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    28 November 2023, Volume 23 Issue 11
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    Contents
    Cover and Contents
    The Chinese Journal of Process Engineering. 2023, 23(11):  0. 
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    Research Paper
    Large eddy simulation for single particle wake characteristics in concave-wall tangential jet
    Jing ZHANG Wenhao HOU Chenghao ZHOU Zhiguo TIAN Bin GONG
    The Chinese Journal of Process Engineering. 2023, 23(11):  1497-1505.  DOI: 10.12034/j.issn.1009-606X.223019
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    Large eddy simulation was used to simulate the influence of spherical particles near the wall on fluid flow characteristics under the action of tangential jets on the concave-wall. The simulated wake vortex results were in good agreement with the experimental tracer image. The vortex structure and its evolution process of particle wake with particle diameter dp=4 mm and radius of curvature of concave wall R=200 mm were studied. The changes of velocity, vorticity, and streamline around the particle were investigated at Reynolds number Re=700~10 000. The results showed that the vorticity in the influence area of particles increased, the peak value of vorticity always appeared on the upstream surface of particles, and the recirculation zone behind the particles shrank significantly with the increase of Reynolds number. When Re=700, there was only one wake vortex behind the particle along the concave wall jet spanwise. When Re≥2000, there were two wake vortices behind particles along the concave wall jet spanwise, and the tangential velocity and vorticity of the fluid fluctuated periodically. The particle lift and resistance were monitored. There was the vortex shedding frequency at Strouhal number St=0.000 854 when Re=2000, and the peak value of the lift power spectrum occurred at St=0.001 52. The frequency peak corresponding to the boundary layer and wake instability was not found in the drag power spectrum when Re=10 000, and the peak of the lift power spectrum occurred at St=0.008 74. The particle wake had a great influence on the flow field. The analysis of the particle wake characteristics in the tangential jet on the concave wall was an in-depth study of the liquid-solid two phase separation mechanism. It provided the theory for the characteristics of single particle wake vortex in the process of heterogeneous separation of the tangential jet from concave wall.
    Experiment and DEM numerical simulation of mixing power of ultrafine powder based on similarity theory
    Hui CHEN Xuedong LIU Wenming LIU Weiwen ZHENG Honghong ZHANG Kaixin LÜ
    The Chinese Journal of Process Engineering. 2023, 23(11):  1506-1517.  DOI: 10.12034/j.issn.1009-606X.222421
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    In order to study the correlation between the stirring power characteristics of ultrafine powder and the operating parameters and the calculation expression of stirring power, the problems of difficult calculation and lengthy calculation time in ultrafine powder stirring simulation were solved. The method of combining experimental research and numerical simulation was used to study the variation law of stirring power and torque of the ultrafine powder mixing process in the mechanical powder mixer. The stirring experiment of light calcium carbonate powder with an average particle size of 10.56 μm was carried out, and the operating parameters in the mechanical powder mixer, including the effects of rotational speed, blade position, and material surface height on the stirring power and torque of ultrafine powder were studied, and the expression of power calculation was obtained. Using the similar principle, the fine particles of the powder were enlarged, and the virtual experiments were carried out on the enlarged coarse particles to obtain the contact parameters. The DEM numerical simulation of the coarse particle stirring process was carried out, and the results of the simulated stirring power and torque were compared with the experimental results. The results showed that the mixing power consumption of ultrafine powder in the mechanical powder mixer was closely related to the parameters of the rotational speed, blade position, material surface height and so on. At the same time, the torque value and power value were positively correlated with rotational speed and material surface height, and negatively correlated with the blade position. The ratios of simulated torque value and power value to experimental torque value and power value were basically consistent with the particle amplification factor, which verified the accuracy of the similar principle applied to study the influence of blade position and material surface height on the stirring power characteristics.
