Ignition and explosion characteristics of micron-scale aluminum–silicon alloy powder

Aluminum–silicon (Al–Si) alloys are used in numerous applications, particularly in the automotive and electronics industries. However, because of the production of dust in the course of alloy production, the associated processes are prone to dust explosion, which can result in considerable damages. To examine the ignition and explosion characteristics of micron-scale Al–Si alloy powder, we varied the ignition energy (Ei), particle size, and dust concentration in our experiments. The effects of particle size and dust concentration on minimum ignition temperature (MIT), and Ei, particle size, and dust concentration on the explosions were studied by testing ignition and explosion parameters in a dust cloud ignition temperature testing device and a nearly spherical 20-L explosion vessel, respectively. The MIT of the Al–Si alloy powder considerably increased with increase in particle size. However, when the particle size reached a certain specific degree, the dust cloud could not be ignited. The MIT of the Al–Si alloy powder initially decreased and then increased with increase in dust concentration. In addition, a specific concentration resulted in the Al–Si alloy powder attaining the MIT, which had the highest explosion hazard. The results of the explosion test indicated that the explosion pressure (Pex) and the rate of explosion pressure rise [(dP/dt)ex] of the sample increased with increase in Ei. Similarly, the lowest Ei increased with increase in particle size; Pex of the sample alleviated as particle size increased, and Pex and (dP/dt)ex of the Al–Si alloy powder first increased and then decreased in the mass concentration range 100–900 g/m3. For four samples, the most severe explosions corresponding to the highest Pex were observed at various concentrations: 600, 700, and 800 g/m3 at an Ei of 5 kJ and 500, 600, 700, and 800 g/m3 at 9 kJ. This result indicated that the attenuation of particle size requires a reduction in the Ei, and at the same time was able to effect the decrease of the most severe explosion concentration and the minimum explosible concentrations. Thermal analysis demonstrated the accelerated oxidation stage of Al–Si alloy powder, which started at 800 °C. In addition, compared with aluminum powder of similar particle size, the continuous oxidation stage started earlier and the oxidation rate was higher. Finally, comparing Al alloy with Al powder, pure Al powder demonstrated a higher Pex in an extensive range of mass concentration, indicating its higher explosion risk.