CN114687821A - Efficient power generation system based on liquefied natural gas and working method thereof - Google Patents
Efficient power generation system based on liquefied natural gas and working method thereof Download PDFInfo
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- CN114687821A CN114687821A CN202210378598.2A CN202210378598A CN114687821A CN 114687821 A CN114687821 A CN 114687821A CN 202210378598 A CN202210378598 A CN 202210378598A CN 114687821 A CN114687821 A CN 114687821A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K11/00—Plants characterised by the engines being structurally combined with boilers or condensers
- F01K11/02—Plants characterised by the engines being structurally combined with boilers or condensers the engines being turbines
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D15/00—Adaptations of machines or engines for special use; Combinations of engines with devices driven thereby
- F01D15/10—Adaptations for driving, or combinations with, electric generators
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K13/00—General layout or general methods of operation of complete plants
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K21/00—Steam engine plants not otherwise provided for
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K25/00—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for
- F01K25/08—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for using special vapours
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K25/00—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for
- F01K25/08—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for using special vapours
- F01K25/10—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for using special vapours the vapours being cold, e.g. ammonia, carbon dioxide, ether
- F01K25/103—Carbon dioxide
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K27/00—Plants for converting heat or fluid energy into mechanical energy, not otherwise provided for
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Abstract
The invention discloses a high-efficiency power generation system based on liquefied natural gas and a working method thereof, and belongs to the technical field of power generation systems. The system mainly comprises a natural gas boiler, a carbon dioxide gas turbine, a primary carbon dioxide heat exchanger, a secondary carbon dioxide heat exchanger, an air heat exchanger, a flue gas heat exchanger, an organic working medium gas turbine, an organic working medium heat exchanger, a liquid natural gas tank, a motor cooling working medium heat exchanger and an ultralow temperature motor. The liquid natural gas fuel is used as a cold source, the cold energy of the liquid natural gas is utilized in a gradient manner, the lower limit of the working temperature of carbon dioxide circulation and organic working medium circulation is reduced, and the low-temperature organic working medium circulation is coupled to absorb the heat released by the carbon dioxide circulation and the heat in the atmospheric environment; the working temperature of the motor is reduced, cooling equipment is saved, and energy consumption is reduced; the overall circulation efficiency is improved, the circulation structure is simplified, the investment and the operation and maintenance cost of the system are greatly reduced, and the overall requirements of energy conservation and emission reduction at present are met.
Description
Technical Field
The invention belongs to the technical field of power generation systems, and particularly relates to a high-efficiency power generation system based on liquefied natural gas and a working method thereof.
Background
With the promotion of market demand and the continuous development of energy utilization and equipment manufacturing technologies, in the past decades, large-scale power generation technologies of Rankine cycle using water vapor as a working medium and Brayton cycle using gas as a working medium are developed towards high parameters and high power. Analysis shows that the development of large-scale power generation technology improves energy conversion efficiency and reduces construction and power generation cost of unit power. However, the high parameters also make the generator set very bulky, the circulation system is extremely complex, and challenges are presented to material strength, equipment manufacturing and operational control. Therefore, the development of large-scale generator sets with high parameters and high power faces an important technical bottleneck.
In recent years, the academic and industrial circles generally pay attention to a closed brayton cycle power generation technology using supercritical carbon dioxide as a working medium, wherein a compressor is used for compressing carbon dioxide in a micro-supercritical state to improve the pressure of the working medium, gaseous carbon dioxide is heated in a boiler to reach the working pressure, then the gaseous carbon dioxide enters a supercritical carbon dioxide turbine to do work, and exhaust gas is subjected to heat regeneration through a plurality of gas-gas heat exchangers to improve the cycle efficiency.
