Wasting the Nation.indd - Groundwork

Chapter 4: The toxic cradle of productionIscor installed its first coke ovens and by-product plant at Vanderbijlpark in the 1950s.They have operated ever since but the difficulty of handling the waste has largelybeen neglected. In 2004, an environmental impact assessment for Mittal reportedthe annual waste from the plant’s coke ovens as 70,000 tonnes of crude tar, 2,400tonnes of tar sludge, 4,000 tonnes of ammonium sulphate and 180,000 tonnes of coke‘breeze’ (fine dust). 72Traditionally, blast furnaces – which are huge steel stacks lined with refractory brick– are used to smelt ore into liquid iron. A mixture of iron ore, coke and limestone isdropped from the top of the stack and descends through blasts of hot air to the bottomover a period of 6 to 8 hours. Very high temperatures result. At the end of the process,the liquid iron is tapped off through one hole while the slag floats to the top and istapped through another. While gas is caught and cleaned by special pipes, some of it isvented to the air or burnt as waste. Emissions include dioxins, sulphur dioxide, carbondioxide, carbon monoxide and breathable iron dust particulates.The Vanderbijlpark plant reportedly produced 28,700 tonnes of iron dust (orparticulates), 13,000 tonnes of gas cleaning sludge, 600,000 tonnes of granulated slagand 36,000 tonnes of blast furnace slag from its two blast furnaces in 2004.The iron dust and gas cleaning sludge are recycled to the sinter plant and the slag isused in the cement industry and for road construction. A sinter plant prepares sinters– pellets of iron and coal dust – to feed into steel making furnaces.Molten iron from the blast furnace, sinters and scrap metal are used as feed for thesteel making furnaces of which there are two kinds: basic oxygen furnaces (BOFs) andelectric arc furnaces (EAFs). Mittal uses both at Vanderbijlpark.In the BOFs, a lance is used to inject oxygen into the furnace at supersonic – and earpiercing– speeds. This drives impurities off the molten steel and raises the temperatureto melt the scrap metal added to the feed. Six storey buildings are needed so thatthe huge oxygen lances can be manoeuvred. Fluxing materials are added to carry off72 These figures, and those below, are given in the Draft Scoping Report for an environmental impact assessmenton the closure of the slag heap and the opening of a new one (right next to it) at the Vanderbijlpark site, preparedby consultants Strategic Environmental Focus.- 100 - groundWork - Wasting the Nation