The Technology Of Production Abrasive Grit With Direct Reduction Of High Temperature From Coal Mixed Pellet Of High Basicity

This paper summarized the development of direct reduction technology at home and abroad. After analyzing characteristic of reducing agent resources and DRI market in our country and studying the mechanic research of pellet, a new method of direct reduction of producing abrasive grit from preparation concentrate of ore in high temperature and high basicity slag is proposed.This research is a new low cost method of producing abrasive grit. It is to put the iron ore concentrate, coal powder, hydrated limed and addition agent together to make coal mixed pellet in prior which is rapidly auto-reduced in high temperature and kept about 10min above 1350℃, and then furnace cooled. The 2CaO·SiO2 of slag phase change,volume increase and natural bloom in reduction process. Finally we obtain no-slag abrasive grit through screen separation , in which the iron yield can be above 90%,the sulfur content can be below 0.05% and carbon content is lower than 4.0%. The abrasive grit we get is prime material for electric steelmaking and converter.The experiment was undertaken in high-temperature carbon tube furnace. Changing the processing parameter of reduction temperature,carbon content,basicity and addition CaF2, we study on the influence of technical and economic target of separation iron from slag, iron yield, desulphurization rate. And we also find out the mechanics of separation iron from slag and factors of abrasive grit growth.The research discovered:①The melting point of slag falls down and promotes abrasive grit growth when CaF2 put in. Putting in proper quantities CaF2 improves affection of separating iron from slag.②Suitable C/O will improve affection of separating iron from slag and increase iron yield and increase desulphurization rate.③The reduction temperature has great influence in constituting slag and iron phase coacervation. High temperature will add iron phase carburize and fall down melting and accelerate iron phase coacervation. The temperature of 1330℃-1380℃will get homogeneous abrasive grit.④Basicity slag has great influence on separating iron from slag. In low basicity, because of the low melting of the slag phase, it is bad for the gas-solid reaction of ferric iron oxide and separating iron from slagThe research discovered: Sulfur can be deprived above 90% during direct reduction. The mechanic of desulphurization is gasification desulphur. Sulfide and organic sulfur of pulverized coal mixed pellet enter gas phase. Some depart from pellet with off-gas; some are combined with CaO existing in the pellet. By changing process parameter of the reduction temperature,carbon content and basicity of slag phase, desulphurization rate during process direct reduction is improved.The research discovered that phosphorus of pulverized coal mixed pellet can be deprived about 30% which can delete the cost of steelmaking. Compared with blast furnace refining and other direct reductions, our technology shows all kinds of advantages.