ID/FD FANS IN COAL-FIRED POWER PLANTS
                     ID/FD FANS IN COAL-FIRED POWER PLANTS
Neel Rao
Writes on Reitzindia Induced draft fan and 
Reitz India's ID Fans and FD Fans.
Coal-fired power plants have boiler systems where different types of industrial 
centrifugal fans are needed. While some of these fans supply adequate air to 
facilitate combustion in boilers, others remove the exhaust smoke or fumes from the 
chamber. This way, the air, and gases are circulated to ensure optimal heat transfer. 
The type of fans to be used depends on the size of the boiler in coal-fired power 
plants and the necessary airflow.
The commonly used draughts fans include induced and forced draft industrial 
process fans.
The article uses the words draught and draft as synonyms while describing the 
industrial process fans. In this article, we are going to discuss how these types of 
fans come in handy in coal-fired power plants.
What are induced and forced draught fans?
Before explaining what these two types of fans do, let’s understand why power 
plants need draught fans in the first place. In coal-fired thermal power plants, 
draught fans are responsible to maintain the flow of gases in the boiler. While forced 
draft fans help in circulating air around the boiler to facilitate better heat transfer 
and combustion, induced draft fans help in drawing the exhaust gases through the 
chimney. A calculated integration of both these fans in thermal power plants 
maintains the right pressure in the chamber for the combustion to take place.
Function of forced draught fans in thermal power plants
Forced draught fans are industrial centrifugal fans. Forced draught fans are 
responsible for supplying the necessary fuel to the combustion chamber. It pushes 
the air to the furnace. These fans are present at the boiler’s inlet and push fresh air 
at high pressure into the chamber. Here, it mixes with the fuel and generates the 
necessary pressure for the combustion to take place.
In thermal power plants using coal, forced draught fans are used as secondary fans. 
This regulates the combustion process and maximizes fuel efficiency. Both outlet and 
inlet dampers are necessary for an FD fan arrangement for controlling the air 
pressure inside the system. Forced draught fans are more efficient compared to 
induced draught fans. Besides, the operating conditions are cleaner and it is easy to 
maintain these fans.
Function of induced draught fans in thermal power plants
The key difference between induced and forced draught fans lies in the way they 
operate. While forced draught fans are responsible for pushing the air toward the 
combustion chamber, induced fans pull the exhaust gases from the combustion 
chamber to the chimney. Therefore, the toxic gases from the chamber get expelled 
into the environment with the help of induced fans. This explains why thermal 
power plants place these fans around the outlet, or between the chimney and the 
dust collector. Induced draught fans create a negative pressure or a suction force to 
expel the gases from the combustion chamber.
Why are both FD and ID fans needed in coal-fired power plants?
For the thermal power plant to operate, it’s imperative to maintain the right flow of 
air. An FD fan circulates air around the combustion chamber to ensure that the 
process takes place in the right way. On the other hand, induced fans draw the flue 
gases from the chamber and ensure a healthy operational environment. Power 
plants run by coal need both these types of draught fans to operate. It balances the 
air system present in the boiler, enhancing the efficiency of the combustion process.
About REITZINDIA
Reitz India has set a benchmark to deliver high quality fans for heavy duty industries 
which can work at precise operating conditions like high temperatures and pressures. 
Reitz offer idealistic Centrifugal Fan and Centrifugal blower design that can be used in 
all large scale process industries like cement, iron & steel, power plants, fertilizers/ 
chemicals and more.
Thank you for spending your precious time in reading this article!