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Reprocessing slop oil is always a headache issue for refiners, in our refinery, we blend recovery oil (one of slop oil from crude tank cleaning) into heavy crude slates (API<28), but suffering problem on desalter operation, higher emulsion layer led to electric field trip and desalter brines contain oil which can result wastewater treatment plant in upset, we would like you could share the operating experience on reprocessing slop oil with minimal impact on these facilities, thank you~
(1). What kind of pre-treating methodology did you apply on slop oil before reprocessing? Water separation or any filtration steps?
(2). Did you use chemicals for slop oil pretreatment?
(3). How did you reprocess slop oil? In-line injection into CDU uint or blend slop oil into crude tank?

24/04/2019 A: Sudhakara Babu Marpudi, Dangote Oil Refinery Company, m_sudhakarababu@yahoo.com
Some times it has to do with what else is mixed up with the Slop recovered in Oil separator basins of ETP. We have come across similar problems of reprocessing (water shots felt in Desalters etc.,) due to three main reasons. 1) The Crude blend was to have a fixed quantity of RCO (AR) from an upstream CDU - This was not honored and total RCO produced in the upstream CDU was sent to our CDU reducing the fresh Crude proportionately. This has converted the Crude Desalting into AR desalting. 2) ETP sludge that had to go for land fill was blended to the Slop Oil recovered from the Oil separator basins of ETP. 3) The Caustic drains were also routed to the OWS collection tank and thus the skimmed oil from OWS tank has uncontrolled quantities of Caustic (due to the issues with Merox units - Higher volumes of Spent Caustic was generated). All put together the SLOP was rendered NOT PROCESSABLE in Desalters / CDU forcing us to sell it off as waste oil.
16/12/2018 A: Satyalal Chakravorty, Sr Consultant, satya1354@yahoo.co.in
Why don't process slop at Coking Unit? Established procedure is there.
14/12/2018 A: Peter Marsh, XBP Refining Consultants Ltd, peter.marsh@xbprefining.co.uk
Many refineries I have worked with blend their slops directly into crude oil with no chemical additives. However, slops from FCC, Visbreaker or Coker units are olefinic and are typically kept segregated from straight run slops to avoid accelerated fouling of the CDU preheat exchanger train and temperature excursion or operability problems in hydroprocessing units downstream of the CDU. Olefinic slops are reprocessed by blending into FCC or Gasifier feed. If olefinic slops are stored in a dedicated tank, anti-oxidants are sometimes injected to mitigate accelerated fouling of heat exchangers in the FCC or Gasifier feed preheat train.
14/12/2018 A: Ingemar Quintero, PETROSINOVENSA, idavidqs@gmail.com
Why is it a headache? Could you be more specific about what you experienced?
1) We just transfer the slop oil to the dilute crude tanks (16 API). No pre-treatment is foreseen.
2) No.
3) Blend slop oil into the crude tank.
14/12/2018 A: Krishna Rao Pulugurti, Retired/Consultant, pkrao2012@yahoo.com
Please check Calcium in the slop oil. If ir ia more than one ppm, it needs removal before it is sent to de-salter.
13/12/2018 A: Vijay Beleri, Rateau energy systems, v_beleri@hotmail.com
Agree. Slop can give all kinds of problems. To address your points of higher emulsion layer. Guess you can control the emulsion layer by using a kar panel (assuming you have an ac voltage desalter). Reduce mix valve delta p in such cases. We have been involved in axrevamp where we significantly increased water / interphase residence time. This allows greater flexibility to handle upsets of emulsion layers, and oil in brine issues. The kar panel tends to reduce rag layer automatically as well.