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The Chinese Journal of Process Engineering 2022, 22 (1): 0-.

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Research progress on photocatalytic treatment of residual xanthate in mineral processing wastewater and improvement of degradation efficiency

Rui LIANG Mingyang LI Xiangpeng GAO Xiankun YU Xiong TONG Hongming LONG

The Chinese Journal of Process Engineering 2022, 22 (1): 1-13. DOI: 10.12034/j.issn.1009-606X.220436

Abstract （209）

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Degrading the residual xanthate efficiently, environmentally, and economically in the mineral processing wastewater is a major problem needing to be solved urgently in the process of building a green mine. Photocatalytic degradation of xanthate in flotation wastewater is an environmentally friendly wastewater treatment process. It has many advantages, such as simple and convenient operation, wide application range, mild reaction conditions, free secondary pollution, etc. This work focuses on the application of photocatalytic degradation methods and reviews the research progress of photocatalysts of xanthate in recent years. It mainly introduces the research overview of photocatalysts according to the different classifications of photo-catalytic materials and their modification methods, and then explores the reaction mechanism and related influencing factors of photocatalytic degradation of xanthate. Moreover, improvement methods based on the factors affecting the degradation rate of photocatalysts are proposed. In the end, the design and process development of catalysts for photocatalytic degradation of xanthate were prospected. The photocatalytic materials currently used in the degradation of xanthate are mostly derived from metal semiconductors, including titanium, bismuth, zinc, copper, tungsten, iron-based compounds, and their modified substances, as well as non-metal semiconductor g-C3N4 and HAP-based photocatalyst. The ultimate goal of studying photocatalytic technology is to treat pollutants efficiently and environmentally. Therefore, how to improve the degradation efficiency is the core issue of the study. The existing literature mainly uses degradation conditions and photocatalysts to determine the factors affecting degradation efficiency and proposes targeted improvements. In addition, to make up for the shortcomings of a single photocatalyst, a combined process will be adopted to maximize the photocatalytic degradation efficiency.

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Experimental research on influence of refrigerant charge on heat transfer characteristic of micro-channel evaporator

Jinli LU Tingting YIN Yafang HAN Yajin LIU

The Chinese Journal of Process Engineering 2022, 22 (1): 14-21. DOI: 10.12034/j.issn.1009-606X.220342

Abstract （228）

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With the advantages of compact structure, small size, high heat exchange efficiency, and low refrigerant charge, the microchannel heat exchanger has broad application prospects in the fields of electronic components, automobiles, heat pumps, air conditioners, etc. According to the literatures, the microchannel heat exchangers are currently used more in electronic components and automobiles, but less in household air conditioners. Therefore, the microchannel heat exchanger was designed and produced based on aluminum materials and employed as evaporator of cabinet air conditioning. The surface temperature distribution, cooling capacity, input power, and energy efficiency ratio (EER) were researched under the conditions of three inlet types (Z-Inlet, Y-Inlet, U-Inlet) and five refrigerant charges (in the range of 800~1600 g). Furthermore, the results were compared with the finned-tube evaporator which was composed of cooper tubes and aluminum fins. The results showed that the Z-Inlet type had uniform flow rate distribution, uniform surface temperature distribution, and excellent heat transfer performance because of the same length of the flow inside of microchannel evaporator. The Z-Inlet type of microchannel evaporator had the highest cooling capacity and EER. Compared with the other two type (Y-Inlet, U-Inlet), the cooling capacity and EER increased by a maximum of 8.8% and 5.7%, respectively. The cooling capacity and EER of microchannel evaporator were significantly higher than that of finned-tube evaporator, with an average increase of 11%, and a maximum of 13.3% (about 600 W). And the EER increased by an average of 9.36%, and a maximum of 12.4%. In addition, compared with finned-tube evaporator, the refrigerant charge of microchannel evaporator can be reduced by 200 g when the cooling capacity and EER with the maximum value. Therefore, the research results of this work can provide data support for the development and design of microchannel evaporators, optimization of operating parameters, and support the application of microchannel evaporators in the field of air conditioning.

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The baffle structure optimization for high and low side?by?side type RFCC stripper

Biao LIU Xiuying YAO Zhenliang MENG Mengxi LIU

The Chinese Journal of Process Engineering 2022, 22 (1): 22-31. DOI: 10.12034/j.issn.1009-606X.220397

Abstract （240）

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A stripper is an important part of a fluid catalytic cracking (FCC) plant, affecting products yields, energy consumption and long-term run of the entire unit greatly. A high-efficiency stripper increases the light oil yield and improves the product distribution, moreover, it also reduces the coke-burning load of regenerator and decreases the hydrothermal deactivation of catalyst. Strippers widely used in fluid catalytic cracking units can be categorized into the packing stripper and the baffle stripper. The former owns the advantages of high stripping efficiency and better space utilization, but is not suitable for residue fluid catalytic cracking (RFCC) units, because the grid is easily blocked up with coke and difficultly cleaned. Therefore, the latter is widely used in RFCC units, benefited from simple structure, high stripping efficiency and long-term operation. Hydrodynamic characteristics of gas phase and solid phase in a commercial stripper with perforated baffle is rarely studied, subject to severe experiment condition and poor measurement methods. In this work, hydrodynamic behavior of the steam and particles in a commercial-scale fluid catalytic cracking stripper is investigated numerically, by using two-fluid model with a drag model which divides the flow region into four parts: dese, sub-dense, dilute and ultra-dilute. The mean bed density from the simulation is in good agreement with the value registered in a commercial unit. Calculation results demonstrate that strict S-shape flow of steam does not exist in stripper. Steam short circuit between the neighboring annular baffles or conical baffles occurs in the region of 0.85<r/R<1 or 0.35<r/R<0.5, respectively. Radial distribution of catalyst concentration above the baffle is uneven. The steam flux of holes on baffles reduces with the decrease in the vertical position of holes, explaining why the phenomena of the gas short circuit appears. Based on the above findings, a new baffle was proposed and adopted in order to distribute steam reasonably. Simulation results show that the steam short circuit is significantly weakened, leading to a smooth catalysts flow above the baffle and an excellent gas and solid contact.

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Simulation of gas-liquid flow and structure optimization in scrubbing-cooling chambers

Yang LIU Zhongshan GUO Yuanqi ZHAO Xiaoping GUAN Ning YANG

The Chinese Journal of Process Engineering 2022, 22 (1): 32-40. DOI: 10.12034/j.issn.1009-606X.221040

Abstract （214）

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The scrubbing-cooling chamber is an important part of a coal gasifier to wash and cool the generated high-temperature syngas. It is composed of a vertical pipe and the liquid bath. However, some technical problems still exist in industrial-scale scrubbers, such as unstable operation, lower washing efficiency, all of which are relevant to gas dispersion in scrubbers. It is of great significance to design a scrubbing-cooling chamber with higher washing efficiency. Due to the difficulty of transforming the scrubbers on an industrial-scale, the CFD simulations were used to understand the complex gas-liquid flow in different structures of scrubbing-cooling chambers and to provide theoretical guide for industrial design and process scale-up. In this work, a new scrubber which combined of branch pipes and a draft tube on the basis of the general scrubbers was proposed to promote gas dispersion and a three-dimensional Euler-Euler two-fluid model was used to simulate the flow behavior in three different scrubber geometry, i.e., no-internals, branch pipes attached on the vertical pipe, a combination of branch pipes and a draft tube. Gas holdup, liquid flow field and gas distribution were compared among the three different geometries. Comparison between the simulation and the experiments in literature showed that the model can accurately predict the gas holdup distribution. Furthermore, simulations indicated that the added branch pipes diverted a portion of gas to the central region of the chambers, which may otherwise be entrained along the wall of the central pipe. The branch pipes promoted the radial dispersion and was helpful to maintain stable operation. Further installation of a draft tube enhanced the amount of gas transported by the branch pipes, and increased the global gas holdup under the liquid surface of the scrubber. It was found that the combination of the branch pipes and the draft tube can effectively intensify gas-liquid circulation and interfacial contact, and improve the washing efficiency.

