| In order to overcome the limitations of traditional oxygen lance in converter steelmaking,solve the technical problems of improving oxygen supply intensity,shortening blowing time,enhancing slag melting effect,improving dephosphorization rate and reducing the occurrence of splashing outside the furnace in the process of blowing,the interaction between the double-parameter oxygen lance and converter molten pool was studied by means of physical simulation,numerical simulation and industrial experiment.Physical simulation was used to analyze the coupling effect of the angle for the big and small nozzles and the flow rate ratio for the big and small nozzles on the key parameters including cavity shape,mixing of molten pool,splashing outside furnace and splashing inside furnace.The blowing characteristics under different structural parameters and operation processes were determined.CFD numerical simulation was applied to study the dynamic characteristics of double-parameter jet,gas-liquid interface behavior and flow field of molten pool at high temperature.The difference between double-parameter oxygen lance and traditional oxygen lance was clarified.On the premise of energy balance equation theory,the energy consumption ratio of each part between oxygen lance jet and molten pool was quantitatively analyzed by CFD-UDF,and the scientific correlation of"jet attenuation-crater formation-bath stirring-splashing"was established.The key smelting indexes of double-parameter oxygen lance were analyzed by industrial experiments,and the blowing characteristics of the new lance were further clarified.The main results are as follows.Physical simulation results show that:1)The jet flow rate of double-parameter oxygen lance has more influence on the cavity depth.When the ratio of big nozzles flow is greater than 0.60,the cavity depth and mixing time for the double-parameter oxygen lance have obvious advantages over the traditional oxygen lance.The impact area(cavity width)of the new lance is greatly affected by the nozzle inclination angle,which is obviously better than that of the traditional lance.When the blowing height(H)is(35-40)d_e,the new lance can obtain the best mixing effect.2)There are three types of splashing in molten pool:splashing sheet(main splashing),splashing finger and droplet.The splashing sheet width decreases with the decrease of lance height.The sheet height increases with the decrease of the lance height and the gas flow rate,while the sheet area increases with the increase of the gas flow rate.It is not conducive to increase the contact area among oxygen slag and molten steel if the splashing form is too concentrated.The splashing form of the double-parameter oxygen lance is relatively dispersed,which has advantages for controlling the splashing out of the furnace mouth.The inclination angle of the small nozzles has a great influence on the splashing sheet area in the furnace,and the flow rate ratio of the large nozzles has a great influence on the splash out of the furnace mouth.With the decrease of lance height,the splashing amount out of the furnace mouth increases first and then decreases.The design reference is that the flow ratio of big nozzles is 0.55-0.60,the inclination angle of big nozzles and small nozzles is 12-13°and 16-17°,respectively.Numerical simulation results show that:1)For the double-parameter oxygen lance,the small nozzles with large inclination angle can delay the jet attenuation,and the big nozzles with large flow rate can enhance the jet intensity.The contour of isovelocity line is approximate to equilateral triangle.Its effective impactive area is larger than that of traditional oxygen lance.The velocity of most steel in the molten pool is less than 0.1m/s and decreases with the increase of pool depth.The double-parameter oxygen lance can stir the molten pool more quickly than the traditional oxygen lance.2)The energy consumption of each part in blowing process is as follows:energy used for jet attenuation>energy used for cavity formation>energy used for splashing>energy used for bath stirring.The energy used for bath stirring and furnace splashing is very low.With the increase of lance height,the energy consumption of jet attenuation and splashing increases,the energy consumption of stirred bath slightly increases,and the energy consumption of cavity formation decreases.When the lance height is 1.8m and the flow rate is 53000 Nm~3/h,the jet attenuation rate of the double-parameter oxygen lance is 4.65%lower than that of the traditional oxygen lance,the energy consumption rate of splashing is 1.41%higher,the energy consumption rate of bath stirring is 0.2%higher,and the energy consumption rate of cavity formation is 3.04%higher.The results of industrial experiments show that:compared with the traditional oxygen lance,the average oxygen blowing time for the double-parameter oxygen lance with big and small nozzles inclination of12°/16°and big nozzles flow rate of 0.60 is 42s shorter,The oxygen consumption is reduced by 2.31Nm~3,the ferrous charges consumption is reduced by 13kg/t,and the dephosphorization rate is increased by 3%. |
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