Dielectric Heating of Oil Shales By Monopoles and Modified Coaxial Applicators

The concept of dielectric heating of oil shales by high-power, high-frequency electromagnetic fields with monopole, dipole and modified coaxial applicators is studied and tested. The various physical and modeling parameters are introduced and discussed in the context of in situ heating of fossil fuels. Based on numerical model results, a radio frequency power delivery system and echoic test reactor chamber were designed and fabricated for high temperature heating experiments at the University of Wyoming. A series of experiments was performed using both monopoles and modified coaxial applicators. Dielectric breakdown near pyrolysis limited the power level for the heating process. A modified coaxial applicator excited at the top with the TEM mode and containing an open-circuit at the bottom confined the fields very well. By extending the outer she ith of the coaxial line beyond the termination of the inner conductor and using appropriate dimensions of the coaxial line for a given frequency it is possible to cut off the dominant TM01 mode at the open circuit. This applicator has potential in large scale field tests.