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Table of Content
05 August 2020, Volume 71 Issue 8
    Reviews and monographs
    Research progress in numerical simulation of rubber vulcanization
    Fei GUO,Zhaoxiang ZHANG,Wei SONG,Xiaohong JIA
    2020, 71(8):  3393-3402.  doi:10.11949/0438-1157.20200400
    Abstract ( 1189 )   HTML ( 35)   PDF (1383KB) ( 1369 )  
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    Vulcanization, as a key process in the molding process of rubber products, determines the performance and dimensional accuracy of the products. Through simulation technology, it helps to achieve accurate control of the vulcanization process and reduce energy consumption. In this paper, the research progress of numerical simulation of rubber vulcanization is reviewed from two aspects of micro scale and macro scale, and the development status of theoretical and empirical vulcanization reaction kinetic model is mainly analyzed. Finally, the development trend of numerical simulation of rubber vulcanization process is pointed out.

    Review on characterization methods of oxygen vacancy in rare earth cerium-based catalysts
    Jingfang SUN, Chengyan GE, Dongqi AN, Qing TONG, Fei GAO, Lin DONG
    2020, 71(8):  3403-3415.  doi:10.11949/0438-1157.20200131
    Abstract ( 1540 )   HTML ( 56)   PDF (3078KB) ( 658 )  
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    Oxygen vacancy (Ov) is a kind of metal oxide defect, and plays an important role in many fields such as heterogeneous catalysis, energy storage materials, energy and chemical industry, its research on theory and experiment has received extensive attention. We take the rare earth CeO2, a catalytic material widely used in energy, environment and other fields as an example, and briefly summarize some common characterization methods for the detection of oxygen vacancy, such as Raman, electron paramagnetic resonance (EPR), positron annihilation lifetime spectra (PALS), solid state nuclear magnetic resonance (ss-NMR), X-ray photoelectron spectroscopy (XPS), scanning tunneling microscope (STM), etc. The analysis of various characterization results is also illustrated by examples. On this basis, some opinions on the future development of oxygen vacancy characterization technology are proposed. It is hoped that it can provide support for the characterization and research of defects related to rare earth cerium-based catalytic materials.

    Research progress on thermochemical conversion of biomass to enhance quality and catalyst
    Li ZHANG, Zonglu YAO, Lixin ZHAO, Zhihe LI, Weiming YI, Peng FU, Chao YUAN
    2020, 71(8):  3416-3427.  doi:10.11949/0438-1157.20200191
    Abstract ( 1178 )   HTML ( 48)   PDF (2025KB) ( 586 )  
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    The preparation of high-quality bio-oils and high-value-added fine chemicals through thermochemical conversion of biomass is an important direction for future industrial development. It is an effective way to solve energy shortages and achieve closed-loop carbon. How to improve the quality and efficiency of biomass thermochemical conversion is a hot spot in academia and industry. This paper reviews the research progress of biomass thermochemical conversion under different technical paths and focus on the reaction mechanism and catalyst types of catalytic pyrolysis, hydrothermal catalysis and chemical-looping conversion. The strategy of improving quality in biomass thermochemical conversion is discussed. Finally, some suggestions of biomass thermochemical conversion are put forward, which is expected to provide reference for the high value utilization of biomass.

    Recent advances in catalytic methods of CO2 hydrogenation to clean energy
    Qi ZHOU, Honglei DING, Detong GUO, Weiguo PAN, Wei DU
    2020, 71(8):  3428-3443.  doi:10.11949/0438-1157.20200115
    Abstract ( 874 )   HTML ( 50)   PDF (2751KB) ( 791 )  
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    Excessive CO2 emissions have caused a serious greenhouse effect. The use of CO2 hydrogenation technology can achieve high-value products while reducing CO2 emissions. Therefore, it has been widely concerned by researchers. In recent years, the research on the hydrogenation of CO2 has gradually increased, but there are few related reviews to comprehensively explore multiple catalytic methods. In this paper, the relatively new CO2 hydrogenation technologies are roughly divided into 4 types: photocatalysis, electrocatalysis, biocatalysis, and plasma catalysis. From the perspective of catalysts, the research status and latest progress of four new CO2 hydrogenation technologies above are summarized, and their reaction mechanisms are briefly introduced. At the same time, based on the analysis of the current research status, the related problems that need to be further studied and solved for the four hydrogenation technologies are pointed out, and the development and industrialization of CO2 hydrogenation technology are prospected.

    Thermodynamics
    Measurement and correlation of vapor-liquid equilibria for ethanol-water-potassium acetate system under atmospheric pressure
    Jinhui TAN, Jumei XU, Yunhai SHI
    2020, 71(8):  3444-3451.  doi:10.11949/0438-1157.20191577
    Abstract ( 986 )   HTML ( 19)   PDF (1016KB) ( 459 )  
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    The vapor-liquid equilibrium data of the ethanol (1)-water (2) and ethanol (1)-water (2)-potassium acetate (3) systems at atmospheric pressure were measured using Ellis vapor-liquid two-phase double-circulation equilibrium distillation apparatus. The results show that an effect of salting-out on ethanol(1)-water(2) binary system appears by adding potassium acetate, and the relative volatility of ethanol to water increases. The azeotropic point of the mixture of ethanol and water does not exist under the concentration of potassium acetate equating 10% (mass), which shows that it can be used as a separating agent for extractive distillation with salt. The equilibrium data for ethanol(1)-water(2) binary system, as well as the system containing 10%(mass) potassium acetate were correlated by using activity coefficient models of electrolyte non-random two-liquid (eNRTL), Wilson and universal quasi-chemical (UNIQUAC), as well as electrolyte non-random two-liquid (eNRTL) integrated with the authorized Aspen Plus simulation software. The calculated results showed that average absolute deviations (AADs) of the equilibrium temperature and vapor phase molar composition are 0.72℃ (eNRTL), 0.78℃ (Wilson) and 0.71℃ (UNIQUAC); 0.0083 (eNRTL), 0.0077 (Wilson) and 0.0101 (UNIQUAC), as well as 0.25℃ and 0.0168 (eNRTL) for the system containing salt respectively. The calculated results are well consistent with the experimental data.

    High-temperature volatility characteristics and pyrolysis mechanism of common sodium salts
    Jian LI, Ge PU, Jiashan CHEN, Qiwen LIU
    2020, 71(8):  3452-3459.  doi:10.11949/0438-1157.20200061
    Abstract ( 3298 )   HTML ( 106)   PDF (1387KB) ( 957 )  
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    The common sodium salts (sodium chloride, sodium carbonate, sodium sulphate, sodium formate, sodium acetate, sodium oxalate) in organic wastewater were selected, and their high-temperature volatility characteristics were examined by thermogravimetric analyzer at 25—1400℃. Based on the principle of Gibbs free energy minimum, the volatility characteristics of NaCl, Na2CO3 and Na2SO4 were calculated thermodynamically. The results showed that in the N2 atmosphere, NaCl began to be released in the form of NaCl(g) and Na2Cl2(g) after reaching the melting point. Na2SO4 decomposed to form Na2O at high temperature, and it continued to decompose to form elemental sodium when the temperature raised. The organic carboxylic acid sodium salt was pyrolyzed to Na2CO3 before 600℃, then it decomposed to form Na2O when the temperature went up, and finally released as sodium vapor. In the air atmosphere, due to the presence of O2, the decomposition reaction of Na2O is suppressed, resulting in the decomposition rate of Na2CO3 is less than that of N2 atmosphere.