Although it has been proven from practice at present that the turbomachinery of the supercritical carbon dioxide brayton cycle is more compact than the equipment of the steam rankine cycle, the following disadvantages are present: (1) in order to improve the cycle efficiency, a scheme of recompression or triple compression is adopted, a scheme of double reheating is also adopted for the gas turbine, the structure is abnormal and complex, and difficulty is brought to system regulation and control; (2) in order to realize multiple compression, multiple reheating and multi-stage heat return, a plurality of temperature intervals are required to be arranged in a boiler for heat transfer in a matching way, so that the efficiency of the boiler is improved; (3) because of compression at a near-critical point, a working medium liquid state phenomenon exists at the inlet of the compressor, so that water erosion is caused to blades, and meanwhile, difficulty is brought to stable control of the compressor; (4) the lowest pressure of the circulation is 7.38MPa, so that the enthalpy drop in the gas turbine is about 160kJ/kg and is far lower than that of the steam circulation, and thus, the flow rate of the working medium needs to be increased to increase the output power of the circulation, which brings fatal influence on the pressure loss of the working medium in a boiler.
Disclosure of Invention
In order to solve the above problems, an object of the present invention is to provide a liquefied natural gas-based high-efficiency power generation system and a working method thereof, which can fully utilize the cold energy of liquefied natural gas and fully release the energy of a carbon dioxide cycle working medium, thereby highly simplifying a boiler and an impeller machine, improving the compactness of a large-scale motor, and realizing high-efficiency conversion from heat energy to electric energy.
The invention is realized by the following technical scheme:
the invention discloses a high-efficiency power generation system based on liquefied natural gas, which comprises a natural gas boiler, a carbon dioxide gas turbine, a primary carbon dioxide heat exchanger, a secondary carbon dioxide heat exchanger, an air heat exchanger, a flue gas heat exchanger, an organic working medium gas turbine, an organic working medium heat exchanger, a liquefied natural gas tank, a motor cooling working medium heat exchanger and an ultralow temperature motor, wherein the natural gas turbine is connected with the air heat exchanger;
the working medium outlet of the natural gas boiler is connected with the inlet of a carbon dioxide gas turbine, the outlet of the carbon dioxide gas turbine is connected with the high-temperature side inlet of a first-stage carbon dioxide heat exchanger, the high-temperature side outlet of the first-stage carbon dioxide heat exchanger is connected with the high-temperature side inlet of a second-stage carbon dioxide heat exchanger, the high-temperature side outlet of the second-stage carbon dioxide heat exchanger is connected with the inlet of an air heat exchanger, the outlet of the air heat exchanger is connected with the inlet of a flue gas heat exchanger, and the outlet of the flue gas heat exchanger is connected with the working medium inlet of the natural gas boiler; the low-temperature side outlet of the first-stage carbon dioxide heat exchanger is connected with the inlet of the organic working medium gas turbine, the outlet of the organic working medium gas turbine is connected with the high-temperature side inlet of the organic working medium heat exchanger, the high-temperature side outlet of the organic working medium heat exchanger is connected with the second low-temperature side inlet of the second-stage carbon dioxide heat exchanger, and the second low-temperature side outlet of the second-stage carbon dioxide heat exchanger is connected with the low-temperature side inlet of the carbon dioxide heat exchanger; an outlet of the liquid natural gas tank is connected with a low-temperature side inlet of the organic working medium heat exchanger, a low-temperature side outlet of the organic working medium heat exchanger is connected with a first low-temperature side inlet of the second-stage carbon dioxide heat exchanger, a first low-temperature side outlet of the second-stage carbon dioxide heat exchanger is connected with a low-temperature side inlet of the motor cooling working medium heat exchanger, and a low-temperature side outlet of the motor cooling working medium heat exchanger is connected with a fuel inlet of the natural gas boiler; the high-temperature side outlet of the motor cooling working medium heat exchanger is connected with the inlet of a motor cooling working medium pump, the outlet of the motor cooling working medium pump is connected with the cooling working medium inlet of the ultra-low temperature motor, and the cooling working medium outlet of the ultra-low temperature motor is connected with the high-temperature side inlet of the motor cooling working medium heat exchanger; the rotor of the ultralow temperature motor is connected with the rotor of the carbon dioxide gas turbine through a coupler, and the rotor of the carbon dioxide gas turbine is connected with the rotor of the organic working medium gas turbine through the coupler.
