RoydadNaft –  Ilam Gas Refinery has used vacuum thermal reclaiming to recover spent MDEA amine solvent at about 80% efficiency, cutting the need to import fresh solvent and keeping heat-stable salts in circulating amine under control.

Alireza Arad, head of process engineering, said iron sulfide and heat-stable salts (HSS) form in MDEA during natural-gas sweetening, degrading the amine, raising corrosion and lowering absorption efficiency, Roydad Naft reported. When performance falls far enough the solvent must be replaced entirely. High-yield reclaiming can avoid that cost.

Among reclaiming options — thermal distillation, ion exchange and electrodialysis — thermal reclaiming is one of the more practical ways to remove impurities and HSS. Conventional thermal reclaiming runs at atmospheric pressure. The newer route uses vacuum distillation because amine is heat-sensitive; vacuum allows regeneration at lower temperature and higher yield.

Benefits include less buying of costly MDEA, less risk that amine shortages under sanctions cut gas output, lower release of toxic material, less chemical waste for disposal and protection of the refinery’s sweetening capacity.

About 350 tons of spent amine were sent to an Iranian knowledge-based firm. Return batches showed HSS falling from 3.21% to about 0.04% by weight and MDEA concentration rising from 35% to about 70% by weight. Overall reclaiming efficiency was calculated at 80%. Arad said the method is suitable for amine units at natural-gas refineries across Iran.