cooling towers system .pdf

Types of cooling systems
Types of cooling towers
Cooling towers calculation
Microbiological contamination

1. COOLING TOWER SEMINAR COOLING TOWER SEMINAR

2. AGENDA AGENDA
1.1.Types Of Cooling Systems. Types Of Cooling Systems.
2.2.Types Of Cooling Towers Types Of Cooling Towers
3.3.Cooling Towers Definitions & Calculation. Cooling Towers Definitions & Calculation.
4.4.Basic Cooling Water Treatment principles. Basic Cooling Water Treatment principles.
5.5.Microbiological Contamination. Microbiological Contamination.
6.6.Veolia Water Approach To Control Legionella. Veolia Water Approach To Control Legionella.

3. 1. TYPES OF COOLING SYSTEM 1. TYPES OF COOLING SYSTEM
X3 kindsof coolingsystems..
9
Once-Through.
9
Closed Loop.
9
Cooling Towers ( Open Circuit).

4. ONCE –THROUGH –BLOCK DIAGRAM
Sea Water Cooling INSea Water Cooling OUT
Drain
HOT
Process Gas/
Liquid
COOL
Process Gas/
Liquid
Heat
Exchanger

5. CLOSED LOOP

6. COOLING TOWERS ( OPEN CIRCUIT)
Circulation
EVAPORATION
APPOINT
Circulation
EVAPORATION
MAKE UP
BLOW DOWN
EXCHANGERS
Circulation
¾Water cooled after having cooled the process on an
atmospheric cooling agent.
¾Air is the cooling agent.
>PRINCIPLE :
T1 Cold Water
T2 Hot Water

7. XDefinition of a Cooling Tower
•
“
A device which provides optimum
air/water contact in order to cool that
water by evaporation”.

8. 2. TYPES OF COOLING TOWERS 2. TYPES OF COOLING TOWERS
¾Water Evaporation, EnhancedWithHigh
Contact Surface : THE FILL
¾Air flow generationmethods:
1.Natural Draft.(
Flowrate Depends on Atmospheric Condition)
2.Mechanical Draft.
(Constant Flowrate)
CoolingPrinciple

9. Rule of Thumb... 1 BTU will raise the
temperature of 1
pound of water 1
degree Fahrenheit.

10. TYPES OF COOLING TOWERS TYPES OF COOLING TOWERS
1.1.NATURAL DRAFT NATURAL DRAFT
:
¾Tall chimney with hyperbolic shape.
¾Warm, moist air naturally rises due to
the density differential to the dry, cooler
outside air. This produces a current of
air through the tower.
Applications :
¾Refinaries.
¾Power Plants.
¾Petrochemicals.

11. TYPES OF COOLING TOWERS TYPES OF COOLING TOWERS
2.MECHANICAL DRAFT COOLING TOWERS
which uses power driven fan motors to force or draw air through the tower.
Three types……
A.Forced draft.
B.Induced draft cross flow.
C.Induced draft counter flow.

12. TYPES OF TYPES OF
MECHANICAL DRAFT COOLING TOWERS
A.Forced Draft Cooling Towers …
¾Water distributed via spray nozzles
¾Air blown through tower by centrifugal fan at air inlet.

13. TYPES OF TYPES OF
MECHANICAL DRAFT COOLING TOWERS
B.Induced Draft Counter Flow CT……
¾
Hot water enters at the top.
¾Air enters at bottom and exits at top.
¾Uses forced and induced draft fans.

14. Module 1.1.0.4
C. Induced Draft Cross Flow CT
¾
Water enters top and passes over fill
¾Air enters on one side or opposite sides
¾Induced draft fan draws air across fill
TYPES OF TYPES OF
MECHANICAL DRAFT COOLING TOWERS

15. Water Flow Diagram - Induced Draft Cross Flow C.Towers
TYPES OF TYPES OF
MECHANICAL DRAFT COOLING TOWERS

16. 3. COOLING TOWERS 3. COOLING TOWERS
DEFINITIONS & CALCULATIONS DEFINITIONS & CALCULATIONS

17. XWater is recirculatedover a cooling tower
and cooled.Makeup replaces
water losses.
XLoss of water occurs from:
••
Evaporation Evaporation
••
Blowdown Blowdown
••
Windage WindageCooling Water Mass Balance

