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 firing (RDF waste in the kiln and calciner). Under this scenario, the plant can achieve net-negative emissions of -181.9 kg_CO2/t_clk.

A comparative techno-economic analysis with alternative CO₂ capture technologies, such as post-combustion solvent process, 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.