Table of Content

28 April 2025, Volume 25 Issue 4

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Cover and Contents

The Chinese Journal of Process Engineering. 2025, 25(4):  0. 

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Research Paper

Numerical simulation of self-baked electrodes in a Titanium slag three-phase arc furnace

Quan LIU Xiaoping GUAN Ning YANG Jun XIAO

The Chinese Journal of Process Engineering. 2025, 25(4):  323-331.  DOI: 10.12034/j.issn.1009-606X.224185

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During the smelting process, the sintering quality of self-baked electrodes determines whether the arc furnace can operate normally. Taking the Panzhihua Steel Titanium Slag Three-Phase Arc Furnace as a prototype, this paper establishes a multi-physics field model of the coupled electromagnetic field and temperature field, and develops a quick calculation method for electromagnetic field and temperature field to accelerate computation. A comparative analysis of current density, Joule heat, and temperature distributions during the baking process of solid/hollow self-baked electrodes is conducted. The results show that both solid and hollow electrodes exhibit a "low at the center, high at the edge" current density distribution, namely the skin effect, with the skin effect of hollow electrodes weaker than that of solid electrodes, resulting in a more uniform current distribution. Besides, the baking regions of solid and hollow electrodes are located within the contact area of the conductive components, indicating that the self-baked electrodes have enough strength to meet the baking requirements. Meanwhile, the time to reach baking equilibrium for solid and hollow electrodes is about 13.4 hours and 12.8 hours, respectively, with the baking time of hollow electrodes being 4.3% shorter.

Simulation of shape of liquid bridge and gas-liquid interface energy between two ellipsoidal wet particles

Wenzhe WANG Guihuan YAO

The Chinese Journal of Process Engineering. 2025, 25(4):  332-340.  DOI: 10.12034/j.issn.1009-606X.224247

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Wet particulate matter widely exists in nature, production and daily life. Surface Evolver was used to investigate the shape of liquid bridge between two ellipsoidal wet particles placed vertically and parallel to each other during the relative rotation and the effects of contact angle, rotation angle, gravity and other parameters were analyzed. Under several different contact angles, the changes in the relative angle between the two particles from 0° to 90° were observed to analyze the changes in the gas-liquid surface area, solid-liquid contact area, and the shape of the contour line obtained by intersecting the plane passing through the center line of the two particles with the surface of the liquid bridge. The differences in the contour line shape of the liquid bridge under the same relative angle with and without gravity were compared. The results showed that the shape of the liquid bridge was a rotationally symmetric body. This body did not satisfy the arc assumption. The variation of the contact angle changed the shape of the liquid bridge. The changes in rotation angle and gravity caused the profile of the liquid bridge to change. Specifically, it changed from an elliptic curve to a hyperbola. The gravity caused the contact line on the upper and lower particles to shift. The rotation of the particles resulted in the reduction of the solid-liquid interface. The gas-liquid interface area of the liquid bridge was sinusoidally related to the relative angle of the particles. The minimum volume required to maintain the liquid bridge under gravity was investigated by gradually reducing the volume of the liquid bridge, and it was shown to be quadratically related to the contact angle and to increase with the increase in liquid density, with the minimum volume required to maintain the liquid bridge when the contact angle was about 90°.

Migration behaviors and deformation characteristics of discrete bubbles in a variable diameter circular tube

Feng LI Liang MING Lei XING Minghu JIANG Lixin ZHAO Shuai GUAN

The Chinese Journal of Process Engineering. 2025, 25(4):  341-353.  DOI: 10.12034/j.issn.1009-606X.224229

