Abstract: A tube mill for dry grinding of a granular material, the mill being formed with one or more grinding compartments charged with grinding bodies and, downstream of the first or sole grinding compartment, a relatively short compartment bounded downstream by a dam ring having a central opening and upstream by a sieving diaphragm for holding back the grinding bodies, but permitting fluidized ground material to flow from the upstream grinding compartment to the short compartment and vice versa, the short compartment being adapted to serve as a reservoir of fluidized ground material.

Abstract: An air-swept tube mill having at least two grinding chambers and a discharge chamber, an internal by-pass means in the last grinding chamber in communication at one end with the grinding chamber immediately preceding the last grinding chamber and at the other end, with the discharge chamber, whereby material ground in the first chamber is transferred through the by-pass directly to the discharge chamber and oversize material is transferred from the discharge chamber to the last grinding chamber for further grinding. A unique method is disclosed in which grinding of material takes place in a first grinding chamber of a tube mill and by-passed into a discharge chamber. The method further comprises feeding oversize materials from the discharge chamber into a last grinding chamber for additional grinding thereof.