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Mass Transfer- II

CALEDONIAN COLLEGE OF

ENGINEERING, SULTANATE OF OMAN 2017 - 2018

LABORATORY MANUAL Semester B

Lab instructor:

Bushra Salim Al

Rahbi

DEPARTMENT OF MECHANICAL & INDUSTRIAL

ENGINEERING

Module Leader

Dr Anna Jesil

Module

Code

ENCH 307

ENCH 307 Mass Transfer- II A/c year 2017 - 18 Rev 11 Semester-B 2

Preface

There will be seven experiments in this module. The experiments are intended to

demonstrate the theoretical concepts learned from a practical point of view.

Emphasis will be on distillation, extraction, leaching and drying. Students are

expected to submit the log report weekly after each experiment and the completed

log reports will be collated and submitted at the end of the semester. Lab reports

have to be hand written with neat presentation of results, analysis and discussion.

Before the start of the experiment, the student must fill the risk assessment form and

get it signed by the concerned authority and submit it along with the log report.


Safety rules to be observed for Mass Transfer II (ENCH 307)

Semester B 2017 -18

Laboratory attendance is mandatory. The following rules must be observed at all times.

1. A lab coat, covered shoes, mask and gloves are to be worn while working in the laboratory.

2. Smoking, eating and drinking in the laboratory is not permitted at any time.

3. Any spilled or broken containers of chemicals should be immediately brought to the attention

of the instructor.

4. Any accident should be immediately reported to the instructor.

5. Sensitive and expensive instruments should be handled with proper care.

6. At the end of the experiment, students are requested to clean the equipment and keep the

glass ware in the appropriate places

7. After finishing the lab work, the equipment is to be switched off, power supply disconnected

and hands are to be washed th

8. Roughly with soap and water before leaving the laboratory.


TABLE OF CONTENTS

Experiment No. Title of the experiment Page No.

1 Packed Bed Distillation 5

2 Simple Distillation 10

3 Steam distillation 15

4 Liquid Liquid equilibrium 17

5 Solid liquid leaching 18

6 Tray Dryer 20

7 Adsorption studies 25

8 Packed bed extractor( Demo) 28


Experiment 1

PACKED BED DISTILLATION

AIM: To determine the number of theoretical plates equivalent to packed column height (HETP) using 1.

Fenske's equation and 2.McCabe-Thiele method

THEORY: Packed columns are often used for distillation, liquid –liquid extraction and humidification as well as for

gas absorption. For distillation, the gas phase is continuous and the liquid flows in rivulets over the

packing. A packed tower can be used as a fractionating column for either continuous or batch

distillation. The column height is usually based on the number of theoretical plates and the height

equivalent to a theoretical plate (HETP). In most cases the upper operating line is slightly steeper than

the equilibrium line and the reverse is true for the lower operating line. The pressure drop per

equivalent plate is generally less than that for a sieve or bubble cap tray, which is an important

advantage for vacuum operation. The smaller pairings have lower values of HETP but they also have

lower capacity and are not likely to be used in large columns.

Packed distillation towers can often be operated over moderate range of flow rates at nearly constant

separation efficiency. As the capacity parameter increases, both the liquid rate and vapor rate

increase because of which HETP is nearly constant. The HETP decreases in the loading region

because of the more rapid increase in liquid hold up and wetted area, bit it then increases sharply as

flooding is approached. With these high capacity packings, the rise in HETP is believed to be due to

the entrainment of the liquid. Structured sheet metal packings give slightly better separations than

dumped packings and the HETP values are nearly constant over a three to four fold range of flow

rates. The more efficient are the gauze type packings. The gauze is completely wetted even at low

flow rates and the HETP can be predicted from fundamental equations for mass transfer in wetted

channels. Low surface tension tends to increase the wetted area but too low values may lead to

foaming which increases HETP.

PROCEDURE: Methanol or ethanol may be used depending on the availability

A Preparing Calibration Chart

Step 1: Mix known volumes of Methanol-Water (0:5. 1:4, 2:3, 3:2, 4:1, 5:0) ml

Step 2: Determine the densities or refractive index (RI) of the mixtures by using specific

gravity bottle or Abbey refractometer,

Step 3: Determine the density or RI of pure methanol and water at room temperature.


