You are currently viewing: Q&A

---

---

• We are having caustic regenration facility in our LPG treating unit. During caustic regneration,Disulpide oil (DSO) will be removed by absorbing with help of naphtha in CFC. We are expreincing higher levels DSO in the regenrated caustic.

  My questions are : 

  1. Does LPG quality will be impacted if regenrating caustic is higher levels of DSO. (Design says NIL)?

  2. What the possible ways to reduce the DSO content in regenerated caustic?

  3. Is there any correlation on DSO based on LPG inlet mercaptans?

  Mar-2024

---

Answers

---

• Marcio Wagner da Silva, Petrobras, marciows@petrobras.com.br

  Based on the information in your question it seems that the LPG sweetening system is overloaded possibly due to an increase of overall sulphur content in the feed stream.

  In this case, it's important to verify the performance of the amine treating system upstream of the LPG sweetening unit once higher H2S content in the LPG will overload the caustic treating and this will lead to a higher production of disulphide oil (DSO). This higher production of DSO can impact the LPG quality if the caustic regeneration system is operating under poor performance or inadequate make up caustic flow rate is carried out.

  Another key question is regarding the solvent applied in the CFC (Continuous Film Contactor) section, the naphtha applied as solvent to wash the DSO needs to present low sulphur content (the ideal is apply hydrotreated naphtha) once the caustic can react with the mercaptans present in the solvent producing mercaptides and raise the sulphur content in the LPG.
  Among the operating variables which can help to reduce the DSO amount in the regenerated caustic are the temperature and the air flow rate to the oxidizer.

  If was observed a significant change in the processed crude oil slate for a high sulfur content crude oil and this will be permanent, should be considered the installation of a caustic pre-wash vessel in the LPG sweetening unit in order to reduce the H2S content in the feed and then improve the performance of the caustic treating.

   

  Mar-2024