HW 16 - Slag
Slag includes ferrous metal slag from steel, manganese, chrome, vanadium etc. processing and non-ferrous metal slag from aluminium etc. processing.
The main by-products produced during the iron and crude steel production are slags (90%), dusts and sludges as illustrated in Figure 4.
Figure : Main by-products of steelmaking (World Bank, 1998)
Waste from the Iron and Steele industry sector in South Africa can be calculated based on the crude steel production figures provided by SAISI (2011) and the by-product estimates and ratio’s provided by the Worldsteel Association (2010). With BF/BOF at about 70% and EAF at about 30%, the total by-product production in SA can be estimated (Table 16).
Sintering operations can emit significant dust levels of about 20 kg per metric ton (kg/t) of steel while pelletizing operations can emit dust levels of about 15 kg/t of steel. Process sold waste from the conventional process, including furnace slag and collected dust, is generated at an average rate raging from 300kg/t of steel manufactured to 500kg/t, of which 30kg may be considered hazardous depending on the concentration of heavy metals present (World Bank, 1998)
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