The Chinese Journal of Process Engineering

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Chin. J. Process Eng.. 2019, 19(3): 0.

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Research progress in preparation and application of high-entropy-alloy powders

Feng QUAN Houzheng XIANG Lei YANG Qihui WU Aiqin MAO Haiyun YU

Chin. J. Process Eng.. 2019, 19(3): 447-455. DOI: 10.12034/j.issn.1009-606X.218259

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As a kind of new alloys, high entropy alloys have become one of the hotspot materials due to their outstanding remarkable physicochemical performances such as high ductility and strength, excellent wear resistance, outstanding corrosion resistance, and superior high temperature stability in recent years. Among these, high-entropy-alloy (HEA) powders have a much wider application, which not only can be used as raw material in the preparing of HEAs bulk, coatings and thin film materials, but also used as functional materials. However, there are few studies on HEA powders, especially on HEA nanoparticles. In this work, according to the current research progress of HEAs, the criterions for solid solution phase formation in HEAs were classified, which mainly include mixed entropy criterion, mixed enthalpy criterion, Ω criterion and Hume?Rothery solid solution theory criterion. Through the summary of each criterion, the solid-solution phase formation rules were also summarized. It provided a theoretical basis for more accurate prediction of the formation law of high entropy alloy solid solution phase and the design of new HEAs. Moreover, the preparation methods for HEA powders were reviewed. The HEA ultrafine powders were produced by mechanical alloying method and gas/water atomization method, and also the preparation methods of the HEA nanoparticles include chemical reduction method, carbothermal shock method, plasma arc discharge method and scanning probe lithography. In addition, the advantages and disadvantages of each method were also discussed, and these offered a wide range of flexible approaches for different type of applications of HEA powders. At the same time, current problems in the field of HEA powders research were pointed out, and the future developments were also prospected. This review had certain guiding significance for the expansion of the application of HEA powder subjects in the future direction.

Mini-review on the preparation of titanium metal by the thermochemical processes

Xiaofang ZHU Qing LI Ying ZHANG Zhigang Zak FANG Shili ZHENG Pei SUN Yang XIA

Chin. J. Process Eng.. 2019, 19(3): 456-464. DOI: 10.12034/j.issn.1009-606X.218279

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Titanium metal and its alloys are popular structural and functional materials due to their excellent properties. Even though titanium element is abundant in the earth, its extraction is very difficult because of its strong chemical affinity to other metals and interstitial elements including O, N, H, C, especially oxygen. The plasticity of titanium metal is sensitive to even trace oxygen content. It has been well acknowledged that it is extremely challenging to produce titanium metal with low enough oxygen. The currently commercialized method to produce Ti metal is the Kroll process, which has been optimized for years and highly matured, but it is costly and energy-intensive. In order to reduce the product cost of titanium metal and thus widen its applications, many new methods have been proposed in recent decades, which can be categorized into two main groups, thermochemical methods and electrochemical methods. This article made a mini-review of the developed thermochemical methods from the aspects of technical features and research status, including the Kroll process, the Hunter process, the ADMA process, the TiRO process, the gas reduction process, the CSIR-Ti process, the ITP-Armstrong process, and the ARC process which using TiCl4 as the precursor, the preform reduction process (PRP), molten salt facilitated Ca reduction process, electronically mediated reaction (EMR) process, Mg reduction?Ca deoxygenation two-step process, and the hydrogen assisted magnesiothermic reduction (HAMR) process which using TiO2 as the precursor, and thermochemical reduction of fluorotitanate. The common reductants are reactive metals and their alloys, including Ca, Mg, Al, and Na. These processes are still at the laboratory or pilot-plant stage, and it is recognized that the potential of industrialization of these methods is different, thus an uncertain time is needed to verify if these methods have advantages over the Kroll process on quality and production cost.

Research progress in modification of alumina support and its application

Kening SUN Xixi MA Ruijun HOU Minxiang LI Chungang ZHANG

Chin. J. Process Eng.. 2019, 19(3): 465-472. DOI: 10.12034/j.issn.1009-606X.218280

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Alumina, which is not only inexpensive and easy to obtain, but also has many advantages such as porosity, large specific surface area, high dispersibility and high thermal stability. Therefore, alumina is often used as catalyst carrier and widely used in the catalysis of petroleum industry. The pore structure of alumina has a great influence on the catalytic reaction of the catalyst, especially in mass transfer. In order to optimize the performance of alumina carrier, a lot of studies have been carried out on the pore expansion of alumina and the modification of alumina by adding additives. Pore enlargement can not only reduce the material diffusion resistance and improve mass transfer, but also improve the effective utilization of active sites and enhance the anti-coking performance. Thus, the yield of hydrogenation catalysis can be increased. The high temperature sintering and phase transformation of alumina support can be effectively inhibited by the addition of catalyst support modified by additives. In this way, the pore structure can be prevented from being destroyed and the service life of the catalyst can be prolonged. In this work, the methods for preparing alumina were pseudo boehmite dehydration and sol?gel method. Pore expanding methods of alumina, including self-assembly method, hydrothermal treatment method and pore expanding agent method, were reviewed. The modification methods of alumina additives were described, including rare earth metal oxides, alkali (earth) metal oxides, other metal oxides and non-metal oxides. The latest research progress of modified alumina carriers was summarized. Finally an outlook for the future research and development of alumina as catalyst support was given. The existing modification methods of alumina still cannot meet the market demand. The preparation of alumina carriers for specific reactions is still the main research content at present. Four key aspects of future research on alumina carriers were proposed.

