An air intake cooling system and method for a combined cycle unit of an LNG power station with cold storage

Abstract

The present invention discloses an air intake cooling system and method for a combined cycle unit of an LNG power plant with cold storage, comprising an LNG cold energy recovery device and a water cold storage device. The air intake cooling system for a combined cycle unit of an LNG power plant with cold storage is operated in a high temperature season, LNG cold energy is recovered through two-stage heat exchange, and is stored using water cold storage technology, and is used to cool the air intake of the combined cycle unit in a timely manner. This not only has no impact on the power generation of the combined cycle unit itself, but also does not cause environmental pollution. At the same time, it can also increase the power generation power and power generation efficiency of the unit and improve the peak load performance of the unit.

Description

Technical Field

[0001] The present invention belongs to the technical field of surplus energy utilization of energy systems, and in particular relates to an air intake cooling system and method for a combined cycle unit of an LNG power station with cold storage. Background Art

[0002] LNG generally refers to liquefied natural gas, which is a liquid alkane mixture formed by drying and purifying natural gas and then cooling and liquefying it through a low-temperature process. Its main components are methane, as well as a small amount of ethane and propane. It is usually stored in low-temperature storage tanks at around -160°C and 0.1MPa. When used as a fuel, LNG carries a large amount of high-grade cold energy. The cold energy released during its gasification process is as high as about 830kJ / kg (including latent heat of gasification and sensible heat of heating to ambient temperature). LNG power plants need to heat and gasify LNG first. During this period, the cold energy of LNG gasification will generally be carried away by external media and discharged, causing losses.

[0003] LNG power plants are generally equipped with large F-class gas turbine combined cycle units. The power generation capacity of combined cycle units usually decreases with the increase of ambient temperature. If the above-mentioned LNG gasification cold energy is stored using water storage technology and used reasonably, and used as a cold source to cool the intake air of the combined cycle units in high temperature seasons, the power generation capacity of the combined cycle units can be effectively increased and the peak-shaving performance of the combined cycle units can be improved.

[0004] At present, the inlet air cooling of combined cycle units is mainly achieved by utilizing the heat extraction steam or low-pressure main steam of the steam turbine as the heat medium to supply the cold source prepared by equipment such as lithium bromide / ammonia absorption refrigerators. However, extracting the high-grade steam source prepared by the unit as the heat medium will have an adverse effect on the unit's power generation capacity and power generation efficiency. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention proposes an air intake cooling system for a combined cycle unit of an LNG power plant with cold storage, which utilizes the cold energy of LNG and combines it with water cold storage technology to realize the recovery and storage of the cold energy of LNG gasification and the air intake cooling of the combined cycle unit. It not only has no impact on the power generation of the unit itself, but also does not cause environmental pollution, and at the same time improves the operating economy of the unit.

[0006] The present invention is achieved through the following technical solutions:

[0007] An air intake cooling system for a combined cycle unit of an LNG power plant with cold storage, comprising an LNG cold energy recovery device for recovering LNG cold energy and a water cold storage device for cooling the air intake of the combined cycle unit;

[0008] The LNG cold energy recovery device comprises a primary cold energy heat exchanger, a refrigerant tank and a secondary cold energy heat exchanger; the cold side of the primary cold energy heat exchanger is connected in parallel with the LNG gasification device, the inlet end of the LNG gasification device is connected to the gas source, and the gas outlet end is connected to the steam turbine, the hot side outlet of the primary cold energy heat exchanger is connected to the cold side inlet of the secondary cold energy heat exchanger, and the cold side of the secondary cold energy heat exchanger is connected in series with the refrigerant tank;

[0009] The water cold storage device includes a naturally stratified cold storage water tank, an upper water distributor and a lower water distributor are arranged inside the tank, the hot side outlet of the secondary cold energy heat exchanger is connected to the inlet of the intake air cooler through the lower water distributor, the outlet of the intake air cooler is connected to the hot side inlet of the secondary cold energy heat exchanger through the upper water distributor, and the intake air cooler is arranged in the intake passage of the gas turbine.

[0010] Preferably, an auxiliary heater is provided at the outlet of the cold side of the first-stage cold energy heat exchanger, and the outlet of the auxiliary heater is connected to the gas turbine through a gas turbine front module.

