A rotary mixer is a cylindrical, rotating device for loosening and mixing bulk materials. It is used in particular in the Pelletising and agglomeration used when powdery materials are to be processed into larger grains (pellets) by controlled moistening, binding or heating.

Rotary mixers are not precision mixers. They only work if the mixing materials are of the same type (bulk density, grain size, flowability, quantity ratios, ...).

Rotary tube mixers consist of an inclined, rotating tube in which the product moves continuously while rotating slowly. Built-in chicanes (e.g. ledges or impact surfaces) promote the mixing, turning and loosening of the bulk material.