Effects of magnesium olivine on the mineral structure and compressive strength of pellets

To study the effect of magnesium olivine on the compressive strength, phase composition and mineral structure of magnetite pellets, six groups of pellets were prepared by changing the content of olivine and the pellets were further subjected to the preheating and roasting processes in tube furnaces. Scanning electron microscopy-Energy dispersive spectrometer (SEM-EDS), X-Ray diffraction (XRD) and Mercury injection apparatus were used to characterise the microstructure and porosity of pellets. Results showed that four types of phases exist in pellets, which are hematite, (Mg,Fe)O-Fe2O3, silicate and incompletely mineralised magnesium olivine. With the addition of olivine, hematite phase content in pellets decreases while other phases tend a varying degree of increase. Mg in pellets mainly exists in the form of (Mg,Fe)O-Fe2O3 and small part in the phase of silicate and incompletely mineralised magnesium olivine. Compressive strength of pellets decreases with the increase in magnesium olivine content. That is mainly because of the increasing porosity and impeded recrystallisation of hematite. The existence of incompletely mineralised magnesium olivine would both increase the porosity and hinder the connect of hematite particles; thus it is not conductive to the strength of pellets.