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Tray Damage during heat-up of Fractionator

Home Forums Coking Technical Fractionation & Process Fractionation Tray Damage during heat-up of Fractionator

This topic contains 7 replies, has 3 voices, and was last updated by  Anonymous 13 years, 4 months ago.

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  • #4091

    Anonymous

    Recently, we started up our Delayed Coking unit and were able to draw only less than 20% of our normal light gas oil volume from the fractionator.  A scan of the tower showed that the trays from just above the LGO draw tray to the HGO cold reflux (Trays 6-15) are holding very little liquid.  Upon further investigation we found a pressure spike from 25 psig to 58 psig during our heat-up of the system.  We were following our normal procedure, but it appears that we had a large water accumulation that flashed at once in the tower.  Our current practice is to initiate the boiler feed water to the coke heater and preheater during this warm-up period.  The top of the tower was not hot enough for the water to make it up at this point during the heat-up.  We also added steam to the valves on the coke drum decks which makes it way to the tower through the recirculation line around the same time as the pressure spike.  We are assuming that we vaporized a slug of water which damaged the tower, but we can’t see why this time would have been any different than before.  To add to the confusion, this is the first start-up that we’ve had DCS so we now have much more data than we’ve ever before.  However, we don’t have the historical data to compare with past heat-up periods. 
     
    Has anyone had similar tray damage during the warm-up / start-up of their unit that might shed some light on the root cause of our problem?

  • #7465

    Anonymous

    Many I know, what main product did you produce in your fractionator….??

  • #7452

    Anonymous

    Cokers are notorious for having tray damage during the startup.
    If this does not happen often feel lucky.

  • #7410

    Anonymous

    we heat up with steam initially, but never back to the tower,  after steaing out and pressuring testing, we introduce nitrogen and try and get all the water out before introducing gas oil to start heat up activities, we never have had a problem

  • #7029

    Lucibar Davalillo
    Participant

    We have drained lot of water from coke condensate drum system right before getting ready for heating up the column; if you have one of those system, it may be the possible source of your problem.

  • #7001

    Claus Graf
    Participant

    In the extra heavy crude upgrader I worked in a few years ago we had tray damage in the coker fractionator and packing damage in the vacuum tower.
     
    The emergency steam system in the vacuum heater had plugged/non working steam traps that allowed water condensate to accumulate. When the emergency steam was activated during a shutdown, water (instead of steam) entered the vacuum heater passes, creating a pressure spike that damaged the bottom packing section of the vacuum tower.
     
    Regards CG

  • #6751

    Anonymous

    I agree with the gentleman who said feel lucky if this doesn’t happen often.
    Tray damage on startup of Cokers is to be expected.
    There is probably some damage during each startup and most drum switchs and cool downs.
    You are injecting large amounts of steam at these times and upsetting the tower.

  • #6750

    Anonymous

    I agree with the gentleman who said feel lucky if this doesn’t happen often.
    Tray damage on startup of Cokers is to be expected.
    There is probably some damage during each startup and most drum switchs and cool downs.
    You are injecting large amounts of steam at these times and upsetting the tower.

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