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Title: Dielectric Properties of Peanut-hull Pellets at Microwave Frequencies

Author
item ANA MARTA, PAZ - Swedish University
item Trabelsi, Samir
item Nelson, Stuart

Submitted to: IEEE Instrumentation & Measurement Society
Publication Type: Proceedings
Publication Acceptance Date: 3/3/2010
Publication Date: 5/3/2010
Citation: Ana Marta, P., Trabelsi, S., Nelson, S.O. 2010. Dielectric Properties of Peanut-hull Pellets at Microwave Frequencies. Proceedings of the 2010 IEEE International Instrumentation and Measurement Technology Conference, CD, pp. 62-66.

Interpretive Summary: Dielectric properties are electrical properties that determine how materials interact with electric fields such as those of high-frequency and microwave electromagnetic energy. Therefore, the dielectric properties of materials determine how rapidly they will heat in microwave ovens and lower radio-frequency dielectric heating equipment. Dielectric properties are also important in low power applications, such as the rapid measurement of moisture content in grain and other commodities. Biofuels are an attractive alternative source of energy to fossil fuels. Moisture content of solid biofuels is an important factor in pricing, conditioning for combustion, and storage management. This paper discusses the measurement of dielectric properties at microwave frequencies between 5 and 18 GHz for pelleted peanut hulls prepared as a biofuel. The moisture contents of the peanut-hull pellets were adjusted to various levels and their dielectric properties were measured from 4% to 13% moisture, as determined by standard methods, over ranges of bulk density and temperature. Analysis of the variations of the dielectric properties of the peanut-hull pellets with moisture content, bulk density, and temperature revealed that the dielectric properties can be used for microwave sensing of moisture content in peanut-hull pellets following the same principles that have been proven for grain and seed. The new data on peanut-hull pellets are of interest to engineers and scientists working on biofuels applications. The microwave measurement method, based on dielectric properties sensing, offers promise for the monitoring of moisture and bulk density in biofuels processing and utilization and can improve the energy efficiency in such applications.

Technical Abstract: Peanut-hull pellets are obtained from a waste product, peanut-hulls, which after pelleting can have several uses, namely as a renewable fuel. Rapid and nondestructive characterization of peanut-hull pellets is important for industrial utilization of this resource. Properties such as water content and bulk density are important for quality control and pricing and control of the energy conversion process. The dielectric properties of peanut-hulls can be used for the development of rapid and nondestructive sensors. In this study, the dielectric properties of peanut-hull pellets were measured at frequencies between 5 and 15 GHz, for water contents between 4% and 13%, temperatures between -15 °C and 38 °C, and bulk densities between 0.54 and 0.69 g'cm-3.