Exercise 7 Text

Pagina 1

Department of Energy Politecnico di Milano Via Lambruschini 4 – 20156 MILANO Exercises of “Fundamentals of Chemical Processes” Prof. Gianpiero Groppi Exercise 7 1) Estimation of the composition of the streams at the exit of an isothermal flash unit A flash unit is maintained at a temperature of 80°C an d at a pressure of 110 kPa. A mixture of nitromethane, acetone and acetonitrile (molar composition zi reported in the table), is sent to the flash unit. Assuming ideal gases and ideal liquid mixture: 1) calculate the bubble pressure and the dew pressure of the mixture at the temperature of the unit 2) calculate the boiling temperature and the dew temperature of the mixture at the pressure of the unit 3) evaluate if a vapor-liquid equilibrium condition is reached at the temperature and pressure of the unit 4) estimate the vaporization ratio and the composition of the liquid stream and of the vapor stream that are produced in the flash unit. For each specie, A i, Bi and Ci are the parameters of Antoine’s equation for the estimation of the vapor pressure. Data Specie Ai B i Ci Acetone 0.450 14.3145 2756.220 228.060 Acetonitrile 0.350 14.8950 3413.100 250.523 Nitromethane 0.200 14.7513 3331.700 227.600     C TkPa PTC BAP SAT i i i i SAT i ln 2) Estimation of the temperature and the composition of the streams at the exit of an adiabatic flash unit A flash unit is maintained at 100 kPa pressure. A mixture of n-hexane, n-octane and n-decane, whose composition in terms of molar fractions (z i) is reported in the table, is sent to the flash unit. The mixture fed to the flash unit is at 130°C and 304 kPa. Assuming ideal gases and ideal liquid mixture, and knowing that the flash drum is adiabatic, calculate the temperature and the co mposition of the streams that exit…