Many different approaches have been used in the past to characterise iron ore sinter mineralogy to predict sinter quality and elucidate the impacts of iron ore characteristics and process variables on the mechanisms of sintering. This paper compares the mineralogy of three sinter samples with binary basicities (mass ratio of CaO/SiO₂) between 1.7 and 2.0. The measurement techniques used were optical image analysis and point counting (PC), quantitative X-ray diffraction (QXRD) and two different scanning electron microscopy systems, namely, Quantitative Evaluation of Materials by Scanning Electron Microscopy (QEMSCAN) and TESCAN Integrated Mineral Analyser (TIMA). Each technique has its advantages and disadvantages depending on the objectives of the measurement, with the quantification of crystalline phases, textural relationships between minerals and chemical compositions of the phases covered by the combined results. Some key differences were found between QXRD and the microscopy techniques. QXRD results imply that not all of the silico-ferrite of calcium and aluminium (SFCA types) are being identified on the basis of morphology in the microscopy results. The amorphous concentration determined by QXRD was higher than the glass content identified in the microscopy results, whereas the magnetite and total SFCA concentration was lower. The scanning electron microscopy techniques were able to provide chemical analysis of the phases; however, exact correspondence with textural types was not always possible and future work is required in this area, particularly for differentiation of SFCA and SFCA-I phases. The results from the various techniques are compared and the relationships between the measurement results are discussed.

Several sinter plants in China are still using significant proportions of local magnetite concentrate in the sinter blend based on supply proximity. However the overall trend is that concentrates are being replaced by more cost effective sinter fines. The fine size of concentrates results in additional challenges for sintering. In this study, granulation and packing experiments were conducted to investigate the influence of concentrate addition level on granule structure and green bed properties under a wide range of moisture and hydrated lime dosage levels. Provided sufficient water is added during granulation, the existence of micro-particles including concentrate and hydrated lime favours granule growth and increases the mass ratio of adhering layer to nuclei. However, at the same moisture and hydrated lime content, the introduction of more concentrate decreases the bed voidage remarkably since the thicker and weaker adhering layer deforms during dynamic packing. Compared to the 100% sinter fines base blend, introducing concentrate has a negative effect on bed permeability and therefore sinter productivity. For the 10% and 30% concentrate blends tested, increasing hydrated lime from 0 wt% to 4 wt% could improve the green bed permeability in JPU from 53.0 to 65.8 and 39.4 to 60.8 respectively. Based on the experimental results, a semi-empirical green bed voidage model was improved in two aspects. One is applying a one dimensional packing algorithm to get the ideal porosity of dry coarse particles utilising size distribution data rather than the simple log-normal deviation parameter. The other is to add a probability term considering the deformation of granules only happens to the adhering layer. Combined with the widely accepted population balance granulation model developed by Litster, the improved model can give more accurate predicted voidage values for modeling the sintering process and optimizing actual production from the properties of raw materials and moisture content.