18. 9MAKE UP WATER.
9RE-CIRCULATION RATE.
9TEMPERATURE DIFFERENTIAL (∆T)
9EVAPORATION RATE.
9BLOW DOWN RATE.
9WINDAGE RATE
PARAMETERS FOR
WATER CALCULATIONS

19. Evaporation
Makeup
Blowdown
Process to be cooled
Re-Circulation Pump
Cold Water In T2
Hot Water Out T
1
Makeup = Evaporation + Blow-down + Windage
Windage
Cold Water Basin
MAKE UP WATER

20. It is the Flow of cooling water being pumped
through the entire plant cooling loop.
RECIRCULATION RATE (R.R)

21. Temperature Differential (∆T)
‰WET BULB TEMPERATUE OF AIR :
Wet bulb temperature indicates how much
water can evaporate into the surrounding air.
‰Wet Bulb temperature can be measured by
using a thermometer with the bulb wrapped in
wet muslin.
‰Performance of cooling tower is dependent
on the wet bulb temperature. Lower wet bulb
temperatures means more evaporation.

22. Temperature Differential (∆T)
Wet bulb
% Capacity
Temperature
Available
85
0
F 10
80
0
F82
79
0
F91
78
0
F
Standard Rating
100
77
0
F 107
76
0
F 112
75
0
F 120
74
0
F 126
73
0
F 131
72
0
F 138
71
0
F 142
70
0
F 148
65
0
F 170
60
0
F 182
¾¾As wet bulb temperature As wet bulb temperature
changes , Performance of changes , Performance of
cooling tower changes. cooling tower changes.

23. Cooling Range : Difference between cooling water
inlet and outlet temperature: Range (°C) = CW inlet temp – CW outlet temp High range= good performance
Cooling Range
Approach
Hot Water Tem.to Tower (in)
Wet Bulb Temperature (Ambient)
85
0
F
70 0
F
65
0
F
Temperature Differential (∆T)
Cold Water Temp. From Tower (out)
Heat Load

24. Approach :
Difference between cooling tower
outlet cold water temperature and
ambient wet bulb temperature: Approach (°C) = CW outlet temp – Wet bulb temp
Temperature Differential (∆T)
Cooling Range
Approach
Hot Water Tem.to Tower (in)
Wet Bulb Temperature (Ambient)
85
0
F
70
0
F
65 0
F
Cold Water Temp. From Tower (out)
Heat Load

25. Effectiveness : Effectiveness %
= 100 x (Range / (Range+Approach)) High effectiveness = Good Performance
Temperature Differential (∆T)
Cooling Range
Approach
Hot Water Tem.to Tower (in) Cold Water Tem. From Tower (out)
Wet Bulb Temperature (Ambient)
Heat Load
85
0
F
70 0
F
65
0
F

26. EVAPORATION RATE (LOSS) EVAPORATION RATE (LOSS) ––E.RE.R
Definition :
Water quantity (GPM) evaporated (Loss) to atmosphere for cooling
duty.
As a rule of thumb …….
For each 10ºF(5.6
0
C) that the re-circulated water needs to be cooled, 1% of
the cooling water is evaporated in the cooling tower.
Evaporation Rate (GPM) = R.R X (∆T/1000)

27. BLOW BLOW--DOWN RATE DOWN RATE ––B.RB.R
Definition :
The portion of the concentrated cooling tower water
intentionally discharged from the cooling tower to maintain
an acceptable water quality in the cooling tower.
Evaporation Rate
Blow-Down Rate (GPM) =
Cycle of Concentration -1

28. CYCLE OF CONCENTRATON CYCLE OF CONCENTRATON ––C.CC.C
Definition :
The number of times the T.D.S content of the cooling water
is increased in multiples of itself.
The cycles of concentration can be estimated by measuring the
T.D.S or conductivity or some specific ion in both the recirculating
water (CW) and the makeup water (MU) and dividing the makeup
number into the tower water number.
Cycles Of Concentration = TDS
CW
/ TDS
MU

29. CYCLE OF CONCENTRATON CYCLE OF CONCENTRATON ––C.CC.C
After Evaporation
Volume: 500 liter.
TDS: 200 ppm
Conc. Factor: 2
Before Evaporation
Volume:1000 liter.
TDS: 100 ppm
Conc. Factor: 0
More Evaporation
Volume: 250 liter.
TDS: 400 ppm
Conc. Factor: 4

30. CYCLE OF CONCENTRATON CYCLE OF CONCENTRATON ––C.CC.C
0
0.5
1
1.5
2
2.5
3
3.5
01234567
Concentration
M ake u
p water (m3/h)
With E = 1 m3/h
WHY CYCLE? High cycles of Concentration Means : 9Low makeup Rate.
9Low blow-down Rate.
9Cutting total operating cost.

