Slags classification

Electric furnaces, 12 286-318 76 144, 145. See also Electric arc furnace (EAF) Fuel-fired furnaces applications for, 12 315-316 arc furnaces, 12 297-306 classification of, 12 286 economic aspects of, 12 313-314 health and safety factors related to, 12 314 induction furnaces, 12 307-313 in phosphorus manufacture, 19 8-11 resistance furnaces, 12 287-297 for secondary slags, 14 759-760 Electric furnace steelmaking processes,... 

The substantial effect on boiler sizing of the coal-ash classification is made clear by comparison of units sized for three types of coal. In general, an increased fouling tendency requires an increase in the furnace surface to lower the gas temperature entering the superheater, and an increased slagging potential of a coal causes furnaces designed for western coals to be substantially more conservative than those designed to fire eastern bituminous coak. 

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. 

Refractories can be classified in two ways. One way is based on chemical composition. The various refractories are silica (Si02), alumina (AI2O3), magnesia (MgO), chromia (Cr203), alumino-silicate, and magnesia-chromia. In the second method, the refractories are classified as acidic, basic, and neutral refractories. This classification is based on the behavior of refractories toward slags. Following is a brief discussion of each of these classes. 

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