Conical Screen Mills (also referred to as Cone Mills) are gentle size reduction mills which are often used to precondition the material prior to its entry into a process, either by delumping or coarse size reduction. These mills utilize a rotating propeller/stationary screen combination to gently compress material against the screen wall and size the material accordingly. Vacuum conveying is often used to move material through the conical screen mill, help improve overall throughput of the process, contain dust or exposure, and also to assist in improvement of end product quality.