What is the major operational challenge posed by heat stable salts (HSS) in amine gas treating systems?

The major operational challenge posed by heat stable salts (HSS) in amine gas treating systems is the reduction of the amine's capacity to absorb acid gases and the increased corrosion rate within the system. Amine gas treating systems use aqueous amine solutions, such as MEA, DEA, or MDEA, to remove acid gases like H2S and CO2 from natural gas streams through chemical reactions. Heat stable salts are formed by the irreversible reaction of the amine with acid gases or other contaminants like oxygen, carbonyl sulfide (COS), or carbon disulfide (CS2). These salts, such as amine sulfates, thiosulfates, formates, acetates, and oxalates, cannot be regenerated by the normal heat-driven regeneration process used for the amine. As HSS accumulate in the amine solution, they effectively neutralize the amine, reducing the concentration of free amine available to react with H2S and CO2. This leads to a decrease in the acid gas removal efficiency of the system, requiring higher amine circulation rates or potentially causing the plant to fail to meet product gas specifications. Moreover, HSS can contribute to corrosion, particularly in the reboiler and other hot sections of the amine system. They can break down the protective passive layer on carbon steel equipment, exposing the metal to corrosive attack by acid gases and other contaminants. The presence of HSS can also lead to foaming in the absorber tower, which reduces the gas-liquid contact and further impairs acid gas removal. To mitigate these effects, amine reclaiming units are used to remove HSS from the amine solution, and careful control of feed gas quality is necessary to minimize the formation of HSS.