Electrical conductivity and optical reflectivity of coal dust-rock dust-water mixtures

Researchers at the US Bureau of Mines have designed and constructed a portable near-infrared monochromatic reflectance meter that measures the concentration of rock dust in homogeneous coal-dust/rock-dust mixtures to within ±2 wt.% rock-dust over the range 0-100 wt.% rock dust. Unfortunately, the presence of moisture in the samples affects the accuracy of this instrument. The purpose of this research was to determine the feasibility of designing a meter that can automatically compensate for the presence of moisture in the dust and thereby avoid the necessity of drying the dust prior to testing. Specifically, this research was directed at determining if simultaneous measurement of the mixture´s electrical conductivity and near-infrared reflectivity could be used to determine the mixture´s moisture and rock-dust concentration simultaneously. It is concluded that the two-parameter approach is feasible