Comprehensive kinetic modeling study of CO2 gasification of char derived from food waste

Chemical kinetics for char originating from biomass devolatization are the essential requirements for studying the thermochemical processes of gasification. While the char kinetics for typical biomass and coal feedstocks are widely available in the literature, the gasification kinetics of char produced from food waste (FW) in CO2 environment are still unknown. Further, the chemical compositions of char and FW are significantly different than those from woody biomass and coal. To address this, an in-depth kinetic study for the CO2 gasification of FW char is presented in this paper. FW is initially pyrolyzed at 800 °C, and the char sample is sieved in the range of 53–100 μm before being gasified in a thermogravimetric analyzer (TGA) under CO2 atmosphere at 850, 900, and 950 °C. The experimental results show that the char conversion rate increases with the reaction times and temperature. Using the TGA data, three different kinetic models, namely, volumetric model (VM), shrinking core model (SCM), and random pore model (RPM), are developed, and their effectiveness is thoroughly investigated. In comparison with the experimental results, SCM shows a high regression at 850 °C, while RPM shows a high regression at 900 and 950 °C. A power law (PL) model is also introduced, and it demonstrates that its regression is higher than 99% at every gasification temperature investigated. Therefore, the PL model most precisely predicts the gasification kinetics, which also agrees well with the RPM