1. CONTRIBUTION OF PARTICLE SIZE TO FLOWABILITY
CONTRIBUTION OF PARTICLE SIZE TO FLOWABILITY OF GROUND LOBLOLLY PINE WOOD
Oginni Oluwatosin and Fasina Oladiran
Biosystems Engineering, Auburn University, Auburn, AL
ABSTRACT
METHODOLOGY
DISCUSSION
Flow index values decreased with a reduction in particle size (Table 1). The flowability changed from easy flowing to cohesive as the particle size reduced.
Compressibility and Hausner ratio decreased with increase in particle size (Fig 1). Reduction in compressibility value and Hausner ratio > 1.25 is an indication of reduced flowability, thus confirming flow test results.
Particle size has a significant effect (p<0.05) on the angle on internal friction (Fig 2). This is indicate that as the particle size reduces, the sample becomes difficult to handle using gravity alone.
The cohesive strength significantly increases with decrease in particle size. (Fig 2).
The angle of wall friction (Fig 3) increases with a reduction in particle size. Angle of wall friction for stainless steel friction lid was significantly lower (p<0.05) than that of mild steel and TIVAR. Angle of wall friction is a dominant parameter in determining the hopper half angle.
Particle size was also found to significantly densities (particle density, tap density and bulk density of ground biomass)
Current study focuses on the amount of fine particles in coarse particles that will change the flowability of the coarse particle from easy flowing to cohesive
This study investigated the contribution of particle size to flowability of ground loblolly pine wood. The experimental samples were prepared by grinding through a 3.2 mm screen hammer mill followed by fractionating into six (6) size classes (using 0.25 mm to 1.4 mm screens). The flow properties of the fractions were then measured. The flow index values showed that the flowability of ground loblolly pine wood changed from easy flowing to cohesive as the particle size decreased. There was an increase in the values of the flow properties measured (compressibility, cohesion, angle of internal friction and angle of wall friction) as the particle size decreased, which also signified a reduction in flowability as particle size reduces. Results from this study showed that fine particles in ground biomass such as loblolly pine plays an important role in reducing the ability to flow out of storage vessels and containers.
Experimental samples ground through 3.2 mm screen hammer mill.
Ground samples were fractionated into six size classes using a vibratory screen separator.
Flow properties (compressibility, Hausner ratio, cohesion, angle of internal friction and angle of wall friction) of fractionated samples were measured.
Tap density apparatus
Powder flow tester
Vibratory screen separator
Retsch camsizer
RESULTS
INTRODUCTION
Table 1: Particle size and flow classification of fractions
Biomass supply logistics is one of the main challenges for cost-effective and wide use of biomass as an energy source.
The use of biomass requires feedstock materials in particulate forms. Obtaining a reliable and consistent flow out of storage equipment without flow obstruction, excessive spillage and dust generation is instrumental to successful downstream biomass conversion processing operations.
Fundamental understanding of the contribution of particle size on flow properties of ground loblolly pine is required in designing an appropriate storage container.
The objective of this study is to investigate the contribution of particle size on flowability of ground loblolly pine wood chips.
Screen size (mm)
dgw (mm)
Sgw (mm)
Flow index
Classification
Raw
1.63
1.64
2.86
Cohesive
1.40
2.14
0.83
4.05
Easy flowing
1.00
1.54
0.69
3.62
0.71
1.28
0.68
2.89
0.50
0.97
0.59
2.68
0.25
0.81
0.72
2.19
<0.25
0.15
0.03
2.01
Fig 1: Effect of particle size on compressibility and Hausner ratio
BIOMASS LOGISTICS AND FLOW PROBLEMS
CONCLUSION
Particle size plays a significant role in biomass logistics as it influences the flow behavior of biomass.
Obtaining a reliable and consistent flow of loblolly pine wood out of storage equipment would be challenging as particle size reduces .
Experimental results showed that discharge aids will be needed for flow of ground biomass out of storage vessels.
ACKNOWLEDGEMENT
Figure 2: Effect of particle size on angle of internal
friction and cohesive strength
Figure 3: Effect of particle size and wall material on
angle of wall friction