Three-stage series joint start-up and shutdown method for large compressed air energy storage system

Abstract

The present invention proposes a three-stage series joint start-up and shutdown method for a large-scale compressed air energy storage system, including a low-pressure compressor, a medium-pressure compressor and a high-pressure compressor used in conjunction with each other. The three-stage series joint start-up method for the compressed air energy storage system ensures the matching of flow and pressure by controlling the boost ratio of each compressor at different time periods according to the different working characteristics of the low, medium and high-pressure compressors. Combined with the operating status of the compressor unit and the operating status of various auxiliary equipment, the compressors are all in a self-circulating and pressure-holding state before gas injection. It is necessary to match the flow of each stage of the compressor and adjust various parameters of the compressor so that the compressor can smoothly inject gas into the salt cavern; the three-stage series joint shutdown method for the compressed air energy storage system controls the unloading rate and the opening of the anti-surge valve so that the three-stage series compressor can be shut down smoothly and safely, while ensuring that the pressure during shutdown is not too high to cause the safety door to operate.

Description

Technical Field

[0001] The invention relates to the technical field of energy storage, and in particular to a three-stage series combined starting and stopping method for a large-scale compressed air energy storage system. Background Art

[0002] Energy storage is a method of storing renewable energy such as wind and light or off-peak electricity in a medium in the form of internal energy, potential energy or mechanical energy after energy conversion. When needed, the medium energy is released and converted into the required energy form. Energy storage technology is an effective means of coordinating the development of new energy technologies, which can play a role in peak shaving and valley filling, and is of great significance to the construction of smart grids.

[0003] Under the macro environment of "carbon peak" and "carbon neutrality", clean energy power generation has achieved unprecedented development. Among them, the development of wind power and photovoltaic power is the general trend, but their inherent volatility and intermittent problems will bring peak and frequency regulation pressure to the power grid when they are connected on a large scale. At the same time, it is difficult to transmit and consume them, and wind and light abandonment occur frequently. The problem of renewable energy consumption needs to be solved urgently. At present, the traditional energy storage methods are battery energy storage and pumped energy storage. The disadvantage of the former is that the subsequent treatment of battery electrolyte is cumbersome, the battery is not resistant to moisture, heat, and cold, the use conditions are relatively harsh, and the service life is short, generally less than 10 years; the bottleneck of the latter is that the construction of energy storage facilities needs to be close to mountains and rivers, the terrain is special, and the resources in some areas have been developed.

[0004] Compressed air energy storage is a low-cost, zero-emission, large-capacity, high-safety, and fast-response energy storage technology with great commercial development potential and application value. It is an important solution for the comprehensive utilization of clean energy and conventional energy in the future.

[0005] Compressed air energy storage is an indirect, large-scale energy storage technology. When the grid load is low, it compresses air through a compressor to store electrical energy, and transports the compressed air to rock caves, abandoned salt caves, abandoned mines or other pressure vessels; during high-load periods, the high-pressure gas in the gas storage is released, heated by a combustion chamber or heat exchanger, and then transported to the turbine after it reaches a certain temperature, converting the potential energy of the compressed air into mechanical work output of the turbine to drive the generator to generate electricity.

[0006] The existing compressed air energy storage system will cause the following three problems if the operation method is improper during the compressor startup and loading process:

[0007] 1. Incorrect startup methods can cause mismatched compressor pressure and flow, compressor surge due to the operating point being too close to the surge curve, large vibration of multi-stage compressors, high outlet temperature, and other abnormal conditions, which not only damage the compressor;

[0008] 2. The startup process is too long, which wastes a lot of electricity and reduces the power exchange efficiency of the unit;

[0009] 3. All operations are performed manually by the operating personnel, which increases the probability of personnel error operation, low unit startup success rate, and high labor intensity for the operating personnel.

[0010] When the compressor is finished working, it needs to be safely unloaded and shut down. There are four problems in the process of unloading and shutting down:

[0011] 1. Incorrect shutdown methods will cause overpressure at the inlet of medium and high pressure compressors, which will cause the compressor itself to surge and the pipeline to be damaged due to overpressure;

[0012] 2. The water vapor in the gas-liquid separator and pipeline during the compression process will affect the service life of the compressor and pipeline;

[0013] 3. The shutdown process is too long, which wastes a lot of electricity and reduces the power exchange efficiency of the unit;

[0014] 4. All operations are performed manually by the operating personnel, which increases the probability of personnel error operation, low unit startup success rate, and high labor intensity for the operating personnel. Summary of the invention

[0015] In order to solve the above technical problems, the present invention proposes a three-stage series combined starting and shutdown method for a large-scale compressed air energy storage system. During startup, the compressor system can be started with one button, which not only reduces the probability of operating personnel's misoperation, improves the success rate of unit startup, and reduces the labor intensity of operating personnel; during shutdown, the compressor unit can be unloaded and shut down with one button, which reduces human operation errors and improves the success rate of safe shutdown of the unit.

