Rectisol and Selexol

 

Rectisol is an acid gas which uses a methanol solvent as a means of removing CO2 from a gas stream. Rectisol has a major advantage in that it removes COS (Carbonyl Sulfide) and other acid gases while preserving the hydrogen and carbon monoxide in the synthesis gas. Rectisol is a relatively flexible method of removing carbon dioxide and other acid gases during the gasification process.

Rectisol can reduce the syngas sulfur content to as low as 2 ppmvd (parts per million by volumetric dry) in the treated gas. However, due to the required refrigeration to cool the methanol, Rectisol can be quite expensive (EPA study 4-9).

 

Selexol is another type of solvent which can absorb CO2 and thus separate it from the gas stream. Selexol has an advantage over Rectisol in that it does not require refrigeration and is therefore less costly, but Selexol cannot achieve the same low Sulfur concentrations as Rectisol. Selexol is overall a less complex process as the Rectisol process.