Expt. 4 - Gas Absorption (Pre & Post)

7/23/2019 Expt. 4 - Gas Absorption (Pre & Post)

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Objectives


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Equipment and Materials


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Turn on the switch of the

equipment.

Turn on

thecompressor and the

pump. Allow the gas to run a flow rate

of170 L/min for15 minutes to

remove any water in the column.

djustthethree-way glass clocks

so that the gas flowing out of the

pressure taps should only be

directed to the leftmanometer.


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After 15 minutes,

reset

the gasrate to 20 L/min.

easure the differential

pressure (mm H20) across the

upper and lower packed beds.

Repeatthe steps, increasing the

gas flow rate by10 L/min until it

reaches140 L/min.

Pressure

drop

in cm H

2

0


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Resetthe gas rate to 20 L/min.Open the liquid control valve andset the

liquid rate to1 L/min.

Observe

thegas flow in the irrigated packed

beds.

easure thepressure drops at various gas

rates and liquid rates and fill out the table.


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24 .8 cm H

2

O


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http://c/Users/User/Documents/4TH%20YEAR/2ND%20SEM/LAB/FLOODING.mp4http://c/Users/User/Documents/4TH%20YEAR/2ND%20SEM/LAB/FLOODING.mp4


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h cm Hg) Liquid Flow Rate L/min)

AFR

L/min) 0 1 2 3 4 5 6 6.5 7

20 0.6 0.2 0.2 1.8 0.8 1 1 1 2

30 0.6 0.2 0.2 2.2 1 1.2 2 1.8 2.2

40 1 0.4 0.2 2.4 1.6 2.4 3.4 3.8 350 1 0.6 0.2 2.6 2.6 2.4 5.6 7.6 9.6

60 1.2 0.6 0.4 2.6 3.2 5 10 11.6 18

70 1.4 0.8 0.4 3 4.8 9.4 17.2 18.6 27.8

80 1.7 1 1.2 4.4 7.6 13 27 39

90 2 1.4 2 5.6 10.4 18.6100 2.6 1.4 3.2 7.2 12.4 25.6

110 2.8 1.6 4.8 8.8 17

120 3.2 3 5.8 11.2 20.4

130 3.4 3.2 6.6 13.4 24.8

140 3.8 4 7.4 15.5


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h (mm Hg) Liquid Flow Rate (L/min)

AFR (L/min) 0 1 2 3 4 5 6 6.5 7

20 6 2 2 18 8 10 10 10 20

30 6 2 2 22 10 12 20 18 22

40 10 4 2 24 16 24 34 38 30

50 10 6 2 26 26 24 56 76 96

60 12 6 4 26 32 50 100 116 180

70 14 8 4 30 48 94 172 186 278

80 17 10 12 44 76 130 270 390

90 20 14 20 56 104 186

100 26 14 32 72 124 256

110 28 16 48 88 170

120 32 30 58 112 204

130 34 32 66 134 248

140 38 40 74 155


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P (Pa) Liquid Flow Rate (L/min)

AFR (L/min) 0 1 2 3 4 5 6 6.5 7

20 58.86 19.62 19.62 176.58 78.48 98.1 98.1 98.1 196.2

30 58.86 19.62 19.62 215.82 98.1 117.72 196.2 176.58 215.82

40 98.1 39.24 19.62 235.44 156.96 235.44 333.54 372.78 294.3

50 98.1 58.86 19.62 255.06 255.06 235.44 549.36 745.56 941.76

60 117.72 58.86 39.24 255.06 313.92 490.5 981 1137.96 1765.8

70 137.34 78.48 39.24 294.3 470.88 922.14 1687.32 1824.66 2727.18

80 166.77 98.1 117.72 431.64 745.56 1275.3 2648.7 3825.9

90 196.2 137.34 196.2 549.36 1020.24 1824.66100 255.06 137.34 313.92 706.32 1216.44 2511.36

110 274.68 156.96 470.88 863.28 1667.7

120 313.92 294.3 568.98 1098.72 2001.24

130 333.54 313.92 647.46 1314.54 2432.88

140 372.78 392.4 725.94 1520.55


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= ()


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e Liquid Flow Rate (L/min)