Step 4: Convert the volume fractions into mole fractions of methanol (more volatile

component).

Step 5: A plot of density or RI (Y-axis) versus mole fraction of methanol (X-axis) is the

required calibration chart.

If density or RI is known mole fraction can be obtained from the calibration chart.

B Experiment part

Step 1: Fill the Reboiler with 2.5 litres of water and 2.5 litres of methanol.

Step 2: Allow water to pass through the condenser at a regulated flow rate.

Step 3: Switch on the heater and open the air vent of condenser.

Step 4: Operate the packed bed at total reflux for about 2 hour.

Step 5: Collect the distillate in a receiver.

Step 6: Note down the distillate temperature and residue temperature along with

rotameter readings

Step 7: Switch off the heater and cool the apparatus.

Step 8: Determine the density/refractive index of both residue and distillate.

OBSERVATIONS AND CALCULATION:

Moles of feed F = [(VA *ρA / MA]methanol + [(VB *ρB)/MB]water

MA & MB are mol. wt of methanol and water

Mole fraction of methanol, xF =

watermethanol

methanolA

]M /) * (V [ ]M / ) * V ([

]M / ) * V [(

BeB AAA

AA

Determination of Number of Theoretical Plates:

(i) Fenske Equation

avg

RD

RDm XX

XXN

ln

])1[(

)]1([ln1


Relative volatility of distillate = DD

DDD

yx

xy

1

1

Relative volatility of residue = RR

RRR

yx

xy

1

1

Average volatility = ) )( ( RD avg

Nm + 1 =

Height of packed bed Z = cm

HETP x Nm = Z

HETP=Z/Nm = cm

(ii) McCabe Thiele method

From graph of y vs. x, at total reflux, Nm=

I Calibration Chart:

Sl.

No.

Volume of Methanol

(ml)

Volume of water

(ml)

Mass of mixture Mole Mixture Mole

fraction of

Methanol

(Xeth)

Refractive Index (RI) (mixture)

Methanol

water

Total

Methanol

water

Total

1 0 5

2 1 4

3 2 3

4 3 2

5 4 1

6 5 0


II. Equilibrium data for water methanol system:

Temp (oC)

x (mole f)

y (mole f)

100 0 0

98.4 0.012 0.068

96.9 0.02 0.121

95.8 0.026 0.159

95.1 0.033 0.188

94.1 0.036 0.215

92.2 0.053 0.275

90 0.074 0.356

88.6 0.087 0.395

86.9 0.108 0.44

85.4 0.129 0.488

83.4 0.164 0.537

82 0.191 0.572

79.1 0.268 0.648

78.1 0.294 0.666

76.5 0.352 0.704

75.3 0.402 0.734

74.2 0.454 0.76

73.2 0.502 0.785

72 0.563 0.812

70.9 0.624 0.835

69.2 0.717 0.877

68.1 0.79 0.91

67.2 0.843 0.93

66.9 0.857 0.939

65.7 0.938 0.971

65 1 1

Experimental data from the compilation by Gmehling, J. and Onken, U. 1977. Vapor-Liquid Equilibrium Data Collection, Dechema, Frankfurt,

Graphs: Calibration Chart:


RESULTS & DISCUSSIONS: (To be filled by the student performing the experiment)

Signature of Module leader/tutor


Experiment No: 2

SIMPLE DISTILLATION

AIM:-

To verify Rayleigh’s equation through simple distillation for a binary mixture of Methanol and

water.

THEORY:-

In the case of a differential distillation, the vapour at any time is in equilibrium with the liquid

from which it rises but changes continuously in the composition. Thus, the Mathematical

approach used must be differential. Assume that L mol of liquid in the still of composition x

mol fraction A and that an amount dD mol of distillate is vaporized, of mol fraction y* in

equilibrium with the liquid.

