catalyst cary over from fccu fractionation tower

[reza35]

hi
in our fccu we are facing with catalyst deposits in equipments downstream of the fractionator.the catalyst seems to be caried over to the the fractionator maybe due to the defficiency of the reactor cyclones . however the caried catalyst is supposed to be catched in fractionator by internal refluxes and enter the slury oil at the botum of the tower but as the unit is runing below 60 % capacity ther is a beleive that the tower internal refluxes are not mainained properly and so can not absorbe the entrained catalyst to downflow to slury oil . please let me know the coment on the mater and if any solution .

 

[kbander]

If you have a problem with the reactor cyclones I would expect you to see a lot of catalyst in the decant from the bottom of the fractionator before you would ever see catalyst go overhead.

Have you analysed the material to confirm that it is really FCCU catalyst and no some other material (i.e., a precipitate) that looks similar?


Good luck!

Bob

 

[reza35]

dear bob
thank you for your reply
we analysed the presipitated material , mostly they are catalyst whereas the catalyst content of slurry oil from bottum of fractoinator is less than 0.2 which is normal . again the question is ; how the bad performance of the tower ( when runing below the turn down capacity ) can cause catalyst cary over to overhead system ?
thanks

 

[Samiran]

You may try 2 things

1. try increasing reactor press as much possible
2. check rx stripping steam or any inadvertant steam entry
2. increase slurry recycle or wash liquid to maximum

May help

 

[25362]

to Samiram,

By increasing the reactor pressure, we'd induce more catalyst circulation. This enhances attrition and the production of fines. This what we wish to avoid, don't we ?

 

[StoneCold]

An easy thing to try would be to increase the reflux ratio of the FCCU Fractionator. The efficiency of the column is probably lower at the turned down rate. If this fixes the problem and you can stand the energy cost then great. You may have bigger problems in the column if increasing the reflux ratio to load up the column does not help.

 

[aybee]

sounds like the flapper valves at the bottom of the dip legs are passing/fallen off causing poor cyclone effy, and carry over...you will get increased wear in your slurry pumps too, check them out