Process Integration of Post-combustion CO2 Capture with Li4SiO4/Li2CO3 Looping in a NGCC Plant

Abstract

Lithium-based sorbents require lower energy requirements for regeneration than other more studied and well known materials such as those used in the calcium looping process; however, thermodynamic assessments of these sorbents in power plants are currently missing. Accordingly, in this work, a thermal integration study of a post-combustion CO2 capture plant using regenerable lithium-based high temperature solid sorbents into a natural gas combined cycle (NGCC) plant has been conducted. A process simulation study has been completed for integration of a Li4SiO4/Li2CO3 looping cycle downstream of the gas turbine in a NGCC plant. A comparison between this technology and a chemical absorption capture plant with two different solvents, namely conventional monoethanolamine (MEA) and a second generation solvent (CESAR-1), has been established based on the European Benchmarking Taskforce (EBTF) methodology. The integration of post-combustion CO2 capture in the power plant results in a decrease of its net electric efficiency. However, capture with Li4SiO4 sorbents decreases the efficiency by 6.9 percentage points, which is lower than the 8.4 and 7.5 percentage points decrease obtained when CO2 capture is based on chemical absorption with MEA and CESAR-1 solvents, respectively. Hence, Li4SiO4/Li2CO3 looping is a promising alternative to amine-based systems when integrated into NGCC plants. Furthermore, additional improvements could be achieved through improved capture process heat integration and optimization.