Correct identification of mineral phases in iron ore sinters is key for further research, in which individual sinter properties are derived directly from mineral phases. Nowadays widespread image analysis and techniques based on the visual quantification may not exactly evaluate mineral type, what has an unfavorable effect on the overall phase analysis and all functions derived from it. Some specifics were demonstrated by microscopic examination of sinter samples and pointing out differences in calcium ferrite identification. It was found the dendritic crystallization may cause such crystal shape of low-Fe SFCA, that it ultimately looks like plates of high-Fe SFCA-I. Aggregates of SFCA-I plates crystallized adherent are misidentifiable as prismatic SFCA crystals. The pathway for SFCA-I crystals covered with SFCA was also discussed.

This paper specifies the mathematical and physical modelling of the iron sintering process in laboratory conditions. The aim is to get the simplest approach (using thermodynamic software “HSC Chemistry”, version 9, Outokumpu Research Oy, Pori, Finland) that allows one to predict the output parameters based on the initial composition analysis. As a part of the application of mathematical modelling, a mass and thermal balance of combustion of carbonaceous fuels (including biomass) and a mass and thermal balance of high-temperature sintering of an agglomeration charge were determined. The objective of the paper was to point out the advantages of modelling using thermodynamic software and apply the results into a simulation of the sintering process. The outcome of mathematical modelling correlates to the outcome of physical modelling for fuel combustion and the agglomerate production in a laboratory sintering pan. The energy required to reach the desired sintering temperatures and acquire the standard quality of agglomerate was calculated using 4.97% of coke breeze. In a real experiment with the laboratory sintering pan, 4.35% of coke was used. When a biomass fuel with a lower calorific value (lignin) is used in the agglomeration charge, the amount of fuel has to be increased to 5.52% (with 20% substitution of coke). This paper also aimed at predicting methodological tools and defining thermodynamic conditions for creating an interactive simulation. In addition, kinetics should be considered to improve the predicting capabilities of the current model and therefore in further research it will be required to optimise the computational program pursuant to the results of the kinetics experiments.

The effort to minimize CO2 emissions leads the existing integrated steel plants to implement alternative biomass-based fuels that dispose of equilibrium carbon balance. The fuel is a key factor in the iron ore sinter production, so it is essential to know its impact not just on mechanical properties of the finished sintered ore but also on the mineral composition as the mineral phases together determine all observed sinter properties. For this purpose the samples prepared by replacing a part of coke breeze with charcoal or walnut shell substitute were subjected to the observation under the light microscope, also using etching, to the phase identification by chemical EDX analysis on the scanning electron microscope and to the phase composition quantification by X-Ray diffraction analysis. The studied microstructure areas in the vicinity of the pores left by fuel grains were neither characterized by different phases nor by changed chemical composition of these phases even thought mineral matter of the used fuels were substantially different in terms of the chemical composition. The only feature of the burned substitute fuels were ash particles arranged in characteristic shapes. The main reason of variation in ratios of respective mineral phases of samples appeared to be thermal conditions that were reflected in the content of unreacted non-ferrous phases. Coke substitution in the sinter mixture has no negative impact on the phase composition of the produced sinters, which confirms the prospective use of biofuels in the sintering process.