Preferably, a carbon dioxide pump is arranged between the outlet of the high-temperature side of the secondary carbon dioxide heat exchanger and the inlet of the air heat exchanger; an organic working medium pump is arranged between the outlet at the high-temperature side of the organic working medium heat exchanger and the inlet at the second low-temperature side of the secondary carbon dioxide heat exchanger; a liquid natural gas pump is arranged between the outlet of the liquid natural gas tank and the low-temperature side inlet of the organic working medium heat exchanger; a motor cooling working medium pump is arranged between the high-temperature side outlet of the motor cooling working medium heat exchanger and the cooling working medium inlet of the ultra-low temperature motor.
Preferably, the ultralow temperature motor, the carbon dioxide gas turbine and the organic working medium gas turbine are coaxially arranged.
Preferably, the first-stage carbon dioxide heat exchanger is a printed circuit board heat exchanger, the second-stage carbon dioxide heat exchanger is a multi-stream printed circuit board heat exchanger, the air heat exchanger is a printed circuit board heat exchanger, the flue gas heat exchanger is a printed circuit board heat exchanger, the organic working medium heat exchanger is a plate-fin heat exchanger, and the motor cooling working medium heat exchanger is a plate-fin heat exchanger.
The invention discloses a working method of the high-efficiency power generation system based on the liquefied natural gas, which comprises the following steps:
the exhaust gas of the carbon dioxide gas turbine sequentially transfers heat to the organic working medium and the liquefied natural gas in the primary carbon dioxide heat exchanger and the secondary carbon dioxide heat exchanger, the gaseous carbon dioxide is changed into liquid, then the heat of the atmospheric environment is sequentially absorbed in the air heat exchanger for heating, and the heat contained in the exhaust smoke of the natural gas boiler is absorbed in the smoke heat exchanger for gasification; heating gaseous carbon dioxide in a natural gas boiler by heat energy released by combustion of natural gas and air to a maximum working temperature; the gaseous carbon dioxide enters a carbon dioxide wheel gas turbine to do work through expansion, and the shaft work drives an ultralow-temperature motor to convert the mechanical work into electric energy;
the exhaust of the organic working medium gas turbine transfers heat to liquefied natural gas in the organic working medium heat exchanger, the gaseous organic working medium is changed into liquid, then the heat released by the carbon dioxide circulation exhaust in the second-stage carbon dioxide heat exchanger and the first-stage carbon dioxide heat exchanger is absorbed in sequence, the gaseous organic working medium is changed into gaseous organic working medium, and the temperature is raised to the highest working temperature; gaseous organic working media enter an organic working media gas turbine to do work through expansion, and the shaft work drives an ultralow-temperature motor to convert mechanical work into electric energy;
the liquid natural gas in the liquid natural gas storage tank enters an organic working medium heat exchanger, the liquid natural gas enters a secondary carbon dioxide heat exchanger after absorbing the heat released by the organic working medium circulating exhaust gas to continuously absorb the heat released by the carbon dioxide circulating exhaust gas, finally the heat in the ultralow temperature motor is absorbed in a motor cooling working medium heat exchanger and is converted into gaseous natural gas, the gaseous natural gas is used as fuel and sent into a natural gas boiler to perform chemical reaction with air, and heat energy is released;
the motor cooling working medium absorbs heat generated by copper loss, iron loss and eddy current loss in the ultra-low temperature motor, natural gas is released in the motor cooling working medium heat exchanger to be converted from liquid state to gaseous state, and the motor cooling working medium enters the ultra-low temperature motor.
Preferably, the outlet pressure of the high-temperature side of the secondary carbon dioxide heat exchanger is 0.55-7.00 MPa.
Preferably, the exhaust pressure of the carbon dioxide gas turbine is below the critical pressure of carbon dioxide.
Preferably, the operating temperature of the ultra-low temperature motor is less than 0 ℃.
