Modelling and simulation of an integrated coupled reactor for hydrogen production and carbon dioxide utilisation in an integrated fuel cell power system

• Recirculation of anode off-gases (AOG) from high temperature soli oxide fuel cell significantly improve thermal efficiency of the coupled reforming reactor. • AOG utilization minimize hydrocarbon fuel consumption and lowers CO 2 production. • Combustor temperature and heat flux to the reformer are significantly increased with AOG utilization. • With AOG utilization combined with increased fluid velocity, reformer length could be reduced to achieve the same conversion. In today's world, the need for sustainable energy solutions is paramount to address the ongoing crisis of increasing greenhouse gas emissions and global warming. Industries heavily reliant on fossil fuels must explore alternative energy sources. Hydrogen, with its high heating value and zero direct emissions, has emerged as a promising fuel for the future. Electrolytic hydrogen production has gained significance as it enables demand-side response, grid stabilization using excess energy, and the mitigation of curtailment from intermittent renewable energy sources (RES) such as solar and wind. Advanced combined heat and power (CHP) systems comprise of Solid oxide fuel cell (SOFC) module and a coupled reforming reactor to capture energy contained in the SOFC exhaust gases from SOFC. In present work, 3D CFD model of an experimental coupled reactor used for onsite hydrogen production is developed and implemented into ANSYS Fluent® software. The study is aimed at optimizing the reactor performance by identifying appropriate kinetic models for reforming and combustion reactions. SOFC anode off-gas (AOG) comprising mainly of unconverted hydrogen is combined with methane combustion to enhance thermal efficiency of the reactor and hence the CHP system. Kinetic models for catalytic reforming and combustion are implemented into ANSYS Fluent® through custom-built user defined functions (UDFs) written in C programming language. Simulation results are validated with experimental data and found in good agreement. AOG assisted combustion of methane shows a substantial improvement in thermal efficiency of the system. Improvement in thermal efficiency and reduction in carbon-based fuel demand, AOG utilization contributes to sustainable hydrogen production and curtailment of greenhouse gas emissions.