Ozone Treatment of Cooling Tower Water

8/10/2019 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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0

2

4

6

8

10

12

14

16

7/1

015

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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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0

2

4

6

8

10

12

14

16

7/10

15

7/11

17

7/12

15

7/13

15

7/14

15

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15

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15

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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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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



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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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Ozone Treatment of Cooling Tower Water

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