Influence of Al2O3 on Reduction-Meltdown Behavior of Sinter in Blast Furnace

At Kimitsu No. 3 sintering machine, a test was performed which produces a low-Al2O3 content (1.50%) sinter in contrast to an ordinary sinter (Al2O3=1.85%). Together with tests performed to check the availability of this sinter at Kimitsu No. 3 and No. 4 blast furnaces, off-line model experiments were conducted with the use of the same sinter. The results obtained are as follows: (1) Keeping the sinter cold strength raised by lowering Al2O3 content at a fixed level has enabled a sintering with low energy (lower FeO content) to be done and the reducibility has been improved from ordinary 60% to 68% in JIS-RI. (2) Through the off-line model experiments using this sinter and the tests with the use of the same sinter at the actual furnaces, the raise of a shaft efficiency of 2.0 to 2.5% has been attained with the raise of JIS-RI of 5% at the lumpy zone of blast furnace. (3) At the cohesive zone accompanied with the formation of melt exceeding 1150°C, the amount of FeO-containing melt formed has decreased and the chance of pores being stopped up by the melt has diminished thanks to the improved reduction efficiency and the decreased Al2O3 and SiO2 contents, which has led to a better permeability at the cohesive zone. Then, the resultant merit has brought the improvement in permeability of the blast furnace, which is verified by the foregoing off-line model experiments and actual furnace tests.