    Catalytic conversion of the by-product bromoethanol in the process of CO2 cycloaddition
    Ruibin GAO Lixin YI Zifeng YANG Li DONG Yifan LIU Hongfan GUO Yunong LI
    The Chinese Journal of Process Engineering. 2023, 23(11):  1518-1529.  DOI: 10.12034/j.issn.1009-606X.222468
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    The rapid and massive accumulation of greenhouse gas CO2 in the atmosphere directly leads to global warming, ecological damage, and other environmental problems. From the perspective of renewable carbon resource utilization, CO2 is a widespread, inexpensive, and easily available C1 resource. The synthesis of ethylene carbonate employing CO2 as raw material provides a feasible industrial scheme for CO2 utilization with the atomic economy. The traditional efficient catalyst for this cycloaddition is halogen ionic liquid. However, the loss of halogen ions in the cycloaddition process leads to the additional consumption of epoxide and the generation of halogenated alcohol, thus decreasing the selectivity and yield of the main product, resulting in separation difficulty and improving equipment requirements. Therefore, it is necessary to develop an ideal catalytic system to inhibit and transform the by-product of halogenated alcohols. In this work, a series of alkalescent ionic liquids had been designed and developed to realize the in?situ conversion of bromoethanol under the condition of cycloaddition (temperature of 130℃, CO2 pressure of 3 MPa, reaction time of 3 h). The effects of different reaction conditions and different alkaline ionic liquids on the conversion of bromoethanol were investigated, including ionic liquid type, reaction temperature, different pressure environment, reaction time, etc. The reaction law of bromoethanol conversion was revealed, among which [Bu4P][HCO3] showed optimal performance. Using gas atmosphere and solvent microenvironment to regulate different reaction paths, the conversion rate of bromoethanol reached 20%~50%. After ethylene carbonate (EC) addition, the by-products with bromine-containing covalent bonds were reduced, which was more conducive to the formation of bromine ions. The conversion of halogen covalent bonds to halogen ions restored part of the catalytic activity of the cycloaddition reaction system. This was a simple versatile approach, which can realize the in?situ regulation of bromoethanol conversion pathways in the CO2 cycloaddition system, and promote the optimization of the CO2 utilization system and the circulation of halogen ions, hence possessing important scientific significance and application value.
    Numerical simulation of blending effectiveness of forcing mixer based on EDEM
    Xu GAO Jie LEI Zhanxia DI Shanping LIU Yunfeng SONG Hongming LONG
    The Chinese Journal of Process Engineering. 2023, 23(11):  1530-1540.  DOI: 10.12034/j.issn.1009-606X.222459
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    The mixing effect of raw materials is an important factor affecting the quality and production efficiency of pellets. The forcing mixer is the core mixing equipment, and the appropriate operating parameters can make the mixed materials achieve the best mixing effect. In industry, the basic performance indicators of pellets are generally used to replace the mixing effect of materials, such as falling strength and compressive strength, resulting in long detection process, large error, and inability to visually obtain material trajectory and dispersion effect. In this study, SOLIDWORKS software is used to establish a forcing mixer model, and EDEM discrete element software is used to simulate the movement behavior of materials in the reactor. The effects of the rotating motion of the rotor, the bottom and the wall of the mixer and the filling rate of the materials on the mixing effect are studied. The results show that increasing the rotor speed can significantly improve the mixing effect, but when the rotation speed reaches ±48 r/min, the improvement of the mixing effect is not obvious. The rotation of the bottom can break through the speed threshold of the double rotor rotation, and the bottom can greatly improve the mixing effect at a lower rotation speed of +30 r/min. On the contrary, the rotation of the wall produces a stacking effect, which inhibits the dispersion of the particles, thereby reducing the mixing effect. The high filling rate is not conducive to the dispersion of materials above the rotor blade position, and the mixing effect is the best when the filling rate is 60%. Considering the enterprise pellet production and mixing equipment running performance requirements, the reasonable operating parameters are rotor rotation speed of ±30 r/min, the bottom rotation speed of +30 r/min, the wall rotation speed of 0 r/min, and filling rate of 60%.
