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Table 4. Elemental Composition of the Wood Dust Elemental Composition C (wt%)
H (wt%)
N (wt%)
S (wt%)
44.84 39.78 48.37
4.35 3.33 4.38
0.57 0.32 0.67
0.81 0.53 0.39
Populus alba
Pinus massoniana
Cinnamonum camphora
Table 5. Thermal Degradation and Char Residue Data by TGA Sample T 5% (°C) T 50% (°C) R peak (%/min)
Char residue at 750 °C (%)
T peak (°C) 371.4 361.1 364.5
159.9 181.6 148.2
358.0 363.1 357.2
15.2 12.1 16.5
12.2
Populus alba
8.2
Pinus massoniana
Cinnamonum camphora 13.4 T 5% : temperature at the mass loss of 5%; T 50% : temperature at the mass loss of 50%
T peak : temperature at the peak; R peak : mass loss rate at the peak Explosion Characteristics of Wood Dust Samples Effect of particle size on explosion pressure and explosion index
Figure 6 shows the pressure evolution during the explosion process for C. camphora dust with a particle size of 63 to 125 μm . When the dust concentrations were 500 g/m 3 and 1250 g/m 3 , the explosion pressure and the pressure rise rate reach their maximum values, respectively. Similar results were also obtained by Calle et al. (2005). According to BS EN 14034-2 (2006), the explosion index ( K st ) is defined as the explosion pressure rise rate (dp/dt) normalized to a 1 m 3 vessel in the explosion pressure rise rate, making the explosion pressure rise rate measured in different containers comparable. It is calculated using the cubic law in Eq. 1, K st = (d p /d t ) × V 1/3 (1) where V is the volume of the explosive container, 20 L. Figure 7 is the relationship between P max or K St of dust samples and particle size. When the particle size increased from 0- 63 μm to 250 - 500 μm, the P max and K St of Pinus massoniana Lamb dust decreased from 7.56 bar to 6.80 bar and from 129 bar·m/s to 59.2 bar·m/s, and the decreasing rate was 10.1% and 54.1%, respectively. The dust samples from C. camphora and P. alba showed similar changing trends to that of P. massoniana dust. Therefore, a conclusion can be drawn that particle size affects K St much more than P max . This result is consistent with the literature (Calle et al. 2005). In addition, it is interesting that P. alba dust had higher P max and K St values than P. massoniana dust and C. camphora dust in the selected particle size. The P. alba dust exhibited a relatively high length to diameter ratio which makes it tend to float in the air for a long period during the explosion test and enhance its explosive power. For the C. camphora and P. massoniana dust, the oval-shaped particles make them relatively difficult to disperse in the air. The explosive characteristics of dust are related to its volatility content, and the more volatile the content, the greater the explosion severity of the dust (Gu and Wang 2008). From the TG curves in Fig. 5, the volatile content of the P. alba dust and C. camphora dust was significantly higher than the P. massoniana dust. Finally, the sulfur elemental content and H/C ratio of the P. alba dust were highest among three types of dust samples. However, compared to C. camphora , the dust from P. massoniana had a higher content of sulfur, but it did not achieve higher values of
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Guo et al . (2019 ). “Explosion of wood d usts,” B io R esources 14(2), 3182-3199.
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