This presentation discusses problems encountered in boiler water such as scale, corrosion, and carryover. Scale is caused by poor pretreatment, contamination, or inadequate chemical treatment and forms on boiler tubes. Common scales include calcium carbonate, calcium phosphate, and iron oxides. Scale reduces heat transfer and causes equipment issues. Corrosion is an electrochemical process where metal returns to its oxidized state. Methods to prevent scale and corrosion include maintaining water quality, using recommended chemicals, and controlling blowdown. Sodium aluminate and phosphate conditioning are discussed as internal treatment methods. Sludge and scale formation, as well as their disadvantages, are also summarized.
Generally soaps create foam in water, but in present of some materials the foam creation is reduced and need more soap for producing foam, and this condition of water is called water hardness.
The presence of Calcium, Magnesium salt i.e. bicarbonates, sulphates, chloride in water is called causes of hardness of water. The water which contains these salts is called hard water. Hard water does not easily form lather with soap as the salt of Calcium and Magnesium react with soap to form insoluble organic salts.
Sources of Water, Hardness of Water, Determination of Hardness of Water by EDTA method, Alkalinity of water, Scale and Sludge formation, Boiler Corrosion, Priming , Foaming, Caustic Embrittlement
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
Generally soaps create foam in water, but in present of some materials the foam creation is reduced and need more soap for producing foam, and this condition of water is called water hardness.
The presence of Calcium, Magnesium salt i.e. bicarbonates, sulphates, chloride in water is called causes of hardness of water. The water which contains these salts is called hard water. Hard water does not easily form lather with soap as the salt of Calcium and Magnesium react with soap to form insoluble organic salts.
Sources of Water, Hardness of Water, Determination of Hardness of Water by EDTA method, Alkalinity of water, Scale and Sludge formation, Boiler Corrosion, Priming , Foaming, Caustic Embrittlement
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
Normal Labour/ Stages of Labour/ Mechanism of LabourWasim Ak
Normal labor is also termed spontaneous labor, defined as the natural physiological process through which the fetus, placenta, and membranes are expelled from the uterus through the birth canal at term (37 to 42 weeks
Macroeconomics- Movie Location
This will be used as part of your Personal Professional Portfolio once graded.
Objective:
Prepare a presentation or a paper using research, basic comparative analysis, data organization and application of economic information. You will make an informed assessment of an economic climate outside of the United States to accomplish an entertainment industry objective.
Biological screening of herbal drugs: Introduction and Need for
Phyto-Pharmacological Screening, New Strategies for evaluating
Natural Products, In vitro evaluation techniques for Antioxidants, Antimicrobial and Anticancer drugs. In vivo evaluation techniques
for Anti-inflammatory, Antiulcer, Anticancer, Wound healing, Antidiabetic, Hepatoprotective, Cardio protective, Diuretics and
Antifertility, Toxicity studies as per OECD guidelines
4. Introduction
Effect of Scale on Boiler Water Systems
Reduces heat transfer efficiency
Decreases unit or production capacity
Over heating of boiler tubes, tube failure
Increased down time and maintenance
Higher operating costs/decreased profits
5. Chemistry
Probable reasons for
Scale Formation
Poor operation of pretreatment
Feed water contaminanation
In adequate chemical treatment
Condensate contamination
8. Scale Inhibition
Methods
Maintain the feed water
quality
• Frequent check of feed water
for contaminants
• Use of chemicals as
recommended
• Control blow down
12. Types of Boiler Water
Corrosion
General Etch
Pitting
Caustic corrosion
Tube failures
13. Feed and Control
Continuous Feed
Routine Testing
Monitoring Program
Effectiveness
Proper Program Maintenance requires the
continuous application of the correct level of
inhibitor:
14. Important Properties in water
chemistry
Natural Water may contain
1) Conductivity 2) Turbidity
3) Color 4) pH
5) Alkalinity 6) Solids
7) Hardness
15. ALKALINITY
• Alkalinity of water is refers to the total
amount of those substance present in water
which tend to increase the concentration of
hydroxide ions on account of dissociation
and hydrolysis in water.