    Phase equilibria for quaternary system Rb+, Cs+, Mg2+ // SO42- - H2O at 298.2 K
    Ying ZENG, Peijun CHEN, Xudong YU
    2020, 71(8):  3460-3468.  doi:10.11949/0438-1157.20200159
    Abstract ( 539 )   HTML ( 13)   PDF (1323KB) ( 285 )  
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    Phase equilibria for the quaternary system Rb+, Cs+, Mg2+ // SO42- - H2O at 298.2 K was studied by an isothermal dissolution equilibrium method. The solubilities, densities, and refractive indices of the system at equilibrium were also determined experimentally. Based on the measured data, the stable phase diagram, and diagrams of density vs composition, refractive index vs composition were plotted. The results show that the quaternary system belongs to a complex type at 298.2 K with the double salts Cs2SO4·MgSO4·6H2O, Rb2SO4·MgSO4·6H2O, and solid solution [(Rb, Cs)2SO4] formed. The phase diagram consists of 4 invariant points, 9 univariant curves, and 6 crystallization zones. Invariant points E1, E2, and E3 belong to commensurate type, while invariant point E4 belongs to incommensurate type. The crystallization zones corrsepond to 3 single salts Rb2SO4, MgSO4·7H2O, Cs2SO4, 2 double salts Cs2SO4·MgSO4·6H2O and Rb2SO4·MgSO4·6H2O, 1 solid solution [(Rb, Cs)2SO4]. The crystallization zone of double salt Rb2SO4·MgSO4·6H2O is the largest, while the crystallization zone of single salt Cs2SO4 is the smallest, which indicating that Rb2SO4·MgSO4·6H2O is most easily crystallized. The densities and refractive indices change regularly with the changing of Cs2SO4 content of the solution. The stable phase diagram of the system will provide a theoretical basis for the development and utilization of resources such as rubidium and cesium in the magnesium sulfate subtype salt lake brine.

    Fluid dynamics and transport phenomena
    Sensitive field characteristics and reconstruction algorithm improvement of ECT measurement with filling method in irregular structure
    Zhao CHEN, Meng CHEN, Jiangjiang WANG, Jiaxing CHANG, Malin LIU
    2020, 71(8):  3469-3479.  doi:10.11949/0438-1157.20200300
    Abstract ( 440 )   HTML ( 3)   PDF (3150KB) ( 122 )  
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    The measurement range of electrical capacitance tomography(ECT) can be extended by transforming the irregular area into regular imaging area by the filling method. First, the characteristics of the sensitive field corresponding to the filling method are analyzed, and then the effects of the sensitive field, the normalized capacitance, the dielectric constant of the filling area and the image reconstruction algorithm on the imaging of the filling method are studied. The Landweber algorithm was improved using the specific boundary conditions of the filling area, and two improved methods were proposed: the transformation matrix method and the split matrix method. The results show that the absolute value of capacitance signal is enhanced and the nonlinearity degree is increased using the filling method. The sensitive field with different background has little influence on the imaging, but the sensitive field with full filling area can enhance the annular flow imaging. The normalized capacitance matrix is benefit for image reconstruction. The reconstruction image changes to be the best when the dielectric constant of the filling material is close to the higher one of the measuring area. The split matrix method reduces the solution dimension, shortens the calculation time, and has a good overall effect on all kinds of flow pattern imaging. Finally, the reliability of the improved method is verified in the general irregular structure. The results show that the improved method can be used to measure the phase holdup distribution in the general irregular structure. It can also be used in the industrial occasions where the electrode cannot be directly installed due to high temperature and corrosion in the future, which has the general significance of improving the multiphase flow measurement method.

    Performance investigation of air-source heat pump heating system with novel thermal storage refrigerant-heated panel
    Suola SHAO, Huan ZHANG, Shijun YOU, Wandong ZHENG
    2020, 71(8):  3480-3489.  doi:10.11949/0438-1157.20200165
    Abstract ( 535 )   HTML ( 6)   PDF (1635KB) ( 216 )  
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    In this paper, a novel refrigerant-heated panel (RHP) is proposed for air-source heat pump (ASHP) heating system to replace the high emission heating systems. Experiments are conducted to test the thermal performance of the RHP and system operation characteristics. Meanwhile, the system efficiency and the economic performance of the proposed system are discussed. The experimental results show that the heating capacity of the RHP is 1044 W at the condensation temperature of 39℃, and the heat stored in the RHP is more than 1000 kJ under the heating conditions. When the outdoor air temperature is 8℃, the system COP is as high as 3.7. In addition, for a residential room of 20 m2, the initial investment cost and total operating cost of the system??s heating are 3174.7 CNY and 510.7 CNY, respectively, and it has greater competitiveness in the winter heating field of residential buildings.

    Realization of microgravity environment by magnetic compensation and study on interior corner flow of magnetic fluid in microgravity
    Yi SHEN, Zeyu ZHANG, Yitao LIANG, Yonghua HUANG, Rui ZHUAN, Liang ZHANG, Shaohua BU
    2020, 71(8):  3490-3499.  doi:10.11949/0438-1157.20200291
    Abstract ( 448 )   HTML ( 3)   PDF (2056KB) ( 187 )  
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    Due to the effect of surface tension, the process of fluid climbing along the inner wall at a certain angle in the microgravity environment is different from that of normal gravity. To study the physical process of capillary flow in microgravity, this paper uses the magnetic compensation method to set up a normal temperature magnetic fluid microgravity compensation experimental platform, which achieves magnetic compensation of less than 5% non-uniformity longitudinally in the target area. Visualized experimental research on the climb process of water-based magnetic fluid along the interior corner of different materials under the condition of different gravity is performed to verify the influence of contact angle and interior corner angle on the fluid transport capacity in the microgravity environment and to reveal the capillary flow law of the magnetic fluid in the microgravity environment. The results show that when the Concus-Finn condition is satisfied, the liquid surface climbing height and the gravity acceleration are approximately inversely proportional. The smaller the contact angle and interior corner angle, the stronger the fluid transport capacity of the material, especially in a good microgravity environment. When the Concus-Finn condition is not satisfied, the liquid surface climbing height and the acceleration of gravity have a linear relationship, and the impact of changes in contact angle and interior corner angle on the fluid transport capacity is not obvious.

    Dynamics of volatile drop on surface of another immiscible liquid
    Chunxi LI, Liyu ZHUANG, Zhixian SHI, Xuemin YE
    2020, 71(8):  3500-3509.  doi:10.11949/0438-1157.20200110
    Abstract ( 569 )   HTML ( 7)   PDF (1513KB) ( 296 )  
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    Aiming at the dynamic process of evaporated droplets on the surface of immiscible and uniformly heated liquid, a set of dimensionless equations are derived based on the lubrication theory. The dynamic characteristics of evaporated droplets were studied by numerical simulation. The results show that the evolution process of the droplets can be divided into two stages: the advancing stage of the droplets dominated by spreading and the backward stage of the continuous fluctuating oscillation dominated by evaporation. The fluidity of droplets is stronger at low viscosity ratio, which leads to more rapid spreading. The increase of viscosity ratio will lead to the decrease of spreading and shrinkage rate. Evaporation affects the interfacial tension and droplets spreading by affecting the temperature distribution of the droplets interfaces. Compared with the pinning phenomenon of drop evaporation on the solid surface, the spreading of evaporated droplets on the immiscible liquid surface is depinned and accompanied by obvious deformation of the liquid substrate.

    Numerical simulation and analysis of lithium-ion battery heat pipe cooling module based on orthogonal analytic hierarchy process
    Sheng TIAN, Jiajiang XIAO
    2020, 71(8):  3510-3517.  doi:10.11949/0438-1157.20200152
    Abstract ( 413 )   HTML ( 6)   PDF (1175KB) ( 482 )  
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    A lithium-ion battery heat pipe-aluminum plate chimeric heat dissipation module is designed to increase the contact area between the heat pipe and the battery and enhance heat exchange. By means of numerical simulation and orthogonal experiment analytic hierarchy process(AHP), the influence degree and specific weight of each factor on the cooling performance of the module were studied, and then optimized the parameters. The results showed that the temperature difference of the battery module was controlled within 3℃ under each experiment scheme, which indicated the temperature uniformity of the battery module was excellent. The influence degree of each factor on the maximum temperature was as follows: the convective heat transfer coefficient of condensation section of heat pipes> the length of condensation section of heat pipes> the thickness of aluminum plates>the spacing between heat pipes. Combined with AHP analysis, the optimal parameters combination was determined as follows: the convective heat transfer coefficient of condensation section of heat pipes was 25 W·m-2·K-1, the length of heat pipes was 117 mm, the thickness of aluminum plates was 2 mm, and the spacing of heat pipes was 20 mm. Under the scheme, the maximum temperature of the system was 41.60℃ and the temperature difference was 1.35℃ when the battery module discharged at a rate of 2C to 20%, which met the cooling requirements.

