تحليل حالة | 6 أسباب ارتفاع استهلاك الطاقة في نظام ضاغط الهواء

في الوقت الحالي, the air compressor system energy consumption accounts for about 6% ~ 9% of country’s total power generation. It ranks third in high power consumption equipment after fans and water pumps. الآن, energy is increasingly tight. Energy saving is an inevitable subject in the air compressor industry. لذلك, it is very import to control the air compressor system energy consumption.  

Compressed air system case

حالياً, the compressed air system contain the following equipment: 5 sets of oil injected screw air compressors and 5 sets of heat regeneration combination desiccant air dryers. The system design pressure is 1.0 MPa. The maximum air flow is about 7300 نانومتر 3 / ساعة. And design dew point of مجفف الهواء المضغوط≤-40℃. The air compressor pressure setting range is 0.86 ~ 0.93 MPa. The average dosage is about 3500 نانومتر 3 / ساعة. The dew point of desiccant air dryer for compressor is about -60°C. Transport them to various air sites through the pipe network. Max air flow of 1#~5# air compressors are as follows: 1152 نانومتر 3 / ساعة, 1074 نانومتر 3 / ساعة, 1074 نانومتر 3 / ساعة, 1326 Nm3/h and 2760 نانومتر 3 / ساعة. فضلاً عن ذلك, the rated power is as follows: 110 كيلوواط, 112 كيلوواط, 112 كيلوواط, 132 kW and 250 كيلوواط. فيما بينها, 1# is vsd air compressor. And 2#~5# are power frequency compressors. The rated air capacity of 1#~4# combination adsorption dryer is 1380 نانومتر 3 / ساعة. They are rated at 11.5 كيلوواط. فضلاً عن ذلك, the air capacity of the 5# combination absorption dryer is 3000 نانومتر 3 / ساعة. Its power rating is 26 كيلوواط. في الوقت الحالي, operation mode of the air compressor system is blow: 5# المكبس الهوائي + 2# أو 3# المكبس الهوائي. Three combination regenerative air dryers are running. Another 2 dryers are on standby. The energy consumption of air compressor system is about 288100 (kW·h)/month. It is equivalent to about 400 (kW·h)/ح. So the energy consumption per unit air supply is 0.114 (kW·h) /نانومتر3. Refer to JB/T 50159 “Energy Classification of Compressed Air Stations” to judge. The power consumption index is only third. Operational efficiency is very low. So there is a lot of room for improvement in system performance.  

Why is the energy consumption of the air compressor system high?

The high energy consumption of compressed air is mainly due to the following reasons:

(1) Improper combination of air compressors

في الوقت الحالي, the air compressor combination is not reasonable. Use large flow power frequency compressor (5#) with small air volume power frequency compressor (2# أو 3#). فضلاً عن ذلك, the air-use sites are scattered. They are more than 20. بجانب, the air use is irregular. لذلك, the total air consumption fluctuates greatly. The amplitude exceeds 20%. علاوة على ذلك, air compressor loading and unloading frequently. And the motor idling often occurs. The energy consumption during unloading is high. It accounts for about 20% ~ 35% of the full load energy consumption of air compressor system. لذلك, the operation efficiency is low.

(2) Air compressor set pressure is too high

في الوقت الحالي, there is only one air-use site that requires the pressure of ≥0.8 MPa. Its usage accounts for about 10% of the total. Other air sites require pressure ≥ 0.70 MPa. But the terminal centralized supply. لذلك, set outlet pressure range at 0.86~0.93 MPa. Overcome filter resistance and pipe resistance. أخيراً, the air terminal pressure is ≥ 0.81 MPa. We need to meet the high pressure needs of a small volume site. Increase the air compressor set pressure by 0.1 MPa. This is clearly unreasonable.

(3) Energy consumption of air compressor dryer is high

We need to make sure the dew point meets requirements. لذلك, the system uses 5 micro-heat combination dryers for drying. The dryer operation consumes a lot of regeneration air. Air consumption is about 7%. This occurs during desiccant heating and cold purge. في الحقيقة, this is the energy consumption of air compressor system. Plus the electricity consumed by the electric heater. Compared with other dryers, the combination dryer consumes higher energy. Assume that the dew point of the compressed air is -60°C. The energy consumption comparison of different dryers is shown in below Table 1. Take the combination dryer with air capacity of 1380Nm3/h as an example. The unit energy consumption is calculated as 0.1(kW·h)/نانومتر3. It can be seen from Table 1: The energy consumption of the micro-heat combination dryer (second type) is high. It is about 5 times that of the traditional waste heat regeneration combined dryer (third type). In addtion, فهو على وشك 10 times that of the new type of waste heat regeneration combined dryer (fifth type). It is only lower than the heatless combination dryer (first type). في نظام ضاغط الهواء, the energy consumption is more than 9%. A single unit can exceed 12 kW of the third type dryer. لذا 3 units consume more than 36 كيلوواط. في الوقت الحالي, the overall energy consumption of air compressor system is about 400 كيلوواط.

(4) Large pressure loss in compressed air system

The compressed air system was completed in batches. The piping layout is complex. Pipe resistance is great. Besides in order to ensure the air quality, installed many precision filters. هناك 20 pcs in total. There are also filters inside the dryers. لذلك, the pressure loss of this air compressor system reaches 0.05 MPa.

(5) There is a air leakage in the air compressor system

There are more than ten system equipments. علاوة على ذلك, the pipeline network is complicated. The main pipeline is over 600 م. هناك اكثر من 20 air-use sites. There are many locations where leaks can occur. About 2% of air leakage are found based on operating conditions and flow comparisons. This also affects the air compressor system energy consumption.

