Michael Gaura, AMETEK Process Instruments, USA, details the importance of an air demand analyser (ADA) in the quest to manage sulfur recovery units (SRUs) more tightly.
W
ith the global economy recovering from the devastating impact of COVID-19 and the restrictions that were put into effect to reduce its spread, energy suppliers are aggressively working to meet deliverable volumes that have not been seen in the past two years. Coupled with the significant change in workforce that many hydrocarbon suppliers and processors have also experienced, as well as the continued push to decrease the amount of sulfur emitted at the plant or end product level, there has been a renewed effort to automate and optimise sulfur recovery unit (SRU) operations. One point within SRU operations that has specifically been receiving more focus is the inlet or feed point. Engineers and consultants are targeting the most efficient and proven method of obtaining detailed and real-time compositional data from the sour water stripper and acid gas as it enters the SRU. It is worth recalling that the purpose of the SRU is to remove as much sulfur from incoming gas streams (feed gas) as
possible, as environmental agencies want to limit the amount of sulfur emitted locally (plant level) and globally (at the point of fuel combustion). Typically, the sulfur entering the SRU is present as hydrogen sulfide (H2S) – a compound that is lethal to human life at very low concentrations (500 ppm). The H2S is present in the sour water stripper (refinery) or acid gas (refineries and natural gas processing plants), as it has been previously scrubbed or removed from the more financially-valuable or desired hydrocarbon streams. The H2S, or any other sulfur compounds that enter the SRU, are converted and removed through reactions in the SRU plant. The most common method of removing > 90% of the sulfur is through the modified Claus process. The most common modified Claus processes currently utilised in the recovery of elemental sulfur (Sx) are based on systems that were described in detail 75 – 140 years ago. Many improvements and modifications have been integrated over this time, but the sulfur removal process HYDROCARBON 15
ENGINEERING
June 2022
