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    28 July 2024, Volume 24 Issue 7
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    The Chinese Journal of Process Engineering. 2024, 24(7):  0. 
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    Research Paper
    Study of flow pattern transition of jet impingement on a non-flat rotating wall
    Zhong CHEN Yuqing QIU Chengjun GU Dongxiang WANG
    The Chinese Journal of Process Engineering. 2024, 24(7):  753-762.  DOI: 10.12034/j.issn.1009-606X.223305
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    The spinning disk reactor, which uses jet to impact the rotating wall to form a high gravity and high shear film flow, is widely used in the fields of material preparation, polymerization and so on. Considering the effects of flow rate, rotational speed and viscosity of experimental materials, the effects of different groove structures on the surface of the reactor on the characteristics and transition rules of the liquid film flow pattern were studied by using the visualization platform. The flow pattern transition phase diagram was drawn and the transition conditions of the spiral broken wave were defined. The results showed that the distribution range of spiral wave in radial grooved disks was the largest among all types of disks, and the larger the number, the larger the flow range of maintaining spiral wave. With the increase of the number of circumferential grooves, the initial formation speed of spiral broken wave decreased, while the radial grooves always maintained a low speed. With the increase of the number of grooves, the operating flow range of spiral broken wave increased significantly, especially in radial grooves. The maximum Rej value of the spiral broken wave on the radial groove disk can reach 17 486, exceeding the upper limit of 12 823 on the circumferential groove disk, and the corresponding α value was 444.5 and 815, respectively, which indicated that the flow range of the spiral broken wave on the radial groove disk was wider and the centrifugal force required for spiral wave breakage was lower. When the viscosity of the experimental medium increased, the critical transition speed of the disk structure was higher than that of the disk in the lower Rej range, and the speed required for full spreading was higher. When the experimental medium was 50wt% glycerol, the Rej value of spiral broken wave maintained on smooth disk was less than 1318, indicating that the existence range of spiral broken wave was narrower than that of other structures. In the higher Rej range, the influence of groove type and distribution on flow pattern transformation was weakened, and the effect of radial groove was better than that of circumferential groove. This study provided a theoretical and applied basis for improving the micro-mixing and reaction performance of rotary reactor by regulating the liquid film flow behavior with non-flat surface.
    Gas flow distribution and optimization at the bottom of catalytic cracking industrial regenerator
    Lingling LU Feng WANG Hui WANG Maoming GONG Xiangping ZHANG
    The Chinese Journal of Process Engineering. 2024, 24(7):  763-771.  DOI: 10.12034/j.issn.1009-606X.223302
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    As one of the core equipment of the catalytic cracking unit of the refinery, the regenerator not only ensures catalyst reutilization but also maintains pressure and heat balance within the reaction-regeneration system. However, the main air distribution at the bottom of the regenerator will give rise to particle agglomeration, flow dead zone and other gas-solid mixed flow problems within the regenerator, which will directly affect the thermal balance and continuous and stable operation of the production unit. In this work, computational fluid dynamics (CFD) method is used to simulate and calculate the bottom area of a 0.5 Mt/a catalytic cracking accumulator. Based on the k-ω turbulence model, the gas phase flow state at the bottom of the existing industrial regenerator can be obtained, which will provide some guidance for the gas-solid distribution in the upper and middle regions. Through simulation calculations, it is shown that the radial distribution of gas phase velocity near the outlet of gas distribution is severely uneven. Based on the existing structure and operating conditions of the bottom of the industrial regenerator, improvements are made to improve the uneven radial distribution of gas velocity. The effects of different inlet velocities, inverted cone structures, and distribution plate aperture sizes on the uniformity of gas velocity distribution are studied. The results indicate that the main air flow rate has a significant impact on the radial uniformity of gas velocity. The height to diameter ratio of the inverted cone and the distance from the inverted cone to the gas distributor have little effect on the uniformity of the radial distribution of gas velocity. By increasing the aperture of the limited flow holes in the main air distributor, the uniformity of the radial distribution of gas phase velocity in the area above the distributor is improved, and for this regenerator device, the gas distributor aperture size of around 18 mm is the most suitable.
