Open breakout Wednesday 10/24/12Topic: Fractionator fouling and HKGO filter foulingFacilitators: Bobby Wright, SES & Evan Hyde, coking.local
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)
