The effect of Al2O3 and MgO contents on the properties of the blast furnace slag

Besides CaO addition to neutralize and slag-off the silica contained in the burden of the blast furnace, other additives, mainly Al2O3 and MgO carrier s, are being added in controlled amounts, so that the slag volume is minimi zed and its desirable properties are optimized. More specifically, however, comparing similar Al2O3 and MgO per cent increa ses in the slag and without changing the basicity ratio, B/A, it turns out that the alumina addition has move advantageous effects with respect to hot metal desiliconization and desulphurization, smoothness of blast furnace o peration, and also slag valorization for the subsequent production of durab le slag cements. Furthermore, in terms of coke consumption alone, the cost incurred by the M gO carriers (i.e. olivine, dolomite, dunite), compared to that for alumina (i.e. bauxite), is above about an order of magnitude higher. In this article the above mentioned effects of varying Al2O3 and MgO conten ts on the properties of blast furnace stall are being evaluated in more det ail and, from a preliminary techno-economic study of the various additives, it appears that the bauxite addition is the most beneficial one.