    Study of flow field characteristics and separation performance of inline cyclone gas-liquid separator
    Ming ZHANG Huan SUN Qiangqiang WANG Jiaqing CHEN Chao SHANG Xiang LI Chunsheng WANG Lingzhen KONG
    The Chinese Journal of Process Engineering. 2024, 24(7):  772-782.  DOI: 10.12034/j.issn.1009-606X.223312
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    The inline cyclone gas-liquid separator has received much attention because of its high separation efficiency and compact structure, but the ability to adapt to a wide range of inlet gas holdup is the key to its practicality. In this work, the flow field characteristics and separation performance of a inline cyclone gas-liquid separator that can adapt to a wide range of gas holdup changes are investigated by computational fluid dynamics (CFD) and experimental tests in air-water media system. The CFD numerical simulation results show that when the inlet gas holdup changes in the range of 10%~90%, the gas-phase separation efficiency is greater than 80% and the amplitude of change is less than 9.9%, and the liquid-phase separation efficiency is greater than 97% and the amplitude of change is less than 2.2%. The experimental results show that when the inlet gas holdup changes in the range of 9.4%~89.2%, the liquid holdup of the gas-phase outlet gradually decreases and the gas holdup of the liquid phase outlet gradually increases with the increase of the inlet gas holdup. The liquid holdup of the gas-phase outlet is less than 4%, and the gas holdup of the liquid-phase outlet is less than 10% except at liquid flow rate of 12 m3/h. Comparing the gas-phase separation efficiency and liquid-phase separation efficiency under different liquid flow rates, the best separation performance is achieved at a liquid flow rates of 8 m3/h. The CFD numerical simulation results are slightly different from the experimental test results, but the overall trend is consistent, which can be used as an effective tool for the design of structure enlargement. The research results show that the inline cyclone gas-liquid separator adopts the action form of "strong cyclone+weak cyclone+gravity", which has high separation efficiency and good resistance to fluctuations in working conditions.
    A thermal analysis kinetics method under flowing conditions based on distributed temperature sensing
    Yang SHEN Qiyue XU Shuliang YE
    The Chinese Journal of Process Engineering. 2024, 24(7):  783-792.  DOI: 10.12034/j.issn.1009-606X.223348
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    Addressing the needs for risk assessment and process optimization in continuous flow production, research was conducted to explore thermodynamic and kinetic calculation methods under flow conditions. By analyzing the thermal balance and material equilibrium of tubular reactors, a thermal analysis kinetics method applicable to flow conditions was designed. Subsequently, a continuous flow reaction experimental platform was constructed based on measurement principles for validation. Initially, temperature sensors distributed at various positions within the pipeline were employed to capture the temperature distribution during the experimental process. The equivalent overall heat transfer coefficient of the reaction pipeline was calibrated, and used in conjunction with segmented temperature distributions to calculate the enthalpy of the reaction. Subsequently, given the tendency to overlook temperature distribution in kinetic analyses, the study integrated calorimetric results and reactor models to compute kinetic parameters. The practicality of this approach was studied using the hydrolysis reaction of ethyl acetate and sodium hydroxide as an example. During the experiments, adjusting flow rates was employed to locate the peak temperature distribution, thereby enhancing the accuracy of calculated reaction enthalpy. The experimental outcomes revealed that under suitable flow conditions, the calculated reaction enthalpy closely matched results from batch experiments and established literature values. Moreover, the flow calorimetric method exhibited higher experimental efficiency, lower liquid holdup, and increased safety during the experiment. The kinetic analysis results were in close alignment with literature values, showing a relative error of less than 3% in the activation energy calculations. Combining calorimetric results with kinetic parameters allowed the use of reactor models to predict temperature distributions under varying conditions, demonstrating a close correlation with measured values. This serves as valuable guidance for subsequent risk assessments and process optimizations in the realm of reaction evaluation and procedural enhancements.
