Fractionator Fouling and HKGO Filter Fouling

[4 drums cokerParticipant]

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

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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