THE INFLUENCE OF TORREFACTION PRE-TREATMENT ON FLASH PYROLYSIS KINETICS IN A CYCLONIC TGA DEVICE

摘要

Torrefaction, mildly roasting of lignocellulosic biomass, is investigated as a pre-treatment option to acquire a better quality pyrolysis oil. To study the effects of torrefaction on the flash pyrolysis process, measurements were performed using a cyclonic TGA device. The cyclonic TGA can mimic the flash pyrolysis process by virtue of its extremely high heating rates, making it possible to study the kinetics of the reaction. Three streams originating from the same batch of mixed waste wood were studied: raw chips, torrefied chips, and torrefied pellets; the materials were ground to particle sizes of <200, 200-500 and 500-800 μm, and the experiments were performed at temperatures between 475-550°C with sample sizes of 0.5 gram. It was determined that only the smallest particle size range was within the kinetically controlled regime. The results show a lower reaction rate and a higher activation energy for torrefied material compared to raw material, consistent with theory that during torrefaction highly active compounds are released. This means longer reaction times in flash pyrolysis reactors. Furthermore, torrefied pellets react faster than torrefied chips, and adding moisture significantly increases the reaction rate.