Enhanced magnetic separation of pyrite from coal after microwave heating

The objective of this research was to improve the magnetic separation of coal and pyrite by enhancing the magnetic susceptibility of pyrite in run-of-mine coal through the use of selective dielectric heating. Separation of pyrite from coal would be facilitated by changing a portion of each pyrite particle to a more magnetic form. Studies included the measurement of the dielectric properties of different coal fractions at frequencies ranging from 1 MHz to 12 GHz. These values were then used to calculate the theoretical heating expected in these materials and their mixtures at 2.45 GHz. The experimental treatment showed general agreement between theoretical and experimental heating and that it is possible to heat pyrite in coal selectively. Data indicated an increase in the apparent magnetic susceptibility of dielectrically heated pyrite samples that was roughly proportional to the time and power of treatment. Magnetic separation tests were conducted on untreated and heated coal samples. Dielectric heating produced more magnetic material in the samples, increased the magnetic susceptibility and slightly improved magnetic separations.