Exercise 7 Solution

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Prof. Gianpiero Groppi – Exercises – Fundamentals of Chemical Processes – A.A. 2023-2024 1 EXERCISE 7/1 Estimation of the composition of the streams exiting an isothermal flash unit A flash unit is maintained at the temperature of 80°C and at the pressure of 110 kPa. A mixture of nitromethane, acetone and acetonitrile with known composition is sent to the flash unit. Assuming ideal gases and ideal liquid mixture with negligible Poynting correction, calculate: 1) The bubble and dew temperature of the inlet mixture at the pressure of the flash 2) The bubble and dew pressure of the inlet mixture at the temperature of the flash 3) The vaporization ratio and the composition of the liquid stream and of the vapor stream that are produced in the flash unit. DATA zi Ai Bi 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 ln𝑝𝑖 𝑆𝐴𝑇 =𝐴𝑖− 𝐵𝑖 𝑇+𝐶𝑖 P in kPa, T in °C Prof. Gianpiero Groppi – Exercises – Fundamentals of Chemical Processes – A.A. 2023-2024 2 EXERCISE 7/2 Estimation of temperature and composition of the streams at the exit of an adiabatic flash unit A flash unit is maintained at the pressure of 100 kPa. A mixture of n -hexane, n-octane, and n- decane with molar composition zi assigned, is fed to the flash unit. The mixture fed to the flash unit is at 130°C and 304 kPa. Assuming ideal gases and ideal liqu id mixture with negligible Poynting correction, and knowing that the flash unit is adiabatic, calculate the temperature and composition of the streams exiting the unit. DATA Composition Ai Bi Ci Antoine law: ln𝑝𝑖 0=𝐴𝑖− 𝐵𝑖 𝑇+𝐶𝑖 P in kPa, T in °C n-hexane 0.300 13.8193 2696.040 224.317 n-octane 0.350 13.9346 3123.130 209.635 n-decane 0.350 13.9748 3442.760 193.858 Thermodynamic properties CPliq…