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Table of Content
28 May 2016, Volume 24 Issue 5
    A paradigm-based evolution of chemical engineering
    Alexandru Woinaroschy
    2016, 24(5):  553-557.  doi:10.1016/j.cjche.2016.01.019
    Abstract ( 2064 )   PDF (718KB) ( 154 )  
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    A short presentation of chemical engineering evolution, as guided by its paradigms, is exposed. The first paradigm-unit operations-has emerged as a necessity of systematization due to the explosion of chemical industrial applications at the end of 19th century. The birth in the late 1950s of the second paradigm-transport phenomena-was the consequence of the need for a deep, scientific knowledge of the phenomena that explain what happens inside of unit operations. In the second part of 20th century, the importance of chemical product properties and qualities has become essentially in themarket fights. Accordingly, it was requiredwith additional and even new fundamental approaches, and product engineering was recognized as the third paradigm. Nowadays chemical industry, as a huge materials and energy consumer, and with a strong ecological impact, couldn't remain outside of sustainability requirements. The basics of the fourth paradigm-sustainable chemical engineering-are now formulated.
    The control and optimization ofmacro/micro-structure of ion conductive membranes for energy conversion and storage
    Xiaoming Yan, Wenji Zheng, Xuehua Ruan, Yu Pan, Xuemei Wu, Gaohong He
    2016, 24(5):  558-571.  doi:10.1016/j.cjche.2016.03.003
    Abstract ( 2254 )   PDF (8948KB) ( 32 )  
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    Ion conductivemembranes (ICMs) are frequently used as separators for energy conversion and storage technologies of fuel cells, flowbattery, and hydrogen pump, because of their good ion-selective conduction and lowelectronic conductivity. Firstly, this feature article reviews the recent studies on the development of new nonfluorinated ICMs with low cost and their macro/micro-structure control. In general, these new non-fluorinated ICMs have lower conductivity than commercial per-fluorinated ones, due to their poor ion transport channels. Increasing ion exchange capacity (IEC) would create more continuous hydrophilic channels, thus enhancing the conductivity. However, high IEC also expands the overall hydrophilic domains, weakens the interaction between polymer chains, enhances the mobility of polymer chains, and eventually induces larger swelling. The micro-scale expansion and macro-scale swelling of the ICMs with high IEC could be controlled by limiting the mobility of polymer chains. Based on this strategy, some efficient techniques have been developed, including covalent crosslinking, semi-interpenatrating polymer network, and blending. Secondly, this review introduces the optimization of macro/microstructure of both per-fluorinated and non-fluorinated ICMs to improve the performance. Macro-scalemultilayer composite is an efficientway to enhance the mechanical strength and the dimensional stability of the ICMs, and could also decrease the content of perfluorosulfonic acid resin in the membrane, thereby reducing the cost of the per-fluorinated ICMs. Long side chain, multiple functionalization, smallmolecule inducing micro-phase separation, electrospun nanofiber, and organic-inorganic hybrid could construct more efficient ion transport channels, improving the ion conductivity of ICMs.
    3D hydrodynamics involving multiple eccentric impellers in unbaffled cylindrical tank
    Houari Ameur
    2016, 24(5):  572-580.  doi:10.1016/j.cjche.2015.12.010
    Abstract ( 1728 )   PDF (14399KB) ( 38 )  
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    In this paper, the numerical predictions of 3D hydrodynamics and power consumption in a vessel stirred bymultiple eccentrically located impellers are presented. The vessel is a flat-bottomed cylindrical one equipped with six-curved bladed impellers. Aqueous solutions of xanthan gum are used, which have a shear thinning behavior with yield stress. The influence of several parameters on themixing efficiency has been investigated, namely:the stirring rate, fluid rheology, impeller number and impeller clearance fromthe tank bottom. Our predicted results are compared with other experimental data and a satisfactory agreement is found.