Compared with the prior art, the invention has the following beneficial technical effects:
according to the efficient power generation system based on the liquefied natural gas, the carbon dioxide power cycle and the cold energy utilization of the liquefied natural gas are combined, the heat which is originally required to be discharged to the outside in the carbon dioxide power cycle is absorbed and utilized by the liquefied natural gas, the lowest pressure of the carbon dioxide power cycle is further reduced, the work capacity of a unit mass working medium is improved, the carbon dioxide flow is reduced, the pressure loss of a boiler is reduced, and the carbon dioxide cycle efficiency is improved; the heat of carbon dioxide circular exhaust is adopted to heat the organic working medium, the organic working medium enters the organic working medium gas turbine to do work, the heat of the exhaust is absorbed by the liquid natural gas to form low-temperature organic working medium power circulation, the exhaust heat of the carbon dioxide circular is fully utilized, and the overall circulation efficiency is further improved.
The carbon dioxide power cycle and the low-temperature organic working medium power cycle both adopt a Rankine cycle form, namely the working medium is cooled into liquid, and when the working medium is pressurized, more mechanical work can be saved than that in the gaseous compression, and the cycle efficiency is improved. After the liquid carbon dioxide is pressurized by the pump, firstly, the heat of the atmospheric environment is absorbed in the air heat exchanger, the heat in the natural environment is fully utilized, secondly, the heat contained in the exhaust gas of the boiler is absorbed in the flue gas heat exchanger, and meanwhile, the temperature limit between a high-temperature heat source and a low-temperature heat source is enlarged through the cooling of the liquid natural gas, and the efficiency of the carbon dioxide circulation is improved.
The exhaust heat of the organic working medium gas turbine is absorbed by the liquefied natural gas, the exhaust temperature is reduced to about-150 ℃, the temperature limit between a high-temperature heat source and a low-temperature heat source of the organic working medium circulation is expanded, and the efficiency of the organic working medium circulation is improved. The liquefied natural gas absorbs the heat of the ultra-low temperature motor during working, reduces the working temperature of the motor to be below 0 ℃, reduces the resistance of the coil, reduces the heat generated by the motor, improves the efficiency of the motor, or improves the current and the magnetic flux in the coil, reduces the size of the motor, and reduces the material and processing cost. Meanwhile, the lowest pressure of the carbon dioxide circulation can be reduced to 0.55MPa, compared with the traditional 7.38MPa, the sealing pressure difference is greatly reduced by sealing the shaft end of the carbon dioxide gas turbine, the sealing technical difficulty is greatly reduced, and the sealing cost is reduced.
The working method of the efficient power generation system based on the liquefied natural gas disclosed by the invention takes the liquefied natural gas fuel as a cold source, the cold energy of the liquefied natural gas is utilized in a gradient manner, the lower limit of the working temperature of carbon dioxide circulation and organic working medium circulation is reduced, and meanwhile, the low-temperature organic working medium circulation is coupled to absorb the heat released by the carbon dioxide circulation and the heat in the atmospheric environment; the working temperature of the motor is reduced, cooling equipment is saved, and energy consumption is reduced; the overall circulation efficiency is improved, the circulation structure is simplified, the investment and the operation and maintenance cost of the system are greatly reduced, and the overall requirements of energy conservation and emission reduction at present are met.
Drawings
Fig. 1 is a schematic diagram of a liquefied natural gas-based high-efficiency power generation system according to the present invention.
In the figure: the system comprises a natural gas boiler 1, a carbon dioxide gas turbine 2, a primary carbon dioxide heat exchanger 3, a secondary carbon dioxide heat exchanger 4, a carbon dioxide pump 5, an air heat exchanger 6, a flue gas heat exchanger 7, an organic working medium gas turbine 8, an organic working medium heat exchanger 9, an organic working medium pump 10, a liquid natural gas tank 11, a liquid natural gas pump 12, a motor cooling working medium heat exchanger 13, an ultralow temperature motor 14 and a motor cooling working medium pump 15.
Detailed Description
The invention will now be described in further detail with reference to the following figures and examples, which are intended to illustrate and not to limit the invention:
the liquid natural gas contains cold energy and cannot be well utilized at present; the current supercritical carbon dioxide circulation has low efficiency and complex system. The efficient power generation system based on the liquefied natural gas combines the carbon dioxide power cycle and the cold energy utilization of the liquefied natural gas, and solves the technical problems existing at present.
