Optimized transformation of compressed air system of 2X350MW unit Huaneng Ruijin Power Plant Wen Zhihua Nie Yunfeng Yang Xingbing Yao Jinhua Xiao Qingyun System optimization, such as pressure, energy saving and consumption reduction, thus improving the reliability and economy of the entire compressed air system.
The compressed air system of the power plant is a very important public system. It provides automatic control instrument gas, ash removal gas and heat engine for miscellaneous gas for the whole unit operation. Its reliability directly affects the safety and reliability of the unit. In addition, the power consumption rate of the compressed air system is about 0.33%, which accounts for about 6% of the power consumption of the plant. Therefore, the optimization and transformation of the compressed air system is of great significance for energy saving and consumption reduction.
The compressed air system of 2X350MW supercritical coal-fired unit of Huaneng Ruijin Power Plant is controlled by the mother. It is designed as the L-200 type oil-injected screw air compressor produced by Shanghai Kangpu Air Compressor Co., Ltd., with a single output of 36.6m3. /min, the operation mode is 3 transport 2 standby. Compressed air is divided into 3 channels for the whole plant to produce gas: one way is treated by two combined dryers with a power output of 42m3/mm, and the other is supplied by the 42m3/mm refrigerating dryer. The gas is removed from the ash; the last one is directly taken out from the outlet of the air compressor as a heat engine to repair the miscellaneous gas. The instrument air dryer and the ash purifier are two independent systems. The compressed air volume is designed to be 25m3/mm, and the compressed air volume is 33.6m3/min. The compressed air system is shown in the figure. Shown.
System operation performance parameters: air compressor output 36.6Nm3/min, exhaust pressure 0.75MPa, air compressor outlet air oil content <3ppm, air dust particle diameter <2pm, air dust content <2ppm, lubricating oil return oil Temperature <70 2 Compressed air system problems 2.1 System design defects 2.1.1 Instrument gas output is not enough Because the 2X350MW supercritical unit compressed air system is designed according to the requirements of 2X 300MW subcritical unit, so that a single drying The gas supply of the machine cannot meet the normal gas consumption.
2.1.2 Poor system reliability The cooling water pipeline is connected directly from the industrial jellyfish pipe to the air compressor room. The pipeline is long. When the cooling water pipeline fails during operation, the entire air compressor system will be cooled. The factory air compressor system is deactivated.
The five air compressor outlets are connected to the compressed air main pipe, and each air compressor outlet has only one manual door. When the manual door fails, it cannot be isolated.
The compressed air mother pipe does not have a hydrophobic point. If the water in the pipe is not discharged in time, it will affect the quality of the compressed air.
The flow rate and pressure of the cooling water are not monitored and the cooling water operation cannot be judged.
2.2 Equipment design defects The automatic drain device installed behind the regulating valve under the air compressor separator is a floating ball type. This valve has poor stability and is prone to failure.
Due to the large amount of sewage discharged from the dryer, the automatic blowdown float valve is often blocked.
There is no bypass at the outlet of the combined dryer, and the pressure of the compressed air is reduced during the troubleshooting, which directly threatens the safe operation of the system.
2.3 Problems in the operation of the system The air compressor has a high exhaust temperature and frequently trips. The main reason is that the air quality of the air compressor cooling water is poor, the heat exchanger surface of the cooler is severely fouled, the heat exchange effect is poor, and the cooling water return water temperature is increased.
Compressed air system instrument air pressure is low, often below 0.55MPa, the main reasons: First, the compressed air storage tank capacity is insufficient; Second, the economizer pump pump ash pipe routing original design is connected to the electric precipitator an electric field After the ash pipeline is sent to the ash silo, it is sent directly to the ash silo, so that the ash removal gas volume is increased. 3 The optimization of the compressed air system 3.1 Optimizing the improvement of the system operation reliability The cooling water pipeline is increased by the equipment pipeline. . From the industrial jellyfish pipe, another pipe is introduced to the air compressor room as a backup pipe for the cooling water pipe to ensure the normal supply of cooling water.
Rice uses closed water as a backup cooling water source for air compressors and freeze dryers.
In order to improve the quality of the cooling water, avoid the high temperature of the air compressor and cause frequent jumps, the cooling water pipeline is modified, and closed water is used as the backup cooling water source for the air compressor and the cold dryer. The water quality of the cooling water is too poor. In an emergency situation, make an emergency backup.
A pressure gauge is installed on the cooling water inlet pipe, and a thermometer is installed on the return pipe to monitor the running state of the cooling water in real time.
The compressed air main pipe is fitted with a trap. In order to discharge the accumulated water in the air compressor room trench, the trench is led to a lower position outside the machine room.
