WO2022257856A1 - 一种朗肯循环系统及朗肯循环方法 - Google Patents

一种朗肯循环系统及朗肯循环方法 Download PDF

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Publication number
WO2022257856A1
WO2022257856A1 PCT/CN2022/096903 CN2022096903W WO2022257856A1 WO 2022257856 A1 WO2022257856 A1 WO 2022257856A1 CN 2022096903 W CN2022096903 W CN 2022096903W WO 2022257856 A1 WO2022257856 A1 WO 2022257856A1
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Prior art keywords
circulating medium
medium
rankine cycle
temperature
regenerator
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PCT/CN2022/096903
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English (en)
French (fr)
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肖刚
王征
纪宇轩
倪明江
岑可法
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浙江大学
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Priority to JP2023574111A priority Critical patent/JP2024520583A/ja
Publication of WO2022257856A1 publication Critical patent/WO2022257856A1/zh

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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
    • 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
    • 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
    • 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
    • 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

Definitions

  • the invention relates to the field of power generation systems, in particular to a Rankine cycle system and a Rankine cycle method.
  • Heating process Water is heated into steam in the boiler, and the heating process can be idealized as a reversible endothermic process at constant pressure.
  • Cooling process The steam is cooled into saturated water in the condenser, and the cooling process can be idealized as a reversible constant pressure cooling process.
  • the supercharging process water is compressed and boosted in the water pump, and the supercharging process can be idealized as a reversible adiabatic compression process, that is, an isentropic compression process.
  • the efficiency of a reversible heat engine is only related to the maximum and minimum temperature of the circulating medium, while in the existing steam Rankine cycle, water is heated to a gaseous state during the heating process and cooled during the cooling process The liquid state close to the ambient temperature limits the operating efficiency of the Rankine cycle system to a certain extent. Therefore, how to further improve the operating efficiency of the Rankine cycle system is an urgent problem to be solved in this field.
  • the purpose of the present invention is to provide a Rankine cycle system with higher operating efficiency.
  • the Rankine cycle system includes a medium circuit formed by sequentially connecting heaters, power devices, coolers, and booster devices.
  • the circulating medium circulates inside the medium circuit.
  • the circulating medium flowing out of the heater is in a supercritical state.
  • the circulating medium The triple point temperature is lower than 0°C, the triple point pressure of the circulating medium is higher than the standard atmospheric pressure, and the circulating medium flowing out of the cooler is in a saturated liquid state, and its temperature T1 is 0°C-20 higher than the triple point temperature Tgls of the circulating medium °C, the pressure P1 of the gaseous circulating medium flowing out from the work device is equal to the saturated vapor pressure of the circulating medium at temperature T1.
  • the circulating medium reaches a supercritical state in the heating device.
  • the number of stages is relatively small, so the turbine equipment in the present invention is much more compact than the turbine structure in the existing steam Rankine cycle, and the smaller volume of the turbine equipment means smaller plant area and more compact cycle process.
  • the ability of the circulating medium to utilize the cooling source provided by the cooler in the Rankine cycle is limited by the triple point temperature of the circulating medium, so according to Carnot's principle, the circulating medium is used in the present invention Heating to a supercritical state higher than the gaseous state, and the circulating medium is cooled in the cooler to a temperature slightly higher than the triple point (that is, 0°C-20°C higher than the triple point), and the corresponding circulating medium is saturated at this temperature
  • the steam pressure is the exhaust pressure of the final stage power device, which can maximize the operating efficiency of the Rankine cycle system; furthermore, the triple point temperature of the circulating medium is lower than 0°C, which can reduce the circulating medium to a lower
  • the temperature and the triple point pressure are higher than the standard atmospheric pressure, so that there is no need to use external equipment to maintain the vacuum in the condenser during the condensation process, and also avoid the leakage of air into the condenser, so that after combining the use of high-quality
  • the Rankine cycle system further includes a regenerator, the hot-side inlet of the regenerator communicates with the medium outlet of the work device, the hot-side outlet of the regenerator communicates with the hot-side inlet of the cooler, and the heat recovery
  • the inlet on the cold side of the regenerator communicates with the medium outlet of the supercharging device, and the outlet on the cold side of the regenerator communicates with the heater.
  • a regenerator is added to the Rankine cycle system, and the gaseous circulating medium at the outlet of the power device enters the regenerator to exchange heat with the cooled and compressed liquid circulating medium in the regenerator, so that the gaseous circulating medium After being cooled in advance in the regenerator, it is passed into the cooler for cooling, and the liquid circulating medium pressurized by the booster device is heated in advance in the regenerator before entering the heater, so that it can
  • the residual heat of the circulating medium is used to reduce the energy required by the heater and cooler, thereby improving the operating efficiency of the Rankine cycle system.
  • the regenerator includes a high-temperature regenerator and a low-temperature regenerator
  • the hot-side inlet of the high-temperature regenerator communicates with the medium outlet of the work device
  • the hot-side outlet of the high-temperature regenerator communicates with the outlet of the low-temperature regenerator.
  • the hot-side inlet is connected, the cold-side outlet of the high-temperature regenerator is connected with the heater, the cold-side inlet of the high-temperature regenerator is connected with the cold-side outlet of the low-temperature regenerator, and the cold-side inlet of the low-temperature regenerator is connected with the booster device.
  • the medium outlet is connected, and the hot side outlet of the low-temperature regenerator is connected with the cooler.
  • the Rankine cycle system also includes a first three-way valve, a second three-way valve and a compressor, and the first three-way valve is respectively connected to the outlet of the compressor, the cold side outlet of the low-temperature regenerator, and the high-temperature regenerator.
  • the cold side inlet of the regenerator is connected, and the second three-way valve is respectively connected with the compressor inlet, the hot side outlet of the low temperature regenerator, and the hot side inlet of the cooler.
  • the regenerator is further set as a high-temperature regenerator and a low-temperature regenerator, so that the waste heat of the working medium flowing out of the power device can be further utilized, and the circulating medium flowing out of the low-temperature regenerator Part of the flow is divided, and a part is directly compressed by the compressor without passing through the cooler, and then combined with the liquid circulating medium after cooling and boosting, and then flows to the heating device, thereby reducing the loss of cold source of the Rankine cycle system and further improving the Rankine cycle system. work efficiency.
