Emergy evaluation of the integrated gasification combined cycle power generation systems with a carbon capture system

Abstract

An Integrated Gasification Combined Cycle (IGCC) power generation system has a significant effect on improving resource utilization efficiency. Carbon capture and storage (CCS) has been widely adopted to control greenhouse gas emissions. The integration of the two systems can further reduce CO2 emissions but cause elevated investment costs. As an effective tool to evaluate resource utilization efficiency and environmental impact, emergy analysis on coal and biomass based IGCC power generation systems with/without CCS is conducted in this paper. The coal based IGCC systems are simulated in Aspen plus to obtain the electricity generated under different CCS scales. For other systems, the data for emergy evaluation are from references. The sustainabilities under different CO2 tax values are compared. The factors impacting the sustainabilities are discussed. The results show that when CCS is not considered, all IGCC systems are superior to coal and biomass direct-fired systems in terms of sustainability. After CCS is integrated, the sustainability of biomass based IGCC system is still higher than that of biomass direct-fired systems, while coal based IGCC systems are less sustainable than coal direct-fired systems under low CO2 tax. The sustainabilities of Texaco-IGCC systems increase with CCS scales when CO2 tax is higher than 0.0220 $/kg, emphasizing CCS at a larger scale. For the Shell-IGCC systems, a higher CO2 tax (0.3880 $/kg) is preferred for the promotion of large scale CCS. In the scenario that the cost emergy transformity improves, the CO2 tax value at the point of sustainabilities reversal will decrease.