Improving the oxidizing kinetics of pelletization of magnetite concentration by high press roll grinding

Abstract

In this paper the effect of the high press roll grinding (HPRG) on the oxidizing kinetics of the pelletization of magnetite concentrate was investigated, which aims to improve the pelletability of the concentrate. The comparison of the roasted pellet strength at various process parameters of roasting system with or without using the HPRG was also conducted. It is shown that the rate of oxidation of magnetite into hematite increases during the roasting of the green pellets made by using the HPRG to pretreat the concentrate, and the apparent activation energy of the oxidation reaction of magnetite is reduced from 49.62 kJ/mol to 33.87 kJ/mol in the range of 650-950°C, which results from the marked increase in specific surface area and the occurrence of lattice deformation of magnetite concentrate by the HPRG's mechano-chemical activation. Under the optimum roasting conditions of preheating at 950°C for 15min and indurating at 1 250°C for 15 min, the compressive strength of product pellets is raised from 3490 to 4540 N per pellet by using the HPRG to replace damp mill to pretreat the concentrate. The improved kinetics of oxidation of magnetite concentrate agrees well with the enhancement of mechanical strength of roasted pellets.