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    28 January 2023, Volume 23 Issue 1
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    Contents
    Cover and Contents
    The Chinese Journal of Process Engineering. 2023, 23(1):  0. 
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    Review
    Exploitation and utilization of fluorite and its strategic significance
    Danxian ZHANG Jianhua KANG Hongjun HUANG Wenxia ZHU Ruolin WANG
    The Chinese Journal of Process Engineering. 2023, 23(1):  1-14.  DOI: 10.12034/j.issn.1009-606X.221373
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    Fluorite, as an important non-renewable non-metallic strategic mineral resource, has been valued by many countries. With the rapid development of science and technology and the national economy, its economic value and strategic position are increasingly prominent. In recent years, the fluorine chemical industry chain has been deepening, and the demand for fluorite resources has increased sharply. Due to the limited reserves of fluorite resources, uneven distribution of resources, trade protectionism, and anti-globalization forces, the global fluorine chemical industry is highly concentrated and highly monopolized. And there are great differences in the economic development, clean and efficient utilization of fluorite resources, and intensive processing technology in different countries and regions, which have a serious impact on the supply and demand of fluorite products and consumption patterns, and intensify the contradiction between fluorite resource reserves and the development of fluorite industry. In this review, the resource reserve, main industrial structure, the consumption structure of supply and demand, and clean utilization technology aspects in detail elaborated on the economic status and the strategic significance of fluorite resources. It is proposed to ensure the global strategic layout of fluorite resources by strengthening the reorganization of fluorite resources, clean and efficient utilization, deep processing technology and equipment research and development, high-end product manufacturing, etc. To further promote the development of the fluorite industry towards the direction of fine, complex, lightweight, environmental protection and energy-saving, recycling economy fluorite chemical products application field and high-tech industry application research and development, ensure the reserve and supply of fluorite resources, achieve the optimal allocation of global fluorite resources and the healthy and sustainable development of fluorite industry.
    Research progress on gas-liquid two-phase flow characteristics of bubble plume
    Xin DONG Yinuo LIU Chen YE Jianwei ZHANG Ying FENG
    The Chinese Journal of Process Engineering. 2023, 23(1):  15-24.  DOI: 10.12034/j.issn.1009-606X.222021
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    Bubble plume is a complex gas-liquid two-phase flow, which is widely used in industrial fields such as wastewater treatment, petroleum processing, environmental protection. The complex flow characteristics of bubble plume are very important for gas-liquid mass, momentum transfer and its industrial application. In this work, the flow characteristics of bubble plume in theoretical and experimental research are analyzed and summarized. The effects of different operating and structural parameters on the hydraulic characteristics such as gas holdup, bubble size distribution, plume width and oscillation are discussed. The simulation methods of observing and capturing the flow characteristics of bubble plume are summarized. In addition, due to the wide application of bubble plume, it is also very important to measure the bubble velocity distribution quickly and accurately. With the rapid development of digital image recognition technology, the combination of high-speed camera and digital image recognition technology provides an effective, intuitive and accurate method for bubble plume velocity. The prediction models and empirical formulas of hydraulic parameters such as gas holdup and bubble diameter are summarized, and the different applicable conditions of the models and formulas are listed. In the practical application of bubble plume, the structural morphology and flow characteristics of bubble plume change due to the complexity of environmental fluid (such as transverse flow in environmental fluid and stratification due to density and temperature difference of environmental fluid). Therefore, the research progress of gas-liquid two-phase flow characteristics of bubble plume in complex environment fluid is presented. The variation of bubble plume flow pattern and the effect of plume destratification in stratified fluid are summarized. The migration behavior and motion of plume in transverse flow environment are analyzed. Finally, the limitations of research methods and theoretical methods of gas-liquid two-phase flow characteristics of bubble plume are discussed. The multi-scale research direction of bubble plume motion law is proposed in further.