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The morphological evolution and migration dynamics of discrete bubbles in variable diameter pipelines have not been clearly analyzed. The deformation dynamics behavior of discrete bubbles in a variable diameter circular tube is an important theory to guide the transport and separation of gas-liquid two-phase mixture. Therefore, high-speed camera technology, combined with numerical simulation, is used to explore the migration and fragmentation mechanism of discrete bubbles in variable diameter pipes. For the structure of a variable diameter circular pipe, a study on the migration behaviors of discrete bubbles in the variable diameter field is conducted under different Reynolds numbers and bubble sizes. The flow pattern, velocity field and bubble deformation characteristics within the variable diameter circular pipe at various inlet Reynolds numbers are analyzed. The aim is to explore the interaction patterns between the flow field characteristics and discrete bubbles and provide theoretical support for revealing the motion and deformation mechanism of discrete bubbles in variable cross-section field. The results indicate that the surrounding fluid velocity is altered by bubbles. The velocity gradients are increased, and the turbulence kinetic energy in the surrounding flow field is elevated. At the same time, the dramatic change of turbulent kinetic energy in the sudden expansion section leads to the rapid deformation or even fragmentation of discrete bubbles in the variable diameter circular tube field. Additionally, as the inlet Reynolds number increases, the fragmentation position of bubbles in the flow field tends to approach the sudden expansion section. When Re=5.16×103, the shortest bubble fragmentation distance is 16.09 mm. When the Reynolds number is constant, as the bubble radius increases from 2.5 mm to 4.5 mm, the dimensionless maximum deformation of the bubble is increased from 0.26 to 0.67. The numerical simulation results demonstrate good agreement with experimental findings.

Simulation of flow and mixing characteristics of binary particles in gas-solid fluidized bed (I): axial/radial flow field distribution characteristics

Guifang WANG Shuangzhu KONG Jian LI Xiuying YAO Yiping FAN Chunxi LU

The Chinese Journal of Process Engineering. 2025, 25(4):  354-363.  DOI: 10.12034/j.issn.1009-606X.224286

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In the fields of petrochemical and chemical engineering, some new processes involving the reactions of gas and catalysts with distinct functions and physical properties have been proposed. Since considerable physical properties difference in density, size and shape between two types of particles,the hydrodynamic behaviors of the binary mixture in the gas-solid fluidized bed are undoubtedly complex. This work presents a numerical investigation on the mixing and flow characteristics of binary particles (Geldart A particles and Geldart D particles) and gas in the bottom region of the gas-solid fluidized bed-riser coupling reactor. Considering the non-uniform structures in intermediate scale, the Eulerian-Eulerian multi-fluid model as well as the drag force model based on the energy minimization multi-scale (EMMS) are used. The axial distributions of bed density and pressure in the binary particle fluidized bed are investigated. By analyzing the turning points of these two parameters, the location of interface between the dense phase zone and the dilute phase zone is determined. The cross-sectional average solid holdup of Geldart A particles and Geldart D particles in the axial direction is also discussed. By comparing the parameter, the relative cross-sectional average solid holdup rates of the two types of catalysts, it is found that most Geldart D particles accumulate at the bottom of the bed in the axial direction. Furthermore, when the binary particle system is composed of coarse particles with low density and fine particles with high density, the distribution of the bed density in the bottom region of the bed layer is steady. In the radial direction, by analyzing the radial distributions of the local solid holdups of the two-solid phase, it is seen that both the Geldart A particles and the Geldart D particles tend to travel towards wall area. By introducing the new parameter, the local relative solid holdup, it is revealed that the Geldart D particle has a stronger tendency towards the wall compared to Geldart A particles.

Simulation of flow and mixing characteristics of binary particles in gas-solid fluidized bed (II): mechanical analysis of radial distribution characteristics of flow field

Guifang WANG Shuangzhu KONG Jian LI Xiuying YAO Yiping FAN Chunxi LU

The Chinese Journal of Process Engineering. 2025, 25(4):  364-372.  DOI: 10.12034/j.issn.1009-606X.224287

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Due to the distinct differences in size, density or shape of the particles' physical properties, the pattern of the two solid phases is complex. The hydrodynamics of binary mixtures of Geldart A particles and Geldart D particles in gas-solid fluidized bed, particularly the radial flow behaviors, are investigated. By comparing relative solid holdup, it is found that Geldart D particles tend to accumulate near the wall. However, few studies have discussed the occurrence for this phenomenon. The Kutta-Joukowski transverse force is introduced to analyze the distribution characteristics of local density and the local fractions of binary particles in the radial direction from the viewpoint of the forces on particles. Considering the fact that non-uniform structures in intermediate scale, the Eulerian-Eulerian multi-fluid model as well as the drag force model based on the energy minimization multi-scale (EMMS) is used. The Kutta-Joukowski transverse force on particles presents a non-uniform distribution in the radial direction. It is related to the gas-solid velocity-difference vector and the particle velocity radial gradient. Based on the radial profile of the Kutta-Joukowski transverse force, the flow regime is divided into three zones, the Kutta-Joukowski uniform influence zone (zone I), the velocity gradient dominant zone (zone II), and the velocity-difference vector dominant zone (zone III). The results show that the Geldart A particles and Geldart D particles exhibit similar tendencies in zone I to move towards the wall, resulting in a uniform distribution. In zone II and III, both Geldart A particles and Geldart D particles are exerted by the Kutta-Joukowski transverse force towards the wall, leading to a core-annulus phenomenon with low concentration at the center and high concentration near the wall. Compared to Geldart A particles, relatively higher Kutta-Joukowski transverse force on Geldart D particles results in a stronger tendency to move towards the wall region in zone II. In zone III, on the other hand, the tendencies for Geldart A particles and Geldart D particles travelling towards the wall are relatively weak.

