Method for extracting metals from metal-containing materials by

Details Method for extracting metals from metal-containing materials by Method for extracting metals from metal-containing materials by

1997-02-05

2000-02-29

Andrews, Melvyn

Specialized metallurgical processes, compositions for use therei

Processes

Free metal or alloy reductant contains magnesium

75694, 75961, 423 38, 423 87, 423 91, 423 97, 423107, 423108, C01G 106, C01G 904, C22B 700

Patent

active

060304332

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention relates to a method for extracting metals from metal-containing materials, especially waste.


BACKGROUND OF THE INVENTION

As is well known, metal-containing waste forms a serious environmental problem. This is particularly true of waste in which the presence of heavy metals which can be leached relatively rapidly, such as cadmium, lead and zinc, entails a potential environmental hazard. Moreover, the metal-containing waste materials form a very heterogeneous group of materials which comprises, inter alia, metal-containing muds, sludges, filter cakes, metal and filter dusts, batteries, accumulators, printing plates, composites, laminates, catalysts and pickling fluids from, e.g., the electroplating industry. Such waste materials show very large differences among themselves with respect to physical appearance and composition (type and content of the metals and minor components present). Depending on the type of waste and the source, in the Netherlands alone this involves many tonnes up to tens of thousands of tonnes per metal-containing waste product per year.
Out of the abovementioned enormous amount of metal-containing waste materials, only 5%, according to estimates, are being worked up in metal recovery processes. This processed portion of the metal-containing waste materials primarily involves waste materials having a (very) high content of valuable metals and a low content of minor components, such as scrap iron, scrap zinc, scrap lead and cabling waste (recovery of copper). By far the greater part of the metal-containing waste materials is therefore dumped, either on the operator's own plant site or at a dump suitable for this purpose.
In principle, two routes are available for processing complex metal-containing waste materials, namely: [1] the hydrometallurgical route and [2] the pyrometallurgical route. Both techniques are used for producing metals from primary raw materials (ores). With respect to processing most metal-containing waste materials, however, these conventional hydro- and pyrometallurgical processes do not always provide the direct answer, since: and chemical composition, differ from natural ores; natural ores; hydro- and pyrometallurgical processes, and product needs to be removed in the subsequent process, which requires a large amount of chemicals and often affords an iron product which should be regarded as a hazardous waste.
Given the major need for an effective reprocessing method for metal-containing waste, Applicant has therefore carried out in-depth research regarding a uniformly applicable method for extracting (at least part of) the metals from the multitude of metal-containing waste materials.


SUMMARY OF THE INVENTION

Surprisingly it was found that the abovementioned object can be achieved if metal-containing materials which contain at least one or more of the metals from the group consisting of Zn, Cd, Pb, Hg, Cu, Sn (as Sn(0) and Sn(II)), As, Sb, Au, Ag and Bi, are made to react at 700-1100.degree. C. with a gas composition which at least comprises 25-45% by volume of water vapour, 0-12% by volume of carbon dioxide and 2-20% by volume of hydrogen chloride, and the metals from the abovementioned group are extracted in the form of volatile metal chlorides.
The pyrohydrolysis according to the invention is based on the principle that, under the process conditions indicated above, the metals Zn, Cd, Pb, Hg, Cu, Sn (as Sn(0) and Sn(II)), Au, Ag, As, Sb and Bi, are converted into volatile metal chlorides and can therefore on this basis be removed from the raw material or waste material, and other metals such as Fe, Cr, Mn, Ni, Kg, Ca, Al, Si, Ti, Co and Zr remain in the oxidic form or are converted into metal oxides or non-volatile metal chlorides which, under the abovementioned process conditions, are not volatile and therefore remain behind in the starting material.
On the basis of the above it is therefore possible, according to the invention, to effect a separation between, on the one hand, metals which under the reaction condition

REFERENCES:
patent: 5004496 (1991-04-01), Aune et al.
patent: 5245120 (1993-09-01), Srinivasachar et al.
patent: 5556447 (1996-09-01), Srinivasachar et al.

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