Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Patent
1994-10-19
1996-06-18
Andrews, Melvyn
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
75672, C22B 700
Patent
active
055273807
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method of recovering a non-ferrous metal from a dross starting material that contains the metal, possibly together with non-ferrous metal scrap, and/or a starting material comprised of such scrap. The method includes the steps of feeding the starting material to a rotary furnace or a rotatable converter provided with a refractory lining, heating the starting material to a temperature above the melting point of the metal while rotating the furnace continuously or intermittently, and removing the resultant molten metal from remaining dross residues and/or from resultant solid dross residues.
BACKGROUND OF THE INVENTION
Methods for recovering non-ferrous metals from dross are known to art. For example, the Canadian Patent 1,255,914 teaches a method for recovering non-ferrous metal from non-ferrous-metal containing dross. The method includes the steps of feeding the dross into a rotary furnace that has a refractory lining, directing a plasma burner into the furnace so as to heat the dross to a temperature above the melting point of the metal, rotating the furnace either continuously or intermittently, and removing the molten, separated metal from the solid dross residue.
It is also known to recover non-ferrous metals from dross and metal waste with the aid of oxy-fuel-burners while using a protective layer of salts. This layer may include sodium chloride (NaCl), potassium chloride (KCl) in roughly equal quantities with respect to weight, and may also contain a flux, for instance cryolite. The effect of the salt layer on the coalescence of aluminum droplets when treating aluminum dross is described, for instance, in the Second International Symposium; Recycling of metals and engineered materials, The minerals, metals and materials Society, 1990, pages 69-84, by Ray D. Petersen, entitled "Effect of salt flux additives on aluminum droplet coalescence". In an article entitled "Interfacial phenomena in molten aluminum and salt systems" published in the same reference, pages 85-103, Francis K. Ho and Yogesh Sahai describe the remelting of aluminum waste beneath a salt layer.
SUMMARY OF THE INVENTION
An object of the present invention is to recover, or win, non-ferrous metal from a dross starting material that contains the metal. The dross starting material may also include non-ferrous metal waste, and/or a starting material containing such waste. The non-ferrous metal is recovered, or winned with the aid of an oxy-fuel-burner and in the absence of a protective salt layer.
Another object of the present invention is to reduce the formation of corrosive salt vapors that are obtained when using protective salt layers, and to obtain an oxidic rest product that is free from water-soluble salts, thereby benefitting the environment.
These objects are achieved with a method for recovering, or winning, a non-ferrous metal from a dross starting material that contains the metal. The dross starting material may also include non-ferrous metal waste, and/or from a starting material that contains such waste. The method comprises the steps of introducing the starting material into a rotary furnace or a rotatable converter provided with a refractory lining; heating the starting material to a temperature above the melting point of the metal, while rotating the furnace either continuously or intermittently; and removing the resultant molten metal from the overlying dross residue. The method is particularly suited for the recovery of aluminum from aluminum-containing dross and from aluminum scrap.
The inventive method is characterized by heating the starting material with a so-called oxy-fuel-burner in the absence of a protective salt layer. The burner is supplied with a fossil fuel and with a gas that contains at least 80% oxygen. The furnace is rotated at a speed of 5 r.p.m or lower.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in more detail with reference to the accompanying drawing, the single Figure of which is a vertical section view of t
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The Alcan Plasma Dross Treatment Process, A New Salt-Free Dross Processing Technology, Lavoie et al., Second International Symposium-Recycling of Metals and Engineered Materials, The Minerals, Metals, & Materials Society, 1990, pp. 451-462.
Grab Hans-Walter
Gripenberg Henrik
Mullerthann Michael
AGA Aktiebolag
Andrews Melvyn
Hoogovens Aluminium Huttenwerk GmbH
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