Loading...
Welcome to visit The Chinese Journal of Process Engineering, Today is

Table of Content

    28 May 2023, Volume 23 Issue 5
    Previous Issue    Next Issue
    Contents
    Cover and Content
    The Chinese Journal of Process Engineering. 2023, 23(5):  0. 
    Asbtract ( )   PDF (2293KB) ( )  
    Related Articles | Metrics
    Review
    Research status and prospect of key installations and flow characteristics of pneumatic conveying
    Jiawei ZHOU Xiangyu YAN Zebing ZHENG Qinghui WANG Linjian SHANGGUAN
    The Chinese Journal of Process Engineering. 2023, 23(5):  649-661.  DOI: 10.12034/j.issn.1009-606X.222192
    Asbtract ( )   HTML ( )   PDF (3837KB) ( )  
    Related Articles | Metrics
    Pneumatic conveying has the characteristics of environmentally friendly, operational safety, spatial intensification, flexible configuration, and easy to automate. In addition, this bulk material handling method also has the advantages of quantitative conveying, conveniently dispersing or centralized conveying, and inert gas protection conveying for unstable materials. The aforementioned characteristics pneumatic conveying to a commonly clean conveying technology for bulk materials. At the same time, pneumatic conveying has been widely applied in chemical, food, pharmaceutical, energy industries, and other fields. However, this method also has a few problems, such as high energy consumption, particle degradation, and pipe erosion. The fundamental cause of the disadvantages lies in the complex conveying process, transient state of particle conveying, and difficulty in accurate prediction. Therefore, the multi-means characterization and prediction of material conveying characteristics in different conveying processes have always been the hot points of this technology. It is well known that the equipment composition is the foundation of pneumatic conveying system performance. In addition, the feeding device is one of the most important factors for conveying processes. In this meaning, this work first summarized the structure of the pneumatic conveying system and the structural characteristics of commonly used feeding devices. Then, this work reviews the application and research of the numerical simulation methods including the two-fluid model in the computational fluid dynamics and the coupling simulation of the computational fluid dynamic discrete element method (CFD-DEM). The application conditions, merits, and demerits of the common numerical method are discussed. What is more, the research and application status of measuring devices commonly used in pneumatic conveying are summarized, including electrical capacitance tomography (ECT), pressure determination, and acoustic emission. Meanwhile, the study mainly focuses on flow pattern evolution and pressure loss in the conveying system, as well as some interesting study points of pneumatic conveying, which are well explored. Finally, several thinking points for future research on this technology are discussed.
    Research Paper
    Experimental study on filtration performance of countercurrent moving bed filter
    Kai XING Han LÜ Yiping FAN Chunxi LU Fuwei SUN
    The Chinese Journal of Process Engineering. 2023, 23(5):  662-671.  DOI: 10.12034/j.issn.1009-606X.222143
    Asbtract ( )   HTML ( )   PDF (13278KB) ( )  
    Related Articles | Metrics
    Granular bed filtration is one of the most promising high-temperature filtration technologies and has good prospects for application in environmental protection or in industrial production. Compared to the fixed bed, the moving bed filters with the stability for long-cycle operation are more in line with practical requirements. The influences of the superficial gas velocity and the regeneration gas velocity on the gas-solid countercurrent moving bed filter are investigated by cold model experiment. Under the dust-free operating conditions, it is found that the bed pressure drop increased parabolically with the superficial gas velocity. It can also be estimated by the modified Ergun formula. Under the operating condition of dust-leaden, on the other hand, it is proved that the variation trend of dust removal efficiency is the same as that of gas residence time. It is positively correlated with the regeneration gas velocity. The gas residence time is mainly influenced by the superficial gas velocity and the accumulation of dust in the filter, which varies as the experiment proceeds. The pressure drop of the bed is positively correlated with the gas velocity whereas is negatively correlated with the gas regeneration velocity. The experimental results show that the dust collection efficiency of this equipment is fairly high. When the superficial gas velocity ranges from 0.122 m/s to 0.305 m/s, with the inlet concentration of 8.175 g/m3, the dust removal efficiency is generally higher than 98.0%. The bed pressure drop always maintains dynamic equilibrium within a certain range, and the maximum rise does not exceed ±0.05 kPa. The fraction efficiency for the fine dusts smaller than 13 μm also achieves 99.99%.
