Optimization of Steam/CO2 Recycle and Energy Use in a Modified Beccs Process

Bioenergy with carbon capture and storage (BECCS) is a carbon-negative energy production technique that is vital to the fulfilling of the 2015 Paris Climate Agreement goal, which seeks to limit the average global temperature increase to less than 1.5℃ above pre-industrial levels by the end of the 21st century. In this study, we investigate the effects of steam and CO₂ recycle on the minimization of heating/cooling utility and the power output of a solid oxide fuel cell in a modified BECCS process which converts biochar into electricity and CO₂ for carbon capture and storage (CCS). Heat integration was performed to optimize the heat exchange network. Thermodynamic models of the biochar gasifier and the operating efficiency of the SOFC were used to analyze and optimize the power output of the process. We found that a steam recycle rate of 0.41 mol H₂O/ mol biochar and a gasifier operating temperature of 1031 K maximizes the SOFC electrical power and minimizes the cost of heating and cooling utilities. The results of this work should give a theoretical upper bound on the overall energy efficiency of a biochar to electricity process using an SOFC.