The Chinese Journal of Process Engineering

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Chin. J. Process Eng.. 2020, 20(10): 0.

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Research status of hydrodynamic characteristic parameters of flotation equipment

Jikang HAN Weizhi WANG Wei ZHANG Zhiwei SHAN Dong WANG

Chin. J. Process Eng.. 2020, 20(10): 1121-1133. DOI: 10.12034/j.issn.1009-606X.220139

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Flotation equipment is an important gas–liquid reaction device in the field of mineral processing engineering. Flotation equipment has been used for one hundred years. With the rapid development of society, flotation equipment has gradually developed towards automation and large-scale. In recent years, more and more researches and analysis of hydrodynamic characteristic parameters in flotation equipment have been carried out, which has further promoted the reasonable enlargement and optimization of equipment. This work briefly introduced the current development and application status of flotation equipment, then summarized in detail the detection methods, principles and the current research status of three important hydrodynamics characteristic parameters in flotation equipment: bubble size, gas holdup and bubble velocity. According to the current development direction of mineral processing equipment, it was pointed out that how to accurately detect the parameters of the flotation bubble and improved the adaptability of the detection device, and widely applied in the industry to improve the flotation index are still a key issue that researchers faced at present. Image processing technology which can detect multiple characteristic parameters in the flotation equipment had been widely used, but bubble image processing methods which the majority of research scholars had put forward at present have limitations, and failed to involve many complicated details and the actual environment of concentrator, leading to the poor stability and low accuracy of bubbles when bubbles feature was extracted. Therefore, it was necessary to develop machine vision technology that was used in a variety of complex environments and had a strong ability to sort complex problems. At the same time, some sophisticated intrusion detection equipment such as conductivity probes still had certain defects in complex flotation environments. How to design and develop intrusive devices that are more conducive to complex flotation environments was one of the current research direction.

Review on magnetic droplet generation and manipulation in microchips

Chao LONG Rui CHEN Chi ZHAI Fei CHEN Chunxi YANG

Chin. J. Process Eng.. 2020, 20(10): 1134-1146. DOI: 10.12034/j.issn.1009-606X.219346

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In recent years, magnetic droplets with microscale, multiphase and contactless properties have received wide attentions from researcher of science and business for their successful applications in biological cell separation and targeted drug therapy. However, the main challenge is how to manipulate magnetic droplets approaching the set position accuracy. Therefore, three aspects including the current methods of generating and manipulating magnetic droplets, the basic mechanism of magnetic droplet manipulation and their control mechanism were summarized in this work. At present, the control methods for magnetic droplets can be divided into three categories. The first type was the permanent magnets-mechanical method where permanent magnets were placed on a mechanically mobile platform. By means of moving the platform, the distance between the permanent magnet and the microchip was changed and then the magnetic field intensity was also regulated. Moreover, the dynamic magnetic droplets were controlled. The second type was the electromagnet-electric method where the situation errors of droplets were detected by high-speed camera and sent to controller and the prebuilding mathematical model to obtain control output in order to regulate magnetic field intensity for manipulates the magnetic droplet. The third type was permanent magnets/electromagnet-electric mixed method where advantages of two methods mentioned above were combined to manipulate magnetic droplets for better control. Finally, the drawbacks and difficulties of current methods of magnetic droplets generating and manipulating were summarized and further possible research techniques and research fields were prospected.

Flow field simulation and structural optimization of purifier based on CFD-DEM method

Wenhao SHEN Yaxin ZHANG Jiang SONG

Chin. J. Process Eng.. 2020, 20(10): 1147-1155. DOI: 10.12034/j.issn.1009-606X.219356

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The discrete element method (DEM) was used to establish the random stacking cylindrical activated carbon in the adsorption filter screen and the computational fluid dynamics (CFD) was used to simulate the flow field in the air purifier. On the basis of simulation and experimental verification, the hole shape, diameter and spacing of the filters with the least pressure drop and the most uniform flow field for air purifier were explored. The results showed that the pressure drop of the air purifier mainly occurred in the axial direction. The inlet gas could be averagely distributed by the pre-filter to improve the purification effect of the gas in the adsorption filter screen. There was a stable linear flow in the chemical filter, which was not conducive to adequate chemical reaction of harmful substances. And there was a phenomenon of reflux and retention in the gas chamber between the filters. The flow state of the activated carbon adsorption filter screen was extremely unstable, and the complex accumulation pattern of particles led to obvious high velocity and gully flow. The pressure drop of adsorption filter was three times higher than that of the other two filters, and it was also the main source of noise and energy consumption. The number of edges had no effect on the uniformity of the flow field and the pressure drop in the adsorption filter of the polygon filling hole structure. When the hole structure was changed to a circle, the pressure drop was reduced by 52 Pa and the energy was saved by 18.4% (49 W). When the diameter of the filling hole increased from 8 mm to 12 mm, the pressure drop was reduced by 48 Pa and the energy was saved by 19.4% (45 W). The filter spacing had no effect on the pressure drop of the air purifier, and the flow field in the adsorption filter with circular and small pore sizes was the most uniform.

