Heat Stable Salts and Corrosivity in Amine Treating Units

Publisher Summary There is a great concern over the corrosion due to the presence of heat-stable salts in amine treating units. The heat-stable salts are essentially the reaction products of alkanolamines and the acids stronger than carbon dioxide (CO 2 ). These acids are usually introduced to the amine units with makeup water and feed gas streams or generated within the units by undergoing the chemical reactions with contaminants such as oxygen (O 2 ), carbon monoxide (CO), and sulfur dioxide (SO 2 ). By nature, the heat-stable salts are non-regenerable under solvent regeneration condition. As such, they remain and accumulate in the absorbent throughout the plant. The accumulation of heat-stable salts not only causes a reduction in CO 2 absorption capacity, but also is claimed to cause a significant increase in the system corrosiveness. Increased corrosion can lead to an increase in the amount of iron carbonate particles in the solution, thus causing other operational difficulties such as foaming, emulsions and fouling. This potentially undermines reliability of the amine units, particularly in terms of operation, throughput, treatment capacity, and productivity. The effect of eight heat-stable salts on corrosion in the amine treating units was investigated using an aqueous solution of 5 kmol/m 3 monoethanolamine (MEA). The test heat-stable salts were acetate, chloride, formate, glycolate, malonate, oxalate, succinate, and sulfate. The major heat stable salts contributing to the increased corrosion rate were identified and the relationship between their concentration levels and corrosion rate were correlated.