Boiler Operation - Firing

Methods of Firing a Boiler

Firing refers to the application of heat to a boiler.  Firing is done by different methods.  

Fuel fired Boilers
The most common method is by burning fuel such as wood, oil, coal or gas.

Waste Heat Recovery Boilers
These boilers function by recovering the heat from the gases or effluents of other industrial processes.  For instance, the exhaust gas from a power plant can be used to heat a boiler. 

Electrically heated Boilers
These boilers are used for heat generation.  They are not used for power generation.  They are generally of small capacity.  They can be used in hospitals for sterilizing equipment.  They can be used for laundry and for domestic heating purposes. 

Nuclear Powered Boilers
These boilers are used in Nuclear Power Plants.  The nuclear fission reaction which occurs in the reactor produces enormous amounts of heat.  This heat can be used to heat water and produce steam.  This steam is used in power plants to generate electricity or to drive submarines

Tangential Firing

Tangential Firing in Boilers is a widely used method in the combustion of fuel, usually, coal.  This method ensures efficient firing of the fuel.  The Tangential Firing method also results in reduced emissions.


In this method, finely powdered coal is blown into the combustion chamber along with air through a series of burner nozzles.  As the coal and air mixture enters the combustion chamber four burners placed in the wall tangential to the fireball are used to fire the mixture.

The method gets its name as the flame from the burners strikes the burning fireball at a tangent.  The burning mass rotates ensuring complete combustion of the fuel particles. 

 

Co-Firing

Co-firing or Co-combustion refers to the combustion of two fuels simultaneously.  For example, biomass fuel can be burnt with coal.  In paper plants, the pith, which is a byproduct of the manufacturing process, can be burnt along with coal.

The fuel which is added to the main fuel is called additional or auxiliary fuel.

Co-firing has many advantages. Co-firing is cheap as it uses fuel which would otherwise have gone waste.  This reduces the cost of steam generation.

Co-firing also has environmental benefits.  Co-firing results in more efficient combustion.  The green house gases emitted are lesser than those emitted when burning a single fuel.

In certain countries, the governments incentivize cofiring as it is beneficial to the environment.