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Preparation and electrochemical properties of Li0.98Ca0.02Mn2O4 Mingsi SHEN Haibo YUAN Doudou ZHANG Jing WANG Gaotian NIU Yangzhou MA Yaxin SUN The Chinese Journal of Process Engineering    2024, 24 (6): 746-752.   DOI: 10.12034/j.issn.1009-606X.223075 Abstract （167）   HTML （7）    PDF （3274KB）（258）       Knowledge map    Save Many research focus on improving the electrochemical properties of LiMn2O4 by chemical doping method. In cubic spinel structure LiMn2O4, the diversity of doping elements and doping positions provides a wide space for improving performance. Doping at the 16d octahedral position occupied by Mn can effectively suppress the Jahn-Teller effect and maintain the stability of the structure. By comparison, using elements with large ion radius to dope at the 8a tetragonal position occupied by Li can enlarge the Li+ diffusion channel and enhance the kinetics diffusion coefficient. In this work, pure phase of Li0.98Ca0.02Mn2O4 was successfully synthesized using the hydrothermal method followed by annealing at 750℃ for 5 h. The crystal structures and the morphologies of the products were analyzed by powder X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The electrochemical properties were characterized by galvanostatic charge/discharge experiments and electrochemical impedance spectroscope (EIS) tests. XRD analysis showed that the lattice constant increased by 0.12% in Ca-doped LiMn2O4 and the expansion of the crystal cell was beneficial to improving the diffusion of Li+. The small aggregates with porous channels formed by stacking nanoparticles were observed by FESEM. The results showed that Li0.98Ca0.02Mn2O4 exhibited the excellent rate capability with the larger discharge capacity at the relatively current rate range of 0.5 C~5 C. Especially, at 0.5 C, Li0.98Ca0.02Mn2O4 delivered the first discharge capacity of 126 mAh/g, which was 17.8% higher than that of undoped LiMn2O4 samples. The capacity retention of both samples was maintained at about 88.8% after 50 cycles. At 1 C, Li0.98Ca0.02Mn2O4 still holded its high discharge capacity of 117.5 mAh/g and capacity retention of 90% after 50 cycles, 80% after 150 cycles, and 60% after 1000 cycles. Undoped LiMn2O4 sample had low capacity of 57.0 mAh/g, but the capacity retention reacheed 67% after 1000 cycles, indicating good cycle stability. The calculated kinetics diffusion coefficient of Li0.98Ca0.02Mn2O4 was 2.5×10-11 cm2/s, which was about 1.6 times of undoped sample. Related Articles | Metrics

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Surface modification and catalytic performance study of Cu-based carbon dioxide to methanol hydrogenation catalyst Qiang YANG Gang WANG Chunshan LI The Chinese Journal of Process Engineering    2024, 24 (10): 1166-1176.   DOI: 10.12034/j.issn.1009-606X.224059 Abstract （449）   HTML （17）    PDF （3618KB）（254）       Knowledge map    Save Development of effective copper-based catalyst for CO2 hydrogenation to methanol is of great significance, considering the utilization of this greenhouse gas. In this work, a series of surface promoter-modified (Mn, In, Mo, Mg, Zr) catalyst were synthesized by coprecipitation-post impregnation method and evaluated for CO2 hydrogenation to methanol in fixed-bed reactor. The role of metal modifier on the physicochemical properties of Cu/ZnO/Al2O3 (CZA) were investigated through CO2-TPD, XRD, XPS and H2-TPR. In addition, the catalytic mechanism for CO2-to-methanol hydrogenation was revealed by employing in situ IR. The results showed that the Mn-modified CZA with good reduction behavior, excellent CO2 adsorption capacity and suitable Cu+/Cu0 ratio exhibited the best performance. The metal element loaded on catalyst strengthened the interactions between the copper and support, suppressing the growth of Cu. The appropriate Cu+/Cu0 ratio facilitates the stabilization and conversion of methoxy, resulting in increased methanol production. Compared to the untreated CZA catalyst, the Mn-modified catalyst has more medium strong base sites on the surface, which helps to adsorb more CO2 for further hydrogenation to form formate, methoxyl and other intermediates. The incorporation of metal component in CZA facilitated the catalyst reduction ability. The catalytic mechanism follows the formate pathway and the methoxyl species is the crucial intermediate. The Cu nanoparticles on the catalyst surface showed an increased capacity for H2 dissociation when using Mn-modified CZA catalysts. This is due to stronger metal-carrier interactions. The presence of interstitial H in the carriers contributed to the generation of formate species. The dissociated H atoms from the surface Cu nanoparticles replenished the consumed interstitial H. The modified catalyst's interstitial H presence and enhanced H2 dissociation ability accelerated the formation and conversion of intermediate species, promoting methanol generation. Related Articles | Metrics

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Research progress of microreactor technology in gas-liquid two-phase flow systems Xinran YE Zan WU Haiou WANG Jianren FAN The Chinese Journal of Process Engineering    2024, 24 (9): 1001-1015.   DOI: 10.12034/j.issn.1009-606X.224035 Abstract （382）   HTML （23）    PDF （3984KB）（221）       Knowledge map    Save Microreactors possess advantages such as high heat and mass transfer efficiency, strict control of reaction parameters, ease of scale-up, and good safety performance, and hold promises for enabling and accelerating the discovery of flow chemistry towards highly efficient and more sustainable chemical synthesis. Gas-liquid multiphase catalytic reaction is commonly encountered in chemical production process, where the reaction stream enters the microfluidic channel in a continuous flow and undergoes rapid reaction. The combination of microreactor technology and gas-liquid multiphase catalytic reaction facilitates the development of efficient and sustainable chemical production techniques. Gas-liquid multiphase catalytic microreactors can be classified as wall-coated or filled-bed microreactors based on catalyst fixation approaches. By optimizing the geometric structure design of the microreactor, it is possible to further reduce the reaction time, minimize the material retention and suppress the occurrence of undesirable reactions, thus improving the microreactor performance. However, the optimization of microreactor structure requires a comprehensive understanding of various physics including the flow characteristics of gas-liquid fluids, the mass transfer mechanism and reaction kinetics within the microreactor. Both the flow pattern and mass transfer of multiphase fluids in microreactors will affect the reactor performance. Investigating the gas-liquid system in microreactors promotes improved design of practical devices. This review mainly summarizes typical gas-liquid microreactor examples, and hope to provide inspiration and guidance for the design, fabrication, and application of microreactors. The review is organized as follows, first, the features of microreactor technology are introduced and the optimization strategies for microreactor structures are presented, which is followed by a detailed discussion on the flow patterns, mass transfer characteristics and bubble breakup dynamics in gas-liquid multiphase systems within microreactors. Then, examples of multiphase catalytic microreactors in applications (mainly focusing on wall-coated microreactors and filled-bed microreactors) and their limitations are introduced. Finally, the research trends and application prospects in gas-liquid multiphase microreactors are envisaged. Related Articles | Metrics