    Numerical simulation of ion transfer during electrodialysis desalination process
    Haitao ZHU, Bo YANG, Yaqin WU, Congjie GAO
    2020, 71(8):  3518-3526.  doi:10.11949/0438-1157.20200185
    Abstract ( 547 )   HTML ( 15)   PDF (1856KB) ( 538 )  
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    A mathematical model of steady-state ion transfer during electrodialysis process was established to study the effects of ion charge number, diffusion coefficient and conductivity of ion-exchange membrane on mass transfer during the desalination process. The changes of ion concentration distribution, electric potential distribution and ion transfer flux distribution were described. The results showed that for the divalent ion concentration difference over the membrane decreased, transmembrane potential drop increased and transfer flux decreased in comparison with the monovalent ion. When ion diffusion coefficient was larger, concentration difference over the membrane became smaller, transmembrane potential drop, total flux and electromigration flux became higher. Additionally, ion-exchange membrane with larger conductivity made concentration difference over the membrane larger, transmembrane potential drop lower and transfer flux higher.

    Research on experimental measurement of spray parameters of nozzle by using trajectory imaging method
    Zhixiong SHI, Kewei PAN, Li PING, Bin YANG
    2020, 71(8):  3527-3534.  doi:10.11949/0438-1157.20191454
    Abstract ( 552 )   HTML ( 6)   PDF (2137KB) ( 272 )  
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    Aiming at the problem of simultaneous measurement of nozzle atomization multi-parameters, a method for measuring nozzle atomization angle, atomization fineness, droplet movement speed and distribution parameters based on image processing is proposed. The measurement system using backlight shadow imaging method, and the process and algorithm based on trajectory imaging method were established. The measurement accuracy of trajectory imaging method was validated by using standard particle measurement. The experimental synchronous measurements of spray parameters of fan-type nozzle with the different apertures on the different atomization pressure were carried out. The results show that, when the atomization pressure remains unchanged, atomization fineness and average velocity of the droplets increase by 26.82% and 10.42%, respectively, and the atomization angle decreases by 16.66% with the aperture of the fan-type nozzle changes from 0.66 mm to 1.10 mm. When the aperture remains unchanged, the atomization angle and the average velocity of the droplets increase by 47.71% and 95.10%, respectively, and the atomization fineness decreases by 44.23% with the atomization pressure increases from 0.1 MPa to 0.4 MPa. It provides an effective tool for the study of atomization droplet characteristics and the evaluation of nozzle performance.

    Characteristics of microbial fouling on Ni-P- (nano) TiO2 composite coating of plate heat exchanger
    Zuodong LIU, Siqi LI, Weiwei XING, Zhiming XU
    2020, 71(8):  3535-3544.  doi:10.11949/0438-1157.20200175
    Abstract ( 558 )   HTML ( 2)   PDF (1458KB) ( 116 )  
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    The problem of microbial fouling of heat exchangers is common in the field of energy and chemical industry. The accumulation of fouling will lead to a substantial increase in the flow resistance, fuel consumption and maintenance cost of equipment. In this paper, a nano-composite coating was prepared to reduce the adhesion and deposition of microbial fouling on heat exchange surface. Firstly, the Ni-P- (nano) TiO2 composite coatings and the controlled Ni-P coatings were prepared on stainless steel 316 plates of a plate heat exchanger by using electroless plating. Secondly, based on the heat exchanger microbial fouling on-line monitoring experimental system, the microbial fouling characteristics of plate heat exchangers coated Ni-P- (nano) TiO2 composite coating were investigated experimentally. The results showed that the friction coefficient (f) and Nusselt number (Nu) of the two coated plate heat exchangers were a little higher than the uncoated one when it is in cleaning conditions. After the microbial fouling experiment, compared with the uncoated plate heat exchanger, the fouling resistance of Ni-P coated plate heat exchanger was reduced by 8.36%—23.07%, while the other one coated Ni-P- (nano) TiO2 was reduced by 16.6%—30.96%. Under the same microbial fouling experimental conditions, the heat transfer and fouling characteristics of the two coatings were compared and analyzed further. The friction coefficient (f) of plate heat exchanger coated Ni-P- (nano) TiO2 coating was reduced by 2.54%—11.82% compared with the coated Ni-P one, while Nu was increased by 8.47%—9.45%, and the fouling resistance was reduced by 10.66%—18.18% correspondingly. The plate heat exchanger coated Ni-P- (nano) TiO2 composite coating showed an excellent microbial fouling inhibition performance in heat mass transfer process.

    Numerical simulation of distributive mixing under a pair of triangular cams
    Baiping XU, Biao LIU, Yao LIU, Shouzai TAN, Yaoxue DU, Chuntai LIU
    2020, 71(8):  3545-3555.  doi:10.11949/0438-1157.20200040
    Abstract ( 498 )   HTML ( 3)   PDF (11004KB) ( 210 )  
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    The mixing process of a highly viscous Newtonian fluid in a cavity stirred by a pair of triangular cams with different staggered angles was investigated numerically. Owing to the symmetry and period of the moving cams, only one-third of the period was calculated by a transient finite element method (FEM) combined with the mesh superposition technique (MST). A fourth-order Runge-Kutta scheme was developed to execute particle tracking based on periodic velocity fields. Mixing was characterized in terms of Poincaré sections, a Lagragian coherent structure (LCS), and a variance index of mixing. The results showed that mixing and energy consumption were insensitive to the different staggered angles. All cases approached the same asymptotical value of the variance index of mixing and shared a similar mixing mechanism where partially chaotic mixing was embedded with regular laminar Komogorov-Arnold-Moser (KAM) islands.

    Catalysis, kinetics and reactors
    Study on the photocatalytic oxidative dehydrogenation of ethane with CO2 over Pd-Rh /TiO2 catalyst
    Qianqian LI, Siyang TANG, Hairong YUE, Changjun LIU, Kui MA, Shan ZHONG, Bin LIANG
    2020, 71(8):  3556-3564.  doi:10.11949/0438-1157.20200172
    Abstract ( 702 )   HTML ( 26)   PDF (3005KB) ( 400 )  
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    Pd-Rh/ TiO2 catalyst was prepared by impregnation reduction method for photocatalytic CO2 oxidative dehydrogenation of ethane to C2H4 at room temperature. Effects of different Pd/Rh ratio of the catalysts on the photocatalytic performances were studied. Morphology characteristics of the catalysts were examined by XRD, EDX-mapping, TEM, HRTEM and XPS. The photocatalytic performances of the catalysts were measured by UV-Vis and PL. The mechanism of oxidative dehydrogenation of ethane was examined with in situ FTIR. The internal electrons transfer between Pd cluster and Rh cluster effectively improves the photocatalytic performance. It reduces the electron density of the Pd surface, and promotes the separation of e- and h+. It also improves the adsorption of C2H4 and CO2 on the surface of the catalyst. The contrast experiments of CO2 and Ar prove that CO2 does help to eliminate carbon deposed on the catalyst and to promote ethylene generating with itself reduced by H2.

    Molecular dynamics investigation on microstructure and diffusion properties of LiF-BeF2 molten salt
    Guoda HE, Rui TANG, Xuezhi DUAN, Leidong XIE, Jie FU, Jianxing DAI, Yuan QIAN, Jianqiang WANG
    2020, 71(8):  3565-3574.  doi:10.11949/0438-1157.20200350
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    LiF-BeF2 molten salt has been paid much attention in recent years as a coolant and nuclear fuel solvent for molten salt reactor, and its diffusion behavior is closely related to the compatibility of nuclear fuel and the corrosion of structural materials. In this paper, Car-Parrinello molecular dynamics simulation was used to investigate the microstructure and diffusion behavior of LiF-BeF2 melts. The results show that Be2+ has a strong complexation ability to form neutral clusters, and its number decreases with the increase of temperature. Liquid LiF-BeF2 consists of neutral clusters and free F-,Li+, BeF3- and BeF42-, rather than completely free F-, Li+ and Be2+. The self-diffusion coefficient and conductivity obtained based on this microstructure are in good agreement with the experimental results, and the change of conductivity with temperature conforms to the Arrhenius model, rather than the linear model of infinitely diluted solutions considered in the literature.

