Vertical shaft impactor

A vertical shaft impactor to process a plurality of different materials, the vertical shaft impactor comprising:

• a housing defining an impacting chamber having a plurality of generally horizontal shelves secured to the periphery of the housing and extending into the impacting chamber;
• and
• an impacting assembly disposed in the impacting chamber, the impacting assembly comprising
• a generally vertical shaft supported by the housing,
• a plurality of rotors concentric with the shaft and rotatable relative to the housing,
• a plurality of key slots defined in the generally vertical shaft at predefined intervals along the generally vertical shaft, and
• a plurality of keys selectively disposable in the key slots, each key including a nub for supporting one of the rotors along the shaft, the keys being interchangeable to vary the vertical position of the rotor relative to the shaft.