    Numerical simulation of flow field characteristics enhanced by cylindrical vortex generator in impinging stream reactor
    Jianwei ZHANG Hongwen WEI Xin DONG Ying FENG
    The Chinese Journal of Process Engineering. 2023, 23(5):  672-680.  DOI: 10.12034/j.issn.1009-606X.222193
    Asbtract ( )   HTML ( )   PDF (1984KB) ( )  
    Related Articles | Metrics
    Impinging stream reactor is widely used in absorption, extraction, and preparation of ultrafine powders due to its good mixing performance. The flow field characteristics of impinging stream reactor are closely related to the mixing performance. Based on impinging stream reactor, the use of a vortex generator and other turbulence elements to improve the flow state of the flow field, enhance the flow performance, and mixing effect of impinging stream reactor needs further research. In this work, the numerical simulation method is used to analyze the flow field characteristics of impinging stream reactor with a cylindrical vortex generator and optimize the size and location parameters of the cylindrical vortex generator. The effects of size and location parameters of cylindrical vortex generators on flow field structure, velocity distribution, turbulence scale, and mixing performance of impinging stream reactor are investigated. The results show that when the diameter of cylindrical vortex generator D is equal to 10 mm, the number of vortices in the impinging stream reactor is the largest, and the influence range of the vortex system is the widest. When the diameter of cylindrical vortex generator D is less than 10 mm, the number of vortices decreases. When the diameter of cylindrical vortex generator D is greater than 10 mm, the influence range of the vortex system decreases. The number of vortexes in the impinging stream reactor decreases and the influence range of the vortex system increases with the increase of the transverse spacing of the column vortex generator. The radial velocity, turbulence scale, and mixing intensity of impinging stream reactor first increase and then decrease with the increase of transverse and longitudinal spacing of cylindrical vortex generators. When the transverse spacing of the cylindrical vortex generator K is equal to 5 mm and the longitudinal spacing of the cylindrical vortex generator J is equal to 70 mm, the mixing effect of the impinging stream reactor is the best.
    Structural optimization and flow field analysis of agitated extraction column based on CFD
    Shenfeng YUAN Lingzhen JIN Zhirong CHEN Hong YIN
    The Chinese Journal of Process Engineering. 2023, 23(5):  681-690.  DOI: 10.12034/j.issn.1009-606X.222269
    Asbtract ( )   HTML ( )   PDF (2958KB) ( )  
    Related Articles | Metrics
    In order to reduce the axial backmixing and increase the throughout flux in the agitated extraction column, the column was modified on the basis of the agitated sieve plate extraction column, and a new agitated extraction column with relatively light backmixing is proposed. Through the simulation of residence time distribution, combined with backmixing model and flow field analysis, the effects of annulus area, annulus position, opening mode, and the height of settling compartments on fluid flow characteristics are studied. The results show that the inter-stage rotating baffles can effectively inhibit axial backmixing in the column, and the larger the diameter of baffles, that is the narrower the annulus in the column, the smaller the backmixing. The optimum diameter of the inter-stage baffles in the agitated extraction column with a diameter of 50 mm should be more than 25 mm, that is, the ratio of the annulus area to the cross-sectional area of the column should not exceed 25%. Under a certain annulus width, the annulus position has little influence on the fluid flow. When the diameter of the inter-stage baffles is roughly equal to the impellers', the backmixing in the column reaches the smallest. Different opening modes also affect the flow characteristic in the column. Both perforated stators and perforated inter-stage baffles increase backmixing, especially the perforated inter-stage baffles just below the impellers. Under the condition of a certain annulus area, the agitated extraction column A6 without pores in stators and inter-stage baffles has the smallest backmixing and its structure is simple. However, if the liquid-liquid dispersion and the dead zone of the light phase are taken into consideration, the agitated extraction column B3 and B4 not only have relatively low backmixing, but also could improve the throughout flux, whose performance can be further studied. The settling compartments can reduce the backmixing, and the higher the height of settling compartments, the smaller the backmixing. Considering the equipment cost in practical application, the optimum ratio of the height of settling compartment to column diameter should be about 0.7.
