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Fractionator Fouling and HKGO Filter Fouling

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    4 drums coker

    Open breakout Wednesday 10/24/12
    Topic: Fractionator fouling and HKGO filter fouling
    Facilitators: Bobby Wright, SES & Evan Hyde,

    Details: 1/8” basket strainer with 20 mesh – high dP after 12 hrs, previously 3-4 days
    Key discussion points

    • Seeing fouling, exact nature unknown, in HKGO and kero draws
    • Group concensus that increasing temperature to strainer should directionally improve the problem if asphaltene solubility is the cause.
    • To test for “gums” – lab filtration followed by solubility test in toluene or other aromatic solvent.  If soluble, apshaltenes, else coke.

    Topic: Coke Cutting
    Details: General question on methods employed
    Key discussion points

    • Typical bore times of 10-15 min
    • Leave some coke in the coke to prevent entire drum collapse
    • Rule of thumb for cutting pressure – 150#/ft-drum
      • May be overkill for large drum diameters where flow become more important.
      • After 5% of nozzle wear on the cutting tool, it should be replaced.  Us a no-go tool sized for cutting and boring nozzles.

      Topic: Drum Overhead Vapor Line Fouling
      Details: Does not seem to be an issue at all sites, why?
      Key discussion points

      • Experience varied from cleaning weekly to every 12-18 mo’s
      • Wetting of the pipe if critical to ensure cleanliness
      • Some sites in the past have tried splitting flow from the horizontal to vertical position, no flow control at the split, but sized for 60% horizontal, 40% vertical-oriented down.  Nozzle plugged in the down orientation due to small orifice size. 
      • Position of insertion, 25%-50% of drum opening.  Little concern about quench flow falling into drum due to vapor velocity in exiting vapor.
      • Heavy slop oil, blowdown bottoms, is also used as vapor quench in lieu of HKGO.
      • One site used light slop from OSBL, with high water content.  See corrosion in piping circuit leading to injection but not after.
      • Cleaning should be done under fresh air due to trapped liquids in the coke.
      • Lieberman rule of thumb – +1% yield for a 8 psig reduction in drum pressure
      • Taking off insulation can increase the fouling resistance and effectiveness of quench.  Ensure use of personal protection if not insulated.
      • Interlocks using drum vapor temperature should be downstream of quench injection to limit coking of thermowell.  Various permissive temperatures were used for interlocks.
        • Site 1 – Vent T < 375F, TUD < 300F
        • Site 2 – Vent T none, TUD < 180C (was 120C, MOC change)


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