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    28 February 2023, Volume 23 Issue 2
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    Contents
    Cover and Contents
    The Chinese Journal of Process Engineering. 2023, 23(2):  0. 
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    Review
    Current application and development of microneedle
    Sibo ZHAO Yiru BAO Min XIE
    The Chinese Journal of Process Engineering. 2023, 23(2):  163-172.  DOI: 10.12034/j.issn.1009-606X.222114
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    Microneedles are micrometer sized single needles or needle arrays that are produced by microfabricating techniques. Microneedles could penetrate the stratum corneum layer of the skin to reach the dermal layer which is favorable for percutaneous drug delivery. Microneedles have a number of advantages in drug delivery, compared with oral administration, microneedles circumvent the metabolic effects of the digestive system on drugs, compared with injection needles, microneedles are able to reduce pain and improve adherence compliance in patients. Due to their special transdermal pathway and precise, convenient application methods, microneedle has also become a hot studies area in biomedicine at present and their applications in vaccination, tissue fluid extraction and biomarker detection, etc. have been well investigated. According to working mechanisms for percutaneous drug delivery, microneedles can be classified as five kinds, including solid, coated, dissolving, hollow, and hydrogel microneedles. This review, combined with relevant articles in the field of microneedle technology in recent years, provides a brief overview of the types and fabricating materials of microneedles, mainly introduces the current applications of microneedles in the field of drug delivery (such as insulin injection for diabetes treatment, local drug delivery for cancer treatment, vaccination, tissue fluid extraction and biomarker detection, etc.) Besides, if the microneedles would be widely applied in the marker for medical application, some factors including mechanic strength, biological safety, sterilization process and biological stability of biomolecules on the micrneedles should be well considered which are also discussed in the review. At last, outlooks on microneedles' future development are prospected, such as developing microneedles based drug delivery system for heart attack treatment, improving biological stability of the biological molecules on the microneedles for convenient vaccination, and combining of microneedles with other techniques, such as sensitive biomarker detection method, microfluidic chip and wearable device, which will open a new prospect for the development of microneedles techniques.
    Research progress on sodium storage mechanism and performance of anode materials for sodium-ion batteries
    Cheng HAN Shaojie WU Chaoyang WU Mingyang LI Hongming LONG Xiangpeng GAO
    The Chinese Journal of Process Engineering. 2023, 23(2):  173-187.  DOI: 10.12034/j.issn.1009-606X.222083
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    The massive use of fossil fuels is bound to cause irreversible damage to the global ecological environment. New energy sources such as solar, wind, and tidal have the advantages of being clean, non-hazardous, and renewable, and can be used to replace fossil fuels to alleviate the environmental crisis. The development and utilization of green energy have led to the rapid development of electrochemical energy storage and conversion technologies to store clean and renewable energy in the grid. Lithium-ion batteries, one of the most successful secondary ion batteries in energy storage, have been used in various electronic products, but expensive and scarce raw material resources limit their applications in the field of large-scale energy storage equipment. Therefore, the search for inexpensive secondary ion batteries with excellent performance is one of the hot research topics nowadays. As a new type of secondary ion battery, sodium-ion battery not only has a similar working principle as a lithium-ion battery but also features low cost, high resource abundance, and high reversible capacity. The extensive exploration by researchers is expected to make it a successful alternative to lithium-ion batteries for commercial production. This work mainly reviews the progress of the research on the performance of sodium-ion battery anode materials, firstly, the three mechanisms of sodium storage in the anode materials, namely the intercalation reaction, alloying reaction, and conversion reaction, are analyzed and summarized according to the different ways of sodium ion storage in the anode materials. Then, according to the performance of sodium-ion battery anode materials, three common modifications of anode materials are summarized: structural modification, elemental doping, and material compounding, and the electrochemical properties of anode materials before and after modification are compared. Then, the research status and problems faced by several key anode materials for sodium-ion batteries, such as carbon-based materials, titanium-based materials, alloy-based materials, conversion-based materials, and organic materials, are highlighted. Finally, the research directions of sodium-ion battery anode materials are prospected based on the actual production and industrial applications.
