Thermodynamic insight into the integration of supercritical water gasification and solid oxide fuel cells for waste plastic energy recovery

Supercritical water gasification (SCWG) offers a viable approach for recycling waste plastics by converting them into hydrogen-rich combustible gas. However, the high flammability and explosion risk associated with hydrogen pose critical challenges for practical application. This study proposes an integrated system that couples SCWG with solid oxide fuel cell (SOFC), enabling the direct conversion of hydrogen-rich gas into safe electrical energy. To evaluate the system's performance, a thermodynamic analysis was conducted to examine exergy transfer across different process units. Sensitivity analysis was performed to assess the impact of key process parameters on output performance, while an environmental impact assessment was carried out to determine the system's sustainability. Results indicated that primary exergy losses were attributable to irreversibility arising from thermal transfer, heat dissipation and electrochemical conversion. Among the examined parameters, feedstock concentration was the most significant impact on system output and environmental impact, whereas pressure exhibited a negligible effect, and process temperature had a moderate effect. Finally, a multi-criteria optimization identified the optimal operating conditions as 850 °C, 23 MPa, and 5 wt% feedstock concentration, resulting in a net power output of 197.59 kW with an energy efficiency of 55.16 % and exergy efficiency of 53.52 %.