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• MUHAMMAD IRFAN MALIK

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Lab Manuals (Experiments)

1. General Safety Precautions 2. Experiment 1 (Gas Diffusion Coefficients Apparatus)

3. Experiment 2 (Ion Exchange Apparatus)

4. Experiment 3 (Ion Exchange Apparatus)

5. Experiment 4 (Batch Distillation Apparatus)

6. Experiment 5 (Batch Distillation Apparatus)

7. Experiment 6 (Batch Distillation Apparatus)

8. Experiment 7 (Continuous Distillation Apparatus)

9. Experiment 8 (Continuous Distillation Apparatus)

10.Experiment 9 (Gas Absorption Apparatus)

11.Experiment 10 (Gas Absorption Apparatus)

12.Experiment 11 (Liquid-Liquid Extraction Apparatus)

13.Experiment 12 (Liquid-Liquid Extraction Apparatus)

14.Experiment 13 (Tray Drier Apparatus)

15.Experiment 14 (Tray Drier Apparatus)

16. Experiment 15 (Fluidized Bed Drier Apparatus)

Page - 1

General Safety Precautions

Precautions: (Common for all experiments) 1. Personal Safety: 

Check the proper working of residual current circuit breaker (RCCB).



Ensure that there is no leakage of any fluid especially water to contact with electrical supply.



Always disconnect equipment from the electrical supply when not in use.



Use fire extinguishers in case of fire or explosion.



Do not smoke because flammable liquids, gases, and vapors can cause fire.

2. Equipment Safety: 

Do not exceed upper limits of operating conditions (T = Temp., P = Pressure, F = Flowrate, S = Speed).



Check proper working of equipment ON/OFF Circuit Breaker or Switch.



Do not use equipment without lab attendant.



Do not try to become a juggler with equipment but if you don’t know anything then report and ask for it.

3. Chemical Safety: 

Drain any residual water present in the apparatus



Do not expose flammable organic fluids with flame or spark.



Do not eat any food in chemical laboratory because its contamination with any dangerous chemical can cause death.



Do not taste any chemical it can cause death.



For dilution purposes of acids and alkalis, the acid or alkali should be added slowly drop by drop into water while stirring. The reverse process surely causes explosive phase change of water. (e.g. H2SO4 dilution).



Gloves and Googles must be worn whenever there is a risk to the eyes.



Wear lab coat.

Page - 2

Experiment 1 (GAS DIFFUSION COEFFICIENTS APPARATUS) Objective: To determine the diffusion coefficient of a gas by evaporation from a liquid surface.

Equipment Setup / Apparatus: Gaseous Diffusion Coefficient Unit

Reagents: Water, Acetone, Detergent.

Theory: The diffusivity of the vapor of a volatile liquid in air can be conveniently determined by WINKLEMANN’S method in which liquid is contained in a narrow diameter vertical tube, maintained at a constant temperature, and an air stream is passed over the top of the tube to ensure that mass transfer of the acetone will take place from the surface of the liquid to the air stream by molecular diffusion.

Page - 3

Consult the book “TRANSPORT PHENOMENA” 2nd Ed., Section “MASS TRANSPORT” by “R. Byron Bird” for further elaboration and derivation of relationships used in calculations.

Procedure: 1) Use detergent solution to clean the capillary tube. A weak solution of the detergent should be injected into the tube slowly as shown below:

2) To empty the tube simply shake the tube whilst it is upside down until all detergent solution has gone. Repeat these two steps for water as a fluid in order to remove any detergent solution left. 3) The capillary tube can now be primed (filled) with acetone using the same procedure. The depth of Acetone should be approximately 35mm when filled. 4) Insert the capillary tube into apparatus. 5) Connect AIR TUBE to one end of the “T” piece. 6) Adjust the object lens in such a way as to see the capillary tube meniscus. 7) Adjust the position of the viewing lens in or out of the microscope body as necessary for clearer vision of meniscus level. (Note that when viewing the capillary tube the image will be upside down, so that the bottom of the tube is at the top of the image.) 8) Record the level inside the capillary tube. 9) Switch on the air pump. Switch on temperature controlled water bath, adjust set point on controller to 40oC and obtain a steady temperature. 10) After some suitable time period, approximately 45 mints record the change in level inside the capillary tube. 11) Repeat the procedure to take at least three to four readings. At the end switch off the apparatus. Page - 4

Data Analysis: (L-Lo) at time t = Reading on Vernier at time (t) - Initial reading on Vernier at (t = 0sec)

Results: Time from commencement

Change in Liquid Level

of Experiment.

(L-Lo)

𝑡 (𝐿 − 𝐿𝑜 )

ks (killo seconds)

mm

ks/mm

1) Plot 𝑡 𝑜𝑛 𝑦 𝑎𝑥𝑖𝑠 (𝐿 − 𝐿𝑜 ) (𝐿 − 𝐿𝑜 ) 𝑜𝑛 𝑥 𝑎𝑥𝑖𝑠 And determine the slope of the plot and name it “s”. 𝑦2 − 𝑦1 𝑆= =? 𝑥2 − 𝑥1 2) Use the following formulas to determine the mass diffusivity:

𝔇𝐴𝐵 = 𝔇𝐴𝐵

𝜌𝐿 𝐶𝐵𝑚 𝑠(2𝑀𝐶𝐴 𝐶𝑇 )

𝑚2 = 𝑀𝑎𝑠𝑠 𝐷𝑖𝑓𝑓𝑢𝑠𝑖𝑣𝑖𝑡𝑦 𝑜𝑓 𝐴𝑐𝑒𝑡𝑜𝑛𝑒 𝑖𝑛 𝐴𝑖𝑟 ( ) 𝑠

𝐶𝐴 = 𝑆𝑎𝑡𝑢𝑟𝑎𝑡𝑖𝑜𝑛 𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝑎𝑡 𝑖𝑛𝑡𝑒𝑟𝑓𝑎𝑐𝑒 (

𝑘𝑚𝑜𝑙 ) 𝑚3

Page - 5

𝜌𝐿 = 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 𝑜𝑓 𝑡ℎ𝑒 𝐿𝑖𝑞𝑢𝑖𝑑 (𝐴𝑐𝑒𝑡𝑜𝑛𝑒) = 790 𝐶𝐵𝑚 =

𝑘𝑔 𝑚3

(𝐶𝐵1 − 𝐶𝐵2 ) 𝑘𝑚𝑜𝑙 = 𝐿𝑜𝑔𝑎𝑟𝑖𝑡ℎ𝑚𝑖𝑐 𝑚𝑒𝑎𝑛 𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑣𝑎𝑝𝑜𝑢𝑟 ( 3 ) 𝐶 𝑚 ln(𝐶𝐵1 ) 𝐵2

𝐶𝐵1 = 𝐶𝑇 𝐶𝑇 =

1 𝑇𝑎𝑏𝑠 𝑘𝑚𝑜𝑙 ( ) = 𝑇𝑜𝑡𝑎𝑙 𝑀𝑜𝑙𝑎𝑟 𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 ( 3 ) 𝑉𝑚 𝑇𝑎 𝑚

𝑚3 𝑉𝑚 = 22.414 𝑘𝑚𝑜𝑙 𝑇𝑎𝑏𝑠 = 273 𝐾 𝑇𝑎 = 313𝐾 = 40𝑜 𝐶 (𝑆𝑒𝑡 𝑃𝑜𝑖𝑛𝑡 𝑇𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒) 𝐶𝐵2 = (

𝑃𝑎 − 𝑃𝑣 )𝐶𝑇 𝑃𝑎

𝑃𝑎 = 101.3

𝑘𝑁 𝑚2

𝑃𝑣 = 𝑉𝑎𝑝𝑜𝑟 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑜𝑓 𝐴𝑐𝑒𝑡𝑜𝑛𝑒 = 𝑓(𝑇) 𝐴𝑡 40𝑜 𝐶 (313𝐾) 𝑡ℎ𝑒 𝑃𝑣 = 56

𝑘𝑁 𝑚2

𝑀 = 𝑀𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝐴𝑐𝑒𝑡𝑜𝑛𝑒 = 58.08

𝑘𝑔 𝑘𝑚𝑜𝑙

𝑃𝑣 𝐶𝐴 = ( )𝐶𝑇 𝑃𝑎 Note: 1) To prevent the acetone from boiling do not set the temperature controller above 50oC. 2) If the experiment is performed with the water bath set to different temperatures than 40oC it will be necessary to obtain suitable values for Pv. 3) The experiment can be repeated at different temperatures and the effect of temperature on the mass diffusivity can be study if necessary.

