300MW; generator set; instrument compressed air system; air compressor Guangzhou Zhujiang Power Plant has a total installed capacity of 4X phase instrument compressed air system equipped with 6 domestic LW-10/7 oil-free lubricating air compressors and related ancillary equipment, It mainly provides control gas for the instrument, valve device and actuator of the generator set. Since the unit was put into production, due to factors such as too small spare capacity of the compressed air system, high failure rate of the air compressor, and abnormal air cooling system of the air compressor, the pressure of the compressed air system is unstable, causing some equipment of the generator set to lose control. In 1995, two units had tripped at the same time due to low pressure in the compressed air system. In order to solve the problems of the compressed air system of the instrument and improve the reliability of the system operation, through the system analysis, the compressed air system and the air compressor cooling water system were improved and improved, and the air compressor was modified to meet the expectations. effect.

1 Quality requirements of compressed air In modern large-scale power plants, with the continuous improvement of unit control technology, the compressed air system of the instrument is required to have high stability and reliability, and the quality of compressed air must meet the pressure requirements ((0.62~ 0.72) MPa), no oil, no water. Only the system continuously provides qualified compressed air, so that the actuator can accurately and effectively control the generator set related equipment according to the system command, in order to ensure the safety and economy of the generator set. 2 According to statistics, the instrument compressed air system since April 1993 During the period from October 1999 to October 1999, the average annual pressure of the compressed air system caused by faults or defects caused the unit to trip or reduce the load for 9 times, of which the air compressor failed 5 times and the compressed air system spare capacity was too small. The cooling water system failed twice, which seriously affected the safe and economic operation of the generator set.

2.1 The system spare capacity is too small. The first and second phases are equipped with 6 domestic LW-10/7 oil-free lubricating air compressors and their ancillary equipment, and supply compressed air for two 300MW generator sets. The first and second phases of the compressed air system operate independently. The rated air displacement of a single air compressor is 10m3/min. According to the original design requirements, in 6 air compressors, 2 sets, 2 sets of spare parts, 2 sets of overhauls, but due to the large amount of gas used in the system, usually 4 sets are required. The operation can meet the requirements of normal instruments, so that only 2 spares or repairs can be made. When there are more than 3 air compressors failing or the output is insufficient, the system pressure cannot be guaranteed, and there is a problem that the system spare margin is too small.

2.2 Air compressor failure Multi--10/7 air compressor is a two-stage two-cylinder double-acting water-cooled oil-free lubrication air compressor. The motor and compressor are driven by the triangular skin. The valve of the valve group of the compressor is in operation. Easy to break, the spring deformation valve group sealing surface, piston ring, support ring and other components are easily damaged, and the pressure regulator fails, the transmission wheel is broken, the crankshaft is damaged, the cylinder is broken, the V-belt is burnt, and so on. In the spring and summer, the air is humid, which may cause short circuit of the open motor coil. The motor has been burnt twice, causing the air compressor output to be reduced or stopped.

2.3 Air compressor cooling water system problem The first and second stage air compressor cooling water use the first and second phase closed circulating cooling water, and the same air cooling machine shares the same circuit cooling water, and each air compressor The cooling water is the first and second stage cooling water and the first and second stage cooling water. The system is complicated. When the main pipe or branch pipe and its valves are leaked or damaged, the cooling water system must be stopped to be disposed of. As a result, the chances of the air compressor being forced to stop when it loses cooling water are high.

2.4 System Pressure Fluctuation The pressure regulator of the air compressor of the original instrument uses a spring-type mechanical regulator, the air source is taken from the system compressed air, and the d10 carbon steel pipe is connected with the regulator to open the opening of the first-stage cylinder intake valve. Control, to achieve the purpose of controlling system pressure. Due to the large amount of impurities in the pipeline, the pressure regulator often fails or is damaged, and the system pressure is out of control. Later, the system pressure adjustment was performed manually by manually operating the first-stage cylinder intake valve opening, and the manual operation adjustment caused the pressure fluctuation of the compressed air system to be large.

3 compressed air system reliability analyzer compressed air system is composed of pipeline valves, air compressors, air compressor motors, buffer tanks, dryers, cooling water system pipeline valves, gas storage tanks, control equipment, etc., compressed air system The process is as shown.

It can be seen that the failure of a certain equipment will affect the stable operation of the compressed air system. In addition, system reliability is closely related to system backup margin. According to the statistics of faults or defects in the annual compressed air system, the air compressor failure is the main cause of the system reliability reduction, followed by the compressed air system backup margin is too small and the cooling water system is faulty.

4 Improvement measures According to the problems existing in the compressed air system and the actual situation on the site, the following improvement measures were taken through reliability analysis: (1) Through investigation, according to the actual gas consumption of the compressed air system and the actual situation at the production site After calculation and comprehensive analysis, it was decided to change 12 domestic LW-10/7 air compressors to 4 Belgian Atlas Copco GA200W fixed screw air compressors.

(3) Optimize the air compressor cooling water system, cut off the connection with the cooling water of the miscellaneous air compressor, and use the primary circuit cooling water alone.

5 instrument with compressed air system to improve the effect of the machine, the total capacity of 160m3 / min, mainly to provide equipment maintenance gas, the air compressor most of the time is in standby state. Through the communication with the miscellaneous compressed air system, the spare margin of the compressed air system is increased by 1.3 times, which improves the safety of the system operation.

It has the characteristics of less quantity, high efficiency, low noise and high degree of automation. Since it was put into operation in August 1999, the system has been running stably, and there are basically no defects or failures. It only needs to be regularly maintained according to the relevant maintenance and maintenance requirements. The reliability of the press operation.

The brain controller inputs the operating parameters into the computer and automatically adjusts and controls the compressor according to the parameter requirements. The pressure adjustment range (0.62~0.72) MPa system pressure changes gently, fully meets the specified requirements, which is beneficial to the stable operation of the controlled equipment.

(Continued on page 67) Revert back to the control target area. The entire adjustment time takes about 6 minutes. Finally, the water level is kept within the range of (10-10 cm), and the decay rate X is about 67%. It can be seen that the feed water regulation performance of No. 2 furnace can gradually approach the target after single shot oscillation. value.

4 Conclusions For the situation that the load rejection of the No. 1 and No. 2 waste incinerators of Qiaosi Power Plant is large, and the adjustment precision of the water supply regulating valve actuator is low and the adjustable range is small, in the conventional three-stroke cascade water level control mode On the basis of the introduction, the fuzzy control strategy is introduced to adjust the PID control parameters, emphasizing the separation of the PID control parameters when the controlled parameters are in different ranges, and implementing the asynchronous control mode for the inner and outer loops in the cascade loop. The debugging results show that under this control mode, the performance parameters such as adjustment time, attenuation rate and overshooting amount all meet the needs of actual operation.

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