HySWEET® Process: An Improvement in Energy Efficiency

Abstract

Abstract Removing mercaptans from sour natural gas has always been considered as a challenge. This is becoming an even more important issue with the global trend towards more stringent commercial gas specifications. Amines have been extensively used because of their ability to meet the most severe H2S and CO2 specifications and their very high acid gas selectivity over hydrocarbons, but present very limited mercaptans removal performances. An additional treatment step is required to achieve the total sulfur specification in the exported gas. Hybrid solvents are more efficient in removing mercaptans, but may have the disadvantage of poor acid gas selectivity over hydrocarbons, resulting in hydrocarbon losses with the separated acid gas. Total, taking advantage of its extensive know-how and experience in gas sweetening with amine mixtures, has developed a new hybrid solvent formulation allowing simultaneous absorption of acid gases and of mercaptans, with limited co-absorption of hydrocarbons. The HySWEET® process using the new hybrid solvent is in operation at the Lacq plant in France since 2008. More than half of the gas production is now treated with this new hybrid solvent, allowing to achieve not only higher global mercaptan removal but also to reduce the overall energy consumption compared to the use of the HiLoadDEA process. This paper emphasis on the energy gain that can be achieved by using the HySWEET® process compared to the conventional HiLoadDEA process. A pilot plant study was carried out to compare the regeneration heat duty requirement of the new HySWEET® process with that of the HiLoadDEA process. This study has actually demonstrated that under similar conditions the HySWEET® solvent requires up to 15 % lower reboiler heat duty compared to the conventional amine solvent. These results have been confirmed during industrial operation of the HySWEET® process at the Lacq plant. This paper also reminds the results of the techno-economic study carried out to evaluate the potential gain achievable by the implementation of the new hybrid solvent. The study lead to identify the application cases for which the new hybrid solvent will allow an economic and complete mercaptan removal without any additional treatment, and a perspective of reduction of the additional treatments for the other cases.