An apparatus for rotationally grinding, pulverizing, or comminuting bulk materials. A material processing component of the apparatus is fed at an input end by a hopper. The material enters the material processing component for processing and is propelled out of an output end through an outlet into a tray or piping. A cylinder of the material processing component is protected by an exterior insulating compartment and a replaceable inner liner. The cylinder defines a horizontal stationary work area. A rotatable shaft penetrates the cylinder along an axis of the working area. A plurality of working bodies are attached to the shaft in a narrowing helical orientation that also narrows in distance between working bodies from front to back. The working bodies are configured to comminute the material and direct it toward the outlet as the material passes through the working area.