关键词: 矿相转化, 等温动力学, 转化率, 反应速率, 微观结构

Abstract: Mineral phase transformation experiments under CO and H2 atmosphere were carried out for hematite in order to perform kinetic analysis of the reduction process,and the phase transformation and microstructural changes were studied by X-ray diffraction and scanning electron microscopy in order to compare the differences in the mineral phase transformation effects of CO and H 2 and the microstructural evolution patterns. The results showed that the increase of the mineral phase transformation temperature could significantly accelerate the reaction rate in the temperature range of 460 ~ 620 ℃ . In CO atmosphere,the best reation model of the reaction kinetics is shrinkage core model,the integral form is G(α) = 1 - (1 - α)1/ 2,the reation activation energy is 8. 35 kJ / mol,and the finger front factor is 0. 21 min-1. In H2 atmosphere,the best reation model of the reaction kinetics is shrinkage core model. The integral form is G(α) = 1 - (1 - α)1/ 3,the reation activation energy is 20. 73 kJ / mol,and the finger front factor is 4. 37 min-1. The SEM analysis results showed that in the process of mineral phase transformation,adsorption of reducing gas and transformation of hematite occur preferentially at the surface and cracks of hematite particles,and the reaction proceeds gradually inward from the surface and cracks of particles,and the cracks generated by temperature stress and phase-transformation stress provide channels for gas diffusion,which is conducive to the internal diffusion of reducing gas and gas products in the particles and accelerates the reaction. Under the same test conditions,the mineral phase transformation effect of H2 is better than that of CO. The results of the study can provide theoretical support for the regulation of the mineral phase transformation process of hematite under H2 and CO atmosphere.

Key words: mineral phase transformation,isothermal kinetics,conversion rate,reaction rate,microstructure