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    28 July 2025, Volume 25 Issue 7
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    Contents
    Cover and Contents
    The Chinese Journal of Process Engineering. 2025, 25(7):  0. 
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    Review
    Current situation and application prospect of tritiated water purification technology in nuclear energy field
    Yan XU Menghan WU Baihua JIANG Yuyong WU Tiantian YU
    The Chinese Journal of Process Engineering. 2025, 25(7):  645-657.  DOI: 10.12034/j.issn.1009-606X.225158
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    In the global context of nuclear energy renaissance and green development, the issue of tritium emissions has garnered significant attention. Reducing tritium emissions is a crucial measure for enhancing the environmental and public acceptance of nuclear energy. However, there is currently a lack of comprehensive and objective analysis of tritiated water purification technologies from the perspective of nuclear energy applications, and the overall technical routes and processes remain unclear. Moreover, given the rapid advancements in this field, existing literature reviews are in urgent need of updates. This review begins by outlining the generation scenarios, characteristics, and regulations of tritiated water in the nuclear energy field, highlighting the pressing demand for tritiated water purification technologies in nuclear power plant, spent fuel reprocessing plant, and future nuclear fusion facilities, in particular, inland nuclear facilities have higher requirements for tritium purification, with typical concentration of tritiated water to be purified ranging from 107 to 1012 Bq/L. Subsequently, the work reviews latest research progress in three mainstream tritiated water purification technologies—water distillation (WD), combined electrolysis and catalytic exchange (CECE), and liquid phase catalytic exchange (LPCE). It identifies the exploration and establishment of tritiated water purification mechanism and key physicochemical parameters, the industrial-scale preparation of efficient hydrogen-water isotope exchange catalysts, and the adaptive modification of electrolytic systems as the current research priorities and challenges. Building on this foundation, this work concludes four feasible tritium purification routes from the perspective of application: WD+storage/electrolysis+cryogenic distillation (CD) route, the CECE+storage/CD route, WD+CECE+storage/CD route, and the LPCE+CD route. It provides a comprehensive analysis of their treatment capabilities, applicable conditions, advantages, and disadvantages, aiming to offer references for tritiated water purification technology and engineering construction.
    Research Paper
    CFD simulation of NbCl5-Ar gas-carrying evaporation in a evaporator tank
    Kai WANG Liang ZHANG Zongbei HE Jiancai PENG Qiushi XU Ning YANG
    The Chinese Journal of Process Engineering. 2025, 25(7):  658-668.  DOI: 10.12034/j.issn.1009-606X.225107
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    In the chemical vapor deposition process of niobium (Nb) coating on fuel particles, the flow rate of the precursor NbCl5 vapor significantly influences the growth and properties of the thin films. However, measuring the vapor flow rate poses challenges due to the strong acidity of NbCl5, rendering the evaporation process a "black box" operation. In this study, a Volume of Fluid (VOF) method is developed to simulate the gas-liquid interface evaporation and wall boiling of NbCl5 in tank evaporator using argon (Ar) as carrier gas. The impact of various operating conditions, including liquid level height, flow rate of Ar carrier gas, and heating temperature, on the two-phase flow and the heat and mass transfer characteristics within the tank evaporator are investigated. Simulation results reveal that liquid level height primarily affects the evaporation area. When the liquid level resides in the near-bottom region of the tank, lowering the liquid level height significantly reduces the evaporation area, resulting in a decreased NbCl5 vapor flow rate at the evaporator outlet. When Ar gas is introduced into the evaporator, two distinct vortex structures are formed: a NbCl5 vapor vortex and an Ar gas vortex. Increasing the Ar gas velocity enables rapid sweeping of NbCl5 vapor from the liquid surface and lowers the saturation vapor temperature at the interface, thereby enhancing the evaporation rate. As the Ar gas velocity increases from 0 m/s to 2.1 m/s, the mass flow rate of NbCl5 vapor rises from 0.047 g/s to 1.095 g/s. Raising the heating temperature increases the liquid temperature at the evaporation interface, accelerating liquid evaporation. As the heating temperature increases from 533 K to 543 K, the NbCl5 vapor mass flow rate increases from 0.280 g/s to 0.359 g/s. These simulation results offer practical guidance for optimizing the operating conditions of the gas-carrying evaporation process and the evaporator structure.