    Numerical simulation of frosting process of flat finned tube heat exchanger based on fluid-solid thermal coupling
    Qinghua CHEN Bin ZHANG Baojie ZHOU Jiadong JI Jiangang WANG Wannan WANG
    The Chinese Journal of Process Engineering. 2023, 23(5):  691-702.  DOI: 10.12034/j.issn.1009-606X.222186
    Asbtract ( )   HTML ( )   PDF (4700KB) ( )  
    Related Articles | Metrics
    Plane finned tube heat exchanger was widely used in household air conditioner, environmental testing chamber, closed heat source tower, and other heat pump refrigeration systems because of its high heat transfer efficiency, low air resistance, and stable mechanical properties. It was easy to form a frost layer on the surface of flat finned tube heat exchanger working in low temperature and high humidity environment, which greatly reduced heat transfer efficiency and caused waste of energy. The study on the frosting growth on the surface of straight finned tube can provide guidance for the design of plane finned tube heat exchanger. The frosting process of plane finned tube heat exchanger is the result of the interaction of wet air, frosting layer, and heat exchanger structure. In this work, based on the fluid-solid thermal coupling calculation method, considering the changes in frost density and thermal conductivity during the frosting process, a more realistic solution domain boundary was defined, and the frosting process of 3D plane finned tube heat exchanger was numerically simulated. The average error between the simulated frost amount and the experimental value is 4.67%, which is better than the results obtained by previous numerical simulation methods. The frost growth was calculated and compared when the wet air inlet velocity was 1.0, 2.0, 3.0, and 3.7 m/s, and the relative humidity was 60%, 70%, and 80%, respectively. The results showed that the frost thickness decreased along the airflow direction, and the growth rate increased with the increase of velocity and relative humidity. The study on the heat transfer coefficient of air side showed that the higher the relative humidity of air was, the higher the heat transfer coefficient was at the beginning of frosting. In the late frosting period, the greater the relative humidity of the air was, the smaller the heat transfer coefficient was.
    Effect of groove structure on performance of proton exchange membrane electrolyzer
    Yuanyue LIU Hongbo LIU Jing HE Jiaxin HAN Tao CHEN
    The Chinese Journal of Process Engineering. 2023, 23(5):  703-712.  DOI: 10.12034/j.issn.1009-606X.222208
    Asbtract ( )   HTML ( )   PDF (15018KB) ( )  
    Related Articles | Metrics
    Proton exchange membrane water electrolysis (PEMEC) is a promising water electrolysis technology, but its development is limited by cost and energy consumption. In order to effectively improve the heat transfer and gas-liquid two-phase transfer ability in the anode channel of proton exchange membrane electrolysis cell and improve the electrolysis performance, the wall structure of the electrolysis cell channel was studied. Based on the electrochemical principle and the theory of mass and heat transfer, a single channel model of three-dimensional non-isothermal proton exchange membrane electrolysis cell was established. The anode channel velocity, temperature, and gas-liquid two-phase distribution of the electrolysis cell were analyzed. The effects of bionic groove and conventional groove on the heat and mass transfer and electrochemical performance of the electrolysis cell were studied. The results showed that: (1) the addition of grooves in the anode channel of the electrolytic cell can optimize the fluid velocity, energy and mass transfer performance and electrochemical performance of the electrolytic cell in varying degrees. (2) Compared with the conventional geometric grooves, the bionic curved surface grooves had more obvious optimization effects on all aspects of the performance of the electrolytic cell. Compared with triangle grooves and V-shaped grooves, the heat transfer coefficients of the anode channel with the bionic curved surface groove increased by 10.8% and 28.2%, and relative optimization rate of the mass transfer rates of liquid water and oxygen reached 47.0% and 83.3%, respectively. (3) Groove spacing affected the degree of fluid disturbance in the channel, and the number of disturbances was positively correlated with the number of grooves. When the channel length was constant, the smaller the groove spacing was, the more frequent the disturbance was, the faster the fluid velocity in the channel of the electrolytic cell was, and the overall performance of the electrolytic cell was improved. The research results can provide certain reference for the further development of proton exchange membrane electrolyzer.
