Table of Content

28 September 2022, Volume 22 Issue 9

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Cover and Contents

The Chinese Journal of Process Engineering. 2022, 22(9):  0. 

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Review

Research progress of bubble separation behavior on electrodes and its strengthening technology

Wei LIN Zhangwei WANG Wei WANG Jimin LI Zixin GUO Jin XIANG Xinyuan QIU Hongyang ZHAN Jiuyang YU

The Chinese Journal of Process Engineering. 2022, 22(9):  1147-1158.  DOI: 10.12034/j.issn.1009-606X.221283

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The rapid development of the global economy inevitably caused the rapid consumption of fossil resources and serious environmental pollution problems. Hydrogen plays an increasingly important role in energy supply and environmental protection as a clean energy, water electrolysis is a way to produce hydrogen on a large scale, so it is very important to enhance the efficiency of water electrolysis for hydrogen energy production. How to improve the electrolysis efficiency of water electrolysis technology has been widely concerned. During electrolysis, the gas produced at both ends of the electrode can go in one of three directions: out of the cell, dissolved in the electrolyte, or attached to the electrode. However, in the electrolysis process, the bubbles attached to the electrode will seriously affect the contact area between the electrode and electrolyte, which directly reduces the electrolysis efficiency. Therefore, reducing the residence time of bubbles on the electrode can effectively increase the contact time between electrolyte and electrode and improve the efficiency of hydrogen production. In this work, the recent progress in promoting the separation of hydrogen and oxygen bubbles from the plate during electrolysis is reviewed. The nucleation, growth, coalescence and separation of bubbles are studied from the aspects of plate properties, current, solution concentration, and external physical field, and the characteristics of various methods to enhance bubble separation are discussed and summarized. The electrolytic efficiency can be improved and the energy consumption of electrolysis can be reduced by promoting the bubble separation on the electrode. The future development direction and route are prospected, this provides fundamental insight and direction for the future design of the bubble separation technology in water electrolysis.

Application of low-temperature plasma in surface modification of electrochemical energy storage devices

Zhengde WANG Kaixiong GAO Bin ZHANG

The Chinese Journal of Process Engineering. 2022, 22(9):  1159-1168.  DOI: 10.12034/j.issn.1009-606X.221355

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Facing the increasingly severe energy crisis, it is necessary to reduce the use of fossil fuels and develop new energy materials. Energy storage materials have attracted widespread attention as the key to the safe and stable operation of the power system after the integration of renewable energy sources. At present, secondary batteries represented by lithium-ion batteries have been widely used as new energy storage devices. Its electrochemical performance is affected by various parts of electrochemical devices, such as electrode materials, separators, and current collectors. Among them, the electrode material is the core component of the secondary battery, which greatly determines the comprehensive electrochemical performance of the secondary battery. However, during the charging and discharging process, the core component electrode material faces problems such as volume expansion and active material dissolution, which further affect the capacity and safety of the secondary battery. Reasonable surface modification of electrochemical energy storage devices is the key to solving the above problems. Recently, plasma technology, owing to its high activity, which can induce rapid and efficient reactions under relatively mild conditions, has been widely used on both industrial and laboratory scales as a very promising and important tool for surface modification of electrochemical energy storage devices. The use of plasma to treat the surface of the electrochemical energy storage devices can effectively inhibit the dissolution of the active material, avoid the occurrence of side reactions, and improve the cycle life and discharge capacity of the secondary battery. This work introduces plasma technology, especially low-temperature plasma, and summarizes the latest progress in low-temperature plasma technology in electrochemical energy storage devices including electrode material and separator. Finally, plasma technology is discussed. The advantages of the method, as well as the challenges and applications it faces in the prospect are analyzed.

Research progress on the adsorption properties and mechanism of titanium dioxide to common dyes

Xiaoteng ZHAO Xintao ZHOU Zhongqiu LUO Yu WEI Xiong LAN Yan LU

The Chinese Journal of Process Engineering. 2022, 22(9):  1169-1180.  DOI: 10.12034/j.issn.1009-606X.221247

