Research On Preparing Oxidized Pellet With Xinjiang Low-grade Iron Ore

With the development of blast furnace ironmaking, acid pellet is becoming indispensable. The blast furnace burden structure of acid pellet with high basicity sinter has been proved to be a very effective burden structure, which has a very positive effect on reducing the coke ratio as well as improving the steel yield and quality. XinXing Ductile Iron Pipes XinJiang Co., Ltd. has a variety of complex raw materials with diverse grades, of which the chemical and physical properties is differ greatly from one another. As a result, the mechanical properties of pellet are inferior, which influence pelletizing and blast furnace iromaking.The research background of this topic is that XinXing Ductile Iron Pipes XinJiang Co., Ltd. uses Xinjiang low-grade iron ore on blast furnace ironmaking. Focusing on the problems of low intensity of the green pellet, poor ballability of the iron ore fines, the ring formation in rotary kiln and high pulverization rate of pellet, a lot of experiments is be done. Firstly, with the single factor test of the moisture ratio of pellet, the ratio of bentonite, the grinding time and the pelletizing time, it is to analyze the physical and chemical properties of various kinds of iron ore fines to determine the appropriate pelletizing parameters. Secondly, the experiments of optimizing the roasting time and roasting temperature to improve the compressive strength of the pellets is be done. Lastly, the experiments of single iron ore fines pelletizing to optimize the raw material proportion to improve the mechanical properties of pellets is be done. Based on the experimental studies above, several conclusions are drown:(1) With the increasing of moisture content of the pellet from 8.1% to 9.6%, the drop strength of green pellet is improved. The compressive strength reaches its extreme value when the moisture content of the pellet is about 8.9%, and the explosion temperature declines gradually. So the appropriate moisture content of green pellet is about 8.9%;(2) With the increasing of bentonite rate from1.2% to 2.4%, various indexes of green pellet become better, including green pellet strength and explosion temperature. And then the rate of qualified size of green pellet reached the maximum when the bentonite ratio is 1.8%~2.1%, the best bentonite rate is 1.8%.(3) After grinding iron ore fines, the powder particle size become more granular, deformation degree of the crystal lattice increased, ballability index size and the rate qualified size green pellet get little better, The strength of raw ball is obviously enhanced, but the thermal stability get lower; With the prolonging of the pelletizing time, the strength of the pellet is improved, and the bursting temperature is reduced;(4) In three factors and three levels of orthogonal test, which research the effect of bentonite ratio, grinding time and pelletizing time on the drop strength and compressive strength of green pellets. The most significant affect factor on drop strength is bentonite ratio, but the most significant affect factor on drop strength is grinding time. So the suitable pelletizing parameters is as follows: bentonite ratio is 2.0%, grinding time is 10 min and pelletizing time is 7min. The experimental results are good.(5) The increasing of roasting temperature and roasting time have a positive effect on the compressive strength of pellets and the microstructure of pellets. When the roasting temperature reaches 1175? and the roasting time is 20 min, it is the most advantageous to the quality and efficiency of production.(6) Beizhan iron ore fines has a good pelletizing performance, all the various indexes of which meet the requirements of pellet production. So in the actual production, Beizhan iron ore fines should be the main raw material. When use Beizhan iron ore, Kezhou iron ore, Jianbao iron ore and Meihui iron ore on the ore proportioning optimization tests, ore proportioning has a great effect on the compressive strength of pellets and microstructure. With the increasing of ratio of Beizhan iron, the compressive strength and microstructure of pellets improves obviously;...