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Published in last 1 year |  In last 2 years |  In last 3 years |  All Please wait a minute... For Selected: Download Citations EndNote Ris BibTeX Toggle Thumbnails Select Study on oxyfuel combustion behavior and the intrinsic kinetics of typically sized coal particles Haolong BAI Liangliang FU Guangwen XU Dingrong BAI The Chinese Journal of Process Engineering    2022, 22 (8): 1115-1123.   DOI: 10.12034/j.issn.1009-606X.221256 Abstract （394）   HTML （5）    PDF （1151KB）（43）       Knowledge map    Save Oxyfuel combustion is a promising technology to facilitate carbon capture from combustion-generated flue gases. Circulating fluidized beds (CFBs), the major commercial-scale boilers, will play a significant role in the energy industry's transition from today's carbon-intensive to carbon neutral in the future. The types of boilers combust coals of wide screening particle sizes of 0~10 mm. The difference in coal particle size inevitably leads to a considerable variation in combustion characteristics, which has not yet been fully understood. In particular, little is known about the dynamic evolution behavior of combustion gas products and the intrinsic kinetics of the in-situ produced nascent char particles when these typically sized coal particles are combusted in fluidized beds. For this reason, an advanced micro fluidized bed reaction analyzer (MFBRA), integrated with a fast-responding process mass spectrometry, was employed to investigate the oxyfuel combustion behavior of two typically sized coal particles (i.e., 1.7~3.35 mm and 0.12~0.23 mm), typical of those in dense region and dilute region in CFBs, at 790~900℃. The use of MFBRA enabled the successful detection and characterization of the dynamic combustion process-sequentially occurring devolatilization and combustions of the in-situ produced volatiles and the nascent char particles. The results demonstrated that the combustions of volatiles and nascent char particles can have similar or different rates depending on the coal particle size. The two major successively occurring dynamic processes were distinctively identified and characterized for the coarse particles but not for the fine particles, which were featured with similar reaction rates for the two processes. The combustion of coarse char particles was rate-controlled by kinetics at low temperatures and changed to interparticle diffusion control at high temperatures. The combustion kinetics of the volatiles and nascent char were analyzed, and the corresponding values of activation energy were 107.2 and 143.9 kJ/mol, respectively. Related Articles | Metrics Select Rigorous modelling and energy performance evaluation for PDH reaction gas separation and hydrogen purification Xuantong LU Jin ZHAO Chun DENG The Chinese Journal of Process Engineering    2023, 23 (1): 144-153.   DOI: 10.12034/j.issn.1009-606X.221334 Abstract （372）   HTML （2）    PDF （1123KB）（133）       Knowledge map    Save Propane dehydrogenation is one of the main processes for propylene production and its reaction gas components are complex, containing products from main reactions and by-product components such as CO2 and CO from side reactions. To obtain polymer grade propylene and purified hydrogen product with a purity of more than 99.90 mol/mol, the separation process of the reaction gas of propane dehydrogenation and the recovery of hydrogen from hydrogen-rich tail gas is modeled and simulated in the Aspen software. The process includes main modules such as MEA decarburization, compressed cryogenic separation, deethanization, propylene distillation and pressure swing adsorption. The CO2 contained in the reaction gas would affect the purity of the propylene product, and it is difficult to remove in the cryogenic process. Thus the CO2 is first removed by the MEA solvent absorption. The reaction gas after decarburization and dehydration enters the deethanizer and the propylene distillation unit, and the hydrogen-rich tail gas enters the pressure swing adsorption unit for further purification. In order to reasonably utilize the energy of the propylene distillation tower, the heat pump distillation process is adopted for the energy integration. Compared with conventional distillation, the energy consumption of propylene heat pump distillation is lower. Sensitivity analysis and optimization of process parameters for hydrogen recovery by pressure swing adsorption are carried out to improve economy and energy efficiency. For the two-bed four-step pressure swing adsorption process, the effects of adsorption pressure, adsorption time and purge ratio on the purity and recovery of hydrogen products are analyzed, and the optimal operating conditions are determined. The simulation results show propylene and hydrogen products meet the requirements. The energy consumption per unit product is 267.46 kg standard oil/t propylene product and 474.44 kg standard oil/t hydrogen product. It has a certain reference significance for the simulation of the actual propane dehydrogenation reaction gas separation process and energy consumption estimation. Related Articles | Metrics Select 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 Abstract （371）   HTML （14）    PDF （1335KB）（51）       Knowledge map    Save 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. Related Articles | Metrics Select Numerical investigation of gas-assisted sludge atomization and breakup based on VOF-DPM coupled model Haihong FAN Zhou LI Binbin LI Lin LI Shuo SHANG Jiayang WANG The Chinese Journal of Process Engineering    2022, 22 (12): 1633-1642.   DOI: 10.12034/j.issn.1009-606X.221412 Abstract （370）   HTML （4）    PDF （3831KB）（81）       Knowledge map    Save Sewage sludge is an unavoidable by-product in the process of sewage treatment. Due to its characteristics of high pollution and difficult to treat, the efficient and harmless treatment of sludge is still facing certain challenges. A new sludge treatment technology, spray drying technology with relatively simple process and high value-added utilization after sludge atomization has a great promotion effect on sludge treatment. The gas-assisted atomizer has a good atomization effect on high-viscosity fluids, and can ensure a better atomization quality at a faster atomization rate. In the study of sludge atomization, many scholars have carried out certain researches, but there is no numerical simulation study of sludge atomization, and numerical simulation can be low-cost, more intuitive study of sludge atomization breakup, has certain advantages. In order to realize the numerical simulation of sludge atomization and breakup, computational fluid dynamics software is used to explore the influence of gas-assisted sludge atomization characteristics and operating parameters (gas velocity, gas-liquid ratio, spray angle) on the effect of sludge atomization. The results show that the density and viscosity of sludge gradually decrease with the increase of moisture content. Gas velocity, gas-liquid ratio and spray angle are the three most important operating parameters that affect sludge atomization and breakup. During the atomization process, the high-speed airflow makes the sludge vibrate and unstable at the front end of the atomizer, resulting in the tearing of the sludge and the breaking of the droplets. The density of droplets in the center area is greater than that in the edge area and there are a few large particles agglomerated. For sludge with moisture content of 87% and a density of 1.065×103 kg/m3, the atomization effect is the best when the gas velocity is 180 m/s, the gas-liquid ratio is 126.3, and the spray angle is 55°. The average particle size of the droplets is about 0.193 mm, and the experimental results are in good agreement with the simulated particle size, and the maximum relative error is 5.80%. Related Articles | Metrics Select Research on the properties of LiNi 0.8 Co 0.1 Mn 0.1 O 2 high nickel ternary cathode material for lithium ion batteries Cheng CAI Haiyan ZHANG Ying WANG Haikuo FU Ling HUANG Renheng TANG Fangming XIAO The Chinese Journal of Process Engineering    2022, 22 (6): 754-763.   DOI: 10.12034/j.issn.1009-606X.221194 Abstract （348）   HTML （19）    PDF （3206KB）（95）       Knowledge map    Save The Ni-rich cathode material (LiNi0.8Co0.1Mn0.1O2) has the advantage of high capacity and is the most potential cathode material for lithium-ion batteries. However, the poor cycle performance and rate capability limit its application. In this work, the structure evolution of the cathode material during the synthesis process and the influence of manufacturing temperature on the material properties were studied, and the potential causes of the structural changes and electrochemical degradation of the cathode material during the cycle were analyzed in detail. The physicochemical characterizations were conducted by employing the thermal gravimetric/differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (HRTEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), etc. The cycle performance, rate performance, and other electrochemical properties were examined by electrochemical testing equipment. The results showed that the cathode material synthesized at 500℃ for 4 h and 750℃ for 14 h presents uniform particle size, good spherical structure, smooth surface of primary particles, compact arrangement, and stable crystal structure, which can alleviate polarization during cycling. Due to the proper particle size obtained at the optimized synthesis temperature, a relatively high initial discharge capacity, small volume changes, and slowly increased interfacial film resistance for the material were achieved, contributing to good Li+ diffusion kinetics. At 0.2 C, the first discharge-specific capacity was 186.2 mAh/g and the first charge-discharge efficiency was 82.5%. At 1 C, the discharge-specific capacity before and after 100 cycles were 185.1 and 175.2 mAh/g, respectively, and the capacity retention rate was up to 95.2%. The study of the synthesis and structural changes of Ni-rich cathode materials in this work can deepen the understanding of the materials and help improve the electrochemical performance of the materials. Related Articles | Metrics Select Recycling of scrap lead paste to prepare lead powder by high efficiency electrolysis in choline chloride-ethylene glycol deep eutectic solvent Haoming HUANG Juanjian RU Yixin HUA Xiao GENG Wenwen ZHANG Mingqiang CHENG Daoxiang WANG The Chinese Journal of Process Engineering    2023, 23 (1): 107-114.   