Transcript
ABSTRACT
Biochemical processes is one of the process occurred in the living things’ cells. Generally there are many processes in the biochemical process and of it is the aerobic diffusion as in the bioreactor stirred tank experiment. The main objective of this experiment is to identify the mass transfer coefficient for each parameter being investigated, such as the effect of the agitation speed, the aeration rate as well as the temperature of the solution into the bioreactor stirred tank. The agitation speed effect can be identified by fixing the aeration rate being supplied into the reactor to be 2 L/min and the fixed temperature is 30 C. The agitation speed effect can be started at the 200 rpm of speed and the nitrogen can be supplied into the bioreactor so that the oxygen concentration can be reduced until it is saturated. Only after that, the flow is stopped and the oxygen can be supplied again at the fixed constant as mention before. The value of the concentration contained in the reaction is measured by recording the pO 2 reading at the panel and this value is the C L value that will be used to plot the graph by using (Equation 1) mentioned in the Theory section. Finally, the steps are repeated for different agitation speed of 400 rpm, 600 rpm, 800 rpm and 1000rpm. The overall step also can be used in determining the effect of the aeration rate but with the different fixed variable, which is by using the agitation speed of 400 rpm and the temperature of 30 C. The aeration rate can be varies from 0.5 L/min, 1.0 L/min, 1.5 L/min and 2.5 L/min. Not only that, that , the overall step also can be used in determining the effect of the temperature but with the different fixed variable, which is by using the agitation speed of 400 rpm and the aeration rate of 2 L/min. The temperature can be varies from 30 C, 35 C, 40 C, 45 C and ˚
˚
˚
˚
˚
˚
50 C. From the graph of ln (C*-C L) against time plotted, the equation for each line can be measured since the slope of the line is the k La value for that parameter. From the results, it shown that the higher agitation speed of the impeller gives the highest the value of the mass transfer coefficient, k La. Besides, the highest aeration rate being supplied into the bioreactor tank also gives the highest value of the mass transfer coefficient, k La. Finally, the highest temperature of a reaction also gives the highest value mass transfer coefficient compared to the lower temperature. ˚
INTRODUCTION
There are many biochemical reactions existed in this life since this reaction is much more efficient rather than another reaction. Biochemical reactions are one of the chemical reactions that take place in living things’ cells. The reactions that happened in an organism are called as metabolism and this is including both exothermic as well as the endothermic reactions (Foundation, 2017). Generally, there are few types of biochemical reactions such as oxidation and reduction, movement of functional groups within or between molecules, addition and removal of water and also the bond-breaking reactions (CliffNotes, 2016). Mostly, these reactions require some amount of oxygen in order for it to operate efficiently and to produce the product of the reaction. In order to achieve the aim, the dissolved oxygen concentration becoming the most needed variable to be supplied into the biochemical reaction continuously. continuously. This is because it is to ensure that the oxygen supplied is maintained throughout the experiment while the organism is consuming the oxygen. Physically, the oxygen is purged into the bioreactor and transferring the air bubbles into the solution. After that, it will breaking up and mixed well in the solution by the stirrer. For this experiment, there parameters is used to determine the difference in the mass transfer coefficient, k La value which is the effect of agitation speed, aeration rate and also the temperature. The importance of studying the mass transfer coefficient shows that the effective transfer process is by ensuring the mass transfer rate of oxygen to the liquid must equal or exceeding the rate at which the cells take up the oxygen. This proved that the process conditions must adequate sufficient amount of oxygen for the cell to consume freely as it will grow (Kane, 2012). Basically, aerobic reaction is using the following formula to utilize graphical method: dCL/dt = Oxygen Transfer Rate (OTR) – (OTR) – Oxygen Oxygen Uptake Rate (OUR) dCL/dt = k La (C* - CL) – qO qO2 . X
INTRODUCTION
There are many biochemical reactions existed in this life since this reaction is much more efficient rather than another reaction. Biochemical reactions are one of the chemical reactions that take place in living things’ cells. The reactions that happened in an organism are called as metabolism and this is including both exothermic as well as the endothermic reactions (Foundation, 2017). Generally, there are few types of biochemical reactions such as oxidation and reduction, movement of functional groups within or between molecules, addition and removal of water and also the bond-breaking reactions (CliffNotes, 2016). Mostly, these reactions require some amount of oxygen in order for it to operate efficiently and to produce the product of the reaction. In order to achieve the aim, the dissolved oxygen concentration becoming the most needed variable to be supplied into the biochemical reaction continuously. continuously. This is because it is to ensure that the oxygen supplied is maintained throughout the experiment while the organism is consuming the oxygen. Physically, the oxygen is purged into the bioreactor and transferring the air bubbles into the solution. After that, it will breaking up and mixed well in the solution by the stirrer. For this experiment, there parameters is used to determine the difference in the mass transfer coefficient, k La value which is the effect of agitation speed, aeration rate and also the temperature. The importance of studying the mass transfer coefficient shows that the effective transfer process is by ensuring the mass transfer rate of oxygen to the liquid must equal or exceeding the rate at which the cells take up the oxygen. This proved that the process conditions must adequate sufficient amount of oxygen for the cell to consume freely as it will grow (Kane, 2012). Basically, aerobic reaction is using the following formula to utilize graphical method: dCL/dt = Oxygen Transfer Rate (OTR) – (OTR) – Oxygen Oxygen Uptake Rate (OUR) dCL/dt = k La (C* - CL) – qO qO2 . X
OBJECTIVES
1. To investigate the effect of agitation speed on volumetric oxygen transfer rate
, in
a stirred tank bioreactor. 2. To investigate the effect of aeration rate on volumetric oxygen transfer rate
, in a
stirred tank bioreactor. 3. To investigate the effect of the temperature on volumetric oxygen transfer rate
, in
a stirred tank bioreactor.
