Degree

Doctor of Philosophy (PhD)

Department

Engineering Science

Document Type

Dissertation

Abstract

This work is an investigation of microwave-assisted biomass pyrolysis and thermocatalytic upgrading of pyrolysis vapors. In the first two chapters, the microwave susceptibility of mixtures of biomass with potential microwave absorbers are characterized by dielectric measurements at microwave frequencies. Dielectric constant and dielectric loss factor of biomass mixtures with char and biomass mixtures with bentonite are found to increase quadratically with increasing weight percent of char or bentonite.

Chapter 3 presents a finite element model, developed in COMSOL Multiphysics, comparing two waveguide applicator configurations for microwave processing using biomass as a model material. A standing wave configuration results in intense hot and cold spots along the length of the material with half wavelength spacing, while the travelling wave configuration provides more even heating along the material, but material temperature is lower. The model was validated experimentally. A continuously moving sliding short was found to provide more homogenous heating along the sample length, without compromising temperature.

Chapter 4 is an experimental investigation of microwave pyrolysis in which pine biomass is mixed with char to assist heating. A single mode waveguide applicator was used and the sliding short configuration developed in Chapter 3 was implemented. Power level and percent char in the biomass/char mixture were studied for their effect on pyrolysis product yields, composition, and calorific value. Microwave-assisted pyrolysis successfully produced high quality products with greater syngas CO and H2, greater bio-oil phenol composition, and greater overall energy balance compared to conventional pyrolysis.

In Chapter 5, an experimental study on pyrolysis vapor upgrading is conducted using low-cost, naturally occurring catalysts as an alternative to synthetic acid zeolites. Biomass is pyrolyzed in an inductively-heated reactor in which pyrolysis vapors pass over a heated catalyst bed. The catalysts studied are montmorillonite-supported iron (III), which were found to be unsuitable for microwave heating due to low dielectric loss and poor thermal stability. For these reasons, the montmorillonite-based catalysts in this study were heated by an electric furnace. Iron-doped montmorillonite K10 catalysts were found to marginally improve the quality of liquid and gaseous products from biomass pyrolysis.

Date

5-30-2018

Committee Chair

Boldor, Dorin

Available for download on Wednesday, May 28, 2025

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