    Research Paper
    Lattice Boltzmann simulation of particle flow characteristics in porous media
    Yuntao CHENG Shuyan WANG Baoli SHAO Zihan YUAN Lei XIE
    The Chinese Journal of Process Engineering. 2023, 23(2):  188-198.  DOI: 10.12034/j.issn.1009-606X.222038
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    The migration and deposition of suspended particles within porous media is of great significance in many applications such as sewage treatment, pollutant purification and well drilling. Especially in the oil industry, the deposition of small particles in the reservoir may affect the recovery of crude oil. The structure of porous media is complex, making it difficult to understand the details of the flow field. Therefore, it is necessary to explore the phenomena and mechanism of suspended particle flow in porous media. The lattice Boltzmann method (LBM) is used to numerically simulate the flow characteristics of suspended particles in porous media. The skeleton particles and suspended particles are constructed by the finite size particle (FSP) method. The Half-Way bounce back format is adopted to realize the interactions between suspended particles and the fluid. By changing the inlet velocity of the liquid phase, porosity and particle diameter, the movement and deposition of suspended particles are analyzed. The simulation results show that the increase in the inlet velocity of the liquid shortens the migration trajectory of the suspended particles and improves the contact force of the particle. There are a large number of suspended particles clogging near the inlet of porous media. The particle retention time and the particle deposition rate decrease with the increase of the inlet velocity, while the granular temperature shows the opposite trend. Meanwhile, the granular temperature first increases and then decreases, and gradually tends to be stable with time passing by. The reduction of porosity strengthens the collisions between the suspended particles. The change of porosity from 0.581 to 0.400 increases the granular temperature by 9 times. As the porosity is enhanced, the particle axial velocity increases, while the particle contact force declines. The granular temperature is raised with the increase of the particle diameter, and the maximum value of the particle axial velocity can reach 11 times of the inlet velocity.
    Cavitation analysis and structure improvement of cage-typed control valve in coal liquefaction industry
    Chang QIU Ruibin GAN Yunfei LONG Qiang RU Jinyuan QIAN Zhijiang JIN
    The Chinese Journal of Process Engineering. 2023, 23(2):  199-206.  DOI: 10.12034/j.issn.1009-606X.221419
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    Aiming at the common cavitation problem of the cage-typed control valve in the coal liquefaction industry, based on the RANS equation, the mixture multiphase flow model and the Zwart cavitation model, a numerical simulation study of the cavitation flow inside the valve was carried out, and the main reason of the cage's failure was determined. Based on the pressure drop analysis and prediction of the cavitation position, a structural improvement scheme of the control valve's cage was proposed and verified. The results showed that the cavitation vapor in the control valve was concentrated in the inner orifice of the cage, which was the main reason for the obvious failure defects in the inner wall of the inner orifice and the cage. Based on the comparisions between pressure drop and cavitation vapor distributions on the horizontal cross section of the valve cage, the two reasons for the serious cavitation in the inner orifice of the cage were concluded. Firstly, the number of depressurization stages was not enough, which led to excessive pressure drop in the second stage, resulting in a local low pressure area, and cavitation occurs violently. Secondly, the depth of the inner orifice was too large, resulting in fully developed cavitation in the inner layer orifice of the cage. Thus, the structure improvement scheme was proposed to control the depressurization intensity and the occurrence area for cavitation development in the cage. By adjusting the straight orifice in the inner layer of the valve cage to stepped orifice, the adjustment from two-stage to three-stage depressurization was realized, which solved the problem of local low pressure area caused by excessive pressure drop, and effectively reduced the strength of cavitation initiation and the distribution range of cavitation. This work has a certain reference value for the design and research of the cage-typed control valve in the coal liquefaction industry.