As shown in fig. 1, the efficient power generation system based on liquefied natural gas of the present invention includes a natural gas boiler 1, a carbon dioxide gas turbine 2, a primary carbon dioxide heat exchanger 3, a secondary carbon dioxide heat exchanger 4, a carbon dioxide pump 5, an air heat exchanger 6, a flue gas heat exchanger 7, an organic working medium gas turbine 8, an organic working medium heat exchanger 9, an organic working medium pump 10, a liquefied natural gas tank 11, a liquefied natural gas pump 12, a motor cooling working medium heat exchanger 13, an ultra-low temperature motor 14, and a motor cooling working medium pump 15.
The working medium outlet of a natural gas boiler 1 is connected with the inlet of a carbon dioxide gas turbine 2, the outlet of the carbon dioxide gas turbine 2 is connected with the high-temperature side inlet of a first-stage carbon dioxide heat exchanger 3, the high-temperature side outlet of the first-stage carbon dioxide heat exchanger 3 is connected with the high-temperature side inlet of a second-stage carbon dioxide heat exchanger 4, the high-temperature side outlet of the second-stage carbon dioxide heat exchanger 4 is connected with the inlet of a carbon dioxide pump 5, the outlet of the carbon dioxide pump 5 is connected with the inlet of an air heat exchanger 6, the outlet of the air heat exchanger 6 is connected with the inlet of a flue gas heat exchanger 7, the outlet of the flue gas heat exchanger 7 is connected with the working medium inlet of the natural gas boiler 1, the low-temperature side outlet of the first-stage carbon dioxide heat exchanger 3 is connected with the inlet of an organic working medium gas turbine 8, the outlet of the organic working medium gas turbine 8 is connected with the high-temperature side inlet of an organic working medium heat exchanger 9, the high-temperature side outlet of the organic working medium heat exchanger 9 is connected with the inlet of the organic working medium pump 10, the outlet of the organic working medium pump 10 is connected with the inlet of the second low-temperature side of the second-stage carbon dioxide heat exchanger 4, the outlet of the second low-temperature side of the second-stage carbon dioxide heat exchanger 4 is connected with the inlet of the low-temperature side of the first-stage carbon dioxide heat exchanger 3, the outlet of the liquid natural gas tank 11 is connected with the inlet of the liquid natural gas pump 12, the outlet of the liquid natural gas pump 12 is connected with the inlet of the low-temperature side of the organic working medium heat exchanger 9, the outlet of the low-temperature side of the organic working medium heat exchanger 9 is connected with the inlet of the first low-temperature side of the second-stage carbon dioxide heat exchanger 4, the outlet of the first low-temperature side of the second-stage carbon dioxide heat exchanger 4 is connected with the inlet of the low-temperature side of the motor cooling working medium heat exchanger 13, the outlet of the low-temperature side of the motor cooling working medium heat exchanger 13 is connected with the fuel inlet of the natural gas boiler 1, the outlet of the motor cooling working medium heat exchanger 13 is connected with the inlet of the motor cooling working medium pump 15, and the outlet of the motor cooling working medium pump 15 is connected with the cooling working medium inlet of the ultra-low-temperature motor 14, the cooling working medium outlet of the ultralow temperature motor 14 is connected with the high-temperature side inlet of the motor cooling working medium heat exchanger 13, the rotor of the ultralow temperature motor 14 is connected with the rotor of the carbon dioxide gas turbine 2 through a coupler, and the rotor of the carbon dioxide gas turbine 2 is connected with the organic working medium gas turbine 8 through a coupler.
The carbon dioxide is pressurized by a carbon dioxide pump 5 and then is heated by an air heat exchanger 6, a flue gas heat exchanger 7 and a natural gas boiler 1 in three stages to change from liquid state to gas state.
The heat of the ultra-low temperature motor 14 cooling medium is absorbed by the natural gas in the motor cooling medium heat exchanger 13.
The heat of the exhaust gas of the carbon dioxide gas turbine 2 is absorbed by the organic working media at the middle and cold sides of the first-stage carbon dioxide heat exchanger 3 and the second-stage carbon dioxide heat exchanger 4.
The secondary carbon dioxide heat exchanger 4 has two cold side working media of natural gas and organic working media.
The heat of the organic working medium heat exchanger 9 is absorbed by the liquefied natural gas at the cold side.
