Aggregate attrition systems, methods, and apparatus

An attrition mill, comprising:

• a tank, said tank having a sidewall defining an interior volume, said sidewall positioned between a lid and a bottom surface of said tank;
• an inlet in fluid communication with said interior volume;
• an outlet in fluid communication with said interior volume, said outlet vertically displaced from said inlet;
• a motor;
• a shaft assembly, said shaft assembly comprising:
• a shaft, said shaft being removably coupled to said motor, said shaft being operably coupled to said motor for rotation of said shaft about a vertical axis, said shaft extending along the vertical axis through an opening in the lid toward the bottom surface and terminating at an end spaced apart from the bottom surface, wherein the lid supports the shaft for rotation about the vertical axis and the end is free of support for rotation about the vertical axis;
• a first propeller, said first propeller comprising a first axial core having a first axially extending outer wall, said first propeller comprising a first plurality of propeller blades mounted to said first axial core, said first propeller removably mounted to said shaft, said first propeller disposed at a first height;
• a second propeller disposed at a second height along said shaft, said second height being higher than said first height;
• a first spacer disposed between said first propeller and said second propeller, said first spacer removably covering a first portion of said shaft, said first spacer abutting said first axial core of said first propeller;
• and
• a second spacer disposed between said second propeller and said opening, said second spacer removably covering a second portion of said shaft, wherein at least one of said spacers at least partially supports at least one of said propellers
• an access opening in said sidewall of said tank;
• an access door displaceably mounted to said tank, said access door having a first position in which said access opening is covered by said access door, said access door having a second position in which said access opening is not covered by said access door, wherein said access opening is sized such that at least one of said first and second propellers is removable from said tank through said access opening.