D E T E R M I N AT I O N O F T H E O R E T I C A L S TA G E S A N D T H E O V E R A L L E F F I C I E N C Y I N A

D I S T I L L AT I O N C O L U M N I N F U N C T I O N O F M I X T U R E C O M P O S I T I O N S , F E E D P O S I T I O N , R E F L U X R AT I O , F E E D F L O W

R AT E A N D P O W E R

W i g b e r t o R e y e s 6 6 3 3 9L u z M . S u á r e z 5 1 6 4 1

S u h e i l y R i v e r a 5 3 9 2 3 L i á n Y. M o r a l e s 5 2 3 5 6

Polytechnic University of Puerto Rico Chemical Engineering Department

CHE 5113-26

Agenda

ObjectivesTheoryEquipment

Schematic Diagram of ApparatusProcedureDataCalculationsSafety

Objectives

Determinate the variation with boil-up rate of pressure drop over the distillation column.

To use a Density Meter to determine mixture compositions.

Determination of the overall column efficiency.

Carry out a distillation at constant reflux ratio, varying top and bottom compositions with time.

Investigate the steady state distillation of a binary mixture under continuous operation.

Investigate the effect of varying the feed position under continuous operation.

Theory

Distillation is a process in which a liquid or vapour mixture of

two or more substances is separated into its component fractions

of desired purity, by the application and removal of heat

Theory

Types of Distillation Process

Flash Vaporization - is a single-stage

operation where in a liquid mixture is

partially vaporized, the vapor is allowed to

come to equilibrium with the residual

liquid, and the resulting vapor and liquid

phases are separated and removed from

the apparatus. It may be batch or

continuous.

Theory

Types of Distillation Process

Differential Distillation - a feed mixture

of a given composition is placed in a

single stage separator and heated to

boiling. The vapor is collected and

condensed to a distillate. The

composition of the remaining liquid

and the distillate are functions of time.

Theory

Types of Distillation Process Continuous Rectification: Binary Systems - is a multistage,

countercurrent distillation operation. For a binary solution it is

possible by this method to separate the solution into its components,

recovering each in any state of purity desired.

Theory

Mc-Cabe-Thiele Method for trayed towers. Estimates:

The number of equilibrium stages

The amount of reflux required

Assumptions: The two components have equal and constant molar latent heats of vaporization.

Sensible enthalpy changes and heat of mixing are negligible compared to latent heats of

vaporization.

Heat losses are negligible.

The pressure is uniform throughout the column (negligible pressure drop).

Theory

Mc-Cabe-Thiele Method for trayed towers.

Theory

Rectifying Section The material balance is:

(1)

(2)

For constant molar overflow:

Then:(3)

*Equation 3 is the operation line for the rectification section

Theory

Rectifying Section Reflux Ratio – is the liquid entering the top stage, Lo, and its ratio to the

distillate rate.

if L0 is constant:

Since:

(8)

(5)

(4)

(6)

(7)

Theory

Rectifying Section Combining equations 3, 7 and 8:

y (9)

*Equation 9 is the most useful form of the operation line for the rectification section

Theory

Stripping Section The material balance is:

(10)

(11)

*Equation 11 is the operation line for the stripping section

Theory

Stripping Section Boil-up ratio – is the vapor rate leaving the reboiler and its ratio to the

bottoms product rate. (12)

Since:

(13)

(14)

Theory

Stripping Section Combining equations 11, 12 and 14:

(15)

*Equation 15 is the operation line for the stripping section

Theory

The point of intersection of the two operating lines will help locate the exhausting-section operating line. Subtracting equations of operating lines of stripping and rectifying sections

will give:

The locus of intersection of operating lines(the q-line) is given by:

(16)

(17)

Theory

q-line

Equilibrium DataFigure of Equilibrium Line for Ethanol/Water Mixture

Theory

Theory

To calculate the number of theoretical plates for a given separation at total reflux, Fenske developed the following formula:

