Abstract: An electrode for use in in situ vitrification of soil comprises a molybdenum rod received within a conductive sleeve or collar formed of graphite. Electrodes of this type are placed on either side of a region containing buried waste material and an electric current is passed therebetween for vitrifying the soil between the electrodes. The graphite collar enhances the thermal conductivity of the electrode, bringing heat to the surface, and preventing the formation of a cold cap of material above the ground surface. The annulus between the molybdenum rod electrode and the graphite collar is filled with a conductive ceramic powder of a type that sinters upon the molybdenum rod, protecting the same from oxidation as the graphite material is consumed, or a metal powder which liquifies at operating temperatures. The molybdenum rod in the former case may be coated with an oxidation protectant, e.g. of molybdenum disilicide.

Abstract: The present invention comprises a system for promoting the destruction of volatile and/or hazardous contaminants present in waste materials during in situ vitrification processes. In accordance with the present invention, a cold cap (46) comprising a cohesive layer of resolidified material is formed over the mass of liquefied soil and waste (40) present between and adjacent to the electrodes (10, 12, 14, 16) during the vitrification process. This layer acts as a barrier to the upward migration of any volatile type materials thereby increasing their residence time in proximity to the heated material. The degree of destruction of volatile and/or hazardous contaminants by pyrolysis is thereby improved during the course of the vitrification procedure.

Abstract: An electrode comprising a molybdenum rod is received within a conductive collar formed of graphite. The molybdenum rod and the graphite collar may be physically joined at the bottom. A pair of such electrodes are placed in soil containing buried waste material and an electric current is passed therebetween for vitrifying the soil. The graphite collar enhances the thermal conductivity of the combination, bringing heat to the surface, and preventing formation of a cold cap of material above the ground surface. The annulus between the molybdenum rod electrode and the graphite collar is suitably filled with a conductive ceramic powder that sinters upon the molybdenum rod, protecting the same from oxidation as graphite material is consumed, or a metal powder which liquefies at operating temperatures. The center of the molybdenum rod, used with a collar of separately, can be hollow and filled with a powdered metal, such as copper, which liquefies at operating temperatures.

Abstract: A detector system for sensing the progress of an ISV process along an expected path comprises multiple sensors each having an input port. The input ports are distributed along the expected path of the ISV process between a starting location and an expected ending location. Each sensor generates an electrical signal representative of the temperature in the vicinity of its input port. A signal processor is coupled to the sensors to receive an electrical signal generated by a sensor, and generate a signal which is encoded with information which identifies the sensor and whether the ISV process has reached the sensor's input port. A transmitter propagates the encoded signal. The signal processor and the transmitter are below ground at a location beyond the expected ending location of the ISV process in the direction from the starting location to the expected ending location.