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Published in last 1 year |  In last 2 years |  In last 3 years |  All Please wait a minute... For Selected: Download Citations EndNote Ris BibTeX Toggle Thumbnails Select First-principles calculation of adsorption mechanism of hydrochloric acid on chalcopyrite surface Xiaoliang LI, Guocai TIAN The Chinese Journal of Process Engineering    2021, 21 (7): 836-846.   DOI: 10.12034/j.issn.1009-606X.220175 Abstract （507）   HTML （2）    PDF （1478KB）（153）       Knowledge map    Save The leaching of chalcopyrite has always been the core of copper sulfide hydrometallurgy, but chalcopyrite is a sulfide mineral that is difficult to be oxidized and decomposed. At present, a large number of macroscopic phenomena are obtained by focusing on experimental research, and the mechanism is mostly inferred. However, the lack of information on atomic or molecular level hinders the clear and effective explanation to these macroscopic phenomena. Therefore, it is necessary to study the surface interaction between liquid medium and chalcopyrite and the influence of medium on the formation of surface products by means of atomic or molecular level calculation and analysis, which are of great significance to reveal the reaction mechanism of leaching process and improve or develop a green hydrometallurgical technology of chalcopyrite. As a common leaching agent, hydrochloric acid can be used in the leaching of chalcopyrite, and it has been widely studied because of its advantages of recyclable leaching agent, high solubility of metal ions, good oxidation reduction performance and fast leaching rate. In this work, the adsorption and reaction mechanism of hydrochloric acid on different sites of chalcopyrite surface were studied with first-principles calculation. It was shown that the reconstructed sulfur terminated chalcopyrite (001) surface [labeled as (001)-S surface] led to the formation of disulphide S22-. Hydrochloric acid was adsorbed on the sulfur terminated surface (001)-S of chalcopyrite in the form of dissociation. In the process of leaching, the adsorption of H+ on sulfur terminated surface (001)-S of chalcopyrite destroyed the S22- formed on the surface. The surface structure of chalcopyrite (001)-S was destroyed by adsorption of chloride ion Cl-. During the adsorption process, the chemical reactions between H+ and Cl- with the surface of chalcopyrite produce the FeCl2 and H2S, which were both beneficial to the leaching of chalcopyrite. The results can provide a theoretical basis and guidance for future research. Table and Figures | Reference | Related Articles | Metrics Select Investigation on direct to blister copper smelting for high?grade copper concentrate Shiwei ZHOU Xiang GUO Kelun ZHANG Ba ZHANG Bo LI Yonggang WEI The Chinese Journal of Process Engineering    2021, 21 (12): 1473-1480.   DOI: 10.12034/j.issn.1009-606X.220421 Abstract （389）      PDF （1423KB）（45）       Knowledge map    Save Conventional copper smelting technology combines two steps of smelting and converting, with oxygen-enriched smelting as a typical representative. Intermittent operations would inevitably cause common issues such as long operation procedures and low-level sulfur dioxide pollution. Therefore, development of short-process for copper smelting technology is particularly necessary. Direct to blister copper smelting technology was carried out in a single furnace. It has the advantages of short process, good environmental benefits, and low investment cost, which is in line with the development direction of modern short-process smelting technology. The high-grade copper concentrate was used as raw ore for direct to blister copper smelting in present, and the method of theoretical calculations combined with experiments in lab-scale was adopted to investigate the phase transformation, blister copper yield, and copper content in the slag during the smelting process. Theoretical calculations indicated that the spinel phase in the melt can be avoided by adding CaO, as the ratio of iron to silicon was controlled to be 0.6 in the raw material. The corresponding chemically dissolved copper content in the slag at 1300℃ was approximately 8.6wt%. The effects of the amount of injected oxygen and settling time on the weight of blister copper and slag properties was discussed. For 80 g raw material, the oxygen-enriched air (50vol% O2) with a