An energy system that couples compressed gas supply and multi-stage industrial gas supply

Abstract

This invention discloses an energy system coupling compressed gas supply and multi-stage industrial gas supply, including a thermal power unit. The thermal power unit includes a boiler assembly, a high-pressure cylinder, and an intermediate-pressure cylinder. A main steam pipeline is provided between the boiler assembly and the high-pressure cylinder. A main diversion pipeline is connected to the main steam pipeline. The main diversion pipeline is connected to a small steam turbine. The small steam turbine is driven by a compressed gas assembly. A cold reheat steam pipeline is provided between the high-pressure cylinder and the boiler assembly. An exhaust steam pipeline is connected to the small steam turbine. A drive steam pipeline is led out from the main steam pipeline. The exhaust steam pipeline and the drive steam pipeline are connected and merged, and then connected to the cold reheat steam pipeline. A low-pressure industrial steam supply pipeline is connected to the exhaust steam pipeline. A high-pressure industrial steam supply pipeline is provided to the main diversion pipeline. A medium-pressure industrial steam supply pipeline is led out from the pipeline connecting the boiler assembly and the intermediate-pressure cylinder. This invention can stably supply compressed gas and simultaneously achieve multi-stage industrial steam supply.

Description

Technical Field

[0001] This invention relates to the field of energy utilization technology, and in particular to an energy system that couples compressed gas supply and multi-stage industrial gas supply. Background Technology

[0002] Currently, most combined heat and power (CHP) units in China use direct heat supply to achieve CHP, such as directly supplying steam and hot water. Urban coal-fired power plants have abundant and diverse steam resources, which can not only provide heat and electricity, but also have the ability to provide compressed air, compressed carbon dioxide, and other products.

[0003] Currently, most chemical plants use gas turbines or electric compressors to produce compressed gas. These methods consume a lot of energy and are not economical.

[0004] By utilizing abundant steam resources through coal-fired power units, compressed gas can be produced by driving steam turbines, achieving cogeneration of electricity and gas, which can realize the production of compressed gas with low energy consumption and high economy.

[0005] Steam that can be used to drive small steam turbines in coal-fired power units can be selected from main steam, cold reheat steam, and hot reheat steam. Among them, the pressure of cold reheat steam and hot reheat steam is reduced, and the exhaust steam after driving the small steam turbine has a high enthalpy value and low energy efficiency. Main steam can be well recovered and reused after driving the small steam turbine. However, the amount of main steam extracted is constrained by the over-temperature of the boiler reheater. Generally, the amount of main steam extracted does not exceed 10% of the main steam flow.

[0006] Meanwhile, in current conventional hot reheat and cold reheat steam extraction heating technologies, it is basically difficult for 350MW-class units to simultaneously meet the demand for 200t / h of medium-pressure industrial steam supply at 2~3MPa and 100t / h of low-pressure industrial steam supply at 1~2MPa.

[0007] There is currently a lack of technology that can produce compressed gas by extracting large-flow main steam from thermal power units, and it has not been possible to achieve large-scale, high-efficiency, and low-cost production of compressed gas products from coal-fired power units. There is also a lack of an energy system that can supply compressed gas products externally and provide multi-level, large-flow industrial steam. Summary of the Invention

[0008] The present invention aims to at least partially solve one of the technical problems in the related art.

[0009] To achieve the above objectives, this invention proposes an energy system that couples compressed gas supply and multi-stage industrial gas supply, including a thermal power unit. The thermal power unit includes a boiler assembly, a high-pressure cylinder, and an intermediate-pressure cylinder. A main steam pipeline is provided between the boiler assembly and the high-pressure cylinder. A main diversion pipeline is connected to the main steam pipeline. The main diversion pipeline is connected to a small steam turbine. The small steam turbine is driven by a compressed gas assembly. A cold reheat steam pipeline is provided between the high-pressure cylinder and the boiler assembly. An exhaust steam pipeline is connected to the small steam turbine. A drive steam pipeline is led out from the main steam pipeline. The exhaust steam pipeline and the drive steam pipeline are connected and merged, and then connected to the cold reheat steam pipeline. A low-pressure industrial steam supply pipeline is connected to the exhaust steam pipeline. A high-pressure industrial steam supply pipeline is provided on the main diversion pipeline. An intermediate-pressure industrial steam supply pipeline is led out from the pipeline connecting the boiler assembly and the intermediate-pressure cylinder.

