mto lab manuals_ all experiments

7/29/2019 Mto Lab Manuals_ All Experiments

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JAYPEE UNIVERSITY OF ENGINEERING & TECHNOLOGY, GUNA

Department of Chemical Engineering

List of Experiments in Mass Transfer OperationsLaboratory

1. LIQUID-LIQUID EXTRACTION IN A PACKED BED COLUMN

2. ADSORPTION IN PACKED BED COLUMN

3. PERFORMANCE OF WATER COOLING TOWER

4. WETTED WALL COLUMN

5. DIFFUSION COEFFICIENT OF ACETONE (VAPOR) IN AIR

6. GAS ABSORPTION IN MECHANICAL AGITATOR

7. BATCH CRYSTALLIZATION

8. DIFFERENTIAL DISTILLATION

9. ABSORPTION IN PACKED BED COLUMN

10. BATCH RECTIFICATION IN PACKED BED COLUMN

11. BATCH RECTIFICATION IN A SIEVE PLATE COLUMN

12. TO DETERMINE THE DIFFUSIVITY COEFFICIENT BY PITOT TUBE

13. STEAM DISTILLATION

14. ROTARY DRYER

15. FORCED DRAFT TRAY DRYER

16. HUMIDIFICATION-DEHUMIDIFICATION COLUMN

17. LIQUID-LIQUID EXTRACTION IN A SPRAY COLUMN

18. SOLID-LIQUID EXTRACTION UNIT (BONNOTTO TYPE)

19. FLUIDIZED BED DRYER

MASS TRANSFER OPERATIONS LAB1


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Experiment No: 01

LIQUID-LIQUID EXTRACTION INA PACKED BED COLUMN



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LIQUID-LIQUID EXTRACTION IN A PACKED BED COLUMN

OBJECTIVE:To study the extraction of benzoic acid from mixture of toluene and benzoic acid (dispersed phase) bywater (continuous phase) in a packed bed.

AIM:

1. To determine overall mass transfer coefficient based on continuous phase (water), Kwa2. To determine overall mass transfer coefficient based on dispersed phase (toluene), Kta3. To determine overall Height of Transfer Unit based on continuous phase (water), HTUow4. To determine Individual Height of Transfer Unit based on continuous phase (water), HTUw and

dispersed phase (toluene), HTUt

INTRODUCTION:Liquid extraction sometimes called solvent extraction is the separation of the constituents of a liquidsolution by contacting with another insoluble liquid. If the substances constituting the original solutiondistributethemselves differently between the two liquid phases, a certain degree of separation will result& this can be enhanced by the use of multiple contacts or their equivalent in the manner of gasabsorption and distillation.

THEORY:Towers filled with some random packing (say raschig rings) are widely used for extraction of valuablechemicals from dilute solutions by liquid-liquid extraction. The packing provides a larger extraction areafor mass transfer and also reduces the axial mixing to some extent. The extraction rate in such columnsdepends on:(a) Choice of either continuous ordispersed phase.(b) Packing and column variables.(c) Velocity of liquid phases in the tower.

The tower performance is generally based on extraction rate data and evaluated in terms of overall heightof transfer unit, based on continuous phase, HTUow and the extraction factor expressed in terms of flow

rate ratios of the liquid phase,t

w

VmV . These two variables are plotted against each other on Cartesian co-

ordinates. As suggested by Colburn, the slope and intercept of such a plot would represent the resistanceof the individual films as:

OVERALL HEIGHT OF TRANSFER UNIT:

HTUow = HTUw + HTUt [mVw/Vt]HTUot = HTUt + HTUw [Vt/mVw]

Where m is the slope of equilibrium curve, m= dCw/dCtUnder equilibrium conditions (e.g. low concentrations) m is a constant.



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V is the superficial velocity of the liquid phase based on empty cross section of the column, subscriptw for continuous phase (water) and t for dispersed phase (toluene). Rate of mass transfer fromdispersed phase to continuous phase is defined as:

( ) ( )( ) ( )[ ]

=

2211

2211

/ln wwww

wwwww

CCCC

CCCCaVK

N

(1)

or( )

=21

21

/ln CC

CCaVK

Nw

(2)

the capacity coefficient based on continuous phase (water), Kwa, is thus defined as:

( ) lnww

CV

N

aK

= (3)

where,( )

=

2

1

2ln

lnw

w

www

C

C

CCC

Similarly, the capacity coefficient based on dispersed phase (toluene), Kta, is defined as:

( )lnt

tCV

N

aK

= (4)

As per Chilton and Colburn, the overall height of transfer unit based on continuous phase (water),HTUow is defined as:

aK

VHTU

w

wow = (5)

and the overall height of transfer unit based on dispersed phase (toluene), HTUot is defined as:

aK

VHTU

t

tot = (6)

DESCRIPTION:In this system two different liquids are used in which the one is heavier (water) which is used as solventand other is lighter in which the solute is present (toluene). The heavier liquid is inserted from top andlighter from the bottom. The interface maintained in the column between the lighter phase and theheavier phase at the top of the column can be adjusted up or down as necessary by regulating thearrangement provided at the water stream leaving the column. The position of the interface to be



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maintained at about 1 inch above the point of introduction of the heavier liquid (water in thiscase) into the column. The samples are taken from the top for lighter liquid and bottom for heavier liquidand are analyzed.

UTILITIES REQUIRED:

1. Compressed Air Supply at 2 Bar, 0.5 CFM2. Drain3. Laboratory Glassware4. Water Supply5. Weighing Balance (least count 1gm)

CHEMICALS REQUIRED:

1. Toluene = 20 Ltrs2. Benzoic Acid = 500gms3. Distilled Water = 20 Ltrs4. N/5 NaOH in alcohol = 500ml5. N/20 NaOH in water = 500ml6. Phenolphthalein as indicator = 10ml

EXPERIMENTAL PROCEDURE:

For the case where continuous phase (water) flow is downwards while the dispersed phase (Toluene +Benzoic Acid) flow is upwards, the extract will be collected through the bottom while the raffinate will

be collected from the top.

1. Prepare a mixture of toluene and benzoic acid as a feed mixture, with the concentration of benzoicacid in the range of 0.1- 0.2 kmol/m3 means 24.4gm/lit or 488gm in 20litres (i.e N/5)

2. Fill the column with the continuous phase (water).3. Allow the dispersed phase (toluene+ benzoic acid) to enter from the bottom of the column at some

minimum rate.4. Adjust the rotameter readings for both the phases (1 to 5 LPH for dispersed phase and 3 to 10 LPH

for continuous phase).5. The interface between the lighter phase and the heavier phase at the top of the column must be

worked up or down as necessary by regulating the valve in the water stream leaving the column. Theposition of the interface is to be maintained at about 1 inch above the point of introduction of theheavier liquid.(water) into the column.

6. In case lighter liquid is the continuous phase, the same arrangement should be used to maintain theinterface.

7. Take the first observation after the steady state has been established i.e after 10 to 20 minutes.8. Collect the samples of extract and raffinate and measure the concentration of benzoic acid in each by

titrating a known volume of sample with standard NaOH solution using phenolphthalein as indicator.Use standard NaOH solution in alcohol (N/5) for titration against toluene and NaOH solution ( N/20)

in water for titration against water.9. Repeat the above steps for 5 to 6 different flow rates of continuous/dispersed phase.



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SPECIFICATION:Extraction Column : Material Borosilicate Glass

Dia. 45mm, Height 750mm (approx)Packing Material : Borosilicate Glass Raschig Rings Size 8-10mm (approx.)Feed Tanks : Material SS, Capacity 20 Ltrs, 2 No.sExtract and Raffinate Tanks : Material SS, Capacity 10 Ltrs, 2 No.sPiping : SS and PVC, Size Feed Circulation : By compressed air Pressure Regulator : 0-2 kg/cm2

Pressure Gauge : Bourdan type, 0-2 kg/cm2

Flow Measurement : Rotamaters (One each for Continuous phase and dispersed phase)

Special arrangement for changing interface zone at any level in extraction column.

OBSERVATION & CALCULATION:

DATA:

Column Diameter, Dc = 40mmPacked height, Z = 750mm

Column cross sectional area = 224

mDc

Effective volume,V = )(432 mzDc

Packing = Raschig ringsDiameter of Raschig ring = 9mmLength of raschig ring = 10mmAmbient temperature = T, C

System : Toluene-Benzoic Acid-Water

Solute : Benzoic Acid

Initial conc. of benzoic acid in Toluene, CT1 = gmol/LInitial conc. of benzoic acid in Water, Cw2 = 0.0 gmol/L (Using pure water)Benzoic Acid: Molecular Formula = C7H6O2

Molecular mass = 122Equivalent wt. = 122

Toluene: Molecular formula = C7H8Molecular mass = 92Equivalent wt. = 92



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OBSERVATION TABLE:

S.No. Flow rate of

toluene phase,

Qt in L/h

Flow rate of water

phase, Qw in L/h

Volume of N/5

NaOH(in alcohol)

used for titration for

10ml of toluene

solution

Volume of N/20

NaOH(in water)

used for titration for

10ml of water

solution

CALCULATION:

A) CONCENTRATION OF BENZOIC ACID IN TOLUENE:

At bottom : (feed concentration)Volume of sample ( Toluene feed solution) V1 = ml

Normality of sample N1 = ?Normality of NaOH (in alcohol) used V2 = mlNormality of NaOH (in alcohol) used N2 = 1/5