rate of 0.4 L/min was injected for 70 min, and then settling for 2 h. The experimental results indicated that the blister copper with a recovery rate of 82.12% could be obtained from a high-grade copper concentrate containing 45.94% Cu via direct to blister copper smelting at 1300℃. SEM-EDS analysis method was used to investigate the microstructure of the slag, which indicated that a large amount of spinel phase existed in the slag, hindering the sedimentation of copper particle. The copper in the form of mechanical entrainment was observed as a result. Related Articles | Metrics Select Impurity removal and hydrothermal heterogeneous cryogenic rapid oxidation of semi-dry desulfurization ash from iron ore sintering flue gas Rufei WEI Yulong ZHU Di ZHOU Yifan WANG Hongming LONG The Chinese Journal of Process Engineering    2021, 21 (8): 951-958.   DOI: 10.12034/j.issn.1009-606X.220223 Abstract （372）   HTML （11）    PDF （1803KB）（270）       Knowledge map    Save The semi-dry desulfurization ash of iron ore sintering flue gas cannot be effectively utilized because it contains a lot of unstable calcium sulfite. Oxidation modification of desulfurization ash is an important means to realize its large-scale or high-value utilization. The results show that the calcium carbonate in the desulfurization ash is the main factor limiting its oxidation modification. Calcium carbonate and calcium sulfite cover each other, which reduces the specific surface area of calcium sulfite oxidation reaction and limits its oxidation rate. Two weak acids, L(+)-ascorbic acid and glacial acetic acid, were used to remove calcium carbonate. Glacial acetic acid with a concentration of 0.4 g/g could increase the content of calcium sulfite to 81.17% with the maximum increase of 69.71%. The effect of different factors on the oxidation rate of calcium sulfite in desulfurization ash was studied by subcritical hydrothermal heterogeneous oxidation method. The results showed that the oxidation rate of calcium sulfite was significantly increased after removing impurities. The oxidation rate of calcium sulfite can be increased by increasing the initial pressure, the reaction temperature and time, and reducing the solid-liquid ratio. When the reaction temperature was 140℃, the reaction time was 30 min, the initial pressure was 2 MPa, the initial solid-liquid ratio was 1:30 and the rotating speed was 300 r/min, the oxidation rate of calcium sulfite was 98.72%, while the oxidation rate of desulfurized ash without impurity removal was only 78.77% at 180℃(other conditions were the same). In this work, the desulfurization ash was oxidized rapidly at low temperature. From the micro morphology point of view, compared with the desulfurized ash without impurity removal, the calcium sulfite after impurity removal was easier to grow along the radial direction, which had preliminary conditions for the preparation of calcium sulfate whiskers with a large aspect ratio, which was of great significance for the preparation of calcium sulfate whiskers. Related Articles | Metrics Select Characteristics of silicon-based substances effect on hot-metal dephosphorization process Guobin SUN Xiaodong XIANG The Chinese Journal of Process Engineering    2021, 21 (8): 944-950.   DOI: 10.12034/j.issn.1009-606X.220183 Abstract （354）   HTML （3）    PDF （663KB）（110）       Knowledge map    Save In the context of increasing domestic demand for hot-metal dephosphorization and advocating the utilization of solid waste, it is of great practical value to understand the effect of silicon impurities on the hot-metal dephosphorization when industrial solid waste is used to prepare dephosphorizer. Therefore, in order to explore the effect of silicon-based substances on dephosphorization efficiency, the dephosphorization experiments were carried out by using ferrosilicon and SiO2 to prepare hot-metals containing different mass fraction of silicon and dephosphorizers containing different mass fraction of SiO2. Meanwhile, to further understand the characteristics of hot-metal dephosphorization when different silicon-based substances were used as initial conditions in the slag-iron system, under the condition of ensuring the same molar amount of silicon-based substances, the dephosphorization experiments were carried out by selecting different silicon-based substances involved in desiliconization process as an additive to hot-metal or