𝔇𝐴𝐵 = 𝑓(𝑇, 𝑃)

Page - 6

Sample Results: A set of typical results are presented overleaf for information. Diffusivity of Acetone in air at 40oC (313K) and atmospheric pressure (Pa = 101.3kPa) from the following experimental data. Time from commencement of Experiment

Liquid Level (L-Lo)

𝑡 (𝐿 − 𝐿𝑜 )

mm 0.00 2.20 4.20 6.30 8.80 10.80 12.40 34.50 36.10 37.30 38.90 40.80 42.00

ks/mm Undetermined Form 1.636 1.714 1.771 1.807 1.850 1.887 2.283 2.314 2.339 2.360 2.385 2.407

ks 0.000 3.600 7.200 11.160 15.900 19.980 23.400 78.780 83.520 87.240 91.800 97.320 101.100 𝑡

Plot of (𝐿−𝐿 ) vs (𝐿 − 𝐿𝑜 ). 𝑜

t/(L-Lo) vs (L-Lo) Line 3.000 2.500 2.000 1.500 1.000 0.500 0.000 0

5

10

15

20

25

30

35

40

45

Page - 7

Sample Calculations: Point-1: (x1, y1) = (2.200, 1.636) Point-2: (x2, y2) = (42.000, 2.407) 𝑆=

𝑦2 − 𝑦1 2.407 − 1.636 𝑘𝑠 𝑠 𝑠 9 7 = = 0.0194 = 0.0194×10 = 1.94×10 𝑥2 − 𝑥1 42.000 − 2.200 (𝑚𝑚)2 𝑚2 𝑚2

𝐶𝑇 =

1 𝑇𝑎𝑏𝑠 ( )= 𝑉𝑚 𝑇𝑎

1 22.414

𝐶𝐵1 = 𝐶𝑇 = 0.0389

𝐶𝐵2

𝑚3

×

273𝐾 𝑘𝑚𝑜𝑙 = 0.0389 313𝐾 𝑚3

𝑘𝑚𝑜𝑙

𝑘𝑚𝑜𝑙 𝑚3

𝑘𝑁 𝑘𝑁 101.3 2 − 56 2 𝑃𝑎 − 𝑃𝑣 𝑚 𝑚 ×0.0389 𝑘𝑚𝑜𝑙 = 0.0174 𝑘𝑚𝑜𝑙 =( ) 𝐶𝑇 = 𝑘𝑁 𝑃𝑎 𝑚3 𝑚3 101.3 2 𝑚

𝐶𝐵𝑚

𝑘𝑚𝑜𝑙 𝑘𝑚𝑜𝑙 (𝐶𝐵1 − 𝐶𝐵2 ) 0.0389 𝑚3 − 0.0174 𝑚3 𝑘𝑚𝑜𝑙 = = = 0.0267 𝐶 𝑘𝑚𝑜𝑙 𝑚3 ln(𝐶𝐵1 ) 0.0389 3 𝑚 𝐵2 ln( 𝑘𝑚𝑜𝑙 ) 0.0174 𝑚3

𝑘𝑁 56 2 𝑃𝑣 𝑚 ×0.0389 𝑘𝑚𝑜𝑙 = 0.0215 𝑘𝑚𝑜𝑙 𝐶𝐴 = ( ) 𝐶𝑇 = 𝑘𝑁 𝑃𝑎 𝑚3 𝑚3 101.3 2 𝑚 𝑘𝑔

𝔇𝐴𝐵

𝑘𝑚𝑜𝑙

790 3 ×0.0267 𝜌𝐿 𝐶𝐵𝑚 𝑚 𝑚3 = = 𝑠(2𝑀𝐶𝐴 𝐶𝑇 ) 1.94×107 𝑠 ×2×58.08 𝑘𝑔 ×0.0215 𝑘𝑚𝑜𝑙 ×0.0389 𝑘𝑚𝑜𝑙 2 3 3 𝑚

−5

𝔇𝐴𝐵 = 1.12×10

𝑘𝑚𝑜𝑙

𝑚

𝑚

𝑚2 𝑠

Page - 8

Experiment 2 (ION EXCHANGE APPARATUS) Objective: To study the demineralization of water and to determine the exchange capacities of a hydrogen ion cation exchanger and an anion exchanger.

Equipment Setup / Apparatus: Ion Exchange Unit, Beaker 500 ml, Glass Stirrer.

Reagents: Cation Exchange Resin, Anion Exchange Resin, HCl, NaOH, Test Water containing dissolved solids, Distilled or Demineralized Water. Page - 9

Theory: (DEMINERALIZATION) The removal of all dissolved salts from water can be achieved by using a two-stage ion exchange process. The water is first passed through a strong cation exchanger working on the hydrogen ion cycle, when cations in the water are replaced by H+ ions, giving a solution of acids. This is then passed through an anion exchanger in the hydroxyl ion form, when the acid ions are replaced by OH- ions, which with the H+ ions, produce water. It is often sufficient to use a weakly basic anion exchanger, which will remove all anions except HC03- (due to dissolved carbon dioxide) and H3Si04- (due to dissolved silica). For a higher quality product water, a strongly basic anion exchanger must be used as the final stage, but it is generally more economical to precede this with a weakly basic anion exchanger of high exchange capacity to remove the bulk of the anions, and a degassing tower to release CO2 from solution. The strongly basic resin is then required only to remove silica and any residuals of other anions which may still be present. This process can reduce total dissolved solids to below 1mg/liter. Demineralization can also be performed in a single stage by using a mixed bed of strong cation and anion exchangers. The water repeatedly comes in contact with the two resins alternately, and is ultimately of very high purity. To enable the two resins to be regenerated with sulphuric acid and sodium hydroxide respectively, they are first stratified with an upward flow of water, the anion resin being of lower density and therefore carried to the top. After regeneration, the two resins are re-mixed by compressed air.

Procedure: A. Preliminary Requirements 1) Fill cation column to a depth of 300mm with a cation exchanger resin in the hydrogen ion form. 2) Fill anion column to a depth of 300mm with an anion exchange resin in the hydroxyl form. 3) Fill tank A with 100ml of a 10% HCl solution. 4) Fill tank B with 100ml of a 5% NaOH solution. 5) Fill tank C with test water containing 800 to 1000 mg/liter of dissolved solids. 6) Fill tank D with distilled or demineralized water.

Page - 10

7) If tap water is used, the concentrations of the principal cations and anions, as well as the total dissolved solids, must be determined if not already known. 8) From a knowledge of the concentrations of the main cations and anions in the water to be used, calculate the total strength in meq/liter. 9) This will be used in calculating the exchange capacities of the two resins. The electrical conductivity should also be measured.

B. Demineralization: 1) Select tank C, open valves 2, 13 and 15. Set flow rate to between 50 and 70 ml/min. 2) Note time at which flow is started and take conductivity readings at 5 minute intervals. 3) At 20 minute intervals draw off samples from valve 10 and measure pH value. 4) Note the time when the conductivity of the demineralized water begins to rise, i.e. the breakthrough point at which one of the resins has become exhausted. 5) As soon as possible after this point, take another small sample from valve no. 16 and measure its pH. 6) If this pH is higher than the values previously recorded, it indicates that the cation exchanger has become exhausted. 7) It is advisable to confirm this by drawing one or two further samples for pH determination. 8) The experiment should be stopped at this point, and the exchange capacity of the cation exchanger calculated. 9) It is then possible to determine the exchange capacity of the anion exchanger in this experiment. 10) If, on the other hand, the pH of the cation exchanger effluent continues at a low value, the rising conductivity of the final effluent indicates that the anion exchanger is exhausted, and its capacity can be calculated. 11) In the latter event, the exchange capacity of the cation exchanger can be determined by continuing the flow of water through the first column only, collecting the water which passes through it and measuring pH values until the breakthrough point, when the pH begins to rise.

Page - 11

In all of the figures:

C. Backwashing: 1) Each column should be separately backwashed. 2) In each case, the rate of backwashing should be controlled to give not more than 50% expansion of the bed. 3) Measure the final depths of the two beds.

Page - 12

D. Cation Regeneration: 1) Regenerate the cation exchanger. 2) Select tank A, open valves 2 and 12. Follow the acid with distilled or demineralized water from tank D, to flush out any surplus acid. 3) Check pH of effluent and continue flushing until pH has returned to above 5.0.

E. Anion Regeneration: 1) Regenerate the anion exchanger. 2) Select tank B, open valves 1 and 15, followed by distilled or demineralized water from tank D until pH of the effluent has returned to below 9.0.

Page - 13

Data Analysis: In the demineralization experiment, the breakthrough point is detected by readings of pH (for the cation exchanger) or conductivity (for the anion exchanger) instead of by direct measurement of concentrations. Time (min)

0

5

10

15

20

25

30

35

40

45

50

55

60

Conductivity PH Values

In order to calculate the exchange capacities in terms of milli-equivalents (meq), it is necessary to convert pH or conductivity readings to meq/liter.

(a) To convert pH values to meq/liter. If pH reading is “x” Hydrogen ion concentration = 10-x moles/liter = 103-x meq/liter

(b) To convert conductivity values to meq/liter. For a water with a given content of salts, the electrical conductivity is closely proportional to the concentration of total dissolved solids. Although these solids consist of several salts of varying electrolytic properties, it is sufficiently accurate to assume that electrical conductivity is also proportional to the the total concentration in terms of meq/liter. The constant of proportionality was established by determination of the electrical conductivity and the strength of meq/liter of the raw water. Hence the electrical conductivity of the demineralized water can be converted to meq/liter. In any event these figures should be very low.

(c) Other Calculations Final Depths: CATION = _______________ ANION = _______________

Page - 14

(π×15×10−3 )2 Wet Volume = ×Final Depth 4 Exchange capacities can now be calculated. 𝐸𝑥𝑐ℎ𝑎𝑛𝑔𝑒 𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦 =

𝑆𝑜𝑑𝑖𝑢𝑚 𝐼𝑜𝑛 𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑊𝑒𝑡 𝐵𝑒𝑑

Page - 15

Experiment 3 (ION EXCHANGE APPARATUS) Objective: To determine the regeneration efficiency of cation resin and an anion resin.

Equipment Setup / Apparatus: Ion Exchange Unit, Beaker 500 ml, Glass Stirrer.

