Post-combustion CO2 capture by absorption-regeneration process: how reducing its energy consumption?

The implementation of Carbon Capture, Utilization and/or Storage (CCUS) process chain appears as a necessity to reduce the CO2 emissions from different industrial sectors, especially “process CO2 emissions” such as for example in the cement, lime, glass and steel industries. Focusing on the most technologically mature carbon capture process, namely the post-combustion absorption-regeneration process using amine(s)-based solvents, one of the major obstacles for its implementation is still its cost and especially its very high energy consumption for the solvent regeneration step. For addressing this issue, different energy reduction pathways were investigated experimentally and/or through the development of Aspen PlusTM simulations. Upstream of the process, the possibility to increase the flue gas CO2 content by applying partial oxy-combustion and/or flue gas recirculation was studied. Inside the process, more efficient and innovative mixtures of solvents such as demixing solutions were envisaged. Moreover, at the configurational level, advanced process configurations were simulated and compared on a techno-economic point of view. Among the results, it was shown that implementing an advanced process configuration (e.g. Inter-Cooling Absorber + Rich Vapor Compression + Rich Solvent Splitting and Preheating, with methyldiethanolamine (MDEA) + piperazine (PZ) as a solvent), such as the use of a demixing process (e.g. composed of diethylethanolamine (DEEA) and methyl-amino-propylamine (MAPA)), are very efficient pathways for reducing the thermal energy demand of the process (i.e. up to 40% savings in comparison with a conventional process using monoethanolamine (MEA)). In terms of CAPEX, the advantage of the demixing technology was highlighted as it allows to achieve very high energy savings but with a more limited CAPEX investment than with a more complex process configuration. The research for new demixing solvents, less volatile and degradable than DEEA+MAPA blends, but keeping similar energy performances, is still under progress.