Design and performance study on a novel gravity heat pipe based energy storage unit for new energy consumption

Shu ZHANG Yuanlin CHENG Hu YU Yi ZHANG Jinlin XIE Xingwei LIAO Ren ZHANG Changhui LIU Yanlong GU

The Chinese Journal of Process Engineering. 2025, 25(4):  373-381.  DOI: 10.12034/j.issn.1009-606X.224288

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As the global climate change issue has been escalating in severity, promoting the transformation of the energy structure has emerged as an irresistible trend. This involves reducing reliance on fossil fuels and enhancing the capacity for new energy consumption, particularly in the field of building heating, which contributes significantly to overall energy consumption. In this work, a solid-liquid phase change/vapor-liquid phase change coupling-based thermal storage heating device is designed, which is essentially a combination of a new type of gravity heat pipe and the phase change material paraffin wax, supplemented by the internal and external heat dissipation fins of the heat dissipation cylinder of the heat dissipation cylinder, enabling the completion of heating through natural convection. The wall temperature characteristics, start-up characteristics, heat transfer performance, and uniform temperature performance of the designed new gravity heat pipe with square liquid cavity are investigated experimentally. Subsequently, the heat storage and release characteristics of the heating unit are studied, and it is concluded that the new gravity heat pipe has good start-up characteristics, heat transfer characteristics, and uniform temperature performance, and its minimum heat transfer thermal resistance can be as low as 0.018℃/W, and the maximum equivalent thermal conductivity is 239.15 kW/(m?℃). The minimum starting temperature is 56.9℃, and the minimum homogeneous temperature coefficient is 0.009. The heating unit has a better heating capacity, with a maximum heating coefficient of 3.83. The design and research results of this new energy storage unit have important reference value for the comprehensive utilization of mobile heating units and distributed energy.

Experimental study on new type of wire plate electrostatic precipitator under synergistic effect of wet chord grid

Houcheng DING Yaqin XUE Quanlong DENG Wenjing ZHANG Zhenyang CHEN

The Chinese Journal of Process Engineering. 2025, 25(4):  382-388.  DOI: 10.12034/j.issn.1009-606X.224304

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In order to improve the dust removal efficiency of fine particulate matter in industry, based on the traditional wet string grid filtration dust removal and electrostatic precipitator theory, a new electrostatic precipitator experimental system was built by dividing wet dust removal and electrostatic precipitator into zones, under the synergistic effect of wet string grid. The influence of wavelength and amplitude of corrugated plates on dust removal efficiency under different voltages and wind speeds was explored through a single electrostatic precipitator experiment, and the optimal wavelength and amplitude values of corrugated plates were obtained. The influence of voltage, wind speed, and atomization pressure on the dust removal efficiency was explored through composite wet electrostatic precipitator experiments, and verified the dust removal effect of corrugated plates as dust collection plates in wet electrostatic precipitator systems. The results indicated that the dust removal efficiency in a single electrostatic precipitator was directly proportional to the voltage and inversely proportional to the wind speed. The dust removal efficiency of corrugated plates with different wavelengths and amplitudes was significantly improved compared to flat plates under different voltage and wind speed conditions, the impact of amplitude on the dust removal efficiency of corrugated plates was more significant, the corrugated plate with a wavelength of 150 mm and an amplitude of 60 mm had the best dust removal efficiency. The dust removal effect of the composite wet electrostatic precipitator system was significantly improved compared to a single electrostatic precipitator system, the dust removal efficiency of the combination of corrugated plate and water in the composite wet electrostatic precipitator system was higher than that of the combination of flat plate and water. The dust removal efficiency increased first and then decreased with the increase of wind speed and atomization pressure, which was proportional to the voltage. When the voltage, wind speed, and atomization pressure are 30 kV, 0.6 m/s, and 6 MPa, respectively, the maximum dust removal efficiency of the system reached 96.08%.

