Hazardous or toxic waste destruction or containment – Containment – Solidification – vitrification – or cementation
Reexamination Certificate
1996-12-12
2001-03-20
Jenkins, Daniel J. (Department: 1742)
Hazardous or toxic waste destruction or containment
Containment
Solidification, vitrification, or cementation
C588S253000, C588S253000, C588S253000, C588S256000, C110S346000
Reexamination Certificate
active
06204427
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains generally to the thermal processing of heterogeneous feedstock and the production of a metal product, a glass ceramic product and a gaseous product. The process includes the capability for thermal treatment of hazardous waste as defined by the Environmental Protection Agency (EPA) which also contains radioactive isotopes in some cases (mixed waste as defined by the Department of Energy) and the production of stable long lived products as a result of treatment. More specifically, this invention relates to a novel process and apparatus whereby an input feed stream of a widely heterogeneous nature in the descriptors of physical form, combustibility, chemical content, and particle size, and contaminated with varying concentrations of hazardous components or radiosotopes is treated in a direct or alternating current graphite electrode arc melter with a contiguous thermal oxidizing reactor for the production of a metal product, a basalt like glass ceramic product and a fully combusted offgas. The apparatus described incorporates an offgas fast quench configuration for the minimization of dioxin formation and for subsequent ease of cleansing of the offgas stream.
BACKGROUND OF THE INVENTION
Joule heated melters have traditionally been used for the production of glass-based products. Graphite electrode arc melters have traditionally been used for the reduction of ores to metals and for the production of value added products from a controlled and well defined input feed steam. Arc melters have also been used for the production of a value added mineral wool product from a well characterized and controlled input feedstock. Plasma arc torch melters have traditionally been used for the production of higher value precious metals such as titanium. The various types of melters commonly used in industry can be classified as low temperature (900° C.-1,200° C.) medium temperature (1,200° C.-1,500° C.) and high temperature (1,500° C.-2,000° C.), with their use defined by the product desired and process required. The joule heated melters commonly used for the production of glass (including borosilicate glass for high level radioactive waste) fall into the low temperature range. Medium temperature melters are required for the production of higher temperature glasses such as aluminosilicate glasses and glass ceramics.
High temperature melters are required for the reduction of ores to metals such as iron ore to iron and for the production of a basalt-like glass ceramic product without the addition of fluxing agents to lower the viscosity. Arc melters use heat generated when an electric arc passes through a gas. The gas is ionized and forms a very high temperature plasma. The plasma temperatures can exceed many thousands of degrees centigrade. The high temperatures enable rapid and intense heating of process materials, making this technology ideal for high temperature metals processing.
Current research and development by government and industry is being pursued for the purpose of applying arc melter technology to the treatment of hazardous and/or radioactive wastes. The application of traditional melter technology and equipment to the safe, efficient and economical treatment of heterogeneous hazardous and/or radioactive waste involves the expansion of the allowable makeup of the input feed stream, the expansion of the flexibility of process operation, and the tightening of specifications for the output products and offgases.
There have been a number of testing or development programs to apply electric arc melter technology to the treatment of radioactive wastes, mixed wastes, municipal wastes, and hazardous wastes. In an arc melter, waste materials are heated to (a) volatilize, pyrolyze, and destroy organics, and (b) melt inorganic materials into molten slag or metal phases. By controlling reaction stoichiometry, mixing, and other operating parameters, the process can be used to chemically oxidize or reduce waste components, or react waste components to form new products.
Leam In U.S. Pat. No. 4,421,037 discusses a waste treatment furnace.
Rackley, et al. In U.S. Pat. No. 5,052,312 discusses a cyclone furnace for hazardous waste incineration and ash vitrification.
Alvi, et al. In U.S. Pat. No. 5,541,386 discusses the plasma arc decomposition of hazardous waste into vitrified solids and non-hazardous gasses.
SUMMARY OF THE INVENTION
The described process and apparatus enables the continuous or intermittent feeding of widely varying heterogeneous input waste streams, the thermal partitioning of the input feed into inert and volatile fractions, the melting and oxidation or reduction of the inert fraction into a glass ceramic (slag) phase consisting of oxidized metals and low vapor pressure materials, the melting and reduction of the inert fraction metals into a metal phase, and the complete combustion and oxidation of the vapor phase. Further, the flexibility of the operation and process enables control of the volatilization of higher vapor pressure materials and forces positioning of these materials to the glass ceramic phase.
The process and apparatus provides for the removal of the metal and glass ceramic phases by high temperature tapping techniques and fast cooling of the offgas from greater than 2000° F. to less than 150° F. in a minimum time period. Further, the process provides for the reclamation of a glass ceramic product via product casting techniques and controlled cooling via insulation or heat addition to control the crystalline phase structure of the final cooled product.
The types of wastes applicable to treatment in the described invention include wastes having widely varying compositions in terms of soil content, metal content, combustible content, organic content and hazardous contaminant content.
The glass ceramic product produced exceeds the current requirements for Toxic Characteristic Leach Procedure (TCLP) as published in the Federal Register on Mar. 29, 1989, and can meet a more narrowly defined product specification suitable for reclamation. This specification may include narrowly defined compositional ranges and physical properties.
The metal product is also suitable for reclamation as industrial scrap metal from non-radioactive input feed and as recyclable metal within the nuclear industry from radioactive contaminated input feedstock.
The offgas is fast quenched from temperatures required for complete combustion and oxidation (>2,000° F.) in minimal time to below the temperatures accepted as the formation temperature for dioxins and furans, thereby minimizing the production of dioxins. Further offgas cleansing enables the partitioning of the offgas particulates to volatile metals fractions and salts.
REFERENCES:
patent: 4421037 (1983-12-01), Leam
patent: 5052312 (1991-10-01), Rackley et al.
patent: 5424042 (1995-06-01), Mason et al.
patent: 5541386 (1996-07-01), Alvi et al.
patent: 5548611 (1996-08-01), Cusick et al.
patent: 5662579 (1997-09-01), Bickford
patent: 5666891 (1997-09-01), Titus et al.
Advanced Mixed Waste Treatment Project Melter System Preliminary Design Technical Review Meeting: Eddy, et al., Pertinent pp. 5-20, 5-24, 5-25, 6-9, 6-16, 6-20, 7-4 and 8-1 to 8-18.
Jenkins Daniel J.
Morrison & Foerster / LLP
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