Effect of Basicity on the Reduction Swelling Performance of Pellets Prepared from Bayan Obo Iron Ore Concentrate Based on Microscopic Characterization

The development of blast furnace smelting technology with a high proportion of pellets is an important means for improving the utilization rate of complex co-associated mineral resources. The effect of basicity on the reduction swelling performance of pellets prepared from Bayan Obo iron ore concentrate is characterized by the aspects of microscopic morphology, element distribution and weight-loss behavior. The results show that with the increase in basicity, the reduction swelling rate and the weight-loss rate of pellets follows the change rule by first increasing and then decreasing. With a basicity of 0.8, the pellets have the largest swelling rate (75.743%) and the largest weight-loss rate (24.77%). The reduction swelling rate is proportional to the porosity and inversely proportional to the amount-of-liquid phase. In the first stage of reduction, pellets with a basicity of 0.8 changed from tabular to granular, and there were a large number of cracks. In the third stage of reduction, pellets with a basicity of 0.8 had coarse iron whiskers. In the same reduction stage, the amount of K and Na elements in the pellets with a basicity of 0.8 entering the iron oxide lattice was much larger than that in the pellets with a different basicity. As the reduction progresses, the ability of alkali metals to enter the iron oxide gradually increases.