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Titanium dioxide (TiO2) has the characteristics of large specific surface area, rich pore structure, stable properties, low manufacturing cost and nontoxicity. It can be used as an adsorbent and photocatalyst to adsorb and treat wastewater containing heavy metals, organic dyes and other pollutants. In this work, the influencing factors in the process of TiO2 adsorption to common organic dyes in wastewater is comprehensively analyzed, the influence of different influencing factors on the adsorption effect is summarized, and the effects of composite modification, doping modification and organic solution modification on the dye adsorption performance of TiO2 are discussed. The literature indicates that modification methods play an important role in enriching the pore structure of TiO2, increasing the specific surface area of the TiO2 based adsorption materials and the active sites on the surface, followed by improving its adsorption performance. The analysis of adsorption kinetics and thermodynamics data exhibits that the kinetics of TiO2 in the process of adsorbing organic dyes in wastewater mainly follows the pseudo-secondary kinetic model, and the thermodynamics accords with the Langmuir model monolayer adsorption or the Freundlich model. Its adsorption mechanism mainly includes electrostatic attraction, the interaction of n-π stacking and hydrogen bonding, and so on. The TiO2 system is used as an adsorbent to adsorb and treat dye molecules in wastewater, it has the advantages of high efficiency, environmental protection, and low production cost. It can play a vital role in the field of wastewater treatment in the future and can be studied as a green material with broad application prospects.

Research Paper

Multiscale CFD simulation of bidisperse turbulent bed reactors with optimization of fine powder entrainment

Honglin DUAN Chenzhe DU Bona LU Youhao XU Wei WANG Jianwen ZHOU Li XU Yingpeng XIE

The Chinese Journal of Process Engineering. 2022, 22(9):  1181-1191.  DOI: 10.12034/j.issn.1009-606X.221420

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S-zorb adsorption desulfurization technology is one of the most important technologies to produce the ultra-low sulfur content gasoline. However, the short operation cycle of the turbulent bed reactor limits the wide application and efficient production of S-zorb process. The main reason is that the fine particles produced by the circulation and attrition of absorbent particles are easily carried upwards to the disengager and then gradually deposited on the filter, leading to the blocking and shutdown of the top filter. In order to improve the design of S-zorb reactor and reduce the entrainment of fine particles, a deep understanding of hydrodynamic behaviors in the reactor is very necessary. In this work, a series of multiscale CFD simulations of the S-zorb reactor with absorbent large particles and fine particles were carried out and the optimization schemes were proposed. As the drag force played very important role in predicting heterogeneous gas-solid fluidized flows, the effects of drag models, i.e., the EMMS-bubbling model and EMMS-ANN model were first investigated. It was found that using both the EMMS-bubbling model and EMMS-ANN model can reasonably predict the flow distribution of absorbent particles and segregation behaviors. Compared to using the EMMS-bubbling model, using the EMMS-ANN model over-predicted the entrainment of fine particles. Then a series of design modification schemes for reducing entrainment of fine powder were investigated. It was found that increasing the height of the disengager from 0.848 to 1.150, the radius of the disengager from 0.909 to 1.212 or adding a horizontal pipe for discharging solids can help reduce the carryover of fine powders. Among these modification schemes, the increase in the disengager radius and adding a horizontal pipe at the transitional section between the reaction zone and disengager were the most effective to reduce the carryover of fine particles. These findings were very helpful for optimization of S-zorb fluidized reactor and process upgrading.

Hydrodynamics and mass transfer in a three-phase bubble column cell culture bioreactor

Shengnan XU Hongfei LIU Xueliang LI Guocheng DU Jian CHEN

The Chinese Journal of Process Engineering. 2022, 22(9):  1192-1202.  DOI: 10.12034/j.issn.1009-606X.221364

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Pneumatic bioreactors, including bubble columns and air-lift reactors, were once considered the most suitable for large scale cell culture. However, their applications quickly declined and research interests diminished when it was suspected that the bubbles bursting at the gas-liquid interface could cause damage to certain cells. Stirred tank reactors, limited to 1~2 m3 working volume, became the industry standard. In recent year, the emergence of new cell-based technology, such as cultured meat, has led people to reconsider the bubble column reactor technology, as such products required reactors in the order of 100 m3 to be economically viable. However, there was generally a lack of up-to-date understanding of the performance of pneumatic reactors in the context of cell culture due to the lack of interest from the industry in the past four decades or so. In this study, cold flow experiments were conducted and CFD simulations were performed to investigate the effect of microcarriers and cell culture media additives such as Pluronic F68 and Antifoam C on the hydrodynamics and mass transfer characteristics of a bench-top bubble column. Foaming and foam control were also investigated. It was found that in the presence of 0.5 and 1.0 g/L Pluronic F68, the bubble size in a simulated culture medium remained almost unchanged as the superficial gas velocity increased from 0.04 cm/s to 0.17 cm/s, dissimilar to the air-water system where the bubble size increased significantly with gas flow due to coalescence. Microcarriers of 14%~20% volumetric fractions were not found to impact the bubble size and Antifoam C of up to 1.60×10-4 was required to suppress the foam, without affecting the bubble size in the column. Despite the smaller bubble size and higher gas holdup, the overall volumetric mass transfer coefficient, kLa was on par with the air-water system, as the medium additives negatively affected the liquid side mass transfer coefficient, kL. In all the experiments, the microcarriers could all be completely suspended. The gas holdup and solid distribution in the three-phase system could be adequately described by an Euler-Euler CFD model.

