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Why Sulfur Testing – a Case Study

SRU Unit


The Plant saw a trend that their Recovery efficiency was dropping significantly.  The plant employs a 3 stage SRU without a TGTU.  The plant was planning to replace all their catalyst.  The Reaction Furnace temperature was running at 1040°C.


Testing was done to this plant wherein samples were taken before and after each converter; feed samples were also tested.  During testing, operations was asked to gather all necessary data from their DCS every 5 minutes.   All major components were identified, including H2S, CO2, COS, CS2, Benzene, Toluene, Xylene and Ammonia.

Using the operating data gathered and testing results, a steady-state simulation was created to assist the engineer in identifying what is causing the SRU to decrease in recovery.

It was found out that there was Benzene and Toluene breaking through the Reaction Furnace and poisoning the first converter catalyst.  The simulation was showing only 70% activity on the first converter which is an indication of deactivated catalyst.  Temperature rise on the top thermocouple was low but the middle and bottom temperature was fine.  This suggests that only the top portion of the bed was deactivated.   Second and Third Converters were achieving 100% activity (fully active).

The plant was advised to replace the first 50% catalyst of the first converter. It was also suggested that minor modification on their Reaction Furnace (e.g. Checker Wall, Choke, Burner) would increase the temperature of the Reaction Furnace.

Testing was requested after the turnaround.  The recovery efficiency was 98.95%, which is normal for a 3 stage SRU.

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Posted by: Noel Vicente

Mr. Vicente has extensive knowledge and experience in the sulfur recovery industry having worked with Sulfur Recovery Engineering, Sulfur Engineering Solutions, and now Sulfur Unit a part of Refining Community. Noel has worked in all aspects of the Sulfur Recovery Unit such as Analytical and Field Testing, Operations and Troubleshooting, Pre-Commissioning and Commissioning, Process Engineering and has been involved with the start-up/ shutdown of various refineries and gas plants worldwide. On top of his credentials, Noel is an experienced instructor/trainer, who is able to make difficult concepts easy to understand for all. He conducts onsite training for sulfur plant operators and key staff for refineries and sour gas processors around the world. Noel also teaches fundamental engineering theory review courses to foreign trained engineers.

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