Reagents: Cation Exchange Resin, Anion Exchange Resin, HCl, NaOH, Test Water containing dissolved solids, Distilled or Demineralized Water. Page - 16

Theory: (REGENERATION) Theoretically, for every milli-equivalent of hardness as CaCO3 removed from the water under treatment, one milli-equivalent of NaCl is required for regeneration, i.e. l g of hardness as CaCO3 removed requires 1.17 g NaCl for regeneration (Molecular weights: CaCO3 50.0, NaCl 58.5). In practice, it is not possible to achieve complete regeneration with this quantity of NaCl, since this would require an unacceptable long contact period. Larger quantities of NaCl are therefore used, generally twice or more the theoretical amount. Tire regeneration efficiency is thus around 50%. A high level of regeneration gives a resin with a high exchange capacity approaching its theoretical, but it is uneconomic to operate at such a rate that this capacity is fully used in softening. In other words, a high regeneration efficiency is associated with a low degree of column utilization, and vice versa. The practical operation of an ion-exchange bed is therefore a compromise in which the regeneration efficiency and the column utilization are both in the region of 50% (Optimization is requires). After regeneration, distilled or demineralized water is passed through the bed to wash out any remaining regenerator. Water to be treated by ion exchange must be free of suspended solids which would block the passage-ways, reduce flow rates and interfere with the exchange process. To remove fine solids which may get into the bed, and to release any air pockets, the column is backwashed periodically by an upward flow of water which fluidizes the bed and agitates the resin beads. The rate of flow of water through the bed in softening is usually not more than 40 ml/(min.cm2) of surface area of bed. Regeneration rates are about one tenth of this.

Page - 17

Procedure: A. For Cation Resin Regeneration Efficiency 1) Fill cation column to a depth of 300mm with a cation exchanger resin in the hydrogen ion form. 2) Fill anion column to a depth of 300mm with an anion exchange resin in the hydroxyl form. 3) Fill tank A with 100ml of a 10% HCl solution. 4) Fill tank B with 100ml of a 5% NaOH solution. 5) Fill tank C with test water containing 800 to 1000 mg/liter of dissolved solids. 6) Fill tank D with distilled or demineralized water. 7) If tap water is used, the concentrations of the principal cations and anions, as well as the total dissolved solids, must be determined if not already known. 8) From a knowledge of the concentrations of the main cations and anions in the water to be used, calculate the total strength in meq/liter. 9) This will be used in calculating the regeneration efficiency of the two resins. The electrical conductivity should also be measured. 10) Backwash: Select tank D, open valves 3 and 6. 11) Regenerate: Select tank A, open valves 2 and 10. Collect whole of the solution.

B. For Anion Resin Regeneration Efficiency 1) To determine the regeneration efficiency of the anion resin it will be necessary to carry out the full demineralization experiment. 2) Since the exchange capacities of cation resins are generally greater than those of anion resins, it is expected that the anion resin will be first to be exhausted.

Page - 18

Data Analysis: Final Depths: CATION = _______________ ANION = _______________

Sodium ion concentration (meq/ml) = (π×15×10−3 )2 Volume of solution used (ml) = ×Final Depth 4 Exchange capacities can now be calculated. Theoretical Exchange Capacity =

Sodium Ion Concentration Volume of NaOH used

Original quantity of NaOH used = Amount of NaOH collected = Actual Exchange Capacity = Original Quantity – Amount Used Regeneration Efficiency =

Actual Exchange Capacity Theoretical Exchange Capacity

Page - 19

Experiment 4 (BATCH DISTILLATION APPARATUS) Objective: To determine the pressure, drop over the distillation column for various boil-up rates.

Equipment Setup / Apparatus: Batch Distillation Apparatus, Measuring Cylinder 250ml, Stop Watch

Reagents: Ethanol, Water

Page - 20

Theory: The total pressure drop across each tray is the sum of that caused by the restriction of the holes in the sieve tray, and that caused by passing through the liquid (foam) on top of the tray. As the velocity of the vapors passing up the column increases then so does the overall pressure drop. The velocity is controlled by varying the boil-up rate which is done by varying the power input to the reboiler. Under conditions with no liquid present, the sieve trays will behave like an orifice in that the pressure drop will be proportional to the square of the velocity. Due to the fact that there is a liquid head however, this square relationship does not become apparent until the head of liquid has been overcome and foaming is taking place. In a graph of pressure drop vs. boil up rate (log/log), at low boil-up rates the pressure drop will remain fairly constant until foaming occurs when the pressure drop would be expected to rise sharply for unit increases in boil-up rate.

Procedure: 1) Make 10 Liters of mixture of 50 mole percent ethanol and 50mol percent water. Species

Formula

Molar Mass Density Mole Fraction (kg/kmole) (kg/m³)

Mixture Data

Ethanol (Component A) C2H5OH

46

789

0.5

H2O

18

1000

0.5

Water (Component B)

Required Volume of Mixture = V = 10 Liters nA nB xA = = 0.5 xB = = 0.5 nT nT nA = 0.5nT = 0.5CV nB = 0.5nT = 0.5CV kg MMixture = xA MA + xB MB = (0.5)(46) + (0.5)(18) = 32 kmole kg ρMixture = xA ρA + xB ρB = (0.5)(789) + (0.5)(1000) = 894.5 3 m kg 894.5 3 ρMixture kmole 1m3 kmole m C= = = 27.9531 × = 0.028 kg MMixture m3 1000L L 32 kmole kmole kmole nA = 0.5×0.028 ×10L nB = 0.5×0.028 ×10L L L Page - 21

nA = 0.14 kmole mA = 0.14 kmole×46

kg kmole

nB = 0.14 kmole mB = 0.14 kmole×18

kg kmole

mA = 6.44 kg mB = 2.52 kg ρA 𝑉𝐴 = 6.44 kg 𝜌𝐵 𝑉𝐵 = 2.52 kg 6.44 kg 2.52 kg 𝑉𝐴 = = 8.1622 𝐿 𝑉𝐵 = = 2.52 𝐿 3 kg kg 1𝑚 1𝑚3 789 3 × 1000𝐿 1000 3 × 1000𝐿 m m So, 8.1622 L of Ethanol and 2.52 L of Water are required for making 10 Liters of Mixture of 0.5, 0.5 Mole Fraction. 2) The equipment will be set up to operate at total reflux meaning all the formed vapor will after condensation return to the column. The charge of feed mixture can be loaded directly in the reboiler through the filler cap provided without first charging the feed tank. At total reflux, there will be no feed or top product or bottom product. 3) Before starting, make sure all valves on the equipment are closed. Open valve V10 on the reflux pipe. Fill the boiler with mixture to be distilled. Make sure the filler cap on the top of the reboiler is firmly replaced. 4) Turn on the power to the control panel. Set the temperature selector switch to T9, the temperature in the reboiler and open valve V5 admitting the cooling water to the condenser at a flow rate on FI1 of approximately 3 liters/ min. 5) On the control panel turn the power controller for the reboiler heating element fully anti-clockwise and switch on the power to the heating element to "power on" position. Another red lamp will illuminate indicating the heating element is on. 6) Turn the power controller clockwise until a reading of approximately 0.75kW is obtained on the digital wattmeter. The contents of the reboiler will begin to warm up and this can be observed on the temperature readout meter. 7) Open valves V6 and V7 which connect base and top of the distillation column, respectively, to the manometer. Initially there will be no pressure difference in the column meaning no reading on the manometer. 8) Close valve V6 and V7. The 1st and 5th plates in the column sections are not insulated so that observation of the sieve plates are possible. Eventually, vapor will begin to rise up the column and the progress of this can be clearly observed as well as detected by the increasing temperatures when switching the temperature selector on T8, T7, T6, T5, T4, T3, T2 and Tl. 9) Vapor will enter the condenser and reappear as droplets into the glass walled distillate receiver vessel. The distillate will build up a small level in the receiver and eventually overflow to the reflux regulator valve. Since the valve is not on (on the control pane!), and it will not be necessary to have it on in this experiment, which is run under total reflux, the condensate vapor will return to the column. 10) The cool distillate is then returning on the top of the column and will cascade down the trays forming a liquid level on the trays and bubbling of vapor passing through the liquid. The system will have reached an equilibrium condition when the temperatures Tl, T2, T3, T4, T5, T6, T7 and T8 are constant. 11) The boil-up rate can be measured by operating valve V3 so that all the condensate is diverted into a measuring cylinder and the time observed to collect a set quantity. This

Page - 22

will not disrupt the equilibrium conditions in the column provided a liquid level is maintained in the condensate feeding pipe. 12) When taking a sample, partially open valve V3 and drain the condensate (in a separate measuring cylinder) from the reflux system until a steady flow is obtained. (Ensure that liquid remains in the flexible connecting tube to prevent vapor from escaping.) 13) Start sample collection and timing at the same time. Collect a sizeable amount approximately 90 ml in a 100ml measuring cylinder. Pour the first non-representative collected amount in a bottle labelled "recyclable Ethanol / Water". 14) After taking the samples, take readings of pressure drops over both the rectifying (top) and the stripping (bottom) sections by opening the valves V6 and V7 on the manometer. 15) When opening the valves, make sure always to open valve V6 then V7 to prevent vapor from the column entering the manometer. If this happens, it can be seen as two separate phases in the U-tube. Close the valves in the same order, when finished the pressure drop reading. 16) Repeat these readings until two in a row agree fairly closely. Allow 5 to 10 minutes between each set of measurements before starting the next set in order for the system to reach equilibrium again. 17) Step up the boil-up rate in 250 Watt increments up to maximum 1.5 kW by adjusting the boiler heater power controller (on the control panel). Take-similar readings of the boil-up rate and pressure drops after having allowed at least 10 minutes to let the column stabilize.

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Data Analysis: Power (kW) 0.50 0.75 1.00 1.25 1.50 1.75

Boil-up Rate (Liters/hr)

Pressure Drop (cm H2O)

Degree of Foaming on Trays

NOTE: The comment "Degree of Foaming on Trays" should be filled in using descriptive words e.g. None Gentle Localized Violent Localized Foaming Gently Over Whole Tray Foaming Violently Over Whole Tray Liquid Flooding in Column From the results, plot the curve relating pressure drop as a function of boil-up rate on log/log graph paper. Result obtained will be like this:

Relate the descriptive comments observed (and noted in the table of results) to zones on the curve.

