Energy and exergy analysis of MSW-based IGCC power/polygeneration systems

Highlights: • Three designs of MSW-based IGCC power/polygeneration systems are addressed. • The CaLG process promotes the DME yield and enhances outlet CO₂ concentration. • The net energy efficiencies of three designs are estimated about 14.1%~25.5%. • The overall exergy efficiencies of three designs are estimated about 45.79%~ 50.95%. • The MSW gasification is diagnosed to improve the overall exergy efficiency. Since municipal solid waste (MSW) is a negatively priced, abundant, and essentially renewable feedstock, energy recovered from MSW is a useful technology to reduce the consumption of fossil fuels, and also reduces the expenses needed to dispose of MSW. Three configurations of MSW-based IGCC power system (Design 1), MSW-based IGCC polygeneration system (Design 2), and CaO-based IGCC polygeneration system (Design 3) are proposed. Design 1 uses a combination of an identified MSW gasifier, an integrated intermittent chemical-loop air separation (IICLAS), and Rankine and Brayton cycles to generate electricity and achieve the high concentration of CO₂ emissions around 93.3%~94.7%. The process for co-production of DME and MeOH in Design 2, which replaces the Rankine cycle in Design 1, could increase the net energy efficiency of Design 1 by 71.6%, but the total CO₂ emissions from Design 2 are merely 7.97% of Design 1. The calcium looping gasification (CaLG) process in Design 3, which replaces the MSW gasifier in Design 2, could increase the production rate of DME of Design 2 by 12.5%. The CO₂ concentration from the calcinator in Design 3 is higher than CO₂ concentration in flue gas from Designs 1 and 2 by 2.0%~3.5%. Through exergy analysis, the overall exergy efficiency of Design 3 is lower than Designs 1 and 2 by 3.2%~10.1% due to the exergy destruction rate and ratio in the gasification zone of Design 3 higher than other designs. The GaLG process could increase the DME yield as well as the outlet CO₂ concentration, but this approach design induces a higher exergy loss.