Improvement in the permeability of sintering beds by drying treatment after granulating sinter raw materials containing concentrates

Abstract

The permeability of the sinter green beds will remarkably deteriorate when magnetite concentrate powder is introduced into the raw blend. To address this problem, a technique of drying after high-moisture granulation is proposed. Using this technique, the permeability can be raised from 40.45 JPU to 46.05 JPU at 7.7 wt% granulation moisture. At the same time, the results show that drying may cause the degradation of granules when the granulation moisture is excessive. Therefore, the final permeability of the stacked bed depends on the combined effect of increasing the bed stiffness and decreasing the average particle size. Fortunately, the addition of hydrated lime (HL) can significantly inhibit granule degradation and improve granulation efficiency, which can further improve the bed permeability to 61.41 JPU with a 2% HL addition level (at 7.7 wt% granulation moisture). Finally, an optimized process is proposed that uses low-grade waste heat during sinter cooling to dry the wet granules. This optimization not only meets the energy needs of drying but also facilitates the grade recovery and cascade utilization of waste heat during the sintering process.