Alternate sources for particle movement

As indicated in the introduction (Section 4.2.3.1) of this section, many different techniques may be applied to induce irregular movement which will cause collisions and, if sufficiently high adhesion forces are present, bonding (agglomeration). In addition to rotating discs, drums, mixers of all kinds, fluidized beds, vibrating and shaking conveyors, etc., many other methods to produce turbulent, statistic particle movement are possible. 

Two such technologies shall be discussed as further examples. One represents a relatively sophisticated approach, the other an extremely low cost application. 

Micrometer and submicrometer particles can be effectively removed from aerosols if they are first converted into agglomerates with a size of, say, 5-20 fim. To accomplish this, acoustic agglomerators can be used. As described in a historic review,accelerated agglomeration of particles in sound fields is, per se, not a new idea. 

Movement of micrometer and submicrometer particles in a carrier gas can be due to Brownian movement, caused by the collision of thermally agitated gas molecules with solid particles and by convection currents or turbulence. In addition, an acoustic field would impose acoustic pressure and velocity. For a typical acoustic sound pressure of 160dB the acoustic velocity will be about 

5 m/s and a typical acoustic frequency of 2000 Hz might cause a fully entrained particle to flit back and forth 2000 times a second over a distance of about 600Particle entrainment is defined by an entrainment factor r pi 

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