The kinetics of hammer milling of maize

The kinetics of breakage of maize were measured in a small laboratory hammer mill, with a rigid blade used as hammer. It was found that breakage was first-order, and that the primary breakage distributions were insensitive to mill conditions or moisture content of the material. The specific rates of breakage were dependent on particle size to approximately the third power; they increased as moisture content of the grain was reduced, showing that the drier material was more brittle; and a minimum rotation speed was necessary to get significant breakage. It appeared that material was thrown to the outer wall, so that only the ends of the hammer were effective, and a major part of fracture occurred by particles being thrown against the wall; an optimum loading exists for maximum breakage rates.