    Effect of Al2O3 on phase transformation and structure of copper slag dilution
    Bo TIAN Yonggang WEI Shiwei ZHOU Bo LI
    The Chinese Journal of Process Engineering. 2023, 23(11):  1541-1548.  DOI: 10.12034/j.issn.1009-606X.222465
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    Copper slag dilution is an important method for the sustainable development of copper metallurgy industry. As high-quality copper concentrates continue to be consumed, low-grade, high-impurity copper concentrates are gradually being utilized. As a typical low-quality copper concentrate, the content of Al2O3 in the copper slag after smelting of high-alumina copper concentrate has increased. With the change in copper slag composition, controlling the slag characteristics is critical to recover copper in the copper slag dilution process and to reduce copper losses in slag. In this work, ISASMELT copper slag was used as raw material. Analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM-EDS), and infrared spectroscopy (FTIR) are used to elucidate the effects of different Al2O3 contents on the phase and structure of copper slag during the copper slag dilution, as well as the effect of phase transformation and structure change on copper loss in slag. The effects of different CaO additions on the phase transformation, structure and copper loss of high-alumina copper slag are also investigated. The results show that with the increase of Al2O3 content, high melting point hercynite can be formed in the slag, and the polymerization of slag increases and the aluminosilicate structure becomes more complex. This increases the slag viscosity and the copper loss of slag. The addition of CaO in the high alumina copper slag would form high melting point hedenbergite, monticellite, and the viscosity increases. However, with the increase of CaO addition, the slag structure tends to simplify and viscosity decreases. At the CaO addition of 2wt%, the slag contains the lowest copper content of 0.78wt%. The addition of small amount of CaO can reduce the copper loss of high-alumina copper slag.
    Effect of low-temperature magnetization roasting on the dissolution and magnetic separation performance of high-iron bauxite
    Zhenxin WAN Chaoyi CHEN Junqi LI Xiaotian DUAN Dong LIANG
    The Chinese Journal of Process Engineering. 2023, 23(11):  1549-1557.  DOI: 10.12034/j.issn.1009-606X.223069
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    Low-temperature magnetization roasting can not only improve the magnetic separation performance of bauxite but also improve the dissolution performance of bauxite. It provides a solution for the industrial utilization of high-iron bauxite. In order to realize the efficient recovery of aluminum and iron elements in high-iron bauxite, the method of "low-temperature magnetic roasting-Bayer digestion-red mud magnetic separation" is adopted to treat high-iron bauxite. The effects of roasting temperature, H2 concentration, and H2 input time on the dissolution and magnetic separation performance of high-iron bauxite were investigated. The effect of roasting on the phase transformation and microstructure of bauxite was analyzed via XRD, SEM, and BET. The results showed that diaspore dehydrated and transformed into transition Al2O3 during roasting. Thermal cracking occured in minerals, the specific surface area increased, and the leaching activity of alumina increased. The relative dissolution rate of alumina could reach 97.65% when the calcination temperature was 530℃, the concentration of H2 was 20vol%, and the time of H2 was 5 min. Magnetization roasting transformed hematite into magnetite with strong magnetism. After the magnetic separation of roasted ore, the grade of iron concentrate was 33.51wt%, and the iron recovery rate was 60.32%. The dissolution process could remove the embedding relationship between aluminum and iron elements. After the magnetic separation of red mud from roasted ore, the grade of iron concentrate reached 62.05%, and the iron recovery rate was 86.36%. The magnetic separation performance of red mud was far better than that of calcined ore. "Low-temperature magnetic roasting-Bayer digestion-red mud magnetic separation" realized the efficient separation of iron and aluminum from diaspore-type high-iron bauxite. The technical goal of removing iron and extracting aluminum had been achieved. It provided the theoretical basis and technical support for the subsequent development and utilization of high-iron bauxite.