Research progress on modification and antifouling properties of anion exchange membrane

Renqiang CAO Zhanli FENG Yujiao LI Zhijuan ZHAO Shaoyuan SHI

Chin. J. Process Eng.. 2019, 19(3): 473-482. DOI: 10.12034/j.issn.1009-606X.218283

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When electrodialysis technology is used in desalination of industrial wastewater, its desalination performance degraded by membrane fouling caused by organic matter and other impurities in the wastewater. The prevention and control of electrodialysis membrane fouling play an important role in promoting the application of electrodialysis in industrial wastewater treatment. Compared to cation exchange membrane (CEM), anion exchange membrane (AEM) is more susceptible to fouling by organic matter. The organic fouling of AEM is mainly caused by organic substances such as humic acid, bovine serum albumin and anionic surfactant, which is mainly affected by electrostatic action, affinity interaction and geometrical factor. Improving the antifouling performance of AEM by membrane modification is an effective way to the prevention and control of electrodialysis membrane fouling. Many investigations related to the membrane modification to improve the antifouling performance of AEM have been reported up to now. Some methods such as chemical modification, plasma modification, surface coating modification, electrodeposition modification, self-polymerization modification and improved basement membrane structure, etc., are used for improving the antifouling performance of AEM. The research progress of anion exchange membrane modification and their antifouling performance were reviewed in this work. The advantages and disadvantages of different methods were analyzed and evaluated systematically. It was found that the physicochemical properties including the negative charge density, hydrophilicity, surface roughness and water uptake, etc. of AEM could be improved by the modification methods, which were beneficial to ameliorate the antifouling performance of membranes. However, the research of modified membranes still has some deficiencies such as the unstable modified layer, unsatisfactory antifouling performance and incompleted antifouling performance test. It is necessary to optimize further the modification method, technology process and modification components to obtain the modified AEM with good and stable antifouling performance in the future.

Research progress in doping of lithium vanadium phosphate cathode materials

Hulin DONG Haiping BAO Hao WANG Jianhong PENG

Chin. J. Process Eng.. 2019, 19(3): 483-491. DOI: 10.12034/j.issn.1009-606X.218245

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A new clean-energy is urgently needed to replace the traditional clean-energy (such as solar energy, tidal energy, and wind energy) with the problem of low conversion efficiency and more difficult energy storage in the face of the rigorous energy and environmental problems. The lithium ion battery is favored by researchers because of its green environmental protection, good safety performance, high discharge capacity, long cycle life and easy to carry, especially Li3V2(PO4)3 (LVP) lithium-ion battery. The LVP is one of the cathode materials of Li-ion batteries attracted most attention due to its higher discharge capacity, higher voltage platform, good safety performance, portability, environmental protection and low cost. However, the instinct drawbacks of monoclinic structure lead to low ionic conductivity and electronic conductivity, which seriously degrade the electrochemical properties of the materials. At present, among the various modified methods, ions doping is one of the most effective ways. The ions doping can optimize the lattice parameters of LVP, enhance the stability of the crystal structure in the process of charging and discharging, and improve the cycle life. In addition, it can also increase the ionic diffusion coefficient and perfect the ionic conductivity via enlarging interstitial void and diffusion path of ions. In present studies, the ions doping of LVP mainly includes doping in Li sites, doping in V sites, anion doping and multibit doping. Meanwhile, the doping in V sites of LVP also includes single doping and co-doping. In this work research processes of ions doping for enhancing the electrochemical performance of Li3V2(PO4)3 were summarized and the development prospect of this material was also reviewed.

Numerical simulation of heat exchange efficiency of evaporative cooler

Haiying LI Dong LIU Chunqi ZHANG Liangxu LIU Xiaobo WANG

Chin. J. Process Eng.. 2019, 19(3): 492-499. DOI: 10.12034/j.issn.1009-606X.218239

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In Lurgi?Thyssen dedusting system of steelmaking converter, the evaporative cooler represented a crucial operating unit, in which the hot dust-laden flue gas had to be cooled by saturation with water. The cooling process of the gas consisted of gas?liquid two phase flow and interphase heat and mass transfer. In this work, k?? standard equation and Lagrange discrete phase model were employed to describe the gas turbulent flow and the heat/mass transfer with droplet evaporation individually. The computational fluid dynamics (CFD) simulation for practical engineering project showed that the large-flux cooling gas was commonly constructed in a nonuniform flow caused by the sharp turnings at the inlet and outlet channels. The simulation results of the model were in good agreement with the actual working condition parameters of the evaporative cooler. The relative error of flue gas outlet temperature was 3.1%, the simulation results were reliable. The smaller the size of atomized droplet was, the shorter the time was required to reach the critical evaporation temperature and complete evaporation. The droplet with a particle size of less than 300 ?m could evaporate completely within 0.62 s. The main temperature drop of flue gas was within 3.5 m downstream of the nozzle. The heat transfer efficiency of droplet and high temperature flue gas was greatly affected by particle size distribution. The mean temperature of the same section corresponding of droplets with d50=340 ?m and d50=95 ?m can differ by 70 K. Using rosin-rammler distribution function to describe droplet size distribution, the effect of particle size distribution on the cooling efficiency of flue gas was studied. The droplet size should not be too large or too small. The particle size was too small to make a reasonable use of evaporative cooler space. The temperature of flue gas dropped unevenly and the droplet evaporation was incomplete due to the large particle size, resulting in wet bottom or wall hanging of the device.