    Discrete modeling of the end-wall effect on particle axial movement in horizontal drum
    Xingkun WANG Xuhui ZHANG Hui GUO Xiaoxing LIU
    The Chinese Journal of Process Engineering. 2023, 23(2):  207-215.  DOI: 10.12034/j.issn.1009-606X.222030
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    Aiming at the short drum system in which only one end face can rotate with the side wall in the slag crushing process, the discrete element method (DEM) is used to simulate and study the influence of the drum length-diameter ratio and rotation speed on the axial flow characteristics of granular materials. Simulation results indicate that distinct axial convention occurs inside the system: particles in the upstream zone tend to move towards the fixed end-wall side, whereas those in the downstream zone are apt to shift towards the rotating end-wall side. At low rotating speed condition, along the transverse direction the axial velocity profile of particles at the free surface presents an asymmetric characteristic. The axial velocity magnitude of particles in the upstream zone is clearly smaller than that of particles in the downstream zone. The axial velocity magnitude of particles in the two zones reaches the maximum value at y/R=±0.725, and the position where the axial velocity is 0 does not appear in the tangential middle position. Such asymmetric characteristic is nearly independent on the axial length of the drum, whereas increasing the rotational speed of the drum will increase the axial velocity of the particles and gradually reduce this asymmetry. Changing the rotating speed of the drum has a greater effect on the axial flow of particles in the upstream zone of the material than on the axial flow of particles in the downstream zone. When the length-diameter ratio of the drum reaches 1.2, the influence area of the rotating end-wall on the axial flow of the material will not change significantly with the increase of the rotating speed of the drum. The simulation results thus provide helpful guidelines for the future optimization of the real drum system used for particle milling.
    Influence of air distribution plate on flow characteristics of non-homogeneous particles in shallow fluidized-bed with immersed pipes
    Huang LIU Nan ZHENG Xiaohui ZHAO Jinjia WEI
    The Chinese Journal of Process Engineering. 2023, 23(2):  216-225.  DOI: 10.12034/j.issn.1009-606X.222071
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    In the next generation high-temperature solar thermal power system, solid particles are the dominant heat absorbing fluid. Special heat exchangers need to be developed for the energy transmission between particles and other functional thermal fluids, considering the poor fluidity of solid particles. Shallow fluidized bed with immersed pipes is a promising technology for extracting heat from high-temperature particles. However, there is still a lack of unanimous criteria for the optimization design of such devices, especially when non-homogeneous particles with great economic benefits are used. As the first step in the research and design program, the fluidization characteristics of polydisperse bauxite particles in a three dimensional shallow fluidized-bed with built-in tubes were investigated via cold state experiments. Bed pressure drops were measured under five different perforated plate distributor with a range of open area ratio from 0.38% to 2.89%. The effects of open area ratio, static bed height and air distribution mode on the characteristic parameters and quality of the fluidization were also investigated. The results showed that there was no obvious abrupt change in the bed pressure drop curve of the non-homogeneous particles, and the whole process could be divided into three stages: fixed bed, semi-fluidization and complete fluidization. The open area ratio had little influence on the characteristic velocities at the boundary of two adjacent stages. For the concerned non-homogeneous particles, the change of standard deviation of bed pressure drop showed a minimum value, and the fluidization stability became the highest when plate with an opening area ratio of 0.79% was used. The air distribution mode has an important influence on the local bed pressure drop in the multi-chamber fluidized bed. The uniform velocity mode could effectively reduce the pressure drop difference between chambers and improve the uniformity of the overall fluidization zone.
