5. RAWWATER
Raw water is water found in the environment that has not
been treated and does not have any of its minerals, ions,
particles, bacteria, or parasites removed. Raw water
includes rainwater, groundwater, water from infiltration wells,
and water from bodies like lakes and rivers.
6. RAWWATER CHEMICAL COMPOSITION
Raw water composition
S.No Composition Including
1Suspendered Solids Soil, Mud, organic Material, and so on
2Organic Material in solution Organic acids
3Dissolved solvents Cations Anions
Calcium Ca2+ Bicarbonates HCO3-
Magnesium Mg 2+ Chlorides Cl-
Sodium Na + Sulfates SO4
2 -
Potassium K + Nitrates NO3
-
Etc…. Etc…
4Dissolved Gas Oxygen, carbonic Gas, Nitrogen
5Micro organisms Algae, bacteria, fungi
7. RO 1 AND RO 2
According to the results the removal efficiency ofTDS, Sodium,
Chloride, and sulfate in RO1 was 90% and RO2 98%
In this research the membrane can operate over a pH range of 5 to
9. the average life of the membrane is three years.
Membrane is clean by a chemical injection
8. DEMIWATER
The major difference between demineralized
water and distilled water is that distilled water
usually has fewer organic contaminants;
deionization does not remove uncharged
molecules such as viruses or bacteria.
Demineralized water most times have fewer
mineral ions; this is dependent on the way it is
produced.
9. REQUIRED OF FEEDWATER
It should have zero Hardness
It must be free from dissolved gases, like O2, and CO2. Ect…
It should be free from suspended impurities
It should be free from dissolved salts and alkalinity
It should be free from turbidity and oil.
It should be free from hardness causing and scale forming constitutes like Ca and
Mg
10. DEAERATOR
WATER
Makeup water for feed:
Makeup water is from an external source and should
be treated and stored
The condensed water steam returned from the
distillation system (condensate return) is combined
with makeup water to make boiler feed water
Deaerator water:
The feed water is contacted with steam to strip
dissolved oxygen
The oxygen scavenger is added before the feed
water goes to the storage system.
11. FACTORS AFFECTING QUALITY
Water quality determined by
1. Ion concentration
2. Dissolved solids
3. Hardness
4.Turbidity
5. Acidity
6. Dissolved Oxygen
7. BDO (Biochemical Demand of Oxygen)
12. BOILER
Types of Boilers
There are two types of steam boilers:
Fire tube boiler ( hot combustion gas passes through the tube
with water surrounding this tube)
Water tube boiler ( hot combustion gas passes outside the tube
and water through the tube)
Classification:
Boilers are classified based on pressure
1. High–pressure boilers (Above 15 bar)
2. Low–pressure boilers ( low 15 bar)
13. BOILER
High-pressure boiler:
1. Scale control
2. Sludge conditioning
3. Correction control
4. Forming control (Steam drum)
Low-pressure boiler treatment :
1. Low-pressure boilers need treatments for
controlling corrosion
14. STEAM BOILER
COMPONENTS
Makeup water treatment
Pre-heater for makeup water
Makeup water storage section
Feed water deaerator
Feed water pre-heater economizer
Feed water treatment with oxygen scavenger
15. BOILER
Steam drum (to produce steam)
Mud drums ( to collect the sediments in the boiler water)
Boiler tube ( connecting mud drum and steam drum)
Super heater ( superheating steam to high temperature)
Steam header ( distributing steam to the process
equipment)
Blow down ( Drum)
Flash drum ( to collect low-pressure steam and utilize for
deaerator heating)
17. STEAM BOILER
In the steam drum steam and water are separated
This steam is further heated to generate superheated
steam
Usually feed water added to the steam drum
Chemical feed for internal boiler treatment may be
added to the steam drum
The blow down is discharged to flash to recover low-
pressure steam and use the steam deaerator
The continuous blowdown water may be used to
preheat make-up water by heat exchanger
18. TDS AND
ALKALINITY
TDS in the boiler:TDS comes from make-up water and chemicals
added and gets concentrated as water is converted into steam.
The control ofTDS levels is critical in boiler operation. A highTDS
level is a high boiler efficiency.Too high interface in the boiler
operation. Blowdown is necessary to controlTDS.
Water is removed continuously from the steam drum.
