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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 （286）   HTML （9）    PDF （3274KB）（591）       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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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 （272）   HTML （6）    PDF （9953KB）（553）       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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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 （425）   HTML （23）    PDF （2886KB）（453）       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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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 （738）   HTML （26）    PDF （3984KB）（428）       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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Effect of oxygen-rich combustion conditions on heating process of slab in reheating furnace Biao LU Xingyin WANG Qingyun HU Yan CHEN Demin CHEN Jin GAO The Chinese Journal of Process Engineering    2024, 24 (7): 805-814.   DOI: 10.12034/j.issn.1009-606X.223306 Abstract （336）   HTML （5）    PDF （4324KB）（421）       Knowledge map    Save Compared with traditional air combustion, oxygen-enriched combustion can increase the flame temperature, strengthen the radiation heat transfer in the furnace, reduce the exhaust heat loss, increase the volume fraction of CO2 in the flue gas, and is conducive to CO2 capture, so it has become a hot spot in the field of industrial furnace research. At present, most studies simply transform the whole heating furnace from conventional air combustion to oxygen-rich air combustion, and are limited to the single factor of oxygen volume fraction. In order to explore the influence of different oxygen-rich combustion arrangement forms and different oxygen volume fractions on the heating furnace thermal characteristics and slab heating process, two oxygen-rich combustion models (JC-1 and JC-2) with oxygen volume fraction of 21vol%~49vol% are established to study the effects of combustion of gas and fuel on the thermal characteristics of the furnace and slab heating characteristics by numerical simulation. The results show that compared with the JC-1 condition, the temperature distribution in the furnace under JC-2 condition is more uniform and the slab temperature is higher, so the oxygen-rich combustion arrangement under JC-2 condition is better than that under JC-1 condition. Slab temperature and furnace thermal efficiency increase with the increase of oxygen enrichment volume fraction, but the increase rate decreases gradually. When the oxygen volume fraction is between 21vol% and 37vol%, the heating furnace slab temperature and furnace thermal efficiency increase at a higher rate. In this volume fraction range, when the oxygen volume fraction of JC-1 and JC-2 increases by 1%, the furnace thermal efficiency increases by 0.44% and 0.47%, and the energy saving rate increases by 1.07% and 1.12%, respectively. Therefore, 37vol% is the optimal oxygen volume fraction for oxygen-enriched combustion. The significance of this study is to provide reference for the existing reheating furnace to implement the transformation of oxygen-rich combustion. Related Articles | Metrics

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Recent progress of heterogeneous catalysts towards selective catalytic reduction of NO by CO under oxygen-rich conditions Yaqi LIU Yan LIU Ke WU Liwen XING Dianxing LIAN Mohaoyang CHEN Jianjun JI Yongjun JI The Chinese Journal of Process Engineering    2024, 24 (3): 284-296.   DOI: 10.12034/j.issn.1009-606X.223136 Abstract （651）   HTML （15）    PDF （3784KB）（413）       Knowledge map    Save Nitrogen oxides (NOx), as one of the predominant atmospheric pollutants mainly derived from automobile exhaust and industrial waste gas, have played the role of an inevitable precursor that led to acid rain, photochemical smog, and other environmental contamination issues. In addition to atmospheric pollution, the growing emissions of NOx pollutants also give rise to a serious threat to agricultural production and human health. Thus, it is of urgent need to develop feasible NOx abatement strategies. Selective catalytic reduction of NO by CO (CO-SCR) is a very promising denitrification technology that can simultaneously remove harmful gases of NO and CO, making it one of the most ideal solutions for flue gas treatment. To promote its industrial applications, CO-SCR should have a low operating temperature ranging from 150℃ to 250℃ and superior resistance to oxygen poison. Therefore, there is an urgent need to develop efficient CO-SCR catalysts used under oxygen-rich conditions for abating severe