    Rheological behavior of hydrolyzed polyacrylamide solution flowing through a molecular weight adjusting device with porous medium
    Lühong Zhang, Jiangtao Wang, Yuqi Zhang, Bin Jiang, Xiaoming Xiao, Li Hao
    2016, 24(5):  581-587.  doi:10.1016/j.cjche.2015.12.013
    Abstract ( 1815 )   PDF (3375KB) ( 74 )  
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    The separate-layer injection in different interlayers and the injection of the same-molecular-weight polymer solution in a layer are necessary in the polymer flooding process because of heterogeneous multilayer sandstone reservoirs in EOR projects. To alleviate the matching problems between the layer permeability and the injected polymer molecular weight, a molecular weight adjusting device with porous medium was designed on the basis of mechanical degradation principle. In terms of four variables (polymer concentration, pore diameter, length of shear component and flow rate), the rheological behavior of hydrolyzed polyacrylamide (HPAM) solution flowing through the device was investigated in detail. The change of these variables is able to control the shear rate of HPAM solutions through ceramic foam, and achieve the desired degree of shear degradation and the final rheological parameters-viscosity loss, viscoelasticity and pressure drop. Therefore, a linear relationship between viscosity loss and shearing ratewas established so as to obtain the targeted viscosity easily. Field tests in the Daqing Oil Field showed that the polymer molecular weight could drop 20% to 50%. In a word, the results could guide the industrial application of the novel device and the further study of polymer degradation flowing through the porous medium.
    CFD study of turbulent jet impingement on curved surface
    Javad Taghinia, Md Mizanur Rahman, Timo Siikonen
    2016, 24(5):  588-596.  doi:10.1016/j.cjche.2015.12.009
    Abstract ( 2042 )   PDF (2720KB) ( 108 )  
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    The heat transfer and flow characteristics of air jet impingement on a curved surface are investigated with computational fluid dynamics (CFD) approach. The first applied model is a one-equation SGS model for large eddy simulation (LES) and the second one is the SST-SAS hybrid RANS-LES. These models are utilized to study the flow physics in impinging process on a curved surface for different jet-to-surface (h/B) distances at two Reynolds numbers namely, 2960 and 4740 based on the jet exit velocity (Ue) and the hydraulic diameter (2B). The predictions are compared with the experimental data in the literature and also the results from RANS k-ε model. Comparisons show that both models can produce relatively good results. However, one-equation model (OEM) produced more accurate results especially at impingement region at lower jet-to-surface distances. In terms of heat transfer, the OEM also predicted better at different jet-to-surface spacings. It is also observed that both models show similar performance at higher h/B ratios.
    Reconstruction of electrical capacitance tomography images based on fast linearized alternating direction method of multipliers for two-phase flow system
    Chongkun Xia, Chengli Su, Jiangtao Cao, Ping Li
    2016, 24(5):  597-605.  doi:10.1016/j.cjche.2016.01.017
    Abstract ( 2083 )   PDF (2154KB) ( 61 )  
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    Electrical capacitance tomography (ECT) has been applied to two-phase flowmeasurement in recent years. Image reconstruction algorithms play an important role in the successful applications of ECT. To solve the ill-posed and nonlinear inverse problem of ECT image reconstruction, a new ECT image reconstruction method based on fast linearized alternating directionmethod ofmultipliers (FLADMM) is proposed in this paper. On the basis of theoretical analysis of compressed sensing (CS), the data acquisition of ECT is regarded as a linear measurement process of permittivity distribution signal of pipe section. A new measurement matrix is designed and L1 regularization method is used to convert ECT inverse problem to a convex relaxation problem which contains prior knowledge. A new fast alternating direction method of multipliers which contained linearized idea is employed to minimize the objective function. Simulation data and experimental results indicate that compared with other methods, the quality and speed of reconstructed images are markedly improved. Also, the dynamic experimental results indicate that the proposed algorithm can fulfill the real-time requirement of ECT systems in the application.
