Cooling water chemistry

1. COOLING WATER
TREATMENT

2. Well Area
Canal Area
Offsite
WT
Onsite WT
CW System
Offsite Introduction

3. Well Area
 32 wells of Raw Water
 06 wells of Drinking Water
 Raw Water comes in High Lift from where it is
pumped to Plant site (both at Onsite and CW
Network)
 Used Only in case of Canal unavailability

4. Canal
 Canal is the basic raw water make up source.
 Now a days due to canal outage we have
been using well water for our plant site useage

5. 1. Offsite Water Treatment
 The type of chemical dosed at Enven offsite
are as follows,
1. Alum
2. Poly Electrolyte

6. 1.Offsite Water Treatment
 Coagulation
Coagulation is the phenomenon in which very fine
suspended particles of turbidity are joined together by
chemical means into masses sufficiently enough to
settle them down.
Factors to be considered for best coagulation,
1. Temperature of the water
2. PH range of the water
3. The presence of strong anion
4. Rapid mixing of the coagulant

7. 1.Offsite Water Treatment
 Coagulation
Following reaction takes place,
1. Al2SO4 + 3Ca(HCO3) = 2Al(OH)3 + 3CaSO4 + 6CO2
(Insoluble gelatinous hydroxide)
2. Al2SO4 + 3Na2CO3 + 3H2O = 2Al(OH)3 + 3Na2SO4 +
3CO2
(Insoluble gelatinous hydroxide)
3. Al2SO4 + 3Ca(OH)2 = 2Al(OH)3 + 3CaSO4
(Insoluble gelatinous hydroxide)

8. 1.Offsite Water Treatment
 Flocculation
It is the phenomenon in which number of
precipitated anhydrous oxides are joined together to
form large volumes of more easily settle able masses.
Poly electrolyte is added for Flocculation.

9. 1.Offsite Water Treatment
Time required to settle down different particles

10. 1.Offsite Water Treatment
Coagulation

11. 1.Offsite Water Treatment
 Coagulation & Flocculation
Coagulate
s
Flocculate

12. 1.Offsite Water Treatment
 Effect on SS with the addition of Coagulant
and flocculent
Poly
electrolyte

13. 1.Offsite Water Treatment
 Effects of insufficient dosing
1. Raw water is used in Ro. If suspended solids
are high, it can damage RO.
2. SS filters will exhaust early.

14. COOLING WATER
CONTROL PARAMETERS

15. 2.Corrosion
 THE REVERSION OF METALS TO THEIR
NATURAL STATE BY OXIDATION

16. 2.Corrosion
 Corrosion propagates in the three steps. It can
be stopped if any of the three steps are slowed
down.
 Cathodic reaction is the slowest one.
 Increased temperature of the water increases
the corrosion.
 Large cathodic area as compared to anodic
area propagates corrosion.

17. Corrosion Inhibition
 Corrosion can be controlled if,
1. Anodic reaction stops
2. Cathodic reaction stops
3. POLARIZATION: Reduce the driving
force(potential difference)by changing the
potential at the reaction sites(anode or
cathode, or both).

18. Corrosion Inhibition
 CORROSION INHIBITOR
Any substance added to the water that
effectively decreases the rate of corrosion
 ANODIC INHIBITOR
Suppresses metal dissolution at the anode
 CATHODIC INHIBITOR
Interferes with oxygen reduction
 MIXED INHIBITOR - Does both

19. Anodic
Inhibitors
Cathodic
Inhibitors
Corrosion Inhibition

20. Corrosion Inhibition
Typical Corrosion Inhibitors
Partially
anodic
Partially
cathodic
Both anodic and cathodic
Chromate Calcium
Carbonate
Organic filming amines
Orthophos
phate
Poly
phosphate
Orthophosphonate
Nitrate Zinc

21. Corrosion Inhibition
 Orthophosphate an anodic inhibitor form layer
of iron phosphate at anode.
 Zinc forms Zinc hydroxide layer at cathode.

22. Corrosion Inhibition
 The orthophosphate in our program act as an
anodic inhibitor
 Zinc in the formulation used as a cathodic
inhibitor by forming a thin strong film Zinc
hydroxide on the metal surface. The film is
very dense and impervious, thus prevents the
electron transfer.

23. Corrosion inhibitor
 Zinc layer is highly sensitive to PH. Zinc
precipitates at higher pH.
 Whenever the pH drops, zinc hydroxide layer
tends to break out thus exposing the cathodic
site to initiate corrosion.