Process and leaching kinetics of extracting copper and cobalt from high silicon low grade copper-cobalt ore by selective reduction ammonia leaching

Ao GONG, Xuangao WU, Xiaoqiang YU, Dingchun WANG, Zhifeng XU, Lei TIAN

Chin. J. Process Eng.. 2020, 20(10): 1156-1165. DOI: 10.12034/j.issn.1009-606X.219351

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The leaching process and kinetics of African high silicon low grade copper cobalt ore in ammonia leaching system were studied. Firstly, the controllable variable method was used to systematically study the effects of leaching agent concentration, additive dosage, reaction temperature, reaction time and liquid/solid ratio on the leaching rate of copper and cobalt through single factor experiments. Secondly, the phase and chemical composition of high silicon low grade copper?cobalt ore and leaching residue were analyzed by X-ray diffraction (XRD), inductively coupled plasma (ICP) and scanning electron microscope-energy spectrum (SEM-EDS). The results showed that the leaching rate of copper and cobalt can reach 97.29% and 95.18% respectively, under the technological conditions of ammonium sulfate as leaching agent with the concentration of 300 g/L, reducing agent of 0.7 g, leaching temperature of 353 K, reaction time of 240 min and liquid/solid ratio of 6:1. Finally, by analyzing the kinetic model of copper extraction by high silicon low grade copper?cobalt ore ammonia leaching, the activation energy, reaction order of ammonium sulfate concentration and particle size are 76.06 kJ/mol, 1.50 and 0.25, respectively, indicating that it should follow the interface chemical reaction control, and the corresponding kinetic equation was established.

Preparation of magnetic coagulant aid from wastes for enhanced pollutant precipitation

Xiaofei MENG Rong HOU He ZHAO Bin XU Linhao YANG

Chin. J. Process Eng.. 2020, 20(10): 1166-1173. DOI: 10.12034/j.issn.1009-606X.219353

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In recent years, with the increasing of water treatment, the production of coagulated sludge has a sharp rise. So, the realization of coagulated sludge resource utilization is necessary. In this research, the coagulated sludge treated by carbonization at high temperature and polymerized ferrous sulfate (PFS) were added together to remove Fe(CN)63? pollutants. And the mechanism of coagulation was further studied. The structure of the coagulated sludge materials was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and magnetic hysteresis curve. The pollutant of Fe(CN)63? coagulated by PFS and coagulated sludge was analyzed by the removal rate, particle size and shape. The results showed that the sludge materials contained a large amount of carbon and it had some functional groups like carboxyl on the surface. Iron and vanadium oxides which had complexation ability were formed on the surface carbonized sludge materials. The crystallinity and grain size of the coagulated sludge were more ordered and more uniform by carbonization at high temperature which could benefit to the growth of flocs in the process of coagulation. The removal of Fe(CN)63? increased by adding coagulated sludge. Especially, the removal of Fe(CN)63? increased to 99.45% by adding the sludge which was carbonized at 700℃ with PFS:RW700=1:1.43. By the analysis of particle size and shape, the coagulated sludge was beneficial to the enhancement of pollutants during coagulation process. By optimizing the ratio of sludge material to PFS, the removal of Fe(CN)63? pollutant was also close to 100% by reducing the dosage of PFS. Compared with the other coagulants, the cost of water treatment decreased. This study provided theoretical and technical basis for the resource recycling of coagulated sludge. This new type of sludge resource utilization had promising application in the field of cyanide removal.