THEORY
The main objective of running this experiment is absolutely to find the mass transfer coefficient, k La for each parameter, which is agitation speed, aeration rate and also the temperature. Firstly, a graph is plotted between ln (C* - C L) which shows how much is the amount of oxygen gas contained in that certain reaction at certain period of time. The y-axis value for the first graph is: y-axis = ln (C* - C L)
(Equation 1)
this values will be plotted against time recorded for each parameter until it reaches 100% of pO2, or at least it reached its constant value of pO 2 which showed that it has already reaching its ‘100% value’. After the graph is drawn, the equation for each line is measured to identify the slope for each line. y = mx + c, where the m is = k La
(Equation 2)
From the equation, the mass transfer coefficient, k La can be directly calculated from the line’s slope and the value is converted into the unit of h -1. Then, these values for each line is plotted to show the relation between the different in parameter with their respected value of mass transfer coefficient.
APPARATUS
1
2
3
4
Figure 1: Bioreactor stirred tank.
No. Descriptions
1.
Bioreactor vessel
2.
Aeration meter
3.
Reader for pO2
4.
Calibration meter
PROCEDURE
LAB 1: The effect of agitation speed study. 1. The agitation of bioreactor is set to 200rpm. 2. Oxygen concentration of the solution is lowered by gassing the liquid out with
2 at
9
L/min until saturate and stop the flow. 3.
2 to
the bioreactor is supplied at flow rate of 2.0 L/min until saturated then the flow
is stopped. 4.
value
is obtained at constant time interval during aeration
5. Steps 2 to 4 is repeated for different agitation speed (400rpm, 600rpm, 800 rpm and 1000rpm). 6. The value of stirred tank reactor is calculated at different agitation speed. LAB 2: The effect of aeration rate study. 1. The aeration of the bioreactor is set to 0.5L/min. 2. Oxygen concentration of the solution is lowered by gassing the liquid out with
2 at
9
L/min until saturate and the flow is stopped. 3.
2 to
the bioreactor is supplied to the bioreactor at fixed agitation rate of 400 rpm and
at temperature of 30 C until saturated and the flow is stopped. ˚
4.
value
is obtained at constant time interval of 5 seconds during aeration.
5. Steps 2 to 4 is repeated for different aeration rate (1 L/min, 1.5 L/min and 2.5 L/min). 6. The value of stirred tank reactor is calculated at different aeration rate. LAB 3: The effect of temperature study. 1. The temperature of the bioreactor is set to 30 C. ˚
2. Oxygen concentration of the solution is lowered by gassing the liquid out with
2 at
9
L/min until saturate and the flow is stopped. 3.
2 to
the bioreactor is supplied to the bioreactor at fixed agitation rate of 400 rpm and
at aeration rate at 2 L/min until saturated and the flow is stopped. 4.
value
is obtained at constant time interval of 5 seconds during aeration.
