Exercise 03 ENG

Pagina 1

Chemical Processes and Technologies (Prof. Laura Pellegrini) Adiabatic flash A mixture of propane, i -butane, n -butane and n -pentane at the temperature of 20°C is expanded through a valve from its bubble pressure to 1.2 bar and it is then fed to a flush-drum. Determine: 1. the pressure of the mixture before the valve; 2. the temperature of the flash-drum; 3. the degree of vaporization, α; 4. the composition of the vapor and of the liquid streams leaving the flash-drum, considering that the operation is adiabatic. Check the validity of the obtained values by solving the problem in the simulation mode, namely giving the temper ature and pressure of the flash -drum and determining the flow rates and compositions of the outlet streams. T he Peng-Robinson Equation of State (PR EoS) can be applied to both vapor and liquid phases for the calculation of vapor-liquid equilibria. T, P F, zFi V, yi L, xi zF A B C CpV [kJ/kmol/K] ΔHev,NBP [kJ/mol] TNB [K] TC [K] PC [atm] ω C3 0.25 15.726 1872.46 -25.16 63.05 18.8 231.1 369.9 42.01 0.1524 i-C4 0.15 15.5381 2032.73 -33.15 88.39 21.3 261.3 408.1 36 0.18479 n-C4 0.32 15.6782 2154.9 -34.42 92.07 22.4 272.7 425.2 37.47 0.20100 n-C5 0.28 15.8333 2477.07 -39.94 126 25.8 309.2 469.6 33.31 0.25389 0ln( ) BPA TC  , with T in [K] and P° in [mmHg]. Dipartimento di Chimica, Materiali e Ingegneria Chimica “Giulio Natta” POLITECNICO di MILANO Peng-Robinson Equation of State      22 3 2 2 2 3 2 2 2 2 1/2 1 2 ( 1 ) ( 2 3 ) 0 0.37464 1.54226 0.26992 11 0.45724( ) 0.07780 or i i i i i i i i i i R Ci i C C i C NC L i i i RT aP v b v bv b Z B Z A B B Z AB B B S k S T RT ka P RTb P a x a                              2 1/2 1 11 2 or or () NC V i i i NC NC L i i V i i ii L L a y a b x b b y b aPA RT  …