Self-sealing system for compressed air energy storage unit

Abstract

The application discloses a kind of compressed air energy storage unit with self-sealing system, mainly solve the technical problems that existing sealing system has double high energy consumption and initial investment, poor system stability, poor start-stop operating condition adaptability and high operation and maintenance cost.The self-sealing system of the application includes air induction unit, purification and drying unit and pressure regulating and stabilizing unit.The input end of air induction unit is connected to the outlet pipeline of the first cylinder compressor or the second cylinder compressor;The input end of the purification and drying unit is connected to the output end of the air induction unit;The input end of the pressure regulating and stabilizing unit is respectively connected to the output end of the purification and drying unit and the output end of the electric shut-off valve, and the three output ends are respectively connected to the shaft end sealing cavity of the first cylinder compressor, the second cylinder compressor and the third cylinder compressor.The self-sealing system of the application has the characteristics of high stability, high air source quality and high safety.

Description

Technical Field

[0001] This invention relates to a self-sealing system, specifically a self-sealing system for compressed air energy storage units. Background Technology

[0002] In current compressed air energy storage (CAES) power plants, the shaft end seals of CAES units (axial / centrifugal) and other pneumatic equipment within the plant (such as instrument valves, pneumatic actuators, etc.) share the same plant-wide instrument air network, supplied by multiple centrally located general-purpose air compressors. The design pressure of the sealing gas is 4-8 bar. Among them, the compressor unit is the largest user of sealing gas, with a single unit typically accounting for 60%-80% of the total instrument air consumption of the entire plant.

[0003] After the sealing gas enters the compressor shaft end sealing cavity, it forms a gas film barrier. Due to the frequent start-stop characteristics of CAES units during the day, the sealing gas needs to be supplied at full capacity during unit operation. During shutdown and turning gear operation, the sealing gas can theoretically be reduced or even cut off for a short time (only the post-isolation gas is retained to prevent lubricating oil from entering the sealing surface). However, in the existing scheme, the air compressor is still selected according to the redundancy principle of "multiple units at full capacity at the same time", and it needs to withstand a severe flow step impact at the moment of compressor start-up and shutdown, resulting in poor system operation stability.

[0004] In summary, the existing solutions have the following drawbacks:

[0005] (1) High energy consumption and high initial investment: The air compressor needs to be redundantly configured according to the maximum air consumption of the CAES unit, and needs to run continuously for 24 hours to cope with start-up and shutdown fluctuations, resulting in high plant power consumption; at the same time, the equipment purchase and civil engineering land occupation costs of large-capacity air compressors are high.

[0006] (2) Poor system stability: During the start-up and shutdown of the CAES unit, the sudden change in the huge demand for sealing gas can cause significant pressure fluctuations in the entire plant's instrument gas pipeline network, which can easily lead to malfunctions of other pneumatic instruments and control valves. When the sealing gas pressure is detected to be lower than the threshold, if the alarm is not cleared after pressure adjustment, the operator is prompted to shut down the system at an appropriate time.

[0007] (3) Poor adaptability to start-up and shutdown conditions: CAES units start and stop frequently. During the shutdown turning cycle, the theoretical demand for sealing gas decreases, but the existing system cannot achieve graded gas supply and still supplies all the gas to the units that have stopped, resulting in a waste of gas source; and if the air compressor fails, the operating units will lose sealing gas and be forced to stop.

[0008] (4) High operation and maintenance costs: Large-capacity air compressor systems not only increase equipment procurement costs and floor space, but also increase the workload of maintenance throughout the entire life cycle (such as lubricating oil replacement, filter replacement, cooling system maintenance, etc.). Summary of the Invention

[0009] The purpose of this invention is to solve the technical problems of existing sealing systems, such as high energy consumption and high initial investment, poor system stability, poor adaptability to start-up and shutdown conditions, and high operation and maintenance costs, and to provide a self-sealing system for compressed air energy storage units.

