CN113586187A - Rankine cycle system and Rankine cycle method - Google Patents
Rankine cycle system and Rankine cycle method Download PDFInfo
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- CN113586187A CN113586187A CN202110632511.5A CN202110632511A CN113586187A CN 113586187 A CN113586187 A CN 113586187A CN 202110632511 A CN202110632511 A CN 202110632511A CN 113586187 A CN113586187 A CN 113586187A
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- 238000000034 method Methods 0.000 title claims description 19
- 239000011555 saturated liquid Substances 0.000 claims abstract description 7
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- 238000001816 cooling Methods 0.000 claims description 15
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- 239000007788 liquid Substances 0.000 claims description 12
- 238000007906 compression Methods 0.000 claims description 8
- 239000003949 liquefied natural gas Substances 0.000 claims description 8
- 230000006835 compression Effects 0.000 claims description 6
- 229920006395 saturated elastomer Polymers 0.000 claims description 5
- 230000007704 transition Effects 0.000 claims description 2
- 230000008569 process Effects 0.000 description 13
- 239000002918 waste heat Substances 0.000 description 11
- 238000010248 power generation Methods 0.000 description 9
- 239000012071 phase Substances 0.000 description 8
- 230000008859 change Effects 0.000 description 5
- 230000002441 reversible effect Effects 0.000 description 5
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- 239000003546 flue gas Substances 0.000 description 4
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- 238000011069 regeneration method Methods 0.000 description 2
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- 238000006467 substitution reaction Methods 0.000 description 2
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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
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D13/00—Combinations of two or more machines or engines
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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
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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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- Engine Equipment That Uses Special Cycles (AREA)
Abstract
The invention provides a Rankine cycle system. The Rankine cycle system comprises a medium loop formed by sequentially connecting a heater, a working device, a cooler and a supercharging device. The circulating medium circularly flows in the medium loop, the circulating medium flowing out of the heater is in a supercritical state, the circulating medium is fully expanded to a gas state slightly higher than the pressure of the triple point of the circulating medium in the acting device, the circulating medium flowing out of the cooler is in a saturated liquid state, and the temperature of the circulating medium is 0-20 ℃ higher than the temperature of the triple point of the circulating medium. The circulating medium is gradually expanded from a high-temperature and high-pressure supercritical state to a theoretical working limit state, namely the vicinity of a triple point pressure, so that the working capacity of the circulating medium is fully exerted.
Description
Technical Field
The invention relates to the field of power generation systems, in particular to a Rankine cycle system and a Rankine cycle method.
Background
In industrial production, some combustion engines tend to have higher exhaust temperature, and in order to realize further utilization of an exhaust high-level heat source, a steam Rankine cycle is usually combined on the bottom layer of the combustion engine to realize efficient combined cycle power generation. Existing steam rankine cycles have four processes:
heating process: the water is heated in the boiler to steam, and the heating process can be idealized to be a constant-pressure reversible endothermic process.
The work doing process: the steam is expanded in the turbine, and the work doing process can be idealized into a reversible adiabatic expansion process, namely an isentropic expansion process.
And (3) cooling: the steam is cooled in the condenser to saturated water and the cooling process can be idealized as a reversible constant pressure cooling process.
In the pressurizing process, water is compressed and pressurized in the water pump, and the pressurizing process can be idealized as a reversible adiabatic compression process, namely an isentropic compression process.
However, according to the carnot principle, the efficiency of the reversible heat engine is only related to the highest temperature and the lowest temperature of the circulating medium, while in the conventional steam rankine cycle, water is heated to a gaseous state in the heating process and cooled to a liquid state close to the ambient temperature in the cooling process, which limits the operating efficiency of the rankine cycle system to a certain extent.
Disclosure of Invention
In view of the drawbacks of the prior art, an object of the present invention is to provide a rankine cycle system with higher operation efficiency.
The Rankine cycle system comprises a medium loop formed by sequentially connecting a heater, a power-applying device, a cooler and a supercharging device, a cycle medium circularly flows in the medium loop, the cycle medium flowing out of the heater is in a supercritical state, the temperature of a three-phase point of the cycle medium is lower than 0 ℃, the pressure of the three-phase point of the cycle medium is higher than standard atmospheric pressure, the cycle medium flowing out of the cooler is in a saturated liquid state, the temperature T1 of the cycle medium is 0-20 ℃ higher than the temperature Tgls of the three-phase point of the cycle medium, and the pressure P1 of a gaseous cycle medium flowing out of the power-applying device is equal to the saturated vapor pressure of the cycle medium at the temperature T1. According to the technical scheme, firstly, in the Rankine cycle system provided by the invention, the circulating medium reaches a supercritical state in the heating device, when the circulating medium is in the supercritical state, the density is higher, and the number of turbine stages required by expansion work is relatively less, so that the turbine equipment is more compact than the turbine structure in the conventional steam Rankine cycle, and the smaller volume of the turbine equipment means a smaller plant area and a more compact cycle flow.
