Particle size and surface area effects on explosibility using a 20-L chamber

Area of Science:

• Mining Engineering
• Materials Science
• Occupational Safety

Background:

• The Mine Safety and Health Administration (MSHA) mandates specific particle size criteria for rock dust used in underground coal mines (30 CFR 75.2).
• A significant percentage (47%) of tested rock dusts failed to meet the 70% passing 200 mesh sieve requirement.
• Some compliant dusts were ineffective in rendering pulverized coal inert, indicating limitations in current MSHA specifications.

Purpose of the Study:

• To evaluate the particle size distribution, specific surface area (SSA), and explosion suppression effectiveness of various rock dusts.
• To investigate the inadequacy of some MSHA-compliant rock dusts in preventing coal dust explosions.
• To propose a minimum SSA threshold for effective rock dust performance.

Main Methods:

• Analysis of particle size distribution using sieve analysis.
• Measurement of specific surface area (SSA) of rock dust samples.
• Assessment of explosion suppression effectiveness in a 20-L chamber and full-scale experiments at the Lake Lynn Experimental Mine.

Main Results:

• A notable portion of rock dusts did not meet the MSHA particle size specification.
• Even dusts meeting the sieve criteria showed inadequate performance in inerting coal dust explosions.
• Particle size, SSA, and full-scale test results correlated with explosion suppression effectiveness.

Conclusions:

• Current MSHA particle size specifications may be insufficient for ensuring effective coal dust explosion prevention.
• Specific surface area is a critical parameter for rock dust efficacy, potentially more so than particle size alone.
• A minimum SSA should be considered for future MSHA rock dust regulations to enhance mine safety.