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Length Grading

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 curveis. You can imagine that if the curve is infinitely narrow and the average length is 2 mm, you can sieve all the 2 mm particles out but never achieve a higher average length. Giving a measured curve and a proposed average length spec, ECO-RIGEN can predict the expected losses with a reasonable accuracy.

The most risky operations with regard to the average length of a catalyst are loading and unloading into and out of the reactor. A poor average length is often caused by vacuum unloading. We therefore recommend not to unload by vacuum unless it cannot be avoided.