environmental pollution problems. This work provides a comprehensive review of the research progress and latest research findings of CO-SCR under oxygen-containing conditions. The research advances of Pd, Ir, Rh, Mn, and Co-based heterogeneous catalysts were introduced, and the effects of active components, promoters, and supports on the catalytic performance of CO-SCR are described in detail. In this section, the preparation method, doping modification, and reaction conditions are analyzed. Meanwhile, the impact of O2, H2O, and SO2 on the catalytic activity of CO-SCR is discussed, in which the inhibition mechanism of O2 is summarized. Finally, the challenges and future developments of CO-SCR under oxygen-rich conditions are summarized and the corresponding coping solutions are proposed. We hope this review can provide an in-depth understanding and useful guidance for the rational design of efficient heterogeneous catalysts for the CO-SCR reaction in practical applications. 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 （1303）   HTML （28）    PDF （3618KB）（392）       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 on preparation of magnetic activated carbon and its application in water treatment Qianyu WANG Yuming ZHANG Yanbin CUI The Chinese Journal of Process Engineering    2024, 24 (3): 259-272.   DOI: 10.12034/j.issn.1009-606X.223228 Abstract （698）   HTML （23）    PDF （2257KB）（388）       Knowledge map    Save Activated carbon (AC) has the characteristics of high specific surface area, porosity, abundant surface functional groups and chemical stability, and these advantages make it a widely used adsorbent in water treatment. After being exhausted (saturated adsorption contaminants), the spent AC needs to be separated from aquatic systems and regenerated which is conductive to materials recycling. However, it is difficult to efficiently separate the powder AC saturated adsorption contaminants from aquatic systems by traditional separation methods (gravitational sedimentation, centrifugation, filtration, and flotation), and the disadvantages for these methods root in many aspects including time-consuming, high-cost, and low separation efficiency. These limit the wide application of activated carbon in the field of water treatment to some extent. Magnetic modification treatment on AC can provide a magnetic activated carbon (MAC) which possesses better performances reflecting in higher adsorption capacity, and can be easier, rapid and efficient separation through external magnetic fields. At the same time, MAC has good catalytic activity, which is useful for enhancing the capability of advanced oxidation process to efficiently degrade organic pollutants in aquatic systems. Therefore, MAC has broad application prospects in the field of water treatment. This work mainly introduces the preparation methods (co-precipitation method, thermochemical method, and mechanical milling method), microstructure and physicochemical properties (specific surface area, pore structure, magnetism, crystal and chemical structure, surface charge) of MAC. The research progress of MAC in wastewater treatment in recent years is reviewed, consisting of organic pollutant removal, heavy metal removal and other applications. The adsorption characteristics (adsorption isotherms and adsorption dynamics) and corresponding influencing factors (adsorption temperature, solution pH, and coexisting ions) are summarized in details. And the regeneration methods of AC are investigated comprehensively. In the end, the development and prospect of the application of MAC in water treatment are also discussed. 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 （498）   HTML （13）    PDF （1939KB）（370）       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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Heat and mass transfer simulation of gas-liquid two-phase flow in a distillation column based on OpenFOAM Yunpeng JIAO Xiaoqing ZHOU Jianhua CHEN The Chinese Journal of Process Engineering    2024, 24 (4): 391-402.   