[0010] This invention increases the steam extraction flow rate of the main steam pipeline by setting up exhaust steam pipelines and drive steam pipelines, exceeding the original 10% steam extraction flow rate limit of the unit. It also achieves a stable, efficient, and reliable supply of compressed gas to coal-fired power units. At the same time, it leads out multi-stage industrial steam supply pipelines on different pipelines, thereby completing the supply of high-pressure, medium-pressure, and low-pressure industrial steam in the same power unit.

[0011] Optionally, a first check valve, a first regulating valve, and a first isolation valve are sequentially installed on the main diversion pipe along the direction from the main steam pipe to the small steam turbine.

[0012] Furthermore, the compressed gas assembly includes a first compressor that is drivenly connected to the small steam turbine, the compressor is connected to a gas source pipeline, the gas source pipeline is connected to a compressed gas source, and the outlet of the first compressor is connected to a gas product pipeline.

[0013] Furthermore, a hot press for mixing the exhaust steam from the small steam turbine and the driving steam is provided at the connection point between the exhaust steam pipe and the driving steam pipe. The hot press is connected to both the driving steam pipe and the exhaust steam pipe, and the outlet of the hot press is connected to the cold reheat steam pipe.

[0014] Furthermore, a second check valve, a second regulating valve, and a second isolation valve are sequentially installed on the drive steam pipe along the direction from the main steam pipe to the hot press.

[0015] Furthermore, a third regulating valve is installed on the main diversion pipeline between the small steam turbine and the high-pressure industrial steam supply pipeline, a fourth regulating valve is installed on the high-pressure industrial steam supply pipeline, a fifth regulating valve is installed on the low-pressure industrial steam supply pipeline, a sixth regulating valve is installed on the exhaust pipeline downstream of the connection point of the low-pressure industrial steam supply pipeline, and an eighth regulating valve is installed on the medium-pressure industrial steam supply pipeline.

[0016] Furthermore, a seventh regulating valve is installed on the return pipe at the position corresponding to the hot press and the cold reheat steam pipe.

[0017] Furthermore, the intermediate pressure cylinder is connected to a deaerator, the deaerator outlet is equipped with a water pump, the water pump outlet is equipped with a water inlet pipe, and the water inlet pipe is connected to the hot press.

[0018] Furthermore, the gas source pipeline is connected to a second compressor, which is an electric compressor.

[0019] Furthermore, the small steam turbine and the compressor are connected by a steam drive shaft.

[0020] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0021] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0022] Figure 1 This is a schematic diagram of an energy system according to the present invention, which couples compressed gas supply and multi-stage industrial gas supply.

[0023] Explanation of reference numerals in the attached figures:

[0024] 1. Boiler assembly; 2. High-pressure cylinder; 3. Intermediate-pressure cylinder; 4. Main steam pipeline; 5. Main diversion pipeline; 6. Exhaust pipeline; 7. Drive steam pipeline; 8. Return pipeline; 9. Cold / reheat steam pipeline; 10. First compressor; 11. Second compressor; 12. Gas source pipeline; 13. Water intake pipeline; 14. Hot press; 15. Small steam turbine; 16. First check valve; 17. First regulating valve; 18. First isolation valve; 19. Second check valve; 20. Second regulating valve; 21. Second isolation valve; 22. Third regulating valve; 23. Fourth regulating valve; 24. Fifth regulating valve; 25. Sixth regulating valve; 26. Seventh regulating valve; 27. Eighth regulating valve; 28. Third check valve; 29. ​​Third isolation valve; 30. Hot / reheat steam pipeline. Detailed Implementation

[0025] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0026] This invention provides an energy system that couples compressed gas supply and multi-stage industrial gas supply, as described below. Figure 1 To elaborate in detail.