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Fault diagnosis based on DA-CycleGAN for multimode chemical processes Wenjing CHEN Changchun DAI Yagu DANG Yiyang DAI Xu JI The Chinese Journal of Process Engineering    2024, 24 (5): 618-626.   DOI: 10.12034/j.issn.1009-606X.223316 Abstract （318）   HTML （9）    PDF （1362KB）（205）       Knowledge map    Save In modern chemical processes, timely and accurate fault diagnosis is important for enhancing the safety and reliability. Data-driven fault diagnosis methods have been regarded as a promising approach in the last decades of research for increasingly complex chemical processes. Data-driven fault diagnosis methods can greatly reduce the dependence on human experience, and realize end-to-end fault diagnosis by automatically extracting features. However, most existing research assumes training and testing data come from the same distribution, while a chemical process may have multiple working conditions. On the one hand, the fault diagnosis performance of the model will deteriorate when the process is run under new working conditions. On the other hand, due to the low probability of failure, some operating conditions may have few fault data in history. To address these issues, in this work, a novel fault diagnosis method, DA-CycleGAN, is proposed for multimode chemical processes. This study is the first to overcome the degradation of model diagnosis performance when only normal data are available under new working conditions. It notes that the normal data is available under any working condition. A two-dimensional CycleGAN is used to capture the temporal and spatial features of fault data. And fault data is generated by combining fault features and normal data under new operating conditions, thus filling a blank in new working conditions for fault data. Furthermore, the domain adaptation method is used to minimize the distribution differences between historical fault data and generated data and to improve the fault diagnostic performance under new operating conditions. To test the performance of this method, four working conditions of the Tennessee-Easthman (TE) process are used in the experiment. The results on twelve condition-changed fault diagnosis tasks show that this method can improve the average fault diagnosis rate by more than 3% compared to the model trained using only historical fault data. Related Articles | Metrics

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Preparation of sodium bicarbonate modified biochar and analysis of its adsorption mechanism for carbamazepine in water Jihuan ZHANG Jinwei ZHANG Wenlong WU Siqiang Lin Yan LI Lei DING The Chinese Journal of Process Engineering    2024, 24 (9): 1106-1119.   DOI: 10.12034/j.issn.1009-606X.223363 Abstract （236）   HTML （15）    PDF （2886KB）（178）       Knowledge map    Save This study used agricultural waste silk gourd complex powder as raw material and sodium bicarbonate as activator to prepare sodium bicarbonate modified biochar (SBC) that can efficiently adsorb carbamazepine (CBZ) in water through impregnation pyrolysis method. The physical and chemical characteristics such as surface morphology, pore size distribution, functional groups, and degree of graphitization are analyzed through characterization methods. The effects of temperature, dosage, pH and other factors on the adsorption of CBZ in water by SBC are studied through batch experiments. The results show that compared to the original biochar (BC), SBC has a higher specific surface area of 531.43 m2/g and a richer pore size structure. The effect of pH on the adsorption of CBZ by SBC is minimal, and SBC is almost unable to adsorb large molecular humic acids. The Sips model can better describe the adsorption equilibrium law of CBZ on SBC, with an adsorption capacity of 125.52 mg/g at 298 K. Thermodynamic analysis shows that the adsorption of CBZ by SBC is a spontaneous endothermic process, with physical adsorption being the main process. By analyzing the energy distribution of SBC sites and density functional theory, the enhanced adsorption mechanism of CBZ on SBC is further explored. The results show that hydrogen bonding, π-π electron acceptor donor, and pore filling are involved in the process of SBC adsorption of CBZ. Methanol can effectively regenerate saturated SBC, and after four adsorption desorption cycles, the adsorption capacity of SBC for CBZ remains at 68.132 mg/g. This article uses agricultural and forestry waste sponge gourd as a carbon source to prepare biochar for removing pollutants from water, providing a feasible approach to simultaneously achieve the resource utilization of agricultural waste and reduce environmental pollution. Related Articles | Metrics

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Simulation of flow field evolution in fluidized bed based on artificial neural network Xueyan WU Tianle SHI Fei LI Sansan YU Chunxi LU Wei WANG The Chinese Journal of Process Engineering    2024, 24 (8): 904-913.   DOI: 10.12034/j.issn.1009-606X.224006 Abstract （237）   HTML （6）    PDF （9961KB）（174）       Knowledge map    Save Computational fluid dynamics (CFD) is a commonly used method to simulate complex gas-solid flow in fluidized beds. Due to the solution of partial/ordinary differential equations, the computational efficiency of this method is still low even if the coarse-grained method is used. The flow field simulation method based on data-driven artificial neural network (ANN) model can avoid the equation solving process and achieve efficient calculation. At present, researchers have applied the ANN model to the prediction of single-phase flow field, and there are only a few studies on the complete fluidized gas-solid two-phase flow field. This work combines CFD and ANN to develop an ANN based field evolution model that quickly obtains the evolution of the flow field in the fluidized bed. Compared with those complex large models, a compact network model has been developed and can be used to complete the prediction of complex two-phase flow field. The model includes different network structures for predictions of particle concentration, gas pressure, and gas-solid two-phase velocity. The results obtained by simulating the fluidized bed with the multiphase particle-in-cell (MP-PIC) method are used as data sets for training. The verification results show that the ANN model successfully realizes the prediction of particle concentration, gas pressure, and gas-solid two-phase velocity in the fluidized bed. In terms of accuracy, the ANN model can accurately predict the flow field in a time step, and there are still obvious errors in the long-term flow field prediction. In terms of computational efficiency, the calculation speed of the ANN model is about 13 000 times that of the MP-PIC method. The multi-time-step continuous prediction performance of current model gradually deteriorates with time, and further research still needs to be done to improve this issue. Related Articles | Metrics

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Research progress in preparation of silicon-based anode materials for lithium-ion batteries by radio-frequency induction thermal plasma Zongxian YANG Yuanjiang DONG Chang LIU Huacheng JIN Fei DING Baoqiang LI Liuyang BAI Fangli YUAN The Chinese Journal of Process Engineering    2024, 24 (5): 501-513.   DOI: 10.12034/j.issn.1009-606X.223230 Abstract （311）   HTML （16）    PDF （7425KB）（171）       Knowledge map    Save As one of the next-generation anode materials with the most promising application prospects, silicon anode benefits from a high theoretical specific capacity, a sufficient working potential, abundant and inexpensive sources, environmental friendliness, safety, and dependability. However, Si will experience significant volume variations throughout the lithiation and delithiation processes. This will result in significant internal stress, which will cause issues including material pulverization, repetitive growth of the solid electrolyte interface (SEI), and electrode failure. Through the utilization of nano-silicon-based anode materials, it is possible to effectively mitigate the volume impact, enhance both conductivity and stability. The utilization of radio-frequency (RF) induction thermal plasma offers several notable benefits, including elevated temperatures, rapid cooling, precise control, and uninterrupted operation. Thermal plasma has the ability to provide particles a unique growth environment and process that is helpful in the creation of products with special morphologies, such as zero-dimensional nanospheres and one-dimensional nanowires. Additionally, the extremely high temperatures can totally evaporate raw materials, guarantee uniformity of product, and be advantageous for doping second-phase materials. Consequently, it serves as a significant method for the production of nano-silicon-based anodes with a controllable morphology and structure, as well as high purity and excellent dispersibility. This work provides a review of the scientific advancements pertaining to silicon-based anode materials for lithium-ion batteries that are fabricated using RF thermal plasma. To commence, a concise introduction is provided for the thermal plasma technology. Then, this work focuses on the synthesis of various essential materials using thermal plasma, including silicon nanospheres (Si NSs), silicon nanowires (Si NWs), silicon monoxide nanowires (SiO NWs), silicon monoxide nanonetworks (SiO NNs), high-silicon silicon suboxide nanowires (SiOx NWs), silicon-based ferrosilicon alloy nanospheres (Si/FeSi2 NPs). Furthermore, the work emphasizes the applications of these materials in the anode electrode of lithium-ion batteries. Finally, the development of thermal plasma technology is prospected. Related Articles | Metrics

