University of Jordan
Faculty of Engineering and Technology
Department of Chemical Engineering
Chemical Engineering Laboratory (3)
1
Experiment Number -1-
Gas absorption
Objectives
1. To study the hydrodynamic characteristics of a packed column.
2. To establish a mass balance on the absorbed gas in the column.
3. To determine mass transfer coefficients, the number of transfer units and the effective height
equivalent to a transfer unit.
Apparatus
The equipment consists of a packed column of 2 meters in height and 7.5 cm in diameter, packed
with 10mm glass Raschig rings. Air compressor is supplied with a flow meter. Carbon Dioxide
cylinder is also available with a flow meter. Water supply tank is available with water pump, and a
flow meter to indicate the flow of water. Mercury manometer and water manometer present to
indicate the pressure drop across the column.
Procedure
1. Fill the water supply tank with water.
2. Make sure that valves V1, V2, and V7 are closed and that V4 and V5 are open.
3. Check that the manometers show zero pressure difference across the column.
4. Switch on air compressor. Adjust valve V2 and take readings of manometers at different
values of air flow rates.
5. Repeat again with packed column in wet.
6. Repeat again with different values of water flow rates.
7. To determine mass transfer coefficient, adjust flow rates of water and air so that the
condition in the absorption column between flooding point and loading point.
8. Allow Carbon Dioxide to enter the column at certain flow rate.
9. At steady state, take a sample of the liquid going to drain and find the concentration of
Carbon Dioxide in it by titrating against NaOH solution.
2
Theory
When a liquid is flowing counter currently to the gas, for low gas flow rates, the effect is as for
the wet packing:
The pressure drop increases, and the pressure drop follows a square law characteristics.
Further increase in gas flow rate or liquid flow rate makes the liquid fails to drain from some sections
of the tower.
Pressure drop for dry packing (kg.m-2
) is given by:
π₯ππ =πΆ. ππ
2
ππ
Where:
ππ= mass velocity of the gas based on the total cross section of the tower (kg.m-2
.s-1
)
ππ= gas density (kg.m-3
)
C= constant which equals to 264 for 10 mm Raschig rings.
Pressure drop for wetted packing (kg.m-2
) is given by:
βπ = π₯ππ . π΄π
ππππ΄π =π΅. ππ
ππ
Where: ππ= liquid flow rate based on the total cross section of the tower (kg.m-2
.s-1
)
ππ= liquid density (kg.m-3
)
B= constant which equals to 0.084 for 10 mm Raschig rings.
For mass transfer characteristic
Consider a packed tower of cross section sectional area A; assume that the effective
interfacial area for mass transfer of liquid film on the packing is a ( π2
π3 ) of the tower volume.
The area for mass transfer in small increment of height dh will be a(A.dh) m2, and the quantity
of solute in the gas passing into solution in this incremental height is d(Gy).
If Kog is the overall mass transfer coefficient based on the gas phase, then:
π πΊπ¦ = πΎππ . π. π΄. π¦β β π¦ .πβ
3
π» = π(πΊπ¦)
πΎππ . π. π΄. π¦β β π¦
π¦1
π¦2
The height of transfer unit π»ππ is
π»ππ =πΊ
πΎππ .π. π΄
The number of transfer unit πππ is
πππ = ππ¦
π¦β β π¦
π¦π‘
π¦π
And H=πππ . π»ππ
Similarly, in terms of the liquid phase;
H=πππ . π»ππ
Calculations
1-Draw the hydrodynamic characteristic curves of the packed column and find the loading point and
the flooding point.
2-Establish a total mass balance on Carbon Dioxide and discuss the difference between the inlet and
outlet Carbon Dioxide amounts.
3-Calculate the overall mass transfer coefficient, the number of transfer unit, and the height of
transfer unit.
4
References
1- J. M. Coulson, and J. L. Richardson, βChemical Engineeringβ vol.2, Pergamon Press.
2- Treybal, R. E; βMass Transfer Operationsβ, McGraw Hill.
3- Foust, A.S; Wenzel, L.A; Clump, C. W; Mans, L; and Anderson, L.B; Principles of Unit
Operationsβ, Wiley-Mass Transfer, chapter 14, 16.
4- Nrman, A.S; βAbsorption, Distillation and Cooling Towersββ, Longman, London-1962.