Effect of nozzle layout in high efficient spray tower of new OG system of primary dedusting system for converter on spray characteristics

Fuping QIAN Xiaoping HUANG Bowen CAO Yongjun XIA Jia HU Deming SHI Yunlong HAN

Chin. J. Process Eng.. 2019, 19(3): 500-509. DOI: 10.12034/j.issn.1009-606X.218255

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The nozzle layout of the high efficient spray tower in OG (Oxygen Converter Gas Recovery) system of the primary dedusting for the converter has an important role on the cooling effect and operating reliability of the spraying system. The discrete phase model was used to simulate the nozzle layout of the high efficiency spray tower. The nozzle layouts of the inlet and main section of the high efficiency spray tower were discussed, and the influence of the nozzle direction and the number of spray layers on the air distribution and cooling effect in the atomizing field were also analyzed. The results showed that the spraying direction of the nozzle and the number of spray layers in the tower had great influence on the air distribution and cooling effect of the atomization field. When the inlet section of the spray tower adopted countercurrent injection, the velocity distribution of the outlet cross section was the most uniform and the cooling effect was the best. When the number of spray layers in the main section of the high efficiency spray tower was five, the flow field of the flue gas in the tower was relatively uniform, and the velocity in the center area was in the range of 2~4 m/s, which helped to increase the time of interaction between gas and droplets. With the increase of the number of spray layers, the temperature gradient in the tower also increased and the distributions of water vapor mass fraction and temperature correspond to each other, and then the average turbulent energy in the tower also gradually increased. Through the above research, the reasonable arrangement of nozzle in the high efficiency spray tower was obtained. The results can provide a theoretical basis for the optimization and improvement of the high efficiency spray tower in the new OG system.

Numerical simulation of performance of spiral separator for natural gas hydrate purification

Xuefeng LI Xia HE Guorong WANG Shunzuo QIU Shouwei ZHOU Qingyou LIU

Chin. J. Process Eng.. 2019, 19(3): 510-515. DOI: 10.12034/j.issn.1009-606X.218273

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In view of the problems of pipeline blockage and equipment wear caused by large sand production in shallow marine gas-hydrate mining under seabed, based on the solid fluidized mining method, the idea of in-situ separation of natural gas hydrate was proposed. The downhole in-situ spiral separator was designed based on the physical parameters of hydrate mixed slurry. The correctness of the model was verified by CFD-Fluent software. Then, the performance of the separation device was studied from three aspects: solid phase hydrate volume concentration, solid phase sand volume concentration and inlet velocity. The results showed that within the scope of the study, the removal rate of sand and the recovery rate of hydrate were both about 80%. As the volume fraction of hydrate increased, the sand removal rate and hydrate recovery rate changed very little, and the separator pressure drop changed little. As the sand volume fraction increased, the sand removal rate decreased sharply, while the hydrate recovery rate increased sharply and the pressure drop increased sharply. As the inlet velocity increased, both the sand removal rate and the hydrate recovery rate increased, and the separator pressure drop also increased. The spiral separator exhibited very good performance in hydrate in situ sand removal purification. The saturation of hydrate had little effect on the performance of the separator, but the influence of silt concentration on the performance of the separator was obvious, and it needed to be considered in engineering application. The inlet velocity played a key role in the separation performance of the separator, and also determined the processing capacity of the separator. Appropriately increasing the inlet velocity could improve the separation efficiency of the separator to a certain extent. The analysis results have certain guiding significance for the exploitation of shallow hydrate reservoirs on the seabed.

Numerical simulation on combustion characteristics of combustor with lobe nozzles

Lijun WANG Jintao JIANG Weiwei YUAN Kuo MEN Yijun XU

Chin. J. Process Eng.. 2019, 19(3): 516-523. DOI: 10.12034/j.issn.1009-606X.218249

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In order to investigate the influence of the lobe-induced vortices on the combustion characteristics of the multi-point injection combustor, a lobe combustion chamber model was established comparing to reference test of swirling multi-point injection combustor to verify model validity of the subsequent combustion process simulations. Combustor model of flow simulation test bench was tested to confirm the model availability of flow characteristic based on the similarity principle. The test bench consisted of a lobe combustion chamber model, a controller, a flow meter and a high-speed camera under the same working conditions as that of multi-point injection swirling combustor test, namely idle, 30% power, cruise and take-off conditions. Flow field vortex structure, multi-quantity field of combustion and combustion characteristics were studied by mathematics and physical simulations. For each working condition, a comparative study of calculation and experimental verification was carried out to verify the creditability of the combustion flow characteristics. The results showed the flow vortex structure in the combustion chamber verified the simulation results. The overall flow field had the similar structures for each working condition. Along the flow direction, the induced vortices structure at the exit of the lobe which mainly formed from streamwise vortex and the orthogonal vortex was similar, the vortices structure variation changed regularly. With the decrease of oil/gas ratio, the streamwise vortex and orthogonal vortex dimensions increased gradually, the NOx emission gradually decreased, the combustion efficiency gradually increased and outlet temperature field quality improved. The lobe nozzle combustion chamber showed the excellent performance and effective control in the multi-point injection lobe combustor by varied operating conditions. The multi-physical fields such as fluid flow and combustion temperature improved more effectively than that of reference. Lobe combustion chamber model had the rationality and application value to its engineering application.

Simulation of enhanced heat transfer in subcooled boiling tube of vortex generator inserts

Xin CHEN Qi XIAO Xiaoping GUAN Ning YANG

Chin. J. Process Eng.. 2019, 19(3): 524-532. DOI: 10.12034/j.issn.1009-606X.218281

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An Eulerian?Eulerian two-fluid model together with the RPI boiling model was used to simulate the three-dimensional unsteady subcooled boiling flow in high pressure tubes. The effect of vortex generator on the subcooled boiling was investigated through the simulation. The tube fluid dynamics of vortex generator in laminar flow and the subcooled boiling process with the vortex generator in turbulent flow were simulated. The simulation indicated that the heat transfer capacity was obviously enhanced under laminar flow conditions by the vortex generator. The heat transfer capacity in the tube was only slightly improved in the case of subcooled boiling, and the bubbles near the wall were affected by the disturbance of the fluid. The bubbles near the wall surface were largely entangled into the delta wing due to the disturbance of the fluid. Therefore, the possibility of generating a gas film near the wall surface was reduced, and delayed the starting point position of subcooled boiling.