Fluid-thermal-structure coupling simulation and structural optimization of combustion chamber of a new pyrolysis furnace

Huaxin GAO Xuedong LIU Wei ZHANG Xiaofeng ZHA Shengnan LÜ Jiajun LIU Kaixin LÜ

The Chinese Journal of Process Engineering. 2022, 22(9):  1203-1212.  DOI: 10.12034/j.issn.1009-606X.221331

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In order to dispose oily sludge, a vertical multi-layer rotating disc pyrolysis furnace is developed independently. The high-temperature gas generated in the combustion chamber provides heat for the pyrolysis furnace. Therefore, the thermal efficiency and safety of the combustion chamber are the guarantee for the stable operation of the entire pyrolysis furnace. In order to determine whether the new pyrolysis furnace structure was safe and feasible, the temperature field and deformation field of the combustion chamber under different structural parameters were studied by using the fluid-thermal-solid coupling method of ANSYS Workbench, and the structure of the combustion chamber of the pyrolysis furnace was optimized by exploring the parameters of the baffle. The results showed that the structural performance of the baffle in the combustion chamber was better than that without baffle. The variation range of the temperature field variation coefficient of the combustion chamber with the baffle was 0.06 smaller than that without baffle, and the temperature field distribution was more uniform. The maximum deformation of the combustion chamber appeared on the partition between the combustion chamber and the pyrolysis chamber. The maximum deformation of the combustion chamber with baffle was 80% less than the maximum deformation of the combustion chamber without baffle, and the maximum deformation with the increase of the position of the baffle to the centre or the length of the baffle showed a trend of first decreasing and then increasing, and the thickness of the baffle had the least influence on the deformation field. When the baffle position was 150 mm, the length of the baffle was 800 mm, and the thickness of the baffle was at 14 mm, the structure of the combustion chamber of the new pyrolysis furnace was optimal. The use of fluid-thermal-solid coupling method for the optimization design of such combustion chamber structure had more reliable engineering significance, and it also provided technical support for the subsequent industrial application of oily sludge pyrolysis technology.

Real-time measurement and characterization of 3D mixing effect driven by mechanical stirring

Yuzhen SU Jinman LI Zexi LI Shuai GAO Xiuli SANG Gang CHEN Jianxin XU

The Chinese Journal of Process Engineering. 2022, 22(9):  1213-1223.  DOI: 10.12034/j.issn.1009-606X.221328

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Mechanical stirring and mixing is one of the essential operation in the fields of food processing, construction, pharmaceuticals, metallurgy, paper making, etc. It has great economic value and application prospects. The mixing uniformity is an important index to measure the quality of mechanical mixing. The study of its mixing uniformity measurement and characterization is still one of the research hot spots in this field. In order to accurately measure the three-dimensional spatial multiphase mixing effect under mechanical stirring drive in real-time, a three-dimensional mixing effect accurate measurement method was proposed, and the overall average mass metric Q was calculated to characterize the mixing effect by analogy with the concept of potential energy, in order to overcome the one-sidedness of the pseudo-uniformity measure of the overlapping two-dimensional point set of particles. The accurate measurement method of three-dimensional spatial mixing effect was experimentally verified, and the overall average mass metric Q was calculated to characterize the uniformity of particle distribution. The relationship between the motor speed and the mean relative motion velocity of red spheres was analyzed, and the results showed that different rotational speeds and frequency conversions had significant effects on the relative motion velocity variation of tracer particles. In particular, the two-dimensional and three-dimensional mixing uniformity were compared in this work, and the two-dimensional mixing homogeneity measurement method was obviously not accurate enough, there was a large deviation, 75% higher than the average deviation of three-dimensional, three-dimensional spatial mixing homogeneity measurement method calculation results had better reflection of the real mixing effect. The two commonly used methods of mixing uniformity measurement, CD and WD, were compared with method of this work, and the characterization of mixing uniformity by CD and WD methods both failed. The feasibility as well as the accuracy of the method in this work was further verified.