DOI: 10.12034/j.issn.1009-606X.223180 Abstract （767）   HTML （16）    PDF （4117KB）（369）       Knowledge map    Save For multiphase mass transfer processes in distillation columns, computational fluid dynamics can be used not only to simulate the flow phenomena, but also to study the heat and mass transfer processes and their interactions with the flow. Based on previous work on gas-liquid flow simulation in distillation trays, this work applied the multiphase flow solver of the OpenFOAM platform. The energy and species transport equations were considered to construct the heat and mass transfer models for the distillation system. The ideal system of cyclohexane-n-heptane and the non-ideal system of ethanol-water distillation were simulated respectively. The distribution of the gas-liquid two-phase flow, component and temperature on the column trays were analyzed. For the ideal system, the ideal solution mass transfer model can provide accurate predictions for the temperature and concentration fields on the trays. However, for non-ideal systems, it was necessary to introduce the activity coefficient model on the basis of the ideal model. To this end, the effects of two activity coefficient models, UNIQUAC and NRTL, were introduced and compared. In the current simulation framework, the activity coefficient models were able to improve the simulation accuracy of temperature and concentration field. The overall trends predicted by the two models were generally consistent with the results in the literature, and the UNIQUAC model agreed better with the literature. In addition, the comparative analysis of gas-liquid two-phase flow field and concentration field distribution showed that the circulating flow of liquid phase can enhance the local mass transfer efficiency of the column tray, resulting in higher efficiency at the liquid inlet and the weir than the tray center. However, the gas-liquid renewal in the circulating region renewed ly, which led to a reduction in the overall mass transfer efficiency of the column tray. This study can be used for the design and optimization of distillation columns, and it is also valuable for simulations of heat and mass transfer in other gas-liquid two-phase flow systems. 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 （367）   HTML （4）    PDF （6337KB）（305）       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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Key technologies and advances of positron emission particle tracking Kun LI Liyun WU Ping CHEN Yan HAN The Chinese Journal of Process Engineering    2024, 24 (4): 381-390.   DOI: 10.12034/j.issn.1009-606X.223266 Abstract （554）   HTML （19）    PDF （2513KB）（284）       Knowledge map    Save Measuring multiphase flow parameters and the understanding of multiphase flow mechanisms are of great importance value for the design, operation, and optimization of industrial process devices. Due to the inherent multiscale nature of multiphase flow, its flow field often has great complexity, which makes our understanding of its flow process relatively limited. There are still many key issues that need to be explored in the mechanism of multiphase flow. Positron emission particle tracing (PEPT) is a new undisturbed and non-destructive imaging method for complex multiphase flows in industrial processes. γ photon detection is used to perform 3D dynamic imaging of radioactive labeled tracer particles. Due to γ photons have high penetration and are not affected by electromagnetic fields, making PEPT a unique advantage in detecting non-transparent and complex industrial multiphase flows. Currently, it is mainly used for measuring multiphase flow phenomena and extracting system physical parameters in industrial fields such as chemical, food, and pharmaceutical industries. However, the difficulties in preparing miniaturized tracer particles and the poor localization effect of multiple tracer particles at the same time seriously hinder the further application and promotion of PEPT technology. In this work, basic principles of PEPT technology are firstly briefly introduced, then the key technologies and research progress of PEPT are discussed from the aspects of tracer particles, algorithms, hardware systems and data processing in applications. The existing problems and potential development directions are pointed out. Finally, the development and application of PEPT is summarized and prospected. 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 （553）   HTML （10）    PDF （1362KB）（275）       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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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 （504）   HTML （27）    PDF （7425KB）（272）       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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Research status and prospect of flash boiling spray Jian GAO Run HONG Wenlong DONG Nian XU Huaqiang CHU The Chinese Journal of Process Engineering    2024, 24 (3): 273-283.   