DOI: 10.12034/j.issn.1009-606X.221422 Abstract （335）   HTML （1）    PDF （2013KB）（91）       Knowledge map    Save As a clean energy source without pollution during use, lead-acid batteries have received close attention. However, lead-acid batteries contain a large amount of polluting heavy metals, and random disposal will pollute the environment and affect the ecological balance. In industry, the recovery of scrap lead paste (SLP) is usually treated by pyrotechnics, but it consumes a lot of energy and also produces pollutants such as sulfur dioxide and lead dust. In view of the existing problems, finding new recycling processes has become a research hotspot. Deep eutectic solvents (DESs) are a new generation of green solvents and have received more and more attention in recent years. Because of their good thermal stability and wide electrochemical window, DESs are widely used in the fields of metal extraction and material preparation. In this work, the recycling of scrap lead paste to prepare lead powders by electrolysis is discussed in choline chloride-ethylene glycol deep eutectic solvent (ChCl-EG DES). Firstly, the phase composition of the scrap lead paste is analyzed by XRD, and the quantitative analysis of the scrap lead paste using Jade software shows that it mainly exists in the form of lead dioxide with a small amount of lead sulfate at the same time. And then, the electrochemical behavior of lead ion in 30 g/L SLP+ChCl-EG solution is investigated by cyclic voltammetry. The phase composition and microscopic morphology of the deposit product at different temperatures are examine using XRD and SEM techniques. The experimental results show that when scrap lead paste is added, Pb(IV) can be reduced preferential to Pb(II) due to the reducibility of ChCl-EG DES. Cyclic voltammetry indicates that the reduction of scrap lead paste to metal lead is a quasi-reversible process in ChCl-EG DES. The constant voltage deposition experiment show that when the temperature rises from 323 K to 363 K, the current efficiency rises from 67.26% to 96.06% and the specific energy consumption decreases from 961.57 kWh/t to 673.28 kWh/t. XRD and SEM results demonstrate that the deposit products obtained at different temperatures are pure metallic lead powders and their microscopic morphology are mainly rod-shaped and slight acicular. Related Articles | Metrics Select Research on seat lip contact characteristics of cryogenic ball valve used in LNG receiving terminal Zhenhao LIN Junye LI Zhijiang JIN Jinyuan QIAN The Chinese Journal of Process Engineering    2022, 22 (6): 819-827.   DOI: 10.12034/j.issn.1009-606X.221159 Abstract （289）   HTML （5）    PDF （1960KB）（50）       Knowledge map    Save The cryogenic ball valve is one of the indispensable fluid pipeline control devices in liquefied natural gas (LNG) receiving terminal. Its reliability directly affects the stability of the entire system, especially, when the ball valve has a serious valve seat seal leakage problem, which will seriously threaten the normal operation of industrial production and the safety of operators. In this work, based on the thermo-solid coupling method, the software of ANSYS Workbench was adopted to simulate the contact characteristics, including contact gap and contact pressure, of the lip seal of the cryogenic ball valve used in the LNG receiving station. Firstly, the distribution of temperature and Mises stress of lip seal under low-temperature conditions were analyzed. It was found that there were significant temperature differences in the lip seal, and the maximum temperature difference of the lip seal ring was 77℃. The temperature on the path from the inner lip seal ring to the outer lip seal ring decreased in order, which results in a significant increase of Mises stress. The maximum Mises stress reaches 204.92 MPa. Secondly, the contact characteristics of the lip seal under normal temperature and low-temperature conditions were analyzed. The results showed that the contact gap between the lip seal ring and the valve body and seat was unchanged, and the maximum contact pressure was evenly distributed along the circumferential direction under normal temperature conditions. While the contact gap of the lip seal increased and the contact pressure decreased under low-temperature conditions. The maximum contact gap reached -0.72 mm. Finally, the effects of different spring forced on the contact characteristics of the lip seal under low-temperature conditions were studied. It was found that the sealing performance of the lip seal could be improved to some extent by increasing the force. When the force of the spring was greater than 7000 N, the contact pressure between the lip seal ring and the valve body was greater than zero, and the precondition for sealing can be reached. This work has a certain reference value for the design and research of the seat seal of a cryogenic ball valve. Related Articles | Metrics Select CFD simulation of thermal runaway esterification reaction in stirred tank Biqing CHEN Xiaoping GUAN Ning YANG Dingrong BAI The Chinese Journal of Process Engineering    2022, 22 (8): 1053-1060.   DOI: 10.12034/j.issn.1009-606X.221317 Abstract （286）   HTML （7）    PDF （4055KB）（115）       Knowledge map    Save Thermal runaway is one of the common risks in chemical process safety. Thermal runaway accidents of various scales cause a lot of economic losses every year. The runaway of batch stirred reactor is particularly dangerous due to the single way to control the reaction rate.From the view point of intrinsic safety, optimal design of reactor and operating conditions can fundamentally prevent thermal runaway. In batch-operated stirred tank reactors, impeller rotation can enhance flow circulation, turbulence intensity, mixing degree, and heat transfer, thus effectively preventing thermal runaway. In this work, according to the esterification reaction of propionic anhydride and isopropanol to produce isopropyl propionate and propionic acid under the catalysis of concentrated sulfuric acid, CFD simulation was carried out to simulate the thermal runaway esterification reaction in stirred tanks. The effects of impeller type (Rushton impeller, 30° pitched blade turbine impeller and 60° pitched blade turbine impeller), rotation direction, and baffle on the temperature evolution were studied. The simulated flow structures were used to explain the effects. Furthermore, divergence criterion was used to compare the performance of resisting thermal runaway for different impellers. The simulation showed that the radial flow agitator performed better than the axial flow agitator at the same rotation speed, and the performance order was Rushton impeller>30° PBTD impeller>60° PBTD impeller. For the 30° PBT impeller, when the operating mode changed from PBTD to PBTU, the capability to resist thermal runaway weakens, though the number of circulation zone increased. The situation of 60° PBT impeller was similar to that of 30° PBT impeller. The addition of baffle can substantially improve the thermal control in the reactor. This research provided fundamentals for design, optimization, and scale-up of reactors. Related Articles | Metrics Select 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 Abstract （277）   HTML （9）    PDF （1083KB）（73）       Knowledge map    Save 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. Related Articles | Metrics Select Green oxidation process for synthesis of 2-methyl-1,4-naphthoquinone from β-methylnaphthalene Jinwen PAN Suohe YANG Guangxiang HE Xiaoyan GUO Haibo JIN Lei MA The Chinese Journal of Process Engineering    2022, 22 (12): 1702-1709.   