5. Steps 2 to 4 is repeated for different temperature (35 C, 40 C, 45 C and 50 C). ˚
˚
˚
6. The value of stirred tank reactor is calculated at different temperature.
˚
RESULTS A. The effect of agitation speed with constant of the temperature (30 ˚C) and the aeration rate (2L/min). Table 1: The reading measured from the experiment for agitation speed effect. Time (s)
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
Agitation speed (rpm) 200 0.00
400 0.00
600 0.00
800 0.00
1000 1.70
1.48
3.06
4.87
5.09
2.72
4.32
8.03
14.70
16.00
10.70
9.91
13.30
23.80
29.80
25.40
11.90
19.70
32.00
43.70
41.40
15.40
26.40
41.10
53.80
56.90
19.30
32.60
50.40
69.80
66.20
23.90
38.60
57.90
72.80
77.30
27.90
45.80
64.80
79.30
83.50
31.80
50.90
70.50
84.10
88.70
35.80
55.80
75.70
88.40
92.00
39.50
60.60
80.50
91.40
94.80
42.70
65.20
84.00
94.00
97.00
46.20
69.20
86.80
95.70
98.00
49.90
73.00
89.40
97.00
99.00
53.00
76.20
91.60
98.30
99.80
55.80
79.20
93.50
99.10
100.00
58.70
81.60
95.10
99.80
61.40
83.90
96.40
100.00
63.90
85.90
97.40
66.50
87.60
98.30
105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230
68.70
89.20
98.90
70.60
90.50
99.50
72.70
91.80
99.90
74.50
93.00
100.00
76.30
94.10
77.90
95.10
79.40
95.90
80.70
96.60
81.90
97.20
83.10
97.80
84.40
98.30
85.50
98.60
86.60
99.10
87.50
99.40
88.40
99.70
89.20
100.00
90.20 90.90 91.60 92.20 92.90 93.50 94.00 94.60 95.00 95.40
235 240 245 250 255 260 265 270 275 280 285 290 295 300 305 310 315 320 325
95.80 96.30 96.70 97.00 97.30 97.60 97.90 98.10 98.40 98.60 98.70 98.90 99.10 99.30 99.40 99.60 99.80 99.90 100.00
Table 2: The value calculated to plot the graph of ln (C*-C L) for agitation speed (rpm)
against time. Time (s)
ln (C* - CL) at 200 rpm
ln (C* - CL) at 400 rpm
ln (C* - CL) at 600 rpm
ln (C* - C L) at 800 rpm
ln (C* - C L) at 1000 rpm
4.61
4.61
4.61
4.61
4.59
5
4.59
4.57
4.56
4.55
4.58
10
4.56
4.52
4.45
4.43
4.49
15
4.50
4.46
4.33
4.25
4.31
20
4.48
4.39
4.22
4.03
4.07
25
4.44
4.30
4.08
3.83
3.76
30
4.39
4.21
3.90
3.41
3.52
35
4.33
4.12
3.74
3.30
3.12
40
4.28
3.99
3.56
3.03
2.80
45
4.22
3.89
3.38
2.77
2.42
50
4.16
3.79
3.19
2.45
2.08
55
4.10
3.67
2.97
2.15
1.65
60
4.05
3.55
2.77
1.79
1.10
65
3.99
3.43
2.58
1.46
0.69
70
3.91
3.30
2.36
1.10
0.00
75
3.85
3.17
2.13
0.53
-1.61
80
3.79
3.03
1.87
-0.11
-
85
3.72
2.91
1.59
-1.61
90
3.65
2.78
1.28
-
95
3.59
2.65
0.96
100
3.51
2.52
0.53
105
3.44
2.38
0.10
0
110
3.38
2.25
-0.69
115
3.31
2.10
-2.30
120
3.24
1.95
-
125
3.17
1.77
130
3.10
1.59
135
3.03
1.41
140
2.96
1.22
145
2.90
1.03
150
2.83
0.79
155
2.75
0.53
160
2.67
0.34
165
2.60
-0.11
170
2.53
-0.51
175
2.45
-1.20
180
2.38
-
185
2.28
190
2.21
195
2.13
200
2.05
205
1.96
210
1.87
215
1.79
220
1.69
225
1.61
230
1.53
235
1.44
240
1.31
245
1.19
250
1.10
255
0.99
260
0.88
265
0.74
270
0.64
275
0.47
280
0.34
285
0.26
290
0.10
295
-0.11
300
-0.36
305
-0.51
310
-0.92
315
-1.61
320
-2.30
325
-
ln (C*-CL) for agitation speed, (rpm) against time, (s)
6.00 ) 5.00 m p r ( d4.00 e e p3.00 s n o i t2.00 a t i g1.00 a r o f )0.00 L C 0 --1.00 * C ( -2.00 n l
ln (C* - CL) @ 200 rpm ln (C* - CL) @ 400 rpm ln (C* - CL) @ 600 rpm ln (C* - CL) @ 800 rpm ln (C* - CL) @ 1000 rpm y = -0.0171x + 5.1407 (200rpm) 50
100
150
200
250
300
350y = -0.0292x + 5.1526 (400 rpm) y = -0.0478x + 5.2738 (600 rpm) y = -0.062x + 5.2101 (800 rpm) y = -0.072x + 5.3261 (1000 rpm)
-3.00
time (s)
Figure 2: The graph of ln (C* - C L) of agitation speed, rpm effect against time, s.
Table 3: The calculated value of k La (h-1) for agitation speed effect given from the previous
graph. Agitation speed (rpm)
k La value (h-1)
200
61.56
400
105.12
600
172.08
800
223.20
1000
259.20
kLa value for agitation speed effect 300.00 250.00 ) 1 - 200.00 h ( e u 150.00 l a v a L k 100.00
kLa value for agitation speed effect
50.00 0.00 0
200
400 600 800 Agitation speed (rpm)
1000
1200
Figure 3: The k La value (h-1) for each of the agitation speed value.
