The mechanism of smelting reduction of chromite ore

Research Project

Project/Area Number	10650733
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Single-year Grants
Section	一般
Research Field	Metal making engineering
Research Institution	KYUSHU UNIVERSITY
Principal Investigator	MORI Katsumi (1999) Kyushu university, Division of Eng., Professor, 工学研究科, 教授 (80037754) 孫海平 (1998) 九州大学, 工学部, 助手 (20226616)
Co-Investigator(Kenkyū-buntansha)	森克巳九州大学, 工学研究科, 教授 (80037754) SUN Haiping Kyushu university, Division of Eng., Asso. Researcher (20226616)
Project Period (FY)	1998 – 1999
Project Status	Completed (Fiscal Year 1999)
Budget Amount *help	¥1,100,000 (Direct Cost: ¥1,100,000) Fiscal Year 1999: ¥1,100,000 (Direct Cost: ¥1,100,000)
Keywords	Chromium / Stainless steel-making / Chromium oxide / Molten iron / Reduction rate / Carbothermic reduction / Molten slag / 還元機構 / 物質移動 / 炭素 / 固体・溶鉄間反応
Research Abstract	The reduction of CrィイD22ィエD2OィイD23ィエD2 is a basic reaction for ferro-chromium production from chromite ore and for chromium recovery from the slag formed during the decarburaization period of stainless steel-making. In order to increase the reduction efficiency of chromite ore, it was strongly desired to clarify its reduction mechanism from the practical and the theoretical points of view. So, the effects of morphology of chromium oxide, kinds of reductant and fluxes and temperature on the reduction rate were examined. The results obtained as follows. The reduction of chromite ore by carbon in iron melt was very slow in a powder state but when silicon was added to iron melt, it was preferentially used for the reduction to form silica, which reacted with ore to promote the dissolution of ore into liquid slag. As a result, the reduction was remarkably promoted. The addition of fluxes such as silica, sodium borate and CaO-SiOィイD22ィエD2 slag to chromite ore favored for the formation liquid slag and then the reduction rate of CrィイD22ィエD2OィイD23ィエD2 was significantly promoted. Apparent activation energies of 200-300 kJ molィイD1-1ィエD1 were obtained for the reduction of CrィイD22ィエD2OィイD23ィエD2 in molten slag and chromite ore by carbon or silicon. It was found from these results that the rate-determing step for CrィイD22ィエD2OィイD23ィエD2 reduction was the diffusion of Cr ion in chromite ore and the dissolution reaction.