HARD WATER :
Hard water does not produce good lather or form with soap and consume more soap. The hard water contains bicarbonates chloride and sulphates of calcium & magnesium.
The hard water when treated with soap i.e. sodium stearate, then no lather will be formed because sodium stearate of soap reacts with salts of calcium and magnesium giving insoluble Ca & Mg stearate.
SOFT WATER :
The soft water when treated with soap produces more lather and consume less soap and this is due to the absence of dissolved salts of Ca & Mg in water.
TYPES OF HARDNESS :
There are two types of hardness.
(1) TEMPORARY HARDNESS
It is due to the presence of only bicarbonate of calcium & magnesium. This type of hardness can be removed by boiling the water.
(2) PERMANENT HARDNESS
This type of hardness is caused by the presence of chloride and sulphates of calcium & magnesium. It can not be removed by boiling the water.
The purpose of the boiler water treatment is:
1 To neutralize acid forming salts in boiler water, i.e. maintain a slightly alkaline condition.
2 To provide scale removing and scale preventing chemicals.
3 To precipitate impurities into a sludge which can be removed by bottom and surface blows,
and
4 To prevent corrosion by oxidation.
Chemicals used
1.To maintain Alkalinity :
Sodium Carbonate (Soda Ash) For low pressure boilers.
React with non alkaline hardness salts either precipitate them or converted them into sodium salts.
Na2 CO3 + H2O --------------- 2Na OH + CO2
Sodium Hydroxide (Caustic soda) For high pressure boilers.
Sodium Hydroxide reacts with magnesium chloride producing harmless precipitate and sodium chloride which remains in the solution.
2Na OH + Mg SO4 --------------- Mg (OH)2 + Na2 SO4
IF Alkalinity is high it may lead to corrosion.
2.To maintain Phosphate Reserve
Used to Neutralize calcium and magnesium salts.
Disodium Phosphate (Na2 HPO4) is dissolved in water to form neutral solution.It react with phosphate of calcium and magnesium and converting into sodium salts.
Trisodium Phosphate (Na3 PO4) It dissolves in water to produce an alkaline solution.
3.Oxygen Scavengers
Hydrazine (N2H4) Continues injection about 35%.
It reacts with oxygen and forms nitrogen and water.
Sodium sulphite It reacts with oxygen and forms sodium sulphate.
4.Coagulants (Starch & Tanin)
To avoid build up of sludge.
5.Neutralising amines
To eliminate dissolved CO
6.Blowdown
To reduce chloride content.
Hard water does not produce good lather or form with soap and consume more soap. The hard water contains bicarbonates chloride and sulphates of calcium & magnesium.
The hard water when treated with soap i.e. sodium stearate, then no lather will be formed because sodium stearate of soap reacts with salts of calcium and magnesium giving insoluble Ca & Mg stearate.
SOFT WATER :
The soft water when treated with soap produces more lather and consume less soap and this is due to the absence of dissolved salts of Ca & Mg in water.
TYPES OF HARDNESS :
There are two types of hardness.
(1) TEMPORARY HARDNESS
It is due to the presence of only bicarbonate of calcium & magnesium. This type of hardness can be removed by boiling the water.
(2) PERMANENT HARDNESS
This type of hardness is caused by the presence of chloride and sulphates of calcium & magnesium. It can not be removed by boiling the water.
The purpose of the boiler water treatment is:
1 To neutralize acid forming salts in boiler water, i.e. maintain a slightly alkaline condition.
2 To provide scale removing and scale preventing chemicals.
3 To precipitate impurities into a sludge which can be removed by bottom and surface blows,
and
4 To prevent corrosion by oxidation.
Chemicals used
1.To maintain Alkalinity :
Sodium Carbonate (Soda Ash) For low pressure boilers.
React with non alkaline hardness salts either precipitate them or converted them into sodium salts.
Na2 CO3 + H2O --------------- 2Na OH + CO2
Sodium Hydroxide (Caustic soda) For high pressure boilers.
Sodium Hydroxide reacts with magnesium chloride producing harmless precipitate and sodium chloride which remains in the solution.
2Na OH + Mg SO4 --------------- Mg (OH)2 + Na2 SO4
IF Alkalinity is high it may lead to corrosion.
2.To maintain Phosphate Reserve
Used to Neutralize calcium and magnesium salts.
Disodium Phosphate (Na2 HPO4) is dissolved in water to form neutral solution.It react with phosphate of calcium and magnesium and converting into sodium salts.
Trisodium Phosphate (Na3 PO4) It dissolves in water to produce an alkaline solution.
3.Oxygen Scavengers
Hydrazine (N2H4) Continues injection about 35%.
It reacts with oxygen and forms nitrogen and water.
Sodium sulphite It reacts with oxygen and forms sodium sulphate.
4.Coagulants (Starch & Tanin)
To avoid build up of sludge.
5.Neutralising amines
To eliminate dissolved CO
6.Blowdown
To reduce chloride content.
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