    Study on the mechanism of Ni2+ and Mg2+ loss and enhanced separation in sulfuric acid leachate of laterite nickel ore during iron removal using neutralization process
    Hao JIANG Xin TENG Jun LUO Changye MANG Xinran LI Wenhao SUN
    The Chinese Journal of Process Engineering. 2023, 23(11):  1558-1567.  DOI: 10.12034/j.issn.1009-606X.223055
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    Neutralization precipitation process is often used to remove impurities such as iron, aluminum and chromium from the nickel laterite acid leach solution, however, it accompanied with the loss of nickel and magnesium metal ions. The precipitation behaviors of Ni2+ and Mg2+ ions in nickel laterite acid leach solution during the neutralization precipitation iron removal process was deeply discussed in this work. Furthermore, a novel precipitation mechanism of Ni2+ and Mg2+ with SO42- during the neutralization precipitation iron removal process was proposed. The results showed that under the condition of fixed Ni2+ and Mg2+ concentrations in simulated leachate, the loss rate of Ni2+ and Mg2+ during neutralization and precipitation respectively were 9.13%~23.23% and 9.79%~15.68% with the increase of Fe3+ concentration in simulated leachate. Under the condition of fixed Fe3+ concentrations, the loss rate of Ni2+ and Mg2+ decreased with the increase of the concentration of Ni2+ and Mg2+. According to the results of solution chemical calculation and the characterization of iron hydroxide precipitation by infrared spectroscopy and scanning electron microscopy, both SO42- ions and Fe(OH)3 colloids could co-precipitate in the form of monovalent or binary complex during the neutralization process, in which the lone pair electrons of SO42- in the monovalent complexes bond with Ni2+ and Mg2+ and adsorb, resulting Ni2+ and Mg2+ in the leachate were co-adsorbed with SO42- by Fe(OH)3 colloid and the loss was caused. In addition, it was found that the surfactant such as cetyl trimethylammonium bromide (CTAB), polyethylene glycol (PEG), sodium dodecyl benzenesulfonatecan (SDBS) was added during the neutralization precipitation process can effectively compete for adsorption with neutralizing precipitated products or impede the combination of SO〖_4^(2-)〗 with Ni2+ and Mg2+ ions, which could enhance the selective precipitation of Fe3+ ions during neutralization process. When the dosage of three surfactants was 2×10-5 mol/L, the retention rates of Ni2+ in the process of neutralization and precipitation of iron could reach about 95%, and Mg2+ could reach 100%.
    Removal of low-concentration toluene with multi-needle corona discharge coupling Ag/TiO2 nanocatalyst system
    Yan YAN Bin ZHU Li XU Yimin ZHU
    The Chinese Journal of Process Engineering. 2023, 23(11):  1568-1576.  DOI: 10.12034/j.issn.1009-606X.223021
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    A plasma-catalytic system was constructed by coupling multi-needle corona discharge with Ag/TiO2 nanocatalyst. The discharge characteristics of the plasma-catalytic system were diagnosed, and the characterization of the Ag/TiO2 nanocatalyst was also performed. The multi-needle corona discharge coupling Ag/TiO2 nanocatalyst system was applied to remove low-concentration toluene from the air. The secondary pollutant of ozone was monitored during toluene removal. Further, the mechanism of toluene removal and suppressed ozone generation during toluene removal was disclosed. It was found that the plasma diffused in the whole discharge region when the discharge voltage was higher than 7.0 kV. The presence of Ag/TiO2 nanocatalyst showed no obvious influence on the discharge. These features facilitated the high plasma density and intimate interaction between reactants, plasma, and Ag/TiO2 nanocatalysts. Ag particles in the Ag/TiO2 nanocatalyst possessed an average size of 6.5 nm, which created large numbers of highly active Ag-TiO2 interfacial sites and endowed Ag/TiO2 nanocatalyst with strong absorption ability for UV-visible light. At a voltage of 7.5 kV, the multi-needle corona discharge obtained toluene conversion and CO2 selectivity of 21% and 7%, respectively. Coupling of multi-needle corona discharge and Ag/TiO2 nanocatalyst made toluene conversion and CO2 selectivity increased to 83% and 61%, respectively. The concentration of ozone in the plasma-catalytic system was 0.02 mg/m3, which had a remarkable decrease compared with the pure discharge (5.12 mg/m3). The performance of the multi-needle corona discharge coupling Ag/TiO2 nanocatalyst system was attributed to the synergetic effect between the light field, electrical field, and catalytic sites, which could modulate the conversion path of intermediates and extend the avenues of toluene removal. This study would provide an important reference for the application and development of plasma-catalysis techniques in indoor air purification.