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Large eddy simulation of inclined interface instability induced by planar shock wave

Yongkang GUAN Yi LIU Lite ZHANG

The Chinese Journal of Process Engineering 2022, 22 (1): 41-49. DOI: 10.12034/j.issn.1009-606X.221057

Abstract （197）

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Interfacial instability and its induced interfacial deformation and turbulent instability are widely used. In medium characteristic scale supersonic combustion, the interfacial instability enhances the mixing of fuel and combustion aids. In small characteristic scale inertial confinement fusion, the turbulent mixing induced by interfacial instability dilutes and cools the fuel twice, thus reducing the reaction rate and even causing ignition failure. In recent years, scholars at home and abroad have deeply studied the interaction between the classical planar shock wave and the phase interface from many angles, but the research on the interaction between the shock wave and the gas-liquid oblique interface is still not systematic and comprehensive. It is of great significance to explore the evolution of shock driving gas-liquid interface instability in practical engineering applications such as supersonic combustion and inertial confinement fusion. In the process of numerical simulation, VOF model is used, combined with large eddy simulation method and appropriate boundary conditions to study the evolution process of shock induced gas-liquid two-phase oblique interface deformation and turbulent mixing in two-dimensional plane. The influence of Mach number of incident shock, initial inclination angle of shock and inclined interface inclination angle on interface instability is analyzed. The results show that the Mach number of incident shock is the most important factor in the development of interface instability. Under the same conditions, compared with the other two factors, increasing the shock Mach number can significantly increase the interface deformation and the development of turbulent mixing. At the same time, the number of serrated structures on the interface increases, the forming speed is obviously accelerated, and the width of turbulent mixing zone increases obviously. In addition, with the increase of the initial angle of shock wave and inclined interface angle, the number and forming speed of serrated structure on the interface increase at the same time, and the width of turbulent mixing zone also increases.

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Numerical simulation analysis of particle concentration field in a super vortex quick separation system under different oil steam parameters

Zhiliang ZHANG Haijun CHEN Tao CHEN Pei MOU Anjun LI Wenjun LI

The Chinese Journal of Process Engineering 2022, 22 (1): 50-61. DOI: 10.12034/j.issn.1009-606X.221092

Abstract （205）

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In order to investigate the movement and concentration distribution characteristics of catalyst particles in the riser outlet super vortex quick separation (SVQS) system, the gas-solid two-phase flow under different oil steam parameters was numerically simulated. Whereafter, particle size, concentration distribution and particles back mixing were analyzed. The simulation result showed that under a certain entrance concentration the particle concentration on the wall of the closing cylinder was greater with the greater density of oil steam or the smaller viscosity of oil steam, and distributed in a spiral strip with different bandwidth. A large number of particles gathered at the cover plate of the flow partition cylinder and formed a particle belt with periodic shedding characteristics. Moreover, the phenomenon of short circuit flow at the bottom of flow partition cylinder that weakened the separation performance of SVQS system. Particles with different sizes were always in a spiral layered arrangement when moving in a downspin, and the separation performance of SVQS system for fine particles with diameter below 0.013 mm was weak. With the increase of oil steam density or the decrease of viscosity, the particles following behavior became better, the particles concentration distribution was more uniform, and the SVQS system had a stronger ability to capture medium and fine particles. Particles back mixing also existed in SVQS system and decreased with the increase of oil steam density or the decrease of viscosity. Meanwhile, reducing particle back mixing and inhibiting particle concentration peak were important ways to improve the separation performance of the system.

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Modification behavior of Sb in electromagnetic separation process of high silicon aluminum silicon alloy

Xiongdong YANG Junpeng WANG Wenhui MA Guoqiang LÜ Aimin XING

The Chinese Journal of Process Engineering 2022, 22 (1): 62-71. DOI: 10.12034/j.issn.1009-606X.220401

Abstract （206）

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Aimed at the electromagnetic separation process of high silicon aluminum silicon alloy, addition of the modifier Sb in the separation process was proposed to and the effects of the addition amount of the modifier Sb, the pull-down rate, and the temperature on the separation effect in the electromagnetic separation process of the high silicon aluminum silicon alloy (45wt% Si) to strengthen the separation of primary silicon and alloy were studied. In the early stage of the directional solidification process, the modification experiment was carried out to perform XRF detection and FEI-SEM scanning of the silicon content in the primary silicon enrichment area of the sample, and the EPMA analysis of the micro morphology of the alloy part. Later, referred to the Sb modification mechanism in the relevant literature, Comsol software was used to simulate the electromagnetic directional solidification process of Al-45wt% Si. The separation theory of primary crystal silicon and the theory of silicon grain refinement were used to discuss the metamorphic behavior of Sb. After the addition of Sb, the eutectic reaction temperature of the aluminum-silicon alloy decreased and the entire solidification process became longer. Theoretically, the primary crystal silicon can obtain more sufficient growth conditions, which was beneficial to the enrichment of the primary crystal silicon. The results showed that after adding the modifier at 1500℃, when the pull-down rate was 10 μm/s, the silicon content in the silicon-rich phase increased from 86wt% to 90wt%. When the pull-down rate was 40 μm/s, the silicon content in the silicon-rich phase increased from 81wt% to 86.5wt%. At the same time, after adding the modifier, the eutectic silicon phase of the alloy was uniformly and continuously distributed in the α-Al matrix, and the morphology was refined.

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Improved sodium storage performance of layered oxide cathode materials via ZrO ₂ coating

Yang SUN Hong WANG Haiying CHE Xiaozhen LIAO Linsen LI Guijia CUI Weimin YANG Zifeng MA

The Chinese Journal of Process Engineering 2022, 22 (1): 72-78. DOI: 10.12034/j.issn.1009-606X.220379

Abstract （345）

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Lithium ion batteries have been successfully applied in portable electronic products, the application of lithium ion batteries is expanding to the fields such as large scale energy storage grid and electric vehicles. However, the considerably increased demand of lithium ion batteries might yield problems in the future with the limit of Li resources. Compared with lithium, sodium is abundant in the earth. Based on its resource and cost advantages, sodium ion batteries hold promise for low-cost energy storage and could be key for smart electric-grid of the future. To date, a large variety of cathode materials with satisfactory performance have been proposed. These cathode materials include layered transition metal oxides, Prussian blue analogues, polyanionic-type compounds and organic-based materials. Layered transition metal oxides NaxMO2 (M=Mn, Fe, Ni, Co, Ti, V, Cr) have been extensively investigated because of their higher capacities and industrial feasibility. Up to now, layered transition metal oxide NaNi1/3Fe1/3Mn1/3O2 has been established as a promising cathode materials for practical sodium ion batteries. Many works have also focused their efforts on NaNi1/3Fe1/3Mn1/3O2 over the years and studied its synthesis method, large scale synthesis, electrochemical reaction mechanism, coating, doping and thermal stability. In this work, ZrO2 coating NaNi1/3Fe1/3Mn1/3O2 cathode was prepared by a solid state method, and the coating effect was evaluated by electrochemical measurements as well as morphological, structural, and chemical composition analyses. The results showed that ZrO2 formed an inert protective layer on the surface of NaNi1/3Fe1/3Mn1/3O2, which effectively separated the contact between electrolyte and cathode material, alleviated the decomposition rate of electrolyte and inhibited the dissolution rate of metal ions, so as to significantly improve the cycle performance and high temperature performance of the battery. After ZrO2 coating modification, the cathode material was significantly improved compared with the uncoated cathode material at 55℃, and the capacity retention rate reached 83.6% after 100 cycles, which was higher than 75.2% of the uncoated cathode material. In addition, the stability of the coated NaNi1/3Fe1/3Mn1/3O2 cathode material was significantly improved after storage in air environment.