[0016] To achieve the above object, the technical solution adopted by the present invention is:

[0017] A three-stage series joint startup and shutdown method for a large-scale compressed air energy storage system, wherein the large-scale compressed air energy storage system includes a low-pressure compressor, a medium-pressure compressor, and a high-pressure compressor used in conjunction with each other, characterized in that: it includes a three-stage series joint startup method for a compressed air energy storage system and a three-stage series joint shutdown method for a compressed air energy storage system, and the specific steps are as follows:

[0018] The three-stage series joint starting method of the compressed air energy storage system:

[0019] Step 1: First, start the low-pressure compressor, the medium-pressure compressor and the high-pressure compressor in sequence. After starting, check all parameters of each compressor for abnormalities. After each compressor is started, open the discharge valve of the gas-liquid separator in time. When starting for the first time, perform mechanical no-load operation for 1-2 hours, and then start to load slowly and manually from the low-pressure compressor, that is, open the guide vane and close the anti-surge valve. When the pressure ratio of the low-pressure compressor reaches about 3-5, start to load the medium-pressure compressor. When the outlet pressure of the high-pressure compressor reaches 1-3Mpa, manually close the discharge valve of the gas-liquid separator and put it into automatic operation at the same time. According to the working point positions of the three compressors, the anti-surge valves of the low-pressure and medium-pressure compressors are slowly put into automatic operation during the loading process, and the guide vanes continue to be manually operated. During the operation, the pressure ratio of the low-pressure compressor is controlled to be greater than the pressure ratio of the medium-pressure compressor by about 1-1.5;

[0020] Step 2: When the outlet pressure of the high-pressure compressor reaches 5-8Mpa, start to manually and slowly close the anti-surge valve of the high-pressure compressor until the flow of the high-pressure compressor is slightly greater than the flow of the medium-pressure compressor by 20,000 Nm³ / h. Then continue to manually load the low-pressure and medium-pressure compressors. When the outlet pressure of the high-pressure compressor reaches 6-10Mpa, increase the cold source in the heat exchanger.

[0021] Step 3: Continue to manually load the low-pressure and medium-pressure compressors. According to the flow conditions of the medium-pressure and high-pressure compressors, manually close the anti-surge valve of the high-pressure compressor to keep the medium-pressure and high-pressure compressors at a deviation of 20,000 Nm³ / h. When the outlet pressure of the high-pressure compressor reaches 10-11Mpa, put the guide vanes of the low-pressure and medium-pressure compressors and the anti-surge valve of the high-pressure compressor into automatic control. Then, manually set the outlet pressure of the low-pressure and medium-pressure compressors to automatically open the guide vanes. If necessary, increase the speed of the high-pressure compressor to increase the outlet pressure of the high-pressure compressor to 12-14Mpa, and set the automatic opening pressure of the outlet electric door of the high-pressure compressor to 12-14Mpa.

[0022] Step 4: After the electric door of the high-pressure compressor outlet is opened, the speed of the high-pressure compressor is increased to increase the gas injection flow rate of the salt cavern. At the same time, the anti-surge valves of the low-pressure, medium-pressure and high-pressure compressors will automatically and slowly close. When the flow rate of the compressor reaches the rated flow rate, the anti-surge valves of the low-pressure, medium-pressure and high-pressure compressors will be completely closed. At this time, the low-pressure, medium-pressure and high-pressure compressors successfully inject gas into the salt cavern;

[0023] The three-stage series combined shutdown method of the compressed air energy storage system:

[0024] Step 1: Prepare for unloading and shutdown, and fully check that the parameters of the low-pressure, medium-pressure and high-pressure compressors and related equipment are normal. Set the low-pressure and medium-pressure compressor inlet guide vanes and high-pressure compressor speed control to manual mode and the anti-surge valve to automatic mode.

[0025] Step 2: Check that the working points of the low-pressure, medium-pressure, and high-pressure compressors are all below the anti-surge curve, and unload the three compressors synchronously. At this time, the speed of the high-pressure compressor is 1-3r / min, and the guide vanes of the medium-pressure and low-pressure compressors are 1-3%. Observe that the anti-surge valves of the three compressors open automatically. After a comprehensive inspection of the equipment, continue to unload. At the same time, the gas injection flow rate of the salt cavern decreases slowly until the flow rate is 0. When the flow rate is 0, speed up the unloading speed. When the outlet pressure of the high-pressure compressor begins to shake, immediately manually close the high-pressure compressor outlet electric door until it is completely closed;

[0026] Step 3: After the electric door at the outlet of the high-pressure compressor is completely closed, the three compressors no longer inject gas into the salt cavern. The three compressors are in a state of pressure holding. It is necessary to pay attention to the surge of the three compressors and check whether the parameters of each device are normal. In the subsequent unloading process, pay attention to the outlet pressure of the low-pressure compressor and the inlet pressure of the medium-pressure compressor; the outlet pressure of the medium-pressure compressor and the inlet pressure of the high-pressure compressor. When the inlet pressure of the medium-pressure compressor is greater than the outlet pressure of the low-pressure compressor and the inlet pressure of the high-pressure compressor is greater than the outlet pressure of the medium-pressure compressor, the compressors at all levels are no longer connected in series. At this time, when the inlet pressure of the medium-pressure compressor is greater than 0.8-0.9Mpa and is still rising, open the shutdown pressure relief valves of the medium-pressure and high-pressure compressors for pressure relief;

[0027] Step 4: Open the shutdown pressure relief valves of the medium-pressure and high-pressure compressors to release the outlet pressure of the high-pressure compressor to 7-9Mpa, then unload the entire compressor unit. The specific actions are: close the inlet guide vanes of the low-pressure and medium-pressure compressors to the minimum opening, reduce the speed of the high-pressure compressor to the minimum, fully open the anti-surge valves of the three compressors, and observe the inlet and outlet pressures of the low, medium and high-pressure compressors. When the outlet pressure of the high-pressure compressor drops to 2-3Mpa, shut down the entire compressor unit.

