Scale formation and sludge formation in boilers, Chemistry

Q. Explain scale formation and sludge formation in boilers. How are they formed?   


Boilers are used for steam generation. When hard water is evaporated, progressively the concentration of dissolved salt is increased. When their saturation points are reached, the dissolved salts of calcium and magnesium along with other soluble impurities are precipitates on the inner walls of boilers and in due course of time adhere to the metal surface in the form of scales and sledges. The sludge are generally form by the substance, which have greater solubility in hot water than cold water. So, sludge is formed in colder parts of boiler.

Theories of scale formation

1.      Decrease in solubility: Certain impurities in water decreases solubility with increase of temperature, so such impurities separates out from water at a higher temperature e.g. In CaSO4solubility decreases with increase of temperature.

2.      Hydrolysis of salts: The soluble magnesium salts are hydrolysed under high temperature conditions to give soft scale.

Mg (Cl2) +2H2O = Mg (OH)2

3.      Chemical decomposition: The decomposition of bicarbonates of calcium and magnesium takes place to give rise two carbonates CaCO3 and MgCO3 respectively.

 Ca (HCO3)2 = CaCO3 + H2O + CO2

i.   Mg (HCO3)2   = MgCO3 + H2O + CO2

MgCO3 may further decomposes near boiling point of water to give Mg (OH)2

MgCO3 + H2O = Mg (OH)2 + CO2

These salts precipitate and deposited inside the boiler as scale and sludge.

4.      Formation of silicates: If small amount of SiO2 is present in boiler feed water it gives rise to formation  

Posted Date: 7/21/2012 9:22:53 AM | Location : United States

what do you mean by caustic embritlement..?
Posted by jitendra kumar | Posted Date: 6/30/2013 5:55:33 AM

Related Discussions:- Scale formation and sludge formation in boilers, Assignment Help, Ask Question on Scale formation and sludge formation in boilers, Get Answer, Expert's Help, Scale formation and sludge formation in boilers Discussions

Write discussion on Scale formation and sludge formation in boilers
Your posts are moderated
Related Questions
Q. What is softening of water? Describe deionization method of water softening with diagram. Ans. Softening of water: The process of removing the hardness causing salts from

Lowest sum rule - iupac system of nomenclature previously it may be noted that, the numbering of the parent chain consisting of two or more substituents was done in such a way

Ionic and covalent bonds are present in: (1)  CCl 4                                               (2)  CaCl 2              (3)  NH 4 Cl

Resonance effect - Effect of substituents on acidity Same as inductive effect, if the resonance producing group exerts minus effect that is, if it withdraws electrons, it raise

After making an ester by heating a carboxylic acid with alcohol in the presence of concentrated sulfuric acid, water is added to the mixture and the ester seperates out as oily lay

How can in understand cosy

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4

DISCOVERY OF SUB-ATOMIC PARTICLES The atomic theory of the Greek philosophers, Leucippus and Democretus (400 B.C.) held that continued subdivision of matter would ultimately yi

A house is air conditioned using solar energy.  Solar radiation heats a pressurized tank such that the temperature is maintained at 175 o C.  1500 kJ must be extracted from the hou