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Experiment 5 (BATCH DISTILLATION APPARATUS) Objective: Use of the refractometer for determining mixture compositions.

Equipment Setup / Apparatus: Batch Distillation Apparatus, Hand Held Refractometer, Measuring Cylinder 100ml Throughout the experimental procedures carried out on the Distillation Column, it is essential to have a convenient quick method of determining the composition of the binary mixture taken from the various sample points on the equipment. Such a method involves the use of a refractometer since the refractive index of these mixtures varies with composition. It is needed to have a suitable container to mix the sample in, and a bottle of each of the pure components of the binary mixture to be analyzed.

Reagents: Ethanol, Water

Theory: For the system, Ethanol / Water, mixtures of known concentration can be made up and their refractive indexes measured. The refractometer measures the critical angle of the liquid under test and each concentration will show a different critical angle Theta. Beyond the critical angle is darkness and refractometers are calibrated along this light/dark boundary.

Page - 25

Procedure: 1) Measure the refractive index (R.I.) of pure Ethanol and pure Water. 2) Make up small quantities of 25 mole percent, 50 mole percent and 75 mole percent Ethanol using the similar procedure as in previous experiment and measure their R.I. 3) Calculate the volume of constituents to use as in the previous experiment:

Data Analysis: Mole Fraction of Ethanol Refractive Index 1.00 0.75 0.50 0.25 0.00 Plot graph of refractive index versus mole fraction of methylcyclohexane in methylcyclohexane / toluene mixture. General trend of this graph is shown below.

For any mixture composition of these two constituents simply measure the refractive index y and read off the composition x.

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Experiment 6 (BATCH DISTILLATION APPARATUS) Objective: To determine the overall column efficiency at varying boil-up rates.

Equipment Setup / Apparatus: Batch Distillation Apparatus, Hand Held Refractometer, Measuring Cylinder 250ml, Stop Watch.

Reagents: Ethanol, Water

Page - 27

Procedure: 1) Make 10 liters of a mixture of 50 mole percent Ethanol and 50 mole percent Water by using the steps of solution preparation of experiment 4. 2) The equipment will be set up to operate at total reflux so the charge of feed mixture can be loaded directly into the reboiler through the filler cap provided without first charging the feed tanks. At total reflux, there will be no feed or top product or bottom product. 3) Start up the unit, set the heat controller high at first then reduce heat; as reflux is introduced to give steady bubbling on all tray and total reflux. Leave the apparatus for at least 30 minutes so that the system can reach an equilibrium condition. 4) Measure the boil-up rate as described under experiment 4 using valve V3. Do this work three times and take an average value. Take a sample of the overheads through valve V3. When doing that, be careful never to drain the condensate return line i.e. partially open valve V3 to leave a small amount of liquid in the line all the time. 5) Generally, when taking samples, drain a "discarding" sample of approximately 5 to 10 ml before taking the representative sample in a small glass. Do not drain too much of the "discarding" sample because of the disturbance of the mass balance. Discard the "discarding" sample in safe way. After the representative sample, has been taken, keep the sample glasses in an upright position. Do not overturn them because of the possibility of evaporation of the sample. 6) Record the refractive index for the taken overhead sample. In a similar manner take a sample of the bottom through valve V2. CAUTION! THIS SAMPLE WILL BE HOT, (take note of T9). Record the refractive index for this sample, too. 7) Repeat this procedure every ten minutes until five samples of both overhead and bottom are obtained. Record the temperatures T8 and T1 to calculate the average column temperature. 8) Repeat this procedure for several different boil-up rates to cover over the operating range of the column. 9) The calibration graph developed in the previous Experiment 5 can be used to determine the concentrations of the components in the taken samples.

Data Analysis:

Boil-up rate = __________________ liters/hour. Overhead Concentration (XA)D = (Mole Percent Ethanol)

a) b) c) d) e) Average = ________________ mole percent of Ethanol. Bottom Concentration (XA)B =

a) b) c) Page - 28

d) e) Average Column Temperature (Top Side) =

___________ oC.

Average Column Temperature (Bottom Side) =

___________ oC.

Overall Average Colum Temperature =

___________ oC.

The curve shown in the next page shows: Vapor-Liquid Equilibrium Data of Ethanol / Water Mixtures

To calculate the number of theoretical plates for a given separation at total reflux. FENSKE’S METHOD Fenske developed the following formula: 𝑛+1=

𝑥 𝑥 log[(𝑥𝐴 )𝑑 ×( 𝑥𝐵 )𝑏 ] 𝐵

𝐴

log(𝛼𝐴𝐵 )𝑎𝑣

Where: Page - 29

𝑛 = 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑝𝑙𝑎𝑡𝑒𝑠 𝑥𝐴 = 𝑀𝑜𝑙𝑒 𝐹𝑟𝑎𝑐𝑡𝑖𝑜𝑛 𝑜𝑓 𝑀𝑜𝑟𝑒 𝑉𝑜𝑙𝑎𝑡𝑖𝑙𝑒 𝐶𝑜𝑚𝑝𝑜𝑛𝑒𝑛𝑡 𝑥𝐵 = 𝑀𝑜𝑙𝑒 𝐹𝑟𝑎𝑐𝑡𝑖𝑜𝑛 𝑜𝑓 𝐿𝑒𝑠𝑠 𝑉𝑜𝑙𝑎𝑡𝑖𝑙𝑒 𝐶𝑜𝑚𝑝𝑜𝑛𝑒𝑛𝑡 𝛼𝐴𝐵,𝑎𝑣 = 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑅𝑒𝑙𝑎𝑡𝑖𝑣𝑒 𝑉𝑜𝑙𝑎𝑡𝑖𝑙𝑖𝑡𝑦 Subscripts D, B indicate distillate and bottom respectively. 𝛼𝐴𝐵,𝑎𝑣 = √𝛼𝐷 . 𝛼𝐵 The efficiency is given by: 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 = 𝐸 =

𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑃𝑙𝑎𝑡𝑒𝑠 ×100 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝐴𝑐𝑡𝑢𝑎𝑙 𝑃𝑙𝑎𝑡𝑒𝑠

Knowing the composition of distillate and bottom and the corresponding volatilities, the column efficiency can be determined.

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Experiment 7 (CONTINUOUS DISTILLATION APPARATUS) Objective: Steady state distillation of a binary mixture under continuous operation.

Equipment Setup / Apparatus: Continuous Distillation Apparatus, Hand Held Refractometer, Measuring Cylinder 250ml, Stop Watch.

Reagents: Ethanol, Water

Page - 31

Theory: Calculation of Number of Plates using McCabe Thiele Method. Rectifying Section Operating Line

Stripping Section Operating Line

Page - 32

Above equations combined with the equilibrium curve can be used to calculate the composition on the various plates working from the condenser down to the still. The plate which has a composition nearest to that of the feed should, be used as the feed plate. Consequently, the number of theoretical plates and position of entry for the feed can be calculated.

Procedure: 1) Charge 10 liters feed mixture of 65 mole percent Ethanol and 35 mole percent Water to feed tank. Volume of individual components required can be calculated from a procedure similar to experiment no-4: 2) Charge the reboiler with 10 liters of a mixture of 25 mole percent Ethanol and 75 mole percent Water. Volume of individual components required can be calculated from a procedure similar to experiment no-4: 3) Make sure the filler cap on the top of the reboiler is firmly placed. Turn on the power to the control panel. Set the temperature selector switch to T9, that is the temperature in the reboiler, and open valve V5 admitting the cooling water to the condenser at a flow rate on FI1 of approximately 3 liters/min. This rate may be varied according to the temperature of the water. 4) On the control panel turn the power controller for the reboiler heating element fully anti-clockwise and turn on the power to the heating element. Another red lamp will illuminate indicating the heating element is on. Turn the power controller clockwise until a reading of approximately 1.5 kW is obtained on the digital wattmeter. The contents of the reboiler will begin to warm up and this can be observed on the temperature readout, meter. 5) Eventually, vapor will begin to rise up the column and the progress of this can be clearly observed as well as detected by the increasing temperatures when switching the temperature selector on T8, T7, T6, T5, T4, T3, T2 and Tl. Vapor will enter the condenser and reappear as droplets into the glass walled distillate receiver vessel. The distillate will build up a small level in the receiver and eventually overflow to the reflux regulator valve. Start the experiment with total reflux, meaning the condensed vapor will return to the column.

Page - 33

6) The cool distillate is then returning to the top of the column and will cascade down the trays forming a liquid level on the trays and bubbling of vapor passing through the liquid. The system will have reached an equilibrium condition when the temperatures Tl, T2, T3, T4, T5, T6, T7 and T8 have reached an average steady temperature (but note cycling due to the intermittent reflux). 7) Before switching on the reflux switch, set the reflux ratio to 5:1, meaning 5 sec back to column and 1 sec to top product receiver. 8) The feed to the column must be admitted on the tray 5. When the column has stabilized at total reflux (it Takes 15 to 30 minutes), the flow of feed and the reflux can be started at the same time. It is advisable to set a feed flow of 2 liters/hr (from the feed pump calibration graph). As the flow into the column becomes established so more vapor will rise up the column and appear as condensate in the distillate receiver, allow this to flow to the top product receiver. 9) After feeding approximately 3 liters take a sample of the overheads through valve V3. When doing that, be careful never to drain the condensate return line i.e. partially open valve V3 to leave a small amount of liquid in the line all the time. Take a further four samples. 10) Generally, when taking samples, drain a "discarding" sample of approximately 5 to 10 ml before taking the representative sample in a sample glass. Do not drain too much of the "discarding" sample because of the disturbance of the mass balance. Discard the "discarding" sample in a safe way. After the representative sample, has been taken, keep the sample glasses in an upright position. Do not overturn them because of the possibility of evaporation of the sample. 11) Record the refractive index for the taken overhead sample. In a similar manner and preferably at the same time take a sample of the bottom through valve V2. CAUTION! THIS SAMPLE WILL BE HOT. Record the refractive index for this sample, too. 12) Repeat the sample taking a further nine times during the experiment (before feed runs out).

