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Abstract
The dielectric properties
of pulverized coal samples from identified sources were measured at 22°C over the frequency
range from 1 MHz to 12 GHz and are presented graphically. Chemical
composition, moisture content, bulk and particle densities, and particle size
distributions were also determined. Run-of-mine samples, as well as dense
pyrite-bearing fractions and light fractions relatively free of pyrite, were
included in the study, Dielectric constants decreased regularly with
increasing frequency and were positively correlated with density. Dielectric
loss factors of pyrite-bearing fractions of lower sulfur
content were high at frequencies below about 50 MHz, and decreased with
increasing frequency to low values at -microwave frequencies. In contrast,
the loss factor of a pyrite-bearing fraction with high sulphur content was
low at the lower frequencies and increased with increasing frequency to high
levels at microwave frequencies. Thus, selective dielectric heating of pyrite
in coal to enhance its magnetic susceptibility for possible removal by
magnetic separation can probably be best accomplished at microwave
frequencies for some coals and at lower dielectric heating frequencies for
others.
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