| The main functions of RH vacuum refining are decarburization,degassing,and removal of non metallic inclusions,etc.The further development of multifunction of RH vacuum refining has become an important research subject to technical improvement in steelmaking industry.The technology of RH desulphurization by powder injection has been developed to solve the problem of intensive desulphurization based on RH vacuum refining.The intensive desulphurization process based on RH has good thermodynamic and kinetic conditions due to its vacuum condition and circulating flow of the liquid steel in the bath.RH desulphurization treatment by powder injection has many advantages.The desulphurization operation is simple,the desulphurization process is easy to control,and the desulphurization effect is superior,etc.Desulphurization treatment based on RH is wildly used in the production of ultralow sulphur steels,ultralow carbon steels and ultralow nitrogen steels.In this paper,a mathematical model about the variation of temperature and sulphur content in liquid steel during RH desulphurization process by powder injection was established based on the consideration of thermodynamics,kinetics,thermal balance,mass conservation and conditions of desulphurization in practical production.It aims at proposing optimization conditions to guide powder injection desulphurization production based on establishing mathematical model about temperature and sulfur concentration changing with treating time according to the injection conditions.The effects of powder injection rate,powder particles diameter,flow rate of driving gas,initial sulphur content in the liquid steel,and initial temperature of the liquid steel on desulphurization process and desulphurization ratio and temperature drop of the liquid steel were mainly studied based on the mathematical model.The specific results can be summarized as follows:1)The effect of powder particles diameter on desulphurization process is obvious,the desulphurization ratio increases with the decrease of powder particles diameter and presents an increasing trend when the particle diameter is controlled in the range of?0.35?1?mm.The desulfurization ratio increases with the decrease of powder particle diameter,but the trend is significantly slower when the particle diameter is controlled in the range of?0.15?0.3?mm.Due to the reduction of penetration ratio of powder particles,the powder particles taken away by the exhaust gas would corresponding increase which causes some adverse effects on the emission of RH exhaust gas.The effect of powder particle diameter on temperature drop of the liquid steel is slight.2)Transitory desulphurization reaction plays an absolute role in the total desulphurization reaction.The contribution ratio of transitory reaction imaintains more than 98.52%and increases with the increase of initial sulphur content in the top slag.3)The higher the initial sulfur content in the liquid steel is,the better the desulphurization process proceeds.The desulphurization ratio slightly increases with the increase of the initial sulphur content in the liquid steel.The effect of initial sulphur content in the liquid steel on the temperature drop of the liquid steel is slight.4)The effect of powder injection rate on desulphurization process is obvious,and the desulphurization ratio is increased with the increase of powder injection rate and presents a decreasing trend.The effect of powder injection rate on the temperature drop of the liquid steel is obvious.5)The smaller flow of the driving gas is,the better the desulphurization ratio is,but the effect is not significant.The effect of driving gas flow on the temperature drop of the liquid steel is very weak.6)The effect of the initial temperature of the liquid steel on desulphurization process is slight,and the desulphurization ratio increases with the increase of initial temperature of the liquid steel.The effect of initial temperature of the liquid steel on the temperature drop of the liquid steel is obvious.7)The lowest sulphur content which is 10×10-6can be obtained when the initial sulphur content of liquid steel is about?30?50?×10-6,the initial temperature of liquid steel is 1873K,the driving gas flow is 130Nm3/h,the powder injection rate is controlled in the range of?250?300?kg/min,and the powder particles diameter is controlled in the range of?0.15?0.4?mm after treating 10min. |
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