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Study on preparation and performance of mullite-corundum catalyst carrier

Jianlin YANG Lu ZHAO Shuhua MA Xiaohui WANG Yuejiao WANG

The Chinese Journal of Process Engineering 2022, 22 (1): 79-88. DOI: 10.12034/j.issn.1009-606X.220381

Abstract （218）

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In order to realize the resource utilization of high-aluminum fly ash and alleviate the huge demand for catalyst carriers, this work developes a new process. That is, using Chinese characteristic high-alumina fly ash as raw material, the mullite-corundum catalyst carrier is prepared by the acid-alkali combined method, and a series of characterization methods such as specific surface automatic physical adsorption instrument (BET), scanning electron microscope (SEM), X-ray diffractometer (XRD), inductively coupled plasma mass spectrometer (ICP-OES) are used for in-depth analysis. The results show that when the acid-alkali combined process is adopted, that is, the acid process conditions are sulfuric acid concentration 1.5 mol/L, the reaction temperature 85℃, liquid-to-solid ratio 7, and the reaction time 90 min; subsequent pretreatment alkali process conditions are NaOH concentration 200 g/L, reaction temperature 95℃, liquid-to-solid ratio 15, and reaction time 150 min, the leaching rate of silica reaches 58.51%, and the leaching rate of amorphous silica is 83.49%. The obtained catalyst carrier with mullite and corundum as the main components has a higher specific surface area and water absorption. They are 39.35 m2/g and 70.01%, respectively. Its heat-resistant temperature reaches 1100℃, revealing that it has the advantages of good heat stability. From the SEM pictures, it can be seen that particle size is between 20~50 μm, and porous spherical structure is bonded by short rods. The X-ray diffraction characterization results show that the carrier mineral phase contains only mullite and corundum, indicating that it has good chemical stability and mechanical strength. The pore distribution analysis results reveal that the catalyst carrier has a wide pore size distribution, and the pore size is mainly 10 nm around. A mullite-corundum catalyst carrier with excellent performance has been prepared successfully, as finding a new way for the high-value utilization of secondary resource fly ash.

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Preparation of tannic acid-dopamine coating nanofiltration membrane for dye separation

Qin JIANG Ziyu LIU Sui ZHAO

The Chinese Journal of Process Engineering 2022, 22 (1): 89-96. DOI: 10.12034/j.issn.1009-606X.221041

Abstract （368）

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The tannic acid (TA)-polyvinylidene fluoride (PVDF) nanofiltration membrane is prepared by simply coating tannic acid and polydopamine. The chemical elements and morphology of the nanofiltration membrane surface are characterized by infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Meanwhile, the hydrophilicity and underwater anti-oil-adhesion performance of the modified membrane are also evaluated. Besides, the separation performance for dyes such as Direct red, Evans blue, Congo red, Reactive yellow, and Brilliant blue is explored. The result shows that the surface roughness of the obtained membrane increases slightly after modification. With the increase of TA concentration, the hydrophilicity of the membrane surface is significantly enhanced. When the TA concentration reaches 2wt%, the surface hydrophilicity of the prepared TA-PVDF nanofiltration membrane is almost stable, and the water contact angle of the modified membrane is 44.6°. Additionally, the obtained membrane with the underwater oil contact angle of 157.2° is characterized as a superoleophobic one. There is a strong interaction between the modified membrane and water molecules. On account of the hydration layer formed on the membrane surface, the obtained membrane can completely resist the contamination of oil under the water. The rejection rate of 2wt% TA-PVDF nanofiltration membrane is more than 96.5% for several dyes, and its permeating fluxes of Direct red, Evans blue, Congo red, Reactive yellow, and Brilliant blue all exceed 65.7 L/(m2?h?bar). In addition, the modified membrane keeps the permeance nearly unchanged during the dyes' separation process, exhibiting strong stability for dyes separation. Compared to the works published recently, the prepared nanofiltration membrane with 97% rejection rate for Congo red has a higher permeating flux. The obtained membrane shows a superior separation capacity and efficiency for the dyes, demonstrating a good application prospect in industrial dye wastewater separation.

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Ketopantoate production from glucose by combining biological and chemical steps

Yao YAO Xiyang LU Lin SHU Qinghui WANG Shaoqi SUN Jian HAO

The Chinese Journal of Process Engineering 2022, 22 (1): 97-107. DOI: 10.12034/j.issn.1009-606X.221036

Abstract （433）

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D-pantothenic acid (vitamin B5) is an essential vitamin to animals and has large markets in the feed, cosmetics, and pharmaceutical industries. The biochemical role of D-pantothenic acid in all organisms is to form the core of the structure of coenzyme A. Biosynthesis of coenzyme A from pantothenate occurs in all organisms, while the synthesis of D-pantothenic acid is absent from animals. Thus D-pantothenic acid is an essential nutrient to animals. Ketopantoate is an intermediate of pantothenate biosynthesis pathway. Ketopantoate can be stereoselectivity converted to D-pantoic acid and further used for D-pantothenic acid production. However, the economic production of ketopantoate is a bottleneck of D-pantothenic acid production from ketopantoate. Hence, this study provided a novel method for synthesis of ketopantoate by aldol reaction of α-ketoisovalerate and formaldehyde, and α-ketoisovalerate was produced from fermentation with glucose as the raw material. 25.2 g/L α-ketoisovalerate was produced by an engineering Klebsiella pneumoniae strain with glucose as the main carbon source. 19.9 g/L Ketopantoate was synthesized from formaldehyde and α-ketoisovalerate by an aldol reaction at basic conditions. The reaction parameters of reaction were optimized and a conversion ratio of 83.5% was obtained at reaction conditions of pH 13 and 45℃. The ketopantoate in the solution was converted to ketopantoyl lactone at acidic conditions of pH<3. Ketopantoyl lactone was extracted to isobutanol with an extraction rate of 50.9%. The organic phase was decolourized, and ketopantoyl lactone crystal was obtained after concentration. Ketopantoyl lactone was converted back to ketopantoate in an aqueous solution in the pH range of 7~10, and ketopantoate crystal was obtained after concentration. Ketopantoate production from glucose via α-ketoisovalerate as an intermediate was set up, which suggested a novel and competitive technical route to produce ketopantoate. The whole processes were combinated biological fermentation and chemical reactions and had a high conversion ratio. This method adopted renewable and cheap original materials rather than highly toxic raw materials. The optimal temperature of the reaction was 45℃, which was in mild conditions. Overall, a novel and promising method for ketopantoate and ketopantoyl lactone production was provided.

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Fluoride migration in the aluminum extraction process of roasting secondary aluminum dross with ammonium sulfate

Binghong LEI Honghui LIU Di ZHANG Yuming DONG Hongling ZHANG Taiping LOU Hongbin XU

The Chinese Journal of Process Engineering 2022, 22 (1): 108-117. DOI: 10.12034/j.issn.1009-606X.220402

Abstract （268）

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Recovery of aluminum from secondary aluminum dross by roasting with ammonium sulfate and leaching with water is one of the most important methods to harmlessly utilizing secondary aluminum dross. However, fluoride leaching toxicity of the leaching residue should satisfy the national standard's prescription (the mass concentration of inorganic fluoride is less than 100 mg/L). Thus, it is necessary to study the F migration in the Al extraction process of roasting secondary aluminum dross with ammonium sulfate and leaching with water. In this work, the regularities about migration and transformation of F in the process of extracting Al from secondary aluminum dross via roasting with ammonium sulfate and leaching with water was investigated by fluoride ion electrode, XRD, XPS, SEM and XRF. The results showed that prolonging the roasting time, elevating the roasting temperature and increasing the mass ratio of ammonium sulfate to secondary aluminum dross could accelerate the migration of F from secondary aluminum dross to roasting off-gas. Additionally, extending the leaching time, increasing the leaching temperature and increasing the liquid-to-solid ratio was beneficial to reduce the content and proportion of F in the leaching residue. About 43.85% of F released from secondary aluminum dross to roasting off-gas in the form of gas, 23.92% of F went into the leaching solution as fluorine ion, and 32.23% of F remained in the leaching residue in the forms of AlF3 and AlF3?3H2O under the most suitable conditions with the roasting temperature of 450℃, the roasting time of 2 h, the mass ratio of ammonium sulfate to secondary aluminum dross of 6:1, the leaching temperature of 85℃, the leaching time of 80 min, and the liquid-to-solid ratio of 6:1. Ammonium sulfate could be recovered from roasting off-gas by spraying after defluorination. Moreover, polyaluminum sulfate as a water treatment agent could be prepared from the leaching solution with the removal of F. The leaching toxicity of the leaching residue was accorded with the national standard.

