che422l06_ab_initial report.pdf
TRANSCRIPT
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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
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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
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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
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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
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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
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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
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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:
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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:
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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
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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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