Furnace slag composition

The composition of blast furnace coke with respect to its Ume, silica and alumina contents also needs to be taken into account when calculating the required sinter composition and corresponding flux additives to give the required blast furnace slag composition. 

Typical Imperial Smelting Furnace slag composition. 

For a furnace with a 50 tonne initial charge the corresponding fuming rates in tonnes of zinc per hour are shown in Figure 8.7 as a funetion of furnace slag composition. 

The high temperatures in the MHD combustion system mean that no complex organic compounds should be present in the combustion products. Gas chromatograph/mass spectrometer analysis of radiant furnace slag and ESP/baghouse composite, down to the part per biUion level, confirms this behef (53). With respect to inorganic priority pollutants, except for mercury, concentrations in MHD-derived fly-ash are expected to be lower than from conventional coal-fired plants. More complete discussion of this topic can be found in References 53 and 63. 

Fig. 2. Cement 2ones in the CaO—AI2O2—Si02 system (5) where B represents basic blast-furnace slag D, cement compositions which dust on cooling E, compositions showing no tendency to set G, aluminous cement and PC, Pordand cement.

Table 4.11 depicts the typical chemical composition of blast furnace iron slag. It is suggested that the chemical composition of blast furnace slags produced in North America has remained relatively consistent over the years. 

Many cements used today are composites of Portland cement and industrial waste materials that can enter into the hydration reactions and contribute to the strength of the hardened product. These substances include pulverized fuel ash (PFA) from burning of pulverized coal in thermal power stations, crushed blast-furnace slag (Section 17.7), and natural or artificial pozzolanas—that is, volcanic ash and similar finely particulate siliceous or aluminosilicate materials that can react with the Ca(OH)2 in Portland cement to form hydrated calcium silicates and aluminates. As noted earlier, the solubility of Ca(OH)2 is such that the pH of pore water in Portland cements will be about 12.7, at which the Si-O-Si or Si-O-Al links in the solid pozzolanas will be attacked slowly by OH- to form discrete silicate and aluminate ions and thence hydrated calcium silicate or aluminate gels. 

C-S-H = poorly crystalline or amorphous calcium silicate hydrate of unspecified composition. Ggbfs = ground granulated blast furnace slag. Hep = hardened cement paste. Pfa = pulverised fuel ash (fly ash). 

Lead smelting using the silicate system is usually carried out between 950 and 1400°C, depending on the type of furnace and the slag composition required. Charge materials to the furnace generally include the following. 

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