[0010] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0011] A self-sealing system for a compressed air energy storage unit includes a first-cylinder compressor, a second-cylinder compressor, and a third-cylinder compressor. The outlet pipe of the first-cylinder compressor is connected to the inlet pipe of the second-cylinder compressor, the outlet pipe of the second-cylinder compressor is connected to the inlet pipe of the third-cylinder compressor, and the outlet pipe of the third-cylinder compressor is connected to a user. The shaft end sealing chambers of the first-cylinder compressor, the second-cylinder compressor, and the third-cylinder compressor are respectively connected to the sealing instrument air outlet of an external air compressor via electric shut-off valves. The control terminal of the electric shut-off valve is connected to the control unit (DCS) of the compressed air energy storage unit.

[0012] Its special feature is:

[0013] It includes an air intake unit, a purification and drying unit, and a pressure regulating and stabilizing unit;

[0014] The input end of the air intake unit is connected to the outlet pipeline of the first cylinder compressor or the outlet pipeline of the second cylinder compressor, and is used to draw out 10-20 bar of raw material gas when the compressed air energy storage unit is working normally.

[0015] The input end of the purification and drying unit is connected to the output end of the air intake unit, and is used to filter and dehydrate the raw gas drawn out by the air intake unit to obtain purified gas.

[0016] The input end of the pressure regulating and stabilizing unit is connected to the output end of the purification and drying unit and the output end of the electric shut-off valve, respectively. The three output ends are connected to the shaft end sealing chambers of the first cylinder compressor, the second cylinder compressor and the third cylinder compressor, respectively, to adjust the gas pressure of the purified gas or the sealing instrument gas to 4-8 bar and then deliver it to the shaft end sealing chambers of the first cylinder compressor, the second cylinder compressor and the third cylinder compressor.

[0017] The electric shut-off valve is used to close when the compressed air energy storage unit is working normally and to open when entering the turning gear condition, so that the compressed air energy storage unit can use the gas generated by itself as the sealing gas when it is working normally and the sealing instrument gas can be used as the sealing gas when it enters the turning gear condition.

[0018] Furthermore, the pressure regulating and stabilizing unit includes a pressure stabilizing tank and three regulating valves;

[0019] The input end of the pressure stabilizing tank is connected to the output end of the purification and drying unit and the output end of the electric shut-off valve, respectively, for storing purified gas or instrument gas for sealing.

[0020] The input ends of the three regulating valves are respectively connected to the output ends of the pressure stabilizing tank, and the output ends are respectively connected to the shaft end sealing chambers of the first cylinder compressor, the second cylinder compressor, and the third cylinder compressor, for adjusting the gas pressure of the purified gas or the instrument gas for sealing to 4-8 bar.

[0021] Furthermore, the capacity of the pressure stabilizing tank meets the following requirements:

[0022] When the compressed air energy storage unit or bleed air is interrupted, the gas stored in the pressure stabilizing tank can maintain the pressure of the shaft end sealing chamber of the first cylinder compressor, the second cylinder compressor and the third cylinder compressor at a level not lower than the safety threshold for at least 5 minutes.

[0023] Furthermore, the regulating valve is a pneumatic diaphragm regulating valve or a self-operated regulating valve.

[0024] Furthermore, a pressure detector is provided at the output end of the regulating valve.

[0025] Furthermore, the purification and drying unit includes a pre-filter, a precision filter, a dryer, and a post-filter arranged sequentially along the gas conveying direction;

[0026] The input end of the pre-filter is connected to the output end of the air intake assembly, and is used to remove large droplets and impurities from the raw gas.

[0027] The precision filter is used to remove tiny liquid droplets from the gas;

[0028] The dryer is used for deep dehydration of the gas;

[0029] The output of the post-filter is connected to the input of the voltage regulating and stabilizing unit for secondary fine filtration of the gas.

[0030] Furthermore, the dryer includes two drying towers;

[0031] The input ends of the two drying towers are respectively connected to the output ends of the precision filter, and the output ends are respectively connected to the input ends of the post-filter.

[0032] Furthermore, the purified gas processed by the purification and drying unit meets the following conditions:

[0033] The dew point reaches below -40℃, the oil content is ≤1ppm, and the particle size is ≤1μm.

