China will strive to peak carbon dioxide emissions before 2030 and achieve carbon neutrality before 2060This means that China, as the largest developing country in the world, will complete the world's highest carbon emission intensity reduction, and achieve carbon neutrality in the shortest time in the world's history, which will undoubtedly be an uphill battle.
In this context, the problem of high energy consumption of air compressor system has gradually become prominent, and new requirements have been put forward for air compressor energy-saving technology. The energy consumption problem of the air compressor system is mainly reflected in:
First, the three major ways of air compressor energy saving, we have been talking about energy saving, how to save energy?There are three main ways: one is to improve the efficiency of electric energy utilization;The second is a high-efficiency drive;The third is to reduce the specific power of the host.
Way 1: Improve the efficiency of electric energy utilization
Strategy 1: Reduce reactive power loss
When we do energy saving, we must do everything we need to do everything we can, and don't ignore the opportunities that can be used. As we all know, the west-to-east power transmission is the use of high-voltage transmission technology, why not use low-voltage?Because the loss is too great with low-voltage transmission. Therefore, one of the strategies to improve power utilization is to reduce reactive power losses, and the solution is to replace the transformer with a high-voltage motor. After all, the reactive power loss of a 10kV to 380V transformer is still relatively serious. Of course, for low-power air compressors, it is not recommended to use voltages above 6kV or 10kv, and it is recommended to use them in the power range above 200kw.
Strategy 2: Reduce line loss
Cables used to transmit electricity also consume electricity. During the operation of the air compressor, we will measure the temperature of the cable and find that the cable is hot. Where does it get its heat?It must have been converted from electricity. However, due to the small transmission current of the high-voltage machine, the cable basically does not heat up.
The strategy to improve the efficiency of electric energy utilization can be summed up as improving the utilization rate of electric energy by using high-voltage electricity.
Approach 2: Efficient drives
Usually, the energy-saving way of the motor is frequency conversion, so the trend of the air compressor industry in the past ten years is to use permanent magnet frequency conversion technology to improve the energy efficiency level of the compressor. Permanent magnet frequency conversion has two benefits, one is that it can reduce losses by eliminating the excitation process;Second, it can be dynamically regulated with the change of gas volume. Therefore, the core of the second way is to use permanent magnet frequency conversion technology to achieve energy saving.
Method 3: Reduce the specific power of the host
According to the author's observation at the Shanghai International Compressor and Equipment Exhibition, there are still many single-stage compression machines. The efficiency of single-stage compression is low, so we need to improve the compression efficiency, one is to reduce the leakage between the teeth, and the other is to use a way close to isothermal compression as much as possible to improve the compression efficiency. Therefore, it is necessary to adopt two-stage compression technology.
To sum up, these three ways correspond to the three major energy-saving technologies in the air compressor industry, namely high pressure, permanent magnet frequency conversion and two-stage compression, so a product called high-pressure permanent magnet frequency conversion two-stage compressor will be born.
Second, the three ways to save energy cause analysis1.Why use high voltage?
Load loss: transformer daily loss = (no-load loss + load loss load factor squared) 24
No-load loss: When the secondary winding of the transformer is open, and the rated voltage of the rated frequency sine waveform is applied to the primary winding, the active power consumed is called no-load loss.
What is the difference between using high-voltage electricity and using low-voltage electricity?Let's assume a statistic, using a common 800kVA transformer as an example. The customer may have a 2000kva, 3150kva, or even larger transformer, let's take a look at how much the loss of an 800kva transformer is.
Taking the loss of 800kVA dry-type transformer as an example, if the load rate of the transformer is 50%, the power consumption of one day is:
The no-load loss of 800kva dry-type power transformer is 1160W, which is about 24 30 116=835.2 kWh.
The load loss of 800kva dry-type power transformer is 5220W, which is about 24 30 5 a month22=3758.4 kWh.
No-load losses are constant losses that are independent of the passing current, but rather the voltage on which the component is subjected.
