305.  doi:10.1016/j.cjche.2016.08.019
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    In this work, the synthesis of epichlorohydrin (ECH) from 1,3-dichloropropanol (DCP) by using solid sodium hydroxide (NaOH) is carefully investigated. Inert organic solvent, 1-octanol, is introduced to ensure reaction intensity under control. The reaction performances with respect to apparent kinetics and selectivity are determined to explore optimized reaction conditions and confirm potentials for enhancing productivity in one batch. The dissolution and liquid phase reaction mechanism and instant reaction assumption are proposed and verified through process analysis. A process design towards free additional water is schematically figured out to manipulate solid NaOH, by-product, and unreacted starting materials to realize a nearly closed circuit. This process allows high selectivity over 97% and complete DCP conversion at 323.2 K within a reaction time less than 20 min. Other advantages include near-zero wastewater emission, economically possible NaOH regeneration fromNaCl, and robust operating condition window.
    High halogenated nitrobenzene hydrogenation selectivity over nano Ir particles
    Lei Ma, JianguoWang, HanbingWang, Qunfeng Zhang, Chunshan Lu, Xiaobo He, Xiaonian Li
    2017, 25(3):  306-312.  doi:10.1016/j.cjche.2016.08.005
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    The selective hydrogenation of halogenated nitrobenzene over noblemetal catalysts (Pd, Pt, and Ir) has attracted much attention owing to its high efficiency and environmental friendliness. However, the effect of size on the catalytic performance varies among different metal catalysts. In this study, sub-nano (<3 nm) Ir and Pd particles were prepared, and their catalytic properties for hydrogenation of halogenated nitrobenzene were evaluated. Results show that high selectivity (>99%) was achieved over small Ir nanoparticles, in which the selectivity over the Pd with same size was much lower than that on Ir nanoparticles. Meanwhile, Ir and Pd have different hydrogen consumption rates and reaction rates. Density functional theory calculations showed that p-chloronitrobenzene (CNB) has different adsorption properties on Ir and Pd. The distance between oxygen (cholorine) and Ir is much shorter (longer) than that between oxygen and Pd. The reaction barriers of dechlorination of p-CNB and p-chloroaniline over different Irmodels aremuch larger than those on Pd. Especially, lower coordination of Ir leads to larger barriers of dechlorination reaction. These theoretical results explain the difference between Ir and Pd on hydrogenation of halogenated nitrobenzene.
    Chemical Engineering Thermodynamics
    Determination of metastable zone and induction time of analgin for cooling crystallization
    Ling Zhou, ZhaoWang, Meijing Zhang, Mingxia Guo, Shijie Xu, Qiuxiang Yin
    2017, 25(3):  313-318.  doi:10.1016/j.cjche.2016.05.046
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    The solubility, metastable zone width, and induction time of analgin for unseeded batch cooling crystallization in ethanol-aqueous system were experimentally determined. The solubility data could be well described by the van't Hoff equation model. The metastable zone width at various cooling rates was measured, and some parameters of nucleation kinetic were calculated using the Ny'vlt theory. Furthermore, the induction period of various temperatures and supersaturation ratios was also measured. According to classical nucleation theory, some nucleation parameters and interfacial energy was calculated through the induction time (tind) data. Homogeneous nucleation tended to occurwhen the supersaturation is high, whereas heterogeneous nucleationwasmore likely to occur when the supersaturation is low.
    Investigation on specific heat capacity and thermal behavior of sodium hydroxyethyl sulfonate
    Hongying Hao, Yadong Zhang, Xiaoya Chen
    2017, 25(3):  319-323.  doi:10.1016/j.cjche.2016.11.008
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    The thermal decomposition process was studied by the TG-DTA analyzer. The results show that the decomposition process of sodiumhydroxyethyl sulfonate consisted of three stages:themass loss for the first, the second and third stagesmay be about the groups of CH3CH2OH, CH3CHO and SO2 volatilized, respectively. The decomposition residuum of three stages was analyzed by FT-IR, and the results of FT-IR agreed with the decomposition process predicted by theoreticalweight loss. The specific heat capacity of sodiumhydroxyethyl sulfonatewas determined by differential scanning calorimetry (DSC). The melting temperature and melting enthalpy were obtained to be 465.41 K and 25.69 kJ·mol-1, respectively. The molar specific heat capacity of sodium hydroxyethyl sulfonate was determinated from 310.15 K to 365.15 K and expressed as a function of temperature.