Experiment and simulation of turbulent fluidization characteristics of phosphogypsum particles

Yulong TIAN Xiushan YANG Xingjian KONG Dehua XU Zhiye ZHANG

The Chinese Journal of Process Engineering. 2022, 22(9):  1224-1231.  DOI: 10.12034/j.issn.1009-606X.221350

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Aiming at the problem of the drag force change in turbulent fluidization system of phosphogypsum particles, on the basis of experiments, considering the existence of nonuniform structures which would influence gas-solid drag force, 2D fluidized bed was simulated using the Gidaspow drag model modified by correcting factor φ. By comparing the simulative results of the Gidaspow model under different φ values with the experimental results, the influence of the changing φ on the simulative results and the variation characteristics of drag force in turbulent fluidization system of phosphogypsum particles with different gas velocities were studied. The results showed that particles aggregated obviously along the horizontal direction in the experimental system, which reduced the drag force between gas and solid phase, the Gidaspow model overestimated the drag force and had a poor prediction capacity on the turbulent fluidization characteristics of phosphogypsum particles. The introduction of appropriate φ can significantly improve the simulative accuracy of Gidaspow model on bed expansion, pressure drop and non-uniformity of the system. The simulative results reflected that the smaller the φ value, the smaller the bed expansion, the more heterogeneous the particle concentration distribution in the bed, and the greater the fluctuation of the bed pressure drop were. As the gas velocity increased (0.144~0.240 m/s), the degree of particle aggregation along the horizontal direction intensified and the value of φ decreased nonlinearly (0.31~0.24). The non-uniformity of fluidization system increased with the increase of gas velocity, the particle concentration was higher near the side walls and lower at the center, a large gradient of particle concentration existed along the radial, ring-core structures appear near the walls on both sides, and the symmetry of flow field distribution was poor.

Numerical simulation of effect of particle shape on tablet particles motion characteristics in a pan coater

Guilong XIONG Wenkang SU Anqi WANG Yize WANG

The Chinese Journal of Process Engineering. 2022, 22(9):  1232-1243.  DOI: 10.12034/j.issn.1009-606X.221329

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The knowledge of the particle shape and motion characteristics in a pan coater is critical to optimize the design and operation of coating equipment. To research the influence of tablet shape on the motion characteristics in a coating device, which based on discrete element method and spray zone approach, the motion characteristics of tablet particles with five shapes including rod, long ellipsoid, oblate ellipsoid, biconvex and spherical was investigated by numerical simulation. Inter-tablet variability of film coating was a critical issue in the production of solid oral dosage forms. Residence time distribution and it's relative standard deviation was developed to characterize the coating process throughout the coating vessel. The effect of tablet shape on energy of granular system, surface particles translational velocity, granular temperatures, residence time distribution and it's relative standard deviation was investigated systematically. The results showed that tablet shape significantly affected the kinetic energy of granular system, particle translational velocity, granular temperatures, residence time distribution and inter-tablet coating variability. Except for the biconvex granular system, the kinetic energy, bed translational velocity and granular temperatures of the other four kinds of granular system decreased with the increasing sphericity. Residence time distribution of the granular system gradually became normal. Weight gain mass coating variability (CVm) was to be inversely proportional to the square root of coating time and in good agreement with the Chang and Leoni experimental results. Except for the rod-shaped granular system, there was a decrease in the average residence time of the granular system in the coating spray area, an increase in the relative standard deviation of the average residence time with the increasing sphericity. Meanwhile, the inter-tablet coating variability also deteriorated. Compared with the spherical granular system, the inter-tablet coating variability of non spherical granular system showed a better behavior.