It is a measure of ability of water to
neutralize acids.
Total Alkalinity =Methyl Orange Alkalinity+
Phenolphthalein Alkalinity
16. CAUSE OF ALKALINITY:
Presence of HCO3
- , HSiO3
- ,SiO3
- :
Presence of salts of Weak acids:
Presence of Buffer forming salts:
17. CLASSIFICATION OF ALKALINITY:
IT IS OF THREE TYPES:
1) OH- (hydroxyl) ALKALINITY
2) CO3
2- (carbonate) ALKALINITY
3) HCO3
- (bicarbonate) ALKALINITY
19. DETERMINATION OF ALKALINITY:
PRINCIPLE: The type and extent of alkalinity
of water sample is determined by
TITRIMETRIC METHOD.
OH- + H+ H2 O
CO3
2- + H+ HCO3
- P
HCO3
- + H+ H2CO3 M
23. PROCEDURE:
KNOWN VOLUME OF WATER SAMPLE + 1-
2 DROPS
OF Phenolphthalein.
APPERANCE OF COLOR
TITRATE WITH STD. ACID
END POINT PINK TO COLORLESS
TITRATE WITH SAME SAMPLE WITH SAME
STD. ACID BY USING Methyl Orange
INDICATOR.
END POINT YELLOWOrange TODARK PINK
THE VOL OF ACID CONSUMED IS NOTED.
24. CALCULATIONS
FOR Phenolphthalein ALKALINITY:
N1V1 = N2V2
(AWS) (STD. ACID)
N1 = N2V2/ V1
PALK = N1 X 50 X 1000 ppm
FOR METHYLORANGE ALKALINITY:
N1V1 = N2V2
(AWS) (STD. ACID)
N1 = N2V2/ V1
MALK = N1 X 50 X 1000 ppm
25. Alkalinity relationships as determined by
titrations.
Hydroxide Carbonate Bicarbonate
P = O O O M
P = M P O O
P = 1/2M O 2P O
P >1/2M 2P - M 2(M - P) O
P <1/2 M O 2P M
2P
RESULT: OH- (hydroxyl) ALKALINITY=--------ppm
2) CO3
2- (carbonate) ALKALINITY=-----------ppm
3) HCO - (bicarbonate) ALKALINITY=-----------ppm
26. HARDNESS OF WATER
It is defined as a characteristic property of
water that prevents the lathering of soap.
Hardness of water may also be defined as
the soap-consuming capacity of water, or
the capacity of precipitation of soap.
27. CAUSE OF HARDNESS
Hard water does not produce lather with soap solutions, but produces white
precipitate (scum). For example, sodium stearate reacts with calcium:
2C17H35COONa + Ca2+ → (C17H35COO)2Ca + 2Na+
calcium stearate
(insoluble in water)
28. Degree Of Hardness Of Water
Soft 0-60 mg/L
Medium 60-120 mg/L
Hard 120-180 mg/L
Very hard >180 mg/L
29. TYPES OF HARDNESS
a)TEMPORARY HARDNESS
/Carbonate/Alkaline
This hardness refers to the amount of carbonate and
bicarbonates of Ca & Mg in solution
It can be removed or precipitated by boiling.
This type of hardness is responsible for the
deposition of scale in hot water pipes and kettles.
b) Permanent/ Non-carbonate hardness/non-alkaline
This hardness is caused by sulfate, chloride or
nitrate of Ca & Mg .
This type of hardness cannot be removed by boiling.
30. UNITS OF HARDNESS:
There are several different scales used to
describe the hardness of water in different
contexts.
1)ppm
2)Mg/l
3)Clark’s Degree
4)Degree french
31. A
Parts per million (ppm)
Usually defined as one milligram of calcium
carbonate (CaCO3) per litre of water.