[0028] As a preferred technical solution of the present invention: the low-pressure compressor, the medium-pressure compressor and the high-pressure compressor are respectively provided with a manual adjustment mode for manually adjusting the working points of the three compressors.

[0029] As the preferred technical solution of the present invention: the inlet pressure of the low-pressure compressor is 0.098Mpa, which is an inlet guide vane control mode; the inlet pressure of the medium-pressure compressor is 0.65-0.85Mpa, which is an inlet guide vane control mode; the inlet pressure of the high-pressure compressor is 6-8Mpa, which is a variable frequency speed control mode.

[0030] As a preferred technical solution of the present invention: in the three-stage series joint starting method of the compressed air energy storage system:

[0031] During the slow manual loading of the low-pressure compressor, observe that the feedback of the guide vanes and anti-surge valve opening of the low-pressure compressor is normal. The working point of the low-pressure compressor is far away from the surge area. If the working point of the low-pressure compressor quickly approaches the surge area, the anti-surge valve should be opened in time. When abnormal parameter changes are found during the loading process of the low-pressure compressor, stop loading immediately and manually shut down the machine depending on the situation.

[0032] As a preferred technical solution of the present invention: in the three-stage series joint starting method of the compressed air energy storage system:

[0033] During the loading process of the medium-pressure compressor, observe that the opening feedback of the guide vanes and anti-surge valve of the medium-pressure compressor is normal. The working point of the medium-pressure compressor is far away from the surge area. If the working point of the medium-pressure compressor quickly approaches the surge area, the anti-surge valve should be opened in time. If abnormal parameter changes are found during the loading process of the medium-pressure compressor, stop loading immediately and manually shut down the machine depending on the situation.

[0034] As a preferred technical solution of the present invention: in the three-stage series joint shutdown method of the compressed air energy storage system:

[0035] The inlet guide vanes of the low-pressure and medium-pressure compressors and the speed control of the high-pressure compressor are switched to the manual adjustment mode and the anti-surge valve automatic mode. There are two modes for the unloading process, namely: first unload the medium-pressure compressor to make its operating point below the anti-surge curve or unload the three compressors synchronously, and increase the unloading range of the medium-pressure compressor during the synchronous unloading process.

[0036] As a preferred technical solution of the present invention: in the three-stage series joint shutdown method of the compressed air energy storage system:

[0037] When the outlet pressure of the high-pressure compressor drops to 1-2Mpa, manually open all the gas-liquid separator discharge valves and the drain valves of the pipeline to drain all the water and then close them.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The three-stage series joint startup method of large-scale compressed air energy storage system can achieve the following three technical advantages:

[0040] 1. During the compressor startup process, appropriate operating steps and adjustments to the unit operating parameters are used to ensure that the operating indicators are within the protection range, so that the compressor can successfully inject gas into the salt cavern smoothly, avoiding unit damage caused by improper startup methods;

[0041] 2. It shortens the startup time, solves the energy consumption during the startup process, and improves the unit's power replacement efficiency.

[0042] 3. The compressor system can be started with one button, which reduces the probability of operator error, improves the success rate of unit start-up, and reduces the labor intensity of operators.

[0043] The three-stage series joint shutdown method of large-scale compressed air energy storage system can achieve the following four technical advantages:

[0044] 1. When the compressor is unloaded and shut down, the correct operating steps and unloading rate are followed to ensure that the operating parameters of the compressor and related equipment are within the normal range during the shutdown process, and the compressor can be shut down safely, thus avoiding the occurrence of overpressure in the unit.

[0045] 2. Drain the remaining water in the system under appropriate pressure to ensure that the entire system is dry and clean.

[0046] 3. It shortens the downtime, solves the energy consumption during the downtime process, and improves the power replacement efficiency of the unit.

[0047] 4. The one-button unloading and shutdown of the compressor unit is realized, thereby reducing human operation errors and improving the success rate of safe shutdown of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is the principle thermodynamic system diagram for compressors in large compressed air energy storage power stations in the prior art;

[0049] Figure 2 is a compressor surge curve diagram in the present invention;

[0050] Figure 3 It is a working point curve diagram after the compressor in the present invention successfully injects gas into the salt cavern;

[0051] Figure 4 This is a one-button start sequence diagram of the present invention;

[0052] Figure 5 This is a one-button shutdown step diagram in the present invention. DETAILED DESCRIPTION

[0053] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments:

[0054] The present invention is based on a large-scale compressed air energy storage power station, and the thermal system diagram is as follows Figure 1 The project established a high-parameter, wide-operating-condition multi-stage centrifugal compressor design system for large-scale non-supplementary compressed air energy storage, proposed an optimal control method for variable-operating-condition operation of the compressor, and developed a multi-stage centrifugal air compressor with the highest parameters.

[0055] The three-stage series joint start-up and shutdown method of a large compressed air energy storage system proposed by the present invention adopts a three-stage compression and intermediate cooling method in the compressor compression process. The air compressed by the low-pressure compressor and the medium-pressure compressor enters the heat exchanger, and heat is exchanged with the heat transfer oil and water in the heat exchanger. The heat transfer oil and water absorb heat and store the heat, and the outlet air continues to enter the high-pressure compressor. After three-stage compression and multiple cooling, the high-pressure air is stored in the salt cavern, and part of the compressed heat is stored in the oil storage tank and the hot water storage tank. An air filter is set at the inlet of the low-pressure compressor, and a flow measuring device is set on the air pipeline at the outlet of the high-pressure compressor, and an electric isolation valve and a manual isolation valve are set. Anti-surge regulating valves are set at the outlets of the low-pressure compressor, the medium-pressure compressor and the high-pressure compressor, and corresponding return pipelines and pressure relief pipelines are set to ensure safe and reliable start and stop of the system. A gas-liquid separator is considered to be provided in the pipeline between each compressor section to ensure that the unit can timely drain the condensed water in the pipeline during the compression process to prevent the occurrence of water inflow accidents in the next compressor section.

