Exercise 05 ENG Multicomponent distillation

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Dipartimento di Chimica, Materiali e Ingegneria Chimica “Giulio Natta” POLITECNICO di MILANO Practical class (informatic laboratory) of Chemical Processes and Technologies (Prof. Stefania Moioli) Multicomponent distillation A liquid mixture at its bubble point containing 4 mol% of n-pentane, 40 mol% of n-hexane, 50 mol% of n-heptane and 6 mol% of n-octane is fractionated in a standard trayed distillation column, operated under continuous, steady-state conditions and at atmospheric pressure. Adopting a reflux ratio, R, equal to 1.5·Rmin, determine the number of ideal trays required to recover 98 % of n-hexane and 1 % of n-heptane in the top product stream. Moreover, compute the thermal power required at the reboiler of the column for a feed stream with a molar flowrate equal to 100 kmol/h. Evaluate the variation of the thermal power required at the reboiler and at the condenser by varying the n-hexane recovery specification in the range 0.95-0.98. Data The vapour pressure is calculated with the Antoine equation: ln( [ ]) [] ev BP mmHg A T K C=− + . Component A B C TNBP [K] ΔHev (@TNBP) [kcal/kmol] <cPV> [kcal/(kmol∙K)] <cPL> [kcal/(kmol∙K)] Tc [K] n-pentane 15.8333 2477.07 -39.94 309.2 6160 31.02 37.614 469.6 n-hexane 15.8366 2697.55 -48.78 341.9 6896 38.86 51.700 507.4 n-heptane 15.8737 2911.32 -56.51 371.6 7576 45.15 56.120 540.2 n-octane 15.9426 3120.29 -63.63 398.8 8225 52.23 63.890 568.8