Summary
Removing mercaptans from sour natural gas has always been considered a
challenge. This is becoming an even more important issue with the global trend
toward more-stringent specifications for commercial gases.
Amines have been used extensively because of their ability to meet the most
severe H2S and CO2 specifications and their very high
acid-gas selectivity over hydrocarbons, but they present very limited
mercaptans-removal performances. They require an additional treatment step to
achieve the total sulfur-content specification in the exported gas. Hybrid
solvents are more efficient in removing mercaptans but have the disadvantage of
poor acid-gas selectivity over hydrocarbons, resulting in hydrocarbon losses
with the separated acid gases.
Total, taking advantage of its extensive knowledge and experience in
acid-gas removal with amine mixtures, has developed a new proprietary
hybrid-solvent formulation allowing simultaneous absorption of acid gases and
of mercaptans, with limited coabsorption of hydrocarbons. (The new hybrid
solvent process is Total's proprietary process known as the HySWEET® process,
which is a registered trademark.) 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 acid-gas- and
mercaptans-removal performances were then validated on a pilot rig.
The performance of the process has been assessed for several field
applications and compared with the performances of conventional amine
processes. This allowed evaluating the potential gain achievable by the
implementation of the new hybrid solvent. The study identifies the application
cases for which the new hybrid solvent will allow an economic and complete
mercaptan removal without any additional treatment and identifies the
perspective reduction of these additional treatments for the other cases.
Besides an economical mercaptan removal, the new hybrid solvent allows a
significant reduction in the energy consumption.
The results of the technoeconomic evaluation of the process have been
confirmed during the first successful industrial application at the Lacq
sour-gas plant in 2008. Half of the gas production is now treated with the
hybrid solvent, allowing the plant to achieve high global mercaptans
removal.
These results are fully documented in the paper, demonstrating that the
newly developed process is a good contender for the development of new sour-gas
fields to achieve the increasingly stringent commercial gas specifications.
© 2011. Society of Petroleum Engineers
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History
- Original manuscript received:
10 February 2010
- Meeting paper published:
8 December 2009
- Revised manuscript received:
11 November 2010
- Manuscript approved:
8 January 2011
- Published online:
26 October 2011
- Version of record:
16 December 2011
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