AFR (L/min) 0 1 2 3 4 5 6 6.5 7

20 0.6325 0.7465 0.7465 0.5114 0.6008 0.5761 0.5761 0.5761 0.5

30 0.6763 0.784 0.784 0.534 0.6211 0.6008 0.5443 0.556 0.5338

40 0.6523 0.7465 0.8084 0.556 0.6008 0.556 0.5176 0.5055 0.5314

50 0.6762 0.7287 0.8262 0.5719 0.5719 0.5807 0.4878 0.4555 0.4313

60 0.6762 0.7465 0.784 0.5921 0.5691 0.5199 0.4459 0.4306 0.3871

70 0.6762 0.7336 0.7973 0.5933 0.5413 0.4684 0.4065 0.3988 0.3606

80 0.6698 0.7247 0.7062 0.5657 0.5056 0.4485 0.3758 0.3421

90 0.665 0.7025 0.665 0.552 0.4849 0.4238

100 0.6481 0.7133 0.6255 0.5359 0.4769 0.4024

110 0.6504 0.7093 0.5913 0.5244 0.4537

120 0.6454 0.6524 0.58 0.5075 0.4438

130 0.6475 0.654 0.5745 0.4968 0.432

140 0.6435 0.6379 0.5701 0.4891

average 0.658415 0.713838 0.696846154 0.540777 0.525158 0.508511 0.479143 0.466371 0.457367


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dry packings

(L=0)

Gas flowrate

Packing

factor

Gas

Loading

Factor, Gf

Liquid

Loading

Factor, Lf Pd (H20/ft) PL (H20/ft) Re (p) Pt (H20/ft)

20 379.4407 2662.72 0 0.524666 0 84.37632 0.524666

30 273.3963 2260.216 0 0.378035 0 143.69 0.37803540 327.2885 2472.971 0 0.452553 0 178.3624 0.452553

50 273.6022 2261.067 0 0.378319 0 239.4093 0.378319

60 273.6022 2261.067 0 0.378319 0 287.2912 0.378319

70 273.6022 2261.067 0 0.378319 0 335.1731 0.378319

80 287.0845 2316.106 0 0.396962 0 375.6305 0.396962

90 297.6104 2358.184 0 0.411516 0 416.5294 0.411516

100 337.7236 2512.085 0 0.466982 0 440.5839 0.466982

110 331.9694 2490.592 0 0.459026 0 487.8308 0.459026

120 344.6038 2537.544 0 0.476496 0 524.6751 0.476496

130 339.2407 2517.721 0 0.46908 0 571.7842 0.46908

140 349.5281 2555.61 0 0.483305 0 608.8586 0.483305


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0

1

2

3

4

5

6

7

8

9

0 100 200 300 400 500 600 700

P vs NRe,p


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AFR G log G log (

P/Z)L=0 L=1 L=2 L=3 L=4 L=5 L=6 L=6.5 L=7

20 58.68386 1.768519 -0.27155 -0.74867 -0.74867 0.205568 -0.14661 -0.0497 -0.0497 -0.0497 0.251325291

30 88.02579 1.94461 -0.27155 -0.74867 -0.74867 0.292718 -0.0497 0.029477 0.251325 0.205568 0.292717976

40 117.3677 2.069549 -0.0497 -0.44764 -0.74867 0.330507 0.154415 0.330507 0.481774 0.530079 0.42741655

50 146.7097 2.166459 -0.0497 -0.27155 -0.74867 0.365269 0.365269 0.330507 0.698483 0.831109 0.932566528

60 176.0516 2.24564 0.029477 -0.27155 -0.44764 0.365269 0.455445 0.649265 0.950295 1.014753 1.2055678

70 205.3935 2.312587 0.096423 -0.14661 -0.44764 0.427417 0.631537 0.923423 1.185824 1.219808 1.394340091

80 234.7354 2.370579 0.180744 -0.0497 0.029477 0.593748 0.831109 1.064239 1.381659 1.54136

90 264.0774 2.421731 0.251325 0.096423 0.251325 0.698483 0.967329 1.219808

100 293.4193 2.467489 0.365269 0.096423 0.455445 0.807628 1.043717 1.358535

110 322.7612 2.508881 0.397453 0.154415 0.631537 0.894778 1.180744

120 352.1032 2.54667 0.455445 0.427417 0.713723 0.999513 1.259925

130 381.4451 2.581432 0.481774 0.455445 0.769839 1.0774 1.344747

140 410.787 2.613617 0.530079 0.552355 0.819527 1.140627


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-1

-0.5

0

0.5

1

1.5

2

1.5 1.7 1.9 2.1 2.3 2.5 2.7

log P/Z) vs log G

L=0

L=1

L=2

L=3

L=4

L=5

L=6

L=6.5

L=7


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Liquid Flow

Rate

Packing

Factor Gf Lf Pd (H20/ft) PL (H20/ft) Pt (H20/ft)