Material Balance

The rate of depletion of liquid is equal to the rate of distillate output. The instantaneous rate

of depletion of a component in the liquid is therefore, In - out = accumulation

0 - dD = dL

Taking balance on more volatile component,

0 – y*dD = d(Lx)

0 – y* dD =xdL+Ldx

y*dL=xdL+Ldx

Therefore rearrangement gives,

F

W

x

x

F

W xy

dx

L

dL*

This equation can be integrated to get the following form which is called the Raleigh’s

Equation,

F

W

x

xxy

dx

W

F*

ln

where, F = moles of feed of composition xF , W = moles of residual liquid of composition xW,

W and xw can be obtained by material balance,

WDF WxDxFx

WDF

VO

M


The integral in Raleigh’s Equation, can be solved analytically (provided the relationship

between y* and x is available) or graphically (calculating the area under the curve for the

plot of 1/(y* − x) vs x.

PROCEDURE:-

Step 1: Take 500ml of methanol and 500ml of water in distillation still.

Step 2: Connect the water tap to the condenser and allow water flow through, then switch

on the heater.

Step 3: Heat the solution till 50% of the liquid in the flask is obtained as a distillate.

Step 4: Switch off the heater. Collect the residue & distillate.

Step 5: Note down the volumes of the distillate and residue.

Step 6: Prepare a calibration chart either by refractive index or by density of mixture in

different volume proportions versus mole fraction.

Step 7: Use this calibration chart to find out the composition of residue and distillate.

Step 8: Calculate the left and right hand side of Rayleigh’s equation and check whether they

are equal.

FORMULAE USED:

mass of water = density of water x volume of water

mass of Methanol = density of Methanol x volume of Methanol Moles of water =

Moles of Mthanol = Mass of Methanol/ Mol. Wt. Of Methanol

Total Moles = moles of water + moles of Methanol

Mole Fraction of Mthanol = Moles of Methanol/ Total Mole

Mole Fraction of water = moles of water

Total moles

waterOf Wt.Mol.

waterof mass


OBSERVATIONS

Sl. No. Description Data

1 Room Temperature (TR,

0C)

2 Density of Water at TR, (ρw , g/cc) 1.000

3 Density of Methanol at TR, (ρf , g/cc) 0.78860

4 Molecular Weight (MW) of Methanol (CH3OH) 32.04

5 Molecular weight (MW)of water (H2O) 18

118

6 Volume of Distillate (VD), ml

7 Volume of Residue (VR), ml

8 Mass/Weight of Distillate (mD), g

9 Mass/Weight of Residue (mR), g

10 Refractive Index of Distillate (RID)

11 Refractive Index of Residue (RIR)

12 Mole fraction of Distillate (XD) (from the calibration chart)

13 Mole fraction of Residue (XR) (from the calibration chart)

Plot a calibration chart by density/refractive index of mixture versus mole fraction of methanol.

I. CALCULATIONS (CALIBRATION DATA/CHART)

Sl.

No.

Volume of Methanol

(ml)

Volume of water

(ml)

Mass of mixture Mole Mixture Mole

fraction of

Methanol

(xmeth)

Refractive Index (RI) (mixture)

Methanol

water

Total

Methanol

water

Total

1 0 5

2 1 4

3 2 3


4 3 2

5 4 1

6 5 0

II. CALCULATIONS PART-A

Sl. No. Description Data

1 Volume of water, ml 500

2 Volume of Methanol, ml 500

3 Density of Water at TR, (ρw , g/cc) 1.0000

4 Density of Methanol at TR, (ρf , g/cc) 0.792

3 Moles of water in the feed (WF) = mass /MW

4 Moles of Methanol in the feed (MF) = mass /MW

5 Total moles in the feed (F) (Moles of water + Moles of Mthanol)

6 Mole Fraction of water in the feed (xW) = WF/ F

7 Mole Fraction of Methanol in the feed (xF) = MF/ F

8 Mole fraction of Methanol in the residue (xR)

(from the graph)

9 Mole fraction of water in the residue = (1- xR)

10 Average molecular Wt.of the residue (MWR)

[(Mol. Wt of water) (1- x) + (Mol.Wt of Methanol) (x)]

