Application of NIRS to the Direct Measurement of Carbonization in Torrefied Wheat Straw Chars

Abstract

Near infrared spectroscopy is demonstrated as a method for measuring of the increase in carbon content for torrefied wheat straw. Wheat straw was torrefied in both batch and continuous systems at the bench and pilot scale, followed by measurement of the elemental composition and diffuse reflectance/absorbance in the NIR spectrum. The changes in absorbance measured in the band from 960 to 1060 nm most closely correlated to the change in carbon content, which increased by more than 10% for the most severely torrefied samples. In general, the absorbance values in the NIR band for the char samples change very clearly and incrementally along with torrefaction severity. The average change in absorbance at each wavelength within the 960–1060 nm band was correlated to the increase in carbon concentration by a linear expression with an average R2 value of 0.949.