    Study on cavitation characteristics of annular central body cavitation nozzle
    Baolong PENG Yong RAO Bin WANG
    The Chinese Journal of Process Engineering. 2025, 25(7):  669-682.  DOI: 10.12034/j.issn.1009-606X.224387
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    Cavitation jet technology, due to its strong impact and cleaning capabilities, is widely used in cleaning and surface treatment fields. As a key component for inducing cavitation jets, the design of the cavitation nozzle is crucial. However, some researchers have focused on optimizing the central body at the axial position to improve cavitation effects, while neglecting the role of fluid near the axis. To address this issue, this study proposes a novel annular central body nozzle based on the traditional organ-pipe nozzle. The annular central body is divided into three structures: forward, reverse, and square. The variations in cavitation volume fraction, pressure, velocity, and turbulent kinetic energy are analyzed to investigate the cavitation characteristics of each new structure. Additionally, the annular central body is combined with an axial central body to further study the cavitation characteristics of the nozzle. The results show that, compared to nozzles without an annular central body, the reverse structure generates the largest cavitation area, while the square structure has the second-largest cavitation area and the highest velocity along the axis. The forward structure, due to the contraction of the jet toward the axis, reduces the overall flow velocity in the inner flow path, and the lower velocity near the wall causes a smaller low-pressure zone, leading to weaker cavitation near the wall. The inlet velocity has little impact on the shape of the cavitation cloud in the flow field but is positively correlated with the cavitation volume. Furthermore, the combination of the annular central body and the axial central body increases the cavitation cloud length, enhancing the cavitation effect behind the central body. These findings provide new theoretical support for the design and optimization of cavitation nozzles.
    Impact of filtered gas pressure gradients at two discrete scales on mesoscale drag force
    Yu ZHANG Ju JIANG Xieyu HE Xiao CHEN Qiang ZHOU
    The Chinese Journal of Process Engineering. 2025, 25(7):  683-694.  DOI: 10.12034/j.issn.1009-606X.224364
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    In gas-solid two-phase flows, complex spatiotemporal mesoscale structures are present, making the development of accurate mesoscale drag models essential for precisely simulating fluidization dynamics. The filtered gas pressure gradient, as a key physical quantity in mesoscale drag modeling, has been extensively studied and applied in the simulation of mesoscale resistance. Typically, during the filtering process, the pressure gradient is derived at two discrete scales: the fine-grid scale and the filter scale. The pressure gradients calculated at these two scales often differ significantly, leading to considerable discrepancies when used in numerical simulations of fluidized beds. These discrepancies can affect the predictive accuracy of mesoscale drag models and hinder their practical application in simulating industrial-scale systems. To address these challenges, an artificial neural network (ANN) approach is employed to systematically analyze the influence of pressure gradients at different filtering scales on the construction of mesoscale drag models. Two drag models are developed based on the pressure gradients at the fine-grid and filter scales, referred to as model A and model B, respectively. Through extensive validation and analysis, the performance of these models is compared across a range of filtering scales and flow regimes. The results reveal that model B, which uses the pressure gradient at the filter scale, exhibits superior predictive capabilities compared to model A, particularly at larger filter scales. This superiority is further substantiated through posterior analysis. Simulations of fluidized beds under three typical flow regimes—bubbling, turbulent, and fast fluidization—demonstrate that model B provides axial solid volume fraction distributions that align more closely with resolved results than those predicted by model A. These findings confirm that constructing mesoscale drag models based on the pressure gradient at the filter scale enhances their accuracy and applicability, making them more suitable for simulating complex fluidized bed dynamics in industrial and research contexts.
