Study on the Temporal and Spatial Release Behavior of Alkali Metals during the Combustion of Different Solid Fuels

In this study, alkali metals (K and Na) released during the combustion of single solid fuels (eucalyptus, bagasse, and Indonesian coal) were analyzed by using CO2 laser ignition technology combined with flame spontaneous emission spectroscopy. The temporal and spatial distribution characteristics were investigated, and the impact of atmospheres on their release behavior was examined. The measurements demonstrate that, during the initial stage of combustion, the flame height and height of maximum K release intensity are as follows: coal < eucalyptus < bagasse. Additionally, the highest point of K release intensity aligns with the flame center position. Compared to the O-2/N-2 atmosphere, the release intensity of K atoms during the combustion process of eucalyptus and bagasse was more uniform in the O-2/CO2 atmosphere. Furthermore, the difference in the distributions between the two fuels became smaller. The K atom release time during coal combustion was longer, and the flame height decreased more gradually. In various environments, the peak release of potassium increased as the concentration of oxygen increased, and the time at which the peak occurred started to appear earlier. The total intensity of potassium release, as an integral for biomass combustion, increased exponentially with an increase in oxygen concentration, whereas for coal combustion, it increased linearly with the increase of oxygen concentration. In addition, the integrated total intensity of released alkali metals is less inhibited by CO2 when O-2 concentration increases. However, the decrease in biomass inhibition is more significant for biomass compared to coal, indicating that CO2 has a more pronounced inhibitory effect on biomass.

Automated summary

This study analyzed the release of alkali metals (K and Na) during the combustion of different solid fuels using CO2 laser ignition technology and flame spontaneous emission spectroscopy. The temporal and spatial distribution characteristics were investigated, and the influence of atmospheres on the release behavior was examined. The results showed that the release intensity of K atoms during the combustion process was more uniform in the O-2/CO2 atmosphere compared to the O-2/N-2 atmosphere. The release time of K atoms was longer and the flame height decreased more gradually during coal combustion. Additionally, the peak release of potassium increased with higher oxygen concentration.