    Application progress of coal petrology in coking coal blending and coal blending optimization technology
    Yan WANG Chengwei YANG Dongying YUAN Yuhong ZHANG Sijian QU
    The Chinese Journal of Process Engineering. 2023, 23(1):  25-37.  DOI: 10.12034/j.issn.1009-606X.222343
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    Scientific and reasonable coal blending technology was very important for the high-quality development of coking enterprises. The core of coking coal blending technology lied in the in-depth understanding of the coal quality characteristics of raw coal. The main factors affected the properties of coking coal include metamorphic degree, maceral composition and third genetic factor-fluorescence characteristics. Therefore, coal petrology was very important for the research and application of coking coal blending technology. This review discussed the development status of three coking coal blending technologies, such as experience coal blending, maceral coal blending and artificial intelligence coal blending, and summarized the overall development trend of coking coal blending technology. Combined with the author's research practice, the application status of coal petrological indexes in coking coal blending was mainly combed. While paying attention to the characteristics of maceral, it also took into account the characterization of coking coal by relevant parameters such as process indicators. In practical application, the selection and utilization of various index parameters need to comprehensively consider the parameter adaptation range and respect the true correspondence of coking coal. Based on the above content, the overall idea of associating geological factors and process indexes such as coal-forming age, producing area, caking index and gum layer index was put forward to realize the scientific and in-depth correlation between coke performance and raw coal characteristics, and to construct a new coal blending technology system of origin-process-result. By summarizing the key role of maceal in coking coal blending and its application status, the manuscript pointed out the development trend of typical coking coal blending technology, and put forward a new system of optimized coal blending technology based on maceral+fluidity, so as to establish a reliable evaluation system for coal blending and coking industry and better meet the market demand.
    Research Paper
    Experimental research on heat transfer of microencapsulated phase change materials slurry containing GO in circular tube
    Jinli LU Xingyu CHEN Yafang HAN Yanhong SUN Zijie YIN Li WU
    The Chinese Journal of Process Engineering. 2023, 23(1):  38-45.  DOI: 10.12034/j.issn.1009-606X.221429
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    Phase change energy storage technology can solve the problem of energy mismatch in time and space due to the latent heat absorption or release in phase change process. It has a wide application in solar energy utilization, building energy saving, waste heat recovery, and other fields. However, the phase change material has leakage problem in the process of use, so the phase change material is encapsulated and mixed with the single-phase fluid to prepare the microencapsulated phase change materials slurry (MPCMS). Furthermore, due to the high thermal conductivity properties of graphene oxide (GO), it was added to MPCM to improve the thermal conductivity of suspension prepared from GO as the substrate, thus further enhancing heat transfer. In this work, the heat transfer characteristics of pure water, 5wt% mass fraction of traditional MPCMS, 5wt% and 10wt% mass fraction of graphene oxide composite microencapsulated phase change material suspension (GO-MPCMS) were tested. And the effects of wall heat flux and Reynolds number (Re) on temperature distribution and heat transfer were analyzed and discussed. The results showed that, the temperature distribution of the tube wall and fluid presented the changing law of rised first, then stay flat and then rised again due to the influence of the phase change process. And under the same experimental conditions, the wall temperature and fluid temperature of suspension were lower than pure water. Both particle mass fraction and GO had great influence on heat transfer. With the same mass fraction (5wt%), the stable local Nusselt number (Nux) can be further increased by 8 percentage point when GO was added, and the Nux increased 20 percentage point when the particle mass fraction was increased from 5wt% to 10wt%. Compared with pure water, considering the influence of GO and microencapsulated particles, the average Nusselt number (Nu) of microencapsulated phase change material suspension can be increased by 1.0~2.0 times under the same experimental conditions.
