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| Environmental Technology Listing |
Title of Listing: | | Desorption and Vapor Extraction |
Category: | | Treatment Technologies |
Subcategory: | * | Waste, Soil, All Listings |
Media: | | Soils, Sludges, Sediments |
Contaminants: | | PCBs, PAHs, pesticides, VOCs, Semivolatile Organics such as Tetraethyl Lead and Mercury |
Web Site: | | |
Email: | | |
Technology Description: | |
RSI's low-temperature, high-volume Desorption and Vapor Extraction (DAVE) system separates toxic and hazardous waste from soils, sludges, and sediments. The process is designed to separate and capture both volatile and semi-volatile organic contaminants from host materials. Nonvolatile inorganic contaminants (such as metals) in the waste feed do not inhibit the process, but are not removed. The clean processed soil (98 to 99 percent or more of incoming feed after rehydration) is returned to the excavation site or used for clean fill. The contaminants are captured and shipped off site for recycling or final disposal. This is accomplished in a closed process, with continuous, real-time monitoring and numerous back-up systems.
The DAVE system is not an incinerator. The system air heater provides a hot gas to which the contaminated host material is exposed. This hot gas, a combination of system recycled process gas and ambient air, is heated and injected into the host material. An oxygen control system maintains 2 percent or less oxygen level in this heated air stream. This design ensures an inert gas blanket throughout the process and provides for safe management of highly volatile compounds. Temperatures within the extractor (heating vapor extraction section of the process) range from 200 to 600 degrees F, depending upon the contaminant being processed. (The average temperature is 320 degrees F). The contaminant compound(s) exit the extractor, along with a small amount of fine particulates and water vapor. This process gas stream is cleansed in the gas treatment section of the process. Contaminant compounds such as PCBs are removed as the gas is condensed in a venturi scrubber, a plate washer, and a mechanical refrigeration and gas reheat unit. The cleansed process gas is then discharged into two gas-phase, activated carbon vessels. These vessels are operated in series with continuous interbed, process gas monitoring. A clean, fresh bed is in standby mode.
Condensate from the gas treatment section is sent to contaminated process water storage tanks. This contaminated process water stream is cleansed in a pressurized filtration system consisting of a prefilter multimedia filter and two activated carbon filters, operated in series. Then clean process water is sent to storage tanks. This water is utilized for incoming contaminated feed hydration, system process water makeup, and clean solids discharge dust suppression. All treated waters are reused within the system; no discharge of process water is necessary.
The process water treatment system is effective in treating high boiling, high density liquid compounds. Insecticides, pesticides, herbicides, and similar agricultural contaminants are concentrated within the condensation units and, if necessary, the units are treated with chemical solvent to remove any residual contaminants that may be present. The solvent if added, is recovered for reuse and the concentrated contaminants sent off site for disposal.
R.S.I. will be considering the use of other demonstrated, cost-effective, process water treatment technologies, which offer a higher degree of flexibility in dealing with multiple contaminants and would make a significant reduction in the amount of activated carbon used in the process water treatment section.
More volatile contaminants with appreciably lower boiling points (TCE, PCE) would be concentrated on gas-phase activated carbon beds. The carbon beds are regenerated. The original DAVE System unit has a processing capacity of 3 to 12 tons per hour with an average capacity of 8.5 tons per hour. This is a mobile unit. A larger DAVE system design has been completed, this unit also will be mobile (over the road portable) and will have a capacity of 40 to 100 tph, with an average capacity of 73 tph.
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Performance Status/
Limitations: | |
Performance Status:
Extensive Patents - A comprehensive group of patents protects RSI's technology, with seven U.S. and numerous foreign patents issued.
Tested - Numerous EPA, state, and local government supervised tests of the DAVE system have verified treatment capabilities.
Limitations:
Certain feed characteristics affect the efficiency of the DAVE system in contaminant removal. These characteristics include:
Soil/sediment particle size distribution - For optimum treatment, feed should be as uniform as possible; however, soils of varying particle sizes may be treated.
Moisture content - The process is applicable to host material with a moisture content ranging from 5 to 50 percent. Host material with a moisture content greater than 50 percent should be dewatered or mixed with dry material. Conversely, process water can be added within the process to increase the moisture content of dry host materials.
Contaminant concentration - The rate of contaminant desorption from host materials is dependent on the concentration of the contaminants. Some material may have to be recycled for more than one pass.
Contaminant boiling point - Contaminants with low boiling points are most easily removed from the host material, though the process can treat most materials which can be vaporized under vacuum or in steam. Operating parameters can be adjusted to meet the requirements of most host materials and contaminants.
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Topics
Hazardous Waste, Technologies, Treatment/Remediation
Additional Topics/Tags/Keywords
Thermal Desorption, Vapor Extraction, PCBs |
Organization: | | RECYCLING SCIENCE INTERNATIONAL, INC. |
Address: | | 175 West Jackson Boulevard
Suite A1934 | Phone: | Description | Number |
City: | | Chicago | | Primary | (312) 663-4242 |
State/Province/Territory: | | IL | 2. | | |
Zip/Postal Code: | | 60604-2601 | 3. | | |
Country: | | United States | 4. | Fax: | (312) 663-4269 |
Branch Locations: | |
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