Effect of stem crushing on the uniaxial bulk compression behaviour of switchgrass and miscanthus

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

The bulk density with current baling technology is too low to utilise the full transportation capacity. For square bales, bulk density is limited by the pressure generated by the baler, density settings, and the ability of baling twine to withstand the expansion forces shortly after ejection from the bale chamber. This study explores crushing the stem on the pressure required to compact the material and the rebounding forces generated after compression. Uniaxial compression tests were conducted on bulk samples of switchgrass at three moisture levels (nominally 10%, 20%, and 45%) and miscanthus at two moisture levels (nominally 10% and 20%) to evaluate crushing. The pressure required to compress the material to 256 dry kg m−3 and the materials' stress relaxation behaviour were used as evaluation metrics. Crushing the material resulted in a significant decrease in the compression required for both crops. The peak stress was reduced from 577 to 441 kPa (a decrease of 23.6%) and from 581 to 365 kPa (a decrease of 37.2%) for switchgrass and miscanthus, respectively. Moisture level was also significant for both crops at the 10% and 20% moisture level with the low moisture material requiring higher pressures to reach the target densities. The final pressure after 5 min of relaxation was significantly lower for crushed material by 37.6% for miscanthus and 24.2% for switchgrass. However, this result from the reduction in peak stress at the end of the compression cycle, and relaxation behaviour was more affected by moisture level than by processing treatment.

Original languageEnglish
Pages (from-to)52-62
Number of pages11
JournalBiosystems Engineering
Volume175
DOIs
StatePublished - Nov 2018

Bibliographical note

Funding Information:
The authors sincerely acknowledge the financial support of the United States Department of Agriculture National Institute of Food and Agriculture Biomass Research and Development Initiative Grant #2011-10006-30363 and CNH Industrial. This is publication No. 18-05-022 of the Kentucky Agricultural Experiment Station and is published with the approval of the Director. This work is supported by the National Institute of Food and Agriculture , United States Department of Agriculture , Hatch- Multistate under 1002344 and 1003563 .

Publisher Copyright:
© 2018 IAgrE

Keywords

  • Baling
  • Biomass densification
  • Density
  • Energy crops
  • Pre-processing
  • Stress relaxation

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Food Science
  • Animal Science and Zoology
  • Agronomy and Crop Science
  • Soil Science

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