Initially the mica is broken into manageable sized particles in a rod mill. The sand and mica mixture that results is separated in spiral washers. These spirals are about 24″ in diameter and stand about 8′ high. They resemble miniature amusement park water slides, and over a thousand are used at the mine. The difference in density allows the sand to be spun away from the mica.

The mica slurry that results is pumped to a vibratory dewatering screen where further washing takes place. Water sprays roll the mica uphill while gravity pulls it down. The tailings from the screen fall into a CP-10 Vincent press.

Previous to purchasing the screw press, the mine was using a Bird centrifuge to remove water. This reduced the mica to a 35% moisture content. Since there is some sand left with the mica, heavy abrasion resulted in severe maintenance costs.

We were surprised that a rental Vincent press was able to achieve 30% moisture. This is of great value to the mine because the dewatered mica must be dried to a bone dry condition in a rotating drum dryer. The trial resulted in the immediate sale of a screw press.

An added benefit is that less degradation of the flakes is occurring in the press. End users have commented favorably on the larger flake size they are now receiving.

Initial operation with the press was a failure because the screens blinded with the mica platelets. This problem was solved by bolting polyurethane wipers to the outer edge of the screw flights. The wipers keep the screens clear.