High dust at crusher discharge

Causes of crusher discharge dust

Crushing breaks rock or ore into smaller pieces and in doing so creates new, dry fine particles that were not present in the feed. The crushing action and the falling product both pump air, and that air carries fines out of any opening around the discharge chute or onto the outgoing conveyor. Screens add to the problem by agitating the material and separating out the finest fraction. Dry feed, hard friable material, high throughput, open discharge points and poor sealing between the crusher and the take-away belt all increase dust levels. Dust often appears at the feed hopper too, where trucks or loaders dump material, so the whole circuit should be considered.

Options to consider

Containment comes first: enclosing the discharge, sealing the chute to the conveyor and providing curtains or a settling zone. Water sprays at the feed can wet the material before crushing, but large quantities may cause clogging or screening problems with sticky materials. Dry fog at the discharge and screen enclosures captures airborne fines with limited added moisture. Dust extraction is an alternative where wetting is not acceptable. For the feed hopper, sprays or fog triggered by the dumping event are often used.

Practical constraints

Crushing areas are subject to vibration, impact and abrasive dust, so nozzle and pipework locations must be protected and accessible. Water quality, freeze risk and the ability to interlock sprays with crusher operation all affect reliability. Screen performance can be affected by added moisture, so the downstream process needs to be considered. Maintenance access for cleaning nozzles and filters should be planned at the layout stage, before guards and walkways are finalised.