To improve the permeability of sinter packed bed for achieving the efficient utilization of low-grade iron bearing minerals, the effect of the returned fines embedding on productivity, yield, flame front speed (FFS) in the vanadium titanium magnetite (VTM) sintering process, tumble index (TI) of sinter, and permeability of the sinter packed bed was clarified. Results indicate that the productivity, yield, flame front speed, and tumble index of the vanadium titanium magnetite sintering process are all increased to a certain extent after embedding different sizes of returned fines, and the optimal sintering indices occur when the particle size of return fines for embedding is 3~5 mm. The optimal mass ratio of return fines for embedding was confirmed at 80%, and a continued increase in the mass ratio results in a decrease in flame front speed, yield, productivity, and tumble strength. Among the five different possible locations of embedded return fine layer, the middle-lower layer corresponds to the highest flame front speed. As the mass ratio of return fines for embedding is enhanced from 0% to 50%, the permeability of the sinter packed bed is improved at each stage of sintering.

Vanadium−titanium magnetite (VTM) is an important raw material for ironmaking under the situation of increasingly demanding scarce resources. To further improve the metallurgical properties of pellets, and to satisfy the requirements of blast furnace slag basicity, finely ground dolomite and limestone have been added to the pellet. In this study, the effect of finely ground dolomite and limestone on the metallurgical properties (green pellet drop strength, cold compression strength, reduction swelling index, and microscopic mineral structure) of VTM pellets were investigated. With the addition of finely ground dolomite and limestone, the drop strength of the green pellet was improved. The effect of adding finely ground limestone was greater than adding finely ground dolomite. Adding more finely ground dolomite and limestone compared to pellets without limestone and dolomite, the cold compression strength was decreased, which was attributed to the decomposition of limestone and dolomite during the induration of pellets. With the addition of dolomite, the reduction swelling index (RSI) increased firstly and then decreased. When the basicity of the pellet was 0.54 to 0.94, the slag phase with the lowest melting point was formed, corresponding to the maximum of the reduction swelling index. For the pellets with added limestone, the reduction swelling of the pellets deteriorated. The reduction index of the pellets increased and reached the maximum (26.6%) at a basicity of 1.54, which belongs to abnormal swelling.