天然イルメナイト鉱石のCOガスによる還元反応速度

Abstract

In order to elucidate the reduction kinetics and mechanism of natural ilmenite ore with carbon monoxide, reduction experiments have been carried out using thermogravimetric technique in the temperature range between 1173 and 1323 K with Australian, Malaysian, Chinese natural ilmenite ores. The reduction rate was analyzed in terms of the mixed-control kinetics by applying a shrinking unreacted-core model, on the basis of the observation of cross section of the partially reduced ilmenite and X-ray diffraction patterns. Reaction rate constant kc and effective diffusivity De determined are expressed by the following equations:(This article is not displayable. Please see full text pdf.) \ oindentwhere R: gas constant (J·mol−1·K−1), T: temperature (K).The activation energy of the reaction is 113, 47.0, 71.6 kJ·mol−1 for Australian, Malaysian and Chinese natural ilmenite ore, respectively. The calculated reduction curves using the rate parameters finely reproduced the experimental data. The reduction rate increases with increasing the reduction temperature. With respect to the rate-determining step for Australian and Chinese ilmenite ores, the relative contribution of resistance of a mass transfer step through the gas film is smaller than that for synthetic ilmenite, while the relative contribution of resistance of a diffusion step of carbon monoxide through pores of the product layer is larger than that for synthetic ilmenite. As for Malaysian ilmenite ore, the overall rate is mainly controlled by a chemical reaction step.