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    28 February 2025, Volume 25 Issue 2
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    Contents
    Cover and Contents
    The Chinese Journal of Process Engineering. 2025, 25(2):  0. 
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    Review
    Research progress of Si3N4/BN composite ceramics
    Lei ZHAO Yue SUN Yulong HU Zheyu FANG Xing JIN Songlin RAN
    The Chinese Journal of Process Engineering. 2025, 25(2):  111-128.  DOI: 10.12034/j.issn.1009-606X.224154
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    Si3N4 is an inorganic nonmetallic material with high hardness, high mechanical strength and high thermal stability. It is widely used in cutting tools, biomedicine, electronics, military and automobile fields. However, due to the hard and brittle characteristics of Si3N4 itself, surface defects are formed during processing, which greatly reduces the reliability of Si3N4 ceramics. A large number of studies show that the composite ceramics prepared with Si3N4 as matrix can effectively make up for the shortcomings of single Si3N4 ceramics. Among them, the composite ceramics prepared by adding BN as the second phase are particularly attractive in advanced engineering applications. BN ceramics exhibit good electrical insulation, oxidation resistance, and corrosion resistance. It has a good application prospect as a heat conductive and insulating material. In addition, the densification process and grain growth of composite ceramics are affected by sintering process, thus changing the properties of composite ceramics. Therefore, the excellent properties of the two materials are taken into account by adding BN to the Si3N4 ceramic matrix, the mechanical properties and dielectric properties of Si3N4-based composite ceramics are improved. In addition to thermal conductivity, Si3N4/BN composite ceramics also have other properties such as burning resistance, thermal shock resistance and microwave absorption. The mechanism research and structural design of sintering technology of Si3N4/BN composite ceramics need to match the current application requirements of ceramic materials, and the further improvement of its properties is still the focus of current research. In this review, the sintering process of Si3N4/BN composite ceramics is introduced, and the research progress of properties of Si3N4/BN composite ceramics in recent years is summarized. Finally, this study outlines the current challenges and areas for further research in Si3N4/BN composite ceramics development.
    Developments and challenges in the evaluation of biological carbon sequestration benefits
    Mengdie WANG Xue XIA Dan WANG Zhao QIN Zhiyao PENG
    The Chinese Journal of Process Engineering. 2025, 25(2):  129-141.  DOI: 10.12034/j.issn.1009-606X.224200
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    With the concentration of carbon dioxide (CO2) in the air rising, the threat of global warming is getting worse. Due to its mild conditions and reaction specificity, the biological carbon sequestration technology shows excellent potential for industrial applications under carbon neutral constraints. However, to be genuinely sustainable, industrial applications must implement low-carbon-footprint technology. Current methods for biological carbon sequestration assessment are few and heterogeneous, with the lack of a harmonized scientific assessment framework. In order to promote the development on the biological carbon sequestration assessment, this article reviews the application of genome-scale metabolic network model (GSM) and life cycle assessment (LCA) in biological carbon sequestration assessment, with a focus on analyzing the bottleneck issues of these two methods in biological carbon sequestration assessment. In addition, this review also provides a systematic outlook on the future development direction of the biological carbon sequestration assessment, elaborates on the significant advantages of machine learning applications, points out the scientificity of evaluation indicators based on atomic economy (AE), standardizes the basic framework for data acquisition, and analyzes important breakthroughs in constructing a multi-level evaluation framework.
    Research Paper
    Data driven modeling of energy consumption and product quality in ethylene glycol distillation process
    Kangkang FENG Xin GENG Qinghui LOU Yu WANG Huajun HU Xiangjian SHI Cuimei BO
    The Chinese Journal of Process Engineering. 2025, 25(2):  142-149.  DOI: 10.12034/j.issn.1009-606X.224158
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    With the rapid development of polyester industry, the increasing demand of ethylene glycol (EG) is in conflict with the shortage of supply in China. Large project of EG production from coal has been receiving more and more attention. In the production of coal-to-ethylene glycol, the optimization of distillation operations represents a vital means to achieve energy saving and consumption reduction, as well as quality enhancement and efficiency improvement. The foundation of optimization lies in the establishment of precise models for the process. However, due to the complex reactions, strong system coupling, and non-linearity inherent in the distillation process, it is difficult to accurately construct models using traditional mechanistic methods. Therefore, this study uses the distillation process of coal-to-ethylene glycol as the research subject, employing a refined least squares support vector machine (LSSVM) algorithm to accurately construct energy consumption and product quality models for the ethylene glycol distillation process. In this process, the actual industrial data from the coal-to-ethylene glycol distillation process was used as the benchmark, the mutual information method was employed to extract the main feature parameters, and variable screening and data pre-processing were conducted. Subsequently, by introducing local target sets and using the UMDA algorithm for iterative optimization, the optimal hyperparameters were derived. After determining the optimal hyperparameters, the improved LSSVM algorithm was used to model the data samples and further compared this model with other purity and energy consumption models established by different algorithms. This comparison confirmed the high efficiency and accuracy of the improved LSSVM algorithm based on UMDA proposed in this work. In summary, compared with traditional support vector machine methods, the LOS-LSSVM model based on the UMDA optimisation process has a clear advantage in data fitting, accurately reflecting the actual situation of the distillation process and effectively improving the operational efficiency of ethylene glycol production.