    Numerical simulation of flow field and power consumption characteristics of double-layer combined impeller in a gas-liquid stirred tank
    Mengyao ZHANG Yafeng XIAO Zhongtian DONG Shaoping MA Shuang WU Mingzhou YU Qinghua ZHANG Chao YANG
    The Chinese Journal of Process Engineering. 2025, 25(7):  695-705.  DOI: 10.12034/j.issn.1009-606X.224353
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    In the realm of chemical synthesis, the aminolytic synthesis of glycine from chloroacetic acid holds significant industrial importance. To surmount the challenges and optimize this process, with a particular emphasis on enhancing gas dispersion performance, elaborate investigation was carried out. Three innovative impeller combinations, namely the double narrow blade propeller (ZCX-ZCX), the narrow blade propeller-parabolic disc turbine (ZCX-PDT), and the narrow blade propeller-staggered fan-shaped parabolic disc turbine (ZCX-SFPDT), were integrated into the gas-liquid mixing operations within stirred tanks. Employing advanced computational fluid dynamics (CFD) techniques, comprehensive comparative analysis was executed. The complex gas dispersion phenomena within the liquid phase were modeled using the Eulerian-Eulerian approach combined with the dispersed k-ε turbulent model to capture the intricate fluid dynamics. It was found that at the same speed, the ZCX-ZCX configuration manifested the lowest values in velocity distribution, turbulent kinetic energy, gas holdup, and power consumption metrics, but the largest average bubble size. Additionally, its distribution uniformity lagged behind that of ZCX-PDT and ZCX-SFPDT, resulting in suboptimal gas-liquid mixing. In contrast to ZCX-PDT and ZCX-SFPDT, the ZCX-SFPDT stirred tank boasted smaller gas cavities and more uniformity of flow field. Notably, under the same Reynolds number regime, ZCX-SFPDT not only curtailed power number by 6.1% compared to the ZCX-PDT tank, but also augmented mass transfer efficiency by 10.9%. It indicated that the arc-shaped structure decreased the form drag on the blade surface and the length of the resistance arm, which was conducive to reducing the stirring power consumption. Generally, these results unequivocally established that ZCX-SFPDT exhibited superior gas-liquid dispersion and mass transfer capabilities, rendering it the prime candidate for gas-liquid stirred tank applications.
    Study on influence of underflow orifice diameter of hydrocyclone on separation efficiency of special slurry systems
    Jiangtao SHANG Shuhua MA Yanjun OU Tao HONG
    The Chinese Journal of Process Engineering. 2025, 25(7):  706-716.  DOI: 10.12034/j.issn.1009-606X.224372
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    Tailings produced by the novel wet beneficiation process for low-grade bauxite exhibit complex morphological characteristics and intricate occurrence states, posing significant challenges for efficient aluminum concentrate recovery. These complexities result in reduced recovery rates and lower concentrate grades. To address this issue, this study systematically investigates the effects of underflow orifice diameter (4, 6, 8, 10, 12 mm) on the internal flow dynamics and separation efficiency of a hydrocyclone. A pilot-scale ?75 mm hydrocyclone system was employed, with the underflow orifice diameter as the sole variable while maintaining other structural and operational parameters constant. Computational fluid dynamics (CFD) simulations, combined with experimental validation, were used to explore how variations in underflow orifice diameter influence turbulent kinetic energy (TKE) distribution and flow field stability, ultimately affecting the efficiency of tailings-aluminum concentrate separation. Simulation results indicated that adjusting the underflow orifice diameter significantly regulated the magnitude and spatial distribution of TKE, which in turn governed the evolution of short-circuit flow and recirculation flow within the hydrocyclone. An optimal balance was observed at underflow orifice diameter of 8 mm, which effectively stabilized the internal flow field, controlled short-circuit and recirculation flow, and enhanced the dissociation of tailings from aluminum concentrate. Experimental results, conducted under feed pressure of 0.3 MPa, feed concentration of 17.15wt%, and an alumina-to-silica mass ratio (A/S) of 2.74, confirmed that the optimized 8 mm underflow orifice hydrocyclone significantly improved separation performance. Compared to the baseline design, the 8 mm orifice increased underflow concentrate yield by 9.33% and improved the A/S ratio by 20.39%, effectively mitigating coarse particle overflow and fine particle entrainment. Strong agreement between CFD simulations and experimental data validated the reliability of the numerical approach. The findings provide a theoretical framework for optimizing hydrocyclone designs in complex slurry separation processes, particularly for low-grade bauxite beneficiation. By elucidating the interplay between TKE modulation and flow structure evolution, this study offers valuable insights for industrial applications, contributing to the development of more efficient hydrocyclone separation strategies.