24. Corrosion effects

25. Stress Corrosion
 Stress corrosion induced by Chlorides

26. Parameters to be controlled
No. Stream Analysis
Operati
ng
Limits
Analysis crossing UPPER Limit Analysis crossing LOWER Limit
Effect Corrective Action Effect Corrective Action
1 CWR Chloride
0-
120ppm
It can cause Stress
corrosion
Increase
Blowdown,Increase
Bromine - -
2 CWR pH 7.8-8.2
Can cause scalling
more rapidly Increase H2SO4 dosing
Can corrode heat
exchanger surfaces
Decrease H2SO4
dosing
3 CWR T.Iron 0-2ppm
An indication of
corrosion
Check CW pH, Increase
Blowdown - -
4 CWR
Orthophos
phate
3-
4.8ppm
Phosphate film may
increase, can
increase scaling
Increase
Blowdown,Decrease
phosphate dosing
Can lead to corrosion if
phosphate (cathodic)
film disrupts increase dosing
5 CWR Zinc Nil
Passivation anodic
film may be disrupted
Increase Zinc
orthophosphate dosing - -

27. 3.MICROBIOLOGICAL
CONTROL

28. 3.Microbiological growth
 Bacteria are classified usually by the type of
problems they cause. e.g.,
1. Slime forming bacteria
2. Iron depositors
3. Sulphate reducers
4. Nitrifying bacteria

29. 3.Microbiological growth
Type of
organism
Type of problems
•Bacteria
Slime
forming
Form dense slicky slime with subsequent fouling
Spore
forming
Become inert when their environment becomes
hostile to them. However, growth recurs
whenever the environment becomes suitable
again.
Iron-
depositing
Cause the oxidation and subsequent deposition of
insoluble iron from soluble iron.
Nitrifying
bacteria
Generate nitric acid from ammonia contamination.
Can cause severe corrosion.
Sulfate-
reducing
bacteria
Generate sulfides from sulfates and can cause
serious localized corrosion.

30. 3.Microbiological growth
Type Type of problems
Anaerobic
corrosive
bacteria
Create corrosive localized environments by
secreting corrosive wastes. They are always
found underneath other deposits in oxygen
deficient locations.
•Fungi
Yeasts and
molds
Cause the degradation of wood in contact with the
water system. Cause spots on paper products.
•Algae Grow in sunlit areas in dense fibrous mats. Can
cause plugging of distribution holes on cooling
tower decks or dense growths on reservoirs and
evaporation ponds.

31. 3.Microbiological growth
 Anerobic bacteria usually found beneath
sludges.
 Iron depositor occurs in the water high in
ferrous enrich system.

32. 3.Microbiological growth
 Nitrifying bacteria oxidizes ammonia into
nitrates.
 Some bacteria encapsulate them from contact
with water

33. 3.Microbiological growth
 Most algae grows in dense mats. Not only plug
the distribution system but also provide space
beneath for the growth of anaerobic bacteria.

34. Bacterial control
 Bacteria can be killed by using following
factors,
 High temperature
 Low temperature
 Toxic chemicals like Phenol, HOCl
 pH control

35. Bacterial control
 With chemical dosing, pH is also an important
factor to be maintained to kill bacteria cells.
 It is observed that at higher pH ranges
nitrifying bacteria is not present.

36. Bacterial Control
 Chlorine is used in most of the systems as an
oxidizing biocide. Which on reaction with water
produces,
Cl2 + H2O Cl- + HOCl
 At our EnVen water treatment system we are
producing hypochloride by electrochlorination
unit.

37. Bacteria Control
 HOCl is very week acid and in water tends to
dissociates as follows on higher pH,
 HOCl H+ + OCl-
 HOCl is most effective under 7.5 pH.

38. Bacteria Control
 HOCl is more oxidizing agent then OCl- .
 So the presence of HOCl is necessary to kill
bacteria.
 HOCl reacts with certain enzymes below 7.5
pH.
 An activating oxidizing agent is necessary to
work above 7.5 pH.

39. Bacteria Control
 The effectiveness of chlorine decreases very
rapidly as the pH rises.
pH HOCl Remaining
6.0 100%
8.0 20%
8.5 10%

40. Bacteria Control
 A chlorine-bromide mixture produces oxidant
species that penetrate the biofilm; chlorine
activates a bromide compound, according to
the reaction
 HOCl +Br- HOBr + Cl-

41. BACTERIUM
Hypohalite
OCl- anionic
Cannot penetrate
hypohalous acid
HOCl , nonionic,
can penetrate
cell wall - kill
The cell wall is
negatively charged
Bacterial Control

42. Bacteria Control
At pH 7.5, 50% of the available chlorine is
present as HOCl, with the balance as OCl.
With hypobromous acid, at pH 7.5, over 90%
of the oxidant is present as HOBr, the more
active form, just as HOCl is more
active than OCl", as mentioned earlier.

43. Summary of advantages of bromine chemistry versus
chlorine chemistry:
•At pH levels above pH 8, most of the cooling systems today,
dissociation is highly in favor of the non charged hypohalous acid,
Which can penetrate cell walls, thus being the toxic part.
•Bromamines are more toxic than chloramines, because they dissociate
more readily into ammonia and hypobromous acid, than chloramines.
•In the presence of ammonia, bromine is more effective than chlorine.
Bacterial Control

44. Bacterial Control
Limitation of oxidizing biocides,
They do not penetrates to the slimes or biofilms
so a relevant biodispersant has to be dosed as
well.

