Determination of carbon in a fly ash sample through comparison to a reference microwave attenuation and phase shift

PCT No. PCT/AU91/00108 Sec. 371 Date Sep. 14, 1992 Sec. 102(e) Date Sep. 14, 1992 PCT Filed Mar. 20, 1991 PCT Pub. No. WO91/14936 PCT Pub. Date Oct. 3, 1991.An apparatus and method to measure the unburnt carbon content of fly ash. A microwave signal is transmitted through or reflected from a fly ash sample and the attenuation or phase shift of the signal received by a detector/detectors is determined with respect to the incident signal and is used to provide a measure of unburnt carbon content. The detectors may be antennae means which also launch the incident signal or may be a completely separate means. A preferred embodiment comprises a microwave oscillator for launching the microwave signal into a fly ash sample in a microwave resonant cavity. Detectors determine the attenuation of phase shift of the received signal with respect to a signal from a reference microwave resonant cavity by the fly ash sample, and a measurement of the unburnt carbon content is obtained.