Contactless Thermal Diagnostics of Acoustically Levitated Biomass under Uniform High Flux Radiation

This study reports a contactless optical system developed for investigating the fast-thermal processes of biomass under high-flux radiation, particularly for understanding the synergy of renewable biomass and concentrated solar energy. A biomass tablet was successfully suspended using a home-built acoustic levitator in a well-controlled oxygen-lean atmosphere and was irradiated under uniform radiation with a high flux of approximately 1 MW/m², i.e., ∼1000 suns. The biomass temperature profile was spatio and temporally recorded using an infrared thermographic camera. Several key thermal parameters of the biomass were determined, including the time-resolved heating rate and the ignition temperature. Three different thermal processes were identified from the temperature profiles. These are an initial fast-heating process, a following slow-heating process, and a final biomass ignition depending on the flux of radiation. At high flux, these three processes are merged, and only a steep linear increase in temperature was observed. The contactless apparatus provides the high-fidelity data of the heating rates of biomass and can benefit the understanding of the fast-thermal process associated with biomass under high flux concentrated solar radiation.