    Effect of elevated pressures and temperatures on the laminar combustion characteristics of n-dodecane/air flames
    Jicheng SHI Tao JIN Bingbing QIU Wenlong DONG Huaqiang CHU
    The Chinese Journal of Process Engineering. 2023, 23(5):  713-723.  DOI: 10.12034/j.issn.1009-606X.222195
    Asbtract ( )   HTML ( )   PDF (4997KB) ( )  
    Related Articles | Metrics
    The combustion of fossil fuels is the main form of energy supply in today's society, but with the depletion of fossil fuels, it is urgent to develop new alternative fuels. n-Dodecane is one of the important components of aviation kerosene, and also an important component of various alternative fuels for aviation kerosene. Laminar combustion characteristics of n-dodecane/air flames were investigated using CHEMKIN/PREMIX, providing a theoretical reference for the development of alternative fuel aviation kerosene. The initial temperatures were set as 400, 403, 423, and 470 K, the initial pressures were set as 0.1, 0.2, 0.3, 0.5, and 1.0 MPa, and the equivalence ratio was set as 0.6~1.6. This study mainly focused on the combustion characteristics of flames, temperature sensitivity analysis, and the distribution of intermediate free radicals. The laminar burning velocity (LBV), adiabatic flame temperature (AFT), net heat release rate (NHRR), and rate of production (ROP) of free radicals were obtained with the increase of initial temperatures and pressures. The results showed that the simulation values of LBV can well-predict other experimental values, whose trend was consistent with other models. The peaks of AFT appeared near the stoichiometric ratio. Similar to other hydrocarbon fuels, the most sensitive reaction was R1 (H+O2?O+OH) in the oxidation process. It was verified that there was an obvious spatial difference between the flame front and fuel pyrolysis through ROP analysis and the distribution of mole fraction. The increase in initial pressures reduced the reaction zone and accelerated the formation rate of free radicals. Laminar premixed combustion characteristics of n-dodecane/air flames were studied using Jetsurf 2.0 mechanism, and the effect of elevated temperatures and pressures was comprehensively discussed. The numerical results can enrich the basis of data at high pressure, which provides a reference for looking for alternative fuels for aviation kerosene.