    Experimental verification of a small medical waste decoupling incineration treatment system
    Xinhua LIU Jian HAN Jiangping HAO Rong LI Hongming XIAN Shanwei HU Nan ZHANG Hao LAN
    The Chinese Journal of Process Engineering. 2023, 23(11):  1577-1586.  DOI: 10.12034/j.issn.1009-606X.223067
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    Due to the potential negative impact on human health and environmental safety of medical waste, it is of great significance for numerous small and medium medical institutions far away from cities or inland to dispose of a small amount of medical waste harmlessly on the spot. However, there still lacks small-scale packaged technology for the clean and high-efficiency treatment of medical waste, so it is difficult to implement the onsite hazard-free reduction disposal of medical waste. In view of some combustion and flue gas treatment problems confronted in the harmless onsite disposal of a small amount of medical waste, this work designed and experimentally verified an integrated decoupling incineration treatment system suitable for the decentralized disposal of medical waste by using the so-called decoupling combustion technology. The results showed that the decoupling incinerator could facilitate the high-efficiency and stable combustion of medical waste and the suppression of emissions of nitrogen oxides (NOx) and dioxins (PCDD/Fs). The small flue gas purification facility based on two-stage wet desulphurization technology enabled rapid cooling of flue gas to avoid the secondary generation of dioxins and simultaneous removal of acidic substances and particulate matter (PM). Treating typical medical waste blending in the small integrated decoupling incineration system, the emissions of NOx, SO2, PM, CO, and PCDD/Fs could be lower than 123, 1.8, 38, 53 mg/m3, and 0.31 ng I-TEQ/m3 on the 11vol% O2 basis, respectively. The newly-developed small medical waste incineration treatment system featured a compact configuration structure and high purification efficiency because of its integrated design of decoupling incinerator and purification equipment so that it can meet the need for onsite clean disposal of daily medical waste in the decentralized medical institutions.
    Numerical simulation on influencing factors of pulverized coal combustion in rotary kiln
    Yanpeng WANG Yilun LIU Heping LI Mingfei LI Xiuzhen GUO Sichao ZHANG
    The Chinese Journal of Process Engineering. 2023, 23(11):  1587-1598.  DOI: 10.12034/j.issn.1009-606X.222400
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    Rotary kiln is a high-energy consumption equipment widely used in metallurgy, chemical industry, environmental protection and other fields. As the main energy source of the thermal process of the rotary kiln, the efficiency of fuel combustion is directly related to the energy-saving operation of the rotary kiln. In order to improve the pulverized coal combustion efficiency in the rotary kiln, the pulverized coal combustion process in the rotary kiln was numerically simulated by ANSYS Fluent 19.0 software. By controlling a single variable and designing a multi index orthogonal test condition, the influence and significance of air excess coefficient, pulverized coal particle size, swirl angle, ratio between internal and external air volume on the pulverized coal combustion in the rotary kiln were analyzed. The influence rules of each factor on pulverized coal combustion and optimal working condition were obtained. The results showed that the increase of air excess coefficient and pulverized coal particle size increased the flame length, reduced the flame diameter and make the flame slender. The increase of swirl angle shortened and thickened the flame shape. With the increase of the ratio of internal and external air volume, the flame length first increased and then decreased, and the flame diameter first decreased and then increased. The four factors ranking in a decreasing order of in?uence were the pulverized coal particle size, ratio between internal and external air volume, air excess coefficient, and swirl angle. The optimal operating parameter combination of pulverized coal combustion in rotary kiln were air excess coefficient of 1.1, pulverized coal particle size of 40 μm, swirl angle of 25°, ratio of internal and external air volume of 0.9. Compared with the original working condition, the flame length and flame diameter of the optimized working condition increased respectively by 8.9% and 13.9%.
