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Question (2) (5marks) A liquid mixture of benzene and toluene is being distilled in a fractionating column at 101.3 kPa. The feed of 100 kmol/h enters the column at a dew point (saturated vapour) and it contains 45% benzene and 55% toluene. A distillate containing 95% benzene and 5% toluene and a bottom containing 10% benzene and 90% toluene is required (specifications). If the amount of liquid fed back to the column at the top is 4 times the distillate product. Calculate: 1. The rate of distillate and the rate of bottom. (1mark) 2. Number of theoretical stages at the operating reflux. (2marks) 3. The minimum number of theoretical stages required at total reflux. (0.5marks) 4. If the actual number of stages are 10, what is: (a) The overall efficiency at operating condition. (0.5mark) (b) The overall efficiency at total reflux. (0.5mark) (c) What is the overall efficiency increased at operating condition compared to the condition of total reflux? (0.5mark) VLE Equilibrium Data Benzene-liquid mole fraction Benzene-vapour mole fraction 1 1 0.78 0.9 0.58 0.777 0.45 0.657 0.258 0.456 0.13 0.261 0 0

          Question (2)
(5marks)
A liquid mixture of benzene and toluene is being distilled in a fractionating column at 101.3 kPa. The
feed of 100 kmol/h enters the column at a dew point (saturated vapour) and it contains 45% benzene
and 55% toluene. A distillate containing 95% benzene and 5% toluene and a bottom containing 10%
benzene and 90% toluene is required (specifications). If the amount of liquid fed back to the column
at the top is 4 times the distillate product.
Calculate:
1. The rate of distillate and the rate of bottom. (1mark)
2. Number of theoretical stages at the operating reflux. (2marks)
3. The minimum number of theoretical stages required at total reflux. (0.5marks)
4. If the actual number of stages are 10, what is:
(a) The overall efficiency at operating condition. (0.5mark)
(b) The overall efficiency at total reflux. (0.5mark)
(c) What is the overall efficiency increased at operating condition compared to the condition
of total reflux? (0.5mark)
VLE Equilibrium Data
Benzene-liquid mole fraction Benzene-vapour mole fraction
1
1
0.78
0.9
0.58
0.777
0.45
0.657
0.258
0.456
0.13
0.261
0
0

$Question (2) (5marks) A liquid mixture of benzene and toluene is being distilled in a fractionating column at 101.3 kPa. The feed of 100 kmol/h enters the column at a dew point (saturated vapour) and it contains 45% benzene and 55% toluene. A distillate containing 95% benzene and 5% toluene and a bottom containing 10% benzene and 90% toluene is required (specifications). If the amount of liquid fed back to the column at the top is 4 times the distillate product. Calculate: 1. The rate of distillate and the rate of bottom. (1mark) 2. Number of theoretical stages at the operating reflux. (2marks) 3. The minimum number of theoretical stages required at total reflux. (0.5marks) 4. If the actual number of stages are 10, what is: (a) The overall efficiency at operating condition. (0.5mark) (b) The overall efficiency at total reflux. (0.5mark) (c) What is the overall efficiency increased at operating condition compared to the condition of total reflux? (0.5mark) VLE Equilibrium Data Benzene-liquid mole fraction Benzene-vapour mole fraction 1 1 0.78 0.9 0.58 0.777 0.45 0.657 0.258 0.456 0.13 0.261 0 0$

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