    Study of effect of montmorillonite on distribution of pyrolysis products of oil shale kerogen based on molecular dynamics simulation
    Xiang LI Jinhui ZHAN Guangwen XU
    The Chinese Journal of Process Engineering. 2023, 23(5):  724-733.  DOI: 10.12034/j.issn.1009-606X.222140
    Asbtract ( )   HTML ( )   PDF (1185KB) ( )  
    Related Articles | Metrics
    In this work, based on the molecular dynamics simulation method of reaction force field (ReaxFF), the pyrolysis reaction process of Green River oil shale kerogen in the presence of montmorillonite was studied, and the product distribution of pyrolysis at different temperatures and the characteristics of non-bonding interaction between minerals and organic matter were analyzed. By comparing the product distribution characteristics of the system with montmorillonite and without montmorillonite during the heating process, it showed that montmorillonite had a strong promotion effect on the pyrolysis of kerogen, and lowered the pyrolysis temperature and widened the temperature span of the pyrolysis process, and the presence of montmorillonite resulted the increase of light oil fraction and the decrease of heavy oil fraction in the pyrolysis reaction of kerogen. The results of thermostatic simulations at a range of characteristic temperatures indicated that the addition of montmorillonite increased the yield of small molecular fragments and inhibited the polymerization of large molecular fragments at high temperatures. Montmorillonite for promoting kerogen pyrolysis was initiated by the adsorption effect, which was reflected in the presence of large non-bonding forces between kerogen and montmorillonite, dominated by VDW interactions. The simulation results showed that in contrast to the fragments of C18H30, C18H38, C20H42, C45H60O of kerogen, there were more significant non-bonding interactions between montmorillonite and fragments of C75H118O5N4, C102H167ONS2, C367H550O10N10S2, with the strongest interaction force in the fragment of C367H550O10N10S2 with montmorillonite.
    Research on impurity occurrence and high-efficient separation of dry process calcium carbide slag
    Yue YANG Ganyu ZHU Ziheng MENG Xinhui LIU Jing YANG Kun YAN Zonggui PENG Qiujian WANG Huiquan LI
    The Chinese Journal of Process Engineering. 2023, 23(5):  734-743.  DOI: 10.12034/j.issn.1009-606X.222117
    Asbtract ( )   HTML ( )   PDF (3137KB) ( )  
    Related Articles | Metrics
    In order to improve the comprehensive utilization rate of calcium carbide slag and solve the separation problem of impurities, this work focuses on the impurity composition and occurrence form of calcium carbide slag. Cyclone separation process was used to separate the impurities from calcium carbide slag efficiently through a physical short range. The composition and occurrence form of calcium carbide slag were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS), and chemical analysis. Finally, the properties of activated calcium oxide products prepared from raw slag, fine slag, and coarse slag were compared. The results showed that the cyclone separation can effectively separate the coarse particles and ferrosilicon components in the calcium carbide slag. The content of particles larger than 106 μm in the coarse slag was 35.21wt%, and the amount were only 0.40wt% and 0.11wt% in the raw slag and fine slag, respectively. The iron enrichment phenomenon in the coarse slag was remarkable, and the content increased from 0.25wt% to 1.14wt%. The content of acid insoluble matter in the fine slag was significantly reduced. The occurrence formed of impurities in calcium carbide slag were not changed during cyclone separation process. Element of carbon mainly existed in the form of simple substance and carbonate, aluminum and silicon mostly existed in the form of aluminosilicate, and sulfur mainly existed in the form of sulfate, sulfide, and mercaptan. The compressive strength of calcium oxide products prepared with fine slag as raw material can reach 5.1 MPa, which was about 50% higher than that of raw slag and coarse slag.
    Structure evolution and performance analysis of blue-coke in the upper part of ferrosilicon furnace
    Yi WANG Cheng MA Chong ZOU Shiwei LIU Nan YU Ruimeng SHI Shengsan ZHAO
    The Chinese Journal of Process Engineering. 2023, 23(5):  744-754.  DOI: 10.12034/j.issn.1009-606X.222156
    Asbtract ( )   HTML ( )   PDF (4916KB) ( )  
    Related Articles | Metrics
    A shaft furnace was used to secondary heat the blue-cokes which were manufactured by different temperatures of carbonization furnaces at the medium heating rate (10℃/min) and final temperatures of 800, 900, 1200, and 1600℃, as a way to simulate the state of the blue-coke during the downward movement of the upper part of the ferrosilicon furnace. The physical and chemical structure and reactivity changes of the incoming blue-coke at different heat treatment temperatures were studied by using nitrogen adsorption, Raman spectroscopy, and thermogravimetric analysis, and the key aspects of the blue-coke affecting the furnace condition were analyzed with the results of industrial experiments. The results showed that with the increase of heat treatment temperature, taking 800 and 1200℃ as the turning points, the specific surface area and pore volume of blue-coke increased, then decreased and then increased until stable; the defects and amorphous structures in carbon chemical composition gradually changed into ordered carbon structures; the reactivity of blue-coke gradually became worse; and taking 1200℃ as the turning points, the resistivity decreased in stages. As the heat treatment temperature increases, the difference in pore structure, carbon chemical composition, reaction properties, and resistivity among different blue-cokes decreased. When the secondary heat temperature was higher than about 1600℃, the pore structure, carbon chemical composition, reaction performance, and resistivity of different blue-coke tend to be stable. In the upper part of the ferrosilicon furnace, the overburning of the blue-coke with a well-developed pore structure and better reaction performance after feeding into the furnace lead to the deterioration of the mechanical strength of the blue-coke and the increase of the charcoal consumption, which were the main factors affecting the difference of the smelting effect of different blue-cokes in the furnace. In the lower part of the ferrosilicon furnace, the physical and chemical properties of blue-cokes with different mass were similar, which was no longer the main factor affecting the furnace condition.