    Numerical simulation optimization of flow characteristics and structure of microalgae column photobioreactor
    Binhua YE Fei HAN Xiangxing SHI Yonggang JIAO Qingyun ZHAO Kaiqiang ZHONG
    The Chinese Journal of Process Engineering. 2023, 23(1):  46-56.  DOI: 10.12034/j.issn.1009-606X.221394
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    As the most potential renewable biomass energy, microalgae has significant advantages in the fields of biological carbon sequestration and biofuel production, which contributes to the realization of carbon peak and carbon neutrality goals. The cultivation efficiency of microalgae can be greatly improved by improving the performance of the aeration device of the reactor. In this work, the spherical aeration structure of the columnar photobioreactor was optimized by numerical simulation. The Euler model and k?ε model were used for the simulation and turbulence model, respectively. The changes of gas holdup, liquid velocity, turbulent kinetic energy, and the flow field in the photobioreactor under different aeration conditions were studied and analyzed. The results showed that the change in the structure of the aeration device had a great impact on the flow characteristics in the photobioreactor. When the aeration device was aerated into the reactor, the gas holdup, liquid velocity, and turbulent kinetic energy increased with the increase of the aeration rate and decreased with the increase of the aeration pore size. According to all relevant parameters, when the total aeration rate was 1400 mL/min, the number of aeration pores was 50, and the aeration pore size was 30 μm, the aerator had the best performance. At this time, the measured gas holdup was 68.6%, the liquid velocity was 0.905 m/s, and the turbulent kinetic energy was 0.149 m2/s2. The numerical simulation provided an effective way to optimize the aeration structure parameters, which benefited the photobioreactor design for microalgae cultivation and sewage treatment associated with CO2 fixation.
    Effect of inlet velocity on flow pattern evolution and flow distribution characteristics in discontinuous microchannels
    Xinsen YUAN Junfei YUAN Lin WANG He JIANG Yifei CAO
    The Chinese Journal of Process Engineering. 2023, 23(1):  57-66.  DOI: 10.12034/j.issn.1009-606X.222024
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    The law of gas-liquid two-phase flow in microchannel is the main factor affecting the heat transfer coefficient and flow field temperature uniformity of microchannel heat exchanger. Using N2 and H2O as working fluids, the initiation, development, and stability of gas-liquid two-phase flow pattern in discontinuous and parallel rectangular microchannel heat exchangers and the uneven flow distribution in parallel channels are numerically simulated. The results show that the inlet Re of the two-phase working medium has an important influence on the evolution process and flow cycle of the flow pattern in the microchannel: when the inlet Re is 450, the gas phase working medium diffuses into the microchannel in a discrete "bulk" shape in the flow sharing cavity, and the gas phase working medium in the parallel channel gradually changes from a slug shape to a bubble shape; When the inlet Re rises to 1600, the gaseous working medium diffuses into the microchannel in a continuous "elliptical" shape in the flow sharing cavity, and the gaseous working medium in the parallel channel gradually changes from annular flow pattern to bubble flow pattern. The channel structure also affects the uniformity of flow distribution between parallel channels. The existence of discontinuous microcavity improves the uniformity of working medium mass flow distribution in the microchannel by 38.7%. By studying the pressure distribution law in the channel, it is found that the uneven distribution of static pressure in the channel is an important reason for the uneven distribution of two-phase working medium when entering the microchannel from the flow sharing cavity. By changing the inlet structure to ensure the uniform distribution of static pressure in each channel, combined with the discontinuous microcavity between continuous channels, the temperature uniformity of flow field can be better guaranteed and better heat transfer performance can be obtained.
    Design of gas wave ejector pressure ports and its impact on performance
    Yiming ZHAO Minghao LIU Haoran LI Dapeng HU
    The Chinese Journal of Process Engineering. 2023, 23(1):  67-77.  DOI: 10.12034/j.issn.1009-606X.221400
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    Using the excess energy of a high-pressure fluid to pressurize a low-pressure fluid for achieving full utilization of pressure energy satisfies the energy-saving, low-carbon, and environmentally-friendly process engineering requirements at present. Therefore, the gas wave ejector (GWE) has a wide range of applications in many industrial processes as a device that can efficiently realize the above-mentioned comprehensive energy utilization process. Because GWE transfers energy through pressure waves formed during the connecting and closing of wave rotor passages to the pressure ports, the proper design of pressure ports distribution positions is the precondition for the device's efficient operation. The design method of pressure ports based on the wave system theory is described, and the influence mechanism of port positions on equipment performance is determined using a combination of three-dimensional numerical simulation and experiment. The results suggest that the equipment performance can reach the optimal value once the port positions satisfy the design method. However, when the port position deviates from the design values, the emergence of adverse effects such as backflow of medium-pressure gas and insufficient low-pressure gas intake result in the equipment performance declining. Due to the different impact mechanisms of different port positions on performance, the function degradation caused by port location deviation is also different. The following four conditions can lead to significant performance degradation: opening the medium-pressure port too late or closing it too early, and opening the low-pressure port too late or closing it too early. These situations should be avoided during GWE design and manufacturing. The presented research results enrich the parameters design theory of GWE, and have important guiding significance for the research and application of this equipment.
