Q & A > Question Details
We are facing issue of LPG product offspec due to total sulfur high. we have a UOP LPG merox treamtent unit (LPG enter from CDU to absorber> filter> coalescer> Prewash>Extractor>sand filter).
design RSH in LPG feed to Merox is 800 wtppm. but currently due to feed, we are processing upto 5000 wtppm. which parameters to be checked thoroughly in order to reduce this offspec.
1. Regen caustic quality (Mercaptide & Disulfide) feed to extractor.
2. LPG to Prewash ?
3. Lead acetate test of which streams will help us to identify at field rather than sending samples and wait for results.
 
Answers
21/11/2015 A: Sanjay Singh, UOP, sanjay.143singh@gmail.com
The feed RSH is higher than design. First check for feed H2S level and how much H2S is coming from Absorber into Prewash. If the quantity is less than 20-30 wppm and no Amine carryover, increase Prewash caustic strength to 20 Be to remove some RSH in Prewash.
Increase the caustic circulation to Extractor. Be more aggressive with more caustic, Catalyst and Air.
Do Shake test at the Lean and check for Lead Acetate Paper on Rich and Lean caustic.
13/05/2015 A: Egbert van Hoorn, Hocon B V, Egbertvh@hotmail.com
There are several possible reasons for this problem.
As indicated in previous comments, the air flow is important, but it should not be too high. Analysing the spent air is therefore important.
You could try to add additional catalyst. If you have added too much air for a long period, you can lose (part of) the catalyst.
Good contact between the LPG and caustic phase is very important. Could fouling have occurred?
Are the distributors designed correctly?
Lots of questions. More information is required to give a good advice.
13/05/2015 A: Muhammad Faisal, OQ integrated energy company (Oman), engr.faisalfraz@gmail.com
issue of high RSH in LPG. what air has to do for LPG merox. Regeneration system for caustic is other unit and they are saying shake test is OK. mercaptide/disulfide are within range. air is also OK in oxidizer.
12/05/2015 A: Bruce Carr, Suncor Inc, matukaze1@hotmail.com
Have you checked the air flow is adequate to ensure the Merox can work properly