Page - 34

Data Analysis:

Sr. No.

Top Product Composition (Mole Bottom Product Composition (Mole Fraction of Ethanol) Fraction of Ethanol)

1 2 3 4 5 6 7 8 9 10 Equilibrium Data for Ethanol / Water can be calculated using Vapor Liquid Equilibrium Curve for this system at 1 atm pressure.

Sample Results: Using a feed of a binary mixture of 60 mole percent Ethanol and 40 mole percent Water. Top product required: XD = 0.75 Bottom product required: XB = 0.44 Reflux Ratio: 5:1 A material balance on the M.V.C. (More Volatile Component), Ethanol gives: Units are of molar flow rates: F=D+B 100 × 0.60 = 0.75 D + 0.44 B And D = 100-B 100×0.60 = 0.75(100-B) + 0.44B B = 48.39 D = 51.61 Ln = 5D Ln = 258.05 Page - 35

V(n+1) = Ln + D V(n+1) = 309.66 𝑦𝑛+1 = 𝑦𝑛+1 =

𝐿𝑛 𝐷 𝑥𝑛 + 𝑥 𝑉𝑛+1 𝑉𝑛+1 𝐷

258.05 51.61×0.75 𝑥𝑛 + 309.66 309.66

𝑦𝑛+1 = 0.83𝑥𝑛 + 0.13 L (bar) = 258.05 + 100 = 358.05 V (bar) = L (bar) – B = 358.05 -48.39 = 309.66 𝑦𝑚+1 = 𝑦𝑚+1 =

𝐿̅ 𝐵 𝑥𝑚 − 𝑥𝐵 𝑉̅ 𝑉̅

358.05 48.39×0.44 𝑥𝑚 − 309.66 309.66

𝑦𝑚+1 = 1.16𝑥𝑚 − 0.07 From the equilibrium curve, 1) Use Equilibrium Curve, and plot specific top and bottom operating line equations on the same diagram. 2) Calculate number of stages:

Page - 36

3) Theoretically, therefore, the distillation column containing eight sieve plates plus the boiler will give the compositions calculated above. However, as the experiment will show this is not in fact correct. 4) Determine average column efficiency.

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Experiment 8 (CONTINUOUS DISTILLATION APPARATUS) Objective: Effect of varying the feed position under continuous operation.

Equipment Setup / Apparatus: Continuous Distillation Apparatus, Hand Held Refractometer, Measuring Cylinder 250ml, Stop Watch.

Reagents: Ethanol, Water

Page - 38

Theory: The rig is provided with three feed positions, one above the top plate, one between the two four-plate sections, (mid-point) and one below the bottom plate. In this way, the rig can be run as a conventional distillation column (feed between the sections), as a rectifying column (feed below the bottom plate) or as a stripping column (feed above the top plate). As the rectifying case is closely approximated, by the batch distillation. The stripping case is chosen for this experiment.

Calculation of Number of Plates using McCabe Thiele Method.

Material Balance of top of the column 𝑉𝑛 = 𝐿𝑛+1 + 𝐷 − 𝐹 With respect to M.V.C. this becomes 𝑉𝑛 𝑦𝑛 = 𝐿𝑛+1 𝑥𝑛+1 + 𝐷𝑥𝐷 − 𝐹𝑥𝐹 𝐿𝑛+1 𝑥𝑛+1 𝐷𝑥𝐷 𝐹𝑥𝐹 𝑦𝑛 = + − 𝑉𝑛 𝑉𝑛 𝑉𝑛 Since the liquid overflow is constant Ln = Ln+1 𝐿𝑛 𝑥𝑛+1 𝐷𝑥𝐷 𝐹𝑥𝐹 𝑦𝑛 = + − 𝑉𝑛 𝑉𝑛 𝑉𝑛

Material Balance of bottom of the column: Vm = Lm+1 - W With respect to M.V.C. this becomes 𝑉𝑚 𝑦𝑚 = 𝐿𝑚+1 𝑥𝑚+1 − 𝑊𝑥𝐵 Page - 39

𝑦𝑚 =

𝐿𝑚+1 𝑥𝑚+1 𝑊𝑥𝐵 − 𝑉𝑚 𝑉𝑚

Since the liquid overflow is constant Lm = Lm+1. As the feed is introduced in the top of the column Lm = Ln and also Vm = Vn. Above equations combined with the equilibrium curve can be used to calculate the composition on the various plates working from the condenser down to the still.

Procedure: 1) Charge 10 liters feed mixture of 63 mole percent Ethanol and 37 mole percent Water to feed tank. Volume of individual components required can be calculated from a procedure similar to experiment no-4: 2) Charge the reboiler with 10 liters of a mixture of 25 mole percent Ethanol and 75 mole percent Water to overflow valve V1. Volume of individual components required can be calculated from a procedure similar to experiment no-4: 3) Make sure the filler cap on the top of the reboiler is firmly placed. Turn on the power to the control panel. Set the temperature selector switch to T9, that is the temperature in the reboiler, and open valve V5 admitting the cooling water to the condenser at a flow rate on FI1 of approximately 3 liters/min. This rate may be varied according to the temperature of the water. 4) On the control panel turn the power controller for the reboiler heating element fully anti-clockwise and turn on the power to the heating element. Another red lamp will illuminate indicating the heating element is on. Turn the power controller clockwise until a reading of approximately 1.5 kW is obtained on the digital wattmeter. The contents of the reboiler will begin to warm up and this can be observed on the temperature readout, meter. 5) Eventually, vapor will begin to rise up the column and the progress of this can be clearly observed as well as detected by the increasing temperatures when switching the temperature selector on T8, T7, T6, T5, T4, T3, T2 and Tl. Vapor will enter the condenser and reappear as droplets into the glass walled distillate receiver vessel. The distillate will build up a small level in the receiver and eventually overflow to the reflux regulator valve. Start the experiment with total reflux, meaning the condensed vapor will return to the column. Page - 40

6) The cool distillate is then returning to the top of the column and will cascade down the trays forming a liquid level on the trays and bubbling of vapor passing through the liquid. The system will have reached an equilibrium condition when the temperatures Tl, T2, T3, T4, T5, T6, T7 and T8 have reached an average steady temperature (but note cycling due to the intermittent reflux). 7) Before switching on the reflux switch, set the reflux ratio to 5:1, meaning 5 sec back to column and 1 sec to top product receiver. 8) The feed to the column must be admitted above the top plate. When the column has stabilized at total reflux (it Takes 15 to 30 minutes), the flow of feed and the reflux can be started at the same time. It is advisable to set a feed flow of 2 liters/hr (from the feed pump calibration graph). As the flow into the column becomes established so more vapor will rise up the column and appear as condensate in the distillate receiver, allow this to flow to the top product receiver. 9) After feeding approximately 3 liters take a sample of the overheads through valve V3. When doing that, be careful never to drain the condensate return line i.e. partially open valve V3 to leave a small amount of liquid in the line all the time. Take a further four samples. 10) Generally, when taking samples, drain a "discarding" sample of approximately 5 to 10 ml before taking the representative sample in a sample glass. Do not drain too much of the "discarding" sample because of the disturbance of the mass balance. Discard the "discarding" sample in a safe way. After the representative sample, has been taken, keep the sample glasses in an upright position. Do not overturn them because of the possibility of evaporation of the sample. 11) Record the refractive index for the taken overhead sample. In a similar manner and preferably at the same time take a sample of the bottom through valve V2. CAUTION! THIS SAMPLE WILL BE HOT. Record the refractive index for this sample, too. 12) Repeat the sample taking a further nine times during the experiment (before feed runs out).

Page - 41

Data Analysis:

Sr. No.

Top Product Composition (Mole Bottom Product Composition (Mole Fraction of Ethanol) Fraction of Ethanol)

1 2 3 4 5 6 7 8 9 10 Equilibrium Data for Ethanol / Water can be calculated using Vapor Liquid Equilibrium Curve for this system at 1 atm pressure.

Sample Results: Using a feed of a binary mixture of 63 mole percent Ethanol and 47 mole percent Water. Top product required: XD = 0.66 Bottom product required: XB = 0.21 Reflux Ratio: 5:1 A material balance on the M.V.C. (More Volatile Component), Ethanol gives: Units are of molar flow rates: F=D+B 100 × 0.63 = 0.66 D + 0.21 B And D = 100-B 100×0.63 = 0.66(100-B) + 0.21B B = 6.67 D = 93.33 Also Ln = 5D Ln = 466.65 Vn = Ln + D – F = 466.65 + 93.33 - 100 Vn = 459.98 Page - 42

𝑦𝑛 = 𝑦𝑛 =

𝐿𝑛 𝐷 𝐹 𝑥𝑛+1 + 𝑥𝐷 − 𝑥𝐹 𝑉𝑛 𝑉𝑛 𝑉𝑛

466.65 93.33×0.66 100×0.63 𝑥𝑛+1 + − 499.98 499.98 499.98 𝑦𝑛 = 0.933𝑥𝑛+1 − 0.003

It is for the top section and the bottom section of the column due to different feed position. From the equilibrium curve, 1) Use Equilibrium Curve, and plot specific operating line equation on the same diagram. 2) Calculate number of stages: 3) Theoretically, therefore, the distillation column containing eight sieve plates plus the boiler will give the compositions calculated above. However, as the experiment will show this is not in fact correct. 4) Determine average column efficiency.

Page - 43

Experiment 9 (GAS ABSORPTION COLUMN APPARATUS) Objective: To measure the absorption of carbon dioxide into water flowing down the tower, using the gas analysis equipment provided.