To keep theTDS in the boiler water just below the maximum
allowed in order to save fuel oilWater and treatment chemicals.
TDS is calculated from Conductivity
19. ALKALINITY
The alkalinity comes from hydroxyl and carbonate ions.
Hydroxide alkalinity is necessary to protect the boiler against corrosion
The high causticity cause foaming
This excess caustic will attack the boiler causing “embrittlement”
Phosphate program removes calcium as calcium phosphate this is precipitated
and removed by the blowdown
The pH should be kept above 10.0 to prevent the formation of sticky sludge
that adheres to the boiler surface
Causticity can be caused by the formation of sodium hydroxide from
bicarbonate. Bicarbonate forms carbonate. Carbon dioxide and water at high
temperatures. The carbonate hydrolyses to give hydroxide and carbon
dioxide.The corban dioxide produced increases the acidity of stream.
20. BOILER WATERTREATMENT AND CONTROL
Deposit Formation
The dissolved solids from sludge as the water get
concentrated during steam generation. So solids like
calcium and magnesium salts become less soluble as
the temperature increases (CaCO3, CaSO4, MgCO4)
21. BOILER DEPOSIT FORMATION
Scale and Sludges
In boilers, water evaporates continuously, and the concentration of the dissolved salts increases progressively. When their concentrations
reach saturation point, they are thrown out of water in the form of precipitates on the inner walls of the boiler.
Formation: The scales may be formed inside the boiler due to
Decomposition of calcium bicarbonate: Ca(HCO3)2 CaCO3 + CO2 + H2O
Deposition of calcium sulphate: The scale consisting of mainly CaCO3 is soft and is the main cause of scale formation in low-pressure boilers.
Whereas in high-pressure boilers, CaCO3 is soluble due to the formation of Ca(OH)2. CaCo3+H2O Ca(OH) 2 + CO2
Disadvantage of Scale and sludge: Wastage of Fuel, Lowering of boiler safety, Decrease in efficiency
Danger of explosion: When thick scales crack due to uneven expansion, the water comes suddenly in contact with an over-heated portion and a large
amount of steam is formed instantaneously. This results in the development of sudden high-pressure that may cause an explosion of the boiler.
22. CORROSION
Boiler corrosion is the destruction of boiler metal. It occurs when the oxygen within the
boiler dissolves into the water. The dissolved oxygen then causes a reaction with iron-rich
(ferrous) boiler metal in a process known as oxidation. Deep holes and cavities develop within
the metal
23. COMMON SCALES IN BOILER
The common scales are calcium and magnesium salts and
iron salts
Calcium carbonate is from the breakdown of calcium
bicarbonate
Calcium sulfate – this is found in boilers when proper
treatment is not taking place – high hardness and low
alkalinity
Calcium carbonate – this will form sludge which can be
removed by blowdown ( if pH is below 11.0, then it deposits)
Iron oxide – it will deposit if a sludge conditioner is not
present
24. FOAMING
CARRIER
Alkalinity, TDS, and suspended solids interact and create foam in
boilers
Heavy foams causes carryover of liquid with steam
So maintain total alkalinity of less than 20% of theTDS and total
suspended solids 8% ofTDS and these levels can control
foaming.
Silica Carryover:
Silica can volatilize and enter the steam. It foams a deposit when
condensed. This is controlled by maintaining low silica in the boiler
water
The deposit that is mostly magnetic oxide is due to the corrosion of
iron.This is controlled by using neutralizing amines.
If the deposit is silica, this can be reduced by blow down or by
removing silica from makeup water (NaOH, Na2CO3, Na2SO4,
Na3PO4)
25. OXYGEN REMOVAL
Hydrazine hydrate is mainly used as a raw material for plastic foaming
agents, with 28% of hydrazine used in water treatment and pH control.
Oxygen dissolved in water causes corrosion. Because hydrazine removes
this oxygen via the reaction N2H4 + O2 → N2 + 2H2O, it is useful in
preventing corrosion.
2Na2SO3 + O2 2Na2SO4
2NH4OH + O2 (NH4)2CO3 + H2O
29. GENERAL INFORMATION ON BOILER
TREATMENT
1. scale formation
2. sludge conditioning
3. corrosion control (o2, CO2)
4. Foam control
5 .Blowdown control
To be continue for Next presentation ….
