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Antifoam on Drum Level Control

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This topic contains 10 replies, has 4 voices, and was last updated by  Gary Pitman 10 years, 6 months ago.

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  • #4397

    coker squirrel
    Participant

    Are there any Cokers running antifoam on Coke Drum level control? It would probably be more efficient way to control antifoam usage. The antifoam should be injected at the top of the Coke Drum 180 degrees from the vapor line. It would work better to have the antifoam tank located on top deck so that response time with an antifoam knock would be more responsive. This would also reduce antifoam usage and would be more effective. CHGO should be used as a carrier. It is heavier than CLGO and would tend to not flash as easy.

  • #7858

    Gary Pitman
    Keymaster

    Having the anti-foam controlled by level does work. We have had this control system for many years. Anti-foam rate is controlled through a metering pump and then injected into the CLGO carrier. The line to the drum is packed and the response time is immediate.
    We can run either CHGO or CLGO we prefer CLGO.
    I would not want any storage of anti-foam on the structure.

  • #7857

    coker squirrel
    Participant

    That is pretty much the same system we have in place right now with the exception of the automatic drum level control. I was looking to improve on this system. It is difficult for us to set up a reliable auto-controlled antifoam injection system. We have to add antifoam as needed with a flow controller. I want a reliable automatically Drum Level Control system. Currently, the Console Operator has to focus his attention on the Drum Level to inject additional antifoam when it is needed. If we had a level controller that would do this, I think that we could possibly minimize our antifoam usage.

  • #7822

    Sangu Narayanan
    Participant

    What type of level measurement are you using? Is it Neutron back scatter or other radiation types? Is there any advantage in using one over the other?

  • #7786

    Anonymous

    Neutron backscatter is a a proactive sensor that operates on the prescence of radiaton. It reads the density of the foam and ,therfore, lets you know the proper time to anti-foam.
    Gamma is more re-active and works on the principal of the absence of radiation and, therefore, has difficulty in defining the type of foam. The best solution is a combination of using neutron backscatter (three to four units) on a drum with gamma level at the top (typically ten feet) for foam over prevention. This combination also allows for monitoring closer to the chord line.

  • #7689

    Anonymous

    You have to remember that Neutron back scatter units measure the hydrogen density so it is not really measuring the top of the foam.  The gamma detectors will respond to anything that is in between the gauge and the radiation source (ie. the top of the foam).  The gamma system is better in determining exactly where the top of the foam is actually located.

  • #7647

    Anonymous

    [quote]ORIGINAL: garypitman

    Having the anti-foam controlled by level does work. We have had this control system for many years. Anti-foam rate is controlled through a metering pump and then injected into the CLGO carrier. The line to the drum is packed and the response time is immediate.
    We can run either CHGO or CLGO we prefer CLGO.
    I would not want any storage of anti-foam on the structure.
    [/quote]

  • #5725

    Anonymous

    we have gamma levels. but i want to now haw to determinate the real fom level using gamma. i have a difference of 5 feet betwen the reactive and real level, is correct? or should i inyect more antifoam? this question do not permit me to control antifoam inyeccion 

  • #5582

    Anonymous

    When using anti-foam, you are never going to get rid of all the foam no matter how much anti foam you use.  The idea is to try and control the amount with the least amount of anti-foam as possible and makes sure that you don’t have a “fluff” up after switch that causes a foam over.  By using the gamma level, you can determine approzimately how much foam you have by tracking the differences from the level at switch to after switching.  This will show you the amount of foam that you had present at switch time.  Normally (depending on types of crude and charge rates) you can have anywhere from 2 feet of foam to 10 feet of foam at switch time even with the full amount of anti-foam being injected.  Remember some crudes are bad about foaming after switch.

  • #5338

    Anonymous

    Anti foam is a unique problem to many cokers and we had many discussions at the coker I worked at about it. We had more problems with foaming toward year end, when RP&S (receiving, Pumping and Shipping) would cook up “cocktail” crudes for us to run and sometimes we’d have light materials mixed into the crude slates as well as crudes with some chemicals in it from normally downstream units. That having been said, under “normal” if there is such a thing on a coker with the varying crude slates, we determined that the coke drum builds a head of foam right from the start of charging it and the foam level (as mentioned above) varies anywhere from 2 to 10 feet and sometimes more. A major determining factor as to coke foaming is the temperature at which you start charging the coke drum. The hotter the better, thence a longer warmup time is the best. Now with shortening cycles, sometimes coke foaming is a trade off for shorter cycle time. Also, anti foam consideration needs to be addressed so that you don’t contaminate your hydrotreater catalysts or your reforming unit catalysts. After all that anti foam has to go somewhere once it’s used in the coke drum and goes in the overhead back to the fractionator on most if not all cokers. It is going to go overhead with the naphtha streams and where is it going to end up? Best case scenario is that you don’t use but a minimal amount of antifoam after the drum you’re switching into in already into warmup and getting ready to switch into it. Worst case is you put antifoam into the drum halfway through it’s charging cycle due to terrible back foaming from raunchy crude slate cocktails and insufficient drum warm up before switching into it. Good luck with your antifoam endeavors. Hope this helps.

  • #5159

    Anonymous

    Hi, can you gents give me a some details (typical) about the measurements you are trying to make?
     
     – Drum diameter
     – Wall thickness
     – range of foam densities
     – overall vertical measurement range needed
     – do you experinece product build up on the walls, if so is this more predominant at particular elevations
     – what type of nukes are you using?
     
    I’d just like to run some calcs..
     
    Thanks,
    Simon
     

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