Corrosion And Corrosion Control Methods In Amine Systems Containing H2S Available to Purchase

Overall H₂S-amine system corrosion rates are determined by the rate of acid oxidation of iron by dissolved forms of H2S and CO₂ in highly buffered basic solutions. Rates of interference with the laydown or removal of the protective layer of iron sulfide corrosion product from the fret: metal are also part of the equation. These two phenomena are functions of the concentration and form of the oxidizing acid, the solution temperature, the fluid velocity, and the concentration of heat stable salt anions. The effect of solution pH, cation content and different heat stable salt anions on the iron sulfide layer and the transport of iron in solution is examined. Maintenance of low heat stable salt anion content in solution is shown to effectively reduce the corrosion. Comparison is made with other control methods, such as strong base addition. Long term benefits of maintenance of low heat stable salt levels are demonstrated.

Alkanolamine solutions are commonly used to, remove acid gas contaminants from various process gas streams in the oil & gas industry, the steel industry, syngas plants, chemical plants, and many others. Much work has been done to understand corrosion mechanisms in alkanolamine (“amine”) systems, so that corrective action may be taken to improve unit operation and reliability.^1-8 It is recognized that the major corrosive agents are the acid gases (H₂S and CO₂) that are the reason for the existence of amine systems. However, since acid gas corrosion can lead to formation of protective layers, attention has been focused on other factors that contribute to corrosion in amine systems. Sometimes the work has been so focused as to exclude acid gas considerations from experiment or interpretation.^2,7 Conclusions drawn from such work, when applied to amine system corrosion, can lead to incomplete understanding and confusion. This paper presents a broad theory of corrosion in amine systems describe, experimental tests which employ the important parameters of the theory, and interprets results in that light.

Heat Stable Salts (HSS) are responsible for increasing the corrosive nature of the amine solution.^2-4,9,10 The increase in the corrosive nature of the amine solution due to HSS leads to operational problems for plant operators. A method for removing HSS from amine systems has betm devised in recent years to keep HSS levels at a low level such that HSS will not contribute to upsets and amine solution losses³ .One alternative proposed method to reduce the corrosive nature of HSS in amine solutions is the addition of caustic or a proprietary neutralizer⁹. However current literature suggests that this method has little effect on lowering corrosion rates, and may in some instances increase the corrosive nature of the amine solution^6,11 . Caustic addition to an operating amine system has resulted in plugging and fouling. ¹² Confusion in expectations for the effect of caustic addition on corrosivity may have stemmed from laboratory work that did not take into account all of the system dynamics of an operating amine plant.