  • the work device includes a first turbine, a second turbine and a third turbine
  • the first turbine utilizes the enthalpy change of the circulating medium in a supercritical state to perform external work
  • the second turbine receives energy from the first turbine The supercritical state of the circulating medium, and use the phase transition of the circulating medium from the supercritical state to the gaseous state to do external work
  • the third turbine receives the gaseous circulating medium from the second turbine, and uses the change of enthalpy of the gaseous circulating medium to externally work.
  • the working device as a multi-stage turbine
  • the heat energy transmitted from the heater to the circulating medium is fully converted into mechanical energy through the multi-stage turbine, and the operating efficiency of the overall circulation system is improved.
  • the multi-stage When the multi-stage When the turbine is a three-stage turbine, the circulating medium in the first turbine is kept in a supercritical state. At this time, the density of the circulating medium is relatively high, and the structure of the first turbine can be more compact, and the circulating medium is further carried out in the second turbine. After adiabatic expansion, it changes from a supercritical state to a gaseous state and then enters the third turbine, where the waste heat of the circulating medium is further utilized, thereby increasing the overall operating efficiency of the circulating system.
  • the circulation medium of the Rankine cycle system is CO2.
  • the current application of CO2 as a circulating medium mainly lies in the supercritical CO2 (S-CO2) Brayton cycle.
  • the high-temperature heat source cycle of the S-CO2 Brayton cycle has high cycle efficiency, low compression power consumption, and compact structure of turbine equipment. It is one of the potential options for high-efficiency power generation with gas turbine exhaust waste heat.
  • the temperature of the cold source must not be lower than the critical temperature of CO2 (31.1 ° C), which limits the operating efficiency of the supercritical CO2 (S-CO2) Brayton cycle system .
  • the triple point of H2O is 0.01°C and 610.75Pa, and the cold end temperature can only drop to above 0°C, and because the triple point pressure of H2O is too low (less than 1kPa), and it is open
  • a vacuum pump is required to do work, and the improvement of the cycle efficiency is relatively limited.
  • the triple point of CO2 is -56.6°C, 0.52MPa, the temperature of the cold source can be lowered, and the pressure of the triple point is above atmospheric pressure, the cycle form is a closed cycle, no need to use a vacuum pump Vacuum makes the whole cycle above the atmospheric pressure, avoiding the infiltration of non-condensable gas at the low pressure of the cycle. In this way, after combining the use of high-quality low-temperature cold sources, from a thermodynamic point of view, the cycle efficiency can be greatly improved.
  • the Rankine cycle system also includes an external cold source, an external heat source and an organic medium Rankine cycle loop
  • the organic medium Rankine cycle loop includes an organic medium heater and an organic medium cooler
  • the external heat source flows through the After the heater, it enters the organic medium heater, and the external cold source communicates with the cooler and the organic medium cooler respectively.
  • the combination of Rankine cycle and organic Rankine cycle can achieve higher cycle efficiency.
  • using the combined cycle system of the present invention can achieve more power generation and improve energy utilization. .
  • the temperature of the external cold source is -162°C-0°C. According to the technical solution, using a cold source with a lower temperature can quickly cool down the gaseous circulating medium to near the triple point, and the low temperature of the cold source is beneficial to improve the operating efficiency of the Rankine cycle system.
  • the external heat source is a gas unit, and the external cold source is liquefied natural gas.
  • the gas-fired unit is used as a heat source, that is, the excess heat (such as high-temperature flue gas) generated by the gas-fired unit is reused.
  • the temperature of the cold source of liquefied natural gas is about -162°C, so that the gaseous state can be quickly circulated.
  • the temperature of the medium is cooled to a saturated liquid state near the triple point, and the low temperature of the cold source is conducive to improving the operating efficiency of the Rankine cycle system.
  • the liquefied natural gas is passed into the cooler as a cold source to exchange heat with the circulating medium and can continue to flow into the cooler.
  • the gas unit is used as fuel, and the excess heat generated by the gas unit can be used as an external heat source to supply heat to the cycle, so as to realize the full and reasonable use of cold source materials.
  • Fig. 1 is a schematic structural view of a Rankine cycle system provided by an embodiment of the present invention
  • Fig. 2 is the structural representation of another kind of Rankine cycle system provided by the embodiment of the present invention.
  • Fig. 3 is a schematic structural diagram of another Rankine cycle system provided by an embodiment of the present invention.
  • the Rankine cycle system comprises: heater 1, working device 2, regenerator 5, cooler 3 and supercharging device 4 are sequentially connected to form medium loop, the circulating medium circulates inside the medium loop, specifically, the triple point temperature of the circulating medium is lower than 0°C, the triple point pressure of the circulating medium is higher than the standard atmospheric pressure, and the circulating medium absorbs heat energy in the heater 1 It becomes a supercritical fluid, and then flows into the work device 2 to expand and do work, thereby converting heat energy into more usable mechanical energy.
  • the gaseous circulating medium passing through the work device 2 enters the regenerator 5, and the waste heat of the circulating medium is reused.
  • each device or equipment is not limited.
  • the power device 2 may be a rotary turbine in some embodiments, and in other embodiments, the power device 2 It can also be a cylinder device with a transmission rod.
  • a simple replacement of the device or equipment in the present invention will not exceed the protection scope of the present invention.
  • the regenerator 5 is a device for reusing the waste heat after the work device 2, that is, in this embodiment, the regenerator 5 is added
  • the preferred scheme of the Rankine cycle has been exemplified, but those skilled in the art can understand that the Rankine cycle system provided by the present invention can not include the regenerator, but directly by the heater 1, the work device 2, the cooler 3 and booster 4 are sequentially connected to form.
  • the triple point temperature of the circulating medium is lower than 0°C, and a lower temperature cold source medium can be used, and the triple point pressure is higher than the standard atmospheric pressure, so that there is no need to maintain the vacuum in the condenser, saving energy. It also avoids leakage of external air into the circulation system while reducing energy consumption. In this way, after combining the use of high-quality low-temperature cold sources, according to the Carnot principle, the circulation efficiency can be greatly improved.
  • the circulating medium reaches the supercritical state in the heating device.
  • the density is relatively high, and the number of turbine stages required for its expansion and work is relatively small. Therefore, in this embodiment, the high-pressure turbine equipment It is much more compact than the turbine structure in the existing steam Rankine cycle, and the smaller volume of the turbine equipment means smaller plant area and more compact cycle flow.
