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Table of Content

    28 July 2022, Volume 22 Issue 7
    Contents
    Cover and Contents
    The Chinese Journal of Process Engineering. 2022, 22(7):  0. 
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    Review
    Research progress of foam separation equipment
    Juan HAN Sihan FANG Wenrui HUANG Jiacong WU Yuanyuan LI Lei WANG Yanli Mao Yun WANG
    The Chinese Journal of Process Engineering. 2022, 22(7):  839-852.  DOI: 10.12034/j.issn.1009-606X.221208
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    Foam separation as a new separation technology has the advantages of simple equipment, low energy consumption, easy operation, high efficiency under the condition of low target object concentration and no pollution. Foam separation has great potential in reducing the cost of separation of surfactant and has been widely used in industry. Foam separation equipment has an important effect on foam separation. In this review, a variety of foam separation equipment which are used to separate and recover proteins, organic pollutants, natural products, metal ions, microalgae and so on in recent literatures were analyzed. According to the development process of foam separation, foam separation equipment is divided into traditional foam separation equipment and improved foam separation equipment. Currently, traditional foam separation equipment is still widely used, but this type of equipment has certain limitations on the adsorption of target object and foam drainage, especially the foam drainage, which makes it difficult to improve the enrichment ratio. However, on the basis of the traditional foam separation equipment, the separation effect of foam separation can be improved by improving the structure of the equipment, including the shape of separation column, the internal components of separation column, and the series separation column. In this review, improved foam separation equipment is divided into improved single-stage foam separation equipment, multi-stage foam separation equipment, and comprehensively improved foam separation equipment. The function mechanism and separation effect of the improved foam separation equipment are emphatically introduced. Compared with the traditional foam separation equipment, the improved foam separation equipment breaks through the limitations of the traditional foam separation equipment, strengthens the adsorption of the separated material in the gas-liquid interface, promotes the foam drainage and improves the enrichment rate of the target to be separated. Although some progress has been made in the study of improved foam separation equipment, there are still some problems to be solved. In this work, the function mechanism and separation effect of various foam separation equipment are summarized, which has positive significance for the development of foam separation equipment in the future.
    Research Paper
    Optimization and scale?up of fermentation process for succinic acid production by Escherichia coli FMME-N-26
    Jia LIU Wenxiu TANG Xueming WANG Liang GUO Xiulai CHEN Cong GAO Liming LIU
    The Chinese Journal of Process Engineering. 2022, 22(7):  853-862.  DOI: 10.12034/j.issn.1009-606X.221265
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    Succinic acid is considered to be one of the most promising bulk chemicals produced by white biotechnology and has a wide range of applications in industry. Microbial production of succinic acid has the advantages of environmental friendliness, and sustainable development, showing a good development prospect. However, a few issues remain with microbial production of succinic acid, such as the low yield, by-products accumulation and low productivity. In order to achieve the efficient production of succinic acid by Escherichia coli (E. coli) FMME-N-26, the fermentation conditions and feeding strategy were optimized in a 3.6 L fermenter. The process involved a two-stage fermentation, with aerobic cell growth followed by anaerobic conditions for succinic acid production. The optimal fermentation conditions were as follows: aerobic fermentation was transitted to anaerobic fermentation at 8 h, MgCO3 was used as pH neutralizer, 2 mmol/L betaine was added as osmoprotectants at 72 h, and glucose concentration was controlled to be 1~5 g/L in the anaerobic stage. The yield of succinic acid and the yield of glucose in anaerobic phase reached 119.2 g/L and 1.08 g/g (97% of the theoretical yield) at 72 h after optimized fermentation, which were 46.4% and 4.8% higher than those of the original fermentation, respectively. Only 2.37 g/L and 0.94 g/L of acetic acid, and lactic acid were accumulated as by-products, which were 37.1% and 49.2% lower than those of the before optimized fermentation, respectively. Then the scale-up production was realized in a 1000 L fermentation tank. The production of succinic acid yield, glucose yield and production intensity by E. coli FMME-N-26 were leading level at home and abroad. Taken together, this study provides a solid foundation for the industrial production of succinic acid and the strategies described here also pave the way to the production of other value-added chemicals.
