Question

A liq mixture of benzene-toluene is to be distilled in a fractionating tower at 101.3 kPa pressure. The feed of 100 kg mol/h is liquid and it contains 45 mole % benzene and 55 mole % toluene and enters at 327.6 K (130 ◦F). A distillate containing 95 mole % benzene and 5 mole % toluene and a bottoms containing 10 mole % benzene and 90 mole % toluene are to be obtained. The average heat capacity of the feed is 159 kJ/ kg mol – K and the average latent heat 32099 kJ/ kg mol.

Calculate the following: (a) Minimum reflux ratio R_m· (b) Minimum number of theoretical plates at total reflux by using the graphical McCabe-Thiele Method. (c) Minimum number of theoretical plates at total reflux by using the Fenske eq.

The equilibrium and the vapor - pressure data are given below for the system benzene-toluene. Make a list of all the important assumptions you are making in your calculations. Note: All plots must be done either by using Excel or on a graph paper.

Mole % Benzene at 101.325 kPa
x	y
1	1
0.78	0.9
0.581	0.777
0.411	0.632
0.258	0.456
0.13	0.261
0	0

		Vapor Pressure
		Benzene		Toluene
T(K)	T(°C)	kPa	mm Hg	kPa	mm Hg
353	80.1	101.3	760
358	85	116.9	877	46	345
363	90	135.5	1016	54	405
368	95	155.7	1168	63.3	475
373	100	179.2	1344	74.3	557
378	105	204.2	1532	86.0	645

Answer 1