Molecular dynamics simulations of binary mixtures of anionic/cationic surfactants at oil-water interface

Jialin LIU Ying REN Wei CHEN Hui YANG Xiujuan HE Yingcheng LI

Chin. J. Process Eng.. 2019, 19(3): 533-543. DOI: 10.12034/j.issn.1009-606X.218260

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In enhanced oil recovery, the use of the binary mixture of anionic/cationic surfactants could lower the interfacial tension and thus results in high oil recovery. A deep understanding of the underlying mechanisms would help the molecular design of the surfactant molecules used in enhance oil recovery and other related usage. In this work, molecular dynamics simulations were used to study the molecular behaviors and properties of the binary mixtures of nonyl-phenol-ethoxylated-carboxylate (PECNa) surfactants and octadecyl trimethyl ammonium chloride (OTAC) with different molar ratios at the oil?water interface to enrich the oil displacement theory with microscopic understanding. The density distribution of characteristic groups/radicals perpendicular to the interface, the characteristic length and the angle of the characteristic groups of the surfactants molecules perpendicular to the interface, the radical distribution analysis of the charged polar groups, and the distribution of counter-ions in the systems for different PECNa/OTAC ratio were compared. The results showed that the mixture of anionic?cationic surfactant molecules possessed better capacity to reduce the oil?water interfacial tension than that of anionic or cationic surfactants alone. With different molar ratios of the two types of surfactants, due to the attraction between the opposite charged head groups of anionic and cationic surfactant molecules, the electrostatic attraction between the charged groups of the surfactant molecules to their respective counter-ions was weakened, especially for the system with equal molar concentration of anionic and cationic surfactants. Meanwhile, the head group of the anionic surfactant had little effect on the orientation of water molecules in the hydration layer of the head group of the cationic surfactants, and vice versa. By adjusting the molar ratio of the surfactant mixture, a more compact adsorption layer can be obtained, which was promising for reducing the oil?water interfacial tension and enhancing oil recovery.

Extraction of glycine using functional ionic liquids

Haiyang XU Xiangzhan MENG Dasha XIA Lanfeng HUI Hui WANG

Chin. J. Process Eng.. 2019, 19(3): 544-552. DOI: 10.12034/j.issn.1009-606X.218298

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Glycine, also known as aminoacetic acid, is the amino acid with the simplest structure and is widely used in food, medicine and pesticides. It is an important chemical raw material and intermediate. Chloroacetic acid ammoniation is one of the main approaches to produce glycine. However, it needs a large amount of toxic and volatile methanol to separate glycine from the ammonium chloride byproduct, with low separation efficiency and the formation of a large amount of waste liquor which is environmental non-benign. Ionic liquids, as a novel green media, have shown great potential in the field of extraction and separation owing to their advantages of low vapor pressure, good thermal stability, adjustable structures and properties. In this work, designable ionic liquids (ILs) were proposed as the extractant to separate glycine. The effects of the ILs structure on the extraction efficiency were studied using imidazolium and quaternary ammonium ILs. The effects of pH, extraction temperature, time, and the initial concentrations of glycine and dicyclohexyl-18-crown-6 (DCH18C6) on the partition coefficient and extraction efficiency were investigated. The IL system was recycled and reused for glycine separation. The extraction mechanism was revealed by FT-IR and quantum chemical calculation. The results showed that choline bis(trifluoromethylsulfonyl)imide ([N1112(OH)][NTf2]) had best extraction efficiency. The addition of DCH18C6 to the system could enhance the extraction efficiency, and that of the [N1112(OH)][NTf2]–DCH18C6 system could reach 85.4%. Under the optimal conditions, the partition coefficient and extraction efficiency reached 10.9 and 94.4%, respectively. The extraction efficiency remained 90% after the IL was recycled 5 times. The strong hydrogen bonds between [N1112(OH)][NTf2], DCH18C6 and glycine played an important role in the extraction of glycine. Thus, the system of [N1112(OH)][NTf2]–DCH18C6 was effective in separating glycine from water and could be an alternative extractant in the industrial glycine purification process.

Effect of calcium borate on sedimentation of copper inclusions in copper slag

Yu SHI Bo LI Guangping DAI Shiwei ZHOU Hua WANG Yonggang WEI

Chin. J. Process Eng.. 2019, 19(3): 553-559. DOI: 10.12034/j.issn.1009-606X.218271

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Taking calcium borate as additive, the effect of additives on the precipitation of copper in copper slag was investigated. Combining the viscosity test of copper slag and the Fourier transform infrared spectroscopy (FT-IR) characterization of copper slag, the mechanism of the influence of calcium borate on copper slag was discussed. At the same time, the influence of additives on the liquids temperature of copper slag was calculated by thermodynamic software FactSage. The results showed that with the increase of additive content, the settlement of copper in copper slag was gradually enhanced. When the content of additives in slag increased from 0 to 6wt%, the copper content of the slag at the bottom of the sample increased from 4.10wt% to 6.85wt%. This is attributed to the fact that additives can effectively reduce the viscosity of copper slag and increase fluidity of slag. The viscosity of copper slag gradually decreased as the additive content increased, but the effect of the additive on the viscosity of the copper slag flat as the temperature increased. The complex silicate structure of copper slag simplified with the increase of additive content in slag, and the additive reduced the viscosity of the copper slag by destroying the complex silicate structure of the copper slag. In addition, the liquidus temperature of copper slag decreased with the increase of additive content. The additive also reduced the viscosity of the copper slag by reducing the amount of solid particles in the slag.

