In a wastewater treatment process, we are concerned about the possible release of the aromatic hydrocarbon benzene to the atmosphere. In the present process, 3.0 gmole/m³ of benzene (solute A, mol. weight 78 g/gmole, C₆H₆) dissolved in water is exposed to air which contains no benzene vapor in the bulk gas phase, i.e. y_A∞ ≈ 0. The mass transfer coefficients for solute A are k_G = 3.0 x 10^–3 gmole/m² s atm, and kx 2.0 gmole/m²s for the gas and liquid films respectively. The process temperature is 20 C, the total system pressure is 1.0 atm. At 20 C, the solubility of benzene vapor in water follows Henry’s law with H 4.0 m³atm/kgmole. The density of the wastewater is 1000 kg/m³.
a. What are c_AL and p_A ?
b. Draw in the operating point directly on the equilibrium diagram. Is the process gas absorption or liquid stripping? Why?
c. What is the overall mass transfer coefficient based on the overall gas phase driving force?
d. What is the flux N_A?
e. What is the partial pressure of solute A right at the gas/liquid interface?