Comprehensive investigation of the liberation characteristics of pyrite and other mineral matter from coal. Semi-annual progress report, July 31, 1996--December 31, 1996

A technique has been developed for generating scanning electron microscope images of sections of polished coal and coal particles that are suitable for the measurement of the linear intercept distribution functions and the distribution of three-phase linear grades. The three phases used are; pyrite, ash forming minerals, and coal. The phase-to-phase transition probabilities for the unbroken ore can also be estimated using conventional image analysis techniques. The distribution of linear intercept lengths through the pyrite, ash and coal phases were found to be described by sums of 2, 3 and 4 exponentials respectively. This reflects the presence of distinct textural regions in the coal. The linear grade distributions were determined in 710 - 1000 micron coal particles that had previously been carefully fractionated using dense liquids. The three phase linear grade distributions reflect the variation in particle composition that results from the fractionation and they provide a detailed picture of the three-phase composition of the various fractions. It is not yet possible to stereologically correct these three-phase distributions. However, the measured uncorrected distributions are very encouraging and a viable stereological correction procedure will be developed during the next phase of work on this project