Entropy production in separation process distillation

Example 4.9 Entropy production in separation process Distillation Distillation columns generally operate far from their thermodynamically optimum conditions. In absorption, desorption, membrane separation, and rectification, the major irreversibility is due to mass transfer. The analysis of a sieve tray distillation column reveals that the irreversibility on the tray is mostly due to bubble-liquid interaction on the tray, and mass transfer is the largest contributor to the irreversibility. 

Nonequilibrium molecular dynamics simulations show that the assumption of local equilibrium in a column with heat and mass transfer is acceptable. The dissipation function in a binary distillation is (Ratkje et al., 1995 Sauar etal., 1997) 

At constant pressure VfiiT = V/rJ is the concentration-dependent part of the chemical potential gradient. Through the Gibbs-Duhem equation, we can relate the chemical potentials of heavy h and light 1 components in the gas phase as follows  

On the other hand, Fourier s law of heat conduction without mass transfer is 

The entropy production rate is determined with quasi-steady-state calculations. The following constant gradients in the gas phase at each stage are used  

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Example 4.9 Entropy production in separation process Distillation Distillation columns generally operate far... 

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