Energy and exergy analysis of power-hydrogen cogeneration system fueled by biogas

This paper aims to examine a combined heating, power, and hydrogen system production using biogas energy. Biogas steam and dry reforming method are designed based on equilibrium data with the EES program. The results show that biogas has two principal roles for combustion and reforming processes simultaneously. The heating energy produced from biogas causes the reforming of biogas and improves the system efficiency by 74%. The maximum exergy efficiency and hydrogen production are obtained at 58.34% and 0.11-0.83 kg/s, respectively. The results also show that the combustion chamber has the highest exergy destruction by about 51% when the amount of electric power plant is considered between 5 to 40 MW. A parametric study for optimizing hydrogen production analyzes the key parameters. The optimal scenarios are when CO2/CH4=0.50-0.66, H2O/CH4=2-3.6, and the reforming temperature is 965-1036K. The conversion of methane and carbon dioxide shows the environmental effect of decreasing greenhouse gases. At 965K or higher, methane and carbon dioxide conversion rates reach 97% and 86%, respectively. This paper aims to develop a novel methodology for identifying thermodynamic cycle conditions and reforming processes only by use of biogas as the source of energy.