Gas velocity in a Air Swept Ball Mill? How much?

Hi everybody!!

I will start with an easy questions( I can't find the answer by my self... :S)

I know that the gas velocity in a normal Ball Mill should be around 1,5 m/s.

Now the problem arrives when I want to use an Air Swept ball mill. So, anybody could tell me an average/normal value for the gas velocity in air swept ball mills?

Thanks¿!!!! ■