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Main advances in preparation technology of zirconia hollow microspheres Baoqiang LI Huacheng JIN Fei DING Chun WANG Fangli YUAN The Chinese Journal of Process Engineering    2024, 24 (6): 627-635.   DOI: 10.12034/j.issn.1009-606X.223297 Abstract （250）   HTML （10）    PDF （1939KB）（164）       Knowledge map    Save Zirconia hollow microspheres have attracted more attention because of their excellent performance, which combines the advantages of the properties of zirconia and hollow structural materials, such as low thermal conductivity, ablation resistance, and chemical corrosion resistance. Zirconia hollow microspheres is an important feedstock for preparing thermal barrier coatings. The thermal barrier coating prepared by zirconia hollow microspheres has the characteristic of excellent insulation and corrosion resistance. The performance of the coating is determined by the characteristics of the powder. The preparation of high quality zirconia hollow spherical powder has become a hot topic in the industry. In this work, the research status of the preparation technology of zirconia hollow spherical powder is analyzed, and the main preparation approaches are introduced, including templating, solvothermal, spray drying, and plasma sintering. In addition, the characteristic of these approaches is briefly summarized. Templating method contributes to obtaining hollow zirconia spheres with perfect morphology. However, some problems such as difficulty both in template synthesis and subsequent template removal, which can cause the material waste and damage to hollow particles. For solvothermal method, the reaction conditions are relatively harsh, and it also involves cumbersome process, such as separation, washing and drying process, which makes it difficult to batch preparation of hollow microspheres. The spray drying method is an effective approach for batch preparation of hollow microspheres. However, the hollow microspheres prepared by spray drying possesses have low strength and become easy to be damaged during application. Importantly, it is considered that the hollow microspheres prepared by spray drying combined with plasma sintering process have the advantages of high sphericity, good fluidity, and controllable particle size distribution, which are more conductive to preparation of coatings. Related Articles | Metrics

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Research progress on the mechanism and influencing factors of microorganisms to increase coalbed methane production Na ZHANG Xuefeng YIN Zichen WANG Hao LIU Minjie HUANG Hao WANG Dongxu LIANG Jianan HU The Chinese Journal of Process Engineering    2024, 24 (6): 636-646.   DOI: 10.12034/j.issn.1009-606X.223310 Abstract （254）   HTML （10）    PDF （1144KB）（139）       Knowledge map    Save Microbially enhanced coalbed methane (MECBM) is an innovative technology for the extraction and utilisation of coalbed methane (CBM), which involves the microbial degradation and conversion of certain organic components of coal into methane gas. MECBM has great potential and environmental characteristics, and offers the prospect of establishing a new type of energy system, which will hopefully lead to the development of a sustainable energy source, and will effectively alleviate the challenges posed by energy shortages and greenhouse gas emissions. However, widespread application of MECBM technology faces the obstacles of historically low natural CBM production and sub-optimal quality. In order to understand the production potential of coal biogenic methane and the factors controlling the process, with a view to advancing the direction of its research towards continuous progress and effectively increasing coalbed methane production. This review summarises the mechanism and influencing factors of microbial CBM production, providing a theoretical basis for microbial CBM production. Firstly, the background and current research status of microbial production of CBM are reviewed. Subsequently, the basic theory and reaction process of coal biogenic methane production are summarised, showing that acidification of methoxy plays a decisive role in the process of coal biogenic methane production. Then, the environmental and biological factors affecting microbial enhancement of coalbed methane production are summarised, including the temperature of the coalbed, inoculum amount, nutrient addition, and pretreatment method. These factors have a significant impact on microbial CBM production, and optimising natural gas production conditions can not only increase CBM production but also significantly improve the methane concentration in CBM. In conclusion, microbial enhanced CBM technology has great potential and is expected to provide new solutions to the problems of energy shortage and greenhouse gas emissions by optimising production conditions and improving the viability and adaptability of microorganisms. Finally, this study outlines the current challenges and areas for further research in biogenic CBM development, providing a theoretical basis for increasing on-site production and enhancing CBM development. Related Articles | Metrics

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Advances in wet particle size-grading technologies and precise grading of aluminum hydroxide Jianqing Pi Mingli WANG Ruyi YANG Haidong ZHANG Xiaona REN Qingshan HUANG Ping LI The Chinese Journal of Process Engineering    2024, 24 (6): 647-659.   DOI: 10.12034/j.issn.1009-606X.223331 Abstract （192）   HTML （8）    PDF （4811KB）（139）       Knowledge map    Save With the booming development of the electrolytic aluminum industry, both modern large-scale prebaked aluminum reduction cells and dry purification technology require sandy alumina as the production raw material. However, domestic alumina enterprises mainly produce intermediate or "quasi-sand" alumina, and the particle size changes periodically. The product quality differs significantly from the world's advanced level, mainly due to differences in raw materials and substandard aluminum hydroxide particle screening technologies in the prior art. Therefore, it is urgent to develop a high-precision and high-efficiency wet particle classification device for aluminum hydroxide to produce high-quality sandy alumina with large and narrow particle size distribution (+80 μm≥90%, -45 μm<8%). The commonly employed and large-scale application of wet particle size-grading technologies in domestic and foreign countries are first reviewed. The performance of hydraulic classification, wet screening, and some new coupling classification technologies are analyzed. Then, a new particle grading method of fluidization followed by screening for precise grading of aluminum hydroxide particles is proposed by combining hydraulic classification and sieve screening. Finally, a small-scale grading device (3.3 m3/h) capable of achieving large-scale continuous production is developed and passed the verification of on-site production siding in the production enterprise. This new type of precise particle classification technology is not only expected to realize energy conservation and emission reduction, transformation and upgrading, reduction of production costs, and significant economic benefits in the alumina industry but also promote the rapid development of mineral processing and fine powder industries, having some important and practical application and promotion values. Related Articles | Metrics

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Removal performance and mechanism of humic acid by persulfate activated with ultraviolet light combined with magnetic ion exchange resin Wenlong WU Yuchen GAO Jinwei ZHANG Ling LI Yan LI Yuchen ZENG Chun YANG Jiapeng LU Lei DING The Chinese Journal of Process Engineering    2024, 24 (5): 566-579.   DOI: 10.12034/j.issn.1009-606X.223268 Abstract （197）   HTML （4）    PDF （5338KB）（132）       Knowledge map    Save Humic acid (HA) in water was removed by activating persulfate with ultraviolet light combined with magnetic ion exchange resin. The removal efficiency of HA, the environmental factors affecting the removal of HA, the generation mechanism of active oxidizing species and the removal mechanism of HA in the ultraviolet light/persulfate/magnetic ion exchange resin (UV/PMS/MIEX) system were explored. The UV/PMS/MIEX synergistic system had a significant removal efficiency for HA in water, and the removal efficiency reached 91.71% after 120 minutes of reaction. The increase in resin dosage and temperature promoted HA removal, and increasing the concentration of persulfate could improve the removal efficiency of HA to a certain extent, but the effect of solution pH on the removal of HA was not obvious. In this system, the removal of HA was mainly through oxidation, and the adsorption effect WAs not significant. The iron oxides on the surface of the resin, the oxygen-containing functional groups and the addition of ultraviolet rays could effectively activate persulfate to produce various active oxidizing species such as ?OH, SO4?-, O2?-, and 1O2. In this system, HA fractions were degraded by the radical and non-radical pathways, and the activation mainly occurs through the radical pathway. Based on the characterization of N2 adsorption-desorption isotherms, Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, and X-ray photoelectron spectroscopy before and after the reaction, it can be found that the magnetic ion exchange resin exhibits good reusability and stability, and can effectively adsorb and remove various by-products in the system. This study provides a new method for HA removal in water, and the constructed oxidation system shows a good application prospect. Related Articles | Metrics

