The Effect of Raw Mixture Properties on Bed Permeability during Sintering

Raw mixes of iron ore sinter feed were prepared under a variety of conditions. The permeability of mixes before ignition and during sintering was examined using a conventional permeameter and a small instrumented sinter pot, respectively. The sinter pot consisted of a gas preheater and a sample bed 29 mm high so that pressure drop of high temperature zones could be measured precisely and easily. As expected, the pre-ignition permeability of the mixes was related to the mean size of the granules which in turn was related to the amount of water used for granulating. The order of permeability of mixes having different moisture contents did not change during or after sintering. Late-addition of coke during granulation resulted in a higher pre-ignition permeability. During sintering, however, the permeability deteriorated considerably. Use of lager particles of coke or limestone resulted in improved permeability before and during sintering. The basicity and coke content of mixes had little effect on the permeability of a bed during and after sintering under the condition of constant total amount of flux (SiO2+CaO). It was concluded that the permeability of the produced sinter cake depended predominantly on the pre-ignition permeability, for mixes of the same ore type and the same total amount of flux. This suggests that some aspect of the structure of a bed of granulated sinter feed is preserved during sintering.