    Research on preparation process and denitrification performance over SCR catalyst at low temperature
    Jiaming XU Lin HUANGFU Yuting SHI Hongfan GUO Shiqiu GAO Changming LI Jian YU
    The Chinese Journal of Process Engineering. 2022, 22(7):  863-872.  DOI: 10.12034/j.issn.1009-606X.221237
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    The NH3 selective catalytic reduction (NH3-SCR) technique is the most popular technology for the controlled emission of NOx from industrial flue gas. The key of this technology is to develop catalysts with high activity and low cost at low temperature. In order to meet the needs of industrialization of NH3-SCR catalysts at low-temperature, the catalytic performance of denitration catalysts prepared with the same composition of oxide powder, industrial metatitanic acid and hydrothermal metatitanic acid as precursors was investigated. While catalyst A and B was prepared using industrial metatitanic acid, catalyst C was made from metatitanic acid and hydrothermal metatitanic acid as Ti sources in a certain proportion. In addition, catalyst A and B were prepared by the traditional honeycomb system preparation process, while catalyst C was prepared by an improved process that can be formed in one step, and the surface structure and properties of the catalysts were analyzed by means of X-ray diffraction, N2 adsorption-desorption, thermogravimetric analysis, and mechanical strength. The results showed that catalyst prepared with hydrothermal metatitanic acid was more suitable for industrial applications. It had good low-temperature activity, compressive strength and molding rate. After calcination at 550℃ for 10 h, the longitudinal compressive strength of the catalyst was 1.06 MPa, and the NO conversion rate of the catalyst at 250℃ was 97.79%. In addition, the monolith honeycomb catalyst was evaluated for denitration activity and apparent kinetic analysis, the denitrification performance of the catalyst activity at different flue gas temperatures at a gas velocity of 1~3 m/s was investigated. The results showed that the denitration performance of the catalyst gradually decreased with the increase of gas velocity. According to the Eley-Rideal mechanism, a kinetic equation was established to calculate the reaction rate constant k of the catalyst, and according to the Arrhenius formula, the activation energy of the SCR denitrification reaction of the catalyst C was 32.15 kJ/mol, and the pre-exponential factor was 15.37×103 L/(g?min), which could provide important reference for the design of SCR denitration system in the actual industrial flue gas.
    Combustion characteristics of natural gas mixed with hydrogen in domestic burners
    Shuaiming FENG Wei DU Qi XIA Chen CHEN Zengliang GAO
    The Chinese Journal of Process Engineering. 2022, 22(7):  873-881.  DOI: 10.12034/j.issn.1009-606X.221284
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    In order to decrease CO2 emission, relieve the pressure of natural gas supply and promote the scale consumption of hydrogen energy, using natural gas mixed with hydrogen for combustion is considered to be one of the most promising ways. At present, the research on natural gas mixed with hydrogen is mainly focused on industry. In this work, the combustion characteristics of a burner for domestic use with natural gas mixed with hydrogen were studied. A two-dimensional axisymmetric model of the burner was developed with Fluent software coupled with GRI 2.11 chemical reaction mechanism file. The numerical model was verified by comparing the numerical simulation results with the reference experimental results. Furthermore, the effects of different amount of premix of fuel and air, and secondary air flow velocity on combustion temperature, main free radical content and combustion pollutants were analyzed. The results showed that with the amount of premix (primary air coefficient) increasing, the peak temperature increased greatly, NO peak mass fraction increased firstly and decreased, CO peak mass fraction increased gradually. As the secondary air velocity (excess air coefficient) increased, the temperature and pollutant content changed little. Compared with the effect of amount of premix, the effect of air velocity was almost negligible.
