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Table of Content
28 April 2017, Volume 25 Issue 4
    Micro-mixing in chemical reactors: A perspective
    Zaisha Mao, Chao Yang
    2017, 25(4):  381-390.  doi:10.1016/j.cjche.2016.09.012
    Abstract ( 2371 )   PDF (1194KB) ( 110 )  
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    Micro-mixing is an important mechanism,which works simultaneously with macro-mixing in chemical reactors in process industries,for achieving the best selectivity with respect to desired products.In about a half century,a huge amount of data and knowledge has been accumulated from theoretical and experimental studies on micromixing.Nevertheless,those results are mostly composites of simplified theoretical and empirical models,and the true nature of interactions of flow inhomogeneity and micro-mixing with chemical reaction has not been fully unveiled.This article reviews the progress in micro-mixing study in chemical reactors to date.A few important topics related to the nature,experimental evaluation,and numerical simulation of micro-mixing are addressed.Some suggestions are given hopefully to motivate more chemical engineers to devote their efforts to better understanding of micro-mixing in chemical reactors.
    Fluid Dynamics and Transport Phenomena
    Numerical and experimental investigations of liquid mixing in two-stage micro-impinging stream reactors
    Tianyu Guo, Bin Ruan, Zhiwei Liu, Muhammad Ali Jamal, Lixiong Wen, Jianfeng Chen
    2017, 25(4):  391-400.  doi:10.1016/j.cjche.2016.11.015
    Abstract ( 1488 )   PDF (2602KB) ( 27 )  
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    A two-stage micro-impinging stream reactor (TS-MISR) that combined a first pre-mixing stage with a second micro-impinging stream reacting stage for continuous multi-component reacting systems has been built from commercial T-junctions and steel micro-capillaries.Both of operating parameters and reactor configurations,such as jet Reynolds number (Rej),volumetric flow ratio (R),the first-stage junction angle (φ),the connecting capillary length (Lc) and connecting capillary diameter (dc),had significant effects on the micromixing efficiency of the reactor.Such effects were investigated for both of the two stage structures,respectively,by experimental and CFD methods and were optimized for the best micromixing performance.Intensified micromixing among at least three reacting components can be achieved in a continuous mode by using TS-MISR;therefore,it is expected that the TS-MISR will produce products of higher quality with more uniform and stable element distribution.
    Separation Science and Engineering
    Effect of surface property on mass flux in a variable-section microchannel
    Weicheng Xu, Yumei Yong, Junbo Xu, Chao Yang
    2017, 25(4):  401-407.  doi:10.1016/j.cjche.2016.10.011
    Abstract ( 1464 )   PDF (1270KB) ( 34 )  
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    For microfluidic systems,interfacial phenomena in micro-reactors are of great importance because they control the transfer and reaction characteristics.This paper dwells on how the surface property and geometry influence the mass flux in a complex microchannel.The lattice Boltzmann method (LBM) with a pseudo potential model and the Shan-Chen model for the interaction between fluid and hydrophobic surface were built up,so a boundary slip effect was added and verified.On this basis,a microchannel with variable-section geometry was simulated.The results indicate that the optimal design and the flow pattern are quite different under hydrophilic and hydrophobic conditions.A microchannel with sequential hydrophilic and hydrophobic surface was also simulated.The numerical results indicate that the hydrophobic wall can improve the mass flux,irrespective of microchannel geometry.Particularly,an empirical correlation with a linearly relationship between length of hydrophobic segment and mass flux was obtained for the straight microchannel.