5
Gas Absorption
Raw Data Sheet part (1)
Dry Packing Wet Packing Water flow Rate= Water flow Rate= Water flow Rate=
Air flow
rate βP
Air flow
rate βP
Air flow
rate βP
Air flow
rate βP
Air flow
rate βP
6
Raw Data Sheet part (2)
Run No. 1 2 3 4 5
Inlet Water Flow Rate
(ml/min)
Inlet Air Flow Rate
(ml/min)
Inlet Carbon Dioxide Flow
Rate(ml/min)
Concentration of NaOH
solution(mol/l)
Volume of sample(ml)
Volume of NaOH titrant
(ml)
Temperature of outlet
solution (ΒΊC)
Instructorβs Signature:
Date:
7
Experiment Number -2-
Distillation
Objectives
1- To demonstrate the effect of variation of reflux ratio upon distillate composition.
2- To determine the number of theoretical plates within the column using the methods of
McCabe and Thiele and Panchon and Savarit.
3- To find the Murphee plate efficiency.
Apparatus
Distillation unit is a semi-pilot plant comprises a reboilet operating on steam. Process vapors
enters at the base of either 80 mm packed column; packed with 10 mm glass Raschig rings, or 80 mm
bubble cap column contains 8 bubble-cap plates. At the top of each column there is an overhead
condenser.
Just below the overhead condenser, there is a liquid distillate separator that leads to reflux
control flow meters; RI.1A and RI.1B, RI.1A indicates the quantity of distillate returned to either column,
while RI.1B indicates the quantity of distillate removed as product.
Product distillate is cooled in the product cooler and passes through a measuring cylinder and
can be either collected in a vessel or returned to the reboiler.
Cooling water is available from the main cooling tower and pumped to the condensers through
the flow-meter FI.2. Temperature indicators are available for measuring temperature of liquid and vapor
along either column.
Procedure
1- Put 20 ml liters of water and methanol (5:1) in the feed vessel.
2- Start the cooling water pump and slowly adjust the flow rate of cooling water using valve
FCV2 to about 4 L/min on flow meter F12. Note that the pressure on PI2 should not
exceed 2 bars. In case no visual indications of water flow, close FCV2 and ask your
supervisor.
3- Making sure that V6 is closed, open V12 and close V13 or vice versa depending on the
column to be operated upon.
4- Open slowly PCV4 to let steam in and also open V11 (steam trap by-pass). Once steady
flow of steam issues from the drain, close V11. Note that the pressure of steam should not
exceed 1.5 bar.
5- When distillate liquid is seen on top of the column, open valve PCV1 to allow flow
through flow meter RI.1B.
8
6- With the aid of measuring cylinder RI.1C and stop watch, flow rate through RI.1B should
be calibrated.
7- Once the calibration is done, adjust flow rate through flow meters RI.1b to give the
desired reflux ratio.
8- Take the temperature readings across the column as well as a sample from the liquid
distillate. Find the refractive index of the sample.
9- The experiment should be repeated at different reflux ratio.
10- Repeat for the other column.
Theory
The distillation column available in the laboratory is an enriching section of a distillation
column. The relationship between vapor (y) and liquid (x) as they pass each other between
theoretical plates is given by (Numbering of plates increase from top to bottom).
π¦π=1 = π
π + 1 ππ +
ππ·
π + 1
Where:
R= Reflux ratio
XD = composition of distillate at the top of the column.
That is the equation of the operating line for McCabe and Thiele method, and passes the points
(y1, XD) and has an intercept of ππ·
π +1 .
For Ponchon and Savarit method, the operating line is given by πΏπ
π·=
ππ·βπ¦π+1
π¦π+1βππ=
π β²βπ»ππ+1
π»ππ+1βπ»πΏπ
Where:
D= Distillate rate.
HVn+1 = Enthalpy of liquid at its dew point.
H Ln = Enthalpy of liquid at its boiling point.
πβ² =ππ + π·π»π·
π·
Where:
9
Q = heat removed in the condenser.
The above equation is the equation of a straight line passes through the points (HVn+1 ,y n+1) and (H Ln , Xn )
and ( πβ² , XD ) at βD (difference point).
Murphee plate efficiency in vapor terms is given by
πΈππ =π¦π β π¦π+1
π¦π β π¦π+1
And in liquid terms:
πΈππΏ = ππβ1 β ππ
ππβ1 β ππ
Calculations
1- Graphically show the relationship between the rotameter scale readings RI.1B and the
actual flow rate.
