Mining Contract: Mechanisms of Coal Dust Explosions and Their Prevention

Contract #	200-2015-64091
Start Date	9/1/2015
Research Concept	This contract aims to explore mine safety related to the activation, dispersion, and cessation of secondary dust explosions.
Topic Area	Explosion Prevention

Contract Status & Impact

This contract is ongoing. For more information on this contract, send a request to mining@cdc.gov.

Research on secondary dust explosions has been primarily empirical in nature. Previous attempts to model the complex processes describing dust lifting by air movement induced from a blast, particle heating, and combustion have not been successful. Only recently has numerical modeling been used to solve these multifaceted activities.

This contract will determine the following:

• How much dust (both inert and coal) is removed and lifted by winds induced from a primary explosion.
• When the thickness of a coal dust top layer is dangerous enough to support a dust explosion.
• Conditions under which a second reactive zone ignites.
• Effect of airborne dust on the ignition and spread of a secondary dust explosion.

The University of Maryland has developed and tested a numerical model of the dust explosion process called the Dust Explosion Simulation (DESIM) code. Through simulation experiments with the chemical reactions “turned off,” this code can determine how fluids and particles interact and react in explosion scenarios. Variable parameters for the DESIM code include the thickness of a coal dust layer, strength of a pressure wave that lifts the coal dust, volatility of coal dust particles, dilution of coal dust with inert particles, and the initial size of those particles.

Under this contract, the University of Maryland will:

• use DESIM to examine the scouring depth and physical mechanisms of lifting dust layers behind explosion-induced winds;
• extend DESIM to include the effect of thermal radiation and multiple dust sizes;
• use DESIM to examine how a thin a layer of reactive coal dust, which has settled on top of a thick layer of inert dust, can initiate and propagate a secondary dust explosion;
• demonstrate the validated code.

Successful completion of these tasks will provide a fundamental theoretical and computational model for understanding the mechanics of coal dust explosions, a better understanding of the relevant existing experimental data, and information on how frequently inert dust should be placed on top of reactive coal dust layers.

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