Electrode Design for Soil Decontamination with Radio‐Frequency Heating

Abstract

Radio‐frequency heating to enhance soil decontamination requires adjusted solutions for the electrode design depending on scale and remediation technique. Parallel plate electrodes provide widely homogeneous field and temperature distributions and are, therefore, most suitable for supporting biodegradation processes. For thermally enhanced soil vapor extraction, certain temperature gradients can be accepted and, therefore, the less‐demanding geometry of rod‐shaped electrodes is usually applied. For electrode lengths of some meters, a design with an air gap has to be used in order to focus heating to the desired depth. Perforated rod electrodes may be simultaneously employed as extraction wells. Placing an oxidation catalyst in situ within the electrodes is an option for handling of highly loaded air flows. Coaxial antenna may be utilized to selectively heat soil compartments far from the surface of the soil.

History Matching of Electromagnetically Heated Reservoirs Incorporating Full-Wavefield Seismic and Electromagnetic Imaging

“…It was also expected that a continuation of the heating would increase the recovery rates even further, with minimal power losses (Bridges et al 1983). Recently, the invention and commercialization of EM heating in a variety of applications (Roland et al 2011(Roland et al , 2012 were expanded for enhanced oil recovery (EOR) (Mutyala et al 2010;Wacker et al 2011).…”

In Situ Radio‐Frequency Heating for Soil Remediation at a Former Service Station: Case Study and General Aspects

“…In situ thermal remediation methods [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] have the potential to enhance efficiency and cost-effectiveness of soil remediation processes. The spectrum of these in situ methods is practically restricted to heating lances (thermal wells operated with electricity or gas), injection of hot air or steam, resistive heating using power-line-frequency energy (usually realized as sixphase heating with 50 or 60 Hz), and dielectric radio-frequency (RF) heating (applying frequencies in the MHz range).…”

“…Among the currently available technologies, direct RF heating [4,[10][11][12][13][14][15][16][17][18] has some unique advantages as it can be applied to a variety of soils and achieve a wide temperature range (potentially up to more than 300°C). Based on a working principle similar to that applied in household microwave ovens, RF heating is characterized by direct heat formation in the soil volume without requiring a heat transfer medium such as hot air or steam or overheated surfaces such as heating lances.…”

“…Based on a working principle similar to that applied in household microwave ovens, RF heating is characterized by direct heat formation in the soil volume without requiring a heat transfer medium such as hot air or steam or overheated surfaces such as heating lances. However, both parameters are nevertheless relevant for combination with soil vapor extraction (SVE) or for the uniformity of temperature profiles especially when using rod electrodes [10,16,17]. Additionally, the heating principle does not depend on the permeability of soil for gas streams (as in the case of steam injection) or thermal conductivity (as for thermal lances).…”

“…Secondly, specially designed rod electrodes, with an air gap, focus energy absorption to the contaminated soil at discrete depths [10,[15][16][17]25]. The RF unit has two specific tools designed to optimize efficiency.…”