dephosphorizer, including ferrosilicon, SiO2 and CaSiO3, and the overall mass transfer coefficient of phosphorus in the three experiments was calculated by theoretical derivation and curve fitting. The results had shown that under the conditions of temperature 1400℃ and initial hot-metal phosphorus content of 0.3wt%, when the initial hot-metal silicon content was 0.4wt%, the highest dephosphorization efficiency can be obtained. The effect of initial SiO2 content in the dephosphorizer on dephosphorization efficiency can be ignored. In addition, under the condition that the molar amounts of silicon, SiO2 and CaSiO3 were the same, a higher overall mass transfer coefficient of phosphorus can be obtained in the hot-metal dephosphorization by using the dephosphorizer containing CaSiO3. Related Articles | Metrics Select Structure design and optimization of thin plate static mixer for dilution water mixing Jianqiu LU Jiaqing CHEN Wenjin LIU Quan LUO Guodong DING Xiaoping WANG The Chinese Journal of Process Engineering    2021, 21 (10): 1196-1206.   DOI: 10.12034/j.issn.1009-606X.220322 Abstract （340）      PDF （2902KB）（170）       Knowledge map    Save The dilution water blending is a key link in the crude oil electrical desalination system of oil fields or refineries, which directly affects the efficiency and operating energy consumption of electrical desalination. In order to further simplify the equipment structure, reduce costs and increase system efficiency, a thin plate static mixer for dilution water mixing was proposed. On the basis of the preliminary structural design of the thin plate static mixer, computational fluid dynamics (CFD) was used to perform three-dimensional numerical simulation of oil-water mixing, the square root of segregation strength (IOS0.5) in a uniform mixing state and pipeline pressure drop (Δp) were used as evaluation parameter, which can indicate the influence of structural parameters on the uniformity of oil-water mixing and the running energy. The structural parameters were the length of water injection pipe, the distance between water injection pipe and thin plate, thin plate guide position and the thickness of bending sheet. Subsequently, with the inner diameter D of the hybrid pipeline as a reference, the key structural parameters were optimized by the response surface method (RSM), and the mixing performance under the optimal combination of structural parameters was predicted. The optimal combination of structural parameters obtained by optimization was as follow: the length of the injection pipe was 1/3D, the distance between the center of the injection pipe and the orifice was 4/25D, the guiding position of the orifice was 1/8π, and the thickness of the orifice was 1/25D. By comparing and analyzing the mixing effect of the thin plate static mixer before and after optimization, it was found that the optimized structure of IOS0.5 was 43.06%, which was lower than before optimization. Qualitative analysis of the water phase velocity cloud diagram and streamline diagram in the thin plate mixer showed that when the water injection ratio was 2%, the oil and water two phases can reach a uniform mixing state at the 3D downstream of the water injection pipe. It can be seen that the thin plate static mixer can quickly achieve uniform mixing of oil and water at a small water injection ratio. Related Articles | Metrics Select Effect of V content on microstructure and mechanical properties of Ti-V complex microalloyed steel Zihao CHEN, Ke ZHANG, Xibin FU, Zhaodong LI, Xi ZHANG, Xiaofeng ZHANG, Xinjun SUN, Jianqing QIAN The Chinese Journal of Process Engineering    2021, 21 (7): 827-835.   DOI: 10.12034/j.issn.1009-606X.221107 Abstract （311）   HTML （2）    PDF （1505KB）（117）       Knowledge map    Save Using the combination of microalloying technology and controlled rolling and controlled cooling technology, the development of microalloyed high-strength steels with well-matched strength and toughness and low cost has gradually become a research hotspot, which mainly improve the properties of microalloyed steel by the soft toughness of ferrite and the precipitation strengthening of nano microalloyed carbonitride. At present, there are few reports about the effect of V content on the strength and plasticity of hot-rolled Ti-V complex microalloyed steel sheet at domestic and abroad. Therefore, the research on the microstructure