Chemical absorption / desorption process

Several solvents are available for the CO₂ capture by chemical absorption. The most used solvent is based on the primary amine monoethanolamine (MEA) or/and secondary/tertiary amines blends with, most of the time, addition of promoters like piperazine. From its earlier experience with CO₂ capture installations and from its know-how in gas liquid absorbers, ANDRITZ will select the most appropriate solvent blend for a given CO₂ concentration in the flue gas and a targeted removal rate. If an alternative solvent is required, ANDRITZ can also design a solution based on the customers´ preference as an EPC-contractor.

As indicated in the process flow sheet, for an amine-based solvent, the CO₂ rich flue gas from the industrial process first enters a pre-scrubber where it is, on one hand, cooled down (or quenched) and, on the other hand, further treated to remove certain contaminants (acid gases, particulate matter, …) which would degrade the solvent.

The flue gas then passes into the absorption unit (or absorption column) where the CO₂ is continuously absorbed (or scrubbed) by the solvent. The absorption process utilizes the reversible chemical reaction of CO₂ with the solvent. The CO₂ lean and clean flue gas leaves the top of the absorber towards the stack. The CO₂ rich solvent is transferred to the desorption unit (or stripper). Hot and partly fresh solvent from the reboiler enters the desorption unit causing the CO₂ to be stripped out of the solvent. As a result, a pure CO₂ stream is collected at the top of the stripper. The CO₂ lean solvent is then being regenerated and circulated back to the absorber. The pure CO₂ stream is further processed, to the required purity, before being compressed, transported or stored for future use (Enhance Oil Recovery, chemical synthesis, geological storage, …).

The energy requirements for the regeneration of the solvent (heat of desorption, sensible heat and heat of vaporization) and the proper energy integration of the CO₂ capture unit into the industrial process are key features of ANDRITZ CO₂ capture offering. Depending on the CO₂ concentration in the flue gas, the required amount of CO₂ to be captured and other site-specific conditions (steam availability, steam pressure, on-site CO₂ storage, …), ANDRITZ will design a unique solution securing the lowest operating costs for removing the CO₂ from the flue gas.