Skip to main content
ARS Home » Southeast Area » Athens, Georgia » U.S. National Poultry Research Center » Quality and Safety Assessment Research Unit » Research » Publications at this Location » Publication #346743
Title: Dielectric characterization of Bentonite clay at various moisture contents and with mixtures of biomass in the microwave spectrum

Author
item ELLISON, CANDICE - Louisiana State University
item MCKEOWN, MURAT - US Department Of Agriculture (USDA)
item Trabelsi, Samir
item MARCULESCU, COSMIN - Louisiana State University
item BOLDOR, DORIN - Louisiana State University

Submitted to: Journal of Microwave Power and Electromagnetic Energy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2017
Publication Date: 1/24/2018
Citation: Ellison, C., Mckeown, M.S., Trabelsi, S., Marculescu, C., Boldor, D. 2018. Dielectric characterization of Bentonite clay at various moisture contents and with mixtures of biomass in the microwave spectrum. Journal of Microwave Power and Electromagnetic Energy. doi:10.1080/08327823.2017.1421407.

Interpretive Summary: Biomass materials are being considered as supplemental energy sources for commonly used fossil fuels. In many instances the processing of biomass materials is challenging in preparing the materials for practical use. This study assessed the potential for using bentonite clay as a microwave absorber in microwave heating-assisted biomass pyrolysis based on the dielectric properties of the different materials. Dielectric properties of bentonite at different moisture contents were measured with a coaxial-line dielectric probe and vector network analyzer in the microwave frequency range from 0.2 to 4.5 GHz at room temperature. In addition, dielectric properties of mixtures of bentonite and biomass materials (pine, Chinese tallow tree, energy cane, and switchgrass) were measured from 1.5 to 20 GHz. As expected, both dielectric constant and dielectric loss factor increased linearly with increasing moisture content. Measurements on biomass and bentonite mixtures show a quadratic increase in dielectric constant and loss factor with increasing bentonite content and with moisture contents ranging from 9.5% (pure bentonite) to 11.4% (pure biomass) wet basis. At 915 MHz, dielectric constant ranged from 2.0 to 6.2 and dielectric loss ranged from 0.2 to 2.7 respectively. At 2450 MHz, dielectric constant ranged from, 1.8 to 5.1, and dielectric loss ranged from 0.7 to 2.6, respectively. This study also showed that bentonite is a good microwave absorber for biomass pyrolysis as the dielectric properties of biomass and bentonite mixtures increased quadratically with increasing bentonite content. The dielectric constant and loss factor of bentonite are greater than those of the biomasses studied. Thus, the effective permittivity of the biomass/bentonite mixtures increases with addition of bentonite. Therefore, bentonite is proven to be a good microwave absorber that can be used to increase microwave heating in biomass materials. The findings show that mixing biomass materials with bentonite can be useful in enhancing the effects of microwave heating for such processes.

Technical Abstract: This study assesses the potential for using bentonite as a microwave absorber for microwave-assisted biomass pyrolysis based on the dielectric properties. Dielectric properties of bentonite at different moisture contents were measured using a coaxial line dielectric probe and vector network analyzer in the microwave frequency range from 0.2 to 4.5 GHz at room temperature. Additionally, dielectric properties of mixtures of bentonite with biomass were measured from 1.5 to 20 GHz. As expected, both dielectric constant and dielectric loss factor increased linearly with increasing moisture content. Measurements on biomass and bentonite mixtures show a quadratic increase in dielectric constant and loss factor with increasing bentonite content and with moisture contents ranging from 9.5% (pure bentonite) to 11.4% (pure biomass) wet basis. At 915 MHz, dielectric constant ranged from 2.0 to 6.2 and dielectric loss ranged from 0.2 to 2.7 respectively. At 2450 MHz, dielectric constant ranged from, 1.8 to 5.1, and dielectric loss ranged from 0.7 to 2.6, respectively.