Study On The Influence Of B₂O₃ On The Agglomerate And Metallogenic Mechanism Of Blast Furnace Burden Of Vanadium-Titanium Magnetite

At present,the utilization process of vanadium-titanium?VT?magnetite in China is still dominated by the blast furnace-converter method,in which the blast furnace burden is mainly composed of VT sinter and pellets.The VT magnet concentrate is known for its high content of titanium,aluminum and magnesium,coarse grain size and high melting point,which severely restrict its mineralization and metallurgical properties during the agglomeration process.In recent years,the successful application of boron mud,boron iron concentrate,boric in the VT magnetite concentrate block,which has become effective measures to improve the metallogenic and metallurgical properties of VT magnetite.However,the strengthening mechanism of B₂O₃-containing additive for the VT magnetite concentrate agglomeration process is still unclear,and the metallogenic strengthening process needs a deeper research.Therefore,based on a large number of literature review,this thesis focuses on investigating the effect of B₂O₃ on the mineralization mechanism of VT burden in the sintering and pelleting process.Through systematic research,this thesis reveals the strengthening mechanism of B₂O₃ in the VT agglomeration process,and clarifies the changes of microstructure and phase distribution of VT sinter and pellets,and expounds the effect of B₂O₃ on metallurgical properties.Based on the thermodynamic calculation software FactSage,the effects of B₂O₃additive on the ore-forming reaction,balance phase and liquid phase of VT sinter and pellet agglomeration were analyzed.The micro-sintering technology was used to carry out the experimental study on the influence of B₂O₃ on the basic characteristics of high-temperature sintering of VT-containing ore powder,including assimilation,liquid phase formation ability,fluidity,binder phase strength,fracture toughness and microstructure.Based on the theoretical analysis of thermodynamics and the study of the basic characteristics of high temperature,the experiments of 85.00 kg scaled sinter pot,disc pelleting and vanadium-titanium pellet baking were carried out.Based on the above studies,the main conclusions are as follows:?1?After the addition of B₂O₃ in the vanadium-titanium magnet concentrate concentrate process,the reaction of B₂O₃ with CaO and SiO₂ can inhibit the formation of 2CaO·SiO₂.After adding B₂O₃,the initial formation temperature of the liquid phase during the VT burden agglomeration process,the liquid phase production increased,and the content of perovskite phase decreased significantly.When the addition of B₂O₃ reaches 5.00%,the VT sinter and pellet balance phases are olivine,titanium-magnesium spinel and olivine,titanium-magnesium spinel,corundum,and augite.?2?The addition of B₂O₃ is beneficial to improve the assimilation of VT iron ore powder.With the increase of B₂O₃ addition,the melting temperature of VT iron ore compacts is significantly reduced,and fluidity index increases.The added amount of B₂O₃ in a certain range is beneficial to improve the strength of the binder phase of the sintered sample.But when the addition is excessive,the strength of the binder phase decreases.The addition of B₂O₃ has no significant effect on the fracture toughness of the sintered sample,and is beneficial to the increase of the amount of magnetite and calcium ferrite,and inhibits the formation of calcium silicate,perovskite and hematite.?3?The results of 85.00 kg scaled sinter pot test show:The influence of B₂O₃addition on the mechanical strength of sinter is firstly increased and then decreased.The optimum addition amount is 3.00%,and the corresponding drum strength is 58%.The low temperature reduction degradation was significantly improved with adding B₂O₃,but the improvement was unobvious after the addition ratio exceeded 1.00%.B₂O₃ can improve the reduction degree,but the addition more than 1.0%will seriously deteriorate the reduction.The softening start temperature and softening end temperature decreased with B₂O₃ addition,and the soft melt interval increased significantly.After adding B₂O₃,the microstructure of VT sinter is gradually changed from a large-area plate-like structure to a small-sized granular and dot-like structure with uniform distribution.The overall porosity is small,but the pore diameter increase and cracks reduce.?4?In the process of pelletizing VT iron powder,the addition of B₂O₃ is not conducive to the falling strength of the green ball.However,with the increase of B₂O₃,the compressive strength and microstructure fracture toughness of the finished ball are improved,the best addition amount is from 1.40%to 1.60%.With the addition of B₂O₃,the reduction degree increases,and it is beneficial to produce a certain amount of high-temperature liquid phase during the pellet firing process,increasing the compactness inside the pellets,and reducing the reduction and pulverization.The addition of B₂O₃ can improve the reduction and expansion properties of VT pellets,but as the addition of B₂O₃ increases,the softening interval increased accordingly.In summary,this thsis systematically reveals the influence of B₂O₃ on the VT iron powder ore-forming mechanism,and explores a new way to further improve the utilization of VT magnetite in China and improve the quality of VT-containing furnace burden.