The purpose of boiler in thermal power plants is to covert water into steam with the help of heat energy generated by the combustion of fuels like coal, wood, oil or natural gas. Boiler systems use several types of fans to maintain air flow, recirculate air and remove exhaust gases. Based on the boiler size and air flow requirement different fans are used with varied capabilities.
Centrifugal fans and blowers have become a preferred choice for most of the industrial applications because of their relatively simpler design, durability and higher efficiency. Since a typical centrifugal fan has the capability to increase the speed of air stream coming through it, these fans are extensively used in industrial processes where large movement of air or gas is necessary. To get the desired high pressure and volume outputs, industries use different types of centrifugal fans with varied blade configurations in series and parallel arrangements. Yet, these fans may not achieve the desired airflow movement which is required for industrial process because of their reduced performance.
Routine maintenance and health check-up of the rotating equipment is essential for trouble free operation of the plant. This would also reduce the down time of the plant. It is recommended to refer the operation and maintenance manual of equipment manufacturer for any preventive measure. In case of any abnormal symptom monitored through sensors, should be attended immediately before the problem gets aggravated.
In many large scale industries centrifugal fans of high capacity provide optimal and cost effective solutions to deliver high pressures of airflow for various process applications. Generally, to get the desired high pressure and volume outputs, industries install two or more centrifugal fans in the series or parallel combinations. Sometimes, the option of multiple fans in the industries, may not be feasible due to limited availability of space in the working area. Hence to meet the demands of large scale applications in industries, a single heavy duty centrifugal fan can be used with high power rating. There are mainly two types of heavy duty fans that are widely used in industries, namely double inlet centrifugal fan and multistage centrifugal fan.
Cement industry is one of the major markets for industrial fans. Fans in cement industry are heavy duty and perform two basic functions i.e., supply of air or removal of exhaust gases and material handling. There are many process fans that find applications in cement industry such as raw mill fans, induced draft fans, cooling fans, raw mill exhaust fans, coal mill fans and cooler exhaust fans.
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.