Acoustic agglomeration is proposed as an intermediate treatment in the flue gas cleanup train of the effluents from coal burning power plants. Acoustic agglomeration causes the micron and submicron sized particles to collide, adhere and form large particles which can be more efficiently removed from the flue gases with particle removal devices. This paper describes the results of acoustic agglomeration tests of coal fly-ash aerosols in a 200-mm dia device at acoustic levels from 140 to 160 dB, frequencies in the 2–3 kHz range and mass loadings in the 1 to 30 g/m3 range with initial log-normal particle size distributions having geometric mean diameters of about 5 micrometers. The primary thrust of the paper is to present a numerical simulation model of the acoustic agglomeration process. The model is based on the recently proven assumption of complete fillup of the agglomeration volume and neglects the effects of gravitational settling, Brownian motion, and acoustically generated turbulence. Good agreement is found between the model predictions and the experimental data.
Acoustic agglomeration (AA) is an intermediate treatment of aerosols containing submicron- and micron-sized particles so that conventional cleaning devices such as electrostatic precipitators, bag houses, and scrubbers can remove these fine particles more efficiently. The high-intensity acoustic field in the AA causes local velocity fluctuations to move the particles relative to one another, collide, adhere, and grow. This paper addresses the question of whether such highly intense acoustic fields (approximately 160 dB) will cause random velocity fluctuations of such a magnitude that this acoustic ‘‘turbulence’’ significantly affects AA. The experimental study results show that only the acoustic velocity fluctuations at the excitation frequency dominate the local velocity and therefore the particle motions. Although some acoustically generated random motion is noted with increasing acoustic intensity above 160-dB sound pressure level, the energy in turbulent fluctuations is about three orders of magnitude lower than the energy in acoustic frequency and harmonics. The paper concludes that acoustically induced turbulence does not play a significant role in AA.
In the advanced glass melter glass batch materials are entrained in gas and then rapidly heated to glass formation temperature by combusting the gas. The glass batch separates on a target where glass formation takes place. A numerical model has been developed to simulate this glass formation process, which differs from the conventional glass formation process because the batch materials are mixed at glass formation temperatures and because the calcination of Na,CO,, CaC03, and MgC03 occurs on the surface of the glass layer, not in the bulk material. The numerical model is based on diffusion-controlled dissolution of sand particles in the liquid glass. Preliminary experimental data support the rapid glass formation rates predicted by the numerical model.
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