DOI: 10.12034/j.issn.1009-606X.223157 Abstract （585）   HTML （17）    PDF （1493KB）（263）       Knowledge map    Save The rapid boiling that occurs when high-temperature fuel is injected into a low-pressure environment is called flash boiling, reasonable use of flash boiling phenomenon can effectively improve the atomization effect of fuel spray and improve engine efficiency. The research on the flash boiling phenomenon can be traced back to more than 60 years ago. With the development of the research on the flash boiling spray, the focus of the spray-related research has gradually shifted to the spray collapse. The related theories of flash boiling spray are summarized in this review, and some visualization techniques commonly used in the observation of flash boiling spray are briefly introduced. The influence of different fuel characteristics on the flash-boiling spray is illustrated by comparing different fuel characteristics. The characteristics of flash boiling spray of multi-component fuel are summarized. The superheat index which can be used to measure the flash boiling spray of multi-component fuel are introduced. The collapse mechanism of non-flash boiling spray and flash boiling spray and the influencing factors of spray collapse are studied by comparing the research status of non-flash boiling spray and flash boiling spray. It is generally considered that the collapse mechanism of non-flash-boiling spray is jet-induced collapse, and flash-boiling spray seriously affects the experimental observation because of too many droplets. Therefore, the understanding of the collapse mechanism of the flash boiling spray is numerous but not certain. In addition, according to the above summary, several feasible research directions are put forward for the spray research: effect of different fuel properties on flash boiling spray, study of parameters to measure the degree of superheat of multi-component fuels, the study on the collapse mechanism of the flash-boiling spray and the study on the suppression of the collapse of the flash-boiling spray. Related Articles | Metrics

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Numerical investigation on scale-up rule of circulating fluidized bed Jinchao XIE Nan ZHANG Tianbo FAN Xinhua LIU The Chinese Journal of Process Engineering    2024, 24 (3): 326-337.   DOI: 10.12034/j.issn.1009-606X.223135 Abstract （440）   HTML （16）    PDF （3613KB）（259）       Knowledge map    Save Circulating fluidized beds have been widely used in industry, and scaling laws have been proposed during research and development from lab-scale units to industry plants. The particle diameter ratio has to be changed to keep the scale-up ratio, which may change the particle classification from Geldart A to Geldart B and even change the fluidization regime, thus limiting the utilization of these scale-up rules. A new scale-up rule, which can keep material properties or operating conditions unchanged, is thus proposed based on the Shi scale-up rule applicable for the same circulating fluidized bed and the Horio scale-up rule suitable for different circulating fluidized beds. The Euler-Lagrange model coupled with the EMMS drag coefficient was used to simulate the flow behavior in a circulating fluidized bed, and the rationality of the Shi scale-up rule was further verified by these simulations. The new scale-up rule proposed was then validated under the conditions of fixed superficial gas velocity, fixed superficial particle diameter and unrestricted combination of the gas velocity and the particle diameter in different circulating fluidized beds. The simulation results showed that the proposed scale-up rule can maintain similarities in the axial solid concentration, radial solid concentration and radial dimensionless velocity distribution. The mesoscopic characteristic distributions were further discussed through the analysis of pressure fluctuations in the time domain and frequency domain. The results showed that the mesoscopic characteristics were different to some extent, which meant that more work should be done to keep the similarities when considering heat and mass transfer in circulating fluidized beds. Related Articles | Metrics

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Study on solid-liquid suspension characteristics in a slurry polymerization reactor with different impeller combinations Yang ZHAO Minghui XIE Jiawei XIANG Xiaoxiao LIU Shuailiang LI Shijun LÜ Liang WU Guozhong ZHOU Qinghua ZHANG Chao YANG The Chinese Journal of Process Engineering    2024, 24 (4): 403-413.   