steam explosion

[Gergely BohaParticipant]

We had a severe steam explosion during coke cutting some time ago. Can anyone tell me if there is a way to predict steam explosions? How can I avoid it? What can be done against it? Is there any connection between the quality of feed (or the change of the feed quality) and steam explosion?
 
Regards,Greg

[Anonymous]

There has been any change (quality) in the feed unit? have you changed the way of cooling?
The type of formed coke (shot, sponge, needle) and their way of cooling can generate these hot spots that usually occur more  during the pilot cut , high contents of asphaltenes can generate Shot coke and that due to poor cooling or a quick cut can generate these events
we had several events (geyser) and what we did was comply with the procedure that during the cutting we keep the spedd of 3 ft / min  to give opportunity to cut water to help cool down, also we introduced a half-hour soaking during the quenching step (the last half hour) and in case of this event the operator rises faster the tool and leaves her there for a few minutes and continued to cut  more slowly
 
Best Regards
 
Espaa2005
 
 

[ted pivoMember]

coke drum erruptions are common to shot or transition coke. this usually happens when the water channels thru the coke causing the hot spots. the first identifier for eruptions is yellow vapors when you remove the top head. When you start the cutting water you will see the steam puffing before the coke blows out of the drum. Bayside engineering and Ruhrpumpem both have enclosures to prevent the coke from escaping. I have seen both they are good devices.let me know if you need anymore ifnormation. I am an ex coke cutter with almost 25 years of experience

[Gergely BohaParticipant]

Hello,
 
We almost never change the way of cooling and we also use the half-hour soaking during the quenching step. However, the quality of feed alters frequently. Generally, our feed is the bottom product of vacuum distillation units, but sometimes hydrocrack residue is mixed in this feed.
We usually, but not always, experience steam eruption when hydrocrack residue is mixed in and/or the asphaltene content is high.
Is there anything else which can be done to reduce the chance for steam eruption? I mean for example FCC slurry oil mixed in DC feed when asphaltene content is high, or rising the coking temperature at the end of coking phase?
If you have DC feed from more sources then it is worth trying to blend a DC feed which has low asphaltene content?
 
 
Regards,
Greg
 

[Anonymous]

Check this document:
 
http://www.fwc.com/publications/tech_papers/oil_gas/shotcoke.pdf

[Claus GrafParticipant]

This is what makes this forum great, people like woodshop00 with lots of operating experience sharing their knowledge.
 
We need to hear MORE from guys with operating experience, so everybody will be safe in their coker.
 
Regards,
 
CG

[Anonymous]

What can you do ?
 
Install an automated top unheading device and cut the drum remotely from a shelter.
 
 

[bobby gawlikParticipant]

I have to agree that feed stock changes, channeling are contributing factors, but I feel proper quenching is the key to preventing these “blowouts” We quench our drums a little different than most as follows: Switch 1am, seperate 1:30am, 4am take out of scrubber or when drum fill indicators are over coke bed, 4:30am to 5:00am approx drain the drum with less than 1.5psi and under 200 degrees on top TI. Also keeping over 30 psi on drum while quenching also helps.

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