TWI737323B - Control method for energy-saving operation of multiple air compressors - Google Patents

Abstract

An energy-saving operation control method for multiple air compressors. The method steps are: establishing the relationship between the intake valve opening degree and power consumption, analyzing and defining the upper and lower limits of the intake valve opening degree and the optimal opening interval of efficiency, and balancing the air The opening degree of the intake valve of the compressor unit is switched from constant pressure control to constant current control at low load, and intelligent adjustment logic is established based on the pressure of the pipe network. Establish energy-saving operation mode of air compressor station, balance the load of each unit, automatically start and stop logic to avoid high pressure of the pipeline network, and apply constant current control at low load to avoid the phenomenon of emissions, provide stable pressure and meet downstream requirements, and achieve provincial The maximum benefit of electricity.

Description

Energy-saving operation control method for multiple air compressors

The invention relates to an energy-saving regulation and control method of an air compressor, in particular to an energy-saving regulation and control method that regulates and regulates a plurality of air compressors to provide stable pressure and meet demands, and achieve the maximum benefit of power saving.

In recent years, due to the popularity of automation equipment in all walks of life, pneumatic equipment is widely used in automation equipment because of its safety, cleanliness, ease of control, and ease of acquisition. However, in order to provide compressed air with suitable pressure and cleanliness, each factory must install and configure a compressed air supply system.

The equipment included in the compressed air supply system includes main components such as air compressors, drying equipment, filtering equipment, and conveying pipelines. Among them, air compressors are the largest energy consumer. Therefore, in terms of energy saving in the compressed air system, high-efficiency operation of air compressors must be required.

In addition, the scientist Saidur and others mentioned that the electricity used by compressed air accounts for one-tenth of all industrial electricity in the European Union. The life cycle cost (LCC) of an air compressor, equipment investment and maintenance costs only account for 22% of the cost of using the air compressor, and the remaining 78% of the cost is the electrical energy required to operate the air compressor. (See the literature R. Saidur, N.A. Rahim, M. Hasanuzzaman, A review on compressed-air energy use and energy savings, Renewable and Sustainable Energy Reviews, 2010.)

To solve this power consumption problem, Bolt et al. developed the "Real-time Energy Management System for Dynamic Compressor Selection, REMS-DCS" (Remote Energy Management System for Dynamic Compressor Selection, REMS-DCS). The location of the compressed air station, and the efficiency of the compressor (power consumption per unit of compressed air, kW/(kg/s)), determine the number of compressor units that should be started every four hours (see literature Bolt, GD; Venter, J .; van Rensburg, JFDynamic Compressor Selection. The Proceedings of Industrial and Commercial Use of Energy Conference, 2012.). Or the U.S. Environmental Protection Agency (USEnvironmental Protection Agency) lists 15 ways to improve the air compression process, of which Install or adjust unloading controls can save 10% of energy consumption per year (see the USEnvironmental Protection Agency, Wise Rules for Industrial Efficiency, 1998). Or Dindorf explains the energy saving method of compressed air system, which shows that reducing the pressure of the pipe network by 0.5kg/cm2 can reduce the power consumption of the compressor by 3% on average (see the literature Ryszard Dindorf, Estimating Potential Energy Savings in Compressed Air Systems, XIIIth International Scientific and Engineering Conference, Procedia Engineering 39, 204-211, 2012).

From past research data, it can be known that air compressors are large-scale power-consuming equipment, but energy-saving goals can be achieved through changes in operating methods; reducing the pressure of the pipe network and providing a supply that just meets the downstream demand can effectively reduce the energy consumption of the air compressor; The technology has been improved, but the overall control and adjustment technology cannot adjust the operation of the air compressor in real time to provide stable pressure and meet the downstream demand to achieve the maximum benefit of power saving.

Therefore, in order to solve the overall control and adjustment technology of multiple air compressor units, and adjust the operation of the air compressor units in real time to provide stable pressure and meet the downstream demand, balance the load of each unit, the intelligent adjustment technology of the air compressor station in this case , By adjusting the operation of the air compressor unit in a timely manner, the maximum benefit of power saving can be achieved.

