Abstract:

The effect of torrefaction on the quality of biofuel was investigated through a small torrefaction experimental equipment with rice husk(RH) and pine sawdust(PS) as the raw materials. The results showed that torrefied rice husk and sawdust exhibited an increase in fixed carbon content by 7.18% and 11.76%, compared with the raw materials. And the C element content with the largest increased of 3.50% and 5.80% for rice husk and sawdust, respectively. The contents of volatile matter and O element decreased significantly, and the content of H element also decreased slightly. The calorific value increased by 11.1%(RH) and 15.9%(PS), respectively. The hemicellulose contents in the torrefied rice husk and sawdust after reaching 300℃ were only 2.41% and 1.06%, respectively. The hemicellulose was decomposed both more than 90%. The relative content of lignin increased significantly, with the largest increases of 119%(RH) and 208%(PS), respectively. After biomass torrefaction, the internal fiber structure was destroyed and the grindability was improved. With the deepening of the torrefaction degree, the particles with the size below 0.15 mm increased significantly after torrefied rice husk being ground. The study found that oxygen-containing functional groups such as -OH and C-O were reduced, and the hydrophobicity of torrefied rice husk and sawdust increased by 28.08% and 25.66%, respectively, when torrefied at 250℃ for 30 min.

Key words: biomass, torrefaction, chemical composition, grindability, hydrophobicity