Amine scrubbing for CO2 capture technology was first evaluated in 1991. Although the technology was used to gas- and coal-fired plants on small scale in the early 1980s, it was not so well appreciated due to the potential high energy consumption and high cost. At present, substantial research has been carried out to finally industrialise this technology, due to high efficiency to separate CO2 from industrial flue gases, and it is considered the most economical technology for postcombustion CO2 capture - yet considered the most expensive one. In fact, amine scrubbing will probably be the dominant technology for CO2 capture for the upcoming years.
The process considers the absorption of CO2 from flue gas, or combustion gas, at ambient temperature into a solution containing water and the organic solvent amine. A concentration of the amine between 20-30 vol.% is commonly considered. The solvent is regenerated by stripping with water vapour at temperatures between 100 - 120 °C, and the water is condensed from the stripper vapour, leaving pure CO2 that can be compressed a pressure between 100 - 150 °C for geological sequestration, or further utilisation.
The most studied amine is monoethanolamine (MEA), but many others can be used, such as piperazine (PZ), diethanolamine (DEA), N-methyldiethanolamine (MDEA), and 2-amino-2-methyl-1-propanol (AMP). However, the high temperatures can cause thermal degradation of the amines and losses through evaporation. Poisoning from SOx and NOx gases can also occur. Amines are also corrosive and harmful to the environment. For these reasons, research continues into improving amine scrubbing.
The regeneration of the amine after the amine-scrubbing process is an important aspect of the cost-effectiveness of the system. As the regeneration is typically performed at temperature around 100 °C, the process uses a high amount of energy. Therefore, decreasing process energy consumption is the main challenge. Researchers are trying to save energy in the absorption process by either increasing the absorption capacity of the absorbent, thus reducing the amount of liquid to be regenerated, or by lowering the regeneration process energy requirement.
Amine scrubbing is a very mature technology, but before being utilised at an industrial scale, substantial research is still necessary. In case you want to know more here there are some interesting links: Is Carbon Capture Storage About To Have Its Day?
Solvents for Carbon Dioxide Capture
Review of amine emissions from carbon capture systems
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