Refinery optimises sulphur pit level transmitter reliability in Claus unit

Endress+Hauser's 80 GHz radar sensor with steam jacketed nozzle improved reliability, enhanced safety, and significantly reduce maintenance costs

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WHEN a North American refinery faced operational challenges with its sulphur pit level transmitters, it turned to Endress+Hauser to implement an 80 GHz radar sensor paired with a steam-jacketed nozzle to enhance safety and increases productivity.

A sulphur pit is a storage facility typically constructed from concrete and located below grade in a refinery’s Claus Unit.

Its primary purpose is to temporarily hold sulphur extracted from the sulphur recovery unit (SRU) and maintain it in a molten state using steam coils submerged in the sulphur.

This molten sulphur is then transported to clients via trucks, railcars, trains or barges.

Molten sulphur often contains dissolved hydrogen sulfide (H2S) and other gases that need to be purified and removed from the process before transportation.

This purification process, known as degassing, is accomplished by sweeping the pit with air. The H2S and other impurities are then sent to treatment systems such as incinerators and thermal oxidisers.

The said refinery’s sulphur pit had, at least, one pump, often two for redundancy, to pump molten sulphur to transport equipment when there is demand and to circulate molten sulphur back to the pit when not pumping out.

The spray nozzles return the molten sulphur back to the pit, assisting with the degassing process.

However, as the sulphur disperses in the vapour space, it can form a residue on equipment and instrumentation such as free space radar cones, guided wave radar rods, thermowells and ultrasonic flowmeter probes.

This residue negatively impacts the accuracy of the measurements. Engineering control methods are required to prevent, eliminate or minimise the buildup, combined with good maintenance practices to ensure safe, accurate and reliable operation of the instruments.