Influence of Oxygen Partial Pressure on Synthetic Coal Slag Infiltration into Porous Al₂O₃ Refractory

Abstract

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.

The effect of a temperature gradient on the phase formation inside a magnesia–chromite refractory in contact with a non-ferrous PbO–SiO2–MgO slag

“…In this paper a refractory sample is placed between the cooling probe and the liquid slag bath, thereby creating a temperature gradient over the refractory sample. This approach differs from the experimental setup currently used by Kaneko et al [12][13][14] where a refractory sample is partially put in the hot zone of a furnace while the bottom of the refractory is kept in a colder part of the furnace resulting in a temperature gradient over the sample. A hole is drilled in the part of the sample in the hot zone and filled with slag.…”

Infiltration Velocity and Thickness of Flowing Slag Film on Porous Refractory of Slagging Gasifiers

“…Solving for Vz yields V2 l0 = 2R{0.5 + 0.05 Re} (13) Average velocity is defined as (17) (18) where Re is the flow Reynolds number, Re = pu (2R)/p. Since the computed average velocities were quite small (between 2.6 pm/s for a 1-h time period and a viscosity of 100 Pa s, and 0.7 mm/s for a 5 s averaging period and a viscosity of 1 Pa s) then the flow Reynolds numbers are much less than one (between 1.8 x 10"9 and 4.8 x 10" 5).…”

“…Enhancing materials stabil ity performance is necessary to prevent the degradation of the po rous refractory material lining that protects the external steel shell. Since the depth of slag penetration determines the volume of degraded material [13], consideration of the factors affecting the depth can be crucial in the development of higher performance refractory materials for slagging gasifiers. Simultaneously, knowl edge of the factors affecting the thickness of the slag layer along the refractory walls can offer insights toward the design of more efficient operating geometries and parameters.…”

Slag Behavior in Gasifiers. Part I: Influence of Coal Properties and Gasification Conditions

“…All these difficulties can be overcome by adding more oxygen to the gasifier in order to burn more coal and generate more heat. However, this reduces the overall efficiency of an IGCC system by increasing the parasitic power load of the air separation unit, reducing syngas yield, and, when a refractory-lined gasifier is used, shortening the life of the refractory [36,37]. For most coals, the ash melting point and the slag viscosity are more constraining than the carbon conversion considerations; therefore, the operating temperature of the gasifier is selected based on the ash slagging temperature or the ash flow temperature and the slag viscosity [9]-characteristics that are important for selecting the appropriate operating temperature of the gasifier to avoid either overfiring or solidifying the slag inside the gasifier.…”