High-temperature solar pyrolysis of coal☆

Abstract Subbituminous coal from Western United States was pyrolyzed by directly exposing 50 mg powdered samples to concentrated solar radiation. It was found that exposure to flux levels > 200 W/cm 2 for 12.5 s devolatilized 51 per cent of the coal. At flux levels between 100 and 200 W/cm 2 devolatilization was slightly less. Gas yield was a maximum of 31 mmol/g coal at a flux of 100 W/cm 2 and decreased slightly with increasing flux. Gas yields were more than twice as great as those obtained by a laser technique developed to simulate solar pyrolysis. In experiments with spectral cut-off filters there was no effect due to changing the wavelength distribution of sunlight.