[0011] Preferably, the refrigerant tank is connected to the inlet of the hot side of the primary cold energy heat exchanger through a refrigerant pump.

[0012] Preferably, the outlet of the lower water distributor is connected to the inlet of the intake air cooler through a cooling water pump, and the outlet of the upper water distributor is connected to the hot side inlet of the secondary cold energy heat exchanger through a cold storage water pump.

[0013] Preferably, a cold storage valve group is arranged between the inlet of the lower water distributor and the outlet of the upper water distributor, and a cooling release valve group is arranged between the outlet of the lower water distributor and the inlet of the upper water distributor, and the cold storage valve group and the cooling release valve group are respectively used to control the working state of the naturally stratified cold storage water tank.

[0014] Preferably, the cold storage valve group includes a first valve arranged at the inlet of the lower water distributor, a second valve and a third valve arranged in sequence at the outlet of the upper water distributor, the inlet of the first valve is connected to one end of the cold storage short-circuit pipe, the other end of the cold storage short-circuit pipe is connected between the second valve and the third valve, and a fourth valve is arranged on the cold storage short-circuit pipe.

[0015] Preferably, the cooling valve group includes a fifth valve and a sixth valve which are sequentially arranged at the outlet of the lower water distributor, and a seventh valve which is arranged at the inlet of the upper water distributor. The inlet of the seventh valve is connected to one end of the cooling short-circuit pipe, and the other end of the cooling short-circuit pipe is connected between the fifth valve and the sixth valve. An eighth valve is arranged on the cooling short-circuit pipe.

[0016] A cooling method for an intake air cooling system of a combined cycle unit of an LNG power plant with cold storage, wherein the cooling method for cooling the intake air of the combined cycle unit using LNG cold energy is as follows:

[0017] LNG enters the cold side of the first-stage cold energy heat exchanger for heat exchange and temperature rise, then enters the steam turbine to do work; the refrigerant on the hot side of the first-stage cold energy heat exchanger exchanges heat with the LNG on the cold side and cools down, then enters the cold side and refrigerant tank of the second-stage cold energy heat exchanger in turn, and then enters the first-stage cold energy heat exchanger again, forming a cold energy recovery cycle;

[0018] The cooling water on the hot side of the secondary cold energy heat exchanger exchanges heat with the refrigerant for cooling, and then enters the lower water distributor. Then the intake air cooler cools the intake air of the combined cycle unit. The heated cooling water enters the upper water distributor, and then enters the hot side of the secondary cold energy heat exchanger again for heat exchange with the refrigerant for cooling, forming a cooling cycle.

[0019] Preferably, when water is stored and not cooled,

[0020] Close all valves in the cooling valve group and the fourth valve on the cold storage short-circuit pipe. The hot water in the upper water distributor enters the hot side of the secondary cold energy heat exchanger for heat exchange. The cooling water after heat exchange and cooling enters the lower water distributor to complete cold storage, until all the cooling water in the upper water distributor enters the lower water distributor, reaching the maximum cold storage limit.

[0021] Preferably, when cooling is performed and water cooling is not performed:

[0022] Close all valves of the cold storage valve group and the eighth valve on the cooling short-circuit pipe. The cooling water in the lower water distributor enters the intake air cooler to cool the intake air of the combined cycle unit. The heated cooling water enters the upper water distributor until the cooling water in the lower water distributor is drained.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] The present invention discloses an air intake cooling system of a combined cycle unit of an LNG power plant with cold storage, comprising an LNG cold energy recovery device and a water cold storage device. The air intake cooling system of the combined cycle unit of an LNG power plant with cold storage is operated in high temperature seasons, LNG cold energy is recovered through two-stage heat exchange, and is stored using water cold storage technology, and is used to cool the air intake of the combined cycle unit in a timely manner. This not only has no impact on the power generation of the combined cycle unit itself, but also does not cause environmental pollution. At the same time, it can also increase the power generation power and power generation efficiency of the unit and improve the peak regulation performance of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of an air intake cooling system for a combined cycle unit of an LNG power plant with cold storage provided by the present invention.

