Exercise 03 ENG

Pagina 1

Page 1 of 3 Dipartimento di Chimica, Materiali e Ingegneria Chimica “Giulio Natta” POLITECNICO di MILANO Practical class (informatic laboratory) of Chemical Processes and Technologies (Prof. Stefania Moioli) 1. Multicomponent vapour-liquid equilibrium (VLE) A flash -drum ( D-101), operated at 765 kPa, is fed with a mixture F = 1 kmol/h having the composition zF (mole fractions) as shown in the table below and a vaporization ratio V/F = 0.25. The liquid stream, taken from the bottom of the flash chamber , is laminated through the isenthalpic valve V-101 so that t he pressure downstream of it is 400 kPa and it is, then, fed to a second flash -drum ( D-102) with in which a heat exchange system is located, which uses an auxiliary fluid in order to control the operating temperature at 325 K. Assuming that both phases can be considered ideal, determine: 1. the composition (mole fractions) and the molar flow rate of the streams leaving the two flash -drums (i.e., of V, L, V’, and L’); 2. the thermal power transferred to the second flash -drum D-102. Perform a simulation of the same process by employing ASPEN HYSYS ® and compare the results obtained with the two calculation methods. Data The vapour pressure is calculated with the Antoine equation : ln( [ ]) [] ev BP mmHg A T K C=− + . Component zF A B C cPV [kJ/kmol/K] ΔHev (@TNBP) [kJ/mol] TNBP [K] TC [K] PC [atm] propane 0.071 15.7260 1872.46 -25.16 63.05 18.80 231.1 369.90 42.01 i-butane 0.215 15.5381 2032.73 -33.15 88.39 21.30 261.3 408.10 36.00 n-butane 0.357 15.6782 2154.90 -34.42 92.07 22.40 272.7 425.20 37.47 i-pentane 0.286 15.6338 2348.67 -40.05 122.00 25.43 302.6 460.35 33.34 n-pentane 0.071 15.8333 2477.07 -39.94 126.00 25.80 309.2 469.60 33.31 Page 2 of 3 2. Adiabatic flash A mixture of propane, i -butane,…