Changes in Strength and Reducibility of Iron Ore Sinters With Increasing Basicity

Abstract

Improving the quality characteristics of iron ore materials is one of the most effective ways to reduce fuel consumption in pig iron production, improving the technical and economic performance of the blast furnace process. The quality of finished products depends on a whole range of technological parameters, advancing along its chain, it is possible to identify the process of formation and nucleation of minerals, because it is the mineral composition of the ore grains bundle that determines and influences of many pyrometallurgical processes, being the main carrier of the strength of fluxed sinters. One of the most important criteria for qualitative evaluation of sinter is its cold strength. Based on the importance of this criterion, a comparative analysis of studies of the cold strength of iron-ore sinters of different chemical compositions has been performed. Understanding that the cold strength index is a tool to analyze the sintering process and mechanical treatment of sintered iron ore allowed us to determine the importance of one of the objectives of the study ‒ to show the change in the character of the strength curve of sintering from the basicity. An additional difficulty was that the initial charge of iron ore concentrates contained magnetite of homogeneous and heterogeneous structure. It is worth distinguishing the ability of magnetites of the two types to participate in the melt formation. Thus, the characteristic feature of homogeneous magnetite is that it takes a direct part in the evolution of bonds, and the growth of strength of sinters occurs as a result of the change of silicate bonds to ferritic ones. As a result of a separate study of magnetite of heterogeneous structure, it was possible to prove that its participation in melt formation is not limited, as previously thought, but excluded, which subsequently led to the hypothesis of predicting the existence of an interval of “failure” of cold strength of offset iron ore sinter, which in the future will allow to predict the quality of the finished product at any layout of charge materials. In addition to the index of cold strength, which determines the blast furnace operation, productivity and coke consumption, we also refer to reducing ability. The MISIS laboratory has carried out the testing on the basis of which the results of determining the reducibility of sinters from charge mixture are presented; the ore part consists of 100% concentrate containing heterogeneous magnetite for three basicity levels (1.4; 1.6 and 3.0 units).