Analysis of the coke particle size distribution and porosity of deadman based on blast furnace hearth dissection

Abstract

Changes in particle size distribution, mineral yield and strength of coke samples from various locations of two Chinese blast furnaces as well as deadman porosity were investigated in the present study for an in-depth understanding about the blast furnace hearth phenomenon. It was found that the percentage of <10 mm coke fines varied from 20% to 49% in majority of the hearth-level regions. The average size of hearth coke was about 20 mm–31 mm. Compared with the feed coke, the hearth coke size was observed to decrease by 43%–63%. The average size of hearth coke particles of a 2 800 m3 blast furnace in diameter direction distributed in “M-shape” in majority of the hearth-level regions while that of a 5 500 m3 blast furnace distributed in inversed “V-shape”. The hearth coke mass was 1.43–2.21 times of the feed coke under the same conditions. The M10 of hearth coke with size larger than 40 mm after drum test was about 11%–18% and the M40 was 75%–79%. The M10 increased with the increasing distance to the tuyere level while the M40 decreased with the distance. Due to the catalytic effect of hot metal on coke graphitization, the M10 of hearth coke in the lower part was increased by 63.6% compared with the coke in the upper part. The average porosity of the edge, the middle and the center areas was 0.334, 0.299 and 0.250, respectively. The average porosity of deadman decreased with the increase of distance to the center line of the taphole and the increasing distance to the furnace wall.