What is Boiler Efficiency ? How Boiler Efficiency can be Improved?

Boiler Efficiency:

It is the ratio of the quantity of heat utilized actually by the water and steam for producing the steam to the quantity of heat supplied in the furnace.

Where,    

m_e = Mass of water actually evaporated or actual evaporation in Kg / Kg of fuel.

C = Calorific value of fuel in KJ /Kg of fuel.

m_s = Total mass of water evaporated into steam in Kg.

m_f  = Mass of fuel in Kg

So,  m_e = m_s / m_f

Boiler Efficiency can be improved by:

1. using economizer: heat of the flue gas coming out from the chimney is recovered to preheat the feed water, thus economizing the cost of fuels. Flue gas from chimney is allowed to pass over coils (tubes) of water inside, water being heated by heat transfer.

2. using air pre-heater: a system of preheating the air before being drawn by the burner. This preheating is done by heat recovered from flue gas going out through chimney.

3.  soot blower: blowing off of soot (carbon deposit etc.) from the body of boiler tubes, drums shell to regain heat transfer capacity. 

4. descaling the boiler shells, tubes etc.

5. ensuring complete combustion of the fuels being burnt.