(6) Electronic timing drainer consumes a lot of air

هناك 27 pcs of drainer in the compressed air system. They can automatically drain according to the season. لكن, compressed air is always discharged during the draining process. In spring and summer, the drainage interval is 1 دقيقة. 5 s each time. فضلاً عن ذلك, in autumn and winter, the drainage interval is 3 minutes. 15 s each time. So average annual drainage interval is 2 دقيقة. 10 s each time. The diameter of the drain core is about 4 مم. The discharge of a single drain is about 0.25 نانومتر 3 / ساعة. Most of them are air. Calculated at 90%. Air loss is about 0.23 نانومتر 3 / ساعة. A total of about 6 نانومتر 3 / ساعة. So about 50,000 Nm3 of compressed air is wasted throughout the year.

Plans to change the energy consumption of air compressor system

(1) Adjust the air compressor combination

Give several different combinations of air compressors to supply air. And count the operating energy consumption. The energy consumption per unit of air production is shown in Table 2. في الحقيقة, the combination includes the desiccant dryer and مجفف الهواء المبرد.

Dryer Type	Air Consumption (/Rated Air Flow)	Power Loss (كيلوواط)	Power Consumption (كيلوواط)	Total Power (كيلوواط)
Heatless Regeneration Combination Dryer	about 14%	19.3	0.5	19.8
Micro Heat Regeneration Combination Dryer	about 7%	9.7	5.8	15.5
Heated Regeneration Combination Dryer	about 4%	5.5	8	13.5
Traditional Waste Heat Regeneration Combination Dryer	about 2%	2.8	0.5	3.3
New Type Waste Heat Regeneration Combination Dryer	0	0	1.5	1.5

Combination Type	Air Compressor System Energy Consumption (KW*h)/ح	Unit Energy Consumption (KW*h)/Nm³
5#+1#	345.6	0.0987
5# + 2# أو 3# (The combination that has been always used)	358.3	0.1024
5# + 4#	360.5	0.103
1#+2#+3#+4#	362.9	0.1037

It can be seen from Table 2: the energy consumption of the combination 5#+1# is the lowest. 1#+2#+3#+4# has the highest energy consumption. The former reduces the energy consumption by about 3.5% compared with the second type.

Energy consumption analysis of air compressor combination

The air compressors load and unload according to the pipe pressure. أحيانا, the actual air consumption is greater than the air supply. في هذا الوقت, the pipe pressure will gradually decrease. Once below the loading set pressure, air compressor starts loading at full capacity. فضلاً عن ذلك, sometimes the actual air consumption is less than the air supply. في هذا الوقت, the pipe pressure will gradually increase. Once exceed unloading set pressure, the compressor begins to unload. في هذا الوقت, the intake valve closes. And the vent valve opens. Vent the high pressure air from the exhaust end to the inlet end. Reduce the inlet and outlet pressure ratio at no-load. في هذا الوقت, the energy consumption accounts for about 20% ل 35% of the full load state. The difference is that the motor speed of power frequency compressor is constant. So it can’t adjust air volume. Changes in the pipe pressure will cause the valves to operate frequently. أخيراً, it will reduce the operation efficiency of air compressor. بجانب, it will affect the stability of the air supply pressure. لكن, the motor speed of VSD compressor can adjust independently. The adjustment range is generally 60%~100%. The intake valve and vent valve operate very little. It can effectively reduce the idling of air compressor system and energy consumption. Air supply pressure is also very stable. لذلك, we plan to use the combination of 5# + 1# المكبس الهوائي. Between them, ال 1# air compressor is variable speed.

(2) Different regional pressure supply

Add a new compressed air system. Supply air separately for the high-pressure air use site. The compressed air terminal operates at reduced pressure. Reduce the air compressor pressure from 0.86~0.93 MPa to 0.76~0.83 MPa. Energy consumption formula: E=∫ Edt=∫PaQaln(p/pa)dt Pa: atmospheric pressure absolute pressure Qa: volume flow in atmospheric state p: absolute pressure of air compressor outlet t: time Either variable can reduce air compressor system energy consumption. Assume the flow and time remain unchanged. For every 0.1 MPa decrease in pressure, energy consumption decreases by about 7%~8%. The new adding compressed air system is as follows: include 2 sets oil-free screw VSD compressors and 2 sets combination dryers. The design working pressure is 1.0 MPa. Each max air capacity is 1068 نانومتر 3 / ساعة. Use permanent magnet variable frequency motor. It can start and stop arbitrarily. And the times is unlimited.

(3) Use GM zero air consumption smart drainer

Don’t use the electronic timing drain again. Change it to GM smart zero air consumption drainer. Its working principle is as follows: condensate flows into the drain. The fluid level in the chamber keeps rising. When reaching high level, the level sensor signals. Activate the solenoid valve to start draining. The condensate level drops to a low level. في هذا الوقت, the sensor sends a signal. Close the solenoid valve to stop draining. The liquid level is still slightly above the drain port. It will form a liquid seal. So prevent the compressed air from escaping. Then it achieves the effect of zero air consumption. Judging from the actual situation on site, there is no air emission during GM drainer working. It really eliminates the unnecessary energy consumption of the air compressor system.

Energy consumption performance of the air compressor system after change

System change completes. The monthly operation energy consumption of the compressed air station is about 239,906 (kW·h). The new adding energy consumption is about 25205 (kW·h). هكذا, total is 265111 (kW·h)/month. Before change, the monthly energy consumption was 288100 (kW·h)/month. لذلك, it saves energy by 22989 (kW·h). It reduce air compressor ystem energy consumption by about 8%. The energy saving effect is very obvious. ختاماً, we should monitor the compressed air system frequently. And need maintain the air compressor, dryer, filters and pipeline well. فضلاً عن ذلك, the system also needs to be optimized and upgraded. So it can reduce the energy consumption of the air compressor system.