2211 NVNV=

1

221

V

VNN =

Conc. of Benzoic Acid in the Toluene at bottom, CT1= N1 gmole/LSimilarly at the top:

1

221

V

VNN =

Conc. of benzoic acid in toluene at top, CT2 = gmole/LVolumetric flow rate of Toluene Phase QT = LPH

Amount of Benzoic acid extracted by water A1 = (CT1-CT2)QT gmole/h

B) CONCENTRATION OF BENZOIC ACID IN TOLUENE:1) Top : Pure water Cw2 = 02) Bottom:

Volume of water sample used for titration = V1 mlNormality of acid in water = N1Volume of NaOH used for titration = V2 mlNormality of NaOH used for titration = N2

1

221

V

VNN = gm eq/L

Concentration of acid in water at bottom = Cw1 g mole/LVolumetric flow rate of water = Qw LPH



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Amount of Benzoic acid recovered by water A2 = (Cw1-Cw2)Qw g mole/h

Average amount of Benzoic Acid recovered,2

21 AAN +=

gmole/h

OVERALL MASS TRANSFER COEFFICIENT ON DISPERSED PHASE:(Kta)

At bottom:

CT1 = g mole/LCw1 = g mole/L

H1 =1TT CatC

t

w

C

C

=

(using the equilibrium data)

CT1 = CT1- (CW1/H1) g mole/L

At Top:

CT2 = g mole/LCw2 = 0

H2 =T

w

C

Cat CT = CT2

CT2 = CT2- (CW2/H2) g mole/L

( )( )12

12ln /ln TT

TTT

CC

CCC

=

(CT)ln = g mole/L

Since N/ = Kt a V (CT)ln

Kt a =( ) lnTCV

N

(g mol/ h-L-gmol/L)

1111 wTw CCHC =

2222 wTw CCHC =

( )

1

2

12ln

lnw

w

www

C

C

CCC

=g mol/L

( ) ln

/

w

wCV

NaK

=

g mol/L-h-C

Overall height of transfer unit based on continuous phase:Superficial velocity of water phase, Vw = Qw/Ac m/hr

HTUow = aK

V

w

w

m



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Overall height of transfer unit based on dispersed phase:Superficial velocity of toluene phase, Vt = Qt/Ac m/hr

HTUOT =aK

V

t

t m

Repeat the above calculations for five different flow rate ratios of continuous and dispersed phase(Vw/Vt) and use equations (1 and 2) to determine the individual Height of Transfer unit based oncontinuous phase (HTU)w and Height of Transfer Unit based on dispersed phase (HTU) t, by plotting

(HTU)ow vst

w

V

Von a simple graph. Determine the slope and

intercept.Intercept = (HTU)wSlope = (HTU)t Slope

Intercept

CALCULATION TABLE:

Run

No.

(HTU)ow m (HTU)oT mm

t

w

V

V

w

t

mV

V (HTU) w m (HTU)T m

Equilibrium data for Benzoic Acid-Toluene-Water

Aqueous Phase, Cw g mole/L, Benzoic Acid Organic Phase, CT g mole/L, Benzoic Acid

0.0000 0.00000.0016 0.00800.0064 0.03360.0080 0.06730.00961 0.08811

0.011211 0.12015


Run

No.

Cw1 gmol/L Cw2 gmol/L CT1 gmol/L CT2 gmol/L Rate of M.T,

N/ gmole/h


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0.012816 0.140970.01442 0.17301

The equilibrium data can be represented by;

23672.44273.12015.0 TTT

w CCHCC +==

and

0019.00745.0 += Tw CC

or slope of the equilibrium line can be assumed to be constant at

0745.0==T

w

dCdC

m

NOMENCLATURE:

Cw1 = concentration of benzoic acid in water at its outlet, kgmol/l

Cw2 = concentration of benzoic acid in water at its inlet, kgmol/l

CT1 = concentration of benzoic acid in toluene at its inlet, kgmol/l

CT2 = concentration of benzoic acid in toluene at its outlet, kgmol/l

C*w = equilibrium solute (benzoic acid) concentration in water phase

C*T = equilibrium solute (benzoic acid) concentration in toluene phaseH = Equilibrium distribution Coefficient (C*w / C*T)

Kwa = Overall mass transfer coefficient based on continuous phase

Kta = Overall mass transfer coefficient based on dispersed phase

N/ = kg mole of benzoic acid transferred from toluene to water per hour

QT = flow rate of toluene, LPH

QW = flow rate of water, LPH

V = is the effective volume of packed section, m3

Vt = toluene flow rate LPH/m2 cross section of column

Vw = water flow rate LPH/m2 cross section of column

PRECAUTIONS AND MAINTAINENCE INSTRUCTIONS;

1. Interface should not be disturbed during the experiment.2. Dont exceed the flow rate beyond 15LPH3. Always use clean water & ensure that there are no foreign particles in it.4. Always clean the column feed tanks & collecting tanks properly after experiment is over.5. Never use feed tanks to store the chemicals used in the experiment.



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6. Always drain the column once before running the experiment on desired second flowrates.

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Experiment No: 02

ADSORPTION IN PACKED BED

COLUMN



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ADSORPTION IN PACKED BED

OBJECTIVE:

Study of Adsorption in a packed bed for a Solid Liquid System.

AIM:

Plotting the break through curve of adsorption for a given system and calculation of length of unusedbed for the system.

INTRODUCTION:

A substantial number of unit operations of chemical engineering are concerned with the problem ofchanging the compositions of solutions & mixtures through methods not necessarily involving chemicalreactions. One of the well known operations for solid liquid contacting is adsorption. The coloredmaterial which contaminates impure cane sugar solution can be removed by contacting the liquidsolutions with activated carbon, whereupon the colored substances are retained on the surface of thesolid carbon.In adsorption the molecules distribute themselves between two phases, one of which is a solid whilst theother can be the liquid or gas. Adsorption suffers one drawback, that the capacity of the adsorbent for theadsorbate in question is limited. At intervals, the adsorbent has to be removed from the process andregenerated, that is restored to its original condition. For this reason, in its early applications in industry,

the adsorption unit was considered to be more difficult to integrate with a continuous process.THEORY:

Adsorption is the selective transfer of a solute froma fluid phase to a batch of rigid particles. The usualselectivity of a sorbent between solute and carrierfluid or between different solutes makes it possibleto separate certain solutes from the carrier or fromone another.

It occurs when molecules diffusing in the fluid

phase are held for a period of time by forcesemanating from an adjacent surface. The surfacerepresents a gross discontinuity in the structure ofthe solid and atoms at the surface have a residue ofmolecular forces which are not satisfied bysurrounding atoms like those in the body of thestructure. These residual or Vander Waals forcesare common to all surface and the only reason thatcertain solids are designated adsorbents is thatthey can be manufactured in a highly porous form,giving rise to a large internal surface.

Feed (a) (b) (c) (d)SolutionConcen- Co Co Co Cotration. Adsorption ZoneAdsZone

EffluentConcen- Ca Cb Cc Cdtration

Breakthrough

Curve

0 Ca Cb Cc o Break Point

Volume of Effluent



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The Adsorption Wave

The Adsorption Wave:

Consider a binary solution, containing a strongly adsorbed solute at concentration C 0. The fluid is to bepassed continuously downwards through a relatively deep bed of adsorbent initially free of adsorbate.The uppermost layer of solid, in contact with the strong solution entering, at first adsorbs solute is left inthe solution is substantially all removed by the layers of solid in the upper part of the bed. The effluentfrom the top of the bed is practically solute-free, as at Ca in the lower part of adjacent figure. Thedistribution of adsorbate in the solid bed is indicated in the sketch in the upper part of this figure at (a),where the relative density of the horizontal lines in the bed is meant to indicate the relative concentrationof adsorbate.

The uppermost layer of the bed is practically saturated, and the bulk of the adsorption takes place over arelatively narrow adsorption zone in which the concentration changes rapidly, as shown. As solution

continues to flow, the adsorption zone moves downward as a wave, at a rate ordinarily very much slowerthan the linear velocity of the fluid through the bed. At a later time, as at b in the figure, roughly half the

bed is saturated with solute, but the effluent concentration CB is still substantially zero. At c in the figurethe lower portion of the adsorption zone has just reached the bottom of the bed, and the concentration ofsolute in the effluent has suddenly risen to an appreciable value CC for the first time. The system is saidto have reached the Breakpoint. The solute concentration in the effluent now rises rapidly as theadsorption zone passes through the bottom of the bed and at d has substantially reached the initialvalue co. The portion of the effluent concentration curve between positions c andd is termed theBreakthrough curve. If solution continues to flow, little additional adsorption takes place since the bed isfor all practical purposes entirely in equilibrium with the feed solution.

Length of Unused Bed Calculation:

Consider the adjacent figure. If the mass-transferrate were infinitely rapid, the breakthrough curvewould be the vertical line at S, which can belocated so that the shaded areas are equal. Theadsorption zone of the figure can then be idealizedas reduced to a plane, with the length of bed ZSupstream of the plane at concentration XT and thelength Z-ZS downstream equal to the length ofunused bed(LUB). At breakthrough, the length ofthe bed is taken to be the sum of LUB and a lengthsaturated with solute in equilibrium with the feedstream.If V=velocity of advancement of the adsorption

plane, then at any time ,Z = V,at time S,Z= VS, and at breakthrough,ZS = VB ; therefore:

LUB = Z-ZS = V(S - B) = Z (S - B) / S (1)

Y0Idealized

Y0

True break through

Y0o

B S r

= time of effluent flow



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DESCRIPTION:

The apparatus is provided for the process of Adsorption in Packed column with Solid phase being static& fluid phase is following. For flow of fluid a pump & rotameter is provided. Three borosilicatecolumns are provided having different diameters & lengths. At the inlet of column, valves are providedto feed only one column at a time. Valves are provided at the bottom of columns & liquid tanks to drainout after running the apparatus. Filters are provided before the column drain valves to prevent thecharcoal from drain.