  • the temperature of the circulating medium in the supercritical state is higher than that of the gaseous circulating medium, so according to Carnot’s principle, under the condition that the cooling source provided by the cooler 3 is certain, the circulating medium in the Rankine cycle system provided by the present invention can reach Higher initial temperature, that is, the Rankine cycle system in the present invention has higher operating efficiency.
  • the circulation medium of the Rankine cycle system is CO2.
  • the current application of CO2 as a circulating medium mainly lies in the supercritical CO2 (S-CO2) Brayton cycle.
  • S-CO2 Brayton cycle has high circulation efficiency of high-temperature heat source, low compression power consumption, and rotary turbine equipment structure. With many advantages such as compactness, small footprint, and low corrosion resistance, it is one of the potential options for efficient power generation with exhaust waste heat from gas turbines.
  • the temperature of the cold source must not be lower than the critical temperature of CO2 (31.1°C), which limits the operating efficiency of the S-CO2 Brayton cycle system.
  • the triple point of H2O is 0.01°C and 610.75Pa, and the cold end temperature can only drop to above 0°C, and because the triple point pressure of H2O is too low (less than 1kPa), and the circulation form is In an open cycle, if you want to cool it to a pressure close to the triple point, you need to use a vacuum pump to pump air, which increases additional energy consumption and has a limited improvement in cycle efficiency.
  • the CO2 circulation form is a closed cycle, and there is no need to use a vacuum pump to evacuate.
  • the triple point of CO2 is -56.6°C, 0.52MPa, and the temperature of the cold source can be lowered, and the triple point pressure is at atmospheric pressure.
  • the specific volume of the CO2 circulating medium is much smaller than that of H2O, which can greatly reduce the size of the work equipment and save the plant area.
  • the heater 1 can be any device capable of heating the circulating medium.
  • the heater 1 can be a heat exchanger that uses an external heat source 6 to heat the circulating medium.
  • One end of the heat exchanger Lead into the external heat source 6, and the other end is passed into the circulating medium, so that the circulating medium absorbs the heat of the external heat source 6 through heat exchange to raise the temperature and change the phase state, so as to facilitate subsequent work.
  • the external heat source 6 can be solar energy, nuclear energy and fossil fuels, and further, the external heat source 6 is a gas-fired unit, so that the waste heat of the high-temperature flue gas after combustion in the gas-fired unit can be reused to save resources.
  • the working device 2 can be a device that can convert thermal energy into mechanical energy by using the expansion of the circulating medium to do work, for example, a cylinder structure that uses gas expansion to push the transmission rod to reciprocate, or a rotary turbine that uses gas expansion to rotate and do work.
  • the working device 2 is taken as an example of a rotary turbine for further description.
  • the rotary turbine includes a first turbine 21, a second turbine 22 and a third turbine 23.
  • the first turbine 21 uses the enthalpy change of the circulating medium in a supercritical state to do work externally
  • the second turbine 22 receives the energy from The circulating medium in the supercritical state of the first turbine 21, and utilizes the phase transition of the circulating medium from the supercritical state to the gaseous state to perform external expansion
  • the third turbine 23 receives the gaseous circulating medium from the second turbine 22, and utilizes The change of the enthalpy value of the gaseous circulating medium acts externally.
  • the heat energy transmitted from the heater 1 to the circulating medium can be fully converted into mechanical energy through the multi-stage turbine to improve the operating efficiency of the overall circulation system, but this Those skilled in the art can understand that setting a single or other number of turbines can achieve the effect of the circulating medium performing work in the work device 2, which does not exceed the protection scope of the present invention.
  • the multi-stage turbine is a three-stage turbine
  • the circulating medium in the first turbine 21 is kept in a supercritical state.
  • the density of the circulating medium is relatively high, and the structure of the first turbine 21 can be more compact, and the circulating medium is further insulated in the second turbine 22. After thermal expansion, it changes from a supercritical state to a gaseous state and then enters the third turbine 23, where the waste heat of the circulating medium is further utilized, thereby increasing the overall operating efficiency of the circulating system.
  • the regenerator 5 can be a device that has two flow paths, cold and hot, and can exchange heat for the media in the two flow paths.
  • the hot side inlet of the regenerator 5 can be connected with the The medium outlet is connected, the hot side outlet of the regenerator 5 is connected with the hot side inlet of the cooler 3, the cold side inlet of the regenerator 5 is connected with the medium outlet of the supercharging device 4, and the cold side outlet of the regenerator 5 is connected with all The heater 1 is connected.
  • the gaseous circulating medium at the outlet of the work device 2 enters the regenerator 5 and exchanges heat with the cooled and compressed liquid circulating medium in the regenerator 5, so that the gaseous circulating medium is cooled in advance in the regenerator 5 Then pass into the cooler 3 for cooling, and the liquid circulating medium pressurized by the supercharging device 4 is heated in advance in the regenerator 5 before entering the heater 1, so that the circulating medium after the work device 2 can
  • the waste heat is utilized to reduce the energy that the heater 1 and the cooler 3 need to provide, thereby improving the operating efficiency of the Rankine cycle system.
  • the regenerator 5 includes a high-temperature regenerator 51 and a low-temperature regenerator 52, the hot side inlet of the high-temperature regenerator 51 communicates with the medium outlet of the work device 2, and the high-temperature regenerator 51
  • the outlet on the hot side communicates with the hot side inlet of the low temperature regenerator 52
  • the outlet on the cold side of the high temperature regenerator 51 communicates with the inlet on the cold side of the heater 1
  • the inlet on the cold side of the high temperature regenerator 51 communicates with the cold side of the low temperature regenerator
  • the inlet of the cold side of the low-temperature regenerator 52 is connected with the medium outlet of the supercharging device 4.
  • the Rankine cycle system also includes a first three-way valve 91, a second three-way valve 92 and a compressor 8.
  • the first The three-way valve 91 communicates with the outlet of the compressor 8, the cold-side outlet of the low-temperature regenerator 52, and the cold-side inlet of the high-temperature regenerator 51
  • the second three-way valve 92 communicates with the inlet of the compressor 8 and the low-temperature regenerator 52 respectively.
  • the hot side outlet of the cooler 3 is in communication with the hot side inlet.
  • the circulating medium first enters the cold side inlet of heater 1, and the high-temperature exhaust gas of the gas unit enters the hot side inlet of heater 1, and the two streams are realized in the heat exchanger.
  • Heat exchange the cooled flue gas is discharged through the hot side outlet of the heat exchanger, and the heated circulating medium flows out from the cold side outlet of the heat exchanger, and continues to enter the work device 2 to expand and perform work.