    Preparation and properties of PPSU/GO mixed matrix membrane
    Shujuan Xiao, Shouwu Yu, Li Yan, Ying Liu, Xiaoyao Tan
    2017, 25(4):  408-414.  doi:10.1016/j.cjche.2017.02.009
    Abstract ( 1687 )   PDF (1460KB) ( 28 )  
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    Polyphenylene sulfone/graphene oxide (PPSU/GO) mixed matrix membranes with different GO contents are prepared by phase inversion technique using,PEG-1000 as porogen,and N,N-dimethylacetamide (DMAC) as solvent.The hydrophilicity and pure water flux of the membrane are investigated.The morphology,hydrophilicity,thermodynamic stability and compatibility of the membranes are characterized by various techniques such as SEM,TGA,FTIR and so on.The permeation properties of the membrane are measured in terms of pure water flux and bovine serum albumin (BSA) retention.The results indicate that when the GO content is 1.5 wt%,an evenly distributed finger structure has been formed in the mixed matrix membranes.Owing to the presence of GO,the hydrophilicity and the thermal stability of the membranes are improved,and the fouling resistance is also enhanced.
    The kinetic analysis of optimization and selective transportation of Cu(II) ions with TNOA as carrier by MDLM system
    R. Donat, Ö. Durmaz, H. Cetisșli
    2017, 25(4):  415-425.  doi:10.1016/j.cjche.2016.08.023
    Abstract ( 1548 )   PDF (6869KB) ( 10 )  
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    This study covers the transportation of Cu (Ⅱ) ions by multi-dropped liquid membrane (MDLM) system and tri-noctylamine (TNOA) as carrier in kerosene.Batch experiments are held to obtain optimum conditions for the transportation of Cu (Ⅱ) ions such as volume of donor,organic,and acceptor phase 100 ml,pH of donor phase 9.00,temperature 298.15 K,concentration of H2SO4 in acceptor phase 1.00 mol·L-1,concentration of TNOA in organic phase 5.00×10-3 mol·L-1 and rate of peristaltic pump 50 ml·min-1.Optimum circumstances of this extraction are as follows:pH of donor phase is 9.00,concentration of TNOA is 5.00×10-3 mol·L-1,1.00 mol·L-1 H2SO4 as acceptor phase,and flux rate is 50 ml·min-1.Cu (Ⅱ) ion transportation is consecutive first order irreversible reaction.Activation energy is found as 5.22 kcal·mol-1(21.82 kJ·mol-1),this process is called as diffusion controlled system.Selective transportation of Cu (Ⅱ) ions with alkaline,alkaline earth,and different heavy metal ions at optimum conditions of single Cu (Ⅱ) extraction was conducted.According to the selective transportation Cu (Ⅱ) ions with alkaline and alkaline earth metal ions,Na+,K+,and Ba2+ ions are not detected in the acceptor phase,but 12.00% of Ca2+ ions is transported from donor phase to acceptor phase.At the end of the simultaneous extraction of Zn (Ⅱ),Fe (Ⅲ),and Mo (VI) with Cu (Ⅱ) ions,2.20% of Mo (VI),0.80% of Fe (Ⅲ) and 3.60% of Zn (Ⅱ) are detected in the acceptor phase.
    Infrared thin layer drying of saffron (Crocus sativus L.) stigmas: Mass transfer parameters and quality assessment
    Mehdi Torki-Harchegani, Davoud Ghanbarian, Vida Maghsoodi, Ahmad Moheb
    2017, 25(4):  426-432.  doi:10.1016/j.cjche.2016.09.005
    Abstract ( 1660 )   PDF (601KB) ( 59 )  
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    Saffron is the most precious and expensive agricultural product.A dehydration treatment is necessary to convert Crocus sativus L.stigmas into saffron spice.To the best of our knowledge,no information on mass transfer parameters of saffron stigmas is available in the literature.This study aimed at investigating the moisture transfer parameters and quality attributes of saffron stigmas under infrared treatment at different temperatures (60,70,…,110℃).It was observed that the dehydration process of the samples occurred in a short accelerating rate period at the start followed by a falling rate period.The effective moisture diffusivity and convective mass transfer coefficient were determined by using the Dincer and Dost model.The diffusivity values varied from 1.1103×10-10 m2·s-1 to 4.1397×10-10 m2·s-1 and mass transfer coefficient varied in the range of 2.6433×10-7-8.7203×10-7 m·s-1.The activation energy was obtained to be 27.86 kJ·mol-1.The quality assessment results showed that the total crocin content increased,when the temperature increased up to 90℃ but,in higher temperatures,the amount of crocin decreased slightly.The total safranal content of the samples decreased slightly when drying temperature increased from 60℃ to 70℃ and then continuously increased up to 110℃.Also,the amount of picrocrocin increased from 83.1 to 93.3 as the drying temperature increased from 60℃ to 100℃