(18)

Where:

n = number of theoretical plates

xA = mole fraction of more volatile component

xB = mole fraction of least volatile component

αABav = average relative volatility

(19)

Subscripts d, b indicate distillate and bottom respectively

Theory

The efficiency is given by:

(20)

Equipment

Diagram of UOP3CC Console

Schematic Diagram of Apparatus

Procedure

Perform the tower at total reflux. Prepares the batch Pump is calibrated

Adjust the power for start evaluating the pressure drop and the boil up rate. Will work at different power Reading was taken of the pressure drop Reading was taken of the boil up rate Only for 0.5 KW sample was taken of xB and xD.

Procedure

For continuous distillation Varying the reflux rate

RR=5:1 RR=9:3

Varying the power Power = 0.5 KW Power =0.9 KW

Varying the feed position Feed Position; middle Feed Position; bottom

Varying the flow rate Flow rate = 1.0 L/h Flow rate = 2.0 L/h

Varying the feed composition Feed composition; 0.5 ethanol and 0.5 water Feed composition; 0.7 ethanol and 0.3 water

Data

Calibration of the pump Variation of Column Pressure Drop

@Total Reflux

Setting Volume (mL)

Time (s)

20406080

Power(KW)

Volume(mL)

Time(s)

Pressure Drop

(mm H2O)

Degree of Foaming On Trays

0.50

0.75

1.00

1.25

1.50

1.75

Data

RR Power(KW)

Feed Position

Flow Rate

(L/hr)

xf xd xb Volume(mL)

Time(s)

∆P(mm H2O)

T1-T14

Total Reflux

0.50 _____ _____ ___

RR Power(KW)

Feed Position

Flow Rate

(L/hr)

xf xd xb Volume(mL)

Time(s)

∆P(mm H2O)

T1-T14

5:1 0.50 Middle 2.0 0.5

9:3 0.50 Middle 2.0 0.5

@Total Reflux

Variation of Reflux Ratio

Data

RR Power(KW)

Feed Position

Flow Rate

(L/hr)

xf xd xb Volume(mL)

Time(s)

∆P(mm H2O)

T1-T14

5:1 0.50 Middle 2.0 0.5

5:1 0.90 Middle 2.0 0.5

RR Power(KW)

Feed Position

Flow Rate

(L/hr)

xf xd xb Volume(mL)

Time(s)

∆P(mm H2O)

T1-T14

5:1 0.50 Middle 2.0 0.5

5:1 0.50 Bottom 2.0 0.5

Variation of Power

Variation Feed Position

Data

RR Power(KW)

Feed Position

Flow Rate

(L/hr)

xf xd xb Volume(mL)

Time(s)

∆P(mm H2O)

T1-T14

5:1 0.50 Middle 2.0 0.5

5:1 0.50 Middle 2.0 0.7

Variation Feed Composition

Calculus

Calibration of the Pump Exercise A: Variation of Column Pressure Drop

Setting

Flow

Rat

e (L

/hr)

0 0.5 1 1.5 2 2.5 30

2

4

6

8

10

12

14

16

18

Boil-up Rate (L/hr)

Pres

sure

Dro

p (m

m H

2O)

Calculus

Exercise B: Use of the Density Meter for Determining Mixture Compositions

Ethanol and Water Fraction

*Repeat the same procedure for determinate the mole fraction at the bottom of the column.

Exercise C: Overall Column EfficiencyFenske Equation (@Total Reflux )

McCabe- ThieleRectifying Section

y Stripping Section

Calculus

Exercise C: Overall Column Efficiencyq- line

Specific Heat of the Mix

Heat of Vaporization

Intercept of q

Exercise C: Overall Column Efficiency

Safety

The major potential hazards associated with this particular equipment are:

Electrical Safety

Hot Surfaces

Hot Liquids and Gases

Chemical Safety

Water Borne Hazards