ANTIFOAMING AGENTS PERFORMANCE EVALUATION * Monazir Imam, Ata Yaseen Abdulgader, Ghulam M. Mustafa, Radwan Al-Rasheed and Ibraheem Al-Tissan Research and Development Center, P.O Box 8328, Al-Jubail, Kingdom of Saudi Arabia Abdul Salam Al-Mobayed and Anwar Ehsan Al-Jubail Desalination & Power Plant, Al-Jubail, Saudi Arabia. ABSTRACT Distillate contamination by salt carry over due to excessive foaming in multistage flash (MSF) distillers and detrimental foaming in deaerator section have been reported in Saline Water Conversion Corporation (SWCC) and other desalination plants. Application of suitable antifoaming agents not only maintains high quality of distillate but also improves release of dissolved oxygen in the deaerator section, thus improving the operating efficiency of MSF plants. Brose Chemical Company (BCC) and Albright and Wilson Limited (A&W) developers of antifoaming agents BCC-74M and Albrivap AF-2 respectively collaborated with SWCC in conducting trial runs to show that their products are as effective and economical as the one currently being used in SWCC plants. Foam control, non interference with the antiscalant performance, distillate purity, and stability over a wide range of temperatures at low dosage levels were some of the important criteria taken while evaluating the performance of these antifoaming agents. Compatibility of these agents were determined initially in the laboratory followed by field trial runs in MSF pilot plant and commercial plants of Al-Jubail phases I&II in order to check the above criteria. During MSF plant runs distillate conductivity and make-up feed dissolved oxygen(DO) levels were maintained in the ranges of 1-27 µS/cm and 5-47 ppb respectively. The higher DO was in Al-Jubail Phase I where deaeration takes place in the last stage of the distiller. These results were achieved at antifoam dose rates of 0.15 to 0.035 ppm. Once again higher dose rates at Al-Jubail Phase I were needed for the same reason mentioned above. Based on these results, one could say that data observed during these test runs showed satisfactory performance and thus conclude that these agents are comparable with the currently used antifoaming agents and can be effectively used in MSF plants of SWCC. *Presented in Second Acquired Experience Symposium, September, 1997, Al-Jubail *This paper is based on Technical Reports No. TR 96002 and TR 96005.
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INTRODUCTION Seawater is not a pure liquid. In addition to 3-4 % inorganic salts, it contains traces of organic compounds that have surface-active properties. As a surface phenomenon, minute quantities of organic compounds and fine particulate matter can promote foaming. Some of the few basic principles related to foaming in MSF desalination plants are highlighted [1] below: 1. Pure liquid do not foam. Presences of surfactant impurities are necessary for foaming to occur and stabilize. 2. Foams are unstable and tend to collapse quickly to separate gas and liquid components. Concentration of surfactant impurities opposes this collapse by several mechanisms. 3. The foam stability depends on many factors. Some of which are film viscosity, surface elasticity, electrical repulsion and gaseous diffusion. Disruption of these conditions enables to control foaming. Antifoaming agents are usually non-ionic surfactants with temperature dependent solubility. They have the important characteristics of low volatility, ease of dispersion, strong spreading power and surface attraction and orientation. They act to lower the surface tension of the vapor/liquid interface, reducing liquid film strength and surface viscosity and speeding drainage from bubbles. Summaries of foam control agents used in various applications other than desalination have been reported [2-3]. The effectiveness of antifoaming agents among more than 60 candidates from seven different chemical classes was determined [1]. The effectiveness of the best one of these was further verified in a 90 day trial run at a TBT of 108 oC on 2.2 MGD MSF recycle plant in CuraCao(Werkspour) of the Dutch Antilles. In this test foaming was suppressed without affecting the scale control agent at a dose rate of 0.03-0.05 ppm[1]. The effect of this antifoam on brine heater and flash chamber scaling using single stage flash evaporator (as a simulation module) at 120oC outlet temperature with normal recycle configuration was also studied[4]. Detrimental effect of foaming is not only found in MSF distillers but also reported in deaerator section [5-8]. It has been reported that during the commissioning period of Jeddah phase III, the deaerator was not performing according to design [5]. A detailed investigation of this problem resulted in the replacement of existing liquid distribution device with a more
