Investigation on the effect of additive to melting behavior in the coal/biomass co-firing combustion

Additive is also applied to reduce the factor that induces slag production due to chemical reaction. In this study kaolin (Al2Si2O5(OH)4) and ammonium sulfate ((NH4)2SO4) is chosen as additive and investigated the influence as compared the results. In order to determine fuel properties, There was carried out the fundamental analysis such as ultimate analysis, proximate analysis, and ICP analysis. In addition, 80kWth test facility in KITECH is used to investigate slag behavior in coal burning condition. The tendency of slag formed when kaolin was added to the fuel during combustion increased significantly unlike in co-firing with woody biomass. When kaolin is added, the content of slag is changed from Ca-Mg silicate with high melting point to K-Al silicate with low melting point. Due to this, the amount of slag increases. However, when (NH4)2SO4 is added, it reacts with K, which increases the formation of slag and sulfate in (NH4)2SO4, and low temperature molten silicate is converted to high temperature molten silicate. Finally, these reactions dramatically reduce the tendency of slag. This is a good agreement with 80 kWth combustion test. Experimental results show that the ash rate is 8.76 g/hr in the case of confluence and the ash rate is 0.97 g/hr in the case of adding (NH4)2SO4, and the ash reduction rate is about 88.9% when the additive is added. As a result, Kaolin (Al2Si2O5(OH)4) and (NH4)2SO4, which are additive for herbaceous biomass foliage, may have different results depending on the characteristics of the fuel.