    Full-loop simulation and stability analysis of a gas-solid circulating fluidized bed
    Boyu JIA Xinhua LIU Ge WANG Huaiyu SUN Bona LU
    The Chinese Journal of Process Engineering. 2023, 23(2):  226-234.  DOI: 10.12034/j.issn.1009-606X.222080
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    The gas-solid fluidized bed has wide application in industry such as refinery, metallurgy, and ore calcination. In the practical operation, it is usually combined with other units like conveying pipe, cyclone, downer and valves to run in a full-loop way. Compared to simulation of a single operating unit, the full-loop simulation of the gas-solid circulating fluidized bed system can reveal interactions between different operating components and diagnose the sudden change of operation, thus being of greater importance in industrial operation. In this study, the full-loop simulation and stability analysis of a gas-solid circulating fluidized bed of virtual process engineering (VPE) are carried out under the framework of two fluid model and kinetic theory of granular flow. The simulation shows that there exists periodic fluctuation of solids volume fraction and pressure drop in the riser where two distinct fluidization states, i.e., dilute fluidization and dense fluidization, appear alternatively, because of the occurrence of gas bypassing. To figure out the underlying cause, the influence of model factors (mainly refer to gas-solid drag) and operating parameters (i.e., solid inventory and superficial velocity) on the periodic fluctuation phenomenon is numerically investigated. It is found that changing the drag model cannot eliminate the fluctuation, while reducing the gas velocity and increasing the solid inventory are conducive to the stability of particle circulating transportation and avoiding the occurrence of "gas bypassing" because of the increase in pressure drop of the Loop-seal. On this basis, the Loop-seal valve which is reported to be closely related to particle conveying is focused on. The simulation with adding a virtual valve in the middle of the inclined pipe is performed and shows that the resistance of particle conveying increases thus ensuring the enough pressure drop of the Loop-seal to operate the full-loop system steadily. The time-averaged axial profile of pressure drop predicted by the simulation agrees with the experimental data. This method is found to be helpful to improve the stability of the full-loop simulation.
    Physical simulation of orifices of turbulence inhibitor on fluid flow characterization in tundish
    Yang WANG Xiaoming LI Jiayu ZHU Jianli WANG Jun WU Ming LÜ Yongkun YANG
    The Chinese Journal of Process Engineering. 2023, 23(2):  235-243.  DOI: 10.12034/j.issn.1009-606X.222093
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    To solve the problems of poor flow field distribution and uneven quality of each stream caused by the unreasonable structure of the orifice of the ten-stream tundish turbulence inhibitor in a steel plant, an experimental 1:3 hydraulic model was established to conduct water model tests by using the similarity principle. On the basis of different orifice structures, the uniformity of each stream was considered fully and then the optimal structure of the orifice and the effect of the orifice structures on the tundish flow field were obtained by means of the comprehensive analysis of the residence time distribution curves of liquid in the tundish and the display characteristics of the flow field. Experimental results showed that for the long-distance and multi-stream tundish of no weir structure, the size, quantity, and direction of the inner diameter of the orifice of the turbulence inhibitor all affected the flow field of the tundish, and the effect of the inner diameter of the orifice was the most significant. The inner diameter of the optimal orifice designed in this work reduced from 53 mm to 30 mm in the prototype, the dead zone ratio reduced from 54.05% to 34.69%, the maximum standard deviation of the F curve reduced from 0.0154 to 0.0035, the flow field of the tundish was improved, and the flow field of each flow was improved. The uniformity among the streams was significantly improved. The number of orifices increased from 1 to 3, the proportion of dead zone increased from 34.69% to 46.05%, and the maximum standard deviation of the F curve increased from 0.0035 to 0.0062. The more the number of orifices was, the higher the proportion of dead zone in the flow field was. The larger the value was, the worse the consistency of the flow field of each nozzle was. For the long-distance and multi-stream tundish, it was recommended to improve the flow field of the tundish by appropriately changing the inner diameter of the orifice, reducing the number of orifices.
    Behavior of inclusions during electroslag process of 15-7PH stainless steel
    Lizhong CHANG Miaomiao XIANG Tao XU Longfei ZHANG Yunlong SU Tao JIN Xiaofang SHI
    The Chinese Journal of Process Engineering. 2023, 23(2):  244-253.  DOI: 10.12034/j.issn.1009-606X.222113
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    In order to clarify the behavior of inclusions in 15-7PH stainless steel and further improve its cleanliness, the consumable electrodes were prepared by UHP electric arc furnace→AOD decarburization→LF refining→mold casting process, and remelted by gas shielded electroslag remelting furnace with voltage swing control. The changes of oxygen and nitrogen before and after electroslag remelting were analyzed by HORIBA gas analyzer. The size, number, chemical composition and morphology of inclusions were analyzed by ASPEX SEM. It was found that the content of oxygen and nitrogen in 15-7PH stainless steel decreased slightly after electroslag remelting, and there was little change in the composition of inclusions, which were mainly composed of nitride inclusions (AlN, TiN), nitride/oxide composite inclusions, oxide inclusions and sulfide-oxygen/nitride inclusions. Among them, nitride inclusions had the largest size and quantity, which were significantly higher than other inclusions, and were worthy of special attention. Electroslag remelting had an obvious effect on the number and size of inclusions. After remelting, the number of inclusions increased greatly, especially nitrides. However, large inclusions were significantly reduced. The main reason for the large amount of nitride inclusions was the high content of Al, Ti, N in the steel. During the electroslag process, due to the adsorption of slag and the dissolution of some nitrides, the large inclusions were reduced, and the rapid cooling in the remelting process inhibited the growth of inclusions which led to the small size but increased of the number of inclusions in the electroslag ingot.