    Liquid-holdup regions research of novel reactive distillation column for C5 fraction separation
    Liang Guo, Tiefeng Wang, Dongfeng Li, Jinfu Wang
    2017, 25(4):  433-441.  doi:10.1016/j.cjche.2016.09.010
    Abstract ( 1908 )   PDF (1700KB) ( 71 )  
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    Recent advances in technologies of reactive distillation (RD) offer various design concepts for chemical processes.For separation of cracking C5 fraction,one of the main challenges is improving the conversion of cyclopentadiene (CPD) and the recovery of isoprene (IP).In the current work,a novel reactive distillation column with several liquid-holdup regions was designed,since it allows long residence time and provides flexibility for narrowing the efficiency gap between reaction and distillation.By use of Aspen Plus,a corresponding mathematic model was established and verified to be accurate.Following that,comprehensive studies were carried out for the design of liquid-holdup regions position.Details and principles about the separation performance with the liquid-holdup regions were revealed and optimized parameters were determined with 100 theoretical plates,feed position of 35th plate,and four liquid-holdup regions at 25th,60th,75th and 90th plate.The designed RD column could well meet the technical requirement,and influence of other important factors including residence time,operating pressure and reflux ratio was further investigated.
    Process Systems Engineering and Process Safety
    Nonlinear constrained optimization using the flexible tolerance method hybridized with different unconstrained methods
    Alice Medeiros Lima, Antonio José Gonçalves Cruz, Wu Hong Kwong
    2017, 25(4):  442-452.  doi:10.1016/j.cjche.2016.07.018
    Abstract ( 1243 )   PDF (3704KB) ( 31 )  
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    This paper proposes the use of the flexible tolerance method (FTM) modified with scaling of variables and hybridized with different unconstrained optimization methods to solve real constrained optimization problems.The benchmark problems used to analyze the performance of the methods were taken from G-Suite functions.The original method (FTM) and other four proposed methods:(i) FTM with scaling of variables (FTMS),(ii) FTMS hybridized with BFGS (FTMS-BFGS),(iii) FTMS hybridized with modified Powell's method (FTMS-Powell) and (iv) FTMS hybridized with PSO (FTMS-PSO),were implemented.The success rates of the methods were 80%,100%,75%,95% and 85%,for FTM,FTMS,FTMS-BFGS,FTMS-Powell and FTMS-PSO,respectively.Numerical experiments including real constrained problems indicated that FTMS gave the best performance,followed by FTMSPowell and FTMS-PSO.Despite the inferior performance compared to FTMS and FTMS-Powell,the FTMS-PSO method presented some advantages since good different initial points could be obtained,which allow exploring different routes through the solution space and to escape from local optima.The proposed methods proved to be an effective way of improving the performance of the original FTM.
    Integration of energy recovery network including recycling residual pressure energy with pinch technology
    Jianqiang Deng, Zheng Cao, Dongbo Zhang, Xiao Feng
    2017, 25(4):  453-462.  doi:10.1016/j.cjche.2016.07.020
    Abstract ( 1450 )   PDF (1660KB) ( 31 )  
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    Work exchange is a promising innovative technology in recovering residual pressure energy.However,at the systematic level,the comprehensive utilization of different energy resources in an energy system has become an issue of concern.In this work,a systematic approach is proposed,one that successively integrates heat,work and adjusts operation parameters.A detailed procedure for building a heat-work coupling transfer network is provided.The synthesis mainly consists of constructing a work exchange sub-network with pinch analysis based on positive displacement type work exchangers.Simultaneously,another kind of sub-network based on turbine-type work exchangers is built as a schematic comparison.The influence of applying a positive displacement work exchanger on the system is investigated.Finally,as a case study,a renovation design of a typical rectisol process in the coal-water slurry gasification section of an ammonia plant is presented.The results show that the added work exchanger has little impact on the existing heat exchange sub-network.Moreover,extra pressure energy is recovered by coupling the transfer network.It is concluded that the heat-work systematic design is a promising and powerful method to use energy more efficiently.