    Boiling flow and heat transfer in rectangular periodic expansion-constriction microchannels
    Guyu XING Junfei YUAN Lin WANG He JIANG Zicheng FENG Mengxuan WANG
    The Chinese Journal of Process Engineering. 2024, 24(7):  793-804.  DOI: 10.12034/j.issn.1009-606X.223357
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    In order to explore the boiling flow and heat transfer characteristics in the rectangular periodic expansion-constriction microchannel, rectangular periodic expansion-constriction microchannels of different sizes are established, and deionized water is used as the working fluid to carry out numerical simulation under the conditions of inlet velocity of 0.2 m/s and heat flux of 50 W/cm2. The results show that there are enlarged and contracted cross-sectional structures in the rectangular periodic expansion-constriction on microchannels. The enlarged part of the microchannel provides a nucleation site, which is conducive to bubble nucleation and increases the heat exchange area. With the increase of the periodic frequency of the expansion-constriction structure, the more intense the coupled heat transfer between cavitation and boiling in the microchannel, there are still more small bubbles in the middle and downstream regions of the channel. The number of small bubbles along the channel increases, the gas content increases, and the heat transfer performance continues to improve. In addition, the maximum temperature of the wall along the microchannel gradually decreases, and the temperature distribution along the channel become more uniform. The rectangular periodic expansion-constriction microchannel reduces the contact area between the bubble and the wall, and reduces the frictional pressure drop between the two phases. But the expansion-constriction of the microchannel increases the resistance to flow in the channel. The pressure drop in the expansion-constriction microchannel increases with the increase of the γ of the structural parameters. At the same time, the comprehensive performance of flow heat transfer in the microchannel increases first and then decreases with the increase of the frequency of the expansion-constriction channel. When the structural parameter of γ is 0.2, the comprehensive performance of the rectangular periodic expansion-constriction microchannel is the best, which is 34% higher than that of the rectangular straight microchannel.
    Effect of oxygen-rich combustion conditions on heating process of slab in reheating furnace
    Biao LU Xingyin WANG Qingyun HU Yan CHEN Demin CHEN Jin GAO
    The Chinese Journal of Process Engineering. 2024, 24(7):  805-814.  DOI: 10.12034/j.issn.1009-606X.223306
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    Compared with traditional air combustion, oxygen-enriched combustion can increase the flame temperature, strengthen the radiation heat transfer in the furnace, reduce the exhaust heat loss, increase the volume fraction of CO2 in the flue gas, and is conducive to CO2 capture, so it has become a hot spot in the field of industrial furnace research. At present, most studies simply transform the whole heating furnace from conventional air combustion to oxygen-rich air combustion, and are limited to the single factor of oxygen volume fraction. In order to explore the influence of different oxygen-rich combustion arrangement forms and different oxygen volume fractions on the heating furnace thermal characteristics and slab heating process, two oxygen-rich combustion models (JC-1 and JC-2) with oxygen volume fraction of 21vol%~49vol% are established to study the effects of combustion of gas and fuel on the thermal characteristics of the furnace and slab heating characteristics by numerical simulation. The results show that compared with the JC-1 condition, the temperature distribution in the furnace under JC-2 condition is more uniform and the slab temperature is higher, so the oxygen-rich combustion arrangement under JC-2 condition is better than that under JC-1 condition. Slab temperature and furnace thermal efficiency increase with the increase of oxygen enrichment volume fraction, but the increase rate decreases gradually. When the oxygen volume fraction is between 21vol% and 37vol%, the heating furnace slab temperature and furnace thermal efficiency increase at a higher rate. In this volume fraction range, when the oxygen volume fraction of JC-1 and JC-2 increases by 1%, the furnace thermal efficiency increases by 0.44% and 0.47%, and the energy saving rate increases by 1.07% and 1.12%, respectively. Therefore, 37vol% is the optimal oxygen volume fraction for oxygen-enriched combustion. The significance of this study is to provide reference for the existing reheating furnace to implement the transformation of oxygen-rich combustion.
