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Table 2. Results of area determinations on output oak wood chips
Grinding output material |
Particle Assumption 1 |
Particle Assumption 2 |
Particle Assumption 3 |
Output particle size (HM) |
A/weight
(m^2/kg) |
Input material particle size |
A/weight
(m^2/kg) |
Input material particle size |
A/weight
(m^2/kg) |
Particle on sieve > 2 mm - assume as flat rectangle |
0 |
Particle on seive > 2 mm - assume as flat rectangle |
0 |
Particle on seive > 2 mm - assume as flat rectangle |
0 |
Particle on seive 1-2 mm - assume as sphere of size = Sqroot of product of upper and low sieve sizes |
6.301 |
Particle on seive 1- 2 mm - assume as flat rectangle of measured particle thickness, length and width of assumed sieve representative size = Sqroot of product of upper and low seive sizes |
14.562 |
Particle on seive 1- 2 mm - assume as flat rectangle of 0.5 original measured particle thickness, length and width of assumed sieve representative size = Sqroot of product of upper and low seive sizes |
25.111 |
Particle on seive < 1 mm - assume as sphere of size = Sqroot of product of upper and low sieve sizes |
3.151 |
Particle on seive < 1mm - assume as flat rectangle of measured particle thickness, length and width of assumed sieve representative size = Sqroot of product of upper and low seive sizes |
18.575 |
particle on seive < 1mm - assume as flat rectangle of 0.5 original measured particle thickness, length and width of assumed sieve representative size = Sqroot of product of upper and low seive sizes |
29.124 |
Total |
4.926 |
|
16.313 |
|
26.862 |
For assumption 1, there was a lack of reasonableness of difference in added surface area due to grinding – which was (negative) – 49.7%. Area after grinding should be greater than the area before grinding. This method of calculation does not yield rationale results. The flaw is assuming a diameter that was greater than the thickness of material being cut.
For assumption 2, this result is more reasonable than method 1. The magnitude of area was greater because the reduced thickness resulted in many more particles for the same volume of solid wood. The new generated surface area per weight increases 21.9% with the area of 16.3 (m2/kg) before grinding and 13.3 (m2/kg) after grinding.
For assumption 3, this result is reasonable. The magnitude of area was even greater than the method 2 because the reduced thickness twice resulted in even more particles for the same volume of solid wood. The new generated surface area per weight increases 53.1% with the area of 17.54 (m2/kg) before grinding and 26.86 (m2/kg) after grinding. This highlights the importance of particle thickness, and the need to closely examine and measure particle dimensions.
In conclusion,
- Existing methods for quantifying particle area are inadequate.
- Accurate particle surface area requires accurate representation of particle shape, and the need to closely examine particles.
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