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FCCU Severity

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This topic contains 1 reply, has 2 voices, and was last updated by  Alan R. English 1 week, 1 day ago.

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  • #27618

    Hedewandro Lucredi

    We had a Consulting service that analyse our FCCU (we have two) and recommends that we done some test in our site in order to increase unit profit.
    They want to increase/decrease some process variables up to:
    -TRX (Reaction temperature) : 555 Celsius
    -TCC (Feed Temperature) : 180 Celsius
    – Main tower bottom temperature : 365 Celsius (maximum LCO recovery)

    Is it common these targets in the FCCU ? What about Fuel Gás production in these conditions ?
    What is it the typical conditions in the FCCU for these variables ?

  • #27619

    Alan R. English

    The process conditions you mention are within the range of normal FCC. It is not possible to comment on if these conditions are right for your unit with studying your constraints and feed/product pricing. 550 C reactor temperature is fairly high. This is justified when conversion, olefinic LPG and/or octane have high value. Gas yield will be high which typically means feed rate must be reduced. Also, expect high gasoline diolefins (potential gum). You must determine if the advantages outweigh the costs. 180 C preheat is on the low end of the typical range. Low preheat is used to increase catalyst/oil ratio and conversion as well as to lower regenerator temperature. Going much lower may adversely affect how well your feed injectors work due to increased feed viscosity. 365 C fractionator bottom temperature is reasonable but keep in mind that this temperature does not determine LCO cut point or recovery. Typically, the bottom pool temperature can be controlled separatly from the flash zone temperature by diverting cool slurry pumparound directly to the fractionator bottom. Adjust slurry pumparound to the shed deck and LCO draw rate to optimize fractionation but be certain to maintain sufficient rate to assure that all surfaces in this section remain wet to prevent coking.

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