    Analysis of influence of alkali metal catalysis on non-uniform deterioration characteristics of blast furnace coke
    Qihang LIU Shangjin LI Shuangping YANG Shilin WENG Qu HU Xiaowei ZHAO
    The Chinese Journal of Process Engineering. 2024, 24(7):  815-824.  DOI: 10.12034/j.issn.1009-606X.223335
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    With the addition of various low-quality raw materials in the blast furnace, the enrichment of alkali metals increases. And in the context of carbon peaking and carbon neutrality, the reduction in coke usage makes its quality more and more important. In order to elucidate the effect of alkali metal catalysis on the non-uniform dissolution and deterioration characteristics of coke, the relationship between matrix and porosity of alkali metal at different reaction stages of coke was studied by coke powder and block coke dissolution experiments and segmented analysis method. Based on the relative size of the chemical reaction rate and the stomatal diffusion rate of the basic characteristics of coke deterioration, the non-uniform deterioration parameter (kv/Deff)1/2 of coke was further improved and optimized to more accurately describe the non-uniform deterioration behavior of coke in the blast furnace. The results showed that during the dissolution process, there was an obvious reaction gradient in the porous structure of coke, that was non-uniformity. Its size was closely related to the matrix reactivity and pore diffusion characteristics of coke, and alkali metals played a positive catalytic role in matrix reactivity, while the pore diffusion coefficient changed with the random evolution of coke pore structure, and the direct relationship with alkali metals was small. Alkali metal catalysis had a significant kinetic effect on the carbon loss process of coke, it can significantly increase the (kv/Deff)1/2, resulting in the formation of a larger reaction gradient inside the porous structure of coke, reducing the deterioration uniformity of coke. This made the particle size distribution of the coke more uneven after the deterioration of the blast furnace, thus greatly reducing the permeability of the blast furnace. The non-uniform deterioration parameters can provide an effective reference for further constructing the mathematical relationship of the dissolution behavior of blast furnace coke, and provide a reference for future blast furnace production.
    Recovery of metal aluminum by electrolysis of AlCl3-NaCl-LiCl-KCl molten salt
    Yahui AN Fengguo LIU Aimin LIU Zhongning SHI Zhaowen WANG
    The Chinese Journal of Process Engineering. 2024, 24(7):  825-832.  DOI: 10.12034/j.issn.1009-606X.223325
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    Over the past few decades, aluminium alloys have been used in a large number of applications in packaging, transport, aerospace and other areas, making them the second most important metallic material after steel. Because of their good corrosion resistance, aluminum alloys can be recycled after reaching the end of their useful life. The recycling of aluminum alloys has the double important significance of saving resources and environmental protection. The traditional cryolite electrolytic alumina process consumes a lot of energy and releases a lot of greenhouse gases. Remelting and recycling of end-of-life aluminum alloys can reduce energy consumption and carbon emissions, but this method affects the purity of the recycled aluminum. Recycling of scrap aluminum by molten salt electrolysis not only reduces energy consumption and carbon emissions, but also improves the purity of the recycled aluminum. In this work, AlCl3-NaCl-LiCl-KCl was used as the electrolyte for aluminum deposition on pure aluminum sheet with scrap aluminum alloy as the anode. The effect of experimental conditions such as current density, electrolysis temperature, and electrolysis time on the recovered metallic aluminum products were investigated, and the electrochemical mechanism of aluminum recovery in AlCl3-NaCl-LiCl-KCl molten salt was analyzed. It was shown that the current efficiency in scrap aluminum alloy could reach 97.3% and the purity of aluminum obtained was about 99.4wt% under the conditions of electrolysis temperature of 100℃, current density of 30 mA/cm2, and electrolysis for 3 h. The cyclic voltammetry curve indicated that only aluminum was involved in the reaction process, and the deposition potential of aluminum was about -0.3 V (vs. Al), and the scrap aluminum alloy dissolved under the action of the current and reacted with AlCl4- in the electrolyte to form Al2Cl7-, and Al2Cl7- near the cathode gained electrons to form an aluminum deposition layer on the cathode surface.
