In this study, the reaction characteristics of reduction of calcined dolomite with ferrosilicon under argon flow to produce magnesium were studied by conducting experiments Pidgeon pellets were used to study the effec...In this study, the reaction characteristics of reduction of calcined dolomite with ferrosilicon under argon flow to produce magnesium were studied by conducting experiments Pidgeon pellets were used to study the effect of reduced temperature, argon flow, and reduced time on the conversion of calcined dolomite reduction by ferrosilicon. The results show that the conversion significantly increases with the increase in the reduction temperature and reduction time. The conversion first increases and then decreases with the increase in argon flow. The highest conversion was obtained when the argon flow rate was 3 L·min^(-1), and a nearly spherical shape, nanoscale magnesium powder was obtained. Then the characters of the circulating argon entrainment process were numerically studied by ANSYS Fluent 17. A physical model of multilayer pellet arrangement was established, and a numerical calculation model of chemical reaction, radiation, heat conduction, and convection heat transfer was constructed. This confirms that high-temperature argon can effectively strengthen the heat exchange between pellets, improve the heat transfer efficiency, and facilitate the pellets to react quickly. When the conversion is 80%, the production efficiency increased by about 28.6%. In addition, the magnesium production efficiency showed an increase tendency with the increase of the argon inlet flow rate.展开更多
The computational cost of numerical methods in microscopic-scales such as molecular dynamics(MD) is a deterrent factor that limits simulations with a large number of particles. Hence, it is desirable to decrease the c...The computational cost of numerical methods in microscopic-scales such as molecular dynamics(MD) is a deterrent factor that limits simulations with a large number of particles. Hence, it is desirable to decrease the computational cost and run time of simulations, especially for problems with a symmetrical domain. However, in microscopic-scales, implementation of symmetric boundary conditions is not straightforward. Previously, the present authors have successfully used a symmetry boundary condition to solve molecular flows in constant-area channels. The results obtained with this approach agree well with the benchmark cases. Therefore, it has provided us with a sound ground to further explore feasibility of applying symmetric solutions of micro-fluid flows in other geometries such as variable-area ducts. Molecular flows are solved for the whole domain with and without the symmetric boundary condition. Good agreement has been reached between the results of the symmetric solution and the whole domain solution. To investigate robustness of the proposed method, simulations are conducted for different values of affecting parameters including an external force, a flow density, and a domain length. The results indicate that the symmetric solution is also applicable to variable-area ducts such as micro-nozzles.展开更多
在精炼进站时采用BaCO_(3)作为示踪剂,对比钢包底吹氩气流量对“120 t BOF→LF→CCM”流程生产的冷镦钢SWRCH35K中DS类夹杂物的影响。结果表明,氩气流量对精炼结束炉渣成分及夹杂物的类型无明显影响;精炼进站到精炼结束采用小氩气和正...在精炼进站时采用BaCO_(3)作为示踪剂,对比钢包底吹氩气流量对“120 t BOF→LF→CCM”流程生产的冷镦钢SWRCH35K中DS类夹杂物的影响。结果表明,氩气流量对精炼结束炉渣成分及夹杂物的类型无明显影响;精炼进站到精炼结束采用小氩气和正常氩气搅拌夹杂物密度分别降低4.5个/mm^(2)和7.1个/mm^(2),精炼结束到中包两种工艺夹杂物变化相差不大,精炼正常氩气搅拌精炼结束、软吹后、中包含Ba的夹杂物比例比小氩气搅拌分别高51.5%、26.1%、39.3%。铸坯中DS夹杂物组成有单相、两相和三相。精炼采用小氩气搅拌和正常氩气搅拌铸坯中检测到含Ba的DS夹杂物占所有DS夹杂物的比例分别为28.6%和39%。所以,控制精炼过程中冶炼的氩气搅拌强度也是控制钢中DS夹杂物的关键。展开更多
