DEVELOPMENT OF INJECTION LANCE WITH HIGH COMBUSTIBILITY FOR HIGH-RATECOAL INJECTION

To attain a high rate injection of pulverized coal into a blast furnac e, it is required to increase a combustion efficiency of pulverized co al in the raceway. Therefore, it is important to design the injection lance with high combustibility based on the essential understanding of combustion behavior of pulverized coal. Previous to the start up of t he high rate injection operation at Fukuyama No.4 BF, a 2-dimensional mathematical model of pulverized coal combustion taking the lance arra ngements and the dispersion of coal particles into account had been ne wly developed. As a result of the analysis using this model, it was fo und that the eccentric double lance, two lances arranged asymmetricall y to avoid the interactions of the pulverized coal flows, had superior characteristics to increase the combustibility in the blowpipe and th e raceway due to the intensified particle dispersion. Since the experi ment using hot model also showed the same effectiveness, the eccentric double lance was adopted to all tuyeres of Fukuyama No.4 BF. During t he high rate injection operation in October 1994, pulverized coal rate was raised to 230 kg/t and little unburnt char was detected in the to p waste dusts and the combustion efficiency of pulverized coal estimat ed by the sampled char from deadman during scheduled shut down just af ter the operation reached over 70%. These results suggests that the hi gh combustion efficiency had been successfully achieved by using the e ccentric double lance.