2020 Volume 60 Issue 6 Pages 1149-1158
Granulation and packing of iron ores are highly essential for having a strong function with packed bed porosity distribution, and further affecting the subsequent sintering process. In this study, high-resolution X-ray computed tomography technique was applied to investigate the influence of moisture, hydrated lime and concentrate levels on granule properties and porosity distribution of packed bed based on the Taguchi orthogonal array tests, and the optimum granulation factors combination was determined by the defined porosity segregation degree for improving packed bed homogeneity. Moisture was found to be the dominant factor affecting granule size with a major percent contribution of 94.42%. Bulk bed porosity was significantly affected by all three selected factors of moisture, hydrated lime and concentrate levels. The percent contribution order was shown as hydrated lime (55.10%)> moisture (29.12%)> concentrate (14.36%). The whole packed bed was found to exhibit significant inhomogeneity. Axial porosity increases from the bottom upwards along the packed bed height, and radial porosity appears a symmetric parabolic distribution where porosity achieves the minimum of 0.3 at bed center and increases sharply near the wall. To achieve the homogeneous packed bed of iron ore granules, the optimum granulation factors combination for decreasing axial and radial porosity segregation are determined as 6.8% moisture, 4% hydrated lime, 0% concentrate and 5.8% moisture, 4% hydrated lime, 0% concentrate, respectively. The results provide the theoretical guidance for granulation and packing in iron ore sintering to improve sintering yield and quality.