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Formation and dissociation characteristics of methane hydrate and distribution of ions in montmorillonite contained saline solution

Hao CHEN Zelin XU Kefeng YAN Xiaosen LI Zhaoyang CHEN Gang LI Chungang XU

The Chinese Journal of Process Engineering 2022, 22 (1): 118-126. DOI: 10.12034/j.issn.1009-606X.221044

Abstract （248）

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Natural gas hydrate accumulation and exploitation is a research focus on the development and application of new energy. However, a group of key issues involving the formation and dissociation characteristics of natural gas hydrate in marine sediments and the effect of salt ions on the hydrate stability remains to be solved. Based on the in situ sampling technique, the formation and dissociation processes of methane hydrate in montmorillonite contained saline solution was explored by in situ scanning electron microscopy and energy dispersive spectrometry. Furthermore, the morphology and ion distribution of methane hydrate during the formation and dissociation processes in montmorillonite adsorbing 0.5 mol/L NaCl solution were systematically analyzed. The results showed that the element distribution changed obviously during the hydrate formation and dissociation processes. NaCl was located on the boundary between hydrate granules caused by the salt-removing effect of hydrate formation and existed as the form of hydrated salt ions. Na+ and Cl- were distributed on the surface of montmorillonite as different layers. The surfaces of montmorillonite present the structure of independent granular while methane hydrate was formed. After the hydrate dissociation, the surfaces of montmorillonite sunk and formed some tiny gas channels. At the same time, the packing structures of montmorillonite were changed. The research demonstrated that the processes of hydrate nucleation, growth, and decomposition took place independently on the special unit between particles. Those processes had a closed relationship with the unit cell structure of hydrate.

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Global optimization of water network in the steel industrial park driven by the strategy of whole process pollution control

Yuehong ZHAO Yongbing XIE Hongbin CAO Hao WEN

The Chinese Journal of Process Engineering 2022, 22 (1): 127-134. DOI: 10.12034/j.issn.1009-606X.220373

Abstract （251）

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As a high water consumption industry, water conservation is one of the challenges needed to be conquered in order to achieve the sustainable development for Chinese iron and steel industry. Based on the idea of Whole Process Pollution Control (WPPC), global optimization of water network in the steel industrial park was carried out in this work. Firstly, the configurational and operational characteristics of the water network in the typical steel industrial park were investigated, and a multi-scale modeling method was proposed to describe the water network. Wherein different scale water systems, including water-use/treatment unit, process-scale water network, park-scale water network, and their interactions were discussed. Secondly, a superstructure was built to represent all possible water network configurations. Thirdly, an optimization model tailored for the steel industrial park was set up with the aim of minimizing the comprehensive water-use cost. The water conservation and pollutants balance of different scale water systems, together with some limits on structure and operation of the water network, were described as constraints. Lastly, to validate the proposed model, global optimization of water network in a steel industrial park with 5 million tons of crude steel production capacity per year was studied by constructing and solving the mathematical model. The results of study cases showed that the case driven by WPCC strategy achieved the best performance compared to other cases, i.e., lowest comprehensive water-use cost and lowest fresh water consumption. Compared to the current water-use index of the studied park, the index of the case driven by WPCC decreased by more than 20% at least. In terms of the results, the case studies also indicated the applicability of the proposed multi-scale optimization model, and all these data can help the steel industrial park to make decisions for implementing global optimization of water network.

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Chemical process fault diagnosis method based on extreme deep factorization machine

Yadong HE Zhuang YUAN Yang LIN Xinjiang GAO Chuankun LI Chunli WANG

The Chinese Journal of Process Engineering 2022, 22 (1): 135-144. DOI: 10.12034/j.issn.1009-606X.221071

Abstract （201）

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The chemical process fault detection and diagnosis technology represented by deep learning has become one of the main ideas to solve the problem in the industry. However, the existing deep learning diagnosis methods only focus on the non-linear high-order interactive features when constructing training models and ignore the complementary of linear features and low-order interactive features to global modeling. In addition, the high-order features extracted by the existing deep models involve only implicit interactive features, whose feature forms are unknown and uncontrollable in order. Based on these problems, this work proposes a extreme deep factorization machine-based fault diagnosis method for chemical processes, which achieves automatic extraction and efficient integration of high-order, low-order and linear features by parallel fusion of three different types of network models (factorization machine, deep neural networks and compressed interaction network). First, the selected data are sequentially subjected to preprocessing operations such as Z-score normalization, label annotation, and format conversion to convert the input data into the format data required by the model. Then, the format data are simultaneously input to the three neural network models to help train the proposed diagnostic model in parallel. Finally, the fault diagnosis results are output based on the optimal diagnosis model. From the perspective of single-fault diagnosis and multi-fault hybrid diagnosis, extensive comparison experiments are conducted on the Tennessee-Eastman process (TE) simulation dataset, and the results show that the proposed method has significant advantages over previous fault diagnosis methods in terms of metrics such as precision and recall rate.

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Cover and Contents

The Chinese Journal of Process Engineering 2022, 22 (10): 0-.

Abstract （143）

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The Chinese Journal of Process Engineering 2022, 22 (10): 1305-1307.

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Multiscale discrete particle simulation for iron and steel industry: progress and prospect

Ji XU Wei GE Limin WANG Jinghai LI

The Chinese Journal of Process Engineering 2022, 22 (10): 1308-1316. DOI: 10.12034/j.issn.1009-606X.222276

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To achieve the carbon peaking and carbon neutrality goals, the steel industry is currently facing an urgent need for transformation and upgrading. Due to the long development cycle and high cost of the experimental methods, simulation methods of high accuracy and high efficiency are playing an important role in realizing the intelligent and green technology of the steel industry. However, the applicable simulation toolkits are lacking due to the complexity and diversity of the iron-making and steel-making processes. This article introduces the possibility to realize a high-performance, more accurate multiscale discrete particle simulation method based on the consistency of the logic and structure between the problem, model, software, and hardware, namely the EMMS paradigm. Some preliminary applications on the optimization of apparatus structures and operating conditions in the steel industry are summarized, e.g., enhancing the iron ore raw material separation process by adding the permanent magnets, optimizing the structure of the inlet region of a sinter vertically arranged cooler for higher heat recovery efficiency, optimizing the operation of the rotating drum to enhance the throughput of dealing with the steel slag, and the operational optimization of the burden distribution in the blast furnace to reduce the coke consumption. These successful applications demonstrate that the multiscale discrete particle simulation method is becoming a powerful tool for the steel industry. Thus, the realization of the higher level tool for transformation and upgrading of the steel industry, namely virtual process engineering (VPE), is prospected, which requires integrating the multi-scale discrete particle simulation with online measurement, artificial intelligence (AI), interactive simulation, virtual reality (VR) and online control.

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Development trend for co-production of steel and chemical in the context of carbon neutrality

Chunyan SHI Guoshuai ZHANG Yi LI Suojiang ZHANG

The Chinese Journal of Process Engineering 2022, 22 (10): 1317-1324. DOI: 10.12034/j.issn.1009-606X.222361

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The by-produced gas, waste heat, and steel slag as well as the current situation on the co-production of steel and chemical in the iron and steel industry are analyzed. The developing trend of green and low-carbon technologies is discussed and the new mode from "carbon fixation by chemical" to "carbon substitution by hydrogen" in carbon-free steelmaking in the future is prospected. Suggestions and measures are put forward to the application of new technologies for steel and chemical co-production. It is expected to establish a new sustainable industrial ecosystem with the steel industry as the leader coupled with the chemical industry to support the realization of China's carbon peaking and carbon neutrality goal.