    Effect of ammonia concentration on dissolution rate of gypsum particles in phosphogypsum-ammonia-water reaction system for carbon sequestration
    Lin WU, Ji LI, Jiahua ZHU, Yuan GONG, Jing GE
    2020, 71(8):  3575-3584.  doi:10.11949/0438-1157.20200200
    Abstract ( 538 )   HTML ( 3)   PDF (2649KB) ( 209 )  
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    The dissolution of gypsum particles in the phosphogypsum-ammonia-water carbon fixation reaction system is a controlling step of the three-phase fluidized mineralization reaction system. The macroscopic dissolution rate was infected by ammonia concentrations because the N—H···O hydrogen bonds between the gypsum surface and ammonia molecules were formed in the ammonia solution. Dissolution data of gypsum particle group with certain particle size distribution were experimentally determined under different ammonia concentrations. The influence regulations of ammonia concentration on gypsum particle group dissolution characteristics were investigated combining with the population equilibrium model and the material balance method. The results indicated that the dissolution rate of gypsum reduced with increase of ammonia concentration. As the gypsum dissolution processing, the dissolution inhibition of gypsum by ammonia has been weakened. Besides, the decrease of gypsum dissolution rate would be smaller with the increase of ammonia concentration. The dissolution rate model of gypsum under different ammonia concentration were established by fit the dissolution dynamics parameters based on experimental data,and to predict the residence time required in two series loops in the TFMS, which provides theoretical support for scale up design of the phosphogypsum - ammonia - water carbon fixation system mineralizing flue gas CO2.

    Effect of Ce doping on catalytic chlorobenzene performance of Ru/TiO2 catalysts
    Wenjun LIANG, Yuxue ZHU, Xiujuan SHI, Huipin SUN, Sida REN
    2020, 71(8):  3585-3593.  doi:10.11949/0438-1157.20200261
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    A single metal Ru/TiO2 catalyst and a Ru-Ce/TiO2 catalyst were prepared by the equal-volume impregnation method to investigate their effect on the catalytic oxidation of chlorobenzene. The catalysts were characterized by N2-desorption,SEM and H2-TPR, which were used to investigate the effect of Ce doping on the catalytic oxidation of chlorobenzene. The results show that the introduction of Ce can maintain high catalytic efficiency while reducing the content of precious metals, and greatly improve the catalytic activity at low temperatures. Compared with the 0.4%Ru/TiO2, T10 and T90 of the 0.4%Ru-1.0%Ce/TiO2 decreased by 50℃ and 60℃, respectively. H2-TPR results showed that the introduction of Ce provided more surface oxygen vacancies on the catalyst, and the formation of Ru-O-Ce enhanced its REDOX capacity. The structure and morphology of the Ru/TiO2 catalyst did not change with the Ce doping, and the mesoporous structure of the catalysts maintained. However, if the content of Ce was too large, some pores on the catalysts could be blocked, which would decrease the adsorption of pollutants and catalytic reaction, and its catalytic performance would be reduced.

    Study on the catalytic pyrolysis of glucose to prepare levoglucosenone
    Kun XU, Yang FANG, Meng GONG, Yingquan CHEN, Xu CHEN, Xianhua WANG, Haiping YANG, Hanping CHEN
    2020, 71(8):  3594-3601.  doi:10.11949/0438-1157.20200345
    Abstract ( 524 )   HTML ( 5)   PDF (1494KB) ( 453 )  
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    Preparation of levoglucosenone (LGO) by catalytic pyrolysis is an important method for biomass to prepare high-value chemicals. A new type of metal sulfonated carbon catalyst was developed for the efficient preparation of LGO. The effects of pyrolysis temperature, catalyst-to-biomass ratio, and the type of metal salt on LGO production were studied. The results indicate that the sulfonated carbon impregnated with metal significantly promoted the selectivity of LGO. Under the action of Ce-SC catalyst, when the catalytic pyrolysis temperature was 300℃ and the raw material/catalyst ratio was 1∶1, the LGO content reached 82%. Under the action of Co-SC catalyst, when the catalytic pyrolysis temperature was 400℃ and the raw material/catalyst ratio was 1∶1, the LGO content reached 64%.

    One-step hydrothermal synthesis of In2S3/CdIn2S4 heterojunction microsphere and its photocatalytic performance
    Kailian ZHANG, Kai YANG, Xiaoxiao LI, Ruowen LIANG, Jie GUAN, Wenqiang LI, Jian HUANG, Changlin YU, Wenxin DAI
    2020, 71(8):  3602-3613.  doi:10.11949/0438-1157.20191475
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    In2S3/CdIn2S4 heterojunction microspheres were successfully prepared by one-step hydrothermal method, and then the photocatalytic performances were evaluated by the photocatalytic degradation of MO, AOⅡ and RhB. The consequence presented that the photocatalytic activity of In2S3/CdIn2S4 was significantly higher than those of In2S3 and CdIn2S4 catalysts, which could decompose 87%中MO, 75% AOⅡ and 96% RhB, respectively. The photogenerated electrons and holes could be separated quickly over In2S3/CdIn2S4 heterojunction microspheres, drawing a conclusion from transient photocurrent response and impedance test. The experiments captured by the main active radicals showed that the superoxide radicals and holes played a key irreplaceable role in the reaction system. Meanwhile, the stability is still at a high level after four successive cycles over In2S3/CdIn2S4 heterojunction microspheres. The enhancing activity can attribute to the heterojunction, which can contribute to the electron transfer and conclusively suppress the recombination of the electrons/holes pairs. In addition, a suitable energy band structure helps to generate a large number of photo-generated electrons, and the combination of electrons and active oxygen ultimately leads to the enhancement of oxidation ability.

    Effect of intercalation anions on catalytic performance of hydrotalcite-like precursor Ni-Al2O3 catalyst for levulinic acid hydrogenation
    Yin ZHANG, Jianjian GUO, Huanjie REN, Juan CHENG, Haitao LI, Jianbing WU, Yongxiang ZHAO
    2020, 71(8):  3614-3624.  doi:10.11949/0438-1157.20200121
    Abstract ( 442 )   HTML ( 3)   PDF (1587KB) ( 358 )  
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    Ni3Al-N-R and Ni3Al-C-R catalysts with Ni/Al mole ratio of 3∶1 were prepared by using NO3- and CO32- intercalated hydrotalcites as precursors respectively, and their catalytic properties for the hydrogenation of levulinic acid were investigated. The precursors and catalysts were characterized by N2-physical adsorption, ICP-OES, TG/DTG, XRD, H2-TPR / TPD, TEM, NH3-TPD, in-situ Py-FTIR and other characterization methods. The results showed that the intercalation anions played an important effect on the active metal-support interaction, active metal dispersion, surface acid properties, and catalytic performance of catalysts for levulinic acid hydrogenation. The catalyst derived from CO32- intercalated hydrotalcite exhibited high metal dispersion, rich L acid acidic centers, high CO hydrogenation activity, and high recycle stability. When methanol was used as the solvent at 160℃ and 4 MPa hydrogen pressure for 1 h, the yield of γ-valerolactone could reach 71.8%.

    Molecular simulation of the effect of doping modification on the adsorption properties of calcium-aluminum-based composites ester exchange catalysts
    Zhipeng LI, Shengli NIU, Kuihua HAN, Chunmei LU
    2020, 71(8):  3625-3632.  doi:10.11949/0438-1157.20200357
    Abstract ( 453 )   HTML ( 1)   PDF (2350KB) ( 488 )  
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    With the help of molecular simulations, the effect of zinc, lanthanum and magnesium doping modification on the transesterification catalyzed by calcium-aluminum composite catalyst was studied. The model for Al2O3(110) and CaO(100) surfaces were constructed and a series of derivative models doped by zinc, lanthanum, and magnesium were then obtained. Doping binding energy of various doped Al2O3(110) surfaces were calculated. The adsorption process of methanol and methyl acetate on CaO(100) and its derivative surfaces were analyzed. The adsorption process of methanol on Al2O3(110) and its derivative surfaces and the Mulliken charge density change were discussed. The results show that the calcium-aluminum composite catalysts doped with zinc, lanthanum, and magnesium can enhance the adsorption performance for methanol, which contribute a lot to catalyzing transesterification reaction.