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controlled and suitable system. The initial application of this device on site immediately showed an improvement in oxygen level from 200 down to about 80 ppb. However, this was still significantly above the guaranteed figure and after a study of the particular antifoam is being used, it became evident that the antifoam being used at the site was not suitable for the full-scale plant deaerator. The antifoam normally used was adequate and sufficient for controlling foam within the distillers, but did not perform satisfactorily at temperature levels of the deaerator. Utilization of alternate antifoam, capable of operating at temperatures of 30oC and below, immediately improved the deaerator performance. This agent brought down oxygen levels to less than 20 ppb as was desired. Thus one can say that antifoaming agents should also serve the purpose of preventing foaming either in the first few stages or in the deaerator, therefore, improving release of dissolved oxygen in the deaerator hence preventing carry over of salts to ejector system[6]. In other words foaming is a major reason for maloperation of deaerator columns [7]. The effluent dissolved oxygen concentration is strongly dependent on the combined action due to antifoam dosage rate and stripping steam [8]. Hence the importance of proper antifoam dosage and stripping steam flow rate on the satisfactory performance of deaerator columns must be emphasized. It has been further reported that deaeration of seawater can be effective in lowering oxygen content down to the range of 80-200 ppb as demonstrated in a test using single spray nozzle. However, for better deaeration i.e., to reduce oxygen level down to less than 20 ppb, antifoaming agents are to be introduced upstream of deaerator nozzles. Efforts to improve the performance and optimize the dosing rate of antifoaming agents are still continuing. In this context certain new advances have been attained particularly by owners of MSF plants in evaluating and optimizing the use of available antifoaming agents [9-10]. Antifoaming agents BCC-74M and Albivap AF-2 are claimed to be highly effective to prevent foaming problems in MSF distillation plants. In addition to this, these antifoaming agents are further characterized by some important and promising features such as their efficiency over a wide range of temperature at low dosage levels, stable dispersion with distillate at typical dosing solution concentrations, and economic viability. Table 1 specifically identify the important properties of these two antifoaming agents.The primary objective of these trial runs is to evaluate the performance of BCC-74M and AF-2 in
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controlling foams without disturbing the effectiveness of scale control additives in MSF pilot plant and commercial plants of Al-Jubail phases I&II. DESCRIPTION OF TESTS Field trial runs on these antifoaming agents were conducted on an MSF Pilot Plant and commercial plants of Al-Jubail Phases I&II. Table 2 summarizes the test conditions of these antifoaming agents. Antifoam dose rate at pilot plant was 0.04 ppm, whereas the dose rate at phase I was varied between 0.15-0.1 ppm. Dose rates for all ten units of Phase II (unit 11 to 20) were varied between 0.05-0.04 ppm. Dose rates of all the other units of phase II except unit 12 were further reduced to the normal antifoam dose rate of 0.035 ppm. The antifoam feed tanks concentrations were checked once per day (for each batch preparation) by chemical analysis to be sure that the concentration was maintained. Solutions of 0.5 % antifoam were separately injected into the make up seawater upstream of deaerators of pilot plant and all units of phase II The solution concentration at Phase I was 1.0%. On-line ball cleaning systems were operated as usual during all these tests to maintain high distiller performance. Miscibility behavior of these antifoaming agents in water was determined in the laboratory prior to field trial runs. Sea water and brine chemistry, distillate conductivity, deaerator performance, distillate contamination by organic carry over and potential for bacterial growth and aftergrowth were closely monitored during performance evaluation of these antifoaming agents. Performance test monitoring also required data logging of flow, temperature and pressure measurements. The most important flow monitoring points were recirculating brine, make-up seawater, distillate, brine heater condensate, and last yet quite important were the monitoring of antiscalant and antifoaming agents dose rates. Brine heater terminal brine recycle and vapor temperatures were also monitored. These data were used to calculate the heat transfer coefficient of brine heater, plant performance ratio or gain output ratio. RESULTS AND DISCUSSION Results of miscibility tests for the antifoaming agents BCC-74M and AF-2 reveal that at a concentration of 0.5% and 1.0%, the antifoam solution remains homogeneous up to 24 hours and then starts settling gradually. This observation was also confirmed during testing in AlJubail commercial MSF units, where settling of antifoam in the preparation tanks as well as
