In power plants the heat energy is generated by boilers. Boilers use industrial fans for the following reasons:
- To supply air required for combustion
- Remove products of combustion
- Deliver fuel to the burners
- Circulate gases for the better heat transfer
Depending on these four functions, fans in power plants are divided into three main types. They are draft fans (induced draft fans, forced draft fans), primary air fans and gas recirculation fans.
A centrifugal fan system loses its optimum quality after a certain period of time. So, it is necessary to perform retrofitting in centrifugal fans to boost the efficiency and performance. The main purpose of retrofitting the centrifugal fan is to increase the flow rate, regulate the variations of static pressure, reduce power consumption and improve the fan speed & efficiency. Retrofitting also has some indirect benefits such as it saves the additional cost, improves fuel efficiency (when run by petroleum liquids), increases productivity of plant and helps in balancing the environment.
Variable pitch axial flow fans are special type of axial fans with adjustable impeller blades that are built to handle broad operating ranges in critical industrial applications. These fans include an internal mechanism that can automatically adjust blade angle while the fan rotor is in motion. Due to their compact design and high efficiency, most of the variable pitch axial flow fans find applications in the thermal power stations where fresh air is needed (forced draft) or process involving high temperatures such as in boilers (induced draft). These type of fans are proven to have negligible loss in power at the output and hence they are also used in pulverizer air fans and flue gas desulphurization (FGD) applications.