CO2H2Sabsorption

CO2/H2S absorption refers to the removal of carbon dioxide (CO2) and hydrogen sulfide (H2S) from gas streams by contact with absorbent solvents, typically in countercurrent packed or tray towers. This process is widely used in natural gas processing, biogas cleanup, refinery gas treatment, and syngas purification to meet product specifications and protect downstream equipment.

The most common approaches employ chemical absorption with alkanolamine solvents such as monoethanolamine (MEA), diethanolamine (DEA), and diisopropylethanolamine (MDEA), often with promoters like piperazine. These amines react chemically with CO2 and H2S to form soluble species, enabling high removal efficiency at moderate temperatures. Physical absorption using solvents such as Selexol, Rectisol, or Sulfinol relies on the gas loading of CO2 and H2S at higher pressures or lower temperatures, offering advantages for gas streams with high acid gas partial pressures. Hybrid or modified solvents are also used to balance capacity, selectivity, and regeneration energy.

In operation, the sour gas contacts the lean solvent in an absorber, where CO2 and H2S are absorbed. The rich solvent is then regenerated in a stripper or regenerator by heating, releasing the acid gases for downstream processing (e.g., sulfur recovery via Claus process) and returning lean solvent to the absorber. Design considerations include solvent loading, mass transfer efficiency, energy requirements for regeneration, corrosion risk, and solvent degradation or foaming.

Applications aim to meet product specifications for CO2 and H2S concentrations, minimize corrosion and environmental impact, and enable subsequent processing or capture of removed gases. The choice of solvent system depends on gas composition, desired residual gas levels, and total operating cost.