[0027] An energy system coupling compressed gas supply and multi-stage industrial gas supply includes a thermal power unit. The thermal power unit includes a boiler assembly 1, a high-pressure cylinder 2, and an intermediate-pressure cylinder 3. A main steam pipe 4 is provided between the boiler assembly 1 and the high-pressure cylinder 2. A main diversion pipe 5 is connected to the main steam pipe. The main diversion pipe 5 is connected to a small steam turbine 15. The small steam turbine 15 is driven by a compressed gas assembly. A cold reheat steam pipe 9 is provided between the high-pressure cylinder 2 and the boiler assembly 1. An exhaust steam pipe 6 is connected to the small steam turbine 15. A drive steam pipe 7 is led out from the main steam pipe 4. The exhaust steam pipe and the drive steam pipe 7 are connected and merged, and then connected to the cold reheat steam pipe 9. A low-pressure industrial steam supply pipe is connected to the exhaust steam pipe 6. A high-pressure industrial steam supply pipe is provided on the main diversion pipe 5. A hot reheat steam pipe 30 is connected between the boiler assembly 1 and the intermediate-pressure cylinder 3. An intermediate-pressure industrial steam supply pipe is led out from the hot reheat steam pipe 30.

[0028] The thermal power unit includes a boiler assembly 1, a high-pressure cylinder 2, and an intermediate-pressure cylinder 3. The main steam pipe 4 of the boiler assembly 1 is connected to the inlet of the high-pressure cylinder 2. The boiler assembly 1 includes a boiler reheater and is also connected to a hot reheat steam pipe 30. The hot reheat steam pipe 30 is connected to the inlet of the intermediate-pressure cylinder 3. The outlets of the high-pressure cylinder 2 and the intermediate-pressure cylinder 3 are connected to a regenerative system. The regenerative system includes a No. 1 high-temperature feedwater heater, a No. 2 high-temperature feedwater heater, a No. 3 high-temperature feedwater heater, and a deaerator feedwater assembly, which are connected in sequence by pipes. The No. 1 high-temperature feedwater heater is connected to the inlet of the boiler assembly 1, and the deaerator feedwater assembly is connected to the intermediate-pressure cylinder 3. The two steam outlets of the high-pressure cylinder 2 are respectively connected to the No. 1 high-temperature feedwater heater and the No. 2 high-temperature feedwater heater. The other steam outlet of the intermediate-pressure cylinder 3 is connected to the No. 3 high-temperature feedwater heater. The No. 1 high-temperature feedwater heater (hereinafter referred to as the high-temperature heater), the No. 2 high-temperature feedwater heater, the No. 3 high-temperature feedwater heater, and the deaerator feedwater assembly are also connected in sequence by a return pipe.

[0029] A portion of steam is drawn from the main steam pipe 4 along the main diversion pipe 5 to power the small steam turbine 15. The small steam turbine 15 drives the compressed gas assembly to perform compressed gas operation. At the same time, a drive steam pipe 7 is installed on the main steam pipe 4, and a portion of steam is drawn from the main steam pipe 4 as drive steam to accelerate the exhaust of the small steam turbine 15, thereby promoting the steam extraction from the main steam pipe 4 by the small steam turbine 15.

[0030] This invention increases the steam extraction flow rate to the main steam pipeline 4 by setting up exhaust pipes and drive steam pipes 7, exceeding the original 10% extraction flow rate limit for the unit. It also achieves a stable, efficient, and reliable supply of compressed gas to the coal-fired power unit. Simultaneously, multiple stages of industrial steam supply pipelines are led out from different pipelines, thus completing the supply of high-pressure, medium-pressure, and low-pressure industrial steam within the same power unit. Furthermore, in the multi-stage industrial steam supply:

[0031] The high-pressure industrial steam supply pipeline can supply 3~15MPa high-pressure industrial steam. The industrial steam supply pressure is adjusted to meet the needs of heat users by adding a desuperheating and pressure reducing device.

