Distillation.pptx

SINGLE STAGE DISTILLATION CHE134P/CPMONTEROLA

TYPES OF DISTILLATION •

•

•

•

•

1. simple batch/differential distillation 2. Flash Distillation 3. simple continuous 4. steam distillation 5. fractional distillation

TYPES OF DISTILLATION •

•

•

•

•

1. simple batch/differential distillation 2. Flash Distillation 3. simple continuous 4. steam distillation 5. fractional distillation

SIMPLE BATCH OR DIFFERENTIAL DISTILLATION

RAYLEIGH EQUATION



 

=αABln

 (1−)

(1−)

F is the Feed  xF is the concentration of more volatile component in the feed W is the Residue  xW is the concentration of the more volatile component in the residue αAB is the relative volatility of A with respect to B

SAMPLE PROBLEM 1 A solution containing 35% by weight toluene and 65% by weight benzene is subjected to a simple batch distillation at atmospheric pressure. For this purpose, assume relative volatility is equal to 3. If the distillation is discontinued when the weight of the distillate amounts to 45% of the charge, calculate the amount of benzene in the distillate as % benzene in the charge. a. 85.93

b. 45.17

c. 72.16

d. 56.26

SAMPLE PROBLEM 2 A 537 kg solution containing 50% by weight heptane and 50% by weight octane is batch distilled until only 4.74 lbmoles remain in the pot. If the relative volatility of the mixture is 2.0, what will be the distillate composition in terms of mole fraction heptane? A. 0.5327

B. 0.4673

C. 0.3889

D. 0.6398

SAMPLE PROBLEM 3 A 100 kgmol liquid mixture containing 45% A and 55% B by mole is differentially distilled until 40 kgmole of A is vaporized. If the relative volatility of A with respect to B is equal to 1, what is the mole fraction of A in the remaining liquid? A. 0.45 B. 0.55

C. 0.38 D. 0.63

EXERCISE 1 A batch differential distillation is made upon a 25 kg mixture of ethanol-water containing 7% weight alcohol. How many kg of distillate must be collected so that it will have an ethanol content of 30% weight? Assume that the relative volatility of the mixture to be equal to 12. A. 5

B. 7

C. 9

D.12

EXERCISE 2 500 moles of a liquid mixture are charged to a distillation unit. This liquid mixture contains 0.25 mole fraction of component A and 0.75 mole fraction of component B. If the mixture is subjected to a simple batch distillation, what will be the liquid/residue composition after 100 moles of component A has been removed with the vapors? Assume the relative volatility of component a with respect to B is 3.15. A. 0.25

B. 0.15

C. 0.10

D. 0.05

EXERCISE 3 A mixture containing 0.65 mole fraction A and 0.35 mole fraction B is subjected to a simple batch distillation until the instantaneous composition of the vapors leaving becomes 0.55 mole fraction A. If the relative volatility for the mixture is constant at 2.5, estimate the average composition of the total distillate collected. A is more volatile than B. A. 0.65

B. 0.74 C. 0.81 D. 0.93

SAMPLE PROBLEM The temperature of a simple batch distillation is maintain at 90°C, the vapor pressure of pure methylbenzene is 53.3 kPa and that of pure 1,2-dimethylbenzene is 20 kPa. What is the composition of the bottoms when the pressure is 0.5 atm? What is the composition of the distillate produced?

SIMPLE CONTINUOUS DISTILLATION

SIMPLE CONTINUOUS DISTILLATION

Relative volatility ,α AB

MRII PROBLEM •

One hundred moles per hour of solution containing 80 moles of A, the rest is B subjected to simple continuous distillation. The distillate contains 72 moles of A. If A is 5 times more volatile than B, concentration of A in the distillate is_____.

