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Crude Atomospheric Tower Bottoms to FCCU feed

Home Forums CatCracking FCC Process Crude Atomospheric Tower Bottoms to FCCU feed

This topic contains 4 replies, has 5 voices, and was last updated by  David Anderson 13 years, 11 months ago.

  • Author
  • #3964

    Mike McCumber

    We are getting ready to introduce Crude ATB into the FCCU low sulfur feed going to the riser no more than 10% of the feed rate. We had done this in years past and coked up the bottom of our main fractionator. We have since replaced our main fractionator and replace trays with structured packing. I was wondering if someone else out there has experienced any ill effects on the reactor side or with the main fractionator from running either reduced crude or vaccum tower bottoms to their FCCU? Or good resluts also. If someone would like to discuss via email, please contact me at or through this forum.

  • #7307

    David Anderson

    I would think an experienced “CATMAN” would fight hard with any Ops Planning people to keep the ATB oil directed to a vacuum tower and out of a FCCU.

  • #7251

    Lucas Revellon

    Yes and No.  If the economics are on the driver seat you don’t have a choice but blend in some of your good feed with ATB’s.  The rule of thumb is to blend around 10% to 15% of your total feed rate.  It can be done, use more catalyst, increase cat circulation and if you can, put naphtha around the ring where the feed vaporizes.  It will help to reduce the viscosity of the feed and hence contact time.  I say go for it and watch it closely.

  • #7151


    Actually, here in the Virgin Islands, we run an average of 65K barrels of resid and the balance VGO to a cat that charges 135-140 kb of feed. We strive to keep the pre-heat up and achieve good catalyst circulation. My only problem is the amount of catalyst that is charged (60-65 k/lbs per day), but hey, I’m not paying for it. LOL.

  • #6205

    Freddy Martinez

    We did that in the past succesfully, it all depends on the quality of the ATB you are charging to your Cat Cracking and how you handle it. In our case we were charging a parafinic ATB wich helps to increase the conversion to gasoline, its crackeability was very good.
    We did that on a MW Kellogg design which has a high dense catalyst phase in the riser, which helps to reduce the impact of the higher concarbon fed to the unit. Additionally an good blend of the ATB and VGO is required for better results, otherwise batches of high concarbon material in the feed will cause major upsets in the catalyst circulation and possibly a unit shut down.
    The economic driver for this operation was excellent, as our refinery did not have Delayed Coker and part of the ATB was send to bunker fuel production.

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