Function of Main column bottom filter

[Anonymous]

We install a filter in the main column bottom circulation loop.
 
Recently we found the inlet line of the filter is plugged.
 
We can not shut down our plant due to the abnormal event.
 
We would like to know how long we can run our plant without this filter.

[Anonymous]

this happened to us in lake charles, we ran until the next t/a and revised the nozzle in the bottom of frac

[antonio saura CebrianParticipant]

Generally when the people  design this system they  conceived to operate one week without them and for that reason this system only have one pump installed in the field (commonly)
 
If the operation of the unit is stable and during the switch of the drums and stripping you dont send  too many coke to the bottom of the fraccionator, this  would avoid that the coke strainer (inside of the fract ) in the  suction line to the heater  pump, begin to plugg with coke, in other words;  while you don’t see any problems by the NPSH of the pumps you can  kept operative the unit
We have had this problem of plugging  due to the emergency valve (butterfly) in this line . Since if you observe these valves internally a line of 6 inches It turns in o almost of 3 inches due to the internal configuration
 
We running  the unit monitoring  the pressure in  the suction and realizing thermography  to the wall of the fraccionator, in order to  seeing the level of coke until I stop the unit for his repair (around 3 months)

[Anonymous]

Have you tried steaming back up into the tower to unplug the line? Make sure that you dry the steam out real good before trying this!
How long you can run depends on how tall the stand-pipe to your furnace charge pump is and how much coke you are carrying over in your daily switch/ blowdown

[Anonymous]

Our nozzle from the frac to the strainer is only a 3″. We realized during the first 2 years of operating this thing, that the nozzle was plugging in the bottom of the frac. The nozzle is too small and also has a vortex breaker thereby contributing to bridging of the coke. We do not even use the strainer loop and have blinded it off. We run about 18 months between turnarounds and typically see about 4′ of coke in the bottom of the frac, which is well below the height of our standpipe.
 
 
 

[Anonymous]

Try back flushing with heavy coker gas oil. It produced better result then steam flushing. In steam flushing there is always a chance that the heater charge pump might loose suction. Back flushing can be done when the unit is online i.e. with out bypassing the reactors. 

[Anonymous]

Stupid question.  Have you tried to blow it back into the column with steam?  And I question the safety of performing that task as it could potentially cause problems with your bottoms pump if you sluff off a big chunk of coke.  I would guess a six month window. . .but guessing is exactly all you can do.  You could proactively reduce charge rate and reduce the amount that you fill the drum so as to reduce the amount of particles entrained.  Or, you could reduce cycle time at the same charge rate to reduce the amount the drum is filled.  Perhaps these options could buy you more time.

[Author]

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