Quality of lean liquid
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What are the quality control standards for the lean liquid in solvent regeneration units? Our company has never measured the CO2 content in the lean solution – has anyone’s facility done that? Why are design documents requiring H2S+CO2 levels in the lean solution to be less than 1 g/l?
The CO2 content in the lean liquid is very low; it should be less than 0.1
During amine solution regeneration, CO2 is more easily decomposed; therefore, the CO2 content in the lean amine solution is very low. Moreover, the amount of CO2 in the reaction system is already relatively low, so the CO2 content is generally not measured.
Although it is said to be about controlling the levels of hydrogen sulfide and carbon dioxide, refineries actually pay primary attention to the level of hydrogen sulfide. Both hydrogen sulfide and carbon dioxide are acidic gases with similar acidity levels. High concentrations of these gases indicate that the regeneration of the lean solution is insufficient; as a result, hydrogen sulfide or carbon dioxide remains combined with the amine solution and returns to the desulfurization tower. This leads to a low concentration of effective amine, thereby reducing the efficiency of desulfurization.
Current amine solutions all have a certain selective absorption for hydrogen sulfide. Excessive CO2 absorption reduces the efficiency of hydrogen sulfide absorption. This is mainly related to the quality of MDEA, and has little to do with the operation.