Underground » Ventilation, Gas Drainage and Monitoring
The scoping study examined dust problems that are being faced by thick seam longwall mine operators, evaluated options and recommend priorities for improvement. The increasing scale of thick seam longwalls challenges the maintenance of safe and healthy face environments in Australian collieries. High production rates, longer faces and higher ventilation quantities and velocities further exacerbate dustiness.
A plan for research and development to identify cost effective approaches to reduce or overcome the problem is put forward to support future improvements. The project included two workshops, one to inform Australian mining personnel about the latest directions in industry practice in combating dust problems and the second to discuss findings of the study.
The project was undertaken as a University of Queensland UniQuest consultancy and has drawn on the expertise of senior technical staff from Australian mines and local and overseas expertise.
Thick seam mining and particularly longwall production is relatively new to Australia and the number of mines involved is increasing. Thick seams are those currently of about 3.8 to 5.0m (and possibly of greater thickness in the future) being extracted in one pass. Thick seam extraction presents additional problems in dust measurement and control above those faced by medium or more traditional extraction heights of 1.8 to 3.0m. These include major face slabbing of coal, the leaving of substantial coal in the roof, high average production rates and peak tonnages and high air velocities required to dilute seam gases and because face length are increased.
Australia is mining at greater seam thicknesses than most similar western countries, and particularly the US. The approaches developed by other countries and previous research and innovation are not necessarily directly transferable.
The project is restricted to the technical issues of measurement and control of dust within the underground mine environment. It focuses on respirable dust problems and has not dealt with the health effects resulting from high dust exposure.
The study involved a number of stages. A detailed survey of six Australian thick seam miner operators to identify individual mine issues was undertaken. A comprehensive literature review, with emphasis on publications from the last ten years was undertaken on Australian and foreign developments. Views and advice from recognized dust experts both within Australia and overseas were sought. Some approaches to assessment of dust compliance and analysis of trends exhibited were undertaken. Workshops were undertaken at the beginning and end of the project. Analysis and evaluation was undertaken of options for improvement. A report was compiled including recommendations as to worthwhile areas for future research and development appropriate to the Australian context.
Recommendations have been given for research and innovation in three areas. These cover topics of airflow and dilution, research into various spray installations, applications of Computational Fluid Dynamics, some engineering approaches and questions of management of dust issues within the mine operating structure. The approaches are directed at thick seam mining although there is no doubt the overlap application to extraction in medium thickness seams. Australia's approach to mining in thick seams is unique. Improvements to the mine atmosphere and dust conditions will be driven through effort undertaken within the country with application where appropriate of overseas developments.