    Heat integrated double solvent extractive distillation process of tetrahydrofuran-methanol-methyl acetate-water
    Chao LOU Ming LI Yi YUN Dehao WAN Deming YANG
    The Chinese Journal of Process Engineering. 2022, 22(7):  882-890.  DOI: 10.12034/j.issn.1009-606X.221316
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    According to the characteristics of multiple binary azeotropes in the tetrahydrofuran-methanol-methyl acetate-water quaternary system, two distillation processes, conventional double solvent extractive distillation, and heat integrated double solvent extractive distillation were proposed. The solvent was selected based on the thermodynamic data calculated by the WILSON equation. The results showed that water was the most suitable solvent for tetrahydrofuran-methanol and methyl acetate-methanol azeotropes, and ethylene glycol was the most suitable solvent for tetrahydrofuran-water and methyl acetate-water azeotropes, the total solvent ratio was 0.65 and the ratio of ethylene glycol to water was 1.3. On this basis, taking energy consumption and total annual cost (TAC) as the evaluation indexes of the distillation process, the proposed conventional double solvent extractive distillation and heat integrated double solvent extractive distillation were simulated. The heat exchange network of the double solvent extractive distillation system was optimized by pinch analysis technology. The results showed that the cold utility consumption of the optimized heat exchange network was reduced by 44.12%, and the heat utility consumption was saved by 42.49%. Compared with the conventional double solvent extractive distillation process, the energy consumption of heat integrated double solvent extractive distillation process was reduced by about 43.29%, TAC was saved by approximately 26.89%, and the thermodynamic efficiency was increased by 3.25%. It can be seen that the heat-integrated double solvent extractive distillation process has better technical and economic advantages for separating the above quaternary system.
    Reduction characteristics and mechanism of ultrafine iron ore powder by CO under mechanical activation
    Rufei WEI Dongxiang MENG Jiaxin LI Hongming LONG Yulong ZHU Zhenying LI
    The Chinese Journal of Process Engineering. 2022, 22(7):  891-899.  DOI: 10.12034/j.issn.1009-606X.221277
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    Low carbon, green, and high-efficiency ironmaking is an essential direction for developing ironmaking technology. Low-temperature reduction of ultra-fine iron ore powder can reduce reaction temperature and carbon dioxide emission, which has broad development prospects. The carbon monoxide reduction characteristics of ultrafine iron ore powder with different degrees of mechanical activation were studied by thermogravimetry. The reduction reaction mechanism was analyzed and discussed by KAS (Kissinger Akahira Sunose) method, kinetic model-fitting method, and activation energy judgment method. The results showed that mechanical activation is conducive to the reduction of iron ore powder with carbon monoxide. When the mechanical activation time was longer, the reaction characteristic temperature was lower. Before 120 min of mechanical activation time, the effect of mechanical activation time on reduction characteristic temperature was greater than that after 120 min. The reaction starts temperature of the sample powder with an activation time of 480 min was 523 K, which was 87 K lower than that of the non-activated sample powder. And the peak temperature of the reaction rate was 1108 K, which was 217 K lower than that of non-activated sample powder. When the mechanical activation time was longer, the reaction activation energy was lower, but the reaction mechanism had not changed, and the interfacial reaction had always been a restrictive step. The activation energy of iron ore powder after activation for 480 min was 31.23 kJ/mol lower than that without activation. With the increase in mechanical activation time, the reason why the activation energy of the reaction decreased was that the mechanical activation reduced the particle size of iron ore powder and the average particle size of iron ore powder, which was more conducive to the diffusion of carbon monoxide gas. Mechanical activation significantly impacted the step-by-step reaction process of carbon monoxide reduction in iron ore powder. For the unactivated iron ore powder, the step-by-step reaction level was not clear, but for the activated iron ore powder, the step-by-step reaction level was clear.