Equipment Setup / Apparatus: Gas Absorption Column Apparatus, CO2 Cylinder with Integral Pressure Regulator, Small Funnel, and Tubing.

Reagents: CO2 Gas, Tap Water, Air, and 300ml of 1.0 molar NaOH solution.

Page - 44

Procedure: 1) First fill the two globes of the absorption analysis equipment on the left of the panel with 1.0 Molar NaOH solution. Adjust the level in the globes to the '0' mark on the sight tube, using drain valve C into a flask to do this. 2) Fill the liquid reservoir tank to three-quarters full with fresh tap water. 3) With gas flow control valves C2 and C3 closed, start the liquid pump and adjust the water flow through the column to approximately 6 liters/minute on flowmeter F1 by adjusting control valve C1. 4) Start the compressor and adjust control valve C2 to give an air flow of approximately 30 liters/minute in flowmeter F2. 5) Carefully open the pressure regulating valve on the carbon dioxide cylinder, and adjust valve C3 to give a value on the flowmeter F3 approximately one half of the air flow F2. (Ensure the liquid seal at the of base of the absorption column is maintained by, if necessary, adjustment of control valve C4. 6) After 15 minutes or so of steady operation, take samples of gas simultaneously from sample points S1 and S2. Analyze these consecutively for carbon dioxide content in these gas samples. 7) Flush the sample lines by repeated sucking from the line, using the gas piston and expelling the contents of the cylinder to atmosphere. Note that the volume of the cylinder is about l00 cm3. Estimate the volume of the tube leading to the device. Then decide how many times you need to suck and expel. (Steps B and C) 8) With the absorption globe, isolated and the vent to atmosphere closed, fill the cylinder from the selected line by drawing the piston out slowly (Step B). Note volume taken into cylinder V1, which should be approximately 20ml for this particular experiment. Wait at least two minutes to allow the gas to come to the temperature of the cylinder. 9) Isolate the cylinder from the column and the absorption globe and vent the cylinder to atmospheric pressure. Close after about 10 seconds (Step D). 10) Connect cylinder to absorption globe. The liquid level should not change. If it does change, briefly open to atmosphere again. 11) Wait until the level in the indicator tube is on zero showing that the pressure in the cylinder is atmospheric. 12) Slowly close the piston to empty the cylinder into the absorption globe. Slowly draw the piston out again (Steps E and F). Note the level in the indicator tube. Repeat steps Page - 45

E and F until no significant change in level occurs. Read the indicator tube marking = V2. This represents the volume of the gas sampled.

HEMPL APPARATUS FOR GAS ANALYSIS

Page - 46

WARNING: If the concentration of CO2 in the gas sampled is greater than 8%, it is possible to suck liquid into the cylinder. This will ruin your experiment and takes time to correct. Under these circumstances, do not pull the piston out to the end of its travel. Stop it at a particular mark, e.g. V1 = 20 on the coarse scale, and read the fine scale.

Data Analysis:

NOTATION: V1 = Volume of Gas sample taken in Hempl Apparatus (ml). V2 = Corresponds to amount of Gas Absorbed in Hempl Apparatus (ml). F = Volumetric Flowrate (liters/sec). G = Gas Flowrate (gmols/sec). Y = Mole Fraction of component in gas phase.

SUBSCRIPTS: T = Total i = Inlet Conditions to Column o = Outlet Conditions from Column

CO2 content of gas samples: From use of Hempl Apparatus, 𝑉𝑜𝑙𝑢𝑚𝑒 𝐹𝑟𝑎𝑐𝑡𝑖𝑜𝑛 𝑜𝑓 𝐶𝑂2 =

𝑉2 𝑉1

For ideal gases, volume fraction = mole fraction = Y. Check that the sample taken from the inlet to the absorption column should give the same value of CO2 fraction as that indicated by the inlet flowmeters:

𝑌𝑖 =

𝑉2 𝐹3 = 𝑉1 𝐹2 + 𝐹3

Page - 47

READINGS AT INLET F3

F2

(CO2)

(Air)

Liters/sec

Liters/sec

From Flowmeters

CALCULATIONS

V1

V2

ml

ml

𝑌𝑖 =

𝐹3 𝐹2 + 𝐹3

𝑌𝑖 =

𝑉2 𝑉1

From Hempl Apparatus and Sample Point S3

Calculation of amount of CO2 absorbed in column from analysis of samples at inlet and outlet. From Analysis with Hempl apparatus, volume fraction of CO2 in gas stream at inlet: 𝑉2 𝑌𝑖 = ( ) 𝑉1 𝑖 And at outlet: 𝑉2 𝑌𝑜 = ( ) 𝑉1 𝑜 If Fa is liters/second of CO2 absorbed between top and bottom, then:

CO2 IN

CO2 OUT

CO2 Absorbed

[𝐹2 + 𝐹3 ]𝑌𝑖 − [𝐹2 + (𝐹3 − 𝐹𝑎 )]𝑌𝑜 = 𝐹𝑎

𝐹𝑎 =

(𝑌𝑖 − 𝑌𝑜 )(𝐹2 + 𝐹3 ) (𝑌𝑖 − 𝑌𝑜 ) = ×(𝑇𝑜𝑡𝑎𝑙 𝐺𝑎𝑠 𝐼𝑛𝑙𝑒𝑡 𝐹𝑙𝑜𝑤) (1 − 𝑌0 ) 1 − 𝑌𝑜 INLET CONDITIONS

GAS FLOWS [liters/sec] Air

CO2

Total

F2

F3

F2+F3

OUTLET GAS

GAS

SAMPLE

SAMPLE

𝑉2 𝑌𝑖 = ( ) 𝑉1 𝑖

𝑉2 𝑌𝑜 = ( ) 𝑉1 𝑜

ABSORBED CO2: Fa [liters/sec]

Note: [Liters/second] can be converted to [gmols/second] as follows: 𝐺𝑎 =

𝐹𝑎 𝐴𝑣𝑔. 𝑐𝑜𝑙𝑢𝑚𝑛 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑚𝑚 𝐻𝑔 273 ×( )×( ) 22.42 760 𝐴𝑣𝑔. 𝑐𝑜𝑙𝑢𝑚𝑛 𝑡𝑒𝑚𝑝. 0𝐶 + 273

Absorbed CO2 Fa = ___________________ Page - 48

Ga = _______________________________

The assumption implicitly made here is that the volume flow is not affected by the pressure drop through the column as this drop should be small in comparison with atmospheric pressure.

Page - 49

Experiment 10 (GAS ABSORPTION COLUMN APPARATUS) Objective: To calculate rate of absorption of CO2 into water from analysis of liquid solutions flowing down absorption column.

Equipment Setup / Apparatus: Gas Absorption Column Apparatus, CO2 Cylinder with Integral Pressure Regulator, and Pyrex Bottle, Pipette, Burette, Flask and Measuring Cylinder.

Reagents: CO2 Gas, Water, Air, Phenolphthalein, 0.0277 Molar NaOH Solution, 0.01 Molar NaHCO3 Solution.

Page - 50

Procedure: 1) Fill the liquid reservoir tank at the base of the column to approximately three-quarters full with (preferably) deionized water. Note the volume added [VT liters]. 2) With gas flow control valves C2 and C3 closed, start the liquid pump and adjust the water flow through the column to approx. 6 liters/minute on flowmeter F1 by adjusting flow control valve C1. 3) Start the compressor and adjust control valve C2 to give an air flow of approx. 10% of full scale on flowmeter F2. 4) Carefully open the pressure regulating valve on the carbon dioxide cylinder, and adjust valve C3 to give a value on the flowmeter F3 approx., one half of the air flow F2 ensure the liquid seal at the base of the absorption column is maintained by, if necessary adjustment of control valve C4. 5) After 15 minutes of steady operation, take samples at 10 minute intervals from S4 and S5. Take 150ml samples at known times in each case. Analyze the samples according to the procedure detailed below.

Analysis of Carbon Dioxide Dissolved in Water: Note: Water used for absorption should be deionized as presence of dissolved salts affect the analysis described below. If tap water is used, no metal ions should be present in greater quantities than 1.0 mg/liter and pH should be just alkaline: 7.1 to 7.8. 1) Phenolphthalein indicator prepared from carbon dioxide – free distilled water. 2) Standard 0.0277M NaOH solution, prepared by diluting 27.70ml of 1M NaOH standard solution to1 liter with carbon dioxide free distilled water. Prepare fresh and protect from carbon dioxide in the atmosphere by keeping in a stoppered Pyrex bottle. 3) Standard 0.01M NaHCO3 solution, prepared by dissolving approximately 0.1 gram of anhydrous NaHCO3 in carbon dioxide free distilled water to 100ml. 4) Withdraw a sample of liquid S5 from the sump tank with the sampler provided, approximate volume of 150ml, or from liquid outflow point S4. 5) Discharge the sample at the base of a 100 ml graduated cylinder, flicking the cylinder to throw off excess liquid above the 100 ml mark. 6) Add 5-10 drops of phenolphthalein indicator solution if the sample turns red immediately, no free C02 is present. If the sample remains colorless, titrate with

Page - 51

standard NaOH solution. Stir gently with a glass rod until a definite pink color persists for about 30 seconds. This color change is the end point - note volume VB of NaOH solution added. For best results, use a color comparison standard, prepared by adding the identical volume of phenolphthalein solution to 100ml of sodium bicarbonate solution in a similar graduated cylinder.

Data Analysis:

NOTATION: Cd = Concentration of dissolved free carbon dioxide (gmol/liter). F = Volumetric Flowrate (liters/sec). VB = Volume of NaOH Solution Added in liquid analysis (ml).