[0032] Medium-pressure industrial steam supply pipelines can supply 2~3MPa medium-pressure industrial steam. The industrial steam supply pressure is adjusted to meet the needs of heat users by adding desuperheating and pressure reducing devices.

[0033] The low-pressure industrial steam supply pipeline can supply 1~2MPa low-pressure industrial steam. The industrial steam supply pressure is adjusted to meet the needs of heat users by adding a desuperheater and pressure reducer.

[0034] In some embodiments, a first check valve 16, a first regulating valve 17, and a first isolation valve 18 are sequentially arranged on the main diversion pipe 5 along the direction from the main steam pipe 4 to the small steam turbine 15. The arrangement of the first check valve 16 and the first isolation valve 18 can facilitate system isolation between the main steam pipe 4 and the small steam turbine, and the first regulating valve 17 can effectively control the amount of steam entering the small steam turbine 15.

[0035] In some embodiments, the compressed gas assembly includes a first compressor 10 drivenly connected to a small steam turbine 15. The compressor is connected to a gas source pipeline 12, which is connected to a compressed gas source. The outlet of the first compressor 10 is connected to a gas product pipeline. The compressed gas source can be various gases such as air, carbon dioxide, and nitrogen. The small steam turbine 15 drives the first compressor 10 to work under the drive of steam extracted from the main steam pipeline 4. The compressed gas source enters the first compressor 10 along the gas source pipeline 12, and the gas is output along the gas product pipeline after being compressed by the first compressor 10.

[0036] In some embodiments, the small steam turbine 15 is connected to the compressor via a steam drive shaft.

[0037] In some embodiments, the gas source pipeline 12 is connected to a second compressor 11, which is an electric compressor. When the thermal power unit or small steam turbine 15 needs maintenance or malfunctions, the second compressor 11 can maintain the gas compression operation normally, thereby ensuring the normal production supply of compressed gas.

[0038] In some embodiments, the exhaust pressure in the exhaust pipe 6 is 1-2 MPa.

[0039] In some embodiments, a hot press 14 for mixing the exhaust steam from the small steam turbine 15 and the driving steam is provided at the connection point between the exhaust steam pipe 6 and the driving steam pipe 7. The hot press 14 is connected to both the driving steam pipe 7 and the exhaust steam pipe 6, and its outlet is connected to the cold reheat steam pipe 9. The hot press 14 can mix and compress the steam in the two pipes and supply it back into the cold reheat steam pipe 9 for reheating of the boiler assembly 1, thereby increasing the gas flow rate entering the boiler assembly 1.

[0040] In some embodiments, a second check valve 19, a second regulating valve 20, and a second isolation valve 21 are sequentially arranged on the drive steam pipe 7 along the direction from the main steam pipe 4 to the hot press 14. The arrangement of the second check valve 19 and the second isolation valve 21 can facilitate system isolation between the main steam pipe 4 and the drive steam pipe 7, and the second regulating valve 20 can effectively control the amount of steam entering the drive steam pipe 7.

[0041] In some embodiments, to facilitate flow control of the high-pressure industrial steam supply pipeline, the medium-pressure industrial steam supply pipeline, and the low-pressure industrial steam supply pipeline, a third regulating valve 22 is installed on the main diversion pipeline 5 between the small steam turbine 15 and the high-pressure industrial steam supply pipeline, a fourth regulating valve 23 is installed on the high-pressure industrial steam supply pipeline, a fifth regulating valve 24 is installed on the low-pressure industrial steam supply pipeline, a sixth regulating valve 25 is installed on the exhaust pipeline downstream of the connection point of the low-pressure industrial steam supply pipeline, and an eighth regulating valve 27 is installed on the medium-pressure industrial steam supply pipeline.

