Observations were made of the raceway of Kimitsu No. 3 BF for the purpose of clarifying the coke behaviour in the raceway and for further understanding of the conditions at the periphery of the raceway. Observations were made by means of an endoscope inserted in a tuyere probe and a 16mm cinecamera capable of photographing at a speed of 3000 frames per second. The results of observation revealed that the quantity of coke flowing into the raceway increases as the blast volume becomes larger. More specifically, the quantity of coke reaches as much as 272 pieces at a blast volume of 6200Nm3/min. It was also found that the higher the blast velocity and the smaller the coke particle size, the greater the flying speed of coke.
From the study based on the observation results, it was found that the change in particle diameter due to breakage of coke in the furnace is slight, coke circulates in the tuyere zone, there exist two kinds of coke; bright and dark, there is a strong possibility of dark coke having been supplied from the root of the cohesive zone to the raceway, and further, it is most probable that an oxidizing atmosphere remains outside the coke circulating zone.