Install one manual door at the outlet of the air compressor. When the air compressor outlet valve is faulty, ensure that the compressed air main pipe does not leak air. In normal operation, the valve on the side of the main pipe is open.
The air compressor separator drain valve is changed from floating ball type to electric control valve to improve its reliability and ensure timely discharge of sewage.
Manual shut-off valves are installed on the air compressor outlet mother pipe and the ash removal and instrument compressed air mother pipes respectively, so as to facilitate the normal operation of the system when the system is installed in the future.
3.2 Optimizing the improvement measures of gas quality The gas quality is mainly reflected in the system output, exhaust pressure, air oil content, dust particle diameter, air dust content and other indicators meet the design requirements.
Ensure that the instrument uses the output and pressure of compressed air. Since the instrument air volume is designed according to the requirements of the subcritical unit, the gas consumption of the single dryer can not meet the normal instrument air supply. Therefore, a connecting pipe and pipe are added between the ash air main pipe and the instrument gas pipe. Use 0133X4mm stainless steel tube and install 1 manual door. When the normal operation, the communication door is closed. When the instrument uses insufficient air output or insufficient pressure, the contact door is opened, and the ash is temporarily replenished with compressed air to ensure the air of the instrument. Normal air supply and maintenance air pressure. At the same time, a check valve is added to the pipeline to prevent the instrument from flowing back with compressed air when the door is opened.
Ensure the output and pressure of compressed air for ash removal. Due to the change of the ash conveying pipeline of the economizer tank pump, the amount of compressed air for ash removal increases, so that the air compressor needs to be equipped with 4 transports and 1 when the double machine is running. If one dryer is in the repair state, the other one fails. It will seriously affect the safe and stable operation of the system. Therefore, a refrigerating dryer and an air compressor are installed in the air compressor room to meet the requirements of the system 4 operation and maintenance.
Control air oil content and dust content. In view of the problem that the dryer has a large amount of sewage and the automatic blowdown float valve is easy to block, the automatic blowdown float valve of the dryer is replaced with an electromagnetic blowdown valve, and the sewage discharge is timed, and the number of manual discharges is increased to ensure the quality of the compressed air.
Further stabilize the compressed air system pressure to further optimize the operating parameters of the air compressor to ensure reasonable loading and unloading of the operating air compressor.
After the air compressor room, an instrument compressed air storage tank and a compressed air storage tank for ash removal are added to increase the gas storage capacity to stabilize the gas pressure.
An electric door is installed on the intake pipe of the gas storage tank for maintenance, which can be controlled locally and remotely. When the exhaust pressure of the air compressor main pipe is low, the gas for maintenance and ash removal and the gas source for the instrument are quickly cut off. open.
The bypass of the combined dryer is added to avoid the pressure of the compressed air used in the instrument during troubleshooting.
3.3 Optimization and improvement measures for system energy saving and consumption reduction Compressed air system is much more complicated than water pump and fan system, and there are more energy saving methods. At present, mainly frequency conversion is the main, but the frequency conversion investment is higher, and the energy saving is not the same as the rotational speed cube. In proportion, the frequency conversion is not the preferred energy-saving technology for compressed air systems, but should be optimized from the process and operation of the entire system to achieve energy savings.
The compressed air system uses centralized control and intelligent automatic adjustment. The air compressor has the function of adjusting the intake valve, that is, 60% 100% air volume automatic adjustment, delay automatic stop and automatic start three kinds of air volume adjustment mode. Any air compressor can be arbitrarily set to run, run standby, and overhaul. The standby operation mode automatically starts the standby air compressor when the running air compressor fails or the pipe network pressure is too low.
It is planned to install a special high-efficiency energy-saving control system at the air compressor station to make the system operating pressure more stable, which can basically eliminate the frequent loading and unloading conditions of the compressor, reduce the power consumption of the air compressor by 25% and 35%, and save more than 3 million electricity per year. kW.h, equivalent to saving more than 950t of standard coal, the energy saving effect is obvious.
4 Conclusion After the cooling water pipeline is added to the equipment pipeline, the compressed air mother pipe is installed with the steam trap, the closed water is used as the backup cooling water source, and the cooling water operation status is monitored immediately, the compressed air system is improved. Sex.
By installing one refrigerating dryer and one air compressor, adding one instrument gas storage tank and one gas storage tank for ash removal, in the ash removal air mother tube and the instrument gas carrier tube After adding one way of connecting pipelines, adding bypass to the outlet of the combined dryer, and further optimizing the operating parameters of the air compressor, the quality of the gas used in the compressed air system is improved.
The centralized control and intelligent automatic adjustment method can help the compressed air system to save energy and reduce consumption; after installing the special high-efficiency energy-saving control system in the air compressor station, the energy-saving effect of the system will be more significant. mouth
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