0 312.6559 2417.057 0 0.43232 0 0.43232

1 205.5321 1959.717 7.789674 0.284334 0.001192 0.285526

2 234.0564 2091.288 15.3928 0.323948 0.002151 0.326099

3 758.6429 3765.064 20.33994 1.050329 0.244396 1.294725

4 856.5372 4000.615 26.72541 1.186333 0.408767 1.595101

5 976.5186 4271.632 32.87301 1.353029 0.706105 2.059134

6 1237.063 4807.834 38.29156 1.714607 1.848951 3.563558

6.5 1374.395 5067.682 40.92594 1.905265 2.837778 4.743042

7 1481.771 5261.919 43.64652 2.054464 3.86141 5.915874


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Pt (H20/ft) Gf Lf/Gf

0.43232 2417.057 0

0.285526 1959.717 0.003975

0.326099 2091.288 0.00736

1.294725 3765.064 0.005402

1.595101 4000.615 0.00668

2.059134 4271.632 0.007696

3.563558 4807.834 0.0079644.743042 5067.682 0.008076

5.915874 5261.919 0.008295


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0

1

2

3

4

5

6

7

2000 2500 3000 3500 4000 4500 5000 5500 6000

x

s

T

e

Axis Title

Pt vs Gf


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1. What are the

characteristics that a packing

should have for it to be

employed in mass transfer

operation?


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1. The characteristics of a packing

should not react with the fluids, be

able to withstand the upcoming

streams without breaking, have low

weight, have a good porosity without

having a very large pressure drop, and

have a good contact between the two

streams.


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2. Explain the mechanism of gas flow

through a packed bed with liquid

flowing counter-currently.


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2. A very simple mechanism in gas absorption

using the packing column is to have liquid flowing

from the top of the column down to the bottom

while the gas is being pumped from the bottom of

the column to the top. The packings inside the

column make the two streams take complicated

paths which greatly increase the surface area and

its spreading. The increase in surface area also

increases the separation of the solute particles in

the gas solution and makes it transfer to the


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3. Differentiate between static

and dynamic or operating

holdup. How does this affect

the pressure drop through a

packed bed column?


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3. A holdup is the ratio of the volume of the fluid and the volume of the packing

inside the packed bed. There are two kinds of operating holdups: Static and

Dynamic.

Static operating holdup is where the flow of the fluid is not drained from

the packing while its supply line is stopped. It is measured by the ratio

of the volume of the fluid and the volume of the packing.

Dynamic operating holdup is the continuous flow of the liquid and

being drained by the packing while its supply line is stopped. It is also

measured by the ratio of the volume of the fluid and the volume of the

packing.

The total holdup is equal to the sum of the total liquid holdup static

and dynamic holdup. Because of the holdups, the calculation for the

pressure drop will be inaccurate. Therefore, Leva 1954) added a

correction factor for the determination of ressure dro .


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4. Define loading and

channeling? Give the

relevance of these two

factors in packed column

operation.


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4. Loading is the start of the flooding event where the

liquid starts to accumulate in the packings.

Channeling is an event where there is less liquid

flowing in an area in the packed column and more

liquid flowing in another area in the packed

column, which results to poor mass transfer.

Channeling can also be the cause of the flooding

event. Poor mass transfer in the area can result to

the start of loading which can lead to flooding in

the packed column.


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5. How does the packing factor

obtained from the flooding

velocity differ from the one

estimated empirically with the

use of the correlation of Lobo

et al?


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5. Equation for packing factor obtained

from Lobo et. al 1945) was simplified

empirically from various experiments with

different packings and different fluids

used on dumped tower packings. They

used charts and derived from those

equations the packing factor. Equation for

the packing factor using flooding velocity.


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Porosity was found by using the Ergun equation, datum from

the experiment, and properties of water and air at standard

conditions. However, there is still a possibility of a large error

because of the temperature and pressure which have slight

fluctuations throughout the experiment, purity of water (which

is assumed to be 100%), purity of air, and the inerts from the

packings. Using the porosity found, packing factor is

calculated using the equation from Lobo et. al. and. There aresome difficulties in the experiment like inaccuracy in reading

the mercury manometer, and fluctuations in the mercury

manometer.


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Also, inaccuracies in reading the flow rate of gas have

occurred due to the lack of measured bars in the flow rate level.

There are also difficulties in computations because some of the

variables are assumed like the density of water and air and theviscosity of water and air. The temperature and pressure were

assumed to be at standard conditions and are constant

throughout the experiment. Also, pressure drops are dependent

with the liquid and gas rates which prove difficult in obtaining

porosity. The effects of liquid holdups were found to be the

cause of increased pressure drop in the packed column. Very

large liquid holdups cause flooding in the packed column.


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FOR

LISTENING!


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