    Characteristics of light-assisted self-coupling algae-bacterial granular sludge treatment system
    Qi CHENG Chengda HE Miao ZHANG Yu XUE
    The Chinese Journal of Process Engineering. 2023, 23(1):  78-87.  DOI: 10.12034/j.issn.1009-606X.221349
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    Self-coupled microalgae-bacterial granular sludge (algal-bacterial granular sludge, ABGS) is a new type of granular sludge. Through the symbiosis of algae and granular sludge, it not only solves the problem that the algae suspension growth is difficult to collect and treat, but also can use the photosynthesis of algae to provide oxygen for aerobic granular sludge, saving a lot of energy consumption. It provides new ideas for solving the problem of excessive energy consumption in sewage plants. Under the background that greenhouse gases have become a serious threat to the ecological environment, to explore when the light-assisted self-coupling algae-bacterial granular sludge treatment system achieves the best treatment effect, the amount of aeration required by the system. In this work, the cultivation process of the system was first described, and then the treatment effect of the system under the condition that algae oxygen supply completely replaced aeration (zero aeration) was investigated. Finally, the treatment effect of the system under the condition of appropriately increasing different aeration rates (0.2, 0.4, 0.6, 0.8 L/min) was explored. The results showed that after 12 h of treatment under zero aeration conditions, the effluent COD, total phosphorus, and total nitrogen concentrations decreased to 76.70, 1.09, and 3.52 mg/L, respectively. The concentration of each index had an obvious downward trend, and the effluent can meet the standard by continuing to increase the hydraulic retention time, but the processing cost will increase accordingly. Therefore, it was necessary to appropriately increase aeration to improve the efficiency of sewage treatment. Compared with several different aeration conditions at the level of one-tenth of the aeration required by the aerobic granular sludge treatment system, under the condition of 0.2 L/min aeration rate, the effect of each effluent index of the system reached the best. The concentrations of COD, total phosphorus, and total nitrogen were reduced to 25.6, 0.40, and 1.67 mg/L, respectively. Therefore, 0.2 L/min was the optimal aeration rate of the system, which can bring considerable effects to the energy saving and emission reduction of the sewage plant while ensuring the treatment effect.