DOI: 10.12034/j.issn.1009-606X.223210 Abstract （607）   HTML （13）    PDF （5209KB）（259）       Knowledge map    Save Slurry process is the main production method for high-density polyethylene. For slurry of high-density polyethylene stirred polymerizer, three-blade-backswept impeller HQ, parabolic disc turbine impeller BTD, three blade hydrofoil impeller KHX, pitched blade disc turbine impellers ZY with blade placement angle of δ=45° and δ=75°, and straight blade disc turbine impellers PY160 were used to form four types of impeller combinations. Solid-liquid suspension experiments were conducted in a cylindrical perspex stirred tank with a diameter of T=480 mm. The CFD software Ansys Fluent 2020R2 combined multiple reference frame method and Euler-Euler multiphase flow model were used to study the solid-liquid suspension of each impeller combination at 30.71% solid holdup. The results showed that when the rotating speed N≤ 250 r/min, a clear liquid layer formed at the top of the mixing tank with impeller combination 2 and 3. Due to the inhomogeneous of solid holdup, the power of impeller combination 3 and 4 showed an inflection point at the rotating speed N=350 r/min. When the rotating speed N≤350 r/min, the combined power of each paddle type from low to high was: 2, 4, 3, 1. When the rotating speed N>350 r/min, the mixing power from low to high was: 2, 3, 4, 1. Impeller combination 1 and 4 can achieve uniform mixing at lower speeds and power, and the power consumption of impeller combination 4 was about 30% lower than that of impeller combination 1, so impeller combination 4 was high efficiency and energy conservation. The simulated results of solid holdup were in good agreement with the experimental values which was measured by the sampling method. The simulated flow field indicated that the flow patterns of impeller combination 4 and 1 were similar, which can effectively avoid the clear liquid layer appearing in impeller combination 2 and 3 at low rotating speeds. 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 （736）   HTML （10）    PDF （2577KB）（258）       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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Study on gas phase oxidation of CO in flue gas catalyzed by steam Bin LIU Zhengyi TANG Jie GAO Yi CHUN Mengbo DAI Tiejun CHUN The Chinese Journal of Process Engineering    2024, 24 (12): 1435-1441.   DOI: 10.12034/j.issn.1009-606X.224028 Abstract （310）   HTML （2）    PDF （2643KB）（257）       Knowledge map    Save The iron and steel industry, as one of the lifebloods of the national economy, has become a key focus of attention in the field of energy conservation and emission reduction as the goals of carbon peaking and carbon neutrality continue to advance. Iron ore sintering is the second largest carbon emission process in the iron and steel industry after blast furnace ironmaking. Existing studies indicate that steam injection onto the sintering bed surface can improve the fuel combustion efficiency of the sinter layer, increase the sintering index, and reduce CO emission concentration of flue gas. In this work, the mechanism of CO emission reduction by injection of steam onto the sintering bed surface was studied. The effect of steam on CO gas oxidation at high temperatures was studied by using a fixed bed experiment to simulate the injection steam onto the sintering bed surface. The results showed that the steam in the gas phase system can significantly promote the oxidation of CO. The gas phase oxidation of CO almost did not occur in the condition of no water vapor, and the steam promoted CO oxidation significantly when the volume fraction was above 2.0%. The CO oxidation reaction catalyzed by steam starts at 650℃, and the reaction accelerates with the increase of temperature. A stable and continuous reaction interval appears at 700℃ and above. With the volume fraction of steam increasing, the beginning time of CO gas phase oxidation was advanced and the duration was extended. Under the conditions of O2 and CO volume fractions of 2.0% and 2.5%, respectively, the steam volume fraction of 12.0% can promote the highest CO oxidation efficiency, and the CO oxidation efficiency can reach at 99.95%. The research was of great significance for improving the theory of steam injection technology on sinter surfaces and guiding production practice. 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 （941）   HTML （22）    PDF （1677KB）（253）       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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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 （304）   HTML （11）    PDF （3092KB）（252）       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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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 （377）   HTML （10）    PDF （4811KB）（248）       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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The mechanism study on flotation of ilmenorutile based on Bayan Obo niobium-bearing minerals with 1-hydroxyoctane-1,1-bisphosphonic acid as collector Wei XU Min ZHANG Hongdong YU Fangfang CHEN Guan PENG Jing LI The Chinese Journal of Process Engineering    2024, 24 (12): 1442-1452.   