Effective Diffusivity and Spalling Models for Slagging Coal Gasifiers

Spalling reduces the lifetime of hot‐face refractory linings in slagging coal gasifiers, and has an important impact on the economics of coal gasification. Spalling is caused by ingress of the molten slag into the porous refractory, followed by reaction with the refractory to produce either volumetric expansion (compressive stresses) or volumetric shrinkage (tensile stresses). In this paper, ingress of the molten slag into the porous refractory is described by an effective diffusivity that treats simultaneous capillary and diffusive mechanisms in terms of the average pore radius and the slag viscosity. This effective diffusivity can be applied in spalling models to estimate spall thicknesses that are useful for determining whether the spall originated from tensile or compressive mechanisms.