The measurement of void fraction in beds of granulated iron ore sinter feed.

Abstract

Iron ore sinter feeds are granulated with water to improve permeability of the bed during sintering. The permeability of a packed bed is a complex function of the effective mean diameter of the granules and the void fraction of the bed.This paper describes a technique for measuring the void fraction of a bed of granulated iron ore sinter feed by filling the voids, under vacuum with kerosene. Kerosene, being immiscible with water, does not penetrate the moist granules.For the hematite ore studied, bed void fraction increased initially as the amount of water used for granulation was increased. This was due most likely to the narrowing of the size distribution of the granules. A maximum void fraction of 0.49 occurred at about 5.3% water. Thereafter, additional water used for granulation resulted in a decrease in bed void fraction due probably to slumping of the granules as they were packed to form a bed.Bulk density measurements on the granulated mixes confirmed the shape of the voidage vs. moisture content relation obtained by kerosene displacement and a satisfactory matching of void fraction values by the two methods was obtained using a value of 4.08g/cm3 for the density of dry sinter feed. This value agreed favourably with the experimentally determined value of 4.03g/cm3 and suggests, for the sinter feed studied, all the internal porosity of granules is filled with water.