Processing fly ash from coal burning power station in a variable radiofrequency field

Experiments with fly ash obtained from a coal-burning power station in NSW, Australia, were conducted in the cold crucible facility at ANSTO using a 30kW variable frequency generator. The generator was configured as a standard Hartley oscillator with the tank capacitor able to vary from 110 pF to 4100 pF giving a frequency span of 5MHz to 18MHz. The applicator consisted of a coil with a water cooled base and top plate that formed an LC resonant cavity, which coupled to the RF generator by a single turn coil. A dark glass, confined inside the applicator, was formed by applying a high frequency electromagnetic field between two copper plates through a sample of fly ash. The temperatures reached were in excess of 1000 °C causing the powder to fuse into glass in a very brief period of a few minutes. The purpose of this experiment was to verify if dielectric and/or induction heating could melt the fly ash in a more rapid manner than conventional (resistive/joule) heating.