VOIDAGE OF FERROUS SINTER BEDS - NEW MEASUREMENT TECHNIQUE AND DEPENDENCE ON FEED CHARACTERISTICS

A new technique for measuring the voidage of a packed bed of wet defor mable granules is described. Rather than attempt to measure voidage in situ, the voidage is calculated from accurate measurements of bed bul k density and separate measurement of granule apparent density by kero sene displacement. The technique is reproducible to +/- 0.005 void fra ction. This technique is used to study in detail the factors which det ermine the voidage of packed beds of granulated ferrous sinter feed. 1 0 sinter feed blends are used varying the type of ore (7 ores), feed s ize distribution and moisture content (3.5% to 8%). As moisture conten t increases, bed voidage passes through a maximum. At low moisture con tents, added water reduces the spread of the granule size distribution and increases the voidage. At higher moisture contents, granule defor mation becomes important. Granules become more deformable as moisture content increases and the bed voidage drops. The key parameter which a ffects granule deformation is the granule layer mass to nuclei mass ra tio (R). All blends show the same relationship between R and voidage. Voidage decreases with increasing R before approaching an asymptotic v alue for large values of R. The effect of feed particle size distribut ion, moisture holding capacity and moisture content on voidage can be explained by their effect on the layer mass to nuclei mass ratio durin g granulation. Hence, with the aid of a suitable granulation model, th e effect of feed blend properties and granulation conditions on bed vo idage can be predicted.