CHE422L06_AB_initial report.pdf

7/25/2019 CHE422L06_AB_initial report.pdf

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Department of Chemical Engineering

University of San Carlos - Technological Center

Nasipit, Talamban, Cebu City

ChE 422L

Chemical Engineering Laboratory 1

Absorption

(Hydrodynamics in a Packed Absorption Column)

An initial report submitted to

Engr May V Tampus


2/17

Engr May V Tampus

1. Objectives

Determine experimentally the pressure drop across a wet column as a function

of the air flow rate and compare the results with theoretically calculated

values.

Determine through visual observation and by graphical methods the loading

and the flooding points of the packed column at pre-set values of water flow

rates.

Construct from experimental data the loading and the flooding curves of the

packed column based on the generalized correlations proposed by Sherwood,

Shipley and Holloway.

2. Results and Discussion

2.1

Pressure drop across a wet column as a function of air flow rate

Table 1. Pressure drop in a wetted column with increasing air flow rate

vg

(L/min)

vg

(m3/s)

h (m

H2O) Pexp(Pa)

vg(m/s) Pth(Pa) Pexp/L Pth/L

30 0.0005 0.0040 39.0518 0.1132 9.4439 26.7478 6.4684

40 0.0007 0.0080 78.1035 0.1509 15.4075 53.4955 10.5531

50 0.0008 0.0120 117.1553 0.1886 22.7790 80.2433 15.6021

60 0.0010 0.0160 156.2070 0.2264 31.5584 106.9911 21.6153

70 0.0012 0.0200 195.2588 0.2641 41.7455 133.7389 28.5928

80 0.0013 0.0230 224.5476 0.3018 53.3406 153.7997 36.5346

90 0 0015 0 0260 253 8364 0 3395 66 3435 173 8605 45 4407


3/17

70 0.0012 0.0200 195.2588 0.2641 41.7455 133.7389 28.5928

60 0.0010 0.0140 136.6811 0.2264 31.5584 93.6172 21.6153

50 0.0008 0.0100 97.6294 0.1886 22.7790 66.8694 15.602140 0.0007 0.0080 78.1035 0.1509 15.4075 53.4955 10.5531

30 0.0005 0.0060 58.5776 0.1132 9.4439 40.1217 6.4684

*operational temperature: Twater= 27.75C, Tair= 27.5C

Tables 1 and 2 show the experimental and theoretical pressure drop in a wetted

column at increasing and decreasing flow rate respectively. In the experiment,

manometer readings with increasing flow rates increases hence pressure drop increases

also. While with decreasing flow rates, manometer reading decreases hence pressure drop

also decreases. In order for the air to flow upward, there must be a pressure difference

between the bottom and the top of the column. So for increasing air flow rate, the

pressure difference must also be increasing. The opposite is happening for decreasing air

flow rate.

400.0000

500.0000

600.0000

700.0000

L(Pa/m)

Increasing airflowrate

Decreasing air

flowrate


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spherical. Whereas, in the experiment, the packings used were cylindrical. Also, the walls

of the column and the water inside the column added to the resistance against air flow

causing pressure drop to be higher than that of the theoretical values.

2.2Loading and flooding points of the packed column at pre-set values of water

flow rates

Table 3. Loading and Flooding Points through Visual Observation

vL(L/min)

Loading Point Flooding Point

vg(L/min)

vg(m3/s) vg (m/s)

vg(L/min)

vg(m3/s) vg (m/s)

1 150 0.0025 0.5659 - - -

2 110 0.0018 0.4150 135 0.0023 0.5093

2.5 100 0.0017 0.3773 125 0.0021 0.4716

3 90 0.0015 0.3395 118 0.0020 0.44523.5 80 0.0013 0.3018 110 0.0018 0.4150

4 70 0.0012 0.2641 105 0.0018 0.3961

5 60 0.0010 0.2264 90 0.0015 0.3395

In table 3, the air flow rate, where loading and flooding points were

observed at pre-set values of water flow rate, are shown. At loading point, water starts

to build up at the bottom of the upper part of the packed of column. Beyond the


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Figure 5. log P/L vs log vg at 3 L/min water flow rate