DOI: 10.12034/j.issn.1009-606X.221426 Abstract （272）   HTML （2）    PDF （1071KB）（39）       Knowledge map    Save 2-methyl-1,4-naphthoquinone (2-MNQ) is an important intermediate of K vitamins, which is widely used in medicine, pesticides, feed additives and other fields. However, this vitamin does not exist in nature, and artificial synthesis is the only way to produce 2-MNQ. In industry, vitamin K3 is prepared using 2-methylnaphthalene (2-MN) as raw material and chromic anhydride as an oxidant. This process produces a large amount of waste residue and wastewater containing chromium, causing irreversible pollution to the environment,and trace amounts of chromium in the product pose a threat to human health. Therefore, a new type of the green oxidation process was used for hydrogen peroxide oxidation. The process used 2-methylnaphthalene (2-MN) as raw material, (NH4)2S2O8 as initiator to prepare peroxygen with 30% H2O2 and glacial acetic acid under the catalysis of sulfuric acid. Acetic acid was added dropwise to the reaction solution to synthesize 2-methyl-1,4-naphthoquinone (2-MNQ) by oxidation, and its structure was characterized by ICIR, GC-MS, and LCMS, and the oxidation reaction mechanism and the type and content of by-products were verified. The main impurities were isomer 6-methyl-1,4-naphthoquinone and its by-products phthalic anhydride and 4-methylphthalic anhydride produced by excessive oxidation. The effects of catalyst, reaction temperature, reaction time, dosage of oxidizer and initiator on the yield and conversion of 2-MNQ were investigated. The conversion rate and yield of 2-MNQ were determined by HPLC (external standard method). The optimum reaction conditions were reaction temperature of 65℃, reaction time of 5 h, n(H2O2):n(2-MN)=26:1. The conversion rate of 2-methylnaphthalene was 99%, and the product yield was 34%. The innovation point of this work was to verify the reaction mechanism and the intermediate process in detail using the original external infrared, that was, the raw material 2-methylnaphthalene was oxidized by peracetic acid, the epoxidation reaction generated the intermediate, and then rearranged to generate 2-methylhydroxyquinone, and the oxidation continued to generate the target product 2-methyl-1,4-naphthalene quinone. The process has the characteristics of environment friendly, simple technology, mild operating conditions and easy availability of raw materials.The process uses 2-methylnaphthalene (2-MN) as raw material, (NH4)2S2O8 as initiator to prepare peroxygen with 30% H2O2 and glacial acetic acid under the catalysis of sulfuric acid. Acetic acid was added dropwise to the reaction solution to synthesize 2-methyl-1,4-naphthoquinone (2-MNQ) by oxidation, and its structure was characterized by ICIR, GC-MS, and LCMS, and the oxidation reaction mechanism and the type and content of by-products were verified. The main impurities were isomer 6-methyl-1,4-naphthoquinone and its by-products phthalic anhydride and 4-methylphthalic anhydride produced by excessive oxidation. The effects of catalyst, reaction temperature, reaction time, dosage of oxidizer and initiator on the yield and conversion of 2-MNQ were investigated. The conversion rate and yield of 2-MNQ were determined by HPLC (external standard method). The optimum reaction conditions were obtained reaction temperature 65℃, reaction time 5h, n(CH3COOOH):n(2-MN) = 26:1. The conversion rate of 2-methylnaphthalene was 98%, and the product yield was 35%. The innovation point of this paper is to verify the reaction mechanism and the intermediate process in detail using the original external infrared, that is, the raw material 2-methylnaphthalene is oxidized by oxyacetic acid, the epoxidation reaction generates the intermediate, and then the rearranges to generates 2-methylhydroxyquinone, and the oxidation continues to generate the target product 2-methyl-1, 4-naphthalene quinone. The process has the characteristics of environment friendly, simple technology, mild operating conditions and easy availability of raw materials. Related Articles | Metrics Select Thermodynamic model for the phase equilibrium of cerium carbonates in the NaCl-H 2O system Feng LUAN Daoguang WANG Junfeng WANG Jianwei ZHANG Penglei CUI The Chinese Journal of Process Engineering    2022, 22 (8): 1103-1114.   DOI: 10.12034/j.issn.1009-606X.221348 Abstract （257）   HTML （7）    PDF （3693KB）（26）       Knowledge map    Save Cerium carbonates are important precursors for the production of CeO2, which have a decisive effect on the properties of CeO2. The crystal characteristics of cerium carbonate compounds depend on the control of supersaturating in reactive crystallization, and the solubility of cerium carbonate compounds in the NaCl-H2O system are important basic data. In this work, cerium carbonates were synthesized by homogeneous precipitation method at the temperature range of 298.15~363.15 K. The generated solids were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM) and thermogravimetric analyzer (TG). The results showed that Ce2(CO3)3?8H2O was obtained below 323.15 K and transferred to CeCO3OH above 343.15 K. The solubility of the two cerium carbonate compounds in the NaCl-H2O system were determined by the classical isothermal method. The results showed that the solubility of Ce2(CO3)3?8H2O increased with the increase of temperature and concentration of NaCl, while the solubility of CeCO3OH increased with the increase of concentration of NaCl, and decreased with the increase of temperature. The solubility of Ce2(CO3)3?8H2O in water at 298.15 K was 4.08×10-6 mol/kg, which was of the same order of magnitude as the solubility of cerium carbonate [Ce2(CO3)3] that was 2.17×10-7~2.17×10-6 mol/kg at 298.15 K. The results indicated the reliability of the experimental data measured in this work. A thermodynamic model for predicting the solubility of Ce2(CO3)3?8H2O and CeCO3OH in the NaCl-H2O system was finally established by using the ELEC-NRTL equation embedded in the Aspen Plus platform. The solubility products of Ce2(CO3)3?8H2O and CeCO3OH were obtained by regression of their solubility data in water on the basis of an infinite dilution assumption. The species such as CeCO3+, CeOH2+, CeHCO32+ were introduced into the thermodynamic model on basis of the speciation method and their equilibrium constants were calculated by Van't Hoff isothermal formula. The new ion pair parameters of Ce3+-HCO3- and Ce3+-Cl- were obtained by regression of the experimental data to improve the predictive ability of the new model. The predicted values of the established thermodynamic model were well in agreement with the experimental data. Related Articles | Metrics Select The jet characteristics of post combustion oxygen lance in a 250 t converter Shuguo ZHENG Miaoyong ZHU The Chinese Journal of Process Engineering    2022, 22 (10): 1438-1446.   DOI: 10.12034/j.issn.1009-606X.222281 Abstract （256）   HTML （11）    PDF （1710KB）（55）       Knowledge map    Save Supersonic jet characteristics of oxygen lance nozzles have a significant influence on smelting. The three-dimensional model of a 250 t steelmaking converter was established by Fluent software. The jet characteristics of a conventional 6-hole oxygen lance with five holes around and one hole in the center and a post combustion (PC) oxygen lance with a single flow channel were compared and analyzed. The interaction between gas-liquid-slag three phases was simulated by VOF multiphase flow model. The results show that the inflow of the left-side secondary hole flow unit quickly converges into the center hole jet, which has a larger radial cross-sectional area; while the right-side secondary hole flow unit converges into the peripheral 5-hole main flow unit. Due to the supplement of the second hole flow unit, the velocity under the oxygen lance is evenly distributed, and the low-velocity area is reduced, slowing down the decay of the center hole jet, resulting in a large center hole jet velocity. Therefore, the post combustion oxygen lance has a larger impact area and impact depth. Therefore, it can efficiently decarbonize and phosphoresce, giving full play to the secondary combustion effect, and is conducive to slagging. Through the three-phase simulation study of gas-liquid-slag, it can be seen that the cavity profile and interface of steel-slag-gas remain unstable due to the propagation of surface waves, and the slag layer at the furnace wall is calmer with time, indicating that there is no scouring of the furnace wall by either the conventional oxygen lance or the secondary combustion oxygen lance. The maximum impact diameter and impact depth of the secondary combustion oxygen lance is 2461 mm and 358 mm, which are 1.16 times and 1.19 times than the conventional oxygen lance, respectively. The industrial tests have shown that the use of secondary combustion oxygen lances increases the furnace temperature and significantly reduces the oxygen supply time, while the post combustion oxygen lance increases the converter temperature by 27.2°C, and shortens the oxygen supply time by 78 s. Related Articles | Metrics Select Numerical simulation of CO 2 hydrogenation system in mixed catalyst bed at particle scale Bo JIN Yaxin ZHANG The Chinese Journal of Process Engineering    2022, 22 (8): 1040-1052.   DOI: 10.12034/j.issn.1009-606X.221292 Abstract （253）   HTML （7）    PDF （7777KB）（70）       Knowledge map    Save The effective conversion of CO2 is important for achieving the goals of peak carbon dioxide emissions and carbon neutrality. Cylindrical particles have better thermal conductivity but smaller surface area when compared with heteromorphic particles, therefore, for better bed performance, the discrete element method (DEM) is used to perform particle-scale CFD simulations of a CO2 hydrogenation system in a mixed bed of heterogeneous particles, to investigate the effect of different stacking methods on the multi-physical field distribution, CO2 conversion and CH4 yield in the bed. The results show as follows: there is a diffusion resistance within the catalyst, as the reaction progress, the material within the particles changes from stratified distribution to uniform distribution. Compared to conventional beds, random mixed beds are less prone to hot spot fluctuations before steady state and has higher yields at steady state, while columnar bed have a more uniform radial heat field and higher hot spot. Of the four regular mixed beds, the two catalyst beds with 4 holes at bottom have more uniform overall flow fields, fewer high velocity zones, larger pressure drops, a larger proportion of high temperature zones and less fluctuation of hot spot before steady state than the two catalyst beds with columnar bottom. 