Constitutive Parameters of Coal at Radio Frequencies Using a Two-Path Interferometer. Progress Report,May 1, 1976--April 30, 1977.

摘要

The development of electromagnetic systems to detect and monitor an in-situ underground coal gasification process requires a knowledge of the electrical properties of coal. Using a two-path interferometer at microwave frequencies (approximately equal to 9GHz),the samples were tested as a function of temperature,electric field polarization,and direction of the coal samples. There were not any significant changes in the electrical properties of coal as a function of temperature from ambient up to 700exp 0 F. However,there were significant variations in the conductivity as a function of polarization,with the vertical polarization possessing lower conductivity. Only slight changes in conductivity were detected as a function of direction,with the butt cleats exhibiting somewhat lower losses. The dielectric constant remained essentially constant,within the measuring accuracy. Measurements of electrical properties of coal were also made in the 0.5-100MHz region using capacitance techniques. In general,there was a decrease in the values of dielectric constant and an increase in conductivity as the frequency increased. (ERA citation 02:050626)