    The correlation between nitrogen species in coke and NOx formation during regeneration
    Teng Li, Chaohe Yang, Xiaobo Chen, Libo Yao, Wei Liang, Xuemei Ding
    2016, 24(5):  606-611.  doi:10.1016/j.cjche.2015.12.019
    Abstract ( 1891 )   PDF (1176KB) ( 75 )  
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    Nitrogen oxides (NOx) emission during the regeneration of coked fluid catalytic cracking (FCC) catalysts is an environmental issue. In order to identify the correlations between nitrogen species in coke and different nitrogencontaining products in tail gas, three coked catalystswithmultilayer structural cokemolecules were prepared in a fixed bed with model compounds (o-xylene and quinoline) at first. A series of characterization methods were used to analyze coke, including elemental analysis, FT-IR, XPS, and TG-MS. XPS characterization indicates all coked catalysts present two types of nitrogen species and the type with a higher binding energy is related with the inner part nitrogen atoms interacting with acid sites. Due to the stronger adsorption ability on acid sites for basic nitrogen compounds, the multilayer structural coke has unbalanced distribution of carbon and nitrogen atoms between the inner part and the outer edge, which strongly affects gas product formation. At the early stage of regeneration, oxidation starts from the outer edge and the product NO can be reduced to N2 in high CO concentration. At the later stage, the inner part rich in nitrogen begins to be exposed to O2. At this period, the formation of CO decreases due to lack of carbon atoms, which is not beneficial to the reduction of NO. Therefore, nitrogen species in the inner part of multilayer structural coke contributesmore to NOX formation. Based on the multilayer structure model of coke molecule and its oxidation behavior, a possible strategy to control NOX emission was discussed merely from concept.
    Modeling-based optimization of a fixed-bed industrial reactor for oxidative dehydrogenation of propane
    Ali Darvishi, Razieh Davand, Farhad Khorasheh, Moslem Fattahi
    2016, 24(5):  612-622.  doi:10.1016/j.cjche.2015.12.018
    Abstract ( 2447 )   PDF (812KB) ( 143 )  
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    An industrial scale propylene production via oxidative dehydrogenation of propane (ODHP) inmulti-tubular reactorswasmodeled. Multi-tubular fixed-bed reactor used for ODHP process, employing 10000 of small diameter tubes immersed in a shell through a proper coolant flows. Herein, a theory-based pseudo-homogeneous model to describe the operation of a fixed bed reactor for the ODHP to correspondence olefin over V2O5/γ-Al2O3 catalyst was presented. Steady state one dimensional model has been developed to identify the operation parameters and to describe the propane and oxygen conversions, gas process and coolant temperatures, as well as other parameters affecting the reactor performance such as pressure. Furthermore, the applied model showed that a double-bed multitubular reactor with intermediate air injection scheme was superior to a single-bed design due to the increasing of propylene selectivity while operating under lower oxygen partial pressures resulting in propane conversion of about 37.3%. The optimized length of the reactor needed to reach 100% conversion of the oxygen was theoretically determined. For the single-bed reactor the optimized length of 11.96 m including 0.5 m of inert section at the entrance region and for the double-bed reactor design the optimized lengths of 5.72mfor the first and 7.32mfor the second reactor were calculated. Ultimately, the use of a distributed oxygen feed with limited number of injection points indicated a significant improvement on the reactor performance in terms of propane conversion and propylene selectivity. Besides, this concept could overcome the reactor runaway temperature problem and enabled operations at the wider range of conditions to obtain enhanced propylene production in an industrial scale reactor.
    Robustness of reinforced gradient-type iterative learning control for batch processes with Gaussian noise
    Xuan Yang, Xiao'e Ruan
    2016, 24(5):  623-629.  doi:10.1016/j.cjche.2015.12.011
    Abstract ( 2148 )   PDF (664KB) ( 132 )  
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    In this paper, a reinforced gradient-type iterative learning control profile is proposed by making use of system matrices and a proper learning step to improve the tracking performance of batch processes disturbed by external Gaussian white noise. The robustness is analyzed and the range of the step is specified by means of statistical technique and matrix theory. Compared with the conventional one, the proposed algorithm is more efficient to resist external noise. Numerical simulations of an injection molding process illustrate that the proposed scheme is feasible and effective.
    Measurement and modelization of VLE of binary mixtures of propyl acetate, butyl acetate or isobutyl acetate with methanol at pressure of 0.6 Mpa
    P. Susial, D. García, R. Susial, Y. C. Clavijo, A. Martín
    2016, 24(5):  630-637.  doi:10.1016/j.cjche.2015.12.017
    Abstract ( 1669 )   PDF (965KB) ( 94 )  
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    The vapor-liquid equilibriumof binarymixtures of propyl acetate, butyl acetate and isobutyl acetate withmethanol has been determined at a constant pressure of 0.6 MPa. Results have been modeledwith the Peng-Robinson equation, a traditional cubic equation of state widely employed in chemical industries, as well as with the perturbed-chain statistical associating fluid PC-SAFT theory of Gross-Sadowski. By correlation of the binary interaction parameters of these equations, the measured vapor-liquid equilibrium data can be accurately predicted. Thus, thiswork shows that thesemodels are able to represent the experimental data for systemswith associating compounds via hydrogen bonding.
