Changes of chemical and mechanical behavior of torrefied wheat straw

Lei Shang, Jesper Ahrenfeldt, Jens Kai Holm, Anand Ramesh Sanadi, Søren Talbro Barsberg, Tobias Thomsen, Wolfgang Stelte, Ulrik B. Henriksen

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Abstract

The purpose of the study was to investigate the influence of torrefaction on the grindability of wheat straw. Straw samples were torrefied at temperatures between 200 °C and 300 °C and with residence times between 0.5 and 3 h. Spectroscopic information obtained from ATR-FTIR indicated that below 200 °C there was no obvious structural change of the wheat straw. At 200–250 °C hemicelluloses started to decompose and were totally degraded when torrefied at 300 °C for 2 h, while cellulose and lignin began to decompose at about 270–300 °C. Tensile failure strength and strain energy of oven dried wheat straw and torrefied wheat straw showed a clear reduction with increasing torrefaction temperature. In addition, Hardgrove Grindability Index (HGI) of wheat straw torrefied at different conditions was determined on a standard Hardgrove grinder. Both results showed an improvement of grindability in the torrefaction temperature range 250–300 °C, which can be well explained by the findings from FTIR analysis. At a torrefaction temperature of 260 °C and with a residence time of 2 h, wheat straw samples produced similar HGI values as coal (RUKUZN) with 0% moisture content. Under this condition, the Anhydrous Weight Loss (AWL%) of the wheat straw sample was 30% on dry and ash free basis (daf), and the higher heating value of the torrefied wheat straw was 24.2 MJ kg−1 (daf). The energy loss compared to the original material was 15% (daf).
Original languageEnglish
JournalBiomass & Bioenergy
Volume40
Pages (from-to)63-70
ISSN0961-9534
DOIs
Publication statusPublished - 2012

Keywords

  • Torrefaction
  • Grindability
  • Tensile strength
  • Hardgrove
  • ATR-FTIR
  • Triticum aestivum L

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