and mechanical properties of hot-rolled Ti-V complex microalloyed steel sheet can provide theoretical basis and process guidance for the development and microstructure and properties control of Ti-V complex microalloyed high strength steel. Two kinds of Ti-V complex microalloyed steels with different V contents were obtained by adding Ti and V microalloying elements. Meanwhile, the effect of V content on the microstructure and mechanical properties of Ti-V microalloyed steels at different coiling temperatures were discussed by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD) and physicochemical phase analysis. The results showed that when the two Ti-V microalloyed steels were coiled at 500~650℃, the microstructure was composed of polygonal ferrite and pearlite, and the formation of pearlite was inhibited by increasing the V content. When coiled at 500~650℃, with the increase of V content, the uniform elongation and total elongation decreased to a certain extent, while the tensile strength and yield strength increased significantly. The coiling temperature had little effect on the uniform elongation and total elongation and the comprehensive mechanical properties of the two experimental steels were up to best when coiled at 600℃. With the increase of V content significantly increased the number of (Ti, V)C particles smaller than 10 nm in size when coiled at 600℃. The precipitation strengthening increment σP of high vanadium steel was about 183 MPa, and the strengthening mechanisms were mainly precipitation strengthening and fine grain strengthening. V content was the main factor affecting precipitation strengthening increment and yield strength of Ti-V complex microalloyed steel. Table and Figures | Reference | Related Articles | Metrics Select Effect of coordination of acoustic wave and chemical agglomeration on fine dust agglomeration in converter Yuqing ZHANG Yimin YIN Haiying LI Qiudong HU The Chinese Journal of Process Engineering    2021, 21 (11): 1323-1329.   DOI: 10.12034/j.issn.1009-606X.220343 Abstract （305）      PDF （978KB）（104）       Knowledge map    Save At present, air pollution caused by heavy industrial products such as iron and steel, thermal power generation and cement is still very serious in China. The main reason is the low dust removal effect of PM2.5 and PM10 particles. To solve the problem of difficult treatment of fine dust in converter flue gas, the collaborative treatment method based on acoustic waves and chemical agglomeration was used to pretreat converter flue gas dust in an evaporative cooler to improve the dust removal efficiency of fine dust. Single-factor experiment and orthogonal experiment were used to study the agglomeration effect of fine dust under different factors, such as the type of flocculants [acrylamide (PAM), sodium carboxymethyl cellulose (CMC) and xanthan gum (XTG)], flocculant concentration, acoustic frequency and acoustic field time. The results of the single-factor experiment showed that the agglomeration effect of the three flocculants was PAM>CMC>XTG from large to small, taking the increase of the peak particle size of the fine dust as the evaluation standard. The agglomerating effect was the best when the concentration of agglomerating agent was 0.1 g/L, the effect was obvious when the acoustic frequency was 33 kHz, and the effect was the best when the acoustic residence time was 15 s. The synergistic effect of the acoustic wave and chemical agglomeration was better than that of chemical agglomeration and acoustic wave alone. The results of the orthogonal experiment showed that when the concentration was 0.1 g/L, the acoustic frequency was 33 kHz, and the acoustic residence time was 15 s, the agglomeration effect was the most significant. The peak particle size increased from 3.311 μm to 43.59 μm, and the dust removal efficiency of the corresponding electrostatic precipitator reached 97%. From the experimental comparison of the coordination mechanism and the single agglomeration mechanism, the synergetic mechanism combined the advantages of a single agglomeration mechanism such as chemistry and acoustic waves, and provided a feasible basis for multi-mechanism dust removal in the industry. The results can provide reliable basic data for improving the removal of fine dust in the flue gas of iron and steel production, and lay a foundation for improving the removal efficiency of fine dust in the industrial flue gas. Related Articles | Metrics Select Study on wettability difference of profiled fiber based on optical measurement Feng CHEN Yuchen HU Jinjie LU Xiaolin WU Zhongli JI The Chinese Journal of Process Engineering    2021, 21 (11): 1330-1337.   