Analysis and treatment of the cause of air compressor surge

Surging will occur, so that the compressor will not work properly, and a slight mistake will cause a serious accident. This paper introduces the main factors of surge occurrence during the working process of the centrifugal centrifugal air compressor of the power center of Guixi Smelting Plant of Jiangxi Copper Group, and compares and analyzes the surge control method.

The Jiangxi Air Group's Guixi Smelter 1 power center's miscellaneous air compressor has 7 sets of equipment details. 1. This paper mainly introduces 4 centrifugal miscellaneous air compressors, all of which are oil-free grade compression.

During the operation of the centrifugal compressor, when the load is reduced to a certain level, the gas discharge will oscillate strongly, and the fuselage will vibrate violently and emit asthma or squeak. This phenomenon is called the surge of the compressor. The number of surges in the centrifugal air compressors has increased, which seriously jeopardizes the safety of the equipment and the stability of production. For this reason, we analyzed the following six factors for the occurrence of surge: 1 flow rate decreases with flow. The outlet pressure of the compressor gradually increases. When the maximum outlet pressure at the speed is reached, the unit enters the surge zone, the compressor outlet pressure begins to decrease, the flow rate also decreases, and the compressor is prone to surge, in actual production. Try to avoid the compressor running under low flow conditions. It is generally believed that the compressor should be lower than the design flow rate at the minimum flow rate of 60.

2 Gas relative molecular mass centrifugal compressor Under the same rotating speed and relative molecular mass and constant pressure operating conditions, the smaller the relative molecular mass, the more likely the surge will occur.

3 inlet pressure Under the operating conditions of constant pressure of the compressor, the lower the inlet pressure, the more likely the compressor is to surge. This is also the reason why the filter should be replaced in time when the differential pressure of the inlet filter increases.

4 inlet temperature constant pressure constant speed constant gas inlet temperature is higher, the more prone to surge. Therefore, for the same centrifugal compressor, summer is more prone to surge than winter.

5 speed turbo-driven compressors often run at different speeds according to different flow requirements of the outside world. Under the condition of the external air volume, the higher the speed, the more likely the surge will occur.

In summary, the root cause of surge is that the flow rate of the compressor is too small, less than the minimum flow of the compressor or because the back pressure of the compressor is higher than its maximum pressure, causing serious gas rotation separation inside the machine; The pressure on the pipe network is higher than the pressure provided by the compressor, causing the gas to reverse and generating a large flow pulsation.

6 Failure of the anti-surge system When the air compressor enters the surge condition, the anti-surge measures set at the end can be effective or the operation is delayed, so that the air compressor enters the surge.

In view of the causes of surge and the operation in recent years, 1 the power center has taken the following preventive measures and improvements for anti-surge.

6.1 When the inlet pressure is too low, it is prone to surge. This is mainly to check the pressure difference of the air filter. The pressure difference of a person like 38 should be less than 200, 20. If such a pressure difference is reached, the filter cloth and the filter core Is there a blockage and replacement in time?

6.2 When the inlet temperature is excessive, the surge is likely to occur, mainly because the atmospheric temperature is too high in summer, and the heating center of the power center fan room is more. In response to this situation, we added a water spray device to cool the east and west gates of the fan room, and installed a water spray device on the roof of the fan room to increase the cooling fan in the plant to achieve a fixed effect, but the inlet temperature is still relatively high. High, at this time we take the small tube from the outlet of the 45 dehumidifier to the inlet pipe of the centrifugal air compressor. The outlet temperature of the dehumidifier is low, which has a good effect on reducing the temperature of the inlet air.

6.3 The change of system pressure will also affect the surge. Our improvement measures are to connect with the miscellaneous pipeline of the 2 power center to make the pressure more stable. With the change of pressure, the small miscellaneous air compressor will be opened or closed in time. , adjust system pressure. This works well in normal operation.

6.4 When the air is compressed, the moisture in the atmosphere condenses into water. Because the inhaled air contains a small amount of copper concentrate powder, the powder contains a certain amount of sulfur and sulfide, and chemically reacts with water at a constant temperature to form acid. The cooling chamber of the air compressor is made of cast steel, which reacts to form iron oxide and falls off from the surface, which affects the cooling effect. Due to the serious blockage of the fins of the intercooler, the air path is not smooth and it is easy to cause surge. The anti-corrosion materials with high temperature and high pressure are sprayed in the interior of the intercooler in a targeted manner. From the operating conditions, the effect is better.

6.5 Single-parameter method Partial airflow deflation method When the compressor intake air volume is reduced to near the working condition, the flow sensor transmits a signal to the servo motor to generate an action-manipulating actuator, that is, the anti-surge vent valve is opened. Then part of the airflow is emptied, the compressor back pressure is immediately reduced, the flow rate is automatically increased, and the operating point is far away from the surge condition. This method will waste part of the compression work and lose some of the gas in vain.

6.6 According to the standardized operation, when the compressor is started or stopped, it is easy to cause the system pressure to change, which is easy to cause surge. Start up first, then slowly load the boost, when the machine is shut down, first open the standby machine, then step down and stop. Strengthen the hydrophobicity of the air bag.

6.7 In response to frequent air compressors, the power workshop contacted the manufacturer's technicians to conduct a surge test on the site, and plotted the actual surge curve of the air compressor and then compared it with the built-in anti-surge slope of the air compressor. The surge slope is indeed too low, resulting in a large venting area, which affects the utilization of the air compressor. Through the careful discussion of the workshop leaders and electromechanical technicians combined with the manufacturer's recommendations, it was finally decided to appropriately increase the anti-surge slope of the air compressor, feed the venting area, expand the normal working range of air pressure, and modify the curve.

Gao Shenqin. Chemical machinery 晟. Beijing Chemical Industry Press, 1992.

Xu Zhong. Revised principle of centrifugal compressors. Beijing Machinery Industry Press, Wei Long, Chang Xinzhong and so on. Centrifugal compressor surge analysis and example knives. General Machinery, 2003.

Gu Feng. Centrifugal Compressor Flow and Surge Control 1. Chemical Equipment and Pipeline, Jiangxi Copper Group Lead Zinc Metal Co., Ltd. is engaged in technical management.

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