    Energy, Resources and Environmental Technology
    Characterization of pyrolytic lignins with different activities obtained from bio-oil
    Furong Leng, Yurong Wang, Junhao Chen, Shurong Wang, Jinsong Zhou, Zhongyang Luo
    2017, 25(3):  324-329.  doi:10.1016/j.cjche.2016.06.015
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    Pyrolytic lignin, the water-insoluble fraction in bio-oil, often shows a high content and has strong intermolecular interactions with other compounds in bio-oil. In order to obtain pure pyrolytic lignin and facilitate the utilization of aqueous phase obtained fromwater extraction of bio-oil,methanol-water extraction method was employed to further separate the bio-oil water-insoluble phase in this paper. Different technologies, including Fourier transform infrared spectroscopy, gel permeation chromatography, and nuclear magnetic resonance, were adopted to characterize the structures of pyrolytic lignins with different activities obtained through this method. Both the heating value and the polymerization degree of high-molecular-weight pyrolytic lignin were higher than those of low-molecular-weight pyrolytic lignin. The molecularweight distribution of high-molecular-weight pyrolytic ligninwas relatively wider, among which the contents of dimers to pentamers all accounted for 12%-18%, while the low-molecular-weight pyrolytic lignin mainly consisted of trimers (75.38%). The pyrolytic lignins had similar basic structures, both ofwhich contained syringyl and guaiacyl units,whereas the low-molecular-weight pyrolytic lignin had more abundant syringyl units, reactive carbonyl groups and hydroxyl groups. Meanwhile, thermogravimetric study revealed that the final char residue yield of low-molecular-weight pyrolytic lignin was lower than that of high-molecular-weight pyrolytic lignin.
    Efficient decolorization of dye-containing wastewater using mycelial pellets formed of marine-derived Aspergillus niger
    Tao Lu, Qilei Zhang, Shanjing Yao
    2017, 25(3):  330-337.  doi:10.1016/j.cjche.2016.08.010
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    In order to improve the efficient decolorization of dye-containing water by biosorbent and understand the biosorption mechanism, the self-immobilization mycelial pellets were prepared using a marine-derived fungus Aspergillus niger ZJUBE-1, and an azo dye, Congo red was chosen as a model dye to investigate batch decolorization efficiency by pellets. The pellets as biosorbent showed strong salt and acid tolerance in biosorption process. The results for dye adsorption showed that the biosorption process fittedwell withmodels of pseudo-second-order kinetic and Langmuir isotherm, with a maximum adsorption capacity of 263.2 mg·g-1 mycelium. During 6 batches of continuous decolorization operation, the mycelial pellets could possess efficient decolorization abilities (>98.5%). The appearance of new peak in the UV-Vis spectral result indicated that the decolorization processmay also contain biodegradation. The mechanism studies showed that efficient biosorption ability of pellets only relies on the active zone on the surface of the pellet, which can be enhanced by nutrition supplement or be shifted outward by a reculture process.
    Simulation and optimization of an industrial gas condensate stabilization unit to modify LPG and NGL production with minimizing CO2 emission to the environment
    M. Bahmani, J. Shariati, A. Nemati Rouzbahani
    2017, 25(3):  338-346.  doi:10.1016/j.cjche.2016.07.006
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    In the present study, a great effort was made to improve the performance of an industrial liquefied petroleum gas (LPG) and natural gas liquid (NGL) production unit in one of the major gas refinery located at Pars special economic zone in Iran. To demonstrate and obtain the optimal condition, the unit was simulated by using a steady-state flow sheet simulator, i.e. Aspen Plus, under different operational conditions. According to the simulation results, the unit was not operational under its optimal conditions due to some defects in the cooling system at top stage of the debutanizer tower (DBT) during hot and humid seasons. Additionally, the vapor pressure of produced LPG and accordingly the amount of its flaring were decreased by reducing the temperature of debutanizer tower at top stages. In the optimization section, the DBT condenser and reboiler heat duty, temperature, and pressure were regulated as adjustable parameters. The simulation results demonstrated that by applying the optimum suggestion in the hot months, the reflux stream temperature was reached about 55℃ which caused an efficient increment in LPG production (about 4%) with adjusting the propane component in LPG, based on the standard range as the plant criteria. Moreover, after applying modifications, about 750 t of LPG product was saved from flaring during five hot months of the year, which resulted in 360000USD extra annual income for the company. Finally, from environmental point of view, this optimization caused to reduce 81 t of CO2 emission to the environment. Therefore, the current investigation must be introduced as a friendly environmentally process.
