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Tarry Drum Discussion Group Notes
10/26/2012
Facilitators: Jennifer Stiglitz, Husky Energy & Evan Hyde, Coking.com
- Verify hydraulic cart can handle the hydraulic load before deheading a tarry drum. One site tested the hydraulics and some hoses failed.
- Move hydraulic controls away from the line of fire – this should be done in the base case but for sure when dealing with a tarry drum.
- Opening the top head before draining can be risky due to boil over risk but it is done because the drum vents are very small, 3-4”. They are installing larger vent lines, 14”.
- How do you determine if a tarry drum exists
- Define site specific process conditions based on experience
- Lieberman target = if not >790F for more than 1 hour, then tarry.
- When can you go back into the drum?
- Extended steaming experiences
- 12hrs+ of velocity steam, no burners in heater
- 12-24hrs of superheated steam. Must consider impacts to convection and heater outlet piping.
- Establishing steam and/or quench ASAP after an event is critical to preventing an unquenched drum scenario.
- Consider the use of double quench or soaking if a tarry drum occurred, especially near the end of cycle to ensure adequate cooling throughout. Unreacted resid could have plugged channels. Extended steam strip as well.
- Drain plugging risk increases with tarry drums. Slide valves mitigate this problem to a certain degree. Common drain headers could plug and lead to issues with the entire unit.
- If a large amount of water is in the drum with the drain plugged on a manual system, consider the use of a sump pump used from the top head to remove some water. Verify tar level using drill stem.
- Use of the drilling water has been used to stir up the drum
- The coke bed could be “cooked” more using very high recycle (50%+ if possible). Increased mass rates at COT will drive tarry material more towards a solid coke bed. Tried successfully at one location.
- One site had alternate drain nozzles on the drum cone, 4 total. Contributes to additional drum stress but useful in upset conditions. They are debating using the same design on a new plant but slide valves are an alternative drain as well.
- Use of chemical cleaning agents, RTI quickturn, has been tried to dissolve some oils before draining the drum. Results unclear.
- Short Drum definitions
- Site 1 = <6 hrs on 16hr cycle
- Site 2 = <6hrs on 20hr cycle
- Site 3 = <4hrs on 12hr cycle
- Other opinions, <3hrs
- Use extra antifoam if going back into a drum after feeding unreacted resid.
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