Normal conversion rates are in the 65 to 75% range on a partial burn FCC. Typical cat losses with healthy cyclones would be in the range of 2 to 5 tons per day. Above 10 TPD and your probably looking at cyclone damage somewhere in the unit and cat particle size should tell you where from.
You say 2 to 5 tons per day catalyst loss, but how much it represent as percentage of the total circulating catalyst. I understand that the 2 to 5 tons has to be replaced as fresh catalysator is that the case?