In the immediate region surrounding the raceway the ash from the injected coal has a major
influence on the slag chemistry and therefore the slag viscosity. This can lead to permeability
issues in the lower zone of the BF and result in lower productivity. The understanding of the
relationship between ash/slag chemistry and slag viscosity is growing and will lead to tighter
controls on amount and composition of the PCI ash. The co-injection of fine BF slag, fine iron ore or
other materials does reduce the effect of PCI ash on slag chemistry.
The influence of ash from injected coal on the physical properties of the dripping slag and the
permeability of the region surrounding the raceway are summarized in Figure 1.
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Figure 1 Ash behaviour in and near the raceway ( after Ichida and others [1])
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[1] Ichida, M., Orimoto, T., Tanaka, T., Sakatani, M., Ueno, H., 2002, Behavior of pulverized coal
ash and physical property of dripping slag under high pulverized coal injection operation, ,
International Blast Furnace Lower Zone Symposium, Wollongong, Australia, 25-27 November 2002.