  • the work device 2 has three turbines.
  • the circulating medium at the outlet of the first turbine 21 and the outlet of the second turbine 22 re-enters the heater 1 to heat up, and then respectively enters the second turbine 22 and the third turbine 23 to expand and perform work 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 on the cold side of the high-temperature regenerator 51, and cools down.
  • the cold side stream of the low temperature regenerator 52 is heat-exchanged and lowered, and then the circulating medium after two cooling passes through the second three-way valve 92 and is divided into two streams: the main stream circulating medium is cooled to a liquid state by the cooler 3 and enters the booster device 4 After pressurization, it enters the low-temperature regenerator 52 to regenerate and heat up; the secondary stream circulation medium directly enters the compressor 8 for pressurization.
  • the two streams of circulating medium merge into one stream through the first three-way valve 91, and then enter the cold side of the high-temperature regenerator 51 to regenerate heat to raise the temperature, and then enter the heater 1 to absorb heat, and the circulation process continues.
  • the regenerator 5 is further configured as a high-temperature regenerator 51 and a low-temperature regenerator 52, so that the waste heat of the working medium flowing out of the power device 2 can be further utilized, and by regenerating the low-temperature
  • the circulating medium flowing out of the device 52 is divided, and a part of it is directly compressed by the compressor 8 without passing through the cooler 3, and then is combined with the cooled and compressed liquid circulating medium and flows to the heating device, thereby reducing the cold source of the Rankine cycle system. loss, further improving the operating efficiency of the Rankine cycle system.
  • the cooler 3 can be any device capable of cooling the circulating medium, specifically, the cooler 3 can be a heat exchanger that uses an external cold source 7 to cool the circulating medium, and the heat exchanger One end of one end is connected to an external cold source, and the other end is connected to a circulating medium, so that the gaseous circulating medium undergoes heat exchange, and its own heat is absorbed by the external cold source, and the circulating medium cools down to near its triple point for subsequent heat absorption. Moreover, the temperature difference between the cold end and the hot end of the Rankine cycle is increased, thereby improving cycle efficiency.
  • the temperature of the external cold source is -162°C-0°C; using a lower temperature cold source can quickly and fully cool the gaseous circulating medium to near the triple point, and the low temperature of the cold source is conducive to improving the Rankine cycle Operating efficiency of the system; preferably, the external cold source 7 can be liquefied natural gas.
  • the cold source temperature of liquefied natural gas is about -162°C, which is conducive to improving the operating efficiency of the Rankine cycle system.
  • the liquefied natural gas can be further passed into the gas unit as fuel after heat exchange with the circulating medium in the cooler 3, generating
  • the high-temperature flue gas can be used as an external heat source 6, thereby realizing the recycling of liquefied natural gas, a high-quality external cold source material.
  • the booster device 4 may be a liquid booster pump. Specifically, the booster device 4 boosts the saturated liquid circulating medium that flows out of the cooler 3 and whose temperature is near the triple point of the circulating medium. Since the pressure of the circulating medium is close to its triple point, the energy that can be converted by the expansion of the circulating medium in the work device 2 in a Rankine cycle system can be used as much as possible.
  • the Rankine cycle system also includes an organic medium Rankine cycle
  • the organic medium Rankine cycle includes an organic medium heater 1a and an organic medium cooler 3a
  • the external heat source 6 flows through After the heater 1, it enters the organic medium heater 1a, and the external cold source 7 communicates with the cooler 3 and the organic medium cooler 3a.
  • this organic medium Rankine cycle system can also include other devices in the above-mentioned Rankine cycle system, as shown in Figure 3, this organic medium Rankine cycle also includes an organic medium working device 2a, an organic medium pressurizing device 4a and In the organic medium regenerator 5a, the flow mode of the circulating medium in the organic medium Rankine cycle system is consistent with the flow mode of the Rankine cycle system provided by the present invention, and will not be repeated here.
  • the combination of Rankine cycle and organic Rankine cycle can achieve higher cycle efficiency.
  • using the combined cycle system of the present invention can achieve more power generation and improve energy utilization. Rate.
  • a Rankine cycle method applied to the above-mentioned Rankine cycle system including the following steps:
  • an external heat source 6 and a circulating medium are provided, and the external heat source 6 is used to heat the circulating medium to make it warm up to a supercritical state; in the working step, the circulating medium in a supercritical state acts externally to become close to the circulating medium The gaseous state at the triple point pressure; the cooling step, providing an external cold source 7, using the external cold source 7 to cool the gaseous circulating medium to obtain a saturated liquid circulating medium close to the triple point temperature below 0°C; compression The step is to pressurize the liquid circulating medium.
  • first and second are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, a feature defined as “first” or “second” may explicitly or implicitly include one or more of these features.
  • “plurality” means two or more, unless otherwise specifically defined.