[0034] Compared with the prior art, the present invention has the following beneficial technical effects:

[0035] (1) Improve system stability: By using the compressor's own outlet airflow to draw gas, which is independent of the external instrument gas pipeline network, the impact of gas intake on the entire plant's gas network is completely eliminated, thus improving the reliability of unit operation.

[0036] (2) Higher quality of gas source: Through targeted precision filtration and deep dehydration treatment, the cleanliness of the output sealing gas is much higher than that of ordinary instrument gas, which effectively extends the service life of the compressor carbon ring seal or labyrinth seal and reduces the amount of seal leakage.

[0037] (3) Enhanced safety: The system has built-in redundant protection logic. Even if the air compressor fails, the sealing gas can still be maintained, avoiding secondary disasters caused by the interruption of the external public gas source, and achieving true "self-sufficiency". Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention. In the figure, TT refers to the temperature transmitter, PT refers to the pressure transmitter, PG refers to the pressure gauge, and PDT refers to the differential pressure transmitter.

[0039] The annotations in the attached figures are explained as follows:

[0040] 01-First cylinder compressor, 02-Second cylinder compressor, 03-Third cylinder compressor, 04-Electric shut-off valve;

[0041] 1- Air intake unit;

[0042] 2-Purification and drying unit, 21-Pre-filter, 22-Precision filter, 23-Dryer, 24-Post-filter;

[0043] 3-Pressure regulating and stabilizing unit, 31-Pressure stabilizing tank, 32-Regulating valve. Detailed Implementation

[0044] To make the objectives, advantages, and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0045] like Figure 1As shown, the existing compressed air energy storage unit includes a first-cylinder compressor 01, a second-cylinder compressor 02, and a third-cylinder compressor 03. The outlet pipe of the first-cylinder compressor 01 (i.e., the output pipe of the heat storage / cooling / separation unit) is connected to the inlet pipe of the second-cylinder compressor 02, the outlet pipe of the second-cylinder compressor 02 is connected to the inlet pipe of the third-cylinder compressor 03, and the outlet pipe of the third-cylinder compressor 03 is connected to the user. The shaft end sealing chambers of the first-cylinder compressor 01, the second-cylinder compressor 02, and the third-cylinder compressor 03 are respectively connected to the sealing instrument air outlet (circuit one) of an external air compressor via an electric shut-off valve 04. The control terminal of the electric shut-off valve 04 is connected to the control unit DCS of the compressor unit. A shut-off valve is provided at the input end of the shaft end sealing chamber of the first-cylinder compressor 01, the second-cylinder compressor 02, and the third-cylinder compressor 03.

[0046] This embodiment discloses a self-sealing system for compressed air energy storage units, which mainly includes an air intake unit 1, a purification and drying unit 2, and a pressure regulating and stabilizing unit 3.

[0047] The input end of the bleed air unit 1 is connected to the outlet pipeline of the first cylinder compressor 01 or the outlet pipeline of the second cylinder compressor 02 (the figure shows that the input end of the bleed air unit 1 is connected to the outlet pipeline of the first cylinder compressor 01). The bleed air port is selected according to the outlet pressure of the first cylinder compressor 01 and the second cylinder compressor 02. It is required to draw out 10-20 bar of raw material gas when the compressor unit is working normally.

[0048] Capacity reduction logic: Since the sealing air consumption of the compressed air energy storage unit accounts for the highest proportion of the instrument air consumption in the whole plant, after this embodiment changes this major user to self-supply, the design capacity of the centralized air compressor in the whole plant can be configured according to "the air consumption during the turning operation of the compressed air energy storage unit + the air consumption of other plant instruments", thereby reducing the equipment investment and operating power consumption of the air compressor.

[0049] The input end of the purification and drying unit 2 is connected to the output end of the air intake unit 1. It is used to filter and dehydrate the raw gas drawn out by the air intake unit 1 to obtain purified gas. The gas meets the following requirements: dew point below -40℃, oil content ≤1ppm, and particulate matter particle size ≤1μm.

[0050] Specifically, the purification and drying unit 2 includes a pre-filter 21, a precision filter 22, a dryer 23, and a post-filter 24 arranged sequentially along the gas conveying direction.

