High Temperature Measurement of the Effective Diffusivity of Gas through Coke and Graphite by the WICKE-KALLENBACH Method

SHIGENO Yoshihito, KOBAYASHI Saburo, OMORI Yasuo

doi:10.2355/tetsutohagane1955.73.3_453

The WICKE-KALLENBACH method had not been applied to the high temperature measurement due to the difficulty of preventing gas leakage from the portion between the diffusion cell and a sample. However, this problem was overcome by devising the Na₂O-SiO₂ cement containing liquid phase at elevated temperatures.<BR>This technique made it possible to evaluate the effective diffusivity of Ar-He system through coke and graphite in a wide temperature range from 20 to 1300°C. The effective diffusivity for CO-CO₂ up to 300°C and permeant fluxes for Ar and He up to 1000°C were also measured.<BR>From these measurements, molecular, KNUDSEN and surface diffusion through pores could be evaluated distinctively, the results of which showed the temperature dependence of molecular diffusivity as T^1·66T^1·69in coincidence with the theoretical value by CHAPMAN-ENSKOG.<BR>The technique proposed in the present work was also applied to the in situ measurement of effective diffusivity of Ar-He through coke in the course of oxidation with CO₂ at 900°C.<BR>The variation of diffusivity with the increase in degree of reaction was found to be several times larger than that expected by the "Parallel pore" model.

High Temperature Measurement of the Effective Diffusivity of Gas through Coke and Graphite by the WICKE-KALLENBACH Method

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