Boilerfeed water

1. BOILER FEED WATER
PRESENTED BY:
DIVYA SHREE R

2. BOILER FEED WATER
1. The water fed into the boiler for the production of steam is called boiler
feed water.
2. Boiler feed water should be free from turbidity,oil,dissolved Gases,alkali
and Hardness causing substances.
3. If hard water obtained from natural source is fed directly into the
boiler,the following troubles may arise.

3. BOILER TROUBLES (OR) DISADVANTAGES OF USING
HARDWATER IN BOILERS
• Formation of deposit (sludge's & scales) in
boilers
• Priming and foaming (carry over)
• Caustic embrittlement
• Boiler corrosion.

4. FORMATION OF DEPOSITS (SLUDGES & SCALES) IN BOILERS ANDHEAT
EXCHANGES
• When water is continuously converted into steam in boilers or
heat exchanges ,the concentration of dissolved salts in water
increases progressively. When the concentration of the Salts
reaches their saturation point, they are thrown out in the form
of precipitates on the inner walls of boilers or heat exchanges.
The least soluble one gets precipitated first.

5. 1. SLUDGE(LOOSE DEPOSIT)
• If the precipitate is loose and slimy
it is called sludge. Sludges are
formed by the substances like
MgCl2, MgCO3. MgSO and CaCl2.
They have greater solubilties in hot
water than cold water.

6. SCALE (HARD DEPOSIT)
• On the other hand , if the precipitate forms hard and
adherent coating on the inner walls of the boiler, it is
called scale.
• Scales are formed by substances like Ca(HCO3)2 , CaSO4
and Mg(OH)2.
Prevention
• At the initial stage , scales can be removed using scraper ,
wire brush etc….
• By using suitable chemicals like dil.acides ( for CaCO3
scale), EDTA (for CaSO4 scale) with which they form
suitable complexes.
• If the scales are loosely adhering, they can be removed by
frequent blow down operation.

7. PRIMING AND FOAMING
• When water is converted into steam,some droplets of water are carried by
steam due to rapid boiling.
• Some droplets of water contain dissolved salts.
• Process of wet steam formation is known as priming
Causes
• High steam velocity
• Very high water level in the boiler
• Sudden boiling of water
• Very poor boiler design

8. FOAMING
• Formation of stable bubbles over the surface of water.
• This bubbles are carried by the steam leading to excessive priming.
Causes
• Presence of oil , grease and finly divided particles in water.
Prevention
By adding anti-foaming agents like synthetic polyamides
Adding coagulants like aluminium hydroxide,sodium aluminate .

9. CAUSTICEMBRITTLEMENT (INTERCRYSTALLINE CRACKING)
• Boiler water usually contains a small proportion of Na2CO3.In high pressure boiler this Na2CO3
undergoes decomposition to give NaOH.
• Na2CO3+H2O-2NaOH+CO2
• This NaOH flows into the minute hair cracks and crevices, usually present on the boiler material by
capillary action and dissolves the surrounding area of iron as sodium ferrote.
• This causes brittlement of boiler parts, particularly stressed parts like bends, joints,riverts etc causing
even failure of boiler.
Prevention
• Using sodium phosphate as softening agent instead of sodium carbonate.
• By adding tannin,lignin to the boiler water which blocks the hair cracks.

10. BOILER CORROSION
• Corrosion in boilers is due to the presence of
• Dissolved oxygen
• Disssolved carbon dioxide
• Dissolved salts
Dissolved oxygen
Dissolved oxygen in water is mainly responsible for the corrosion of boiler.
This dissolved oxygen in water attacks the boiler material at higher temperature.
Removal of dissolved oxygen
Dissolved oxygen can be removed by chemical or mechanical method.

11. DISSOLVEDCO2
• Dissolved carbon dioxide in water produces carbonic acid, which is acidic and corrosive in
nature.
• CO2+H2O-H2CO3
Removal of dissolved CO2
• CO2 can be removed from water by adding a calculated amount of NH4OH into water.
• CO2 along with O2 can also be removed by mechanically by de-aeration method.

12. DISSOLVED MGCL2