    Study on freezing process and component migration characteristics of salty droplet under acoustic field
    Linfang ZHANG Jian CONG Penghui GAO Donghai ZHANG
    The Chinese Journal of Process Engineering. 2022, 22(7):  900-908.  DOI: 10.12034/j.issn.1009-606X.221231
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    In order to reveal the internal mechanism of ultrasonic-assisted freezing and clarify heat and mass transfer law and component migration characteristics during the freezing under the action of sound, the cavitation and thermal effects of the ultrasonic wave were analyzed according to the sound field theory. Based on the conservation of energy and mass, a mathematical model of droplet freezing and salt migration in the effect of the ultrasonic wave was established, which presented the heat and mass transfer and the salt migration law. The model can reflect the effect of the sound field on the freezing and was used to analyze the phase change freezing process, which involved the ultrasonic cavitation effect and the state change of bubbles. In different conditions, some important parameters, such as temperature variation, liquid ratio, concentration ratio, and salinity were studied, which can provide the path to improve the freezing efficiency and the brine separation effect. The results showed that ultrasound was helpful for heat and mass transfer. The dropping temperature drops rapidly, ultrasound was conducive to the freezing of drops. It was that the low-frequency ultrasound will increase the growth cycle of bubbles in droplets and the maximum diameter of bubbles, to strengthen heat and mass transfer. The higher the salt concentration was, the slower the freezing process was. It was that the smaller the diameter, the greater the mass transfer and heat dissipation caused by the cavitation effect. When the droplet diameter was 2 mm, the time to reach the freezing point was 15 s when the salt concentration was 5wt%, and 20 s when the salt concentration was 8wt%. When the concentration of salt in the droplet was low, the change range of salt migration became more intense. It was that the lower the concentration of droplets, the stronger the driving force of salt migration potential difference, and the range of salt migration was becoming more and more intense.
    Extractive distillation of benzene-cyclohexene azeotrope with deep eutectic solvents
    Yanhong WANG Chao HUA Min YIN Ping LU Fang BAI Hai LI
    The Chinese Journal of Process Engineering. 2022, 22(7):  909-916.  DOI: 10.12034/j.issn.1009-606X.221142
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    High efficiency separation of benzene/cyclohexene azeotropic system at atmospheric pressure is the focus of current research. Extractive distillation is considered to be the most promising method for separation azeotropes. Therefore, it is necessary to screen suitable extractant for extractive distillation. The deep eutectic solvents (DES) formed by the combination of hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) has a good application prospect in the separation of aromatic/nonaromatic azeotropes. In order to explore the influence of HBA and HBD on the separation performance of benzene/cyclohexene azeotropic system, the three kinds of DES were investigated in this work. The three kinds of DES consisted of HBA [tetrabutylammonium bromide (TBAB), choline chloride (ChCl)] and HBD [ethylene glycol (EG), levulinic acid (LA)] with the mole ratio of 1:2, which were marked as TBAB:EG (1:2), TBAB:LA (1:2), and ChCl:LA (1:2), respectively. The corresponding isobaric vapor-liquid equilibrium (VLE) of cyclohexene-benzene-DES were experimentally determined. The effect of HBA and HBD on separation performance were discussed systematically. By correlating the VLE data with the nonrandom two-liquid (NRTL) model, the binary parameters were fitted. The results showed that the separation performance of the three DES follows the order ChCl:LA (1:2)>TBAB:LA (1:2)>TBAB:EG (1:2). It was indicated that choosing HBA which had the lower steric hindrance effect and HBD which had the weaker polar bond were conducive to form an efficient extractant for benzene/cyclohexene azeotropic system separation. Subsequently, the extractive distillation process used ChCl:LA (1:2) as extractant were designed with Aspen Plus V7 to evaluate the separation energy consumption. For comparison, N,N-dimethylacetamide (DMAC) which is a traditional extractant was evaluated in the same condition. The process simulation results showed that using ChCl:LA (1:2) as extractant, the molar reflux ratio decreased from 3.8 to 0.30 and the total reboiler heat duty reduced 16.57%, compared with those of DMAC used as extractant.