11

Total No. of moles in the residue (R)

12 Mole of water in the residue (WR) = R (1- xR)

13 Mole of Methanol in the residue (MR) = R (xR)

(NOTE: From the calibration chart (RI versus mole fraction of Methanol) we can obtain on

the mole fraction of Methanol in the residue)

(OVERALL MATERIAL BALANCE) In = Out

F = R + D, D = F – R = ___________

Where: F = Total no. of moles in the feed, R = Total no. of moles in the residue,

D = Total no. of moles in the distillate

residue theofMol.Wt Average

residue theofWeight


MATERIAL BALANCE ON THE METHANOL

MF = MR + MD MD = MF – MR = _______________

Where : MD = Moles of Methanol in the distillate

MATERIAL BALANCE ON THE WATER

WF = WR + WD WD = WF - WR = ______________

Where: WD = Moles of water in the distillate

III. CALCULATIONS PART-B

Rayleigh’ s Equation is :

Mole fraction of methanol in the feed =xF =

Mole fraction of methanol in the residue = xR =

Note: Use Interpolation if XF and XR are in between two known mole fraction values.

Ref Vapor liquid equilibrium data from literature

Plot 1/ y-x versus x. The integral is obtained by finding the area under the curve :

RESULTS & DISCUSSIONS: (To be filled by the student performing the experiment


x y y- x 1/y-x

xF

-------------

-------------

-------------

xR

--------------

--------------

--------------

Rx

Fx y

dY

R

Fln

x


Experiment No: 3

STEAM DISTILLATION

AIM To verify the principle of immiscible liquid mixture boiling by steam distillation.

and to find the vaporization efficiency.

APPARATUS Steam Distillation setup, measuring jar, receiving jar [500ml beaker], condensate collecting

jar [100ml beaker], separating funnel etc.

PROCEDURE

1. Check the water level in boiler and sump tank and then switch on the steam boiler.

2. Weigh 100ml of Turpentine and pour into the still through the funnel and close the

feed valve.

3. Switch on the pump and allow water to flow through the condenser.

4. Open slightly the steam outlet valve on the boiler.

5. The flow rate of the steam is maintained constant throughout the experiment.

6. The temperature inside the flask starts rising up and at a particular temperature it

remains constant. Note down this value as boiling point of mixture.

7. Collect the condensate in the given flask.

8. After the operation is over completed collect the residue in a separating funnel.

9. Transfer the distillate [receiving jar] into a separating funnel and allowed to settle

into two phases.

10. Separate the two phases of both residue and distillate and measure their volumes

and note them down.

CALCULATION 1) Volume of Turpentine (TP) = 100ml

Density of Turpentine = residue =

Mass of water in the distillate = Volume of water x density of water. Mass of TP in the distillate = Volume of TP x Density of TP Molecular weight of water (MA) = 18


Molecular weight of TP (MB) = 136 Boiling point of the mixture =

2) Theoretical Weight Ratio (of B to A) =

AA

BB

MP

MP

Where PA = Partial pressure of steam at boiling point of the mixture (steam table) PB = Partial pressure of TP = Total pressure – PA

Experimental Weight Ratio = distillatein water of Mass

distillatein TP of Mass

Vaporization Efficiency = r = 100ratio weight lTheoretica

ratio weight alExperimentx %



Experiment No: 4

LIQUID LIQUID EQUILIBRIUM

AIM: To determine the equilibrium distribution data for the given system and to obtain an

equation to fit in the data.

SYSTEM: Benzene – Water – Acetic acid.

PROCEDURE: Take 6 nos. of 250 cc bottles with stoppers and clean them well. To each

one of them add 50 cc of benzene and 50 cc of distilled water from separate burette. Add to

the mixture glacial acetic acid from a burette 1 cc, 5 cc, 10 cc, 15 cc, 20cc and 25 cc in the

1st, 2nd, 3rd, 4th, 5th and 6th bottles respectively.