Recovery of manganese from the mother liquor after vanadium precipitation during vanadium extraction with calcified roasting and acid leaching process

Juhua ZHANG Yue LIANG Wei ZHANG Zhengliang XUE

Chin. J. Process Eng.. 2020, 20(10): 1174-1181. DOI: 10.12034/j.issn.1009-606X.219354

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Recovering manganese resource from the mother liquor on one hand can improve the economic benefit of the whole process, and on the other hand is beneficial to realizing closed cycle of mother liquor and then can increase the environmental interest of the whole process because it can avoid the enrichment of Mn in the solution during recycling mother liquor which will bring side effect to the quality of vanadium pentoxide. Using oxalic acid to effectively separate the Mn2+ from the mother liquor was proposed and the effects of the solution pH, adding amount coefficient of oxalic acid, reaction temperature and time on the recovery rate of Mn and phases composition of the precipitations were investigated, and the effect of the numbers of recycling mother liquor treated by oxalic acid to recover manganese on the leaching process was studied as well. The results showed that oxalic acid can effectively separate the manganese from the mother liquor and the recovery rate of manganese reached 94.33% under the conditions that the solution pH was 4.0, adding amount coefficient of oxalic acid was 1.5, reaction temperature was 50℃ and the reaction time lasted for 60 min. The obtained product was hydrated manganese oxalate with purity of 98%, present as tabular crystals and formed in flower cluster-like. After treated with oxalic acid to remove manganese, the mother liquor was recycled to leach the roasted slag, and it was found that the recycling numbers have little effect on the vanadium leaching rate and the concentration of manganese contained in the vanadium-bearing solution, indicating the proposed method was helpful for realization of closed-cycle of the waste water in the whole process of vanadium extraction with calcified roasting and acid leaching.

Effects of salt ions on the hydration and expansion characteristics of montmorillonite

Yuanqing TAO Kefeng YAN Xiaosen LI Hao CHEN

Chin. J. Process Eng.. 2020, 20(10): 1182-1189. DOI: 10.12034/j.issn.1009-606X.219364

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As an important component of natural gas hydrate reservoir, montmorillonite is of great research significance to the exploitation and application of natural gas hydrate. The inhibition of salt ions in seawater on the hydration expansion of montmorillonite has important effects on the distribution of free water and bound water in hydrate reservoirs. Water content in montmorillonite with NaCl solution was measured by thermogravimetric method combined with several pretreatment methods (the centrifugal method, the direct drying method and the freeze-dried method). The effects of salt concentration on bound water and free water content of montmorillonite were analyzed. The variations of total water content and bound water content in montmorillonite with different NaCl solution concentration were discussed. The hydration and expansion characteristics of montmorillonite and the inhibition of salt ions were studied. The results indicated that the hydration expansion of montmorillonite was inhibited by salt ions. The existence of salt ions reduced osmotic hydration force. Meanwhile, it affected the van der Waals force between water molecules, the hydrogen bonding force and the electrostatic attraction force between water molecules and the surface of montmorillonite. The total water content of montmorillonite decreased with the increase of salt ions concentration. In the same time, bound water content of montmorillonite was inverse related to the salt ions concentration, and approached the minimum when the salt ions concentration was 0.2 mol/L, as the inhibition effect of salt ions on the hydration expansion of montmorillonite reached the peak. When the ion concentration was greater than 0.2 mol/L, the content of free water and bound water did not change significantly with the increase of salt ion concentration. Therefore, the study on the influence of salt ions on hydration and expansion characteristics of montmorillonite, so as to further explore the influence of salt ions on the formation of hydrate in montmorillonite, has important guiding significance for the study of hydrate distribution characteristics in deep-sea sediments.

Thermodynamic and kinetic analysis of the process of preparing Al?Si alloy from polysilicon cutting waste by diamond-wire

Ting XIAO Guoqiang Lü Junpeng WANG Xiongdong YANG Wenhui MA

Chin. J. Process Eng.. 2020, 20(10): 1190-1197. DOI: 10.12034/j.issn.1009-606X.219333

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The diamond wire saw powder composition and its silicon oxides were analyzed by X-ray diffraction analysis (XRD), X-ray fluorescence spectrum analyzer (XRF) and Fourier transform infrared spectrometer (FT-IR). The possible reaction process for alloying between aluminum and diamond wire saw powder was analyzed, and its thermodynamics were determined by HSC Chemistry 6.0 software. The kinetics process of aluminum thermal reduction of SiO2 was discussed, and the Al?Si alloy preparation by using diamond wire saw powder with aluminum was experimentally investigated. The results showed that the diamond wire saw powder melted with aluminum in different mole proportion during the alloying process at the temperature range of 800~1600℃ with the influence of electromagnetic stirring. Meantime, SiO2 impurities can be reduced to Si during aluminum thermal reduction. The apparent activation energy was 364.1 kJ/mol, while the reaction order was 0.91. Finally, phase composition of alloy and slag were analyzed by EPMA, XRD, and the results were in agreement with the thermodynamic and kinetic analysis. This work provided a new idea for effectively solving the problem of silicon waste recovery and utilization during the photovoltaic industry.

