Exercise 8 Text

Pagina 1

aINDUSTRIAL ORGANIC CHEMISTRY – EXERCISE 8 Proof test The production of styrene (St) is carried out by catalytic dehydrogenation of ethylbenzene (EB). A fresh feed (1) consisting of ethylbenzene, benzene (B) and toluene (Tol) is fed to an isothermal flash operating at 3 bar. The liquid stream (2) leaving the flash is then vaporized in HE -1 and mixed with water steam (5). The resulting stream (6) is fed to the first adiabatic reactor (R -1) where the synthesis of styrene is carried out. The stream leaving the first reactor is heat up in a furnace and fed to t he second reactor (R-2) to increase the ethylbenzene conversion. Hypothesis: • The gas mixture is ideal and consists of ideal gas. The liquid mixture is ideal and the Poynting correction is negligible • The flash (F -1) is designed to recover in the outlet liqu id stream (2) the 85% of ethylbenzene contained in stream (1) • The pressure in each unit is equal to 3 bar and pressure drops are negligible • Both reactors are adiabatic • Benzene and toluene can be considered inert in both reactors • The water steam (5) is preheated to 950 K • The stream (4) leaving HE-1 reaches a temperature of 650 K • The ratio between the molar flowrate of ethylbenzene and water steam fed to R -1 (stream (6)) is 1:10 • The reactor R-1 and R-2 operate under thermodynamic equilibrium • The overall conversion of ethylbenzene in reactor R-1 and R-2 is 40 % It is required to evaluate: 1. The dew point and bubble point of the inlet stream mixture at the flash operating pressure 2. The flash temperature and the extent of vaporization (𝛼) 3. The molar flowrate of the liquid (2) and vapor (3) streams leaving the flash 4. The molar composition of the liquid stream (2) and vapor (3) leaving the flash 5. The heat supplied to the heat exchanger…