The effects of an acoustic field on the enhancement of coal combustion are investigated. A flat flame burner using methane-air mixtures as the fuel is used for the experiments. Micronized coal particles 20–70 μm in diameter are injected into the burning gas stream at the same velocity as the gas. The light intensity emitted from the flame, temperature and pictures of the flame with and without an acoustic field are recorded. The nominal values of the intensity of the acoustic field are between 140–160 dB and the frequency is between 500–3500 Hz. A definite increase in the rate of combustion of the coal particles is observed with the application of an acoustic field. The enhancement can be seen from the increased light intensity of the flame and the flame width. This paper presents the data and a discussion of light intensity emitted by the flame as a function of acoustic parameters.
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.
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