[0056] like Figure 2-5 As shown: The present invention proposes a three-stage series joint start-up and shutdown method for a large-scale compressed air energy storage system, wherein the large-scale compressed air energy storage system includes a low-pressure compressor, a medium-pressure compressor, and a high-pressure compressor used in conjunction with each other, including a three-stage series joint start-up method for a compressed air energy storage system and a three-stage series joint shutdown method for a compressed air energy storage system, and the specific steps are as follows:

[0057] The three-stage series joint starting method of the compressed air energy storage system:

[0058] Step 1: First, start the low-pressure compressor, the medium-pressure compressor and the high-pressure compressor in sequence. After starting, check all parameters of each compressor for abnormalities. After each compressor is started, open the discharge valve of the gas-liquid separator in time. When starting for the first time, perform mechanical no-load operation for 1-2 hours, and then start to load slowly and manually from the low-pressure compressor, that is, open the guide vane and close the anti-surge valve. When the pressure ratio of the low-pressure compressor reaches about 3-5, start to load the medium-pressure compressor. When the outlet pressure of the high-pressure compressor reaches 1-3Mpa, manually close the discharge valve of the gas-liquid separator and put it into automatic operation at the same time. According to the working point positions of the three compressors, the anti-surge valves of the low-pressure and medium-pressure compressors are slowly put into automatic operation during the loading process, and the guide vanes continue to be manually operated. During the operation, the pressure ratio of the low-pressure compressor is controlled to be greater than the pressure ratio of the medium-pressure compressor by about 1-1.5;

[0059] Step 2: When the outlet pressure of the high-pressure compressor reaches 5-8Mpa, start to manually and slowly close the anti-surge valve of the high-pressure compressor until the flow of the high-pressure compressor is slightly greater than the flow of the medium-pressure compressor by 20,000 Nm³ / h. Then continue to manually load the low-pressure and medium-pressure compressors. When the outlet pressure of the high-pressure compressor reaches 6-10Mpa, increase the cold source in the heat exchanger.

[0060] Step 3: Continue to manually load the low-pressure and medium-pressure compressors. According to the flow conditions of the medium-pressure and high-pressure compressors, manually close the anti-surge valve of the high-pressure compressor to keep the medium-pressure and high-pressure compressors at a deviation of 20,000 Nm³ / h. When the outlet pressure of the high-pressure compressor reaches 10-11Mpa, put the guide vanes of the low-pressure and medium-pressure compressors and the anti-surge valve of the high-pressure compressor into automatic control. Then, manually set the outlet pressure of the low-pressure and medium-pressure compressors to automatically open the guide vanes. If necessary, increase the speed of the high-pressure compressor to increase the outlet pressure of the high-pressure compressor to 12-14Mpa, and set the automatic opening pressure of the outlet electric door of the high-pressure compressor to 12-14Mpa.

[0061] Step 4: After the electric door of the high-pressure compressor outlet is opened, the speed of the high-pressure compressor is increased to increase the gas injection flow rate of the salt cavern. At the same time, the anti-surge valves of the low-pressure, medium-pressure and high-pressure compressors will automatically and slowly close. When the flow rate of the compressor reaches the rated flow rate, the anti-surge valves of the low-pressure, medium-pressure and high-pressure compressors will be completely closed. At this time, the low-pressure, medium-pressure and high-pressure compressors successfully inject gas into the salt cavern;

[0062] The three-stage series combined shutdown method of the compressed air energy storage system:

[0063] Step 1: Prepare for unloading and shutdown, and fully check that the parameters of the low-pressure, medium-pressure and high-pressure compressors and related equipment are normal. Set the low-pressure and medium-pressure compressor inlet guide vanes and high-pressure compressor speed control to manual mode and the anti-surge valve to automatic mode.

[0064] Step 2: Check that the working points of the low-pressure, medium-pressure, and high-pressure compressors are all below the anti-surge curve, and unload the three compressors synchronously. At this time, the speed of the high-pressure compressor is 1-3r / min, and the guide vanes of the medium-pressure and low-pressure compressors are 1-3%. Observe that the anti-surge valves of the three compressors open automatically. After a comprehensive inspection of the equipment, continue to unload. At the same time, the gas injection flow rate of the salt cavern decreases slowly until the flow rate is 0. When the flow rate is 0, speed up the unloading speed. When the outlet pressure of the high-pressure compressor begins to shake, immediately manually close the high-pressure compressor outlet electric door until it is completely closed;

[0065] Step 3: After the electric door at the outlet of the high-pressure compressor is completely closed, the three compressors no longer inject gas into the salt cavern. The three compressors are in a state of pressure holding. It is necessary to pay attention to the surge of the three compressors and check whether the parameters of each device are normal. The unloading rate can be appropriately accelerated thereafter. In the subsequent unloading process, pay attention to the outlet pressure of the low-pressure compressor and the inlet pressure of the medium-pressure compressor; the outlet pressure of the medium-pressure compressor and the inlet pressure of the high-pressure compressor. When the inlet pressure of the medium-pressure compressor is greater than the outlet pressure of the low-pressure compressor and the inlet pressure of the high-pressure compressor is greater than the outlet pressure of the medium-pressure compressor, the compressors at all levels are no longer connected in series. At this time, when the inlet pressure of the medium-pressure compressor is greater than 0.8-0.9Mpa and is still rising, open the shutdown pressure relief valves of the medium-pressure and high-pressure compressors for pressure relief;