The air heat exchanger 6 absorbs heat from the ambient environment to raise the temperature of the liquid carbon dioxide.
In a preferred embodiment of the present invention, the ultra-low temperature electric machine 14, the carbon dioxide gas turbine 2 and the organic working medium gas turbine 8 are arranged coaxially.
In a preferred embodiment of the present invention, the primary carbon dioxide heat exchanger 3, the secondary carbon dioxide heat exchanger 4, the air heat exchanger 6 and the flue gas heat exchanger 7 are printed circuit board heat exchangers, wherein the secondary carbon dioxide heat exchanger 4 is a multi-stream printed circuit board heat exchanger; the organic working medium heat exchanger 9 and the motor cooling working medium heat exchanger 13 are plate-fin heat exchangers.
The working method of the efficient power generation system based on the liquefied natural gas comprises the following steps:
the exhaust gas of the carbon dioxide gas turbine 2 transfers heat to the organic working medium and the liquefied natural gas in the first-stage carbon dioxide heat exchanger 3 and the second-stage carbon dioxide heat exchanger 4 in sequence, the gaseous carbon dioxide is changed into liquid, and the liquid carbon dioxide is pressurized to the highest working pressure of carbon dioxide circulation through a carbon dioxide pump 5. And then, the heat of the atmospheric environment is absorbed in the air heat exchanger 6 in sequence to be heated, and the heat contained in the exhaust smoke of the natural gas boiler 1 is absorbed in the smoke heat exchanger 7 to be gasified. The gaseous carbon dioxide is then heated in the natural gas boiler 1 by the heat energy released by the combustion of the natural gas and air, raising the temperature to the maximum operating temperature of the carbon dioxide cycle. Finally, gaseous carbon dioxide with certain temperature and pressure enters the carbon dioxide gas turbine 2 to do work through expansion, and the shaft work drives the ultralow-temperature motor 14 to convert the mechanical work into electric energy.
The exhaust of the organic working medium gas turbine 8 transfers heat to the liquefied natural gas in the organic working medium heat exchanger 9, the gaseous organic working medium is changed into liquid, and the liquid is pressurized to the highest working pressure of the organic working medium circulation through the organic working medium pump 10. And then the organic working medium absorbs the heat released by the carbon dioxide circulating exhaust in the secondary carbon dioxide heat exchanger 4 and the primary carbon dioxide heat exchanger 3 in sequence, the heat is converted into a gaseous state, and the temperature is raised to the highest working temperature of the organic working medium circulation. Then the gaseous organic working medium with certain temperature and pressure enters the organic working medium gas turbine 8 to do work through expansion, and the shaft work drives the ultralow temperature motor 14 to convert the mechanical work into electric energy.
The liquefied natural gas in the liquefied natural gas storage tank 11 is delivered to the organic working medium heat exchanger 9 through the liquefied natural gas pump 12, and the heat released by the organic working medium circular exhaust is absorbed. And then enters the secondary carbon dioxide heat exchanger 4 to continuously absorb the heat released by the carbon dioxide circulating exhaust gas. Finally, the heat in the ultralow temperature motor 14 is absorbed in the motor cooling working medium heat exchanger 13 and is converted into gaseous natural gas which is used as fuel and sent into the natural gas boiler 1 to react with air to release heat energy.
The motor cooling working medium absorbs heat generated by copper loss, iron loss and eddy current loss in the ultra-low temperature motor 14, and is released to natural gas in the motor cooling working medium heat exchanger 13, so that the natural gas is subjected to phase change and is converted from a liquid state to a gaseous state. The motor cooling medium is then forced into the ultra-low temperature motor 14 by the motor cooling medium pump 15.
The discharge pressure of the carbon dioxide gas turbine 2 is lower than the critical pressure of carbon dioxide, i.e., 7.38 MPa.
The operating temperature of the ultra-low temperature motor 14 is less than 0 deg.c.
The intake air temperature of the carbon dioxide gas turbine 2 is about 630 ℃.
The inlet temperature of the organic working medium gas turbine 8 is about 150 ℃, and the outlet temperature is about-150 ℃.