    Study on purification of human serum albumin by novel electrostatic coupled affinity chromatography
    Sidong WANG Liuyang WANG Xue FENG Songping ZHANG Wanzhong ZHANG Jian LUO
    The Chinese Journal of Process Engineering. 2023, 23(11):  1599-1607.  DOI: 10.12034/j.issn.1009-606X.223062
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    Human serum albumin (HSA), the most abundant protein in human serum, accounting for about 40%~60% of the total serum protein content. When purified by commercialized albumin affinity medium (Cibacron Blue F3GA), the yield of albumin is low, meanwhile, the ligand of Cibacron Blue F3GA had disadvantages of high toxicity and easily to fall off. In this study, a novel electrostatic coupling affinity medium was prepared and used to purify albumin from human serum by one-step chromatography. New electrostatic coupling affinity medium DASA-Sepharose (3,5-diaminobenzoic acid n-octyl succinic anhydride-Sepharose) was prepared with n-octyl succinic anhydride as affinity ligand coupled to agarose microsphere with 3,5-diaminobenzoic acid as spacer arm. The carboxyl functional group on the DASA-Sepharose spacer arm adsorbed albumin through electrostatic interaction, and then cooperated with the n-octyl succinic anhydride affinity ligand to achieve electrostatic coupling affinity adsorption, which greatly improved the adsorption capacity and maintained the high specificity of affinity adsorption. The effects of different NaCl concentrations and pH values on adsorption equilibrium were investigated with BSA as model protein. When NaCl concentration was 0.025~0.06 mol/L, the saturated adsorption capacity (Qm) was almost unaffected. When NaCl concentration was 0.1 mol/L or above, Qm decreased significantly. The Qm for BSA reached 75.43 mg/mL medium in 20 mmol/L PBS at pH=5.00. Compared with the Qm (20 mg/mL medium) of the commercialized albumin affinity medium Cibacron Blue F3GA, the Qm of DASA-Sepharose increased by about 2.7 times. The HSA could be directly extracted from human serum using the novel electrostatically coupled affinity chromatography medium with high purity (98.20%) and high yield (94.34%).The secondary structure and small molecule drug binding activity of purified albumin were determined by circular dichroism spectrum and warfarin sodium method, which were basically consistent with the standard human serum albumin. The results demonstrated that the electrostatic coupling affinity chromatography can be efficiently used for HSA purification from human serum, which provided a new approach for the HSA separation from plasma.
    On monitoring distillation processes energy consumption status under control
    Chen YE Jiamin REN Tong XU Chi ZHAI
    The Chinese Journal of Process Engineering. 2023, 23(11):  1608-1615.  DOI: 10.12034/j.issn.1009-606X.223001
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    Distillation is the most widely used separation technology in the chemical industry, and its high energy consumption has been a major concern. Traditional distillation process control usually focuses on controlled variables, such as tower top and bottom temperature. Engineering process control (EPC) on the operating variables can maintain the control output in a given range. In real-time production, regulation of EPC might cause shifts in the mean value of the manipulation variables, and energy waste might occur when both the cold and hot utilities increase spontaneously. Under carbon peaking and carbon neutrality, it is important to seek an accurate monitoring/control strategy to realize the energy-saving operation of the distillation processes. This work proposes to combine statistical process control (SPC) and EPC, i.e., SPC charts are introduced to determine the disturbance scenario as well as EPC is adopted to control the process. According to the analysis of SPC charts, the interference source could be identified, which might assist in the control decision on EPC. To demonstrate the monitoring effect, a benzene separation column is taken as a case study where decoupling control is implemented for temperature disturbance rejection. Then, step and slope disturbances are introduced into the system to locate or predict shifts of the manipulated/control variables, afterwards, root cause analysis is implemented. The simulation results show that while EPC could maintain tower temperature within a specific range for a relatively long period, SPC might suggest abnormal working status, which would cause unnecessary consumption of energy. The results show that combining EPC and SPC could effectively enhance the understanding of the process run-away conditions, and assist reduce the unnecessary energy consumption of the distillation process.