Reduction mechanism of Pidgeon process of magnesium metal

Jing YOU Yaowu WANG

Chin. J. Process Eng.. 2019, 19(3): 560-566. DOI: 10.12034/j.issn.1009-606X.218236

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Pidgeon process using dolomite as materials and using ferrosilicon as reductant is the main method of magnesium metal production, and the low reduction rate of MgO is one of the main problems for this method. Some experiments of Pidgeon process were carried out in this work. The phase compositions of reductant and ferrosilicon alloy were analyzed. XRD and SEM?EDS were used to study the phases and the distribution of phases in reduction slag obtained at different reduction temperatures. The reduction mechanism of Pidgeon process was explored by studying the diffusion process of silicon, magnesium and calcium element. The reason for low reduction rate of MgO was investigated by studying the existent form of ferrosilicon in reduction slag and conversion of ferrosilicon in reduction process. The results showed that the reduction process of Pidgeon was a simple solid?solid reaction process, and the initial reduction temperature of MgO by silicon was about 900?950℃. The reduction rate of MgO was very low when the reduction temperature was lower than 1000℃, and the reduction rate was accelerated when the reduction temperature was over 1050℃. The reaction was carried out at the interface of CaO?MgO particles and silicon particle, and the MgO was reduced to magnesium vapor which escapes from the reaction layer and condenses on crystallizer, then silicon diffuse outwards crossed the reaction layer and continued to reduce MgO. In reduction process, all the silicon in the form of simple substance took part in the reduction reaction of MgO and reacted with CaO to form Ca2SiO4, but only part of FeSi2 decomposed to FeSi and Si. The reduction temperature of FeSi and Fe2Si3 which obtained by the reaction of FeSi with FeSi2 was higher and they were difficult to reduce MgO at industrial reduction temperature, so they remained in the reduction slag which lead to lower utilization of silicon and low reduction rate of MgO in Pidgeon process.

Effect of BaSO₄ on the compressive strength of pellets

Jiantao JU Wenguo LIU Xiangdong XING Jiabin YAO Guoshuai JIAO

Chin. J. Process Eng.. 2019, 19(3): 567-574. DOI: 10.12034/j.issn.1009-606X.218242

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The magnetite concentrate powder and bentonite which were obtained from a domestic iron and steel enterprise were used as raw material to produce pellets. The chemical composition of pellets was adjusted by adding different proportions of raw materials, and the effect of BaSO4 on compressive strength of pellets was studied on the basis of the thermogravimetric experiment results in this paper. The influence mechanism of BaSO4 on compressive strength of pellets and the transformation behavior of barium in pellets were analyzed mostly by using the mercury porosimetry, mineral phase microscope and scanning electron microscope?energy dispersive spectroscopy (SEM?EDS). The results showed that the compressive strength of preheated pellets changed little and the compressive strength of roasted pellets increased firstly and then decreased gradually with the mass fraction of BaSO4 increasing. As far as the roasted pellets were concerned, the porosity increased slightly and interior oxygen partial pressure was also increased when BaSO4 content was less than 1.5wt%, which contribute to the oxidation of magnetite and recrystallization of regenerated hematite in pellets. In addition, the degree of bonding between grains was strengthened. Owing to the above-mentioned reasons, the compressive strength of pellets increased. However, when the mass fraction of BaSO4 was further increased, the large size pores were produced, which destroys the integrity of the matrix inside the pellets and decreased the degree of crystalline between the grains. Therefore, the compressive strength of pellets was reduced when the content of BaSO4 was more than 1.5wt%.

Hybrid molding characteristics of three components of biomass based on SLMD

Haiyun SUN Peiyong MA Yongqiang XING Xianjun XING Mingming CHEN

Chin. J. Process Eng.. 2019, 19(3): 575-580. DOI: 10.12034/j.issn.1009-606X.218274

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In order to study the effects of three components of biomass, cellulose, hemicellulose and lignin, on biomass molding characteristics, the simplex lattice mixing design method (SLMD) in the mixing experiment method was used to optimize the mixing of three components of biomass samples with different mixing ratios, the mathematical regression model of biomass compact molding performance index was established, and the mathematical regression model was verified by experiments. The results showed that the correlation coefficient of the regression equation of relaxation density and specific energy consumption was more than 0.9998, biomass forming process was not a simple superposition of a single three component compact forming process, there was a certain interaction between the three components in the process of biomass molding, the higher the content of cellulose, the greater the specific energy consumption and the smaller the relaxation density. The higher the lignin content, the smaller the specific energy consumption, but when the lignin content was too high, the energy consumption had a slight upward trend. The higher the content of hemicellulose, the greater the relaxation density, therefore, in order to make biomass had good molding characteristics, that is, relatively low specific energy consumption and relatively high relaxation density, biomass with less cellulose content and higher hemicellulose and lignin contents should be selected as solid fuel. The experimental verification by using cotton straw, bamboo and corn straw showed that the best biomass species for specific energy consumption prediction was corn stalk, and the best biomass species for relaxation density was bamboo, with relative error of 1.54% and 0.8000%, respectively, and the maximum relative error of the regression model of specific energy consumption and relaxation density was 2.64% and 1.0342%, respectively, which indicated that the model had certain prediction effect on actual biomass.

Effect of electroslag remelting mould rotation on solidification process of M2 high speed steel

Jiashun CHEN Kaihua CHANG Fuzhou ZHENG Zhang ZHANG Lizhong CHANG?