Clark degrees (°Clark)/English degrees (°e or e)
One degree Clark is defined as equivalent of CaCO3
per 70,000 parts of water.
French degrees (°F or f)
One degree French is defined as 10 milligrams of
calcium carbonate per litre of water, equivalent to
10 ppm.
RELATIONSHIP:
1ppm= 1 mg/l = 0.07 °Clark =0.1 °F
32. EXPRESSION OF HARDNESS:
THE EQUIVALENT OF CaCO3 FOR A HARDNESS
CAUSING SALT IS GIVEN BY:
* EQUIVALENT OF CaCO3 = W X 50
E
W=MASS OF HARDNESS PRODUCING
SUBSTANCE
E= EQUIVALENT MASS OF CaCO3
36. HEXADENTATE IONIC
STRUCTURE OF EDTA:
It is also represented as H2Y2- it is a strong chelating
ligand,forms complex with bivalent cations like Ca &
mg ions. The complex formed are stable in alkaline
medium i.e. pH=8-10.
37. Metal- Edta complex:
Edta being a chelating
ligand react with
multivalent metal ions
to form stable complex.
In hard water, bivalent
cations like Ca & Mg
ions are present which
form complex with edta.
That`s why this method
is used to determine
hardness in water.
40. SLUDGE FORMATION IN BOILERS:
In boilers, because of continuous evaporation of water, the
concentration of salts increase progressively and after the
saturation point is reached, precipitate form on the inner
walls of boiler.
SLUDGE: Sludge is a soft, loose and slimy precipitate
formed within the boiler. It is formed at comparatively
colder portions of the boiler and collects in the area where
flow rate is slow.
These are formed by substances which have greater
solubilities in hot water than in cold-water.
E.g.. MgCO3, MgCl2, CaCl2, MgSO4.
41. Disadvantages:
a. As the sludge’s are poor conductor of
heat they cause loss of heat.
b. The working of the boiler is disturbed
because of chocking of pipes by the
sludge.
PREVENTION:
a. By using well softened water.
b. By drawing off a portion of
concentrated water frequently.
42. scales
SCALES: Scales are hard, adhering precipitates formed on
the inner walls of the boilers. They stick
very firmly on to the inner wall surface and are difficult to
remove with chisel and hammer.
causes of scale formation: Following are the causes
a. decomposition of calcium bicarbonate:
Ca(HCO3)2 CaCO3 + H2O + CO2
In low pressure boilers,CaCO3 causes scale formation.
In High pressure boilers,CaCO3 becomes soluble.
CaCO3 + H2O Ca(OH)2 + CO2
43. b. Decomposition of calcium sulphate:
The solubility ofCaSO4 in water decreases with
rise of Temperature. In super heated water CaSO4
is insoluble.This is the main cause in high-
pressure boilers.
c. Hydrolysis of Magnesium salts:
Dissolved Magnesium salts undergo hydrolysis
formingMg(OH)2 preci
44. SCALES:
Scales are hard, adhering precipitates formed on the
inner walls of the boilers. They stick very firmly on
to the inner wall surface and are difficult to remove
with chisel and hammer.
causes of scale formation: Following are the causes
a. decomposition of calcium bicarbonate:
Ca(HCO3)2 CaCO3 +H2O + CO2
In low pressure boilers,CaCO3 causes scale
formation.
In High pressure boilers,CaCO3 becomes soluble.
45. b. Decomposition of calcium sulphate:
The solubility of CaSO4 in water decreases with rise
of Temperature. In super heated water CaSO4 is
insoluble.
This is the main cause in high-pressure boilers.
c. Hydrolysis of Magnesium salts:
Dissolved Magnesium salts undergo hydrolysis
forming Mg(OH)2 precipitate.
MgCl2 + 2H2O Mg(OH)2 + 2 HCl
Mg(OH)2 so found by hydrolysis of Magnesium
salts is a soft type of scale.
