The Research Of The Charge Physical Chemistry Change In BF When Injecting Coal Gas

To simulate the physical and chemical process of BF charge injectted coal gas, thechange of the physical and chemical process of BF charge was analysed with someequipments such as stereoscan, X-ray diffractometer, X-ray fluorescence analyzer and soon. During the experiment, the pulverization of the BF charge in low temperature, thecontrolling segment of iron ore reduction in gas-solid state, carburizing anddecarburization of BF charge. The course of forming slag in high temperature and thedistribution of carbon are studied. The results show:1. Temperature is main factor of the reduction degradation of charge, the reductiondegradation of charge is most serious in 500℃, which is not existed ultimately in 900℃,between 500℃and 900℃,the rate of reduction degradation of charge reduces as thetemperature rises; the rate of reduction degradation of charge increases as the content of H2rises in the same temperature, which reduces as the content of CO₂ increases. In terms ofdifferent charge, the rate of reduction degradation of charge in low temperature of sinter ishigh, which of spheric agglomeration and ore is lower than that of sinter.2. The formation of primary slag is related with charge structure. The primary slagformed by acid spheric agglomeration and ore is the slag system composed by a largenumber of unreduced aluminosilicate and FeO; the primary slag formed by sinter is theacid slag system of CaO-Al₂O₃-MgO-SiO₂.The generation process of the slag in the bosh is that: in the course of primary slagformed by acid spheric agglomeration and ore descend, which merge with the primary slagformed by sinter, and absorb CaO and MgO, then turn to the slag system between CaO—Al₂O₃—MgO—SiO₂. The binary basicity of the slag in the bosh is less than the binarybasicity calculated in theory, the main reason is that limestone do not take part in theprocess of the building of slag and unbalanced limestone in sinter.3. The influence of the gas component to charge carburizing is analyzed in lowtemperature zone .After injecting coal gas ,the charge carburizing mainly finish accordingto Boudouard Reaction in 400～800℃zone, the charge carburizing mainly concentrate inedge because of influences of CO diffusion control in charge and so on; H2 is favorable toiron carburizing in 500℃～700℃, H2 has no effect on iron carburizing at 900℃.4. From lower of furnace stack to bosh, the carbon content of iron has a reducingcourse at 1300℃, then the carbon content of iron increases as temperature increasing. Thisis mainly caused by the early slag just form at 1300℃. When the early slag which containshigh level of FeO contacts to liquid iron, [C] is oxidized by FeO in slag, it make the carboncontent of iron reduce. 5. In bosh, the carbon content of iron gets to saturation. The carbon content of iron isdecreased during molten iron drop passing final slag. The main reasons are: the reaction(FeO)+[C]=Fe+CO also occur during molten iron drop passing final slag, the slag has lowlevel of FeO ,but it still has strong decarburizing capability. In addition, during molten irondrop passing final slag, the dynamic conditions of decarburizing reaction is well, it makethe carbon content of liquid iron reduce.