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Research progress of lithium extraction technology from lepidolite Hong YANG Wei ZHONG Faping ZHONG Jiahui ZHAO Dong LI Lei ZHANG Xueyi GUO The Chinese Journal of Process Engineering    2024, 24 (11): 1251-1262.   DOI: 10.12034/j.issn.1009-606X.224019 Abstract （338）   HTML （14）    PDF （1677KB）（129）       Knowledge map    Save Lithium and its compounds are indispensable materials in modern industry and have important applications in the fields of batteries, ceramics and lubricants. China is rich in lithium resources, most of which occur in salt lake brine. However, due to the limitation of resource endowment and geographical location and climate, its production capacity cannot meet the needs of the rapid development of new energy industry in China, and lithium extraction from ores has become an important source of lithium products. Yichun, Jiangxi province has the largest associated lepidolite resources in China, and the development and utilization of lepidolite resources is of great significance to ensure the sustainable development of lithium resources in China. In this review, the principle, advantages and disadvantages of the existing lithium extraction processes from lepidolite are summarized. Based on the understanding of the existing methods, typical lithium extraction processes from lepidolite such as acid method, alkali method and salt method are summarized and evaluated. Among them, the acid method is mature, but there are some problems such as difficulty in impurity removal from leaching solution, low efficiency in lithium extraction and equipment corrosion. Although the alkali process has high efficiency of extracting lithium, its reaction mechanism is not clear, and the waste residue is difficult to use. Although the salt process has high selectivity to lithium and simple process, it also has the problems of high energy consumption and large amount of slag. The development direction of lepidolite extraction technology should focus on the collaborative treatment of multiple technologies to achieve efficient, economical and environmentally friendly extraction of valuable elements. Therefore, some measures to improve the process are put forward, aiming at providing reference for the future research, development, optimization and industrial application of the process. Related Articles | Metrics

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Numerical simulation of low nitrogen combustion in CFB boiler based on post-combustion technology Xiaojie LIU Shunsheng XU Runjuan KONG Jianbo LIU The Chinese Journal of Process Engineering    2024, 24 (8): 914-925.   DOI: 10.12034/j.issn.1009-606X.224031 Abstract （193）   HTML （3）    PDF （6337KB）（127）       Knowledge map    Save Severe environmental protection policies have put forward higher requirements for coal combustion power generation. As a mature clean coal power generation technology, the circulating fluidized bed (CFB) boiler has broad research prospects. CFB post-combustion technology is a new type of fluidized bed out-of-stock technology that has been applied to 75 t/h CFB coal slime boilers and achieved ultra-low NOx emissions. Exploring the feasibility and effectiveness of post-combustion technology in larger-scale CFB boilers has become the focus of future research. In this study, a numerical model of the flow and combustion of a 150 t/h CFB boiler in full-loop was established using the method of computational particle fluid dynamics (CPFD). The availability of the model was verified by comparing it with industrial data. The effects of excess air ratio in CFB, primary air ratio, and ratio of upper and lower secondary air on furnace combustion and NOx emissions were studied after the addition of post-combustion technology. The results showed that there was a typical core-circulation structure in the furnace. On the one hand, oxygen-poor combustion inhibited NOx generation, and on the other hand, the high CO concentration zone caused by combustion was also conducive to NOx reduction. After the use of post-combustion technology, the reduction atmosphere of the furnace increased, and the NOx emission reduced from 174.6 mg/m3 to 114.2 mg/m3. Combined with the air stage, optimizing the primary air ratio and the ratio of upper and lower secondary air, CO emission increased from 3.4×10-5 in the basic working condition to 7.1×10-5, the combustion efficiency was slightly reduced, and NOx emission was further reduced. Under optimal working conditions, NOx emission decreased from 174.6 mg/m3 to 76.3 mg/m3, NOx emission decreased by 56.3%, and the furnace temperature distribution was uniform. The research results can provide valuable theoretical insights for the application of post-combustion technology in CFB boilers and provide support for its practical application. Related Articles | Metrics

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Analysis of new blade structure and mixing characteristics of horizontal mixer Shen LI Linsheng XIE Guo LI Yu WANG Yulu MA The Chinese Journal of Process Engineering    2024, 24 (8): 875-883.   DOI: 10.12034/j.issn.1009-606X.223364 Abstract （180）   HTML （8）    PDF （3092KB）（127）       Knowledge map    Save The dynamic mixer is the mainstream of today's mixing equipment, and the mixing effect not only affects the production efficiency of the equipment, but also directly determines the performance of the final product. Among them, the structure of the mixing element in the dynamic mixer directly determines its mixing effect on the processed material. Due to the complex structure of the dynamic kneading mixer, the theoretical research on its mixing characteristics is very limited. In this work, the blade structure of the horizontal mixer was optimized and improved, and the structure design of the main and auxiliary blades was adopted to improve the mixing effect of the mixer. By constructing the three-dimensional model and finite element model of the mixer with a new type of blade structure, the mixing characteristics of the mixer were investigated by means of numerical simulation using the computational fluid dynamics software Polyflow, and the influence of blade speed on the mixing performance of the mixer was analyzed. Mixing index, separation scale, average tensile rate, logarithmic tensile rate, and cumulative depolymerization power were used to characterize the dispersion and distribution mixing ability of the mixer, and the accuracy of numerical simulation results was verified by visual experiments. The results of simulation and experiment showed that the simulation results were consistent with the visual experiment results. The material flow type in the mixer with the new blade structure was shear flow, accounting for about 85%. The average tensile rate and average logarithmic tensile rate in the flow field were always positive, indicating that the mixer had good distribution and dispersion mixing ability. The increase of blade speed had little influence on the flow type of materials in the flow field, but can effectively improve the performance of distributed mixing and dispersed mixing of the mixer. When the blade speed increased from 30 r/min to 120 r/min, the average separation scale of the mixer's transverse distribution mixing decreased by 50%, and the average tensile rate increased by 300%. The average cumulative depolymerization work increased by 1500%. Related Articles | Metrics

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Study on stability of SiO/C slurry and semi-dry homogenization process Feng LIU Cheng LU The Chinese Journal of Process Engineering    2024, 24 (9): 1080-1087.   DOI: 10.12034/j.issn.1009-606X.223365 Abstract （225）   HTML （8）    PDF （4869KB）（125）       Knowledge map    Save Si based anode has become a research hotspot for high energy density lithium batteries due to its high specific capacity, and the preliminary production and application of SiO has been realized. The electrical performance, lifetime and consistency of lithium-ion battery are directly related to its electrode performance, and homogenization is a key process in the electrode production. The stability of SiO/C anode slurry was studied and a semi-dry homogenization process was innovatively developed. The stability of SiO/C-1 and SiO-2 with 1.6wt% and 3.1wt% of carbon was compared in aqueous slurry, and the gas production of SiO/C-1 was obvious in the water due to the fact that Si reacted with H2O to form H2 under alkaline condition, while there was no gas production of SiO/C-2, and the condition of the slurry and the electrode was better. SEM, EDS, and TEM showed that SiO/C-2 had a uniform carbon coating layer with a thickness of 20~30 nm, which can block water and improve the stability, and in the application of SiO/C, it was necessary to pay attention to the carbon coating of the material. In order to improve the stability of SiO/C anode electrode slurry to improve the homogenization efficiency, a semi-dry homogenization process was developed, through the testing of slurry solid content, viscosity, fineness, rheology, gas production and the peeling force, resistance of the electrode, SEM, as well as the cycling performance of the cell was analyzed. The results showed that the developed semi-dry homogenization process was able to achieve a high solid content of 51.8wt%, viscosity of 4900 mPa?s and fineness of 20 μm. The viscosity of the slurry was 10 000 mPa?s after 24 h, and the slurry was basically free of gas production for 48 h. The peeling force of the anode electrode was 15 N/m, and the resistivity was 0.106 Ω/cm. The high-temperature cycle life of the 330 Wh/kg pouch cell made with high-nickel NCM (Ni9) can reach 800 cycles, which was obviously superior to that of the ordinary wet homogenizing process. Related Articles | Metrics

