The burden distribution simulation model was indispensable so as to ensure smooth blow-in and stable operation with high productivity of Keihin No. I blast furnace, which is one of the largest blast furnace with bell-less top. For this purpose, basic factors governing the burden distribution in the bell-Iess top for a large blast furnace were examinedthrough the I /1 O scale model experiment on the basis of the burden distribution simulation model formerly developed for FukuyamaNo. 2 blast furnace. By incorporating these results and considering the particle size change during discharge, a burden distribution simulation model suitable for Keihin No. I blast furnace was newly constructed. It has been applied for the operation of Keihin No. I blast furnace. As a result, a productivity of I .9t/d•m3 was achieved in only two weeks after b]ow-in. Further use of this burden ditribution simulation model has permitted stable continuation of highproductivity of 11 OOOt/d for a period of about a year.

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To attain a high rate injection of pulverized coal into a blast furnace, it is required to increase a combustion efficiency of pulverized coal 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 the high rate injection operation at Fukuyama No.4 BF, a 2-dimensional mathematical model of pulverized coal combustion taking the lance arrangements and the dispersion of coal particles intoaccount had been newly developed. As a result of the analysis using this model, it was found that the eccentric double lance, two lances arranged asymmetrically to avoid the interactions of the pulverized coal flows, had superior characteristics to increase the combustibility in the blowpipe and the raceway due to the intensified particle dispersion. Since the experiment using hot model also showed the same effectiveness, the eccentric double lance was adopted to all tuyeres of Fukuyama No.4 BF.During the high rate injection operation in October 1994, pulverized coal rate was raised to 230 kg/t and little unburnt char was detected in the top waste dusts and the combustion efficiency of pulverized coal estimated by the sampled char from deadman during scheduled shut down just after the operation reached over 70%. These results suggests that the high combustion efficiency had been successfully achieved by using the eccentric double lance.

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