Vaccine particle integrity-based purification of recombinant hepatitis B surface antigen using silica gel adsorption/desorption

Shengjie HU Yongdong HUANG Lan ZHAO Kai ZHU Zhuang MIAO Fei WANG Hongchao JIN Jian LI Jun YANG Hemu WANG Guanghui MA Hongshui YUAN

Chin. J. Process Eng.. 2020, 20(10): 1198-1209. DOI: 10.12034/j.issn.1009-606X.219329

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Low stability was one of the biggest problems during traditional purification process of recombinant hepatitis B surface antigen (rHBsAg). A combination process of silica gel adsorption/desorption and hydrophobic interaction chromatography was proposed in this work. The effect of pH on HBsAg stability was studied from the particle integrity of view using static light scattering, fluorescence spectrum and dynamic light scattering, respectively. HBsAg was purified by silica gel adsorption/desorption using response surface methodology for experimental design, followed by hydrophobic interaction chromatography, and both its morphology and particle integrity were studied. In acidic solution, the electrostatic repulsion of HBsAg particles decreased leading to aggregation when pH of solution was close to the isoelectric point of HBsAg. In alkaline solution, hydrophobic patches inside HBsAg particles were likely to be exposed leading to disaggregation. The silica gel adsorption/desorption process was optimized. When HBsAg activity recovery was taken as the response value, the optimum operating condition was as follows: adsorption pH was 7.43, desorption pH was 10.48 and desorption temperature was 55.4℃, and HBsAg activity recovery was 39.1%. When purification fold was taken as the response value, the optimum operating condition was as follows: adsorption pH was 7.16, desorption pH was 10.52 and desorption temperature was 55.1℃, and purification fold was 1.90. After hydrophobic interaction chromatography, HBsAg activity recovery was 49.73% and the particle integrity was 85.79% respectively. Compared with conventional hydrophobic interaction chromatography, the efficiency of HBsAg purification was improved greatly using this combination method, etc., HBsAg activity recovery increased by 31.99%, the particle integrity by 20.90%, and the particle stability by 22.93%, respectively. It provided a new idea for both high efficient recombinant HBsAg purification and improvement of antigen particle integrity.

Secretory of a multicopper oxidase in Escherichia coli

Tao YANG Jian CHEN Fang FANG

Chin. J. Process Eng.. 2020, 20(10): 1210-1217. DOI: 10.12034/j.issn.1009-606X.219370

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Biogenic amines (BAs) are organic compounds that present in fermented foods. The excessive intake of BAs is harmful to human health. Some enzymes belonging to the multicopper oxidase (MCO) family exhibit the activity of degrading a variety of BAs. Thus, they may have good application prospects in reducing ammonia (amine) hazards levels in fermented foods. It is of great significance to accomplish the secretion of multicopper oxidase for the purpose of modification of enzyme catalytic properties for its industrial production and applications. In this work, the secretion of multicopper oxidase in Escherichia coli was achieved by fusing the signal peptide PhoA to the N-terminal of MCOB from Bacillus amyloliquefaciens with an extracellular activity of 69.8 U/L. Secretory of MCOB was improved by optimizing the induction and secretion conditions. The optimal fermentation conditions for MCOB were determined to be: the induction temperature was 25℃, the IPTG concentration was 0.05 mmol/L, induced when the cell density (OD600) reached 1.0, and 150 mmol/L glycine was added after 6 h of induction. After 40 h of fermentation, the extracellular activity of MCOB reached 238.1 U/L, which was 3.4 times of that before optimization.

Preparation of ceramic ultrafiltration membrane with high performance from dense ultrafine spherical Al2O3 powders

Pan LUO Yuge OUYANG Fei DING Junmei FAN Fangli YUAN

Chin. J. Process Eng.. 2020, 20(10): 1218-1226. DOI: 10.12034/j.issn.1009-606X.219378