46. Disadvantages of scale:
wastage of fuel: The scale formation causes
decreases of heat transfer. As a result over
heating is required this causes consumption of
fuel.
Danger of Explosion: The hot scale cracks
because of expansion and water suddenly
comes in contact with overheated Iron plates.
This causes in formation of large amount of
steam suddenly. This results high pressure
causing boiler to burst.
Bagging: distortion of boiler material
Reduce efficiency of boiler.
47. PREVENTION:
a. External treatment: Efficient softening
of water is to be carried out.
b.Internal treatment: Suitable chemicals
are added to the boiler water either to
precipitate or to convert scale in to
compounds.
48. INTERNAL TREATEMENT:
Internal treatment of boiler water is carried
out by adding proper chemicals to
precipitate the scale
forming impurities in the form of sludge
and to convert the scale forming chemicals
into compounds
which will stay in dissolved form in water.
49. CONDITIONING:
COLLODIAL CONDITIONING: The addition of organic
substances such as Kerosene, tannin, Gel etc., to the surface
in low pressure boilers may prevent the scale formation.
These substances gets coated over the scale forming
precipitates and gives a loose and non-sticky precipitates
which can be removed by using blow-down operation.
PHOSPHATE CONDITIONING: The addition of sodium
phosphate in hard water reacts with the hardness causing
agents and gives calcium and magnesium phosphates which
are soft and non-adhere and can be removed easily by blow-
down operation. In this way, scale formation is removed in
high-pressure boilers.
3CaCl2 + 2 Na3PO4 → Ca3(PO4)2 + 6NaCl
50. CARBONATE CONDITIONING: In low-pressure
boilers, scale-formation can be avoided by adding
sodium carbonate to boiler water, when CaSO4 is
converted into calcium carbonate in equilibrium.
CaSO4 + Na2CO3→ CaCO3 + Na2SO4
Consequently, deposition of CaSO4 as scale doesn’t
take place and calcium is precipitated as loose sludge
of CaCO3 which can be removed by blow-down
operation.
51. CALGON CONDITIONING: Involves in
adding calgon to boiler water. It prevents the
scale and
sludge formation by forming soluble complex
compound with CaSO4 .
Calgon = Sodium hexa Meta phosphate
Na2 [Na4 (PO3)6]→ 2Na+ + [Na4P6O18]2-
2CaSO4 + [Na4P6O18]2- → [Ca2P6O18]2- +
2Na2SO4
52. SODIUM ALUMINATE:
Sodium aluminate gets hydrolyzed yielding NaOH and a
gelatinous precipitate of aluminum hydroxide.
NaAlO2 + 2H2O→ NaOH + Al (OH)3
The sodium hydroxide, so-formed, precipitates some of the
magnesium as Mg (OH)2.
MgCl2 + 2NaOH → Mg (OH)2 + 2NaCl
The flocculent precipitate of Mg (OH)2 plus aluminum
hydroxide, produced inside the boiler, entraps finely suspended
and colloidal impurities, including oil drops and silica. The loose
precipitate can be removed by pre-determined blow-down
operation.
54. Boiler Corrosion:
The chemical or electro chemical eating
away of metal by its environment in a boiler
is known as boiler corrosion. The main
reason for this problem is the presence of
excess of oxygen in water. It can be
prevented by mechanical de-aerator, pre-
heating and chemical treatment.
56. Caustic Embrittlement:
The formation of brittle and incrystalline cracks in
the boiler shell is called caustic embrittlement.
It is a type of boiler corrosion and the main
reason for this, is the presence of alkali-metal
carbonates and bicarbonates in feed water and
also the presence of sodium sulphate.
In lime-soda process, it is likely that, some
residual Na2 CO3 is still present in the softened
water. ThisNa2CO3decomposes to give NaOH
and CO2, due to which the boiler water becomes
“Caustic”.
Na2CO3+ H2O → NaOH+ CO2
57. -
This caustic water flows inside the boiler
and causes some minutes hair-cracks, by
capillary action.