Chin. J. Process Eng.. 2019, 19(3): 581-588. DOI: 10.12034/j.issn.1009-606X.218272

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A new electroslag furnace with mould rotation was designed, and the effect of mould rotation speed on M2 high speed steel solidification process was studied. A double-electrode series-electroslag remelting method was used in the experiment, the secondary dendrite, cooling rate, permeability and slag thickness of M2 high speed steel prepared at different mould rotational speeds were analyzed, calculated and counted. The results showed that the dendrites of M2 high-speed steel at the center and the edge were broken with the increase of the mould rotational speed, and the faster speed of mould rotate, the dendrite was broken more obviously. When the mould rational speed was increased from 0 to 19 r/min, at center and edge of M2 high speed steel, the average secondary dendrite spacing decreased by 19.47% and 25.23%, and the permeability decreased by 34.94% and 44.04%, the average cooling rate increased by 97.01% and 148.06%, respectively. The mould rotation reduced the thickness of the slag skin by 40.41%, and the variance of the thickness of the slag skin was reduced from 0.163 to 0.003, and the slag skin became uniform. On the one hand, the slag skin became thinner and uniform, which increased the heat transfer of the molten metal pool to the mould, so that the molten metal pool became shallow, on the other hand, the dendrites were broken, the reduction of the average secondary dendrite spacing and the decrease of permeability of M2 high speed steel can control the segregation of M2 high-speed steel during solidification. The solidification quality of the M2 high speed steel was improved by mould rotation.

Dilution of copper slag under reduction of rubber seed oil

He ZHENG Bo LI Hao ZHOU Yonggang WEI Hua WANG

Chin. J. Process Eng.. 2019, 19(3): 589-596. DOI: 10.12034/j.issn.1009-606X.218284

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For the sake of solve the problem of large amounts of carbon dioxide emissions and the environmental pollution caused during the process of copper slag dilution, a new method was proposed that using rubber seed oil replaced the diesel oil as a reducing agent for copper slag dilution. For proving the conception, the thermodynamic theory in the process of copper slag dilution was studied. The reaction mechanism of copper slag from rubber seed oil was analyzed. A large number reduction experiments were done that the rubber seed oil was also injected at different temperatures and time. Meanwhile the changes of magnetic iron content and viscosity of copper slag also were analyzed. The slag after dilution reduction was analyzed by XRD and SEM. The results showed that in the process of injection reduction the main reductant were carbon simple substance, hydrogen and carbon monoxide produced by rubber seed oil pyrolysis. Firstly, the magnetic iron was reduced to iron monoxide by the pyrolysis products (hydrogen, carbon monoxide, carbon simple substance), which could be produced by the rubber seed oil at high temperature. Meanwhile the iron monoxide combined with silicon dioxide in copper slag to form fayalite (ferric metasilicate). Secondly, the magnetic iron content in copper slag and the viscosity of copper slag can be reduced by increasing the temperature of dilution reduction. Copper in copper slag was collided and aggregated. Finally, the sediment accumulated at the bottom of the crucible. The ferrite phase increased and the magnet phase decreased during the dilution process. Copper particles first accumulated at the bottom of the crucible, then it increased from 1 cm to 3 cm slowly. The recovery rate of copper reached 86%.

Effects of operating parameters on the electrostatic migration and coalescence of water droplets of W/O emulsion

Zhiqian SUN Yantao ZHOU Bochuan LIU Yan JIANG Zhenbo WANG?

Chin. J. Process Eng.. 2019, 19(3): 597-602. DOI: 10.12034/j.issn.1009-606X.218261

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The electrocoalescence technology has been applied widely in refineries to separate water-in-oil emulsion because of the high efficiency, fast and large throughput. Despite there are many successful and promising industrial applications, the design for more efficient and stable elereocoalescence is essential. High-voltage and high-frequency electrocoalescence need to be designed to avoid short circuit caused by the bridge of the chain between electrodes. Although high-voltage and high-frequency electrocoalescence have been proposed many years ago, it is not applied widely in refineries. In order to investigate the influence of operating parameters on coalescence and migration of water droplets in high frequency pulsed electrocoalescence process, the effects of water content, emulsifying strength and temperature for the electrocoalescence of the water drops in W/O emulsions formed by conducting oil and water under high frequency pulsed electric field were studied through microscopy experiment in this work. The results showed that the theoretical analysis on collision rate and dipole attraction corresponded with the experiment when the water content was low. When the water content was high, the dehydration became worse because of the formation of long water chain. As emulsifying strength rose, the collision rate increased and the dipole attraction decreased. Temperature-induced emulsifying strength minimization was most suitable for electroalescence. As the temperature rose, the Brown movement strengthened and the continuous phase viscosity and the resistance of film drainage decreased. These all enhanced the electrocoalescence.

Subcritical hydrothermal heterogeneous oxidation of semi-dry desulfurization ash from iron ore sintering flue gas

Rufei WEI Longzhi CHEN Hongming LONG Yifan WANG Jiaxin LI Yafei LI Ming XUAN

Chin. J. Process Eng.. 2019, 19(3): 603-608. DOI: 10.12034/j.issn.1009-606X.218291

