Study on the characteristics and influencing factors of micron/nano carbon material dust explosions

Abstract

Because of the wide range of applications of lithium ion batteries, the combustible and explosive carbon material dust of a negative electrode material requires additional attention. Few explosion test data of carbon material dust are available. In this paper, the thermodynamic and explosion parameters of allotropes of carbon dust and the same type of carbon material dust with different particle size distributions were determined. The results showed that the explosion pressure of micron/nano carbon material dust ranged from 0.4 to 0.7 MPa; the maximum deflagration index Kst ranged from 4 to 10 MPa · m/s; and the minimum ignition temperature was approximately 600 °C. The proportion of the small dust particles was an important factor that caused a change in the initial oxidation weight loss temperature and apparent activation energy of the same type of carbon dust. The variation trend among the initial oxidation weight loss temperature, apparent activation energy and particle size distribution of different carbon dust materials was not obvious, and mainly depended on the difference in molecular structures. Different molecular structures resulted in different apparent activation energies of the carbon allotropes. The apparent activation energy played a leading role in the change in the dust deflagration index. The smaller the apparent activation energy was, the smaller the energy required for carbon-carbon chemical bond breaking. The faster the carbon-carbon bond-breaking rate was, the larger the deflagration index. The dust particle size distribution, specific surface area and other characteristics had little influence on the deflagration index. Furthermore, the apparent activation energy had a greater impact on the deflagration index than the explosion pressure. The dust explosion pressure was mainly limited by oxygen in the test equipment, and its maximum value remained relatively constant. The minimum ignition temperature of dust clouds decreased with decreasing activation energy and increasing pre-exponential factor. The lower the initial oxidation weight loss temperature was, the lower the measured dust cloud minimum ignition temperature.