To achieve the above objective, the present invention discloses an energy-saving operation control method for multiple air compressors, which is used to establish an energy-saving operation mode of an air compressor station. Analyze the relationship between the power consumption rate of each air compressor unit and the opening of the intake valve; analyze and define the upper and lower limits of the intake valve opening and the optimal opening interval of the efficiency, and analyze the relationship between the aforementioned power consumption rate and the opening of the intake valve , Define the upper and lower limits of the intake valve operation of each air compressor unit, and the optimal intake valve opening range of the energy-saving operation interval; balance the intake valve opening of each air compressor unit, and apply each air compressor The average opening of the inlet valve of each air compressor is used to fine-tune the output pressure of each air compressor. Through the use of different outlet pressure settings for each air compressor, adjust the settings so that the opening of the inlet valve of each air compressor is similar; The constant pressure control is converted to constant current control. The air compressor control program is modified. When the air discharge is reached, the operating current is controlled to the lowest operating constant current to avoid the air compressor at low load and reduce the emission loss; according to the pipe network pressure Set up and establish intelligent adjustment logic, in order to maintain the high energy efficiency operation of the air compressor station, avoid oversupply situation, design intelligent operation start-stop logic, according to the pressure of the pipe network Force and air compressor unit opening determine the operation of starting and stopping each air compressor unit.

Further in implementation, the operating data analyzes the relationship between the power consumption rate of each air compressor unit and the opening of the intake valve, and maintains the air compressor unit to operate at medium and high loads, which can improve energy efficiency.

Further in implementation, the maximum value of the intake valve opening of each air compressor unit is 100%, and the minimum value of the intake valve opening is when the discharge valve of each air compressor unit is open.

Further in implementation, in order to reduce the problem of excessive adjustment of the intake valve opening of each unit in response to pressure load changes, the outlet pressure setting value of the air compressor unit far from the outlet end is increased, and the air intake of the air compressor unit far away from the outlet end is increased. The valve opening degree reduces the degree of difference of the intake valve opening of each air compressor unit.

Further in implementation, when the pipe network pressure is within the set value range, the operation of each air compressor unit remains unchanged, and the range of the same operation of each air compressor unit is when the pipe network pressure is within ±3 of the set value. ~5%.

Further in implementation, when the pipeline network pressure is less than the set value range, the unloaded air compressor unit is started, or the air compressor unit with the longest stop time is started.

Further in implementation, when the pipe network pressure is higher than the set value range, the air compressor unit that is unloaded or stopped operating for the longest time is determined according to whether the intake valve opening is at the low opening setting value and the duration. When the pipe network pressure is higher than the set value range, but when the intake valve opening is greater than the low opening set value, the operation of each air compressor unit remains unchanged. When the pipe network pressure is higher than the set value range, and the duration of the intake valve opening less than the low opening set value does not reach the set value, the operation of each air compressor unit remains unchanged.

The best energy-saving operation strategy for air compressor stations is to provide Under this principle, the compressed air used has no compressed air discharge and the air supply pressure is stable and not high, which is an energy-saving operation. Through the method of this case, with the air compressor station as the goal, develop the air compressor station adjustment technology for multiple air compressors. Through the air compressor start and stop adjustment logic, the air compressor station operating units are automatically adjusted to reduce the energy consumption of the air compressor station.

The energy-saving operation technology of the air compressor station in this case includes: 1. Apply historical process data to establish the relationship between intake valve opening and power consumption, and analyze and define the upper and lower limits of intake valve opening and the best efficiency opening range. 2. Using historical process data, establish the air compressor intake valve strain speed relationship, adjust the setting so that the intake valve opening of each air compressor is similar, and balance the intake valve opening of each air compressor unit. 3. When the load is low, the constant voltage control is converted to constant current control to avoid waste of emissions. 4. Establish intelligent adjustment logic based on the pipeline network pressure, use the intake valve opening and pipeline network pressure information to design automatic start-stop logic, and automatically decide the start and stop of the air compressor.

This case establishes an energy-saving operation mode for the air compressor station, balances the load of each unit, automatic start-stop logic to avoid high pressure in the pipeline network, and applies constant current control when the load is low to avoid emissions. The intelligent adjustment logic of this case is actually applied to the air compressor station, and the results show that it can reduce the emission loss and reduce the chance of high pressure in the pipeline network, and effectively achieve the energy-saving goal.

