è‚€*High Bureau Water Public Centrifugal Air Compressor Application in Guohua Taishan Power Plant B Plant Zhang Jiliang Niu Zhenhua (Guangdong Guohua Radio Mountain Power Co., Ltd., Taishan 529228, Guangdong Province, safety and economy, occupied in the system of the unit More and more important position. The article explains the structural characteristics, control methods and strategies of centrifugal air compressor from the perspective of thermal maintenance, and also analyzes the problems and solutions encountered in the operation of centrifugal air compressor. .

Control Strategy 1 Overview Units 6 and 7 of Guohua Taishan Power Plant B Plant jointly set up 5 centrifugal air compressors and their aftertreatment system equipment, including 3 sets of operation, 1 set of hot standby and 1 set of maintenance. The hot spare air compressor is required to quickly input the air compressor of the hot standby when the outlet pressure of an air compressor in operation is lowered and the shutdown standard is reached. If the hot spare air compressor cannot be put into service, immediately start the maintenance of the spare air compressor.

Centrifugal compressor means that the movement of gas in the compressor is in a radial direction perpendicular to the axis of the compressor. During the rotation of the working wheel of the compressor, the pressure of the gas is increased and the speed is increased due to the action of the centrifugal force of rotation and the diffusing flow in the working wheel. The speed energy is then further converted into pressure energy in the diffuser, through which the pressure of the gas can be increased to meet the demand for compressed air during operation of the unit.

2 Structure of centrifugal air compressor 2.1 Flow chart of compression process of centrifugal compressor Centrifugal air compressor is a three-stage compression, two-stage cooling machine. The air is first sucked by the air inlet through the first stage of compression and then enters the primary cooler for cooling. After the second stage of compression, it enters the secondary cooler for cooling, and then is compressed by the third stage to reach the required pressure, and finally after the cooling. The device provides the user with clean, high-pressure air that is completely oil-free below 40*C.

2.2 Structural characteristics of centrifugal air compressor The general centrifugal compressor consists of the following parts: suction chamber, intake deflector, impeller, diffuser, curve and return, volute, seal and lubricating oil system, etc. . The centrifugal air compressor used in our factory is three-stage compression and two-stage cooling. The air is first sucked by the air inlet through the first stage of compression and then enters the primary cooler for cooling. After the second stage of compression, it enters the secondary cooler for cooling, and then is compressed by the third stage to reach the required pressure, and finally after the cooling. The device provides the user with clean, high-pressure air that is completely oil-free below 40*C, and the flow is as shown. The system diagram of the centrifugal air compressor system: Centrifugal air compressor frame centrifugal air compressor control strategy 3.1 Control system introduction The air compressor PLC control system adopts Siemens S7-200, including its own start/stop, interlock control, etc. The chain between the air compressors is completed by DCS. The two-way data communication interface MODBUS (RS485) communication protocol is used between the DCS and the DCS to complete the communication by addressing the address table. The air compressor's own running/starting and stopping status, air compressor remote/local control status, pressure, temperature and vibration signals can be communicated to the DCS and can accept signals such as start/stop commands.

3.2 Centrifugal air compressor control mode Single air compressor has four control modes: basic control mode, air intake throttle mode, intermittent mode control mode and automatic dual mode control mode. In combination with the actual situation of Units 6 and 7 of Taishan Power Plant B Plant, only the first two control modes are used: basic control mode and air intake throttling mode.

3.2.1 Basic control mode. The basic control mode maintains the set pressure of the compressor by adjusting the unloading valve. When the plant air demand is reduced, the unloading valve opens to remove excess gas. The motor current is designed to be maintained by adjusting the intake control valve/vane. The exhaust pressure and the maximum motor current must be set in the basic mode operation.

The characteristic curve is as shown: Basic mode 3.2.2 Intake throttling mode. The air intake throttling mode reduces the motor current by air intake throttling while meeting the requirements of the plant air system. This mode is similar to the basic mode except that it is throttled when the plant air system needs are met. The intake control valve/vane can throttle the intake air until the minimum current set point is reached.