Flow field numerical simulation and mixing performance optimization of impinging stream reactor

Jianwei ZHANG Juchao NIU Xin DONG Ying FENG

The Chinese Journal of Process Engineering. 2022, 22(9):  1244-1252.  DOI: 10.12034/j.issn.1009-606X.221336

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Impinging stream reactor were used in various applications including pharmaceuticals, petroleum and provisions due to their high mass transfer efficiency, especially in fluid mixing processes, and the difference in structure was a key factor affecting the mixing effect of the reactor, thus optimizing the structure of the impinging stream reactor was beneficial for its further industrial applications. In this work, numerical simulations were used to analyze the internal flow field of a multi-nozzle symmetric impinging stream reactor to optimize the reactor structure. The effects of different nozzle numbers and feed conditions on the velocity field and turbulence characteristics in the impinging stream reactor were investigated, and the mixing effect was characterized by the mixing uniformity. The results showed that the velocity distribution in the impinging stream reactor with different number of nozzles was bimodal, the velocity gradient decreased with the increase of the number of nozzles under the condition of equal velocity, and the distribution range of high shear force increased and then decreased with the increase of the number of nozzles. By analyzing the turbulence scale distribution, it was found that the small-scale vortices were mainly concentrated in the impingement zone, while the large-scale vortices were mainly concentrated in the development zone, and the average shear stress and vortex size gradient in the four-nozzle impinging stream reactor were the largest, and the high shear stress and vortex size gradient were beneficial to increase the fluid turbulence intensity, so the average turbulent kinetic energy in the impinging stream reactor was increased and then decreased with the increase of the nozzle number, in which the average turbulent energy in the four-nozzle impact reactor was the largest, and the four-nozzle structure was more conducive to enhanced mixing. In this study, the four-nozzle structure was the optimal structure for mixing in the impinging stream reactor.

Unsteady turbulence characteristics in impingement region of plane impingement baffle separator

Xueping WANG Junjie FU Yuhui ZHANG Bin GONG

The Chinese Journal of Process Engineering. 2022, 22(9):  1253-1261.  DOI: 10.12034/j.issn.1009-606X.221310

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The purpose of this work is to acquire the flow field distribution characteristics in the liquid-liquid gravity separator at different geometric dimensions. The flow flield structure of initial incoming fluid needs to be rectified in order to make the fluid more uniform and stable before entering the separation zone of liquid-liquid gravity separator. The flat impingement baffle is improved to the entire height rectangular baffle. A numerical simulation based on the volume of fluid (VOF) method was executed using Ansys Fluent 16.2 to analyze the characteristic of flow flield structure of impacted area caused by rectaugular section. The relative unevenness (Mf) and mean turbulence intensity (Iave) were used to investigate the effect of geometric dimensions in the separator, i.e., the effect of inlet diameter of the nozzle (d), length of the impingement baffle to the inlet (lb) and width of the baffle plate (w0). The results of research showed when relative unevenness and mean turbulence intensity were considered together, the separation of two phase was more favorable with the range of the inlet diameter (d/w) equal or greater than 0.16 (w is half of the width of the liquid-liquid gravity separator), the range of the preferred distance between the baffle and the inlet (lb/w) was from 0.33 to 0.53, and the separation of two phase effect was best when the range of the baffle width (w0/w) was equal or greater than 0.27. After the normalization of the uniformity and turbulence intensity at the baffle plate, the d/w interval should be given priority in analyzing the change rate of the total interval before or after weighting. In addition, there was a good linear correlation between turbulence intensity and uniformity at impingement baffle and baffle plate in the d/w interval, and the turbulence intensity increased with the increase of uniformity.

Study on NO catalytic oxidation by manganese-based catalysts supported on high alumina fly ash

Yiyuan WANG Shuhua MA Xiaohui WANG Yanjun OU Lizhen GAO

The Chinese Journal of Process Engineering. 2022, 22(9):  1262-1270.  DOI: 10.12034/j.issn.1009-606X.221416

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Catalytic oxidation of nitrogen oxides is an important development direction of flue gas denitration technology. In this work, manganese-based NO oxidation catalysts were prepared by sol-gel method using the high alumina fly ash with spherical hollow structure as the carrier, and manganese nitrate as the source of the active component. Scanning electron microscopy (SEM), X-ray diffractometer (XRD), N2 physical adsorption, H2 programmed temperature analyzer (H2-TPR), and X-ray photoelectron spectroscopy (XPS) were used to analyze the catalyst performance and NO catalytic oxidation mechanism. The results showed that the particle size of the carrier, manganese loading, calcination temperature of manganese nitrate gel, and the catalytic oxidation temperature of NO had a great influence on the catalytic activity of the catalyst. The optimum temperature for calcining manganese nitrate gel was determined to be 500℃. The best catalytic oxidation effect with an oxidation rate of 77.8% at the NO catalytic oxidation reaction temperature of 290℃ was obtained when the particle size of the carrier is between 100~200 mesh and the manganese mass loading was 8wt%. SEM results showed that the manganese oxide particle diameters prepared by the sol-gel method were between 100~200 nm and relatively uniformly loaded on the carrier. N2 physical adsorption showed that the pore structures of the catalyst were mainly mesoporous and exhibit an H3 hysteresis loop. Chemisorption of oxygen Oβ proportion on manganese-based catalysts and Mn4+ concentration firstly increased with the increase of manganese loading and then decreased. This was consistent with the trend of catalytic oxidation performance, indicating that Oβ and Mn4+ are the decisive factors affecting the catalytic oxidation of NO.