UTILITIES REQUIRED:

DrainElectricity Supply : 1 Phase, 220Volt AC and 1 KWFloor Area : 1.2 m x 1mColorimeter or Spectrophotometer.

CHEMICALS REQUIRED:

Activated Charcoal : 1 KgKMnO4 : 15 gms.


1. Check that all the valves are properly closed.2. Fill the colored liquid in the feed tank (upper tank) and Activated Charcoal in columns.3. The colored solution made; should not be too concentrated.4. Open the valve of column to be operated.5. Start the pump and the stop watch.6. Fix a minimum flow rate using Rotameter.7. Take the samples of the output from column after fixed time intervals.8. Measure the Optical Density and hence concentration of color in the liquid.9. Note down flow rate, time & concentration.10. Run the fluid till the change in color of output liquid becomes almost stable.11. Close the pump & valve of the column.12. Now run for second & third columns.

SPECIFICATION:

Borosilicate Glass Column (3 nos.) : 1. Diameter = 30 mm, Length = 1000 mm

2. Diameter = 45 mm, Length = 500 mm3. Diameter = 55 mm, Length = 300 mm

Liquid Flow Measurement : Rotameter (4 to 40 LPH)Liquid Tank (2 nos.) : One each for Input and Output,Material : Stainless Steel (SS)

Liquid Circulation : Magnetic Pump made of Polypropylene to Circulate Liquid phase.Maximum working temperature is 850C.



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FORMULAE:

LUB = Z-ZS = V(S - B) = Z (S - B) / SV = Z / S

OBSERVATION & CALCULATIONS:

A calibration curve between Optical Density & Concentration is plotted, as shown below.

O. D. vs Concentration (low concentration)

1E -06

8E -07 y = 2E 06 x

6E -07

4E -07

2E -07

0E +00

0 0.1 0.2 0.3 0.4 0.5

O.D.

Optical Density vs Concentration (high concentration)

1.2E -05

1.0E -05 y = 3E 06x2 5E -07x + 6E - 07

8.0E -06

6.0E -06

4.0E -06

2.0E -06

0.0E +00

0.0 0.5 1.0 1.5 2.0O.D.



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Data :

Initial Optical density = I0

Initial Concentration = C0 (Using calibration chart)

Height of Charcoal in 1st column = Z1

Height of Charcoal in 2nd column = Z2

Height of Charcoal in 3rd column = Z3

OBSERVATION TABLE :

Flow rate = F LPH

Height of bed in first column = Zm

Time - Optical Density of Product - I Wt. of product collected - W

CALCULATIONS:

A curve between & C is plotted, which is called Breakthrough Curve. A curve between W& C mayalso be plotted. ZS is calculated using flow rate V and saturation time B. Then length of unused bed is Z-ZS Also velocity of advancement of adsorption plane can be calculated as Z/S.

CONCLUSIONS:

NOMENCLATURE:

C0 = Concentration of adsorbate in feed solution, moles solute/mass adsorbent.

I = Optical density of fluid at exit at time .

V = Velocity of advancement of the adsorption plane, m/s.

XT = Adsorbate concentration in equilibrium with entering fluid, moles solute/mass adsorbent.

Z = Actual height of adsorbent column, m.

ZS = Length of adsorber bed in equilibrium with feed, m.



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B = Time when the color of product start changing rapidly, min.

S = Time required for idealized breakthrough, min.

T = Time required for bed saturation, min.

PRECAUTIONS & MAINTENANCE INSTRUCTIONS:

1. Before starting the pump ensure that bypass valve is not fully closed & rotameter is properlyclosed.

2. Before starting apparatus check properly that the drain valves of all the columns are properlyclosed.

3. It should be ensure that there is no leakage from the bottom of the column.

4. Check properly that only one feed valve is open at a time.5. The apparatus should be drained off as soon as possible as the color of liquid would clot over the

inner surfaces of the apparatus, making the apparatus yield incorrect results.6. Pump should not be switched on at low voltage.7. Carefully note the bed height & initial solution concentration.

TROUBLESHOOTING:

In case of any problem regarding operation of the apparatus; the apparatus should be quickly switchedoff and electric supply should be cut off.

Electrical :

Electric shock : It means that either earth wire inside the panel is loose or there is no earth provide inthe socket to which the equipment is plugged. So make it sure that the equipment is earthed properly.

General :

Leakage : The point of leakage should be detected & the concerned part is tightened properly. If theproblem still persists then the part is removed & Teflon tape is wrapped on the threads properly & thepart is then refitted carefully.

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Experiment No: 03

PERFORMANCE OF

WATER COOLING TOWER



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PERFORMANCE OF WATER COOLING TOWER

OBJECTIVE:

Study of the heat and mass transfer in Water Cooling Tower for different flow & thermodynamicconditions.

AIM:To measure Tower Characteristic parameter( KaV/L) for various liquid and air flow rates(L/G) in acounter-current Forced draft Cooling Tower. To determine the effect of L/G on [KaV/L] and estimatethe values of mass transfer coefficient Ka for various values of L/G

INTRODUCTION:Water from condensers and heat exchangers is usually cooled by an air stream in spray ponds or inCooling Towers using natural draft or forced flow of air. Mechanical draft towers are of the forced drafttype, where the air is blown into the tower by a fan at the bottom. The forced draft materially reduces theeffectiveness of cooling.

THEORY:Water may be cooled by the air as long as its temperature is above the wet bulb temperature of theentering air. Markels theory is used which is based on enthalpy potential difference as the driving force.

Air Output (G, T3, T4, h1) Water In (L, T5)

Packing

Cooling Tower

Air In (G, T1, T2, h2) Water Out (L, T6)



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Each particle of water is assumed to be surrounded by a film of air and the enthalpy difference betweenthe film and the surrounding air provides the driving force for the cooling process. In the integrated formMarkels equation can be written as:

=5

6

T

Thh

dT

L

KaV

Tower characteristic can be evaluated numerically by:

( )

+

+

+

=

=

4321

65 1111

4

5

6hhhh

TT

hh

dT

L

KaVT

T aw

hw1= value of hw at temperature= T6 + 0.1(T5-T6)hw2= value of hw at temperature= T6 + 0.4(T5-T6)hw3= value of hw at temperature= T6 - 0.4(T5-T6)hw4= value of hw at temperature= T6 - 0.1(T5-T6)

ha1=h1 + 0.1(L/G) (T5-T6)

ha2=h1 + 0.4(L/G) (T5-T6)ha3=h2 - 0.4(L/G) (T5-T6)ha4=h2 - 0.1(L/G) (T5-T6)

andii awi

hhh =

The carrying of liquid with gas stream is termed as Liquid Entrainment. This may be due to a high rateof air flow. This should be avoided to get better performance. This can be avoided by following theOperational limits of the equipment.

DESCRIPTION:

The apparatus is provided for the process of Forced draft countercurrent cooling of hot water using air.The water to be cooled is heated in a heating tank using a heater. It is then circulated; through arotameter; to the top of the cooling tower mounted over the heating tank. Cooled water is then re-circulated to the heating tank. A blower is provided for the cooling air. A valve is provided in air line toregulate the flow rate of air. There is an Orificemeter mounted with its taps connected to a manometer tofind the flow rate of air. A set of two temperature sensors are provided both at inlet and outlet of airstream. These sensors give Dry bulb and Wet bulb air temperatures. The cooling tower is packed withAluminium expanded wire mesh.

Description of the temperature sensors are as follows:T1= inlet dry bulb temperature of air



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T2= inlet wet bulb temperature of airT3= outlet dry bulb temperature of airT4= outlet wet bulb temperature of airT5= inlet water temperatureT6= outlet water temperature

UTILITIES REQUIRED:

Water SupplyDrainElectricity Supply:1 Phase, 220V AC, and 3kW.Floor area of 1.2m 1m

EXPERIMENTAL PROEDURE:

(1) Fill the heating tank with water, set the temperature with the help of D.T.C and switch on heater.(2) Switch on pump & blower after desired temperature achieved.

(3) Set the flow rate of water and air.(4) Record the flow rate of water and manometer reading after steady state achieved.(5) Record the temperatures.(6) Steps 3 to 5 may be repeated for different water and air flow rates within operational range.

Operational Parameter Range:

Liquid rate: L=5 to 20LPHAir rate: G= 10 to 88 mm of manometric difference (with water as manometric fluid)L/G: 0.75 to 1.5

SPECIFICATION:

Tower : Material Stainless Steel, Size- Cross-section 66, Height 30Packing : Expanded wire mesh made of Aluminium.Air Flow Measurement : Orificemeter with U-tube manometer.Water Flow Measurement : RotameterHot Water Tank : Material Stainless Steel, Double wall, insulated with ceramic woolHot Water Circulation : Magnetic Pump made of Polypropylene to circulate Hot Water.Maximum

working temperature is 85.Heater : 1.5 kWTemperature Sensors : 7 No.sDry & Wet bulb Temp.-- Measurement : RTD PT-100 type SensosControl Panel comprising of-Digital Temp. Controller : Range:0-200C. (for hot water tank)Digital Temperature Indicator: Range:0-200C, with multi-channel switch.