Secondly, from the thermodynamic perspective, increasing the temperature of the heat source during the cycle and decreasing the temperature of the heat sink during the cycle can further increase the cycle efficiency. However, when the temperature is below the triple point, the constant pressure cooling will cause the circulating medium to desublimate directly from the gaseous state to the solid state without passing through the liquid phase region. However, because the solid circulating medium cannot flow, the utilization capacity of the circulating medium in the Rankine cycle to a cold source provided by the cooler is limited by the temperature of the triple point of the circulating medium, so according to the Carnot principle, the circulating medium is heated to a supercritical state higher than the gas state in the invention, and the circulating medium is cooled to a temperature slightly higher than the triple point in the cooler (namely 0-20 ℃ higher than the triple point), and the corresponding saturated vapor pressure of the circulating medium at the temperature is the exhaust pressure of the last stage working device, so that the working efficiency of the Rankine cycle system can be improved to the maximum extent; furthermore, the temperature of the triple point of the circulating medium is lower than 0 ℃, the circulating medium can be reduced to a lower temperature, and the pressure of the triple point is higher than the standard atmospheric pressure, so that the vacuum in the condenser is not required to be maintained by external equipment in the condensation process, and the air is prevented from leaking into the condenser, therefore, after a high-quality low-temperature cold source is combined and utilized, the circulation efficiency can be greatly improved from the thermodynamic aspect.
Preferably, the rankine cycle system further comprises a regenerator, a hot side inlet of the regenerator is communicated with the medium outlet of the power device, a hot side outlet of the regenerator is communicated with a hot side inlet of the cooler, a cold side inlet of the regenerator is communicated with the medium outlet of the supercharging device, and a cold side outlet of the regenerator is communicated with the heater.
According to the technical scheme, the heat regenerator is added into the Rankine cycle system, the gaseous circulation medium at the outlet of the acting device enters the heat regenerator to exchange heat with the liquid circulation medium after cooling and compressing in the heat regenerator, so that the gaseous circulation medium is cooled in the heat regenerator in advance and then enters the cooler to be cooled, and the liquid circulation medium pressurized by the pressurizing device is heated in the heat regenerator in advance before entering the heater, so that the waste heat of the circulation medium behind the acting device can be utilized, the energy required to be provided by the heater and the cooler is reduced, and the operating efficiency of the Rankine cycle system is improved.
Preferably, the regenerator comprises a high-temperature regenerator and a low-temperature regenerator, a hot side inlet of the high-temperature regenerator is communicated with a medium outlet of the power device, a hot side outlet of the high-temperature regenerator is communicated with a hot side inlet of the low-temperature regenerator, a cold side outlet of the high-temperature regenerator is communicated with the heater, a cold side inlet of the high-temperature regenerator is communicated with a cold side outlet of the low-temperature regenerator, a cold side inlet of the low-temperature regenerator is communicated with a medium outlet of the supercharging device, and a hot side outlet of the low-temperature regenerator is communicated with the cooler.
Preferably, the rankine cycle system further comprises a first three-way valve, a second three-way valve and a compressor, wherein the first three-way valve is respectively communicated with the outlet of the compressor, the outlet of the cold side of the low-temperature heat regenerator and the inlet of the cold side of the high-temperature heat regenerator, and the second three-way valve is respectively communicated with the inlet of the compressor, the outlet of the hot side of the low-temperature heat regenerator and the inlet of the hot side of the cooler.
According to the technical scheme, the heat regenerator is further arranged to be the high-temperature heat regenerator and the low-temperature heat regenerator, so that the waste heat of the working medium flowing out of the acting device can be further utilized, the circulating medium flowing out of the low-temperature heat regenerator is shunted, and a part of the circulating medium is directly compressed by the compressor without passing through the subcooler and flows to the heating device after being gathered with the liquid circulating medium after cooling and pressurization, so that the cold source loss of the Rankine cycle system can be reduced, and the operating efficiency of the Rankine cycle system is further improved.