2- Calculate the number of theoretical plates using the methods of McCabe and Thiele and
Ponchon and Savarit for bubble cap column for one reflux ratio only.
3- Graphically show the relationship between reflux ratio and the top composition for both
column and compare between the results.
4- Find Murphee plate efficiency.
10
Equilibrium data for Methanol- Water system @ P= 681 mmHg.
TEMPERATURE x1 (methanol) y1 (methanol)
Β°C mol/mol mol/mol
97.0596 0 0
95.4691 0.01 0.0755924
93.7949 0.02 0.139381
92.293 0.03 0.193918
90.9367 0.04 0.241082
88.5793 0.06 0.318613
86.5944 0.08 0.379801
84.8944 0.1 0.42947
81.5234 0.15 0.521318
78.9814 0.2 0.585619
76.9566 0.25 0.634452
75.2727 0.3 0.673881
73.8227 0.35 0.707274
72.538 0.4 0.736645
71.3732 0.45 0.763266
70.2974 0.5 0.787979
69.2886 0.55 0.811353
68.3317 0.6 0.833787
67.4154 0.65 0.855558
66.532 0.7 0.876864
65.6757 0.75 0.897837
64.8425 0.8 0.918569
64.0296 0.85 0.939118
63.2349 0.9 0.959519
62.9217 0.92 0.967645
62.6112 0.94 0.975754
62.303 0.96 0.983847
62.1499 0.97 0.987889
61.9973 0.98 0.991928
61.8453 0.99 0.995965
61.5566 1 1
11
Enthalpy Data for Methanol-Water mixture
HL( J/g.mole) X Y HV( J/g.mole)
6061 0 0 47652
5267 0.05 0.273 45144
4723 0.1 0.418 43681
4389 0.15 0.517 42678
4138 0.2 0.579 42009
3929 0.3 0.665 41089
3846 0.4 0.729 40379
3804 0.5 0.779 39835
3804 0.6 0.825 39334
3804 0.7 0.87 38832
3804 0.8 0.915 38331
3816 0.9 0.958 37871
3887 0.95 0.979 37620
3954 1 1 37453
12
Distillation
Raw Data Sheet
Run # RI.1A RI.1B T3 T2D T2C T2F T2E TI.1
1
2
3
4
5
Instructorβs Signature:
Date:
13
Experiment Number -3-
Water Cooling Tower
Objective
To study the mass transfer characteristics of a packed water cooling tower.
Apparatus
A forced draught laboratory packed tower is used. The tower is mounted in the Chemical
Engineering main laboratory, pilot plants area. The total depth of packing (z) is 1.27m. Dry and
wet bulb temperatures of all streams could be measured by mercury thermometers located at
different point in the column. Air flow rate can be measured by an orifice meter. Water flow rate
is measured by a flow meter.
Calculations
1.For each run, calculate the overall mass transfer coefficient ky.a using the relation:
Z=HtOG . NtOG
Z = total depth of packing=1.27m
HtOG = height of transfer unit. (m)
NtOG = number of transfer unit .
HtOG=aky
Gs
.
Gs= mass flow rate of inert gas. (Kg/hr)
NtOG=
2
1
*
H
HHH
dH== area under the curve of (1/(H
*-H) vs. H)
H =Enthalpy of air at wet and dry temperatures. (KJ/kg)
H*=Enthalpy of air at equilibrium. (KJ/kg)
14
The integral is to be evaluated using a graphical integration method.
2. The values of ky.a at different gas and liquid flow rates are correlated by the relation:
Ky.a= )(
L
Gs
, = constants
References
1-Treybal; R.E., βMass Transfer Operationsβ, McGraw Hill.
2-J.M.Coulson, and J.L. Richardson, βChemical Engineeringβ, vol. 1, Pergamon press.
15
Water Cooling Tower
Raw Data Sheet
Instructorβs Signature:
Date:
Run No. 1 2 3 4 5
Inlet water Flow
Rate(kg/hr)
Inlet air Flow Rate
(m3/hr)
Inlet air dry bulb
temperature (ΒΊC)
Inlet air wet bulb
temperature (ΒΊC)
Outlet air dry bulb
temperature (ΒΊC)
Outlet air wet bulb
temperature (ΒΊC)
Inlet water
temperature (ΒΊC)
Outlet water
temperature (ΒΊC)
16
Experiment Number -4-
Liquid-Liquid Extraction
Objectives:
To examine the mass transfer coefficientβs dependence on liquid flow rate for counter current
liquid-liquid extraction in a packed column.
