Measurement of gaseous diffusion coefficients in porous reaction products

A new method has been developed for the measurement, under simulated reaction conditions, of diffusion rates in the porous solid products of gas-solid reactions. The method is based on the dusty gas model and thus separately evaluates the contributions made by Knudsen diffusion, molecular diffusion, and pressure driven flow. Results are presented for irons produced by the hydrogen reduction of hematite and the hydrogen reduction of ferrous chloride and for lime produced by the decomposition of calcium carbonate. The results show the method giving reproducible results at both high and low temperatures, such results being of great significance to the kinetics and reaction mechanisms of the gas-solid reactions.