Minimum H2S loading in lean amine systems

[DieguitoI]

In one project specification is said that over stripping of amine shall be avoided as increased corrosion rate can occur if not enough H2S is left in lean amine solution to form iron sulphide passivating film on vessels and pipe walls. In one article from Amine Experts (Spooner & Sheilan - Iron sulphides friend or foe?) is said the opposite thing: in lean solution (downstream the lean/rich exchanger) low temperatures, low H2S partial pressure and poor CO2/H2S ratio hinder the formation of the type of iron sulphide which would form a protective layer (pyrrhotite or pyrite) instead mackinawite will forms as suspended solid particles in the amine solution. Thus, the indication is to strip H2S as much as possible to minimize mackinawite formation in lean amine solution.
Which of the two views is correct?

 

[Dhurjati Sen]

Both are correct. These two scenarios are not identical. Need to compare the material spec., partial pressure of H2S in both the cases. Surely, they would be different.

DHURJATI SEN