Possible Causes of Excessive Catalyst Loss
- Inability of the cyclone diplegs to discharge the collected catalyst
- Flapper plates on the tickle valves have either fallen off or worse, partially closed
- Coke, refractory materials or wet catalyst has partially restricted in the cyclone dustbowls and/or diplegs
- Catalyst bed level underneath trickle valves is not uniformly fluidized
- Mechanical damage to the air distributor or the stripping steam distributor
- Holes in the cyclones, cyclone crossover and/or plenum
- Excessive catalyst attrition caused by:
- Steam to the torch nozzles
- Blast steam into the riser/J-bend
- Partially plug nozzles in the steam distributor
- Very high cyclone velocities
- Very high velocities in the air distributor
- Missing restriction orifices in the purge taps and/or aeration nozzles
- Soft fresh catalyst