[0066] Step 4: Open the shutdown pressure relief valves of the medium-pressure and high-pressure compressors to release the outlet pressure of the high-pressure compressor to 7-9Mpa, then unload the entire compressor unit. The specific actions are: close the inlet guide vanes of the low-pressure and medium-pressure compressors to the minimum opening, reduce the speed of the high-pressure compressor to the minimum, fully open the anti-surge valves of the three compressors, and observe the inlet and outlet pressures of the low, medium and high-pressure compressors. When the outlet pressure of the high-pressure compressor drops to 2-3Mpa, shut down the entire compressor unit.

[0067] Three-stage series joint starting method for large compressed air energy storage system:

[0068] The designed inlet pressure of the low-pressure compressor is 0.098Mpa, which is controlled by the inlet guide vane; the designed inlet pressure of the medium-pressure compressor is 0.65-0.85Mpa, which is controlled by the inlet guide vane; the designed inlet pressure of the high-pressure compressor is 6-8Mpa, which is controlled by the variable frequency speed. The three compressors have different surge curves due to their different performances. The entire startup process is to ensure that the compressor cannot enter the surge area. Because the compressor automatically loads quickly, the guide vane adjustment process is prone to excessive adjustment, resulting in abnormal changes in some parameters of the compressor during the adjustment process. Therefore, the manual adjustment method was invented. One is to ensure that the compressor increases slowly without too much disturbance, and the other is to make preliminary explorations for the corresponding loading rate for one-button automatic startup. The direction of manual adjustment is to keep the working points of all compressors running below the anti-surge curve, so that the compressor can operate safely and stably, and its efficiency can always be guaranteed to be the highest.

[0069] Since it is a three-stage compression, the three compressors are started in sequence first. After starting, all parameters of the compressors are checked to see if there are any abnormalities. At the same time, in order to prevent water from entering the compressors, the discharge valve of the gas-liquid separator is opened in time after the entire compressor group is started. During the first startup, since all equipment has not been run-in, 1-2 hours of mechanical no-load operation is performed, and then the low-pressure compressor is slowly loaded manually (guide vanes are opened and anti-surge valves are closed). During the loading process, attention should be paid to the normal feedback of the guide vanes and anti-surge valve opening of the low-pressure compressor, and the working point of the compressor should be away from the surge area. If the working point approaches the surge area quickly, the anti-surge valve should be opened in time. During the loading process, attention should also be paid to the bearing temperature, vibration, etc. of the compressor. If abnormal changes in parameters are found, loading should be stopped immediately and manual shutdown should be performed depending on the situation. When the boost ratio of the low-pressure compressor reaches about 3-5, the medium-pressure compressor begins to be loaded. During the loading process, the operating parameters are also monitored. When the outlet pressure of the high-pressure compressor reaches 1-3Mpa, the discharge valve of the gas-liquid separator is manually closed and automatically put into operation. According to the working point position of the compressor, the anti-surge valves of the low- and medium-pressure compressors are slowly automatically put into operation during the loading process, and the guide vanes continue to be manually operated. During the operation, the boost ratio of the low-pressure compressor is generally controlled to be about 1-1.5 larger than the boost ratio of the medium-pressure compressor to prevent the low and medium-pressure compressors from causing abnormal changes in related parameters due to excessive flow differences. When the outlet pressure of the high-pressure compressor rises to about 5-8Mpa, the flow deviation of the low-pressure compressor, the medium-pressure compressor, and the high-pressure compressor is large. Because the opening of the anti-surge valve of the low-pressure compressor is large, the flow of the low-pressure compressor is the largest, but the flow of the high-pressure compressor is 30,000-40,000 larger than that of the medium-pressure compressor. If the high-pressure compressor is not adjusted and the low- and medium-pressure compressors are continuously loaded, the high-pressure compressor will cause over-flow operation. In severe cases, the parameters of the high-pressure compressor will reach the protection value and act.

[0070] When the outlet pressure of the high-pressure compressor reaches 5-8Mpa, start to manually and slowly close the anti-surge valve of the high-pressure compressor until the flow of the high-pressure compressor is slightly greater than the flow of the medium-pressure compressor by about 20,000 Nm³ / h, and then continue to manually load the low- and medium-pressure compressors. When the outlet pressure of the high-pressure compressor reaches 6-10Mpa, the compressor system is fully checked. At this time, the vibration of the first stage of the high-pressure compressor becomes significantly larger. After testing with the on-site spectrum analyzer, it is found that it is caused by half frequency. It is also found that the sealing system of the high-pressure compressor has a large air leakage after startup. At the same time, there is an obvious vortex sound at the first stage of the high-pressure compressor volute, which is judged to be caused by the large vibration caused by air flow excitation. In order to alleviate the vibration pressure, the amount of cold source in the heat exchanger is increased, the inlet temperature of the air is reduced, and the volume flow rate of the compressor air is reduced, thereby reducing the seal leakage of the high-pressure compressor, improving the air flow excitation at the first stage of the high-pressure compressor, and reducing the vibration value of the first stage of the high-pressure compressor.