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Research progress of fluidized bed direct reduction at Institute of Process Engineering

Chuanlin FAN Zhan DU Feng PAN Zheng ZOU Jun LI Hongzhong LI Qingshan ZHU

The Chinese Journal of Process Engineering 2022, 22 (10): 1325-1332. DOI: 10.12034/j.issn.1009-606X.222325

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Under the background of carbon peaking and carbon neutrality, iron and steel industry urgently needs low-carbon reconstruction. Hydrogen direct reduction (usually called "hydrogen metallurgy") is an important research field in the domestic and overseas. Fluidized bed (FB) direct reduction has been the research direction at Institute of Process Engineering (IPE) for more than 60 years. On the occasion of commemorating the 120th anniversary of Professor Chu-Phay Yap's birth, this work reviews and summarizes a series of important achievements on basic researches and industrial applications of FB direct reduction at IPE. In the basic researches respect, the competition of adhesive force and rupturing force for particle sticking, the behaviors of agglomerate fluidization and slow defluidization, the growth mechanisms and sticking characteristics of newly formed iron with different morphologies were revealed; and a series of methods for anti-defluidization were successively established, including particle coating and iron morphology regulation to reduce the adhesive force, and enhance particle motion, particle size increase, using external field forces to increase the rupturing force. Furthermore, several pilot plants with various iron ores were constructed and operated to promote the industrial application of new technologies, including hydrogen FB direct reduction of 100 kg/d iron ore concentrate, 1 t/d vanadium bearing titanomagnetite and FB direct reduction-electric furnace smelting of 2000 t/a vanadium bearing titanomagnetite. Currently, IPE is cooperating with Ansteel Group to establish the world's first FB direct reduction pilot plant of 10 000 t-DRI/a using green hydrogen. This paper aims to commemorates Professor Chu-Phay Yap, Professor Mooson Kwauk and other scientists of the older generation, and also to propel advance of basic theory and technology in FB direct reduction, for promotion of the low-carbon development for the iron and steel industry of China.

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Analysis and thinking of low-carbon technology in non-ferrous metal industry

Shili ZHENG Shufeng YE Qian WANG Shuhua MA Zhi WANG Zhi SUN Shan QIAO Xiaomeng ZHANG Yi ZHANG

The Chinese Journal of Process Engineering 2022, 22 (10): 1333-1348. DOI: 10.12034/j.issn.1009-606X.222282

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Reduction of carbon dioxide emission in the non-ferrous metal industry is critical for realizing the carbon peaking and carbon neutrality goals in China. State-of-the-art of carbon dioxide emissions in the non-ferrous metal industry were summarized and analyzed here. Based on this, the low-carbon technology path of non-ferrous metal industry, especially the key smelting industry, was put forward. The analysis shows that the aluminum smelting industry is the core of carbon dioxide emission reduction in the non-ferrous metal industry. It is expected that the non-ferrous metal industry will achieve a peak of carbon dioxide emission in 2025 with the peak value being 750 million tons carbon dioxide. The carbon dioxide reduction technology path of the non-ferrous industry mainly includes four parts, which are, green energy substitution, advanced low-carbon technologies and equipment, metal recycling, and carbon capture and utilization (CCU). Among them, metal recycling is the key path for the non-ferrous industry to support the realization of the national carbon peaking and carbon neutrality goals.

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Research progress of chemical engineering technology in the process intensification of biohydrometallurgy

Cailong SHEN Yan JIA Yanzhen CHEN Guangji ZHANG Chao YANG

The Chinese Journal of Process Engineering 2022, 22 (10): 1349-1359. DOI: 10.12034/j.issn.1009-606X.222246

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With the depletion of high-grade minerals, traditional pyrometallurgy with high cost and serious environmental contamination is no longer suitable for the sustainable development of the economy and society of China. Biohydrometallurgy is a bacterial-assisted leaching process to solubilize or expose the metals contained in different minerals, and the main role of the bacteria is to regenerate ferric ions and protons. Since the 1980s, biohydrometallurgy including heap bioleaching and tank bioleaching has been widely used for the recovery of metals such as copper and gold from low-grade and complex minerals because of its easy operation, low cost, and environmental advantages. Up to now, about 15% of the world's copper production can be attributed to the heap bioleaching of copper ore and about 5% of the world's gold production can be attributed to the biooxidation of refractory gold ore in continuous stirred tank reactors. However, the relatively slow reaction velocity of biohydrometallurgy is the main limitation to its further development. The application of biohydrometallurgy has been promoted remarkedly by the development of chemical engineering technology in history such as chemical reaction engineering and chemical separation technology. The process intensification of biohydrometallurgy based on chemical engineering technology is still one of the most important research interests in the future. Therefore, the research progress of chemical engineering technology in the process intensification of biohydrometallurgy was reviewed in this paper to help a better understanding. The influencing factors of efficiency in heap bioleaching and tank bioleaching were discussed mainly from an industrial point of view, and future research prospects were also put forward.

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Technical consideration on the transition from "ultra-low emissions" to "reduction of pollution and carbon emissions" in China's iron and steel industry

Tingyu ZHU Xiaolong LIU

The Chinese Journal of Process Engineering 2022, 22 (10): 1360-1367. DOI: 10.12034/j.issn.1009-606X.222353

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The iron and steel industry plays an important role in China's national economy, and it is also the largest pollution-carbon emission in China. In April 2019, five ministries and commissions jointly issued the "Opinions on Promoting the Implementation of Ultra-low Emissions in the Iron and Steel Industry", leading to a beginning of ultra-low emissions for industrial flue gas, and the air pollution emissions of China's steel industry achieved a significant reduction. Since the "14th Five-Year Plan", under the background of carbon peaking and carbon neutrality, with the proposal of pollution and carbon reduction, the problem of carbon incremental effect caused by ultra-low emission technologies has gradually become prominent, which has brought new technological needs to the steel industry. This work expounds the technological progress of ultra-low emissions in China's steel industry, summarizes the development direction of pollution and carbon reduction in the steel industry, and puts forward suggestions for the green and low-carbon development of the steel industry in the future, providing a reference for promoting the high-quality green development of China's steel industry.

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Research progress of biomass application in EAF steelmaking

Chengjin HAN Rong ZHU Guangsheng WEI

The Chinese Journal of Process Engineering 2022, 22 (10): 1368-1378. DOI: 10.12034/j.issn.1009-606X.222321

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In the current context of carbon peaking and carbon neutrality, the steel industry is under tremendous pressure to reduce carbon emissions in the long term, which is a major emitter of CO2. Therefore, developing electric arc furnace (EAF) steelmaking with lower carbon emissions will be an effective measure for the steel industry to achieve carbon emission reduction. However, although the carbon emission of EAF steelmaking is greatly lower than that of the traditional "Blast furnace-Converter" long-process steelmaking, it still needs to use a large number of coal resources to meet the smelting requirements. Therefore, using a suitable carbon source to replace coal as a carburizing and foaming agent in EAF steelmaking is of great significance to further reduce carbon emissions from EAF steelmaking. Biomass resources as the only renewable carbon source will be the first choice of alternative carbon sources. In this work, a series of studies on the application of biomass in EAF steelmaking conducted by domestic and international scholars had been introduced and the existing research results were also presented. On this basis, the future research direction of biomass application in domestic EAF steelmaking was prospected.

