Acid Gas Removal Unit
This unit consists of a dryer to remove the water, an amine tower to remove contaminates of CO2, water vapor, hydrogen sulphide and oxygen, also a nitrogen rejection unit which removes the nitrogen.
The dehydrator removes the water moisture content from the gas by injection of glycol liquid into the stream. This is carried out in the glycol tower and as the glycol particles absorb the water they fall to the bottom, the dry gas rising to the top for the next process.
The glycol is regenerated by boiling of the water which has a lower flash point, leaving the glycol for reuse.
The gas now passes to the amine tower where it has the amine injected into its stream removing the sulphur contaminates and CO2. The gas now passes through a nest of filter pipes where it looses velocity and the remaining contaminates fall to the bottom sections. The gas if finally passed through cyclones where centrifugal force knocks out any remaining water vapour or small particles.
The hydrogen sulphide, CO2 and amine solution can be removed from the bottom of the tower and sent for processing to form sulphur which has commercial value. This is a yellow powdery substance much like the element produced in several parts of the world. Whilst an engineer at sea I served on a sulphur tanker, shipping the stuff from Port Sulphur in Louisiana down the Mississippi through the gulf of Mexico and across the Atlantic Ocean to Rotterdam. There were steam coils in the sulphur tanks and every so often a charge of powdered sulphur would erupt from the vent goosenecks onto the deck. What a reek! It also turned all the brass black, I was glad I was an engineer and not working on deck.
Anyway, after the gas sweetening process the residue is pumped from the bottom of the amine tower to the sulphur reclaiming plant. The heart of this is the Claus Process which uses catalytic and thermal reaction to reclaim the element.