    Research on influence of oxygen lance area position on flow characteristics of large copper smelting oxygen bottom blowing furnace
    Baocheng JIANG Tao XIAO Songsong WANG Xueyi GUO Qinmeng WANG
    The Chinese Journal of Process Engineering. 2025, 25(2):  150-158.  DOI: 10.12034/j.issn.1009-606X.224173
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    With the increasing demand for clean smelting of complex copper containing resources in China, oxygen bottom blowing copper smelting technology is playing an important role, and higher requirements are being put forward for its core equipment's (bottom blowing furnace) smelting capacity. Compared with other bottom blown furnaces, large oxygen bottom blown furnaces have larger specifications and more complex structures, and a high degree of matching between structure and function will be a very important issue. The position of the oxygen lance area is an important factor affecting the fluid flow and mass transfer inside a large oxygen bottom blowing furnace, thereby having a significant impact on the smelting effect. This work takes a large-scale copper smelting oxygen bottom blowing furnace of a certain enterprise as the research prototype, and uses numerical simulation methods to study the influence of the position of the oxygen lance on the flow characteristics of the large-scale oxygen bottom blowing furnace. The main focus is to investigate the influence of the position of the oxygen lance on the functional area and flow field inside the furnace. The results indicate that adjusting the position of the oxygen lance area can alter the distribution pattern of the functional areas inside the furnace. The "one end reaction and one end settlement" mode results in an asymmetric distribution of functional areas within the furnace. The effective extension of the settlement zone is conducive to the full separation of slag and matte. Offsetting the oxygen gun area towards the copper discharge port by 2300 mm form a "reaction at one end and settling at the other" mode. The settling area in front of the slag port is extended by 53.74%, and copper matte and copper slag achieve a more comprehensive and reasonable transition, full separation, and can be used as a directional control measure to optimize production.
    Reaction and gas-solid flow characteristics of calcium carbide synthesis in a fluidized bed
    Xu WANG Guohui SU Ting LI Zhennan HAN Liangliang FU Guangwen XU
    The Chinese Journal of Process Engineering. 2025, 25(2):  159-168.  DOI: 10.12034/j.issn.1009-606X.224166
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    Calcium carbide (CaC2) synthesis is a typical high-temperature solid-phase reaction. By reducing the particle sizes of raw material, the intra- and interparticle heat and mass transfer can be significantly improved, thus realizing calcium carbide synthesis at relatively low temperatures and then driving technological revolution. Based on this, a fluidized bed CaC2 synthesis process was proposed in this study, and the reaction characteristics and hydrodynamics of CaC2 synthesis from small-particle raw materials were investigated in a fixed bed and spouted fluidized bed, respectively. Besides, the reactions on the particle surface and its morphological changes during the reaction were analyzed, and the defluidization mechanism was further explored. The results showed that for raw materials with particle sizes of 147~178 μm, CaC2 synthesis reaction can occur at 1500℃, and the reaction rate significantly increased when the temperature was above 1600℃. At 1600℃, the C2H2 yield and CaO conversion rate can reach up to 101~105 mL/g and 25%~26%, respectively. As the C:Ca molar ratio of raw materials was less than 9.6, the defluidization occured when the fluidized bed was operated at 1500~1600℃, and a large number of coke particles were found to adhere to the surface of CaO particle. The bed defluidization was caused by the particle agglomerates, which were formed through the sintering of CaO particles and bonding between CaO and coke particles. It was found that the former was the dominant factor causing defluidization, and increasing the concentration of coke particles in the bed can avoid this. Therefore, this study verified the feasibility of fluidized bed solid-phase CaC2 synthesis and provided a novel approach and data support for technological revolution in the field of CaC2 production.