Preferably, the work-doing device comprises a first turbine, a second turbine and a third turbine, the first turbine uses the enthalpy value change of the circulating medium in the supercritical state to do work externally, the second turbine receives the circulating medium in the supercritical state from the first turbine and uses the phase state change of the circulating medium from the supercritical state to the gaseous state to do work externally, and the third turbine receives the gaseous circulating medium from the second turbine and uses the enthalpy value change of the gaseous circulating medium to do work externally.
According to the technical scheme, the acting device is set to be the multistage turbine, so that heat energy transmitted to the circulating medium in the heater is fully converted into mechanical energy through the multistage turbine, the operation efficiency of the whole circulating system is improved, when the multistage turbine is three-stage transparent, the circulating medium in the first turbine is kept in a supercritical state, the density of the circulating medium is higher at the moment, the structure of the first turbine can be more compact, the circulating medium enters the third turbine after being further subjected to adiabatic expansion in the second turbine and is changed into a gas state from the supercritical state, and the waste heat of the circulating medium in the third turbine is further utilized, so that the operation efficiency of the whole circulating system is improved.
Preferably, the circulation medium of the rankine cycle system is CO 2.
According to the technical scheme, the application of CO2 as a circulating medium is mainly characterized by the advantages of supercritical CO2(S-CO2) Brayton cycle, high-temperature heat source circulating efficiency of the S-CO2 Brayton cycle is high, compression power consumption is low, a turbine device is compact in structure, small in occupied space, low in corrosivity and the like, and the method is one of potential choices for efficient power generation by waste heat of gas turbine exhaust. However, in the supercritical CO2(S-CO2) Brayton cycle, the temperature of the heat sink must not be lower than the critical temperature of CO2 (31.1 ℃), which limits the operating efficiency of the supercritical CO2(S-CO2) Brayton cycle system.
Furthermore, the triple point of H2O is 0.01 ℃ and 610.75Pa, the temperature of the cold end of the H2O can be reduced to more than 0 ℃ at the lowest, and because the triple point pressure of H2O is too low (only less than 1kPa) and is an open cycle, if the triple point pressure is reduced to be close to the triple point pressure, a vacuum pump needs to be used for pumping work, so that the improvement on the cycle efficiency is limited. In contrast, the triple point of the CO2 is-56.6 ℃ and 0.52MPa, the temperature of a cold source can be reduced to be lower, the pressure of the triple point is above the atmospheric pressure, the circulation form is closed circulation, and the circulation is not required to be vacuumized by a vacuum pump, so that the whole circulation is above the atmospheric pressure, and the non-condensable gas is prevented from permeating into the low-pressure part of the circulation. Therefore, after the high-quality low-temperature cold source is utilized, the circulation efficiency can be greatly improved from the thermodynamic perspective.
Finally, the corrosiveness of the CO2 circulating medium is much higher than that of H2O steam, and the requirement on corrosion resistance of high-temperature component equipment materials can be greatly reduced.
The Rankine cycle system further comprises an external cold source, an external heat source and an organic medium Rankine cycle circuit, the organic medium Rankine cycle circuit comprises an organic medium heater and an organic medium cooler, the external heat source enters the organic medium heater after flowing through the heater, and the external cold source is respectively communicated with the cooler and the organic medium cooler.
According to the technical scheme, higher cycle efficiency can be realized by adopting a cycle mode of combining Rankine cycle and organic Rankine cycle, and more power generation and energy utilization rate can be improved by using the combined cycle system of the invention for the same heat source.
Wherein, the temperature of the external cold source is preferably-162 ℃ to 0 ℃. According to the technical scheme, the gaseous circulating medium can be rapidly cooled to the position near the triple point by using the cold source with lower temperature, and the low temperature of the cold source is favorable for improving the working efficiency of the Rankine cycle system.
Wherein, preferably, the external heat source is the gas unit, and the external cold source is liquefied natural gas.
According to the technical scheme, the gas turbine set is used as a heat source, namely, the redundant heat (such as high-temperature flue gas) generated by the gas turbine set is recycled, in addition, the temperature of a cold source of the liquefied natural gas is about-162 ℃, so that the gaseous circulating medium can be rapidly cooled to a saturated liquid state near a triple point, the low temperature of the cold source is favorable for improving the operating efficiency of a Rankine cycle system, further, the liquefied natural gas is used as the cold source and is introduced into a cooler to be used as fuel after exchanging heat with the circulating medium, the redundant heat generated by the gas turbine set can be used as an external heat source to supply heat to the cycle, and therefore the cold source material can be fully and reasonably utilized.
