Exercise 02 ENG

Pagina 1

Chemical Processes and Technologies (Prof. Laura Pellegrini) 1. Bubble- and dew-point calculations The vapor-liquid equilibrium of a chloroform-methanol mixture can be re presented, at low pressure, by the Raoult’s law: 0()i i iPy P T x . Compute the bubble -point pressure and the dew -point pressure for a 40% chloroform mixture at 53.5°C. For the same mixture, compute the bubble-point temperature and the dew-point temperature at 1 bar. Data The vapor pressure is calculated with the Antoine equation: 0 10log ( ) BPA TC  , with T in [°C] and P in [mmHg]. Component A B C chloroform 6.95465 1170.966 226.232 methanol 8.08097 1582.271 239.726 Dipartimento di Chimica, Materiali e Ingegneria Chimica “Giulio Natta” POLITECNICO di MILANO 2. Multicomponent vapor-liquid equilibrium (VLE) A flash-drum (D-101), operating at P = 765 kPa, is fed with a mixture F = 1 kmol/h having a vaporization ratio V/F = 0.25 and a composition as shown in the table below. The vapor stream, taken from the top of the flash chamber, is depressurized through expansion in a single stage turbine ( C-101), while the liquid str eam is laminated through the is enthalpic valve V-101. The pressure downstream of the two parallel lines is balanced at the level of 400 kPa. After expansion, the liquid stream is sent to a second flash-drum (D-102) within which a heat exchange system (E-101) is loc ated, which uses an auxiliary fluid in order to con trol the operating temperature (T = 325 K). Assuming that both phases can be considered ideal, determine: 1. the compositions and flow rates of the streams coming out from the two flash-drums; 2. the thermal power transferred to the second flash-drum and the work output of the turbine, assuming an ideal isentropic expansion. F, zFi D-101 V-101 C-101 L’, xi’ E-101…