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Ceramic membranes with the advantages of excellent thermal, chemical and higher permeable properties have attracted more attention and have been applied in turbidity removal, sanitary wastewater and other important industries. However, the ceramic membrane required “coating-drying-sintering” process, in which the process inevitably leads to cracks and wide pore size distribution. In this study, ceramic ultrafiltration membranes with narrow pore size distribution and high permeability were prepared by the dip?coating method using ultrafine spherical alumina powders with high density and smooth surface synthesized by thermal plasma. The microstructure evolution of prepared membranes could be controlled by adjusting the sintering temperature, and the ceramic membranes with a narrow pore size distribution of 25?65 nm and a high pure water permeability of 986.4 L/(m2?h) were sintered at 1250℃. The sintering mechanism of the ceramic membrane was fully investigated and it was found that the narrow pore size distribution of membranes came from the spherical Al2O3 powders with the narrow particle size distribution and high density synthesized by thermal plasma, and the homogeneous sintering necks formed at 1250℃. The result indicated that the pure water flux of the membranes decreased as the sintering temperature increased. It can be explained that the surface of ceramic membranes became denser with the increase of the sintering temperature, resulting in the decrease in porosity and the average pore size. In addition, the prepared membranes were employed to filter the nano-silicon dispersion slurry to evaluate the performance of the membranes sintered under different temperatures. The result indicated that the membrane sintered at 1250℃ showed a higher removal rate of turbidity (99.96%), and the turbidity of the permeate was 0.231 NTU. Finally, the reduction of the permeate flux of the nano-silicon dispersion slurry were analyzed using pore blocking models, and it was found that the cake filtration model was suitable to the prepared membranes.

Effect of nano-Nb addition on microstructure and wear resistance of Fe-based alloy coatings by plasma transferred arc welding

Lulu XU Wenxu ZHANG Longsheng ZHAN Mingxi LI

Chin. J. Process Eng.. 2020, 20(10): 1227-1233. DOI: 10.12034/j.issn.1009-606X.219359

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Plasma transferred arc welding is a kind of surface modification technology. Plasma transferred arc is used as a heat source and alloy powder is sprayed on the surface of metal materials to prepare a wear-resistant coating with excellent performance. In order to further improve the wear resistance of Fe-based alloy, hard particles are often used as the reinforcements of composite materials. At present, there are few researches on in-situ formed NbC reinforcements in Fe-based alloy coatings, and the density of NbC is very close to that of Fe-based alloy, which can be very evenly distributed in the coatings. In this work, Fe-based alloy coatings without nano-Nb and with mass fraction of 1wt%, 3wt% and 5wt% nano-Nb powder were prepared on Q235 surface by plasma transferred arc welding. The phase composition, microstructure, microanalysis and worn surface observation of the coatings were investigated by means of optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD), respectively. The microhardness and wear resistance of the coatings were tested using microhardness tester and pin-on-disc wear machine. The results showed that the main phases of Fe-based alloy coatings were composed of α-Fe, γ-Fe and Cr7C3. NbC phase was identified in the coating by adding nano-Nb powder, and Cr23C6 phase appeared with addition of 5wt% nano-Nb. The untransformed γ-Fe increased and the microstructure changed from approximately equiaxed microstructure to dendrite with addition of nano powder, and the greatly refined microstructure was obtained by adding 5wt% additive. The microhardness of coatings was improved, which was about 766 HV0.3 increased by about 250 HV0.3 with 1wt% and 3wt% nano-Nb. The wear resistance of coatings was also improved. The minimum friction coefficient of 0.48 was obtained by adding 3wt% nano-Nb. The wear mechanism changed from adhesive wear to abrasive wear.

New broaching exploitation method and feasibility analysis of marine gas hydrate reservoirs

Zhen SONG Kaili LI Jiahang SUN Zhonglei Lü

Chin. J. Process Eng.. 2020, 20(10): 1234-1240. DOI: 10.12034/j.issn.1009-606X.219377

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At present, the main methods for extracting natural gas hydrates are thermal extraction, vacuum extraction and chemical reagent extraction. They are mainly used for the development of diagenetic hydrate reservoirs in tight cap rocks, and cannot be used to extract shallow non-diagenetic hydrates that account for 85% of deep water resources. Taking the Shenhu area of the South China Sea as the mining target area, a new type of broaching exploitation method was proposed on the basis of solid-state fluidization theory. A three-dimensional model of broaching exploitation method was established, the working principle, working steps and stope distribution of the new technology were explained in detail, and a broaching tube was designed for broaching, collecting and transportation mining tools. Use the knowledge of geotechnical mechanics to analyze the shear stress of the goaf produced by the broaching exploitation method can ensure that the goaf does not collapse and obtain the maximum stope volume. The force analysis of the broached pipe according to the mining conditions ensured that the broached pipe can work safely and stably. Finally, the daily gas production of the broaching technology was estimated. The results showed that the larger the goaf radius and the mining angle were, the more obvious the shear stress concentration in the goaf. The maximum shear stress occurred at the start and end positions of the upper part of the goaf. The maximum stress of the broaching tube during the mining process was less than the yield stress of the material. The daily gas output of the broaching technology was estimated to be 142000 m3, which had practical application potential.

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