DOI: 10.12034/j.issn.1009-606X.221226 Abstract （280）      PDF （2070KB）（115）       Knowledge map    Save Gas-liquid coalescence filtration is widely used in process industry. The wettability of fiber material is the key factor affecting the filtration performance of coalescing element. Based on the optical measurement method, the wettability difference of liquid on the surface of single triangular, trilobal and cruciform fiber was studied. The change process of liquid contact angle and volume was analyzed, and the influence of liquid type, fiber inclination angle and profiled degree on wettability was investigated. The results showed that with the decrease of liquid surface tension, the contact angle reduced and therefore the wettability enhanced. However, the volatility of liquid was easy to cause the actual contact angle to be greater than the theoretical one. The contact angle of triethylene glycol, dioctyl sebacate and silicone oil did not change with time. The contact angle of water and ethanol gradually decreased with time, and the decreasing rate of ethanol was greater due to the higher evaporation rate. The contact angle of liquid presented a "V" shape distribution with the inclination angle of the profiled fiber, that was, there was a minimum point (inclination angle of 30°) to make the fiber wettability reach the best. When the profiled degree of the fiber increased, the contact angle difference between different liquid decreased and the overall wettability improved, which indicated that the fiber with higher profiled degree should be selected as the material of prefilter layer or drainage layer. Related Articles | Metrics Select Influence of the dilution gas flow rate on SiO 2 deposition on the powder surface during the fluidized vapor deposition Zhaoyang WU Zihan GAO Hui KONG Chen XIAN Jixiang JIA Xiangwei LIAO The Chinese Journal of Process Engineering    2021, 21 (8): 959-968.   DOI: 10.12034/j.issn.1009-606X.220257 Abstract （259）   HTML （3）    PDF （4268KB）（148）       Knowledge map    Save Using Fe(Si) alloy particles as deposition basement materials and tetraethoxysilane as gas SiO2 precursor, Fe(Si)/SiO2 composite powders were synthesized under fluidized vapor deposition. The influence of Ar dilution gas flow rate on deposition process of SiO2 insulating medium, and the formation Ar dilution gas flow rate range of complete Fe(Si)/SiO2 core-shell heterostructure were investigated. The results showed that the microstructure of SiO2 insulating medium on the Fe(Si) particle base surface varied from submicron clusters to integrated films to porous films with the increasing of Ar dilution gas flow rate during a fluidized vapor deposition process, while the deposition rates SiO2 insulating medium first decreased, then increased and decreased again. The homogeneity of the SiO2 insulating medium was the best and the deposition rate was 0.069 nm/s when the Ar dilution gas was at a flow rate of 250 sccm. In addition, when reaction temperature, reaction time, gas SiO2 precursor content and carrier gas flow rate was 930 K, 60 min, 9 mL and 100 sccm respectively, the conversion from Fe(Si) alloy particles to complete Fe(Si)/SiO2 core-shell heterostructure particles during the fluidized vapor deposition occurred within the Ar dilution gas flow rate range from 200 sccm to 300 sccm. The results of the performance test indicated that the Fe(Si)/SiO2 core-shell heterostructure led to a substantial enhancement in the electrical resistivity of the particles and reduction in their saturation magnetization, but hardly affected the coercive force. Compare to Fe(Si) alloy particles, the Fe(Si)/SiO2 core-shell heterostructure particles exhibited much higher electrical resistivity. The varying trend of Fe(Si)/SiO2 core-shell heterostructure particles was consistent with the deposition rate of SiO2 insulating medium. The results in this study may provide a foundation for future kinetics investigations and the application of fluidized vapor deposition technology. Related Articles | Metrics Select Comparative study on typical vertical flame spread characteristics of EPS insulation material under concave structure Xinjie HUANG Jinda GAO Zhijie ZHOU Xiaofeng ZHANG Junjie HU The Chinese Journal of Process Engineering    2021, 21 (11): 1315-1322.   