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Prospect on high ratio pellet utilized in blast furnace under the background of carbon peaking and carbon neutrality

Xindong WANG Yonglong JIN

The Chinese Journal of Process Engineering 2022, 22 (10): 1379-1389. DOI: 10.12034/j.issn.1009-606X.222239

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Carbon peaking and carbon neutrality are important measures taken by China to shoulder its responsibility as a major country in addressing climate issues and promote ecological progress and high-quality development. High carbon emissions are a key factor limiting the steel industry's ability to achieve carbon peaking and carbon neutrality goals. In order to achieve the goal of low-carbon development, on the one hand, breakthrough low-carbon metallurgical processes should be developed and applied, or enough high-quality scrap resources be supplied. On the other hand, the merits of existing blast furnace process, i.e., mature, high efficiency, high quality and low cost, etc., will be brought to full play to. And combining with the condition of iron ore resources, making full use of pellets' excellent metallurgical performance, low energy consumption and low emissions advantages of the production, developing blast furnace optimized burden structure and the related operation system by using high percentage of pellets, the best energy consumption and carbon emissions in the system level will be achieved. The overall competitiveness of existing processes will be improved. Significant progresses have been made in the research, development and application of technologies related to the use of high proportion of pellets in blast furnace at home and abroad. In China, some enterprises have certain resource advantages, and a large number of preliminary studies have been carried out. The future development will have a positive effect on China's steel industry to achieve the goal of low carbon emission.

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Research progress on high efficiency metallurgy and clean extraction of vanadium-titanium magnetite ore in Panxi area

Chenguang BAI Xuewei LÜ Guibao QIU Shengfu ZHANG

The Chinese Journal of Process Engineering 2022, 22 (10): 1390-1399. DOI: 10.12034/j.issn.1009-606X.222302

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The vanadium-titanium magnetite ore is an important characteristic resource in Panxi area of China, but it is difficult to smelt because of its high TiO2 content and complex mineral phase. As early as June 1958, Mr. Chu-Phay Yap issued a written opinion on "urgent problems of iron ore bearing titanium in Panzhihua". Among them, the "urgent problem" is to break through some foreign scholars' judgment: "smelting this ore with blast furnace has little hope of success", and rely on domestic scientific research to overcome the problems of smelting vanadium-titanium magnetite ore with blast furnace in Panxi area. With the cooperation of related industries and research forces in China, it has been successfully broken through that difficult problem of smelting of vanadium-titanium magnetite ore with blast furnace in Panxi region, and further improved the level of smelting, reaching the world higher level in whole. In recent years, in addition to the continuous improvement of smelting level, the level of comprehensive utilization of that kind ore has also carried out a lot of original research work. Chongqing University is one of the earliest research institutes on comprehensive utilization of vanadium-titanium magnetite ore smelting. Over the years it has always took the vanadium-titanium magnetite smelting and its efficient utilization as the primary of metallurgical science research topic in the Chongqing University, and the unique processes of blast furnace smelting vanadium-titanium magnetite ore are studied systematically in the theory and technology, that has formed distinctive research features. In recent years, it has also been made that breakthroughs in theoretical and experimental research methods and made good progress in close cooperation with enterprises on smelting technology of high ratio vanadium-titanium magnetite ore in blast furnace, titanium extraction from titanium-containing blast furnace slag and titanium slag smelting technology in large electric furnace, as well as efficient and clean extraction technology of vanadium resources. This review gives a brief introduction on the clean metallurgy and efficient extraction research progress on Panxi vanadium-titanium magnetite ore in Chongqing University, to commemorate the contribution of Chu-Phay Yap and Yanxian Lin et al. scientific workers for the development and utilization of Panxi vanadium-titanium magnetite ore, and uphold their feet on the ground, as well as the innovation of scientific spirit. To promote the development of green and intelligent metallurgy and resource efficient utilization of vanadium-titanium magnetite ore in Panxi region under the carbon peaking and carbon neutrality goals.

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Thermal simulation technique for solidification process of continuous casting and its application

Huazhi YUAN Honggang ZHONG Qijie ZHAI

The Chinese Journal of Process Engineering 2022, 22 (10): 1400-1413. DOI: 10.12034/j.issn.1009-606X.222310

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Solidification is an important process governing the quality of metallurgical products, but the study of solidification process under continuous casting condition is extremely difficult result from the high temperature, opaque, large-scale and continuous production. The current research methods mainly include numerical simulation, physical simulation and thermal simulation, among which thermal simulation method is of great interest because the experimental data similar to the production conditions can be directly obtained. This work systematically introduces the methods of thermal simulation for continuous casting solidification. The principles of thermal simulation techniques are briefly described, and the applications of the mold thermal simulation method and the characteristic unit thermal simulation method are summarized. Among them, the thermal simulation methods for dendritic growth of continuous casting billet and hot tearing based on the heat conduction similarity have successfully "condensed" the solidification process of a dozen tons of cast billet into a laboratory study with 100 grams of steel. Both the methods can not only reveal the influences of composition, pouring and cooling conditions on solidification process, microstructure and solute distribution, but also can observe the morphology of solid-liquid interface, diffusion of solute, evolution of inclusions, and the possibility of hot tearing formation, that are regarded as extremely important issues in metallurgy filed but cannot be obtained by other means.

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Prospect of resource recycling technology frontier of metallurgical industry with carbon peaking and carbon neutrality strategy

Huiquan LI Yufeng WU Yunfa CHEN

The Chinese Journal of Process Engineering 2022, 22 (10): 1414-1417. DOI: 10.12034/j.issn.1009-606X.222360

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Resource recycling is an important way for the metallurgical industry to ensure the safe supply of key metal resources and achieve carbon peak and carbon neutrality. From the perspective of carbon peaking and carbon neutrality strategy, this work outlines the overall status and the development trend of green low-carbon transformation in the resource recycling of metallurgical industry, prospects the development frontier of resource recycling technology in the metallurgical industry from multiple perspectives such as the scientific basis of material recycling, the revolutionary technology of "waste free metallurgy", the coupling of resource recycling and carbon cycle, the high-quality recycle of secondary metal resources, and the reconstruction of intellectual property rights based on digital technology. A series of view points is proposed to be useful reference for the green and low-carbon transformation and development of metallurgical industry.

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Secondary resources utilization, problems and countermeasures of the domestic and oversea steel industry

Daqiang CANG Lingling ZHANG Yang LIU Zhaohou CHEN Bingyang HE

The Chinese Journal of Process Engineering 2022, 22 (10): 1418-1424. DOI: 10.12034/j.issn.1009-606X.222345

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In order to improve the steel industrial secondary resources utilization level (steel slag as an example), the different gas, liquid, and solid phase secondary resources (wastes) from the steel industry are introduced first, and then the recent situation of the solid phase secondary resources is introduced. The problems and the relevant countermeasures are put forward for steel slag future utilization. So far steel slag is one of the most difficult proposals and utilization of solid secondary resources, and has become a hot topic in the world steel industry. So new steel slag technologies and product development are urgently needed for high efficiency, cleaner, and high value-added utilization for steel slag utilization.So new steel slag technologies and product development are urgently needed for high efficiency, cleaner, and high value-added utilization for steel slag.

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The technical development for water saving and pollution control in iron and steel industry under carbon peaking and carbon neutrality background

Yongbing XIE Di ZHANG He ZHAO Yuehong ZHAO Fengqiang LIU Hongbin CAO

The Chinese Journal of Process Engineering 2022, 22 (10): 1425-1428. DOI: 10.12034/j.issn.1009-606X.222357

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The iron and steel industry plays an important role in Chinese economic development. It is a pillar industry of our country, but also an industry with high energy and water consumption, high pollution, and high carbon emissions. Under the new situation that China has formulated the carbon peaking and carbon neutrality goal, the end treatment of wastewater pollution in the iron and steel industry is still disconnected from the production process, and the efficiency of water and energy usage still needs to be improved. It is difficult to meet the control needs of low-carbon development of the industry, so it is urgent to promote the overall planning of pollution control and carbon emission reduction. This work puts forward the research ideas for the development of water-saving and pollution-reduction technology in the iron and steel industry under this background, which concludes the comprehensive planning of water supply, water use, wastewater treatment, and water recycling, low-carbon collaborative control of water pollution across different mediums, the whole process control and intelligent optimization of wastewater pollution, the common prosperity and collaborative development of steel enterprises and local cities. It is expected to further enhance the scientific and technological support for water conservation and pollution reduction in the iron and steel industry in the future, and help the green and low-carbon development of the industry.