DOI: 10.12034/j.issn.1009-606X.224116 Abstract （227）   HTML （4）    PDF （4707KB）（246）       Knowledge map    Save This study proposed an improved method for synthesizing 1-hydroxyoctane-1,1-bisphosphonic acid (HOBA), and ilmenorutile (one of the important representative niobium-bearing minerals in Bayan Obo) was selected as the research object. Compared with octyl hydroxamic acid (OHA), the flotation mechanism of the synthetic ilmenorutile and HOBA is systematically investigated through contact angle, Zeta potential, FTIR, SEM-EDS, and XPS methods. The results show that under acidic conditions, HOBA can be chelated with ions on the surface of ilmenorutile and stably adsorbed on the surface of ilmenorutile through chemical adsorption, which could improve the floatability of ilmenorutile. Its selectivity for ilmenorutile was significantly better than that of OHA, well explaining the superior flotation results of HOBA over OHA for the actual niobium-bearing minerals in Bayan Obo. Solution chemistry calculation provided more information for the interaction of HOBA and ions on the surface of ilmenorutile in the flotation process, and the reasons for the inhibition effect of Ce3+ and the synergetic enhancement effect of Pb2+ in the interaction between HOBA and ilmenorutile were further discussed. This study indicates that HOBA can serve as an effective collector for ilmenorutile and other niobium-bearing minerals in Bayan Obo under appropriate pH range and ion conditions, and the optimization of its synthesis route provide the possibility for industrial application. 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 （421）   HTML （18）    PDF （9961KB）（245）       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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Porous PLGA microsphere as a vaccine adjuvant against COVID-19 Lingjiao ZOU Yu ZHANG Hua YUE Guanghui MA The Chinese Journal of Process Engineering    2024, 24 (3): 360-370.   DOI: 10.12034/j.issn.1009-606X.223218 Abstract （581）   HTML （19）    PDF （1841KB）（245）       Knowledge map    Save Poly (lactic-co-glycolic acid) (PLGA) nano-/microspheres have been proven to be effective as vaccine adjuvants. In current studies, the investigations on PLGA vaccine delivery microspheres have mainly focused on improving antigen loading/adsorption efficiency or co-delivery of multiple adjuvants to enhance the immunization effect. However, there is still a lack of discussion on the impact of the structural diversity of microspheres in promoting the vaccination effects. By rationalizing the design of the microsphere structure, we describe that the development of an effective SARS-CoV-2 vaccine adjuvant was achieved by the post-loading of SARS-CoV-2 antigen into porous PLGA microspheres, which provided non-destructive loading and prolonged release of antigen. In this work, PLGA porous microspheres and solid microspheres were prepared with the emulsification method, and there was no significant difference in microsphere particle size and surface potential between the two, except for the porous microspheres having cavities internally and tiny pores on the surface. Such characteristics of "large inner pores and tiny outer pores" enabled the antigen encapsulation efficiency to reach 10.81% at the antigen input concentration of 5.71 mg/mL. In terms of prolonging the in vivo retention of the antigen, the release endpoint in the antigen-loaded porous microspheres was prolonged to 15 days compared with that of the free antigen at 3 days and that of the solid microsphere-mixed antigen at 5 days. Concerning the enhancement of humoral immunization, compared with the solid microsphere vaccine group mixed with SARS-CoV-2 antigen, the porous microsphere vaccine group loaded with SARS-CoV-2 antigen had a higher onset of effect as the maximum value of the IgG titer rising rate, Vmax was 1.73 times higher; and the onset of effect was much earlier, as the time to reach the Vmax was 2.8 days earlier; also, the IgG antibody titer of which was higher during 6~16 weeks post-immunization, presenting a better antibody maintenance effect. Related Articles | Metrics

