99.9+% sulphur recovery and extremely low levels of SO2 are achieved with Shell Claus Off-Gas Treating.

The Claus unit design is based on the experience of decades across Shell wide variety of operations globally and focuses on reliability and safety with high conversion. As owners and operators of refineries across the world, we employ the SCOT process to achieve sulphur recovery levels as high as 99.98% or less than 150 mg /Nm3 SO2. Well-operated Claus tail gas units are required for today’s refineries and gas plants to meet strict environmental regulations. The SCOT process catalytically converts the remaining sulphur dioxide in Claus tail gas to hydrogen sulphide. Hydrogen sulphide is then stripped from the tail gas and reprocessed.

More stringent environmental regulations require sound and innovative off-gas treatment processes.

The current World Bank standards prescribe that refineries should emit no more than 150 mg/Nm3 sulphur dioxide (SO2). Impending emissions restrictions on carbon monoxide also loom. All of these changes mean that oil and gas operators need to adopt proven processes quickly. 

To better meet these needs, the SCOT technology has been further enhanced and is now available as SCOT ULTRA. SCOT ULTRA employs sharper design rules, improved catalyst technology and a new advanced proprietary JEFFTREAT-ULTRA solvent. The new technology lowers operating costs, achieves higher performance in warmer climates, and improves resilience to process changes and upsets. The technology can be retrofitted to existing tail gas units as well as new grassroots applications.

In some cases, greater flexibility can be achieved by employing Shell’s Cansolv SO2 flue gas scrubbing technology as an alternative line up to the SCOT or SCOT ULTRA process. In this case, all sour gas streams are incinerated and the SO2 scrubbed from the incinerator flue gas with using our proprietary amine. Our experienced design team can work with you to tailor the solution that best meets your specific requirements. 

Shell Operator on top of a Shell Bitumen tank during SCOT process

Shell’s SCOT process, with our advice, achieves less than 1% unscheduled downtime.

The process is highly flexible and can operate over a wide range of sulphur intakes with a turndown ratio of less than 10% of design throughput. The unit requires little upkeep and ongoing maintenance which helps decrease the associated operating costs and enables higher profit margins. Reduce CO and SO2 emissions while maximising your profitability.

Sulphur Recovery

Our reliable and robust operations with Claus, SCOT, sulphur degassing and THIOPAQ O&G sulphur recovery technologies secure gas production.


Gas absorptions solutions that help meet product specifications and restrictive emissions limits within a lower cost structure.

Contact Shell Catalysts & Technologies

Contact Shell Catalysts & Technologies to meet the challenges petrochemical plants face with confidence.