Electrical discharge phenomena application for solid fossil fuels in-situ conversion

Abstract

The application of high voltage to oil shale initiates partial discharges (PDs) with the following treeing like in insulating dielectrics. Critical PDs and treeing with a high propagation rate occur under the low electrical intensity ~102 V/cm due to oil shale's high porosity, heterogeneity and anisotropy. The completed discharge occurs as a result of these phenomena. Carbonization is initiated around a plasma channel at the treeing stage and extended during electromagnetic action time. Carbonized rock electrical resistance decreases by 8÷10 degrees to 10 ohm·cm, and shale and coal could be heated by Joule heat in carbonized volume and discharge plasma. A high-current supply is necessary for this heating stage. Also, a high- voltage supply with steep-grade characteristics can be used for PDs and treeing initiating and heating the carbonized rock with low resistance. Thus, these phenomena allow in-situ processing in order to produce a flammable gas and synthetic oil from inferior solid fossil fuels by pyrolytic conversion. Computations show that the ratio between energy derived from gas flaming and energy for shale conversion is more than fifty. Therefore, oil shale conversion with the help of electrical discharge phenomena application can be very efficient, as it needs little energy.