Chemical Engineering - Industrial Organic Chemistry

Full exam

INDUSTRIAL ORGANIC CHEMISTRY September 15 th, 2016 SURNAME : __________________ NAME : __________________ ID NUMBER : ________________ A mixture of hydrogen, n -hexane , n -octane , n -decane (0.3, 0. 2, 0. 4,0.1 v/v), initially at 270 °C and 20 bar, is fed to an isothermal flash unit, where thermodynamic equilibrium conditions are reached. The flash is operated at 8 bar . The extent of vaporization is equal to 0. 35 . The vapor phase can be described as an ideal mixture of ideal gases and the liquid mixture is ideal. The Poynting correction is assumed to be negligible. Hydrogen can be assume d as incondensable. 1) Evaluate the dew te mperature of the feeding mixture Dew tem perature 2) Evaluate operating temperature of the flash unit Flash temperature 3) Calculate amount and composition of the vapor and liquid streams leaving the flash unit. hydrogen n-hexane n-octane n-decane Liquid composition Vapor composition 4) Evaluate the thermal duty of the flash (assume positive heat entering in the system): Thermal duty : Antoine’s equation (P VAP in bar, T in K) Ai Bi Ci hydrogen - - - log 10 ������������������� = �������− ������� ������+ ������� n-hexane 4.00266 1171.530 -48.784 n-octane 4.04867 1355.126 -63.633 n-decane 4.07857 1501.268 -78.670 Thermodynamic properties : �������,������������� [J/mol/K] �������,������������� [J/mol/K] ∆������������������������������ [J/mol] hydrogen - 29.2 - n-hexane 195.6 143.3 31573 n-octane 255.7 175.9 41495 n-decane 313.3 233.1 51392 The heat capacities for the vapor and gas phase are constant as well as the heat of vaporization (evaluated at the feed temperature).