[0042] The third regulating valve 22 and the fourth regulating valve 23 work together to facilitate steam supply regulation in high-pressure industrial steam supply pipelines. Since the steam supply to the main intake pipeline 5 needs to be adjusted according to the high-pressure industrial steam supply, the third regulating valve 22 is used to regulate the total steam supply to the main intake pipeline 5. The fourth regulating valve 23 further controls the flow rate in the high-pressure steam supply pipeline. The fifth regulating valve 24 and the sixth regulating valve 25 work together to facilitate steam supply regulation in low-pressure industrial steam supply pipelines. Since the steam supply to the exhaust pipeline 6 needs to be adjusted according to the low-pressure industrial steam supply, the fifth regulating valve 24 is used to regulate the total steam supply to the exhaust pipeline 6. The sixth regulating valve 25 further controls the flow rate in the low-pressure steam supply pipeline. The eighth regulating valve 27 controls and adjusts the steam flow rate in the medium-pressure industrial steam supply pipeline.

[0043] In some embodiments, in order to facilitate the isolation of the gas supply system subsequently connected to the medium-pressure industrial steam supply pipeline from the hot reheat steam pipeline 30 to avoid steam backflow, a third check valve 28 and a third isolation valve 29 are sequentially provided on both sides of the eighth regulating valve 27 along the steam flow direction on the medium-pressure steam supply pipeline.

[0044] In some embodiments, a seventh regulating valve 26 is provided on the return pipe 8 at a position corresponding to the hot press 14 and the cold reheat steam pipe 9, which can control the steam flow rate supplied by the hot press 14 to the cold reheat steam pipe 9.

[0045] In some embodiments, to adjust the steam temperature within the hot press 14, desuperheating water needs to be supplied from the outside. Considering that the original thermal power unit's regenerative system includes a deaerator feedwater assembly for deaerating and cooling the steam, this assembly includes a deaerator connected to the intermediate-pressure cylinder 3. A feedwater pump is installed at the deaerator outlet, and a water inlet pipe 13 is installed at the feedwater pump outlet. The water inlet pipe 13 is connected to the hot press 14, supplying a portion of the condensate from the regenerative system to the hot press 14 for cold / warm water supply. This reduces the need to reintroduce water from the external environment, thus reducing manpower and material costs. The exhaust steam from the small turbine 15 is fed into the hot press 14 as the injected steam. The main steam and the exhaust steam from the small turbine 15 are mixed and blended in the hot press 14, supplemented by a portion of desuperheating water, adjusting the exhaust steam pressure and temperature to match the cold reheat steam pressure. Then, the exhaust steam flows to the boiler reheater inlet in the boiler assembly 1.

[0046] Furthermore, in order to provide sufficient steam supply, the main steam extraction rate needs to be significantly increased, exceeding the original unit's 10% extraction flow limit. A comparison of no steam extraction, traditional steam extraction, and this solution is as follows:

[0047] 1) Under non-extraction conditions, when the main steam flow rate is 1Q, the main steam extraction rate is 0, the total extraction rate of No. 1 high-temperature feedwater heater and No. 2 high-temperature feedwater heater is 0.15Q, and the cold reheat steam is 0.85Q. This inlet flow rate is the safe operating flow rate of boiler component 1 (at this time, the cold reheat steam flow rate is the inlet flow rate of the boiler reheater).

[0048] 2) Traditional steam extraction scheme: When the main steam flow rate is 1Q, the maximum main steam extraction rate is 0.1Q, the total extraction rate of No. 1 high-temperature feedwater heater and No. 2 high-temperature feedwater heater is 0.15Q, and the cold reheat steam is 0.75Q under the condition that the boiler reheater does not overheat (0.75Q is the minimum flow rate for the reheater to not overheat, and at this time the cold reheat steam flow rate is the inlet flow rate of the boiler reheater).

[0049] 3) The present invention can achieve the following when the main steam flow rate is 1Q: 0.2Q of steam is extracted to the small steam turbine 15, 0.2Q of steam is extracted to the drive steam pipeline, the total steam extraction rate of the No. 1 high-temperature feedwater heater and the No. 2 high-temperature feedwater heater is 0.15Q, the cold reheat steam is 0.55Q, and the boiler reheater inlet flow rate is 0.85Q (the boiler reheater inlet flow rate is equal to the cold reheat steam flow rate plus the mixed steam flow rate).