S1, S2, S3, S4, S5: steps

Figure 1 is a flow chart for establishing an energy-saving operation mode of an air compressor station for this case.

Figure 2 is a logical schematic diagram of the start and stop of the adjustment operation of this case.

Figure 3 shows the relationship between air compressor power consumption rate and intake valve (IGV) opening.

Figure 4 is a diagram showing the relationship between operating current and intake valve (IGV) opening.

Figure 5 shows the ratio of the average opening of the intake valve (IGV) of each air compressor unit in the empty station.

Figure 6 shows the standardized opening ratio diagram of each air compressor unit inlet valve (IGV) of the air compressor station.

Figure 7 shows the change trend of the intake valve (IGV) at different pressure set points in the air compressor station.

Figure 8 shows the trend chart of the variation of the intake valve (IGV) at different pressure setting points in the air compressor station.

Figure 9 is a diagram showing the difference in power consumption between constant current and non-constant current when the air compressor unit is in the lowest load state.

Figure 10 is the first implementation case of the start-stop adjustment situation and power-saving situation of this case.

Figure 11 is the second implementation case of the start-stop adjustment situation and power-saving situation of this case.

In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be described clearly and completely in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only It is a part of the embodiments of the present invention, but not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained under the premise of equivalent changes and modifications made by persons of ordinary skill in the art shall fall within the protection scope of the present invention.

Please refer to Figure 1 for the flow chart of establishing the energy-saving operation mode of the air compressor station for this case. This case discloses an energy-saving operation control method for multiple air compressors, which is used to establish an energy-saving operation mode of an air compressor station. The method includes the following steps: Step S1: establish the relationship between intake valve opening and power consumption, and apply long-term operation data Analyze the relationship between the power consumption rate of each air compressor unit and the opening of the intake valve. Step S2: Analyze and define the upper and lower limits of the intake valve opening and the best efficiency opening interval, analyze the relationship between the aforementioned power consumption rate and the intake valve opening, and define each air compressor The upper and lower limits of the intake valve operation of the group, and the optimal intake valve opening range of the energy-saving operation interval; Step S3: Balance the intake valve opening of each air compressor unit, and apply the intake valve of each air compressor unit Average opening, fine-tuning the output pressure of each air compressor, through each air compressor using different outlet pressure settings, adjust the settings so that the opening of the intake valve of each air compressor is similar; Step S4: Set by setting when the load is low The pressure control is converted to constant current control, and the air compressor control program is modified. When the air discharge is reached, the operating current is controlled to the lowest operating constant current to avoid the air compressor at low load and reduce the emission loss; Step S5: According to the management The establishment of network pressure establishes the intelligent adjustment logic, in order to maintain the high energy efficiency operation of the air compressor station and avoid oversupply, the intelligent operation start-stop logic is designed, and each station is started and stopped according to the pipe network pressure and the opening of the air compressor unit. Operation of air compressor unit.

The principle of the foregoing steps is explained in detail as follows: The following explanation takes the air compressor station with 12 AC1~AC12 air compressor units as an example. Figure 3 shows the relationship between the air compressor power consumption rate and the intake valve (IGV) opening degree. The relationship between the power consumption rate of each air compressor unit and the intake valve (IGV) opening degree is analyzed based on the operating data of 2 months. It can be clearly seen that the trend is similar to a smile curve. When the load is low (low IGV opening), the air compressor power consumption rate is significantly higher than that of the medium and high load, and the power consumption rate of the medium and high load is similar. Operation at medium to high loads can improve energy efficiency.

The exceptions are: the relationship between the AC10 of the air compressor unit is very different from that of other units, and presents an unreasonable chaotic state. Therefore, the relationship between the operating current of the air compressor unit AC10 and the IGV opening is further compared, as shown in Figure 4 The relationship between the current and the opening of the intake valve (IGV) shows a reasonable and normal relationship between the current and the opening of the IGV. From this, it is judged that the air compressor AC10 should be an abnormal condition of the air flow meter. Another anomaly Therefore, the air compressor AC12 maintains the IGV opening 100% operating state for a long time, so there is no other IGV opening operating data, so the AC12 will not participate in the adjustment temporarily.