B. The effect of aeration rate with constant of the agitation speed (400 rpm) and the temperature (30 ˚C). Table 4: The reading measured from the experiment for aeration rate effect. Time (s)
Aeration rate (L/min) 0.5 L/min
1.0 L/min
1.5 L/min
2.5 L/min
5
-1.70
-1.40
-1.70
-1.90
10
-1.80
-1.30
-1.40
-1.20
15
-1.70
0.58
0.57
1.48
20
-1.20
3.40
4.29
6.22
25
0.65
7.89
9.16
12.00
30
3.38
11.80
13.90
18.40
35
6.53
15.40
19.60
25.80
40
10.20
20.30
25.10
31.70
45
14.30
24.00
29.40
36.60
50
17.80
28.10
34.40
41.30
55
21.60
32.20
38.80
46.40
60
25.20
35.50
42.80
49.40
65
29.00
39.30
46.60
53.80
70
32.00
42.20
50.00
56.80
75
35.20
45.80
52.90
59.70
80
38.70
48.20
55.70
62.40
85
40.90
51.10
58.40
64.60
90
43.80
53.20
60.80
66.70
95
46.40
55.70
62.70
68.50
100
48.80
58.00
64.70
69.90
105
51.10
59.90
66.60
71.30
110
53.10
61.70
68.30
72.80
115
55.20
63.70
69.70
73.90
120
57.30
65.30
71.30
74.80
125
58.90
66.90
72.40
75.60
130
61.10
68.40
73.40
76.30
135
62.70
69.60
74.80
77.10
140
64.20
71.10
75.50
77.80
145
65.90
72.30
76.30
78.30
150
67.20
73.30
77.20
78.80
155
68.70
74.30
78.00
79.20
160
69.80
75.30
78.50
79.70
165
71.30
76.20
79.00
80.10
170
72.40
77.20
79.80
80.40
175
73.60
77.90
80.80
80.80
180
74.60
78.60
80.90
81.00
185
75.60
79.20
81.10
81.10
190
76.80
80.00
81.40
81.20
195
77.50
80.80
81.80
81.40
200
78.30
81.10
82.10
81.60
205
79.40
81.50
82.70
81.80
210
80.10
82.10
82.70
81.90
215
80.90
82.70
83.00
82.00
220
81.40
83.00
83.20
82.20
225
82.10
83.50
83.50
82.40
230
82.70
83.90
83.80
82.60
235
83.40
84.10
83.90
82.70
240
84.00
84.50
84.00
82.80
245
84.50
84.80
84.30
82.90
250
85.00
85.10
84.50
83.00
255
85.60
85.60
84.50
83.00
260
86.00
85.70
84.70
83.10
265
86.60
86.00
84.80
83.20
270
86.80
86.20
84.90
83.20
275
87.20
86.50
85.00
83.30
280
87.70
86.70
85.10
83.30
285
88.20
86.80
85.30
83.40
290
88.50
87.00
85.40
83.50
295
88.80
87.00
85.50
83.60
300
89.10
87.30
85.60
83.70
305
89.50
87.50
85.60
83.70
310
89.80
87.60
85.80
83.80
315
90.00
87.70
86.00
84.10
320
90.30
87.80
86.10
325
90.50
88.10
86.20
330
90.70
88.20
86.30
335
91.10
88.40
86.40
340
91.30
88.40
86.60
345
91.40
88.50
86.70
350
91.70
88.60
355
92.00
88.70
360
92.20
88.80
365
92.30
88.80
370
92.40
88.90
375
92.50
88.90
380
92.60
89.00
385
92.70
89.10
390
92.80
89.20
395
93.00
89.20
400
93.20
89.20
405
93.30
89.30
410
93.40
89.30
415
93.40
89.40
420
93.60
89.40
425
93.70
89.50
430
93.70
89.50
435
94.00
89.60
440
94.00
89.60
445
94.10
89.60
450
94.10
89.70
455
94.20
89.70
460
94.40
89.70
465
94.40
89.70
470
94.40
89.70
475
94.50
480
94.60
485
94.60
490
94.70
495
94.70
500
94.80
505
94.80
510
94.80
515
94.90
520
94.90
525
94.90
530
95.00
535
95.10
540
95.10
545
95.10
550
95.20
555
95.20
560
95.20
565
95.20
570
95.20
Table 5: The value calculated to plot the graph of ln (C*-C L) for aeration rate (L/min) against
time.
