1. Field of the Disclosure
Embodiments described herein relate generally to amine solvent solutions that absorb acid gases and more particularly to additives that decrease the presence of amine-derived contaminants in- and/or degradation of such amine solvent solutions.
2. Description of the Related Art
Plants such as refineries, processing plants, industrial plants and the like, may include an amine treating system to treat liquid and/or gas feed streams. Generally, such feed stream treatment includes an amine solvent solution to absorb acid gases from the feed stream. Acid gases include gases such as hydrogen sulfide (H2S), carbon disulfide (CS2) carbonyl sulfide (COS), and carbon dioxide (CO2). Acid gases may later be removed from the amine solvent solution to regenerated and recycle the amine solvent solution for additional use.
Amine-derived contaminants, however, can accumulate in the amine solvent solution. If left unchecked, these contaminants can have an adverse effect on the amine treating system. For instance, amine-derived contaminants are associated with a decrease in the amine solvent solution's ability to absorb acid gases and an increase in corrosion within the amine treating system.
Generally, amine-derived contaminants result from a reaction or association between the amine in the amine solvent solution with another molecule resulting in another contaminant or a reaction intermediate involving a contaminant. These other contaminants/intermediates include acid gases, oxygen, strong anions, carboxylic acids, and others. Contaminants such as acid gases may come from the feed stream being treated, but contaminants may come from any source such as the make-up water for the amine solvent solution or any other source.
One type of amine-derived contaminant is heat-stable salts. Heat-stable salts form when a strong anion, such as chloride, formate, or acetate, reacts with or binds an amine cation. The resultant salts are heat-stable because the addition of heat does not readily regenerate the amine solvent solution.
Another type of amine-derived contaminant is amine-derived degradation products. Generally, amine-derived degradation products result from the breakdown of amine molecules into a different chemical species. The chemistry of degradation product formation is complex, and in many cases, the reactions are irreversible. A simplified example included the reaction of oxygen or an acid gas with the amine eventually to form an amine-derived degradation product. Alternatively or additionally, oxygen or an acid gas may react with another contaminant to form an intermediate that reacts with the amine to form the amine-derived degradation product. Of course, formation of amine-derived degradation products is not limited to the forgoing, much simplified, examples.
Since there are many ways in which heat-stable salts and amine-derived degradation products can be produced, they can, and usually are, both be present in an amine treating system at the same time. Furthermore, amine treating systems can tolerate only so much accumulation of such amine-derived contaminants before it must be addressed. There are many different ways to clean an amine treating system once the contaminants are produced, but there remains a need for ways to avoid or to decrease amine-derived contaminants from forming in the first place.