On evaporation of water, the dissolved
caustic soda increases its concentration
which attacks the surrounding area, thereby
dissolving Iron of boiler as Sodium ferrate.
This causes embrittlement of boiler parts
such as bends, joints, reverts etc, due to
which the boiler gets
fail.
58. -
Therefore, caustic embrittlement can be
prevented.
a. By maintaining the pH value of water
and neutralization of alkali.
b. By using Sodium Phosphate as
softening reagents, in the external
treatment of boilers.
c. Caustic embrittlement can also be
prevented by adding Tannin or Lignin
or Sodium sulphate which prevents the
infiltration of caustic-soda solution
blocking the hair-cracks
59.
60. . Boiler Blow Down
•Controls ‘total dissolved solids’ (TDS) in the water that is
boiled
•Blows off water and replaces it with feed water
•Conductivity measured as indication of TDS levels
•Calculation of quantity blow down required:
Blow down (%) =Feed water TDS x %
Make up water
Maximum Permissible TDS in Boiler
water
61. continue
Two types of blow down
•Intermittent
•Manually operated valve reduces TDS
•Large short-term increases in feed water
•Substantial heat loss
•Continuous
•Ensures constant TDS and steam purity
•Heat lost can be recovered
•Common in high-pressure boilers
62.
63.
64. When blow down required
If boiler drum water quality increase
Conductivity, TDS, silica, Phosphate level
high.
65. Boiler drum water quality
PH 9.0-9.3
Conductivity 30 µs/cm
TDS 15 ppm
Silica as Sio2 0.1 ppm
Phosphate as Po4 2-4 ppm
66. Boiler Blow Down
Benefits
•Lower pretreatment costs
•Less make-up water consumption
•Reduced maintenance downtime
•Increased boiler life
•Lower consumption of treatment
chemicals
67. Boiler Feed Water
Treatment
•Quality of steam depend on water treatment
to control
• Steam purity
• Deposits
• Corrosion
•Efficient heat transfer only if boiler water is
free from deposit-forming solids
68. Boiler feed water quality
PH @ 25°C 8.8-9.2
Conductivity 0.2 µs/cm
Total hardness NIL
Silica as Sio2 0.01 ppm
Copper as cu 0.002 ppm
Iron as Fe 0.005 ppm
Dissolved oxygen 0.007 ppm
Sodium as Na 0.005 ppm
Residual hydrazine 0.01-0.02 ppm
Chloride as cl 0.003 ppm
69. Steam purity
PH @25°C 8.8-9.2
Silica as Sio2 0.01 ppm
Copper as cu 0.002 ppm
Iron as Fe 0.005 ppm
Chloride as Cl 0.003 ppm
Sodium as Na 0.005 ppm
70. Boiler Feed Water Treatment
Deposit control
•To avoid efficiency losses and reduced heat
transfer
•Hardness salts of calcium and magnesium
•Alkaline hardness: removed by boiling
•Non-alkaline: difficult to remove
•Silica forms hard silica scales
71. Boiler Feed Water Treatment
Internal water treatment
•Chemicals added to boiler to prevent scale
•Different chemicals for different water types
•Conditions:
•Feed water is low in hardness salts
•Low pressure, high TDS content is tolerated
•Small water quantities treated
•Internal treatment alone not recommended
72. External Water Treatment
Mechanical de-aeration
•O2 and CO2 removed by heating feed water
•economical treatment process
•Vacuum type can reduce O2 to 0.02 mg/l
•Pressure type can reduce O2 to 0.005 mg/l
73. External Water Treatment
Chemical de-aeration
•Removal of trace oxygen with scavenger
•Sodium sulphite:
•Reacts with oxygen: sodium sulphate
•Increases TDS: increased blow down
•Hydrazine
•Reacts with oxygen: nitrogen + water
•Does not increase TDS: used in high pressure
boilers