The outlet pressure of the high-temperature side of the secondary carbon dioxide heat exchanger 4 can be reduced to 0.55MPa at the lowest, and the temperature is about-55 ℃.
The above description is only a part of the embodiments of the present invention, and although some terms are used in the present invention, the possibility of using other terms is not excluded. These terms are used merely for convenience in describing and explaining the nature of the invention and are to be construed as any additional limitation which is not in accordance with the spirit of the invention. The foregoing is merely an illustration of the present invention for the purpose of providing an easy understanding and is not intended to limit the present invention to the particular embodiments disclosed herein, and any technical extensions or innovations made herein are protected by the present invention.
Claims (8)
1. A high-efficiency power generation system based on liquefied natural gas is characterized by comprising a natural gas boiler (1), a carbon dioxide gas turbine (2), a primary carbon dioxide heat exchanger (3), a secondary carbon dioxide heat exchanger (4), an air heat exchanger (6), a flue gas heat exchanger (7), an organic working medium gas turbine (8), an organic working medium heat exchanger (9), a liquefied natural gas tank (11), a motor cooling working medium heat exchanger (13) and an ultralow temperature motor (14);
a working medium outlet of the natural gas boiler (1) is connected with an inlet of a carbon dioxide gas turbine (2), an outlet of the carbon dioxide gas turbine (2) is connected with a high-temperature side inlet of a first-stage carbon dioxide heat exchanger (3), a high-temperature side outlet of the first-stage carbon dioxide heat exchanger (3) is connected with a high-temperature side inlet of a second-stage carbon dioxide heat exchanger (4), a high-temperature side outlet of the second-stage carbon dioxide heat exchanger (4) is connected with an inlet of an air heat exchanger (6), an outlet of the air heat exchanger (6) is connected with an inlet of a flue gas heat exchanger (7), and an outlet of the flue gas heat exchanger (7) is connected with a working medium inlet of the natural gas boiler (1); the low-temperature side outlet of the first-stage carbon dioxide heat exchanger (3) is connected with the inlet of the organic working medium gas turbine (8), the outlet of the organic working medium gas turbine (8) is connected with the high-temperature side inlet of the organic working medium heat exchanger (9), the high-temperature side outlet of the organic working medium heat exchanger (9) is connected with the second low-temperature side inlet of the second-stage carbon dioxide heat exchanger (4), and the second low-temperature side outlet of the second-stage carbon dioxide heat exchanger (4) is connected with the low-temperature side inlet of the carbon dioxide heat exchanger (3); an outlet of the liquid natural gas tank (11) is connected with a low-temperature side inlet of the organic working medium heat exchanger (9), a low-temperature side outlet of the organic working medium heat exchanger (9) is connected with a first low-temperature side inlet of the secondary carbon dioxide heat exchanger (4), a first low-temperature side outlet of the secondary carbon dioxide heat exchanger (4) is connected with a low-temperature side inlet of the motor cooling working medium heat exchanger (13), and a low-temperature side outlet of the motor cooling working medium heat exchanger (13) is connected with a fuel inlet of the natural gas boiler (1); a high-temperature side outlet of the motor cooling working medium heat exchanger (13) is connected with an inlet of a motor cooling working medium pump (15), an outlet of the motor cooling working medium pump (15) is connected with a cooling working medium inlet of an ultra-low temperature motor (14), and a cooling working medium outlet of the ultra-low temperature motor (14) is connected with a high-temperature side inlet of the motor cooling working medium heat exchanger (13); the rotor of the ultralow temperature motor (14) is connected with the rotor of the carbon dioxide gas turbine (2) through a coupler, and the rotor of the carbon dioxide gas turbine (2) is connected with the rotor of the organic working medium gas turbine (8) through the coupler.
2. The LNG-based high-efficiency power generation system as claimed in claim 1, wherein a carbon dioxide pump (5) is arranged between the outlet of the high-temperature side of the secondary carbon dioxide heat exchanger (4) and the inlet of the air heat exchanger (6); an organic working medium pump (10) is arranged between the high-temperature side outlet of the organic working medium heat exchanger (9) and the second low-temperature side inlet of the second-stage carbon dioxide heat exchanger (4); a liquid natural gas pump (12) is arranged between the outlet of the liquid natural gas tank (11) and the low-temperature side inlet of the organic working medium heat exchanger (9); a motor cooling working medium pump (15) is arranged between the high-temperature side outlet of the motor cooling working medium heat exchanger (13) and the cooling working medium inlet of the ultra-low temperature motor (14).
