Entropy Flow and Energy Efficiency Analysis of Extractive Distillation with a Heavy Entrainer

The minimization of the entropy production is equivalent to minimizing the work or energy consumption required by a separation process. Sources of entropy creation during the extractive distillation of a minimum- and maximum-boiling azeotropic mixture with a heavy entrainer are evaluated at each column stage in accordance with the second law of thermodynamics, and the distribution of entropy flow in different sections of the column is analyzed. Results show that mixing on feed trays and heat exchange in the reboiler and condenser are the main sources of entropy production. The temperature of the main feed and entrainer feed does not significantly affect the irreversibility of the process at the reference temperature of all flows. Although optimal values can be proposed to achieve a minimum isothermal work, the energy loss of the real process steadily increases with increases in the entrainer/feed flow rate ratio and reflux. The influence of the feed tray shows that product purity tends to vary inversely with energy loss.