No-load loss is only to power the transformer, there is no load behind, and only the transformer consumes power. Its no-load loss is about 1160 watts, which can consume more than 800 kilowatt-hours of electricity in a month, and these more than 800 kilowatt-hours of electricity are wasted. When loaded, the loss of the transformer can reach more than 5,000 watts, and more than 3,700 kilowatts of electricity will be wasted in a month.
Won't the high-voltage machine have this kind of loss?There will be. For example, there are also losses in its upper stage transformers, such as 35kv, 110kv, and 220kv to 10kv. However, the loss is less than 10kV to 380V, so it will also lose some power.
2.Why use a permanent magnet synchronous motor?
Why is the permanent magnet motor energy-efficient?The stator coil of an ordinary asynchronous motor is energized to produce a rotating magnetic field, the magnetic field cuts the rotor, and the rotor generates an alternating current, which generates a magnetic field, and the stator magnetic field drives the rotor magnetic field to rotate. In this process, the rotor consumes electricity, because the rotor itself is not magnetic, and its magnetic field energy is obtained by absorbing electrical energy from the grid. The permanent magnet variable frequency synchronous motor, because the rotor permanent magnet has its own magnetic field, when the motor stator coil is energized to produce a rotating magnetic field, the stator rotating magnetic field can directly drive the rotor magnetic field to rotate, so as to eliminate an excitation link.
The efficiency and power factor of permanent magnet motor do not change much with load rate and speed, while the efficiency and power factor of ordinary asynchronous motor change very much with load rate and speed.
3.The energy-saving principle of inverter control
Asynchronous motors will have low efficiency at low loads, so permanent magnet motors are more suitable for regulation. As can be seen from the comparison chart of the efficiency of different types of motors, the power factor varies a lot.
4.Constant pressure air supply
Everyone understands the principle of constant pressure gas supply, but there are some differences when everyone does it. For example, if the customer wants an 8kgf model, it does not mean that the customer needs 8kgf constant pressure gas supply, if the compressor supplies air according to 8kgf constant pressure, it will be a waste of energy. The commissioning is to adjust the compressor to the customer's optimal use state, not to adjust the compressor to the factory state. Therefore, it is very important to debug this link, and it is necessary to adjust the pressure to the pressure state of the customer's real needs, that is, the best working condition of the air compressor.
The pressure of the air compressor does not need to be adjusted very high, because it is too high for the customer to have no use, as long as it meets the needs of the customer, it saves the original process of adding and unloading, and saves the excess pressure in the yellow shaded area in the figure below, so this part of the work does not need to be done, so it saves electricity bills.
5.Two-stage compression is closer to isothermal compression
Looking at the PV diagram above, in the process of inhalation-compression-exhaust, the single-stage compression is directly compressed from point A to point C, and then exhausted;If it is a two-stage compression, it will be compressed from point A to point B, then go to point F after a heat exchange, and finally start from point F, and the second stage of compression will go to point D. This part of the work of the green area is to be saved, which is also the core principle of two-stage compression and energy saving.
Let's take a look at the efficiency comparison, under normal circumstances, the specific power of the 8kgf model, the single-stage compression is not less than 7, and it is more difficult to achieve less than 7. If you use the form of two-stage compression, you can do less than 6.
6.Reduce in-host leakage
Why does a host leak consume energy?Because compressed air is an energy source with a relatively low conversion rate, the compressed air that is finally compressed returns to the starting point through the leakage triangle, resulting in a reduction in compression efficiency, which is a big waste.
How to reduce leakage?It is necessary to reduce the area of this leakage triangle (see the figure below on the right), which is also an important means for us to improve the efficiency of the air compressor. Of course, now with the rise of China's machining technology, the accuracy of the main engine has been greatly improved.
So how can we further reduce the leakage loss?This requires two stages of compression. Leakage from the second stage outlet to the first stage inlet, there is a pressure difference in the middle, the compressed gas can not be directly returned to the inlet, it will have an expansion process between stages, when it expands and the volume becomes larger, and then through the first stage leakage, the leakage will be smaller. This is another reason why two-stage compression is more energy-efficient than single-stage.
