The Production Practice Research Of Pellet Production With Limonite Using Chain Grate-rotary Kiln Process

Limonite is a kind of hydrous ferric oxide ore which is formed by the weathering effect of other iron-bearing mineral and is widely distributed in nature. The superior performance of limonite are it’s loose structure, small density and it’s strong water absorption capacity. The crystal water and free water are removed after roasting process, which increase the porosity rate and improve the reducing performance. And because of the dehydration effect of roasting process, the total iron content increased by the decreasing of total ore weight, which has a positive impact on blast furnace iron making process. If limonite are used in sinter and pallet production, because of it’s poor roasting performance, some production defects might occur such as the ring formation of rotary kiln and low compressive strength of pellet. At present, there isn’t any chain grate-rotary kiln pellet production line using limonite as raw material. In order to make good use of the rich limonite resource of Jiangxi Tiekeng and to reduce the cost of pellet, the pellet producing of XinYu Iron&steel group adopted new idea of adding limonite to the pellet raw material to increase the resources categories. Under current circumstance of magnetic ore concentrate shortage and price rise abroad, the beneficial use of limonite as pellet material could improve the survive and competition ability of the company.This paper aims at the actual producing pelleting situation of chain grate-rotery kiln in XinYu Iron&steel group Co., LTD.according to a series of measures to adopting theory analysis and industrial practice. The balling property and roasting property of Tiekeng limonite are studied experimentally, the suitable ratio of Tiekeng limonite at the actual pellet producing situation in chain grate-rotary kiln are determined based on experimental research and industrial application. The optimum parameters such as the relationship of pulverized coal and bentonite are explored. The conclusions are made as follows:(1)Limonite powder has better balling property and faster balling rate and better green ball strength.(2)The moisture rate of limonite green ball is high, longer drying time or higher air volume are needed.(3) Increasing the preheat temperature from950to1000℃or rising the preheat volume could promote the preheat effect of green ball; the overall performance of limonite pellet is poorer than magnetite pellet, but still can meet the needs of blast furnace.(4)The defects of limonite pellet producing by chain grate-rotary kiln can be avoided by adopting higher preheat air volume, reducing roasting temperature and prolonging drying time.(5)According to industrial application result, the smaller pellet size and ratio of limonite addition of5%to10%could result in the best pellet performance and economic profit.(6)In the process of limonite pellet practice by chain grate-rotary kiln, the economic profit could be further improved by optimizing ingredient model and dry component composition, changing the bentonite type.(7)Limonite can effective cooperatively used with sulfuric acid slag and the iron-bearing by-product to reduce pellet cost.