Geoscience Reference
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Solution: Calculate the collection efficiency based on the design data given by the vendor. The con-
tact power theory is an empirical approach relating particulate collection efficiency and pressure
drop in wet scrubber systems. It assumes that particulate collection efficiency is a sole function of
the total pressure loss for the unit.
P T = P G + P L
P G = 0.157∆ p
P L = 0.583 p L ( Q L / Q G )
where
P T = Total pressure loss (hp/1000 acfm).
P G = Contacting power based on gas stream energy input (hp/1000 acfm).
P L = Contacting power based on liquid stream energy input (hp/1000 acfm).
p = Pressure drop across the scrubber (in. H 2 O).
p L = Liquid inlet pressure (psi).
Q L = Liquid feed rate (gal/min).
Q G = Gas flow rate (ft 3 /min).
The scrubber collection efficiency is also expressed as the number of transfer units:
N t = α( P T ) β = ln[l/(l - η)]
where
N t = Number of transfer units.
α and β = Characteristic parameters for the type of particulates being collected.
P T = Total pressure loss (hp/1000 acfm).
η = Fractional collection efficiency.
Calculate the total pressure loss ( P T ). To calculate the total pressure loss, we need the contacting
power for both the gas stream energy input and liquid stream energy input. Calculate the contacting
power based on the gas stream energy input ( P G ) in hp/1000 acfm. Because the vendor gives the
pressure drop across the scrubber, we can calculate P G :
P G = 0.157∆ p = (0.157 × 5.0) = 0.785 hp/1000 acfm
Calculate the contacting power based on the liquid stream energy input ( P L ) in hp/1000 acfm.
Because the liquid inlet pressure and liquid-to-gas ratio are given, we can calculate P L :
P L = 0.583 p L ( Q L / Q G ) = 0.583 × 80 × (50/10,000) = 0.233 hp/1000 acfm
Calculate the total pressure loss ( P T ) in hp/1000 acfm:
P T = P G + P L = 0.785 + 0.233 = 1.018 hp/1000 acfm
Calculate the number of transfer units N t :
N t = α( P T ) β
The values of α and β for a lime kiln operation are 1.47 and 1.05, respectively. These coefficients
have been previously obtained from field test data. Therefore,
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