Consider an interphase mass-transfer process for the chlorine dioxide (ClO2)-air-water system at 20∘C, where ClO2 gas (solute A) is sparingly soluble in water. At the current conditions of operation, the mole fraction of ClO2 in the bulk gas phase is yA=0.040 and the mole fraction of ClO2 in the bulk liquid phase is xA=0.00040. The mass density of the liquid phase is 992.3kg/m3 and is not dependent on the very small amount of ClO2 dissolved in it. The molecular weight of water is 18g/gmole, and the molecular weight of ClO2 is 67.5 g/gmole. The total system pressure is 1.5 atm. The liquid film mass-transfer coefficient for ClO2 in water is kx=1.0 gmole/m2⋅s, and the gas film mass-transfer coefficient ClO2 in air is kG=0.010gmole/m2⋅s⋅atm. The equilibrium distribution data for the ClO2-water-air system at 20∘C are provided below:
pAxApAxA100E−022.40E−041.20E−012.81E−033.00E−027.19E−041.30E−013.06E−035.00E−021.15E−031.40E−013.28E−037.00E−021.64E−031.50E−013.52E−031.00E−012.34E−031.60E−013.78E−031.10E−012.58E−03
a. Plot out the equilibrium line in pA−cAL coordinates, and the operating point (pA,cAL). Is the process gas absorption or liquid stripping?
b. What is the equilibrium relationship as n equal to?
c. What is kL for the liquid film?
d. If the ClO2 mole fraction in the bulk gas phase is maintained at 0.040 under 1.5 am total system pressure, what is the maximum possible dissolved ClO2 concentration (gmole A/m3) in the liquid phase that could possibly exit the process-i.e., cAL∘?
e. What are the compositions at the gas-liquid interface, pA,i and cAL,i?
f. What is Ky, the overall mass-transfer coefficient based upon the overall gas-phase mole fraction driving force? There are several valid approaches for calculating Ky based on the information provided. Show at least two approaches that lead to the same result.
g. What is the mass-transfer flux NA for ClO2 in units of gmole/m2⋅s?