With Standard make On/Off switch, Mains Indicator and fuse etc.A good quality painted rigid MS Structure is provided to support all the parts.

FORMULAE:

Head in terms of air,

=1

100 air

waterRH



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Flow rate of air, HgCaa

aaQ d

= 2

21

22

210

Mass flow rate of air, 0Qm air=Mass flow rate of dry air, G= [m/(1+Y1)]/cross-sectional area of column

Rate of humidification= mass flow rate of dry air (Y2-Y1) kg moisture/sec

OBSERVATION & CALCULATION:

DATA:Orifice dia., d1 = 34mmCross section area of Orifice, a1 = 9.110-4m2

d2 = 68mmOrifice constant, Co = 0.6water = kg/m3

air = kg/m3Acceleration due to gravity g = 9.81 m/s2

Cross section area of Chamber, A = 0.0232m2

Height of Packing = 0.75m

From the Psychometric Chart for air-water vapor at 1 atm. pressure, determine the followingcorresponding to dry bulb and wet bulb temperature of the entering and leaving air:Y1, (corresponding to T1 and T2)h1 (corresponding to T5)Y2, (corresponding to T3 and T4)h2 (corresponding to T6)

OBSERVATION TABLE:

S.No R (in m) Flow

rate of

water

(LPH)

Water temp. (C) Air Temperature (C)

Inlet Outlet

h1 h2 Inlet Outlet Dry

Bulb

Wet

Bulb

Dry

Bulb

Wet

Bulb

CALCULATIONS:

Calculate flow rate of air Q0 and mass flow rate of air mFor flow of compressible fluid, mass flow rate is to be multiplied by an Expansion factor .For the pressure ratio nearly equal to one, = 1Mass flow rate of dry air, G = [m/(1+Y1)]/A kg dry air/h-m2

Rate of humidification= mass flow rate of dry air (Y 2-Y1)L/G ratio is calculated from the L & G calculated as above.The values ha are found at different temperatures as below:

T, C ha, kJ/kg of dry airT6 ha=h1



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T6 +0.1 (T5-T6) ha=h1 + 0.1(L/G) (T5-T6)T6 +0.4 (T5-T6) ha=h1 + 0.4(L/G) (T5-T6)T5 -0.4 (T5-T6) ha=h2 - 0.4(L/G) (T5-T6)T5 -0.1 (T5-T6) ha=h2 - 0.1(L/G) (T5-T6)T5 ha=h2=51.2237

hw data is calculated at the specified temperatures from the psychometric chart to calculate h is. Nowaccording to Markels Theory; the cooling tower characteristic KaV/L is calculated as below:

( )

+

+

+

=

=

4321

65 1111

4

5

6hhhh

TT

hh

dT

L

KaVT

T aw

CONCLUSIONS:

NOMENCLATURE:

a = Contact area, m2/m3 of tower volumeA = Cross section Area of Chamber, m2

a1 = Cross section area of Orifice, m2

a2 = Cross section area of pipe, m2

C0 = Orifice constant

d1 = Diameter of Orifice, m

d2 = Diameter of pipe in which Orificemeter is installed, m

g = Acceleration due to gravity, m/s2

G = Mass flow rate of air, kg dry air/s.m2

G' = Mass flow rate of air, kg air/s.

H = enthalpy of air stream, kJ/kg

h' = enthalpy of saturated air, kJ/kg

ha = enthalpy of air-water vapor mixture at its wet bulb temperature, kJ/kg of dry air

hw = enthalpy of air-water vapor mixture at bulk water temperature, kJ/kg of dry air

K = mass transfer coefficient, kg of water/h-m

2

KaV/L = tower characteristic parameter

L = flow rate of water, kg of water/h-m2

M = Mass flow rate of air, kg air/s-m2

R = Oifice manometer reading (for air flow), m

V = active cooling volume m3/m2 of plan area

V0 = Velocity of air at Orifice, m/s

Y1 = Percentage saturation at inlet, kg moisture/kg air

Y2 = Percentage saturation at outlet, kg moisture/kg air



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= Coefficient of contraction for Orificemeter

==== X ====



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Experiment No: 04

WETTED WALL COLUMN



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WETTED WALL COLUMN

AIM:

To study the rates and phenomena of diffusion into gases flowing through the pipe and also to comparethe results obtained with literature values (Sherwood& Gilliland).

THEORY:

A thin film of liquid falling down the inside of a vertical pipe through which the gas flows, constitutes awetted wall column. Wetted wall column have been used successfully as absorbers for Hydrochloric acidgas, Ammonia, Acetone, Benzene and other volatile liquids. They have also been used for theoreticalstudies for mass transfer because the interfacial surface between the phases is kept under control and is

measurable.The height of a wetted wall column required for many mass transfer operations is excessive andconsequently this is not widely used. Where large quantities of liquid or gas have to be handled it would

be necessary to arrange many vertical pipes in parallel and this leads to difficulties in the distribution ofthe liquid into the inner surface of the tubes. The gas pressure drop from this type of equipment is verylow, however since it is almost entirely confined to skin friction effects, with few or no expansion orcontraction losses.

Mass transfer rates for fluids flowing through pipes have been studied more completely than other cases.The rates of diffusion into gases flowing through pipes have been studied with the help of wetted wall

columns, shown schematically in Figure. A volatile liquid is permitted to flow down the inside surface ofa circular tube, while a gas is blown upward or downward through the center of the pipe.

Measurement of the rate of evaporation of liquid into the gas stream over the known surface permits thecalculation of the mass transfer coefficient for the diffusion of the vapor into the gas stream. Since theliquids may be pure liquids, the concentration gradient for the diffusion exists entirely within the gasstream and coefficient KG may be obtained directly from the data. Sherwood and Gilliland conducted aseries of experiments of this sort, using a variety of volatile liquids with air in turbulent flow. Forgraphical representation refer to Coulson & Richardson volume 2. Here the mass transfer coefficients inthe form of a dimensionless group are plotted against the Reynold number of the gas for the system Air-Water (SC=60).Similar data obtained for volatile liquids is shown in the upper line. For gases, values of

Re from 2000 to 35000 were covered and Sc from 0.6 to 2.5 with gas pressure varying from 0.1 to 3.0atm.

The average slope of the line in graph is 0.83 so that the groups (KG*d/D)* (PB,M/P) and (KL*d/D) vary asRe0.83. In another graph the intercepts of these lines at Re = 1000 are plotted against the correspondingvalues of Sc on logarithmic coordinates. The principal line of this graph has a slope of 0.333. Theequation, which describes all the data, for both the liquid and gas flow, is therefore,

(KG*d/D)* (PB,M/P)* (KL*d/D) = 0.023 Re0.8 Pr0.3

This empirical relation is quite remarkable in the manner in which it generally confirms the relationshipbetween heat, mass and momentum transfer developed theoretically. It should be noted that the



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evaporation of the volatile liquids in a wetted wall column results in cooling of the liquidsand consequent simultaneous heat transfer between liquid and gas.The heat transfer rates are somewhat higher than those given by the equation,

H*D/K = 0.023 Re0.8 Pr0.3

Owing to ripples and waves on the liquid surface, it should also be noted that data for gases only ingraphs (Sc = 0.6 to 2.5) are correlated empirically better by the relation,

(KG*d/D)*(PB, M/P) = 0.023 Re0.83 Sc0.44 (broken line in the graph)

DESCRIPTION OF EQUIPMENT:

Air is supplied to the column at the bottom by means of blower. Bypass valve V1 and control valve V2are used for varying the airflow rate. The condition of air at inlet and outlet from the column aremeasured by the wet bulb and dry bulb thermometer, respectively. Water inlet and outlet temperatures

are measured by the thermometers T1 and T2. A wire mesh screen is placed over the surface of the tube.Manometer M1 and M2 measure the pressure drop across column and air flow rates. Water flow rate ismeasured by rotameter readings.

PROCEDURE:

Water is fed to the column at a rate at which complete wetting with a minimum of rippleformation is visible.

The blower is started and a minimum flow of air is maintained. After about 5 minutes when steady state conditions could have reached, the humidity of air inlet

and outlet are determined by the readings of the wet and dry bulb thermometers and by the use ofa psychrometric chart.

Water flow rate and inlet and outlet temperatures are recorded. From steam tables vapor pressure at the water temperature is noted.

OBSERVATION TABLE:

Run No. Air F.R.

(QA) lpm

Water

F.R. (Qw)

lpm

AIR TEMPERATURE

Inlet

(C)

Outlet

(C)

td1 tw1 td2 tw2

*** 1 12.7 3 24.9 24 26.7 26.4

***Sample observations



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CALCULATIONS:

Length of tube L = 1000 mmDiameter of tube d = 25 mmAir flow rate = 0.0095 k-mole / sec

Driving force at inlet of air (at bottom)

PW1 = Pw1-pw1Where,

Pw1 = pure component vapor pressure of water at outlet water temperature T 1

= can be evaluated by using ANTOINE EQUATION.

pw1 = Partial pressure of water at bottom (can be calculated by using humidityand pressure relation).

Driving force at outlet of air (at top)

Pw2 = Pw2-pw2Where,

Pw2 = pure component vapor pressure of water at inlet water temperature T 2.

pw2 = Partial pressure of water at top .