Drawings
FIG. 1 is a schematic diagram of a Rankine cycle system provided by an embodiment of the invention;
FIG. 2 is a schematic diagram of a further Rankine cycle system provided by an embodiment of the invention;
FIG. 3 is a schematic structural diagram of another Rankine cycle system provided by an embodiment of the invention.
Description of the reference numerals
1-a heater; 2-a power-applying device; 21-a first turbine; 22-a second turbine; 23-a third turbine; 3-a cooler; 4-a pressure boosting device; 5-a heat regenerator; 51-high temperature regenerator; 52-low temperature regenerator; 6-external heat source; 7-external cold source; 8-a compressor; 91-a first three-way valve; 92-a second three-way valve; 1 a-an organic medium heater; 2 a-an organic medium work-applying device; 3 a-organic medium cooler; 4 a-organic medium pressurizing means; 5 a-organic medium regenerator.
Detailed Description
The present invention will be described in further detail with reference to the following specific examples and the accompanying drawings. The present invention is not limited to the embodiments described below, and various modifications, changes, combinations, and improvements based on the technical idea of the present invention adopted within the knowledge of those skilled in the art are included in the scope of the present invention.
1. Integral structure
As shown in fig. 1, the rankine cycle system provided by this embodiment includes a medium loop formed by sequentially connecting a heater 1, a working device 2, a heat regenerator 5, a cooler 3 and a pressure increasing device 4, wherein a circulating medium circulates inside the medium loop, specifically, the temperature of the triple point of the circulating medium is lower than 0 ℃, the pressure of the triple point of the circulating medium is higher than the standard atmospheric pressure, the circulating medium absorbs heat energy in the heater 1 and becomes a supercritical fluid, and then flows into the working device 2 to perform expansion and work, so as to convert the heat energy into mechanical energy more convenient to use, the gaseous circulating medium passing through the working device 2 enters the heat regenerator 5, the waste heat of the circulating medium is reused and then enters the cooler 3 to be cooled, and the gaseous circulating medium is cooled to a saturated liquid at a temperature T1(Tgls < T1< Tgls +20 ℃) slightly higher than the temperature of the triple point Tgls of the circulating medium, the circulating medium enters a supercharging device 4 for supercharging, and the supercharged liquid circulating medium enters a heat regenerator 5 for absorbing the exhaust waste heat of the acting device and reenters the heater 1 for new circulation, so that the heat energy is circularly converted into mechanical energy.
It should be noted that, in the present embodiment, the structure of each device or apparatus is not limited, for example, the work-doing device 2 may be a rotating turbine in some embodiments, and in other embodiments, the work-doing device 2 may also be a cylinder device with a transmission rod, and similarly, the device or apparatus in the present invention may be simply replaced without departing from the technical solution of the present invention, and the scope of the present invention is not exceeded.
In addition, as can be understood by those skilled in the art, the regenerator 5 is a device for reusing the waste heat after the working device 2 in the present embodiment, that is, a preferred solution of adding the rankine cycle of the regenerator 5 in the present embodiment is illustrated, but those skilled in the art can understand that the rankine cycle system provided by the present invention may not include a regenerator, and directly consists of the heater 1, the working device 2, the cooler 3, and the pressure boosting device 4 which are connected in sequence.
In the embodiment, firstly, the triple point temperature of the circulating medium is lower than 0 ℃, a cold source medium at a lower temperature can be utilized, the triple point pressure is higher than the standard atmospheric pressure, so that the vacuum in the condenser is not required to be maintained, the energy consumption is saved, and meanwhile, the external air is prevented from leaking into the circulating system, so that the circulating efficiency can be greatly improved according to the carnot principle after the high-quality low-temperature cold source is utilized.
Secondly, the circulating medium reaches a supercritical state in the heating device, when the circulating medium is in the supercritical state, the density is high, the number of turbine stages required by expansion work is relatively small, therefore, in the embodiment, the high-pressure turbine equipment is more compact than the turbine structure in the existing steam Rankine cycle, and the smaller volume of the turbine equipment means a smaller plant area and a more compact circulation flow.
Finally, the temperature of the circulating medium in the supercritical state is higher than that of the gaseous circulating medium, so that the circulating medium in the rankine cycle system provided by the invention can reach a higher initial temperature under the condition that the cold source provided by the cooler 3 is constant according to the carnot principle, namely the operation efficiency of the rankine cycle system provided by the invention is higher.
