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Aerosol particle charging by free electrons

1989; Elsevier BV; Volume: 20; Issue: 3 Linguagem: Inglês

10.1016/0021-8502(89)90007-4

1879-1964

David B. O'Hara, J. Sidney Clements, W.C. Finney, Robert H. Davis,

Atmospheric chemistry and aerosols

The strong dependence of electrostatic precipitator efficiency on particle charge has initiated a number of investigations of charge enhancement techniques. Measurements of free electron charging of aerosol particles reported here for nitrogen and argon confirm the earlier evidence (DuBard et al., J. Aerosol Sci.14, 5, 1983) that free electron charging in nitrogen produced a substantially higher particle charge than charging by ions. The measured particle charge was 2–10 times larger for free electron charging than for ionic charging depending upon the experimental conditions. The dependence of free electron charging upon the gas, electric field, particle radius, and the charging parameter N0t has been measured. Previously available charging theories do not predict the observed dependence of free electron charging on the various parameters. The importance of electric-field-enhanced electron temperatures is recognized for diffusion charging, and a new high electron temperature continuum-regime field-diffusion charging model is presented which utilizes the Boltzmann relation as an approximate solution for the electron densities near the particle. The predictions of this model are dependent upon the boundary conditions utilized at the particle surface, but are in satisfactory agreement with the data (considering the possible sensitivity of electron charging to gas impurities).