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ARS Home » Southeast Area » Athens, Georgia » U.S. National Poultry Research Center » Quality and Safety Assessment Research Unit » Research » Publications at this Location » Publication #334007
Title: Microwave sensing of moisture in flowing biomass pellets

Author
item MCKEOWN, MURAT - US Department Of Agriculture (USDA)
item Trabelsi, Samir
item NELSON, STUART - US Department Of Agriculture (USDA)
item TOLLNER, ERNEST - University Of Georgia

Submitted to: Biosystems Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/23/2016
Publication Date: 1/27/2017
Citation: Mckeown, M.S., Tollner, E.W., Nelson, S.O., Trabelsi, S. 2017. Microwave sensing of moisture in flowing biomass pellets. Biosystems Engineering. 155:152-160. https://doi.org/10.1016/j.biosystemseng.2016.12.009.
DOI: https://doi.org/10.1016/j.biosystemseng.2016.12.009

Interpretive Summary: The production of pelleted biomass represents a significant emerging industry in the United States. Solid biomass can be formed from the waste products of many different natural and manufactured products. Moisture content of biomass materials is an important factor in determining their behavior in handling, processing, and value determination. Dielectric properties are those electrical characteristics of materials that determine their interaction with electric fields, and they have been found useful for sensing the moisture content of such materials. Therefore, a study was initiated on the dielectric properties of pelleted biomass materials. In this study, a microwave system designed for moisture sensing on flowing bulk material was utilized to determine feasibility in sensing moisture content of biomass materials. Two types of pelleted biomass derived from peanut hulls and pine sawdust were used for moisture content determination by microwave measurements. Both pine pellets and peanut-hull pellets were conditioned to a range of moisture contents for the tests. At each moisture content three different material flow rates were tested and compared to the moisture content determined by measurements on static materials. By using a calibration function developed for static measurements; moisture content of flowing material was also predicted. Results showed that moisture contents determined by static and flowing measurements were comparable. These findings constitute a foundation for work aimed at implementing a microwave moisture meter in an industrial pelleting process, providing benefits for the biomass industry and consumers of biomass products.

Technical Abstract: Production of pelleted biomass is an emerging industry in the United States. A primary quality attribute of pelleted biomass is moisture content. This parameter is critical in pricing, binding, combustion, and storage of pelleted biomass. To produce pellets of high quality, moisture content must be tightly controlled. In this study, a microwave system designed for moisture sensing in flowing bulk material was used to determine feasibility in sensing biomass from measurement of the dielectric properties at microwave frequencies. Two types of pelleted biomass derived from peanut hulls and pine sawdust were used for moisture content determination. Moisture contents ranging from 5.4% to 9.9% (wet basis) were tested for pine sawdust pellets and from 8.9% to 14.5% were tested for peanut hull pellets. At each moisture content, three different material flow rates were tested, and moisture content predictions were compared to those obtained with static measurement. Moisture content of flowing material was predicted by using a permittivity-based density-independent moisture calibration function. Root mean square deviations were computed for comparisons between reference moisture content, and predicted moisture contents for both static and flowing materials. Results showed that predicted moisture contents under static and flowing conditions were comparable.