Thermal performance and reduction kinetic analysis of cold-bonded pellets with CO and H2 mixtures
来源期刊：International Journal of Minerals Metallurgy and Materials2018年第7期
论文作者：Rong-rong Wang Jian-liang Zhang Yi-ran Liu An-yang Zheng Zheng-jian Liu Xing-le Liu Zhan-guo Li
文章页码：752 - 761
摘 要：Cold-bonded pellets, to which a new type of inorganic binder was applied, were reduced by H2–CO mixtures with different H2/CO molar ratios（1:0, 5:2, 1:1, 2:5, and 0:1） under various temperatures（1023, 1123, 1223, 1323, and 1423 K） in a thermogravimetric analysis apparatus. The effects of gas composition, temperature, and binder ratio on the reduction process were studied, and the microstructure of reduced pellets was observed by scanning electron microscopy–energy-dispersive spectrometry（SEM-EDS）. The SEM-EDS images show that binder particles exist in pellets in two forms, and the form that binder particles completely surround ore particles has a more significant hinder effect on the reduction. The reduction equilibrium constant, effective diffusion coefficient, and the reaction rate constant were calculated on the basis of the unreacted core model, and the promotion effect of temperature on reduction was further analyzed. The results show that no sintering phenomenon occurred at low temperatures and that the increasing reaction rate constant and high gas diffusion coefficient could maintain the promotion effect of temperature; however, when the sintering phenomenon occurs at high temperatures, gas diffusion is hindered and the promotion effect is diminished. The contribution of the overall equilibrium constant to the promotion effect depends on the gas composition.
Rong-rong Wang1，Jian-liang Zhang1，Yi-ran Liu2，An-yang Zheng1，Zheng-jian Liu1，Xing-le Liu1，Zhan-guo Li1
1. School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing2. School of Chemical Engineering, University of New South Wales
摘 要：Cold-bonded pellets, to which a new type of inorganic binder was applied, were reduced by H2–CO mixtures with different H2/CO molar ratios（1:0, 5:2, 1:1, 2:5, and 0:1） under various temperatures（1023, 1123, 1223, 1323, and 1423 K） in a thermogravimetric analysis apparatus. The effects of gas composition, temperature, and binder ratio on the reduction process were studied, and the microstructure of reduced pellets was observed by scanning electron microscopy–energy-dispersive spectrometry（SEM-EDS）. The SEM-EDS images show that binder particles exist in pellets in two forms, and the form that binder particles completely surround ore particles has a more significant hinder effect on the reduction. The reduction equilibrium constant, effective diffusion coefficient, and the reaction rate constant were calculated on the basis of the unreacted core model, and the promotion effect of temperature on reduction was further analyzed. The results show that no sintering phenomenon occurred at low temperatures and that the increasing reaction rate constant and high gas diffusion coefficient could maintain the promotion effect of temperature; however, when the sintering phenomenon occurs at high temperatures, gas diffusion is hindered and the promotion effect is diminished. The contribution of the overall equilibrium constant to the promotion effect depends on the gas composition.
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