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clogging in the antifoam dosing system were not noticed. Hence, it can be said that the antifoaming agents BCC-74M and AF-2 are fully dispersible in water at the solution concentration of 1.0% and 0.5% as normally practiced in phase I and C2/C3 units of AlJubail Phase II plants. On the other hand, settling started much earlier for higher concentration of 1.5% i.e., as the residence time increases; turbidity of antifoam solution was noticed to decrease significantly. Thus it is essential that for such high concentration extensive miscibility tests have to be conducted taking into consideration actual plant operating conditions. As earlier stated, excessive foaming in the MSF distiller results in the contamination of distillate by salt carry over. Antifoaming agents are added to the make-up feed to maintain distillate quality by preventing foaming and hence salt carry over. Graph (a) of Figures 1 through 4 show the variation in distillate conductivity versus time. The maximum values of distillate conductivity in the pilot plant and commercial units of Al-Jubail Phase II were recorded to be 27 and 4µS/cm respectively for antifoaming agents BCC-74M and AF-2 except in unit 13 for AF-2, where the conductivity was found varying in the range of 8-20 µS/cm. These values are well within the design acceptable limits and satisfying the specification of these plants. Higher distillate conductivity in unit 13 was due to the fouled condition of demister pads prior to the trial run of AF-2, while in Pilot plant is mainly due to the violent flashing in limited number of distiller stages. Moreover, the lower demister height and the limited overall volume of MSF pilot unit contribute to the higher conductivity of the distillate. Detrimental foaming in the deaerator section has been reported in many MSF desalination plants. Selection of proper antifoam improves deaerator performance [5-8]. Hence, monitoring of dissolved oxygen in the make up feed downstream of deaerator was essential to assess the ability of the antifoaming agents in preventing foaming in deaerator section and subsequently maintaining acceptable oxygen levels. Variation in dissolved oxygen in make up stream after deaeration is shown in graph (b) of Figures 1 through 4. The maximum level of dissolved oxygen in make-up stream of Al-Jubail pilot plant as well as phase II units varied in the range of 9-15 ppb for both antifoaming agents. These values were within the acceptable limits of less than 20 ppb after deaeration, which implied the integrity of these antifoaming agents within the operating temperature range of phase II deaerators. On the
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other hand the dissolved oxygen content in the recycle brine in phase I varied in the range of 45-47 ppb. These values are considerably higher compared to pilot and phase II units because (as earlier pointed out) at phase I deaeration takes place within the last stage of the distiller in the absence of external deaerator. Maintenance of effective scale control is the most crucial factor in MSF desalination process. Some of the effective antifoams may reduce antiscalant activity resulting in 40-50% more scale[1]. Therefore, the compatibility of these antifoaming agents with antiscalant under use was checked by calculating plant performance ratio (PR) or gain output ratio (GOR) along with the overall heat transfer coefficient (HTC). Variation in brine heater heat transfer coefficients in pilot and Al- Jubail Phase I plants are shown in graph (c) of Figures 1 and 2. These values of heat transfer coefficients in both plants remained stable throughout the test runs for both antifoaming agents and did not show any kind of deterioration in their performance at top brine temperatures (TBT) of 112 and 90 0C in the same order as above. Brine heater heat transfer coefficients of unit 12 were also found stable at a TBT of 104 0C as shown in graph (c) of Figure 3. Heat transfer coefficients of brine heater in unit 13 showed some variation in the case of BCC-74M only as shown in graph (c) of Figure 4, which can be attributed to load change. The calculated performance parameters in terms of Gain Output Ratio (GOR) in pilot plant and Al-Jubail phases II&I are shown in graph (d) of Figures 1 through 4. During the trial runs, there was no marked decline in the performance of any distiller under test. These results basically indicate that no significant scale precipitation took place in brine heaters or in the heat recovery section during trial runs using these antifoaming agents. Some specific conditions and results obtained during these tests are also shown in Tables 3 and 4, which also confirm the effectiveness of these two antifoaming agents It is also possible that the antifoaming agents may contaminate the distillate by its constituents. Frequent analysis of distillate was therefore necessary to ascertain the presence/absence of any organic pollutants carried over into the distillate. Organic carryover was monitored by Gas Chromatography-Mass Spectrometer (GC/MS) technique using USEPA 625 method. Figure 5 represents chromatogram of the distillate samples obtained by GC/MS. It can be seen from the figure that neither the antifoam as whole nor any toxic components derived from antifoaming agents were carried over into the distillate. Hence it
