Dielectric characterization of corn stover for microwave processing technology

• Microwave dielectric properties of corn stover were analyzed during pyrolysis.
• Dielectric properties are greatly influenced by the pyrolysis temperature.
• The microwave absorbing property of the biomass increases in the char region.

The aim of this paper was to investigate the microwave dielectric properties of corn stover at 915 and 2450 MHz from room temperature to 700 °C under nitrogen (N2) environment. Cavity perturbation method was used to measure the dielectric constant and loss factor. The heating process was divided into three distinct stages, namely drying, pyrolysis, and char stage. Dielectric properties during drying and pyrolysis stages were inversely proportional to the temperature, whereas directly proportional to the temperature in char stage. The maximum microwave penetration depth of 8.5 m was obtained at 392 °C and 915 MHz, just at the end of the pyrolysis reaction zone. The experimental data were fitted using regression fit and based on this the dielectric properties model related to the temperature was developed.

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