Study On Difference Of Ballability Between Artifical Magnetite And Natural Magnetite

There is a big difference in magnetic propertis and surface physicochemical properties between artificial magnetite and natural magnetite. The difference made a significant impact on ballability and roasting property of two kind of magnetic pellets. This thesis studies the raw material properties, law of pelleting, quality of green pellet, oxidation and roasting properties of natural magnetite concentrate and artificial magnetite concentrate as well as reveals the difference on pellet equipment of the two kinds of concentrate, providing theoretical evidence on the appliance of artificial magnetite concentrate.The study manifested that: the quality of two different kinds of magnetite concentrate pellets is influenced by the specific surface area, hydrophilicity, grit size and grain size composition, etc. Higher specific surface area, stronger hydrophilicity, smaller grit size and border coverage of grain size composition will contribute to pellet strength. The data of artificial magnetite concentrate on specific surface area, hydrophilicity, grit size of artificial magnetite concentrate are superior to natural magnetite concentrate which can be reflected on pellet quality. Under the best pelleting condition of using 2.5% bentonite, the shatter index and compressive strength of green pellet of artificial magnetite concentrate could reach 19.13N/a and 14.1 times/0.5m while the green pellet of natural magnetite concentrate were only 14.3 N/a and 3.9 times/0.5m.However, being roasted by high temperature, the surface of artificial magnetite concentrate was highly reactive and hydrophilic, so the green pellet of artificial magnetite concentrate was of higher percentage of water, which made the shock temperature lower than 300℃, far behind the requirements of industrial production.Mixed magnetite concentrate which consisted of 80% natural magnetite concentrate and 20% artificial magnetite concentrate was used to conduct pelleting experiment. Under optimum condition of using 2.5% bentonite, the shatter index and compressive strength of green pellet could reach over 16.0 N/a and 5.0 times/0.5m, and the shocking temperature could be over 450℃, meeting the requirements of pellet production.Difference also existed between the oxidation property of the two kinds of magnetite concentrate. Compared with natural magnetite concentrate, the Fe3O4 crystallization within artificial magnetite concentrate was not complete, with much voids, which made it more easily to be oxidized easily. Oxidation degree of artificial magnetite concentrate at 400℃ was the same as that of natural magnetite concentrate at 1000℃.Roasting property of the two kinds of magnetite concentrate pellets was also studied in this thesis. With same preheat roasting time, pellet strength of natural magnetite concentrate meet requirements at relatively low temperature of 1100℃ while emperature needed by artificial magnetite concentrate is over 1250℃. Pellets of two kinds of magnetite concentrate are roasted at 1200 ℃ for different time. Roasting time of natural magnetite concentrate pellets was obviously less than that of artificial magnetite concentrate pellets. Compressive strength of natural magnetite concentrate pellet reacheed 3000N/a after being roasted for 15 minutes while artificial magnetite concentrate pellet need 30 minutes to reach 3000N/a. Natural magnetite with addition of artificial magnetite as pelletizing raw material, can improve the quality of green balls and roasting performance magnetite pellets.