Evolution of chemical functional groups during torrefaction of rice straw

• Published in: Bioresource technology Vol. 320; no. Pt B; p. 124328
• Main Authors: Xiaorui, Liu, Longji, Yuan, Xudong, Yang
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.01.2021
• Subjects: Biomass; Functional groups; Gases; Nitrogen; Oryza; Straw; Temperature; Torrefaction; Torrefaction; Nitrogen; Functional groups; Straw
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2020.124328

•Mass yield under isothermal and non-isothermal torrefaction was compared.•The evolution of N-functionalities during torrefaction was investigated.•The concentrations of NH3 and HCN had the same order of magnitude as CO.•Distribution of torrefaction products was less sensitive to the device type. The evolution of CHON functional groups during torrefaction of rice straw at 200–300 °C were investigated. The results showed that 300 °C was more suitable for rice straw torrefaction due to the ideal fuel ratio, energy densification, energy-mass co-benefit index and the significantly improved HHV of the torrefied products. The functional groups such as O–H, N–H, C–H, C = O in the solids decreased with rising temperature accompanied by the releases of H2O, CH4, CO2, CO and NH3, et al. At 300 °C, 40.04% of fuel-N was released in the form of NH3, HCN, HNCO et al. due to the decomposition of N-A which was the overall N-functionality in the raw rice straw. It is worth noting that the absorbance of NH3 and HCN has the same order of magnitude as CO. Therefore, the releases of N-containing gases should be highly concerned for the application of torrefaction technology from the environmental perspective.