Experimental Analysis of Intrinsic Kinetics and Rate Profiles for Coal Char Conversion under Different Atmospheres

This study focuses on determining intrinsic kinetic parameters and interpreting and simulating the rate profile. First, reactivity of coal char prepared at different temperatures was analyzed. Results showed that when coal pyrolysis temperature increases, coal char reactivity decreases; however, activation energy for coal char conversion does not always increase. Next, the weight loss process in non-isothermal conversion was discussed, and results illustrated that the weight loss mechanisms differ in each stage. The weight loss at the second stage was slightly influenced by residual volatile matter and gas diffusion, and the activation energy at this stage was close to an intrinsic value. Meanwhile, discussions on the effects of kinetic analysis methods in determining activation energy showed that Friedman and advanced isoconversional methods can obtain a true activation energy profile, whereas the Kissinger-Akahira-Sunose method was unsuitable. The rate profiles of isothermal conversion were then studied. The results demonstrated that occurrence of a maximum was an inherent feature but the gas change operation could shift or even cover up the true position of the maximum. Moreover, an increase in particle temperature could intensify the maximum value but slightly shift its position. Finally, an intrinsic reaction model that combines random pore model and the derived intrinsic kinetic parameters properly reproduced the rate profile of isothermal conversion (e.g., maximal conversion deviation was less than 5%).

Automated summary

This study focuses on determining intrinsic kinetic parameters and interpreting and simulating the rate profile of coal char. It analyzes the reactivity of coal char at different temperatures, discusses the weight loss process in non-isothermal conversion, and studies the effects of kinetic analysis methods. It also examines the rate profiles of isothermal conversion and the influence of particle temperature. Finally, an intrinsic reaction model is developed to reproduce the rate profile of isothermal conversion accurately.