    Thermodynamic processes optimization of multiple effect evaporation system of water for injection
    Yiwen XIAO Shuying WU Deqi PENG Zhimin WU
    The Chinese Journal of Process Engineering. 2022, 22(7):  917-926.  DOI: 10.12034/j.issn.1009-606X.221165
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    Aiming for the problems of large energy loss and unstable water production in multiple effect evaporation water for injection system, different preheating methods were designed to improve the water production process, and the Matlab/Simulink multi-body toolbox was used to simulate the system and optimize the thermodynamic process. According to the equations of mass and energy conservation, the mathematical models of evaporator, preheater and condenser were established with the loss of steam flow resistance. Based on the Matlab/Simulink multi-body toolbox, the iterative solution was carried out by the equal area method. The experimental data were compared with the results which were simulated by the Matlab/Simulink multi-body toolbox. The maximum error was 6.71%. Considering the waste of secondary steam energy in multiple effect evaporation system, different preheating methods were used to recover the residual heat. The influence of the number of effects and the preheating mode on the thermal performance of the system was analyzed. The results indicated that with the growth of the number of effects the specific exergy consumption decreased, specific heat transfer area and gained output ratio of the system increased, and the latter two have decreased rate of change. When the number of effects was less than 5, using the condensate preheating scheme was more excellent. When it was more than 5, using the mixture preheating scheme was superior. While the number of effects was greater in scheme mixture preheating, temperature drop and pressure drop which caused by the flow of steam rapidly rised, gained output ratio weakened and specific exergy consumption tended to be constant. This work proposed a new preheating method for the multiple effect evaporation system, which improved the utilization rate of energy in this system by recovering the residual heat of the last-effect secondary steam. The new preheating method can provide a reference for the design and transformation of the multiple effect evaporation system.
    Thermodynamics and kinetics analysis of phosphorus production by electric-furnace method
    Zhiwei ZHU Yuan TANG Zhili LI Dongsheng HE Yuan YAO
    The Chinese Journal of Process Engineering. 2022, 22(7):  927-934.  DOI: 10.12034/j.issn.1009-606X.221241
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    Yellow phosphorus is an important industrial raw material for the development of phosphorus chemical industry in China. The yellow phosphorus production by electric-furnace method has always been the core of thermal process for phosphate rock treatment. The electric-furnace method should be able to make direct use of the low-grade phosphate rocks, especially those with high silicon content, but this would consume a lot of energy. The researchers note that attention should be given to the formation of eutectic and the adjustment of eutectic temperature. A large number of experimental studies are obtained to discuss the macroscopic effect of different strengthening means of phosphate rock reduction. However, the mechanism is mostly inferred. At present, the lack of objective presentation of the eutectic composition and transformation hinders the clear explanation of those mechanisms. Thus, it is necessary to study the phase diagram of slag and the melting aid effect in the phosphorus production process by means of chemical thermodynamics computation. It is of great realistic and scientific significance to reveal the interaction mechanism and improve an electric-furnace technology of phosphorus production. In this work, the phase diagram and melting mechanism in the phosphorus production process by electric-furnace method were studied with FactSage 8.0 computation. It showed that levels of Al2O3 had a certain effect on the formation of eutectic and the adjustment of eutectic temperature. With the proper increase of Al2O3 content, the phosphorus production process was improved. In contrast, the single MgO as a flux was unable to effectively promote the charge melting and the eutectic temperatures were likely to rise. Beyond these points, the melting reduction reaction of the phosphate rock was demonstrated to be consistent with the first-order reaction characteristics.
