Analysis of biogas reforming and proton electrolyte membrane fuel cell integrated system

Abstract

This study presents a thermodynamic analysis of biogas reforming process to produce hydrogen for a proton electrolyte membrane fuel cell (PEMFC). Different reforming processes considered are dry reforming, steam reforming and steam reforming of upgraded biogas that carbon dioxide is removed. The objective is to determine an optimal process for hydrogen production from biogas in the PEMFC system. The consumption of energy and the formation of carbon are considered in the hydrogen production. The simulation results show that increases in the steam-to-methane ratio and reformer temperature can improve the hydrogen yield and reduce the carbon formation. The steam reforming of biogas is a suitable process for hydrogen production from biogas due to the lowest energy consumption and complete carbon elimination. The optimal operating conditions are temperature of 800˚C, biogas ratio (CO₂/CH₄) of 0.4, and steam-to-methane ratio (H₂O/CH₄) of 1. From the performance analysis of the PEMFC system integrated with the suitable biogas reforming process in terms of the fuel cell and overall system efficiencies, it is found that when the PEMFC is operated at high temperature, the efficiencies of the PEMFC and overall system can be improved. The performance of the PEMFC system with the installation of a water gas shift membrane unit in the hydrogen purification step is slightly increased, compared with the conventional process, because the high pressure operation of the membrane unit requires high energy consumption.