Surface structure modulation of CeO2/N-doped carbon composites and the dye removal properties

Yaohua HUANG Hao ZHANG Yanqi LIU Binghui WANG Richuan RAO

The Chinese Journal of Process Engineering. 2025, 25(4):  389-398.  DOI: 10.12034/j.issn.1009-606X.224210

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In this work, the surface structure of CeO2/nitrogen-doped carbon composites was tuned by controlling the feeding order of cerium nitrate and melamine in their synthesis process. Upon the characterization by TEM, XRD, TG, Zeta potential, and N2 adsorption-desorption isotherms, the synthesized CeO2/N-doped carbon composites were confirmed to be mainly composed of CeO2 and a large amount of N-doped carbon with different structures. Interestingly, it was found that the feeding order had a great influence on the nitrogen content, CeO2 dispersion, surface charge distribution, pore structure as well as specific surface area of CeO2/N-doped carbon composites. Compared to the CeO2/N-doped carbon composites prepared first by adding melamine (MCe), the CeO2/N-doped carbon composites prepared first by adding cerium nitrate (CeM) in their synthesis process had a much higher nitrogen content, which promoted the CeO2 dispersion on N-doped carbon surface and led to the formation of a predominantly positively charged surface in this sample, despite their lower specific surface area and unfavorable pore structure. The removal of Congo red by adsorption was employed to investigate the correlation between the surface structure of adsorbents and their adsorption capacities. It was discovered that the pore structure and specific surface area of CeO2/N-doped carbon composites were not the predominant factors for the adsorption removal of Congo red. Since Congo red presented an anionic state in aqueous solution, the formed Congo red anions could adsorb onto the positively charged surface of the sample via an electrostatic adsorption interaction, achieving high efficient removal of Congo red from the dye waste solution. Therefore, CeM exhibited a higher removal efficiency of Congo red. The adsorption capacities of the CeO2/N-doped carbon composites were further investigated to reveal the effect of different adsorption conditions such as inorganic salt, Congo red concentration, pH value, adsorbent dosage, and adsorption temperature.

Leaching behavior of valuable metals from paleo-terrestrial sedimentary rare earth ore leaching residue in sulfuric acid solution

Xingyu MAO Xianquan AO Yang CAO Yu GUO

The Chinese Journal of Process Engineering. 2025, 25(4):  399-407.  DOI: 10.12034/j.issn.1009-606X.224199

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Paleo-terrestrial sedimentary rare earth ore is a new type of rare earth ore, the process produces a large amount of rare earth residue after acid leaching separation of rare earth elements. Al, Fe, and Ti present in the rare earth residue are important metals, and the separation and extraction of metal elements from the rare earth residue can improve the utilization value of rare earth ores and solve the solid waste disposal problems. Sulfuric acid solution was used to leach the residue from rare earth ore processing to investigate the effect and reaction mechanism of sulfuric acid solution on the leaching behavior of Al, Fe, and Ti. The results showed that the sulfuric acid solution could effectively dissolve silica-aluminate and hematite in the rare earth ores, selectively leach Al and Fe. In contrast, anatase did not easily react with the sulfuric acid solution, and the leaching rate of Ti was low, which stayed in the leaching residue together with Si. The optimal reaction conditions were optimized using one-way and orthogonal experiments, and the leaching rates of Al, Fe and Ti reached 86.44%, 94.00%, and 7.14%, respectively, under the optimal reaction conditions of reaction temperature of 115℃, reaction time of 6 h, acid residue mass ratio of 2.1 g/g and liquid-solid ratio of 4 g/g. It was found that the reaction temperature significantly affected the leaching rates of Al and Fe. Then (NH4)2SO4 was added to the leaching solution, and Al could be converted to NH4Al(SO4)2 crystals and precipitated, and Al2O3 was produced by roasting to realize the separation of Al and Fe. This study realized the selective recovery of Al and Fe elements in rare earth residue, and enriched Si and Ti elements in the leaching residue, which was conducive to the recovery of Ti elements in the next step.