    Separation engineering
    Study on crystallization separation of ursolic acid and oleanolic acid in ionic liquid
    Yi GAO, Yahui CAO, Jieping FAN
    2020, 71(8):  3633-3643.  doi:10.11949/0438-1157.20200003
    Abstract ( 535 )   HTML ( 6)   PDF (1154KB) ( 228 )  
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    To expand the scope of crystallization solvent and improve the performance of crystallization separation of ursolic acid and oleanolic acid, ionic liquids were introduced as the crystallization solvent. The solubility data of ursolic acid and oleanolic acid in six ionic liquids + ethanol mixed solutions were measured. Then the 1-octyl-3-methylimidazole hexafluorophosphate + ethanol mixed solution was selected as the solvent for crystallization separation of ursolic acid and oleanolic acid, and the crystallization process was optimized by single factor experiments. The best process conditions are as follows: mass fraction of 1-octyl-3-methylimidazole hexafluorophosphat 5%, mass ratio of ursolic acid to oleanolic acid 1.5∶1, crystallization temperature 30℃, crystallization time 14 h. In this case, the mass fraction of oleanolic acid in the crystals can reach about 85%.

    Study on the absorption of nitric oxide by benzoic acid-based deep eutectic solvents
    Lyuhong ZHANG, Haopeng MA, Xiaowei TANTAI, Na YANG
    2020, 71(8):  3644-3651.  doi:10.11949/0438-1157.20200116
    Abstract ( 618 )   HTML ( 7)   PDF (1038KB) ( 186 )  
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    Deep eutectic solvents (DESs) have been extensively studied and applied to the absorption of acid gases. This study found that benzoic acid DESs can reversibly and efficiently absorb nitric oxide (NO). A series of DESs based on benzoic acid (BA), thiourea, urea, imidazole as hydrogen bond donors (HBDs) and ionic liquids as hydrogen bond acceptors (HBAs) were prepared. The NO absorption results showed that DESs based by tetrabutylphosphine chloride (P4444Cl) as HBA and BA as HBD exhibited the higher NO absorption rate and NO equilibrium absorption. BA/P4444Cl (1∶2) DES exhibited the NO absorption of 2.75 mol/mol at 101.3 kPa and 303.15 K. The NO absorption capacity decreased continuously with the increasing temperature. The results of TGA measurement and regeneration experiments demonstrated that BA/P4444Cl (1∶2) DES possessed desirable thermostability and reusability. The absorption mechanism of NO by BA/P4444Cl (1∶2) DES was studied by FTIR, 1H NMR and Gaussian simulations. It was found that there was chemical interaction between NO and hydrogen-containing oxygen atom of BA, and the easily deprotonated nature of BA facilitates the absorption of NO.

    Mass transfer performance and resistance analysis of chemical absorption of NOx based on ceramic membrane contactor
    Xin ZHUO, Minghui QIU, Ping LUO
    2020, 71(8):  3652-3660.  doi:10.11949/0438-1157.20200242
    Abstract ( 462 )   HTML ( 10)   PDF (2387KB) ( 143 )  
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    To overcome the problems of large device, high operating cost and catalyst poisoning and deactivation in the selective catalytic reduction technology (SCR), Al2O3 ceramic membrane with an average pore diameter of 100 nm was hydrophobic modified and assembled into a membrane contactor, NaClO2 was used as absorbent to carry out the application research of ceramic membrane contactor in the field of denitration of flue gas. The stability of ceramic membrane contactor in chemical absorption denitrification and the effect of the process parameters (i.e. gas flow rate, concentration of absorbent, liquid of absorbent, pH of absorbent) on NO removal efficiency and mass transfer flux were investigated in detail. Based on the resistance series model, the total mass transfer coefficient equation was established. The experiments showed that the NO removal efficiency and mass transfer flux of NO were stable at about 99% and 0.038 mol·m-2·h-1 during 600 min operation of the ceramic membrane contactor. The increase of the intake air flow will promote the absorption of NO, and the absorption liquid has the highest oxidation absorption performance at pH=3, while increasing the concentration of the absorption liquid will enhance the removal effect of NO. The mass transfer performance of NO is controlled by the resistance of the gas phase, liquid phase and the membrane phase at the same time. The mass transfer resistance analysis results show that the increase of gas flow rate can decrease the gas phase resistance, increasing the concentration of the absorbent and the lower pH can reduce liquid phase resistance. The study has a good application prospect in denitration of flue gas.

    Process system engineering
    Optimal method of selecting silicon content data in blast furnace hot metal based on k-means++
    Linzi YIN, Yuyin GUAN, Zhaohui JIANG, Xuemei XU
    2020, 71(8):  3661-3670.  doi:10.11949/0438-1157.20191115
    Abstract ( 410 )   HTML ( 9)   PDF (1278KB) ( 234 )  
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    High-quality data sets are the basis for accurate prediction of silicon content in blast furnace hot metal. There are some difficulties in processing the silicon content in hot metal. One challenge is the uneven recording, especially multiple silicon contents have a large fluctuation in some sample periods. Another is that silicon content is difficult to correlate with input variables. Aiming at these problems, we proposed an optimal method of selecting silicon content data in hot metal based on k-means++ clustering algorithm. Firstly, the fast clustering ability of k-means++ is utilized to divide samples to represent different furnace conditions. Secondly, the frequency histogram of the silicon content of each cluster is counted to determine the high frequency interval. Finally, using the high frequency range as the criterion, we select the best silicon content value associated with the sample. Taking a 2650 m3 blast furnace in a certain steel works as an example, established the deep learning models respectively based on multi-layer perceptron and LSTM for prediction. The results indicated that compared with the traditional averaging method, the mean square error (MSE) can be reduced by 0.003 and the hit rate is increased by more than 10%. Thus, this method has a good guiding significance for preprocessing the silicon content data in hot metal.

    Surface and interface engineering
    Study on startup operation of dry gas seal with steam lubrication
    Yu FAN, Pengyun SONG, Hengjie XU
    2020, 71(8):  3671-3680.  doi:10.11949/0438-1157.20200134
    Abstract ( 476 )   HTML ( 3)   PDF (1331KB) ( 108 )  
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    Steam is an actual gas, so it is of great significance to study the starting process of steam-lubricated dry gas seals for the start-up and operation of steam turbine seals. The GW contact model is used whose contact model parameters are determined by experiments. The results show that the contact model parameters determined by way of experiment: asperity curvature radius R=3.7310 μm, asperity area density η=0.1458 μm-2. During the opening process, as the rotating speed increases, the gas film bearing capacity continues to increase, and the closing force remains unchanged, but the contact force rapidly decreases to zero. When the rotating speed reaches certain value, the bearing capacity of the gas film is equal to the closing force, and the sealing end face is completely separated from each other. When the curvature radius R of the micro-convex body is used as a variable, the gas film bearing capacity increases, and the contact force decreases with R decreasing. With micro-convex body area density η being a variable, the contact force increases, the gas film bearing capacity reduces. By comparing the contact model data of this paper with the model data of Etsion et al., the influence of contact model parameters on the opening performance is analyzed. It is found that based on the contact model data obtained in this paper, the contact force is slightly smaller, and both the opening force and the pressure at the groove root are mildly larger. The leakage rate is slightly smaller, and the ratio of the opening force to the leakage is lightly larger at low speed.

    Phase-distribution regularity and sealing performance of supercritical carbon dioxide dry gas seal
    Ruqi YAN, Xianzhi HONG, Xin BAO, Jie XU, Xuexing DING
    2020, 71(8):  3681-3690.  doi:10.11949/0438-1157.20200376
    Abstract ( 514 )   HTML ( 4)   PDF (2961KB) ( 285 )  
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    Taking the supercritical carbon dioxide dry gas seal as the research object, the real gas effect and viscosity change of carbon dioxide are described by the Viri equation and Lucas equation. While considering the choked flow effect, the finite difference method was used to solve the Reynolds equation considering centrifugal inertia force effect and the energy control equation, and the influence of operating condition parameters and groove structure parameters on the phase distribution and sealing performance was analyzed and discussed. The research shows that in the flow process of S-CO2 from the inlet of the seal end face to the outlet, if the operating condition parameters are set properly, it will gradually change from supercritical state to gaseous state without liquid state. Low inlet pressure, inlet temperature and rotation speed will easily lead to potential condensation flow. Compared with the influence of operating condition parameters on the phase distribution, the influence of groove parameters on the phase distribution is small and almost negligible. Except that the opening force decreases with the increase of inlet temperature, it increases with the increase of inlet pressure, rotation speed, groove depth and spiral angle. The leakage rate decreases with the increase of inlet temperature and rotation speed, but it increases with the increase of inlet pressure, groove depth and spiral angle. These results provide some support for the further study of supercritical carbon dioxide dry gas seal.