Figure 6. log P/L vs log vg at 3.5 L/min water flow rate


7/17

Figure 8. log P/L vs log vg at 5 L/min water flow rate

Table 4. Loading and Flooding Points through Graphical method

vL(L/min)

Loading Point Flooding Pointvg

(L/min)vg(m

3/s) vg (m/s)vg

(L/min)

vg

(m3/s)

vg (m/s)

1129.8266 0.0022 0.4898 - - -

2115.7081 0.0019 0.4365 132.8506 0.0022 0.5012

2.596.2423 0.0016 0.3631 115.7081 0.0019 0.4365

391.9102 0.0015 0.3467 110.5002 0.0018 0.4169

3.580.0504 0.0013 0.3020 105.5270 0.0018 0.3981

471.3449 0.0012 0.2692 96.2418 0.0016 0.3631


8/17

while the rest have almost the same results. Comparing results of flooding points for

both methods, results obtained graphically are a little less than that obtained by visual

observation. This may be due to human error, the loading and the flooding points may

not be observed really well.

2.3Loading and Flooding Curves based on the generalized correlations

proposed by Sherwood Shipley and Holloway

Figure 9. vs based on visual observation

0.00E+00

5.00E-03

1.00E-02

1.50E-02

2.00E-02

2.50E-02

0 1 2 3

loading

curve vo

flooding

curve vo


9/17

Figures 9 and 10 show the loading and flooding curves based on the correlation

by Sherwood, Shipley and Holloway. It is a plot of the capacity parameter versus the

flow parameter. This correlation estimates loading and flooding at given water to gas

rates. Operation of a packed column is most desirable in the area between the two

curves. The two graphs show that the capacity parameter decreases with increasing

flow parameter. This is because increasing the water flow rate, which then increases

the flow parameter, decreases the ratio of the kinetic energy of the gas to the potential

energy of the liquid therefore a decrease in the capacity parameter.

3. References

Foust, A.S et al. (1980) Principles of Unit Operations, 2nded, John Wiley and

Sons, Inc., New York

Geankoplis C.J. (2003) Principles of Transport Processes and Separation

Processes, 4thed, Pearson Education Inc., Prentice Hall, New Jersey.

McCabe, W.L et al. (1993) Unit Operations of Chemical Engineering, 5 thed,

McGraw-Hill Inc., Singapore


10/17


11/17

Velocity of gas at loading point for 2 L/min water flow rate:

Velocity of gas at flooding point for 2 L/min water flow rate:

Liquid mass rate for 2 L/min water flow rate:


12/17

Capacity parameter at loading point for 2 L/min water flow rate:

Flow parameter at loading point for 2 L/min water flow rate:

Capacity parameter at flooding point for 2 L/min water flow rate:


13/17

4.2 Processed Data Tables

Table 5. Constant Parameters

Diameter of the column, Dc(m) 0.075

Length of the column (m) 1.46

Diameter of the packing, Dp(m) 0.009

Total area of the packing, ap(m2/m3) 420

Porosity of packed bed, 0.63

Gravitational Constant, g (m/s2) 9.81

cross-sectional area of the column, Ac(m2) 0.004417865

Packed bed height, L (m) 1.46

Table 6. Physical Properties of Water and Air at different temperature

vL

(L/min)

Water Air

Tave(C) L (kg/m3)

L(kg/m.s) Tave(C) G (kg/m3) G (kg/m.s)

1 27.75 996.31 8.41E-04 27 1.1793 1.8534

2 27.5 996.38 8.45E-04 28 1.1754 1.8577

2.5 27.5 996.38 8.45E-04 28 1.1754 1.8577

3 27.5 996.38 8.45E-04 28 1.1754 1.8577

3.5 27.5 996.38 8.45E-04 28 1.1754 1.8577

4 27.5 996.38 8.45E-04 28 1.1754 1.8577

5 27.5 996.38 8.45E-04 28 1.1754 1.8577


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Table 8. Pressure drop in a packed column at 2L/min water flow rate

vg

(L/min)

vg

(m3/s)

h (m

H2O) Pexp(Pa)

