Scale formation and sludge formation in boilers, Chemistry

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

Ans

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. Define Egg foam stability? The two factors of utmost importance in egg white foams are stability and volume. Several factors influence one or both of these characteristics


WHAT ARE THE APPLICATIONS OF LAW OF CHEMICAL COMBINATION

Q. Show the properties of Tetrahydrido borate? Tetrahydrido borate anion BH - 4 has a tetrahedral structure which can be explained on the basis of sp 3 hybridisation of boron

Molecular formula of gaseous hydrocarbons   (Eudiometry) Eudiometry is a direct method for calculation of molecular formula of gaseous hydrocarbons without ascertaining the pe


Volumetric analysis Volumetric analysis is a quantitative analysis. It includes the measurement of the volume of a known solution needed to bring about the completion of the r

Electron enters the sub-shell for which (n+l)  value is minimum. This is enunciated as: (1) Hund's rule (2) Aufbau principle (3) Heisenberg uncertainty principle (4) P

Electron transfer is the easiest type of redox process, an example being A majority of reactions of that type are very fast, but oxidation by some complexes (especially of

Q. Illustrate important catalyst of aluminium? Anhydrous AlCl 3 is an important catalyst, used in organic synthesis and in the cracking of petroleum. Al 2 (S0 4 ) 3 as such o