NOTE: The partial pressure can be calculated from the humidity values obtained from psychrometricchart by using recorded wet and dry bulb temperature of air at top and bottom.

SAMPLE CALCULATIONS:

(for sample observations)

Mean driving force,

PW,M = (Pw1- Pw2) / ln (Pw1/Pw2)

= 0.95 /1.2267

=0.7743Amount of water absorbed by air (evaporated)

Nw = QA ((pw2-pw1)/P) K-mole/sec

Where, QA is air molar flow rate (K-mole/s)

= 0.0095*2.5/760

NW = 0.00003125



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Wetted surface in the column = A = *d*L (m2)

Where,d = ID of the column

L = Effective length of the column

In terms of mass transfer coefficient Kg the rate of mass transfer is given by,

Nw /A = K G*(PB, M)

KG = NW / (A*PB,M) k-mole/m2.s.mm Hg

= 0.00003125/3.14*0.0254*0.7743)

= 0.0005060 k-mole/m2.s.mmHg

CONCLUSIONS:

NOTES:

(1). ANTOINE EQUATION:

lnP = A-B/(T+C)where,A = 18.3036; B = 3816.44; C = -46.13 (for water)

(2). PERRYS EQUATION (HUMDITY RELATION FOR PARTIAL PRESSURE)

H = [pw/(P-pw)]*(Mwater/Mair)

Where,H = absolute humidity

P = atm. pressure

Mwater = 18 kg/Kg-mole

Mair = 29 Kg/Kg-mole

==== X ====



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Experiment No: 05

DIFFUSION COEFFICIENT OF

ACETONE (VAPOR) IN AIR



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DIFFUSION COEFFICIENT OF ACETONE (VAPOR) IN AIR

AIM:

To determine diffusion coefficient or diffusivity, of given liquid (acetone) in air by using ARNOLDscell.

APPARATUS:Arnolds cell, Thermometer and Scale for measuring drop in height of solvent.

CHEMICALS: Acetone

THEORY:This is the case of pseudo-steady state diffusion in which one of the boundaries shift with time the effectthat the length of the diffusion path changes, though only by a small amount over a long period ofexposure.When this condition exists:

The molar flux at any instant in the gas phase

NA,Z = (DAB/Z)(P/RT)(1/PB,lm)(PA1-PA2)

Where,

Z = Z1 - Z2 = the length of the diffusion path in time t.

The molar flux of A leaving the liquid at any instant

NA,Z = (A,L/M)(dz/dt)

(A,L/M)(dz/dt) = (DAB/Z)(P/RT)(1/PB,lm)(PA1-PA2)

Where A,L/M = molar density of air liquid phase

Under pseudo-steady-state conditions,

DAB(P/RT)(1/PB,lm)dt = (A,L/M)Zdz

Upon integration this yields

(DAB)(P/RT)(1/PB,lm)(PA1-PA2)t=(A,L/M)(1/2)(z12-z22)

PROCEDURE:

Acetone is filled in capillary tube and air bubble, if present, is removed from the tube carefully.

Note down the initial height (H0) of the acetone level in the tube.



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The tube is placed in a water bath to maintain the constant temperature. Note down thetemperature of the water by thermometer.

Switch on blower, which blown air across the opening of capillary tube continuously to remove thevapors evaporated that rises from the surface of the liquid.

At regular interval of time note down the drop in the level of acetone. Do necessary calculations and find out the diffusivity (D) from the equation.

Also calculate the diffusivity from the GILLILANDs equation (as given below) at the sametemperature using standard data and compare the result with the experimental one.

Repeat the same procedure for two-three different temperatures by increasing and maintainingconstant temperature of the water bath and calculate the diffusivity by both the methods. State yourconclusion precisely at the end.

D = (4.310-4)(T)1.5(1/MA+1/MB)0.5/(P(VA1/3+VB1/3))

OBSERVATION TABLE:

SR.NO. TEMP (C) INITIAL HEIGHT

OF LIQUID (mm)

FINAL HEIGHT OF

LIQUID (mm)

TIME (Sec.)

CALCULATIONS:

1. Vapor pressure of acetone at given temp.

PA1 = ___________________ mm Hg

2. PB1 = P-PA1

3. PA2 = 0 (Since pure B(air) is flowing)

4. PB2 = P-PA2

PB,lm = (PB2-PB1)/ln(PB2/PB1)

5. A = ______________________kgmol/m2sec

6. Z1 = __________cm , Z2 = __________cm

7. DAB = ___________ m2/sec

DATA:

1. P = 1 Std. atm = 760 mm Hg = 101325 N/m2

2. R = 8314 N. m/kmol K

3. Room Temp = ________C



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4. Density of acetone

5. Molecular wt. of acetone___________kg/m3

DIFFUSIVITY BY GILLILANDs METHOD:

D = (4.310-4)(T)1.5(1/MA+1/MB)0.5/(P(VA1/3+VB1/3))

VA = molar volume of acetone

= ________________m3/kmol

VB = molar volume of air

=_________________m3/kmol

MA = molecular weight of acetone

=_________________kg/kgmol

MB = molecular weight of air

= _________________kg/kgmol

T = Absolute temp.

=__________K

D = ____________m2/sec from Gillilands equation

RESULTS:

CONCLUSIONS:

==== X ====



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Experiment No : 06

GAS ABSORPTION IN

MECHANICAL AGITATOR



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GAS ABSORPTION IN MECHANICAL AGITATORAIM:

To find the absorption efficiency of the mechanical agitator vessel.

THEORY:

The process of absorption of the gas in the liquid is really entirely a physical one. However in number ofcases in which the gas on absorption reacts chemically with a components of the liquid phase. Thus inabsorption of CO2 by NaOH the CO2 reacts directly with the NaOH and the process of absorbed in

Ethanolamine solutions there is direct chemical reaction between the Amine and the gas. In such casesthere is a liquid film followed by a reaction zone.

The effective interfacial area a in the gas liquid contractor is an important mass transfer characteristic inthe design of the contractor.

The system used in this experiment is a gaseous solvent A dissolving in a liquid acid simultaneouslyreacting with the reactant B present in the liquid phase.

A + bB AB Products

The new products AB formed diffuse towards the main body of the liquid. The concentration of B at theinterface falls; this results in diffusion of B from the bulk of the liquid phase to the interface. Since thechemical reaction is rapid, B is removed very quickly so that it is necessary for the gas A to diffusethrough the part of the liquid film before meeting B. There is thus a zone of reaction between A and Bwhich moved away from the gas liquid interface taking up some position towards the bulk of the liquid.The final position of the reaction zone will be such that the rate of diffusion of A from the gas liquidinterface is equal to the rate of diffusion of B from the main body of the liquid. When this condition has

been reached the concentration of A, B and AB can be indicated as shown in the figure.According to the film model if the reaction is fast enough the solute A will be consumed by the reactionin the liquid film itself and its concentration will be zero at the end of the liquid film. The condition for afast second order reaction is,

[ ]( )OAA BKD ** 2/ LK >3 (1)

Where,DA - Diffusivity of A, m2 / secKA - Second order reaction constant, m3 /kmol. Sec[Bo] - Concentration of B in bulk liquid, kmol / m3KL - Liquid side mass transfer coefficient, m /sec



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In such a case the reaction occurs simultaneously with the diffusion process in the liquid film andtherefore enhances the rate of absorption significantly. If the reactant B is present in far excess of thestoichiometric requirements for the reaction in the film, then the depletion of the reactant concentrationin the film is negligible. The condition for such a case is given by,

[ ]( ) [ ]( ) [ ]( )**/*/** 2 oAoBLoAA AbDBDKBKD


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The reaction rate constants determined by Himmelblau and Babb (1958) at 200C are

Reaction I k = 2.77 105 sec-1

Reaction II k = 0.0149 sec-1

The first reaction is operative in the absorption of carbon dioxide by caustic solutions. Since this is a fastreaction the factors controlling the absorption are the rates of diffusion of the reactants in the liquidphase. The second reaction is slow and controls the rate of absorption in carbonate solutions. Nijsing etal. (1958, 1959) have investigated the kinetics of absorptions by caustic and carbonated solutions inWetted-wall columns and Danckwerts and Kenddedy (1959) discuss the results obtained fromexperiments of absorption in a liquid film on a rotating drum. The experimental results on the absorptionof carbon dioxide by alkaline solutions are usually expressed as the overall gas film coefficient becausethe concentration gradient in the liquid is unknown. Justification of this procedure is afforded by thework of Pozin (1947) who showed that the rate of absorption in a batch absorber was proportional to the

partial pressure of carbon dioxide in the gas phase.

The results of spector and Dodge show that the coefficient KGa is inversely proportional to the squareroot of the absolute gas pressure and tends to decrease as the packed height is increased. The datashowed good agreement with results from a commercial installation. The coefficients for caustic potashsolution were 20 to 30 % higher than those for caustic soda of the same normality.

The dependence of the coefficient on the gas flow rate is an indication that at very low concentrationsthe absorption of carbon dioxide is partially controlled by the gas phase coefficient. Tepe and dodge(1943) showed that at higher concentrations (2% CO2) the absorption is wholly controlled by the liquidfilm. The coefficient was independent of the gas rate and proportional to the 0.28 power of the liquidrate.

Effect of temperature and the effect of the sodium hydroxide concentration and the degree of conversionto sodium carbonate. The coefficient value when the total sodium concentration is 1.8 normal.