    Bioreduction and biomineralization of indigenous bacteria for the remediation of uranium-contaminated groundwater
    Guohua WANG Ying LIU Jiali WANG Jinjing XIANG Yingjiu LIU Fa ZHAO Jinxiang LIU
    The Chinese Journal of Process Engineering. 2023, 23(1):  88-97.  DOI: 10.12034/j.issn.1009-606X.222013
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    In recent years, microbial technology for remediation of uranium-contaminated groundwater has attracted the attention of scholars, because of its advantages of low cost, self-reproduction, no ease to cause secondary contamination, and less disturbance to the environment. The mechanisms of microbial remediation include biosorption, bioaccumulation, bioreduction, and biomineralization. Among them, bioreduction and biomineralization were two promising methods that could be utilized in situ shortly. Previous studies had shown that adding organophosphate compound to uranium-contaminated groundwater may give rise to remediation mechanisms such as bioreduction and biomineralization. To explore the coupling mechanisms of these two methods mediated by the indigenous microorganism, β-glycerol phosphate disodium salt was added in this study to stimulate the indigenous microorganism to treat neutral artificial uranium-containing groundwater. In the control group, glycerol was added to stimulate the bioreduction activity of the microbes only. The results showed that the removal rate of uranium in the experimental group was more than 98%, and the removal efficiency and effect were better than that of the control group under the same condition. After 21 days of the experiment, the scale-like precipitation on the cell surface could be observed via SEM. XRD analysis confirmed that the products were CaU(PO4)2 and Mg(UO2)2(PO4)2?10H2O, which possessed excellent resistance against reoxidation. XPS also indicated the presence of U(IV) and U(VI) in the products. Mechanism analysis showed that β-Glycerol phosphate disodium salt activated both bioreduction and biomineralization microbial community. Dysgonomonas, Propionispora, Macellibacteroides, unclassified_Rhizobiaceae and unclassified_Rhodocyclacea may be involved in the reduction of U(VI), NO3-, and SO42-, and Acinetobacter facilitated the process of biomineralization. while Methyloversatilis and unclassified_Enterobacteriaceae may take part in the reduction of U(VI)-phosphate minerals. In the early stage of the reaction, bioreduction and biomineralization were both involved in the immobilization process, and biomineralization was the main mechanism. Subsequently, the formed U(VI) precipitate was gradually reduced to U(IV) precipitate by microorganisms. This work would provide a new theoretical insight for the research on the long-term stability of bioremediation of uranium-contaminated groundwater in the future.
    Preparation of enhanced vanadium phosphorus oxide catalysts by alkaline earth metal-alcohols deep eutectic solvents
    Xingsheng WANG Zhi CHANG Liuzhu WU Manyuan ZHANG Ruirui ZHANG Ruixia LIU
    The Chinese Journal of Process Engineering. 2023, 23(1):  98-106.  DOI: 10.12034/j.issn.1009-606X.222040
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    Vanadium phosphorus oxide (VPO) catalysts are the only industrial catalyst for the selective oxidation of n-butane. Doping with metal additives and modulation with organic additives are effective means to improve the performance of VPO catalysts. In this work, the simultaneous organo-metallic modification was achieved by adding magnesium chloride-alcohols deep eutectic solvents (MgCl2/alcohol) during the synthesis of VPO catalyst precursors. The VPO precursors and catalysts were analyzed by scanning electron microscope (SEM), BET automatic specific surface and porosity analyzer (BET), X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FT-IR), Raman spectrometer (Raman) and X-ray photoelectron spectroscopy (XPS), et al. The effect of deep eutectic solvents with different hydrogen bond donors about ethylene glycol (EG), 1-4 butanediol (BDO), and glycerol (GL) on VPO catalysts was investigated. The microscopic morphology, specific surface area, physical phase, surface properties, and crystalline phase transition temperature of VPO precursors as well as catalysts were analyzed in detail. The performance of VPO catalysts was evaluated in the fixed bed reactor for n-butane oxidation selectivity to maleic anhydride. The results showed that the introduction of deep eutectic solvent MgCl2/EG in the synthesis of VPO catalyst precursors can modulate the morphology and crystalline phase composition, thus improving the catalyst performance. The use of MgCl2/EG to modulate the preparation of VPO precursors can obtain catalysts with better dispersion, larger specific surface area, the highest total acid, and a number of active surfaces. VPO-MgCl2/EG catalysts had good dispersion, large specific surface area, a high number of active surfaces (020), enrichment of surface P atoms, and low average valence state of surface V. Furthermore, (VO)2P2O7 and VOPO4 crystalline phases synergistically improved the performance of VPO-MgCl2/EG catalysts. In conclusion, VPO-MgCl2/EG exhibited excellent catalytic performance in the reaction of n-butane oxidation selectivity to maleic anhydride, which provides a new idea for the preparation of VPO catalysts.
