Patent Number: 060692901
Section: summary

TECHNICAL FIELD OF THE INVENTION This invention relates to waste treatment processes, and particularly to a treatment process utilizing molten alkaline metal alloys for chemically reacting with waste materials. The invention also encompasses a reactant metal alloy for use in the waste treatment process. BACKGROUND OF THE INVENTION Many waste treatment processes utilize thermal energy to break up waste materials into their constituent elements or more desirable compounds. The use of thermal energy generally to break down materials is referred to as pyrolization. Molten metals have been used as a reactant for pyrolizing certain waste materials. In particular, molten aluminum has been used to react with halogenated hydrocarbons and produce aluminum salts. U.S. Pat. No. 4,469,661 to Schultz described the destruction of PCB and other halogenated hydrocarbons by contacting the PCB vapor with molten metallic aluminum. The aluminum was contained in low-boiling eutectic mixtures of aluminum and zinc or aluminum, zinc and magnesium. Schultz also suggested eutectic reactant mixtures containing iron, calcium, and other metals. U.S. Pat. No. 5,000,101 to Wagner disclosed a process for pyrolizing hazardous waste material in molten alkaline metal alloys. The molten metal alloy comprised approximately 50% aluminum, 5% to 15% calcium, 5% to 15% copper, 5% to 15% iron, and 5% to 15% zinc. U.S. Pat. No. 5,167,919 to Wagner disclosed a reactant alkaline metal alloy composition comprising between 40% to 95% aluminum, 1% to 25% iron, 1% to 25% calcium, 1% to 25% copper, and 1% to 25% zinc. The '919 Wagner patent also disclosed that magnesium could be substituted for calcium but this substitution was seen as having no advantage. In both of these Wagner patents, the waste material was reacted in the molten alloy held at about 800 degrees Celsius. In the process disclosed in the above-described Wagner patents, chlorine atoms in the waste material was stripped from the waste compound by the highly reactive aluminum in the reactant molten alloy. The aluminum and chlorine combined to form aluminum chloride. Both the aluminum chloride and carbon released from the waste material in the pyrolization process sublimed to a gaseous state at the 800 degree Celsius reaction temperature and were drawn off and separated. SUMMARY OF THE INVENTION It is an object of the invention to provide a waste treatment process for treating halogenated hydrocarbons and particularly chlorinated hydrocarbons to produce carbon compounds and useful chlorine salts. Another object of the invention is to provide reactant alkaline metal alloy compounds for producing useful chlorine salts from chlorinated hydrocarbons. In order to accomplish these objects, the present waste treatment process utilizes a molten reactant metal alloy compound including significant quantities of magnesium or lithium, or both, to react with the chlorine atoms in the waste compound being treated. One preferred reactant metal alloy comprises an alloy of magnesium, aluminum, zinc, calcium, and copper. In another preferred form of the invention, the reactant alloy comprises lithium, aluminum, zinc, calcium, and copper. In yet another embodiment of the invention, the reactant alloy comprises magnesium, lithium, aluminum, zinc, calcium, and copper. In each case, the alloy is heated to a molten state and to at least 770 degrees Celsius. The reactant alloy is preferably heated by a fossil fuel burner although any suitable heating arrangement, such as an induction heater, may be used within the scope of the invention. The particular reactant alloy is held in the molten state in a reactor container isolated from oxygen. The isolation from oxygen prevents excessive oxide formation and prevents oxidation of the elemental carbon released in the pyrolization process. The waste material, and particularly chlorinated hydrocarbons, are introduced directly to the reactant molten alloy preferably below the surface of the molten material. The magnesium or lithium in the reactant alloy chemically strips chlorine atoms from the chlorinated hydrocarbons to form magnesium chloride salt or lithium chloride salt. These chlorine salts along with carbon freed from the waste material in the form of elemental carbon, CH, CH.sub.2, or CH.sub.3 sublime to a gaseous state at the temperature of the molten alloy. Carbon, CH, CH.sub.2, and CH.sub.3 produced in the pyrolization process according to the invention will be referred to herein as char. The gas released in the treatment process is drawn off and scrubbed in an aqueous scrubber/separator to produce a slurry of char and salt solution. The salt solution is then separated and processed to recover the chlorine salt while the separated char is dried. These and other objects, advantages, and features of the invention will be apparent from the following description of the preferred embodiments, considered along with the accompanying drawings.