Electric heating – Metal heating – By arc
Reexamination Certificate
2000-12-20
2003-04-22
Paschall, Mark (Department: 3742)
Electric heating
Metal heating
By arc
C219S121430, C219S121480, C219S121590, C588S900000, C110S246000
Reexamination Certificate
active
06552295
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for plasma furnace disposal of hazardous wastes.
2. Discussion of the Background
In the field of chemical waste disposal, there are a number of complicating technical and legal requirements which must be managed. For example, as the government designated operational authority in all matters related to chemical weapons disposal, the Army requires that nerve-gas contaminated solid waste material which is disposed from its possession must be certified to have met a 5X standard which requires that the material has been to 540° C. for 15 min. Given that many of neurological bio-hazards, such as sarin are in liquid form, this presents significant complication. For example, processes which might be used on solid waste such as simple closed containment heating to 540° C., if used will create extreme pressures. A container filled with sarin will upon heating become over-pressured once the boiling point 147° C. of sarin is reached. Such an over-pressurized container upon leakage or rupture would disperse its contents rapidly into the surrounding environment. This scenario presents an unacceptable risk to the environment and personnel at disposal sites. In addition to the 5X standard, any effluent discharged from a waste disposal unit must have stack concentrations less than 0.3 ug/m
3
of VX, sarin, and mustard gas agents. The public perception is that the effluent must show zero detection of nerve gas agents by best available detection means.
Chemical weapons materials for disposal comes in a variety of forms. In the simplest situation, containers for disposal contain only a nerve gas agent such sarin in liquid form. In practice, containers for disposal contain a wide variety of materials. For example, garments and filters which have been used by personnel in handling sarin containers become themselves laced with sarin. These articles are packed in drums and stored. This material constitutes nerve gas contaminated waste and must be disposed by the Army. Effluent from these drums is no longer pure, rather the effluent will contain significant amounts of water vapor and hydrocarbons. In addition, the articles packed in the drums have a variety of shapes and compositions which presents gas stratification problems with different components volatilizing in the drum at different depths in the drum.
A number of approaches have been developed for disposing of industrial waste products. Incineration is one such approach. Industrial waste products are oxidized into benign exhaustible products as they transit a high temperature combustion flame. U.S. Pat. No. 3,766,866 to Krum teaches a thermal waste converter with primary and secondary chambers for the pyrolysis and combustion of waste material. In a patent which shows the sophistication of incineration techniques, U.S. Pat. No. 5,743,196 to Beryozkin et al. shows a mobile waste incinerator to provide a mobile device for incineration of wastes on site and between sites. Unfortunately, incineration techniques produce considerable exhaust to the atmosphere which poses significant safety concerns given that 100% destruction of the hazardous nerve gas agents may not be certain. Some fraction of the nerve gas agents entrained in the feedstock to the incinerator can by-pass or blow-by of the combustion flame. Typically, this risk is mitigated at permanent facilities by installing multiple burner stages to insure complete incineration of the nerve gas agents. This redundancy adds to the cost of the facility and its operation.
Currently, a $650 million incineration system is being used on site at the Tooele Army Depot in Utah to destroy 27 million pounds of nerve and mustard agents from a variety of munitions stored in nearby bunkers. Despite the remote location, the incineration facility still attracts a significant amount of public scrutiny and watch-dogging. In addition, it is politically unacceptable to permit shipment of loads of nerve gas agents across the country to central disposal facilities. Indeed public law now prohibits transport of nerve gas agents from site-to-site across the United States.
Furthermore, establishing incineration systems at a multitude of storage sites (many which are closer to larger population concentrations) is financially and politically unacceptable. Yet, smaller stores of nerve gas agents are to be found at a variety of sites. Of particular concern, the U.S. Army has identified 224 sites where nerve gas agents have been potentially buried. These sites include 96 locations in 38 states, the District of Columbia and the Virgin Islands. Accidental discoveries of chemical waste material by the public have demonstrated the seriousness of the buried weapons problem. In 1995, workers during construction of a housing development found a chlorine-filled projectile at Fort Lewis in Washington, D.C., and contractors digging utility lines at the Mississippi State Fairgrounds in Jackson uncovered glass vials containing chemical agents. Eventually, more than 260 vials containing phosgene, mustard, and lewisite were found at the Fairgrounds site, only a few blocks from the Mississippi state capitol.
Thus, alternatives to centralized incineration facilities are needed wherein chemical weapons materials can be safely disposed of on-site at the storage sites without transporting those materials to central incineration sites. These alternatives need to process such as nerve gas agents thoroughly and with significant throughput. An estimated 13,000 metric tons of sarin are stockpiled at 9 different storage sites. Compounding this disposal problem is a stockpile of additional containers of sarin-contaminated waste products. These contaminated waste containers include for example, charcoal granules contaminated with varying degrees of sarin. The granules were once exterior protective linings on jump-suits used by workers as they handled the nerve gas agents. The charcoal has been ground into granules and is stored in 55 gallon drums. There are an estimated 250,000 such drums which all must be treated to the 5X standard before they can be disposed. The concentrations of sarin in these drums vary significantly from one drum to another, and in addition many drums are contaminated with water.
Recently, alternatives to combustion-based incinerators have been investigated. U.S. Pat. No. 5,798,496 to Eckhoff et al. teaches a mobile plasma-based waste disposal system which utilizes an arc-torch plasma technology to dispose of industrial waste. U.S. Pat. No. 5,288,969 to Wong et al. teaches an inductively coupled rf plasma torch technology operating at atmospheric pressures for the dissociation of hazardous waste. While these approaches have been shown to be effective in converting toxic agents, they too suffer with similar problems to the combustion processes. Gas by-pass of the plasma regions are possible, and large amounts of effluents or end-products are produced in which a large percentage of this effluent comes from the addition of processing gasses to stabilize the torch operation. Alternatively, U.S. Pat. No. 5,256,854 to Bromberg et. al. teaches a method and apparatus for simultaneously bombarding toxic gases with high energy electron irradiation and rf inductive fields to destroy vaporized toxic materials. U.S. Pat. No. 5,028,452 to Beatty teaches a closed-loop low-pressure system and process for conversion of gaseous or vaporizable organic and/or organo-metallic compounds to an inert solid matrix resistant to solvent extraction. U.S. Pat. No. 5,779,991 to Jenkins teaches an apparatus for destroying hazardous compounds in a gas stream using a cylindrical labyrinth passage wherein a plurality of electric fields are used for generating and sustaining a plasma or corona discharge through different zones within the gas labyrinth. These systems use low power operations to convert the waste gas stream into more benign end-products. Unfortunately, the low power level limits the quantity of hazardous waste products which can be converte
Hendry Robert C.
Markunas Robert J.
Posthill John B.
Thomas Raymond
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Research Triangle Institute
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