    Catalyst and reaction rate constant prediction methods of coupling reaction based on convolutional neural network
    Ting YANG Yachao DONG Jian DU
    The Chinese Journal of Process Engineering. 2024, 24(7):  833-842.  DOI: 10.12034/j.issn.1009-606X.223308
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    Cross-coupling reactions are one of the most effective methods of forming carbon-carbon bonds in modern organic synthesis. Effective screening and optimization of reaction conditions, such as catalysts, play an important role in improving the efficiency of drug and fine chemical development. In this work, the convolutional neural network models and methods based on an organic reaction database are developed for Suzuki-Miyaura and Buchwald-Hartwig cross-coupling reactions to predict suitable reaction catalysts (with ligands) and rate constants. A comparative model is also established based on the random forest algorithm. The results show that the catalyst prediction model based on the convolutional neural network can accurately recommend reaction catalysts with 85% of top 3 accuracy in the Suzuki-Miyaura cross-coupling reaction dataset, and 92% of top 3 accuracy in the Buchwald-Hartwig cross-coupling reaction dataset. After obtaining the catalyst recommended by the model, the ECFP4 molecular fingerprint and K-Means algorithm are used to cluster the reaction based on the structural characteristics of the catalyst, and on this basis the reaction rate constant is predicted. In order to create a reaction fingerprint that describes the entire reaction, the random number labels are generated from the catalyst text and then concatenated with the ECFP4 molecular fingerprint of the reactants and products. Rate constant prediction models are established based on the datasets and compared respectively. The results show that the performance of the rate constant prediction model using the clustering method is significantly improved on the two types of cross-coupling reaction datasets, which indicates that the reaction clustering method based on the structural characteristics of catalyst has a significant improvement in predicting the rate constant of the cross-coupling reaction. This cross-coupling reaction catalyst and rate constant prediction methods based on the convolutional neural network are expected to be applied to other organic synthesis reactions and further use the formed model for reaction condition control and optimization.
    Adsorption separation and its process simulation of trace Na+ and K+ in the preparation of electronic grade hydroxyethyl acrylate
    Shoutianbao CHEN Kai ZHANG Zhenliang XU Liang CHENG Sunjie XU Yongming WEI
    The Chinese Journal of Process Engineering. 2024, 24(7):  843-851.  DOI: 10.12034/j.issn.1009-606X.223313
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    Hydroxyethyl acrylate (HEA) is a widely used chemical raw material. With the development of science and technology, the purity requirements of electronic chemicals in the field of integrated circuit semiconductors have reached the electronic level. Therefore, the separation purification process is crucial. However, there is not much research reports about the separation purification of electronic grade HEA. In this work, the ion exchange resin adsorption method is used to remove Na+ and K+ while avoiding the problem of polymerization and reducing the purity of the product in the high-temperature environment of HEA. Na+ and K+ dynamic adsorption model and its characteristics were obtained through the static adsorption experiments of ion exchange resin. The fitting degrees of Langmuir isothermal adsorption model and Freundlich adsorption model were compared. The isothermal adsorption curves and maximum adsorption capacities for Na+ and K+ on the ion exchange resin were obtained. The penetration curves for Na+ and K+ on the ion exchange resin were acquired by the dynamic adsorption experiments. And the dynamic adsorption process was simulated using Aspen Adsorption. The relationship between the working state of resin bed and adsorption time was obtained. The experimental values were good agreements with model values. At the same time, the Langmuir model was better than the Freundlich model. The experimental results showed that the pseudo-first-order kinetic model could be better in line with the actual situation, and the adsorption rate of Na+ was slightly faster than that of K+. The penetration curve was also consistent with characteristics of Na+ that it had faster adsorption speed and penetration speed. The simulation results of Aspen Adsorption showed that the experimental values were consistent with the model values. The adsorption experimental results for industrial grade HEA showed that the removal rates of K+ and Na+ on the ion exchange resin were more than 99%. Therefore, the simulation and experimental results provided relative parameters data supports for the practical application of electronic grade HEA.
