Particle-Gas Flow Behavior And Desulfurization In Refining Ladle With Bottom Powder Injection

The level of clean steel production has become an important manifestation of the comprehensive competitiveness of enterprises.The sulfur element has many adverse effects on the performance of the steel and becomes the main removal or control element of clean steel production.The low sulfur steel production with high-efficiency,low-cost high-quality is an important guarantee for enterprises to develop high-quality,high value-added strategic products.At the present,the main process of low sulfur steel is hot metal pretreatment?converter?ladle refining(LF,RH).The process has many shortcomings,such as long process,low efficiency,high cost and inflexibility.Therefore,Northeastern University independently developed a new generation of desulfurization technology,named L-BPI(Ladle-Bottom Powder Injection).The technology significantly enhances the efficiency and effectiveness of secondary refining,shortens the iron and steel industry production processes,improves production efficiency and reduces costs.Therefore,it is necessary to carry out research on particle-gas flow behavior and desulphurization kinetics in refining of ladle-bottom powder injection.The research contents and achievements of this paper are drawn as follows:(1)Numerical simulation of powder flow behavior in the process of bottom powder injection.The mathematical model describes the gas-liquid-powder multiphase transport behavior in the process of bottom powder injection,established by using Fluent simulation software.The circulation law of molten steel is studied under different argon blowing rates.The trajectory of particles in different particle diameters has different dwell times.The powder injection process not only has the reaction interface of the top slag-gold boundary,but also the reaction interface of the powder during the rise of process.Small particles of the powder stay in the molten steel for a longer time,which improves the slag-gold interface area and the time of desulphurization reaction,making desulfurization and deoxidation more fully.Thereby the refining of ladle-bottom powder injection obviously increases the desulfurization efficiency.(2)Study on desulphurization kinetics of ladle-bottom powder injection.Desulfurization model can be viewed as the continuous contact reaction model of the top slag-gold boundary and the short contact reaction model of the powder followed with bubbles.The effect low of powder particle effective utilization coefficient,different dusting mood and sulfur distribution ratio on desulphurization rate of ladle-bottom powder injection refining is studied.The results show that the high-speed and short-time dusting mode is better than the low-speed and long-time dusting mode under the same dusting amount.Improving the effective utilization of powder particles can greatly improve the efficiency of the desulfurization.With the increase of Ls,the desulfurization efficiency increases rapidly.When Ls exceeded 300,the desulfurization efficiency has little effect.When the effective utilization coefficient of powder is between 0.2 and 0.4 and the distribution ratio of sulfur is between 200 and 300,the desulphurization rate of ladle-bottom powder injection is stable above 80%.(3)Thermal test of 1.5t induction furnace-bottom powder injection.Through the cold test of air brick and thermal test of 1.5t induction furnace-bottom powder injection,the applied feasibility of the new technology of bottom powder injection is checked.Through the sample analysis,the desulfurization rate was 51.4%,The reason is that the volume of induction furnace is small and the net height is low,making the powder in the molten steel for a short time,so the desulfurization efficiency could not reach 80%.These methods which using the synthetic slag with CaC2,Ca and Mg powder,changing top slag,and reducing the exposed surface area can be made to improve the desulfurization rate.(4)Basic study on ladle-bottom powder injection.In refining process with L-BPI,the temperature drop factors include ladle lining heat,slag layer heat and exposed surface heat dissipation and powder consumption heat.The refining time is about 20 minutes,the time of small amount of argon blowing is about 8 to 10 minutes,the temperature drop rate is 1?/min,the time of powder injection is about 10 to 12 minutes,the temperature drop rate is 2.3?/min,the temperature is expected to drop 30-35?.For most of the steel,it is entirely possible without heating device to meet the requirements of the continuous casting and of the converter.