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Study on preparation and properties of electrospinning nanofiber membrane for air filtration Simin CHENG Fuping QIAN Chen ZHU Lumin CHEN Wei DONG Huaiyu ZHONG The Chinese Journal of Process Engineering    2024, 24 (5): 599-608.   DOI: 10.12034/j.issn.1009-606X.223252 Abstract （386）   HTML （5）    PDF （4750KB）（125）       Knowledge map    Save It has been proved by long-term practice that because the source of atmospheric aerosol particles is very wide, small size, the composition is very complex, the harm to the environment and human health is very serious. Although the government has taken a series of effective measures to control the pollution sources, it still takes a long time to completely solve the PM2.5 pollution problem. If the public wants to reduce the harm caused by particulate matter, specific measures must be taken to conduct individual protection and indoor air purification. At present, the simplest and most effective method for individual protection and indoor air purification is to filter the particles in the air through fiber filtration materials, thus reducing their content in the air. However, traditional fiber filtration materials have the disadvantages of low filtration efficiency, high filtration pressure drop and high energy consumption in the process of use. Meanwhile, filtration fibers with high filtration efficiency are often accompanied by higher filtration resistance. In order to develop high efficiency and low resistance fiber membrane for air filtration, polyacrylonitrile (PAN) electrospinning nanofibers were prepared by electrospinning. In the preparation process, the mass fraction of PAN and the duration of electrospinning were changed, and the electrospinning nanofiber films with different morphologies and filtration properties were obtained. The morphologies and filtration properties of electrostatic spinning nanofibers were tested and analyzed by field emission scanning electron microscopy and filtration test platform, and the preparation parameters of the best performance PAN electrostatic spinning nanofiber membranes were obtained with PAN mass fraction of 9wt%, electrospinning time of 5.0 h. Under the optimum condition, the film thickness of electrospinning nanofibers was 0.0240 mm, the average fiber diameter was 396 nm, the PM2.5 filtration efficiency was 99.99%, the filtration pressure drop was 67 Pa, and the highest quality factor was 0.137 Pa-1. Related Articles | Metrics

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Study of flow field characteristics and separation performance of inline cyclone gas-liquid separator Ming ZHANG Huan SUN Qiangqiang WANG Jiaqing CHEN Chao SHANG Xiang LI Chunsheng WANG Lingzhen KONG The Chinese Journal of Process Engineering    2024, 24 (7): 772-782.   DOI: 10.12034/j.issn.1009-606X.223312 Abstract （306）   HTML （9）    PDF （6151KB）（125）       Knowledge map    Save The inline cyclone gas-liquid separator has received much attention because of its high separation efficiency and compact structure, but the ability to adapt to a wide range of inlet gas holdup is the key to its practicality. In this work, the flow field characteristics and separation performance of a inline cyclone gas-liquid separator that can adapt to a wide range of gas holdup changes are investigated by computational fluid dynamics (CFD) and experimental tests in air-water media system. The CFD numerical simulation results show that when the inlet gas holdup changes in the range of 10%~90%, the gas-phase separation efficiency is greater than 80% and the amplitude of change is less than 9.9%, and the liquid-phase separation efficiency is greater than 97% and the amplitude of change is less than 2.2%. The experimental results show that when the inlet gas holdup changes in the range of 9.4%~89.2%, the liquid holdup of the gas-phase outlet gradually decreases and the gas holdup of the liquid phase outlet gradually increases with the increase of the inlet gas holdup. The liquid holdup of the gas-phase outlet is less than 4%, and the gas holdup of the liquid-phase outlet is less than 10% except at liquid flow rate of 12 m3/h. Comparing the gas-phase separation efficiency and liquid-phase separation efficiency under different liquid flow rates, the best separation performance is achieved at a liquid flow rates of 8 m3/h. The CFD numerical simulation results are slightly different from the experimental test results, but the overall trend is consistent, which can be used as an effective tool for the design of structure enlargement. The research results show that the inline cyclone gas-liquid separator adopts the action form of "strong cyclone+weak cyclone+gravity", which has high separation efficiency and good resistance to fluctuations in working conditions. Related Articles | Metrics

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Effect of La content on the microstructure and TiN precipitation behavior of high-titanium steel during slow cooling solidification Yong WAN Chuansheng TANG Guangwei YANG Xuejian ZHANG Yonghong WEN The Chinese Journal of Process Engineering    2024, 24 (7): 852-862.   DOI: 10.12034/j.issn.1009-606X.223309 Abstract （145）   HTML （5）    PDF （9953KB）（124）       Knowledge map    Save In this work, the effects of four kinds of La content on the microstructure and TiN precipitation behavior of high-titanium steel are studied by high temperature melting experiment, optical microscope (OM) and scanning electron microscope (SEM). It is intended to give scientific basis and experimental data for La treatment to refine the size of TiN and the microstructure in the center region of cast ingots of high-titanium steel. The results show that the solidification structures of all experimental steels are equiaxed grains when the solidification cooling rate is 0.17℃/s. La shows obvious ability of deoxidization, S and Al at low La content (0.0013wt%), so LaAlO3 and La2O2S are mainly formed in its steel. La just began to show obvious ability of deoxidization, S and Al at high La content (0.0052wt%, 0.0223wt%). With the consumption of a large amount of O atoms, the deoxidization and sulfur ability of La increased rapidly. Therefore, La2O2S is the predominant precipitate that forms in the steel, and some La2O2S particles will nucleate and grow on the surface of LaAlO3 particles that have previously precipitated. TiN mainly precipitates in the Liquid+δ two-phase region in this experimental steel. LaAlO3 and La2O2S precipitate before TiN, and their small lattice misfit with TiN are the primary cause of their propensity to act as the cores of TiN heterogeneous nucleation. When the La content in the steel is 0wt%, 0.0013wt%, 0.0052wt%, 0.0223wt%, the average axial grain size of each experimental steel is 354, 223, 154, 126 μm, respectively. The maximum size of TiN is 19.1, 11.7, 11.4, 10.4 μm, the TiN area density in each experimental steel is 42.2, 82.9, 86.3, 90.7 No./mm2, the maximum size of TiN is 19.1, 11.7, 11.4, 10.4 μm, and the average size of TiN is 7.8, 4.6, 4.5, 4.4 μm. Related Articles | Metrics