Preferably, the circulation medium of the rankine cycle system is CO 2.
In the embodiment, the application of the CO2 as the circulating medium is mainly in the supercritical CO2(S-CO2) brayton cycle, and the S-CO2 brayton cycle has many advantages of high cycle efficiency of a high-temperature heat source, low compression power consumption, compact structure of a rotating turbine device, small occupied area, low corrosivity and the like, and is one of potential choices for efficient power generation by waste heat of exhaust gas of a gas turbine. However, in the S-CO2 Brayton cycle, the temperature of the heat sink must not be lower than the critical temperature of CO2 (31.1 ℃), which limits the operating efficiency of the S-CO2 Brayton cycle system.
Further, the triple point of H2O is 0.01 ℃, 610.75Pa, the cold end temperature can only be reduced to above 0 ℃ at the lowest, and because the triple point pressure of H2O is too low (only less than 1kPa), and the circulation form is open circulation, if the pressure is cooled to be close to the triple point, a vacuum pump needs to be used for pumping work, extra energy consumption is increased, and the improvement on the circulation efficiency is limited. In contrast, the CO2 circulation form is closed circulation, vacuum pumping is not needed, the triple point of CO2 is-56.6 ℃ and 0.52MPa, the temperature of a cold source can be reduced to be lower, and the pressure of the triple point is above the atmospheric pressure, so that leakage of non-condensable air outside the condenser to the inside of the circulation is avoided. Therefore, after the high-quality low-temperature cold source is utilized, the circulation efficiency can be greatly improved from the thermodynamic perspective.
In addition, the corrosiveness of the CO2 circulating medium is much higher than that of H2O steam, so that the requirement on corrosion resistance of high-temperature component equipment materials can be greatly reduced.
Finally, the specific volume of the CO2 circulating medium is much smaller than that of H2O, so that the size of working equipment can be greatly reduced, and the area of a plant is saved.
Next, the rankine cycle apparatus provided in the present embodiment will be described in more detail.
1. Heater 1
In this embodiment, the heater 1 may be any device capable of heating a circulating medium, specifically, the heater 1 may be a heat exchanger that heats the circulating medium by using an external heat source 6, one end of the heat exchanger is connected to the external heat source 6, and the other end of the heat exchanger is connected to the circulating medium, so that the circulating medium absorbs heat of the external heat source 6 through heat exchange to raise temperature and convert a phase state, so as to perform subsequent work, preferably, the external heat source 6 may be solar energy, nuclear energy, fossil fuel, or the like, further, the external heat source 6 is a gas turbine, so that waste heat of high-temperature flue gas after combustion in the gas turbine can be reused, and resources are saved.
2. Work application device 2
In the present embodiment, the working device 2 may be a device capable of converting thermal energy into mechanical energy by using expansion work of the circulating medium, for example, a cylinder structure that pushes the transmission rod to reciprocate by gas expansion, or a rotary turbine structure that performs work by rotating by gas expansion, and the present embodiment is further described by taking the working device 2 as a rotary turbine as an example.
Preferably, the rotary turbine includes a first turbine 21, a second turbine 22 and a third turbine 23, the first turbine 21 externally performs work by utilizing enthalpy change of the circulating medium in a supercritical state, the second turbine 22 receives the circulating medium in the supercritical state from the first turbine 21 and externally expands work by utilizing phase state transition of the circulating medium from the supercritical state to a gaseous state, and the third turbine 23 receives the gaseous circulating medium from the second turbine 22 and externally performs work by utilizing enthalpy change of the gaseous circulating medium.
In the present embodiment, the working efficiency of the overall circulation system is improved by setting the power generation device 2 as a multi-stage turbine, so that the heat energy transmitted to the circulating medium in the heater 1 is fully converted into mechanical energy by the multi-stage turbine, but those skilled in the art can understand that the effect of performing work on the circulating medium in the power generation device 2 can be achieved by setting a single or other number of turbines, without exceeding the protection scope of the present invention, wherein when the multi-stage turbine is three-stage transparent, the circulating medium in the first turbine 21 is maintained in a supercritical state, at this time, the density of the circulating medium is higher, the structure of the first turbine 21 can be more compact, the circulating medium enters the third turbine 23 after further adiabatic expansion in the second turbine 22, after changing from the supercritical state into a gaseous state, the waste heat of the circulating medium is further utilized in the third turbine 23, thereby increasing the overall operating efficiency of the circulation system.