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Study on technology of super gravity step separation of rare earth elements in Bayan Obo rare earth ore

Xi LAN Jintao GAO Zhancheng GUO

The Chinese Journal of Process Engineering 2022, 22 (10): 1429-1437. DOI: 10.12034/j.issn.1009-606X.222303

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The rare earth reserves of Bayan Obo mine in China rank first in the world, and its rare earth minerals are mainly light rare earth, of which cerium, lanthanum, praseodymium and neodymium account for more than 97% of the total rare earth oxides, which has important industrial value. Since the rare earth elements have extremely similar physical and chemical properties, it is difficult to realize the separation of different rare earth elements from each other in the current treatment process. In this work, a green and efficient method was proposed for respectively recovering rare earth elements under supergravity from rare earth concentrate. Based on the evolution of mineral phases and elemental migration laws of the rare earth concentrate, it was found that different rare earth phases would be precipitated in different temperature intervals during the melting and cooling precipitation process. It could be concluded that the rare earth elements (REEs: Ce, La, Pr, Nd) were discovered to be precipitated as the rare earth oxide, rare earth ferrate and britholite phases respectively at various temperature ranges of 1400~1500, 1200~1400, and 1100~1200℃, respectively. However, the rare earth phases were intimately intertwined with each other in the normal gravity. Consequently, the respective separation of REEs (Ce, La, Pr, Nd) at their corresponding precipitation temperatures was conducted under the supergravity. 98.38% of Ce was firstly enriched into the rare earth oxide and separated from the concentrate as driven by the supergravity, 97.70% of La was enriched into the rare earth ferrate and separated subsequently, and the Pr and Nd were precipitated further into britholite and separated from the system. Accordingly, the high purity of rare earth oxide, rare earth ferrate, and britholite phases were attained respectively, and the stepwise separation of Ce, La, Pr and Nd in the rare earth concentrate were achieved, achieving the green and efficient recovery of REEs (Ce, La, Pr, Nd) from the Bayan Obo rare earth concentrate with no additives, no hazardous waste, and no secondary pollution.

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The jet characteristics of post combustion oxygen lance in a 250 t converter

Shuguo ZHENG Miaoyong ZHU

The Chinese Journal of Process Engineering 2022, 22 (10): 1438-1446. DOI: 10.12034/j.issn.1009-606X.222281

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Supersonic jet characteristics of oxygen lance nozzles have a significant influence on smelting. The three-dimensional model of a 250 t steelmaking converter was established by Fluent software. The jet characteristics of a conventional 6-hole oxygen lance with five holes around and one hole in the center and a post combustion (PC) oxygen lance with a single flow channel were compared and analyzed. The interaction between gas-liquid-slag three phases was simulated by VOF multiphase flow model. The results show that the inflow of the left-side secondary hole flow unit quickly converges into the center hole jet, which has a larger radial cross-sectional area; while the right-side secondary hole flow unit converges into the peripheral 5-hole main flow unit. Due to the supplement of the second hole flow unit, the velocity under the oxygen lance is evenly distributed, and the low-velocity area is reduced, slowing down the decay of the center hole jet, resulting in a large center hole jet velocity. Therefore, the post combustion oxygen lance has a larger impact area and impact depth. Therefore, it can efficiently decarbonize and phosphoresce, giving full play to the secondary combustion effect, and is conducive to slagging. Through the three-phase simulation study of gas-liquid-slag, it can be seen that the cavity profile and interface of steel-slag-gas remain unstable due to the propagation of surface waves, and the slag layer at the furnace wall is calmer with time, indicating that there is no scouring of the furnace wall by either the conventional oxygen lance or the secondary combustion oxygen lance. The maximum impact diameter and impact depth of the secondary combustion oxygen lance is 2461 mm and 358 mm, which are 1.16 times and 1.19 times than the conventional oxygen lance, respectively. The industrial tests have shown that the use of secondary combustion oxygen lances increases the furnace temperature and significantly reduces the oxygen supply time, while the post combustion oxygen lance increases the converter temperature by 27.2°C, and shortens the oxygen supply time by 78 s.

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Cover and Contents

The Chinese Journal of Process Engineering 2022, 22 (11): 0-.

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Analysis method for outflow percentage of water model data of tundishes

Yuqian LI Chao CHEN Guoguang CHENG Tianyang WANG Linbo LI Mengjiao GENG Jinping FAN

The Chinese Journal of Process Engineering 2022, 22 (11): 1447-1457. DOI: 10.12034/j.issn.1009-606X.221436

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Mixing phenomena by means of tracer technology are vitally important to understand the flow in metallurgical reactors, for example, continuous casting tundish. The widely used analysis methods are RTD (Residence Time Distribution) curve or F curve, which is a time dependent integral of RTD E curve. For the two methods, in the normalization process, the outflow percentage of a single-strand tundish or the summation of the outflow percentages of each strand in the multi-strand tundish are all limited to 100%. Thus, the total amount of tracer outflow information is concealed, which may lead to the problem of inaccurate results. This study proposes an analysis method of the outflow percentage, and proposes the calculation method to convert the physical experiment results into the real-time outflow percentage curve. In addition, based on the outflow percentage curve, the time-weighted average variance and the residual tracer percentage can be calculated and used to evaluate the uniformity of each strand and dead volume, respectively. In this study, the water model experimental data of a single-strand tundish and a four-strand delta shape tundish, which is installed by double weir or U-shaped weir, under normal condition and one strand blockage conditions are all analyzed by the proposed outflow percentage method. The results show that the experimental results can be proofread by using the outflow percentage method to further verify the repeatability of the water model experiments. Meanwhile, the difference in the percentage of outflow at the end of the monitoring time and the proportion of the dead zone at twice of the theoretical residence time can be compared in double weir four-strand tundish and U-shaped weir four-strand tundish. It can also intuitively compare the uniformity of each strand of different multi-strand tundishes, and the distribution and uniformity of the tracer in other outlets after one of the strands is blocked.

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Numerical simulation of turbulence heat transfer enhancement and optimization of jet layer in circulating jet mixing tank

Yanfang YU Lingmin KONG Huibo MENG Bowen SHI Dongzhou LIU Jianhua WU

The Chinese Journal of Process Engineering 2022, 22 (11): 1458-1467. DOI: 10.12034/j.issn.1009-606X.221345

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Circulating jet mixing tank (CJT) as a process intensification can improve the turbulent mixing and reaction selectivity of flowing working medium. In order to further improve its industrial application value, the heat transfer capacity of the flow field inside the CJT was analyzed and the number of jet layers was optimized. Under the condition of constant wall temperature, the SST k-ω model was used to analyze the flow heat transfer performance of the flow field in the non-steady state calculation. The heat transfer uniformity of the wall and the heat transfer characteristics in the flow field was studied at Re= 3260~16 303 and the number of jet layers M=5~9. The variation coefficient Ch of convective heat transfer coefficient decreased and the uniformity of wall heat transfer increased by 2.8%~19.3% with the increasing Re for M=9. The field-synergy between flow field and temperature field increased with the increase of Re and the synergy angle at Re=16 303 is 75.5o, which is 0.5° less than that at Re=3260. The Ch decreased and the heat transfer uniformity increased by 2.7%~16.3% with the increasing M for Re=9782. The field-synergy between velocity vector and temperature gradient decreased with the increasing M. Compared with synergy at M=5, the global synergy decreased by 6.1% at M=9. When M=7, the field-synergy angles in the central mixing region and the jet mixing region were between 73° and 74°, and the heat transfer capacity between the two regions was well matched. The synergy of central mixing region was better than that of jet mixing region for M<7, and the situation was opposite when M>7. The influence of Re and M on the heat absorption and transfer performance of the CJT was studied. It was found that the change of Re had more influence on the heat absorption of the CJT with respect to M.