    Recycling of scrap lead paste to prepare lead powder by high efficiency electrolysis in choline chloride-ethylene glycol deep eutectic solvent
    Haoming HUANG Juanjian RU Yixin HUA Xiao GENG Wenwen ZHANG Mingqiang CHENG Daoxiang WANG
    The Chinese Journal of Process Engineering. 2023, 23(1):  107-114.  DOI: 10.12034/j.issn.1009-606X.221422
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    As a clean energy source without pollution during use, lead-acid batteries have received close attention. However, lead-acid batteries contain a large amount of polluting heavy metals, and random disposal will pollute the environment and affect the ecological balance. In industry, the recovery of scrap lead paste (SLP) is usually treated by pyrotechnics, but it consumes a lot of energy and also produces pollutants such as sulfur dioxide and lead dust. In view of the existing problems, finding new recycling processes has become a research hotspot. Deep eutectic solvents (DESs) are a new generation of green solvents and have received more and more attention in recent years. Because of their good thermal stability and wide electrochemical window, DESs are widely used in the fields of metal extraction and material preparation. In this work, the recycling of scrap lead paste to prepare lead powders by electrolysis is discussed in choline chloride-ethylene glycol deep eutectic solvent (ChCl-EG DES). Firstly, the phase composition of the scrap lead paste is analyzed by XRD, and the quantitative analysis of the scrap lead paste using Jade software shows that it mainly exists in the form of lead dioxide with a small amount of lead sulfate at the same time. And then, the electrochemical behavior of lead ion in 30 g/L SLP+ChCl-EG solution is investigated by cyclic voltammetry. The phase composition and microscopic morphology of the deposit product at different temperatures are examine using XRD and SEM techniques. The experimental results show that when scrap lead paste is added, Pb(IV) can be reduced preferential to Pb(II) due to the reducibility of ChCl-EG DES. Cyclic voltammetry indicates that the reduction of scrap lead paste to metal lead is a quasi-reversible process in ChCl-EG DES. The constant voltage deposition experiment show that when the temperature rises from 323 K to 363 K, the current efficiency rises from 67.26% to 96.06% and the specific energy consumption decreases from 961.57 kWh/t to 673.28 kWh/t. XRD and SEM results demonstrate that the deposit products obtained at different temperatures are pure metallic lead powders and their microscopic morphology are mainly rod-shaped and slight acicular.
    Acidification process and kinetics of silicon slag from aluminum fluoride production
    Yijun AI Tingting LI Jupei XIA
    The Chinese Journal of Process Engineering. 2023, 23(1):  115-123.  DOI: 10.12034/j.issn.1009-606X.222009
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    Silicon slag is a kind of solid waste produced in the reaction between fluorosilicate and aluminum hydroxide when aluminum fluoride is produced by fluorosilicate method. Aluminum fluoride is mainly used as auxiliary solvent in electrolytic aluminum industry in China and the demand is huge. Therefore, a large number of silicon slag wastes are produced. Enterprises usually store silicon slag by stockpiling, resulting in large land occupation and environmental pollution. Silicon slag contains valuable elements which can be reused is a protection of resources. In this work, a silicon residue in Yunnan Province is used as the research object. The silicon residue is acidified by concentrated sulfuric acid and the leaching rate is calculated according to the residual amount of aluminum and fluorine after acidification. A single-factor experimental scheme for the acidification process of silicon slag is designed by studying the effects of acid dosage, reaction temperature and reaction time in the acidification process of silicon slag. The phases of silicon slag, acid slag and final product are analyzed by XRD. The results show that when concentrated sulfuric acid with 1.3 times the amount of theoretical acid (23.66 g) is added, the reaction temperature is 170℃ and the reaction time is 90 min, the leaching rate of aluminum is greater than 99%, the leaching rate of fluorine is greater than 97%, and the purity of SiO2 is rapidly increased to more than 99.00%. The acidification process of silicon slag is studied by kinetic experiments. The results show that the acidification process of silicon slag conformed to the shrinking unreacted core model in the liquid-solid multiphase reaction. The activation energy of the reaction is 62.97 kJ/mol and the leaching process is controlled by chemical reactions. The proposed method provides a new idea for the utilization of silicon slag, which has the advantages of short reaction time, less water consumption and high leaching rate of valuable elements after acidification.
