Underground » Ventilation, Gas Drainage and Monitoring
The main objective of the project was to develop and demonstrate optimum goaf gas drainage and control strategies for improved gas management in longwall panels in order to reduce gas delays on the face. The project has combined extensive field studies together with computational fluid dynamics (CFD) models of gas flow to characterise goaf gas flow patterns and develop effective goaf gas control strategies. The project work specifically involved review of gas control issues at field sites, comprehensive goaf gas monitoring, tracer gas investigations, CFD simulations and extensive field trials and demonstration studies.
Analysis of the gas data from different collieries showed that longwall gas emissions are increasing substantially over the years and simply increasing the number of goaf holes in the panel or decreasing hole spacing seems to be not effective in controlling the high goaf gas emissions. Gas data analysis also revealed that the standard practice of draining gas from just 1 to 2 goaf holes near the face is not an efficient strategy for reducing gas delays in the panel. Bleeder ventilation systems for gas control is effective only up to 600 to 800 m of face retreat from the panel start-up area.
This project developed optimum goaf gas drainage strategies based on the fundamental understanding of goaf gas flow dynamics obtained through various field studies and modelling investigations. Field studies were conducted at Central and Appin Collieries. After implementation of the optimum gas drainage strategies, the total goaf gas drainage flow rates at Central Colliery have reached 1,600 - 1,800 l/s, i.e., around 50% improvement over the previous panels' goaf holes performance. Similarly, at Appin Colliery the total goaf gas drainage flow rates have increased from around 2,000 l/s in LW405 to over 3,000 l/s levels in LW406 panel.
This project demonstrated that the new optimum strategies were highly successful in improving the overall efficiency of goaf gas drainage systems at both the field sites. Technology transfer to the industry through implementation of the newly developed techniques at mine sites has been one of the projects highlight.