    Numerical study on thermodynamic performance of turbulent fluid flow in shell side of spiral casing heat exchanger
    Cuihua WANG Guangyu LI Fangzheng SU Bin GONG Jianhua WU
    The Chinese Journal of Process Engineering. 2022, 22(7):  935-943.  DOI: 10.12034/j.issn.1009-606X.221209
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    In this work, computational fluid dynamics software was used to numerically simulate the turbulent flow and heat transfer performance of the shell side fluid of the spiral casing heat exchanger with a threaded tube. The effect of Reynolds number and groove height on the turbulent flow and heat transfer performance of the shell side fluid was investigated. The field synergy principle was used to reveal the mechanism of fluid heat transfer enhancement by thread compound spiral flow. The results showed that the thread protrusions of the threaded inner tube had a significant effect on the disturbance and conduction of shell side fluid of the spiral casing heat exchanger, and the heat transfer efficiency of the shell side fluid of the spiral casing heat exchanger with the inner tube as a threaded tube was up to 22.1% higher than that of the model with the inner tube as a smooth tube. When the structural parameters were the same, with the increase of Reynolds number, Nusselt number of the shell side fluid of the spiral casing heat exchanger gradually increased, flow resistance gradually decreased, and the comprehensive evaluation factor ψ gradually decreased. Within the scope of the research, Nusselt number increased by 85.6, flow resistance decreased by 0.008, and the comprehensive evaluation factor ψ decreased from 1.35 to 1.18. When Reynolds number was certain, the equivalent height h' increased, flow resistance gradually increased, and Nusselt number first increased and then decreased. According to the analysis of field synergy principle, when the equivalent height h' was 0.220, the temperature field and velocity field synergy performance of the shell side fluid was better under the action of thread protrusion disturbance and diversion, and the comprehensive evaluation factor ψ was the largest. The optimal equivalent height h' of the thread should be about 0.220.
    Numerical simulation of pulsed feeding flow disturbance in high temperature pressurized micro-fluidized bed
    Wei ZHANG Wenjin LIU Yuming ZHANG Jiazhou LI Junrong YUE
    The Chinese Journal of Process Engineering. 2022, 22(7):  944-953.  DOI: 10.12034/j.issn.1009-606X.221234
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    The gas-solid micro-fluidized bed reaction analyzer (MFBRA) has been successfully applied to the analysis of reaction kinetics because of its isothermal differential characteristics. However, its application is limited to normal pressure conditions at present, and its applications under pressurized conditions are not established yet. Micro-fluidized bed (MFB) is the core part of an MFBRA. It is of great significance to investigate the behavior of the pulsed feeding gas injection in an MFB under high temperature and high pressure conditions by computational fluid dynamics. It is in gread need to reveal the disturbance of the pulsed feeding gas to the bed material fluidization, deepen the theoretical understanding and provide guidance for the usage, and optimization of a pressurized MFB. In this work, a three-dimensional simulation was performed to simulate the pulsed feeding gas injection into an MFB under high temperature pressurized conditions, and to improve the structure of the feeding tube. The fluidization inside the MFB was described by two-fluid method (TFM). It was confirmed that the model adopted here captured the pressure drop inside an MFB, agreed with experimental data. It was found that temperature and pressure had opposite effects on the fluidized bed disturbance caused by the pulsed feeding gas. Increasing the pressure could enlarge the disturbance of the feeding gas to bed fluidization because the kinetic energy of the feeding gas increased, while increasing the temperature could reduce the fluidized bed disturbance. By expanding the feeding tube in axial and radial direction, the decreasing effect of gas velocity caused by tube expansion could be stronger than the increasing effect of gas velocity caused by the non-slip wall condition. Therefore, the terminal velocity of the feeding gas decreased, and its disturbance to the bed could be weakened. Compared with radial expansion, axial expansion was more effective to weaken the disturbance and should be the main method for improving the structure of the feeding tube.