[0026] In the figure: 1 is an LNG low-temperature storage tank; 2 is an LNG drying and purification device; 3 is an LNG gasification device; 4 is a gas turbine front module; 5 is a gas turbine; 6 is an air intake channel; 7 is a waste heat boiler; 8 is a chimney; 9 is a refrigerant tank; 10 is a refrigerant pump; 11 is a refrigerant valve; 12 is a primary cold energy heat exchanger; 13 is an auxiliary heater; 14 is a secondary cold energy heat exchanger; 15 is a cold storage water pump; 16 is a naturally stratified cold storage water tank; 17 is a lower water distributor, 18 is an upper water distributor, 19 is a cold storage valve group; 20 is a cooling valve group; 21 is a cooling water pump; 22 is an intake air cooler. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below in conjunction with the accompanying drawings, which are intended to explain the present invention rather than to limit it.

[0028] See also Figure 1 An air intake cooling system for a combined cycle unit of an LNG power plant with cold storage includes an LNG cold energy recovery device arranged next to an LNG low-temperature storage tank 1, and a water cold storage device arranged near the air intake of the combined cycle unit.

[0029] The LNG low-temperature storage tank 1 is connected to the inlet of the LNG gasification device 3 through the LNG drying and purification device, the outlet of the LNG gasification device 3 is connected to the inlet of the gas turbine pre-module 4, the outlet of the gas turbine pre-module 4 is connected to the gas turbine 5, the gas turbine 5 is connected to the generator, an intake air cooler 22 is provided in the intake channel 6 of the gas turbine 5, the exhaust port of the gas turbine 5 is connected to the waste heat boiler 7, and the waste heat boiler 7 is provided with a chimney 8.

[0030] The LNG cold energy recovery device includes a primary cold energy heat exchanger 12 , a refrigerant valve 11 , a refrigerant pump 10 , a refrigerant tank 9 and a secondary cold energy heat exchanger 14 .

[0031] The inlet of the cold side of the primary cold energy heat exchanger 12 is connected to the inlet of the LNG gasification device 3, and an auxiliary heat device 13 is provided at the outlet of the cold side of the primary cold energy heat exchanger 12. The outlet of the auxiliary heat device 13 is connected to the outlet of the LNG gasification device 3, so that the cold side of the primary cold energy heat exchanger 12 is connected in parallel with the LNG gasification device 3.

[0032] The hot side outlet of the primary cold energy heat exchanger 12 is connected to the cold side inlet of the secondary cold energy heat exchanger 14, and the cold side outlet of the secondary cold energy heat exchanger 14 is connected to the refrigerant tank 9, the refrigerant pump 10, the refrigerant valve 11 and the hot side inlet of the primary cold energy heat exchanger in sequence, and the hot side of the secondary cold energy heat exchanger 14 is connected to the intake air cooler 22 through a water cold storage device.

[0033] The cold water storage device includes a cold storage water pump 15 , a natural stratification cold storage water tank 16 and a cooling water pump 21 .

[0034] An upper water distributor 18 and a lower water distributor 17 are provided in the naturally stratified cold storage water tank 16. The hot side outlet of the secondary cold energy heat exchanger 14 is connected to the inlet of the lower water distributor 17. The outlet of the lower water distributor 17 is connected to the inlet of the intake air cooler 22 through a cooling water pump 21. The outlet of the intake air cooler 22 is connected to the inlet of the upper water distributor 18. The outlet of the upper water distributor 18 is connected to the hot side inlet of the secondary cold energy heat exchanger 14 through a cold storage water pump 15.

[0035] The inlet and outlet of the naturally stratified cold storage water tank 16 are provided with a cold storage valve group 19 and a cooling valve group 20. The cold storage valve group 19 includes a first valve arranged at the inlet of the lower water distributor 17, and a second valve and a third valve arranged at the outlet of the upper water distributor 18 in sequence. The inlet of the first valve is connected to one end of the cold storage short-circuit pipe, and the other end of the cold storage short-circuit pipe is connected between the second valve and the third valve. A fourth valve is arranged on the cold storage short-circuit pipe.