    Energy and environmental engineering
    Simulation and test of solid sorption vehicle air-conditioning system driven by exhaust heat
    Yicong TIAN, Jiao GAO, Yunfei LI, Liwei WANG, Guoliang AN
    2020, 71(8):  3691-3698.  doi:10.11949/0438-1157.20200231
    Abstract ( 428 )   HTML ( 5)   PDF (1234KB) ( 376 )  
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    The air conditioner of diesel vehicles consumes the fuel of engine, which reduces the economic benefits of diesel vehicles especially in areas with strong solar radiation. To solve this problem, a set of solid sorption vehicle air-conditioning system driven by the exhaust gas of engine is built. The system consists of two solid sorption beds filled with CaCl2/MnCl2/expanded natural graphite treated with sulphuric acid (ENG-TSA) composite sorbent, an evaporator, a condenser, a liquid storage tank, and valves. It uses ammonia as refrigerant. Natural wind cools the solid sorption bed and provides continuous cooling effect to the cabin, while the heating phase for generation is completed by exhaust gas. The system is simulated, and the refrigeration effect is tested by experiments. The simulation results show that the optimal cycle time of the system is 45 min, and theoretical average cooling power of the system can reach more than 3.5 kW, while the system COP is between 0.2 and 0.25. The experimental results show that the system can generate an average cooling capacity of 3 kW under the exhaust gas temperature of 230℃. Under the ambient temperature of 40℃, the average temperature difference of the system at the inlet and outlet of the evaporator is 6.5℃, and the average cooling capacity is 3.2 kW.

    Efficient low-carbon dolomite calcination process based on CO2 looping and recovering
    Binfan JIANG, Dehong XIA, Keke AN, Peikun ZHANG, Wenqing AO
    2020, 71(8):  3699-3709.  doi:10.11949/0438-1157.20191466
    Abstract ( 719 )   HTML ( 9)   PDF (1963KB) ( 236 )  
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    Dolomite (CaCO3·MgCO3) is a widely-used raw material in metallurgy, building materials and chemical industry. Aiming at the problem of serious CO2 emission during dolomite calcination, a new process of low-carbon calcined shaft kiln based on CO2 cycle heat carrying and resource recovery was constructed. According to thermochemistry, Gibbs free energy change of CaCO3·MgCO3 decomposition in pure CO2 environment is analyzed which shows that increase of temperature (50—100 K) is an efficient way to overcome the reaction depression by high CO2 concentration. Thermogravimetric analysis of CaCO3 decomposition in pure CO2 atmosphere is conducted, which confirms the feasibility of dolomite calcining in high CO2 concentration. The effect of CO2 pressure (PCO2) on CaCO3·MgCO3 decomposition is investigated. The heat transfer between gas and solid can be enhanced attributed to the high PCO2, which therefore improve the dolomite calcination efficiency. Afterwards, thermal analysis of the dolomite calcination system with CO2 loop is conducted, which turns out that the theoretical energy consumption is 140 kg/(t MgO), and more than 70% CO2 emission would be reduced from the calcination process.

    Simulation on lithium ion battery discharge process with large current
    Ti DONG, Peng PENG, Yiwei WANG, Wenjiong CAO, Yaodong ZHENG, Bo LEI, Fangming JIANG
    2020, 71(8):  3710-3721.  doi:10.11949/0438-1157.20200279
    Abstract ( 604 )   HTML ( 13)   PDF (4432KB) ( 247 )  
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    With the widespread application of lithium-ion batteries, the demand for batteries to operate at higher power and higher rates is becoming more and more urgent. It is necessary to explore the electro-thermal behavior and internal key parameters of lithium-ion batteries at high current operation. In this paper, a combined model of the electrochemical- thermal (ECT) coupling model and the thermal model for abusive reaction of battery materials is established. The electrical-thermal behaviors of a prismatic single-layer LiCoO2/C cell during discharge processes of various C-rates are simulated. The key electrochemical parameters and their dynamics for the cell during 1C and 14C discharge processed are analyzed and compared. The results show that with the increase of discharge current, heat accumulation in the battery will trigger the exothermic reactions of battery materials, making the battery vulnerable to thermal runaway. Besides, the concentration of Li-ion in the electrolyte, the transfer current density, the over potential, the electrolyte potential and the lithium concentration at the surface of solid particles fluctuate greatly during high C-rate discharge processes, leading to significant differences of species concentration, density and electric potential in the relevant regions inside the battery.

    Rapid industrial enrichment of nitrifying bacteria
    Zongyue LIU, Hong YANG, Shaolun WANG, Jiawei WANG
    2020, 71(8):  3722-3729.  doi:10.11949/0438-1157.20200256
    Abstract ( 487 )   HTML ( 6)   PDF (1725KB) ( 202 )  
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    To explore an effective method of rapid enrichment of nitrifying bacteria, the industrial bioreactor was used to complete the rapid enrichment of nitrifying bacteria. From the data results and high throughput results, 24—27 d is the best economic sludge extraction period, and sludge concentration 3000—4000 mg·L-1 is the best bacterial growth control concentration, and the daily sludge output in stable operation stage is 0.3 kg·(m3·d)-1. Comparing and analyzing the changes of activated sludge and sludge community in different levels in the whole culture process, it is found that the screening and production of functional bacteria can be realized in a short time. It is proved that the industrial bioreactor is feasible for the rapid enrichment and cultivation of nitrifying bacteria on a large scale and stable mud production. It provides a technical route for the large-scale application of embedding and immobilization technology in the preparation of bacterial sources. Through the exploration of nitrifying bacteria cultivation experiments, the cultivation cycle was optimized, and the evolution of bacteria was analyzed.

    Treatment of high-strength wastewater generated in cosmetics raw materials production using polymer flocculants
    Lanhe ZHANG, Sa WAN, Zicheng CHEN, Jingbo GUO, Suiyi ZHU, Yanping JIA, Zheng LI
    2020, 71(8):  3730-3740.  doi:10.11949/0438-1157.20200211
    Abstract ( 489 )   HTML ( 6)   PDF (3456KB) ( 217 )  
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    The wastewater produced during the production of cosmetic raw materials has complex water quality components, high organic content, and is difficult to degrade. The use of coagulation technology to treat this wastewater can slow down the burden of biochemical treatment units and improve the efficiency of wastewater treatment. To reveal the mechanisms of pollutants removal and the change of sludge properties in the coagulation process using inorganic polymer coagulant, the effects of the dosage of poly aluminum chloride (PAC), poly ferric sulfate (PFS) and poly aluminum ferric chloride (PAFC) as coagulants and polyacrylamide (PAM) as coagulant aid on the removal efficiencies of pollutants and the sludge properties were investigated. The functional groups, surface morphology, elemental composition and thermal stability of sludge flocs were analyzed by using Fourier transform infrared spectroscopy (FTIR), X-ray energy spectroscopy (EDX), scanning electron microscopy (SEM) and thermogravimetric analyzer (TGA), respectively. The molecular weight distribution of organic compounds and the changes of organic composition in the wastewater were analyzed by three-dimensional fluorescence spectroscopy (3D-EEM) and ultrafiltration, respectively. The operation conditions of the coagulation process were then optimized based on the above results. It showed that natural organic matter (NOM) in the influent had high fluorescence intensity. The molecular weight distributions of organic compounds were higher than 100×103 and lower than 3×103, which accounted for 22.89% and 50.57%, respectively. When influent COD was 6700—7500 mg/L and PAM concentration was 0.03 g/L, the removal efficiencies of COD were 87.20%, 79.89% and 83.74% and the effluent turbidity were 2.54 NTU, 9.3 NTU and 5.51 NTU under 2.8 g/L of PAC, 2.8 g/L of PFS and 3.0 g/L of PAFC, respectively. The fluorescence intensity of NOM decreased obviously. The removal of organic compounds was the highest when PAC and PAM were used simultaneously and the molecular weight of organic compounds in the effluent mainly distributed in the range of (10—30)×103 and <3×103 with a proportion of 31.84% and 25.92%, respectively. The formed flocculation sludge had a good thermal stability, fluffy surface and porous network structure. The coagulation process can adsorb lipid macromolecules and improve the biodegradability of the high-strength wastewater generated in the cosmetics raw materials production.

