In the distillation of a benzene/toluene mixture, a vapor richer in the more volatile component benzene is produced from the benzene/toluene liquid solution. Benzene is transferred from the liquid to the vapor phase, and the less volatile toluene is transferred in the opposite direction, as shown in the figure below. At the system temperature and pressure, the latent 

heats of vaporization of benzene (A) and toluene (B) are 30 and 33 kJ/gmole, respectively. Both components are diffusing through a gas film of thickness δ. Develop the final, integrated form of Fick€™s flux equation to predict the steady-state mass transfer of benzene through the gas film. The equation must include terms for the bulk gas-phase mole fraction of benzene, the gas-phase mole fraction of benzene in equilibrium with the liquid solution, the diffusion coefficient of benzene in toluene, the diffusion path δ, and the total molar gas concentration, and the latent heats of vaporization for benzene (ΔH_v,A) and toluene (ΔH_v,B). Assume that distillation is an adiabatic process.

Transcribed Image Text:

Benzene (A) / toluene (B) bulk vapor Gas film (5) NA vaporization Adiabatic wall NB condensation Saturated liquid mixture of A + B