SUBSCRIPTS: T = Total i = Inlet Conditions to Column o = Outlet Conditions from Column

The amount of free CO2 in the water sample is calculated from: 𝐶𝑑 =

𝑔𝑚𝑜𝑙 𝑉𝐵 ×0.0277 𝑜𝑓 𝑓𝑟𝑒𝑒 𝐶𝑂2 = 𝑙𝑖𝑡𝑒𝑟 𝑚𝑙. 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒

Note: Solubility of CO2 in water is a strong function of temperature. And the accuracy of this titrimetric method is approximately ±10%.

F1 = _________________ liters/sec. VT = _________________ Volume of Water in System (liters).

Page - 52

From Sump Tank S5 (Correspond to conditions at top of

S4

tower)

Time from Start (minutes)

From Liquid Outlet Sample Point

VB ml

Cd in tank [Cdi] gmol/liter

VB ml

Cd at outlet [Cdo] gmol/liter

10 20 30 40 50 60

CO2 absorbed over a time period (e.g. 30 minutes): 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑅𝑎𝑡𝑒 =

[𝐶𝑑𝑖 𝑎𝑡(𝑡 = 40) − 𝐶𝑑𝑖 𝑎𝑡(𝑡 = 10)]×𝑉𝑇 𝑔𝑚𝑜𝑙/𝑠𝑒𝑐 30×60

CO2 absorbed across the column at any particular time: Inlet flow of dissolved CO2 = F1×Cdi gmol/sec. = _____________________ gmol/sec. Outlet flow of dissolved CO2 = F1×Cdo gmol/sec. = ____________________ gmol/sec. 𝐴𝑏𝑠𝑜𝑟𝑝𝑡𝑖𝑜𝑛 𝑅𝑎𝑡𝑒 = 𝐹1 [𝐶𝑑𝑖 − 𝐶𝑑𝑜 ] 𝑔𝑚𝑜𝑙/𝑠𝑒𝑐

Page - 53

Experiment 11 (LIQUID-LIQUID EXTRACTION APPARATUS) Objective: To determine the Distribution Coefficient for the system Trichloroethylene – Propanoic Acid – Water and to show its dependence on concentration.

Equipment Setup / Apparatus: 250ml Conical Stoppered Flask or Beaker, 250ml Measuring Cylinder, 250ml Separating Funnel, Pipette with Rubber Bulb, Burette, and Funnel.

Reagents: 0.1 Molar NaOH Solution, Phenolphthalein, Propionic Acid, Trichloroethylene, Water.

WARNING: Concentrated Sodium Hydroxide can form explosive volatile products when in contact with Trichloroethylene. Ensure that diluted Sodium Hydroxide (NaOH) is used when performing this experiment.

Page - 54

Theory: The solvent (water) and solution (trichloroethylene/propionic acid) are mixed together and then allowed to separate into the extract phase and the raffinate phase. The extract phase will be water and propionic acid and the raffinate phase is trichloroethylene with a trace of propionic acid. The Distribution Coefficient K, is defined as the ratio: 𝐾=

𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 𝑖𝑛 𝑡ℎ𝑒 𝑒𝑥𝑡𝑟𝑎𝑐𝑡 𝑝ℎ𝑎𝑠𝑒 𝑌 = 𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 𝑖𝑛 𝑡ℎ𝑒 𝑟𝑎𝑓𝑓𝑖𝑛𝑎𝑡𝑒 𝑝ℎ𝑎𝑠𝑒 𝑋

It is assumed that phase equilibrium exists between the two phases. At low concentrations, the distribution coefficient is dependent on the concentration and thus Y = KX.

Procedure: 1) Make up in a conical flask a mixture of 50ml trichloroethylene and 50ml of demineralized water. 2) Add 5ml of propionic acid. 5ml can be pipetted into the flask using a pipette with a rubber bulb. 3) Place a stopper into the flask and shake for a minimum of 5 minutes. 4) Pour into a separating funnel, leave for 5 minutes and remove the lower aqueous layer. 5) Take a 10ml sample of this layer and titrate against 0.1M NaOH solution using phenolphthalein as an indicator. 6) Repeat the experiment for two further concentrations of propionic acid i.e. for initial additions of 3ml and 1ml of propionic acid.

Data Analysis:

Volume of Propionic Acid

0.1M NaOH

Added (ml)

Solution used. (ml)

Propionic Acid

Propionic Acid

Concentration

Concentration

in Aqueous

in Organic

Layer

Layer

Y

X

Distribution Coefficient 𝐾=

𝑌 𝑋

5 3 1 Page - 55

Page - 56

Experiment 12 (LIQUID-LIQUID EXTRACTION APPARATUS) Objective: To demonstrate how a mass balance is performed on the extraction column, and to measure the mass transfer coefficient and its variation with flowrate with the aqueous phase as the continuous medium.

Equipment Setup / Apparatus: Liquid-Liquid Extraction Apparatus, 250ml Conical Stoppered Flask, 250ml Measuring Cylinder, Pipette with Rubber Bulb, Burette.

The solvent metering pump is calibrated in percentage of maximum flow which varies slightly from pump to pump. The pump should be calibrated initially by setting F2 to 100%, setting valve V8 to the calibrate position and measuring the flow from the pump, using a measuring cylinder and stopwatch. Calculate the flow rate produced settings of 10% intervals (ml per minute), then plot a graph of ml per minute against percentage of metering pump stroke. Thereafter any selected flow may be obtained by using the graph.

Page - 57

Reagents: 0.1 Molar NaOH Solution, Phenolphthalein, Propionic Acid, Trichloroethylene, Water.

Procedure:

WARNING: Concentrated Sodium Hydroxide can form explosive volatile products when in contact with Trichloroethylene. Ensure that diluted Sodium Hydroxide (NaOH) is used when performing this experiment.

1) Add 100ml of propionic acid to 10 liters of trichloroethylene. Mix well to ensure an even concentration then fill the organic phase feed tank (bottom tank) with the mixture. 2) Switch the level control to the bottom of the column (electrode switch S2). Page - 58

3) Fill the water feed tank with 15 liters of clean de-mineralized water, start the water feed pump and fill the column with water at a high flow rate. 4) As soon as the water is above the top of the packing, reduce the flow rate to 0.2 liters/min. 5) Start the metering pump and set at a flow rate of 0.2 liters/min. 6) Run for 15-20 minutes until steady conditions are achieved, monitor flow rates during this period to ensure that they remain constant. 7) Take 15ml samples from the feed, raffinate and extract streams. 8) Titrate 10ml of each sample against 0.1M NaOH using phenolphthalein as the indicator. (To titrate the feed and raffinate they may need continuous stirring using a magnetic stirrer). 9) Repeat the experiment with both the water and trichloroethylene flow rates being increased to 0.3 1iters/min.

Data Analysis: NOTATION: Vw = Water flowrate (Liters/sec) V0 = Trichloroethylene flowrate (Liters/sec) X = Propionic acid concentration in the organic phase (kg/liter) Y = Propionic Acid concentration in the aqueous phase (kg/1iter) SUBSCRIPTS: 1 = Top of Column 2 = Bottom of Column

The equations are given for the system Trichloroethylene-Propionic Acid-Water. Propionic acid extracted from the organic phase (raffinate) = 𝑉𝑜 (𝑋1 − 𝑋2 ) Propionic acid extracted by the aqueous phase (extract) = 𝑉𝑤 (𝑌1 − 0) Therefore: 𝑉𝑜 (𝑋1 − 𝑋2 ) = 𝑉𝑤 (𝑌1 − 0) Mass transfer coefficient (based on the raffinate phase) kD: 𝑘𝐷 =

𝑅𝑎𝑡𝑒 𝑜𝑓 𝐴𝑐𝑖𝑑 𝑇𝑟𝑎𝑛𝑠𝑓𝑒𝑟 𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑃𝑎𝑐𝑘𝑖𝑛𝑔 × 𝐿𝑜𝑔 𝑀𝑒𝑎𝑛 𝐷𝑟𝑖𝑣𝑖𝑛𝑔 𝐹𝑜𝑟𝑐𝑒

Page - 59

𝐿𝑜𝑔 𝑀𝑒𝑎𝑛 𝐷𝑟𝑖𝑣𝑖𝑛𝑔 𝐹𝑜𝑟𝑐𝑒 =

∆𝑥1 − ∆𝑥2 ∆𝑥 𝑙𝑛 (∆𝑥1 ) 2

Where: ∆𝑥1 = 𝐷𝑟𝑖𝑣𝑖𝑛𝑔 𝐹𝑜𝑟𝑐𝑒 𝑎𝑡 𝑡ℎ𝑒 𝑡𝑜𝑝 𝑜𝑓 𝑡ℎ𝑒 𝑐𝑜𝑙𝑢𝑚𝑛 = (𝑋2 − 0) ∆𝑥2 = 𝐷𝑟𝑖𝑣𝑖𝑛𝑔 𝐹𝑜𝑟𝑐𝑒 𝑎𝑡 𝑡ℎ𝑒 𝑏𝑜𝑡𝑡𝑜𝑚 𝑜𝑓 𝑡ℎ𝑒 𝑐𝑜𝑙𝑢𝑚𝑛 = (𝑋1 − 𝑋1∗ ) 𝑋1∗ = 𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝑖𝑛 𝑡ℎ𝑒 𝑜𝑟𝑔𝑎𝑛𝑖𝑐 𝑝ℎ𝑎𝑠𝑒 𝑤ℎ𝑖𝑐ℎ 𝑤𝑜𝑢𝑙𝑑 𝑏𝑒 𝑖𝑛 𝑒𝑞𝑢𝑖𝑙𝑖𝑏𝑟𝑖𝑢𝑚 𝑤𝑖𝑡ℎ 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝑌1 𝑖𝑛 𝑡ℎ𝑒 𝑎𝑞𝑢𝑒𝑜𝑢𝑠 𝑝ℎ𝑎𝑠𝑒. The equilibrium values can be found using the distribution coefficient found in the previous experiment.

