Integration of gas switching combustion and membrane reactors for exceeding 50% efficiency in flexible IGCC plants with near-zero CO2 emissions

Abstract

• Gas switching combustion and membrane reactors are integrated in an IGCC plant. • The proposed plants produce flexible electricity/H 2 with CCS to balance renewables. • IGCC benchmarks with/without CCS incorporate hot gas clean-up and H-class turbines. • Electric/H 2 LHV efficiencies up to 50.3%/62.4% with >98% CO 2 capture are achieved. • The energy penalty is less than 2%-points relative to the unabated IGCC plant. Thermal power plants face substantial challenges to remain competitive in energy systems with high shares of variable renewables, especially inflexible integrated gasification combined cycles (IGCC). This study addresses this challenge through the integration of Gas Switching Combustion (GSC) and Membrane Assisted Water Gas Shift (MAWGS) reactors in an IGCC plant for flexible electricity and/or H 2 production with inherent CO 2 capture. When electricity prices are high, H 2 from the MAWGS reactor is used for added firing after the GSC reactors to reach the high turbine inlet temperature of the H-class gas turbine. In periods of low electricity prices, the turbine operates at 10% of its rated power to satisfy the internal electricity demand, while a large portion of the syngas heating value is extracted as H 2 in the MAWGS reactor and sold to the market. This product flexibility allows the inflexible process units such as gasification, gas treating, air separation unit and CO 2 compression, transport, and storage to operate continuously, while the plant supplies variable power output. Two configurations of the GSC-MAWGS plant are presented. The base configuration achieves 47.2% electric efficiency and 56.6% equivalent hydrogen production efficiency with 94.8–95.6% CO 2 capture. An advanced scheme using the GSC reduction gases for coal-water slurry preheating and pre-gasification reached an electric efficiency of 50.3%, hydrogen efficiency of 62.4%, and CO 2 capture ratio of 98.1–99.5%. The efficiency is 8.4%-points higher than the pre-combustion CO 2 capture benchmark and only 1.9%-points below the unabated IGCC benchmark.