Procedure:
1. Prepare approximately 20 liters of 0.5 N solution of benzoic acid in toluene and place in
feed tank.
2. Fill water storage tank with approximately 20 liters of distilled water.
3. Start water pump and set water flow rate to 200ml/min.
4. Once the extraction column is filled with water, start the feed tank pump.
5. Keep the interface between the organic and aqueous phases constant so that steady state
could be achieved.
6. Operate for thirty minutes and then take a sample of each outlet stream and toluene-
benzoic acid inlet stream.
7. Titrate the aqueous phase sample with 0.05 M sodium hydroxide solution and the organic
phase samples with 0.20 M ethanolic sodium hydroxide solution.
8. Repeat sampling after 5 minutes and the run to be stopped if two successive readings are
the same.
9. Repeat for different flow rates of water.
Calculations:
Calculate the mass transfer coefficient and find its dependence on liquid flow rate.
References:
1. J. M. Coulson, and J. L. Richardson, βChemical Engineeringβ vol. 2, Pergamon Press.
2. Treybal, R. E., βMass transfer Operationsβ, McGraw Hill.
3. T. J. Appel and J. C. Elgin, Counter Current Extraction of Benzoic Acid between
Water and Toluene, Ind. Eng. Chem. Vol. 29, No. 4, pg 451-459.
17
Liquid-Liquid Extraction
Data Sheet
Concentration of aqueous NaOH: β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦..
Concentration of ethanolic NaOH: β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦
Run No. 1 2 3 4 5
Water flow rate
Volume of ethanolic
NaOH titrant needed
for feed solution
Volume of ethanolic
NaOH titrant needed
for Raffinate
Volume of aqueous
NaOH titrant
Instructorβs Signature:
Date:
y = -0.016x2+ 0.876x + 1.463
0
2
4
6
8
10
12
14
0 5 10 15 20 25
Co
nce
ntr
atio
n o
f B
ezo
ic a
cid
-aq
uo
es
ph
ase
(Ib
mo
l/ft
3)*
10
-4
Concentration of Benzoic acid-organic phase (Ibmol/ft3)*10-3
19
Experiment Number -5-
Determination of Diffusion Coefficient
Objectives:
1. To determine the diffusion coefficient of acetone vapor into a stagnant non-diffusion air film.
2. To determine the convective mass transfer coefficient kc of the evaporation of pure Acetone into air
film.
Introduction:
The diffusivity or diffusion coefficient D depends upon the temperature, pressure and the nature of
the components of the system. When a stream of air is blown across the top of the tube at a sufficient
rate, evaporation of pure liquid Acetone at the bottom of the narrow tube will take place and the liquid
boundary will move with time .If the length of the diffusion path changes a small amount over a long
period of the time the pseudo-steady state diffusion model may be used to calculate the diffusion
coefficient of Acetone into air.
Procedure:
1. Fill the narrow tube with Acetone to within 20mm of top of the tube. 2. Immerse the cell in the constant temperature water bath which is maintained at 30β°C. 3. Measure the length of the initial diffusion path (Z0) using the vernier caliber. 4. Connect the air tube to the air source and open the air valve. 5. Measure the length of the diffusion path after 90 min and after 180 min.
Air
Z
Aceton
e
20
Determination of Diffusion Coefficient
Raw Data Sheet
Temperature: ____________________
Density of Acetone: _____________________
Atmospheric Pressure: __________________
Time Height
Instructorβs Signature:
Date:
21
Experiment Number -6-
Wetted Wall column
Objectives
1. To measure the Sherwood number for mass transfer from the wall into turbulent air flow
for different liquids with varied air flow rates.
2. To Correlate the result in the form: 6.0Re cb Scash ; and find a, b, and c.
3. To Compare the experimental results with the various available analogies between
momentum , heat and mass transfer e.g. Reynolds Analogy, Van Karman Analogy ,
Colburn β Chilton Analogy and Sherwood Gilliland correlation.(See ref. (1) and (3) ).
Equipment
The wetted wall column consists mainly of a vertical pipe of known diameter and length.
Liquid flows down the inside wall of the column and air is blown counter currently up the
column. Heaters are provided for both the air and the liquid. Air and liquid rates are measured by
flow meter. Air and liquid temperature are measured with thermometers.
The evaporation rate may be measured by observing the rate of change of liquid level in the
liquid reservoir.
