Rapid measurements of the moisture content in biofuel

• Main Author: Nyström, Jenny
• Format: Doctoral Thesis
• Language: English
• Published: Mälardalens högskola, Institutionen för samhällsteknik 2006
• Subjects: radiofrequency measurement; moisture content measurement; fuel characterization; biofuel; time domain measurement; Bulk measurement; Multivariate data analysis
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-130; http://nbn-resolving.de/urn:isbn:91-85485-08-X

An increasing number of power plants in Scandinavia are beginning to use biofuel instead of coal or oil. The material in the new fuel is a mixture of woodchips, mostly Pine, Spruce and Salix, bark, GROT (tops and branches from felling waste) and sawdust from sawmills. It is heterogeneous, having a moisture content varying from 15% up to 65%. The moisture content affects the combustion of the fuel and therefore its commercial value. The industry is now interested in obtaining a method for measuring the moisture content of biofuel, quickly and reliably; preferably on delivery at the power plant. The measuring technique presented in this thesis is the first reported in the literature capable of measuring the moisture content of a large sample of such an heterogeneous material as biofuel. The equipment is today calibrated for a sample volume of 0.1 m3. A radio frequent signal is supplied from an antenna and penetrates the biofuel. Its reflection is modeled using partial least squares. As part of the work presented in this thesis, a new type of measuring rig and an analysis method for measurement of the moisture content of large samples of heterogeneous material have been developed. A statistical model for moisture content measurements of five different biofuel materials using radio waves has been built, having a root mean square error of prediction of 2.7. The interactions between biofuels and radio frequent signals have been demonstrated, indicating a variation of the reflection with varying types of biofuel material and variation in the reflection and delay of the signal with varying moisture content.