    An adaptive neuro-fuzzy sliding mode controller for MIMO systems with disturbance
    Mahmoud M. Saafan, Mohamed M. Abdelsalam, Mohamed S. Elksas, Sabry F. Saraya, Fayez F. G. Areed
    2017, 25(4):  463-476.  doi:10.1016/j.cjche.2016.07.021
    Abstract ( 1423 )   PDF (12128KB) ( 44 )  
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    This paper introduces the mathematical model of ammonia and urea reactors and suggested three methods for designing a special purpose controller.The first proposed method is Adaptive model predictive controller,the second is Adaptive Neural Network Model Predictive Control,and the third is Adaptive neuro-fuzzy sliding mode controller.These methods are applied to a multivariable nonlinear system as an ammonia-urea reactor system.The main target of these controllers is to achieve stabilization of the outlet concentration of ammonia and urea,a stable reaction rate,an increase in the conversion of carbon monoxide (CO) into carbon dioxide (CO2) to reduce the pollution effect,and an increase in the ammonia and urea productions,keeping the NH3/CO2 ratio equal to 3 to reduce the unreacted CO2 and NH3,and the two reactors' temperature in the suitable operating ranges due to the change in reactor parameters or external disturbance.Simulation results of the three controllers are compared.Comparative analysis proves the effectiveness of the suggested Adaptive neurofuzzy sliding mode controller than the two other controllers according to external disturbance and the change of parameters.Moreover,the suggested methods when compared with other controllers in the literature show great success in overcoming the external disturbance and the change of parameters.
    Biotechnology and Bioengineering
    Transformation mechanism of nutrient elements in the process of biochar preparation for returning biochar to soil
    Shuangshuang Tian, Zhongxin Tan, Alfreda Kasiuliene., Ping Ai
    2017, 25(4):  477-486.  doi:10.1016/j.cjche.2016.09.009
    Abstract ( 1492 )   PDF (5709KB) ( 40 )  
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    Returning biochar to soil is a heavily researched topic because biochar functions well for soil improvement.There is a significant loss of nutrients,which occurs during biochar preparation before biochar is returned to soil,thereby seriously undermining biochar's efficacy.Therefore,the transformation mechanisms of biochar pH,mass,nutrients and metals during pyrolysis under different atmospheres and temperatures were studied such that the best method for biochar preparation could be developed.Several conclusions can be reached:(1) a CO2 atmosphere is better than a N2 atmosphere for biochar preparation,although preparation in a CO2 atmosphere is not a common practice for biochar producers;(2)350℃ is the best temperature for biochar preparation because the amount of nutrient loss is notably low based on the premise of straw transferred into biochar;and (3) transforming mechanisms of pH,N,P and K are also involved in the biochar preparation process.
    Preparation of cross-linked enzyme aggregates of nitrile hydratase ES-NHT-118 from E. coli by macromolecular cross-linking agent
    Liya Zhou, Haixia Mou, Jing Gao, Li Ma, Ying He, Yanjun Jiang
    2017, 25(4):  487-492.  doi:10.1016/j.cjche.2016.08.027
    Abstract ( 1855 )   PDF (891KB) ( 19 )  
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    Cross-linked enzyme aggregates (CLEAs) of nitrile hydratase (NHase) ES-NHT-118 from Escherichia coli were prepared by using ammonium sulfate as precipitating agent followed by cross-linking with dextran polyaldehyde for the first time.In this process,egg white was added as protein feeder for facilitating the formation of CLEAs.The optimal conditions of the immobilization process were determined.Michaelis constants (Km) of free NHase and NHase CLEAs were also determined.The NHase CLEAs exhibited increased stability at varied pH and temperature conditions compared to its free counterpart.When exposed to high concentrations of acrylamide,NHase CLEAs also exhibited effective catalytic activity.
