Length grading

Length grading is a special operation for length improvement.

Length grading is a special sieving operation with the objective to increase the average length of the catalyst, thereby decreasing the pressure drop in your reactor. This means, obviously, that you will lose the shortest part of the catalyst, so you will need regenerated make-up catalyst if you reload the batch in the same reactor.

Whether it is feasible or not to achieve a certain length spec by length grading depends on how wide or narrow the particle size distribution curves. Giving a measured curve and a proposed average length spec we can predict the expected losses with a reasonable accuracy. A poor average length is often caused by vacuum unloading. We therefore recommend gravity unloading instead of vacuum unloading unless it cannot be avoided.