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For different species, the threshold of dust concentration was not identical. For example, for the dust of P. alba and P. massoniana , the threshold, 750 g/m 3 , was higher than that of C. camphora , 500 g/m 3 . The thermal degradation data in Table 5 shows that the mass loss rate of C. camphora dust first reached 5% at 148 °C. The higher the concentration of C. camphora dust, the smaller the number of particles involved in the subsequent explosion reaction, resulting in a lower dust concentration threshold. The dust concentration values corresponding to the maximum explosion pressure and the maximum pressure rise rate are different, as shown in Fig. 6. Obviously, the maximum speed and the maximum acceleration of the explosion reaction do not necessarily occur at the same time. Accordingly, in the testing procedure of the explosion, a series of experiments were repeated for a range of dust concentrations. This conclusion is consistent with the literature reports (Amyotte et al. 2012; Tascón et al. 2016; Cao et al. 2017). Similarly, among the three types of wood dust with a particle size of 0 to 63 μm , Populus alba dust exhibited the highest values of P max and K St , and the Pinus massoniana Lamb dust had the lowest. Synergistic effects of particle size and dust concentration on the explosion severity of the wood dust Figure 8 shows that for the explosion pressure of the three types of wood dust, the threshold of dust concentration is 500 g/m 3 or 750 g/m 3 . The dust concentration of 500 g/m 3 or 750 g/m 3 were used as examples to discuss the synergistic effects of particle size and dust concentration on explosion severity. In Fig. 9, for the dust samples of P. alba and C. camphora with the same dust concentration, the explosion pressure increased with decreasing particle size. The smaller the particle size, the larger the specific surface area and the larger the contact area between dust particles and the oxygen, resulting in faster heat release during burning. Besides, the convective heat rate of the dust and the gas in the explosion sphere is accelerated with decreasing particle size, thus shorting the ignition time of the dust. However, for the P. massoniana dust with a dust concentration of 500 g/m 3 , the explosion pressure did not reach above the changing trend, and its P max corresponded to the particle size range of 63 to 125 P m instead of 0 to 63 P m. This result may be caused by the fact that the P. massoniana dust contains a large amount of turpentine that makes small dust reunion and thus reduces its explosion severity.
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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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