The available studies in the literature on physical and mathematical modeling of the argon oxygen decarburization (AOD) process of stainless steel have briefly been reviewed. The latest advances made by the author wi...The available studies in the literature on physical and mathematical modeling of the argon oxygen decarburization (AOD) process of stainless steel have briefly been reviewed. The latest advances made by the author with his research group have been summarized. Water modeling was used to investigate the fluid flow and mixing characteristics in the bath of an 18 t AOD vessel, as well as the 'back attack' action of gas jets and its effects on the erosion and wear of the refractory lining, with sufficiently full kinematic similarity. The non rotating and rotating gas jets blown through two annular tuyeres, respectively of straight tube and spiral flat tube type, were employed in the experiments. The geometric similarity ratio between the model and its prototype (including the straight tube type tuyeres) was 1:3. The influences of the gas flow rate, the angle included between the two tuyeres and other operating parameters, and the suitability of the spiral tuyere as a practical application, were examined. These latest studies have clearly and successfully brought to light the fluid flow and mixing characteristics in the bath and the overall features of the back attack phenomena of gas jets during the blowing, and have offered a better understanding of the refining process. Besides, mathematical modeling for the refining process of stainless steel was carried out and a new mathematical model of the process was proposed and developed. The model performs the rate calculations of the refining and the mass and heat balances of the system. Also, the effects of the operating factors, including adding the slag materials, crop ends, and scrap, and alloy agents; the non isothermal conditions; the changes in the amounts of metal and slag during the refining; and other factors were all considered. The model was used to deal with and analyze the austenitic stainless steel making (including ultra low carbon steel) and was tested on data of 32 heats obtained in producing 304 grade steel in an 18 t AOD vessel. The changes in the bath composition and temperature during the refining process with time can be accurately predicted using this model. The model can provide some very useful information and a reliable basis for optimizing the process practice of the refining of stainless steel and control of the process in real time and online.展开更多
在相对真空下以CaSi_(2)为还原剂进行预制球团提镁过程的研究。利用扫描电子显微镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)分别对还原渣的形貌、化学成分和物相进行分析。结果表明,小的氩气流量可以极大地提高氧化镁的还原率,在相对真空...在相对真空下以CaSi_(2)为还原剂进行预制球团提镁过程的研究。利用扫描电子显微镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)分别对还原渣的形貌、化学成分和物相进行分析。结果表明,小的氩气流量可以极大地提高氧化镁的还原率,在相对真空下以CaSi_(2)为还原剂的预制球团提镁过程可以用F_(1)模型解释,CaSi_(2)还原氧化镁为固液反应,此过程为化学反应控制,温度对还原率影响很大,表观活化能为108.99 k J/mol。还原渣的物相分析表明,渣中的MgO含量对Ca_(2)SiO_(4)的晶型转变有影响。展开更多
基金supported by Key Program of the National Natural Science Foundation of China (Grant No.92062223)the National Natural Science Foundation of China (Grant No.51804277)Anhui University Natural Science Research Project (KJ20190048)。
文摘In this study, the reaction characteristics of reduction of calcined dolomite with ferrosilicon under argon flow to produce magnesium were studied by conducting experiments Pidgeon pellets were used to study the effect of reduced temperature, argon flow, and reduced time on the conversion of calcined dolomite reduction by ferrosilicon. The results show that the conversion significantly increases with the increase in the reduction temperature and reduction time. The conversion first increases and then decreases with the increase in argon flow. The highest conversion was obtained when the argon flow rate was 3 L·min^(-1), and a nearly spherical shape, nanoscale magnesium powder was obtained. Then the characters of the circulating argon entrainment process were numerically studied by ANSYS Fluent 17. A physical model of multilayer pellet arrangement was established, and a numerical calculation model of chemical reaction, radiation, heat conduction, and convection heat transfer was constructed. This confirms that high-temperature argon can effectively strengthen the heat exchange between pellets, improve the heat transfer efficiency, and facilitate the pellets to react quickly. When the conversion is 80%, the production efficiency increased by about 28.6%. In addition, the magnesium production efficiency showed an increase tendency with the increase of the argon inlet flow rate.