2-layer mixed stacking-bottom 4 holes catalyst bed has maximum steady-state exit CO2 conversion and CH4 yield. The 4-layer mixed stacking-bottom 4 holes catalyst bed has high percentage of the high temperature region, which tends to increase as the reaction progress, resulting in significant decrease in CO2 conversion and CH4 yield. Related Articles | Metrics Select Hydration of lanthanum ions clusters in aqueous solution: a DFT study Zhaoyang JU Mengting YU Tingyu LEI Haixiang CHENG Lanhui REN Chengsheng GE The Chinese Journal of Process Engineering    2022, 22 (6): 764-773.   DOI: 10.12034/j.issn.1009-606X.221184 Abstract （251）   HTML （16）    PDF （3536KB）（48）       Knowledge map    Save As one kind of acid and shape-selective catalyst, zeolites Y have been widely used in the fields of drying and clean filtration, adsorption and separation because of its neat and uniform pore structures. The production of rare earth (RE) zeolites generally utilized RE ion aqueous to replace in NaY zeolites by Na-RE ion exchange reaction. However, the structures of RE ion hydration and the microscopic mechanism of the clusters crossing the pores of zeolites were still unclear. This work mainly focused on the structural prosperities of La3+ hydration and different valent hydration clusters based on density functional theory (DFT) calculations at M06-2X-D3/def2-SVP (LANL2DZ for La3+) and SMD=water implicit solvent level. The dimensions of the clusters, Mulliken charges, binding energies, and energy decomposition had been analyzed in this work. It could be found that the structures of clusters were flexible, it was not greater than a certain hydration number of the clusters to pass through the pores of zeolites. With the expanding number of hydration in clusters, the average radius of La-O(H2O) would increase. From the analysis of binding energy, the La3+ tended to be a more stable structure with high hydration in aqueous solution. In addition, the binding energies of La-O(OH-) were stronger than that of La-O(H2O). When n≤9 in the [La(H2O)n]3+ clusters, the electrostatic interaction occupied the dominant proportion, and the following items were induction, exchange repulsion and dispersion energy in the system based on the energy decomposition. When n＞9 in the [La(H2O)n]3+ clusters, the proportion of electrostatic interaction would decrease, the induction item would increase at the same time. The proportion changes of exchange repulsion and dispersion energy were not obvious with the increasing numbers of hydration. This work would provide some guidance for understanding the structure of La3+ hydration and basic aid for production of the RE zeolites. Related Articles | Metrics Select A multi-objective optimization and decision?making method of carbon-hydrogen-oxygen symbiosis network in EIPs Hongchuan DENG Wenxu LU Xiaoyong LUO Yanlin LÜ Wan WANG The Chinese Journal of Process Engineering    2022, 22 (8): 1137-1146.   DOI: 10.12034/j.issn.1009-606X.221249 Abstract （249）   HTML （3）    PDF （1050KB）（53）       Knowledge map    Save In view of the carbon-hydrogen-oxygen symbiosis networks (CHOSYNs) in eco-industrial parks (EIPs), a multi-objective optimization and decision-making method is proposed based on multi-scale atomic targeting method, considering economic and environmental factors and the reuse of by-product of carbon-hydrogen-oxygen compounds, and the optimal scheme is obtained from the alternatives. In this method, the mathematical programming method is adopted, and the global optimization is carried out with the minimum total annual cost (TAC) and carbon-dioxide annual emission (CAE) as the objective functions respectively, and the mixed-integer nonlinear programming (MINLP) model is established. Using the ε-constraint method, the CAE is transformed into constraint conditions, and the Pareto front of the TAC and CAE is obtained. It is found that the TAC is inversely proportional to CAE. The linear programming technique for multidimensional analysis of preference (LINMAP) and technique for order preference by similarity to ideal situation (TOPSIS) methods are used to make the optimal decision on the Pareto frontier. It is found that they choose the same point as the optimal decision. Based on the proposed method, an industrial park is optimized. The results show that the rational use of the existing by-product of carbon-hydrogen-oxygen compounds can reduce the cost of the raw materials, and reduce the TAC and CAE by 63.44% and 76.99%, respectively. Related Articles | Metrics Select 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 Abstract （248）   HTML （4）    PDF （1303KB）（66）       Knowledge map    Save 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. Related Articles | Metrics Select Effect of Na 2O/SiO 2 ratio on structure and properties of reduction smelting slag for treating decoppering anode slime in Caldo furnace Xiaotian ZHANG Yaru CUI Guohua WANG Ze YANG Junxue ZHAO Ze WANG Ailin HU The Chinese Journal of Process Engineering    2022, 22 (9): 1279-1286.   DOI: 10.12034/j.issn.1009-606X.221314 Abstract （246）   HTML （5）    PDF （3786KB）（26）       Knowledge map    Save Caldor smelting is one of the most important methods for treating decoppering anode slime by pyrometallurgy. This research aims to solve the serious problems of poor melting performance and large precious metals loss of reduction smelting slag for treating decoppering anode slime emerged in a domestic enterprise. Therefore, the process optimization and regulation on the Na2O/SiO2 ratio of reduction smelting slag in the Caldor furnace is carried out. The thermodynamic analysis by Factsage software is employed; simultaneously, the physicochemical properties of reduction smelting slag are measured combined with the XRD analysis and Raman spectroscopy characterization. According to the liquid phase diagram and the tested physicochemical properties of the PbO-Na2O-SiO2-BaO system, appropriately increasing Na2O/SiO2 ratio can effectively decrease the melting temperature and viscosity of reduced smelting slag, without changing the slag rate and the adding amount of total flux. The structure of reduction smelting slag varies from dimer structure silicate of Si2O76- to tetrahedron structure silicate of SiO44- when the Na2O/SiO2 ratio of reduction smelting slag changes from 0.42 to 0.60. The increase of network modification of Na2O results in more bridging oxygens converting to non-bridging oxygens in the reduction of smelting slag, and the ratio of Si2O64- chain structure silicate and Si2O52- sheet structure silicate decrease also, which lead to the lower of polymerization degree of slag. The analysis results show that the Qn of bridged oxygen is consistent with the silicate structure of the smelting slag. Simultaneously, the hemispherical melting temperature of slag decreases from 1178℃ to 950℃, and the viscosity can decrease about 45.2% at a smelting temperature of 1100℃ when the Na2O/SiO2 ratio of the reduction smelting slag varies from 0.42 to 0.60. As a result, the fluidity of reduction smelting slag is improved obviously, which can verify the above change trend of slag microstructure from the view of macroscopic properties. The results prove that it is feasible to regulate the Na2O/SiO2 ratio of reduction smelting slag to lower the bridging oxygen number and polymerization degree of complex anionic, to improve the physicochemical properties. Related Articles | Metrics Select Flow field numerical simulation and mixing performance optimization of impinging stream reactor Jianwei ZHANG Juchao NIU Xin DONG Ying FENG The Chinese Journal of Process Engineering    2022, 22 (9): 1244-1252.   