In thermal power plants, the transportation of fuel and the production of power generation are inseparable from the use of fans. Many thermal power plants use primary fans to supply air at the front end of the combustion equipment. There are many types of such primary fans, among which centrifugal primary fans are used more , the following editors have sorted out the working principle and characteristics of the centrifugal primary fan in thermal power plants for your reference.
1)Working principle of centrifugal primary fan
Centrifugal primary fan is mainly composed of working impeller and spiral casing. device) and other components. Its shaft is connected to the motor shaft through a coupling or a pulley and a belt. When the motor drives the impeller to rotate, the air also rotates with the impeller. Under the action of inertia, the air is thrown around and collected into the screw casing. In the process of air flowing to the exhaust port in the screw casing, due to the continuous expansion of the cross section, the speed gradually becomes slower, most of the dynamic pressure is converted into static pressure, and then it is pressed out from the exhaust port at a certain pressure.
When the air in the impeller is discharged, a certain degree of vacuum is formed in the center of the impeller, and the air outside the suction port is sucked into the impeller under the action of atmospheric pressure. The primary fan transfers energy to the air through the rotation of the impeller, so as to achieve the purpose of conveying air. The suction port (inlet) of the centrifugal fan is negative pressure, and the exhaust port (outlet) is positive pressure, so it can not only blow air into the boiler of the thermal power plant, but also draw air (or exhaust air) from the furnace.
2) the characteristics of the centrifugal primary fan
1. High wind pressure: Because the primary air not only plays the role of drying and supporting combustion, but also needs to send a large amount of pulverized coal into the furnace, and must be fully mixed with the pulverized coal in this process. There needs to be enough wind pressure to maintain power. Compared with the axial flow fan, the centrifugal fan itself has a higher wind pressure, and the adjustment method is also simpler.
2. Large flow rate: The fuel delivery and combustion support can be completed only with a large enough air flow rate. During the operation of the centrifugal fan, the flow rate is generally proportional to the speed of the impeller, and the size of the impeller The larger it is, the greater the flow rate, while having a smaller footprint than an axial fan.
3) The role that centrifugal primary fans can play
1. Heating and drying the pulverized coal: The primary air heated by the air preheater is sent to the pulverizing system for preliminary heating and drying of the pulverized coal, and provides power for the pulverized coal. It is sent into the furnace through the powder pipe for coal burning.
2. Seal the pulverizing system: Some thermal power plant boiler sealing air is taken from the primary air main pipe and passed into the coal feeder to seal the equipment and prevent pulverized coal. leakage.
3. Preliminary combustion support for the fuel: The pulverized coal and the primary air are fully mixed in the fueler and sent to the furnace to help the pulverized coal burn.