What are the reasons for severe corrosion of the valves in the circulation pipelines of the LNG amine solution system?
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Has anyone experienced severe leakage in the pipeline valves of the amine liquid circulation system used in LNG decarbonization processes? What are the reasons?
It’s normal for corrosion to occur after using it for a certain period of time
The material was not selected correctly; the solution contains impurities such as chloride ions
It came online in 2017, and the carbon steel pipeline valves had corrosion-induced pinholes; this year we started planning to replace them with stainless steel ones, not sure if that will make a difference.
We’re starting to prepare for the switch to stainless steel now; the quality of natural gas is really poor, to the point that the amine solution has turned soy sauce-colored :L
Is your decarbonization also scheduled after desulfurization?
No wonder then – it can remove both sulfur and carbon. Hydrogen sulfide causes greater corrosion than carbon dioxide and similar substances. Moreover, when the solution absorbs moisture from natural gas, it forms weak acids that also cause corrosion; combined with the corrosion caused by other substances and physical erosion, it’s not easy for ordinary carbon steel pipes to last even 7 years
It’s the same with us; it’s been less than a year since operations started, and this is already the situation – mainly because the quality of the natural gas isn’t good
In the decarburization and desulfurization process, amine solutions react to form certain organic acids and salts; notably, CO2 reacts with iron to produce iron carbonate, which reacts with water to form iron hydroxide, and it also reacts with hydrogen sulfide to form iron sulfide, thereby causing pipeline corrosion； In addition, the pipeline is corroded directly by hydrogen sulfide; moreover, corrosion caused by organic acids cannot be ruled out. This is also one of the reasons why the amine solution turns black after being used for a while. Therefore, the amine solution needs to be filtered and activated in order to ensure absorption efficiency while reducing corrosion. To put it simply, it’s not a comprehensive explanation