Westinghouse Hanford Company
Description
Vacuum extraction will remove the volatile organics from the contaminated soil. A high pressure system has been designed to treat feed streams that contain dilute concentrations of volatile organic compounds (VOCs). The organic vapor/air separation technology involves the preferential transport of organic vapors through a non-porous gas separation membrane (diffusion process analogous to putting hot oil on a piece of wax paper). In this system, the feedstream is compressed and sent to a condenser where the liquid solvent is recovered. The condenser bleed stream, which contains approximately 5000 ppm of the VOC, is then sent to the membrane module. The membrane module is comprised of spiral bound modules of thin film membranes separated by plastic mesh spacers. The membrane and the spacers are wound spirally around a central collection pipe. In the membrane module the stream is further concentrated to 3% VOC. The concentrated stream is then returned to the compressor for further recovery in the condenser.
Technical Performance
Cost. Capital Equipment (7000 scfm) is $2.5M; Operations and Maintenance is $6K (replacement every 3 yrs); Information on life-cycle will be available upon completion of testing; and Emissions Treatment is $2 to 5/lb of VOC recovered.
One of the limitations of this technology is its ability to handle foulants (e.g., lard oil) that are in soil. Radon will not effect the functionality of the membrane separation unit.
Projected Performance
Based upon a VOC effluent concentration of 1000 ppm, there is a 95% removal efficiency. The remaining 5% is polished using granulated activated carbon (GAC).
Future work involves sizing the pilot plant to handle fluctuations in the VOC flows from the well field, and fouling of the membrane with other constituents.
Waste Applicability
The targeted contaminants are VOCs, carbon tetrachloride, and chloroform in gas streams.
Status
This technology is being tested at a Hanford site where VOCs will be obtained by vacuum extraction. Carbon tetrachloride and chloroform will preferentially be removed from the gas stream. This technology and system are available immediately. Testing will be complete before the end of FY1993.
Regulatory Considerations
The 1990 Clean Air Act Amendments must be considered when treating VOCs.
Potential Commercial Applications
This technology is applicable to the treatment of any waste stream emitting VOCs and presents a cost-effective alternative to treatment by GAC adsorption currently used by industry.
Baseline Technology
The baseline technology for treatment of VOCs is GAC adsorption. GAC adsorption generates a secondary waste that requires disposal or regeneration on a regular basis. The membrane system would minimize the secondary waste stream while providing a recyclable product.
Intellectual Property Rights
Membrane Technology and Research, Inc. owns several patents.
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References
Go to the Remediation Technology Profiles Index