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 (SiO 2 , CaO, and K 2 O) 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 SiO 2 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 K 2 O and Fe 2 O 3 could enhance the performance of oxygen carrier during CLG.