[0071] Continue to manually load the low and medium pressure compressors, and manually close the anti-surge valve of the high pressure compressor according to the flow of the medium and high pressure compressors (always maintain a deviation of 20,000 Nm³ / h). When the outlet pressure of the high pressure compressor reaches 10-11Mpa, the guide vanes of the low and medium pressure compressors and the anti-surge valve of the high pressure compressor can be put into automatic control to prevent abnormal situations caused by untimely manual adjustment at the moment of air intake. After that, the outlet pressure of the low and medium pressure compressors can be manually set to automatically open the guide vanes. If necessary, the speed of the high pressure compressor can be slightly increased to increase the outlet pressure of the high pressure compressor to 12-14Mpa. Because the pressure of the salt cavern is generally around 12-14Mpa, the automatic opening pressure of the outlet electric door of the high pressure compressor is set to 12-14Mpa. In this way, after the outlet door of the compressor is opened, it can be ensured that the outlet check valve of the high pressure compressor will not frequently operate due to pressure fluctuations after gas injection.

[0072] After the electric door at the high-pressure compressor outlet is opened, the speed of the high-pressure compressor can be increased slightly to increase the gas injection flow rate into the salt cavern. At the same time, the anti-surge valves of the low, medium and high-pressure compressors will automatically and slowly close. When the flow rate of the compressor reaches the rated flow rate, the anti-surge valves of all compressors will be completely closed, indicating that the compressor has successfully injected gas into the salt cavern.

[0073] The three-stage series joint startup method of the compressed air energy storage system can achieve the following three technical advantages:

[0074] 1. During the compressor startup process, appropriate operating steps and adjustments to the unit operating parameters are used to ensure that the operating indicators are within the protection range, so that the compressor can successfully inject gas into the salt cavern smoothly, avoiding unit damage caused by improper startup methods;

[0075] 2. It shortens the startup time, solves the energy consumption during the startup process, and improves the unit's power replacement efficiency.

[0076] 3. The compressor system can be started with one button, which reduces the probability of operator error, improves the success rate of unit start-up, and reduces the labor intensity of operators.

[0077] Three-stage series joint shutdown method for large compressed air energy storage system:

[0078] The low-pressure compressor adopts inlet guide vane control mode; the medium-pressure compressor adopts inlet guide vane control mode; and the high-pressure compressor adopts variable frequency speed control mode.

[0079] At this time, the anti-surge valves of the low, medium and high pressure compressors are closed. It can be found that due to the different performance of the compressors, the working point of the medium pressure compressor deviates from the anti-surge zone by a large distance. If the three compressors are automatically unloaded at the same time, the medium and high pressure compressors will cause overpressure operation. Therefore, the manual unloading operation method was invented. First, it is to observe the changes of the relevant parameters of each compressor at different stages of unloading through manual slow operation, so as to find a better operation method for future operations. Second, it is to ensure that the equipment parameters are normal during the entire shutdown process to lay the foundation for finding the relevant operation sequence and unloading rate for the future one-key shutdown.

[0080] Prepare to unload and shut down, comprehensively check the compressor and related equipment parameters to make sure they are normal, switch the inlet guide vanes of the low and medium pressure compressors and the speed control of the high pressure compressor to manual and automatic modes of the anti-surge valve. There are two modes for the initial unloading process. Because the working point of the medium pressure compressor deviates far away, the unloading process can be carried out first to make the medium pressure compressor below its working point or the three compressors can be unloaded synchronously, and the unloading amplitude of the medium pressure compressor can be increased during the synchronous unloading process. The principle of the two operations is to keep the working points of the three compressors on the lower curve, so as to prevent the medium pressure compressor from running at overpressure at the outlet, because continuing to unload when the compressor is at the working point will cause its own anti-surge valve to open automatically. If the working point of the medium pressure compressor is not on the lowest curve, the anti-surge valve will not open automatically. In this way, the opening of the anti-surge valve of the high pressure compressor will cause the outlet pressure of the medium pressure compressor to overpressure (this method can be used when the working point of the compressor deviates far).

[0081] Check that the working points of the three compressors are all below the anti-surge curve. At this time, the three compressors can be unloaded synchronously at a rate of 1-3r / min for high-pressure compressors and 1-3% for guide vanes of medium and low-pressure compressors. Observe that the anti-surge valves of the three compressors open automatically. After a comprehensive inspection of the equipment, continue to unload. At the same time, the gas injection flow rate of the salt cavern slowly decreases until the flow rate is 0. When the flow rate is 0, the unloading speed can be accelerated to prevent the high-pressure compressor outlet reverse door from frequently operating at this time, affecting the safety of the equipment and pipelines. When the outlet pressure of the high-pressure compressor begins to shake, immediately manually close the high-pressure compressor outlet electric door until it is completely closed.

[0082] At this time, the compressor unit is no longer injecting gas into the salt cavern. The three compressors are under pressure. Attention should be paid to the surge of the compressors and the parameters of each device should be checked to be normal. The unloading rate can be appropriately accelerated afterwards. In the subsequent unloading process, special attention should be paid to the outlet pressure of the low-pressure compressor and the inlet pressure of the medium-pressure compressor; the outlet pressure of the medium-pressure compressor and the inlet pressure of the high-pressure compressor. Because in the unloading process to a certain extent, the inlet pressure of the medium-pressure compressor will be greater than the outlet pressure of the low-pressure compressor and the inlet pressure of the high-pressure compressor will be greater than the outlet pressure of the medium-pressure compressor. This is because when the anti-surge valve of the compressor is gradually opened, most of the flow at the outlet of the compressor at this level flows to the inlet, so that the inlet pressure is getting higher and higher. When the inlet of the lower compressor is greater than the outlet of the upper compressor, the compressors at all levels are no longer working in series, and because the anti-surge of the high-pressure compressor is gradually opened, the inlet and outlet pressures of the medium-pressure compressor are rising rapidly. Therefore, when unloading to this point, if it is found that the inlet pressure of the medium-pressure compressor is greater than 0.8-0.9Mpa and is still rising, it is necessary to open the medium and high-pressure shutdown pressure relief valves for pressure relief to prevent damage to the compressor and related pipelines due to excessive pressure.