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CFD simulation and temperature regulation of the coke drum Boyan CHEN Yuting CAO Yong ZHANG Guogang SUN Yindong LIU Luhai WANG The Chinese Journal of Process Engineering    2024, 24 (4): 414-424.   DOI: 10.12034/j.issn.1009-606X.223145 Abstract （376）   HTML （12）    PDF （4792KB）（244）       Knowledge map    Save Coke drum is the conventional reactor for processing heavy oil into light chemicals in petrochemical industry. Because of the high operation temperature within the reactor, experimental monitoring is particularly difficult. The complex processes within the coke drum involve the fluid flow, heat transfer and reaction, and the heterogeneous temperature distribution make it challenging for precise regulation. This study considers the distribution of gas phase, liquid oil, and solid coke in the reactor and adopts continuous medium model (Eulerian model) to simulate the motion of three phases and couples the heat transfer model and seven-lumped reaction kinetics model, so as to establish a multiscale model for the coke drum reactor. The accuracy of this model is validated by comparing the simulation and experiment results in the kettle reactor. Furthermore, the feeding process and the coke growth from mesoasphaltene are modelled, and the flow field, temperature distribution, and coke generation rate under different operating conditions are studied. The results show that the coking process and the heterogeneous distribution of multi-physical field in the reactor are greatly influenced by temperature. The mass fraction and growth rate of coke and gas products increase a lot at high temperature. In order to regulate the distribution and growth rate of the coke product, the mesoasphaltene, which is the precursor product of the coke, is generated with temperatures no more than 450℃ at feeding stage, so that the coke growth rate is restricted. Afterwards, the temperature is improved by heating reactor walls and injecting high-temperature steam, in which the reaction rate of mesoasphaltene towards coke product increases and the uniform distribution of coke can be obtained. This study provides an important case for regulating distribution and growth of coke product by coordinating the temperature field and flow characteristics within the coke drum. Related Articles | Metrics

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Numerical simulation of multiphase flow process and structural improvement measures in the quench chamber of a gasifier Bing YUAN Jinjun GUO Xiaofei LI Junhui LIANG Zhenxiang Li Xiaodong LONG Congbin JIANG The Chinese Journal of Process Engineering    2024, 24 (3): 315-325.   DOI: 10.12034/j.issn.1009-606X.223196 Abstract （402）   HTML （9）    PDF （5039KB）（237）       Knowledge map    Save The entrained flow coal gasification technology is one of the important means for the clean utilization of coal. In the syngas cooling device, the quench chamber with riser-downcomer structure is widely used in the coal gasification device. There is a situation where synthetic gas escapes from the black water outlet in the quench chamber of this type of quench chamber, resulting in a waste of resources. In this work, the gas-liquid two phase flow in the quench chamber is stuided with the numerical simulation method. The causes of syngas escape problem from the black water outlet in the quench chamber are analyzed, and three improved structures for the quench chamber are proposed as follow: extending the black water outlet pipe (structure A), extending the riser pipe downwards (structure B), adding a baffle on the rising pipe near the black water outlet (structure C). The simulation results indicate that all three improvement schemes can avoid the problem of syngas escape. In addition, the liquid-solid two phase flow in the black pool with four structures (structures A, B, C, and the original structure) are simulated, and the carry-out rate of ash particles with different particle sizes under the same conditions are compared in different structures. The results show that the carry-out rate of ash particle in the improved structure C is the smallest, followed by the structure A. These two structural schemes are suitable for the situation where the residual carbon in the filter cake is not recycled, and the low carry-out rate of ash by black water is beneficial for improving the water quality of the water circulation system. Compared with the original structure, the structure B has a higher carry-out rate for particles size smaller than 20 μm, but a low carry-out rate for large particles, which is suitable for recycling the residual carbon in the filter cake. Related Articles | Metrics