[0051] The input of the pre-filter 21 is connected to the output of the induced draft assembly, used to remove large droplets and impurities from the raw gas (preliminary filtration); the precision filter 22 is used to remove small droplets from the gas using a condensation method; the dryer 23 is used for deep dehydration of the gas; the dryer 23 includes two drying towers; the inputs of the two drying towers are respectively connected to the output of the precision filter 22, and the outputs are respectively connected to the input of the post-filter 24. The output of the post-filter 24 is connected to the input of the pressure regulating and stabilizing unit 3 (loop two), used for secondary fine filtration of the gas.

[0052] The pressure regulating and stabilizing unit 3 includes a pressure stabilizing tank 31 and three regulating valves 32.

[0053] The input end of the pressure stabilizing tank 31 is connected to the output end of the purification and drying unit 2 and the output end of the electric shut-off valve 04, respectively, for storing purified gas or instrument gas for sealing.

[0054] Specifically, the pressure stabilizing tank 31 is designed to have an emergency capacity, and the capacity of the pressure stabilizing tank 31 meets the following requirements:

[0055] When the compressed air energy storage unit trips or the bleed air supply is interrupted, the gas stored in the pressure stabilizing tank 31 can maintain the pressure of the shaft end sealing chamber of the first cylinder compressor 01, the second cylinder compressor 02 and the third cylinder compressor 03 at a level not lower than the safety threshold for at least 5 minutes, ensuring that it can be switched to air compressor supply in a steady state.

[0056] The input ends of the three regulating valves 32 are connected to the output ends of the pressure stabilizing tank 31, and the output ends are connected to the shaft end sealing chambers of the first cylinder compressor 01, the second cylinder compressor 02, and the third cylinder compressor 03, respectively. Pressure detectors are installed at the output ends of the regulating valves 32. The regulating valves 32 are pneumatic diaphragm regulating valves or self-operated regulating valves (PCV), used to regulate the gas pressure of purified gas or sealing instrument gas to 4-8 bar. A shut-off valve and a check valve are respectively installed at the inlet and outlet of the self-operated regulating valve (PCV).

[0057] Normal operation: The pressure is adjusted by a self-regulating pressure regulating valve to maintain a constant pressure.

[0058] The mechanics logic for the rotating gear air supply is as follows: When the compressed air energy storage unit enters the rotating gear mode after a normal shutdown, the DCS detects the compressor speed (e.g., <500 r / min), and the electric shut-off valve 04 of the original air compressor circuit opens. At this time, it automatically switches to "rotating gear mode"—the original air compressor sealing gas (circuit one) is automatically put into operation as the sealing gas source, providing an appropriate sealing gas flow rate according to the requirements of the rotating gear state. This design saves air consumption. When the compressed air energy storage unit receives the "restart" command, as the pressure of the self-sealing system sealing gas (circuit two) is established, the electric shut-off valve 04 will automatically close, automatically switching to the self-sealing system.

[0059] Since the amount of induced draft air is negligible compared to the amount of compressed air in the compressed air energy storage unit, the flow field at the induced draft air inlet location was simulated, and the impact is negligible.

[0060] The self-sealing system of this embodiment was built on the DCS simulation platform, and it was verified that it can respond quickly and stabilize the pressure within the set value ±0.1 bar under different load conditions (30%-100%).

