1 CHEM-E7130 Process Modeling Exercise Multicomponent mass transfer

2 Solution of a two-film model Given: bulk compositions thermodynamic properties (equilibrium model, diffusion coefficients, etc.) Unknown: mole fractions at the interface, total flux N t

3 Solution of a two-film model xbxb xIxI y I =Kx I ybyb mass transfer direction 1. Guess interfacial compositions x I and total flux N t 2. calculate gas phase interfacial compositions 3. calculate mass transfer rate factor for both phases

4 Solution of a two-film model xbxb xIxI y I =Kx I ybyb mass transfer direction 4. calculate diffusion fluxes 5. and mass transfer fluxes

5 Solution of a two-film model xbxb xIxI y I =Kx I ybyb mass transfer direction n-1 independent equations 1 equation n+1 unknowns and n+1 equations!

6 Some common assumptions Linearized mass transfer theory was already used (constant D and c t ) K values and [D] are calculated with bulk compositions Thermodynamic correction neglected Mass transfer coefficient matrix from binary coefficients, or by matrix approximations

7 Let’s take a look at the Excel sheet, where two-film mass transfer is solved with MS approach