    Isothermal and nonisothermal crystallization kinetics of bio-sourced nylon 69
    Zhijuan Sun, XiaoWang, Fei Guo, Chunyue Jiang, Qinmin Pan
    2016, 24(5):  638-645.  doi:10.1016/j.cjche.2015.12.021
    Abstract ( 2158 )   PDF (1107KB) ( 128 )  
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    Bio-sourced nylon 69, one of promising engineering plastics, has a great potential in developing sustainable technology and various commercial applications. Isothermal and nonisothermal crystallization kinetics of nylon 69 is a base to optimize the process conditions and establish the structure-property correlations for nylon 69, and it is also highly beneficial for successful applications of nylon products in industry. Isothermal and nonisothermal crystallization kinetics has been investigated by differential scanning calorimetry for nylon 69, bio-sourced even-odd nylon. The isothermal crystallization kinetics has been analyzed by the Avrami equation, the calculated Avrami exponent at various crystallization temperatures falls into the range of 2.28 and 2.86. In addition, the Avrami equation modified by Jeziorny and the equation suggested by Mo have been adopted to study the nonisothermal crystallization. The activation energies for isothermal and nonisothermal crystallization have also been determined. The study demonstrates that the crystallization model of nylon 69 might be a twodimensional (circular) growth at both isothermal and nonisothermal crystallization conditions. Furthermore, the value of the crystallization rate parameter (K) decreases significantly but the crystallization half-time (t1/2) increases with the increase of the isothermal crystallization temperature. To nonisothermal crystallization, the crystallization rate increases as the cooling rate increases according to the analysis of Jeziorny's theory. The results of Mo's theory suggest that a faster cooling rate is required to reach a higher relative degree of crystallinity in a unit of time, and crystallization rate decreases when the relative degree of crystallinity increases at nonisothermal crystallization conditions.
    Improving oil recovery in the CO2 flooding process by utilizing nonpolar chemical modifiers
    Yong Yang, Xiangliang Li, Ping Guo, Yayun Zhuo, Yong Sha
    2016, 24(5):  646-650.  doi:10.1016/j.cjche.2015.12.002
    Abstract ( 1765 )   PDF (799KB) ( 75 )  
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    By means of experiments of CO2 miscibility with crude oil, four nonpolar chemicals were evaluated in order to enhance the miscibility of CO2 with crude oil. Through pre-slug injection and joint injection of toluene in CO2, crude oil displacement experiments in the slim-tube were conducted to investigate effects of the tolueneenhanced CO2 flooding under simulated subterranean reservoir conditions. Experimental results showed that toluene can enhance extraction of oil into CO2 and dissolution of CO2 into oil with the increment of 251% and 64% respectively. Addition of toluene can obviously improve the oil recovery in either pre-slug injection or joint injection, and the crude oil recovery increasedwith the increase of the toluene concentration. The oil recovery can increase by 22.5% in pre-slug injectionwith the high toluene concentration. Pre-slug injectionwas recommended because it can consume less toluene than joint injection. This work could be useful to development and application of the CO2 flooding in the oil recovery as well as CO2 emission reduction.
    Application of response surface methodology to the chemical cleaning process of ultrafiltration membrane
    Caihong Wang, AishuWei, HaoWu, Fangshu Qu, Weixiong Chen, Heng Liang, Guibai Li
    2016, 24(5):  651-657.  doi:10.1016/j.cjche.2016.01.002
    Abstract ( 1972 )   PDF (7258KB) ( 39 )  
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    A numericalmodelwas established to predict and optimise the chemical cleaning process of Polyvinylidene Fluoride (PVDF) Ultrafiltration (UF) membraneswith the results fromthe experiment that applied the Response SurfaceMethod (RSM) and Central Composite Design (CCD). The factors considered in the experimental designwere sodium hydroxide (NaOH) concentration, sodium hypochlorite concentration (NaClO), citric acid concentration and cleaning duration. The interactions between the factors were investigated with the numerical model. Humic acid (20 mg·L-1)was used as themodel foulant, and chemical enhanced backflush (CEB) was employed to simulate the chemical cleaning process. The concentrations of sodium hydroxide, sodium hypochlorite, citric acid and cleaning duration tested during the experiments were in the range of 0.1%-0.3%, 100-300 mg·L-1, 1%-3% and 0.5-1.5 h, respectively. Among the variables, the sodium hypochlorite concentration and the cleaning duration showed a positive relationship involving the increased efficiency of the chemical cleaning. The chemical cleaning efficiency was hardly improved with increasing concentrations of sodium hydroxide. However, the data was sharply decreased when at a low level of sodium hydroxide concentration. In total, 54 sets of cleaning schemes with 80% to 100% cleaning efficiency were observed with the RSM model after calibration.