[0036] The cooling valve group 20 includes a fifth valve and a sixth valve which are sequentially arranged at the outlet of the lower water distributor 17, and a seventh valve which is arranged at the inlet of the upper water distributor 18. The inlet of the seventh valve is connected to one end of the cooling short-circuit pipe, and the other end of the cooling short-circuit pipe is connected between the fifth valve and the sixth valve. An eighth valve is arranged on the cooling short-circuit pipe.

[0037] The cooling method of the air intake cooling system of the LNG power plant combined cycle unit with cold storage provided by the present invention is described in detail below.

[0038] The LNG cold energy recovery device and the LNG gasification device 3 are connected in parallel, and a valve group is used for coordination and regulation. When the LNG cold energy recovery link is not needed, the LNG cold energy recovery link is closed by adjusting the valve group. After the LNG in the low-temperature storage tank 1 is dried and purified, it is gasified into natural gas by the gasification device 3 such as the original high-pressure water bath gasifier of the power station, and enters the gas turbine front module 4 as fuel to supply the gas turbine 5.

[0039] When the LNG cold energy recovery device is needed to work, the LNG cold energy recovery device is opened by adjusting the valve group. A part of the LNG treated by the drying and purification device 2 enters the primary cold energy heat exchanger 12, is supplied to the unit through refrigerant heat exchange and gasification, and the gasified cold energy is recovered by the refrigerant. The other part is supplied to the unit through the original gasification device 3 of the power station to ensure the normal power generation gas of the combined cycle unit.

[0040] The LNG entering the LNG cold energy recovery device enters the cold side of the first-stage cold energy heat exchanger 12 for heat exchange and temperature increase, then enters the gas turbine pre-module 4 after being heated by the auxiliary heat device, and finally enters the steam turbine to perform work; the refrigerant on the hot side of the first-stage cold energy heat exchanger 12 exchanges heat with the LNG on the cold side for temperature reduction, and then enters the cold side of the second-stage cold energy heat exchanger 14, the refrigerant tank 9, the refrigerant pump 10 and the refrigerant valve 11 in sequence to enter the first-stage cold energy heat exchanger 12 to form a cycle.

[0041] The cooling water on the hot side of the secondary cold energy heat exchanger 17 exchanges heat with the refrigerant for cooling, then enters the lower water distributor 17, and then enters the intake air cooler 22 through the cooling water pump 21 to cool the intake air of the combined cycle unit. The heated cooling water passes through the upper water distributor 18, and enters the hot side of the secondary cold energy heat exchanger 17 again through the cold storage water pump 15 to exchange heat with the refrigerant for cooling, thus forming a cooling cycle.

[0042] When water cooling is performed without cooling, that is, the cold energy of LNG is recovered, and the intake air of the combined cycle unit is not cooled.

[0043] Close all valves of the cooling valve group 20 and the fourth valve on the cold storage short-circuit pipe, and open all other valves of the cold storage valve group 19. The hot water in the upper water distributor 18 enters the cold storage water pump 15 through the second valve and the third valve, and enters the hot side of the secondary cold energy heat exchanger 14 for heat exchange after being pressurized by the cold storage water pump 15. The cooling water after heat exchange and cooling enters the lower water distributor 17 through the first valve to complete the cold storage, until all the cooling water in the upper water distributor 18 enters the lower water distributor 17, reaching the maximum cold storage limit.

[0044] When cooling is performed without water cooling, the combined cycle unit inlet air is cooled, and the cold energy of LNG is not recovered.

[0045] Close all valves of the cold storage valve group 19 and the eighth valve on the cooling short-circuit pipe, and open all other valves of the cooling valve group 20. The cooling water in the lower water distributor 17 is pressurized by the cooling water pump 21 and enters the intake air cooler 22 to cool the intake air of the combined cycle unit. The heated cooling water enters the upper water distributor 18 through the seventh valve until the cooling water in the lower water distributor 17 is drained.

[0046] The water storage device of the air intake cooling system of the combined cycle unit of the LNG power station with cold storage of the present invention uses cheap and easily accessible water as the cold storage medium, and uses the sensible heat of water to store cold. When the ambient temperature is too high, it is used to cool the unit intake, reduce the unit intake temperature, and improve the unit's operating economy.