DOI: 10.12034/j.issn.1009-606X.220315 Abstract （254）      PDF （2621KB）（99）       Knowledge map    Save The vertical upward and downward flame spread characteristics of insulation material EPS in the concave structure were studied by building a small-scale flame spread experimental platform. The changes of parameters such as flame structure characteristics, flame spread speed, mass loss rate, flame temperature were comparatively analyzed. The research results showed that in the process of vertical upward spreading, EPS appeared stagnant combustion; this was mainly caused by the large gas flow generated by the chimney effect. However, in the process of vertical downward spreading, the flame spread speed was obviously accelerated due to the increase of EPS accumulated in the process of flame spread and the effect of the reverse stack effect. During the upward spreading process, the length of the pyrolysis zone was significantly longer than the pyrolysis zone spreading downwards. At the same time, the flame was basically inclined to both sides of the concave groove, and the molten dripping of the material can be clearly seen, but it was spreading downwards almost no molten spilled liquid. The mass loss rate in the process of flame spread was affected by the flame height to a great extent, which was mainly manifested in two stages: initial oscillation stage and stable oscillation stage. The influence of the stack effect on it was transient and temporary. In the unburned area, the flame temperature experienced two temperature peaks, and the first peak was larger than the second peak in the case of upward spread; while the first peak was smaller than the second peak for downward propagation. This was mainly due to the structure of the flame and the directional characteristics of the chimney effect, resulting in the generation of two different peak sizes. The research results of this work can provide early theoretical and reference value for the study of flame spread characteristics under actual concave structures. Related Articles | Metrics Select Dilution of Isa copper smelting slag by carbothermic reduction with waste cathode carbon Guodong WU Lei LI Kongzhai LI Yong YU The Chinese Journal of Process Engineering    2021, 21 (10): 1187-1195.   DOI: 10.12034/j.issn.1009-606X.220327 Abstract （249）      PDF （1967KB）（148）       Knowledge map    Save Massive waste cathode carbon block are produced from the electrolytic aluminum process each year, which is mainly composed of carbon, sodium fluoride and other compounds. The fluoride and cyanide components in it cause serious environment pollution if it accumulated and exposed to air for a long time. It is regarded as a hazardous waste by various environmental bodies. An innovative method for resource processing of this waste cathode carbon block was proposed in this work. Using this waste cathode carbon block as the reducing agent can realize the effective dilution and recovery of copper from the smelting slag of Isa copper through a reduction process. According to thermodynamic analysis, the influence of the amount of waste cathode carbon addition, reduction temperature, holding time and CaO addition on the recovery ratio of copper dilution in Isa copper smelting slag was studied. The results showed that the recovery ratio of copper dilution can reach 98.24% under the conditions of waste cathode carbon addition amount of 2.0%, reduction temperature of 1300℃ and holding time of 60 min. At the same time, the F in the waste cathode carbon can be transferred and fixed in the diluted tailings in the form of CaF2. The toxic leaching concentrations of F? and CN? in the tailings were far lower than the national permissible emission standard. The research has realized the high-efficiency recovery of copper from Isa copper smelting slag and the resource utilization of waste cathode carbon. Related Articles | Metrics Select Leaching of valuable metals from nickel sulfide ores by mechanical activation Xiaohong ZHENG Weiguang LÜ Hongbin CAO Nan CAI Jin ZHAN Qingchun LI Fei KANG Zhi SUN The Chinese Journal of Process Engineering    2021, 21 (9): 1064-1073.   