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Effect of finish rolling temperature on microstructure and mechanical properties of bridge weathering steel with low yield ratio Wensheng LIU Ke ZHANG Dangwei XU Shaobo MENG Zhong HUANG Zhisheng XIA Mingya ZHANG Xinjun SUN The Chinese Journal of Process Engineering    2024, 24 (4): 462-469.   DOI: 10.12034/j.issn.1009-606X.223247 Abstract （409）   HTML （4）    PDF （2801KB）（228）       Knowledge map    Save The effect of the finish rolling temperature on the microstructure and mechanical attributes of Cu-Cr-Ni bridge weathering steel, characterized by a low yield ratio, was exhaustively explored in this study. Advanced testing methodologies including the Gleeble-3800 thermal simulation tester, tensile tester, and Vickers hardness tester were employed, in conjunction with characterization techniques such as optical microscope (OM) and electron backscattered diffraction (EBSD). This comprehensive approach aimed to elucidate the specific mechanisms governing these transformative changes. The results of the investigation unveiled pivotal transformations within the microstructure of Cu-Cr-Ni bridge weathering steel. Initially rolled at 880℃, the steel exhibited a granular bainitic microstructure. A reduction in the finish rolling temperature to 800℃ ushered in the formation of acicular ferrite, which gradually increased in prevalence. Simultaneously, the average size of the M/A islands expanded from 1.3 to 3.3 μm, accompanied by an increase in the area fraction from 21.7% to 32.3%. Notably, a marked elevation in dislocation density within the matrix was observed, primarily attributed to the considerable reduction in the degree of matrix restitution. Furthermore, these microstructural modifications were mirrored by notable enhancements in the material's mechanical properties. The hardness and yield strength of the Cu-Cr-Ni bridge weathering steel experienced a pronounced upswing with diminishing finish rolling temperatures. The yield strength, in particular, exhibited a remarkable increase from 435 to 496 MPa. Contrarily, tensile strength remained relatively stable at approximately 710 MPa. These mechanical variations were intricately linked to the prevalence of acicular ferrite within the microstructure, the presence of M/A constituents, and the heightened dislocation density. Importantly, the yield ratio exhibited an increasing trend, albeit generally maintaining a level below 0.7, indicative of a subtle improvement in plasticity. This research not only advances the understanding of materials science but also offers valuable insights for optimizing the manufacturing process of high-performance bridge steels, thereby contributing to the continued progress of the bridge structure. Related Articles | Metrics

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Model development and validation of a structural two-fluid model for gas-solid bubbling fluidized beds Jiewen LUO Yabin WANG Wen LI Guosheng WANG Bidan ZHAO Junwu WANG The Chinese Journal of Process Engineering    2024, 24 (4): 435-444.   DOI: 10.12034/j.issn.1009-606X.223225 Abstract （565）   HTML （15）    PDF （3392KB）（226）       Knowledge map    Save Bubbling fluidized beds have been widely used in industrial applications because of its good mass and heat transfer behavior, where the heterogeneous structures such as bubbles are widely present, and these complex structures significantly affect the mass, momentum, and heat transfer as well as chemical reactions in the fluidized bed. The continuum model is selected to simulate the industrial fluidized beds by considering both of the computer cost and efficiency. In order to improve the accurate prediction of the continuum method simulation, it's very important to quantify reasonably the relationship between heterogeneous structures and three transfers/chemical reactions. The structure two-fluid model has been proposed as a novel continuum model, which has taken into account the influence of the heterogeneous structures such as particle clusters in the governing equations and the constitutive relations, therefore, this method is a complete and logically self-consistent in terms of heterogeneous structures. In this study, the structural two-fluid model is extended to the numerical simulation of bubbling fluidized bed: in the deducing the governing equations, the heterogeneous gas-solid system is divided as the particle-dominated emulsion phase and gas-dominated bubble phase, which are defined as two continuous fluids and permeate each other; for closing the constitutive relations, the involved bubble diameter, solid fraction in the emulsion phase and its viscosity have considered the influence of heterogeneous structures such as bubbles by some empirical correlations. As shown in the simulated results, the structural two-fluid model can successfully predict the hydrodynamics characteristics of gas-solid flow in the bubbling beds, thus validating the applicability of the structural two-fluid model in the simulation of bubbling fluidized beds. Moreover, the bubble size as an essential factor has an impact on the interaction between bubble phase and emulsion phase, which leading to the different simulation results with different bubble size correlations. 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 （769）   HTML （13）    PDF （6151KB）（209）       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