Effect of Coal Ash on Fe-Based Oxygen Carrier in Coal Char Chemical Looping Gasification

Abstract

Abstract Chemical looping gasification (CLG) is a cost-effective alternative to the traditional fossil conversion process. In this article, the effects of three different types of coal ash on Fe-based oxygen carrier in coal char CLG were investigated. The composition of coal ashes and the microstructure of Fe4Al6 oxygen carrier were characterized by SEM-EDS, XRD and BET. The effects of different components of coal ash (SiO2, CaO, and K2O) were examined, and their effect mechanisms were analyzed. The findings suggested that the effect of coal ash on Fe4Al6 oxygen carrier could be divided into three aspects: (i) inhibition effect by forming low-melting-point compounds; (ii) enhancement effect through catalysis or formation of specific structure; and (iii) neutral effect by integrating with oxygen carrier. In addition, the formation of low-melting-point compounds, which is mainly due to SiO2 and CaO, was found to cause sinter and agglomeration of oxygen carrier. Moreover, potassium salts were found to either act as catalysts or cause the formation of K-Fe-O compounds; they promoted the release of lattice oxygen from oxygen carrier while enhanced oxygen carrier’s stability. The findings suggested that coal ash containing high content of K2O and Fe2O3 could enhance the performance of oxygen carrier during CLG.