Shake the bottles frequently and settle them, repeat this process for an hour. Mean

while prepare IN NaOH solution and standardize with oxalic acid solution with

phenolphthalein solution as indicator.

Separate the two layers in each bottle with the help of a 250 cc separating funnel.

Find weight and volume of each layer. Use phenolphthalein solution as indicator and

estimate the acid contents of each of the layers with standard NaOH solution. When titrating

the organic layer initially add about 10 cc of distilled water.

Calculate the weight fraction of acid in each layer and tabulate the data.

Draw a graph between the conc. of the acid in organic layer against the conc. of

acid in aqueous layer on a rectangular graph sheet.

If it is a curve plot the data on log-log graph sheet and obtains the equation, which

fits the experimental data of the system.

Results & Discussions: (To be filled by the student performing the experiment)



Experiment No: 5

SOLID LIQUID LEACHING

AIM:

To Estimate the recovery of solute after three stages in cross current solid liquid leaching.

INTRODUCTION

Leaching is widely used in the extraction of valued chemicals from solids into liquids. The

desired components from the solid diffuse into suitable solvent which they are soluble when

they are brought into intimate contact through agitation. The solute diffuses through the solid

to the bulk solvent. The block diagram representing the process has been shown in Fig 5.1.

Fig 5.1 Schematic of a single stage extraction

V= Mass of overflow solution

L=Mass of liquid in slurry solution

B= Mass of dry solute free solid

N=Mass of dry solute free solid (B)/ Mass of solution retained (L)

xA = Composition of A in overflow solution

yA= Composition of A in slurry solution


PROCEDURE

STANDARDISATION OF 1N HCl:

Prepare standard solution of Sodium carbonate (1N) was prepared by dissolving 5.3g of

sodium carbonate in 100ml of water.

Wash 50ml burette and rinse with the prepared HCl of approximately 1N. Pipette out 20ml of

std. sodium carbonate into conical flask and titrate it with HCl in burette using methyl orange

indicator. The end point is the appearance of red color.

LEACHING STUDIES:

1. Take 200 gm of sand in a beaker and 10 gm of Sodium carbonate. Add 200 ml of

distilled water and stir it well for 10 minutes.

2. After allowing time for equilibration and settling of solids, decant the clear solution

and analyze for sodium carbonate by titration with HCl.

3. The above procedure is repeated by adding same amount of solvent to the solid

slurry for two more times.

OBSERVATIONS AND CALCULATIONS:

S.No Set Volume of

Decantant(ml)

Burette reading Volume of

HCl(ml)

Na2CO3

(g) Initial Final

Volume of sodium carbonate = V1 = 20 ml

Normality of sodium carbonate = N1 =

Volume of HCl = V2 = ml

Normality of HCl = N2 = 1 N

RESULT: (To be filled by the student performing the experiment)


Department of Mechanical and Industrial Engineering


Experiment No: 6

TRAY DRYER

AIM: To determine the drying characteristics of wet sand using a Tray dryer. INTRODUCTION:

Drying is removing relatively small amounts of water from material. In drying water is usually removed

as a vapor by air. In evaporation large amounts of water is removed from material when the water

reaches its boiling point.

If the wet stock is kept in a compartment over a tray/plate and air is

passed over it by a blower, the dryer is known as atmospheric tray

dryer. When a slab of wet stock is placed in contact with air, water

evaporates from its surfaces and diffuses as vapor through the air film that covers the surface. The

concentration of the moisture on the surface de slab as there is continuous supply creases. A

concentration difference is setup, which makes them moisture in the interior to diffuse to the surface or

it moves by capillary action. The drying rate at this point is constant and independent of moisture

content of the slab as there is continuous supply of moisture to the surface, provided the air velocity,

temperature, and humidity do not change. During this constant-rate period the rate of drying is

controlled by the rate of vapor diffusion through the air film and is, therefore, depends upon the

humidity across the film and the thickness of the film.

When the moisture content become less than a certain value known as the critical moisture content,

the rate of diffusion of moisture from interior of the slab to the surface begins to fall hence the rate of

drying decreases. This is known as the falling rate, which continues till equilibrium moisture content is

reached, after further drying is not possible under the particular drying conditions.