If the plant system demand continues to drop, the unloading valve will automatically adjust to maintain the set pressure. The exhaust pressure, maximum motor current, and minimum motor current are required for the air intake throttle mode operation. The characteristic curve is as shown: air intake throttle mode 4 centrifugal air compressor thermal protection centrifugal air compressor. When the following conditions occur during operation, the compressor will automatically shut down to ensure the safety of the air compressor equipment: too high Inlet air inlet temperature; low oil pressure; low speed pinion excessive vibration; high speed pinion excessive vibration; microprocessor failure; manual emergency trip; motor current sensor failure; oil pressure sensor failure; oil temperature RTD failure The system pressure sensor fails; the intake air temperature RTD fails; the low speed pinion vibration sensor fails; the high speed pinion vibration sensor fails; the exhaust pressure sensor fails.

Table 1 Protection Setting Table Lubricating Oil Pressure Low Jumping Machine Low Reporting Lubricating Oil Temperature High Jumping Machine High Alarm Motor Current Low Jumping Machine Final Stage Intake Air Temperature High Jumping Machine High Alarm Low Speed ​​Vibration Value High Jumping Machine High Alarm High Speed ​​High Vibration Value Trip high alarm front bearing temperature high jump machine high report 聱 post bearing temperature high jump machine high alarm stator temperature high jump machine high alarm 5 centrifugal air compressor in operation common problems and treatment methods 1-5 centrifugal empty More than two years of application of the press in Taishan Power Plant, here are some typical and common faults and solutions encountered. It is worth noting that when the compressor can't overcome the factory air pressure, it will surge, but when the operating conditions are stable, the surge point can be avoided by ensuring the accurate setting of the minimum and maximum motor current values.

5.1 Causes of Compressor Surge: The air system has foreign matter and the intake filter is dirty. Take measures: remove foreign matter from the air system, clean or replace the filter core.

Cause: The temperature between the compressor stages is too high. Take action: Open the cooling water valve and check the cooling water temperature and flow.

Cause: The exhaust pressure is set too high. Take action: Adjust the exhaust pressure to the set value.

Cause: The maximum/small current setting is incorrect. Take action: Adjust to the set point and adjust the minimum current away from the surge point.

5.2 The compressor cannot reach the designed exhaust pressure. The exhaust pressure set value is too low. Take action: Adjust the exhaust pressure setpoint to the design value.

Cause: The unloading valve is in the manual state. Take action: Check the control mode of the valve to automatic mode.

Cause: The exhaust pressure sensor has failed. Take action: Replace the sensor.

Cause: The air system demand is too large. Take action: start another compressor.

5.3 Causes of excessive vibration: Excessive accumulation of impeller dust. Take measures: clean the impeller.

Cause: The air contains water. Take measures: Check the condensate drain “V” type groove valve, if it is blocked, it must be cleaned; check the intermediate cooler for leaks and repair or replace the bundle if necessary.

5.4 Intake or unloading valve can not operate or unstable operation Cause: The air valve of the intake valve actuator is leaky or has foreign matter. Take measures: remove foreign objects or repair the leak. Cause: The intake valve positioning link is stuck. Take action: repair or replace.

Cause: The intake valve I/P sensor has failed. Take action: recalibrate replacement.

Cause: The PID ratio band is not set to an appropriate value or the reset is not set correctly. Take action: The set point can be changed by experiment.

6 Conclusion The centrifugal air compressor of Taishan Power Plant B plant was used for the first time in Taipower, which is much better than the first phase screw machine. The first stage air compressor uses a screw type, which belongs to the volumetric compressor. The basic principle is to change the volume in the compression chamber and increase the pressure. For example, the formula: P1V1=P2V2. As mentioned above, the B plant uses a centrifugal compressor, which is a kinetic energy type. Compressor, the basic principle is to use the impeller to increase the kinetic energy of the gas, and the kinetic energy is converted into pressure energy through the diffuser. Generally speaking, a screw compressor is similar to a pumping cylinder, and a centrifugal compressor is similar to an electric fan. In principle, it can reduce the energy loss of friction and heat transfer, and the generated compressed air is completely oil-free, and can also achieve the purpose of energy saving and consumption reduction. *

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