An experimental study of rheological properties and stability characteristics of biochar-glycerol-water slurry fuels

Published Date

doi:10.1016/j.fuproc.2016.07.026

Research article

Author 

• Pengfei Liu
• Mingming Zhu ^,
• Zhezi Zhang
• Yee-kwong Leong
• Yang Zhang
• Dongke Zhang

• Centre for Energy (M473), The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia

Received 21 May 2016. Revised 26 July 2016. Accepted 26 July 2016. Available online 5 August 2016.

Highlights

• Biochar-glycerol-water slurries with desirable rheological properties were prepared.
• •
  Yield stress and viscosity increased as glycerol content increased.
• •
  Slurry fuels became more shear-thinning with higher glycerol content.
• •
  Slurry fuels became more stable with higher glycerol content.

Abstract 

The rheological behaviour and stability characteristics of biochar-glycerol-water slurry fuels were experimentally investigated, emphasising the effect of glycerol addition. A pine sawdust biochar with a size fraction of < 32 μm and a median particle size (D₅₀) of approximately 12 μm was used. A biochar-glycerol-water slurry fuel was prepared by dispersing biochar particles in a premixed glycerol/water solution as the suspending medium with glycerol content varying from 0 to 100 wt%. 2 wt% lignosulfonic acid sodium salt (LASS) (on the basis of dry weight of biochar) was added to the suspending medium as a dispersant. The effect of glycerol content on the rheological properties and stability characteristics of the slurry fuels were studied. The yield stress was measured with a Brookfield vane viscometer and the dependence of apparent viscosity and shear stress on the shear rate was characterised using a Haake VT550 cone and plate viscometer. The stability characteristics of the slurry fuels were characterised by using a “drop rod” method. As glycerol content increased, the maximum biochar loading decreased from 50 to 10 wt% while the calorific values of the slurry fuels first increased and then decreased, reaching a maximum of 21 MJ kg^{− 1} at 90 wt% glycerol content. For a given biochar loading, increasing glycerol content increased the viscosity of the suspending medium and therefore the viscosity of the slurry fuels, displaying higher yield stress, more apparent shear-thinning behaviour and higher stability due to the enhanced flocculation of biochar particles.

Keywords

Biochar

Calorific value

Glycerol

Rheology

Slurry fuels

Stability

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• ⁎ 
  Corresponding author.

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