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Flare liquid in the DCU

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This topic contains 6 replies, has 3 voices, and was last updated by  Hedewandro Lucredi 3 years, 8 months ago.

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  • #24667

    Hedewandro Lucredi
    Participant

    We usually process flare liquid on the vessel top main tower. This liquid has +/- EP 350 Celsius and is mainly HC with some water (+/- 30 %). Besides all problem that we have with our DCU from flare liquid processing (fouling on the equipment, etc) we intend to reduce the flare liquid “produced” in all units (FCCU, DCU, Hydrotreater, destillation). Anybody has this problem ? How can I measure the liquid flare production on each unit and each PSV and so on ?

  • #24668

    Evan Hyde
    Keymaster

    Interesting question. I have not seen flare KO pot reprocessing on the DCU before. Seems reasonable but yes, I would expect fouling to be concern. Many units used to reprocess their slops (BD mainly) directly in the fractionator but stopped due to fouling issues.

    Flare releases are heavily scrutinized in some places like california. So great care is taken to understand all the sources. Downstream of the PSV or other sources, you can put sensitive TI/PI to indicate if someone is “in” the flare. Also, PSVs will start to leak at 90% of their setpoint so find all the equipment and processes who are near this limit.

  • #24731

    Hedewandro Lucredi
    Participant

    We are studying to send to blowdown this flare liquid, but we already sent recovered oil from API to this systems and oil from SWS also. Your ideia to put sensitive TI/PI is good or even using infrared , but I am concerned how to measure the flowrate in the BL (battery limit) of each unit. We need to do a “mass balance” of this liquid from each unit to flare. Also, if you have any ideia I will appreciate.

  • #24733

    Evan Hyde
    Keymaster

    In my experience, if the flow to the flare is sufficient to be seen on a mass balance….. you have a big problem! DCU matbal are typically +/-3-5% with the best being 1-2%. If 1% of some flow is going to the flare, you should see it very clearly. What is the flow to the flare system right now, absolute and a % of feed rate?

    Flare flows are typically too low relative to pipe diameter to have a reliable flow measurement.

  • #24741

    Hedewandro Lucredi
    Participant

    Evan
    As I told, we process all liquid flare from our refinery in our DCU and this liquid is not from our DCU only. We process +/- 0.7 % related with the feed rate. We need to discover all point from all refinery unit in order to check any leakage to flare that would be possible to produce “liquid” in the blowdown flare.

  • #25012

    Mike Kimbrell
    Participant

    It is fairly common to have the combined slop stream from the refinery processed through the Coker. That would include liquid from the flare header and drips from the fuel gas system. Both of those streams can have a lot of water in them, so it is important to remove the water before processing that stream in the Coker. As the composition of slop can vary widely, it is typically injected into the fractionator just above the shed decks so that any high boiling fractions do not contaminate the lower boiling products.

    Your question seems to be more about slops management than it is about reprocessing slops in the Coker. It can be challenging to find the source of slop production. If you think it is coming from relief valves leaking by, this can be checked with an acoustic device that senses the high frequency noise generated when a relief valve is leaking. If the relief valve is leaking only during a portion of the cycle, finding this source of slop can be quite difficult. Wireless acoustic sensors could be placed on all the relief valves in an area and monitored that way over several drum cycles. That could assist in determining an intermittent source

    Routine testing of the hydrocarbon phase of the slop using simulated distillation (SimDist) can show differences in the hydrocarbons produced (higher or lower boiling fractions) which can provide insight into where the slop is being generated.

  • #26245

    Hedewandro Lucredi
    Participant

    We checked our PSV’s and PV with ultrasom and we observed that some PV’s had leakage to the flare. We are fixing these valves. In the field and in the DCS these valves were closed but they had some leakages. Also we found one PSV with some leakage.

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