Smelter slags

Mine wastes, tailings, and smelter slag and emissions can contain complex mixtures of minerals that are typically a predictable function of the geologic characteristics of the deposit type being mined, coupled with the ambient climate/ environmental characteristics and the mining or mineral processing method used. See Chapter 9.05 and Plumlee (1999) for a detailed discussion. 

Smelter slag is typically composed primarily of an amorphous, silica- and calcium-rich material... 

Soils that have been contaminated by mine wastes, tailings, smelter slags, or smelter particulates can contain a complex mixture of minerals present in the soils prior to contamination minerals contributed by the contaminants minerals formed by soil weathering, biological reactions, and chemical reactions with infiltrating waters and soil moisture windblown dust, and other anthropogenic materials (Ruby et al, 1999). For example, reactions of lead oxide with soil moisture in alkaline soils can precipitate lead carbonate, whereas reactions in acidic soils can precipitate lead sulfate. 

There is only one day of capacity between the zinc fume recovery process in the smelter and the fume leach process in the zinc plant. Therefore, if there is an upset in the leach circuit, it is necessary to stop the slag fuming process for zinc recovery and stockpile smelter slag for recovery in the future. The same is true for the flow of residue from the zinc plant circuits to the smelter. Residue slurry is transported from the zinc plant to the smelter, where it is... 

W. Curlook, V.G. Papangelakis, "Pressure and Leaching of Non-Ferrous Smelter Slags for the Recovery of their Base Metal Values," Pressure Hydrometallurgy 2004, Collins, Papangelakis Ed., CIM, Montreal 2004, 823-837. 

I. Perederly, V.G. Papangelakis, I. Mihaylov, "Nickel Smelter Slag Microstructure and Its Effect on Slag Leachability," T.T. Chen Symposium, Wang, Dutrizac, Free, HWang, Kun, Ed., TMS, Orlando, 2012, 225-237. 

Smelter revenues are also boosted by an ability to recover and sell by-products such as sulfuric acid and copper, as weU as some minor elements such as antimony in the form of antimonial lead alloys, mercury and cadmium. In some instances zinc can be recovered from smelter slags by fuming. 

The first commercial installation of the standard slag fuming furnace was at the Asarco, East Helena lead smelter in Montana in 1927, and this furnace design has subsequently been applied at a number of other major lead smelters. Copper smelter slags rich in zinc are also processed in conventional slag turners such as at Boliden s Ronnskar smelter in Sweden, and at the Hin Flon smelter of Hudson Bay Mining and Smelting Company. 

Increased environmental regulations affecting the gas and fugitive dust emissions from the smelter, as well as constraints on the wastes produced, such as smelter slags. 

With treatment at high pH or temperatures above 55°C there is a tendency for sodium to enter the solid phase as NaPb2(C03)2(0H), and if sodium carbonate is present in excess, the double salt Na2C03.2PbC03 can form. These effects will incorporate sodium into the desnUnrised paste, as can the presence of NaCl in the solution, which is usually the case for industrial grade soda ash. Hence one to two per cent Na is usually always present in paste desulfurised by this method. Conversion of lead to carbonate is also lower at around 85 to 90 per cent and the sodium must be discarded in smelter slag (Queneau et al, 1998 Stout, 1993). 

In some cases the bullion produced can be rich in antimony and to achieve high antimony recoveries under these circumstances it is necessary to avoid speiss formation, and hence keep the iron input relatively low. In turn this means that slags are lower in iron than normal primary smelter slags with Fe0 Si02 ratios at 0.8 1 and Ca0 Si02 at 0.9 1. This compares with typical primary smelter slag ratios of 1.3 and 0.7 respectively. The lead content of slag is typically between one and three per cent. 

Cadmium is normally volatilised during sintering and smelting and reports to fumes from those processes. Otherwise some may report to smelter slag, similar to zinc. 

Iron predominantly reports to smelter slags and any matte formed. The content of iron in bullion is not significant, and any present is removed as matte during copper drossing. 

Kontopoulos, a., Komnitsa, K. Xendis, a. 1996. Environmental characterisation of lead smelter slags in Laviron. In Minerals, Metals the Environment, Prague, September 3-6, 1996. Institution of Mining and Metallurgy, 405-420. 

Weathering results in the release of arsenic in soluble forms and it is estimated (3) that 45 X 106 kg/year enter the ocean. Atmospheric contributions comprise very roughly 18 x 108 kg/year from volcanic activity, and 26 x 106 Kg/year from soils and sediments as volatile arsines (4). Human activities result in introduction of (a) up to 26 X 106 kg/year to the atmosphere (5), mainly from nonferrous metal production (b) about 100 X 106 kg/year to land from mine tailings, smelter slags and water, coal fly ash and bottom ash, and commercial product wastage, etc., and (c) about 40 x 106 kg/year into aquatic systems from domestic waste water, electric generating plants, and ferrous smelters, etc, (6). 

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