Rectisol

Rectisol is a gas purification process used to remove CO2, H2S and other acid gases from natural gas, synthesis gas (syngas), and refinery or petrochemical feeds. It is a physical absorption process that operates at low temperatures, using chilled methanol as the solvent. The low-temperature operation enhances selectivity for CO2 and H2S, allowing very low residual acid gas contents.

In typical flow, the feed gas is cooled and contacted with circulating methanol in a rich solvent absorber. Acid gases are preferentially absorbed into the methanol, while the sweet gas exits. The laden solvent is then circulated to a regeneration stage where it is heated and, often, depressurized in a stripping column to release CO2 and H2S. The regenerated methanol is cooled and recycled to contactor. The acid gas stream is often sent to sulfur recovery (Claus process) or other disposal. Water removal can be incorporated upstream or within the solvent system.

Rectisol installations can consist of multiple absorption and regeneration trains to handle varying feed compositions and to maximize CO2/H2S removal. Compared with other amine or solvent processes, Rectisol offers high tolerance to water and sulfur compounds and the ability to achieve very low acid gas contents, but it requires substantial refrigeration capacity and careful solvent management to control methanol losses and corrosion.

Historically developed and widely implemented in natural gas and chemical production, Rectisol remains one of the standard acid gas removal options, alongside other solvent-based processes such as Selexol and conventional amines.