Kinetic study on the CO2 gasification of biochar derived from Miscanthus at different processing conditions

The CO2 gasification is an emerging process that can improve the quality of syngas and enhance the CO2 circular utilisation. This paper presents a comprehensive analysis on the CO2 gasification of Miscanthus-derived biochar produced at varying processing conditions. The gasification behaviour, kinetics and biochar reactivity were investigated and the correlations to the biochar preparation conditions and their microstructure were developed. Results showed that the preparation and gasification reaction conditions had major impact on the biochar reactivity. The order of significance that affected the biochar reactivity was gasification temperature, biochar preparation temperature and processing atmosphere. Increasing heating rate could enhance the biochar reactivity, while increasing preparation temperature could reduce the reactivity in N2 and He atmosphere. At 600 and 1000 °C, He atmosphere resulted in the most activity biochar, followed by N2 and CO2. At 800 °C, CO2 atmosphere gave the highest reactivity, followed by He and N2. The Activation Energy (E) of gasification reaction calculated by the Hybrid Model (HM) was mainly in the range of 78.09–212.46 kJ mol−1. The E decreased with the increase of carbon conversion rate. A great kinetic compensation effect between E and A was identified during the CO2 gasification process