Slag fuming design

With increased focus on the recovery of metal values in stockpiled slags and residues, impurity control becomes an even more important consideration. Operation of the KIVCET furnace at design capacity and the restart of one of the older slag fuming furnaces have enabled treatment of these stockpiles. As the stockpiles were being accumulated they formed natural bleeds for undesirable impurities such as the halides, and now the challenge will be to control... 

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. 

Recovery of zinc was not required by Gold Fields of Namibia and the slag contains approximately 11% zinc. Levels below 4% lead are not required in this design in order to minimise fuming of zinc, though in practice, levels of 2% lead were routinely obtained. 

An important development in concrete mix design has been the addition of so-called supplementary cementitious materials. Two classifications apply to these compoimds Pozzolans, such as fly ash and silica fume, react with the cement hydration products, notably calcium hydroxide hydraulic materials, such as granulated blast furnace slag, undergo direct hydration reactions. As these materials are of lower cost than conventional cement and essentially represent environmental waste products, there are obvious incentives for blending them in concrete mixes. As pointed out by Hansson, these materials can improve the strength and durability of concrete, with the important proviso that the concrete is cured adequately. 

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