3. Liquefied natural gas-based high-efficiency power generation system according to claim 1, wherein the ultra-low temperature motor (14), the carbon dioxide gas turbine (2) and the organic working medium gas turbine (8) are coaxially arranged.
4. The liquefied natural gas-based high-efficiency power generation system according to claim 1, wherein the primary carbon dioxide heat exchanger (3) is a printed circuit board heat exchanger, the secondary carbon dioxide heat exchanger (4) is a multi-stream printed circuit board heat exchanger, the air heat exchanger (6) is a printed circuit board heat exchanger, the flue gas heat exchanger (7) is a printed circuit board heat exchanger, the organic working medium heat exchanger (9) is a plate-fin heat exchanger, and the motor cooling working medium heat exchanger (13) is a plate-fin heat exchanger.
5. The method of operating an LNG based high efficiency power generation system of any one of claims 1 to 4, comprising:
the exhaust gas of the carbon dioxide gas turbine (2) transfers heat to organic working media and liquefied natural gas in a primary carbon dioxide heat exchanger (3) and a secondary carbon dioxide heat exchanger (4) in sequence, gaseous carbon dioxide is changed into liquid, then the heat of the atmospheric environment is absorbed in an air heat exchanger (6) in sequence for heating, and the heat contained in the exhaust gas of the natural gas boiler (1) is absorbed in a flue gas heat exchanger (7) for gasification; the gaseous carbon dioxide is heated by the heat energy released by the combustion of natural gas and air in the natural gas boiler (1), and the temperature is raised to the highest working temperature; gaseous carbon dioxide enters a carbon dioxide wheel gas turbine (2) to expand to do work, and the shaft work drives an ultralow temperature motor (14) to convert mechanical work into electric energy;
the exhaust of the organic working medium gas turbine (8) transfers heat to liquefied natural gas in the organic working medium heat exchanger (9), the gaseous organic working medium is changed into liquid, and then the heat released by the carbon dioxide circular exhaust in the second-stage carbon dioxide heat exchanger (4) and the first-stage carbon dioxide heat exchanger (3) is absorbed in sequence, is changed into gaseous, and is heated to the highest working temperature; gaseous organic working media enter the organic working media gas turbine (8) to expand to do work, and the shaft work drives the ultralow temperature motor (14) to convert the mechanical work into electric energy;
liquid natural gas in a liquid natural gas storage tank (11) enters an organic working medium heat exchanger (9), after absorbing heat released by organic working medium circulating exhaust gas, enters a secondary carbon dioxide heat exchanger (4) to continuously absorb heat released by carbon dioxide circulating exhaust gas, finally absorbs heat in an ultralow temperature motor (14) in a motor cooling working medium heat exchanger (13), is converted into gaseous natural gas, is used as fuel and is sent into a natural gas boiler (1) to perform chemical reaction with air, and heat energy is released;
the motor cooling working medium absorbs heat generated by copper loss, iron loss and eddy current loss in the ultra-low temperature motor (14), natural gas is released in the motor cooling working medium heat exchanger (13) to be converted from liquid state to gas state, and the motor cooling working medium enters the ultra-low temperature motor (14).
6. The working method of the liquefied natural gas-based high-efficiency power generation system according to claim 5, wherein the outlet pressure of the secondary carbon dioxide heat exchanger (4) on the high-temperature side is 0.55 to 7.00 MPa.
7. The method for operating a liquefied natural gas-based high-efficiency power generation system according to claim 5, wherein a discharge pressure of the carbon dioxide gas turbine (2) is lower than a critical pressure of carbon dioxide.
8. The operating method of the liquefied natural gas based high efficiency power generating system as claimed in claim 5, wherein the operating temperature of the ultra-low temperature motor (14) is lower than 0 ℃.
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