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can be stated that the distillate purity was unaffected during the trial runs of these antifoaming agents. Increased bacterial after growth and consequently higher fouling potential could be due to supply of nutrients by the antifoaming agent. Bacterial growth and after growth were thus determined in samples of: (i) raw seawater (ii) make-up feed (iii) antifoam mixing tank, and (iv) product water which is used as diluent in mixing tank. Results of bacterial counts for bacterial growth and after growth potentials are presented in Tables 5 and 6. These showed that bacterial after growth obtained from samples containing antifoam were either lower or similar to raw sea water samples. It is therefore concluded that the antifoam is not enhancing nor contributing to the bacterial growth and would not be anticipated to result in fouling of antifoam dosing system. CONCLUSIONS 1. Antifoaming agents BCC-74M and AF-2 solutions were fully dispersible in water at a concentration of 0.5 and 1.0%, as no settling of antifoam in preparation tanks nor clogging in the dosing system was noticed. 2. Bacteriological analysis of make-up water and antifoaming agents showed that, they are not a source of contamination. Furthermore after growth potentials for bacteria indicated that the antifoaming agents were not enhancing growth and consequently biofouling. 3. Dissolved oxygen levels in the make-up feed after deaerations were within acceptable limits of less than 20 ppb. The only exception of Al-Jubail Phase I unit which varied between 45-47 in the recycle stream. 4. Distillate quality was maintained within the acceptable range of 1-27 µS/cm. On the other hand carry-over of any steam-volatile component related to the antifoam was also not detected, thus maintaining the distillate purity over the entire duration of these test runs. 5. At dose rates of 0.15 down to 0.035 ppm these antifoaming agents were effective at all
MSF operating temperatures (TBT 90-1120C) and found compatible with the antiscalant presently under use. Moreover, the overall performances of monitored distillers were found satisfactory during these trial periods, (see attached Tables 3 and 4 also Figures 1 to 4). Hence, it can be concluded that the subject antifoaming agents are acceptable for MSF application.
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RECOMMENDATIONS 1. The results of these evaluation tests indicate that the performance of BCC-74M and AF2 are quite satisfactory and can be used in MSF plants as effective antifoam agents. 2. The observed performance of antifoaming agents BCC-74M and AF-2 in pilot and commercial plants of Al-Jubail phase II at dose rates of 0.04 and 0.035 ppm and TBT of 112 and 92 0C respectively was satisfactory. It is therefore recommended that further dose rate optimization is to be carried out.
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REFERENCES 1. Auerbach, M. H., O.Neill J. J., Reimer R. A. and Walinsky S. W. (1981) Foam Control Additives in MSF Desalination, Desalination, 38, 159-167. 2. Owen, M. J.(1985) Antifoaming Agents, In Encyl. of polymer Science and Engineering, 2nd edn; (Edited by Mark, H. F., Bikales N. M., Overberger C. G. and Menges G.) A Wiley Interscience, USA, 164-171. 3. Lichtman, J. and Gammon T. (1979) Defoamers, in Encycl. of Chemical Technology, 3rd edn; Edited by Kirk-Othmer) A wiley Interscience, USA, 430-448. 4. Auerbach, M. H. and Carruthers M. S. (1979) Laboratory Application Testing of Desalination Antiscalants, Desalination, 31, 279-288. 5. Abkar, A. A., Girgis F. and Von Loebbecke H. D. (1986) Operating Experience Related to SWCC Desalination plant Jeddah III in the Kingdom of Saudi Arabia, Topics in Desalination, SWCC, Saudi Arabia, 104-105. 6. Nada, N., Khumayyis D. and Al Hussain M. (1985) Economical Evaluation of Al-Khobar Phase II 50 MIGPD at Three Different Mode of Operation, Desalination, 55, 43-54. 7. Eckert, J. S. (1970) Selecting the Proper Distillation Column Packing, Chemical Engineering Progress, 66(3), 39-44. 8. Rabas, T. J., Inoue S. and Shimizu A. (1987) An Update on the Mass Transfer of Counterflow, Packed Deaerators Containing Pall ring Packing, Desalination, 66, 91-107. 9. Imam, M., Abdulgader A. Y., Mustafa G. M., Al-Rasheed R., Al-Tissan I., Al-Mobayed A. S., Ehsan, A. and Dayley D. (1996) Performance Evaluation of Antifoam Additive BCC-74M on MSF Pilot plant and Commercial Plants of Al-Jubail Phase I&II, R&D Center, SWCC, Al-Jubail, Technical Report No. TR96002. 10.Pujadas, F., Fukomoto Y. and Isobe K. (1991) Performance Test of Antiscalant Aquakreen KC-550 under a wide range of temperature conditions at the MSF Desalination Plant in Abu Dhabi, Desalination, 83, 65-75.
