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Claus plants play a key role in refinery productivity. They process concentrated hydrogen sulfide (H2S) fractions, converting them into sulfur dioxide (SO2) and ultimately elemental sulfur They can also remove pollutants, particularly those caused by decomposing ammonia.
Today, many refinery operators are challenged to manage rising H2S levels. On the one hand, dwindling reserves mean the average S-content of crude oil is rising in many regions. In addition, operators are more frequently reaching to the bottom of the barrel to convert heavier fractions into valuable “white products” such as gasoline and diesel. And stricter environmental regulations are lowering permissible H2S content – at a time when H2S and ammonia feed streams to Claus plants are rising. This means that Claus plants can end up bottlenecking refinery operations.
Oxygen enrichment (O2e) of the process air is a proven, flexible way to debottleneck operations while increasing flexibility. As air is approximately 79% nitrogen and 21% oxygen, the use of air to supply the oxygen for combustion of H2S to SO2 also introduces a large quantity of nitrogen, which has to be heated and does not contribute to the reaction. If air is replaced with oxygen-enriched air or pure oxygen, this eliminates the nitrogen ballast, also reducing the volume flow through the sulfur recovery unit (SRU). This means more acid gas can be fed into the system without the need for significant modifications to existing equipment or major changes to the process plant pressure profile.
Benefits of oxygen enrichment in Claus plants
- Increased sulfur handling capacity and removal of bottlenecks
- Increased productivity without changing the pressure drop
- Greater flexibility to handle a wider operating envelope with the option to modify process intensification on demand
- More effective treatment of ammonia-containing feeds
- Less effort for tail gas purification (reduced nitrogen flow)
- Greater redundancy – especially with multi-train systems
Here at Linde, we have been working on the development and delivery of O2e technologies for SRUs for over 25 years. Through our SURE® oxygen enrichment portfolio, we cover the full spectrum from low to high end to meet all application and productivity needs during maintenance, modification and greenfield projects. Highlights of our SURE oxygen enrichment portfolio include our OXYMIX®oxygen injector and our OXYMIX Flowtrain measurement and control system for safe and reliable oxygen dosing. And for those requiring oxygen enrichment beyond 28% we have our SURE burner technology.