7.Optimized piping to reduce pressure loss
After so many of the above energy-saving methods are introduced, let's take a look at some energy-saving methods around the compressor:
The use of the least elbows and the maximum use of straight pipes minimizes pressure loss and improves the efficiency of the air compressor
By improving the air control technology, the air compressor can be started at light load and the stability of the equipment can be improved
The use of pipeline multi-stage sealing ferrule to ensure the reliability of pipeline sealing through ** sealing, to prevent pipeline leakage;
Optimize the air intake system piping to reduce the suction pressure loss
The oil is designed with secondary oil return and oil control to reduce the waste of compressed air
Improving the coarse separation effect of oil and gas barrels can effectively reduce the pressure loss of oil separator core.
1) In the design process, use elbows as little as possible, maximize the use of straight pipe design, or bend a bend with a relatively large arc, can use 90 degrees without 180 degrees, can use 45 degrees without 90 degrees, can do straight pipe without 45 degrees of elbows. In addition, the pipe diameter can be increased. Increasing the diameter of the pipe reduces the flow rate and minimizes pressure loss.
2) It is necessary to make it easier to start the compressor through the control technology, because the starting current of the compressor is very large. Permanent magnet frequency conversion will make the air compressor sleep, and its power consumption will be greatly increased when it needs to be started frequently.
3) Compus** pipeline sealing technology can effectively prevent pipeline leakage.
4) Optimize the intake line to reduce the suction pressure loss. There are two important coefficients for the main machine: the suction temperature coefficient and the suction pressure coefficient. If you want to do a good job in these two coefficients, you must achieve a reasonable layout.
The first is to reasonably design the installation position of the air filter, so that the air filter can inhale cold air, so as to improve the suction temperature coefficient and reduce energy consumptionThe second is to reduce the inlet and exhaust resistance, which can improve the suction pressure coefficient, and is also conducive to improving the heat dissipation efficiency of the radiator and reducing the power consumption of the fan motorThird, the complete cold and heat exchange cycle is more in line with the principle that the cold air enters from the bottom and the hot air is discharged from the top.
5) The oil control design of the secondary oil return controls the amount of oil return, and the oil flow into the machine head is screw oil as much as possible, rather than compressed air.
6) It is necessary to do a good job in the separation effect of oil and gas barrels. Why the effect of oil and gas barrels will save energy if it is done well, this point may not be understood. We make this assumption that when the oil separator core has been in the state of saturated filter oil, the resistance must be large. Some people will say that the oil produced by the oil manufacturer is not good, and the pressure loss is relatively large. This statement is sometimes true, and it is true that the oil separation core is not up to standard. But there are also some cases, it may be that the oil and gas drum design is not very good, because there is a large amount of oil mist that needs to be filtered, so the pressure loss is large. We need to separate as much oil as possible from oil and gas barrels to reduce the pressure loss of oil and thus achieve energy savings.
3. Application of energy-saving technology in Comps compressor products1Explosion-proof permanent magnet frequency conversion technology is applied to frequency conversion air compressors used in coal mines: compared with traditional air compressors, the starting impact is smaller, and the operation is reliableVariable frequency control reduces power waste;Smaller in size, more suitable for tight spaces underground.
2.High-voltage permanent magnet frequency conversion technology: low-voltage transformer is omitted, the transmission loss of transformer is reduced, and the power utilization rate is highThe built-in frequency conversion system adjusts the speed in real time to reduce the power loss caused by gas fluctuationsThe starting current is small, which reduces the impact of the power grid and makes it safer to use.
3.Permanent magnet inverter dry oil-free screw machine: The rotor is super coated to prevent leakage caused by wear and tear, ensuring stable and long-lasting running performanceThe reliable cooling system effectively reduces the power consumption of the compressor and improves the efficiency of the main engineFrequency conversion control, wider gas volume adaptation range.
Permanent magnet high-speed inverter centrifugal compressor: The unique processing technology manufactures a more efficient one-time forming impeller to improve the compression efficiencyThe ternary flow impeller design is adopted to make the gas flow efficiency higherEquipped with a high-speed permanent magnet synchronous motor, it achieves better results with minimal energy consumption.
The above are some of the author's sharing on air compressor energy saving, I hope it will be helpful to the development and progress of the industry!