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Oxidation modification is an effective way to improve stability of materials. In this work, the semi-dry flue gas desulfurization ash was oxidized by a new method: subcritical hydrothermal heterogeneous oxidation. The effects of reaction temperature, reaction time, initial pressure and mass ratio of solid to liquid on the oxidation of desulphurization ash were studied. The results showed that the desulphurization ash can be oxidized to calcium sulfite by subcritical hydrothermal oxidation, and the oxidation effect was well. The highest oxidation rate reached 99.70%. The oxidation rate of calcium sulfite in desulfurization ash was improved by increasing the initial pressure, reaction temperature, reaction time and decreasing the mass ratio of solid to liquid. When the initial pressure was 4 MPa, the reaction temperature was 240℃, the mass ratio of desulfurization ash to water was 1:20, and the reaction time was 90 min, the oxidation rate of calcium sulfite was 92.26%. In the subcritical hydrothermal system, calcium sulfite was dissolved and ionized to form Ca2+ and SO32? firstly, then SO32? was oxidized by the free oxygen in water, and finally calcium sulfate was formed. Increasing the initial pressure and decreasing the mass ratio of solid to liquid increased the dissolution and ionization quality of calcium sulfite and then increased the oxidation rate of calcium sulfite. With the decrease of mass ratio of solid to liquid, the microstructure of the sample changed obviously from spherical to fibrous. Under the conditions of initial pressure 4 MPa, temperature 240℃, reaction time 120 min and mass ratio of solid to liquid 1:30, calcium sulfite precipitated directionally to form calcium sulfate whisker. It provided the possibility for the simultaneous synthesis of calcium sulfate whiskers by subcritical oxidation of desulfurized ash.

Preparation and properties of a new alkali-resistant rProtein A chromatographic medium

Wei WEI, Yongdong HUANG Lan ZHAO Xuexing WU Tianxiao ZHU Dongxue LI Haibo JIN Rongyue ZHANG Zhiguo SU Guanghui MA

Chin. J. Process Eng.. 2019, 19(3): 609-616. DOI: 10.12034/j.issn.1009-606X.218246

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Monoclonal antibodies (mAb) have been applied for curing a wide range of diseases and is considered to be a major source of new therapies in the next decades. mAb?s production has been received worldwide attention and efficient purification strategies have been always explored. Protein A chromatography was one of the most popular methods for mAb purification. Cleaning-in-place has been widely used in protein A chromatography for meeting the demand of high quality, and therefore an alkali-resistant ligand is necessary. Since protein A from natural sources is not alkali-resistant, it should be genetically modified. In this study, a new alkali-resistant rProtein A was constructed based on C-region gene construction followed by being coupled to epoxy-activated agarose-based microspheres under optimized conditions, and a new rProtein A chromatographic medium was prepared. Both confocal laser scanning microscopy and quartz crystal microbalance were used for analyzing the binding of hIgG to rProtein A chromatographic medium. The results showed that it was transparent and full bright. It had a uniform particle size distribution with an average diameter of 84 μm. This medium had good hydraulics properties with a maximum flow rate of 1400 cm/h. This new rProtein A chromatographic medium had a higher hIgG dynamic binding capacity of 62.0 mg/mL than that of commercial ligand. Also, this medium had a better cleaning-in-place performance and the dynamic binding capacity was kept to 84% of the initial value after 40 cycles, as beneficial for its application on an industrial scale. At the beginning of adsorption to the medium, hIgG was bound quickly to the surface coupled with rProtein A, however, the binding rate decreased gradually due to mass transfer resistance from the inner part of the medium. The desorption rate had a similar tendency to that of the adsorption. The new rProtein A chromatographic medium had great prospects in mAb purification and gave a good basis for its application in the future.

Preparation and properties characterization of microencapsulated phase change materials using acrylic resin copolymers/n-dodecanol

Jinli LU Yang LI Yafang HAN Fuping QIAN

Chin. J. Process Eng.. 2019, 19(3): 617-622. DOI: 10.12034/j.issn.1009-606X.218282

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With the characteristics of high energy storage density, approximate constant temperature of phase change and convenient to storage or transport, the microencapsulated phase change materials (MEPCM) have wide application prospect in the fields of energy storage, transport and utilization. However, the traditional MEPCM particles use formaldehyde as the shell material, which would release harmful substances during application process. Therefore, it is necessary to develop a new type of formaldehyde-free MEPCM. A novel MEPCM particles with n-dodecanol as core material and acrylic resin copolymers as shell material using suspension polymerization under ultrasound irradiation condition were prepared in this work. The scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermo-gravimetric analyzer (TGA) and laser particle size analyzer (LPSA) were employed to characterize the performance of MEPCM particles. The results indicated that the MCPM particles were almost regular and had a uniform particle size. The particle sizes of MEPCM were 638.14~1478.65 nm, and the median diameter d50 was 933.91 nm which reaches nanometer scale. Two types of crystals were formed in core materials of all MEPCM particle during crystallization. The melting latent heat and the encapsulation efficiency of MEPCM reached to the maximum value of 93.31 kJ/kg and 86%, respectively. The melting temperature of MEPCM was 22.26℃, and the degree of supercooling reduced from 4.61℃ to 2.13℃. The proportion of core was 43%, it was closed to the design value of 50%. The shell material did not react with the core material. The mass reduce starting temperature of MEPCM was slightly higher than that of pure n-dodecanol, indicating that the thermal stability of the phase change material can be improved after encapsulation. In summary, the MEPCM had a good potential for energy storage and high response speed when face to temperature fluctuation.

