Study On Jet Characteristics Of Double Structure Oxygen Lance And Interaction With Molten Pool

Oxygen lance is the main process equipment in converter steelmaking.Its jet characteristics and the interaction between jet and molten pool will directly affect the smelting effect and blowing time.With the continuous improvement of the cost and efficiency requirements in the steel industry,the performance requirements of oxygen lance are also increasingly high.However,the traditional five hole and six hole oxygen lances which are mainly used in industry have the problems of low oxygen supply intensity and insufficient stirring capacity.Therefore,a new type of double structure oxygen lance nozzle is designed to ensure the mixing effect of oxygen jet to the molten pool,improve the oxygen supply intensity and reduce the occurrence of splash.Taking the oxygen lance of 260 t converter in a steel plant as the research object,the jet characteristics of traditional five hole and six hole oxygen lance nozzle and three kinds of double structure oxygen lance nozzle with large and small hole flow ratio(55%-45%,60%-40%,65%-35%)are studied by numerical simulation.After obtaining the optimal flow ratio,the influence of operation parameters on the jet coalescence characteristics of double structure oxygen lance is studied.By establishing a 1:7 hydraulic model,the effects of top blowing flow rate and lance position on the splash amount,impact pit size and mixing time of traditional five hole and six hole oxygen lance nozzle and double structure oxygen lance nozzle were investigated.The results show that:(1)Compared with the traditional oxygen lance,the supersonic zone of the double structure oxygen lance is longer,and the negative pressure zone is far from the nozzle outlet.In the double structure oxygen lance with the flow ratio of three large and small holes,as the flow of large holes increases,the length of the supersonic region increases and the impact area increases.Comprehensive analysis shows that the scheme of 65%-35% flow ratio of large and small holes has the best jet characteristics in the double structure oxygen lance.(2)With the increase of the distance from the nozzle outlet,the jet stream gradually shifts to the center axis of the nozzle under the action of the pressure difference between the inside and outside and finally merges with each other.The greater the operating pressure,the higher the ambient temperature,the stronger the interaction between the jet streams,the faster the fusion speed,and the earlier the mixing time of the jet boundary.(3)Compared with the six hole oxygen lance nozzle,the traditional five hole oxygen lance nozzle has a smaller number of spray holes,and the jet stream impinging on the surface of the molten pool is more dispersed,so the impact area is larger,the amount of splashing at the furnace mouth is less,and the impact pit formed is large in area and shallow in depth.(4)Compared with the traditional six-hole oxygen lance nozzle,the double structure six-hole oxygen lance nozzle with a flow ratio of 65%-35% large and small holes has less spray volume.The diameter of impact pit is increased by 10% on average.The impact pit depth of jet on molten pool is larger,and the advantage is more obvious under low lance position.The mixing time is significantly shortened,with an average of 10s.