DOI: 10.12034/j.issn.1009-606X.220146 Abstract （248）      PDF （3050KB）（242）       Knowledge map    Save The demand for nickel resources has increased significantly in recent years due to the large-scale application of high-nickel ternary lithium batteries in the field of new energy electric vehicles. To alleviate the shortage of nickel resources in China, the nickel extraction from nickel-containing minerals has received widely attention. As an important nickel-containing minerals, the composition of nickel sulfide ore is complex and it is difficult to be leaching under atmospheric conditions. Therefore, green, high efficient, and low-cost technologies for extracting nickel from nickel sulfide ore resources have attracted much attention. In this work, the mechanical activation was introduced to increase the reactivity of nickel sulfide ore, then Na2S2O8 was used to leaching activated nickel sulfide ore under atmospheric conditions. Various conditions including rotation speed, ball-to-material ratio and ball milling time as well as the acid concentration, oxidation concentration, leaching time, liquid-to-solid ratio, stirring rate and temperature in the leaching process were optimized and the mechanism was further discussed. It was found that the mechanical activation process reduced the particle size and increased the degree of amorphization of nickel sulfide ore resulting in an increase in its reactivity, and the leaching process converted part of the S2- to sulfur by Na2S2O8 reducing the release of harmful gas H2S during the reaction. At the optimal conditions (rotation speed of 613 r/min, ball-to-material ratio of 20:1, ball milling time of 120 min, acid concentration of 2 mol/L, Na2S2O8 concentration of 0.42 mol/L, leaching time of 60 min, liquid-to-solid ratio of 5:1, stirring rate of 400 r/min and temperature of 80℃), leaching rate of Ni, Co, Cu and Fe were 98.9%, 97.7%, 98.2% and 98.7%, respectively, while the content of Ni, Co and Cu in residues were 0.45%, 0.03% and 0.14%, respectively. With this research, it was expected to provide theoretical and technical support for the efficient extraction of valuable metals from nickel sulfide ores. Related Articles | Metrics Select Study on uniaxial/triaxial impact dynamic properties of structurally heterogeneous coal Weimin LIANG, Heng LIU, Minmin LI, Gaowei YUE The Chinese Journal of Process Engineering    2021, 21 (7): 817-826.   DOI: 10.12034/j.issn.1009-606X.220178 Abstract （236）   HTML （2）    PDF （2763KB）（85）       Knowledge map    Save As a heterogeneous, anisotropic and porous porous brittle material, the coal body has a large number of micro-scales such as bedding, joints, cracks, etc. so that the blasting and cracking effects in different directions will be significantly different. Based on this, a split Hopkinson pressure bar (SHPB) experimental device was used to perform impact loads of 0.1, 0.15, 0.2, 0.3, 0.5 MPa on the coal samples taken from the vertical and parallel bedding directions. The uniaxial/triaxial SHPB impact test was used to compare the uniaxial/triaxial impact dynamics performance of the anisotropic coal body stress-strain, peak stress, average strain rate, etc. after the impact. The results showed that under the action, the uniaxial and triaxial stress-strain curves had the same trend, and the peak stress and average strain rate increased with the impact load, and the growth trend was also the same. When the uniaxial impact, the stress of the coal sample followed the strain which can reach the peak stress quickly and dropped down quickly to complete the unloading. During triaxial impact, this stage was relatively smooth and had a longer elastoplastic deformation, so its dynamic mechanical properties were also improved well. Due to the relatively weak bonding surface between coal layers, the dynamic compressive strength was relatively smaller than the dynamic compressive strength in the vertical bedding direction; the triaxial SHPB impact had the peak stress and average strain rate under the constraint of the axial and confining pressures on the coal sample compared to the uniaxial improved, and the peak stress increased the most when the impact load was 0.15~0.2 MPa, increasing by about 50%. The dynamic performance improvement in the vertical bedding direction was slightly better than that in the parallel bedding direction. The effect of pressure had certain limitations, that was a certain confining pressure had a certain limit to improve the mechanical properties of coal samples. Table and Figures | Reference | Related Articles | Metrics Select Effect of particle size on thermal decomposition kinetics of micron magnesium hydroxide Yingchun CHEN Hang CHEN Jianguo YU The Chinese Journal of Process Engineering    2021, 21 (12): 1463-1472.   