Reduction of hematite pellets using H 2 -CO mixtures with a wide range of H 2 /CO by molar (1:0, 3:1, 1:1, 1:3, and 0:1) at different reducing temperatures (1073, 1173, and 1273 K) was conducted in a program reducing furnace. Based on an unreacted core model, the effective diffusion coefficient and reaction rate constant in several cases were determined, and then the rate-control step and transition were analyzed. In the results, the effective diffusion coefficient and reaction rate constant increase with the rise in temperature or hydrogen content. Reduction of iron oxide pellets using an H 2 -CO mixture is a compound control system; the reaction rate is dominated by chemical reaction at the very beginning, competition during the reduction process subsequently, and internal gas diffusion at the end. At low hydrogen content, increasing temperature takes the transition point of the rate-control step to a high reduction degree, but at high hydrogen content, the effect of temperature on the transition point weakens.
In recent years, Chinese steel companies suffered a spate of blast furnace hearth incidents, such as hearth sidewall breakout or temperature abnormal increase, causing Chinese blast furnace ironmakers to pay a great deal attention on long hearth service life technology. In this paper, the progress of Chinese blast furnace long hearth service life design concept was analyzed deeply from design of hearth structure, selection of hearth refractory, arrangement of hearth cooling system and establishment of online hearth monitoring system, and the future design proposal for long hearth service life of Chinese blast furnace was put forward.KEY WORDS: metallurgy; blast furnace ironmaking; long hearth service life; hearth breakout; temperature increase.
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