3. Regenerator 5
In this embodiment, the regenerator 5 may be a device that has two flow paths, i.e., a cold flow path and a hot flow path, and exchanges heat with media in the two flow paths, specifically, a hot side inlet of the regenerator 5 may be communicated with a media outlet of the acting device 2, a hot side outlet of the regenerator 5 is communicated with a hot side inlet of the cooler 3, a cold side inlet of the regenerator 5 is communicated with a media outlet of the pressure boosting device 4, and a cold side outlet of the regenerator 5 is communicated with the heater 1.
In the embodiment, the gaseous circulating medium at the outlet of the acting device 2 enters the heat regenerator 5 to exchange heat with the liquid circulating medium after cooling and compression in the heat regenerator 5, so that the gaseous circulating medium is cooled in the heat regenerator 5 in advance and then enters the cooler 3 to be cooled, and the liquid circulating medium pressurized by the pressurizing device 4 is heated in the heat regenerator 5 in advance before entering the heater 1, so that the waste heat of the circulating medium after the acting device 2 can be utilized, the energy required to be provided by the heater 1 and the cooler 3 is reduced, and the operating efficiency of the rankine cycle system is improved.
Further, as shown in fig. 2, the regenerator 5 includes a high-temperature regenerator 51 and a low-temperature regenerator 52, a hot-side inlet of the high-temperature regenerator 51 is communicated with a medium outlet of the power-generating device 2, a hot-side outlet of the high-temperature regenerator 51 is communicated with a hot-side inlet of the low-temperature regenerator 52, a cold-side outlet of the high-temperature regenerator 51 is communicated with a cold-side inlet of the heater 1, a cold-side inlet of the high-temperature regenerator 51 is communicated with a cold-side outlet of the low-temperature regenerator, a cold-side inlet of the low-temperature regenerator 52 is communicated with a medium outlet of the pressure-increasing device 4, the rankine cycle system further includes a first three-way valve 91, a second three-way valve 92 and the compressor 8, the first three-way valve 91 is respectively communicated with an outlet of the compressor 8 and a cold-side outlet of the low-temperature regenerator 52, the cold side inlet of the high temperature regenerator 51 is communicated, and the second three-way valve 92 is respectively communicated with the inlet of the compressor 8, the hot side outlet of the low temperature regenerator 52 and the hot side inlet of the cooler 3.
As an operation example, as shown in fig. 2, in a rankine cycle system, a cycle medium firstly enters a cold side inlet of a heater 1, high-temperature exhaust gas of a gas turbine unit enters a hot side inlet of the heater 1, two streams realize heat exchange in a heat exchanger, cooled flue gas is discharged through a hot side outlet of the heat exchanger, and the heated cycle medium flows out from the cold side outlet of the heat exchanger and continues to enter an acting device 2 to perform expansion and work. The work-doing device 2 has three turbines, and the circulating mediums at the outlet of the first turbine 21 and the outlet of the second turbine 22 enter the heater 1 again to be heated and then enter the second turbine 22 and the third turbine 23 respectively to do work through expansion again. The circulating medium at the outlet of the third turbine 23 enters the hot side of the high-temperature regenerator 51, exchanges heat with the circulating medium at the cold side of the high-temperature regenerator 51 to cool, and the circulating medium after being cooled once enters the hot side of the low-temperature regenerator 52 again to exchange heat with the cold-side stream of the low-temperature regenerator 52 to cool, and then the circulating medium after being cooled twice is divided into two parts by the second three-way valve 92: the main flow stock circulating medium is cooled to a liquid state by the cooler 3, enters the supercharging device 4 for supercharging, and then enters the low-temperature heat regenerator 52 for heat regeneration and temperature rise; the secondary stream of circulating medium is directed to compressor 8 for pressurization. Then, the two circulation media are merged into one stream through the first three-way valve 91, and then enter the cold side of the high temperature regenerator 51 for heat regeneration and temperature rise, and then enter the heater 1 for heat absorption, and the circulation process is continued.
In the present embodiment, the regenerator 5 is further provided as the high temperature regenerator 51 and the low temperature regenerator 52, so that the residual heat of the working medium flowing out of the power generation device 2 can be further utilized, and by dividing the circulation medium flowing out of the low temperature regenerator 52, a part of the circulation medium is directly compressed by the compressor 8 without passing through the cooler 3 and then is collected with the liquid circulation medium after cooling and compression and flows to the heating device, so that the cold source loss of the rankine cycle system can be reduced, and the operating efficiency of the rankine cycle system can be further improved.
