Tarball

[cokballParticipant]

We just experiance a tarball in one of our coke drums that knocked it offline for a couple of days while we cleared the tarball.  The investigation indicated that there was a ring of coke left in the drum from the drilling.  My question would be has anyone heard of a tarball being created from a ring of coke falling after the drum is switched into?  To clarify further the drum had a normal warm up the condensate drum looked good temp and level were alright.  The only thing that looked out of place was the bottom TI never raise above 132 degrees during warmup and after the switch.  When the drum was switched into the level immediatly rose to 55+ and was knocked back down with anti foam.  Then about 1 hour later the level came back up, we were unsuccessful in knocking the level down again so the drum was switched out of.  Total cycle time was 1 hour 50 min.    Thanks for any help you can provide.

[Claus GrafParticipant]

Good day,
 
Question: Where is this TI located ?
 
Regards, CG

[cokballParticipant]

The bottom drum TI is located about 20 feet up from the delta valve. 

[Anonymous]

Sounds about right, but your tarball was probly not specifically created from the coke left in the coke drums, but this is probly the root cause.  The tar ball was because you only had an hour and half feed time and couldnt get long enough time for that time/heat cracking to take place.  Because of the coke left in the drum you had to switch out of it way to early, rule of thumb we use is to try to shoot for at least 8 hours of feed time if conditions exist, if not your probly gonna get a tar ball.

[Anonymous]

Thanks CG  I will go with that as being the root cause of the problem. 

[antonio saura CebrianParticipant]

The phenomenon of foam experienced during the first few minutes of switch the  drums, can be motivated by a drum usually too cold or accumulation of liquid in the bottom of the drum, because the temperature indicator is not increased during the warming  of the drum it seem to exist a plugging  on the bottom line that could allow the drum filled with liquid  (How long was the time for warming the drum ?).
 
Over the years and during my  first years of operation in these units, I note that the minimum time to ensure that residue  in order to converted into coke was between 7 to 8 hours of coking time, as long as the top temperature was above the drum 805 degrees F
 
Best Regards

[antonio saura CebrianParticipant]

I Forgot to tell you that we develop a procedure for cases where the drum had less than 6 hours in service for any eventuality that no allow  the completion of the cycle , The procedure was inject flushing oil ( in ours service header, we have a 2″  line of flushing oil) we inject steam (standard procedure) and simultaneously be injected washing oil  during the same amount of time it was the drum in service.
 later this mix was sent to the coke condensate system (always remains some of steam at the bottom of the drum)
 
This was done for 3 times, and then washed system coke condensate to
to ensure the displacement of this system.  when we opened the drum we not found nothing in the drum
 
This procedure was applied in almost 6 opportunities without any upset, avoiding presence of residue in the pit or pad
 
Im sorry for my english

[Author]

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