An amine contactor removes hydrogen sulphide and carbon dioxide from a gas stream by washing it counter-currently with a circulating amine solvent. It is the front end of almost every gas treating train, and the point where treat specification is either met or missed.

Two things go wrong in practice. The column fails to reach treat spec because vapour and liquid are not contacting properly across each stage. Or it meets spec but carries expensive amine overhead into the downstream system, where it fouls, foams and costs money to replace.