Calculations
The mass transfer coefficient in the gas phase could be calculated from:
mg PAKNA
22
Where
NA mass transfer rate gm/s
Kg = mass transfer coefficient , gm/cm2
.s.atm.
A = area of gas- liquid interphace, cm2.
mP = logarithmic mean driving force difference, atm.
For Sh, Sc, and Re, see references.
References
1. R.E. Treybal , Mass Transfer Operation , 3 rd Ed.
McGraw β Hill Book Co.
2. W.L. Badger and J.T. Banchero , Introduction to Chemical engineering ,
McGraw β Hill Book Co.
3. O.C , Bennet and J.C Myero, Momentum Heat and Mass Transfer , 3 rd Ed.
McGraw β Hill Book Co.
23
Wetted Wall Column
Raw Data Sheet
Run No. 1 2 3 4 5
water Flow Rate
Air Flow Rate
Inlet water
temperature (ΒΊC)
Outlet water
temperature (ΒΊC)
Inlet air dry bulb
temperature (ΒΊC)
Inlet air wet bulb
temperature (ΒΊC)
Outlet air dry bulb
temperature (ΒΊC)
Outlet air wet bulb
temperature (ΒΊC)
Instructorβs Signature:
Date:
24
Experiment Number -7-
Adsorption of Dye Solution on Activated Carbon
Objectives:
1. To produce Concentration βTime curve for the adsorption of dye solution by activated
carbon.
2. To investigate the effect of initial dye concentration and speed of agitation on the
Concentration- Time curves.
3. To construct the equilibrium isotherm for the adsorption of solute on adsorbent.
Introduction:
Activated carbon adsorption is one of the physical purification techniques which offer one of
the most efficient processes available for removing certain organics and in-organics from waste
water.
Physical adsorption results from the action of Vander Waals forces comprised of London
dispersion forces and classical electro-static forces between adsorbate and adsorbent.
Apparatus:
The apparatus comprises of 3Γ2 L beakers, 3 variable motors, 50 small bottles (about 10-15 ml),
and visible spectrophotometer.
Materials:
Activated carbon and dye solutions
25
Procedure:
a) Isotherms 1. Make up 2 liters dye solution by dissolving exactly 1g dye in 2 liters of
distilled water.
2. Using the small bottles, weigh out 0.001, 0.002, 0.004, 0.008, 0.012, 0.016,
0.020, 0.030, 0.040, 0.080, 0.100,and 0.15 (g carbon).
b) Batch studies 1. Fill the beaker to 1.7 liter of dye solution; adjust the speed of agitator to three
different values in the beakers (100,200,300rpm).
2. Add .085 g of carbon to each beaker. Time sample should be taken for the
three beakers after (1, 2, 3,4, 6, 9, 15, 25, 35, 49, 64, and80 min).
3. Repeat step 1 and 2, but change the amount of carbon to 1.2g.
Calculations:
1. Plot (Cf/C0) vs. time for the three different speeds.
2. Plot the equilibrium isotherm curve and find the Freunlich equation constants
References:
1. Treybal, R.E, βMass Transfer Operationβ, McGraw Hill.
2. Perry and Chilton, βChemical Engineerβs Handbookβ ,McGraw Hill.
26
Adsorption of Dye Solution on activated Carbon
Raw Data Sheet (1)
a. Isotherms
Volume of Solution
Initial Concentration of Solution
Mass of Carbon (g) Reading of (Absorbance OR
Transmittance) at equilibrium
0.001
0.002
0.004
0.008
0.012
0.016
0.020
0.030
0.040
0.080
0.100
0.150
27
Raw Data Sheet (2)
b. Batch Studies
Run Number: ______1_______
Volume of the Solution
Mass of Carbon
Speed of Agitator
Initial Concentration of Solution
Time Reading of (Absorbance OR Transmittance)
1
2
3
4
6
9
15
25
35
49
64
80
28
Run Number: _____2________
Volume of the Solution
Mass of Carbon
Speed of Agitator
Initial Concentration of Solution
Time Reading of (Absorbance OR Transmittance)
1
2
3
4
6
9
15
25
35
49
64
80
29
Run Number: ____3_________
Volume of the Solution
Mass of Carbon
Speed of Agitator
Initial Concentration of Solution
Time Reading of (Absorbance OR Transmittance)
1
2
3
4
6
9
15
25
35
49
64
80
30
Run Number: ____4_________
Volume of the Solution
Mass of Carbon
Speed of Agitator
Initial Concentration of Solution
Time Reading of (Absorbance OR Transmittance)
1
2
3
4
6
9
15
25
35
49
64
80
Instructorβs Signature:
Date:
31
0
5
10
15
20
25
0 10 20 30 40 50 60 70 80 90 100
Co
nce
ntr
atio
n(p
pm
))
Trasmittance(%)
32
0
10
20
30
40
50
60
70
80
90
100
-0.01 0.01 0.03 0.05 0.07 0.09 0.11 0.13 0.15
(Tra
nsm
itta
nce
)
Mass (g)
Isotherm
33
Experiment Number -8-
Soxhlet Extraction
Objectives:
- To study Solid-Liquid extraction process using Soxhlet extractor.
