| The oxygen lance used in RH refining furnace is unlike the oxygen lance used in converter,which should have the functions of vacuum chamber baking,decarburization by vacuum oxygen blowing and heat compensation.The research on flow and combustion behavior of RH multifunctional oxygen lance is of great significance to optimize the structure of RH oxygen lance and realize effective injection and efficient heating of RH refining furnace.In this paper,based on the design principle of the lance nozzle,the main hole structure of the original lance is analyzed and improved,aiming at the problems of low oxygen utilization and serious steel splash of the existing RH multifunctional oxygen lance in a steel mill.Based on the high-speed jet characteristics of oxygen lance and the simulation study of oxygen combustion of coke oven gas,the jet behavior of oxygen main hole under decarburization and combustion-supporting flow,as well as the jet and combustion behavior under atmospheric environment were analyzed.The influence laws of technological parameters on the length of the core area of the jet and the impact area of the improved oxygen lance,as well as the influence laws of the combustion temperature and the uniformity of the temperature in the furnace were studied.Based on the theory of jet mixing and combustion,under the condition that the structure of the main oxygen hole of the original lance is unchanged,the influence rules of the position,angle and flow rate of gas injection on the coal-oxygen interface mixing effect are discussed.The external mixing mode of oxygen and gas is analyzed,which is the theoretical basis for the structural design and optimization of RH multifunctional oxygen lance.Research contents and results are as follows:(1)Based on the theoretical analysis of oxygen lance design,it is shown that the serious expansion wave at the outlet of the original oxygen lance is caused by the design of small flow rate and large flow rate,which is the main reason for the instability of the flow and the serious steel splash.(2)The main oxygen hole size of oxygen lance was designed with large flow rate,and the jet characteristics of two lances were compared:The length of supersonic zone is about 1.59 times that of the original lance,and the impact force increases at the decarburization flow rate.The length of supersonic zone and dynamic pressure of the new oxygen lance increase with the increase of the ratio of inlet and outlet pressure.When the oxygen flow ratio to the design flow ratio changes within the range of 1.0-1.2,the length of the jet core area increases slightly,and the impact area is the same.The new oxygen lance has good adaptability to the variable working condition with the increase of flow rate.(3)The combustion process of fuel gas and oxygen through the new oxygen lance and the original oxygen lance under atmospheric environment was analyzed.Temperature distribution,speed and baking effect in vacuum chamber were affected by changing the position of oxygen lance,oxygen-fuel ratio and gas flow rate.The results show that:the average combustion temperature of the mixed gas injected by the new oxygen lance increases by 172K.When the lance position is 6.5m and the oxygen-fuel ratioγis 1,the heat generated by the fuel combustion reaction has the best heating effect on the whole vacuum chamber lining.With the increase of gas flow rate,the change rate of the average temperature in the vacuum chamber decreases.(4)Analyzing the coal oven gas and oxygen mixing behavior of the original lance,it is concluded that:The oxygen flow rate is certain,and changing the gas flow rate,the angle and position of the sub-hole have little effect on the flow rate of the oxygen lance outlet;when the angle of the sub-hole is 65°and the position is at 0.6L_e,the premixing uniformity of the outlet section of the oxygen lance is the best.When coal and oxygen are mixed inside,the average temperature of flue gas is 1693K,which is 538K higher than that of the external mixing structure.When coal and oxygen are mixed outside,the high temperature zone of combustion is far away from the outlet of oxygen lance,which can avoid the damage of the lance. |