DOI: 10.12034/j.issn.1009-606X.221336 Abstract （245）   HTML （4）    PDF （2060KB）（66）       Knowledge map    Save Impinging stream reactor were used in various applications including pharmaceuticals, petroleum and provisions due to their high mass transfer efficiency, especially in fluid mixing processes, and the difference in structure was a key factor affecting the mixing effect of the reactor, thus optimizing the structure of the impinging stream reactor was beneficial for its further industrial applications. In this work, numerical simulations were used to analyze the internal flow field of a multi-nozzle symmetric impinging stream reactor to optimize the reactor structure. The effects of different nozzle numbers and feed conditions on the velocity field and turbulence characteristics in the impinging stream reactor were investigated, and the mixing effect was characterized by the mixing uniformity. The results showed that the velocity distribution in the impinging stream reactor with different number of nozzles was bimodal, the velocity gradient decreased with the increase of the number of nozzles under the condition of equal velocity, and the distribution range of high shear force increased and then decreased with the increase of the number of nozzles. By analyzing the turbulence scale distribution, it was found that the small-scale vortices were mainly concentrated in the impingement zone, while the large-scale vortices were mainly concentrated in the development zone, and the average shear stress and vortex size gradient in the four-nozzle impinging stream reactor were the largest, and the high shear stress and vortex size gradient were beneficial to increase the fluid turbulence intensity, so the average turbulent kinetic energy in the impinging stream reactor was increased and then decreased with the increase of the nozzle number, in which the average turbulent energy in the four-nozzle impact reactor was the largest, and the four-nozzle structure was more conducive to enhanced mixing. In this study, the four-nozzle structure was the optimal structure for mixing in the impinging stream reactor. Related Articles | Metrics Select Floating and sinking experiment and mechanism of calcite coating?acid reaction Rongdong DENG Dingquan XING Jianghui ZHOU Shiqi LI Ruiqi ZHAO The Chinese Journal of Process Engineering    2022, 22 (8): 1094-1102.   DOI: 10.12034/j.issn.1009-606X.221225 Abstract （244）   HTML （5）    PDF （2240KB）（17）       Knowledge map    Save Calcite, as a major gangue mineral, is often found in other calcium-bearing minerals. Froth flotation is the main method to separate calcite from other calcium minerals. However, due to the similar physicochemical characteristics of calcium-containing minerals, it is difficult to separate these minerals effectively by the conventional flotation method. Different from non-carbonate minerals, calcite has the characteristics of reacting with an acid to generate CO2 bubbles. These CO2 bubbles can effectively reduce the apparent specific gravity of calcite in a short time. Polyvinyl alcohol film has selective permeability, which can allow H+ to pass through and as a barrier to CO2 bubbles. The high polymer film can bind the generated CO2 bubbles on the surface of calcite. When there are enough CO2 bubbles, the calcite particles will float spontaneously and be separated from the calcium-containing non-carbonate minerals. The coating effect directly affects the separation effect. Therefore, it is necessary to determine conditions of appropriate coating and acid reaction to improve the effectiveness of calcite coating-acid reaction. In this work, the main factors that affect the calcite coating-acid method were systematically studied through single factor experiments and orthogonal experiments. The optimum conditions of sulfuric acid concentration, PVA type and concentration, methyl isobutyl carbinol (MIBC), and sodium dodecyl sulfonate (SDS) concentration were screened by a single factor test. The orthogonal test was carried out for three factors, acid concentration, PVA concentration, and MIBC concentration. The results showed that the coating-acid reaction method can realize the self-floating of calcite particles (1 mm). The optimum conditions of the calcite coating-acid reaction method were sulfuric acid concentration of 2.0wt%, PVA type of P139546, PVA concentration of 2.4wt%, and 40 mg/L MIBC which was conducive to the floating of calcite. Under these conditions, the floating rate of calcite was 84.9%, and the average floating time was 28.8 s. The combination of SDS and PVA can effectively improve the floating time of calcite, while the floating rate was lower than that without SDS. PVA concentration and acid concentration were the main factors affecting the calcite coating-acid reaction method. Related Articles | Metrics Select Study on stability of surfactant-driven droplet spreading over topographic substrate Chunxi LI Haozhe SU Jiaming TONG Xuemin YE The Chinese Journal of Process Engineering    2022, 22 (8): 1019-1029.   DOI: 10.12034/j.issn.1009-606X.221311 Abstract （243）   HTML （7）    PDF （1537KB）（59）       Knowledge map    Save When a droplet laden with surfactant landing on a thin film, spontaneous spreading driven by surface-tension gradient occurs. Affected by the non-linear impact, the initial small disturbances lead to an unstable fingering phenomenon during the spreading, which is closely related to the topographic substrates. Based on the evolution equations of liquid film height and surfactant concentration derived from the lubrication approximation, FreeFEM++ is employed for simulation coding, and the Microsoft MS-MPI runtime library is applied for parallel computing. The influence of the topographic substrates on the instability is examined, the power spectrum is employed to analyze the growth law of disturbance energy corresponding to different wavenumbers, the relation between the Marangoni effect, the capillary effect, and the disturbance energy is investigated, as well as the internal mechanism of the topographic substrate on instability is explored. The results show that the topographic substrates deal little influence on the fingers, but a lot on the region downstream. Disturbance energy with different wavenumbers present different evolution characteristics, and the dominant wavenumbers in this study are 20 and 7. On the notch base, wavenumbers selected from random disturbance is consistent with transient growth analysis (TGA), which means that notch base does not change the wavelength select mechanism. The maximum disturbance energy appears at the position setting the initial condition. Compared with the flat base, the notch base can inhibit the development of disturbances, and the total disturbance energy is reduced to approximately 80%. Whereas the corrugated base can promote the development of disturbances, and the total disturbance energy is increased to about 105%, and the corrugated base has a strong promotion on the disturbances corresponding to specific wavenumbers in the initial stage, which is consistent with TGA. In general, the topographic substrate affects the disturbance energy by changing the concentration distribution of surfactants, thereby influencing fingering phenomena. Related Articles | Metrics Select 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 Abstract （242）   HTML （8）    PDF （917KB）（56）       Knowledge map    Save 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. Related Articles | Metrics Select Entrainment and elutriation of particles in a gas-solid fluidized bed Qi WANG Zhunzhun MA Hongfang MA Weixin QIAN Qiwen SUN Haitao ZHANG Weiyong YING The Chinese Journal of Process Engineering    2022, 22 (12): 1623-1632.   DOI: 10.12034/j.issn.1009-606X.222004 Abstract （241）   HTML （1）    PDF （1286KB）（58）       Knowledge map    Save The experimental work on the entrainment and elutriation of glass beads and white fused alumina powder with a wide particle size distribution was carried out in a fluidized bed with an inner diameter of 0.5 m and a total height of 6 m. The two powders were passed through the sieve distribution ratio to obtain experimental materials with different particle size distributions belonging overall to the Geldart groups A or B particles. Fluidization tests were carried out in a steady state at velocities of 0.25~0.76 m/s, the effects of superficial gas velocity, bed material particle size distribution and particle size on particle entrainment and elutriation rate were investigated. The elutriation rate constant of the powders under different conditions was obtained. In order to ensure that the transport disengaging height (TDH) was reached under various conditions, the entrained particles in the fluidization column were sampled axially and analyzed for particle size distribution. The experimental results showed that an increase of the concentration of fine particles in the experimental materials increased the total entrainment flux, but reduced the elutriation rate constant (Ki*). The total entrainment flux and the elutriation rate constant increased exponentially with increases of the superficial gas velocity. In addition, at a given superficial gas velocity, the elutriation rate constant first increased with the decrease of particle size, until reaching a critical particle size (dcrit), after which the elutriation rate constant would tend to flatten or decrease, that changes in the elutriation rate may be attributed to the interparticle adhesion forces. A new empirical correlation was proposed based on the experimental results and theory of dimensional analyses to estimate the elutriation rate constant of particles below the critical particle size. The correlation could agree well with the experimental data. The proposed empirical correlation can be used to scale up fluidized beds. Related Articles | Metrics Select Research on vibration regeneration of granular bed based on Brazil nuts effect Jianhong WANG Xiaoyan MO Huiqi ZHANG Minshu ZHAN The Chinese Journal of Process Engineering    2022, 22 (8): 1085-1093.   