The interaction of spherical Al₂O₃ particles with molten Al₂O₃-CaO-FeO_x-SiO₂ slags

The present paper investigates the rate of chemical dissolution of Al₂O₃ particles in synthetic Al₂O₃-CaO-FeO_x-SiO₂ slags as a function of time under an atmosphere where Fe²⁺ would be the stable state for iron ions dissolved in the slag. Two aspects of the interaction between the Al₂O₃ spheres and slags were studied, namely (i) the speed at which the particle sinks into the slag and (ii) how rapidly the particles dissolve. The objectives are to elucidate interactions between oxide particulate material, either from the refractory wall or from the mineral constituents in the fuel feedstock, with the slag formed at the wall in entrained-slagging gasifiers. The particle settling was found to proceed first rapidly, but subsequently slowing down and this behavior was in qualitative agreement with model predictions based on a balance between gravity-, drag-, capillary-, and added mass forces. The effect of increasing temperature and FeO_x content are investigated and it is shown that both contribute towards increasing the dissolution rate. The rate appears to be governed by a combination of the driving force for dissolution and transport properties in the slag.