Observations on the release of gas-phase potassium during the combustion of single particles of biomass

One of the more significant characteristics of solid biomass fuels as compared to coal is the quantity of potassium that they contain. Potassium content influences ash deposition and corrosion mechanisms in furnaces, the effects of which may differ depending on phase transformations of potassium species in the gas phase and condensed phase. The fate of potassium from the fuel during the combustion process is therefore an important concern. To investigate this, an experimental method is presented in which the release patterns from single particles of various biomass fuels are measured by use of flame emission spectroscopy implemented using a custom-built photo-detector device. Single particles of fuel are combusted in a methane flame with a gas temperature of ∼1800 K. The observed potassium release patterns for thirteen solid biomass materials are presented. The data are analyzed to examine the relationships between: the level of potassium in the fuel particle; the fraction of potassium released at each stage of combustion and the peak rate of release of potassium to gas-phase during combustion. Correlations between these quantities are identified with key trends, patterns and differences highlighted. The analyses provide useful information for the development and validation of modelling of potassium release during combustion of biomass.