Experimental Simulation Of Pre-Desulfurization Of Molten Iron With Magnesium Vapor In Bottom Blowing

Molten iron pretreatment has been recognized as the most economical process to reduce the sulfur concentration in the steel during the process of blast furnace—converter—continuous casting.At present,domestic and foreign commonly used the KR mechanical mixing method and the magnesium injection method to reduce the sulfur concentration.Professor Zhang workgroup presented with China's independent intellectual property rights "desulfurization by in-situ mechanical stirring method",on the basis,group proposed a new method "combined with mechanical stirring using inert gas to carry magnesium vapor bottom blowing desulfurization".To study this new method,this paper established the water model device based on the similarity principle and carried out the experiment.Experimental through the high-speed camera pictures,used PIV system to study the motion of fluid particle,used dimension analysis method to get the criterion equation of volumetric mass transfer coefficient,and through stimulus response technique,used conductivity meter to measure the conductivity in the molten pool to study the influencing factors in mixing time.During the experiment,the main factors of the study are impeller,rotation speed,gas flow rate,the depth of impeller,nozzle structures and eccentricity.In addition,through the center bottom blowing and eccentric top blowing compared the difference between the two desulfurization methods in the molten pool bubble disintegration and dispersion and the mixing time.The results of this paper are as follows:(1)Considering the high temperature,the molten iron ladle may reduce work hours with high velocity of molten iron.So,one hole vertical nozzle,two holes horizontal nozzle and four holes horizontal nozzle should be used.Under this condition,the fluid flow has little dead band and uniform velocity field.Compared with eight holes horizontal nozzle,the fluid flow of air brick nozzle has less dead band.(2)In the center bottom blowing mode,the bubble disintegration and dispersion optimal conditions are:SSB-D impeller,rotation speed 250 rpm,gas flow rate 1.0 m3/h,impeller immersion depth 250 mm,eccentric 0.4.Under this condition,the fluid flow has little dead band and uniform velocity field.(3)Based on the homogeneous principle and Bai Jinhan's law established the similarity criterion,used the experiment data get the corresponding fitting and obtained the criterion equation.(?)The fitting equation is consistent with experimental data.(4)In the center bottom blowing mode,the molten pool mixing time optimal conditions are:SSB-D impeller?rotation speed 150 rpm,gas flow rate 1.0m3/h,impeller immersion depth 250mm,eccentric 0.4,8 hole horizontal nozzle.The minimum mixing time is only 7.33 s.(5)Under the same experimental conditions,compared with the center bottom blowing and eccentric top blowing in the mixing time and the fluid flow.Experimental results showed that the center bottom blowing both in the fluid flow or the mixing time was significantly better than the eccentric top blowing.In conclusion,"combined with mechanical stirring using inert gas carrying magnesium vapor bottom blowing desulfurization" is conducive to improve the fluid flow of molten iron,shorten the mixing time,to prolong the residence time of the bubble in the molten pool,enhance the desulfurizer desulfurization efficiency,and to shorten the removal time of sulfur,reduce the desulphurization temperature drop,and is benefit to reduce the environmental load,to the sustainable development.