31. WINDAGE WINDAGE
¾
Windage is commonly calculated using the following equation.
Definition : The droplets of cooling water carried by the wind and lost
from the system.
Windage = Re-Circulation Rate x 0.001

32. EXAMPLE EXAMPLE……
A cooling tower system currently ci rculates water at the rate of 10,000 GPM
and the cooling tower needs to cool the warmed water exiting the heat
exchanger from 90ºF to 80ºF degrees(or reduce the temperature of the water
by 10ºF), TDS of make up water is 100 ppmand cooling water 500 ppm. XCalculate The Following :
•
Evaporation Rate
•
Cycle Of Concentration
•
Blow-down Rate.
•
Windage.
•
Makeup Rate

33. 4. Basic Cooling Water Treatment principles 4. Basic Cooling Water Treatment principles
Water Treatment is the most important factor Water Treatment is the most important factor
affecting the life and energy efficient operation affecting the life and energy efficient operation
of cooling towers equipments of cooling towers equipments

34. COOLING SYSTEM WATER PROBLEMS
CORROSION
MICRO
ORGANISIM
FOULING
SCALE

35. MINERAL SCALE
™Cooling Water contains many different minerals -- normally
these minerals are dissolved in the water
™Under certain conditions minerals can come out of solution and
form into hard, dense crystals called SCALE
.

36. COMMON SCALES
ƒCalcium Carbonate
ƒMagnesium Silicate
ƒCalcium Phosphate
ƒCalcium Sulfate
ƒIron Oxide
ƒIron Phosphate
Scaled Heat Exchanger Tubes

37. SCALING
Insulating Film
Possibility Of Corrosion
Under Deposit
Blockage Of
Tubes & Pipe works
Pitting
Reduces
Flow rate
SCALING
Reduces
Heat Transfer
Increase in Temperatures
&
Pressures
Whyisitsoimportant to control it?

38. ™PH
™TEMPRATURE.
™CONCENTRATION OF IONS e.g HCO
3
-
, Ca
+2
, Mg
+2
™Total Dissolved Solids.
PARAMETERS AFFECTING THE RATE OF
SCALE FORMATION

39. PARAMETERS AFFECTING THE RATE OF
SCALE FORMATION
SOLUBALISATION
SUPERSATURATION
NUCLEATION
CRYSTAL GROWTH
Water & Soluble Minerals
THE SEQUENCE OF EVENTS THAT LEADS TO THE CRYSTALLISATION OF A SALT MAY BE DEFINED AS :
SCALE

40. PARAMETERS AFFECTING THE RATE OF
SCALE FORMATION
HYDREX
TM
ANTISCALANT CHEMICAL ADDITIVES.
(MECHANISM TO CONTROL SCALE DEPOSITION) 1. THRESHOLD EFFECT
Chemicals which , when used is sub-stoichiometric
amount is capable of preventing the
precipitation of salts from a supersaturated solution
.
2. CRYSTAL GROWTH INHIBITION / CRYSRAL DISTORTION.
Chemical interference to normal crystal growth produces irregular crystal structure with
poor scale forming ability
3. DISPERSANCY :
Chemical which can adsorb onto scale surface causing the particles to remain in suspension.

41. METHOD OF CONTROLING
SCALE FORMATION
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IONS
PROTONUCLEI
NUCLEI
CRYSTALS
Growth
ordering

42. METHOD OF CONTROLING
SCALE FORMATION
No-Scale
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IONSPROTONUCLEI
NUCLEI
Growth
ordering
Distorted crystal Lattice

43. STEP 3 STEP 3
STEP 2 STEP 2
STEP 1 STEP 1
STEP 4 STEP 4
XStep 1
:At the anode, pure iron begins to break down in contact with the cooling water.
XStep 2
:Electrons travel through the metal to the cathode.
X
Step 3
:At the cath ode, a chemical reaction occurs between the electrons and oxygen in cooling
water to forms hydroxide.
XStep 4
:Dissolved minerals in the cooling water complete the electrochemical circuit back to the anode.
FOUR STEP CORROSION MODEL FOUR STEP CORROSION MODEL

