Process For Improved Mercaptan Removal

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 specifications for commercial gases. 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. 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 know-how and experience in acid gas removal with amine mixtures, has developed the HYSWEET® process, using a new hybrid solvent formulation allowing simultaneous absorption of acid gases and of mercaptans, with limited coabsorption 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…etc. The new solvent's acid gas and mercaptans removal performances were then validated on a pilot rig. The performance of the HYSWEET® 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 leads 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. Besides an economical mercaptan removal, the new hybrid solvent allows a significant reduction in the energy consumption. The results of the techno-economic evaluation of the HYSWEET® 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.

Vapor–Liquid Equilibria of H2S in Aqueous Mixtures of N-Methyldiethanolamine + Piperazine + Sulfolane

“…The Sulfinol process has been reported to resist corrosion . HySWEET, , Lurgis Amisol, and Flexsorb PS are other commercial solvent formulations in sour gas treatment in which, mixtures of thiodiglycol + water + amine, methanol + MEA/DEA, and moderately hindered amine + physical solvent + water have been applied, respectively, as hybrid solvents.…”

Hydrogen Sulfide Solubility in Aqueous N-Methylpyrrolidone Solution

“…Recently, numerous experimental data of acid gas absorption capacity have been investigated and reported in the literature. − Newly, to bring together the advantages of both types of solvents, hybrid solvents have been established for gas treating and separating purposes. , A number of hybrid solvents have been marketed so far from the sulfinol process ,, with three main chemical components, namely, diisopropanolamine (DIPA), sulfolane (SFL), and H 2 O; subsequently, methyldiethanolamine (MDEA) has been substituted by DIPA and was branded Sulfinol-M . HySWEET, , Lurgi Amisol, and Flexsorb PS technologies are other marketed solvents for gas processing, which are all classified as hybrid solvents.…”

HySWEET® Process: An Improvement in Energy Efficiency

“…As presented in previous papers [4,5], the capability of the solvent to reach the low mercaptan concentrations was verified in a real absorber column of pilot plant, where besides equilibrium, reaction kinetics, physical properties of the solvent such as viscosity; mass transfer and contactor efficiency also play an important role. Experiments showed that, for high levels of C1SH in the raw gas (up to 1270 ppmv) and low acid gas content, it was possible to reach a mercaptan specification between 4 and 14 ppmv ( Figure 4).…”

“…This paper briefly reminds the key points of the process development already presented in previous papers [2,3,4]: selection and physico-chemical characterization of the solvent at the laboratory scale, with a particular attention given to operation related constraints as corrosion, foaming, degradation; validation of the process performances on a pilot plant. The techno-economic study presented previously [5] enabled to identify the typical application cases for which the new hybrid solvent alone will allow to reach specifications required for mercaptans, and reduction of the downstream mercaptan removal units for the other cases.…”