Document liquid sulphur levels in a Sulphur Recovery Unit (SRU) Reactor during a catalyst wash.

Posted by Margaret Bletsch

Feb 27, 2018 9:54:19 PM

Are you planning to “wash” a catalyst bed in a reactor and need to monitor process conditions?

Using Tru-Scan™ technology to detect liquid levels in pressure vessels and catalyst levels in reactors is a fast and extremely reliable measurement performed online. One of the problems operations staff faced when planning a catalyst “wash” was not having an indication of any accumulated liquid level in the bottom of the vessel to monitor the procedure. Read more on how Tracerco was able to assist a customer with monitoring the liquid level throughout their planned wash campaign.


Case study project scope – monitoring liquid level during a catalyst wash procedure
A large refiner was planning a procedure to “wash” the catalyst bed of a Sulphur recovery reactor. During the “wash” process any liquid sulfur would accumulate in the bottom of the reactor. The reactor was not equipped with a level instrument so the Engineer inquired whether Tracerco could monitor the level. Any liquid “washed” from the bed would accumulate slowly so a continuous measurement was not required. Our proposal was to perform a baseline scan followed by several scans over a period of days to document the liquid sulfur level during the procedure. After the “wash” was completed and the liquid sulfur reheated one additional scan was done before the reactor returned to normal operations to ensure that all the liquid had been removed.
Scan results identify accumulated liquid level over a period of several days
The first scan of the reactor on Day 1 was used to obtain baseline data (blue dashed scanline) and to verify that the catalyst bed was in its proper place. As the catalyst wash began three additional scans were performed that indicated no liquid sulfur accumulation.

The following day six additional scans were completed but still no indication of accumulated liquid. On Day 3 the results of the scans showed the density in the bottom of the reactor had increased, signifying the presence of accumulated liquid (black solid scanline). The reactor level was monitored throughout the day at one hour intervals revealing that the liquid level rose slowly but steadily over the course of the day. The orange solid scanline was the final scan performed on Day 3.

Early on the morning of Day 4 the reactor was scanned showing the liquid level had risen to the bottom of the I-Beam support for the catalyst bed. This was the highest liquid level observed (red solid scanline). At this point the washing of the catalyst bed had been completed and further scans performed were used to monitor the liquid level receding. The reactor was scanned two more times after the completion of the wash on Day 5 with each scan indicating a continuing drop in the liquid level.

The final scan performed on Day 8 (green solid scanline) indicated that the reactor had returned to the baseline condition.

Scanning played a key role in this plant maintenance process to monitor the status of the reactor whilst being washed. The monitoring of the liquid level was done to keep the level from getting too high where it could potentially plug some outlet nozzles.

If you are planning to “wash” a catalyst bed of a reactor or any other unusual procedure and have the need to monitor process conditions consider using Tru-Scan™, stationary monitoring or PhaseFinder™ neutron scans to provide insight during the project. If you have any additional questions complete the enquiry form on our Tracerco website at

Click here to download a copy of our Tracerco Diagnostics™ Services for the Refining and Petrochemcial Industries brochure highlighting our Process Diagnostic™ applications.

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Topics: Tru-Scan, gamma scan, liquid restriction, SRU Unit, coke, Sulphur Recovery Unit, catalyst bed wash

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