Ultra-low emissions cement production via hybrid oxyfuel-solvent CO2 capture

This paper proposes and evaluates a hybrid process for decarbonizing cement clinker manufacturing that combines partial oxy-fuel combustion in the pre-calciner with post-combustion CO2 capture (PCC) using monoethanolamine (MEA)-based chemical absorption. Unlike traditional CCS approaches, this design aims to leverage the synergy between the two processes: partial oxyfuel calcination to efficiently tackle most of the direct CO2 emissions from CaCO3 calcination and solvent-based post-combustion CO2 capture for processing both the rotary kiln flue gas and the unrecovered CO2 from partial oxyfuel (i.e., the CO2 purification vent stream). The study examines different designs and integration parameters for implementing this CO2 capture solution in existing cement plants, identifying a configuration with 50% oxygen enrichment and a 3+3-stage preheater as the best balance between retrofit complexity and thermal efficiency. A key feature of this hybrid architecture is its thermal autonomy: heat integration analysis shows that waste heat recovered from the cement plant, especially exhaust air from the clinker cooler, can fully meet the solvent regeneration requirements, eliminating the need for auxiliary steam generation even at capture rates above 99%. Furthermore, the research highlights the decarbonization potential of combining this hybrid capture process for cement with 100% alternative fuel (RDF waste) firing (in the kiln and calciner). Under this scenario, the plant can achieve net-negative emissions of -181.9 kgCO2/tclk. A comparative techno-economic analysis with alternative CO2 capture technologies, such as post-combustion solvent process (conventional or electrified), full-oxyfuel, and partial oxyfuel, identifies the proposed hybrid process as a highly competitive strategy for deep decarbonization of cement making. Although partial oxyfuel configurations present marginally lower CO2 avoidance costs, the hybrid process features a CO2 avoidance rate close to 100% (or greater in case of biomass/waste fuel usage in the calciner), effectively coping with a high carbon tax scenario.