Photothermal method of determining calorific properties of coal

Abstract

Predetermined amounts of heat are generated within a coal sample (11) by directing pump light pulses (14) of predetermined energy content into a small surface region (16) of the sample (11). A beam (18) of probe light is directed along the sample surface (19) and deflection of the probe beam (18) from thermally induced changes of index of refraction in the fluid medium adjacent the heated region (16) are detected. Deflection amplitude and the phase lag of the deflection, relative to the initiating pump light pulse (14), are indicative of the calorific value and the porosity of the sample (11). The method provides rapid, accurate and non-destructive analysis of the heat producing capabilities of coal samples (11). In the preferred form, sequences of pump light pulses (14) of increasing durations are directed into the sample (11) at each of a series of minute regions (16) situated along a raster scan path (21) enabling detailed analysis of variations of thermal properties at different areas of the sample (11) and at different depths.

Dependencies are inferred from the claim text.