    Bulk and bubble-scale experimental studies of influence of nanoparticles on foam stability
    Nurudeen Yekeen, Ahmad Kamal Idris, Muhammad A. Manan, Ali Mohamed Samin, Abdul Rahim Risal, Tan Xin Kun
    2017, 25(3):  347-357.  doi:10.1016/j.cjche.2016.08.012
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    Influence of silicon oxide (SiO2) and aluminum oxide (Al2O3) nanoparticles on the stability of nanoparticles and sodium dodecyl sulfate (SDS) mixed solution foams was studied at bulk and bubble-scale. Foam apparent viscosity was also determined in Hele-Shaw cell In order to investigate the foam performance at static and dynamic conditions. Results show that themaximum adsorption of surfactant on the nanoparticles occurs at 3wt% surfactant concentration. Foam stability increases while the foamability decreases with the increasing nanoparticle concentration. However, optimum nanoparticle concentration corresponding to maximum foam stability was obtained at 1.0 wt% nanoparticle concentration for the hydrophilic SiO2/SDS and Al2O3/SDS foams. Foam performance was enhanced with increasing nanoparticles hydrophobicity. Air-foams were generally more stable than CO2 foams. Foam apparent viscosity increased in the presence of nanoparticles from 20.34 mPa·s to 84.84 mPa·s while the film thickness increased from 27.5 μm to 136 μm. This study suggests that the static and dynamic stability of conventional foams could be improved with addition of appropriate concentration of nanoparticles into the surfactant solution. The nanoparticles improve foam stability by their adsorption and aggregation at the foam lamellae to increase film thickness and dilational viscoelasticity. This prevents liquid drainage and film thinning and improves foam stability both at the bulk and bubble scale.
    Materials and Product Engineering
    Polymorphism of D-mannitol: Crystal structure and the crystal growth mechanism
    Weiyi Su, Na Jia, Hongshi Li, Hongxun Hao, Chunli Li
    2017, 25(3):  358-362.  doi:10.1016/j.cjche.2016.09.002
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    The polymorphismof D-Mannitol (mannitol) is reviewed in this paper. It was found that the structure of the stable form is consistent in most literatures, but different authors have given different information about the twometastable forms. Therefore the commonly used nomenclature of mannitol was summarized based on the crystal unit cell parameters with the help of X-ray powder diffraction. Moreover, the crystal growth mechanism of mannitol polymorphs was summarized. Considering the lack of kinetic data for themetastable form especially, a reportedmethod was attempted to apply to δ mannitol in an aqueous cooling crystallization process based on the induction time previouslymeasured, and itwas identified that the growth of the δ form follows the two-dimensional (2D) nucleationmediated mechanism. The results also indicate that themethod based on induction timeand supersaturation should have the potential to be expanded to the metastable polymorphs for the growth property study in a bulk system.
    An ecofriendly approach for corrosion control of 6061 Al-15%(v) SiC(P) composite and its base alloy
    Charitha B. P., Padmalatha Rao
    2017, 25(3):  363-372.  doi:10.1016/j.cjche.2016.08.007
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    Corrosion inhibition characteristics of bio polymer dextran was studied for the corrosion control of 6061 Al-15%(v) SiC(p) composite and its base alloy in 1 mol·L-1 HCl. Standard electrochemical techniques such as potentiodynamic polarization (PDP) measurements and electrochemical impedance spectroscopy (EIS) method were adopted for corrosion rate measurement. Surface morphology was studied by scanning electron microscopy (SEM) and elemental mapping was done by energy dispersive X-ray (EDX) analysis. Suitable mechanism was proposed for corrosion and inhibition process. Results indicated that dextran acts as an excellent anticorrosive agent for the corrosion control of 6061 Al-15%(v) SiC(p) composite, with maximum inhibition efficiency of 91% for the concentration of 0.4 g·L-1 at 303 K. Dextran acted as a mixed type of inhibitor, and got physically adsorbed both on composite and base alloy by obeying Langmuir adsorption isotherm. Dextran is proved to be a green inhibitor with environmental and economic benefits.
    A novel green inhibitor for C-steel corrosion in 2.0 mol·L-1 hydrochloric acid solution
    A. Y. El-Etre, A. I. Ali
    2017, 25(3):  373-380.  doi:10.1016/j.cjche.2016.08.017
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    The corrosion inhibition characteristics of aqueous extract of seeds of Melia azedarach L. (MA) have been studied as eco-friendly green inhibitor for corrosion control of C-steel in 2 mol·L-1 HCl solution by gravimetric and electrochemical methods. The results depict that, the extract inhibits efficiently the corrosion of carbon steel in hydrochloric acid. The efficiency of extract is increased with increasing the extract concentration but independent on the studied temperature. The adsorption of the extract components onto the steel surface was found to be spontaneous, and follows Langmuir adsorption isotherm. The surface morphology of C-steel, in the absence and presence ofMA extract in 2.0 mol·L-1 hydrochloric acid solution, was studied using scanning electron microscopy (SEM).