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
Ammonia is a gas for which reliable analytical methods are available to explain concentration in other gases.  To measure ?ow in a 15 inch schedule 40 natural gas pipeline, pure am

Q. Explain about Electron-Dot Structures? Write an electron-dot structure for a impartial atom of arsenic an element used in semiconductor materials because of its electron con

The stability of a complex relies on 1. Nature of central ion:  the word nature means the charge density on the central ion i.e. greater is the charge density or larger the c

Semisynthetic polymers These polymers are mainly derived from naturally taking place polymers by chemical changes. Since cellulose is naturally taking place polymers, cellulose

Wavelength associated with electron motion: (1) Increases with increase in speed of electron   (2)Remains same irrespective of speed of electron (3) Decreases with increa

electronic vinyas of led

what happens to the reaction rate when the concentration changes

Hello. PVC processors use a very high molecular weight acrylic processing aid for production of Rigid PVC foamsheet of high thickness. I would like to know the type of Acrylic mate

The order of reaction is the number of moles whose concentrations verify the rate of a reaction at a given temperature

radioactive decay order