The research made several advances in the area of explosible coal dust, and investigated the explosion characteristics of nine Bowen Basin (Central Queensland) dust samples. A suitable explosion chamber and dust concentration probe were developed for this purpose.
The 20 litre explosion chamber is based on a novel design, and uses rotation of the main body of the chamber together with air jets for dust dispersion. The chamber design allows different types of explosion initiators to be tested, and analyses of the explosion characteristics of coal dust/methane mixtures of varying concentrations to be undertaken. The dispersion system was effective in generating stable dust clouds to a maximum concentration of approximately 1 700 g/m3.
A new approach to the measurement of coal dust concentration led to the development of a dielectric dust concentration probe, and a capacitive micrometry technique was successfully adapted to this purpose. This uses a ratio-transformer bridge for measurement of small changes in a capacitive probe designed to sample a representative volume in response to changes in dust concentration. The device is accurate, is capable of operating in the hostile environment within the explosion chamber, and has several advantages over optical dust probes which are extensively used elsewhere in explosible dust research.
The explosion chamber and dust probe were used to characterize the explosibility of coal dust samples by determination of the dust lean limit concentration in varying mixture with methane. Plots of lean limit points over a range of methane concentrations present an explosion curve for each sample which indicates the potential of the coal dust/methane to explode under the conditions of initiation available in the chamber. The explosion curve obtained for each sample presents a unique signature which appears to reflect the physical and chemical characteristics of the dust.
A mine phase of the project measured the rate of methane accumulation in a newly formed longwall goaf, and sought to determine the potential for an underground ignition from this source.
Results from a series of laboratory and field experiments are discussed and potential areas of interest for further investigation and likely directions of future research and development are examined.