    Bubble coalescence model considering bubble shape variations and bubble-induced turbulence
    Weibin SHI Shanshan LONG Xiaogang YANG Hui HUANG Nian DUAN
    The Chinese Journal of Process Engineering. 2025, 25(2):  169-178.  DOI: 10.12034/j.issn.1009-606X.224140
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    For mathematical modelling of bubble coalescence, the cross-sectional area of the collision tube and the turbulent kinetic energy carried by the colliding bubbles are two key factors to determine the bubble coalescence rate due to turbulent collision. In most coalescence models, the shape of colliding bubbles is assumed to be spheric and the mean turbulent velocity correlation under shear turbulence (ST) condition is used to calculate the turbulent kinetic energy of the colliding bubbles. However, for the gas-liquid bubbly flow, the shape of bubbles transforms gradually from sphere to ellipsoid and spherical-cap with the increase of the bubble's volume. Furthermore, the influence of bubble-induced turbulence (BIT) has shown to be significant in the gas-liquid bubbly flow, especially along with the increase of the volume fraction of gas bubbles. When the bubble coalescence rate is calculated, the shape of bubbles affects the frequency of collision while the dominated turbulence mechanism affects the probability of a successful coalescence event. Based on the Prince and Blanch coalescence model, the present study proposed a coalescence model that considered the bubble shape variations as well as the joint effect of ST and BIT. Also, the turbulent kinetic energy transfer and the eddy-bubble response in the wake of spherical-capped bubble has been considered for the bubble coalescence due to BIT wake entrainment. Population balance model (PBM) has been used in the computational fluid dynamics (CFD) simulations for bubble columns to validate the proposed model. Comparisons have been made via simulation results of bubble size distributions (BSD) predicted by coalescence models with/without considering bubble shape variations and BIT. It is found that considering the shape of bubbles and the joint effect of shear turbulence and BIT, the proposed coalescence model significantly improves the prediction results of BSD and further affects the predictions of other important fluid dynamic parameters.
    Preparation of calcium carbonate nanoparticles by microbubble-enhanced carbonation
    Wenxin TIAN Hao DU Biao LIU Shaona WANG
    The Chinese Journal of Process Engineering. 2025, 25(2):  179-189.  DOI: 10.12034/j.issn.1009-606X.224147
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    CO2 mineralization is a promising method for the resource utilization of low-grade limestone and calcium-containing solid waste. Therein, adopting the acetic acid medium to achieve indirect mineral carbonation process to fixing CO2 is considered as an innovative and environmentally sustainable method owing to the reusability of the acetic acid medium. Nevertheless, the conversion efficiency of carbonation in this technique remains limited, with less than 20% efficiency at pressure of 5 MPa. Even with the addition of an extractant for acetic acid, the conversion efficiency of carbonation is still below 30%, significantly impeding the industrial applicability of this technology. In order to address the low conversion efficiency of carbonation in the acetic acid system, this study developed a new method for the preparation of calcium carbonate nanoparticles by microbubble-enhanced carbonation. The impacts of various factors such as medium calcium concentration, reaction temperature, reaction time, the value of pH, and aperture size of aerator on the efficiency of the carbonation reaction were systematically investigated. The results showed that: (1) Under optimal conditions (reaction time of 1 hour, reaction temperature of 80℃, initial pH of 7.2, initial calcium content of 70.07 g/L, and aperture size of aerator of 0.22 μm), the conversion rate of carbonation can reach 19.17% under atmospheric pressure, equivalent to the conversion rate achieved under 3 MPa. Meanwhile the regeneration cycle of the acetic acid medium can avoid wastewater generation at the source. (2) By integrating tributyl phosphate (TBP) with microbubble technology, the conversion efficiency of carbonation was improved to 57.5%, marking a 13.4 percentage point improvement over the reported pressurized extraction process. (3) At atmospheric pressure, rod-like aragonite nano-calcium carbonate products were synthesized with length of 400~800 nm and width less than 100 nm.
    Research on behavior and mechanism of flotation entrainment of microfine-grained serpentine
    Jiajun LIU Guofan ZHANG
    The Chinese Journal of Process Engineering. 2025, 25(2):  190-200.  DOI: 10.12034/j.issn.1009-606X.224160
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    In the flotation system of copper-nickel sulfide ores, fine-grained vein minerals, mainly serpentine, are very susceptible to be entrained into the concentrate with the froth, resulting in negative impacts on the concentrate product and the subsequent smelting process. In order to understand the influencing factors and whether there was any interaction in the process of froth entrainment of fine-grained serpentine and other vein minerals in the flotation system of copper-nickel sulfide ores, a response surface analysis (RSA) test was carried out on the basis of a one-factor test, and the effects of the interaction of the three factors, namely, foam agent dosage, gas volume velocity, and the foam layer thickness, were analyzed to determine the effects of the mechanical entrainment. The results of flotation entrainment showed that the foam agent dosage and pulp concentration affected the mechanical entrainment recovery of serpentine by influencing the water recovery and entrainment degree, while the gas volume velocity, particle size, and thickness of the foam layer only affected the entrainment degree and thus the recovery. The response surface test predictions were basically the same as the actual values, indicating that the predictions of the regression model were more accurate and can be used to analyze and predict the test results. The effects of the three factors investigated on the mechanical entrapment recovery of serpentine were foam agent dosage>foam layer thickness>gas volume velocity. Foaming agent dosage and foam layer thickness had significant influence on the mechanical entrainment of serpentine, which was a significant influence factor. The response surface method generally optimized the flotation conditions for the useful minerals rather than the vein minerals, and the interaction analysis showed that the different factors did not interact with each other on the mechanical entrainment of serpentine.
