Attrition mill

An attrition mill apparatus comprising:

• a grinding chamber having at least one grinding stage;
• an axial impeller;
• said grinding chamber having a chamber inlet for admitting coarse particles;
• said grinding chamber having a chamber outlet through which fine particles exit from the chamber;
• a separator stage comprising a separator inlet and said chamber outlet through which fine particles exit from the chamber;
• a classification stage within the grinding chamber, said classification stage being upstream of the separator inlet for classifying between coarse and fine particles based on mass of the coarse and fine particles;
• wherein said classification stage comprises a classifier element defining a first surface driven in rotation about an axis, and
• a second surface spaced from and facing the first surface so as to define a radially extending separation passage therebetween;
• and
• wherein the separator stage is devoid of a separator screen or comprises a screen which has orifices of larger dimension in comparison with the dimensions of fine particles exiting the chamber at the outlet,
• said chamber outlet being a separator outlet;
• wherein said impeller includes grinding elements;
• said grinding chamber at least partially filled with a slurry including grinding media which passes generally axially through the chamber;
• said separator stage comprising a separator element having one or more axial holes therethrough upstream of, and adjacent to, the separator outlet, said separator element mainly directing the grinding media radially outwardly from the impeller, upstream of the axial holes;
• wherein the separator element surrounds the separator outlet wherein at least some of the slurry flowing towards the separator outlet passes in an axial direction through the holes in the separator element.

An attrition mill for grinding particles in a fluid as a slurry comprising:

• a mill chamber having an inlet and an outlet,
• a grinding chamber defined as a portion of said mill chamber, said inlet being in communication with said grinding chamber,
• an axial impeller located in said grinding chamber,
• rotatable grinding discs attached to said axial impeller;
• a rotatable classifier disc downstream, relative to flow of the slurry, of said grinding discs,
• a rotor downstream of said classifier disc;
• said mill outlet being downstream of said rotor;
• said classifier disc having a surface opposed to a surface of said rotor;
• said opposed surfaces being located sufficiently close to each other to centrifugally classify particles in said slurry by mass in a classification zone defined between said opposed surfaces,
• said opposed surfaces being substantially flat annular disks of substantially equal outer diameter.

An attrition mill for grinding particles in a fluid as a slurry comprising:

• a mill chamber having an inlet and an outlet,
• a grinding chamber defined as a portion of said mill chamber, said inlet being in communication with said grinding chamber,
• an axial impeller located in said grinding chamber,
• rotatable grinding discs attached to said axial impeller;
• a rotatable classifier disc downstream, relative to flow of the slurry, of said grinding discs,
• a rotor downstream of said classifier disc;
• said mill outlet being downstream of said rotor;
• said classifier disc having a surface opposed to a surface of said rotor;
• said opposed surfaces being located sufficiently close to each other to centrifugally classify particles in said slurry by mass in a classification zone defined between said opposed surfaces,
• wherein the classification zone has an absence of screens for classification of said particles.