In the illustrative example, the air compressor station is composed of 12 air compressor units. The maximum IGV opening of each air compressor unit is 100%, but the minimum opening degree is subject to the surge line of each air compressor unit. ) Is different. Through analyzing the data in operation, when the discharge valve (BOV) of each air compressor unit is opened, it means that the IGV opening is closed to the minimum at this time, and it touches the anti-surge line (anti- surge line), the discharge valve (BOV) starts to open to protect the air compressor unit. The following table shows the maximum (MAX) and minimum (MIN) openings of each air compressor unit AC1~AC12. Among them, the air compressor unit AC12 The minimum opening is much higher than the other units. The reason is that no emissions are produced when the air compressor AC12 is running. This minimum is the minimum opening that has ever occurred in the running state.

By establishing the aforementioned long-term operating data, the relationship between intake valve opening and power consumption can be established, and the upper and lower limits of intake valve opening and the optimal opening range for efficiency can be analyzed and defined.

In the air compressor unit of the air compressor station, because each air compressor is located at a different position in the pipeline, facing the same pipe network pressure value, the compressed air flow rate that each air compressor unit can produce is different, so that each air compressor The IGV opening degree of the unit is different. This phenomenon causes the IGV opening degree of the air compressor unit to be reduced when the pipe network pressure rises to maintain the same pressure output. However, at this time, the air compressor at the back end of the pipeline can no longer reduce the IGV opening. At this time, the BOV will be turned on to discharge compressed air to prevent the air compressor from entering a surge state. Further statistics on the average opening of the intake valve (IGV) of each air compressor unit (as shown in Figure 5), it is found that the opening distribution of each air compressor unit is different. For example, the air compressor AC12 is basically 100% operation, while air compressor units AC5, AC6, AC7, AC9 all operate at 50-60%.

進行標準化後，其開度狀況如圖6所示，可以發現空壓機組AC5、AC6、AC7、AC9都在運轉開度範圍的40%左右。此現象會造成整體空壓站調節能力變低且耗電量提升，因為當壓力變動時，中高負載機組IGV還有調節能力時，但低負載機組經確開始BOV排放。 If the opening degree of each air compressor unit is based on the formula

After standardization, the opening status is shown in Figure 6, and it can be found that the air compressor units AC5, AC6, AC7, and AC9 are all around 40% of the operating opening range. This phenomenon will cause the overall air compressor station's regulation ability to be lower and power consumption to increase, because when the pressure changes, the medium and high load unit IGV still has the regulation ability, but the low load unit does start BOV emission.

Since each air compressor unit of the air compressor station can independently set its outlet pressure setting value, in order to reduce the problem of excessive IGV adjustment difference of each air compressor unit in response to pressure load changes, the implementation of this method will place the air compressor unit far away from the outlet end. The outlet pressure setting value is increased, so under the same pipeline pressure, due to the higher pressure setting value state, the IGV opening degree will be greater than the lower pressure setting value state. This method is used to increase the IGV opening degree far away from the outlet end of the unit. Reduce the degree of difference in IGV opening of each unit.

Figure 7 shows the change trend of the intake valve (IGV) at different pressure set points in the air compressor station. Figure 7 analyzes the average IGV opening of each air compressor during operation. Before the pressure setting has been changed, the average opening of the air compressor AC6 is 51.48%. When the air compressor AC6 outlet pressure setting value is changed to 5.55kg /cm2, the average opening of the air compressor unit AC6 operation increased to 72.35%. When the air compressor AC7 outlet pressure setting value is also changed to 5.55kg/cm2, the average opening of the air compressor AC7 operation increases to 74.58%. this The results show that increasing the outlet pressure setting can prevent the air compressor units at the end of the pipeline from being in low-load operation for a long time, but the average opening of the air compressor units AC6 and AC7 is increased at the same time, the air compressor units AC2, AC4 and AC5 The operating opening of the air compressor is a drop phenomenon. Further analysis of the average operating opening variation of the 8 units of the air compressor station (as shown in Figure 8), the IGV opening variation is 17.8 before the setting is changed, when the air compressor AC6 pressure is set When the change is made, the IGV opening variation is reduced to 14.8. When the AC7 pressure setting of the air compressor is changed, the IGV opening variation is reduced to 13.7 again. Therefore, the air compressor using different outlet pressure settings can reduce the average opening between the units. Degree variation.

