SLAG FROM THE UTILIZING OF MUD OF ALUMINA PRODUCTION

Abstract

In Central Slovakia nearly 10 million tons (DW) of red and brown mud of alumina production is located in the pond. Despite the long-time research in the world (approx. 90 million tons of red mud from Al₂O₃ production is generated in the world annually) and in Slovakia its effective utilization has not been achieved yet. We have suggested and experimentally verified the model for two-stage utilizing mud of aluminium oxide production in grey cast iron production. We have achieved partial replacement of limestone (slag forming additive) and reduction of abrasion of cupola furnace’s refractory clay. A by-product of this process is pilot water-quenched cupola foundry slag (granulated slag). In this article the mineral structures of pilot slag are investigated and compared with the mineral structures of slags from standard production of grey cast iron.

Pilot granulated slag and granulated slag from standard production of grey cast iron contain a very small proportion of mineral phase (crystal fraction). Air-cooled slag has a little bit higher proportion of the crystal fraction than granulated slag, however, the proportion of the mineral phase in the total slag volume is very small also in this case. We conclude from that differences in  mineral phase content of particular types of cupola slag shall not affect possible differences in characteristics of products with slag addition, e.g. in cement making or concrete production. Much more powerful effect on characteristics of products with cupola slag addition can be brought about by differences in chemical composition and in surface conditions depending on cooling, grinding and milling cupola slag.