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Multifractal analysis of concentration-time series in double-layer impinging stream mixer

Jianwei ZHANG Jun TANG Xin DONG Ying FENG

The Chinese Journal of Process Engineering 2022, 22 (11): 1468-1478. DOI: 10.12034/j.issn.1009-606X.221440

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The concentration field of a double-layer impinging stream mixer was measured by the planar laser-induced fluorescence (PLIF) technique. The multifractal characteristic of the concentration-time series was investigated by using the multifractal detrended fluctuation method (MF-DFA). The multifractal singular spectrum under different nozzle spacing and jet Reynolds number was analyzed to realize the quantitative characterization of flow field characteristics. The results showed that the singularity of the concentration-time series increased with the jet Reynolds number. With the increase of the nozzle spacing, the singularity of the concentration-time series became weakened, and the influence of nozzle spacing on the singularity of concentration-time series was more significant than that of Reynolds number. The stronger the singularity of concentration signal of the double-layer impinging stream mixer, the more intense the motion of fluid particles, and the stronger the mixing effect. The promoting effect of nozzle spacing on mixing effect was greater than jet Reynolds number. According to the variation of multifractal spectrum of concentration time series of double-layer stream mixer, the singular spectrum parameters of concentration time series were obtained. Based on the distribution of the multifractal spectrum parameters (Δα, αmin, α0) along the radial position in the multifractal singular spectrum, the flow field in the double-layer impinging stream mixer was divided into axial impingement zone, vortex zone, and radial impingement zone from the impact center downward. The singularity of concentration signal of double-layer impinging stream mixer was larger than the primary impact region and larger than the vortex region. The effect of secondary impact zone on mixing was stronger than that of primary impact area and stronger than that of vortex area. It can provide a theoretical basis for revealing the flow pattern of the impinging stream system and the complex and disordered flow mechanism of the impinging stream.

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Liquid-liquid two-phase flow patterns and mass transfer kinetics for vanadium extraction in microchannels

Jing LUO Jiawei WEN Chunming LAN Xihua ZHANG Pengge NING

The Chinese Journal of Process Engineering 2022, 22 (11): 1479-1489. DOI: 10.12034/j.issn.1009-606X.221320

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The liquid-liquid flow pattern and extraction mass transfer kinetics for V(V) were investigated in microchannels using primary amine N1923 extractant. 15vol% N1923 was used as the continuous phase and V(V) aqueous solution as the dispersed phase. The flow patterns of two immiscibility phases at different flow rates and the effects of residence time and microchannel diameter on mass transfer as a function of flow rate were studied. The study found that compared to 1:1, with the increase of the two-phase flow velocity, the slug flow length and the specific interface area remained unchanged, and two phase fluid by Raydrop microchannel flowed into the external capillary microchannel because of the expansion of microchannel changed the way of two-phase flow, made the same experimental conditions at the same time appeared a variety of flow pattern in the microchannel. At the same time the two-phase flow velocity was positively correlated with the total mass transfer coefficient, it showed that the influence of flow pattern on mass transfer can be ignored in this research system. In addition, the residence time was negatively correlated with the total mass transfer coefficient in the same channel, which indicated that significant mass transfer occurred at the entrance of the two-phase contact channel, and the mass transfer rate was the highest at this time. After the diameter of the external capillary microchannel was changed, the mass transfer effect of 254 μm tube diameter was 9 times that of 750 μm tube diameter at the same mixing rate, which indicated that the inner circulation strength and specific interface area of small tube diameter were more significant. Finally, the experimental results of the total volume mass transfer coefficient were correlated with the empirical formula of the total volume mass transfer coefficient, which provided a theoretical basis for the realization of green metallurgical technology of microchannel amplification.

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Influence of interface between dense and dilute phases on microscopic drag force in gas-solid suspensions at low Reynolds numbers and its modeling

Teng MA Xiao CHEN Qiang ZHOU

The Chinese Journal of Process Engineering 2022, 22 (11): 1490-1503. DOI: 10.12034/j.issn.1009-606X.222019

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Gas-solid two-phase flow is widely encountered in energy and chemical industries and the interphase drag force is believed to be the dominant factor affecting the flow. Although the homogenous microscopic drag models, e.g. the BVK drag law (AIChE Journal, 2007, 53(2): 489-501), could accurately predict the drag force for homogenous regions, i.e. the dilute or dense phases, they failed to predict the drag at the interface of dense and dilute phases where the surface of particle clusters was located. To study the influence of the interface on the drag force, the particle-resolved direct numerical simulation (PR-DNS) was performed on the process of fluid flowing through different particle clusters at low Reynolds numbers. The results showed that at the interface of dense and dilute phases, the predictions of the BVK drag model were significantly different from the PR-DNS results. Meanwhile Chen et al.'s model (Int. J. Multiphase Flow, 2020, 128:103266), which considered the influence of the interface, cannot accurately predict the drag force where the solid holdup of the dilute phase was not zero. Therefore, this work proposed a method of decomposing the mesh near the interface to predict the drag force. To validate the proposed model, PR-DNSs of flow past various particle clusters, were performed and the predictions of several drag force models were calculated. It was found that the new model not only had a similar predictability with Chen et al.'s model when the dilute phase solid holdup approaches 0, but also had better Pearson correlation coefficients and fitness than the Chen et al.'s model when the solid holdup of the dilute phase was not zero. In conclusion, the proposed drag model could accurately account for the influence of the interface on drag force with different dilute and dense solid volume fractions, and it recovered the BVK law when the local gradient of volume fraction approached zero.

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Preparation of CNT supported MnFe ₂O ₄ nanomaterial based on high-gravity technology and its application for the adsorption of Pb(II)

Yusong GAO Guisheng QI Wenchao YAN Da GUO Youzhi LIU

The Chinese Journal of Process Engineering 2022, 22 (11): 1504-1511. DOI: 10.12034/j.issn.1009-606X.221431

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In order to overcome the agglomeration problem of MnFe2O4 nanoparticles in practical applications, the high-gravity technology combining with the in?situ support of multiwalled carbon nanotubes (CNT) is proposed to prepare the CNT supported MnFe2O4 nano-material (MnFe2O4/CNT). The typical heavy metal pollution Pb(II) is selected as the research object to study the adsorption performance of MnFe2O4/CNT. First, the effects of different MnFe2O4 loads on the adsorption capacity toward Pb(II) are investigated, and the optimal MnFe2O4 load is determined to be 83.3wt%. The obtained MnFe2O4/CNT in the optimal MnFe2O4 load is charactered by XRD, SEM, N2 adsorption-desorption specific surface analyzer and VSM, and which exhibits an excellent magnetic property with a high saturation magnetization of 35.85 emu/g. Thus, the obtained MnFe2O4/CNT can be applied for the magnetic separation of pollutants in water. The results of adsorption experiments show that under the conditions of initial Pb(II) 300 mg/L and solution pH=6, the adsorption of Pb(II) on MnFe2O4/CNT in solution reached equilibrium after 180 min, and the adsorption equilibrium capacity is 80.7 mg/g, which is much higher than pure CNT (28.4 mg/g). The kinetic study demonstrates that the adsorption behavior of Pb(II) on MnFe2O4/CNT is most consistent with the Elvoch kinetic model,which suggests there exists a chemical adsorption in the adsorption mechanisms. Freundlich isotherm model describes well the adsorption process of Pb(II) on MnFe2O4/CNT, which represents a multilayer adsorption process on heterogeneous surfaces. In addition, the maximum adsorption capacity of MnFe2O4/CNT obtained from adsorption isotherm experiment is 106.2 mg/g, which displays excellent adsorption performance for Pb(II) and has a great potential in heavy metals removal in solution. According to the X-ray photoelectron spectroscopy analysis, it can be concluded that the adsorption mechanisms involve the complexation between Pb(II) and the hydroxyl groups on the surface of MnFe2O4.

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