    Selective sulfurization method for recycling spent lithium-ion batteries
    Shiliang CHEN Xiutao GUAN Youqi FAN Xin WANG Zhipeng GUO Hu LI Wenlong TAN Chao DING Jian WU Sen ZHAO Yonglin YAO
    The Chinese Journal of Process Engineering. 2025, 25(7):  717-727.  DOI: 10.12034/j.issn.1009-606X.224310
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    The short-process recycling of valuable metals in waste lithium-ion batteries is a key challenge for ensuring the supply of raw materials for the new energy industry. With the development of the new energy industry, achieving the short-process recycling of valuable metals in waste lithium-ion batteries is an important link in the new energy industry chain. Based on the basic principle of the sulfurization method, the thermodynamic analysis of the sulfurization of LiCoO2 positive electrode materials with three typical sulfurizing agents [S8, SO2, sulfide minerals (FeS, CuFeS2, ZnS)] was carried out using Factsage 7.3 thermodynamic software. The effects of sulfurization temperature and sulfurizing agent dosage on the sulfurization products were studied. Through software simulation calculations, it was proved that all sulfurizing agents can thermodynamically sulfurize LiCoO2. Li in LiCoO2 was sulfurized into water-soluble Li2S or Li2SO4, while Co generates sulfides or oxides that were insoluble in water. Through leaching separation experiments, efficient separation of Li and Co was achieved. The results of the sulfurization recovery experiment showed that the three types of sulfurizing agents can achieve different degrees of sulfurization on LiCoO2. Among them, S8 was affected by reaction kinetics and had the worst sulfurization effect, with a sulfurization rate of only 2.51%; SO2 had a poor sulfurization effect when used as a sulfurizing agent, with a sulfurization rate of 34.07%, while when SO2 and the reducing agent C synergistically sulfurize, the sulfurization rate increased significantly to 72.03%. When sulfide minerals were used as sulfurizing agents, ZnS showed the best sulfurization effect, with a sulfurization rate of 96.14%, while the sulfurization effects of both CuFeS2 and FeS were quite poor. This study can provide new ideas for the short-process recovery of valuable metals in waste Li-ion batteries.
    Self-assembled ZnO nanoparticle/graphene nanosheet composites and their photocatalytic performance and mechanism for methylene blue degradation
    Mingrui CAO Shenghan LÜ Xin JIN Guangrong LIU Jinli ZHAI Qiang HUNAG
    The Chinese Journal of Process Engineering. 2025, 25(7):  728-735.  DOI: 10.12034/j.issn.1009-606X.224341
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    The high-quality ZnO/graphene nanostructured composites have wide application prospects in optoelectronic devices, sensors, photocatalysis, and other fields. In this study, bulk ZnO was used as the raw material to prepare ZnO nanoparticles, which were in-situ precipitated onto graphene nanosheets. The bulk ZnO was dissolved in a choline chloride-urea eutectic solvent, and then an ethanol-water mixed anti-solvent was dropwise added to precipitate ZnO nanoparticles in the presence of graphene nanosheets. After heat treatment, ZnO nanoparticle/graphene nanosheet composites (ZnO@G) were obtained. The physicochemical properties of the composites were characterized by TEM, XRD, ICP, Raman, FTIR, and UV-visible absorption spectroscopy, and their photocatalytic performance for methylene blue degradation was investigated. The results showed that ZnO nanoparticles were evenly dispersed on graphene surface, and thus expanding the light absorption range. The interface was connected via Zn-O-C bonds, providing an electron transfer channel between the two phases. By adjusting the composition ratio of the anti-solvent, the particle size and precipitation amount of ZnO can be controlled. ZnO@G can efficiently degrade methylene blue under both full-spectrum and visible light irradiations. The main active species were identified as superoxide radicals (O_2^(?-)) generated from the oxidation of H2O by photoinduced holes and the reduction of dissolved oxygen by photoinduced electrons. This work provides a novel method for transforming bulk ZnO into nanostructured ZnO and uniformly precipitating onto the surface of graphene sheets. The self-assembled ZnO@G enables efficient photocatalytic degradation of methylene blue, and the experimental results and presumed generation pathways of active species provide insights into the photocatalytic mechanism of ZnO/carbon composites.
