Investigation into Biomass Thermal Transformations During High Temperature Feeding

Biomass, as a source of energy, has been increasing in popularity due to its widespread availability, low cost, and benefits to the environment. Especially in United States, biomass feedstock research and development has received additional funding in an effort maximize the potential of the vast forestlands and curb the country’s dependence on conventional fossil fuels. However, variability in biomass feedstock properties, especially during high temperature processes, is the biggest obstacle in developing better models and technologies. The objective of this research is to investigate the thermal transformation of a biomass feedstock during a high temperature feeding process. A high temperature screw feeder that experienced plugging issues was investigated. A 3D model and thermal simulation was used to develop the thermal profile of the screw feeder in the axial direction. Then, a thermal model was created to determine the temperature profile of the biomass in the radial direction at each flight section on the screw feeder. The predictions made by the model were then validated through characterization of the biomass deposit. Characterization was conducted using optical microscopy, scanning electron microscopy (SEM), and electron dispersive spectroscopy (EDS). Additionally, cross-sectional examination and nano-indentation were performed. The locations where the model predicted the biomass would begin to burn was validated by the characterization results. There is also uneven heating in the biomass deposit according to proximity from the tip and the contact interface with the screw feeder. Additionally, it was found that residence time has a significant influence on the heating of the biomass deposit. Plastic deformation discovered on the edges of the flight that have led to additional biomass accumulation as well as increased residence times. The findings from this research are beneficial to the biomass feedstock industry. It will be useful in informing future screw feeder models and processes for screw feeders to improve efficiency and mitigate failures