A. 0.85 these

b. 0.80

c. 0.533

d. none of

STEAM DISTILLATION

STEAM DISTILLATION

SAMPLE PROBLEM 1 If naphthalene were to be steam distilled at 200°C and 1 atm, how many moles of steam would be needed per mole of naphthalene? Assume the vapor pressure of naphthalene at 200°C to be equal to 475 mm Hg. A. 0.0844 B. 0.60 C. 0.80 D. 0.4482

SAMPLE PROBLEM 2 Glycerin is steam distilled at 190°C under 26-in vacuum. A test shows a steam consumption of 1.0 pound per pound of glycerin distilled. What percent excess steam , referred to that theoretically needed, is actually used? Vapor pressure of glycerin at 190°C is 29 mm Hg. A. 110 B. 100 C. 85 D. 170

SAMPLE PROBLEM 3 A totally immiscible liquid system composed of water and an organic liquid boils at 90°C when the barometer reads 734 mm Hg. The distillate contains 73% by weight of the organic liquid. What is the molecular weight of the organic liquid? A. 112 B. 123 C. 132 D. 100

SAMPLE PROBLEM 4 If steam is blown into the still containing a mixture of water and chlorobenzene and the total pressure is 130 mm Hg. Estimate the temperature of boiling and the composition of the distillate. The two components are immiscible in the liquid. Vapor pressures of chlorobenzene and water are given below: Pressure, mm Hg

100

50

30

26

Temperature °C, Chlorobenzene

70.4

53.7

42.7

34.5

Temperature °C, Water 

51.7

38.5

29.9

22.5

EXERCISE 1 Calculate the weight of water required to steam distill 500 mg of bromobenzene at 95C. The vapor pressure of water at this temperature is 640 Torr, bromobenzene, 120 Torr. Bromine is 79.9.

EXERCISE 2 A mixture contains 100 kg of water and 100 kg of ethylaniline ( mol wt. = 121.1kg/kg mol), which is immiscible with water. To purify ethylaniline, it is steam distilled by bubbling saturated steam into the mixture at a total pressure of 101.32 kPa. Determine the boiling point of the mixture and the composition of the vapor. The vapor pressure of each of the pure compounds is as follows: K

°C

Pwater (kPa)

Pethylanilin e(kPa)

353.8

80.6

48.5

1.33

369.2

96.0

87.7

2.67

372.3

99.15

98.3

3.04

RAYLEIGH EQUATION 2



ln = 

   −

SAMPLE PROBLEM: RAYLEIGH EQUATION DIFFERENTIAL DISTILLATION A mixture of 100 mol containing 50 mol% n-pentane and 50 mol% n-heptane is distilled under differential conditions at 101.3 kPa until 40 mol is distilled. What is the average composition of the total vapor distilled and the composition of the liquid left? The equilibrium data are as follows, where x and y are mole fractions of n-pentane: X

Y

X

Y

X

Y

1.0

1.0

0.398

0.836

0.059

0.271

0.867

0.984

0.254

0.701

0

0

0.594

0.925

0.145

0.521

11.3-2 GEANKOPLIS EXERCISE 3 A mixture containing 70 mol% benzene and 30 mol% toluene is distilled under differential conditions at 101.32 kPa. A total of one-third of the moles in the feed is vaporized. Calculate the average composition of the distillate and the composition of the remaining liquid. Use the data below: X

Y

X

Y

X

Y

1.0

1.00

0.411

0.632

0

0

0.780

0.9

0.258

0.456

0.581

0.777

0.130

0.261

OLD BOARD PROBLEM •

•

A solvent-water mixture is to be distilled at 95˚C. The vapor pressure of the solvent at this temperature is 130 mmHg and that of water is 640 mmHg. The solvent is immiscible in water and has a molecular weight of 150. The weight of the solvent in kg that will be carried over in the distillate with 200 kg of water is A. 358.73

B. 423.57 C. 338.54

D. 524.63

FRACTIONAL DISTILLATION

FRACTIONAL DISTILLATION

RECTIFYING SECTION

Operating line equation

LIQUID-VAPOR EQUILIBRIUM CURVE

RECTIFYING SECTION MCCABE-THIELE METHOD

Slope = L/V Yint = DXd/V

PERRY PAGE 13-18

REFLUX RATIO, R PERRY PAGE 13-19

STRIPPING SECTION

Operating line

STRIPPING SECTION (MCCABE-THIELE METHOD)

Slope = L’ /V’ Yint = -BXb/V’

PERRY PAGE 13-19

FEED SECTION

UALITY OF FEED (PERRY PAGE 13-19)

FEED SECTION (MCCABE-THIELE)