Pexp/L

(Pa/m) vg (m/s)

log

Pexp

/L log vg20 0.0003 0.0060 58.5777 40.1217 0.0755 1.6034 -1.1223

40 0.0007 0.0140 136.6814 93.6174 0.1509 1.9714 -0.8213

60 0.0010 0.0260 253.8369 173.8609 0.2264 2.2402 -0.6452

80 0.0013 0.0520 507.6738 347.7218 0.3018 2.5412 -0.5203

100 0.0017 0.0840 820.0884 561.7044 0.3773 2.7495 -0.4234

110 0.0018 0.1320 1288.7103 882.6783 0.4150 2.9458 -0.3820

120 0.0020 0.1560 1523.0213 1043.1653 0.4527 3.0184 -0.3442

125 0.0021 0.1840 1796.3841 1230.4001 0.4716 3.0900 -0.3265

130 0.0022 0.2260 2206.4283 1511.2523 0.4904 3.1793 -0.3094

135 0.0023 0.7000 6834.0700 4680.8699 0.5093 3.6703 -0.2930

Table 9. Pressure drop in a packed column at 2.5 L/min water flow rate

vg(L/min)

vg(m3/s)

h (mH2O) Pexp(Pa)

Pexp/L(Pa/m) vg (m/s)

logPexp/L log vg

20 0.0003 0.0060 58.5777 40.1217 0.0755 1.6034 -1.1223

40 0.0007 0.0200 195.2591 133.7391 0.1509 2.1263 -0.8213

60 0.0010 0.0460 449.0960 307.6000 0.2264 2.4880 -0.6452

70 0.0012 0.0620 605.3033 414.5913 0.2641 2.6176 -0.5783

80 0.0013 0.0900 878.6661 601.8261 0.3018 2.7795 -0.5203

90 0.0015 0.1200 1171.5549 802.4348 0.3395 2.9044 -0.4691100 0.0017 0.1560 1523.0213 1043.1653 0.3773 3.0184 -0.4234

110 0.0018 0.1960 1913.5396 1310.6436 0.4150 3.1175 -0.3820

120 0.0020 0.4800 4686.2194 3209.7393 0.4527 3.5065 -0.3442


15/17

Table 11. Pressure drop in a packed column at 3.5 L/min water flow rate

vg

(L/min)

vg

(m3/s)

h (m

H2O) Pexp(Pa)

Pexp/L

(Pa/m) vg (m/s)

log

Pexp

/L log vg20 0.0003 0.0100 97.6296 66.8696 0.0755 1.8252 -1.1223

40 0.0007 0.0280 273.3628 187.2348 0.1509 2.2724 -0.8213

50 0.0008 0.0480 468.6219 320.9739 0.1886 2.5065 -0.7244

60 0.0010 0.0700 683.4070 468.0870 0.2264 2.6703 -0.6452

70 0.0012 0.1060 1034.8735 708.8174 0.2641 2.8505 -0.5783

80 0.0013 0.1480 1444.9177 989.6696 0.3018 2.9955 -0.5203

90 0.0015 0.2000 1952.5914 1337.3914 0.3395 3.1263 -0.4691

95 0.0016 0.2600 2538.3689 1738.6088 0.3584 3.2402 -0.4456

100 0.0017 0.3280 3202.2499 2193.3219 0.3773 3.3411 -0.4234

110 0.0018 0.7000 6834.0700 4680.8699 0.4150 3.6703 -0.3820

Table 12. Pressure drop in a packed column at 4 L/min water flow rate

vg(L/min)

vg(m3/s)

h (mH2O) Pexp(Pa)

