高炉微粉炭多量吹き込み操業条件を考慮した低SiO_2焼結鉱の品質評価

概要

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In order to evaluate qualities of low SiO_2 sinter such as reduction degradation behavior, reducibility and softening-melting properties, laboratory tests simulating in-furnace conditions at high PCI operation were carried out using three types of commercial sinters with varying SiO_2 content. The main results obtained are as follows : (1) Under high PCI operating conditions, reduction degradation of sinter is decreased. This suppression is due to the shortening of retention time in a temperature range between 500 and 600℃ by decreasing the heat flow ratio. This tendency of reduction in sinter degradation has been confirmed by operation trials at Fukuyama blast furnaces No.3 and No.4. (2) Hematite phase and micro pores increase with a decrease in SiO_2 content of sinter, and consequently reducibility increases due to an improvement in reduction gas diffusion through the reduced layer. (3) The temperature at which softening commences and that at which the pressure drop rises are higher for low SiO_2 sinter than the corresponding temperatures for high SiO_2 sinter. This result suggests an improvement in the permeability of the cohesive layer in the blast furnace under high PCI operating conditions. (4) This evaluation has confirmed that low SiO_2 sinter is superior to high SiO_2 sinter as the blast furnace burden under high PCI operation even though the value of RDI is relatively high.
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