    Separation of lead and antimony in lead-antimony alloy by gas pressure filtration
    Yang MEI Lei GUO Zhancheng GUO
    The Chinese Journal of Process Engineering. 2023, 23(2):  254-262.  DOI: 10.12034/j.issn.1009-606X.221441
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    Lead and antimony metals are important basic raw materials and strategic materials for the development of the national defense industry, biomedicine, battery research and development, semiconductor production and other fields. At present, the Pb-Sb alloy separation process in domestic and foreign smelters has complex operation, large pollution, high energy consumption, long production process and low recovery rate. The effective development and utilization of lead and antimony resources not only has practical significance, but also has important strategic significance for promoting national economic development and scientific progress. This work introduced the gas pressurization technology, and by virtue of its technical characteristics of enhanced filtration and separation, put forward a new method of efficient and environmentally friendly separation and extraction of Pb-Sb resources. In this work, the theoretical purity and recovery rate after separation were calculated according to the phase diagram of Pb-Sb alloy using the lever principle, and the effects of different filtration temperatures, filtration pressures, filtration times, screen and melt composition on the separation results were discussed, and the separation mechanism of pressurized filtration separation was clarified. The results of SEM-EDS, metallographic microscope and XRF showed that lead migrated to the lower crucible along the pressure direction, and almost all antimony remained in the upper crucible. With the decrease of filtration temperature, the size of precipitation crystal increased, the viscosity of molten liquid phase increased, and the resistance of filter cake to liquid phase increased. The best separation conditions were obtained through experiments, under the conditions of filtration temperature T=553 K, screen N=100, filtration pressure p=0.2 MPa, and four filtration times, the upper enriched Sb phase with a content of more than 90wt%, and the lower enriched Pb phase with a content of 85wt% were successfully obtained, which was close to the theoretical value calculated from the Pb-Sb phase diagram.
    Synthesis of zeolite SOD from potassic rocks activated by NaOH-NaCl sub-molten salt method
    Wenzhuo LIU Yang LIU Yun LI Hongfei GUO Jilin CAO
    The Chinese Journal of Process Engineering. 2023, 23(2):  263-271.  DOI: 10.12034/j.issn.1009-606X.222081
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    Potassic rocks are aluminosilicate crystals containing abundant potassium elements, which could be used to produce K-fertilizers by extracting K+, synthesizing zeolites, and preparing valuable industrial products. To realize the efficient utilization of potassic rocks, the sub-molten salt method was used to activate potassic rocks using NaOH-NaCl as the activating agent. The effects of the addition of NaOH, NaCl, and H2O on the leaching rate of K+ were investigated, respectively. The raw materials, activated products and filtration were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and titration method. The experimental results showed that the optimal activation conditions are m(NaOH)/m(potassium rocks) of 0.7, m(NaCl)/m(potassium rocks) of 0.7, m(H2O)/m(potassium rocks) of 1.0, activation temperature of 160℃, and activation time of 120 min. The leaching rate of K+ could reach about 92%, and the alkali concentration was decreased to 41wt%. Comparative investigations were made with the effect of activation of potassic rocks using the NaOH sub-molten method concerning the leaching rate of ions of K+, SiO32- and Al3+ and activated products in the identical reaction conditions. The concentrations of K+, SiO32- and Al3+ in the mother liquor obtained from NaOH-NaCl sub-molten system were significantly increased in contrast with that from the system in the absence of NaCl, demonstrating the promotion effect of NaCl for the activation of potassic rocks and the peaks assigned to SOD zeolite were greatly intensified with the introduction of NaCl. Compared with the activation effect and conditions of other additives in the sub-molten salt method reported in the literature, NaOH-NaCl sub-molten system exhibited a satisfactory leaching rate of K+ under the condition of significantly decreased alkali concentration at a low temperature (160℃) for short time (120 min), which greatly reduced energy consumption and time wasting. According to the compositions of mother liquor after sub-molten salt activation, the circulating process for the activation of potassic rocks in the NaOH-NaCl mixed sub-molten salt system was designed to realize the recycling of NaCl. This work provides an energy-saving and effective method for the activation of potassic rocks, paving a new way to realize the comprehensive utilization of potassic rocks.