    Oxidation kinetics of pellets prepared from iron concentrate with different specific surface areas
    Baoshu GU Xuxu MA Zikang ZHU Baigen DING Bangcao LUO Tiejun CHUN
    The Chinese Journal of Process Engineering. 2023, 23(5):  755-762.  DOI: 10.12034/j.issn.1009-606X.222148
    Asbtract ( )   HTML ( )   PDF (10457KB) ( )  
    Related Articles | Metrics
    Iron concentrate pellets are an important burden for ironmaking in blast furnaces and high pellets rate is an effective way to reduce carbon emissions. The oxidation kinetics of pellets can be improved to optimize the pellet production process and increase the yield. In this work, the pellets prepared from the iron concentrates with different specific surface areas (SSAs) are oxidized at different temperatures for different time. The result shows that the oxidation rate increases dramatically with increasing temperature and time in the early stage, but increases slowly in the late stage. The apparent oxidation rate constant decreases with the incremental SSA of iron concentrates. The unreacted core model was used to establish the oxidation kinetic equations. For the pellets with SSA of 849 cm2/g, the activation energy is 55.19 kJ/mol in the early oxidation stage and that is 26.72 kJ/mol in the late oxidation stage. For the pellets with SSA of 1445 cm2/g, the activation energy is 61.73 kJ/mol in the early oxidation stage and that is 27.88 kJ/mol in the late oxidation stage. The restrictive steps for the oxidation of the two pellets are consistent. Chemical reaction controls the early stage of oxidation and the late stage of oxidation is controlled both by chemical reaction and gas internal diffusion. High SSA leads to a decrease in the porosity of the oxidized pellets, which affects the gas diffusion from the surface to the interior of the particles. Thus, both the oxidation degree and oxidation rate decrease.
    Thermodynamic analysis and properties of Fe-V alloy prepared by direct reduction of vanadium slag
    Weibin WANG Ziyang ZHANG Haitao LIU Wei WANG
    The Chinese Journal of Process Engineering. 2023, 23(5):  763-770.  DOI: 10.12034/j.issn.1009-606X.222223
    Asbtract ( )   HTML ( )   PDF (34754KB) ( )  
    Related Articles | Metrics
    Vanadium slag is considered to be a secondary resource of polymetallic symbiosis for the reason that it contains various metal elements such as iron, vanadium, chromium, etc. Currently, a variety of technologies for extracting vanadium and chromium from vanadium slag have been explored in detail. While the treatment of iron in vanadium slag is reported rarely. What's more, a great deal of iron elements cannot be effectively recovered and enter the tailings in the existing research, which leads to the waste of iron resources. For achieving the synergistic recycle of vanadium and iron in vanadium slag, Fe-V alloy was prepared successfully by high-temperature carbothermal reduction smelting with vanadium slag and high-iron red mud. Thermodynamic analysis of the whole reduction system is carried out by using thermodynamic information such as oxygen potential diagram and phase diagram. The result indicates that the oxides of iron and vanadium can be deoxidized easily at high temperature and developed a completely miscible alloy in solid and liquid phases. Therefore, it is feasible to prepare Fe-V alloy in this way. Experimental studies have been made in this work systematically and comprehensively for the effect of raw material ratio on metal recovery rate as well as the impact of adding Na2CO3 and coke on the microstructure and performance of the alloy. The results indicate that the addition of high-iron red mud can improve the basicity of the mixture, and Na2CO3 can improve the reduction conditions of Fe2SiO4 and FeAl2O4, which is beneficial to improving the reduction efficiency of the reaction system. When the addition amounts of Na2CO3 and coke are 8wt% and 30wt%, respectively, the recovery rate of Fe and V in the raw material is the highest. Furthermore, V can promote the pearlite transformation during the solidification, which improves the mechanical properties of the alloy. This work is able to provide a new and reasonable pathway for high value utilization of vanadium slag.