[0083] When the medium and high pressure shutdown pressure relief valves are opened to release the outlet pressure of the high pressure compressor to 7-9Mpa, the entire compressor unit can be unloaded. The specific actions are: the inlet guide vanes of the low and medium pressure compressors are closed to the minimum opening, the speed of the high pressure compressor is reduced to the minimum, and the anti-surge valves of all compressors are fully opened. Observe the drop in the inlet and outlet pressures of the low, medium and high pressure compressors. When the outlet pressure of the high pressure compressor drops to 2-3Mpa, the entire compressor unit is shut down.

[0084] In order to prevent residual moisture in the pipelines and gas-liquid separators after shutdown from corroding the compressor and the inside of the pipelines, and to maintain a cleaner air quality for the next startup, when the outlet pressure of the high-pressure compressor drops by 1-2Mpa, manually open all the gas-liquid separator discharge valves and the drain valves of the pipelines to drain all the remaining water and then close them.

[0085] The three-stage series joint shutdown method of large-scale compressed air energy storage system can achieve the following four technical advantages:

[0086] 1. When the compressor is unloaded and shut down, the correct operating steps and unloading rate are followed to ensure that the operating parameters of the compressor and related equipment are within the normal range during the shutdown process, and the compressor can be shut down safely, thus avoiding the occurrence of overpressure in the unit.

[0087] 2. Drain the remaining water in the system under appropriate pressure to ensure that the entire system is dry and clean.

[0088] 3. It shortens the downtime, solves the energy consumption during the downtime process, and improves the power replacement efficiency of the unit.

[0089] 4. The one-button unloading and shutdown of the compressor unit is realized, thereby reducing human operation errors and improving the success rate of safe shutdown of the unit.

[0090] The above description is only a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent change made based on the technical essence of the present invention still falls within the scope of protection required by the present invention.

Claims

1. A three-stage series combined startup and shutdown method for a large-scale compressed air energy storage system, wherein the large-scale compressed air energy storage system comprises a low-pressure compressor, a medium-pressure compressor and a high-pressure compressor used in conjunction with each other, characterized in that: It includes a three-stage series joint startup method for a compressed air energy storage system and a three-stage series joint shutdown method for a compressed air energy storage system, and the specific steps are as follows: The three-stage series joint starting method of the compressed air energy storage system: Step 1: First, start the low-pressure compressor, the medium-pressure compressor and the high-pressure compressor in sequence. After starting, check all parameters of each compressor for abnormalities. After each compressor is started, open the discharge valve of the gas-liquid separator in time. When starting for the first time, perform mechanical no-load operation for 1-2 hours, and then start to load slowly and manually from the low-pressure compressor, that is, open the guide vane and close the anti-surge valve. When the pressure ratio of the low-pressure compressor reaches about 3-5, start to load the medium-pressure compressor. When the outlet pressure of the high-pressure compressor reaches 1-3Mpa, manually close the discharge valve of the gas-liquid separator and put it into automatic operation at the same time. According to the working point positions of the three compressors, the anti-surge valves of the low-pressure and medium-pressure compressors are slowly put into automatic operation during the loading process, and the guide vanes continue to be manually operated. During the operation, the pressure ratio of the low-pressure compressor is controlled to be greater than the pressure ratio of the medium-pressure compressor by 1-1.5; Step 2: When the outlet pressure of the high-pressure compressor reaches 5-8Mpa, start to manually and slowly close the anti-surge valve of the high-pressure compressor until the flow of the high-pressure compressor is greater than the flow of the medium-pressure compressor by 20,000 Nm³ / h. Then continue to manually load the low-pressure and medium-pressure compressors. When the outlet pressure of the high-pressure compressor reaches 6-10Mpa, increase the cold source in the heat exchanger. Step 3: Continue to manually load the low-pressure and medium-pressure compressors. According to the flow conditions of the medium-pressure and high-pressure compressors, manually close the anti-surge valve of the high-pressure compressor to keep the medium-pressure and high-pressure compressors at a deviation of 20,000 Nm³ / h. When the outlet pressure of the high-pressure compressor reaches 10-11Mpa, put the guide vanes of the low-pressure and medium-pressure compressors and the anti-surge valve of the high-pressure compressor into automatic control. Then, manually set the outlet pressure of the low-pressure and medium-pressure compressors to automatically open the guide vanes, increase the speed of the high-pressure compressor, increase the outlet pressure of the high-pressure compressor to 12-14Mpa, and set the automatic opening pressure of the outlet electric door of the high-pressure compressor to 12-14Mpa. Step 4: After the electric door of the high-pressure compressor outlet is opened, the speed of the high-pressure compressor is increased to increase the gas injection flow rate of the salt cavern. At the same time, the anti-surge valves of the low-pressure, medium-pressure and high-pressure compressors will automatically and slowly close. When the flow rate of the compressor reaches the rated flow rate, the anti-surge valves of the low-pressure, medium-pressure and high-pressure compressors will be completely closed. At this time, the low-pressure, medium-pressure and high-pressure compressors successfully inject gas into the salt cavern; The three-stage series combined shutdown method of the compressed air energy storage system: Step 1: Prepare for unloading and shutdown, and comprehensively check whether the parameters of low-pressure, medium-pressure and high-pressure compressors and related equipment are normal. Set the inlet guide vanes of the low-pressure and medium-pressure compressors and the speed control of the high-pressure compressor to manual mode and the anti-surge valve to automatic mode. Step 2: Check that the working points of the low-pressure, medium-pressure, and high-pressure compressors are all below the anti-surge curve, and unload the three compressors synchronously. At this time, the speed of the high-pressure compressor is 1-3r / min, and the opening of the guide vanes of the medium-pressure and low-pressure compressors is 1-3%. Observe that the anti-surge valves of the three compressors open automatically. After a comprehensive inspection of the equipment, continue to unload. At the same time, the gas injection flow rate of the salt cavern decreases slowly until the flow rate is 0. When the flow rate is 0, speed up the unloading speed. When the outlet pressure of the high-pressure compressor begins to shake, immediately manually close the high-pressure compressor outlet electric door until it is completely closed; Step 3: After the electric door at the outlet of the high-pressure compressor is completely closed, the three compressors no longer inject gas into the salt cavern. The three compressors are in a state of pressure holding. It is necessary to pay attention to the surge of the three compressors and check whether the parameters of each device are normal. In the subsequent unloading process, pay attention to the outlet pressure of the low-pressure compressor and the inlet pressure of the medium-pressure compressor; the outlet pressure of the medium-pressure compressor and the inlet pressure of the high-pressure compressor. When the inlet pressure of the medium-pressure compressor is greater than the outlet pressure of the low-pressure compressor and the inlet pressure of the high-pressure compressor is greater than the outlet pressure of the medium-pressure compressor, the compressors at all levels are no longer connected in series. At this time, when the inlet pressure of the medium-pressure compressor is greater than 0.8-0.9Mpa and is still rising, open the shutdown pressure relief valves of the medium-pressure and high-pressure compressors for pressure relief; Step 4: Open the shutdown pressure relief valves of the medium-pressure and high-pressure compressors to release the outlet pressure of the high-pressure compressor to 7-9Mpa, then unload the entire compressor unit. The specific actions are: close the inlet guide vanes of the low-pressure and medium-pressure compressors to the minimum opening, reduce the speed of the high-pressure compressor to the minimum, fully open the anti-surge valves of the three compressors, and observe the inlet and outlet pressures of the low, medium and high-pressure compressors. When the outlet pressure of the high-pressure compressor drops to 2-3Mpa, shut down the entire compressor unit.

