Tarry Drum Discussion Group Notes10/26/2012Facilitators: Jennifer Stiglitz, Husky Energy & Evan Hyde, coking.local
- 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.
