Microwave Soil Vapor Treatment CHA Corporation Field DemonstrationWINTER 2004 CHA Corporation 372 W. Lyon Laramie, WY Telephone:(307) Fax:(307) Website: Background The National Institute for Health has awarded a SBIR Phase I grant to CHA Corporation to build a prototype microwave reactor system capable of recovering chemicals from soil vapors produced during hazardous site remediation without using catalytic oxidation. Early Phase I work included designing and fabricating a prototype system to be field-tested, which was completed in the summer of In the second year the prototype was transported to the former McClellan Air Force Base, where it was operated for two months to obtain data needed to evaluate the technical and economical feasibility of the microwave process. The field demonstration was completed in December The results proved that this microwave technology is a viable alternative to conventional catalytic oxidation that will result in significant cost savings and environmental benefits. Principles of Technology The CHA microwave-based gas cleanup process is designed to capture and recover a wide variety of both chlorinated and non- chlorinated volatile organic compounds (VOCs), many of which are commonly found at industrial and military sites. AFRPA at McClellan has completed a cost-benefit analysis for replacing the currently operating oxidizers with a central microwave carbon reactivation system and vapor carbon adsorbers. Due to favorable results from this evaluation, URS Corp. and CHA Corp. are currently conducting additional field testing for AFRPA to gather additional information about this microwave system.  On-site Carbon Reactivation  Closed Circulation System  Zero Contaminant Discharge  Chemical Recovery for Recycle or Disposal CHA Corporation CHA Corp Microwave Carbon Regeneration & Chemical Recovery System

Activated carbon readily adsorbs most VOCs, allowing removal efficiencies near 100% if sufficient carbon adsorbent and appropriate contact times are utilized. As the carbon continues to adsorb VOCs, the available adsorption sites are diminished and the carbon becomes saturated. Microwave energy is used to reactivate the saturated carbon. Rapid on-site reactivation of the carbon facilitates continuous, cost effective removal of VOCs by reusing the carbon in adsorption systems. When using microwaves, VOCs desorbed from the carbon are efficiently condensed in a condenser and recovered as a liquid. Overall, the process uses granular activated carbon (GAC) to remove VOCs from the air stream, continuously reactivates the used GAC with microwaves, and recovers the VOCs desorbed from the GAC by condensation. There are three main components of the CHA Microwave Soil Vapor Treatment System: Adsorber vessel Microwave carbon reactivation reactor Two-stage condenser system Adsorber Vessel The inlet and outlet of the adsorber vessel will be connected to an on-site SVE (soil vapor extraction) system. The contaminated air stream from the discharge side of the SVE main blower enters the bottom of the adsorber and passes upward through the GAC adsorption bed. Normally, the cleaned air will exit the adsorber and will be discharged to the atmosphere. However, in this field demonstration, the cleaned air is recycled back to the inlet of the SVE FTO (flameless thermal oxidizer). This provides a closed system for the contaminated air, resulting in zero emissions discharge into the atmosphere. As the GAC in the adsorber becomes saturated, the saturated GAC is transported to the microwave reactivation reactor by means of a pneumatic conveyor system. Consequently, the reactivated GAC above the clean gas outlet moves towards the bottom of the adsorber, allowing continuous operation of the adsorber. Microwave Carbon Reactivation Reactor The moving bed microwave carbon reactivation reactor consists of two stainless steel hoppers with cone-shaped bottoms, a quartz tube reactor, a rotary valve with variable speed drive motor, a multimode cavity applicator, and a 3-kW microwave generator. Saturated carbon is transported from the bottom of the adsorber to the top feed hopper by the pneumatic conveyor system. The carbon passes through the quartz tube reactor, where it is exposed to microwave energy in the multimode cavity applicator. The rotary valve is used to control the carbon flow rate through the quartz tube reactor. The reactivated carbon is stored in the receiver hopper until it is returned to the top of the adsorber. Two-Stage Condenser System The two-stage condenser system is used to recover organic chemical vapors as the carbon is reactivated. Nitrogen is used as a total recycle sweep gas to remove chemical vapors desorbed from the carbon. If there is accumulation of excess sweep gas, a slight pressure rise in the reactivator is detected, causing a valve to open, venting the excess gas back to the adsorber inlet. Again, no vapors are allowed to leave the closed reactivation system. Condensed liquid in the nitrogen stream is collected in a knockout pot prior to entering the compressor. In order to separate the remaining chemical vapors in the nitrogen stream, the outlet of the compressor flows into the second water-cooled condenser. Chemical vapors in the nitrogen stream are cooled in the second condenser and the condensed liquid is collected in the second knockout pot. Vapor free nitrogen is recycled back to the microwave reactivator. Microwave Soil Vapor Treatment  Provide on-site reactivation of GAC, eliminating handling and transporting of hazardous saturated carbon.  Restore the original adsorption capacity of GAC and eliminate the need for supplying fresh GAC.  Reduce the volume of air containing VOCs and other contaminants that require further treatment.  Recover VOCs and other contaminants in soil vapors and avoid the generation of secondary air pollutants.  Provide an effective means to replace the existing catalytic oxidizers and acid gas scrubbers by GAC adsorbers.  Save energy by eliminating natural gas used in catalytic oxidizers and flameless thermal oxidizers.  Recycle valuable recovered chemicals such as fuels and solvents.  Reduce the life-cycle cost for base cleanup significantly. Technological Advantages