PROCEDURE:

Step 1: Take about 50 gm of the given sample (sand) in the tray, spread it uniformly.

Step 2: Add about 10-15 ml of water to the sample &Note down the initial weight of the sample .Also

record the wet bulb and dry bulb temperature of atmospheric air.



Step 3: Set the temperature at desired level (say 1.5°C), when the temperature is around 55 °C

switch on the blower. Start the stop clock only when the temperature reaches the desired level.

Step 4: Note down the time taken for the digital balance for every 2 gm loss in weight. Or after 10

mint take down the weight balance.

Wet bulb

temperature,ºC

Dry bulb

temperature,ºC

Manometer

reading Rm, m Hot air

temperature Th

Room

temperature TR,

OBSERVATIONS AND CALCULATION:

Sl

No

Moisture

content, X

Weight

change, dw(gm)

Time

taken, sec

dw/dt

x 10-

3Kg/sec

Ө

kg/m2 sec

1 / Ө x 10-3

(sec)-1

Density of air RT

PMair

3m

kg (at room temp)

Density of water 2

Rhmwater

TTatT

_______________________________ Kg/m3

Drying area, A = = _________________________ m2

Weight of dry solid WS = 0.25 Kg

Drying rate, dtA

dW

, where dw = change in weight = 0.002 Kg

Orifice diameter, Do = 0.028 m



Pipe diameter, Dp = 0.05 m

Area of the orifice = A0= 4

D2

0

Co-efficient of discharge of orifice meter Cd = 0.62

pipeD

D0 = 0.028 / 0.05 = 0.56

Chamber dimensions = 400mm x 300mm x 200 mm

Cross section area of the duct = Ac = 300mm x 200 mm = 60000 mm2 = m2

Pressure drop across orifice meter is )( airwm gRP _____________________ N/m2

Velocity of air at orifice = Vo Vo =

Mass of air 00 AVM air ______________________ Kg/sec

Mass of air in the chamber, cairair AVM

Velocity of air in the chamber,Ac

MV

airair

m/sec

Mass velocity of air airair VG _______________________Kg / (m)2 sec

Heat transfer co-efficient h = 24.2 x G 0.37 =

W/m-0C

Moisture Content X=Ls

LsW

Ls= bone dry weight W= wet weight Humidity at temperature Th (from chart) H 2 = Kg / Kg dry air H1 = initial humidity

sec / m )(

P) x 2 ( x

) - (1

C

21

21

2/14

d

air



Mass transfer Co-efficient ,kg = Ө / (H 2 - H1) kg = _____________________________ Kg / (m2 ) (sec)(unit humidify difference) I Graph X vs T Slope at different points of the curve gives different values of dX/dt.

II. Graph of ө vs X III Graph of 1/Ө vs X

Constant rate

period

Xc

Ө

X



Time of constant rate period,

c

cinitialsc

A

XXLT

Time of falling rate period,

dXA

LT

X

cX

sF

1

TF =( Ls /A)( S) = sec RESULTS & DISCUSSIONS: (To be filled by the student performing the experiment)


1 / Ө

X

S=area under the

curve



Experiment No: 7

ADSORPTION STUDIES

AIM: To determine the adsorption constants for the adsorption isotherm of Oxalic acid on

activated carbon

THEORY: At a given temperature, the mass of adsorbate adsorbed by a solid adsorbent for

various concentrations is given by the following equation:

n

1

kcm

xq

The above equation is known as the Freundlich adsorption isotherm where x is the mass of

the adsorbate adsorbed by mg of the adsorbent at various concentrations of the adsorbate.

The values of k and n are constants at a given temperature for the given solid adsorbent and

adsorbate

PROCEDURE:

1. Transfer 1 g of the activated carbon to each of the six reagent bottles. Number the

reagent bottles.

2. Add 60, 50, 40, 30, 20, 10ml of 1 N Oxalic acid to each bottle and add adding 0, 10, 20,

30, 40 and 50 ml of distilled water to the above.

