Ash melting and slagging and residual K ion content in biomass pellet combustion

Combustion of biomass pellets is an effective way to reduce greenhouse gas emissions and achieve carbon neutrality. However, the alkali metal content (represented by K) in ash directly affects its slagging behavior, which can corrode the reactor and shorten its service life. In this study, the ash fusion slag and residual K ion contents were investigated at different combustion times (2, 5, 10, 20, 30 and 60 min) and temperatures (600, 700, 800, 900 and 1000°C). At the same combustion temperature, the residual content of K ions in ash decreases as the combustion time increases; at the same combustion time, the residual content of K ions decreases as the combustion temperature increases. The addition of 5% CaO promotes K precipitation, but at 10% CaO addition, the K precipitation rate is less than that at 5% CaO addition, indicating that the addition of CaO is beneficial to K ion precipitation only within a certain range. Adding CaO also generates high-melting-substances, such as CaSiO3 and calcite, which improve the overall slag resistance of the fuel.