    Development of a new cleaner production process for cassava ethanol
    Ke Wang, Xinchao Yang, Xidong Ren, Jianhua Zhang, Zhonggui Mao
    2017, 25(4):  493-498.  doi:10.1016/j.cjche.2016.10.002
    Abstract ( 1689 )   PDF (1294KB) ( 79 )  
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    A new cleaner production process for cassava ethanol has been developed,in which the thin stillage by-product was treated initially by anaerobic digestion,and the digestate further processed by hydrogen-form cation exchange resin before being recycled as process water to make mash for the next ethanol fermentation batch.Thus wastewater was eliminated and freshwater and energy consumption was significantly reduced.To evaluate the new process,ten consecutive batches of ethanol fermentation and anaerobic digestion at lab scale were carried out.Average ethanol production in the recycling batches was 11.43%(v/v) which was similar to the first batch,where deionized (DI) water was used as process water.The chemical oxygen demand (COD) removal rate reached 98% and the methane yield was 322 ml per gram of COD removed,suggesting an efficient and stable operation of the anaerobic digestion.In conclusion,the application of the new process can contribute to sustainable development of the cassava ethanol industry.
    Energy, Resources and Environmental Technol
    Multi-objective regulation in autohydrolysis process of corn stover by liquid hot water pretreatment
    Huisheng Lü, Xingfang Shi, Yonghui Li, Fanmei Meng, Shuangyan Liu, Li Yan
    2017, 25(4):  499-506.  doi:10.1016/j.cjche.2017.01.007
    Abstract ( 1689 )   PDF (2088KB) ( 23 )  
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    Increasing reducing sugars (xylose and glucose) yield for bioethanol from corn stover depends strongly on optimization of pretreatment conditions.The optimum reaction conditions of two-stage liquid hot water (LHW) pretreatment based on total sugars yield were investigated.Under optimal conditions,the recovery of glucose of corn stover after two-stage LHW pretreatment and 72 h enzymatic digestion,reached 89.55%.In addition,acetic acid-rich spent liquor pretreatment and one-stage LHW pretreatment have been carried out to make comparisons with two-stage LHW treatment.Glucose yield 89.55% is superior to the recovery 83.38% using acetic acidrich spent liquor pretreatment or 80.58% using one-stage LHW pretreatment.The production of total sugars was increased by 7.8% when compared with one-stage pretreatment.Moreover,the structural features of the treated corn stover solid residues were also investigated by XRD and SEM technology in order to clarify the effects of the reaction on corn stover.The results indicated that the two-stage LHW pretreatment was an effective pretreatment method of corn stover to get most massive resource utilization,and it could be successfully applied to corn stover.
    Suppressing secondary reactions of coal pyrolysis by reducing pressure and mounting internals in fixed-bed reactor
    Shuai Cheng, Dengguo Lai, Zhen Shi, Leisheng Hong, Jianling Zhang, Xi Zeng, Shiqiu Gao, Guangwen Xu
    2017, 25(4):  507-515.  doi:10.1016/j.cjche.2016.09.013
    Abstract ( 1769 )   PDF (3164KB) ( 21 )  
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    Pyrolysis of Shenmu coal was performed in fixed-bed reactors indirectly heated by reducing operating pressure and mounting internals in the reactor to explore their synergetic effects on coal pyrolysis.Mounting internals particularly designed greatly improved the heat transfer inside coal bed and raised the yield of tar production.Reducing pressure further facilitated the production of tar through its suppression of secondary reactions occurring in the reactor.The absolute increase in tar yield reached 3.33 wt% in comparison with the pyrolysis in the reactor without internals under atmospheric pressure.The obtained tar yield in the reactor with internals under reduced pressure was even higher than the yield of Gray-King assay.Through experiments in a laboratory fixed bed reactor,it was also clarified that the effect of reducing pressure is related to volatile release rate in pyrolysis.It did not obviously vary tar yield at pyrolysis temperatures below 600℃,while the effect was evident at 650 and 700℃ but became limited again above 800℃.Under reduced pressure the produced tar contained more aliphatics and phenols but less aromatics.