Time (s)
ln (C* - CL) at 0.5 L/min
ln (C* - C L) at 1.0 L/min
ln (C* - CL) at 1.5 L/min
ln (C* - CL) at 2.5 L/min
5
4.57
4.51
4.48
4.45
10
4.57
4.51
4.48
4.45
15
4.57
4.49
4.46
4.41
20
4.57
4.46
4.41
4.36
25
4.55
4.40
4.35
4.28
30
4.52
4.36
4.29
4.19
35
4.48
4.31
4.21
4.07
40
4.44
4.24
4.12
3.96
45
4.39
4.19
4.05
3.86
50
4.35
4.12
3.96
3.76
55
4.30
4.05
3.87
3.63
60
4.25
3.99
3.78
3.55
65
4.19
3.92
3.69
3.41
70
4.15
3.86
3.60
3.31
75
4.09
3.78
3.52
3.19
80
4.03
3.73
3.43
3.08
85
3.99
3.65
3.34
2.97
90
3.94
3.60
3.25
2.86
95
3.89
3.53
3.18
2.75
100
3.84
3.46
3.09
2.65
105
3.79
3.39
3.00
2.55
110
3.74
3.33
2.91
2.42
115
3.69
3.26
2.83
2.32
120
3.63
3.19
2.73
2.23
125
3.59
3.13
2.66
2.14
130
3.53
3.06
2.59
2.05
135
3.48
3.00
2.48
1.95
140
3.43
2.92
2.42
1.84
145
3.38
2.86
2.34
1.76
150
3.33
2.80
2.25
1.67
155
3.28
2.73
2.16
1.59
160
3.23
2.67
2.10
1.48
165
3.17
2.60
2.04
1.39
170
3.13
2.53
1.93
1.31
175
3.07
2.47
1.77
1.19
180
3.03
2.41
1.76
1.13
185
2.98
2.35
1.72
1.10
190
2.91
2.27
1.67
1.06
195
2.87
2.19
1.59
0.99
200
2.83
2.15
1.53
0.92
205
2.76
2.10
1.39
0.83
210
2.71
2.03
1.39
0.79
215
2.66
1.95
1.31
0.74
220
2.62
1.90
1.25
0.64
225
2.57
1.82
1.16
0.53
230
2.53
1.76
1.06
0.41
235
2.47
1.72
1.03
0.34
240
2.42
1.65
0.99
0.26
245
2.37
1.59
0.88
0.18
250
2.32
1.53
0.79
0.10
255
2.26
1.41
0.79
0.10
260
2.22
1.39
0.69
0.00
265
2.15
1.31
0.64
-0.11
270
2.13
1.25
0.59
-0.11
275
2.08
1.16
0.53
-0.22
280
2.01
1.10
0.47
-0.22
285
1.95
1.06
0.34
-0.36
290
1.90
0.99
0.26
-0.51
295
1.86
0.99
0.18
-0.69
300
1.81
0.88
0.10
-0.92
305
1.74
0.79
0.10
-0.92
310
1.69
0.74
-0.11
-1.20
315
1.65
0.69
-0.36
-
320
1.59
0.64
-0.51
325
1.55
0.47
-0.69
330
1.50
0.41
-0.92
335
1.41
0.26
-1.20
340
1.36
0.26
-2.30
345
1.34
0.18
-
350
1.25
0.10
355
1.16
0.00
360
1.10
-0.11
365
1.06
-0.11
370
1.03
-0.22
375
0.99
-0.22
380
0.96
-0.36
385
0.92
-0.51
390
0.88
-0.69
395
0.79
-0.69
400
0.69
-0.69
405
0.64
-0.92
410
0.59
-0.92
415
0.59
-1.20
420
0.47
-1.20
425
0.41
-1.61
430
0.41
-1.61
435
0.18
-2.30
440
0.18
-2.30
445
0.10
-2.30
450
0.10
-
455
0.00
-
460
-0.22
-
465
-0.22
-
470
-0.22
-
475
-0.36
480
-0.51
485
-0.51
490
-0.69
495
-0.69
500
-0.92
505
-0.92
510
-0.92
515
-1.20
520
-1.20
525
-1.20
530
-1.61
535
-2.30
540
-2.30
545
-2.30
550
-
555
-
560
-
565
-
570
-
ln (C*-CL) for aeration rate, (L/min) against time, (s) 6.00 ) 5.00 n i m / 4.00 L ( e t 3.00 a r n o 2.00 i t a r e 1.00 a r o f 0.00 ) L 0 C * -1.00 C ( n -2.00 l
ln (C*-CL) @ 0.5 L/min ln (C*-CL) @ 1.0 L/min ln (C*-CL) @ 1.5 L/min 100
200
-3.00
300
time (s)
400
500
600
ln (C*-CL) @ 2.5 L/min
y = -0.0114x + 5.0528 ( 0.5 L/min ) y = -0.0142x + 4.9189 ( 1.0 L/min ) y = -0.0162x + 4.7422 ( 1.5 L/min ) y = -0.0179x + 4.5323 ( 2.5 L/min )
Figure 4: The graph of ln (C* - C L) of aeration rate, L/min effect against time, s.
