Experimental Study on the Reduction Rate of Sinter under the Conditions in a Blast Furnace

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To obtain the rate equations expressing the reduction rate of sinter in a blast furnace. the following experiments and analyses were carried out, and conclusions have been obtained as follows:1. The methods estimating the physical-property values and other constants were examined. Mass transfer from naphthalene-coated sinter was measured and the equation for mass transfer coefficient in a gas film of sinter was derived in consideration of shape factor.2. Single particles of sinter were reduced stepwise and directly with CO- <CO_2> - <N_2> or <H_2> - <H_2> O- <N_2> gas mixtures over a temperature range of 500゜ to 1000゜C, and reduction curves were measured gravimetrically.3. Partially reduced samples were cooled quickly in a nitrogen stream, and their cross sections were observed in a microscope.4. Fixed beds of sinter (500g) were reduced stepwise over the same temperature range as in item 2; fractional reduction was evaluated from gas analysis by an infrared gas analyzer and a gas chrom … More atograph for CO- <CO_2> - <N_2> and <H_2> - <H_2> O- <N_2> reduction experiments, respectively.5. From the experimental results in items 2-4, the reduction rates were analyzed on the basis of the unreacted-core shrinking models for one and three interfaces; kinetic parameters in the models were evaluated and the temperature dependencies of the parameter values obtained in each case were presented. Results from single particle experiments scattered badly, while results from fixed bed experiments reproduced well. Calculated reduction curves using the equations for the rate parameters as a function of temperature sescribed the measured ones satisfactoryly.6. Fixed bed reduction experiments were done under temperature and gas concentration variant conditions simulated in a blast furnace. Comparison of these experimental results with the calculated ones based on three interface model using the equations for the rate parameters in item 5 showed that both results were much the same except at high temperatures. Less