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Research on CNN-LSTM coupling model for chemical process early warning Jingsong CUI Bo JIA Xuesheng LI Yaru WANG Haihang LI Haining WANG Qifu BAO The Chinese Journal of Process Engineering    2024, 24 (8): 937-945.   DOI: 10.12034/j.issn.1009-606X.223280 Abstract （155）   HTML （0）    PDF （1184KB）（123）       Knowledge map    Save In consideration of the real-time, multi-dimensional, and nonlinear nature of chemical process parameters, as well as the complexity of chemical processes with numerous mutually interfering factors and single warning method, this work proposes an early warning method combining deep learning regression prediction and ADF (Augmented Dickey-Fuller) test. For monitoring and early warning analysis of over-temperature abnormal conditions in condensation reactions, convolutional neural network, and long short-term memory (CNN-LSTM) models are employed in this study to predict crucial process parameters for the next 400 s. Simultaneously, the ADF test is utilized to examine the trend of temperature time series parameters. When the result is an unstable trend and the CNN-LSTM model predicts that the temperature will exceed the alarm threshold at a specific time point, security personnel will be alerted accordingly. The results showed that during the condensation reaction's over-temperature anomalies at feed rates of 700 and 800 kg/h, the CNN-LSTM model's regression forecasting for temperature metrics manifested R2 values of 0.9827 and 0.9882. Correspondingly, the model elicits RMSE (Root Mean Square Error) values of 0.1425 and 0.1453, and MAE (Mean Absolute Error) values of 0.1184 and 0.1234. These indices testify to the model's exceptional fidelity and precision, surpassing the conventional LSTM model's predictive accuracy as reflected in its R2, RMSE, and MAE values. The ADF test results on the temperature time series data corroborate the presence of an unstable trend, aligning with the actual process behavior. By combining both methods, the early warning model is able to detect temperatures exceeding the alarm threshold 18 and 16 s earlier than the simulated alarm point, respectively, and issues a timely alert. The dual application of these methods provides a robust means of monitoring chemical process parameters, enabling the early detection of abnormal conditions in chemical processes and advancing the field of chemical process parameter monitoring. Related Articles | Metrics

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Flocculation and sedimentation behavior of kaolinite in acidic systems Xinhuang YU Shiqi LI Xinlei ZHAN Bao GUO Rongdong DENG Kaixi JIANG Hongzhen XIE The Chinese Journal of Process Engineering    2024, 24 (8): 993-1000.   DOI: 10.12034/j.issn.1009-606X.224024 Abstract （145）   HTML （9）    PDF （3494KB）（119）       Knowledge map    Save In the acid pulp leaching solution of non-ferrous metals, there are often fine silicate minerals, which are charged on the surface, can form a stable system in the acid pulp, and it is difficult to settle, which leads to the extraction and electrodeposition process. Moreover, most non-ferrous metal hydroxides are insoluble in water and cannot neutralize the surface electricity of silicate minerals by adjusting pH, which also brings difficulties to the separation of silicate minerals in acidic systems. Polyacrylamide (PAM) is an effective flocculant, which is widely used in water treatment and paper making. Polyethylene oxide (PEO) is widely used in pharmaceutical industry, oil mining, light industry textile and other fields, and has been shown to be effective in flocculating silicate minerals. Polystyrene sulfonate (PSS) has a large amount of negative charge, which can effectively reduce the surface potential of silicate minerals in acidic pulp. Tannic acid (TA) can make the polymer compound associate, thereby increasing the apparent length of molecular chain and improving its flocculation performance. Therefore, in order to solve the problem of silicon removal in acid leaching pulp, the flocculation and sedimentation behavior of fine kaolinite in acid system was investigated by using -2000 mesh (6.5 μm) kaolinite as raw material in this work. The results showed that the flocculation performance of polyacrylamide was stronger than that of polyethylene oxide. Coagulant aid PSS can further improve the flocculation effect. The flocculation effect of PAM and PEO was the best when combined with 100 g/t PSS. The effect of TA on coagulation was not obvious. Using the focused beam reflectance measurement (FBRM), it was found that the size of flocs produced during flocculation was positively correlated with the amount of drug used, but the larger the flocs, the weaker the shear resistance, and the failure process of flocs was irreversible. Zeta potential indicated that PSS can effectively reduce its surface potential, which was the main mechanism of kaolinite flocculation in acidic system. Related Articles | Metrics

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Preparation of high-purity copper by electrolytic refining in nitric acid system Mengyang LI Liang XU Tao GE Rui HE Xiaoyu HAN Cheng YANG Zhuo ZHAO The Chinese Journal of Process Engineering    2024, 24 (8): 955-963.   DOI: 10.12034/j.issn.1009-606X.223333 Abstract （230）   HTML （4）    PDF （2577KB）（118）       Knowledge map    Save High-purity copper has been widely used in semiconductor materials, optoelectronics and other fields due to its excellent physical and chemical properties such as ductility, thermal conductivity and electric conductivity. With the rapid development of electronic information industry, the copper product with high purity is pressing needed. Numerous methods such as zone melting, electron beam melting and electrolytic refining have been developed for the preparation of high-purity copper. Among these technologies, electrolytic refining has been investigated extensively and used in the industrial production for high-purity copper owing to its operation flexibility, simple-process and environmental-friendliness. In general, the electrolytic refining methods for the preparation of high-purity copper could be divided into nitric acid system and sulfuric acid system electrolytic refining. The electrolytic refining for high-purity copper preparation in sulfuric acid system has been widely used in industry. However, the high-purity copper prepared in sulfuric acid system generally contains the higher content of impurity elements such as S than in nitric acid system. Therefore, in this study, the 5N purity of copper was prepared from the raw materials of 4N copper in nitric acid system by one-step electrorefining. The effects of H2O2 addition, current density, electrolyte pH, Cu2+ concentration during the electrorefining process were systematically studied. Under the optimum conditions of Cu2+ concentration of 80 g/L, pH of 1.0, H2O2 addition of 0.10 mL/100 mL, and current density of 200 A/m2, the electrolytic product deposited on the cathode surface exhibited the smooth morphology, and the current efficiency during the electrorefining process was over 97%. Furthermore, the impurity elements including S, Ni, Se, As, Sb, Pb, Bi in the electrolytic product were detected by ICP-MS. The results showed that the purity of the copper prepared under the optimum conditions reached the 5N grade, which was consistent with the national standard of 5N high-purity copper. Related Articles | Metrics

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Process simulation of pressure swing adsorption technology optimization based on low concentration methane enrichment Mingjun QIU Xiaomin LI Hua SHANG Jiangfeng YANG Jinping LI The Chinese Journal of Process Engineering    2024, 24 (8): 884-893.   DOI: 10.12034/j.issn.1009-606X.224042 Abstract （196）   HTML （3）    PDF （4718KB）（115）       Knowledge map    Save Methane enrichment is a necessary measure to develop and utilize low concentration coalbed methane. Among many separation technologies, pressure swing adsorption technology has become the most widely used technology in recent years due to its advantages of low energy consumption and low cost. In order to better realize the methane enrichment effect (purity and recovery), it is necessary to study the relationship between the adsorbent and the pressure swing adsorption process, that is, to select a suitable pressure swing adsorption process for the adsorbent. This work uses Aspen adsorption process simulation software to study two different types of adsorbents (N2 selective adsorbent MIL-100(Cr) and CH4 selective adsorbent Silicalite-1) in common and optimal vacuum pressure swing adsorption (adding buffer tank). Simulation results shows that the optimal vacuum pressure swing adsorption process can effectively improve the CH4 recovery, and MIL-100(Cr) has a significantly better recovery improvement effect compared with Silicalite-1. However, when the CH4 content of the coalbed methane is less than 30%, CH4 recovery of 100% can be achieved by using Silicalite-1 adsorbent in the optimal vacuum pressure swing adsorption process. In the actual process of enriching coalbed methane, methane purity and recovery are very important indicators. Therefore, the single cycle efficiency index is proposed to comprehensively evaluate the efficiency of the methane enrichment process. The results show that compared with the common vacuum pressure swing adsorption process, the optimal vacuum pressure swing adsorption process using MIL-100(Cr) adsorbent has a single cycle efficiency improvement of more than 30 percentage point, while that of Silicalite-1 adsorbent even slightly decline 1 percentage point. Comparative analysis shows that the common vacuum pressure swing adsorption process is suitable for Silicalite-1 adsorbent, and the optimal vacuum pressure swing adsorption process with buffer tank is more suitable for MIL-100(Cr) adsorbent. Related Articles | Metrics