[0050] In summary, this invention can achieve large-flow main steam extraction, thus ensuring the implementation of a multi-stage industrial steam supply scheme.

[0051] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0052] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0053] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. An energy system coupling compressed gas supply and multi-stage industrial gas supply, comprising a thermal power unit, the thermal power unit comprising a boiler assembly, a high-pressure cylinder and a medium-pressure cylinder, a main steam pipe being provided between the boiler assembly and the high-pressure cylinder, a main bleeding pipe being provided in communication with the main steam pipe, a small steam turbine being in communication with the main bleeding pipe, a compressed gas assembly being drivingly connected to the small steam turbine, a cold reheat steam pipe being provided between the high-pressure cylinder and the boiler assembly, an exhaust steam pipe being provided in communication with the small steam turbine, a driving steam pipe being provided in communication with the main steam pipe, the exhaust steam pipe and the driving steam pipe being in communication with the cold reheat steam pipe, a low-pressure industrial gas supply pipe being provided in communication with the exhaust steam pipe, a high-pressure industrial gas supply pipe being provided in communication with the main bleeding pipe, and a medium-pressure industrial gas supply pipe being provided in communication with the boiler assembly and the medium-pressure cylinder. A heat presser for mixing exhaust steam of the small steam turbine and driving steam is provided at a position where the exhaust steam pipe and the driving steam pipe are connected, the heat presser being in communication with the exhaust steam pipe and the driving steam pipe, and a backflow pipe being provided in communication between the heat presser and the cold reheat steam pipe. An oxygen remover is in communication with the medium-pressure cylinder, a feed water pump is provided at an outlet of the oxygen remover, and a water supply pipe is provided in communication with the heat presser.

2. An energy system coupling a supply of compressed gas and a supply of multi-stage industrial gas supply as defined in claim 1, wherein, A first non-return valve, a first regulating valve and a first isolation valve are provided in sequence along the main steam pipe from the main bleeding pipe to the small steam turbine.

3. An energy system coupling a supply of compressed gas and a supply of multi-stage industrial gas supply as defined in claim 1, wherein, The compressed gas assembly comprises a first compressor drivingly connected to the small steam turbine, a gas source pipe being in communication with the first compressor, the gas source pipe being in communication with a compressed gas source, and a gas product pipe being provided in communication with an outlet of the first compressor.

4. An energy system to couple a supply of compressed gas and a supply of multi-stage industrial gas supply as defined in claim 1, wherein, A second non-return valve, a second regulating valve and a second isolation valve are provided in sequence along the driving steam pipe from the main steam pipe to the heat presser.

5. An energy system to couple a supply of compressed gas and a supply of multi-stage industrial gas supply as defined in claim 1, wherein, A third regulating valve is provided between the small steam turbine and the high-pressure industrial gas supply pipe, a fourth regulating valve is provided in the high-pressure industrial gas supply pipe, a fifth regulating valve is provided in the low-pressure industrial gas supply pipe, a sixth regulating valve is provided in the exhaust steam pipe downstream of the low-pressure industrial gas supply pipe, and an eighth regulating valve is provided in the medium-pressure industrial gas supply pipe.

6. An energy system to couple a supply of compressed gas and a supply of multi-stage industrial gas supply as defined in claim 1, wherein, A seventh regulating valve is provided in the backflow pipe between the heat presser and the cold reheat steam pipe.

7. An energy system to couple a supply of compressed gas and a supply of multi-stage industrial gas supply as defined in claim 5, wherein, A third non-return valve and a third isolation valve are provided in sequence along the medium-pressure industrial gas supply pipe on both sides of the eighth regulating valve.

8. An energy system to couple a supply of compressed gas and a supply of multi-stage industrial gas supply as defined in claim 3, wherein, A second compressor is provided in communication with the gas source pipe, the second compressor being an electric compressor.

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