The sintering behavior of Fe-based oxygen carrier with straw ash and sawdust ash by thermodynamic and thermomechanical analysis

In this study, the effects of straw ash (high-potassium ash) and sawdust ash (high-calcium ash) on the sintering behavior of two Fe-based oxygen carriers (iron ore and ilmenite) were analyzed by the thermodynamic (Facts-age) and thermomechanical analysis (TMA). It is indicated that the high shrinkage rate of ilmenite above 1170 degrees C is owning to the massive slag formation from the melting of spinel and rutile, while the low shrinkage rate of iron ore is mainly related to the spinel mineral. Both the straw ash sawdust ash accelerate the shrinkage of oxygen carrier, and the obvious shrinkage is observed above 900 degrees C for iron ore and 1100 degrees C for ilmenite. Further, the shrinkage rate of ilmenite with sawdust ash is much higher. The interaction between oxygen carrier and biomass ash was well explained by Factsage from the phase evolution view. The addition of biomass ash prompts the transformation of corundum to slag phase in oxygen carrier. Additionally, the potassium in straw ash reduces the initial formation temperature of slag, however, the calcium in sawdust ash enhances the slag content of ilmenite by facilitating the conversion of pseudobmokite to calcium iron oxide and titanium oxide above 1200 degrees C.