COMBUSTION BEHAVIOR OF PULVERIZED COAL IN A RACEWAY CAVITY OF BLAST-FURNACE AND A LARGE AMOUNT INJECTION TECHNOLOGY

For a large amount of pulverized coal injection into a blast furnace, the combustion of pulverized coal in a raceway cavity has been studied theoretically and experimentally. The theoretical formula, which can estimate the combustion efficiency of pulverized coal in a raceway cavity, were derived. The effects of the injecting and operating conditions on the limit of pulverized coal combustion in a raceway cavity were evaluated. The effect of the mixing of pulverized coal with oxygen on the combustion rate of pulverized coal was studied in a combustion test using both empty and coke packed furnace. From the results, the validity of the derived theoretical equation was verified, and it was also confirmed that the making sure of a raceway depth and the adoption of a injection technique which promotes the mixing of pulverized coal with oxygen are important to promote the combustion of pulverized coal. Based on these discussions, the upper limit of pulverized coal injection rate in the hot blast furnace operation was estimated. To inject a large amount of pulverized coal more than the actually accomplished amount, it is necessary to increase the oxygen concentration in blast and to adopt a injection technique which promotes the mixing of pulverized coal with oxygen.