Coal-fired power plants rely on boilers to burn coal for power generation. If coal is to be fully burned, it is necessary to provide sufficient oxygen into the boiler, which requires an air supply device that can provide a certain pressure, flow and primary air. It is the primary fan. Various fans including centrifugal fans can provide primary air. Is the primary fan a centrifugal fan?
1) The role of the primary fan
The primary fan is one of the three major fans of the coal-fired generator boiler. Its function is to provide enough primary for the boiler combustion, for the boiler system to carry out fuel delivery, drying and sealing, as well as the power equipment for the combustion air. The specific functions are as follows:
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 boiler sealing air is taken from the primary air main pipe and passed into the coal feeder to seal the equipment. 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.
2)the requirements of the primary fan on the equipment
1. High wind pressure: Because the primary air not only plays the role of drying and combustion support, but also needs to send a large amount of pulverized coal into the furnace, and it must be fully mixed with pulverized coal in this process. There needs to be enough wind pressure to maintain power.
2. Large flow rate: This is due to the combination of the primary air transporting a large amount of fuel and the extensive role of combustion support and sealing. Only the air volume with a large enough flow can complete the fuel delivery and combustion support.
3)most of the primary fans are centrifugal fans
The requirements of the primary fan on the equipment are determined. Most of the primary fans are centrifugal fans, because the wind pressure of the centrifugal fan is higher, and the wind pressure of the axial fan cannot reach, even if the high wind pressure requirements are met. , the noise will be much larger than the centrifugal fan, under the same performance parameters, the axial fan is also larger than the installation size of the centrifugal fan. The working principle of centrifugal fan for primary fan is as follows:
When the motor of the centrifugal fan 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 impeller rotates continuously, and the air is continuously sucked in and pressed out.