2. The three-stage series combined startup and shutdown method for a large-scale compressed air energy storage system according to claim 1 is characterized in that: The low-pressure compressor, the medium-pressure compressor and the high-pressure compressor are respectively provided with a manual adjustment mode for manually adjusting the working points of the three compressors.

3. The three-stage series combined startup and shutdown method for a large-scale compressed air energy storage system according to claim 2 is characterized in that: The inlet pressure of the low-pressure compressor is 0.098Mpa, which is an inlet guide vane control mode; the inlet pressure of the medium-pressure compressor is 0.65-0.85Mpa, which is an inlet guide vane control mode; the inlet pressure of the high-pressure compressor is 6-8Mpa, which is a variable frequency speed control mode.

4. The three-stage series combined startup and shutdown method for a large-scale compressed air energy storage system according to claim 1 is characterized in that: In the three-stage series joint starting method of the compressed air energy storage system: During the slow manual loading of the low-pressure compressor, observe that the feedback of the guide vanes and anti-surge valve opening of the low-pressure compressor is normal. The working point of the low-pressure compressor is far away from the surge area. If the working point of the low-pressure compressor quickly approaches the surge area, the anti-surge valve should be opened in time. When abnormal parameter changes are found during the loading process of the low-pressure compressor, stop loading immediately and manually shut down the machine depending on the situation.

5. The three-stage series combined startup and shutdown method for a large-scale compressed air energy storage system according to claim 1 is characterized in that: In the three-stage series joint starting method of the compressed air energy storage system: During the loading process of the medium-pressure compressor, observe that the opening feedback of the guide vanes and anti-surge valve of the medium-pressure compressor is normal. The working point of the medium-pressure compressor is far away from the surge area. If the working point of the medium-pressure compressor quickly approaches the surge area, the anti-surge valve should be opened in time. If abnormal parameter changes are found during the loading process of the medium-pressure compressor, stop loading immediately and manually shut down the machine depending on the situation.

6. The three-stage series combined startup and shutdown method for a large-scale compressed air energy storage system according to claim 1 or 2, characterized in that: In the three-stage series joint shutdown method of the compressed air energy storage system: The inlet guide vanes of the low-pressure and medium-pressure compressors and the speed control of the high-pressure compressor are switched to the manual adjustment mode and the anti-surge valve automatic mode. There are two modes for the unloading process, namely: first unload the medium-pressure compressor so that its operating point is below the anti-surge curve or unload the three compressors synchronously, and increase the unloading range of the medium-pressure compressor during the synchronous unloading process.

7. The three-stage series combined startup and shutdown method for a large-scale compressed air energy storage system according to claim 1 is characterized in that: In the three-stage series joint shutdown method of the compressed air energy storage system: When the outlet pressure of the high-pressure compressor drops to 1-2Mpa, manually open all the gas-liquid separator discharge valves and the drain valves of the pipeline to drain all the water and then close them.

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