Pyrolysis of an organic polymeric precursor of zirconium carbide ceramics

Weijia KONG Shouquan YU Min GE Weigang ZHANG Lingzhong DU

Chin. J. Process Eng.. 2019, 19(3): 623-630. DOI: 10.12034/j.issn.1009-606X.218299

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To meet the requirement of rapid development in near spacecraft, continuous research efforts have been focused on the anti-oxidation materials which can be applied in very harsh environmental conditions. Carbon fiber reinforced SiC matrix (C/SiC) composites have overall advantages including lower density, good mechanical performance, and strong anti-oxidation capability, etc. Therefore, it can be used as various aerospace structural materials. However, C/SiC composites can only endure the short-time use (1000 s) when the temperature is lower than 1800℃, and longer-time use below 1600℃ in oxidizing environment. In this case, ZrC has been considered as a good candidate, owing to its melting point of 3540℃. Adding ZrC could increase the anti-oxidation capability of C/SiC composites, and besides, preceramic polymer processing is a good way to obtain ceramic matrix composites at a relatively low temperature. Various precursors of ceramic have been synthesized, but very little systematic work has been done regarding to the pyrolysis mechanism of polymeric precursor to zirconium carbide ceramics. In this work, pyrolysis process of an organic polymeric precursor of zirconium carbide (PZC) was investigated, the conversion mechanism of the precursor to ceramics was studied in detail as well. The methodology involved the microstructure analysis and phase composition of products by FT-IR, XRF, TG?DSC, MS-online, XRD and SEM. Furthermore, thermodynamics of carbothermal reduction reaction was calculated as well. The results showed that there was the decomposition of PZC with the temperature up to 600℃, including the release of small-molecule gases, such as water vapor, carbon monoxide, carbon dioxide, methane, acetone, and tetrahydrofuran, which were formed from the rearrangement of pyrolysis species. Then the solid inorganic products of amorphous-free carbon and m-ZrO2 were formed with the temperature range from 600℃ to 1200℃. Cubic ZrC crystalline in nano size can be formed above 1300℃, via the carbothermal reduction reaction between carbon and m-ZrO2, and this temperature was lower than the temperature from thermodynamic calculations. The ceramization of PZC could be completed with temperature at 1500℃, and the yield of ceramic was 33.45%.

Recovery technology of NaNO₂ from flue gas desulfurization and denitration wastewater by an oxidation process

Yan CHEN Chenye WANG Xingrui WANG Ziheng MENG Huiquan LI

Chin. J. Process Eng.. 2019, 19(3): 631-636. DOI: 10.12034/j.issn.1009-606X.218244

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The wastewater from the processes of desulfurization and denitration contained complex components, and the recovery of wastewater was limited by the co-existence of nitrates and nitrites. By now, this type of wastewater was mostly directly discharged after a simple treatment or was sent to the sewage treatment plant for further disposal, leading to series of environmental problems or causing instability of biochemical section in sewage treatment plants. Moreover, the cost of the recovery process will decrease via recovering the nitrogenous valuable salt. In this work, a low-cost process with high efficiency of desulfurization and denitration was developed. There were only nitrite ions as nitrogen-containing anions in the wastewater of desulfurization and denitration. Using steel slag slurry combined with ozone oxidation, this process achieved high desulfurization and denitration rate with accessory ingredient of Na2S2O3. There were cations such as Na+, Mg2+, Ca2+, Mn2+, Fe2+, etc. and anions such as NO2?, S2O32?, SO42?, etc. existing in the as-generated wastewater. The water pollution and marketable salt resources waste from wet flue gas desulfurization and denitration via a gas phase oxidation?wet absorption process was mainly solved in this work. A technology of pH adjustment?decalcification via adding sodium carbonate-evaporating crystallization to recovery NaNO2 from wastewater was proposed. The effects of pH, addition methods of sodium carbonate, concentrated total salt concentration, and crystallization temperature on the crystallization rate and purity of NaNO2 were discussed. The results indicated that the crystallization rate and the purity of NaNO2 from desulfurization and denitration wastewater were mainly affected by pH and total concentrated salt concentration. Under the optimal conditions, in which pH was 11, addition method of sodium carbonate was concentrated solution, total concentrated salt concentration was 70wt%, and crystallization temperature was 50℃, the crystallization rate of NaNO2 was greater than 60%. The products of NaNO2 met the quality requirement of national standard (GB/T 2367-2016).

Co-combustion characteristics and kinetic analyses of rice straw and pulverized coal

Xianjun XING Zeyu CHEN Yongling LI Chengcheng ZHU Xuefei ZHANG

Chin. J. Process Eng.. 2019, 19(3): 637-643. DOI: 10.12034/j.issn.1009-606X.218277

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The synergistic interaction and kinetics of rice straw (RS), pulverized coal (PC) and their blends in the combustion process were investigated in this study. The content of PC in the blends were 30wt%, 50wt% and 70wt%, respectively. The experiments were carried out at different heating rates (10, 20 and 40℃/min) under air atmosphere with a flow rate of 60 mL/min and the temperature ranged from room temperature to 1000℃ in a thermogravimetric simultaneous thermal analyzer. Meanwhile their activation energy during combustion was studied by Kissinger?Akahira?Sunose (KAS) and Flynn–Wall–Ozawa (FWO) methods. The results indicated that the RS showed one more weight loss peak than the PC in the derivative thermogravimetric (DTG) curves and the residual mass of RS was lower than PC. The different mass of PC in the samples had no obvious effect on the co-combustion weight loss characteristics at the low temperature stage, but there was significant effect in the high temperature zone. As the heating rate increasing, the DTG curves of all samples were shifted to the high temperature side, resulting in thermal hysteresis. The interaction between RS and PC was inhibited in the temperature range of 320~520℃. When the temperature was above 530℃, there existed positive synergistic interaction between the combustion process of RS and PC, especially at 600℃. The kinetic analysis showed that the values of average activation energies calculated by KAS and FWO methods were highly consistent. When the content of PC was 50wt%, the activation energy reached the lower level, 76.0 kJ/mol by KAS and 83.2 kJ/mol by FWO, which indicated that the chemical reaction was easy to complete.

Treatment of antibiotic pharmaceutical wastewater by three sludge method

Jianfa CHEN

Chin. J. Process Eng.. 2019, 19(3): 644-650. DOI: 10.12034/j.issn.1009-606X.218344

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