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PCB's (polychlorinated biphenyls) are mostly associated with cooling oil applications in transformers and capacitors, which when they leak, result in the liquid contamination of any surrounding materials. PCB's are also used as plasticizers in polystyrene coffee cups, frozen food bags, bread wrappers, plastic liners for baby bottles, printing inks, carbonless multi-page paper, and as waxes for making metal casting molds. Therefore, it is readily apparent why PCB's find their way into the environment, landfills and other disposal sites.

Our primary focus is on applications involving the use of PCB's in mineral oil that was originally intended for improved fire resistance and heat transfer characteristics in oil. This oil was commonly used in the electrical industry in transformers and capacitors. Though not dangerous in the applications themselves, the PCB-laden oils have a particular physical bonding affinity with soils, causing a serious environmental problem. Although PCB's are only slightly water soluble, they readily combine with fatty acids and oils within organic species, including human beings, seriously increasing the risk of cancer and other anomalies.

The EnviroWave process for organic contaminant remediation involves the use of microwave energy in treating soil or other material that has been exposed to PCB's, PAH's or other organic hazardous material. Since the contaminants are a small part - by weight - of the overall material, the primary consideration for microwave reduction is the contaminated material itself. Microwaves will preferentially be absorbed by soil, but also effect the breakdown or destruction of the PCB's or other organic contaminates into simpler, safe products. A typical commercial mixture of PCB's will contain 40-60% chlorine by weight. Those chlorine atom bonds are easily broken when exposed to microwave energy.

Verification of the destruction progress is confirmed by an on-line gas chromatograph (GC) system, using an Electron Capture Detector (ECD) system. In conjunction with an ECD System, a Polycarborane-Siloxane Column is employed for low level PCB detection, high resolution and good stability throughout a temperature range from -20 to 370 °C. (-4 to +698 °F.). Those temperatures insure the destruction of all 209* congeners or chlorinated biphenyl derivatives. U.S. EPA Regulation 40CFR, Part 761, Subpart E requires continuous GC monitoring during remediation efforts.

PCB's are slightly soluble in water, but readily soluble in organic solvents, thus the reason for the use of organic solvents during remediation and/or analysis. The use of polar organic solvents readily improves microwaves absorption, although the presence of moisture in soil results significantly in preferential microwave absorption and temperature uniformity. With the typical boiling point of PCB's, one can clearly see that the fastest route to increasing the temperature is paramount. When water molecules are subjected to dipolar polarization by microwaves, the temperature rise occurs exponentially, rapidly increasing the heat of adjacent material as well. As the soil temperature increases, the dielectric constant is reduced, and the loss factor increases, the soil temperature proceeds to rise exponentially. The EnviroWave process raises the material temperature to equilibrium where it remains until the gas chromatogram verifies that the PCB content of the soil is below minimum EPA requirements.

* PCB's manufactured under trade names such as Arochlor, Askerel, Clorphen, Chlorextol, Chiorinol, Diachlor, Dykanol, Elemex, Eucarel, Fenchlor, Hyvol, Inerteen, Kanechlor, Noflamol, Phenoclor, Pyralene, Pyranol, Pyroclor, Santotherm, Sovtol, Therminol, etc.

PCB's are formed by the reaction of biphenyl with chlorine in the presence of a catalyst, which results in substitution of some of the biphenyl hydrogen atoms with chlorine. The initial amounts of chlorine, reaction time and temperature determine the amount of chlorination of the biphenyl molecule. Although,
the majority of PCB's are liquids, some are solids, with relatively low melting points.

The chlorine bond to the biphenyl molecule is the weakest and therefore microwave excitation will cause this bond to break first. The biphenyl bond will break second, and the remaining aryl radical will finally open, leading to the formation of chain hydrocarbons. A zeolite converter with catalyst will enhance opening of the aryl radical, and improve reduction efficiency. Additional microwave excitation will result in simple paraffin and olefin molecules, which may be readily released to the atmosphere. However, prior to any release to atmosphere, the vapor stream will be drawn through a liquid scrubber containing Sodium Hydroxide (NaOH), to neutralize any hydrochloric acid vapors.

Incineration of PCB's is considered to be a viable method for PCB destruction; however, incineration in the presence of air is known to form dibenzofurans, dioxins and hydrofurans, which are also carcinogens. The EnviroWave avoids any combustion in the reduction chamber by the use of a continuous purge with nitrogen gas, provided by an on-site nitrogen generator. The nitrogen generator employs the use of a molecular sieve to provide 98% pure nitrogen gas.

Portable Microwave Applicator	Generator Panels in Control Trailer

Safety features incorporated into the applicator and control design insure an absolute minimum of risk to the operator and the environment. Potential for microwave leakage during the processing of material is extremely low. In fact, there are more detectable microwaves emitted from a 1kW home microwave oven than from a 500kW EnviroWave applicator. All EnviroWave microwave apparatus and controls are designed to give maximum efficiency and require a minimum of maintenance.

Efficiency is obtained by a combination of an applicator chamber that has been specifically designed for the process, monitoring the status, condition and cooling of the magnetrons and the patented method of mode stirring incorporated into the EnviroWave equipment. Operation of the microwave generators is entirely automated and controlled by fast scan rate PLC's that monitor the status of all the components within the EnviroWave process.

The EnviroWave apparatus for soil remediation is a portable design. Apparatus size is determined by the type of material being processed and the desired throughput. A standard 500kW remediation design consists of two trailers. One trailer is a standard box design that becomes the control room and contains the microwave generators, nitrogen generator, scrubber and other auxiliary equipment. The other is typically a flat bed type trailer upon which the microwave applicator is mounted.

For more information about the EnviroWave Corporation and its remediation process equipment please click on Contact Us link in the left panel.