Formation of the strength of pelletized multiphase dicalcium silicate sinter

Abstract

To ensure the comprehensive use of mineral raw materials and the widespread use of waste instead of minerals, it is necessary to deepen the search and scientific substantiation of the relevant reserves. The main waste of alumina production is red mud (RM), which has a complex chemical composition with the main content of iron oxide, which makes it possible to use the sludge in ferrous metallurgy as an additive to increase the strength of iron ore pellets. The degree of urgency of this task is quite high, since RM and iron ore raw materials of domestic and foreign deposits have their own specifics and give different strengthening effects. The nature of the hardening of the agglomerate with the addition of RM is based on the stabilization of the dicalcium silicate present in the pellet structure. A technique has been developed for the mechanism of formation of the multiphase sinter strength and a laboratory setup has been created that makes it possible to obtain a sample on a platinum loop at heat treatment temperatures of 1400 C with subsequent testing of stability and strength. The method of hardening mechanism takes into account the temperature level, shape and size of the obtained sample. The effect of calcium ferrite mineralizer on the stabilization of dicalcium silicate depending on its content in the charge was studied. It was determined that calcium ferrite in the amount of 10–15 % sharply accelerates the synthesis of dicalcium silicate. When recalculating the composition of a stable sinter to the composition of a fluxed pellet, at least 1.5–2.0 % of RM is required to achieve the stability of β-dicalcium silicate. The quality of the sinter, its stabilization or spontaneous crumbling were determined visually during the cooling of the sinter, the completeness of the crumbling process was determined by sieve analysis of the decomposition product.