The effect of varying the carbon dioxide concentration in the gas phase over a rang e form 3 to 28% hasbeen investigated by Blum, Stutzmanb and Dodds (1952). The overall gas film coefficient, KGa wasfound to be independent of the gas flow rate but dependent on the liquid flow rate, the concentration(normality) of the alkali, and on the partial pressure of carbon dioxide in the gas. The experiments ofabsorption in sodium hydroxide solution showed that KGa increased with the normality of the sodiumhydroxide up to 1.5N, but was not affected by a further increase in concentration.

The effect of the partial pressure of the carbon dioxide was a function of the normality of the liquid. Athigh normality (above 1.5 N) KGa decreased as the average partial pressure had no effect on thecoefficient. At lower normality (0.99 N) the coefficient decreased as the partial pressure increasedthroughout the range of the experimental data. The coefficient decreased progressively as the sodiumhydroxide was converted to carbonate. The volumetric coefficient, KGa appeared to be independent ofthe packing size. The coefficients of absorption of carbon dioxide in potassium hydroxide wereappreciably higher than those for sodium hydroxide under equivalent conditions. It was assumed that thefollowing chemical reactions occur in solution:

=+ 32 HCOCOOH +=+ 323 COOHHCOOH

+=+ 3223 2HCOOHCOCO



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The second reaction was throught to be rapid and the third reaction irreversible in the presence of OH-

ions. The rate of absorption Na (lb.mole/hr.) in a tower of unit cross section (1ft2) and height h (ft.)

( )( ( ) mCOOHhKNa '/' 3 =

Where K is a function of the liquid rate and is the lonic strength of the solution. A satisfactorycorrelation of the results was obtained when

m = 1.09K = 0.0176L0.84

Where L is the liquid flow rate in lb.Mole/(hr.)(ft2)

The absorption of carbon dioxide by sodium and potassium carbonate solutions has been studied byPayne and Dodge (1932), Comstock and Dodge (1937) and Furnas and Bellinger (1941). The rate ofabsorption is controlled by a slow chemical reaction in the liquid phase. It is independent of the gas rateand decreases with increasing normality of the solution and with conversion of the carbonate to

bicarbonate. Payne and Dodge noted that the coefficient is approximately proportional to the liquid hold-up in the tower.

One of the most important industrial applications of carbon dioxide absorption lies in the production of

synthesis gas for synthetic ammonia or the manufacture of hydrocarbon products by the Fischer-Tropschprocess. The synthesis gas, which may be produced by the partial combustion of natural gas or by thegasification of coke in producer gas or water gas plants, contains a high proportion of carbon dioxidewhich must be removed by absorption in a suitable solvent. To overcome the relatively low solubility ofcarbon dioxide, the absorption is usually carried out at a pressure of 10 to 50 atm. At high pressure it is

possible to remove the carbon dioxide by solution in water, but this has the disadvantage that thepumping costs are high owing to the large quantities of water which must be circulated through theabsorption towers. The liquid flow rates can be reduced by absorbing the carbon dioxide in a solution ofsodium or potassium carbonate or mono-or diethanolamine. The solution is regenerated by heating at alower pressure to drive off the carbon dioxide.

Benson, Field and Jimeson (1954) Benson, Field and Haynes (1956) have discussed the relative meritsof carbonate and amine solutions for the removal of carbon dioxide from synthesis gas at 300 lb / in2

pressure. Potassium carbonate is preferred to sodium carbonate owing to its greater solubility in waterand the reduced risk of deposition of solid bicarbonate in the absorber. A comparison of potassiumcarbonate and mono-ethanolamine showed that the farmer had two important advantages; less heat isliberated in the absorber owing to the smaller heat of solution of carbon dioxide in potassium carbonatesolution, and the regeneration can be carried out at a lower temperature. This made it possible to carryout the absorption and regeneration of potassium carbonate solution over the same temperature range(225 to 2400F) and considerable savings in heat could be effected. The absorption was carried out at agas pressure of 300 lb / in2 and the solution regenerated by reducing the pressure to 5 lb / in2 gauge andstripping the solution with steam.



40/121


PROCEDURE:

Initially start the air compressor and collect sufficient air in the pressure tank so as the pressure isabout 3-4 kg/cm2. Prepare the dilute NaOH solution in the tank. Open the valve of the pressuretank and allow the air to pass through the column. Set the air flow at the desired value and thenopen the valve on the CO2 cylinder and adjust the flow rate to predetermined value. Aftersometime take the sample at various points (liquid as well as gas) and analyze them.

Initially start the liquid flow at sufficiently high rate to ensure that the agitation in the vesselshould be well.

The flow rates of gas and liquid are adjusted at predetermined values. The CO2 flow rate shouldbe such that the % CO2 in the mixed gas is about 8-10%. The gas velocity has no effect on theinterfacial area in a vessel.

Hence a value of VG between 0.1-0.2 m/s may be chosen for all the experiments and keeping itconstant. The linear superficial liquid velocity V is the most important variable. The range for Vshould be fixed between 0.001-0.007 m/s.

The system is allowed to reach steady state after fixing the liquid level in the bottom section at amarked height. Inlet and outlet liquid samples are withdrawn for analysis. This procedure is to berepeated for 6-7 different values of VL chosen in such a way that the range indicated is fullycovered.

OBSERVATIONS:

System (CO2 + Air) - Aq. NaOH SolutionAgitator used - Flat blade turbineVessel Dia - 300 mmVessel Height - 400 mmTurbine Dia - 100 mmTurbine width - 20 mmSparger type - Ring

Number of holl - 8Holl Dia - 3 mmRing Dia - 90 mm

Chemical Reaction:

CO2 + NaOH NaHCO3NaHCO3 + NaOH Na2CO3 + H2O

Final Reaction:

2NaOH + CO2 Na2CO3 + H2O

Here, NaOH is excess material so stochemetrically reaction is 2:1 ratio.

OBSERVATION TABLE:



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Sr. No. Flow rate of

Air LPM

Flow rate of

CO2 LPM

Burette

Reading ml

Time Sec.



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CALCULATION:

The concentration of NaOH used should be between 2 2.5 g mol/lt. The inlet CO2percentage iskept around 10%. Under these conditions the equations (1) and 92) are satisfied and the

absorption of CO2 is accompanied by a fast pseudo first order reaction. 5 ml of sample (or 10 ml) is titrated against standard HCl of molarity (approx. 1 gmol/litre) usingphenolphthalein as an indicator. Titrate Value (V1) = . ml.

Initially feed of NaOH in gmol/min.Feed normality of NaOH solution is = gmol/min.

After steady state titrate the product with 0.1 N HCl solution use phenolphthalein as an indicator. gmmoles of CO2 in feed = [(Flow rate*10-3*density) / Molecular weight] * 1000

= [(...*10-3*1.5) / 44] * 1000= . mmmoles / min.

gmmoles of NaOH in feed

= Normality of feed==

Burette reading = . mlSo, NaOH consumed = . gm moles / minCO2 absorbed = . gm moles / min

(because stochiometrically this is 2:1 ratio)% CO2 absorbed = (CO2 reacted / CO2 feed) * 100

= ( .. / ..) * 100=

RESULT:

CONCLUSION:

==== X ====



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Experiment No : 07

BATCH CRYSTALLIZATION



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BATCH CRYSTALLIZATION

OBJECTIVE:Study of crystallization

AIM:

To study the crystallization of MgSO4.7H2O in a batch crystallizer.To verify the material balance around the crystallizer.To determine the yield of MgSO4.7H2O crystals.

INTRODUCTION:Crystallization is the formation of solid particles within a homogeneous phase. Its wide use has a two-fold basis, a crystal formed from an impure solution is itself pure and crystallization affords a practicalmethod of obtaining pure chemical substances in a satisfactory condition for packing and storing. Thisoperation involves both heat and mass transfer.

THEORY:Crystallization is the process whereby a solid separates from a solution because conditions have beenimposed on the solution to allow the solid phase to form and particles of crystalline character to grow to

a size sufficiently large to allow separation by physical methods.A saturated solution containing the solute is altered by either cooling, evaporation of solvent, or additionof another substance so that the ability of the solvent to dissolve the solute is lessened, and a fraction ofthe solute forms a solid phase, which may be removed from the mixture.

From the solubility or phase diagram the effect of changes in the temperature and solute and solventconcentrations can be seen.

Based on the material balance, the yield of crystals resulting from cooling and or loss of solvent due toevaporation can be estimated from:

( )[ ]( )11

1

2

21

=RC

VCCWRY

The physical properties of saturated solutions and slurries may be obtained from:

( ) pF

Fp

sXX

+=

1

Viscosity:



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( )( )

+

= 64.011.4

efs

( In many cases slurries have20% solids, 8.0=

8.1=

f

c

SATURATED SOLUTION:

A saturated solution is a solution which is in equilibrium with a solid phase of the dissolved material. Asaturated solution has in it the maximum quantity of the solute at that temperature.

If the saturated solution is cooled or solvent evaporated, a non-equilibrium condition is establishedwhich can be remarkably stable. That is, a solid phase will not immediately precipitate in order to re-establish the equilibrium. This non-equilibrium solution where in the liquid has dissolved more than the

equilibrium quantity of solute is called super saturated solution.The super saturation of a given solution cannot become infinitely large. There is a limit. This limit isencountered when there occurs a spontaneous formation of solid crystals known as nuclei.

