<報文>Wicke-Kallenbach法によるコークスおよび還元鉄の有効拡散係数の評価

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  • Wicke Kallenbachホウ ニヨル コークス オヨビ カンゲン テツ
  • <Original Papers>Evaluation of Effective Diffusivities of Gases in Coke and Reduced Iron by Wicke-Kallenbach Method

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Diffusive fluxes through a glass filter, a disk of coke and reduced iron made of iron oxide pellet were measured by Wicke-Kallenbach method in the temperature range of 18～150℃. Based on the results obtained, the effective diffusivities in the porous media at high temperature were estimated. The results are summarized as follows. 1) In the Ar-He system, the ratio of the diffusive fluxes was found to obey the "square-root law" that the diffusive flux ratio for binary mixtures is equal to (M_1/M_2)^<1/2>, but to deviate from that law in the CO-CO_2 system. The deviation for the latter system might be attributed to surface diffusion of gaseous molecules. 2) Permeability of Ar and He in formed coke was measured. This data and the measurement of diffusive flux were analysed by the dusty gas model. By use of the calculated parameters characterizing a porous media in the model, the ratio of surface diffusion flux to total flux was estimated to be 20% for CO_2 and 7% for CO, respectively. 3) The correlation between diffusibility and porosity was established for unreacted and gasified formed cokes. The effective diffusivity was found to be proportional to T^<1.5>. From the results the effective diffusivity at 1000℃ was estimated and then compared with the data obtained according to the overall reaction rate of coke with CO-CO_2 mixture. These values were found to be in close agreement. 4) The diffusive flux of CO-CO_2 system through the iron reduced at 600,800,and 1000℃ by H_2 was measured. Effective diffusivity was found to be proportional to T^<1.5～1.7>. The effective diffusivities at high temperature thus estimated were compared with the values determined both by use of a canister and according to overall reduction rate of iron oxide pellets by H_2.

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