The Study Of Acoustic Agglomeration To Control The Fine Particles From Coal-Fired Power Plants

In recent years, with rapid economic growth, fine particle PM2.5 pollutions in the environment is getting worse, and has made an enormous impact on people’s living conditions. The burning of coal and other fossil fuels is one of a major particulate pollution sources. Controlling and removing of particles from coal fired power plants have become an urgent and important issues in the areas such as energy and environment. Acoustic agglomeration is a pretreatment technology installed in the front of the filter, which is easy to operate and whose effects are relatively obvious. Because of that, the acoustic agglomeration has caught more and more researchers’ attention. In view of this, the study of experiments and simulation of acoustic agglomeration of fly ash is carried out in this paper.In the experimental study, the low-frequency acoustic agglomeration experimental facility is designed and built. Different coal-fired fly ashes from power plants are used as the experiment aerosol. During experiments the range of changing parameters is sound pressure levels which is from 133 d B-146 d B, frequency from 1000Hz-2400 Hz, initial number concentration of aerosol from 1.33×105cm-3-3.55×105cm-3respectively. Experimental results show that, when the frequency is 1400 Hz, and the sound pressure level is 146 d B, the efficiency of agglomeration is the highest. With the increase of sound pressure level and initial concentration, the agglomeration effect is increasing. But taking the energy consumption problem into account, the sound pressure levels and initial concentrations should be appropriately selected.In the aspect of theory, the agglomeration mechanism of fine particles are explored and studied on numerical simulation. Firstly, the kernel function of Orthokinetic agglomeration mechanism is much higher than the others. For the fine particles whose diameter is 2.5μm or 1μm, the best frequency is both above 10 k Hz. Then, we made simulation of the acoustic agglomeration based on the improved grouping method. And it’s found that under the influence of frequency, sound pressure level and initial concentration of aerosols, the simulation results are consistent with the experimental results. In the simulations of the temperature, agglomeration effect is getting slower with the increase of temperature, especially after 300℃. Finally, in order to study the influence of different mechanisms and find the most suitable model applied in acoustic agglomeration on fine particles from coal-fired power plant, the acoustic agglomeration of different numerical models are simulated and compared with the experimental results. The results show that particle size distribution of four different models are consistent with the experimental results, slight deviation only appears in portion size. The Brown mechanism made a major role in particles whose diameter is smaller than 0.1μm, and the influence can negligible for particles whose diameter is bigger than 0.1μm.