Multistage hammer mill and a residue processing system incorporating same

A multistage hammer mill comprising:

• a plurality of milling stages arranged concentrically about each other;
• the plurality of milling stages arranged so that substantially all material in a first inner most of the milling stages passes through at least one subsequent adjacent milling stage, the plurality of milling stages including a first milling stage and a second milling stage,
• a central feed opening enabling material flow into a primary impact zone of the first milling stage;
• the first milling stage comprising an impact mechanism and a first screen arrangement, the impact mechanism located in the primary impact zone and arranged to impact material entering the primary impact zone and accelerate the impacted material in a radial outward direction, the impact mechanism being capable of rotating about a rotation axis, the first screen arrangement disposed circumferentially about and radially spaced from the impact mechanism, the first screen arrangement being provided with a plurality of apertures through which impacted material of a first size range can pass;
• the second milling stage comprising a second screen arrangement disposed circumferentially about and radially spaced from the first screen arrangement, the second screen arrangement being provided with a plurality of apertures through impacted material of a second size range can pass, the second size range being the same as or different to the first size range, and
• one or more impact elements disposed between the first screen arrangement and the second screen arrangement.