Lead blast furnace slags fuming

BeU, R C, Turner, G H and Peters, E, 1955. Fuming of zinc from lead blast furnace slags, J of Metals, March, p472. 

In lead smelting, the oxygen-enriched blast has been used in lead cupola and slag fuming furnaces. Oxygen enrichment of the copper blast furnace is also common. 

In non-carbonated and chloride-free concrete, the concentration of hydroxyl ions (OH ) varies from 0.1 M to 0.9 M, due to the presence of both NaOH and KOH (the latter is predominant, especially in Portland cement). Other ions, e. g. Ca and S04 , are present only in very low concentrations. Addition of blast furnace slag or fly ash to Portland cement results in a moderate reduction of ionic concentration, and thus in pH. From hydroxyl ion concentrations in Table 2.1, values of pH of 13.4-13.9 can be calculated for Portland cement, and pH values of 13.0-13.5 for blended cements. Addition of condensed silica fume in higher percentages may lead to a decrease in the pH to values to below 13 [4, 10]. 

The sulfur content of blast furnace bullion is around 0.5 per cent and slag around 1.5 per cent. The remaining sulfur reports to furnace off-gases. Some may be captured as a basic lead sulfate in fume, which is recycled to the sinter plant, otherwise the remainder reports as SO2 in filtered off-gases and is normally discharged to attnosphere. 

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