Steam gasification of Miscanthus derived char: the reaction kinetics and reactivity with correlation to the material composition and microstructure

Abstract

This work presents a comprehensive study on the steam gasification kinetics and reactivity of Miscanthus chars (MC) prepared at different temperatures (600 °C, 800 °C and 1000 °C) with the correlations to their composition and microstructure. The results showed that the order of gasification reactivity was MC600 > MC800 > MC1000, and the microcrystalline structure and the content of inherent alkali and alkaline earth metals in the MC were the main factors affecting their reactivity under steam gasification. The reactivity also increased with the increase of gasification temperature, and the impact of gasification temperature on the reactivity of MC was greater than that of the char production temperature. High heating rate could also effectively promote the gasification reactivity of MC. The kinetics of the steam gasification process were analyzed by different modelling methods. The Random Pore Model (RPM), among the three methods compared, was the most suitable one to describe the kinetics of isothermal gasification process, of which, the activation energies were in the range of 176–203 kJ/mol with a good kinetic compensation effect between activation energy and pre-exponential factor. The master-plots analysis proved that the F 2 mechanism was suitable for describing the early stage (X < 50%) of the MC gasification reaction, and the D 1 mechanism was suitable to the late stage (X > 50%) of the MC gasification process.