Estimation of Effective Diffusion Coefficient of Gaseous Species in MgO–C Refractories by Shrinking Core Model

Abstract

Different content of various anti-oxidants, Mg, Al, Si, SiC and B₄C was added to MgO–C refractories, ranging from 1 to 7 wt.%. Exposed to the air at 1200°C, weight changes of cylindrical specimens were measured by a thermo gravimeter (TG). Based on shrinking core model, a mathematical model was modified by introducing anti-oxidant consumption factor. And the effective diffusion coefficient of gaseous species in refractories with different anti-oxidants was calculated by measuring results of weight change. The phase changes of the anti-oxidants' oxidation process were researched by XRD, and the volume expansions of this process were derived according to theoretical calculation. It was found that Mg had negative effect on diminishing the effective diffusion coefficient, while Al, Si, SiC and B₄C had positive effect on it. For B₄C's largest volume expansion at the oxidation process, effective diffusion coefficient in samples with B₄C addition was smaller than that in samples with other additions.