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Table 1. Technical specifications of BCC-74M and AF-2 S.No. 1 2 3 4
Properties Specific gravity (20 0C) pH(1%aqueous dispersion) Solubility in water Appearance
5
Odor
AF-2 1.02 7
BCC-74M 1.02 7
Dispersible Pale amber liquid Faint
Dispersible Pale yellow liquid Oily
Table 2. Test Conditions S.N o. 1 2 3 4 5 7 8 9
Parameters
AF-2 PP 7
Ph II 30
BCC-74M PP 7
Ph I 7
Ph II 21
Test duration (days) No. of units 1 10 (11-20) 1 1(5) 10 (11-20) (distiller no.) TBT ( 0C) 112 105/92 112 88 105/92 Concentration 1.38-1.4 1.34-1.41 1.38-1.4 1.391.34-1.41 ratio 1.41 Antiscalant used DSB(M) BEV2000 DSB(M) DSB(M) DSB(M) Antiscalant dose 2.0 1.5/1.0 2.0 1.0 1.5/1.0 rate (ppm) Antifoam dose 0.04 .05/.04/.035 0.04 0.15/0.1 .05/.04/.035 rate (ppm) Antifoam tank 0.5% 0.5% 0.5% 1.0% 0.5% conc.
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Table 3. Typical Plant Performance Data Parameters
Unit
m3/hr ’’
0.35 6.53
AF2 U12, PhII 125 9200
Production Make up
’’ ’’
1.15 2.15
1060 3025
945 2500
1.15 2.15
970 2750
1121 3175
Blow down
’’
-
2100
1725
-
1750
2190
Inlet to Brine Heater Outlet of Brine Heater Condensate Recovery tube inlet Make up Seawater Brine Heater HTC
o
90 112 117 35 34 18 4030
96.3 103.1 108.8 34.5 34 28 2662
88.2 94.8 100.3 36 36 28 2800
90 112 117 35 34 18 2850
80.6 88 92 34 34 24 3715
96 104 109 35 35 27 2914
2.8
8.77
7.77
2.4
7.84
8.76
PP
Flow Rate
Temp.
Condensate Brine recycle
GOR (kg distillate/ kg steam
C ’’ ’’ ’’ ’’ ’’ W/m2 C
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U13, PhII 125.8 10000
PP 0.35 6.53
BCC-74M U5, U12, PhI PhII 128 132 10800 9210
U13, PhII 117-136 1030010500 900-1050 21002650 17002150 84-88 92-95 95-100 34 34 27 25004200 7.6-8.17
Table 4. Typical Chemical Analysis Data Parameters
Unit
AF-2 PP
Sea water
Make-up Recycle Brine
Blow down
Distillate
Chlorides Conductivity M-alkalinity as CaCO3 pH Residual chlorine Dissolved oxygen Chlorides Conductivity
ppm µS/cm ppm ppm ppb ppm µS/cm
22727 59600 129 8.36 6-9 31148 73800
U12, PhII 23550 60200 131 8.24 0.3 10-17 31553 76400
pH Conc. ratio Dissolved oxygen Chlorides Conductivity pH Conductivity pH
ppb ppm µS/cm µS/cm -
8.68 1.38 34953 80100 8.8 23.1 6.62
8.64 1.34 35375 83600 8.85 1.89 6.82
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BCC-74M U13, PhII 23500 60200 131 8.24 0.3 10-17 32834 79500
PP 22350 59350 130 8.23 5-9 31273 76837
U5, PhI 23700 61200 131 8.35 0.25 33200 80450
U12, PhII 23660 60786 131 8.27 0.25 12 31684 76717
U13, PhII 23660 60783 131 8.27 0.25 12 33019 79950
8.61 1.4 36250 85700 8.75 9.97 6.76
8.61 1.39 34820 84890 8.71 25-27 6.67
8.71 1.4 45-47 36268 86040 8.78 1.55 6.75
8.72 1.34 36096 85200 8.85 2.57 6.75
8.65 1.39 36383 86000 8.75 1.53 6.73
Table 5. Mean counts of bacterial growth and after growth Potential (N=9) of various samples on day 2 Sample
