ozone treatment of cooling tower water
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OZONE TREATMENT
OF
COOLING TOWER WATER
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Cooling Tower Stats
45MW Two Stage Oxygen Compressor
325m3/hr Circulation Rate
102m3
Basin Volume
2 Heat Exchangers in Parallel
Cooling Oxygen from 125C to below 30C
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Cooling Tower Trial Objectives
Reduce water consumption
Improve Heat transfer efficiency
Stop Chemical Treatment
Improve quality of Blow Down Water
Ultimately save on power and operating
costs
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|
Flow diagramm of a typical cooling water
treatment system with ozone
Basin
Power Supply
Unit incl. PLC
Cooling TowerOzone-
Generator
Feedgas Options:
Liquid Oxygen, Dry Air
VSA Oxygen
O3
Blow Down
: Optional dosing points
Make-upWater
Ozone Monitoring
Circulation Pump
Heat ExchangerO3
O3
O3
Side stream
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Cooling Tower Problems
Biological counts and fouling
Corrosion
Scale formation/Increased powerconsumption
Chemical handling Water consumption
Blowdown water disposal
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Water Quality before ozone treatmentMake Up Basin Make Up Basin
31-Mar 31-Mar 10-Jul 10-Jul
Conductivity
(mS/m @25'c) 240 86 16 44
pH 7.8 8.1 7.8 8.2
TSS
(mg/l @105'C)
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Heat Exchanger Efficiency
Hot
gas
Cooled
gas
Cold
Water
Heated
WaterMonitor
Difference
H E h Effi i
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Heat Exchanger Efficiency
0
2
4
6
8
10
12
14
16
7/1
015
7/1
113
7/1
117
7/1
211
7/1
215
7/1
311
7/1
315
7/1
411
7/1
415
7/1
511
7/1
515
7/1
611
7/1
615
Date
DeltaTem
p
17/07/2006 B f O
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17/07/2006 Before Ozone
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20/07/2006 After Ozone
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17/07/2006
Before Ozone
20/07/2006
After Ozone
H t E h Effi i
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Heat Exchanger Efficiency
0
2
4
6
8
10
12
14
16
7/10
15
7/11
17
7/12
15
7/13
15
7/14
15
7/15
15
7/16
15
7/17
11
7/18
11
7/19
11
7/20
11
7/21
13
7/22
11
7/23
11
7/24
11
7/25
11
7/26
11
7/27
11
7/28
10
Date
DeltaTemp
Water Quality after ozone treatment
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Water Quality after ozone treatmentMake Up Basin Make Up Basin
14-Aug 14-Aug 15-Aug 15-Aug
Conductivity
(mS/m @25'c) 244 651 242 615
pH 7.4 8.2 9.7 8.7
TSS
(mg/l @105'C) 18 46 26 10
TDS
(mg/l @180'c) 144 4106 1420 4018
Total Alkalinity(CaCO3) 132 211 255 278
Total Hardness
(CaCO3) 202 636 84 507
Ca Hardness
(mg/l) 141 444 34 150
Mg Hardness
(mg/l) 61 192 50 157
Cl (mg/l) 278 950 199 780
Na (mg/l) 351 1084 435 1233
Fe (mg/l) 0.39
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Water Quality after ozone treatment
0
2
4
6
8
10
12
Hours
pH
0
2000
4000
6000
8000
10000
12000
14000
C
onductivity
(uS/cm
)
Make-up Water pH Basin pH
Make-up Water Conductivity Basin Conductivity
Water Quality after ozone treatment
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Water Quality after ozone treatment
Difference Between Wet Bulb and Basin water Temperatures
0
2
4
6
8
10
12
14
1 3 5 7 9
1
1
1
3
1
5
1
7
1
9
2
1
2
3
2
5
2
7
2
9
3
1
3
3
3
5
3
7
3
9
4
1
4
3
4
5
4
7
4
9
5
1
5
3
5
5
5
7
5
9
6
1
6
3
6
5
6
7
6
9
7
1
7
3
7
5
7
7
7
9
8
1
8
3
8
5
Hours
w et dif f Linear (w et dif f)
Saturation Index
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Saturation Index
1) P1 = log 10 (calcium * 2.5 * total alkalinity)
2) P2 = (max. system water temp,F * 0.00912) + P1
3) P3 = ((log 10 (conductivity * 0.8) * 0.1) + 12.27
4) pH saturation = P3 P2
5) SI = pH of cycled water - pH saturation
Inserting values from latest analysis gives a value of 2.18
POSI Number
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POSI Number
Maximumum conductivity :
= 10 (1/(log(CaxMg)/(Na+Cl)]xlog(Alk/10) x cond(mu)
(Practical Ozone Scaling Index)
Using this formula = 3.74 cycles of concentration
Current cycles of concentration = 4.82
Cycles of concentration
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Cycles of concentration
0.00
1.00
2.00
3.00
4.00
5.00
6.00
31-Mar 10-Jul 19-Jul 25-Jul 8-Aug 14-Aug 15-Aug 22-Aug
Cl Na Ca Cond
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Ozone Consumption
inCooling Towers
0.3 to 0.6 g O3/ m3 in the total recirculation flow
For average cooling tower of 1500m3
recirculation flow= 216kg Oxygen consumption per day per tower
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Expected Results per Ave. Tower
Current Expected Savings
Tower Volume (m3) 650.00 650.00 0.00
Recirculation Rate (m3/hr) 1,500.00 1,500.00 0.00
Evaporation Loss (m3/hr) 9.90 9.90 0.00
Drift Loss (m3/hr) 1.50 1.50 0.00
Blow Down Rate (m3/hr) 4.38 0.60 3.78
Make Up Water (m3/hr) 15.78 12.00 3.78
Concentration Ratio 4.38 20.00
Cost of Make up water (R/month) 23,859.53 18,114.00 5,745.53
Cost of Treatment (R/month) 7,385.00 9,536.00 -2,151.00
Total Costs (R/Month) 31,244.53 27,650.00 3,594.53
TOTAL Savings (R/month) 3,594.53
Advantages of ozone
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Advantages of ozone
treatment Excellent cooling water quality, e.g. very good
visibili ty depths
Long term protection against bio-fouling Reduction of colony forming units
Effective control of Bacteria Legionella
Improved heat transfer
Reduced waste water costs because COD and AOX are
clearly under the discharge limits Corrosion rates < 0.1 mm/y (carbon steel)
Improved industrial safety due to no storage, and
handling of hazardous chemicals
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Thank youThank you
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