Potassium release mechanism of potassium?bearing minerals in ammonium molybdate production process

Qihang LIU Shunzhi TIAN Shuangping YANG Lidong WANG Kai HE

The Chinese Journal of Process Engineering. 2022, 22(9):  1271-1278.  DOI: 10.12034/j.issn.1009-606X.221368

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Potassium is a harmful element in ammonium molybdate and subsequent molybdenum products, and its content is usually desired to be as low as possible. Through exploring the effects of changing cooling mode, roasting temperature, mineral particle size, washing temperature, and adding Na2CO3 on washing potassium reduction, qualitative analysis of minerals in different stages of ammonium molybdate production process was carried out by ICP, spectrophotometer, and SEM-EDS while quantitative analysis was carried out by advanced MLA technology. The results showed that rapid cooling, increasing the temperature of water washing, fine grinding molybdenum calcine, and adding Na2CO3 can improve the effect of potassium reduction in water washing. However, increasing the roasting temperature was not conducive to the release of potassium in water in molybdenum calcine, and changing the particle size of molybdenum concentrate had no significant effect on potassium reduction in water washing. Because the potassium content in molybdenum concentrate was very low, the traditional phase detection method had some errors. Through MLA detection, it could be found that there are four potassium-bearing minerals in the ammonium molybdate production process, namely muscovite, orthoclase, anandite, and illite. The potassium releasing behavior of potassium-bearing minerals was analyzed and the difficulty of four potassium-bearing minerals entering ammonium molybdate products was as follows: orthoclase>muscovite>anandite>illite. The results of MLA analysis showed that the muscovite can decompose into orthoclase and anandite during the roasting process of molybdenum concentrate. The initial reaction temperature of decomposing mica into orthoclase was 727 K. As the most harmful mineral in the process of ammonia leaching potassium mineral, orthoclase was not only from the raw material of molybdenum concentrate but also produced in the process of high-temperature roasting. The transformed muscovite decomposed extremely easy and thus greatly improved the proportion of orthoclase in the subsequent washing and ammonia leaching process, which was extremely difficult to remove and hence the formed orthoclase was relatively easy to enter into the ammonia immersion compromised product quality. The research results are of great significance for the production and application of low potassium molybdenum products.

Effect of Na₂O/SiO₂ ratio on structure and properties of reduction smelting slag for treating decoppering anode slime in Caldo furnace

Xiaotian ZHANG Yaru CUI Guohua WANG Ze YANG Junxue ZHAO Ze WANG Ailin HU

The Chinese Journal of Process Engineering. 2022, 22(9):  1279-1286.  DOI: 10.12034/j.issn.1009-606X.221314

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Caldor smelting is one of the most important methods for treating decoppering anode slime by pyrometallurgy. This research aims to solve the serious problems of poor melting performance and large precious metals loss of reduction smelting slag for treating decoppering anode slime emerged in a domestic enterprise. Therefore, the process optimization and regulation on the Na2O/SiO2 ratio of reduction smelting slag in the Caldor furnace is carried out. The thermodynamic analysis by Factsage software is employed; simultaneously, the physicochemical properties of reduction smelting slag are measured combined with the XRD analysis and Raman spectroscopy characterization. According to the liquid phase diagram and the tested physicochemical properties of the PbO-Na2O-SiO2-BaO system, appropriately increasing Na2O/SiO2 ratio can effectively decrease the melting temperature and viscosity of reduced smelting slag, without changing the slag rate and the adding amount of total flux. The structure of reduction smelting slag varies from dimer structure silicate of Si2O76- to tetrahedron structure silicate of SiO44- when the Na2O/SiO2 ratio of reduction smelting slag changes from 0.42 to 0.60. The increase of network modification of Na2O results in more bridging oxygens converting to non-bridging oxygens in the reduction of smelting slag, and the ratio of Si2O64- chain structure silicate and Si2O52- sheet structure silicate decrease also, which lead to the lower of polymerization degree of slag. The analysis results show that the Qn of bridged oxygen is consistent with the silicate structure of the smelting slag. Simultaneously, the hemispherical melting temperature of slag decreases from 1178℃ to 950℃, and the viscosity can decrease about 45.2% at a smelting temperature of 1100℃ when the Na2O/SiO2 ratio of the reduction smelting slag varies from 0.42 to 0.60. As a result, the fluidity of reduction smelting slag is improved obviously, which can verify the above change trend of slag microstructure from the view of macroscopic properties. The results prove that it is feasible to regulate the Na2O/SiO2 ratio of reduction smelting slag to lower the bridging oxygen number and polymerization degree of complex anionic, to improve the physicochemical properties.

