Removal of Thermal Stable Salts from MDEA and DEA Solvents via Vacuum Distillation

The formation of thermal stable salts (TSS) in amine-based natural gas sweetening processes is a major operational challenge that compromises the efficiency and longevity of solvent systems. This study explores the degradation mechanisms of methyldiethanolamine (MDEA) and diethanolamine (DEA) solvents used in the gas treatment units at the Shurtan Oil and Gas Production Department. It was identified that the presence of impurities such as COS and chloride ions—introduced from upstream zeolite purification units—significantly accelerates solvent degradation, leading to the accumulation of TSS, surfactants, and organometallic compounds. These degradation products not only reduce absorption efficiency but also promote corrosion, foaming, and viscosity increases, resulting in higher energy consumption and more frequent solvent replacement. Elemental analysis of degraded solvent samples revealed high concentrations of sulfur, calcium, potassium, and corrosion-related metals such as iron, chromium, and manganese. To address these issues, a two-stage vacuum distillation system was designed and evaluated. The first stage involves atmospheric distillation to concentrate the solution, followed by vacuum steam stripping in the second stage to remove degradation products and recover purified amine. Experimental results demonstrate a solvent recovery rate exceeding 90%, with significant reductions in TSS and degradation byproduct concentrations. This method offers a practical and efficient approach to solvent reclamation, extending the service life of amine solutions and improving the stability and sustainability of gas sweetening operations. The proposed technology aligns with international practices and holds potential for broader adoption in natural gas processing facilities where solvent degradation is a persistent issue.