Industrial electric heating furnaces – Induction furnace device – With means for manipulation of the charge or melt
Reexamination Certificate
1999-03-23
2001-02-27
Lazarus, Ira S. (Department: 3743)
Industrial electric heating furnaces
Induction furnace device
With means for manipulation of the charge or melt
C110S237000, C110S250000, C110S346000, C219S674000, C219S677000, C373S138000, C588S001000, C588S253000, C588S900000
Reexamination Certificate
active
06195382
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to molten metal reactors and, more particularly, to an inductively heated molten metal reactor capable of operating at high temperatures.
BACKGROUND OF THE INVENTION
Molten metal reactors may be used to treat a wide variety of waste materials including wastes which include halogenated hydrocarbons, biomedical waste, and radioactive wastes. Molten metal reactors utilize a bath of molten reactant metal which may include aluminum, magnesium, and/or lithium, for example, along with other metals. The atmosphere above the bath is preferably purged of oxygen. When waste material is placed in contact with the molten reactant metal, the metal reacts with the organic molecules in the waste material to strip halogen atoms and form metal salts. The reaction also liberates carbon along with other elements such as hydrogen and nitrogen. Carbon, hydrogen, nitrogen, and some metal salts may be removed from the molten metal reactor in a gaseous form. Metals which may be included in the waste material, or are liberated from the waste material, may alloy with the bath. Other reaction products or liberated materials collect at the surface or bottom of the bath and may be removed by suitable means.
Molten metal reactors require a heating arrangement to heat the reactant metal to a molten state and then maintain the reactant metal in a molten state at a desired temperature as waste material is added to the bath. U.S. Pat. No. 5,000,101 to Wagner shows a molten metal reactor having an induction heater for heating the reactant metal. U.S. Pat. No. 5,271,341 to Wagner discloses a two-chamber molten metal reactor having a hydrocarbon-fired heater in one of the chambers. This two-chamber arrangement allows the reactant metal to be heated with hydrocarbon-fired burners while maintaining a separate area in which reaction products may collect for removal.
Hydrocarbon-fired heaters are desirable for many molten metal reactor applications. However, other applications for molten metal reactors cannot accommodate heating using hydrocarbon-fired burners. For example, a molten metal reactor may be highly desirable for treating biomedical wastes and other wastes generated aboard a ship. However, a sufficient hydrocarbon supply may not be readily available aboard the ship to provide the required heating.
Induction heaters are well-suited for fixed plants which have access to a suitable electric power supply. However, the electromagnetic field produced by induction heaters has, prior to the present invention, limited the temperatures at which the molten metal reactor could be operated. This temperature limitation arose from the fact that portions of the electromagnetic field extended beyond the molten reactant metal and passed through the reactor vessel and related equipment. The electromagnetic field generated heat in these metallic structural elements as well as in the reactant metal. Therefore, structural elements associated with the molten metal reactor had to be comprised of metals which maintained strength at high temperatures. Operating temperatures still had to be kept low enough to maintain the structural integrity of structural elements associated with the molten metal reactor.
The temperature limitations associated with prior molten metal reactors also effectively limited the types of wastes which could be treated. For example, although wastes which included transuranic elements (all elements having an atomic number greater than uranium), could be treated in prior molten metal reactors, the treatment was slowed by the temperature of the molten metal bath. In prior art molten metal reactors, the molten metal temperature was insufficient to cause transuranic metals to go to a molten state. Thus, transuranic metals dissolved relatively slowly in prior art molten metal reactors, and the transuranic elements alloyed with the reactant metals only after this relatively slow dissolution process.
SUMMARY OF THE INVENTION
It is an object of invention to provide an inductively heated molten metal reactor capable of operating at high temperatures and suitable for shipboard and other, fixed, applications. It is also an object of the invention to provide a method for treating wastes in a high temperature molten metal reactor. A further object of the invention is to provide an apparatus and method for treating transuranic wastes.
In order to accomplish these objects, a molten metal reactor according to the invention includes a unique induction heater arrangement and reactor vessel structure. The reactor vessel includes a heating section and a reaction section. The heating section of the vessel is preferably made of a dielectric material, while the reaction section may include conducting metals but is preferably also made entirely of dielectrics. An induction heating coil is associated with the heating section of the reactor vessel and is driven to produce an electromagnetic field in a field area which passes through at least part of the reactor vessel heating section. However, the reaction section of the reactor vessel is located outside of the field area.
The reactor according to the invention also includes a circulating device, also preferably located outside of the field area. The circulating device causes the molten metal contained in the reactor vessel to circulate between the heating section of the reactor vessel and the reaction section of the vessel. The reactor also preferably includes a waste input arrangement and a reaction product removal arrangement, both of which are preferably associated with the reaction section of the vessel, and located outside of the field area.
In operation, the electromagnetic field developed by the induction coil melts the reactant metal in the heating section of the reactor vessel and maintains the reactant metal in a molten state at a desired operating temperature. The circulating arrangement circulates the molten reactant metal from the heating section of the reactor vessel to the reaction section where waste material may be introduced and reacted. Although the introduction and reaction of waste material cools the molten reactant metal in the reaction section of the reactor, the circulation induced by the circulating arrangement constantly adds fresh molten reactant metal to the reaction section and carries the cooled reactant metal back to the heating section of the reactor vessel for re-heating.
Because no unprotected metallic structural elements are located within the field area, the operating temperature of the reactor is not limited by the strength limitations of such structural elements. Thus, the molten reactant metal may be maintained at a very high temperature. For example, molten reactant metal temperatures of approximately 1800 degrees Celsius may be used for wastes which include Thorium.
In the order to ensure that the electromagnetic field does not substantially heat metallic structural elements which may be associated with or located near the reactor, the invention preferably employs a dielectric spacing material to isolate electrically conductive components from the field. The spacing means or arrangement may include a variety of different dielectric materials. These materials are positioned around the induction heating coil and heating section of the reactor vessel. The material used for the spacing arrangement may comprise any material which is substantially unaffected by the electromagnetic field, that is, any material which is not substantially heated by the interaction of the field and the material.
Although the spacing material and other materials positioned in the area encompassed by the electromagnetic field are preferably restricted to dielectric materials, conducting materials may also be included in the field area if such materials are properly protected. Examples of such protected materials are structures built up from alternating layers of electrically conductive materials and dielectrics. Also, conductive materials in the field area may be protected by heat transfer to a circulating coolant.
I
Ciric Ljiljana V.
Clean Technologies International Corporation
Culbertson Russell D.
Lazarus Ira S.
Shaffer & Culbertson LLP
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