(39c) Kinetic Studies on the CO2 Gasification of Biochar for Use with SOFCs As a Bioenergy with Carbon Capture and Sequestration (BECCS) Process

Bioenergy with Carbon Capture and Sequestration (BECCS) has the potential to remove carbon dioxide from the atmosphere while producing electricity. We propose a BECCS process to gasify biochar to synthesis gas (primarily carbon monoxide) to power solid-oxide fuel cells (SOFCs), enabling lower-cost separation of the CO₂ and N₂ compared to traditional combustion processes. In this study, we examine the kinetics of CO₂ gasification of biochar (the Reverse Boudouard reaction) using thermogravimetic analysis. Biochar samples were made from waste biomass via pyrolysis of four different feedstocks: pistachio shell, walnut shell, corncob, and pumpkin seed. Isothermal tests were performed at reaction temperatures between 875-950°C, within typical operating temperatures of SOFCs. Walnut and corncob were found to be the most reactive of the tested feedstocks. Mass conversion data was fitted against various gas-solid reaction models, and the random pore model (RPM) was found to describe the reaction rate the best. However, a modification to the RPM, based on the catalytic effects of the ash on the Reverse Boudouard reaction, was more successful in fitting the data. This indicates the importance of the ash content of the biochar, giving a useful criterion to judge the viability of other potential feedstocks.