    Water model experiment on motion and melting of scarp in gas stirred reactors
    Rongwang YANG Chao CHEN Yaocheng LIN Yu ZHAO Jian ZHAO Jiangjun ZHU Shishun YANG
    The Chinese Journal of Process Engineering. 2022, 22(7):  954-962.  DOI: 10.12034/j.issn.1009-606X.221274
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    Due to economic reasons, great efforts have been made to increase the scrap usage in basic oxygen furnaces (BOF) and in secondary refining ladles. The mechanism of melting of scrap in above mentioned reactors is not clear. Water models can be used to simulate the motion and melting process of scraps. In this study, the ice sphere and ice sphere made by saturated KCl solution, which can simulate the light and heavy scraps, are used in water mode experiment to study the motion process and melting mechanism in BOF-like vessels and ladles. The results show that the melting time of ice samples are not affected by freezing time when the freezing time is longer than 18 hours. The shape of ice sphere and ice sphere made by saturated KCl solution during melting is spherical or ellipsoidal. The diameter of both sphere decreases linearly with time. With the increase of bath temperature, the melting of both ice samples accelerates. Furthermore, the mechanism of motion of ice sphere and ice sphere made by saturated KCl solution is significantly different due to the flow field difference with respect to the variance of liquid level and gas flowrate. Specifically, the melting time of ice sphere decreases with the increase of liquid level, while the melting time of ice sphere made by saturated KCl solution decreases dramatically first and then increases slightly. The melting time of the ice sphere made by saturated KCl solution is the lowest at the position where the ratio of liquid level to the diameter of the reactor is 0.94. In addition, adding ice sphere made by saturated KCl solution above the gas plume will significantly reduce the melting time when the liquid level is low (the ratio of liquid level to the diameter is 0.42~0.73). However, the addition position will not change the melting time when the liquid level is high (the ratio of liquid level to the diameter is 0.83~1.04).
    Flooding model of concentric-ring high gravity rotating bed
    Wenbo YAO Zhongjun ZHANG Chengwei LIU Yumin LI Jianbing JI
    The Chinese Journal of Process Engineering. 2022, 22(7):  963-969.  DOI: 10.12034/j.issn.1009-606X.221275
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    Concentric-ring high gravity rotating bed is a new type of high gravity rotating bed. Liquid flooding is an important characteristic of hydrodynamics of high gravity rotating bed. The liquid droplets in the ring space between the liquid distributor and the inner edge of the rotor of the concentric-ring high gravity rotating bed are entrained by the gas. In terms of centrifugal force and drag force of gas that exerts the liquid droplets, a differential equation is established, from which a radial distance of the liquid droplets at radial velocity of the liquid droplets of zero is obtained. As the radial distance of the droplets at radial velocity of zero is less than that of the ring space, the entrainment flooding occurs. Thus, an entrainment flooding model of concentric-ring high gravity rotating bed was established. Experiments were carried out in a concentric-ring high gravity rotating bed with a rotor of 1000 mm diameter and 100 mm height using air-water system. Change of gas pressure drop between inlet and outlet of the concentric-ring high gravity rotating bed with superficial gas velocity was measured at various rotational speeds and superficial liquid velocities. The gas pressure drop increased slowly at first and then rapidly with increase of superficial gas velocity. The superficial gas velocity at flooding point was determined by both a derivation of gas pressure drop with apparent gas velocity and visual observation of a large amount of liquid entrained by gas at the gas outlet in the eye of the rotor. Thus, coefficient k of entrainment flooding model was obtained by the superficial gas velocity at flooding point and then coefficient k was correlated. Calculated values agreed well with experimental values, with an average deviation of 3.1%. The entrainment flooding model was superior to Sherwood's flooding model, and providing design basis for the industrial application of concentric-ring high gravity rotating bed.