DOI: 10.12034/j.issn.1009-606X.221384 Abstract （239）   HTML （3）    PDF （2228KB）（28）       Knowledge map    Save In order to explore a low-cost and environment-friendly regeneration method of the granular bed, the effects of the average particle size ratio and volume ratio of the granules/dust, vibration frequency, acceleration as well as amplitude on the vertical vibration separation of the granules/dust on Brazil nuts effects were studied by taking photos after vertical vibration. The results showed Brazil nuts could be formed when the average particle size ratio of slag/talc powder and slag/fly ash was not less than 75, and the average particle size ratio of quartz sand/talc powder and quartz sand/fly ash was not less than 65 and 15.3 respectively. When the vibration acceleration and amplitude of slag/dust exceeded the critical value at the vibration frequency of 20~100 Hz, slag/dust changed from mixed state to Brazil nuts. With the increase of vibration frequency, the critical acceleration first increased and then decreased, reached the lowest value at 45 Hz, and then continued to increase. The critical amplitude first decreased with the increase of vibration frequency, reached the lowest value at 45 Hz, and then continued to increase. The optimum vibration frequency of Brazil nuts formed by the slag/dust system was 45 Hz, which was not affected by the slag particle size, dust type, and slag/dust volume ratio. However, the larger the particle size of slag and the larger the volume ratio of slag/talc was, the easier the separation of slag/talc was, and the formation of Brazil nuts was easier in slag/talc than in slag/fly ash. At the optimal frequency of 45 Hz, slag/talc powder and slag/fly ash could realize vertical vibration separation at low amplitudes of 1.01 mm and 1.36 mm, respectively. The vertical vibration method based on Brazil nuts effect is feasible to separate the dust from the granules in the granular bed, which is beneficial to the reuse of the granular material and improves the ability of the granular bed to capture fine dust. The vertical vibration is a promising method of regeneration of the granular bed. Related Articles | Metrics Select 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 Abstract （237）   HTML （6）    PDF （2094KB）（47）       Knowledge map    Save 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. Related Articles | Metrics Select Hydrodynamics and mass transfer in a three-phase bubble column cell culture bioreactor Shengnan XU Hongfei LIU Xueliang LI Guocheng DU Jian CHEN The Chinese Journal of Process Engineering    2022, 22 (9): 1192-1202.   DOI: 10.12034/j.issn.1009-606X.221364 Abstract （237）   HTML （3）    PDF （3614KB）（99）       Knowledge map    Save Pneumatic bioreactors, including bubble columns and air-lift reactors, were once considered the most suitable for large scale cell culture. However, their applications quickly declined and research interests diminished when it was suspected that the bubbles bursting at the gas-liquid interface could cause damage to certain cells. Stirred tank reactors, limited to 1~2 m3 working volume, became the industry standard. In recent year, the emergence of new cell-based technology, such as cultured meat, has led people to reconsider the bubble column reactor technology, as such products required reactors in the order of 100 m3 to be economically viable. However, there was generally a lack of up-to-date understanding of the performance of pneumatic reactors in the context of cell culture due to the lack of interest from the industry in the past four decades or so. In this study, cold flow experiments were conducted and CFD simulations were performed to investigate the effect of microcarriers and cell culture media additives such as Pluronic F68 and Antifoam C on the hydrodynamics and mass transfer characteristics of a bench-top bubble column. Foaming and foam control were also investigated. It was found that in the presence of 0.5 and 1.0 g/L Pluronic F68, the bubble size in a simulated culture medium remained almost unchanged as the superficial gas velocity increased from 0.04 cm/s to 0.17 cm/s, dissimilar to the air-water system where the bubble size increased significantly with gas flow due to coalescence. Microcarriers of 14%~20% volumetric fractions were not found to impact the bubble size and Antifoam C of up to 1.60×10-4 was required to suppress the foam, without affecting the bubble size in the column. Despite the smaller bubble size and higher gas holdup, the overall volumetric mass transfer coefficient, kLa was on par with the air-water system, as the medium additives negatively affected the liquid side mass transfer coefficient, kL. In all the experiments, the microcarriers could all be completely suspended. The gas holdup and solid distribution in the three-phase system could be adequately described by an Euler-Euler CFD model. Related Articles | Metrics Select Simulation of carbon segregation during electroslag remelting of H13 die steel Yiru DUAN Baokuan LI Xuechi HUANG Zhongqiu LIU Yuying CHAI The Chinese Journal of Process Engineering    2022, 22 (8): 1074-1084.   DOI: 10.12034/j.issn.1009-606X.221357 Abstract （233）   HTML （3）    PDF （5841KB）（40）       Knowledge map    Save Macrosegregation generally exists in the electroslag remelting (ESR) ingot, which seriously affects the homogeneity and quality of the ingot. A three-dimensional unsteady ESR mathematical model was established to study the macrosegregation phenomenon during ESR of large H13 die steel, and the interaction between alloying elements was considered. The anisotropic porous media model was used to simulate the momentum attenuation in the mushy zone. And solute redistribution behavior was calculated by the lever algorithm. The accuracy of the model was verified by experiments, and the distribution trend of carbon segregation index between simulation results and experimental results agree well. The simulation results showed that, at the beginning of melting, the metal pool was shallow and flat, and the metal rapidly solidified under the action of the cooling water in the bottom tank. With the progress of melting, the cooling effect of the bottom tank was weaker than the sidewall of the crystallizer, the metal pool profile deepened, and the carbon element was enriched at the bottom of the metal pool, and the concentration increased gradually. The bottom and edge of the ESR ingot showed negative segregation, while the center and top showed positive segregation. And the distribution of carbon segregation in ESR ingot did not change whether the initial element mass fraction and operating current were changed or not. When other initial elements were constant, the initial mass fraction of silicon increased from 0.8wt% to 1.2wt%, and the positive segregation index of carbon increased by 8.57%; The initial mass fraction of molybdenum increased from 1.1wt% to 1.75wt%, and the positive segregation index of carbon decreased by 1.89%. Under the condition of increasing the initial mass fraction of silicon and molybdenum, the distribution of carbon can be more uniform. When the working current decreased from 3700 A to 3100 A, the maximum positive segregation index of carbon decreased from 0.0856 to 0.0837, decreasing by 2.22%. Related Articles | Metrics Select 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 Abstract （233）   HTML （4）    PDF （853KB）（44）       Knowledge map    Save 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. Related Articles | Metrics Select Preparation and characterization of liquid-paraffin phase change microcapsules with narrowed size dispersion Ying ZHANG Hui WANG Enda CI Xiaoqing LI Jianqiang LI The Chinese Journal of Process Engineering    2022, 22 (6): 745-753.   DOI: 10.12034/j.issn.1009-606X.221172 Abstract （232）   HTML （6）    PDF （2981KB）（66）       Knowledge map    Save Microencapsulated phase change materials have excellent ability to store energy and resist the leakage of phase change materials during the solid-liquid phase change process. Traditional mechanical agitation emulsification method has intrinsic difficulty in preparing phase change microcapsules with uniform and controllable particle size. In this work, premix membrane emulsification was employed to prepare emulsion, and liquid paraffin/melamine-formaldehyde resin microcapsules with narrowed particle size dispersion were successfully prepared by taking advantages of the combination of premix membrane emulsification and in?situ polymerization. The result showed that transmembrane pressure and passes had a great effect on particle sizes and distributions of the resulting microcapsules. And the particle sizes and distributions of microcapsules can be effectively controlled by adjusting the transmembrane pressure and passes. When SPG (Shirasu Porous Glass) membrane with an average pore size of 10.1 μm was used, the liquid paraffin microcapsules with narrowest particle size distribution can be obtained by using transmembrane pressure of 0.2 MPa and transmembrane pass of 4 times. And these microcapsules had an average particle size of 10.84 μm and a relative standard deviation of 0.16. But the relative standard deviation of the particle size of the microcapsules prepared by using the combination of mechanical agitation emulsification and in?situ polymerization was 0.89. It indicated that microcapsules with a narrower particle size distribution can be synthesized effectively by employing the premix membrane emulsification. The surfaces of the microcapsules were smooth and dense, and without any adhesion and reunion. They exhibited excellent heat resistance and cold/heat cycle stability, and the encapsulation ratio was about 80%. Besides, the preparation efficiency of the paraffin microcapsules was greatly improved by using the methods of premix membrane emulsification coupled with in?situ polymerization. These results indicated that the combination of premix membrane emulsification and microencapsulation technology was a promising candidate for the preparations of low temperature alkane phase change microcapsules with narrowed size dispersion. Related Articles | Metrics Select Scenario deduction on chemical plant accidents using FRAM Qianlin WANG Wenhui TIAN Dongsheng ZHANG Feng WANG Xulong HEI Guoan YANG The Chinese Journal of Process Engineering    2022, 22 (6): 782-791.   