4. Cooler 3
In this embodiment, cooler 3 can be for wantonly can carry out the device that cools off the cooling to the circulating medium, specifically, this cooler 3 can be for utilizing outside cold source 7 to carry out refrigerated heat exchanger to the circulating medium, the outside cold source is let in to the one end of this heat exchanger, the other end then lets in the circulating medium to gaseous state circulating medium passes through the heat exchange, self heat is absorbed by outside cold source, the circulating medium cools down to near its triple point, so that follow-up heat absorption, and, the temperature difference of rankine cycle cold junction and hot junction has been improved, thereby improve circulation efficiency.
Wherein, the temperature of the external cold source is-162 ℃ -0 ℃; the cold source with lower temperature can be used for quickly and fully cooling the gaseous circulating medium to be near the triple point, and the low temperature of the cold source is favorable for improving the working efficiency of the Rankine cycle system; preferably, the external cold source 7 may be liquefied natural gas. The cold source temperature of the liquefied natural gas is about-162 ℃, which is beneficial to improving the operating efficiency of the Rankine cycle system, in addition, the liquefied natural gas can be further introduced into the gas turbine set as fuel after being subjected to heat exchange with a circulating medium in the cooler 3, and the generated high-temperature flue gas can be used as an external heat source 6, so that the cyclic utilization of the liquefied natural gas which is a high-quality external cold source material is realized.
5. Supercharging device 4
In the present embodiment, the pressure increasing device 4 may be a liquid booster pump, and specifically, the pressure increasing device 4 increases the pressure of the saturated liquid-state circulation medium flowing out of the cooler 3 and having a temperature in the vicinity of the triple point of the circulation medium. Because the pressure of the circulating medium is close to the three-phase point of the circulating medium, the energy which can be converted by the expansion work of the circulating medium in the working device 2 in the primary Rankine cycle system is exerted as much as possible.
Preferably, as shown in fig. 3, the rankine cycle system further includes an organic medium rankine cycle circuit including an organic medium heater 1a and an organic medium cooler 3a, wherein the external heat source 6 flows through the heater 1 and then enters the organic medium heater 1a, and the external cold source 7 communicates with the cooler 3 and the organic medium cooler 3 a.
Further, the organic medium rankine cycle system may also include other devices in the rankine cycle system, as shown in fig. 3, the organic medium rankine cycle further includes an organic medium power-applying device 2a, an organic medium pressure-increasing device 4a and an organic medium heat regenerator 5a, and a flow manner of the circulating medium in the organic medium rankine cycle system is consistent with a flow manner of the rankine cycle system provided by the present invention, which is not described herein again.
In the present embodiment, a higher cycle efficiency can be achieved by adopting a cycle form in which the rankine cycle and the organic rankine cycle are combined, and a larger amount of power generation and an improved energy utilization rate can be achieved for the same heat source by using the combined cycle system of the present invention.
In addition, the present embodiment provides a rankine cycle method applied to the rankine cycle system, including:
a heating step, providing an external heat source 6 and a circulating medium, and heating the circulating medium by using the external heat source 6 to raise the temperature of the circulating medium to a supercritical state; a working step, in which the circulating medium in a supercritical state applies work to the outside and is changed into a gaseous state close to the pressure of the three-phase point of the circulating medium; a cooling step, namely providing an external cold source 7, and cooling the gaseous circulating medium by using the external cold source 7 to obtain a saturated liquid circulating medium with the temperature being lower than 0 ℃ and close to the triple point; and a compression step, namely pressurizing the liquid circulating medium.
Those of skill in the art will appreciate that the specific features of the various embodiments may be adaptively separated or combined. Such splitting or combining of specific features does not cause the technical solutions to deviate from the principle of the present invention, and therefore, the technical solutions after splitting or combining will fall within the protection scope of the present invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless specifically limited otherwise.
So far, the technical solutions of the present invention have been described in connection with the embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of the present invention is obviously not limited to these specific embodiments. Equivalent changes or substitutions of related technical features can be made by those skilled in the art without departing from the principle of the invention, and the technical scheme after the changes or substitutions can fall into the protection scope of the invention.