[0047] The water cold storage device is in a naturally stratified water cold storage tank, and two water distributors are set up at the top and bottom to evenly distribute the water flow. During operation, by adjusting the cold storage water pump and the cold storage valve group, the low-temperature cooling water that has recovered the cold energy of LNG slowly flows into the lower water distributor of the cold storage water tank, and the high-temperature cooling water is pumped out from the upper water distributor and enters the secondary cold energy heat exchanger for cooling, forming a cold storage cycle. By adjusting the cooling water pump and the cooling valve group, the high-temperature cooling water continuously flows in from the upper water distributor, and the low-temperature chilled water continuously flows out from the lower water distributor, entering the intake air cooler to cool the intake air of the combined cycle unit, forming a cooling cycle.

[0048] The LNG cold energy recovery device includes a two-stage cold energy heat exchange system. When working, the refrigerant in the refrigerant tank of the first-stage cold energy heat exchange system enters the first-stage cold energy heat exchanger through the refrigerant pump and the refrigerant valve, enters the second-stage cold energy heat exchanger after heat exchange with LNG, and returns to the refrigerant tank after heat exchange with the cooling water in the water storage and utilization link, forming a cycle. After heat exchange with the refrigerant, the LNG is heated by the auxiliary heater, completely gasified and enters the gas turbine front module as fuel to supply the combined cycle unit for power generation. The two-stage cold energy heat exchanger in the LNG cold energy recovery link needs to be arranged at a suitable position near the LNG low-temperature storage tank according to the detailed heat exchange calculation design. Similarly, the intake air cooler in the water storage and utilization link also needs to be arranged at a suitable position in the intake channel of the gas turbine of the combined cycle unit according to the detailed heat exchange calculation design.

[0049] Although adding a heat exchanger to the gas turbine inlet duct will cause a certain amount of resistance loss on the air side of the unit's thermal system, preliminary calculations of the M701F4 gas turbine combined cycle unit show that the gas turbine inlet resistance loss does not exceed 1.4kPa, the unit's thermal system resistance loss is very small, and the heat exchanger resistance can be further reduced through optimized design. Therefore, it will not change the trend of overall performance optimization of the unit.

[0050] In the high temperature season, the air intake cooling system of the combined cycle unit of the LNG power plant with cold storage is operated. The LNG cold energy is recovered through two-stage heat exchange, and the water cold storage technology is used to store it. It is used to cool the combined cycle unit air intake in time. It not only has no effect on the power generation of the combined cycle unit itself, but also does not cause environmental pollution. At the same time, it can also increase the power generation and power generation efficiency of the unit and improve the peak load performance of the unit. For example, if the air intake temperature of the M701F4 gas turbine combined cycle unit is cooled from 42°C to 35°C, the power generation of the unit will increase by about 26MW, and the power generation efficiency will increase by about 0.5 percentage points.