Table 6: The calculated value of k La (h-1) for aeration rate effect given from the previous
graph. Aeration rate (L/min)
k La value (h-1)
0.50
41.04
1.00
51.12
1.50
58.32
2.50
64.44
kLa value of the aeration rate effect 70.00 60.00 ) 50.00 1 h ( 40.00 e u l a v 30.00 a L k
kLa value of the aeration rate effect
20.00 10.00 0.00 0.00
0.50
1.00 1.50 2.00 Aeration rate (L/min)
2.50
3.00
Figure 5: The k La value (h-1) for each of the aeration rate value.
C. The effect of temperature with constant value of the agitation speed (400 rpm) and the aeration rate (2 L/min). Table 7: The reading measured from the experiment for the temperature effect.
Time (s)
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105
30˚C 45.00
35˚C 11.70
Temperature (˚C) 40˚C -
50.50
11.90
7.80
0.00
-0.10
55.90
13.40
15.90
2.77
2.46
61.00
17.70
24.20
9.97
8.60
65.50
24.00
31.50
17.70
19.80
69.60
31.10
40.70
28.10
31.80
73.30
39.10
47.80
37.50
43.00
77.20
46.30
55.50
46.50
52.80
79.50
52.70
61.80
55.30
62.50
82.40
58.90
68.30
63.30
70.20
84.60
64.50
72.90
68.90
77.70
86.30
69.30
77.70
75.20
84.50
88.10
73.50
81.40
79.90
89.30
89.80
77.50
85.40
84.30
93.90
91.20
81.00
87.90
88.00
97.50
92.40
84.00
90.90
91.50
100.00
93.50
86.70
93.00
94.20
94.60
88.80
95.20
96.90
95.30
90.80
96.70
98.60
96.10
92.40
98.40
100.00
96.80
93.90
99.50
97.40
95.20
100.00
45˚C -
50˚C -
110 115 120 125 130 135
97.80
96.30
98.30
97.50
98.70
98.30
99.00
99.00
99.30
99.70
99.50
100.00
99.80
140
100.00
145
Table 8: The value calculated to plot the graph of ln (C*-C L) for temperature ( C) against ˚
time. ln (C* - C L) at 30˚C
ln (C* - CL) at 35˚C
ln (C* - CL) at 40˚C
ln (C* - C L) at 45˚C
ln (C* - C L) at 50˚C
4.01
4.48
5
3.90
4.48
4.52
4.61
4.61
10
3.79
4.46
4.43
4.58
4.58
15
3.66
4.41
4.33
4.50
4.52
20
3.54
4.33
4.23
4.41
4.38
25
3.41
4.23
4.08
4.28
4.22
30
3.28
4.11
3.96
4.14
4.04
35
3.13
3.98
3.80
3.98
3.85
40
3.02
3.86
3.64
3.80
3.62
45
2.87
3.72
3.46
3.60
3.39
50
2.73
3.57
3.30
3.44
3.10
Time (s)
0
55
2.62
3.42
3.10
3.21
2.74
60
2.48
3.28
2.92
3.00
2.37
65
2.32
3.11
2.68
2.75
1.81
70
2.17
2.94
2.49
2.48
0.92
75
2.03
2.77
2.21
2.14
-
80
1.87
2.59
1.95
1.76
85
1.69
2.42
1.57
1.13
90
1.55
2.22
1.19
0.34
95
1.36
2.03
0.47
-
100
1.16
1.81
-0.69
105
0.96
1.57
-
110
0.79
1.31
115
0.53
0.92
120
0.26
0.53
125
0.00
0.00
130
-0.36
-1.20
135
-0.69
-
140
-1.61
145
-
ln (C*-CL) for temperature, (˚C) against time, (s)
6.00
ln (C* - CL) @ T = 30 5.00 )
ln (C* - CL) @ T = 35
C
˚ ( 4.00 e r u t a r 3.00 e p m e 2.00 t r o f ) 1.00 L C * 0.00 C ( n 0.00 l
ln (C* - CL) @ T = 40 ln (C* - CL) @ T = 45 ln (C* - CL) @ T = 50
y = -0.0366x + 5.1725 ( T = 35˚C) y = -0.0345x + 4.3614 ( T = 30˚C ) 20.00
40.00
60.00
80.00
100.00
120.00
140.00
-1.00 -2.00
160.00 y = -0.0456x + 5.274 ( T = 40˚C) y = -0.0449x + 5.3622 ( T = 45˚C) y = -0.0514x + 5.1123 ( T = 50˚C)
time (s)
Figure 6: The graph of ln (C* - C L) of temperature, C effect against time, s. ˚
Table 9: The calculated value of k La (h-1) for temperature effect given from the previous
graph. Temperature (˚C)
k La value (h-1)
30
124.2
35
131.76
40
164.16
45
161.64
50
185.04
kLa value of the temperature effect 200.00 ) 180.00 1 h ( 160.00 e r 140.00 u t a r 120.00 e p m 100.00 e t r 80.00 o f e u 60.00 l a v 40.00 a L k 20.00
kLa value of the temperature effect
0.00 0.00
10.00
20.00 30.00 Temperature (˚C)
40.00
50.00
60.00
Figure 7: The k La value (h-1) for each of the temperature value.
