Preliminary experimental study of acoustic agglomeration of coal-fired fine particles

摘要

Respirable particulate matter, especially fine particles are doing great harm to human health and the environment nowadays, but the removal efficiency of traditional dust removal devices for PM_(2.5) is quite low. Acoustic agglomeration is a pretreatment technology of dust removal which uses sound wave with high intensity to make fine particles get agglomerate and grow up, and improves the efficiency of traditional dust removal devices for PM_(2.5) and thus reduces the concentration of fine particle emissions. In this paper, the experimental set-up of acoustic agglomeration is designed and reconstructed. Coal-fired ashes are mixed with air to simulate aerosol emissions from coal-fired power plants. A travelling wave acoustic field is generated in a vertical agglomeration chamber in which the residence time of the aerosol is around 4s.Preliminary experimental study of the influence of acoustic frequency, SPL and the initial concentration of aerosol on the acoustic agglomeration is conducted. It is found that the efficiency of agglomeration is very sensitive to the change of acoustic frequency and there exists an optimal frequency which in this paper is 1400Hz. The effect of acoustic agglomeration has a linear relationship with SPL and it is enhanced with the increase of SPL. The increase of the initial number concentration of aerosol can also enhance the agglomeration effect, but the rate of the increase of the agglomeration effect decreases while the initial concentration is getting bigger. When the acoustic frequency is 1400Hz, the SPL is 142dB and the initial concentration is 4.04x10~5cm~(-3), the number concentration of aerosol can be reduced to 35% of the initial value.