[0051] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. An air intake cooling system for a combined cycle unit of an LNG power plant with cold storage, characterized in that: It includes an LNG cold energy recovery device for recovering LNG cold energy and a water cooling device for cooling the intake air of a combined cycle unit; The LNG cold energy recovery device comprises a primary cold energy heat exchanger (12), a refrigerant tank (9) and a secondary cold energy heat exchanger (14); the cold side of the primary cold energy heat exchanger (12) is connected in parallel with the LNG gasification device (3), the inlet end of the LNG gasification device (3) is connected to the gas source, and the gas outlet end is connected to the steam turbine; the hot side outlet of the primary cold energy heat exchanger (12) is connected to the cold side inlet of the secondary cold energy heat exchanger (14), and the cold side of the secondary cold energy heat exchanger (14) is connected in series with the refrigerant tank (9); The water cold storage device comprises a natural stratified cold storage water tank (16), an upper water distributor (18) and a lower water distributor (17) are arranged inside the tank, the hot side outlet of the secondary cold energy heat exchanger (14) is connected to the inlet of the intake air cooler (22) through the lower water distributor (17), the outlet of the intake air cooler (22) is connected to the hot side inlet of the secondary cold energy heat exchanger (14) through the upper water distributor (18), and the intake air cooler (22) is arranged in the intake passage (6) of the gas turbine (5); The outlet of the lower water distributor (17) is connected to the inlet of the intake air cooler (22) via a cooling water pump (21), and the outlet of the upper water distributor (18) is connected to the hot side inlet of the secondary cold energy heat exchanger (14) via a cold storage water pump (15); A cold storage valve group (19) is provided between the inlet of the lower water distributor (17) and the outlet of the upper water distributor (18), and a cooling release valve group (20) is provided between the outlet of the lower water distributor (17) and the inlet of the upper water distributor (18), and the cold storage valve group (19) and the cooling release valve group (20) are respectively used to control the working state of the natural stratified cold storage water tank (16); The cold storage valve group (19) comprises a first valve arranged at the inlet of the lower water distributor (17), a second valve and a third valve arranged in sequence at the outlet of the upper water distributor (18), the inlet of the first valve being connected to one end of the cold storage short-circuit pipe, the other end of the cold storage short-circuit pipe being connected between the second valve and the third valve, and a fourth valve being arranged on the cold storage short-circuit pipe; The cooling valve group (20) includes a fifth valve and a sixth valve which are sequentially arranged at the outlet of the lower water distributor (17), and a seventh valve which is arranged at the inlet of the upper water distributor (18). The inlet of the seventh valve is connected to one end of the cooling short-circuit pipe, and the other end of the cooling short-circuit pipe is connected between the fifth valve and the sixth valve. An eighth valve is arranged on the cooling short-circuit pipe.

2. The air intake cooling system of a LNG power plant combined cycle unit with cold storage according to claim 1, characterized in that: An auxiliary heat device (13) is provided at the outlet of the cold side of the primary cold energy heat exchanger (12), and the outlet of the auxiliary heat device (13) is connected to the gas turbine (5) via the gas turbine front module (4).

3. The air intake cooling system of a LNG power plant combined cycle unit with cold storage according to claim 1, characterized in that: The refrigerant tank (9) is connected to the inlet of the hot side of the primary cold energy heat exchanger (12) via a refrigerant pump (10).

4. A cooling method for an air intake cooling system of a LNG power plant combined cycle unit with cold storage according to any one of claims 1 to 3, characterized in that: The cooling method for using LNG cold energy to cool the intake air of a combined cycle unit is as follows: LNG enters the cold side of the first cold energy heat exchanger (12) for heat exchange and temperature rise, and then enters the steam turbine to perform work; the refrigerant on the hot side of the first cold energy heat exchanger (12) exchanges heat with the LNG on the cold side for temperature reduction, and then enters the cold side of the second cold energy heat exchanger (14) and the refrigerant tank (9) in sequence, and then enters the first cold energy heat exchanger (12) again, forming a cold energy recovery cycle; The cooling water on the hot side of the secondary cold energy heat exchanger (14) exchanges heat with the refrigerant for cooling, and then enters the lower water distributor (17), and then the intake air cooler (22) cools the intake air of the combined cycle unit. The heated cooling water enters the upper water distributor (18), and then enters the hot side of the secondary cold energy heat exchanger (14) again for heat exchange with the refrigerant for cooling, forming a cooling cycle.

5. The cooling method of the intake air cooling system of the LNG power plant combined cycle unit with cold storage according to claim 4, characterized in that: When water is stored and not cooled, All valves of the cooling valve group (20) and the fourth valve on the cold storage short-circuit pipe are closed, and the hot water in the upper water distributor (18) enters the hot side of the secondary cold energy heat exchanger (14) for heat exchange, and the cooling water after heat exchange and cooling enters the lower water distributor (17) to complete cold storage, until all the cooling water in the upper water distributor (18) enters the lower water distributor (17), reaching the maximum cold storage limit.

6. The cooling method of the intake air cooling system of the LNG power plant combined cycle unit with cold storage according to claim 4, characterized in that: When cooling is performed and water cooling is not performed: All valves of the cold storage valve group (19) and the eighth valve on the cooling short-circuit pipe are closed, and the cooling water in the lower water distributor (17) enters the intake air cooler (22) to cool the intake air of the combined cycle unit. The heated cooling water enters the upper water distributor (18) until the cooling water in the lower water distributor (17) is drained.

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