Abstract
This work aims to analyze the torrefaction process with Norwegian birch and spruce as feedstocks. Torrefaction experiments were performed in a macro-TGA (thermogravimetric analysis) reactor with provisions for continuous volatile measurements through micro-GC (gas chromatography) and FTIR (Fourier transform infrared spectroscopy). The process temperature (225 and 275 °C), holdup time (30 and 60 min), and sample size (10 and 40 mm cubes) were included as variations in the experimental matrix. Fuel characterizations, DTG (derivative thermogravimetric) curves, product yields, hydrophobicity tests, grinding energies, and particle-size distributions are discussed. The raw fuels were used as a reference for the comparisons. It was found that the birch has a higher devolatilization rate than the spruce under all tested conditions, resulting in a larger percentage increase in its carbon content. An increase in the temperature has the strongest effect on the properties of the torrefied product among all of the studied parameters. At 275 °C, the solid yield decreased to 63% and 75% for the torrefied birch and spruce, respectively. In terms of torrefied product properties, the torrefied samples absorbed approximately one-third of the moisture compared to the raw fuels. The total grinding energy decreased up to 40–88% for the torrefied samples of both feedstocks. An increased percentage of fine particles (<180 μm) was found in the particle-size distributions of most of the torrefied samples. Overall, considerable improvements were observed in the properties of the torrefied products for both feedstocks. Results obtained from this study form the basis of a torrefaction feasibility study in Norway. Copyright © 2012 American Chemical Society