3. Shake the bottles vigorously and leave for 30 minutes in a thermostat at desired

temperature with intermittent shaking.

4. Filter the solution from each bottle using filter papers and collect the filtrate in a labelled

conical flask.

5. Titrate 10 ml of each filtrate against standard NaOH (1N) using phenolphthalein as the

indicator to obtain the concentration of acetic acid.

6. Plot a graph of log(x/m) vs log c

OBSERVATIONS

Estimation of Oxalic acid after adsorption:

Standard NaOH vs Oxalic acid

Indicator: Phenolphthalein



End point: Appearance of pale pink color

Temperature:

Bottle

No

S.No Volume of Oxalic

acid, ml

Burette

reading

Volume of

NaOH, ml

Concordant

value, ml

Initial Final

1

2

3

V NaOH x N NaOH

Normality of Oxalic acid after adsorption= ------------------------------= N final

V Oxalic acid

c= N final converted to g in 60 ml

Change in concentration of the oxalic acid = N final - N initial = a in g /ml

Amount of Oxalic acid adsorbed in 60 ml ,

x = (a x Eq wt x 60/1000) g/ 60 ml



Bottle

No

Concentration of Oxalic

acid, N

Weight of

oxalic acid

adsorbed g /60

ml

Amount of

Oxalic acid

adsorbed in 60

ml

Weight of

activated

carbon, g

x/m Log(x/

m)

Log c

N initial N final X

Plot Graph of log(x/m) vs log C

Slope = 1/n =

Intercept = log k=

RESULTS & DISCUSSIONS: (To be filled by the student performing the experiment)



ENCH 307 Mass Transfer- II A/c year 2017 - 18 Rev 09 Semester-B P28 | P a g e age 1

Experiment No: 8

PACKED BED EXTRACTOR (DEMO)

AIM: To determine the limiting flow rates in the packed tower using water as a continuous medium and

Kerosene as dispersed medium and to correlate the limiting flow rates.

APPARATUS: Packed column, conical flask, measuring cylinder. CHEMICALS: Kerosene, distilled water INTRODUCTION: Limiting flow rates are required for the purpose of tower design and to fix the operating flow rates in

packed towers as a percentage of the limiting flow rates. Two immiscible liquids are admitted in

counter current direction in the given tower. The dispersed phase Kerosene is being admitted at the

bottom as a spray for any fixed flow rate of the continuous phase. If the flow rate of the dispersed

phase is increased, a condition will be reached when the dispersed phase will be rejected at the

bottom of the tower and flows out with the continuous phase. This is because the number of droplets

in the column increases as the flow rate of the dispersed phase is increased and the flow rate of the

continuous phase is gradually decreased. The free cross sectional area for the rising of the drops

decreased and encounters larger resistance. In addition the continuous phase keeps pushing the

dispersed phase droplets. These two effects are responsible for rejection of the dispersed phase

through the bottom of the tower. The maximum flow rate of the dispersed phase at which the tower

can operate with the two phases flowing in counter current direction is called the limiting flow rate for

the set continuous phase. This condition can also be reached by fixing the flow rate of the dispersed

phase and gradually increasing the continuous phase flow rate. Thus the flow rates of the other phase

at this point are the limiting flow rates with respect to each other,the velocities are expressed in m/hr.

PROCEDURE:

1. Fill the feed tanks with water and kerosene acetate and close the valves.


ENCH 307 Mass Transfer- II A/c year 2017 - 18 Rev 09 Semester-B P29 | P a g e age 1

2. Switch on the compressor.

3. After the required pressure is developed, open the air inlet valve.

4. Open the water inlet valve and allow the water to fill the column.

5. Adjust the Kerosene flow rate to a required value ( say 15 lph). Observe that the column is

getting filled up with droplets of Kerosene.

6. Adjust the level of the interface in the top section of the column by adjusting the extract phase

rotameter.

7. Note down the flow rates of water and kerosene when the level of the interface is constant.

8. Repeat the experiment for different heights of the interface and record the readings.

9. Plot a graph of EV versus WV

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