    Thermodynamic model for calculating sulfur distribution ratio between Na2O-TiO2-SiO2-CaO-Al2O3-V2O5-MnO-MgO-FeO slags and hot metal
    Xuejie YIN Desheng CHEN Lina WANG Hongxin ZHAO Yulan ZHEN Tao QI Meng WANG
    The Chinese Journal of Process Engineering. 2023, 23(1):  124-135.  DOI: 10.12034/j.issn.1009-606X.222055
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    A model for the action concentrations calculation of structural units in Na2O-TiO2-SiO2-CaO-Al2O3-V2O5-MnO-MgO-FeO slags and a thermodynamic model of the sulfur distribution ratio between slag and hot metal have been developed based on the ion-molecule coexistence theory (IMCT), and the model was verified by sodium oxide smelting experiments. The theoretical calculation results showed the composition of the main structural units and the activities of Na2O, CaO, MnO, MgO, and FeO in slag at 1200℃. The formation of compounds with a low melting point can be promoted by the addition of Na2O, meanwhile, the content of substances with high melting points decreases, which led to a decrease in the melting temperature of slag and the improvement of dynamic conditions of desulfurization reaction. Besides, the activities of Na2O and CaO increased with the increase of Na2O, thereby the activity of S2? decreased, and the desulfurization reaction between slag and hot metal can also be enhanced. The experimental results revealed that the sulfur distribution ratio between slag and hot metal improved by the increase in RN/C, which was beneficial to the deep desulfurization process of hot metal, and the sulfur can be removed to less than 0.0005wt%. The theoretical calculation results of the sulfur distribution ratio were in good agreement with the experimental results, which indicated that the sulfur distribution ratio can be well predicted by the model during the sodium oxide smelting process. The sulfur distribution ratios of basic oxide in the slag increased with the RN/C increasing and were ranked as Na2O>CaO>MnO>FeO>MgO. The IMCT was successfully applied to the investigation of the mechanism for the desulfurization reaction process between slag and hot metal in the Na2O-TiO2-SiO2-CaO-Al2O3-V2O5-MnO-MgO-FeO slags, which provided a theoretical basis for the optimization of slags in the deep desulfurization process of hot metal.
    Study on the mechanism of enhanced Ga electrodeposition on three-dimensional porous electrodes
    Ling LIU Chuchu CAI Binxin DONG
    The Chinese Journal of Process Engineering. 2023, 23(1):  136-143.  DOI: 10.12034/j.issn.1009-606X.222200
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    Ga is usually extracted from alkaline solution with low Ga concentration by electrodeposition method in industry, where the hydrogen evolution side reaction and low mass transfer rate are the main reasons for the low current efficiency. In this work, three-dimensional porous electrodes were applied for Ga electrodeposition on account of their high surface area. The hydrogen evolution characteristics of the different electrode materials (foam metal and porous carbon) were studied. And on this basis, Ga electrodeposition behavior of each material under different electrolysis temperatures and current density was researched. The results showed that Cu foam and graphite felt (GF) had low hydrogen evolution activity, but the electrodeposition performance of Ga on the two electrodes was very different. The current efficiency (QE) of Cu foam at 40℃ and 0.1 A/cm2 was 22.5%, which was much higher than that of Cu plate (10.7%). Under the same conditions, the QE value of GF electrode was only 9.6%, which was lower than that of Cu plate and would be related to the hydrophobicity of the electrode surface. The electrodeposition behavior of Ga on electrodes with high hydrogen evolution activity (Fe foam, Ni foam, and reticulated vitreous carbon) was greatly affected by electrolysis temperature and current density. At high current density, the Fe foam electrode showed a QE value only second to that of Cu foam, and Ga electrodeposition was difficult to occur at low current density. The electrodeposition of Ga occurred only below the melting point of Ga (20℃) at Ni foam and reticulated vitreous carbon (RVC) electrodes, but it was difficult to occur at 40℃ above the melting point of Ga due to the high activity of the electrodeposited liquid Ga. Therefore, the hydrogen evolution activity of the electrode materials had a great influence on Ga electrodeposition. The key factors affecting the current efficiency of Ga electrodeposition included electrolysis temperature, current density, and hydrophilicity of the electrode surface.
