화학공학소재연구정보센터
Fuel Processing Technology, Vol.169, 288-294, 2018
Transformation behavior of alkali metals in high-alkali coals
Burning a coal containing a high content of alkali metals (Na, K) in utility boilers may result in ash-related problems such as slagging, fouling and corrosion on the heat transfer surfaces. This study investigated the transformation behavior of Na in four typical high-alkali coals including one Zhundong (ZD) coal and three Taer (TR) coals during combustion. The Na content in the coal is much higher than the K content, and different high alkali coals have difference in the aspect of their existing forms. Measurement results of the tested coals showed that most of the Na in the coal is H2O-soluble Na. During combustion, the released alkali metals increase with the elevated temperature. The H2O-soluble Na and NH4Ac-soluble Na in the ash decrease after the coal is burnt. This indicates that the released Na is originated from the H2O -soluble and NH4Ac-soluble Na, with the H2O -soluble Na being the dominant constituent. The investigation also reveals that some of the H2O -soluble Na in the ash might be converted into HCl-soluble Na and insoluble Na through reacting with Si-Al minerals. Furthermore, the low volatility of Na for ZD and TR coals is closely associated with the content of Cl, Si and Al in the coal.