In Situ Measurement of Potassium Release during Biomass Combustion Using Laser-Induced Breakdown Spectroscopy: Effect of Silicate on Potassium Release
Haibo Zhao, M. A. Wakil, Jan Viljanen, Qiang Song, Qiang Yao, Philip Kwong, Zeyad T. Alwahabi
Abstract
In this study, an improved calibration method for the in situ measurement of potassium (K) concentration in the flame field was developed using laser-induced breakdown spectroscopy. The temporal behaviors of K release and particle temperature were recorded simultaneously during biomass combustion. During combustion of raw willow wood, the majority of K was released during the ash-cooking stage, followed by char combustion stage, and only a small amount of K was released during the initial devolatilization stage. The results indicated that during the devolatilization stage, K was released because of the decomposition of organic K. Char-K was subsequently converted to K2CO3, and most K2CO3 was subsequently released during the final ash-cooking stage. In the case of rice straw combustion, K was mainly released during the initial devolatilization stage, most likely as KCl. The transformation of char-K and the K–Si reaction forming K–silicates mainly occurred during the char combustion stage; K was found to be released slowly from K–silicates during the ash-cooking stage. The combustion of willow wood with different Si contents demonstrated that Si significantly inhibited the K release during both char combustion and the ash-cooking stage.