SAMPLE CALLCULATION
In experiment 2, for aeration rate effect on the bioreactor experiment:
For 0.5 L/min of aeration rate; The C* = 95.2 at 550 s, C L = -1.7 at 5 s The y-axis value is calculated by (Equation 1) as in the theory section: ln (C* - C L) = ln [95.2 – (-1.7)] ln (C* - C L) = 4.574 The value of 4.574 is then drawn into a graph against time for each time until it reaches its maximum value as shown in the Figure 3 above.
From the graph plotted of the ln (C* - C L) against time, the equation of the best fit for each rate was calculated as below: Since y = mx + c So, y = -0.0114x + 5.0528 Thus, the slope, m for the reaction is = -0.0114
From the theory section for (Equation 2), it is understood that the slope of the graph is equal to the k La value of that parameter at that condition. Hence, k La value for the 0.5 L/min of the aeration rate effect is = 0.0114 s-1.
The second graph is plotted based on the k La value measured before against each parameter as shown in the Figure 4. Before plotting the graph, the value is converted into h -1 unit first, as shown below: k La (at 0.5 L/min) = 0.0114 s -1 x 60 s x 60 min k La (at 0.5 L/min) = 41.04 h -1.
The value of 41.04 h -1 is then plotted against the each of the aeration rate experimented as shown in the Figure 4. The explanation of the graph will be discussed in the Discussion section.
DISCUSSIONS
Based on the results tabulated and plotted above, it is generally concluded that the higher the values of the parameters, the higher the values of the mass transfer coefficient, k La. For the first experiment which is the effect of the difference reading of the agitation speed in rpm, it showed that the agitation speed of 1000 rpm reactions gives the faster reaction to reached 100% value of pO 2 reading compared to 200 rpm, 400 rpm, 600 rpm and 800 rpm. It took only 80 s to achieve that value, while 800 rpm reaction took about 90 s, 600 rpm took about 120 s, 400 rpm took about 180 s and finally the 200 rpm reaction took about 325 s to reach 100%. From the value recorded for every 5 seconds, the difference between the maximum concentration, C* and the value of each concentration for each time is calculated thus measuring the value of the ln (C*-C L) to plot the first graph. From Figure 2, it clearly shown that the 1000 rpm reaction gave the steeper line compared to another speed due to the time taken for it achieving 100% much faster than another. For that reason, the slope of that line much higher than another which is – 0.072. The negative sign indicate that the graph has negative slope and does not effect on the real value of the mass transfer coefficient. Then, the slope is taken as the value of the coefficient and converted it in the unit of per hour (h -1). The 1000 rpm reaction gave about 259.2 h -1 for the mass transfer coefficient value, while 800 rpm about 223.2 h -1, 600 rpm about 172.08 h -1, 400 rpm about 105.12 h -1, and 200 rpm about 61.56 h -1. The graph plotted in the Figure 3 proved that the higher the agitation speed in rpm, the higher the mass transfer coefficient. This is due to the agitation speed affect the problems on the bubble size, bubble retention time and the mixing of the solution. The 1000 rpm reaction efficiently breaking down the air bubbles since it has higher sectional area. Then, it will affecting the superficial area of the bubbles than enhanced the transfer rate of the oxygen. To that aim, the mass transfer coefficient for this reaction is much higher than another speed while the lower speed does not have enough traps to hold up the air bubbles and make the superficial area of the bubbles decreasing, thus lowering the value of the transfer coefficient (Karimi, 2013). Next is the effect of the aeration rate on the mass transfer coefficient of a reaction. Based on the results tabulated and plotted above, it is generally concluded that the higher the values of the parameters, the higher the values of the mass transfer coefficient, k La. It showed that the aeration rate of 2.5 L/min reactions gives the faster reaction to reached 100% value of
pO2 reading compared to 0.5 L/min, 1.0 L/min and 1.5 L/min. It took only 315 s to achieve that value, while 1.5 L/min reaction took about 345 s, 1.0 L/min took about 470 s and 0.5 L/min took about 550 s to reach 100%. From the value recorded for every 5 seconds, the difference between the maximum concentration, C* and the value of each concentration for each time is calculated thus measuring the value of the ln (C*-C L) to plot the first graph. From Figure 4, it clearly shown that the 2.5 L/min reaction gave the steeper line compared to another speed due to the time taken for it achieving 100% much faster than another. For that reason, the slope of that line much higher than another which is – 0.0179. The negative sign indicate that the graph has negative slope and does not effect on the real value of the mass transfer coefficient. Then, the slope is taken as the value of the coefficient and converted it in the unit of per hour (h -1). The 2.5 L/min reaction