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Abstract

本发明提供了一种朗肯循环系统。该朗肯循环系统包括由加热器(1)、做功装置(2)、冷却器(3)、增压装置(4)依次接通形成的介质回路。循环介质在介质回路内部循环流动，从加热器(1)流出的循环介质为超临界状态，循环介质在做功装置(2)中充分膨胀至略高于其三相点压力的气态，从冷却器(3)流出的循环介质为饱和液态，温度比循环介质的三相点温度高0-20℃。由于循环介质由高温高压的超临界状态逐步膨胀至其理论做功极限状态—三相点压力附近，从而充分发挥了循环介质的做功能力。

Description

一种朗肯循环系统及朗肯循环方法 技术领域
本发明涉及发电系统领域，特别涉及一种朗肯循环系统及朗肯循环方法。
背景技术
在工业生产中，一些燃机往往具有较高的排气温度，为了实现对排气高位热源的进一步利用，人们通常在燃机底层结合蒸汽朗肯循环来实现高效联合循环发电。现有的蒸汽朗肯循环具有四个过程：
加热过程：水在锅炉中被加热为蒸汽，加热过程可以理想化为定压可逆吸热过程。
做功过程：蒸汽在汽轮机中膨胀，做功过程可以理想化为可逆绝热膨胀过程，即等熵膨胀过程。
冷却过程：蒸汽在冷凝器中被冷却成饱和水，冷却过程可以理想化为可逆定压冷却过程。
增压过程，水在水泵中被压缩升压，增压过程可以理想化为可逆绝热压缩过程，即等熵压缩过程。
其中，根据卡诺原理，可逆热机的效率仅与循环介质的最高温度与最低温度有关，而在现有的蒸汽朗肯循环中，水在加热过程中被加热到气态，在冷却过程中被冷却至接近环境温度的液态，在一定程度上限制了朗肯循环系统的作业效率，因此，如何进一步提高朗肯循环系统的作业效率，是本领域亟需解决的问题。
发明内容
针对现有技术中的缺陷，本发明的目的是提供一种作业效率更高的朗肯循环系统。
该朗肯循环系统包括由加热器、做功装置、冷却器、增压装置依次接通形成的介质回路，循环介质在介质回路内部循环流动，从加热器流出的循环介质为超临界状态，循环介质的三相点温度低于0℃，循环介质的三相点压力高于标准大气压，从冷却器流出的循环介质处于饱和液 态，其温度T1比循环介质的三相点温度Tgls高0℃-20℃，从做功装置流出的气态循环介质压强P1等于循环介质在温度T1下的饱和蒸汽压力。根据该技术方案，首先，在本发明提供的朗肯循环系统中，循环介质在加热装置中达到超临界状态，当循环介质处于超临界状态时，密度较高，其膨胀做功所需的透平级数相对较少，因此在本发明中透平设备要比现有的蒸汽朗肯循环中的透平结构紧凑很多,更小的透平设备体积意味着更小的厂房面积、更紧凑的循环流程。
其次，从热力学角度而言，提高循环过程中的热源温度和降低循环过程中的冷源温度可以进一步提高循环效率。但当温度低于三相点时，定压冷却将使循环介质直接由气态凝华为固态，而不经历液相区。但由于固态的循环介质无法流动，因此朗肯循环中循环介质对冷却器提供的冷源的利用能力受到循环介质的三相点温度的限制，所以根据卡诺原理，在本发明中将循环介质加热到高于气态的超临界状态，并且，循环介质在冷却器中冷却到略高于三相点的温度(即高于三相点0℃-20℃)，此温度下对应的循环介质饱和蒸汽压力即为最末级做功装置的排气压力，可以最大限度提高朗肯循环系统的作业效率；进一步地，循环介质的三相点温度低于0℃，能够将循环介质降低至更低的温度，三相点压力高于标准大气压，使得在冷凝过程中不需要借助外部设备维持冷凝器内真空，也避免了空气向冷凝器内的渗漏，这样在结合利用优质低温冷源之后，从热力学角度上来说，能够大幅提高循环效率。
其中，较优地，该朗肯循环系统还包括回热器，回热器的热侧入口与做功装置的介质出口连通，回热器的热侧出口与冷却器的热侧入口连通，回热器的冷侧入口与增压装置的介质出口连通，回热器的冷侧出口与加热器连通。
根据该技术方案，在该朗肯循环系统中，加入回热器，做功装置出口的气态循环介质进入回热器与冷却压缩后的液态循环介质在回热器中进行换热，从而气态循环介质在回热器中被提前冷却后再通入冷却器进行冷却，而经增压装置加压后的液态循环介质在进入加热器之前在回热器中被提前加热，从而能够对于做功装置后的循环介质的余热进行利用，降低加热器与冷却器所需要提供的能量，从而提高朗肯循环系统的作业效率。
其中，较优地，回热器包括高温回热器和低温回热器，高温回热器 的热侧入口与做功装置的介质出口连通，高温回热器的热侧出口与低温回热器的热侧入口连通，高温回热器的冷侧出口与加热器连通，高温回热器的冷侧入口于低温回热器的冷侧出口连通，低温回热器的冷侧入口与增压装置的介质出口连通，低温回热器的热侧出口与冷却器连通。
其中，较优地，朗肯循环系统还包括第一三通阀、第二三通阀和压缩机，第一三通阀分别与压缩机出口、低温回热器的冷侧出口、高温回热器的冷侧入口连通，第二三通阀分别与压缩机入口、低温回热器的热侧出口、冷却器的热侧入口连通。
根据该技术方案，进一步地将回热器设置为高温回热器和低温回热器，从而可以对做功装置流出的工作介质的余热进一步地利用，并且，通过将低温回热器流出的循环介质进行分流，一部分不经过冷却器而直接通过压缩机进行压缩再与冷却增压后的液态的循环介质汇总后流向加热装置，从而可以降低朗肯循环系统的冷源损失，进一步提高朗肯循环系统的作业效率。
其中，较优地，做功装置包括第一透平、第二透平和第三透平，第一透平利用超临界状态循环介质的焓值变化对外做功，第二透平接收来自第一透平的超临界状态的循环介质，并利用循环介质从超临界状态到气态的相态转变对外做功，第三透平接收来自第二透平的气态循环介质，并利用气态循环介质的焓值变化对外作功。
根据该技术方案，通过将做功装置设置为多级透平，从而将加热器中传输给循环介质的热能通过多级透平充分转换为机械能，提高整体循环系统的作业效率，其中，当多级透平为三级透平时，第一透平内的循环介质保持在超临界状态，此时循环介质的密度较高，第一透平的结构可以更加紧凑，循环介质在第二透平内进一步地进行绝热膨胀后，从超临界状态变为气态后进入第三透平，在第三透平中对于循环介质的余热进行进一步地利用，从而增加循环系统整体的作业效率。
其中，较优地，该朗肯循环系统的循环介质为CO2。