    Integrated ozone–photo–Fenton process for the removal of pollutant from industrial wastewater
    P. Asaithambi, Baharak Sajjadi, Abdul Raman Abdul Aziz
    2017, 25(4):  516-522.  doi:10.1016/j.cjche.2016.10.005
    Abstract ( 1402 )   PDF (1045KB) ( 48 )  
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    The use of hybrid advanced oxidation processes (AOPs) for the removal of pollutants from industrial effluents has been extensively studied in recent literature.The aim of this study is to compare the performance of the photo,Fenton,photo-Fenton and ozone-photo-Fenton processes in terms of color removal and chemical oxygen demand (COD) removal of distillery industrial effluent together with the associated electrical energy per order.It was observed from the experimental results that the O3/UV/Fe2+/H2O2 process yielded a 100% color and 95.50% COD removals with electrical energy per order of 0.015 kW·h·m-3 compared to all other combinations of the AOPs.The effects of various operating parameters such as H2O2 and Fe2+ concentration,effluent pH,COD concentration and UV power on the removal of color,COD and electrical energy per order for the ozone-photo-Fenton process was critically studied and reported.The color and COD removals were analyzed using a UV/Vis spectrometer and closed reflux method.
    Materials and Product Engineering
    Modelling of adsorption of textile dyes over multi-walled carbon nanotubes: Equilibrium and kinetic
    Danilo Vuono, Enrico Catizzone, Alfredo Aloise, Alfonso Policicchio, Raffaele G. Agostino, Massimo Migliori, Girolamo Giordano
    2017, 25(4):  523-532.  doi:10.1016/j.cjche.2016.10.021
    Abstract ( 1450 )   PDF (1723KB) ( 36 )  
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    The paper deals with the application of multiwall carbon nanotubes (CNTs) to the adsorption of dyes from wastewater.Textile dyes are dangerous and diffused pollutant in wastewater,and the paper results confirmed the good adsorption ability of CNTs,with respect to classic active carbon,even for different dye types.The effect of surface treatments of CNTs was primarily investigated,revealing that neither the presence of residual catalyst nor common surface treatment (oxidation) affects the CNT's performances.Therefore less expensive nonpurified CNTs were assessed as good and economically convenient alternative for the process.In order to gain in generality in adsorption kinetic modelling,the parameters of the "best fitting" pseudo-second order model have been correlated to the main process variables (the dye initial concentration and the specific mass of CNTs.) setting-up a predictive kinetic model useful design new application of these materials in currently operating industrial operations for adsorption.In addition,isothermal data were used to screen all the relevant adsorption isotherms models and the Temkin model was confirmed as the more effective to accurately fit equilibrium data for any of the considered different dye types.
    Corrosion performance of Al–Al2O3 cold sprayed coatings on mild carbon steel pipe under thermal insulation
    Xiaomin Bai, Jianqun Tang, Jianming Gong, Xiaoliang Lü
    2017, 25(4):  533-539.  doi:10.1016/j.cjche.2016.10.004
    Abstract ( 1307 )   PDF (14269KB) ( 25 )  
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    This paper focused on the corrosion resistance of cold spray Al-Al2O3 composite coatings used on carbon steel pipe surfaces under thermal insulation.Al-Al2O3 coatings were produced on the carbon steel pipe surface by cold spray (CS) technology.Experimental apparatus was built to test the corrosion resistance of coatings beneath mineral wool insulation under isothermal,thermal cycling and wet/dry conditions.The results showed that when α-Al2O3 was added in spraying powder,the coating could obtain higher hardness and a denser microstructure.From corrosionunder-insulation (CUI) tests,Al-Al2O3 CS coatings were proven to be efficient in protecting carbon steel pipe from CUI mainly owning to lamellar microstructures of coatings.There was no evidence to show that α-Al2O3 might bring any negative effect on corrosion resistance.Al-Al2O3 CS coatings were sensitive to the chloride ion concentration.When these coatings were exposed to higher concentrations of NaCl,the coating's exhibited faster degradation.