DOI: 10.12034/j.issn.1009-606X.221235 Abstract （229）   HTML （14）    PDF （5910KB）（34）       Knowledge map    Save There are more and more accidents in the chemical plants due to high risk state and difficult safety management, such as unplanned shutdown, serious leakage of toxic and harmful chemicals, fire and explosion, and so on. These accidents have a huge negative impact on the society, economy, and environment. Accident causation model is an important technique for accident scenario construction and deduction; however, those traditional models cannot fully capture the dynamic and nonlinear interaction between system elements, or precisely stick to the cause analysis of system element errors and effective development of elimination measures. Therefore, the functional resonance analysis method (FRAM) was introduced to deduce the potential accident scenario of chemical plants from a perspective of systematical function features. There were four major procedures in the FRAM, including the identification and description of basic functions, the performance change assessment of every function, the possibility determination of functional resonance, and the response measure development of performance change. To illustrate its validity, the BP Texas City refinery explosion was selected as a test case in this work. Particularly, each functional performance change and functional failure connection of the raffinate section were clearly illustrated in the functional network diagram. It mainly involved the raffinate splitter tower, heating furnace, heat exchanger, blowdown drum and stack, different kinds of instruments, as well as operators. Results from the above-mentioned accident showed that this method was competent to deeply trace the accident occurrence process and evolution scenario, which could be further applied to reveal the cause mechanism of chemical plant accidents and excavate the weak points of chemical plants. Moreover, the FRAM was also compared with two other traditional methods-sequentially timed events plotting (STEP) and accident map (AcciMap). In summary, the introduced FRAM was verified to be feasible, effective, and reasonable for the accident scenario deduction of chemical plants. Related Articles | Metrics Select Study on the ignition and combustion characteristics of aluminum/ethanol based nanoslurry fuels Peng GUO Weiqi CHEN Yunlan SUN Baozhong ZHU The Chinese Journal of Process Engineering    2022, 22 (6): 811-818.   DOI: 10.12034/j.issn.1009-606X.221236 Abstract （227）   HTML （5）    PDF （1234KB）（22）       Knowledge map    Save With the rapid development of aerospace, the requirements for liquid hydrocarbon fuels with the high energy density are increasing. The energy density of traditional hydrocarbon fuels is low, which cannot meet the application requirements. Aluminum powder has a high energy density. The addition of nano-aluminum powder to hydrocarbon fuels can increase the energy density and improve the ignition and combustion characteristics. To determine the effect of the change of nano-aluminum powder from low concentration to high concentration on the ignition and combustion characteristics of liquid hydrocarbon fuels, the ignition and combustion characteristics of aluminum/ethanol based nanoslurry fuel droplets with different concentrations (2.5wt%, 10wt%, 15wt%, and 20wt%) of nano-aluminum powder were studied by a droplet hanging method. The whole combustion process of the droplet was captured by a high speed photography system. The ignition delay time, the ignition temperature, and the droplet life were analyzed by a temperature acquisition system and an image collection system. The results showed that the temperature and the concentration of nano-aluminum powder had great influence on the droplet combustion characteristics. The ignition delay time and ignition temperature of the ethanol droplet can be reduced by adding nano-aluminum powder, and the droplet life can be shortened. Especially, the ethanol droplet with 2.5wt% nano-aluminum powder had the shortest ignition delay time. The ignition delay time and droplet life of sample S2, ignition temperature of sample S3, can be decreased by 42.20%, 18.43%, and 28.57% contrast to sample S1 at 750℃, respectively. With the increase of temperature, the ignition delay time and the ignition temperature of ethanol and aluminum/ethanol nanoslurry fuel droplets were significantly reduced. When the temperature was higher than 750℃, their decrease amplitude decreased. The concentration of nano-aluminum powder was closely related to the micro-explosion of droplet. The degree and the duration of the micro-explosion of droplet increased with the increase of nano-aluminum powder concentration, while this trend became stable when the concentration of nano-aluminum powder exceeded 10wt%. It was proved that the concentration of nano-aluminum powder and the ambient temperature were both important factors to affect the combustion characteristics of the aluminum/ethanol nanoslurry fuel droplet. Related Articles | Metrics Select 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 Abstract （223）   HTML （9）    PDF （7595KB）（52）       Knowledge map    Save 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. Related Articles | Metrics Select Study on technology of super gravity step separation of rare earth elements in Bayan Obo rare earth ore Xi LAN Jintao GAO Zhancheng GUO The Chinese Journal of Process Engineering    2022, 22 (10): 1429-1437.   DOI: 10.12034/j.issn.1009-606X.222303 Abstract （223）   HTML （5）    PDF （3910KB）（63）       Knowledge map    Save The rare earth reserves of Bayan Obo mine in China rank first in the world, and its rare earth minerals are mainly light rare earth, of which cerium, lanthanum, praseodymium and neodymium account for more than 97% of the total rare earth oxides, which has important industrial value. Since the rare earth elements have extremely similar physical and chemical properties, it is difficult to realize the separation of different rare earth elements from each other in the current treatment process. In this work, a green and efficient method was proposed for respectively recovering rare earth elements under supergravity from rare earth concentrate. Based on the evolution of mineral phases and elemental migration laws of the rare earth concentrate, it was found that different rare earth phases would be precipitated in different temperature intervals during the melting and cooling precipitation process. It could be concluded that the rare earth elements (REEs: Ce, La, Pr, Nd) were discovered to be precipitated as the rare earth oxide, rare earth ferrate and britholite phases respectively at various temperature ranges of 1400~1500, 1200~1400, and 1100~1200℃, respectively. However, the rare earth phases were intimately intertwined with each other in the normal gravity. Consequently, the respective separation of REEs (Ce, La, Pr, Nd) at their corresponding precipitation temperatures was conducted under the supergravity. 98.38% of Ce was firstly enriched into the rare earth oxide and separated from the concentrate as driven by the supergravity, 97.70% of La was enriched into the rare earth ferrate and separated subsequently, and the Pr and Nd were precipitated further into britholite and separated from the system. Accordingly, the high purity of rare earth oxide, rare earth ferrate, and britholite phases were attained respectively, and the stepwise separation of Ce, La, Pr and Nd in the rare earth concentrate were achieved, achieving the green and efficient recovery of REEs (Ce, La, Pr, Nd) from the Bayan Obo rare earth concentrate with no additives, no hazardous waste, and no secondary pollution. Related Articles | Metrics Select 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 Abstract （218）   HTML （6）    PDF （1395KB）（33）       Knowledge map    Save 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. Related Articles | Metrics Select 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 Abstract （218）   HTML （3）    PDF （7087KB）（18）       Knowledge map    Save 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). Related Articles | Metrics Select Leaching kinetics of lead from fire assay cupel in acetic acid-H 2O system Guang'an ZHANG Fuyuan ZHANG The Chinese Journal of Process Engineering    2022, 22 (6): 774-781.   