This is about a LPG Merox unit in our refinery. Since the content of RSH(mercaptan) in the feedstock has more than doubled, this makes it difficult to regenerate the caustic. The content of mercaptide and disulphide in regenerated caustic has greatly increased. Frequent replacement of caustic and increased air flow and temperature in the oxidizer doesn't solve the problem. How can we solve the problem if we can not change the feedstock?
Answers
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16/03/2021
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ARIT SEAL, Indian Oil Corporation Limited, sealarit@gmail.com
As per my understanding, the overall sulphur content of your feedstock has increased. In that case, there can be multiple ways out:
1. First check whether you are operating at the design strengths of caustic as well as upstream amine absorber.
2. Increase lean amine flow in your upstream amine absorber/ scrubber. Higher H2S content downstream in your amine absorber can overload your caustic.
3. If the H2S content in your LPG inlet of the caustic scrubber is less, then check whether you are dosing the oxidation catalyst as per design quantity.
4. As you have already optimized your air flow and caustic temperature, then check whether the solvent you are using to wash DSO from the regenerated caustic is hydrotreated as per design spec.
If your solvent is not hydrotreated, caustic will react with your solvent’s mercaptans, build up mercaptides, and back-extract sulphur into your LPG.
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21/02/2021
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Lorenzo Spagnuolo, DOW, lspagnuolo@dow.com
You should maximize the removal of mercaptans in the upstream LPG amine absorber to reduce the load in the Merox. Some formulated amines can significantly improve this aspect.
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19/02/2021
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Lorenzo Spagnuolo, DOW, lspagnuolo@dow.com
You could maximize the removal of mercaptans in the sour LPG in the upstream gas treating system. We have several solutions in the Dow gas treating portfolio.
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10/02/2021
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Egbert van Hoorn, Hocon B V, Egbertvh@hotmail.com
A review of your operating conditions will be required as well as a review of your equipment sizing.
You have clearly tried out the most obvious possibilities.
Could you indicate which oxygen range you are operating at?
Please contact me for further details at egbertv@sulfurrecovery.com
We have quite some experience with Merox units
Egbert van Hoorn
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