Ana Paz

Influence of Temperature in Radio Frequency Measurements of Moisture Content in Biofuel

A method that permits the determination of moisture content in biofuel in a fast and representative way is under development. The method uses radio frequency waves within the range of 310 MHz to 800 MHz and measures the reflection coefficient in samples with volume of about 0.1 m3. The influence of sample temperature in the measurements is shown in this study. Two biofuel types were used, with moisture content varying between 31% and 63% and temperature varying between 1degC and 63degC. The data was evaluated with multivariate data analysis. Results show that it is not possible to identify the sample temperature as a principal component in a principal component analysis and partial least squares regression shows no correlation between temperature and the radio frequency data. For the frequency interval and the temperature range studied, it was not possible to detect any influence of sample temperature on moisture content prediction with the radio frequency method

Measurement of the Dielectric Properties of Sawdust Between 0.5 and 15 GHz

The aim of this paper was to measure the broadband dielectric properties of sawdust. Knowledge of dielectric properties is important in improving understanding of a material and can lead to the development of methods for determining physical properties such as moisture and salt content. The broadband dielectric properties of sawdust were measured with an open-ended coaxial-line dielectric probe. Measurements on granular materials with the dielectric probe are dependent on the density of the measured region, which may differ from the average density of the sample. In this paper, a method was developed for determining the actual density for measurements with the dielectric probe. It consists of measurement of the dielectric constant with a different method (in this instance, a free-space transmission method) at a frequency common to both methods and identifying a relationship between the measured dielectric constant and density. The dielectric properties of sawdust samples with moisture content levels between 13% and 45% are presented for frequencies between 0.5 and 15 GHz.

Dielectric properties of peanut-hull pellets at microwave frequencies

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 moisture content and bulk density are important for quality control and pricing and control of the energy conversion process. The dielectric properties of peanut-hulls pellets 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 moisture contents between 4% and 13%, temperatures between −15 °C and 38 °C, and bulk densities between 0.54 and 0.69 g·cm−3.