If these nuclei are allowed to grow, crystals are formed and the system reverts to the equilibrium state.The process of crystallization is show in figure:

1. A saturated solution can be madesupersaturated by a change of temperature

(cooling) or a reduction in solvent content.This supersaturated solution can remain ina meta-stable equilibrium for very long

period of time.2. In the meta-stable zone crystal growth can

occur if there are seed crystals upon whichthe solids may deposit, but spontaneousnucleation will take place.

3. In the labile zone there will be a suddenspontaneous formation of crystal nuclei thatwill produce so many very small particles.

Unstable region of

Nucleatic Metastable & -Supersaturated

2

1

Stable &Unsaturated

Temp.Coolin

gEquilibrium Solubility

BATCH CRYSTALLIZATION: Batch crystallization is characterized by the fact that the system isalways in the unsteady state. The initial super saturation at which crystallization starts will drop quickly



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from relatively high value to the saturation value. If crystal growth is to continue, thesolution must be maintained in the meta-stable region. As a consequence, cooling must continue and the

batch temperature must continue to drop during the growth period. In batch crystallization it iscomparatively easy to penetrate the labile zone producing a fine mass of fine crystals. By usingcontrolled seeding the solution will not become labile thereby aiding crystal growth.

T vs Concentration

504540353025

2015 C = 0.494 T + 25.851005

0

0 5 10 15 20 25 30 35 40 45

T (0C)

DESCRIPTION:Cooling type agitated batch crystallizer set up consists of an open jacketed stirred vessel provided withwater heating and cooling arrangement. The feed is prepared in the crystallizer itself with hot water andstirrer. The hot super saturation solution in the crystallizer is then cooled by circulation of cooled waterand crystals are formed.

UTILITIES REQUIRED:

Water SupplyDrainElectricity Supply: 1 Phase, 220V A.C, 1.5kW

Required Chemicals: MgSO4.7H2O


1. Prepare a saturated solution of MgSO4.7H2O in water at 80C by dissolving 66.2gmMgSO4.7H2O in 100gms of solution (1.9856gm MgSO4.7H2O per gm of free water). The crystallizershould be filled to 3/4th the capacity. Prepare about 1.5L of solution of MgSO4.7H2O and water.During mixing, the agitator should be used for effective mixing.2. After uniform mixing has been achieved, stop the electric supply to the electric heater.3. Allow the flow of cold water (20C) to pass through the jacket at a pre-fixed flow rate with thehelp of water by-pass valve & a Rotameter. Record the flow rate (flow rate may be fixed such thatthe rise in cooling water temperature is maximum around 5-7C maintain by using ice.)


Concentration(gm

solid/gms

olution)


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4. Record the temperature of inlet water and solution temperature with the help ofrespective sensors.5. Put 10gm MgSO4.7H2O in the crystallizer when the temperature rises to 50C for seeding.6. Carry out the crystallization process for about 2 hours.7. After 2 hours, stop the cooling water supply, open the valve fixed at the cone of the crystallizer

and collect the slurry in the bottom receiving tank that is fixed with a mesh at the top. The crystalsshall be collected on the mesh and liquid in the tank.8. Collect all the crystals from the mesh on a filter paper and weigh. Let the weight of the productcrystals be P (kg). For collecting all the crystals you may flush the crystallizer tank with 100-200mlof saturated MgSO4 solution.9. Steps 1-8 may be repeated with the addition of known weight of seed crystals at step 6.10. Steps 1-8 may also be repeated for different values of cooling water flow rates.

SPECIFICATION:

Crystallizer = Material SS, Capacity: 2Ltrs with (jacketed) conical bottom.Stirrer = FHP

Heater = Nichrome Wire Heater Cooling Water Tank = Material SS, Capacity 30 Ltrs, fitted with

pumpFlow measurement = Rotameter for cooling water Pump = FHPReceiving Tank = Material SS, Capacity 2Ltrs, with SS sievePiping = SS and PVC Temp. Sensors = RTD PT-100 typeControl Panel consists of:Digital Temp. Indicator = 0-199.9C, RTD PT-100 Type with multi-channel switch

With Standard make on/off switch, Mains Indicator etc. the whole set up is well designed and arrangedin a good quality painted structure.

FORMULAE:

Amount of wet crystals of MgSO4.7H2O collected after 2 hrs = P kgCrystal yield = Feed Mother LiquorThis must be equal to P the observed yield.

% Recovery = P/ (Crystal Yield)

ldCrystalYie

Pery =covRe%

OBSERVATIONS AND CALCULATIONS:

Sample Observations and Calculations:

DATA:

Concentration of feed solution of MgSO4.7H2O at 80C = 66.2gm/100gm of solutionWt. of Feed solution, F = 2.9856gmMgSO4.7H2O = 1.9856gmFree Water = 1.0000kg

Solubility of MgSO4.7H2O at 20C = 53.8gm/100gm of solution



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= 1.1645 gmMgSO4.7H2O/gm of water

Wt. of MgSO4.7H2O taken = 2.9856 kgAmount of water added = 1.9856 kgConc. of feed solution at 50C = 1.9856 gm MgSO4.7H2O per gm of

free water= 0.662 gm MgSO4.7H2O in 1 gm ofsolution

OBSERVATIONS:

Time T, min Cooling Water Solution Temperature, TsC

Inlet, Twi Outlet, Two

Amount of crystal MgSO4.7H2O collected after 2 hours = P kgWt. of mother liquor = M kg

CALCULATIONS:

Initial conc. of feed, C1 = 0.662 MgSO4.7H2O per gm of solutionAt 80C solubility of MgSO4.7H2O = 0.662 gm/gm of solutionApplying material balance:Final amount of soluble MgSO4.7H2O in the solution

gmOfWater

OHgmMgSo

)662.01(

7.662.0 24

= 1.9586 gm MgSO4.7H2O /gm of water

MATERIAL BALANCE:

Total MgSO4.7H2O Free Water MgSO4.7H2O

Free Water

FeedMother liquor

Material balance as expressed in the table can be compared with the actual quantities recorded during theexperiment. Discrepancy if any should be accounted for.

Amount of wet crystal of MgSO4.7H2O collected after 2 hours, P = ---------kg

Crystal Yield = ---------kg

This must be equal to P the observed yield.



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% Recovery = 100305.3

P

CONCLUSIONS:

NOMENCLATURE:

C1 = Initial solution concentration, kg of anhydrous salt/kg of solvent.C2 = Final solution concentration, kg of anhydrous salt/kg of solvent.R = Ratio of molecular wt. of hydrate and anhydrous salt.V = Solvent lost by evaporation kg/kg of original solvent.W = Initial wt. of solvent (Water), kgX = Wt. fraction of solids in slurry.Y = yield of crystal, kgc = density of crystal, kg/m3

f = Fluid density, kg/m3

p = solid particle density, kg/m3s = slurry density, kg/m3

s = Viscosity of slurry, cPf = Viscosity of saturated solution, cP = Fraction of liquid in slurry.

PRECAUTIONS AND MAINTANENCE INSTRUCTIONS:

1. For proper crystallization feed solution should be saturated.2. During cooling the temperature should be near to 0C.3. Priming or seeding should be done at 40-45C.4. Dont switch on the heater before filling the feed solution in the crystallizer.5. Proper cleaning is necessary with hot water.

TROUBLESHOOTING:

1. If any type of suspended particles comes in the rotameter, then remove the rotameter, clean thetube and then fit it at its place.

2. If there is any leakage, tight that part or remove that and re-fix that again after wrapping Teflontape.

3. If D.T.I display I on display board it means sensors connection are not O.K tight that.4. If switch ON the heater but temperature cant rise but panel LED is ON it means bath heater had

burned replace that.

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Experiment No: 08

DIFFERENTIAL DISTILLATION



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DIFFERENTIAL DISTILLATION

AIM:

To verify Rayleighs Equation by carrying out differential distillation of Binary Mixture.

THEORY:

Differential distillation is a batch operation. The operation is used to separate a liquid mixture whosecomponents have fairly large difference in their boiling points. This type of distillation is frequentlyemployed in laboratory to concentrate one component in the distillate or residue and where some loss ofthe material is tolerated.

Differential distillation is a process of infinite number of successive steps, where, in each step an

infinitesimal portion of a liquid is vaporized and the resulting vapor, which is in equilibrium with theliquid, is removed. Distillation is continued until the desired composition of the distillate is obtained.Rayleigh developed a mathematical equation to give the composition of the distillate and the bottoms.

BINARY DIFFERENTIAL DISTILLATION:

Let L be the number of moles of the mixture at a given instant. Let x be the mole fraction of morevolatile components in liquid mixture.Let y* be the mole fraction of more volatile component in vapor. Y* is in equilibrium with x.

If dL differential amount of liquid vaporized, then by applying the material balance with respect to the

more volatile component we get:

Lx =(L-dL)(x-dx)+y*dL

=L x-x dL -L dx + dL dx + y*dL

Omitting the product dx.dL, we get:

Y*dL = xdL + Ldx

dL(y*-x)= Ldx

(dL/L) = ( dx/y*-x)

The boundary conditions are:

Initially, L = F and x = xF; F = moles of feed mixtureFinally L = B and x = xB; B = moles of bottom mixture

(dL/L)= (dx/y*-x)

ln(F/B)= (dx/y*-x)



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Using the vapor-liquid equlibrium data for the binary system, the plot is made of 1/(y*-x) vs. x. Areaunder the curve between the ordinates at xB and xF gives the value of the integral on the R.H.S. of the

above equation.