- To investigate the effect of residence time and solvent type on the extraction of oil
from Olive cake.
- To calculate the Soxhlet extraction efficiency.
Equipment:
The experiment apparatus (Figure (1)) consists of:
Soxhlet extractor - 40 mm ID, with 500-mL round bottom flask.
Thimble
Condenser
Heating mantel
Figure (1): A schematic diagram of a Soxhlet extractor
1. Solvent
2. Still pot
3. Distillation arm
4. Thimble
5. Solid
6. Siphon top
7. Siphon exit
8. Expansion adapter
34
The solid material containing some of the desired compound is placed inside a thimble made
from thick filter paper, which is loaded into the main chamber of the Soxhlet extractor. The
extraction solvent to be used is taken into a distillation flask and the Soxhlet extractor is then
equipped as shown in fig (1).
The solvent is heated to reflux. The solvent vapor travels up the distillation arm and floods into
the chamber housing the thimble of solid. The condenser ensures that any solvent vapor cools,
and drips back down into the chamber housing the solid material.
The chamber containing the solid material is slowly filled with warm solvent. Some of the
desired compound will then dissolve in the warm solvent. When the Soxhlet chamber is almost
full, the chamber is automatically emptied by a siphon side arm, with the solvent running back
down to the distillation flask. This cycle may be allowed to repeat many times, over hours or
days.
After extraction the solvent is removed, typically by means of a rotary evaporator, yielding the
extracted compound.
Theory:
Solid liquid extraction (leaching) means the removal of a constituent from a mixture of solids by
bringing the solid material into contact with a liquid solvent that dissolves this particular
constituent. In this experiment oil is extracted from olive cake.
The amount of oil extracted (oil percentage) can be calculated as follow:
ππ’π₯ π©ππ«πππ§πππ π = πππ’π π‘π π¨π π¬π¨π₯π’π ππππ¨π«π ππ±ππ«ππππ’π¨π§ β πππ’π π‘π π¨π π¬π¨π₯π’π πππππ« ππ±ππ«ππππ’π¨π§
πππ’π π‘π π¨π π¬π¨π₯π’π ππππ¨π«π πβ πππ%
ππ±ππ«ππππ’π¨π§ ππππ’ππ’ππ§ππ² =ππ±π©ππ«π’π¦ππ§πππ₯ π¨π’π₯ π©ππ«πππ§πππ π
ππ‘ππ¨π«πππ’πππ₯ π¨π’π₯ π©ππ«πππ§πππ π β πππ%
Procedure:
Part 1: Residence Time effect
1. Weigh about 10 grams of olive cake sample.
2. Put the solid sample into a previously weighed thimble and then put into the Soxhlet
apparatus.
3. Add 100 ml of Hexane solvent to the extraction chamber.
35
4. Turn the heat on and start the experiment.
5. End the experiment after 3 extraction cycles (3 siphons).
6. Turn off the heater and wait until it cools down. Remove the thimble and leave it in the
fume hood to dry out.
7. Repeat steps (1-6) three times doing 6, 9 and 12 cycles.
8. The next day, when the thimbles containing the olive cake are completely dry, record the
weight of each thimble.
Part 2: Solvent Type effect
1. Perform the experiment as in (Part 1) using (100 ml Hexane) and end it after 8 cycles.
2. Repeat the experiment using (100 ml Isopropanol) and end it after 8 cycles.
Note: Either Part 1 or Part 2 is done in the lab.
Calculations:
- Calculate oil percentage for each run.
- Draw the percentage of oil as a function of number of cycles done.
- Calculate the extraction efficiency.
- What are the optimum conditions (number of cycles and solvent type) for Soxhlet
extraction of oil from olive cake, why?