    Preparation and electrochemical properties of perovskite-type La(Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)O3 high-entropy oxide
    Xia SHAO Yanggang JIA Jie CHENG Daolai FANG Aiqin MAO Jie TAN
    The Chinese Journal of Process Engineering. 2023, 23(5):  771-780.  DOI: 10.12034/j.issn.1009-606X.222242
    Asbtract ( )   HTML ( )   PDF (11914KB) ( )  
    Related Articles | Metrics
    Perovskite-type (ABO3) oxides have attracted great attention as one of the most promising energy storage materials owing to the advantage of good electric conductivity and electrochemical activity. However, severe volume change for conventional metal oxides during the electrochemical reaction processes is likely to result in severe polarization of the electrodes and inferior kinetic properties as well as fast capacity fading. Transition-metal-based high-entropy oxides (HEOs) are an emerging kind of single-phase solid solution materials, which exhibit improved lithium storage properties and excellent cycling stability due to the multi-principal synergistic effect and entropy stabilization. In this work, transition metal-based perovskite-type La(Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)O3 HEO lithium-ion batteries (LIBs) anode material are prepared by solid-state reaction method and compared with the conventional binary perovskite-type LaCoO3. The crystal structure, microstructure, and elemental composition of HEOs are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) in detail. The electrochemical properties of LIBs anode are elucidated. XRD results show that the impurity phase in the perovskite structure disappears gradually and the crystallinity increases with the increase of reaction temperature from 750℃ to 950℃ and sintering time from 30 min to 4 h. SEM/EDS results confirm the as-synthesized spherical powder has a homogeneous distribution throughout the entire particle at the micrometer level. The electrochemical performance study illustrates that the La(Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)O3 anode material delivers higher specific capacity, excellent cycle stability, and rate performance than LaCoO3 mainly due to the entropy-stabilized crystal structure and the multi-principal synergistic effect. The reversible specific capacity of La(Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)O3 is 331 mAh/g after 100 cycles at 200 mA/g currrent density, which is fairly approximate to the theoretical capacity of 332 mAh/g, while the reversible specific capacity of LaCoO3 is only 185 mAh/g. Moreover, the capacity retention rates of La(Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)O3 and LaCoO3 are 72.5% and 61.6% at 1000 mA/g. This strategy on high entropy chemistry not only opens new insights into the development of advanced electrode materials but also provides a new design concept and strategy for the low content cobalt or free cobalt direction of electrode materials.