45. Biofilm and Scale Formation
Biofilm lowers water velocity(time), laminar layer on the tube wall/
/skin temp. will increase, biofilm provides nucleation sites.

46. Biodispersants
/Biodetergents
Effect on biofilm
• To enhance the effect of biocides,
biodispersants or biodetergents can be
used:
Before addition of biodetergent
After addition of biodetergent
Dispersed
particles

47. Parameters to be controlled
No. Stream Analysis
Operati
ng
Limits
Analysis crossing UPPER Limit Analysis crossing LOWER Limit
Effect Corrective Action Effect Corrective Action
1 CWR
Free
Chlorine
0.3-
0.5ppm
It can cause
corrosion Decrease hypo dosing
It can cause
microbiological growth
Increase hypo
dosing

48. 4.SCALE & DEPOSITS

49. 4.Scale and deposits
Deposits are most often an accumulation of
sediments or settled solids that drop out at
some point in a system where the water
velocity falls to a level too
low to support the material in the stream.

50. 4.Scale and deposits
 Sources of deposits
1. Water supply itself
2. Air
3. Leakage of process fluid
4. Lubricants applied to the valves, pumps etc
5. Chemical precipitation

51. Scale
Any of the following deposits in closed
cooling water system can cause scaling
1. Calcium carbonate
2. Calcium phosphate
3. Iron phosphate
4. Iron oxides
5. Manganese oxides
6. Calcium sulfate
7. Magnesium silicate
8. Silica
9. Zinc phosphate
10. Zinc carbonate, hydroxide
11. Aluminum phosphate
12. Calcium fluoride

52. 4.Scale and deposits
 Process of scale deposition
Water
dissolved
solids
Super
saturation
Particle
formation
Clusters
formation
Crystal growth
Concentratio
n
Time
Nucleation
Scale
formation

53. Scale control
Precipitated Calcium
carbonate particles
Dispersed Calcium
carbonate particles

54. Scale control
 Scale can be controlled by keeping the pH at
lower sides.
 Scale can be controlled by adding the
dispersent that can make the salts more
soluble on that specific temperature.

55. Scale control
 Phosphonates are organic compounds
containing C-PO(OR)2 groups.
 Phosphonates are effective chelating
agents that binds tightly to di- and trivalent
metal ions. Thus keeping them away from
carbonates and sulfates etc.

56. The effects of Scale in tubes

57. Parameters to be controlled
No. Stream Analysis
Operati
ng
Limits
Analysis crossing UPPER Limit Analysis crossing LOWER Limit
Effect Corrective Action Effect Corrective Action
1 CWR TH
0-
1000pp
m
Scaling on the heat
transfer surface
Increase blowdown
Increase Polymer
phosphonate - -
2 CWR
Ca
Hardness
0-
600ppm
Scaling on the heat
transfer surface
Increase
Blowdown,Increase
Polymer phosphonate - -
3 CWR
Conductivit
y
0-
2000uS/
cm
Scaling on the heat
transfer surface Increase Blowdown - -
4 CWR TSS 0-25ppm
Can choke and form
deposites on heat
transfer surfaces
Increase flow from side
stream filters,Check main
filters DP - -
5 CWR pH 7.8-8.2
Can cause scalling
more rapidly Increase H2SO4 dosing
Can corrode heat
exchanger surfaces
Decrease H2SO4
dosing
6 CWR M-Alkalinity
100-
200ppm
Scaling on the heat
transfer surface Increase H2SO4 dosing Can cause corrosion
Decrease H2SO4
dosing

58. 5.Acid dosing
 Acid dosing is carried out to control the pH of
cooling water.
 Ammonia in the system can cause the
production of ammonium hydroxide.
 Increased alkalinity in the cooling water can
cause the pH to be raised.
 To control the pH , H2SO4 is the only solution.

59. Chemicals at EnVen
 BULAB 7024
Combination of phosphonate and polymer to control the
precipitation of calcium carbonate and deposition due to silt or
other particulate material.
 BULAB 9063
Zinc and inorganic phosphate, which will provide both anodic and
cathodic corrosion protection.
 BLS 9067
Polymer to control the precipitation of calcium phosphate & stabilize
the Zinc.
 BULAB 8006
Is a combination product, designed to inhibit slime build up in the
cooling water system and would be needed to enhance the
effectiveness of microorganism control.

60. Chemicals at EnVen
BULAB 6041
Bromine technology oxidizing biocide used in
cooling water systems with pH above 7.2.
BULAB 3847
This product is a very broad biocide formulation to
prevent growth of Bacteria, Fungi, Algae and
Sulfate Reducing Bacteria (SRB). Proven
effectiveness in ammonia containing cooling
waters.
BULAB 9050
A zinc-based, corrosion inhibitor that provides
protection of mildsteel piping and equipment in
cooling water systems

61. THANK YOU