Infiltration characteristics of industrial coal slag into alumina (Al 2 O 3 ) refractory material with a temperature gradient induced along the slag's penetration direction are compared to those obtained under near-isothermal conditions. Experiments were conducted with a hot-face temperature of 1450°C and a CO/CO 2 ratio of 1.8, which corresponds to an oxygen partial pressure of~10 À8 atm. The refractory under the near-isothermal temperature profile, with higher average temperatures, demonstrated a greater penetration depth than its counterpart that was under the steeper temperature gradient. Slag that did not infiltrate into the refractory due to the induced temperature gradient, pooled and solidified on the top of the sample. Within the pool, a conglomerated mass of troilite (FeS) formed separately from the surrounding slag. Microscopy of the crosssectioned infiltrated refractories revealed that the slag preferentially corroded the matrix regions closer to the top surface. Furthermore, the formation of a thick layer of hercynite (FeAl 2 O 4 ) at the top of refractory/slag interface significantly depleted the slag of its iron-oxide content with respect to its virgin composition. A qualitative description of the penetration process is provided in this article.W. Lee-contributing editor Manuscript No. 29382.

The viscosity of the molten ash (slag) resulting from the mineral constituents in carbon feedstock used in slagging gasifiers is critical for controlling the gasification process. The viscosity of two synthetic slags with compositions resembling the mineral impurities in average eastern and western coal feedstock was examined at temperatures from 1300–1500 °C using a rotating bob viscometer. A few combinations of atmospheres and experimental materials were investigated with respect to one another to determine slag viscosity. A CO/CO2 atmosphere (CO/CO2 = 1.8, corresponding to a P O2 = 10–8 atm) is required to sustain ferrous ions in FeO-containing slags, an environment that is oxidizing to most metals. Iron oxide in the slag prevents usage of Fe parts. In unpurified Ar, the Fe metal surface oxidizes. Using purified argon prevents iron measurement components from oxidation; however, the metallic surfaces act as nucleation sites for the reduction of the Fe oxide in the slag into metallic Fe. Dissolution of ceramic materials into the slag, including Al2O3 and ZrO2, occurs in both atmospheres. Therefore, evaluating slag properties in the laboratory is challenging. The measured viscosities of two synthetic slags in this study diverged depending upon material selection. This difference is likely attributable to container/spindle-slag interactions. Viscosity measurements of the eastern coal slag using all ceramic parts agreed best with FactSage prediction above 1350 °C, with an average activation energy of 271.2 kJ. For western coal slag, the dissolution of container/spindle materials was substantial during the measurement, with precipitation of crystalline phase noted. The experimental viscosity data of the western coal slag agreed best with Kalmanovitch prediction above 1350 °C. The activation energy changed dramatically for both data sets of western coal slag, likely indicating the Newtonian-to-non-Newtonian transition.

The infiltration characteristics of synthetic coal slag into Al2s3 refractory material with a temperature gradient induced along the slag's penetration direction were investigated with respect to time and oxygen partial pressure of the experimental atmosphere. Synthetic slag, which is representative of an average of the ash contents from United States coal feedstock, was melted in either an oxidizing air atmosphere or a reducing CO/CO2 gas mixture with a ratio of 1.8. The experiments were conducted with a hot‐face temperature of 1450°C, and the slags were deposited onto refractory samples in the same atmospheres as they were originally melted. A comparison between the infiltrations in the CO/CO2 and air atmospheres revealed that differences in oxygen partial pressure changed the mode in which the slag interacted with the refractory. While infiltrations in CO/CO2 atmosphere demonstrated elevated Al2O3 concentrations in the slag owing to refractory dissolution, infiltrations in air atmosphere showed enrichment of SiO2 and Al2O3 in the slag because iron‐oxide from the slag incorporated into the corundum refractory. For both cases, the reactions led to increases in viscosity, but the effect was more profound in the air atmosphere, where penetrations were found to be shallower. The oxygen partial pressure's influence on the slag's composition, primarily with iron‐oxide species, and on viscosity played a pivotal role in governing the effective penetration into the refractory.