MEA, Piperazine & Ammonia

The solvent originally proposed for CO2 capture was monoethanolamine (MEA).  High strength piperazine was proposed later, along with ammonia, especially as chilled ammonia in an Alstom Power process.  But MEA has retained its position as the benchmark solvent to which newer  candidates are almost always compared.

All the amines, including MEA and piperazine, are subject to degradation to varying extents when oxygen is present in the gas being treated.  As long as the solvent can be reclaimed, however, this is not a huge issue.  Piperazine is more volatile than MEA but issues associated with amine volatility can be readily overcome by the addition of two or three wash trays at the top of the absorber.  Learn more here and here about these and other solvents for carbon capture