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Circulating catalyst without feed

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This topic contains 3 replies, has 1 voice, and was last updated by  Anonymous 11 years, 1 month ago.

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  • #2090

    Freddy Martinez

    How long would you feel comfortable circulating catalyst without feed in your FCC? Using torchoil to heat the catalyst in the regen and steam in the reactor to keep velocities up and keep it hot

    If it’s more that 4-5 days, what kinds of things besides sour water make, catalyst fines in the slurry circuit, catalyst fines at the scrubber and maintaining heat on the reactor to prevent building a concrete block inside, would you worry about? Just curious as to how long folks have run this waywe feel like we might be treading new ground.

    Most importantly, we don’t want to set ourselves up for next years conference with a Lessons Learned presentation!

  • #4872


    Ken & Bob: We are here at the Duesseldorf Conference. We’ll be opening your question for discussion with the delegates on Friday. Here’s our response until then:

    The greatest period of time for hot/dry catalyst circulation we have personally observed was 7-8 days (Ken), 10-11 days (Bob). Sour water, catalyst attrition/fines generation, maintaining adequate heat in the reactor are concerns but are easily managed.

    What is more difficult is balancing the regenerator temperature…too hot and slide valve position, and fluidization/circulateability (catalyst flow control). There is an increased chance of damaging the reactor internals if the reactor temperature gets away from you (it would be good to know is you have carbon steel (good to 1050 degF) or 1.25 Cr/0.5 Mo (good to 1150 degF)). A lower regenerator temperature (<1275 degF) would help but there would a tendency toward higher CO emissions and cyclone hanger temperatures (from afterburn). The “best” is to strike a balance for minimum regenerator bed temperature for catalyst circulation stability/control and a maximum for CO emissions control. You can operate at low air rates and low regenerator pressure to keep regenerator cyclone velocities elevated. If available, you can pressure up your overhead accumulator with fuel gas to establish the reactor and main fractionator pressures. This may help to establish better slide valve deltaP for stabilizing your catalyst circulation. Keep reactor/stripper hot (at least 500 degF) to avoid steam condensation and catalyst wetting.

    We would expect losses in catalyst activity (MAT) and pore volume (PV) as well as increasing bulk density (ABD) due to lengthy exposure to a very hot flame front near each of the torch oil injection nozzles. You can add fresh catalyst at a rate to make up for losses and perhaps somewhat higher to achieve a slight build in bed level to counter the activity and physical property shifts. Send out equilibrium catalyst samples frequently to track the Ecat properties and assess the potential for having to replace a portion of the inventory when you want to return to normal operations.

  • #4871


    postscript from Ken & Bob:

    If you need to replace a portion of your inventory then reduce your regenerator bed level to minimum, reload with GOOD QUALITY Ecat to maximum bed level, circulate for 2-4 hours, repeat the steps (dump to min, reload with the good Ecat, circ for 2-4 hrs), then dump to minimum and reload with good Ecat to your normal operating level. Follow up with your fresh catalyst additions at a rate of about 1.5 times the normal usage for the next 3-4 days. This should help restore the inventory catalyst quality more quickly.

    If you would like/need to have a discussion then let us know and we’ll set up a conference call.

  • #4870


    feedback from conference delegates:
    > select “good” quality torch oil, if possible, to avoid pH swings in sour water
    > batch stripper catalyst from time-to-time to keep it hot and avoid mudding up
    > check velocities where steam is injected; adjust conditions to keep <200 FPS for attrition reasons
    > send gasoline to riser versus steam; helps add carbon on catalyst (less torch oil use) and steam usage (less SW); refiner practiced for this procedure for 12 days with success
    > sample fractionator overhead accumulator for buildup of oxygen; vent at some frequency

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