CO2scrubbing

CO2 scrubbing is the process of removing carbon dioxide from gas streams or ambient air to reduce CO2 levels for process efficiency, product purity, or life-support needs. It is used in industrial gas purification, post-combustion capture, indoor air quality control, and closed-environment systems such as submarines, spacecraft, and diving devices.

The main approaches are chemical absorption, physical absorption, and solid sorption. In chemical absorption, CO2 reacts with alkaline solvents such as aqueous amines (for example monoethanolamine or diethanolamine) and is later released by heating for solvent regeneration. Other chemical systems use potassium carbonate or calcium-based sorbents. Physical absorption uses solvents whose gas solubility increases with pressure, such as Selexol or Rectisol, and may be complemented by membranes or adsorption processes. Regeneration occurs by reducing pressure or increasing temperature, returning CO2 to a concentrate stream for sequestration or utilization.

Solid sorbents include amine-functionalized resins, zeolites, and activated carbons. They capture CO2 and are regenerated by heating or pressure swing adsorption. Lime-based scrubbing, using calcium hydroxide (lime) or soda lime, remains common in life-support and diving systems; CO2 reacts to form calcium carbonate and water. These systems are conceptually simple but require management of capacity, moisture, and byproducts.

Regeneration energy and process integration are major considerations in industrial applications. CO2 scrubbing is employed to reduce emissions from power plants, to treat natural gas, and to provide breathable air in enclosed environments. Safety and environmental concerns include solvent degradation products and potential emissions of amines or other additives.