From this we can obtain the value of B, the amount of bottoms to be left to attain the given compositionxB of the liquid. Alternatively if we want to calculate the composition of bottoms, when B is known, thenL.H.S. of the above equation can be found out and value of xB adjusted to obtain the area under the curveequal to ln (F/B).For an ideal system, relative volatility is constant. Therefore for an ideal system we can use:

y* = ( x /1 + ( -1)x)

Substituting the value of y* in equation

ln(F/B) = (dx/(( x/1+( -1)x)-x)

= (1/( -1)(1/x +/(1-x)dx

ln(FxF/BxB) = ln(F(1-xF)/B(1-xB))

Both these equations are known as Rayleighs equations.

EXPERIMENTAL SETUP:

The experimental set up to study the differential distillation consist of a 2000 ml single neck round

bottom flask with suitable heating mantle (with sun wig regulator to control the temperature, ON/OFFswitch and indicator lamp), a still head with thermo-pocket (to measure the temperature) is providedover the flask to route the vapors emerging from the flask to the Lei big type water condenser 400 mmlong). Condensed vapors are collected in collecting beaker and the entire assembly is supported with thehelp of a stand.


1. The distillation assembly is charged with 700-750 gm of binary mixture after noting therefractive index with the help of Abbes Refractometer.

2. The heating mantle is turned ON with the regulator set near to 40% and the condenser water isthen started.

3. The distillation is continued for sufficient time so that 70% of the distillate is collected.

4. The weight of the bottoms and refractive index is noted after cooling down to roomtemperature. Similarly the weight and refractive index of the distillate is noted.

5. Using Abbes Refractometer prepare a graph of the more volatile component vs. refractiveindex. For this initially take 10 ml of comp. A and 90 ml of component B. Measure therefractive index and convert the composition of the mixture in mole fraction. Repeat the same

for (20+80, 30+70, 40+60, 50+50, 60+40, 70+30, 80+20, 90+10). You will find this plot to be a



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linear one and this can now be used to determine the composition in terms of molefraction once the refractive index is known.

OBSERVATION AND CALCULATIONS:

Weight of sample feed = WF = kg; F = kg mole

Weight of bottoms = WB = kg; B = kg mole

Weight of distillate = WD = Kg; D = kg mole

Composition of feed = XF = mole fraction

Composition of Bottoms = XB = mole fraction

Composition of Distillate = XD = mole fraction

Plot 1/(y-x) vs. x and calculate xB.

Compare the value of xB obtained graphically with the experimental value.

Use the equation with relative volatility () assuming it to be as constant and calculate the xB andcompare it with experimentally obtained value.

SAMPLE CALCULATIONS:

To find mol. Fraction of water (molar volatile component) in feed

1) Normality of Acetic Acid (A.A.) solution.

N1 V1= N2 V2

2) Weight of A.A. in feed solution

= 31.053) Weight of water in feed solution

= Total wt. of feed- wt. of A.A.

= 230-31.05 = 198.95 gms.

Total moles of feed solution F

= (31.05/60.05)+ (200/ 18) = 11.628

4) Mol. Fraction of water in feed solution (xF)



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= (200/18)/11.628 = 0.955

To find mole fraction of water (molar volatile component) in distillate in residue after distillation.

1) Normality of residue

N1 V1 = N2 V2

N1 = 115.2/5 = 3.04 N

Wt. of A.A. in feed solution

= Normality Eq. weight vol. of solution

= 3.04 60.050.058

= 10.58 gms.

2) Wt. of water in residue solution

= Total wt. of residue- wt. of A.A.

= 58- 10.58= 47.41 gms.

3) Total moles in residue

= (10.58/60.05) + (47.41/18)

= 2.8099

4) Mole fraction of water in residue (xW)

= (47.41/18)/2.8099

= 0.9373

For Rayleighs Equation

Ln(F/W) = ln(2.633/2.8099)

= 0.9329

CONCLUSIONS:



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Experiment No: 09

ABSORPTION IN

PACKED BED COLUMN



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ABSORPTION IN PACKED BED COLUMN

AIM: To determine the absorption efficiency of the packed bed column.

THEORY:

The process of absorption of the gas in the liquid is entirely a physical one. However in number of casesin which the gas on absorption reacts chemically with a component of the liquid phase. Thus inabsorption of CO2 by NaOH the CO2 reacts directly with the NaOH and the process of mass transfer ismade much more complicated. Similarly when CO2 is absorbed in Ethanolamine solutions there is directchemical reaction between the Amine and the gas. In such cases there is a liquid film followed by areaction zone.

The effective interfacial area a in the gas liquid contactor is an important mass transfer characteristic inthe design of contactor. In the case of packed column a is determined by the velocity of the liquid(dispersed phase) and properties like wetting characteristic of packing etc. this experiment is designed toverify the theory of absorption accompanied by a fast chemical reaction. Due to fast chemical reactionthe concentration of CO2 is bulk of the liquid is always zero and hence the liquid phase residence timeneed not be determined.

In packed column a increases very rapidly with VL initially (at low values of VL in the range of 0.001-0.004 m/s). The increase in a become less significantly at higher values of VL and eventually the lot ofaVs. VL flattens. The value of VL beyond which there is no significant increase a is called the minimumwetting velocity (MWV).

The system used in this experiment is a gaseous solvent A dissolving in a liquid acid simultaneouslyreacting with the reactant B present in the liquid phase.

A + bB AB Product

The new product AB formed diffuses towards the main body of the liquid. The concentration of B at theinterface falls, this results in diffusion of B from the bulk of the liquid phase to the interface. Since thechemical reaction is rapid, B is removed very quickly so that it is necessary for the gas A to diffusethrough the part of the liquid film before meeting B. there is thus a zone of reaction between A and Bwhich moved away from the gas liquid interface taking up some position towards the bulk of the liquid.

The final position of the reaction zone will be such that the rate of diffusion of A from the gas liquid.Interface is equal to the rate of diffusion of B from the main body of the liquid. When this condition has

been reached the concentration of A, B and AB can be indicated as shown in the figure.

According to the film model if the reaction is fast enough the solute A will be consumed by the reactionin the liquid film itself and its concentration will be zero at the end of the liquid film. The condition for afast second order reaction is,

[ ]( ) 3/** 2 >LOAA KBKD -- (1)

Where,



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DA Diffusivity of A, m2/secKA Second order reaction constant, m3 /kmol.sec[BO ] Concentration of B in bulk liquid, kmol/m3

KL Liquid side mass transfer coefficient, m/sec

In such a case the reaction occurs simultaneously with the diffusion process in the liquid film andtherefore enhances the rate of absorption significantly. If the reactant B is present in far excess of thestoichiometric requirements for the reaction in the film, then the depletion of the reactant concentrationin the film is negligible. The condition for such a case is given by,

[ ]( ) [ ] [ ]( )**/*/** 2 OAOBLOAA AbDBDKBKD


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coefficient The coefficient decreased progressively as the sodium hydroxide was converted to carbonate.The volumetric coefficient, KG a appeared to be independent of the packing size

EXPERIMENTAL SETUP:

The equipment consists of one column arranged on the top of the other. Liquid re-distributor andsampling point (pressure tapping) is provided at the top, bottom of the assembly. Rota meters to measurethe flow rate of Carbon Dioxide, Air and dilute solution of Sodium Hydroxide individually are alsoincluded. The CO2 is supplied from the cylinder provided and air from the air compressor. Onlinemixture is provided for the gases and then they enter the column assembly from the bottom with the helpof gas distributor. The column is filled with Rasching rings of 12 mm size. Aq. NaOH solution issprayed with the help of a SS tank, pump, bypass line and pre calibrated Rotameter in counter currentmanner to the gas flow. Liquid level adjuster is also provided to ensure liquid seal at the bottom. Onemanometer is provided to measure the pressure drop across the columns. The vent of the top column

shall always be kept open. Sample collection bottle is also provided along with it.

PROCEDURE:

Initially start the air compressor and collect sufficient air in the pressure tank so as the pressure is about3-4 kg/cm2. Prepare the dilute NaOH solution in the tank. Open the valve of the pressure tank and allowthe air to pass through the column. Set the air flow at the desired value and then open the valve on theCO2 cylinder and adjust the flow rate to predetermined value. Now start the pump for the NaOH solutionand using the bypass valve and feed valve set the desired value of flow rate. After sometime take thesample at various points (liquid as well as gas) and analyze them.

Initially start the liquid flow at sufficiently high rate (VL = 0.03 m/s) to ensure that all the packing arewetted. The flow rates of gas and liquid are adjusted at predetermined values. The CO 2 flow rate should

be such that the %CO2 in the mixed gas is about 8-10%. The gas velocity has no effect on the interfacialarea in a packed column. Hence a value of VG between 0.1-0.2 m/s may be chosen for all theexperiments and keeping it constant. The linear superficial liquid velocity V is the most importantvariable. The range for V should be fixed between 0.001-0.007 m/s.

The system is allowed to reach steady state after fixing the liquid level in the bottom section at a markedheight. Inlet and outlet samples are withdrawn for analysis. This procedure is to be repeated for 6-7different values of VL chosen in such a way that the range indicated is fully covered.

OBSERVATIONS:

System : (CO2+Air) + Aq. NaOH solutionPacking Used : Rasching ring of size 12 mmColumn Diameter : mm(ID)Pressure : k-N/m2

Packed Height : mm (in each column)VG : m/sec


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