Behaviour of iron ore–fuel oil composite pellets in isothermal and non-isothermal reduction conditions

Abstract

Self-fluxing iron ore pellets as an alternative to the agglomeration process led to the use of low price fuel oil as a binder and reducing material. Composite pellets containing 5–15% fuel oil were isothermally and non-isothermally reduced at 750–1000°C in a flow of H₂ or N₂ gases. The total weight loss resulting from O₂ removal from the reduction of Fe₂ O₃ and from the thermal decomposition of fuel oil was continuously recorded as a function of time at different reduction conditions. The actual reduction extent at a given time was calculated from the chemical analysis of partially reduced samples at a given time and temperature. Microscopic examination and X-ray phase analysis were applied to characterise the reduction products. The isothermal reduction of composite pellets indicated that the reduction rate increased with the increase in fuel oil content at the early stages. At the later stages, the reduction rate increased in the order 12>10>5> 15% fuel oil containing pellets. The non-isothermal reduction of composite pellets in N₂ atmosphere showed the presence of an incubation period at initial reduction stages. The low intensity magnetic separation technique was applied with the aim of increasing the iron content at the expense of associated impurities. The magnetic and non-magnetic fractions were analysed and the overall recovery was determined.