Dielectric properties of coal

Dielectric measurements of UK coals have shown that electric permittivity decreases with coal rank (dry, mineral free basis), however, the moisture and mineral matter content may increase the bulk coal electric permittivity. Electric permittivity increases with low rank coals as a result of increasing moisture levels associated with low rank coals. The relative real permittivity of coal is greater than most composite mineral matter with the exception of pyrite, which may increase the bulk coal electric permittivity if present in sufficient quantity. No significant changes in electric permittivity were detected in the frequency range tested.