44. CORROSION CORROSION
Corrosion product
Cooling Tower Suction Line
Corrosion product
Cooling Tower Circulation Pump

45. CORROSION
¾
Factors affecting corrosion rate zTemperature
zpH
zWater velocity
zProduct Solubility
zMetallurgy

46. 100
10
0
5678910
Corrosion Rate, Relative Units
pH
CORROSION VS. WATER PH

47. Corrosion Rate
Temperature
In general, for every 18°F in
water temperature, chemical
reaction rates double.
CORROSION VS. WATER TEMPERATURE

48. Corrosion Control
Common corrosion inhibitors for open
cooling water systems:
¾Molybdate
¾Zinc
¾HPA (all organic)
¾Silicate
¾Phosphate
¾Polyphosphates

49. Corrosion Inhibition
Cathode
(+)
Anode
(-)
Metal Surface
HPA
Zn
Si
MO
PO
4
HPA
Zn
Si
MO
PO
4

50. METHODS TO CONTROL CORROSION
™
HYDREX
TM
CORROSION INHIBITOR
Copper Metal Corrosion Inhibitor ORGANIC INHIBITOR
Cathodic Inhibitor ZINC
Anodic Corrosion Inhibitor MOLYBDATE
FUNCTION
ACTIVE MATERIALS

51. METHODS TO CONTROL CORROSION
1. ANODIC INHBITOR (MOLYBDATE).
9Protect bulk of metal surface by forming oxide film.
9PH control not required.
9Does not promote bacterial growth.
2. CATHODIC INHIBITOR (ZINC).
9Stifles the cathodicreaction.
9Prevents corrosion from proceeding ahead.
Both the cathodic& anodic sites are protected to
ensure low overall corrosion rates
Two Types Of Corrosion Inhibitors :

52. MONITORING TOOLS TO CONTROL CORROSION
Designed By
Metito/Veolia Water Solutions & Technologies

53. A. ON LINE CORRATER INSTRUMENT
™
CORROSION RATE SYSTEM DESIGNED FOR COOLING WATER SYSTEMS.
™
MEASURMENT OF CORROSION RATE ( MPY ) ON CONTINOUS BASIS.
™
DATA LOGGING WITH CORRDATA PLUS SOFTWARE

54. B. CORROSION & DEPOSITE MONITORING SYSTEM
THIS SYSTEM CAN BE USED BY METITO/VEOLIA WATER TO MONITOR AND CONTROL
CORROSION / DEPOSIT IN HEAT EXCHANGER.

55. C. CORROSION COUPONS
Steel test plate
Plastic rod
Stainless
steel rod
Area (mm2) x N(days) x density (g/cm2)
∆w (g)x 365
C (µm/year)=

56. 5.0 MICRO-BIOLOGICALCONTAMINATION
¾BACTERIA (MICROSCOPIC ANIMALS)
ƒAerobic
ƒAnaerobic
¾ALGAE (MICROSCOPIC PLANTS)
¾Fungi/yeast (‘timber-eaters’)
Micro-Organism Contamination caused by…..

57. ALGAE ALGAE
¾Large quantities of polysaccharides (slime) can be produced during
algal metabolism.
¾Plug screens, restrict flow and accelerate corrosion.
¾Provide excellent food source.
¾Exist between 5 to 65 C and pH 4 to 9.

58. ¾Although yeast and some aquatic fungi are normally unicellular, most
fungi are filamentous organisms
¾Fungi form solid structures which can reach a considerable size.
¾Fungi require presence of organic energy source.
¾Exist at between 5 to 38 C and pH 2 to 9 with an optimum of 5 to 6.
FUNGI FUNGI

59. EFFECTS OF
MICROBIAL GROWTH MICROBIAL GROWTH
¾Fouling of: tower, distribution pipework, heat exchangers
¾Reduction in heat transfer efficiency
¾Lost production
¾Under deposit corrosion
¾Inactivation/interference with inhibitors

60. FACTORS CONTRIBUTING TO MICROBIAL GROWTH FACTORS CONTRIBUTING TO MICROBIAL GROWTH
¾Rate of incoming contamination
¾Amount of nutrient present
¾pH
¾Temperature
¾Sunlight
¾Availability of oxygen/carbon dioxide
¾Water velocities

61. Closed Systems
Closed loop water systems can be used
to cool or heat an area or process.

62. CLOSED LOOP

63. Closed Systems
¾Water loss is usually less than 0.5% of the
system volume in a year.
¾No water loss –no makeup.
¾No concentration of solids so scale is
generally of no concern.
¾Corrosion controlled by establishing a good
film barrier.

