Post-combustion CO2 capture process by absorption-regeneration applied to cement plant flue gases: techno-economic comparison between the use of a demixing solvent technology and an advanced process configuration

The implementation of CCUS (Carbon Capture Utilization and/or Storage) appears as a necessity to significantly reduce the CO2 emissions from the cement industry. With the purpose of reducing the cost of the post-combustion CO2 capture process by absorption-regeneration applied to cement plant flue gases, two innovative solutions were compared on techno-economic aspects, namely: (i) the implementation of an advanced process configuration (Rich Vapor Compression (RVC) with Inter-Cooled Absorber (ICA) and Rich Solvent Splitting and Preheating (RSSP), with methyldiethanolamine (MDEA) – piperazine (PZ) blend); and (ii) the use of a demixing process (diethylethanolamine (DEEA) + methyl-amino-propylamine (MAPA) blend as case study) allowing, thanks to the separation of the two immiscible phases formed after the CO2 absorption, to regenerate a lower solvent flow rate with a higher CO2 loading. These two solutions were compared to a reference case (conventional process configuration using monoethanolamine (MEA) 30 wt.%) both in terms of operating (OPEX) and capital (CAPEX) costs. These different configurations were implemented in Aspen PlusTM considering as case study a BAT (Best Available Technology) cement plant (3000 tons of clinker per day) generating a flue gas containing 20 mol.% of CO2. The configurations were simulated considering the same calculation hypotheses and the same study boundaries (from the flue gas cooling to the CO2 compression), allowing to perform a relevant comparison. It was pointed out that the solvent regeneration energy of the advanced process configuration and of the demixing system (namely 1.97 GJ/tCO2 and 2 GJ/tCO2) are quite similar, corresponding to more than 40% savings in comparison with the MEA process (3.36 GJ/tCO2). While the addition of a decanter in the demixing system does not impact too much the equipment costs (1.6% increase in comparison with MEA system), the advanced process leads to an increase of 8.8% of these costs (e.g. addition of a compressor and exchangers for the RVC and RSSP). Globally, the implementation of an advanced process configuration (48.72 €/tCO2) or a demixing system (47.08 €/tCO2) leads respectively to a decrease of 23.7% and 26.3% of the total CO2 capture costs in comparison with the MEA conventional process (63.88 €/tCO2). These solutions represent therefore interesting options to significantly reduce the cost of the post-combustion CO2 capture process applied to cement plant flue gases even if the implementation of a demixing system is possible with a lower CAPEX than with the advanced configuration investigated.