Mining Project: Improved Ventilation Effectiveness in Underground Coal Mines

Research Summary

Available mine ventilation strategies and methane control systems have been challenged by recent developments in mining methods and designs, such as increased face advance rates, increased productivities, increased longwall panel sizes, and by possible interactions of a sealed area in a previously mined working above and below the current operation. This project's goal was to enhance worker safety by decreasing the likelihood of explosions produced by hazardous underground methane concentrations.

In this project, three tasks were performed to advance the understanding of methane sources, migration and control strategies, interactions of sealed and active gobs with working sections, and to improve ventilation methods through a complete understanding of bleeder system effectiveness to enhance worker safety. The research investigated methane migration issues from overlying and underlying gassy coal seams, possible gas-bearing strata, and previously mined and abandoned workings that can be within the emission zone of sealed and active gob and to the working areas.

This project involved the following tasks:

• Task 1. Determine the interactions involved in methane emissions from gas migration that can originate from numerous sources (gassy coalbeds, strata, previously mined workings) which are both overlying and underlying the active workings. 
• Task 2. Determine the interactions involved in methane emissions from sealed gobs which, under decreasing atmospheric pressure, can discharge large quantities of gob gas, including methane-rich air, into ventilation systems. NIOSH determined the controlling factors for these sealed gob emissions.
• Task 3. Investigate the effectiveness and limitation of current bleeder systems to safely remove gasses from the active longwall panel and adjoining gobs. Numerical modeling (wire frame and computational fluid dynamics) techniques that were calibrated using field data were used to determine controlling factors on bleeder system designs. Guidelines to improve bleeder effectiveness were provided to the longwalling industry.

The ultimate goal of this research project was to provide recommendations to the industry and regulatory agencies for improved monitoring and sampling methods, optimized face and bleeder ventilation techniques, and enhanced methane control designs to prevent any future mine explosion disasters.