Study on the Influence of Water Spray on the Agglomeration Characteristics of Coal Dust under Acoustic Wave Perturbation

To investigate the aggregation mechanism of coal dust in water spray influenced by acoustic wave perturbation, based on the theory of acoustic agglomeration, a self-developed acoustic excitation platform was used to excite the wetted coal dust through the independently constructed simulation platform for dust reduction by water spray under acoustic wave perturbation and scanning electron microscope experiments to study the influence of different acoustic wave parameters on the diffusion and distribution law of coal dust particles, analyze the influence of liquid droplets on the agglomeration effect of coal dust particles under the acoustic wave disturbance, and reveal the mechanism of water spraying to increase the efficiency of dust reduction under the acoustic wave disturbance. The results showed that when acoustic wave and water spray synergistic dust reduction, with the increase of sound pressure level (SPL), the dust concentration was decreasing in an exponential function trend; with the increase of acoustic frequency, the dust concentration was decreasing and then increasing in a parabolic trend, and the dust reduction effect was optimal when f=1,300 Hz and SPL=120 dB. Compared with the dust reduction effect of water spray alone, the average dust reduction efficiency of total dust and respiratory dust increased by 10.05% and 28.95%, respectively, and the dust reduction efficiency of respiratory dust was more prominent. The microscopic morphology of coal dust showed that the volume of coal dust agglomerates increased with the enhancement of SPL, and the best agglomeration effect was achieved at 1,300 Hz acoustic frequency. Acoustic waves promote the diffusion and distribution of coal dust and effectively enhance the collision frequency between droplets and coal dust. Meanwhile, the pressure wave generated when the acoustic wave propagated will deform the droplets, increased their surface area and surface energy, which can adsorb more small particles, promote the wetting and agglomeration of coal dust, and improved the efficiency of dust reduction.