Pexp/L(Pa/m) vg (m/s)

logPexp/L log vg

20 0.0003 0.0140 136.6814 93.6174 0.0755 1.9714 -1.1223

30 0.0005 0.0220 214.7851 147.1131 0.1132 2.1677 -0.9462

40 0.0007 0.0360 351.4665 240.7304 0.1509 2.3815 -0.8213

50 0.0008 0.0600 585.7774 401.2174 0.1886 2.6034 -0.7244

60 0.0010 0.0960 937.2439 641.9479 0.2264 2.8075 -0.6452

70 0.0012 0.1200 1171.5549 802.4348 0.2641 2.9044 -0.578380 0.0013 0.1940 1894.0137 1297.2696 0.3018 3.1130 -0.5203

90 0.0015 0.2780 2714.1021 1858.9740 0.3395 3.2693 -0.4691

100 0.0017 0.6400 6248.2926 4279.6524 0.3773 3.6314 -0.4234


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Table 14. Using Correlations of Sherwood, Shipley and Holloway based on visual observation

vL

(L/min)

vL

(m3/s)

vL

(m/s)

Loading Point Flooding PointL

(kg/m3)

G

(kg/m

3)

L

(kg/m.s)

L

(kg/m

2s)

Loading Flooding Loading

vg(L/mi

n)

vg(m3/

s)

vg(m/

s)

vg(L/mi

n)

vg(m3/

s)

vg(m/

s)

G(kg/

m2s)

G(kg/

m2s)

1.00

00

0.00

00

0.00

38

150.0

000

0.00

25

0.56

59 - - -

996.3

100

1.17

93

0.00

08

3.75

86

0.66

73 - 0.0191

0.19

38 - -

2.00

00

0.00

00

0.00

75

110.0

000

0.00

18

0.41

50

135.0

000

0.00

23

0.50

93

996.3

800

1.17

54

0.00

08

7.51

78

0.48

78

0.59

86 0.0102

0.52

94 0.0127

0.43

13

2.50

00

0.00

00

0.00

94

100.0

000

0.00

17

0.37

73

125.0

000

0.00

21

0.47

16

996.3

800

1.17

54

0.00

08

9.39

73

0.44

34

0.55

43 0.0085

0.72

79 0.0109

0.58

23

3.00

00

0.00

01

0.01

13

90.00

00

0.00

15

0.33

95

118.0

000

0.00

20

0.44

52

996.3

800

1.17

54

0.00

08

11.2

767

0.39

91

0.52

32 0.0069

0.97

05 0.0097

0.74

02

3.50

00

0.00

01

0.01

32

80.00

00

0.00

13

0.30

18

110.0

000

0.00

18

0.41

50

996.3

800

1.17

54

0.00

08

13.1

562

0.35

47

0.48

78 0.0054

1.27

38 0.0084

0.92

64

4.00

00

0.00

01

0.01

51

70.00

00

0.00

12

0.26

41

105.0

000

0.00

18

0.39

61

996.3

800

1.17

54

0.00

08

15.0

356

0.31

04

0.46

56 0.0041

1.66

37 0.0077

1.10

92

5.00

00

0.00

01

0.01

89

60.00

00

0.00

10

0.22

64

90.00

00

0.00

15

0.33

95

996.3

800

1.17

54

0.00

08

18.7

945

0.26

61

0.39

91 0.0030

2.42

63 0.0057

1.61

75

Table 15. Using Correlations of Sherwood, Shipley and Holloway based on graphical method

vL(L/m

in)

vL

(m3/

s)

vL(m/

s)

Loading Point Flooding Point L(kg/m

3)

G(kg/

m3)

L(kg/

m.s)

L

(kg/

m2s)

Loading Flooding Loadingvg

(L/mi

n)

vg

(m3/

s)

vg(m/

s)

vg

(L/mi

n)

vg

(m3/

s)

vg(m/

s)

G

(kg/

m2s)

G

(kg/

m2s)

1.00

00

0.00

00

0.00

38

149.0

608

0.00

25

0.56

23 - - -

996.3

100

1.17

93

0.00

08

3.75

86

0.66

32 - 0.0188

0.19

50 - -

2.00 0.00 0.00 110.5 0.00 0.41 132.8 0.00 0.50 996.3 1.17 0.00 7.51 0.49 0.58 0.0103 0.52 0.0123 0.43


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CHE422L06_AB_initial report.pdf