Research on transient leakage characteristics and consequence of LNG tanker accident

Jinlong MEN Hongbing JI Chongchong CAI Bibo XIONG

The Chinese Journal of Process Engineering. 2022, 22(9):  1287-1296.  DOI: 10.12034/j.issn.1009-606X.221312

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The classical model of liquid phase leakage can not accurately analyze the accident quantitatively. In this work, the leakage of LNG tank car is improved in combination with the ideal gas state equation, the change relationship between liquid level and pressure and between liquid level and time are explored, the relationship is introduced into the empirical formula, the change relationship between leakage rate and time is deduced, and the function expression is simulated. The results show that the leakage rate decreases exponentially with time. The dangerous concentration range of material leakage is calculated by combining the functional relationship with Gaussian diffusion. The error between the results and fluent model is within 26%. On the basis of modifying the traditional Gaussian model, the dynamic smoke diffusion model with time and pressure is obtained. The modified dangerous concentration range is used as the basic data to quantitatively analyze the mass of substances involved in explosion. The Thornton cone model is also used to explore the risk and influence range of fire and explosion by considering the flame jet angle, flame direction and environmental factors. The results show that jet fire, steam cloud explosion and boiling liquid expansion steam explosion cause death within 15, 15 and 298 m respectively. Compared with Aloha model, the overall error of the results is within 10.37%. It shows that the model is applicable to the theoretical calculation of LNG tank car leakage. The leakage at any time can be obtained by using the improved leakage model. Combined with the Gaussian diffusion of time factors, the dynamic diffusion process can be better described, and the calculated fire and explosion hazard range is more accurate, which provides a theoretical basis for emergency pre judgment, in-process response and crisis law analysis. It provides a scientific reference for taking flexible rescue measures in different injury areas.

Rational construction of hydrophobic interface to separate oil from water

Yao WANG Zikang ZENG Qiuwen LI Min LIU Yuzhu PANG Chengfu ZHANG Yujun LIANG Yongsheng HAN

The Chinese Journal of Process Engineering. 2022, 22(9):  1297-1304.  DOI: 10.12034/j.issn.1009-606X.221342

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A mass of oil-water mixture is generated in oil exploitation, and a large amount of oil-water wastewater is produced in our daily life. If these oily wastewaters are not treated effectively, direct discharge would cause serious damage to the natural ecology. How to deal with these oil-water mixtures is a critical issue of environmental protection and sustainable development. Due to the different composition and dispersion form of oily wastewater, and the harsh condition in the actual treatment process, the separation method should be selected to satisfy the separation requirements. Membrane separation is a common oil-water separation method. The separation principle is based on the different affinity of oil and water to the solid film surface. However, due to the diversity of separation environments and the limited mechanical properties of membrane materials, membrane separation has encountered kinds of challenges in industrial applications, especially for the high concentration of oil in water. In this work, nickel foam with good mechanical properties is used as filtration materials, and nano-structures are constructed on its surface to enhance the roughness of substrate surface and the underwater oil-repellency, so as to improve the oil-water separation performance. By electrochemical deposition method, copper particles are deposited on the surface of nickel foam. The surface structure and properties of the separation film are characterized by X-ray diffractometer, surface roughness tester and contact angle tester. The oil-water separation property to different kinds of oil and the stability of the prepared separation film are tested. The results show that the membrane has a high separation efficiency for different kinds of oil and good cycling separation performance, and the separation efficiency is more than 95% after ten cycles. This study shows the effectiveness of surface engineering in the development of efficient membrane for oil-water separation, and expands the applications of electrodeposition approach to surface modification.