36
Soxhlet Extraction Data Sheet
Part 1: Residence Time effect
Type of
solvent
No. of
cycles
Thimble's
weight (g)
Olive cake
weight (g)
Final
weight (g)
Part 2: Solvent Type effect
Type of
solvent No. of cycles
Thimble's
weight (g)
Olive cake
weight (g)
Final
weight (g)
Instructorβs Signature:
Date:
37
Experiment Number -9-
Tray Drier
Objectives:
1. To produce drying rate curve for a wet solid in air of fixed temperature and humidity.
2. To investigate the effect of air temperature, air velocity on drying rate.
3. To calculate the total heat transfer coefficient, and mass transfer coefficient for a wet solid in
air.
Equipment:
The apparatus comprises of an air duct mounted on a floor-standing frame. Air is drawn into
the duct by a motor whose speed can be controlled. The air passes over an electrically-heated
element into the central section of the duct where trays of the material to be dried are suspended
in the air stream. The trays are carried on a support frame which is attached to a digital balance
mounted above the duct.
Air is discharged to the atmosphere through an outlet duct section in which is mounted a
digital anemometer for measurement of air velocity. Wet and dry bulb temperatures of the air are
measured using an aspirated psychrometer.
Procedure:
1. Place one or more of the trays available with the experiment on the support frame inside the
air duct and record the weight.
2. Put some sand in one or more of the trays, and record the weight again.
3. Add some water to the sand and record the weight.
4. Switch on the unit and set the fan speed to the midpoint.
5. Switch on the heaters as well as the stop clock.
6. Record the weight of the wet sand + trays+ support frame together at regular time intervals as
well as the dry and wet bulb temperatures of air before and after the trays.
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7. Record the velocity of air.
8. Once drying is complete, switch off the unit.
9. The procedure can be repeated with another variable such as air speed, or different material.
Theory:
Immediately after contact between the wet solid and drying medium (air), the solid
temperature adjusts until it reaches a steady state. The drying rate becomes constant and remains
constant until it reaches certain critical moisture content.
The constant rate of drying is given by:
cR = dryTh
- wetT .A
Rc =constant rate of drying (kg/hr)
h = heat transfer coefficient (KJ/hr.m2.k).
Ξ» = latent heat of evaporation of water. (KJ/Kg)
Td,Tw = temperature of inlet dry &wet air.(K)
A = area of tray (m2)
The rate of drying (Rc) also depends upon the rate of diffusion of vapor into the bulk gas stream
and is given by:
cR = dh . .A ( w - )
hd = Mass transfer coefficient. (m/hr)
A =Area of tray/ trays. (m2)
Ο =Density of the gas. (kg/m3)
w = Humidity of the gas saturated with vapor at the inlet wet bulb temperature. (Kg/Kg)
= Humidity of the inlet gas .(Kg/Kg).
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Also amount of water evaporated (drying rate) can be given by:
.cR M A d ( 2 - 1)
M.Ad=V. Ο .Ad
V = air velocity. (m/hr)
Ad = cross-sectional area of duct. ( m2)
Ο = air density. (kg/m3)
2 , 1 = specific humidity of air at outlet and inlet of trays. .(Kg/Kg)
M = air mass flow rate per unit area (Kg/hr. ( m2)
Calculation:
1. Draw graph of moisture contents vs. time.
2. From the above curve, draw graph of drying rate vs. moisture contents and locate the critical
Points.
3. Calculate the mass transfer coefficient and heat transfer coefficient.
4. Perform a mass balance to get rate of drying and compare the results with the difference in
Weights.
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Raw Data Sheet
Speed of Fan = ---------------------------- Scale Reading of Heater = --------------------
Mass of (holder + empty tray) = ---------------------------- Mass of (holder + empty tray+ dry solid) =------
Mass of (holder + empty tray+ wet solid) =------------------------
Time
(min)
Total
Mass
(g)
Inlet Air
Temperature
outlet Air
Temperature
Time
(min)
Total
Mass
(g)
Inlet Air Temperature outlet Air
Temperature
Dry
Bulb(ΒΊC)
Wet
Bulb(ΒΊC)
Dry
Bulb(ΒΊC)
Wet
Bulb(ΒΊC)
Dry
Bulb(ΒΊC)
Wet
Bulb(ΒΊC)
Dry
Bulb(ΒΊC)
Wet
Bulb(ΒΊC)