    Effect of La content on the microstructure and TiN precipitation behavior of high-titanium steel during slow cooling solidification
    Yong WAN Chuansheng TANG Guangwei YANG Xuejian ZHANG Yonghong WEN
    The Chinese Journal of Process Engineering. 2024, 24(7):  852-862.  DOI: 10.12034/j.issn.1009-606X.223309
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    In this work, the effects of four kinds of La content on the microstructure and TiN precipitation behavior of high-titanium steel are studied by high temperature melting experiment, optical microscope (OM) and scanning electron microscope (SEM). It is intended to give scientific basis and experimental data for La treatment to refine the size of TiN and the microstructure in the center region of cast ingots of high-titanium steel. The results show that the solidification structures of all experimental steels are equiaxed grains when the solidification cooling rate is 0.17℃/s. La shows obvious ability of deoxidization, S and Al at low La content (0.0013wt%), so LaAlO3 and La2O2S are mainly formed in its steel. La just began to show obvious ability of deoxidization, S and Al at high La content (0.0052wt%, 0.0223wt%). With the consumption of a large amount of O atoms, the deoxidization and sulfur ability of La increased rapidly. Therefore, La2O2S is the predominant precipitate that forms in the steel, and some La2O2S particles will nucleate and grow on the surface of LaAlO3 particles that have previously precipitated. TiN mainly precipitates in the Liquid+δ two-phase region in this experimental steel. LaAlO3 and La2O2S precipitate before TiN, and their small lattice misfit with TiN are the primary cause of their propensity to act as the cores of TiN heterogeneous nucleation. When the La content in the steel is 0wt%, 0.0013wt%, 0.0052wt%, 0.0223wt%, the average axial grain size of each experimental steel is 354, 223, 154, 126 μm, respectively. The maximum size of TiN is 19.1, 11.7, 11.4, 10.4 μm, the TiN area density in each experimental steel is 42.2, 82.9, 86.3, 90.7 No./mm2, the maximum size of TiN is 19.1, 11.7, 11.4, 10.4 μm, and the average size of TiN is 7.8, 4.6, 4.5, 4.4 μm.
    Microstructure and properties analysis of Microstructure and properties analysis of welded joint of 22MnB5/QStE550TM dissimilar steel
    Ming ZHANG Leilei ZHOU Enrong LIANG Zhigang ZHU Pengyan ZHANG
    The Chinese Journal of Process Engineering. 2024, 24(7):  863-874.  DOI: 10.12034/j.issn.1009-606X.223321
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    In the experiment, different thickness of 22MnB5 steel with 1.8 mm thickness and QStE550TM steel with 2 mm thickness are welded by TIG welding. The microstructure of the characteristic area of the welded joint of different steel is observed by optical microscopy (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The mechanical properties of dissimilar steel welded joints are analyzed by universal mechanical testing machine and Vickers hardness tester. The experimental results show that the microstructure of the heat affected zone on the QStE550TM side is granular bainite, the microstructure of the weld area and the heat affected zone on the 22MnB5 side is lath bainite, and part of the oxide inclusion in the heat affected zone on the 22MnB5 side induces the formation of acicular ferrite. The average grain size in the weld area is 4 μm, and the proportion of grain boundaries with large angle in the weld area is about 53%. The second phase Ni-Cr-Fe solid solution was found in the characteristic region of the dissimilar steel welded joint. The average tensile strength of the two groups of tensile samples is 660.5 MPa. The highest hardness area of the welded joint is 22MnB5 base metal, and the lowest hardness area is QStE550TM side heat affected zone. There is carbon migration in the heterogeneous steel joint. A carburized layer of about 43 μm appears near the fusion interface of 22MnB5 side, and a decarburized layer of about 35 μm appears in the heat affected zone of QStE550TM side. However, combined with the analysis of the mechanical properties of the dissimilar steel welded joint, the carbon migration phenomenon of the welded joint has no obvious effect on the mechanical properties.