A packed column is designed to absorb ammonia from a gas stream. Given the operating
conditions and type of packing (see below), calculate the height of packing and column diameter(USEPA-84/09, p. 106).
Given
Gas mass flow rate = 5000 lb/h
NH3 concentration in inlet gas stream = 2.0 mol%
Scrubbing liquid = pure water
Packing type = 1-in. Raschig rings
Packing factor, F = 160
HOG of the column = 2.5 ft
Henry’s law constant m = 1.20
Density of gas (air) = 0.075 lb/ft3
Density of water = 62.4 lb/ft3
Viscosity of water = 1.8 cp
Generalized flooding and pressure drop correction graph (USEPA-84/09, p. 107)
Figure 10.2: graphical representation of the packed column
The unit operates at 60% of the flooding gas mass velocity; the actual liquid flow rate is 25% more than the minimum and 90% of the ammonia must be collected to meet state regulations. Figure 10.2