Corrosion of refractory silica crown brick in glass-melting. furnaces is a serious problem in oxy-fuel furnaces. To better understand and to quantify this process we utilize analytical models to evaluate the importance of three potential rate-limiting processes: 1) gas-phase transport of NaOH to the crown surface; 2) diffusion of sodium-containing reactants through a liquid product layer that forms on the brick face; and 3) gas-phase diffusion of NaOH into refractory pores. Predictions are compared with reported corrosion rates and product compositions previously determined by post-mortem analysis of refractory samples. We conclude that corrosion occurs largely by reaction and removal of material from the exposed brick face, rather than by transport of reactants into the porous bricks. The rate is limited by process (1). The observed presence of corrosion products deep within the brick pores is consistent with capillary suction of liquid products from the hot face into the interior. Although computed corrosion rates based on mass transport through a gas boundary layer are somewhat greater than those observed, the results are very sensitive to the gas-phase concentration of NaOH and to the refractory temperature, both of which contain significant uncertainties. We also present a new thermodynamic analysis of the Sio(2)-CaO-NaO that provides an explanation for the increased corrosion rates observed in lime-containing silica relative to low- or no-lime silica. Finally, we combine our analytical model with results of the Athena CFD furnace code to predict corrosion rates in an oxygen-fuel furnace. The results are encouraging, but suggest that accurate knowledge of both NaOH(gas) concentrations and refractory temperatures is needed to validate these models.
