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low flow recovery

Home Forums Coking Technical Heaters & Furnaces low flow recovery

This topic contains 5 replies, has 3 voices, and was last updated by  coker squirrel 15 years, 8 months ago.

  • Author
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  • #4351

    Christy Bohannon
    Participant

    I am trying to put together a procedure for what to do after flow is lost due to a charge pump cavitation or trip. What I am evaluating is at what tube temperature it is safe to reintroduce feed and remove emergency steam to minimize the chance of fouling (this is assuming that the tube temperature rises). I assume that if the charge pump just cavitates that no-one would shut it down completely if the temperatures increased, but when should emergency steam be decrease back to velocity steam, and is there a certain flow rate you look for? If the pump trips, what tube temperature would you recommend before re-introducing feed?

  • #7807

    coker squirrel
    Participant

    You not only need an Emergency Procedure for Loss of Heater Feed but you also need a Safety Interlock System (SIS) to protect your Heater. You should have it set up to trip the Heater Fuel Gas and inject steam or boiler feed water that would protect your coils from coking up and plugging.

  • #7804

    Christy Bohannon
    Participant

    We do have both a procedure and SIS to inject emergency steam and cut fuel gas temperature in a low flow situation. What I am evaluating is when it is ok to re-introduce feed / cut back emergency steam to velocity steam. If the pump simply cavitates, I assume you would not want to shut it down even if the skin temps are a little high, but you would want to keep as much steam going through the passes as possible. If the pump trips, at what temperature / other process condition do you want to re-start the pump?

  • #7802

    coker squirrel
    Participant

    Skins <1300°F and outlet <880°F is the general rule of thumb I go by.

  • #7784

    Anonymous

    If you need more feedback on this topic I offer the following.
    Your heater trip logic should be set such that upon cavitation the burners should trip based upon low flow to the heater. Cavitation, which will cause both the flow and the temperature to rise and fall rapidly should be dealt with quickly and the logic should be set accordingly. When the initial cavitation ocurs flow will drop (which should cause a trip) and if the heater does not trip temperatures will rise quickly and heater tube coking rates can increase immediately. Once heat is out of the heater and the cavitation has been corrected it will depend upon the level in the drum being fed as to the actions that should be taken. If the drum level is less than half then cold feed can be re-introduced to the drum and heater temperatures quickly brought back to normal levels. If the drum is close to being full then cold feed should not be re-introduced as the cold feed can lead to excessive foaming and potential carry over. With a full drum the heater outlet should be routed back to the fractionator bottoms and feed brought back to the heater while a drum switch is prepared for and when the new drum has been vapor heated the heater can be re-introduced to the coke drum.

  • #7778

    Anonymous

    garyville coker if would shoot me an e-mail i may be able to help you with this. We have recently done work on our low flow trips. I can reached at notid10t@yahoo.com. By the way how are you guys dong over there anyway?

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