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Bed characterization and flow heat transfer simulation of fixed bed reactor with low tube to particle diameter ratios Weinan MO Youyong SU Dongdong ZHU The Chinese Journal of Process Engineering    2024, 24 (6): 692-704.   DOI: 10.12034/j.issn.1009-606X.223294 Abstract （234）   HTML （7）    PDF （6094KB）（113）       Knowledge map    Save Tubular fixed beds are widely used in high-temperature catalytic cracking processes. Investigating the structural characteristics of fixed beds with low tube to particle diameter ratios and the flow heat transfer laws at high temperatures can provide valuable insights for optimizing the fixed bed high-temperature catalytic cracking process. To address the issues of inaccurate particle description in the discrete element method and difficulty in mesh delineation in the particle resolution method, a new contact point method is proposed. This method does not alter the particle and bed size and shape parameters, adapts to various particle shapes, and significantly reduces the difficulty of model contact processing. Three cylindrical particle beds with different ratios of the inner diameter of the reaction tube to the equivalent diameter of spheres of equal specific surface area of the cylindrical particles (tube-diameter ratio D/dp) and one spherical particle bed are generated to investigate the effects of tube size ratio and particle shape on bed structure and flow heat transfer characteristics. The results show that the overall void ratio of the bed layer decreases with increasing tube to particle diameter ratio, the particle stacking is distributed in circles, and the radial distribution curves of radial void ratio and axial mean velocity are highly consistent. Additionally, the pressure drop is generally consistent with Eisfeld modified equation. Furthermore, the bed flow field distribution is highly correlated with the bed structure, and the size of the flow channel voids directly affects the generation of channel flow phenomena, which further impacts its temperature field distribution and heat transfer performance. The sphere particle bed exhibits a more uniform temperature field distribution, but its heat transfer performance is not as good as that of the cylind particle bed. Related Articles | Metrics

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CFD-DEM-based simulation of Ca(OH)2/CaO thermochemical energy storage process in a novel baffled moving bed reactor Jianyi CHEN Min XU Cang TONG Caifeng HUANG Xiulan HUAI The Chinese Journal of Process Engineering    2024, 24 (8): 894-903.   DOI: 10.12034/j.issn.1009-606X.224048 Abstract （196）   HTML （7）    PDF （11216KB）（111）       Knowledge map    Save The Ca(OH)2/CaO thermochemical energy storage technology has garnered significant attention owing to its attractive features of high energy storage density and cost-effectiveness, positioning it as a promising advancement in energy storage methodologies. Nonetheless, traditional fixed bed reactors may pose challenges with their potential to yield a diminished heat storage rate for Ca(OH)2 particles. To address the challenge of low heat storage rate in conventional fixed bed reactor, a novel baffled moving bed structure is introduced. The heat storage process of Ca(OH)2 particles in the moving reactor bed under the influence of gravity is studied by using the coupled method of computational fluid dynamics and discrete element method (CFD-DEM). Compared to porous media models, CFD-DEM offers a closer approximation to real flow conditions and provides detailed physical information at the particle scale. The results indicate that the moving bed achieves a higher heat storage rate compared to its fixed bed counterpart under identical conditions, providing evidence for the feasibility of employing a moving bed as a thermochemical reactor. The introduction of baffles in the moving bed is able to extend the particle residence time in the reactor, consequently amplifying both the heat storage rate and energy storage efficiency. However, it concurrently results in an increased pressure drop on the gas side. The simulations under various inlet conditions reveal that elevating the gas temperature at the reactor inlet positively impacts the heat storage rate. Within specific ranges, an increase in the inlet gas flow rate can improve the energy storage rate, albeit with caution against excessively high flow rates that could induce blockages and diminish the overall heat storage rate. Notably, the inlet solid flow rate exhibits an optimum value, maximizing the comprehensive heat storage rate of the reaction bed. Related Articles | Metrics

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Research on the removal process and mechanism of aluminum/iron impurities from wet phosphoric acid through deep extraction Youzhi DAI Ganyu ZHU Ziheng MENG Huiquan LI Chengjin XU Guoxin SUN Fang LI Lei HE Yongfang ZHANG The Chinese Journal of Process Engineering    2024, 24 (10): 1241-1250.   DOI: 10.12034/j.issn.1009-606X.224056 Abstract （225）   HTML （5）    PDF （4480KB）（104）       Knowledge map    Save The presence of impurities in phosphoric acid hinders its application in downstream processes. The development of wet-process phosphoric acid deep purification technology enables the direct preparation of phosphate-based new energy materials through a simplified process, which represents the mainstream direction for industry advancement. The solvent extraction method was employed for the extraction and separation of Al and Fe impurities in wet-process phosphoric acid. The effects of different extractants, temperature, O/A ratio, time, and extractant content on the separation efficiency of Al and Fe impurities were investigated. Optimal conditions were determined as follows: N,N-N-octyl amine di (methylene phenylphosphonic acid) (OADMPPA) extractant, extractant content of 20wt%, time of 3 min, temperature at 25℃, O/A ratio of 1:1 and 3-stage cross-flow extraction. Under these conditions, the extraction rates for Al and Fe reached 54.5% and 99.6%. Consequently, the contents of Al and Fe impurities in phosphoric acid decreased from 0.857wt% and 0.175wt% to 0.717wt% and 0.015wt%. Additionally, the MER value reduced from 9.037% to 7.227%. Further optimization of stripping process of OADMPPA extractant loaded with Al and Fe was carried out, ammonium oxalate was identified as the optimal stripping agent. The optimized stripping conditions were as follows: 25℃, 5-stage cross-flow stripping, O/A ratio of 2:1, time of 15 min, and concentration of the stripping agent at 0.2 mol/L; the stripping efficiencies for loaded extractant Al and Fe reached 96.4% and 88.3%, effectively achieving their separation from the extractant phase. Finally, the mechanism behind Al or Fe extractants was investigated by stoichiometric calculation and Fourier infrared analysis during the extraction process. It was found that during this process, one molecule of Al combined with one-and-a-half molecules of OADMPPA extractant while one molecule of Fe combined with two molecules of OADMPPA extractant; functional groups involved in these interactions included P=O and P-O-H bonds. A competitive mechanism exists in the extraction process between Al and Fe, where Fe is more easily extracted. Related Articles | Metrics

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Experimental analysis of enhanced absorption of CO2 by NaOH solution in Kenics static mixer Yanfang YU Henglei YU Huibo MENG Puyu ZHANG The Chinese Journal of Process Engineering    2024, 24 (10): 1149-1157.   DOI: 10.12034/j.issn.1009-606X.224110 Abstract （193）   HTML （7）    PDF （2644KB）（99）       Knowledge map    Save The carbon peaking and carbon neutrality goals has been concerned, and the current global warming problem caused by excessive carbon dioxide emissions is very serious. In order to alleviate global ecological problems and better achieve the dual-carbon strategy, the research and development of carbon dioxide capture technology is indispensable. In order to enrich the application of static mixers in the field of carbon dioxide absorption, Kenics static mixer (KSM) was used as the enhanced reaction equipment. Based on sodium hydroxide aqueous solution and carbon dioxide (NaOH-CO2) system, the absorption efficiency of carbon dioxide concentration in the range of 25%~33% volume concentration was analyzed using KSM and empty tube structures under different sampling positions and gas-liquid flow rates. The absorption efficiency of carbon dioxide was measured by automatic potentiometric titration. The absorption performance of the KSM structure was compared with that of the empty pipe. The results showed that the maximum absorption efficiency of CO2 in KSM was 72.3% higher than that of the empty pipe. The absorption efficiency of CO2 decreased with the increase of the liquid phase flow rate (QL) at a certain gas phase flow rate (QG) in the empty pipe structure. In contrast, the absorption efficiency of CO2 increased with the increase of QL when KSM elements were installed in the pipe. The volume energy dissipation rate (ε) of KSM structure was analyzed, and it was concluded that the minimum ε was 4.85 m2/s3 when the CO2 absorption efficiency reached more than 90%. The ε increased by 14.7% when total gas-liquid flow rate (QT) varied from 20 L/min to 22 L/min at QG=6 L/min from the first sampling point (Z1) to second sampling point (Z2) in the pipeline. However, the ε increased by 7.83% when QT changed in the same range at QL=14 L/min. The results showed that the change of ε was more affected by QL than QG, and the system energy consumption and reaction were more obvious from Z1 to Z2 in the pipeline. When the gas superficial velocity (UG) was constant, the Darcy friction coefficient (f) decreased with the increase of the liquid superficial velocity (UL), and when the UL was constant, the f decreased with the increase of the UG. The empirical correlation among the UG, UL, and f was obtained by fitting the experimental data with R2=0.999, the correlation deviation ranged from -0.88% to 0.82%. Related Articles | Metrics

