To clarify the effect of pulverized coal injection on coke disintegration behavior in the raceway, hot model experiments were carried out and changes in reaction mechanisms of coke in the raceway were examined by a mathematical model. Furthermore, a coke disintegration model had been newly developed to analyze the effects of the pulverized coal injection and the coal combustibility on the coke disintegration rate quantitatively.
As the result of the analysis using this model, pulverized coal injection had a great effect on increasing the coke disintegration rate due to the shrinkage of the oxidation zone existing in front of the tuyere that had a burn-out effect of the degraded layer on coke particles generated by the solution-loss reaction in the depths of the raceway. However, the disintegration rate could be decreased by improvement of the combustibility of the pulverized coal. It was assumed that increase in consumption of carbon dioxide by the pulverized coal resulted in suppress the formation of the degraded layer on the coke particles.
Based on above mentioned results, the injection lances at Fukuyama No.5 blast furnace were changed from the conventional single lance to the eccentric double lance with high combustibility, then the permeability at the lower part of the blast furnace was considerably improved, and it was suggested that the improvement of the lance structure could be an effective way to restrain the generation of coke fines from theraceway.