DOI: 10.12034/j.issn.1009-606X.221167 Abstract （217）   HTML （5）    PDF （1627KB）（26）       Knowledge map    Save The fire assay cupel containing heavy metal lead is an intermediate waste product in the process of cupellation. The comprehensive disposal of cupel waste with high lead content is of great significance to reduce heavy metal pollution and recycle lead. The metal oxides mainly exist in the form of Al2O3 and sintered MgO in the fire assay cupel, and the melting points are 2054 and 2852℃, respectively, which seriously affects the normal process of melting. The wet process can effectively avoid the influence of magnesia-aluminum oxides with high melting point substances. Because of resource and harmless treatment of fire assay cupel, the thermodynamic of lead leaching is analyzed, the effects of excess coefficient of acetic acid, leaching temperature, reaction time, stirring speed, and liquid-solid ratio on the leaching rate of lead were investigated and leaching kinetics of lead were studied in the acetic acid-H2O system. With the increase of the mole fraction of acetate ions, lead ions and acetate ions in an aqueous solution are easily complexed to form a lead acetate complex which is difficult to ionize, and the concentration of lead ions in the solution decreases, which promotes the leaching reaction of lead to a certain extent. Under the optimized condition that the excess acetic acid coefficient of 1.6, the liquid-solid ratio of 6:1, the leaching temperature of 80℃, the stirring speed of 200 r/min, and the reaction time of 40 min. By first leaching and secondary leaching to the leaching residue, the primary leaching rate of lead is 98.31%, the secondary leaching rate is 95.53%, and total leaching efficiency reached 99.96%. The leaching process of lead is consistent with the shrinking particle model and controlled by diffusion, conforms to the kinetic equation 1-2/3φ-(1-φ)2/3=kt, the calculation result of apparent activation energy is 38.949 kJ/mol. Related Articles | Metrics Select Research on transient leakage characteristics and consequence of LNG tanker accident Jinlong MEN Hongbing JI Chongchong CAI Bibo XIONG The Chinese Journal of Process Engineering    2022, 22 (9): 1287-1296.   DOI: 10.12034/j.issn.1009-606X.221312 Abstract （216）   HTML （0）    PDF （995KB）（29）       Knowledge map    Save The classical model of liquid phase leakage can not accurately analyze the accident quantitatively. In this work, the leakage of LNG tank car is improved in combination with the ideal gas state equation, the change relationship between liquid level and pressure and between liquid level and time are explored, the relationship is introduced into the empirical formula, the change relationship between leakage rate and time is deduced, and the function expression is simulated. The results show that the leakage rate decreases exponentially with time. The dangerous concentration range of material leakage is calculated by combining the functional relationship with Gaussian diffusion. The error between the results and fluent model is within 26%. On the basis of modifying the traditional Gaussian model, the dynamic smoke diffusion model with time and pressure is obtained. The modified dangerous concentration range is used as the basic data to quantitatively analyze the mass of substances involved in explosion. The Thornton cone model is also used to explore the risk and influence range of fire and explosion by considering the flame jet angle, flame direction and environmental factors. The results show that jet fire, steam cloud explosion and boiling liquid expansion steam explosion cause death within 15, 15 and 298 m respectively. Compared with Aloha model, the overall error of the results is within 10.37%. It shows that the model is applicable to the theoretical calculation of LNG tank car leakage. The leakage at any time can be obtained by using the improved leakage model. Combined with the Gaussian diffusion of time factors, the dynamic diffusion process can be better described, and the calculated fire and explosion hazard range is more accurate, which provides a theoretical basis for emergency pre judgment, in-process response and crisis law analysis. It provides a scientific reference for taking flexible rescue measures in different injury areas. Related Articles | Metrics Select Study on particle aggregation behavior in shear-thinning fluid Songhao TONG Xufeng HAN Fukang ZHOU Xiaofei XU The Chinese Journal of Process Engineering    2022, 22 (6): 792-801.   DOI: 10.12034/j.issn.1009-606X.221233 Abstract （213）   HTML （3）    PDF （2330KB）（49）       Knowledge map    Save In shear-thinning fluid, there is a special rheological behavior that the apparent viscosity decreases with the increase of shear rate. As the viscosity changes during lateral migration, the lift force acting on particles will also change, so the particle migration and aggregation laws in Newtonian fluids are not completely applicable to shear-thinning fluid. Integrating microfluidic technology, high-speed microscopic image acquisition technology and digital image processing technology, combined with the solved velocity and shear rate equations of shear-thinning power-law fluids, the force analysis of particles is completed, and the influences of particle size, channel flow rate, apparent viscosity and shear-thinning characteristics on particle aggregation are investigated. Results indicate that, in the shear-thinning fluid sodium carboxymethyl cellulose (CMC) aqueous solution, with the increase of channel flow rate, the equilibrium position of inertial lift ΔF=0 gradually approaches the wall surface, and the migration and aggregation location of particles gradually tends to the side of higher shear rate. This leads to the gradual change of the particle distribution from relatively uniform distribution to aggregation at specific locations. As the particle size increases, the aggregation in the shear flow becomes more and more obvious, and gradually closing to the wall. Combining experimental study and theoretical analysis, it is proved that the greater the consistency coefficient K (represent greater apparent viscosity), the more the aggregation position is towards the low shear rate, and the smaller the power law index n (represent stronger shear thinning characteristic), the more concentrated the position is towards the high shear rate. K increases and n decreases with the increase of CMC mass fraction which leads the aggregation position constantly shifting towards the side with lower shear rate. This shows that the consistency coefficient has a greater influence on the migration and aggregation of particles in shear-thinning power-law fluids. It needs to be paid attention to the research of solid-liquid two-phase separation in non-Newtonian fluids in the future. Related Articles | Metrics Select Preparation of particle stabilized bubbles for contrast ultrasound imaging Qing ZHANG Jie WU Guanghui MA The Chinese Journal of Process Engineering    2022, 22 (6): 828-838.   DOI: 10.12034/j.issn.1009-606X.221185 Abstract （211）   HTML （7）    PDF （4303KB）（51）       Knowledge map    Save Ultrasound imaging is widely used in the diagnosis of a variety of diseases due to its plenty of advantages, such as non-invasive, painless, real-time monitoring and low cost. However, some issues are with weak echoes. As a result, it is necessary to enhance the ability of ultrasound imaging by using an ultrasound contrast agent (microbubbles) with strong echo characteristics. At present, most of the microbubbles approved for clinical use consist of surfactants or phospholipids. Because of their strong compressibility, these bubbles can enhance the ultrasonic Doppler signal of blood flow and improve the clarity and resolution of ultrasonic images. But they still have some disadvantages, such as their limited stabilization effect and short blood circulation time, which limits the ability to inspect lesions that need long-term observation such as small lesions. Particle stabilized bubbles (PSBs) are bubbles formed by particles instead of surfactants stabilizing the gas-liquid interface. Compared with surfactant stabilized bubbles, the PSBs system has higher stability, because the particles are irreversibly adsorbed at the gas-liquid interface, which makes them a great potential ultrasound contrast agent. However, there are few studies on the preparation and application of particle-stabilized bubbles. The main reason is that the system requires a very narrow range of contact angles for particles. Once the range exceeds the defined range, the bubbles will burst rapidly. This work aims to prepare stable PSBs and to solve the problem of lacking research on PSBs at present. In this experiment, we did an extensive screening of different hydrophilic and hydrophobic particle stabilizers, then we investigated the influence of their charge, concentration, particle size, water phase and gas equal factors in forming PSBs. Finally, we prepared PSBs stabilized by chitosan nanoparticles (CNPs). On this basis, the biocompatibility of the system was evaluated by cytotoxicity test, hemolysis test and pathological section test. The contrast-enhanced performance of the system in vitro and in vivo was explored by a small animal ultrasound imager. These experimental results showed that CPSBs have good biocompatibility and imaging ability, indicating that the CPSBs system could be used as an ultrasonic contrast agent. Related Articles | Metrics Select 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 Abstract （211）   HTML （7）    PDF （1943KB）（67）       Knowledge map    Save 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. Related Articles | Metrics Select 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 Abstract （210）   HTML （3）    PDF （749KB）（54）       Knowledge map    Save 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. Related Articles | Metrics page Page 1 of 7 Total 255 records First page Prev page Next page Last page