Claims (9)
1. A Rankine cycle system comprises a medium loop formed by sequentially connecting a heater, a work doing device, a cooler and a supercharging device, wherein a circulating medium circularly flows in the medium loop, and is characterized in that the temperature of a three-phase point of the circulating medium is lower than 0 ℃, the pressure of the three-phase point of the circulating medium is higher than standard atmospheric pressure, the circulating medium flowing out of the heater is in a supercritical state, the circulating medium flowing out of the work doing device is in a gaseous state, the circulating medium flowing out of the cooler is in a saturated liquid state, the temperature T1 is 0-20 ℃ higher than the temperature Tgls of the three-phase point of the circulating medium, and the pressure P1 of the circulating medium flowing out of the work doing device is equal to the saturated vapor pressure of the circulating medium at the temperature T1.
2. The Rankine cycle system of claim 1, further comprising a regenerator, a hot side inlet of the regenerator in communication with the media outlet of the work device, a hot side outlet of the regenerator in communication with a hot side inlet of the cooler, a cold side inlet of the regenerator in communication with the media outlet of the pressure boosting device, and a cold side outlet of the regenerator in communication with the heater.
3. The Rankine cycle system of claim 2, wherein the regenerator includes a high temperature regenerator and a low temperature regenerator, a hot side inlet of the high temperature regenerator being in communication with a media outlet of the power plant, a hot side outlet of the high temperature regenerator being in communication with a hot side inlet of the low temperature regenerator, a cold side outlet of the high temperature regenerator being in communication with the heater, a cold side inlet of the low temperature regenerator being in communication with a media outlet of the pressure boosting device,
the Rankine cycle system further comprises a first three-way valve, a second three-way valve and a compressor, wherein the first three-way valve is respectively communicated with the outlet of the compressor, the outlet of the cold side of the low-temperature heat regenerator and the inlet of the cold side of the high-temperature heat regenerator, and the second three-way valve is respectively communicated with the inlet of the compressor, the outlet of the hot side of the low-temperature heat regenerator and the inlet of the hot side of the cooler.
4. The Rankine cycle system of claim 1, wherein the power device includes a first turbine that uses enthalpy changes of the circulating medium in the supercritical state to externally produce work, a second turbine that receives the circulating medium in the supercritical state from the first turbine and uses phase state transitions of the circulating medium from the supercritical state to a gaseous state to externally produce work, and a third turbine that receives the gaseous circulating medium from the second turbine and uses enthalpy changes of the gaseous circulating medium to externally produce work.
5. The Rankine cycle system of any one of claims 1-4, wherein the circulating medium is CO 2.
6. The Rankine cycle system of any one of claims 1-4, further comprising an external cold source, an external heat source, and an organic media Rankine cycle circuit comprising an organic media heater and an organic media cooler, the external heat source entering the organic media heater after flowing through the heater, the external cold source being in communication with the cooler and the organic media cooler, respectively.
7. The Rankine cycle system of claim 6, wherein the external heat sink has a temperature of-162 ℃ to 0 ℃.
8. The Rankine cycle system of claim 6, wherein the external heat source is a gas turbine and the external heat source is a liquefied natural gas storage tank.
9. A rankine cycle method comprising the steps of:
a heating step, providing an external heat source and a circulating medium, and heating the circulating medium by using the external heat source to raise the temperature of the circulating medium to a supercritical state;
a working step, in which the circulating medium in a supercritical state applies work to the outside and is fully expanded to a gaseous circulating medium close to the pressure of the triple point of the circulating medium;
a cooling step, providing an external cold source, and cooling the gaseous circulating medium by using the external cold source to make the gaseous circulating medium become a saturated liquid circulating medium;
and a compression step, namely pressurizing the liquid circulating medium.
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| WO2013102537A2 (en) * | 2012-01-03 | 2013-07-11 | Abb Research Ltd | Electro-thermal energy storage system with improved evaporative ice storage arrangement and method for storing electro-thermal energy |
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| CN110685757A (en) * | 2019-10-10 | 2020-01-14 | 中南大学 | LNG-based gas turbine-supercritical CO2ORC cycle parallel power generation system |
| CN110925041B (en) * | 2019-12-03 | 2022-04-05 | 中国船舶重工集团公司第七一九研究所 | Combined cycle high-efficiency coal-fired power generation system |
| CN113586187A (en) * | 2021-06-07 | 2021-11-02 | 浙江大学 | Rankine cycle system and Rankine cycle method |
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| CN108425709A (en) * | 2018-02-05 | 2018-08-21 | 西安交通大学 | A kind of carbon dioxide low temperature Rankine cycle electricity generation system |
| CN108661732A (en) * | 2018-05-10 | 2018-10-16 | 西安热工研究院有限公司 | A kind of liquefied natural gas (LNG) production system of combustion gas-supercritical carbon dioxide combined power |
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