Dilute Solutions Henrys Law

For dilute solutions and when Henry s law applies, the equilibrium curve and the operating lines are straight lines. Overall mass-transfer coefficients are convenient in this case. The expression for the height of packing can be written as 

Hi0G = overall height of a gas-phase transfer unit (HTU) Ni0G = overall number of gas-phase transfer units (NTU) 

In equation (5.22), K is the gas-phase overall mass-transfer coefficient as defined 

Consider the ethanol absorber of Example 4.4, packed with 50-mm metal Hiflow rings. Estimate the packed height required to recover 97% of the alcohol, using pure water at a rate 50% above the minimum and with a gas-pressure drop of 300 Pa/m. The system ethanol-C02-water at the given temperature and pressure obeys Henry s 

The conditions specified correspond to those of Example 4.4, where the tower diameter (D = 0.738 m) and the volumetric mass-transfer coefficients for both phases were evaluated. The amount of ethanol absorbed is (180)(0.02)(0.97) = 3.5 kmol/h. The inlet gas molar velocity is 

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