    Modeling and simulation of wet desulfurization system dynamic process
    Shuangchen MA, Quan ZHOU, Jianzong CAO, Qi LIU, Wentong CHEN, Shuaijun FAN, Yakun YAO, Chenyu LIN, Caini MA
    2020, 71(8):  3741-3751.  doi:10.11949/0438-1157.20200149
    Abstract ( 748 )   HTML ( 10)   PDF (1561KB) ( 357 )  
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    The chemical mechanism model of the desulfurization tower in limestone-gypsum flue gas desulfurization was established, and the chemical process of flue gas desulfurization in the tower was dynamically simulated. Based on the material balance and chemical balance in the desulfurization tower, the model is described as a differential equation and solved by the special calculation software. Based on the actual operation data of the desulfurization system of a power plant, the changes of various indexes of the desulfurization system, such as pH, desulfurization rate, etc., and the axial spatial distributions of some important chemical substances, such as H +, SO2, are predicted. According to the calculation results, the influence of pH on the desulfurization rate is analyzed, and the boundary conditions of the operating parameters are explored and found. The results of this study put forward optimization suggestions for the design and operation of the actual desulfurization tower, and strengthen the anticorrosive performance at the flue gas inlet. The pH of the power plant slurry should be controlled at 4.2—5.3.

    Evaluation of biotoxicity of iron-carbon micro-electrolysis treatment of printing and dyeing wastewater by E.coli
    Yanping JIA, Zhen ZHANG, Zewei TONG, Wei WANG, Lanhe ZHANG
    2020, 71(8):  3752-3760.  doi:10.11949/0438-1157.20200148
    Abstract ( 453 )   HTML ( 4)   PDF (1447KB) ( 139 )  
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    The composition of printing and dyeing wastewater is complex, with high chroma and strong toxicity. By analyzing the morphology, antioxidant enzymes and biomarkers of E. coli (Escherichia coli), the biological toxicity of printing and dyeing wastewater before and after treatment with iron-carbon micro-electrolysis process was studied. The results showed that E.coli cells were broken in the influent and most of E.coli cells were in normal shape in the effluent. Compared with the influent, antioxidant enzyme, malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD ), catalase (CAT), and total antioxidant ability (T-AOC) in the effluent group decreased by 80.85%, 53.73%, 67.74%, 44.90% and 43.38%, respectively. After the printing and dyeing wastewater was treated by the iron-carbon micro-electrolysis process, its toxicity was reduced and the antioxidant system of E.coli was nearly in normal level. The glucose consumption inhibition rates of the influent and the effluent were 85% and 47%, respectively. Compared with the influent group, calorific value increased by 21.95%, endogenous fluorescent protein increased by 112.96%, and nucleic acid content decreased by 44.04% in effluent wastewater, respectively. Therefore, the iron-carbon micro-electrolysis process could reduce the biological toxicity of dyeing wastewater.

    Structure characterization of pine lignin extracted by different alcohol solvents
    Dongling WANG, Wenjin WANG, Zifang PENG, Ying XU, Jianguo LIU, Haiyong WANG, Chenguang WANG, Qi ZHANG, Longlong MA
    2020, 71(8):  3761-3769.  doi:10.11949/0438-1157.20191523
    Abstract ( 845 )   HTML ( 20)   PDF (1839KB) ( 445 )  
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    To further understand the impact of lignin extracted by organic solvent and the influence of their structure, the effects of solvent polarity on the yield of lignin extracted by 6 organic alcohol solvents (methanol, ethanol, n-propanol, glycol, 1,3-propylene glycol and 1,4-butanediol) were systematically studied. At the same time, SEM (scanning electron microscope), GPC (gel permeation chromatography), NMR and other methods were used to further explore the effect of different alcohol solvents on lignin morphology, molecular weight and functional groups. The results showed that the polarity, length of carbon chain and number of hydroxyl groups had significant effects on lignin yield and the characteristic, such as morphology, molecular weight and functional groups. With the same number of hydroxyl groups, the longer the carbon chain and the weaker the polarity, the higher the lignin yield as well as the higher the average molecular weight they were. The content of C and H elements in lignin extracted from monohydric alcohol solvent system decreased with the increase of carbon chain length, while the content of C and H elements in lignin extracted from dihydric alcohol system showed an opposite trend. With the increase of hydroxyl groups, the yield and the average molecular weight of lignin decreased.

    Numerical simulation of performance of thermally regenerative ammonia-based battery with copper foam electrode
    Yongsheng ZHANG, Liang ZHANG, Jun LI, Qian FU, Xun ZHU, Qiang LIAO, Yu SHI
    2020, 71(8):  3770-3779.  doi:10.11949/0438-1157.20200126
    Abstract ( 405 )   HTML ( 12)   PDF (1776KB) ( 186 )  
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    A steady-state mathematical model that coupled the mass transfer and electrochemical reaction in a porous medium was proposed for a thermally regenerative ammonia-based battery (TRAB) with copper foam electrode. The battery performance and internal mass transfer characteristics of the porous electrode were obtained and the effects of electrolyte concentration and electrode porosity on battery performance were studied. The results showed that the anode ammonia and cathode copper ions were gradually consumed from the mainstream to the inside of the porous electrode, which led to a concentration gradient. With the increase of the reaction current, the concentration gradient increased obviously. In a certain range, with the increase of the concentration of anodic ammonia and cathode copper ions, the material transfer from the main flow area to the porous electrode improved. As the concentration of ammonium sulfate increases, the electrolyte conductivity increases, and the battery performance gradually improves, but the increase decreases gradually. In addition, the porous electrode porosity will also affect the battery performance. In this study, TRAB obtained the highest maximum power (15.3 mW) when the electrode porosity was 0.6.

    Influences of Pt-Ir electro-codeposition potentials on hydrogen production with ammonia electrolysis
    Yudong YAO, Zhonghua WANG, Zhibin LIN, Xiaohui HU, Jin CHEN, Songsheng ZHENG, Zhaolin WANG
    2020, 71(8):  3780-3788.  doi:10.11949/0438-1157.20200009
    Abstract ( 847 )   HTML ( 31)   PDF (2276KB) ( 230 )  
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    To study the feasibility of on-line electrolysis of ammonia water to provide hydrogen for hydrogen fuel cell, Pt-Ir catalyst was prepared by electrochemical co-deposition under different deposition conditions. Performance of Pt-Ir catalyst for ammonia electrolysis was studied by cyclic voltammetry (CV) and chronoamperometry (I-t) combined with SEM, XPS and XRD. The results show that the deposition potential affects the composition, crystal form, and grain size of the alloy catalyst, which further affects the performance of the electrode in the ammonia catalysis process. For a certain deposition potential, the morphology, structure and composition of the catalyst are stable in certain range. In the ammonia electrooxidation reaction process, the catalyst prepared at -0.05 V (vs. SCE) had not only better persistence and stability, but also the lowest catalyst load and overpotential. Because of the different potential between electrochemical electrolysis of ammonia and water, it is possible to supply hydrogen for the fuel cell via ammonia electrolyzing. When at low current density(<10 mA/cm2), fuel cells could provide energy to ammonia electrolysis cell while still having more than 40% additional power for other usages.

    Performance of biogas engine driven air source heat pump system under variable conditions
    Jiying WU, Yimin MA, Wensheng CAO
    2020, 71(8):  3789-3796.  doi:10.11949/0438-1157.20191417
    Abstract ( 447 )   HTML ( 2)   PDF (1139KB) ( 407 )  
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    To efficiently use biogas resources and reduce environmental pollution, an experimental device for energy comprehensive utilization of airsource heat pump driven by a biogas engine was constructed, focusing on the effects of evaporation temperature, cooling water flow rate, biogas engine speed and other parameters on system performance. Experiment results show that while total condenser load increases with rising evaporator temperature and cooling water flow rate, the rate of increase is small. The recovered biogas engine waste heat decreases with rising evaporator temperature although the rate of decrease is not large, but cooling water flow rate increase can improve the recovered rate of biogas engine waste heat and the total heating capacity of the system at the time. Effect of cooling water flow rate on system coefficient of performance (COP) is not monotonic, and there exists an optimum cooling water flow rate under certain working conditions. Different cooling water flow rate has different effect on primary energy ratio (PER), and lesser PER increase corresponds larger cooling water flow rate. Under the experiment conditions, the maximum system COP and PER are 5.15 and 1.68 respectively.

