Gas Processors Association Europe

Renaud Cadours, TOTAL, Paris, France

Removing mercaptans from sour natural gas is a challenge, particularly with more stringent commercial gas specifications. Amines have been extensively used for the removal of H2S and CO2 because of their ability to meet the most severe specifications and their very high acid gas selectivity over hydrocarbons, but have very limited mercaptan removal. Hybrid solvents are more efficient in removing mercaptans, but have poor acid gas selectivity over hydrocarbons, resulting in hydrocarbon losses with the separated acid gases.

Total, with its extensive experience in acid gas removal with amine mixtures, has developed a new hybrid solvent for simultaneous absorption of acid gases and of mercaptans, with limited co-absorption of hydrocarbons. The solvent was selected at the laboratory scale, with a particular attention given to operation related constraints e.g., cost, corrosion, foaming, degradation.  The new solvent’s performance was validated on a pilot rig.

The first industrial scale demonstration occurred at the Lacq sour gas processing plant in one of the amine units due for shutdown in July 2007.  After its success, the new HYSWEET process was implemented in 2008 in one of the two remaining units of the Lacq plant. Half of the gas production is treated with the hybrid solvent, giving higher global mercaptans removal. These results are fully documented in the paper showing that the process is a good contender for the development of new sour gas fields.