根据该技术方案，目前CO2作为循环介质的应用主要在于超临界CO2(S-CO2)布雷顿循环，S-CO2布雷顿循环的高温热源循环效率高、压缩耗功小、透平设备结构紧凑占地小、腐蚀性小等诸多优势，是燃气轮机排气余热高效发电的潜在选择之一。但在超临界CO2(S-CO2)布雷顿循环中，冷源温度不得低于CO2临界温度(31.1℃)，该冷源温度限制了超 临界CO2(S-CO2)布雷顿循环系统的作业效率。
进一步地，H2O的三相点为0.01℃、610.75Pa，其冷端温度最低也只能降到0℃以上，而且由于H2O的三相点压力过低(只有不到1kPa)，且为开式循环，若要其使其降至接近三相点压力，需使用真空泵进行抽气做功，对循环效率的提升较为有限。相比之下，CO2的三相点为-56.6℃、0.52MPa，其冷源温度可以降到更低，而且三相点压力在大气压之上，循环形式为闭式循环，不需要使用真空泵抽真空，使得循环整体处于大气压之上，避免了在循环低压处渗入不凝气体。这样在结合利用优质低温冷源之后，从热力学角度上来说，能够大幅提高循环效率。
最后，CO2循环介质的腐蚀性相比H2O蒸汽温和很多，可大大减轻对高温部件设备材料的耐蚀要求。
其中，较优地，该朗肯循环系统还包括外部冷源、外部热源和有机介质朗肯循环回路，有机介质朗肯循环回路包括有机介质加热器和有机介质冷却器，外部热源流经所述加热器后，进入有机介质加热器，外部冷源分别与冷却器以及有机介质冷却器连通。
根据该技术方案，采用朗肯循环与有机朗肯循环联合的循环形式可以实现更高的循环效率，对于相同的热源，使用本发明的联合循环系统能够实现更多的发电量、提高能量利用率。
其中，较优地，外部冷源的温度为-162℃-0℃。根据该技术方案，使用较低温度的冷源可以迅速地使气态的循环介质降温至三相点附近，且冷源温度低有利于提升朗肯循环系统的作业效率。
其中，较优地，外部热源为燃气机组，外部冷源为液化天然气。
根据该技术方案，将燃气机组作为热源，即对于燃气机组产生的多余热量(例如高温烟气)进行再次利用，此外，液化天然气的冷源温度为-162℃左右，从而可以迅速将气态的循环介质降温至三相点附近的饱和液态，且冷源温度低有利于提升朗肯循环系统的作业效率，进一步地，液化天然气作为冷源通入冷却器中与循环介质换热后能够继续通入燃气机组作为燃料，燃气机组产生的多余热量又可以作为外部热源向循环中供给热量，从而实现对于冷源材料的充分合理利用。
附图说明
图1是本发明的实施方式提供的一种朗肯循环系统的结构示意图；
图2是本发明的实施方式提供的又一种朗肯循环系统的结构示意 图；
图3是本发明的实施方式提供的还一种朗肯循环系统的结构示意图。
附图标记说明
1-加热器；2-做功装置；21-第一透平；22-第二透平；23-第三透平；3-冷却器；4-增压装置；5-回热器；51-高温回热器；52-低温回热器；6-外部热源；7-外部冷源；8-压缩机；91-第一三通阀；92-第二三通阀；1a-有机介质加热器；2a-有机介质做功装置；3a-有机介质冷却器；4a-有机介质增压装置；5a-有机介质回热器。
具体实施方式
结合以下具体实施例和附图，对本发明作进一步的详细说明。本发明的实现并不限于下述实施方式，在本领域技术人员所具备的知识范围内所采用的本发明技术构思下的各种变形、变换、组合和改进均属于本发明的保护范围。
1.整体结构
如图1所示为本实施方式提供的一种朗肯循环系统，该朗肯循环系统包括:加热器1、做功装置2、回热器5、冷却器3和增压装置4依次接通形成的介质回路，循环介质在介质回路内部循环流动，具体地，循环介质的三相点温度低于0℃，循环介质的三相点压力高于标准大气压，循环介质在加热器1中吸收热能后变为超临界流体，之后再流入做功装置2中膨胀做功，从而将热能转化为更便于利用的机械能，经过做功装置2的气态循环介质进入回热器5，对循环介质的余热进行再次利用后进入冷却器3进行降温，将气态的循环介质冷却至略高于循环介质的三相点温度Tgls的温度T1(Tgls<T1<Tgls+20℃)下的饱和液体后，循环介质进入增压装置4进行增压，增压后的液态循环介质进入回热器5中吸收做功装置排气的余热，并重新进入加热器1中进行新的循环，从而循环地将热能转化为机械能。
需要注意的是，在本实施方式中，并未对各个装置或者设备的结构进行限定，例如该做功装置2在一些实施方式中可以为旋转透平，在另一些实施方式中，该做功装置2也可以为具有传动杆的气缸装置，同理，在不违背本发明的技术方案的前提下，对本发明中的装置或设备进行简 单的替换，均未超出本发明的保护范围。
另外，本领域技术人员能够理解的是，回热器5在本实施方式中是用于对做功装置2后的余热进行再次利用的装置，即在本实施方式中对于增加了回热器5的朗肯循环的优选方案进行了举例说明，但是，本领域技术人员能够理解的是，本发明提供的朗肯循环系统可以不包括回热器，而直接由加热器1、做功装置2、冷却器3和增压装置4依次连接组成。
在本实施方式中，首先，循环介质的三相点温度低于0℃，能够利用更低温的冷源介质，三相点压力高于标准大气压，使得无需维持冷凝器中的真空，在节省能耗的同时也避免了外部空气漏入循环系统，这样在结合利用优质低温冷源之后，根据卡诺原理，能够大幅提高循环效率。
其次，循环介质在加热装置中达到超临界状态，当循环介质处于超临界状态时，密度较高，其膨胀做功所需的透平级数相对较少，因此在本实施方式中高压透平设备要比现有的蒸汽朗肯循环中的透平结构紧凑很多，更小的透平设备体积意味着更小的厂房面积、更紧凑的循环流程。
最后，超临界状态的循环介质的温度高于气态的循环介质，所以根据卡诺原理，在冷却器3提供的冷源一定的情况下，本发明提供的朗肯循环系统中的循环介质能够达到更高的初温，即本发明中的朗肯循环系统作业效率更高。
其中，较优地，该朗肯循环系统的循环介质为CO2。
在本实施方式中，目前CO2作为循环介质的应用主要在于超临界CO2(S-CO2)布雷顿循环，S-CO2布雷顿循环具有高温热源循环效率高、压缩耗功小、旋转透平设备结构紧凑占地小、腐蚀性小等诸多优势，是燃气轮机排气余热高效发电的潜在选择之一。但在S-CO2布雷顿循环中，冷源温度不得低于CO2临界温度(31.1℃)，该冷源温度限制了S-CO2布雷顿循环系统的作业效率。