    Material science and engineering, nanotechnology
    Fabrication and controlled-release properties of intestinal-targeted Ca-alginate-based capsules
    Shuang WEN, Xiaojie JU, Rui XIE, Wei WANG, Zhuang LIU, Liangyin CHU
    2020, 71(8):  3797-3806.  doi:10.11949/0438-1157.20200418
    Abstract ( 573 )   HTML ( 13)   PDF (2292KB) ( 759 )  
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    Ca-alginate-chitosan/protamine/silica (ACPSi) composite microcapsules were prepared by using capillary coextrusion technology combined with electrostatic adsorption and bionic silicification. The prepared composite ACPSi capsules have good monodispersity and the average particle size is about 3.18 mm. The rigid outer silica layer of the microcapsules can effectively inhibit the capsule swelling at pH 6.8 to improve the mechanical stability of the microcapsules. In addition, drug release behavior of microcapsules can be further controlled by embedding HPMCP enteric microspheres into the shell of ACPSi capsules as “micro-valves”. When the concentration of indomethacin is 22.5 mg/ml, the cumulative release rate of the ACPSi capsules is 0.33% at pH 2.5 for 3 h, after transferring to pH 6.8 buffer solution for 19 h, the cumulative release rate reaches 77.78%. The cumulative release rate can be increased by about 4% when HPMCP microspheres embedded into the capsule shell. The proposed ACPSi composite capsules exhibit good intestinal-targeted controlled-release performance, which provides a new strategy for developing oral intestinal-targeted drug delivery systems.

    Application of PVA membrane filled with hydrophilic ZSM-5 molecular sieve on separation of water from ethyl acetate
    Wei WANG, Xueying JIANG, Yue LI, Liping SU, Yun ZOU, Zhangfa TONG
    2020, 71(8):  3807-3818.  doi:10.11949/0438-1157.20200577
    Abstract ( 613 )   HTML ( 10)   PDF (2366KB) ( 227 )  
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    To remove trace water from ethyl acetate with low energy consumption and high efficiency, PVA/ZSM-5 mixed matrix membranes (MMMs) were prepared by adding the hydrophilic ZSM-5 zeolite material into polyvinyl alcohol (PVA) polymer. The morphology, physicochemical properties of MMMs were characterized by SEM, FTIR, XRD, TGA and contact angle. The swelling behavior of the membrane materials in various solutions and the influence of filler content, feed temperature and feed concentration on the performance of pervaporation separation of ethyl acetate and water mixture were investigated by single factor experiments. The results showed that ZSM-5 particles were evenly dispersed into PVA polymer. In addition to the inherent hydrophilicity of ZSM-5, there is also a hydrogen bond interaction between ZSM-5 and PVA, but there is no chemical interaction between them. With the increase of feed concentration, the permeate flux increased, while the separation factor decreased. With the increase of feed temperature, the permeate flux and separation factor increased. With the increase of ZSM-5 filling content, the permeate flux and separation factor increased first and then decreased. When filling content of ZSM-5 was 6%(mass), the permeation flux and separation factor reached the maximum value of 1231 g/(m2·h) and 6072, respectively, which was 2.9 times higher than the pure PVA membrane separation index (PSI). The newly designed PVA/ZSM-5 mixed matrix membranes (MMMs) can be used at the industrial level for the dehydration of ethyl acetate and other similar compounds.

    Preparation of supramolecular-assemble hydrogels as pesticide carriers based on amphiphilic amino-amide compounds
    Li HAO, Dandan HUANG, Mei GUAN, Hongjun ZHOU, Xinhua ZHOU
    2020, 71(8):  3819-3829.  doi:10.11949/0438-1157.20200199
    Abstract ( 582 )   HTML ( 9)   PDF (3178KB) ( 388 )  
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    To improve the water dispersibility of hydrophobic pesticides, herein, an intelligent and controllable amphiphilic supramolecular hydrogel system is developed. This system consists of a kind of amphiphilic molecules named amino-amide and polycarboxylic acids including maleic acid and citric acid as examples, which was formed at a lower concentration [5.8%(mass)] via self-assembled by hydrogen bonding. Such supramolecular hydrogels exhibited a stable three-dimensional cross-linked network structure. The performance and structure of two kinds supramolecular hydrogels were compared by means of differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), 1H nuclear magnetic resonance (1H NMR), scanning electron microscope (SEM), dynamic light scattering (DLS) and viscosity test, which two supramolecular gels exhibited different stimulus responsive phase behaviors and different morphologies. Specifically, amino amide/citric acid supramolecular had thermal responsive phase behavior in a reversible conversion of sol-gel, and supramolecular gel state could be obtained at 70—80℃ with a critical gelation temperature of 76℃, and its freeze-dried state gel possessed a cross-linked spherical structure. Comparatively, amino amido/maleic acid supramolecular possessed pH induced reversible conversion of sol-gel cycle, and could form hydrogel state between pH of 7—8, and its corresponding freeze-dried gel exhibited pillar-like vesicle structure. The encapsulation rate of amino-amide/citric acid supramolecules to pesticides is slightly higher than that of amino-amide/maleic acid. Compared with dicarboxylic acids, supramolecules formed by tricarboxylic acids and amino-amides, from the perspective of structure and charge, it is more conducive to achieve the intelligent slow-release effect of pesticides.

    Mechanism research of organic pesticides detection by rich electronic LMOF
    Ling DI, Fang CHEN, Rongrong FU, Chen YANG, Yang XING, Xiaoning WANG
    2020, 71(8):  3830-3838.  doi:10.11949/0438-1157.20191568
    Abstract ( 508 )   HTML ( 6)   PDF (2544KB) ( 272 )  
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    A blue fluorescent electron-rich metal organic framework LMOF-a was used to realize fast and efficient luminescence detection of organic pesticides chlorothalonil, herbicide, trifluralin and 2,6-dichloro-4-nitroaniline. Spectral analysis and density functional theory calculations indicated that the detection mechanism of nitrofen by LMOF-a is attributed to charge transfer while the detection mechanisms of trifluralin, chlorothalonil, and 2,6-dichloro-4-nitroaniline by LMOF-a are attributed to charge transfer and fluorescence resonance energy transfer. The Stern-Volmer equation was applied to fit the detection data. LMOF-a demonstrated the highest detection efficiency of 2,6-dichloro-4-nitroaniline with KSV up to (4.778±0.590) L/mmol, and the minimum detection limit down to 0.014 mmol/L. This research provides theoretical reference and technical support for the development of fast and high-efficiency detection of organic pesticides.

    Process safety
    Dynamic assessment of consequences for poisoning accidents caused by H2S release on offshore platforms
    Dongdong YANG, Guoming CHEN, Yuan ZHU, Jihao SHI
    2020, 71(8):  3839-3848.  doi:10.11949/0438-1157.20200318
    Abstract ( 428 )   HTML ( 2)   PDF (3017KB) ( 327 )  
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    A dynamic assessment approach for the consequences of H2S-containing natural gas leakage accident is proposed, the temporal-spatial variation of released gas and emergency evacuation are both considered. The proposed approach is applied to a hypothetical accident scenario concerning H2S-containing natural gas leakage on an offshore platform. A time-varying leakage profile is adopted considering the interference of emergency shutdown system (ESD) and blowdown system. An emergency evacuation time model is established considering the time sequence of emergency evacuation. In addition, the results obtained with the proposed approach are compared with that obtained with static assessment approach and semi-dynamic assessment approach. The inhalation dose of H2S based on the static assessment method, semi-dynamic assessment method, and dynamic assessment method are 1.062×105,7.230×104 and 6.020×104, while the corresponding mortality rates are 5.396×10-2,2.848×10-3 and 4.571×10-4. The comparison results show that the proposed dynamic evaluation method more carefully considers the dynamic factors in the accident scene, which can effectively improve the accuracy of accident consequence prediction.