Faculty of Chemical Engineering CPE553 Chemical Engineering Thermodynamics

Semester March-July 2013 28 March 2013

ASSIGNMENT 1 Group assignment 2 or 3 persons per group 1. A process stream contains light species 1 and heavy species 2. A relatively pure liquid stream

containing mostly species 2 is desired, obtained by a single-stage liquid/vapor separation. The equilibrium compositions are x1 = 0.002 and y1 = 0.950. Determine T(K) and P(bar) for the separator. Assume that modified Raoults law applies. Use data given below. The calculated P should validate this assumption. For the liquid phase,

2 21 2 2 1ln 0.93 ln 0.93x x

1 1 2 2

ln

10.08, 2572, 11.63, 6254

sat ii i

BP bar A

T K

A B A B

2. A binary system acetone(1)/ acetonitrile(2) consists of liquid and vapor in equilibrium. The liquid

mixture of this system to a good approximation,

2 21 2 2 1ln ln 2.573 0.00126Ax Ax where A T

a) Determine the temperature and vapor phase compositions that is in equilibrium with liquid containing 20 mole% acetone at pressure of 100 kPa.

b) Determine the temperature and liquid phase compositions that is in equilibrium with vapor containing 65 mole% acetonitrile at pressure of 100 kPa.

c) Sketch T-x1-y1 diagram for condition a) and b).

(Show calculation in details. Calculate pressure and temperature to two decimal places; A, and mole fraction to four decimal places).

3. Assuming Raoults law to be valid, prepare a P-x1-y1 diagram for a temperature of 338.15K for ethanol(1)/toluene(2) system by using Microsoft Excel. (Attach the calculation values in Microsoft Excel. Show a sample of calculation for pressure and vapor phase compositions at x1 = 0.3). Determine the following points from the diagram and show their values: a) Saturation pressure of ethanol and toluene at 338.15 K. b) Pressure and vapor phase composition of ethanol that is in equilibrium with liquid

containing 52 mole % toluene at 338.15 K. c) Pressure and liquid phase composition of toluene that is in equilibrium with vapor

containing 66 mole % ethanol at 338.15 K.

d) Liquid and vapor phase composition of ethanol that is in equilibrium at temperature 338.15 K and pressure 40 kPa.

4. A stream from reactor consists of 388 kmol/h methane, 388 kmol/h propane and 55 kmol/h cyclohexane. This stream is fed into a partial condenser maintained at a pressure of 17 bar, where its temperature is brought to 30C (303.15 K). Assuming the validity of Raoults law, determine the flow rate of vapor and its compositions at the exit of the condenser.

Faculty of Chemical Engineering CPE553 Chemical Engineering Thermodynamics

Semester March-July 2013 28 March 2013

5. An equimolar stream containing ethanol(1) and methanol(2) is fed to a flash separator operating at 75oC (348.15 K). The liquid produced at the exit stream is 40% of the feed on one mole basis. By assuming Raoults law, a) Determine the pressure at which this separator should be operated.

[Hint the pressure is between 112 kPa and 115 kPa] b) Determine the composition of liquid and vapor phases at the exit stream. c) Sketch P-x1-y1 diagram showing the points in a) and b).

Date of submission: 10th April 2013 before 5 pm