    Rigorous modelling and energy performance evaluation for PDH reaction gas separation and hydrogen purification
    Xuantong LU Jin ZHAO Chun DENG
    The Chinese Journal of Process Engineering. 2023, 23(1):  144-153.  DOI: 10.12034/j.issn.1009-606X.221334
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    Propane dehydrogenation is one of the main processes for propylene production and its reaction gas components are complex, containing products from main reactions and by-product components such as CO2 and CO from side reactions. To obtain polymer grade propylene and purified hydrogen product with a purity of more than 99.90 mol/mol, the separation process of the reaction gas of propane dehydrogenation and the recovery of hydrogen from hydrogen-rich tail gas is modeled and simulated in the Aspen software. The process includes main modules such as MEA decarburization, compressed cryogenic separation, deethanization, propylene distillation and pressure swing adsorption. The CO2 contained in the reaction gas would affect the purity of the propylene product, and it is difficult to remove in the cryogenic process. Thus the CO2 is first removed by the MEA solvent absorption. The reaction gas after decarburization and dehydration enters the deethanizer and the propylene distillation unit, and the hydrogen-rich tail gas enters the pressure swing adsorption unit for further purification. In order to reasonably utilize the energy of the propylene distillation tower, the heat pump distillation process is adopted for the energy integration. Compared with conventional distillation, the energy consumption of propylene heat pump distillation is lower. Sensitivity analysis and optimization of process parameters for hydrogen recovery by pressure swing adsorption are carried out to improve economy and energy efficiency. For the two-bed four-step pressure swing adsorption process, the effects of adsorption pressure, adsorption time and purge ratio on the purity and recovery of hydrogen products are analyzed, and the optimal operating conditions are determined. The simulation results show propylene and hydrogen products meet the requirements. The energy consumption per unit product is 267.46 kg standard oil/t propylene product and 474.44 kg standard oil/t hydrogen product. It has a certain reference significance for the simulation of the actual propane dehydrogenation reaction gas separation process and energy consumption estimation.
    Research and optimization on battery thermal management system with refrigerant cooling based on mini-channels
    Xiaojun WANG Hengyun ZHANG Xinghua HUANG Kang LI
    The Chinese Journal of Process Engineering. 2023, 23(1):  154-162.  DOI: 10.12034/j.issn.1009-606X.222043
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    The small-scale vapor compression system based on a mini-channel heat sink was investigated in this work for battery thermal management. The single-factor experiment was carried out to determine the optimal refrigerant charge of the refrigerant cooling battery thermal management system. Based on the optimal refrigerant charge, the influence of different system parameters on thermal management performance was examined. Finally, the system problem was optimized, and the solution was proposed and verified by simulation software. Taking the coefficient of performance (COP) as the performance index, the optimum refrigerant charge of this system was 250 g, which was applied in the following experiments. Then the heating power of the battery module was fixed and the opening of the expansion valve (OEV) was adjusted to investigate the influence of OEV on cooling performance. The result showed that with the increase of OEV, the heat transfer coefficient of the mini-channel heat sink increased continuously, but the battery temperature decreased first and then increased. Thus, there was an optimal OEV to obtain the best cooling effect of the system. The heating power of the battery module was changed, and then the OEV was adjusted to make the temperature of the battery reach the minimum under different heating power conditions. The result indicated that with the increase of heating power of the battery module, the outlet dryness of the mini-channel heat sink continuously decreased, the heat transfer coefficient of the mini-channel increased, and the temperature of the battery also increased. The variation of ambient temperature was simulated by altering the indoor temperature with an air conditioner. The study showed that though the increase in ambient temperature had an impact on the cooling effect, the battery temperature can still achieve sub-ambient cooling even at the high ambient temperature of 35℃. A scheme of increasing condensation area to reduce compressor exhaust temperature was proposed, and the model was built based on AMEsim software for verification. The model analysis showed that the method of increasing the heat transfer area of the condenser can effectively reduce the exhaust temperature and improve the heat transfer effect.