    Preparation of chromic oxide green by thermal decomposition of CrOOH with base center orthorhombic structure and trigonal structure
    Panpan MU Hongling ZHANG Taiping LOU Peng ZHOU Haiqin SHI Linming CHEN Hongbin XU
    The Chinese Journal of Process Engineering. 2023, 23(2):  272-279.  DOI: 10.12034/j.issn.1009-606X.222052
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    Through hydrogen reduction of alkali metal chromates, chromic oxide green can be prepared by the thermal decomposition of chromium oxyhydroxide (CrOOH). It was reported that the crystal structures of CrOOH have a significant effect on the color of the chromic oxide green obtained. However, the mechanisms remain unclear and need to be systematically studied. In this work, two kinds of CrOOH with different crystal structures were prepared by aqueous hydrogen reduction of sodium chromate. The chemical composition, phase structure, and morphologies of the prepared CrOOH were characterized by chemical titration, FT-IR, XRD, and SEM. The thermal decomposition processes were discussed according to the TG-DSC results. Subsequently, CrOOH with different crystal structures were used as the raw materials to prepare chromic oxide green with different color performance. The structure and morphologies of the chromic oxide green obtained were characterized by XRD and SEM. The color performance data of chromic oxide green was reported by a Datacolor 110 colorimeter using the CIE L*a*b* (1976) colorimetric system according to the International Commission on Illumination. The results showed that the CrOOH samples prepared were of base center orthorhombic structure and trigonal structure, respectively. The morphology of the CrOOH samples was flaky and hexagonal sheet shape, respectively. Their compositions could be expressed as Cr2O3?1.49H2O and Cr2O3?1.12H2O, respectively. Compared with the chromic oxide green sample obtained by the thermal decomposition of trigonal CrOOH, the chromic oxide green sample obtained by the thermal decomposition of CrOOH with base center orthorhombic structure yielded a smaller particle size, more uniform particle size distribution, and a brighter yellower color. Finally, chromic oxide green pigments with different color performances, such as bright yellow-green, blue-green, and dark green, were obtained using different ratios of CrOOH raw materials with base center orthorhombic and trigonal structures.
    Application of ultra-thin ePTFE nanofibrous membranes in high-efficient removal of PM2.5
    Feng LIU Hongmiao WU Shengui JU Zhaoxiang ZHONG Weihong XING
    The Chinese Journal of Process Engineering. 2023, 23(2):  280-290.  DOI: 10.12034/j.issn.1009-606X.222082
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    Recently, expanded polytetrafluoroethylene (ePTFE) nanofibrous membranes have received extensive attention in the treatment of fine particulate matter (PM2.5). But until now, the influence of membrane structure on the PM2.5 filtration process is still under-investigated. And the application of ultra-thin ePTFE nanofibrous membrane in the treatment of PM2.5 of medium-high concentration has received little report yet. Therefore, three kinds of ultra-thin ePTFE nanofibrous membranes with particle/membrane size ratio (dP/dm) ranging from 0.86 to 4.46 and membrane thickness ≤1 μm were chosen to examine the PM2.5 filtration performance at medium to high concentration (200~1000 mg/m3). All the three membranes showed high PM2.5 filtration efficiencies (>99.5%) and low initial pressure drop (30~130 Pa) benefit from the ultra-thin few-layered crosslinked-network-like structures. In addition, the surfaces of ePTFE menbranes were smooth with roughness commonly less than 1 μm, which reduced the adhesion of the cake layer and hence made it prone to fall off. As a result, the membrane exhibited good regeneration performance in a 4-cycle regeneration experiment. From the comparison of the three nanofibrous ePTFE membranes, it showed the one with the lowest dP/dm ratio (0.86) provided the lowest filtration pressure drop (30 Pa) as well as excellent filtration efficiency (99.93%) and good regeneration performance. But further increasing the membrane pore size may lead to more serious pore-plugging and lower filtration efficiency which had fatal impacts on the PM2.5 filtration performance. In summary, the ultra-thin ePTFE nanofibrous membrane exhibited superior comprehensive performance in filtration of PM2.5 at medium to high concentration which showed a broad application prospects in air purification.
