Numerical Simulation Of Staggered Multiple-Nozzles Oxygen Lance Jet

In the basic oxygen furnace(BOF)steelmaking process,the oxygen lance plays a very important role.The oxygen lance blows oxygen into the molten bath from the top of the converter,meanwhile the oxygen can better react with the molten bath,and the kinetic energy carried by the oxygen jet can also stir the molten bath to strengthen the reaction rate between oxygen and molten bath.With the increasing capacity of the converter,more oxygen is needed in the smelting process.Converter oxygen lances developed from single-nozzles to multiply-nozzles.Not only the number of nozzles in the oxygen nozzle was increased,but also the nozzle diameter and angles began to change constantly,in order to adapt to the larger converter.However,the traditional oxygen lance has problems such as insufficient stirring ability and low oxygen supply intensity in practical application.In order to solve these problems,a new type of multiply-nozzle oxygen lance was designed with 3 large nozzles and 3 small nozzles which are staggered central layout.Large nozzle with the small angle to provide the stirring ability of the oxygen stream,and the small nozzle with the large angle to provide the basis of ensuring a sufficient effective impact area.The new design form is beneficial to ensuring a sufficient effective impact area and enhance the stirring ability of the oxygen stream.In the thesis,a 260 t converter oxygen lance in a steel plant is taken as the research object.Combining with on-site technology,the structural parameters of a new type of staggered multiply-nozzles oxygen lance is designed and calculated.Appropriate mathematical models are selected based on theories of aerodynamics,theories of jet,numerical heat transfer,and verified by jet experiments.FLUENT was used to numerically simulate the jet characteristics of a new staggered porous oxygen lance nozzle with a large nozzle angle of 12° ? 14 °,a small nozzle angle of 16 ° ? 18 °,and a flow ratio of 60% to 40%.The thesis mainly analyzed the effects of the changes in the angles of the large and small nozzles on the oxygen lance jet shape,effective impact area and dynamic pressure.The optimal angle ratio of large and small holes in the new staggered oxygen lance was discussed.Through research,the results show that:(1)The large nozzle angle of 14o and the small nozzle angle of 17o are the optimal angles of the new staggered multiply-nozzles oxygen lance when the flow ratio of the large and small nozzles is 60% to 40% which has the largest effective impact area and the longest fusion distance.Compared with the traditional Five-Nozzle oxygen gun,the dynamic pressure is 5% higher and the effective impact area is 4% smaller;(2)The larger the radial distance of multiple jets,the longer the fusion distance,and the larger the effective impact area.Increasing the angle of the oxygen lance nozzle is beneficial to improving the effective impact area of the oxygen lance.The large hole angle increased from 12 ° to 13 °,and the small hole angle increased from 17 ° to 18 °,which has a greater impact on the effective impact area.(3)Between 0 and 20 De,the large nozzle with small angle helps to increase the impact of the large nozzle jet on the molten pool.(4)The change of the large nozzle angle has a greater effect on the jet flow pressure,and the change of the small nozzle angle has a greater effect on the effective impact area.