DOI: 10.12034/j.issn.1009-606X.220362 Abstract （223）      PDF （1746KB）（32）       Knowledge map    Save The non-isothermal pyrolysis kinetics of micron Mg(OH)2 is studied with the thermogravimetric analyzer under nitrogen atmosphere. It mainly focuses on clarifying the effects of particle size on the pyrolysis process. The measured thermogravimetric curves show a stepwise characteristic. At the main decomposition stage, the pyrolysis of Mg(OH)2 is rapid with a sudden mass loss. At the subsequent stage where conversion rate is larger than 0.8, the rate of weight loss decreases significantly because the diffusion of product water vapor is hindered by the product of MgO film. As for the main decomposition stage with conversion rate of 0~0.8, the Starink method and combined kinetic analysis are applied to fit and analyze its kinetic model. It is found that particle size has no distinct effect on the pyrolysis kinetics of micron Mg(OH)2. The model fitting results show that the pyrolysis reaction activation energy of micron Mg(OH)2 is 129.4 kJ/mol, the pre exponential factor is 1.820×1010 min?1, the pyrolysis reaction process follows the mechanism of random nucleation and growth of nuclei (A1.5). Compared to the experimental results, the thermogravimetric curves reconstructed based on these fitting parameter have the deviation less than 5%, which indicates that the kinetic model is reasonable. Meanwhile, it can be concluded that the pyrolysis process is controlled by decomposition reaction in the investigated range with the conversion rate from 0 to 0.8. The resistance effect of particle heat conduction and product water vapor diffusion is weak relatively. The main process of Mg(OH)2 weight loss is approximate to a homogeneous reaction. Considering the current investigation mainly focuses on the main decomposition stage of Mg(OH)2 with the conversion rate from 0 to 0.8, the kinetics of second stage of weight loss process remains to be studied further. Related Articles | Metrics Select Effect of external magnetic field on cleanliness of electroslag ingot Xiaofang SHI Chunli ZHU Tao XU Lizhong CHANG The Chinese Journal of Process Engineering    2021, 21 (12): 1481-1490.   DOI: 10.12034/j.issn.1009-606X.221010 Abstract （215）      PDF （1034KB）（40）       Knowledge map    Save In order to further remove the large inclusions, an electroslag remelting furnace with electromagnetic stirring is designed and the effects of external magnetic field and different electrical parameters on the cleanliness of electroslag ingot are studied. The gas content is analyzed by oxygen and nitrogen analyzer, and the morphology, composition and size of inclusions are observed and analyzed by scanning electron microscope. It is found that the oxygen content in ESR ingot increases obviously after electroslag remelting whether the external magnetic field is applied or not, but the nitrogen content decreased slightly. The oxygen content in consumable electrode increased from 0.0007% to 0.0052%, and the growth rate is as high as 7 times. However, the types of inclusions are basically unchanged, which are mainly composed of alumina, manganese sulfide, manganese sulfide oxide composite inclusions and oxides, among which alumina is the most. After remelting with external magnetic field, the diameter of the largest inclusion in the consumable electrode decreased from 89.6 μm to 12.1 μm in ESR ingot (1.1 kA/108 Gs), the proportion of small inclusions increases and the number of large inclusions decreases. However, excessive electromagnetic force is not conducive to the removal of large inclusions. When the remelting current is 1.5 kA and the magnetic induction is 108 Gs, the electromagnetic force is the largest, and the maximum diameter of inclusions is up to 30.6 μm which is larger than that in electroslag ingot without magnetic field. The increase of oxygen content after electroslag remelting is caused by air pollution and unstable oxides in slag. The electromagnetic force generated by external magnetic field increases the contact area between slag and metal, thus absorbing large inclusion. Related Articles | Metrics