    Multiphase reaction fabrication and ablation resistance of carbon fiber-reinforced ultra-high temperature ceramic matrix composites
    Qian SUN Huifeng ZHANG Chuanbing HUANG Shouquan YU Shirui YANG Shige FANG Weigang ZHANG
    The Chinese Journal of Process Engineering. 2023, 23(2):  291-300.  DOI: 10.12034/j.issn.1009-606X.222017
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    In this work, to improve the ablation resistance and oxidation performance of carbon fiber-reinforced carbon matrix (C/C) composites widely applied as aerospace high-temperature structural materials in an oxidizing environment above 2000℃, C/C-SiC-ZrB2-ZrC composites were fabricated by hybrid processes of ZrB2 slurry impregnation, ZrC-SiC precursor infiltration-pyrolysis and reactive melt infiltration with a Si-Zr10 eutectic alloy. The matrix microstructure and the evolution mechanism of the prepared composites were investigated in detail by phase composition, microstructure analysis, model experiments, and thermodynamic calculation. The mechanical properties and ablation resistance of the composites were tested by three-point bending tests and an atmospheric plasma torch, respectively. The results showed that in the cooling stage after infiltration, in situ solid-liquid reaction between ZrC ceramics and residual Si melt resulted in the formation of ZrSi2 and SiC, characterizing as such submicron SiC particles evenly embedded in the ZrC-ZrSi2 binary phases and finally generated a ZrC-ZrSi2-SiC complex micro-region. The obtained composites with a density of 3.18 g/cm3 and an open porosity of 2.77% showed a flexural strength of 121.46±13.77 MPa and a flexural modulus of 21.78±5.56 GPa. Moreover, numerous fibers were pulled out and obvious interfacial debonding was observed in the fracture section, indicating that the failure mode of the composites was a ductile fracture. After plasma-arc ablation at 2000℃ for 300 s, the C/C-SiC-ZrB2-ZrC composites exhibited excellent ultra-high temperature ablation behavior. The mass and linear ablation rates were 1.37×10-3 g/s and 3.43×10-3 mm/s, respectively. It was found that a unique double-layer oxide structure was formed in the ablation center. The ZrO2 layer as the inner layer can inhibit heat conduction into the internal matrix to further improve the high-temperature resistance of the composites. The composite oxide layer composed of solid-phase ZrO2 particles and liquid-phase SiO2-ZrO2 melt rich in SiO2 as the outer layer can not only resist mechanical scouring of high-speed gas flow but also inhibit the inward oxygen diffusion.