进一步地，H2O的三相点为0.01℃、610.75Pa，其冷端温度最低也只能降到0℃以上，而且由于H2O的三相点压力过低(只有不到1kPa)，且循环形式为开式循环，若要将冷却至接近三相点的压强则需要利用真空泵进行抽气做功，增加了额外能耗，对循环效率的提升较为有限。相比之下，CO2循环形式为闭式循环，不需要使用真空泵抽真空，CO2的三相点为-56.6℃、0.52MPa，其冷源温度可以降到更低，而且三相点压力 在大气压之上，避免了冷凝器处外部不凝性空气向循环内部的渗漏。这样在结合利用优质低温冷源之后，从热力学角度上来说，能够大幅提高循环效率。
此外，CO2循环介质的腐蚀性相比H2O蒸汽温和很多，可大大减轻对高温部件设备材料的耐蚀要求。
最后，CO2循环介质的比容相比H2O小很多，可大大减少做功设备的尺寸，节约厂房面积。
下面，将对本实施方式提供的朗肯循环的装置进行更详细地说明。
1.加热器1
在本实施方式中，加热器1可以为任意能够对循环介质进行加热的装置，具体地，该加热器1可以为利用外部热源6对循环介质进行加热的换热器，该换热器的一端通入外部热源6，另一端则通入循环介质，从而循环介质通过热交换吸收外部热源6的热量升温并转换相态，以便于后续做功，较优地，该外部热源6可以为太阳能、核能和化石燃料等，进一步地，该外部热源6为燃气机组，从而能够对于燃气机组内燃烧后的高温烟气的余热进行再次利用，节约资源。
2.做功装置2
在本实施方式中，做功装置2可以为能够利用循环介质的膨胀做功将热能转换为机械能的装置，例如，利用气体膨胀推动传动杆往复运动的气缸结构，或者利用气体膨胀旋转做功的旋转透平结构，本实施方式以做功装置2为旋转透平为例进行进一步地说明。
优选地，旋转透平包括第一透平21、第二透平22和第三透平23，第一透平21利用超临界状态循环介质的焓值变化对外做功，第二透平22接收来自第一透平21的超临界状态的循环介质，并利用循环介质从超临界状态到气态的相态转变对外膨胀做功，第三透平23接收来自第二透平22的气态循环介质，并利用气态循环介质的焓值变化对外作功。
在本实施方式中，通过将做功装置2设置为多级透平，从而将加热器1中传输给循环介质的热能通过多级透平充分转换为机械能，提高整体循环系统的作业效率，但本领域技术人员能够理解的是，设置单个或其它数量的透平均可实现循环介质在做功装置2内进行做功的效果，均 未超出本发明的保护范围，其中，当多级透平为三级透平时，第一透平21内的循环介质保持在超临界状态，此时循环介质的密度较高，第一透平21的结构可以更加紧凑，循环介质在第二透平22内进一步地进行绝热膨胀后，从超临界状态变为气态后进入第三透平23，在第三透平23中对于循环介质的余热进行进一步地利用，从而增加循环系统整体的作业效率。
3.回热器5
在本实施方式中，回热器5可以为具有冷热两条流路并且对两条流路内介质进行换热的装置，具体地，回热器5的热侧入口可以与做功装置2的介质出口连通，回热器5的热侧出口与冷却器3的热侧入口连通，回热器5的冷侧入口与增压装置4的介质出口连通，回热器5的冷侧出口与所述加热器1连通。
在本实施方式中，做功装置2出口的气态循环介质进入回热器5与冷却压缩后的液态循环介质在回热器5中进行换热，从而气态循环介质在回热器5中被提前冷却后再通入冷却器3进行冷却，而经增压装置4加压后的液态循环介质在进入加热器1之前在回热器5中被提前加热，从而能够对于做功装置2后的循环介质的余热进行利用，降低加热器1与冷却器3所需要提供的能量，从而提高朗肯循环系统的作业效率。
进一步地，如图2所示，回热器5包括高温回热器51和低温回热器52，高温回热器51的热侧入口与做功装置2的介质出口连通，高温回热器51的热侧出口与低温回热器52的热侧入口连通，高温回热器51的冷侧出口与加热器1冷侧入口连通，高温回热器51的冷侧入口与低温回热器的冷侧出口连通，低温回热器52的冷侧入口与所述增压装置4的介质出口连通，朗肯循环系统还包括第一三通阀91、第二三通阀92和压缩机8，第一三通阀91分别与压缩机8出口、低温回热器52的冷侧出口、高温回热器51的冷侧入口连通，第二三通阀92分别与压缩机8入口、低温回热器52的热侧出口、冷却器3的热侧入口连通。
作为一个运行例，如图2所示的朗肯循环系统，循环介质首先进入加热器1的冷侧入口，燃气机组高温排气进入加热器1热侧入口，两流股在换热器中实现热交换，降温后的烟气通过换热器热侧出口排出，升温后的循环介质从换热器冷侧出口流出，继续进入做功装置2中膨胀做 功。做功装置2有三个透平，第一透平21出口和第二透平22出口的循环介质重新进入加热器1升温后分别进入第二透平22、第三透平23再次膨胀做功。第三透平23出口的循环介质进入高温回热器51热侧，与高温回热器51冷侧的循环介质换热降温，经过一次降温的循环介质再进入低温回热器52热侧，与低温回热器52冷侧流股换热降温，随后两次降温后的循环介质经过第二三通阀92分为两股：主流股循环介质经冷却器3冷却至液态，进入增压装置4增压后，再进入低温回热器52中回热升温；副流股循环介质直接进入压缩机8增压。接着，两股循环介质通过第一三通阀91汇合成为一条流股，再进入高温回热器51冷侧回热升温，然后进入加热器1中吸热，持续循环过程。
在本实施方式中，进一步地将回热器5设置为高温回热器51和低温回热器52，从而可以对做功装置2流出的工作介质的余热进一步地利用，并且，通过将低温回热器52流出的循环介质进行分流，一部分不经过冷却器3而直接通过压缩机8进行压缩后再与冷却压缩后的液态的循环介质汇总并流向加热装置，从而可以降低朗肯循环系统的冷源损失，进一步提高朗肯循环系统的作业效率。
4.冷却器3
在本实施方式中，冷却器3可以为任意能够对循环介质进行冷却降温的装置，具体地，该冷却器3可以为利用外部冷源7对循环介质进行冷却的换热器，该换热器的一端通入外部冷源，另一端则通入循环介质，从而气态的循环介质通过热交换，自身的热量被外部冷源吸收，循环介质降温至其三相点附近，以便于后续吸热，并且，提高了朗肯循环冷端和热端的温度差，从而提高循环效率。
