Energy and exergy analyses of CCHP (combined cooling, heating and power) system based on co-firing of biogas and syngas produced from biomass

Abstract

This paper focuses on a CCHP (Combined Cooling, Heating and Power) system based on co-firing in an Internal Combustion Engine (ICE) of biogas from anaerobic digestion and syngas produced by biomass gasification. From an energy perspective, in order for the mixture to make sense, a relationship setting the threshold percentage of methane in the biogas has been established. Gasification and Organic Rankine Cycle (ORC) models developed in Aspen Plus software and thermodynamic modeling of the Internal Combustion Engine (ICE) have been validated by comparison with experimental work conducted by other authors. The results show a decrease in energy efficiency with an increase in the percentage of methane in biogas and the mass ratio of the mixture. For extraction rates of 80 % and 90 %, respectively, exergy efficiency increases with an increase in the percentage of methane in biogas and the mass ratio of the mixture. Additionally, an increase in gasification temperature improves the efficiencies, while an increase in biogas temperature reduces them. The ICE is a significant source of exergy destruction.

Keywords

• Biomass
• Gasification
• Biogas
• CCHP
• Aspen plus
• Co-firing