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where:

0 to dg, a dg = the geometric median diameter irg = the geometric standard deviation x = any particle diameter of interest.

Thus, the right side of Equation 5.18(6) gives on integration the fraction of particles whose diameters are less than or equal to x. Integrating between limits of x = 0 to ro gives a result of 1, and between limits of x result of 0.5.

Two particle size distributions must be considered in scrubber design. Besides the size distribution of the dust to be collected, the grade efficiency must also be considered when the collector operates under specific conditions. As previously discussed, according to Calvert et al. (1972), the grade efficiency can be effectively represented by the aerodynamic cut diameter dac. If da ficiency of 50% is estimated; if dad collection efficiency is 84%. Hence, for any level of effi ciency and a log-normal aerosol, the use of Equation 5.18(6) determines the equivalent dac.

Figure 5.18.15 represents an integrated form of Equation 5.18(6) which gives any collection efficiency (50% or greater) as a function of the ratio dac/dg with ig as a parameter. Thus, for example, if a collection efficiency of 99% is needed for a log-normal, unit-density aerosol with dg = 5.0 /m and ig = 2, Figure 5.18.15 shows that a multiplication factor of about 0.2 is indicated. The required dac is then 5 X 0.2 = 1 /m.

= dg, a collection ef-dg/og, the estimated

0 0

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