    Efficiently CO2 capture by superbase ionic liquid-amine-water blending solvents
    Kaixuan WANG Tao LI Yu LI Yinge BAI Shaojuan ZENG Baozeng REN Xiangping ZHANG Haifeng DONG
    The Chinese Journal of Process Engineering. 2023, 23(5):  781-789.  DOI: 10.12034/j.issn.1009-606X.222175
    Asbtract ( )   HTML ( )   PDF (1539KB) ( )  
    Related Articles | Metrics
    The increasing carbon dioxide (CO2) emissions have a serious impact on climate change. As one of the most important technologies for achieving carbon emission reduction, CO2 capture has attracted widespread attention from academia and industry. Chemical absorption is an effective and suitable CO2 capture technology for low CO2 partial pressure areas, such as flue gas. The commonly used flue gas CO2 capture method in industry is the monoethanolamine (MEA) absorption method, which has the advantages of mature technology, simple operation, and high absorption rate, but the disadvantages are high energy consumption for regeneration and easy degradation of absorbent. The development of an efficient, low-energy, and environmentally-friendly absorbent has been a difficult and hot research topic in this field. As a class of green solvents, ionic liquids (ILs) provide a new opportunity for CO2 capture due to their tunable structure, fast reaction rate, and high absorption capacity, and have become a promising solvent for CO2 capture. However, the low CO2 absorption capacity of conventional ILs and the high cost and viscosity of functionalized ILs have limited the industrial application of ILs in CO2 capture. ILs mixed with organic amine are a potential CO2 capture solvent, which can not only maintain high absorption capacity but also avoid the problem of viscosity and high cost. In this work, a superbase IL (1,8-diazabicyclo[5,4,0]undec-7-ene imidazole, [HDBU][Im]) was mixed with MEA to obtain IL blending solvents to improve the CO2 absorption capacity of the absorbent and reduce the viscosity of the solvent after absorption. The effects of IL concentration, absorption temperature, and CO2 partial pressure on the CO2 capture performance of the IL blending solvents were investigated, and the physical properties, such as density and viscosity of the IL blending solvents under different CO2 absorption capacities were analyzed. The results showed that 30wt% MEA+10wt% [HDBU][Im] had a better absorption capacity, and at the temperature of 40℃, the CO2 absorption capacity was 0.1453 g CO2/g solvent, and the viscosities before and after CO2 absorption were 2.312 and 4.303 mPa?s, respectively, which were significantly lower than those of IL absorbents. Therefore, it is a promising absorbent for CO2 capture.
    Multimodal process fault monitoring of LNS-PCA based on local information
    Zhongshuai YUAN Sitong SUN
    The Chinese Journal of Process Engineering. 2023, 23(5):  790-798.  DOI: 10.12034/j.issn.1009-606X.222183
    Asbtract ( )   HTML ( )   PDF (1476KB) ( )  
    Related Articles | Metrics
    Led by market demand, the industrial process needs to switch to a variety of working modes, the industrial process detection system is becoming more and more complex, and data often presents the characteristics of the multi-mode complex distribution. It is of great significance to study multi-mode fault detection technology for ensuring the safe operation of industrial processes. The statistical process control method represented by principal component analysis (PCA) is a typical fault detection method based on the data drive. It is widely used to analyze whether there is a fault in the production process through the data collected by the system, which does not depend on prior knowledge and mathematical model. However, it requires that the data must conform to the Gaussian distribution, which cannot be satisfied in the multi-mode production process. To improve the performance of industrial process fault detection and eliminate the multi-modal and non-Gaussian characteristics of data, this work proposes a multi-mode process fault monitoring method based on local information LNS-PCA (LLNS-PCA). Firstly, the Gaussian mixture model (GMM) was used to divide the sample into several local samples. Secondly, for each sample data, the mean and variance of the local sample are standardized to make the data follow the Gaussian distribution. Finally, the data of each local sample were combined and PCA model was trained to obtain T 2 statistics and SPE statistics for fault monitoring. The LLNS-PCA algorithm was validated with numerical examples and penicillin production data as training samples. Under the same conditions, PCA, KPCA, and LNS-PCA are used to detect anomalies. The results showed that the LNS-PCA based on local information proposed in this work has a better detection effect. In conclusion, LLNS-PCA was superior to PCA, KPCA, and LNS-PCA, which was worth promoting.