    Investigation on the catalytic hydrolysis activity of COS from blast furnace gas over the γ-Al2O3-based catalysts
    Panting GAO Yuran LI Yuting LIN Qiang CAO Liping CHANG Jiancheng WANG Tingyu ZHU
    The Chinese Journal of Process Engineering. 2023, 23(2):  301-310.  DOI: 10.12034/j.issn.1009-606X.221446
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    Desulfurization for blast furnace gas is one of the keys to achieve ultra-low emissions for the multi-process in the iron and steel industry. The sulfur component in blast furnace gas is mainly organic sulfur-carbonyl sulfur (COS), which is usually removed by the catalytic hydrolysis method with γ-Al2O3 based catalyst, but its hydrolysis activity and antioxidant capacity need to be improved. In this work, three kinds of catalysts with Fe or La as an active component were prepared by the impregnation method. The physical and chemical properties of the catalysts were characterized by ICP, XRD and TPD. The diffusion effect of gas hourly space velocity (GHSV) and particle size on the catalytic hydrolysis of COS were investigated on a fixed bed-gas chromatography combined device. The structure-activity relationship between the physicochemical properties of the catalysts and the hydrolysis activity of COS and the action mechanism of O2 were also analyzed. The results showed that the addition of Fe or La as active components can obviously improve the COS hydrolysis activity on the catalyst, due to the much more alkaline sites on the surface of the γ-Al2O3 based catalyst at conditions of 80℃ and 160000 h-1. The abundant pore structure and suitable pore size can also reduce the internal diffusion resistance of COS and H2S, enhance the mass transfer process of H2S from the catalyst surface to the gas phase. Fe/Al2O3 catalyst can collaboratively remove H2S and simultaneously maintain a high hydrolytic activity. But the presence of O2 enhanced the adsorption of H2S on the catalyst surface and the sulfidation reaction between H2S and metal Fe. While La/Al2O3 catalyst had better activity and stability for COS hydrolysis, and the active component La can significantly improve the desorption of H2S from the catalyst surface to the gas phase, and then improve the anti-oxygen toxicity ability of the catalyst.
    Photocatalytic ozonation of ceftriaxone sodium by Cu2O/TiO2 under visible light
    Guanhua MENG Linsen ZHANG Baohe LIU Yu WANG Zhenghui LI Wen LI Yongbin JIANG
    The Chinese Journal of Process Engineering. 2023, 23(2):  311-322.  DOI: 10.12034/j.issn.1009-606X.222075
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    Antibiotics are commonly used drugs for the treatment of various infectious diseases in humans and animals, but the residual antibiotics released into the aquatic environment will threaten the ecological system. Therefore, it is important to explore efficient methods to remove antibiotics from the water environment. Photocatalytic ozonation technology has received extensive attention for its effective degradation and mineralization of persistent organic pollutants from the water matrix. In this work, Cu2O/TiO2 composite was prepared by the impregnation-chemical reduction method and was used as a catalyst for photocatalytic ozonation of ceftriaxone sodium (CRO) under visible light irradiation. The morphology, structure, and optical properties were investigated by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscopy (TEM), nitrogen adsorption-desorption isotherms (BET) and ultraviolet-visible diffuse reflection (UV-Vis DRS). The effects of Cu2O/TiO2 ratio, Cu2O/TiO2 dosage, ozone concentration, initial concentration of ceftriaxone sodium, and initial pH value of the solution on visible-light-induced photocatalytic ozonation of ceftriaxone sodium were comprehensively investigated. The results showed that the doping of Cu2O on TiO2 increased the specific surface area and pore volume, reduced the energy gap, and improved the catalytic performance under visible light. The photocatalytic ozonation process had achieved a much higher removal rate of ceftriaxone sodium from an aqueous solution than the photocatalysis and ozonation processes. When the molar ratio of Cu2O:TiO2 was 0.2:1, the visible light irradiation time was 120 min, the initial pH value of the solution was 6.12, the concentration of ceftriaxone sodium was 10 mg/L, the dosage of Cu2O/TiO2 was 0.2 g/L and ozone concentration was 1.5 mg/L, the removal rates of ceftriaxone sodium and TOC were 81.05% and 52.16%, respectively, and the ozone utilization rate was 50.84%. The free radical capture experiments showed that photogenerated holes (h+) and superoxide radicals (?O2-) played a major role in the visible-light-induced photocatalytic ozonation of ceftriaxone sodium. Moreover, Cu2O/TiO2 exhibited satisfactory stability and reusability for 5 consecutive cycles. The findings of this study suggest that the photocatalytic ozonation process induced by visible light is a promising treatment technology for the abatement of ceftriaxone sodium pollution in an aqueous solution.