In power plants and most production enterprises, centrifugal fans are required to form an air supply system to provide the necessary air volume for boilers. However, due to the differences in the production capacity of each enterprise, it is not necessary to select the corresponding type of fans to achieve energy saving. Efficient operation, especially after long-term operation of fans, requires maintenance and energy-saving transformation to achieve the purpose of low-consumption and high-efficiency production.
1) Energy saving transformation method of centrifugal fan
1. Transformation of fan duct system
Generally, the piping system of boiler fans mainly includes fans, air inlets, diffusion sections, filters and heating devices, as well as related accessories such as flues, air ducts, mixing sections, mufflers and filters, which directly affect the performance of centrifugal fans. Depending on the relative resistance of the system, when carrying out energy-saving renovation, the flow field at the inlet and outlet of the fan should be uniform, and the performance of the fan should not be affected by the relevant system effects, and the flow resistance of the system should be reduced as much as possible. As follows:
(1) The arrangement of the relevant pipes must ensure that the airflow can enter the impeller evenly when passing through, and fill the inlet section of the impeller;
(2) The air outlet should be set with a straight pipe section of 3 to 5 times the pipe diameter, especially when the installation position is limited and turning and diversion are required, a forward elbow should be used, and guide vanes should be reasonably set in the elbow to ensure Air flow is smooth, and the shunt branch remains sleek when overdone.
2. Air leakage transformation of fan system
The air leakage locations of the entire centrifugal fan system include air leakage from the preheater, air leakage from the boiler, air leakage from the air and smoke ducts, and air leakage due to lax closing of the damper. In addition, it is necessary to observe and analyze the temperature changes at the inlet of the fan and the related flow changes, and then timely detect the air leakage of the wind and smoke system, and take effective measures to block the leakage.
3. Adjust the resistance of the fan system
Control the resistance of each related equipment in the centrifugal fan system within an appropriate range. During operation, the resistance of each equipment in the fume and smoke system is detected, especially the resistance changes of the muffler, air heater, preheater and dust collector, etc., to control the resistance increase not too fast:
(1) Muffler: The resistance should be kept at 200Pa, and should be checked immediately when it exceeds 400Pa;
(2) Air heater: The resistance should be controlled at 300Pa, if it exceeds 500Pa, measures such as soot blowing should be put in, and when it is greater than 800Pa, it needs to be shut down;
(3) Air preheater: When the flue gas resistance exceeds 1300Pa, the soot blowing frequency should be increased. If it exceeds 1500Pa, the equipment will not be able to operate, the centrifugal fan should be stopped, and the preheater should be thoroughly cleaned;
(4) Dust collector: the resistance should be controlled below 300Pa;
(5) Mist eliminator: The resistance should be controlled below 200Pa.
2)Precautions for energy-saving renovation of centrifugal fans
1. Before the transformation of the centrifugal fan, the air leakage should be controlled first, and the process operation should be optimized to achieve a stable and good production state as much as possible.
2. In the actual normal operation, the system operating conditions also change, so when selecting the model, most of the actual operating conditions should be in the high-efficiency area of the performance curve.
3. During the selection of centrifugal fans in the process design stage, the operating conditions of the fans should be calibrated several times, and the data intervals such as air volume, air pressure, medium temperature, and dust concentration required for the normal operation of the system should be grasped as much as possible. The margin (5%~10%), but the air volume demand for extreme working conditions should not be considered in the fan selection factor.
4. In the design of energy-saving retrofit of fans, changes in civil foundations and fan interfaces should be minimized. One is to save investment and reconstruction time; the other is to replace the original fan after the failure of the pre-fan reconstruction to keep the production running normally and reduce the risk of failure.
5. Since the full-pressure efficiency of the fan after the transformation has a strong calibration and a large error, it can be agreed with the fan manufacturer to convert it into a visual assessment and settlement based on the reduced value of the motor operating power after the transformation. If the total pressure efficiency of the fan after the transformation is lower than 70%, it can be regarded as a failure of the transformation of the high-efficiency fan.
6. After the centrifugal fan is installed with a frequency converter, if there is no special need, the air volume control valve of the fan inlet and outlet should be removed, and the air volume should be adjusted by adjusting the fan speed as much as possible to reduce the system resistance and reduce the fan consumption.