Regarding the air compressor constant current control, in order to prevent the air compressor from reaching the anti-surge line (anti-surge line) and triggering the discharge valve (BOV) discharge, the air compressor control program was modified and the setting was not set. Before reaching the anti-surge line (anti-surge line), it is constant pressure control, and when it reaches the anti-surge line (anti-surge line), it will be converted to constant current control, the operating current is controlled to the lowest operating current, and the emission is no longer turned on Valve (BOV) to reduce emission losses. Taking the air compressor AC5 as an example, when the air compressor AC5 is tested at the lowest load, in the non-constant current control and constant current control modes, its unit flow power consumption is improved by 9.7% (as shown in Figure 9). Show).

In order to maintain the high energy efficiency operation of the air compressor station and avoid oversupply, the intelligent operation start-stop logic is designed, and the start-stop operation is determined according to the pipe network pressure P and the opening of the air compressor unit. Figure 2 illustrates the logic diagram of the start and stop of the adjustment operation in this case. It can only be executed when there is a stopped unit. If there is no stopped air compressor unit, the operation will remain unchanged. In the condition of a stopped air compressor unit, P_low and P_high are the high and low setting values of the pipe network pressure P, generally set to ±3~5% of the pipe network demand pressure When the pipe network pressure P is within the set value (when P_low<P<P_high), the operation of each air compressor unit remains unchanged. When the pipe network pressure P is less than the set value range (when P<P_low), the unloaded air compressor unit is started, or the air compressor unit with the longest stop time is started. When the pipe network pressure P is higher than the set value range (when P_high<P), IGVset is the low opening setting value of the air compressor intake valve. Generally, the opening can be set to 50~60%, depending on the intake valve opening Whether it is at the low opening setting value (IGVset) and the duration of t minutes (generally t is set to 10 minutes) determine the unloading or shutdown of the air compressor unit for the longest time. When the pipe network pressure P is higher than the set value range, but when the intake valve opening is greater than the low opening setting value (IGVset<IGV), the operation of each air compressor unit remains unchanged. When the pipe network pressure P is higher than the set value range, when the intake valve opening is less than the low opening set value (IGV<IGVset), but its duration does not reach the set value t minutes, the air compressor units cannot operate at this time Change.

Through the method of this case, the actual application cases are as follows. A one-month start-stop test was conducted. To confirm the stability of the automatic loading and unloading program, a manual test was initially conducted. When the pressure is too high and the IGV is too low, an unloading alarm will be issued to warn the operator to adjust. The following two adjustment cases are compared with Figure 10 and Figure 11 to illustrate the adjustment situation and the power saving situation.

First, in the implementation case 1 (Figure 10), when the pipe network pressure is too high, the system issues an alarm at this time, and the operator immediately adjusts an air compressor to stop, after which the pipe network pressure is still maintained at about 5 kg, which satisfies Downstream demand. When the pressure begins to drop, it means that downstream demand increases. Therefore, the operator starts to load an air compressor unit. Adjust the unit, the power consumption will still be maintained at 8200kW, and the pressure of the pipeline network will be biased. High. When shutting down an air compressor unit, the total power consumption becomes lower, but the pressure still meets the downstream demand, so the total power consumption can be saved.

Also in the second implementation case (Figure 11), when the downstream load decreases, the pressure is too high and the system issues an alarm. The power returns to the state before adjustment, so the adjustment benefit is the difference in power consumption before and after adjustment.

The following table shows the difference in average power consumption before and after unloading and the unloading time of the two adjustment cases. The saved power consumption in case 1 is 1672 kWh, and the saved power consumption in case 2 is 518 kWh.

After a month of testing, the statistical test results show that when the pressure is high, the system has issued a total of 430 alarms. Among them, the operator did change the operation of the air compressor according to the alarm. A total of 141 adjustments were made. The average adjustment is about 4-5 times a day. Adjust once every 6 hours. Under each adjustment, the difference in power consumption for half an hour is about 500kW, and the one-month test section shows a saving of 100,000 yuan in electricity costs. During the 141 adjustments, there was no problem with the on-site operation and the pressure on the pipeline network was also Both can meet downstream demand. Therefore, if the shutdown warning is adjusted every time, the expected annual power saving benefit is greater than 3.5 million yuan.

