Step 1. What is the number of overall gas transfer units NOG? Remember that the height of packing Z is given by:
where
Z = height of packing
HOG = height of an overall gas transfer unit
NOG = number of transfer units
Because HOG is given, we only need NOG to calculate Z. NOG is a function of the liquid and gas flow rates; however, it is usually available for most air pollution applications.
What is the equilibrium outlet liquid composition x1 and the outlet gas composition y2 for 90% removal? Recall that we need the inlet and outlet concentrations (mole fractions) of both streams to use the Colburn chart.
Calculate the equilibrium outlet concentration x1∗ at y1 = 0.02. According to Henry’s law, x1∗ at y1/m, the equilibrium outlet liquid composition is needed to calculate the minimum Lm/Gm:
where
x1 ∗ = outlet concentration
y1 = inlet gas mole fraction
m = Henry’s law constant
Lm = liquid molar flow rate, pound-moles per square foot-hour
Gm = gas molar flow rate, pound-moles per square foot-hour
Calculate