文摘The computational cost of numerical methods in microscopic-scales such as molecular dynamics(MD) is a deterrent factor that limits simulations with a large number of particles. Hence, it is desirable to decrease the computational cost and run time of simulations, especially for problems with a symmetrical domain. However, in microscopic-scales, implementation of symmetric boundary conditions is not straightforward. Previously, the present authors have successfully used a symmetry boundary condition to solve molecular flows in constant-area channels. The results obtained with this approach agree well with the benchmark cases. Therefore, it has provided us with a sound ground to further explore feasibility of applying symmetric solutions of micro-fluid flows in other geometries such as variable-area ducts. Molecular flows are solved for the whole domain with and without the symmetric boundary condition. Good agreement has been reached between the results of the symmetric solution and the whole domain solution. To investigate robustness of the proposed method, simulations are conducted for different values of affecting parameters including an external force, a flow density, and a domain length. The results indicate that the symmetric solution is also applicable to variable-area ducts such as micro-nozzles.
文摘在精炼进站时采用BaCO_(3)作为示踪剂,对比钢包底吹氩气流量对“120 t BOF→LF→CCM”流程生产的冷镦钢SWRCH35K中DS类夹杂物的影响。结果表明,氩气流量对精炼结束炉渣成分及夹杂物的类型无明显影响;精炼进站到精炼结束采用小氩气和正常氩气搅拌夹杂物密度分别降低4.5个/mm^(2)和7.1个/mm^(2),精炼结束到中包两种工艺夹杂物变化相差不大,精炼正常氩气搅拌精炼结束、软吹后、中包含Ba的夹杂物比例比小氩气搅拌分别高51.5%、26.1%、39.3%。铸坯中DS夹杂物组成有单相、两相和三相。精炼采用小氩气搅拌和正常氩气搅拌铸坯中检测到含Ba的DS夹杂物占所有DS夹杂物的比例分别为28.6%和39%。所以,控制精炼过程中冶炼的氩气搅拌强度也是控制钢中DS夹杂物的关键。
文摘The available studies in the literature on physical and mathematical modeling of the argon oxygen decarburization (AOD) process of stainless steel have briefly been reviewed. The latest advances made by the author with his research group have been summarized. Water modeling was used to investigate the fluid flow and mixing characteristics in the bath of an 18 t AOD vessel, as well as the 'back attack' action of gas jets and its effects on the erosion and wear of the refractory lining, with sufficiently full kinematic similarity. The non rotating and rotating gas jets blown through two annular tuyeres, respectively of straight tube and spiral flat tube type, were employed in the experiments. The geometric similarity ratio between the model and its prototype (including the straight tube type tuyeres) was 1:3. The influences of the gas flow rate, the angle included between the two tuyeres and other operating parameters, and the suitability of the spiral tuyere as a practical application, were examined. These latest studies have clearly and successfully brought to light the fluid flow and mixing characteristics in the bath and the overall features of the back attack phenomena of gas jets during the blowing, and have offered a better understanding of the refining process. Besides, mathematical modeling for the refining process of stainless steel was carried out and a new mathematical model of the process was proposed and developed. The model performs the rate calculations of the refining and the mass and heat balances of the system. Also, the effects of the operating factors, including adding the slag materials, crop ends, and scrap, and alloy agents; the non isothermal conditions; the changes in the amounts of metal and slag during the refining; and other factors were all considered. The model was used to deal with and analyze the austenitic stainless steel making (including ultra low carbon steel) and was tested on data of 32 heats obtained in producing 304 grade steel in an 18 t AOD vessel. The changes in the bath composition and temperature during the refining process with time can be accurately predicted using this model. The model can provide some very useful information and a reliable basis for optimizing the process practice of the refining of stainless steel and control of the process in real time and online.
基金supported by the National Natural Science Foundation of China(Nos.U1508217,51504058)the Fundamental Research Funds for the Central Universities of China(No.N162504003)。
文摘在相对真空下以CaSi_(2)为还原剂进行预制球团提镁过程的研究。利用扫描电子显微镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)分别对还原渣的形貌、化学成分和物相进行分析。结果表明,小的氩气流量可以极大地提高氧化镁的还原率,在相对真空下以CaSi_(2)为还原剂的预制球团提镁过程可以用F_(1)模型解释,CaSi_(2)还原氧化镁为固液反应,此过程为化学反应控制,温度对还原率影响很大,表观活化能为108.99 k J/mol。还原渣的物相分析表明,渣中的MgO含量对Ca_(2)SiO_(4)的晶型转变有影响。
