Underground coal mines apply finely powdered limestone rock dust to inertize explosive coal dust deposits created during the mining process. Rock dusting creates a cloud of nuisance dust downwind, preventing other work in the area. Applying a wet or foam mix of rock dust eliminates the nuisance dust, but may impact the dispersion and explosion prevention capability and thus, may render the rock dust ineffective. Dispersibility tests were conducted in a full-size mine explosion test drift at the Colorado School of Mines. Tests include dry, wet, dry-misted, and foam applications using three types of rock dust: conventional, hydrophobic, and rock dust meeting stricter German specifications. Results show that dried dust forms large, agglomerated particles that may not be effective in suppressing coal dust explosions. Hydrophobic rock dust maintains better dispersibility even when applied wet or applied dry then misted. German specification dust disperses better than U.S. conventional rock dust.
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