Study On Resource Utilization Of Low Ti-bearing Blast Furnace Slag

Titanium-bearing blast furnace slag is a by-product of blast furnace smelting vanadium-titanium magnetite.As for the slag's large yield,pollution to the environment as well as the valuable and rare TiO₂ in the slag,a number of scientific researchers and manufacturer focus on the comprehensive utilization of titanium-bearing blast furnace slag.However,no feasible and industrial technology of comprehensive utilization of titanium-bearing blast furnace slag has been found so far.In this paper,the low-titanium blast furnace slag was used as the research object?w?TiO₂?=6.72?10.21%?,As slagging in the early stage of semi-steel smelting is difficult,the dephosphorization rate is low and low-titanium blast furnace slag has comparatively high content of CaO,SiO₂,MgO,Al₂O₃ and S,low content of FeO and P,we propose to make semi-steel slagging ball and LF desulfuration slag by low titanium blast furnace slag after the slag is desulfurized.Firstly,the basic properties of low-titanium blast furnace slag with different cooling methods?water cooling,air cooling,crucible cooling,furnace cooling?were studied by optical microscope,XRD,EPMA and XPS.The result shows that as the cooling rate is lowered,the glass in the low titanium blast furnace slag is sharply reduced,the content of gehlenite,perovskite,merwinite increases.The scattering of S changes from clustering dots into big pieces and facet,S gathers from varieties of minerals to gehlenite.The form of S in water quenched slag is SO₃^2-and SO₄^2-.The form of S in slow cooling slag is S^2-?SO32?and SO₄^2-.Secondly,we use thermal calculation and experiment to study CO₂ blowing desulfuration and parameters.Results shows:H2CO3 is formed by the reaction between CO₂ and H2O and H⁺ is ionized,the gas H2S and SO₂ gas is formed by H⁺ reacts respectively with S^2-and SO₃^2-.The H⁺ in desulfurization comes from HCO3-and H⁺ by H2CO3 ionization.After the experiment,the optimal desulfurization material and parameters are:particle size of cold blast furnace slag-160 mesh,liquid-solid ratio is 3.0.CO₂ flow is 2.5L/min,reaction time is 90 min,reaction temperature is 40?,stirring strength is 150 r/min,the rate of desulfurization is 80.0%.The experiment result shows that:the desulfurization rate of 'hundred kilo ' semi-industrial experiment is 66.59?78.01%,The content of residue S in the slag is 0.137?0.283%,the S content satisfies the material requirement of steel tempering and LF refining.Thirdly,adopting coexistence of molecule and ion principle,Factsage and industrial experiment to study semi-steel slagging and dephosphorization.The result shows that:In the experiment,the appropriate ratio of low sulfur and low titanium blast furnace slag to iron oxide skin is 65.0-70.0%and 25.0?30.0%.Semi-steel is smelted by semi-steel slag ball,the slag basicity is controlled to be 4.0,it is good for slag smelting in early semi-steel smelting and has little influence on dephosphorization in early stage slag.Through comprehensively analyzing the data of 150t converter,the amount of semi-steel slag is 15.0-20.0%of the total amount of slag,which is about 1.8?2.4t.And the condition is suitable for semi-steel smelting.And early stage dephosphorization rate of the original process increase from 37.32%to 58.59%by semi-steel slag ball smelt semi-steel.Semi-steel slag improves the slagging and effect of dephosphorization of the pre-slag.The per ton lime consumption reduces 3.48kg/t and the[O]in final steel reduces 112 ppm,the slagging and dephosphorization effect is good.Fourthly,adopting thermal calculation,relevant simulation experiment and industrial experiment,etc to study the desulfurization capability,melting effect and desulfurization effect of LF refining slag.The result shows that,use low S,low titanium blast furnace slag with CaO,Al₂O₃ to make low basicity low Al₂O₃ LF desulfuration slag.The slag system has comparatively high sulfur capacity and viscosity and melting point is suitable for LF refining.The basic experiment proves that:the rate of desulfurization of LF slag is between 51.43?85.54%on condition of de-oxidation by FeSi and Al.The sulfur distribution rate is between 9.21?49.96,which shows good desulfurization effect.During the industrial experiment of smelting HRB400E rebar,the slagging refining process of molten steel desulfurization rate is between 10.0-41.5%.The end point[S]content meets the requirements of steel,and products are qualified.This study adopts CO₂ blowing to desulfurize the low titanium blast furnace slag,making the oxides in the slag return to steel procedure.The high efficient desulfurization and utilization of low titanium blast furnace slag is realized,and slagging of early stage semi-steel smelting and low rate of desulfurization problem is solved.The study sets the theoretical and experimental base for low titanium blast furnace slag utilization and explore the new direction of application.