Method for chemically reducing metals in waste compositions
First Claim
1. A method for the indirect chemical reduction of an oxygen-containing metal compound of a metal-containing waste composition, comprising the steps of:
- a) directing the metal-containing waste composition into a molten bath, including a first reducing agent which, under the operating conditions of the molten bath, chemically reduces the oxygen-containing metal compound in the metal-containing composition to form a metal oxide; and
b) directing a second reducing agent into the molten bath, the second reducing agent, under the operating conditions of the molten bath, chemically reducing the metal oxide, and being directed into the molten bath at a rate, relative to the rate at which the metal of the oxygen-containing metal compound is directed into the molten bath, sufficient to cause essentially all subsequently formed metal oxide to dissolve in the molten bath, thereby indirectly chemically reducing the oxygen-containing metal compound of the metal-containing composition.
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Abstract
An environmentally sound process is described for the remediation of waste materials and oxides of metals that allows the separation, recovery and decontamination of metals. The method includes chemically reducing essentially all of a reducible toxic and potentially hazardous metal oxide of a metal-containing composition. A metal-containing composition is directed into a molten bath, including a first reducing agent which, under the operating conditions of the molten bath, chemically reduces a first metal oxide of a metal in the metal-containing composition to form a bath-soluble transient second metal oxide. A second reducing agent is directed into the molten bath. The second reducing agent, under the operations of the molten-bath, chemically reduces the second metal oxide, provided that the second reducing agent has a Gibbs free energy lower than that of the second metal oxide. The rate at which the second reducing agent is directed into the molten bath, relative to the rate at which the metal-oxide of the metal-containing composition is directed into the molten-bath, is sufficient to cause essentially all subsequently formed second metal oxide to dissolve in the molten bath, thereby chemically reducing essentially all of the metal oxide of the metal-containing composition. This indirect reduction technology can remediate a variety of materials, including ash metal-contaminated municipal waste, vitreous stag-like materials and spent metal catalysts, while allowing the recovery of remediable metals.
141 Citations
40 Claims
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1. A method for the indirect chemical reduction of an oxygen-containing metal compound of a metal-containing waste composition, comprising the steps of:
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a) directing the metal-containing waste composition into a molten bath, including a first reducing agent which, under the operating conditions of the molten bath, chemically reduces the oxygen-containing metal compound in the metal-containing composition to form a metal oxide; and b) directing a second reducing agent into the molten bath, the second reducing agent, under the operating conditions of the molten bath, chemically reducing the metal oxide, and being directed into the molten bath at a rate, relative to the rate at which the metal of the oxygen-containing metal compound is directed into the molten bath, sufficient to cause essentially all subsequently formed metal oxide to dissolve in the molten bath, thereby indirectly chemically reducing the oxygen-containing metal compound of the metal-containing composition. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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32. A method for the indirect chemical reduction of at least two oxygen-containing metal compounds of a metal-containing waste composition, comprising the steps of:
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a) directing the metal-containing waste composition into a molten bath, including a first reducing agent which, under the operating conditions of the molten bath, chemically reduces a first oxygen-containing metal compound of the metal-containing composition to form a metal oxide; and b) directing a second reducing agent into the molten bath, the second reducing agent, under the operating conditions of the molten bath, chemically reducing the metal oxide, and being directed into the molten bath at a rate, relative to the rate at which the metal of the oxygen-containing metal compound is directed into the subsequently formed metal oxide to dissolve in the molten bath, thereby indirectly chemically reducing the first oxygen-containing metal compound of the metal-containing composition; and
thereafterc) directing a sacrificial metal into the molten bath after the second reducing agent has reduced at least a significant portion of the second metal oxide, the sacrificial metal being substantially soluble in the metal bath and having a lower free energy of oxidation than the second reducing agent, whereby the sacrificial reacts with a second oxygen-containing metal compound of the waste composition, the second oxygen-containing metal compound being substantially inert to the first and second reducing agents at the temperature of the molten bath, thereby chemically reducing the second oxygen-containing metal compound of the waste composition. - View Dependent Claims (33, 34, 35, 36, 37, 38)
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39. A method for indirect chemical reduction of an oxygen-containing metal compound, comprising the steps of:
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a) directing the oxygen-containing metal compound into a molten bath, whereby an oxygen-containing metal compound phase is formed in the presence of a molten bath phase, wherein the two phases are substantially immiscible, the molten bath including a first reducing agent which, at the operating conditions of the molten bath, chemically reduces a significant portion of the oxygen-containing metal compound to form a metal oxide and a reduced metal of oxygen-containing metal compound at a surface of the molten bath phase which is in contact with the oxygen-containing metal compound phase, and wherein both the metal oxide and the reduced metal substantially dissolve in the molten bath; and b) directing a second reducing agent into the molten bath to chemically reduce the metal oxide at a rate comparable to that of the dissolution of the reduced metal of the metal oxide into the molten bath.
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40. A method for chemically remediating a oxygen-containing metal contaminant of a metal-containing composition, comprising the steps of:
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a) directing the metal-containing composition into a molten bath which includes a first reducing agent that, under the operating conditions of the molten bath, chemically reduces the oxygen-containing metal contaminant of the metal-containing composition to form a metal oxide and a reduced metal component of the metal-containing metal composition; b) directing a second reducing agent into the molten bath which, under the operating conditions of the molten bath, reduces the metal oxide, and at a rate, relative to the rate at which the metal-containing composition is directed into the molten bath, which is sufficient to cause essentially all subsequently formed metal oxide to dissolve in the molten bath; and
thereafterc) reclaiming the reduced metal component of the metal-containing composition from the molten bath.
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Specification