64. Closed Systems
Treatment objectives:
¾Prevention of deposits from corrosion
by-products
¾Prevention of microbiological fouling
(glycol can be a nutrient)

65. Water Treatment
¾Corrosion Inhibitors
9Nitrite-Borate-Triazole
9Nitrite-Polyphosphate
9Molybdate-Borate-Triazole
¾Oxygen Scavenging
¾Side-Stream Filtration
¾Microbiological Control
¾Glycol Systems and pH

66. Sodium Nitrite
XNaNO
2
XSodium nitrite is an oxidizing agent which
functions as an anodic inhibitor by forming
an impervious oxide film to protect the
metal from further attack.
XLayer is formed by the combined action of
nitrite and dissolved oxygen and then kept
in repair by the nitrite alone.

67. Silicates
XSodium silicate (CAS Number 1344-09-8) is
the generic name for a series of compounds
derived from soluble silicate glasses and
described as water solutions of sodium oxide
(Na
2
O) and silicon dioxide (SiO
2
).
XThe ability to change the proportion of silica to
sodium and the solids content provides us
with products of widely different functional
and handling properties.

68. XThe most widely used azolein water treating is
tolyltriazole(TT).Also used are benzotriazole
(BZT)and mercaptobenzo-thiazole(MBT).
XWhile TT and BZT have roughly equivalent
performance and stability, BZT costs more than TT.
XTT is about three times as effective as MBT and is
much more stable to heat, oxidation, and light.
Azoles

77. ”Recirculation Rate.
”Temp at C.T Top.
”Temp at C.T Sump.
”Max Skin Temp (Condenser)
”C.T Lood.
”M.U Rate m
3
/day
”Blow down Rate
”Pre-treatment equipments
”Current Treatment
”Current Dosing System
”Current Monitoring
Total Alkalinity
Fe
Cl
-
Calcium Hardness
Total Hardness
TDS
pH
Cooling Make-up Description

80. 1For normal M.U water : Max Lsi2.5
2Softnedor R/O M.U water : Max S.S is100
- For LowS.S use C = 10
- For High S.S use C = 5
CONCENTRATION FACTOR

81. COOLING TOWER CALCULATION
Evaporation Rate (E) = 0.01 x ∆T (
0
C) x R
5.5
Blow Down = E
C-1
Windage = 0.001 x R M.U = E + B + W

82. ¡Corrosion control
¡Scale control
¡Suspended Solids Control
¡Microbological Control
TREATMENT PROGRAMME

83. Testing & Monitoring
Cooling Testing - What, Where & Why ?
SampleReason Analysis
Makeup
T.D.S. Hardness
Alkalinity
Cycle of
Concentration
pH
Scaling / Corrosive
Treated water
(where applicable)
As above
To ensure correct
operation of pre-treatment plant
Recirculating
Water
T.D.S. Hardness
Alkalinity
Cycles of concentration
+ scale formation
Treatment reserve
High
Low
waste
reduced protection
Iron levels Highcorrosion

84. What if ? Cooling
LOW CONCENTRATION
RATIO
NO
HIGH CONCENTRATION
RATIO
NO
LOW CORRECTED*
TREATMENT RESERVE
NO
HIGH CORRECTED*
TREATMENT RESERVE
NO
MICROBIAL
COUNT
LOW
NO ACTION
REQUIRED
START
ACCEPT
MAKEUP
QUALITY
NO
CHECK
PRE-TREATMENT
PLANT IF
BLEED VALVE
AND CONTROLLER
OPERATION
RECITIFY
CHECK PROBE
& CLEAN
INCREASE DOSE
RATE OF INHIBITOR 10%
REDUCE DOSE
RATE OF INHIBITOR 10%
DOUBLE DOSE
BIOCIDE
OK
YES
YES
YES
NO
YES
YES
APPLICABLE OR
SOURCE OF SUPPLY
*CORRECTED TREATMENT RESERVE
= MEASURED RESERVE x
e.g. 20 x
= 10 ppm
SPECIFIED TDS
ACTUAL TDS
2000
4000
IF WATER
QUALITY
CHANGES
PERMANANTLY,
NOTIFY ATCI
REPAIR
CHECK
PUMP
OK
NO
HIGH WHY?