Impact of Temperature on Fuel Characteristics and Grindability of Torrefied Agroforestry Biomass
Hewei Jiang, Yangtian Ye, Ping Lu, Dandan Chen
Abstract
Agroforestry biomass involving cedar wood (CW), poplar wood (PW), corn stalk, and wheat straw was torrefied in a fixed-bed reactor at the torrefaction temperature (T) of 200–300 °C and the holding time (τ) of 40 min to prepare herbaceous plant chars (WSC and CSC) and woody chars (PWC and CWC). The impacts of torrefaction temperature on fuel characteristics and grindability of torrefied biomass were studied based on the particle size distribution and the component analysis of ground raw biomass and torrefied biomass. The results indicated that the ash and fixed carbon contents increase and the volatile matter content decreases with the increase in torrefaction temperature. The energy and mass yields decreased, and the higher heating value and energy enhancement factor bound in the four torrefied biomasses increased with the increase in torrefaction temperature. The contents of hemicellulose and cellulose all decrease but the lignin content increases as the torrefaction temperature increases from 200 to 300 °C. Increasing the torrefaction temperature can improve the grindability of the char of herbaceous plants significantly, but it has a different effect on the grindability of the two woody chars. The mass fraction of particle size less than 150 μm in the char of the herbaceous plants produced at 300 °C is close to 100%. The higher the cellulose decomposition coefficient (λc), the better the grindability of the char of herbaceous plants. The cellulose decomposition coefficient and the data of 60% could be used as a critical index to evaluate the grindability of the char of herbaceous plants.