Sour gas treatment

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Sour gas treatment

Sour gases are those which contain hydrogen sulphide (H₂S) in excess of 100 parts per million (ppm) or carbon dioxide (CO₂) levels greater than 2%.
Sour gas accounts for one third of total gas reserves. These gases must be treated before they can be liquefied or marketed. The challenge is to improve treatment procedures in order to reduce costs and improve the energy efficiency of these gases.

Improving treatment processes means:

reducing the sulphur (S) content of sour gases. Standards for sour gas impose a maximum sulphur content of 30ppm and a maximum hydrogen sulphide level of 4 ppm,
adding value to sour gases: some fields have very high proportions of H₂S or CO₂. CO₂ emissions are expensive due to carbon taxation, the sulphur market is in a slump and some fields are in areas where sulphur exportation is not viable. The challenge is to develop economically viable ways of reinjecting H₂S and CO₂ into underground reservoirs or finding other ways of adding value to these elements.

Research areas

IFP’s teams are studying different ways of improving the treatment of sour gases. These research projects should improve the existing amine treatment procedures which are traditionally used to sweeten gases.

Eliminating sulphur carbonyl (COS)

IFP is examining several ways of improving COS elimination, for example by identifying a specific activator or developing new absorber liners. The goal is to obtain an overall sulphur content in compliance with required specifications after passage through the amine unit. These procedures would avoid the need for post treatment.

Eliminating mercaptans

IFP teams are developing a new procedure to eliminate mercaptans, which add to the total sulphur. As traditional amine treatments have very little impact on mercaptans, the new IFP process will significantly reduce the cost of treating sour gases.

Developing new absorber liners

IFP aims to develop new absorber liners, which will:

improve H₂S/CO₂ selectivity,
provide improvements with regard to absorber size.

Improving the precision of software tools

IFP research also covers the thermodynamic properties and kinetics of reactions between amines and sour gases. The goal is to improve the precision of software packages used to size treatment units.

Project with industrial partner

Total

IFP and Total have developed the SPREX® process, which pre-treats acid gases with a high H2S content. This cryogenic procedure creates pressure and temperature conditions so that the H2S gathers in liquid form at the base of the column. As a result, it is easy to reinject.

Economic studies have shown that the SPREX® process, when used before standard amine treatment procedures, can reduce investment and operating costs by 5 to 25% depending on the circumstances. An 18-month pilot project at the Lacq site confirmed these results.