Shell Claus Off-Gas Treatment

Reductive Tail Gas Treatments. It was largely as a result of the effort to achieve better than 99% recovery that the reductive tail gas desulfurization processes (46) were developed in the 1970 s. The two main methods are the Beavon Sulfur Removal (BSR) (47) and the Shell Claus Off-Gas Treatment (SCOT) (48) processes. Both of these processes are now widely used as tail gas desulfurization units on sulfur recovery plants and can readily achieve point source emission levels below 250 ppm and below 100 ppm if necessary to meet regulatory standards. 

H2S released from the stripper is treated in an O2- or air-blown Claus plant that oxidizes H2S to elemental sulfur. The tail gas from the Claus plant, still rich in sulfur compounds, is then treated in a Shell Claus off-gas treatment plant where those elements are catalytically converted to H2S and then recycled back to the absorption column of the AGR unit. 

The H2S concentration in the tail gas of a conventional Claus plant is still some 5%. This H2S is normally incinerated to S02 and released to the atmosphere. Due to stricter environmental regulations a large number of new technologies based on Claus tail gas treatment have been developed to minimise the S02 exhaust from sulphur recovery units. The Superclaus process and the Shell Claus Off-Gas Treating (SCOT) process are treated below. For descriptions of other tail-gas processes, the reader is referred to [2],... 

---