    Optimization strategy of soft magnetic composites properties based on interfacial reaction engineering and carbonyl iron powder doping
    Kaixuan LI Yang LIU Xingyi WU Rui WANG Huaqin HUANG Zhaoyang WU
    The Chinese Journal of Process Engineering. 2025, 25(7):  736-747.  DOI: 10.12034/j.issn.1009-606X.224380
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    Insulation cladding through interfacial reaction engineering is an important way to optimize the properties of soft magnetic composites (SMCs), but the traditional method faces the problem of lattice mismatch between the insulating layer and soft magnetic powder leading to interfacial cracks. In this study, a carbonyl iron powders (CIPs) doping strategy is innovatively proposed to construct CaSiO3?Ca2Al2O5?CaO composite insulating layer by utilizing their high plasticity and high specific surface area properties in synergy with the thermal decomposition of alkaline compounds. The results show that Ca(OH)2 decomposes into solid-phase CaO and gas-phase H2O during thermal treatment, where CaO tends to nucleate on the surface of FeSiAl soft magnetic powder matrix and grows along the doped CIPs, ultimately forming a composite insulating layer composed of CaSiO3?Ca2Al2O5?CaO. The combination of high plasticity CIPs and the cladding layer effectively fills the internal pores of the SMCs. The high specific surface area of the small particle size CIPs provides more reaction sites for the decomposition of Ca(OH)2 and the growth of the composite insulating layer, which promotes the uniform distribution of the insulating layer on the surfaces of the soft magnetic powders and the CIPs, and realizes the effective doping of the CIPs inside the insulating layer, which weakens the negative impacts of the lattice mismatches between the insulating layer and the soft magnetic powders. The negative effect of the lattice mismatch between the insulating layer and the soft magnetic powder is weakened. By changing the doping amount of CIPs, the magnetic properties of SMCs can be precisely regulated, and when the doping amount of CIPs is 20wt%, the SMCs show the best comprehensive magnetic properties. At 10 mT, 200 kHz, the saturation magnetization intensity reaches 145.1 A?m2/kg, the permeability is 40.5, and the loss is as low as 50.6 kW/m3, which is ideal for high-performance electromagnetic components. Compared with other insulating layer preparation strategies based on interfacial reaction engineering, the method proposed in this study takes advantage of the high plasticity and high specific surface area of CIPs, and the combination with interfacial reaction engineering is expected to be a new idea for solving the lattice mismatch between insulating layers and soft magnetic powders, which provides an ideal solution for performance optimization of SMCs.
    Numerical simulation of optimization on combustion of high-temperature gas-solid preheating fuel in rotary kiln
    Yuchen DING Junjie WANG Jun CAI Zhiping ZHU
    The Chinese Journal of Process Engineering. 2025, 25(7):  748-760.  DOI: 10.12034/j.issn.1009-606X.224343
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    Fluidized preheating combustion technology used in rotary kilns can effectively reduce the fuel consumption per unit product and has advantages such as wide fuel adaptability and low NOx emissions. However, compared to pulverized coal, the combustion characteristics of preheated fuel are significantly different. This work employs computational fluid dynamics (CFD) to study the effects of preheating temperature, excess air coefficient within the rotary kiln, and the momentum of the axial flow air passage of the burner on the combustion process of high-temperature preheated fuel within the rotary kiln. Combining the author's previous research on the swirl number of multi-channel burners, an orthogonal design method combined with matrix analysis is used to obtain the importance of the effects of these four factors on combustion characteristics and the optimal parameter combination for comprehensive combustion performance. The results show that as the preheating temperature increases, the flame becomes thicker and shorter; as the excess air coefficient increases, the flame first becomes longer, then shorter; as the momentum of the axial flow air passage of the burner increases, the flame first becomes shorter and thicker, then longer and thinner. The importance of the effects of these four factors on combustion characteristics is in the order of preheating temperature>momentum of the axial flow air passage of the burner>swirl number>excess air coefficient. The optimal parameter combination is a swirl number of 0.2, a preheating temperature of 850℃, an excess air coefficient of 1.1, and a momentum of the axial flow air passage of the burner of 0.5 N/MW. The optimized conditions, compared to the original conditions, result in a 47% increase in flame length, a 37% increase in the average heat flux of the wall in the firing zone, and an 80% increase in the maximum heat flux of the wall in the firing zone.