    Model for seawater fouling and effects of temperature, flow velocity and surface free energy on seawater fouling
    Dazhang Yang, Jianhua Liu, Xiaoxue E, Linlin Jiang
    2016, 24(5):  658-664.  doi:10.1016/j.cjche.2016.01.012
    Abstract ( 1953 )   PDF (906KB) ( 85 )  
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    A kinetic model was proposed to predict the seawater fouling process in the seawater heat exchangers. The new model adopted an expression combining depositional and removal behaviors for seawater fouling based on the Kern-Seaton model. The present model parameters include the integrated kinetic rate of deposition (kd) and the integrated kinetic rate of removal (kr),which have clear physical significance. A seawater-foulingmonitoring devicewas established to validate themodel. The experimental data werewell fitted to themodel, and the parameters were obtained in different conditions. SEM and EDX analyses were performed after the experiments, and the results show that the main components of seawater fouling are magnesium hydroxide and aluminum hydroxide. The effects of surface temperature, flow velocity and surface free energy were assessed by the model and the experimental data. The results indicate that the seawater fouling becomes aggravated as the surface temperature increased in a certain range, and the seawater fouling resistance reduced as the flowvelocity of seawater increased. Furthermore, the effect of the surface free energy ofmetals was analyzed, showing that the lower surface free energy mitigates the seawater fouling accumulation.
    Warpage prediction of the injection-molded strip-like plastic parts
    Chaofang Wang, Ming Huang, Changyu Shen, Zhenfeng Zhao
    2016, 24(5):  665-670.  doi:10.1016/j.cjche.2015.12.012
    Abstract ( 2238 )   PDF (1268KB) ( 118 )  
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    Formost strip-like plastic injectionmolded parts, whose cross section size is much smaller than their length, the traditionalHele-Shawmodel and three-dimensionalmodel do notworkwell in the prediction of thewarpage because of their special shape. A newsolutionwas suggested in thiswork. The strip-like plastic partwas regarded as a little-curved beam macroscopically, and was divided into a few one-dimensional elements. On the section of each elemental node location, two-dimensional thermal finite element analysis was made to obtain the nonuniform thermal stress caused by the time difference of the solidification of the plastic melt in the mold. The stress relaxation, or equivalently, strain creep was dealt with by using a special computing model. On the bases of in-mold elastic stress, the final bendingmoment to the beamwas obtained and thewarpagewas predicted in good agreement with practical cases.
    Thermodynamic analysis on the direct preparation of metallic vanadium from NaVO3 by molten salt electrolysis
    WeiWeng, Mingyong Wang, Xuzhong Gong, ZhiWang, Zhancheng Guo
    2016, 24(5):  671-676.  doi:10.1016/j.cjche.2016.01.006
    Abstract ( 2052 )   PDF (1984KB) ( 103 )  
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    A novel and environmentally friendly route to directly prepare metallic vanadium from NaVO3 by molten salt electrolysis is proposed. The feasibility about the direct electro-reduction of NaVO3 to metallic vanadium is analyzed based on the thermodynamic calculations and experimental verifications. The theoretical decomposition voltage of NaVO3 to metallic vanadium is only 0.47 V at 800℃ and much lower than that of the alkali and alkali earth metal chloride salts. The value is slightly higher than that of low-valence vanadium oxides such as V2O3, V3O5 and VO. However, the low-valence vanadium oxides can be further electro-reduced to metallic vanadium thermodynamically. The thermodynamic analysis is verified by the experimental results. The direct preparation of metallic vanadium from NaVO3 by molten salt electrolysis is feasible.