其中，外部冷源的温度为-162℃-0℃；使用较低温度的冷源可以迅速、充分地使气态的循环介质降温至三相点附近，且冷源温度低有利于提升朗肯循环系统的作业效率；较优地，外部冷源7可以为液化天然气。液化天然气的冷源温度为-162℃左右，有利于提升朗肯循环系统的作业效率，此外，液化天然气在冷却器3中与循环介质进行热交换后可进一步通入燃气机组中作为燃料，产生的高温烟气又可作为外部热源6进行使用，从而实现了对于液化天然气这一优质外部冷源材料的循环利用。
5.增压装置4
在本实施方式中，增压装置4可以为液体增压泵，具体地，增压装置4对冷却器3流出的、温度在循环介质的三相点附近的饱和液态循环介质进行增压。由于循环介质的压力靠近其三相点，从而尽可能地发挥了一次朗肯循环系统中循环介质在做功装置2中膨胀做功所能转换的能量。
其中，较优地，如图3所示，该朗肯循环系统还包括有机介质朗肯循环回路，有机介质朗肯循环回路包括有机介质加热器1a和有机介质冷却器3a，外部热源6流经加热器1后，进入有机介质加热器1a，外部冷源7与冷却器3以及有机介质冷却器3a连通。
进一步地，该有机介质朗肯循环系统也可以包括上述朗肯循环系统中的其它装置，如图3所示，该有机介质朗肯循环还包括有机介质做功装置2a、有机介质增压装置4a和有机介质回热器5a，循环介质在有机介质朗肯循环系统中的流动方式与本发明提供的朗肯循环系统的流动方式一致，在此不做赘述。
在本实施方式中，采用朗肯循环与有机朗肯循环联合的循环形式可以实现更高的循环效率，对于相同的热源，使用本发明的联合循环系统能够实现更多的发电量、提高能量利用率。
另外，在本实施方式中还提供一种应用于上述朗肯循环系统的朗肯循环方法，包括如下步骤：
加热步骤，提供外部热源6和循环介质，利用所述外部热源6对所述循环介质进行加热，使其升温至超临界状态；做功步骤，超临界状态的循环介质对外做功，变为接近循环介质三相点压力的气态；冷却步骤，提供外部冷源7，利用所述外部冷源7对气态的循环介质进行冷却降温，得到低于0℃的接近三相点温度的饱和液态循环介质；压缩步骤，对液态的循环介质进行增压。
本领域技术人员能够理解的是，可以对各个实施方式中的具体技术特征进行适应性地拆分或合并。对具体技术特征的这种拆分或合并并不会导致技术方案偏离本发明的原理，因此，拆分或合并之后的技术方案都将落入本发明的保护范围内。
此外，术语“第一”、“第二”仅用于描述目的，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有 “第一”、“第二”的特征可以明示或者隐含地包括一个或者更多个该特征。在本申请的描述中，“多个”的含义是两个或两个以上，除非另有明确具体的限定。
至此，已经结合附图所示的多个实施方式描述了本发明的技术方案，但是，本领域技术人员容易理解的是，本发明的保护范围显然不局限于这些具体实施方式。在不偏离本发明的原理的前提下，本领域技术人员可以对相关技术特征作出等同的更改或替换，这些更改或替换之后的技术方案都将落入本发明的保护范围之内。

Claims (9)

  1. 一种朗肯循环系统，包括由加热器、做功装置、冷却器、增压装置依次接通形成的介质回路，循环介质在所述介质回路内部循环流动，其特征在于，所述循环介质的三相点温度低于0℃，所述循环介质的三相点压力高于标准大气压，从所述加热器流出的循环介质为超临界状态，从所述做功装置流出的循环介质为气态，从所述冷却器流出的循环介质为饱和液态，温度T1比循环介质的三相点温度Tgls高0℃-20℃，从所述做功装置流出的循环介质的压强P1等于循环介质在温度T1下的饱和蒸汽压力。
  2. 如权利要求1所述的朗肯循环系统，其特征在于，还包括回热器，所述回热器的热侧入口与所述做功装置的介质出口连通，所述回热器的热侧出口与所述冷却器的热侧入口连通，所述回热器的冷侧入口与所述增压装置的介质出口连通，所述回热器的冷侧出口与所述加热器连通。
  3. 如权利要求2所述的朗肯循环系统，其特征在于，所述回热器包括高温回热器和低温回热器，所述高温回热器的热侧入口与所述做功装置的介质出口连通，所述高温回热器的热侧出口与所述低温回热器的热侧入口连通，所述高温回热器的冷侧出口与所述加热器连通，所述低温回热器的冷侧入口与所述增压装置的介质出口连通，
    所述朗肯循环系统还包括第一三通阀、第二三通阀和压缩机，所述第一三通阀分别与所述压缩机出口、所述低温回热器的冷侧出口、所述高温回热器的冷侧入口连通，所述第二三通阀分别与所述压缩机入口、所述低温回热器的热侧出口、所述冷却器的热侧入口连通。
  4. 如权利要求1所述的朗肯循环系统，其特征在于，所述做功装置包括第一透平、第二透平和第三透平，所述第一透平利用超临界状态循环介质的焓值变化对外做功，所述第二透平接收来自所述第一透平的超临界状态的循环介质，并利用循环介质从超临界状态到气态的相态转变对外做功，所述第三透平接收来自所述第二透平的气态循环介质，并利用气态循环介质的焓值变化对外作用。
  5. 如权利要求1-4中任一项所述的朗肯循环系统，其特征在于，所述循环介质为CO2。
  6. 如权利要求1-4中任一项所述的朗肯循环系统，其特征在于，还包括外部冷源、外部热源和有机介质朗肯循环回路，所述有机介质朗肯 循环回路包括有机介质加热器和有机介质冷却器，外部热源流经所述加热器后，进入所述有机介质加热器，外部冷源分别与所述冷却器以及所述有机介质冷却器连通。
  7. 如权利要求6所述的朗肯循环系统，其特征在于，所述外部冷源的温度为-162℃～0℃。
  8. 如权利要求6所述的朗肯循环系统，其特征在于，所述外部热源为燃气机组，所述外部冷源为液化天然气储罐。
  9. 一种朗肯循环方法，其特征在于，包括如下步骤：
    加热步骤，提供外部热源和循环介质，利用所述外部热源对所述循环介质进行加热，使其升温至超临界状态；
    做功步骤，超临界状态的循环介质对外做功，充分膨胀至接近其三相点压力的气态循环介质；
    冷却步骤，提供外部冷源，利用所述外部冷源对气态的循环介质进行冷却降温，使其成为饱和液态循环介质；
    压缩步骤，对液态的循环介质进行增压。
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