    Dissolution and separation of alumina from Guangxi high-iron bauxite
    Hao WU Shuhua MA Yanjun OU
    The Chinese Journal of Process Engineering. 2025, 25(2):  201-209.  DOI: 10.12034/j.issn.1009-606X.224050
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    Taking the unserviceable Guangxi high-iron composite bauxite as the research object, a new three-step process is developed based on clarifying the occurrence forms of alumina in bauxite, the results indicates that they are gibbsite, boehmite, Al-goethite, hematite, anatase, quartz and so on. Among these, iron oxides includes 72.22wt% exists in the form of Al-goethite and 27.78wt% exists in the form of hematite, and the substitution rate of aluminium for iron in Al-goethite is 24.5 mol/mol; Alumina in bauxite exists in three forms, namely gibbsite, boehmite and Al-goethite, each accounting for 37.48wt%, 3.89wt%, and 42.46wt% of the total alumina. Firstly, extract alumina in the forms of gibbsite and boehmite under conditions of Na2O 100 g/L, reaction temperature 180℃, and reaction time 1 hour, which can be easily and completely dissolved, while Al-goethite mineral is difficult to transform under this mild conditions, as seriously affects the economy of this new process. In order to solve the problem of alumina dissolution in Al-goethite, low-temperature roasting is adopted to transform Al-goethite into hematite and activated alumina in order to solve the problem of aluminium leaching from Al-goethite based on the thermal transformation mechanism from goethite to hematite at a certain temperature. By roasting this iron-rich phase for 0.5 h at a temperature of 450℃, about 57wt% of the alumina in Al-goethite is released outside the hematite lattice, thus aluminium-iron separation and phase transformation are achieved. In the third step, the transformed minerals are dissolved again under the conditions of low alkali concentration (Na2O 100 g/L), reaction temperature of 220℃, and reaction time of 1 h. Under these conditions, the activated alumina outside the hematite lattice is dissolved. The total dissolution rate of alumina in the three-step process reaches 85.92%, and the iron oxide in the mineral is greatly enriched in the tailings after dissolution, and its iron oxide content reaches 83.06wt%, which can be used as raw material for ironmaking.
    Preparation and property of colourless polyimide composite films modified with two-dimensional polyaramid
    Zijian LI Renzhao WU Haifeng DONG Fenyun YI Yan WANG Defu CHEN Yufu CAI
    The Chinese Journal of Process Engineering. 2025, 25(2):  210-220.  DOI: 10.12034/j.issn.1009-606X.224184
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    Colourless polyimide (CPI) is widely used as covers, substrates and touch panels for flexible displays, which require high glass transition temperatures (Tg), low coefficients of thermal expansion, excellent optical transparency and good mechanical properties. CPI is mainly obtained by introducing fluorine-containing groups to change the chemical structure of the molecular chain. This method of preparation allows for the production of CPI with high light transmittance, although it concomitantly results in a reduction in thermal and mechanical properties. By modifying two-dimensional inorganic materials, the thermal and mechanical properties of CPI can be effectively improved. However, technical difficulties such as poor compatibility with CPI and the complicated modification process also limit the application of two-dimensional inorganic materials in CPI modification. Therefore, a new method for modifying of CPI by a two-dimensional organic polymer, a two-dimensional polyaramid (2DPA) was proposed in this study, 2DPA/CPI composite films were prepared by the solution phase mixing method and the two-step thermoimide method. The structure and properties of 2DPA were analyzed, and the effects of 2DPA additives on the properties of 2DPA/CPI composite films, such as light transmittance, water absorption, Tg, and tensile strength were investigated. The results showed that without compromising the light transmission, the best effect was achieved when the addition of 2DPA in 2DPA/CPI composite films was 1wt%, and the Tg was increased from 338℃ to 358℃ compared to that of CPI films. The tensile strength reached 71.44 MPa, and elongation at break reached 4.34%, which were increased by 21.37% and 24.36%, respectively; and the water absorption rate was reduced by 39%, from 3.33% to 2.03%. The successful preparation of this CPI composite modified with two-dimensional organic material offers new ideas for the research and application of high-performance CPI-based composite materials, holding significant research value.