Bacterial Count (cfu/ml) AF-2
BCC-74M
Zero hour
24 hours
72 hours
Zero hour 24 hours
72 hours
Raw Seawater
4.2 x 103
8.1 x 104
1.9 x 105
4.2 x 103
8.1 x 104
1.9 x105
Mixing tank
3.9 x 102
3.2 x 105
5.1 x 105
-
3.99×10 5
1.82 x 105
Make-up feed
4.9 x 103
3.9 x 105
3.9 x 105
-
4.7 x 105
1.82 x 105
Product water
3.0
0
0
3.0
0
0
Table 6. Mean counts of bacterial growth and after growth Potential (N=9) of various samples on day 7 Sample
Bacterial Count (cfu/ml) AF-2 Zero hour 3
BCC-74M
24 hours
72 hours
Zero hour
24 hours
72 hours
4
5
2
-
3.17 x 106
Raw Seawater
3.7 x 10
7.9 x 10
1.8 x 10
Mixing tank
2.9 x 103
1.3 x 104
1.0 x 105 5.73 x 104
-
2.8 x 103
Make-up feed
2.9 x 103
1.0 x 105
2.2 x 105 2.93 x 103
-
4.07 x 105
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1.67 x 10
Conductivity, uS/cm
BCC(Cond)
30
AF2(Cond)
28 26 24 22
Graph (a)
20 50
100
150
200
BCC(DO)
20
AF2(DO)
15 10 5
Graph (b)
0 0
50
100
150 BCC(HTC)
5
Heat Transfer Coeff., kW/m 2 K
Dissolved Oxygen, ppb
0
200 AF-2(HTC)
4 3 2 1
Graph (c)
0
Gain Output Ratio
0
50
100
150 BCC(GOR)
4
200 AF2(GOR)
3 2
Graph (d)
1 0
50
100
150
Time, Hours
Figure 1. Performance of Antifoaming Agents in RDC Pilot Plant at Al-Jubail
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200
BCC(Cond)
Conductivity, uS/cm
4 3 2 1
Graph (a)
0
Dissolved Oxygen, ppb
50
Heat Transfer Coeff., kW/m 2 K
0
5
50
100
150
200 BCC(DO)
45
Graph (b)
40 0
50
100
150
200 BCC(HTC)
4
Graph (c) 3
Gain Output Ratio
0
50
100
150
10
200
BCC(GOR)
9 8
Graph (d)
7 0
50
100
150
Tim e,H ours
Figure 2. Performance of Antifoaming Agent BCC-74M in Al-Jubail Phase I Unit 5
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200
Conductivity, uS/cm
BCC(cond)
5 4 3 2 1
Graph (a)
0
Dissolved Oxygen, ppb
0
Heat Transfer Coeff., kW/m 2 K
AF2(cond)
100
200
300
400
500
600
700
BCC(DO)
20
AF2(DO)
15 10 5
Graph (b)
0 0
100
200
300
400
500
600
BCC(HTC)
5
700 AF2(HTC)
4 3 2 1
Graph (c)
0
Gain Output Ratio
0
100
200
300
400
500
BCC(GOR)
10
600
700
AF2(GOR)
9
Graph (d)
8 7 0
100
200
300
400
500
600
Time, Hours
Figure 3. Performance of Antifoaming Agents in Al-Jubail Plant Phase II Unit 12
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700
Conductivity, uS/cm
BCC(Cond)
20 15 10 5
Graph (a)
0
Heat Transfer Coeff., kW/m K
Dissolved Oxygen, ppb
0
100
200
300
400
500
600
700
BCC(DO)
20
AF2(DO)
15 10 5
Graph (b)
0 0
100
200
300
400
500
600
BCC(HTC)
5
700 AF2(HTC)
4 3 2 1
Graph (c)
0 0
Gain Output Ratio
AF2(Cond)
100
200
300
400
500 BCC(GOR)
10
600
700 AF2(GOR)
9
Graph (d)
8 7 0
100
200
300
400
500
600
Time, Hours
Figure 4. Performance of Antifoaming Agents in Al-Jubail Plant Phase II Unit 13
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700
BCC-74M
AF-2
Figure 5. Chromatograms of distillate samples
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