Radio Frequency System for Measuring Characteristics of Biofuels

In this paper, a measurement system for making rapid measurements of moisture content, fuel mixture, volume and the bulk density of bio fuels is presented. The method uses radio frequency spectroscopy, and is a small scale version of what is intended to be used directly in the fuel containers arriving to the power plants. The advantages with the method are that it is fast and reliable, and it can be used for measuring mean value characteristics of large amounts of biofuel. Reflection characteristics for frequencies from 310 to 1300 MHz are simulated and measured for sawdust. The attenuation is evaluated in frequency and time domain. It is concluded that a calibration of the whole system is needed to compensate for disturbances in the test system. Both the surface and the bottom reflection are possible to detect in time domain. The simulated and measured attenuation in frequency domain have a similar periodic behavior up to around 800 MHz. Above 800 MHz the system is disturbed by the higher order modes