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
can dipole induce dipole forces present between non polar atom?

Determine the Coordination number (CN) of HCP  In HCP unit cell, the base centered atom touches six corner atoms in the similar plane, three atoms in a plane above and thre

what is the effectof mesomerism on aromatic compounds.

Physical Properties - Alkenes (i) Alkenes are odourless and colourless. (ii) Alkenes are soluble in organic solvents and insoluble in water. (iii) Physical state of Alken

Uses of Proteins (a) Proteins constitute as necessary part of our food. Meat, eggs, fish, cheese offer proteins to human beings. (b) In textile: Casein (a milk protein) is u


WHAT IS EBT

The combustion of propane occurs via the reaction: C3H8(g)+5O2(g)-->3C02(g)+4H2O(g) Hoe many grams of oxygen are required to burn completely 10.0g of propane?


The electronic configuration of an element is  1s 2 , 2s 2 2p 6 3s 2 3p 6 3d 5 4s 1 . This represents its: (1) Excited state (2) Ground state        (3)Cationic for