Author
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Nelson, Stuart |
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Submitted to: Progress in Electromagnetics Research
Publication Type: Abstract Only Publication Acceptance Date: 7/7/1997 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Interest in the permittivities or dielectric properties of coal and minerals arises from their influence on electromagnetic wave propagation in exploration, in control of mining processes, and in possible dielectric heating applications for modifying coal characteristics or in rock fragmentation. Federal regulations require rock dusting to ensure that "the incombustible content of the combined coal dust, rock dust, and other dust shall not be less that 65 percentum" in coal mines to limit explosion hazards. Recent measurements of permittivities were made on pulverized samples of Pittsburgh coal, rock dust (limestone), and a 35%-65% mixture of coal and limestone to learn how different the dielectric properties of these materials might be and whether there might be potential for developing techniques of rapidly sensing coal and rock dust concentrations. . Permittivity measurements were made at 11.7 GHz with an X-band measurement system and the short-circuited waveguide method. The cube roots of the dielectric constants of the three pulverized samples measured in this work were entirely linear with bulk density and could be accurately described by the Landau & Lifshitz, Looyenga dielectric mixture equation. Values for both the dielectric constant and the loss factor were obtained by calculating the complex permittivities from the mixture equation. Values of both the dielectric constants and loss factors of coal and limestone are sufficiently different to justify further studies aimed at determining rock dust content in coal and rock dust mixtures by dielectric sensing techniques. |
