Dielectric properties of coal

Dielectric measurements of UK coals have shown that electric permittivity d ecreases with coal rank (dry, mineral free basis), however, the moisture an d mineral matter content may increase the bulk coal electric permittivity. Electric permittivity increases with low rank coals as a result of increasi ng moisture levels associated with low rank coals. The relative real permit tivity of coal is greater than most composite mineral matter with the excep tion of pyrite, which may increase the bulk coal electric permittivity if p resent in sufficient quantity. No significant changes in electric permittiv ity were detected in the frequency range tested. (C) 2001 Elsevier Science Ltd. All rights reserved.