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Ensifer adhaerens CAS22-03 fermentation process optimization and enzymatic preparation of D-p-HPG Ranfeng HE Yu YANG Xianbing SONG Xiaolian LI Ziqiang WANG Peng WANG Yunshan WANG The Chinese Journal of Process Engineering    2024, 24 (9): 1096-1105.   DOI: 10.12034/j.issn.1009-606X.224040 Abstract （136）   HTML （3）    PDF （1943KB）（94）       Knowledge map    Save In order to study the influence factors of the expression activities of D-Hydantoinase (D-Hase) and N-Carbamoyl hydrolase (D-Case) from Ensifer adhaerens CAS22-03, and to improve the catalytic efficiency of the whole-cell catalyzed preparation of D-p-Hydroxyphenylglycine (D-p-HPG) by Ensifer adhaerens CAS22-03, the single factor test and orthogonal test were adopted to optimize the carbon and nitrogen sources, and the fed-batch fermentation process of Ensifer adhaerens CAS22-03 was established. The enzymatic properties of D-Hase and D-Case were analyzed, and the D-p-HPG enzymatic production process based on the whole cell catalysis of Ensifer adhaerens CAS22-03 was developed. The results showed that the optimal carbon and nitrogen sources for Ensifer adhaerens CAS22-03 fermentation were sucrose and yeast extract. In the fed-batch fermentation process, the activities of D-Hase and D-Case were up to 243.6 and 55.8 U/g, which were increased by 56.9% and 46.4%, respectively. The optimal reaction temperature of D-Hase and D-Case is 45℃, and the optimal reaction pH is 9 and 8 respectively. In the process of the whole-cell catalytic preparation of D-p-HPG by Ensifer adhaerens CAS22-03, when the substrate concentration was 40 g/L and the enzyme dosage was substrate:bacterium=5:1, the substrate conversion reached more than 95% with the condition of 40℃ and 200 r/min for 10 h, laying the foundation for the industrial enzymatic production of D-p-HPG. Related Articles | Metrics

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The kinetic mechanism of magnesite thermal decomposition under N2 and CO2 atmospheres Xiaoyu MA Bo LIU Gong CHEN Lihua FAN Dexi WANG The Chinese Journal of Process Engineering    2024, 24 (8): 946-954.   DOI: 10.12034/j.issn.1009-606X.223345 Abstract （166）   HTML （1）    PDF （4143KB）（94）       Knowledge map    Save In response to the challenges posed by the high energy consumption, poor environmental performance, and low production efficiency associated with the lightly burnt magnesia rotary kiln, researchers have introduced a promising solution in the form of a new calcination furnace that exhibits substantial energy-saving potential. However, to further enhance the effectiveness of this innovative furnace and refine the production processes, it is imperative to gain a more comprehensive understanding of the thermal decomposition kinetics of magnesite. This research is rooted in an analysis of the gas phase composition within the furnace during the actual production of magnesite calcination. Employing the TG-DTA thermal analysis technique, the study investigates the thermal decomposition kinetics of magnesite under N2 and CO2 atmospheres. The findings reveal that under N2 atmosphere, the thermal decomposition kinetics of magnesite involves two distinct stages: the phase boundary reaction shrinkage columnar mechanism and the random nucleation and growth mechanism. On the other hand, under the CO2 atmosphere, the kinetics process consists of three stages with two mechanism modes, including the random nucleation and growth mechanism, as well as the phase boundary reaction shrinkage spherical mechanism. Furthermore, the study's analysis indicates that the impact of CO2 on the thermal decomposition process of magnesite is twofold. On one hand, CO2 raises the activation energy of the reaction, resulting in an elevated decomposition reaction temperature. Conversely, CO2 also has the capacity to induce the nucleation and growth of the product CO2, thereby making the decomposition reaction rate more sensitive to the change of temperature. The present work's elucidation of the kinetic mechanisms governing magnesite thermal decomposition under N2 and CO2 atmospheres not only provides valuable data to support the optimization of the new type of calcination furnace, which has important engineering application prospects, and can also provide reference value for further research . Expanding upon these insights through further research and development endeavors holds the potential to drive substantial advancements in the field of magnesite processing and contribute to the overall sustainability of industrial processes. Related Articles | Metrics

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Recent advances of kinetic promoters for the formation of light hydrocarbons and carbon dioxide hydrates Xiaomei YANG Peng XIAO Changyu SUN Guangjin CHEN The Chinese Journal of Process Engineering    2024, 24 (10): 1137-1148.   DOI: 10.12034/j.issn.1009-606X.223332 Abstract （170）   HTML （5）    PDF （1331KB）（94）       Knowledge map    Save Hydrate-based carbon sequestration in deep ocean is a highly promising way for carbon sequestration. The formation of carbon dioxide hydrate is the basis of hydrate-based carbon sequestration. However, the formation rate of gas hydrate is very slow without human intervention. Among the methods that intensify gas hydrate formation, the use of kinetic promoters has been proven to be the most effective one. Though the kinetic promoters have been extensively and deeply studied, they are mainly used for intensifying the formation of light hydrocarbons hydrates, which is the basis of hydrate-based industrial technologies, such as hydrate-based gas storage and gas separation. However, the kinetic promoters that is suitable for the formation of light hydrocarbons hydrates are not necessarily suitable for the formation of carbon dioxide hydrate. Therefore, in order to find out the most effective kinetic promoters to intensify the formation of carbon dioxide hydrate, it is necessary to distinguish the kinetic promoters of carbon dioxide hydrate from that of light hydrocarbon hydrates. Aiming at the intensification of the formation of carbon dioxide gas hydrate, the evolution and the current research status of kinetic promoters are reviewed. The effects of different kinetic promoters on the formation of the same gas hydrate, and the effects of the same kinetic promoter on the formation of above two kinds of gas hydrates are compared. The different effects of kinetic promoters on promoting light hydrocarbons hydrates and carbon dioxide hydrate are revealed. Based on the research status of the kinetic promoters, the study of the intensification mechanisms of the kinetic promoters on different gas hydrates, the establishment of the criteria for assessing the kinetic promoters, the enhancement of the removal of the formation heat of gas hydrates, and the further improvement on intensifying gas hydrate formation are proposed, to provide new methods for the practical application of hydrate-based carbon sequestration. Related Articles | Metrics

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Cover and Contents The Chinese Journal of Process Engineering    2024, 24 (9): 0-.   Abstract （116）      PDF （2131KB）（92）       Knowledge map    Save Related Articles | Metrics