Characterization of biofuel mixtures by online near infrared spectroscopy

Off-line measurements of NIR spectra of fuel mixtures (coal, peat, biofuel) were carried out. Eleven mixtures were made according to a mixture triangle. For each mixture ten replicate NIR measurements were made with an InGaAs spectrometer measuring between 911 and 1709 nm in 128 bands. The reference measurements were moisture, energy and ash, all carried out according to laboratory standards. All these reference measurements were done in triplicate. The data analysis consists of a PCA analysis to explain the structure of the spectra. Different PLS models for calibration were tested. Some important conclusions are reported. The replicates allow the determination of bias and standard deviation for the obtained predictions. Energy and moisture content can be measured to a reasonable precision. Ash content can also be measured, but with larger errors.