gave about 64.44 h -1 of the mass transfer coefficient value meanwhile 1.5 L/min about 58.32 h -1, 1.0 L/min about 51.12 h -1 and 0.5 L/min about 41.04 h -1. The graph plotted in the Figure 5 proved that the higher the aeration rates in L/min, the higher the mass transfer coefficient. This is due to the aeration reaction will produced small bubbles with uniform size of distribution and will lead to the increasing of the mass transfer area between the gas and the liquid solution. This increasing mass transfer area is the major reason for the transfer rate being increased as the aeration supplied increased in L/min (Painmanakul, 2009). Lastly is the effect of the temperature on the mass transfer coefficient of a reaction. Based on the results tabulated and plotted above, it is generally concluded that the higher the values of the parameters, the higher the values of the mass transfer coefficient, k La. It showed that the temperature of 50 C reactions gives the faster reaction to reached 100% value of pO 2 ˚
reading compared to 30 C, 35 C, 40 C and 45 C. It took only 75 s to achieve that value, ˚
˚
˚
˚
while 45 C reaction took about 95 s, 40 C took about 105 s, 35 C took about 135 s and 30 C ˚
˚
˚
˚
took about 145 s to reach 100%. From the value recorded for every 5 seconds, the difference between the maximum concentration, C* and the value of each concentration for each time is calculated thus measuring the value of the ln (C*-C L) to plot the first graph. From Figure 6, it clearly shown that the 50 C reaction gave the steeper line compared ˚
to another speed due to the time taken for it achieving 100% much faster than another. For that reason, the slope of that line much higher than another which is – 0.0514. The negative
sign indicate that the graph has negative slope and does not effect on the real value of the mass transfer coefficient. Then, the slope is taken as the value of the coefficient and converted it in the unit of per hour (h -1). The 50 C reaction gave about 185.04 h -1 of the mass ˚
transfer coefficient value meanwhile 45 C about 161.64 h -1, 40 C about 164.16 h -1, 35 C ˚
˚
˚
about 131.76 h -1 and 30 C about 124.20 h -1. ˚
The graph plotted in the Figure 7 proved that the higher the temperature in C, the ˚
higher the mass transfer coefficient. This is due to the higher temperature caused the concentration of the dissolved oxygen to be reduced. Thus, the mass transfer driving force, which is (C*-CL) also being decreasing. This can be best explained by understanding that higher temperature lead to the increasing of the air bubbles and increasing in the diffusivity of the oxygen in the liquid film. After all, the mass transfer coefficient also being increased (Ahmad, September 2017 - January 2018).
CONCLUSION
To be concluded the increasing in the agitation speed lead to the increasing in the mass transfer coefficient. Same goes with the aeration rate effect on the transfer coefficient. The higher the aeration rate supplied into the bioreactor, the higher the value of the mass transfer coefficient. Lastly, the higher the temperature of the bioprocess system gives the highest mass transfer coefficient of that reaction. This is because the transfer rate at the high temperature much faster than the lower temperature. However, there is slightly little error in this temperature experiment, where at the temperature 45 C there is a little decreasing in ˚
value due to the error in conducting the experiment. Theoretically, the highest value of mass transfer coefficient is af fected by the highest agitation speed of the bioreactor’s impeller, highest aeration rate being supplied into the reactor as well as the highest temperature being supplied through the temperature probe.
RECOMMENDATIONS
REFERENCES
Ahmad, I. N. (September 2017 - January 2018). Transport Processes in Stirred Tank Bioreactors. Retrieved November, 2017 CliffNotes. (2016). The Scope of Biochemistry. Retrieved December, 2017, from Types of Biochemical
Reactions:
https://www.cliffsnotes.com/study-
guides/biology/biochemistry-i/the-scope-of-biochemistry/types-of-biochemicalreactions Foundation, C.-1. (2017). cK-12. Retrieved December, 2017, from Types of Biochemical Reactions:
https://www.ck12.org/biology/types-of-biochemical-
reactions/lesson/Types-of-Biochemical-Reactions-BIO/ Kane, J. (1 March, 2012). BioProcess International . Retrieved December, 2017, from Measuring
kLa
for
Better
Bioreactor
Performance:
http://www.bioprocessintl.com/upstream-processing/bioreactors/measuring-kla-for better-bioreactor-performance-328029/ Karimi, A. (7 January, 2013). US National Library of Medicine National Institutes of Health . Retrieved December, 2017, from Oxygen mass transfer in a stirred tank bioreactor using
different
impeller
configurations
for
environmental
purposes:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3561095/ Painmanakul, P. (November, 2009). THEORETICAL PREDICTION OF VOLUMETRIC MASS TRANSFER COEFFICIENT (kLa) FOR DESIGNING AN AERATION TANK. Engineering Journal, 13(3), 14. doi:10.4186/ej.2009.13.3.13
