Initial stages of coal slag interaction with high chromia sesquioxide refractories

Slagging coal gasifiers operate at temperatures as high as 1650°C in a reducing environment, requiring combustion chambers to be lined with refractories. The liner materials of choice are semi-porous high chromia refractories. Recently, a new series of high-chromia aluminia sesquioxide refractories have been developed. Both long term and short term tests are being conducted to evaluate the performance of these materials. In this study, the initial stage of slag-refractory interactions was analyzed. Samples of gasifier slag were compacted and placed upon the surface of these new chromia refractories and the temperature was raised consistent with start-up operating conditions of commercial gasifiers. The slag was completely molten by the time the furnace achieved a temperature consistent with gasifier operation conditions: 1350°C. Measurement of the slag contact angle, slag spread along the slag-refractory interface, and the loss of slag due to slag infusion into the refractory were monitored by camera. Analysis suggests a single phenomenon with an activation energy of approximately 54 kcal may be the controlling factor. Cross-section analysis of the sample and analysis of slag chemistry indicate that slag infusion preceded the slag-refractory interface front movement and that the iron component of the slag was becoming concentrated at the slag-refractory interface leading to the formation of a chromium-iron spinel phase. Results of these short term tests are critical in characterizing and understanding the results long term slag-refractory interactions.