Specialized metallurgical processes – compositions for use therei – Processes – Electrothermic processes
Patent
1986-10-27
1987-11-10
Rosenberg, Peter D.
Specialized metallurgical processes, compositions for use therei
Processes
Electrothermic processes
75445, 75 65R, 75 72, C22B 1100
Patent
active
047055626
DESCRIPTION:
BRIEF SUMMARY
The present invention is concerned with a method of working-up waste products which contain valuable metals and which predominantly comprise organic constituents, into a product form from which the valuable metal content thereof can be readily recovered. More specifically the invention relates to the expulsion of organic constituents by pyrolysis and/or by combusting said constituents in a reactor which can be rotated about its longitudinal axis and which is charged and emptied through one and the same reactor opening. The invention relates in particular, although not exclusively, to the working-up of combustible copper scrap, such as electric-cable scrap and electronic scrap materials, which often contain other essential metal values, such as precious metals for example. In addition to such materials, the invention can also be used to work-up other secondary materials which contain metal values, for example lead scrap, such as battery scrap, and alloyed steel scrap, such as stainless steel. By metal values is meant here, and in the following, primarily non-ferrous metals, such as copper, nickel, cobalt, lead, tin and precious metals. The organic substances present are often from the group of plastics, rubber, paper, oil, tar, and greases. When working-up secondary materials of the aforesaid kind, it is essential that losses are kept low, both from an economic aspect and an environmental aspect.
According to a method devised by Boliden and described and illustrated in SE-B-8104490-1 and other, corresponding national specifications, for example U.S. Pat. No. 4,415,360, metal-bearing waste products containing substantial quantities of organic material are worked-up by pyrolysis and/or combustion of the organic material in a rotating reactor, in the manner indicated in the opening paragraph of this specification. When practising this known method, the inorganic metal-bearing product which remains after expelling all the organic constituents present in the original starting material is removed from the reactor in the form in which it is found upon completion of the pyrolysis/combustion process, optionally after at least partially melting-down the residual product. According to this prior art publication, the reactor temperature is therewith raised to 1050.degree.-1100.degree. C. with the aid of an oil-gas burner, thereby partially melting-down the metals present in the scrap. This partially molten content is then removed from the reactor and is allowed to cool in a ladle, to form a porous lump which is held together by a solidified metal layer at the bottom of the lump. The pyrolysed or combustion residue material is thereafter transferred in its then solid form to a suitable pyrometallurgical smelter, in which it is worked-up and the metal content thereof extracted, or is optionally partially melted-down and solified to form porous lumps, prior to being charged to the smelter. This smelter may be a Pierce-Smith-converter in which, in accordance with conventional copper manufacturing techniques, the copper matte is converted to blister copper, while slagging the iron content of the copper matte and oxidizing its sulphur content. The smelting of scrap material in copper converters, however, creates many problems, even though a number of the problems normally encountered can be substantially overcome by practising the method described and illustrated in our earlier patent specification. One of the most serious problems encountered in this respect is that combusted scrap residues contain a large quantity of finely divided material, which creates large amounts of dust when handled and when charged to the converter. As indicated above when describing the scrap combusting method of our earlier published specification, this problem can be overcome to a large extent by partially melting-down the combustion residue, such that part of the fine fraction thereof is melted-down or absorbed in the resultant molten bath.
Due to their weight and size, however, the porous lumps obtained when practising the aforedescribed known
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Boliden Aktiebolag
Rosenberg Peter D.
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