The advantage of this case is that, with the air compressor station as the goal, the development of air compressor adjustment technology for multiple air compressors, through the air compressor start and stop adjustment logic, balance the load of each unit, and automatic start and stop logic to avoid high pressure in the pipeline network , And when the load is low, apply constant current control to avoid emissions. The intelligent adjustment logic of this case is actually applied to the air compressor station, and the results show that it can reduce the emission loss and reduce the chance of high pressure in the pipeline network, and effectively achieve the energy-saving goal.

However, the above are only preferred embodiments of the present invention, and should not be used to limit the scope of implementation of the present invention, that is, simple equivalent changes and modifications made in accordance with the scope of the patent application of the present invention and the description of the invention, All are still within the scope of the invention patent.

S1, S2, S3, S4, S5: steps

Claims (8)

An energy-saving operation control method for multiple air compressors is used to establish an energy-saving operation mode of an air compressor station. The method includes the following steps: establishing the relationship between intake valve opening and power consumption, and analyzing each air compressor using long-term operating data The relationship between the group power consumption rate and the intake valve opening degree; analyze and define the upper and lower limits of the intake valve opening degree and the best efficiency opening range, analyze the relationship between the aforementioned power consumption rate and the intake valve opening degree, and define each air compressor unit The upper and lower limits of the intake valve operation and the optimal intake valve opening range in the energy-saving operation interval; balance the intake valve opening of each air compressor unit, and apply the average opening of the intake valve of each air compressor unit, Fine-tune the output pressure of each air compressor unit. Through each air compressor unit adopts different outlet pressure settings, adjust the settings so that the opening of the intake valve of each air compressor is similar; when the load is low, it is converted from constant pressure control to constant current control. , Modify the air compressor control program to control the operating current to the lowest operating constant current when the air discharge is reached, to avoid the air The air compressor station can maintain high energy efficiency operation, avoid oversupply, design intelligent operation start-stop logic, and determine the start and stop operation of each air compressor unit according to the pipeline network pressure and the opening of the air compressor unit; when the pipeline network When the pressure is within the set value range, the operation of each air compressor unit remains unchanged. The operating range of each air compressor unit remains unchanged when the pipe network pressure is within ±3~5% of the set value. When it is higher than the set value range, the air compressor unit that is unloaded or stopped for the longest operation is determined according to whether the intake valve opening is at the low opening setting value and the duration. The energy-saving operation control method for multiple air compressors as described in claim 1, wherein the operation data analysis is each The relationship between the power consumption rate of the air compressor unit and the opening of the intake valve can maintain the air compressor unit to operate at medium and high loads, which can improve energy efficiency. The energy-saving operation and control method for multiple air compressors as described in claim 1, wherein the maximum intake valve opening of each air compressor unit is 100%, and the minimum intake valve opening is the emission of each air compressor unit When the valve is open. The energy-saving operation and regulation method of multiple air compressors as described in claim 1, in which, in order to reduce the problem of excessive adjustment of the intake valve opening difference of each unit in response to pressure load changes, the outlet pressure of the air compressor unit far from the outlet end is set The value is increased to increase the opening of the intake valve of the air compressor unit away from the outlet side, and reduce the degree of difference in the opening of the intake valve of each air compressor unit. The energy-saving operation control method for multiple air compressors as described in claim 1, wherein when the pressure of the pipe network is less than the set value range, the unloaded air compressor unit is started. The energy-saving operation control method for multiple air compressors as described in claim 1, wherein when the pipe network pressure is less than the set value range, the air compressor unit with the longest stop time is started. The energy-saving operation control method for multiple air compressors as described in claim 1, wherein when the pipe network pressure is higher than the set value range, when the intake valve opening is greater than the low opening setting value, each air compressor unit operates constant. The energy-saving operation regulation method of multiple air compressors as described in claim 1, wherein when the pipe network pressure is higher than the set value range, the duration of the intake valve opening less than the low opening set value does not reach the set value, The operation of each air compressor unit remains unchanged.

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