Oil refineries, natural gas processing units and coal gasification and other chemical plants use the Claus process to recover elemental sulfur from H-2-S containing gas streams. This Claus plant is often called the sulfur recovery unit, the SRU unit or the sulfur plant. An optimized Claus plant can achieve sulfur recovery of up to 98.5%. This leaves about 1.5% or more of the sulfur species in the tail gas.
Typically, in order to comply with local environmental regulations, a tail gas treatment (TGT) process, will be installed downstream of the SRU to take care of the remaining sulfur before it is all incinerated to SO2 and vented to the atmosphere. There are various types of TGT processes including as amine-based processes, sub-dew point processes or oxygen-enriched processes. They all have different ways of operating, different efficiencies, different investment costs and different plot space requirements.