Catalytic Kinetics and Mechanisms of KCl with Different Concentrations on Gasification of Coal Char

Abstract

In this work, the influence of KCl concentration on the gasification characteristics of lignite coal char between 800–1100 °C is studied through the experiments of temperature programmed gasification and isothermal gasification using a thermogravimetric analyzer. The gasification kinetics, characteristic parameters, and the reaction mechanism of catalytic gasification is explored using the random pore model (RPM). In view of temperature programmed gasification, the gasification rate of coal char is relatively slow when the temperature is below 700 °C, and only when the temperature is higher than 700 °C, the gasification starts to accelerate. Results show that with the existence of a catalyst, the temperature required for gasification reaction is reduced and the gasification reaction rate is increased. Furthermore, the higher concentration of KCl leads to the shorter half reaction time, the higher gasification rate, and the stronger catalysis. In addition, the activation energy of AW-char (the char from acid-washed coal) is the highest, while the activation energy and the energy level required for the gasification reaction are reduced by adding KCl. Based on the analysis of the catalytic mechanism, it is found that the unified mechanism of catalytic gasification of alkali and alkaline earth metals is applicable for the KCl catalysis on coal char gasification.