Rich (hydrogen sulphide saturated) alkanolamine solution streams from the process units' amine absorbers are collected and routed into low pressure flash drums where dissolved hydrogen, hydrocarbon gases, and some hydrogen sulphide is flashed off. These flash gases are sweetened with a lean amine slipstream to remove the hydrogen sulphide present before routing them to fuel. The now rich amine slipstream also enters the flash drums.
The resulting rich amine solution is preheated and introduced into two parallel regenerators where additional heat, in the form of striping steam, is applied to break the chemical bond between the amine molecules and hydrogen sulphide molecules. Subsequently, the hydrogen sulphide is removed from the solution and sent to the Claus Unit for conversion into elemental sulphur. The regenerated (lean) amine solution is cooled and returned to the absorbers for use.
Diagram used with permission (© SAIT Polytechnic, MacPhail School of Energy, 2009)