Phase equilibria and thermodynamics of the sodium benzenesulfonate-Na2SO4-H2O ternary system

Jiahui YI Benren LIAO Peng CHEN Jingyu WEI Han YAO Huiting HUANG Zhihao LU Lehua ZHANG

The Chinese Journal of Process Engineering. 2025, 25(4):  408-415.  DOI: 10.12034/j.issn.1009-606X.224274

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Industrial organo-sulfonic acid wastewater contains high concentrations of inorganic salts and various organo-sulfonates, causing significant challenges for their efficient removal, separation, and recovery. These waste streams often arise from complex industrial processes, and their intricate compositions make effective treatment and recycling more difficult. Herein, the phase equilibrium data for the sodium benzenesulfonate (BSNa)-sodium sulfate (Na2SO4)-water (H2O) ternary system were measured at temperatures of 273.15, 283.15, and 313.15 K using both the isothermal dissolution equilibrium method and Schreinemakers' wet residue method. Thermodynamic analysis of the dissolution process was performed using the van't Hoff equation, offering valuable insights into the system's behavior under different temperature conditions. At 313.15 K, the phase diagram indicated one invariant point, two univariant curves, and three distinct crystallization regions, corresponding to Na2SO4, BSNa, and their co-crystal mixture. However, at the lower temperatures of 273.15 and 283.15 K, the system displayed only one invariant point, one univariant curve, and two crystallization regions, specifically for Na2SO4?10H2O and a co-crystal region consisting of Na2SO4?10H2O and BSNa. Notably, no distinct crystallization region or solubility curve for BSNa was observed at these lower temperature ranges. Additionally, freeze crystallization experiments demonstrated no evidence of double salts or eutectic mixtures forming within the ternary system. This suggested that separating the components at lower temperatures, particularly around 283.15 K, was not only more efficient but also more cost-effective for obtaining pure salts. The thermodynamic analysis further revealed that the dissolution of Na2SO4 in this system was an endothermic, non-spontaneous process with an increase in entropy. The changes in enthalpy significantly influence the Gibbs free energy of dissolution, impacting the separation process. This research provided insight into the effective separation and recovery of BSNa and Na2SO4 from industrial wastewater, offering a solid foundation and practical guidance for improving wastewater treatment processes in industrial applications.

Study on influence of dust concentrations and moisture contents on formation characteristics of dust cake and filtration performance of coated filter media

Lumin CHEN Haijin LI Chen ZHU Wenyuan HU Fuping QIAN Zhimin ZHENG

The Chinese Journal of Process Engineering. 2025, 25(4):  416-424.  DOI: 10.12034/j.issn.1009-606X.224303

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In order to meet the latest national ultra-low emission standards, effective management of industrial dust is the key to achieving the goal. This study establishes an experimental test system for filter materials to investigate the influence of dust concentration and dust moisture content on the dust cake formation characteristics and filtration performance of coated filter media by analyzing the pressure drop, filtration efficiency, dust deposition per unit area, the thickness of dust cake and the standard deviation of thickness. The results show that with the extension of the filtration time, the thickness and inhomogeneity of the dust cake gradually increased from the top to the bottom in the vertical direction, however, the unevenness of the dust cake thickness stabilized after a period of time. With the increase of dust concentration, the thickness and inhomogeneity of the dust cake gradually increase. When the dust concentration is low, the overall increase in the thickness of the dust cake from the top to the bottom is slow, and the thickness difference is small. When the dust concentration is high, the thickness of the top of the dust cake increases slowly and the thickness of the bottom increases rapidly. With the increase of dust concentration, the pressure and the dust deposition per unit area increase, the filtration efficiency is around 99.9%, and the porosity gradually decreases overall. With the increase of dust moisture content, the uniformly of dust cake varies significantly, the dust cake uniformity is poor when the dust moisture content is 9% and 13%, and the distribution of dust cake is relatively uniform when the dust moisture content is 10%~12%. The effect of dust moisture content on the filtration performance is mainly reflected in the change of pressure drop, and the increase of dust moisture content helps to reduce the pressure drop of the dust cake, and the effect on the filtration efficiency is not significant.