Patent ID: 7578459

Claim:
A method of comminuting particulate material by inter-particle comminution in a bed of particulate material, using at least two rollers and a grinding track in a vertical roller mill, the grinding track supporting the bed of particulate material, the method comprising the steps of: passing a bed of particulate material between the at least two rollers and the grinding track, the bed of particulate material being set at a height H m in a range of 1 mm to 150 mm, applying a compressive force to the bed of particulate material using the at least two rollers while rotating the at least two rollers about axes of rotation which intersect one another and which intersect an upright axis of rotation of the grinding track in a plane above the grinding track and spaced from the grinding track by a distance equal to the height H m of the bed of particulate material, to achieve a pure rolling action of the at least two rollers relative to the bed of particulate material, and engaging the bed of particulate material with the at least two rollers with the substantially pure rolling action to crush the particulate material to one of a ground product free of fines and a ground product at least with a limited proportion of fines.