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A self-sealing system for a compressed air energy storage unit, the compressed air energy storage unit comprising a first-cylinder compressor (01), a second-cylinder compressor (02), and a third-cylinder compressor (03); the outlet pipe of the first-cylinder compressor (01) is connected to the inlet pipe of the second-cylinder compressor (02), the outlet pipe of the second-cylinder compressor (02) is connected to the inlet pipe of the third-cylinder compressor (03), and the outlet pipe of the third-cylinder compressor (03) is connected to a user; the shaft end sealing chambers of the first-cylinder compressor (01), the second-cylinder compressor (02), and the third-cylinder compressor (03) are respectively connected to the sealing instrument air outlet of an external air compressor via an electric shut-off valve (04); the control terminal of the electric shut-off valve (04) is connected to the control unit DCS of the compressed air energy storage unit; Its features are: It includes an air intake unit (1), a purification and drying unit (2), and a pressure regulating and stabilizing unit (3); The input end of the air intake unit (1) is connected to the outlet pipeline of the first cylinder compressor (01) or the outlet pipeline of the second cylinder compressor (02) to draw out 10-20 bar of raw material gas when the compressed air energy storage unit is working normally. The input end of the purification and drying unit (2) is connected to the output end of the gas induced unit (1) and is used to filter and dehydrate the raw gas introduced by the gas induced unit (1) to obtain purified gas. The input end of the pressure regulating and stabilizing unit (3) is connected to the output end of the purification and drying unit (2) and the output end of the electric shut-off valve (04) respectively. The three output ends are connected to the shaft end sealing chambers of the first cylinder compressor (01), the second cylinder compressor (02) and the third cylinder compressor (03) respectively. The gas pressure of the purified gas or the instrument gas for sealing is adjusted to 4-8 bar and then delivered to the shaft end sealing chambers of the first cylinder compressor (01), the second cylinder compressor (02) and the third cylinder compressor (03). The electric shut-off valve (04) is closed when the compressed air energy storage unit is working normally and opened when entering the turning gear condition, so that the gas generated by the compressed air energy storage unit itself is used as the sealing gas when the compressed air energy storage unit is working normally, and the sealing instrument gas is used as the sealing gas when entering the turning gear condition.

2. The self-sealing system for a compressed air energy storage unit according to claim 1, characterized in that: The pressure regulating and stabilizing unit (3) includes a pressure stabilizing tank (31) and three regulating valves (32); The input end of the pressure stabilizing tank (31) is connected to the output end of the purification and drying unit (2) and the output end of the electric shut-off valve (04) respectively, and is used to store purified gas or instrument gas for sealing. The input ends of the three regulating valves (32) are respectively connected to the output ends of the pressure stabilizing tank (31), and the output ends are respectively connected to the shaft end sealing chambers of the first cylinder compressor (01), the second cylinder compressor (02) and the third cylinder compressor (03) to regulate the gas pressure of the purified gas or the instrument gas for sealing to 4-8 bar.

3. The self-sealing system for a compressed air energy storage unit according to claim 2, characterized in that, The capacity of the pressure stabilizing tank (31) meets the following requirements: When the compressed air energy storage unit or the bleed air is interrupted, the gas stored in the pressure stabilizing tank (31) can maintain the pressure of the shaft end sealing chamber of the first cylinder compressor (01), the second cylinder compressor (02) and the third cylinder compressor (03) at least 5 minutes below the safety threshold.

4. A self-sealing system for a compressed air energy storage unit according to claim 2 or 3, characterized in that: The regulating valve (32) is a pneumatic diaphragm regulating valve or a self-operated regulating valve.

5. A self-sealing system for a compressed air energy storage unit according to claim 4, characterized in that... : A pressure detector is provided at the output end of the regulating valve (32).

6. The self-sealing system for a compressed air energy storage unit according to claim 1, characterized in that: The purification and drying unit (2) includes a pre-filter (21), a precision filter (22), a dryer (23), and a post-filter (24) arranged sequentially along the gas conveying direction; The input end of the pre-filter (21) is connected to the output end of the air intake assembly, and is used to remove large droplets and impurities from the raw material gas; The precision filter (22) is used to remove tiny droplets from the gas; The dryer (23) is used to dehydrate the gas; The output end of the post-filter (24) is connected to the input end of the voltage regulating and stabilizing unit (3) for secondary filtration of the gas.

7. A self-sealing system for a compressed air energy storage unit according to claim 6, characterized in that: The dryer (23) includes two drying towers; The input ends of the two drying towers are respectively connected to the output end of the precision filter (22), and the output ends are respectively connected to the input end of the post-filter (24).

8. A self-sealing system for a compressed air energy storage unit according to claim 1 or 6, characterized in that, The purified gas processed by the purification and drying unit (2) meets the following conditions: The dew point reaches below -40℃, the oil content is ≤1ppm, and the particle size is ≤1μm.

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