    Abnormal condition detection in chemical process based on PCA-SVDD
    Yang LIN Yadong HE Zhuang YUAN Chuanpeng WU Chengdong GOU Chuankun LI
    The Chinese Journal of Process Engineering. 2022, 22(7):  970-978.  DOI: 10.12034/j.issn.1009-606X.221399
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    Due to the large number of hazardous materials and serious accident consequences, it has been attracting continuous attentions in the abnormal detection of the chemical plant. Although many detection methods are proposed in the literature, the actual anomaly detection is subject to two challenges. On the one hand, the advanced distributed control system (DCS) can provide massive information about the real-time operating statue of the device, but it also results in a high-order features of training dataset. On the other hand, there is scarce abnormal data in the establishment of abnormal training samples along with the continuous improving device reliability. As a response, this work proposes a PCA-SVDD-based abnormal condition detection method in chemical process under no abnormal data by combing principal component analysis (PCA) and support vector data description (SVDD). Firstly, PCA is employed to reduce the dimensionality by decomposing training samples, which consist of normal data, into the principal subspace and the residual subspace. Then, according to the target type data, an anomaly detection model based on SVDD is established. Further, the Gaussian kernel function is introduced to improve the anomaly detection effect. Finally, the normal data in Tennessee-Eastman (TE) process data is used as training samples to validate the PCA-SVDD. And the two indicators of detection precision (DP) and detection time (DT) are employed to characterize the effect of detection model. In contrast, traditional PCA and SVDD is introduced to carry on anomaly detection of TE process under the same condition. By the comparison, it concludes that the PCA-SVDD-based abnormal condition detection method proposed in this work has better detection effect (higher accuracy and less detection time). In summary, PCA-SVDD can realize the early warning of abnormal working conditions without abnormal data in the chemical process, and has certain significance to ensure the smooth operation of the device.
    Rational construction and adsorption properties of Brij30/β-FeOOH/GO composite for tetracycline hydrochloride
    Runping TAO Weiqiang DONG Qingsong HU Jing ZHU Zhixin WANG Yiqun XU
    The Chinese Journal of Process Engineering. 2022, 22(7):  979-988.  DOI: 10.12034/j.issn.1009-606X.221259
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    The antibiotic resistance caused by misuse of the consequences has become a public health problem. It is urgent to remove these antibiotics before they enter into water cycling system. FeOOH, a functional material with great development potential, requires further development in the treatment of antibiotic wastewater. Graphene oxide (GO) has been widely employed in wastewater treatment due to its unique physical and chemical properties and has achieved certain effects. In this work, polyoxyl lauryl ether (Brij30) was employed to modify the surface of β-FeOOH, and Brij30/β-FeOOH/GO was prepared via hydrothermal method. The composition and microstructures of the as-prepared samples were studied by X-ray powder diffractometer, transmission electron microscope, X-ray photoelectron spectrometer, infrared spectrometer and Zeta potential. In order to determine the optimum adsorption conditions, the adsorption performance was explored on account of the adsorbent dosage, pH value and coexisting ions. And the adsorption mechanism of tetracycline hydrochloride was investigated. The experimental results demonstrated that structure-controlled tetracycline hydrochloride adsorption. The optimal adsorption conditions were observed at adsorbent of 0.01 g, solution pH of 5, adsorption time of 10 h, initial concentration of tetracycline hydrochloride of 40 mg/L. And the adsorption capacity of tetracycline hydrochloride reached up to 65.97 mg/g. The experimental results of adsorption thermal kinetics indicated that the adsorption behavior conform to the pseudo-second-order model and Freundlich isotherm model, its belonged to the multilayer molecular layer adsorption, which was the coexistence of chemical adsorption. The adsorption mechanism of tetracycline hydrochloride was driven by electrostatic interactions between tetracycline hydrochloride and unsaturated Fe sites. The π-π interactions (tetracycline hydrochloride benzene ring and the β-FeOOH's ligand) and pore fillings play an important role in the removal of tetracycline hydrochloride. The results obtained will help to understand surface interactions between Brij30/β-FeOOH/GO and tetracycline hydrochloride and fabricate efficient β-FeOOH-based adsorbents in environment purification.