Flowrate of Aqueous Phase: Flowrate of Organic Phase: Volume of 0.1M NaOH

Concentration of Propionic

solution used in titration

Acid

(ml)

kg/liters

Feed: Raffinate: Extract: Propionic acid extracted from the organic phase: Propionic acid extracted from the aqueous phase: Mass Transfer Coefficient kD

Page - 60

Experiment 13 (TRAY DRIER APPARATUS) Objective: To produce drying and drying rate curves for a wet solid being dried with air of fixed temperature and humidity.

Equipment Setup / Apparatus: Tray Drier Apparatus, Digital Weight Balance, Wet and Dry Bulb Thermometer, and Stop Watch.

Reagents: Sand, Air.

Theory: Immediately after contact between the wet solid and the drying medium, the solid temperature adjusts until it reaches a steady state. The solid temperature and the rate of drying may increase or decrease to reach the steady state condition. At steady state, the temperature of the wet solid surface is the wet bulb temperature of the drying medium. Temperatures within Page - 61

the drying solid also tend to equal the wet bulb temperature of the gas but lag in movement of mass and heat in some deviation. Once the stock temperatures reach the wet bulb temperature of the gas, they are quite stable and the drying rate also remains constant. This is the constant rate drying period which ends when the solid reaches the critical moisture content. Beyond this point the surface temperature rises, and the drying rate falls off rapidly. The falling rate period can take a far longer time than the constant rate period even though the moisture removal may be less. The drying rate approaches zero at some equilibrium moisture content which is the lowest moisture content obtainable with the solid under the drying conditions used.

Procedure: 1) Take dry sand to fill the four trays to a depth of about 10 mm each should be accurately weighed before being saturated with water in a container. 2) The sand should be removed from the container and drained of excess “free” water before being loaded evenly and smoothly into the sand drying trays, taking care to avoid any spillage. 3) The total weight of the wet sand should be noted before drying commence. 4) At some arbitrary time (t=0), switch on and set the fan speed control to mid-position and the heater power control to maximum letting them remain constant throughout the experiment. 5) Record the total weight of sand in the trays at regular time intervals until drying is complete. NOTE: It is recommended that the laboratory be well ventilated to ensure that warm moist air discharged from the drier does not affect the original inlet conditions over the period of the experiment.

Data Analysis: Weight of dry sand = ________________ kg. XE = Equilibrium Moisture Content Time (min)

0

Weight of wet sand (kg) Moisture Content XE

Page - 62

𝑋𝐸 =

𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝐿𝑖𝑞𝑢𝑖𝑑 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑊𝑒𝑡 𝑆𝑎𝑛𝑑 − 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝐷𝑟𝑦 𝑆𝑎𝑛𝑑 = 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝐷𝑟𝑦 𝑆𝑎𝑛𝑑 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝐷𝑟𝑦 𝑆𝑎𝑛𝑑

From the results, plot the drying curve relating moisture content as a function of time. Carefully differentiate data from this curve to produce the drying rate - moisture content plot, attempting to identify the points (A, B, C and D) at which the drying passes from one regime to the next.

Comment upon the results obtained and relate the curves to the mechanism by which drying occurs. What is the significance of the equilibrium moisture content?

Page - 63

Experiment 14 (TRAY DRIER APPARATUS) Objective: To investigate the influence of air temperature on the drying rate of a wet solid in air at fixed velocity.

Equipment Setup / Apparatus: Tray Drier Apparatus, Digital Weight Balance, Wet and Dry Bulb Thermometer, and Stop Watch.

Reagents: Sand, Air.

Procedure: 1) Take dry sand to fill the four trays to a depth of about 10 mm each should be accurately weighed before being saturated with water in a container. 2) The sand should be removed from the container and drained of excess 'free' water before being loaded evenly and smoothly into the drying trays, taking care to avoid any spillage. 3) The total weight of the wet sand should be noted before drying commences. Page - 64

4) At some arbitrary time (t=0), switch on and set the fan speed control to produce an air velocity of about 0.5 m/s, Measure the velocity of the air flow through the drier using the digital anemometer. 5) Set the heater power control to a nominal setting and measure the dry and wet bulb air temperatures upstream of the sand trays using the aspirating psychrometer. 6) Record the total weight of sand in the trays at regular time intervals until drying is complete. 7) The experiment should be repeated for other air temperatures by increasing the power supplied to the heater up to the maximum setting. 8) It is important to keep the air velocity constant and to use the same weight and distribution of sand in each of the tests.

NOTE: It is recommended that the laboratory be well ventilated to ensure that moist air discharged from the drier does not affect the original inlet conditions over the period of the experiments.

Data Analysis: The drying rate of a wet solid in air changes throughout the drying period since the controlling factors are different for each major section of the drying rate curve. However, many wet solids exhibit a period during which the drying rate is essentially constant and: 𝑅𝑐 ∝ ℎ𝑣 (𝑇𝑣 − 𝑇𝑖 ) Where: 𝑅𝑐 = 𝐷𝑟𝑦𝑖𝑛𝑔 𝑅𝑎𝑡𝑒 𝑑𝑢𝑟𝑖𝑛𝑔 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 𝑟𝑎𝑡𝑒 𝑝𝑒𝑟𝑖𝑜𝑑 ℎ𝑣 = 𝐻𝑒𝑎𝑡 𝑇𝑟𝑎𝑛𝑠𝑓𝑒𝑟 𝐶𝑜𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑡 𝑇𝑣 = 𝑇𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑑𝑟𝑦𝑖𝑛𝑔 𝑔𝑎𝑠 𝑇𝑖 = 𝑇𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑙𝑖𝑞𝑢𝑖𝑑/𝑔𝑎𝑠 𝑖𝑛𝑡𝑒𝑟𝑓𝑎𝑐𝑒 The temperature of the drying gas (Tv) is the normally measured dry bulb temperature. At steady state, the temperature of the liquid-gas interface (Tj) is equal to the wet bulb temperature of the drying air. Thus, the drying rate is proportional to the difference between the dry and wet bulb temperatures of the air.

Page - 65

Air Velocity = ____________________ m/sec. Weight of dry sand = _______________ kg. Dry Bulb Temp. Tv oC Wet Bulb Temp. Ti oC (Tv-Ti) oC Time (min)

0

0

0

Wet Sand Weight (kg) Moisture Content XE

𝑋𝐸 =

𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝐿𝑖𝑞𝑢𝑖𝑑 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑊𝑒𝑡 𝑆𝑎𝑛𝑑 − 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝐷𝑟𝑦 𝑆𝑎𝑛𝑑 = 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝐷𝑟𝑦 𝑆𝑎𝑛𝑑 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝐷𝑟𝑦 𝑆𝑎𝑛𝑑

From the results, plot the drying curves relating moisture constant and time for each test. Differentiate data from, these curves to produce the drying rate-moisture content curves:

Comment upon the results obtained, noting the influence that (Tv - Ti) had upon the drying rate during the constant rate period.

Page - 66

Experiment 15 (FLUIDIZED BED DRIER APPARATUS) Objective: To: 1. Investigate the simple drying of a material to give moisture content and the drying time required. 2. Determine the drying curves to assess the feasibility of fluidized bed drying of a material on an industrial scale. 3. Calculate heat transfer coefficient (It is important in drier design and comparison of fluidized beds with other drying methods).

Equipment Setup / Apparatus: Fluidized Bed Drier Apparatus, Digital Weight Balance, and Wet and Dry Bulb Thermometer.

Reagents: Any suitable solid particles which are wet and need to be dried, Air. Page - 67

Procedure: 1) Determine the optimum bed depth the optimum bed depth is that which can be fluidized at the required temperature by relative high air velocity. The optimum bed depth will vary appreciably with the material-an initial bed depth of about 75mm is typical. 2) Remove any excess water from the solid sample by decanting and / or using a filter pump. 3) Place the sample of material in the jar to an appropriate bed depth. Weigh the jaar alone then with the material. 4) Fix the sealing ring into the groove. 5) Switch on the mains supply and select the drying temperature required (select three temperatures). 6) Note the wet and dry bulb temperatures of the inlet air to the fan and outlet air from the fluidized bed. 7) Weigh the jar with material at 2 minute intervals for about 16 minutes (or as long as it takes to attain constant weight) recording the wet and dry bulb temperature before removing the jar for weighing. Continue until constant weigh is achieved indicating that the equilibrium moisture content has been reached. 8) Record the drying time and moisture content.

Data Analysis: From the results, plot the drying curve relating moisture content as a function of time. Carefully differentiate data from this curve to produce the drying rate - moisture content plot, attempting to identify the points (A, B, C and D) at which the drying passes from one regime to the next.

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CALCULATION OF HEAT TRANSFER COEFFICIENT: Heat lost by entering gas = Heat transferred to solids to vaporize the liquid Therefore: 𝑑𝑤 1 = −ℎ𝐴(𝑇𝑎 − 𝑇𝑠 )log 𝑚𝑒𝑎𝑛 × 𝑑𝑡 𝐿 This equation can be integrated to give: ℎ=

(𝑊0 − 𝑊𝑐 )×𝐿 𝑡×𝐴×(𝑇𝑎 − 𝑇𝑠 )log 𝑚𝑒𝑎𝑛

Where: dw/dt = Constant drying rate [kg/s] L = Latent heat of vaporization [J/kg] H = Heat transfer coefficient [W/(m2×oC)] A = Surface area [m2] Ta = Dry bulb air temperature [oC] Ts = Wet bulb air temperature, [oC] Wo = Initial moisture content [kg water/kg dry solid] Wc = Critical moisture content at end of constant rate period [kg water/kg dry solid] t = Constant rate drying time [sec]

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