JP7658622B2 - Rankine cycle system and Rankine cycle method - Google Patents

Description

The present invention relates to a Rankine cycle system and a Rankine cycle method in the field of power generation systems.

In industrial production, the exhaust temperature of some combustion engines is often relatively high. To further utilize the high-level heat source of the exhaust, it is common to achieve efficient combined cycle power generation by combining a steam Rankine cycle with the lower layer of the combustion engine. A conventional steam Rankine cycle has the following four processes:

A heating process in which water is heated to steam in a boiler. Ideally, the heating process is a constant pressure reversible endothermic process.

The operating process in which steam expands in a steam turbine. Ideally, the operating process is a reversible adiabatic expansion process, i.e. an isentropic expansion process.

A cooling process in which steam is cooled to saturated water in a condenser. Ideally, the cooling process is a reversible constant pressure cooling process.

A compression process in which water is compressed by increasing the pressure of a water pump. Ideally, this compression process is a reversible adiabatic compression process, i.e. an isentropic compression process.

According to Carnot's theorem, the efficiency of a reversible heat engine is related only to the maximum and minimum temperatures of the circulating medium. However, in a 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. Therefore, it is an urgent task in this technical field to further improve the operating efficiency of the Rankine cycle system.

The present invention aims to provide a Rankine cycle system with higher operating efficiency, addressing the above-mentioned deficiencies of the conventional technology.

The Rankine cycle system includes a medium circuit formed by sequentially connecting a heater, an operating device, a cooler, and a pressurizing device, the circulating medium flows in a circulating manner inside the medium circuit, the circulating medium flowing out of the heater is in a supercritical state, the triple point temperature of the circulating medium is less than 0°C, the triple point pressure of the circulating medium is higher than standard atmospheric pressure, the circulating medium flowing out of the cooler is a saturated liquid, its temperature T1 is 0°C to 20°C higher than the triple point temperature Tgls of the circulating medium, and the pressure P1 of the gaseous circulating medium flowing out of the operating device is equal to the saturated vapor pressure of the circulating medium at temperature T1.

According to the technical solution, firstly, in the Rankine cycle system provided by the present invention, the circulating medium reaches a supercritical state in the heating device, and when the circulating medium is in a supercritical state, its density is high and the number of turbine stages required for the work caused by its expansion is relatively small, so in the present invention, the turbine device is much more compact than the turbine structure in the conventional steam Rankine cycle. The smaller turbine device volume leads to a smaller factory area and a more compact circulating flow.

Next, from a thermodynamic point of view, the circulation efficiency can be further improved by increasing the temperature of the heat source in the circulation process and decreasing the temperature of the cold source in the circulation process. However, if the temperature is lower than the triple point, constant pressure cooling causes the circulating medium to change from gas to solid without passing through the liquid phase region, causing sublimation. However, since the solid circulating medium cannot flow, the utilization efficiency of the circulating medium in the Rankine cycle to the cold source supplied by the cooler is limited by the temperature of the triple point of the circulating medium. Therefore, according to Carnot's theorem, in the present invention, the circulating medium is heated to a supercritical state beyond gas, and is cooled in the cooler to a temperature slightly higher than the triple point (i.e., higher than the triple point of 0°C-20°C). The saturated vapor pressure of the circulating medium corresponding to this temperature is the exhaust pressure of the last operating device. As a result, the operating efficiency of the Rankine cycle system can be maximized. Furthermore, since the triple point temperature of the circulating medium is lower than 0°C, the circulating medium can be lowered to a lower temperature, and since the triple point pressure is higher than standard atmospheric pressure, there is no need to maintain a vacuum in the condenser via an external device during the condensation process, and air leakage into the condenser is also avoided. In this way, by using a good low-temperature cold source in combination, the circulation efficiency can be significantly improved thermodynamically.

The Rankine cycle system preferably further includes a regenerator, the heating side inlet of the regenerator being connected to the medium outlet of the operating device, the heating side outlet of the regenerator being connected to the heating side inlet of the cooler, the cooling side inlet of the regenerator being connected to the medium outlet of the pressurizing device, and the cooling side outlet of the regenerator being connected to the heater.

According to this technical proposal, a regenerator is added to the Rankine cycle system, and the gaseous circulating medium at the outlet of the operating device enters the regenerator and exchanges heat with the liquid circulating medium cooled and compressed in the regenerator. The gaseous circulating medium is pre-cooled in the regenerator and then introduced into the cooler where it is cooled, and the liquid circulating medium pressurized by the pressurizing device is pre-heated in the regenerator before entering the heater. This makes it possible to utilize the residual heat of the circulating medium from the operating device, reduce the energy required by the heater and cooler, and improve the operating efficiency of the Rankine cycle.

Among them, it is preferable that the regenerator comprises a high-temperature regenerator and a low-temperature regenerator. It is preferable that the heating side inlet of the high-temperature regenerator is connected to the medium outlet of the operating device, the heating side outlet of the high-temperature regenerator is connected to the heating side inlet of the low-temperature regenerator, the cooling side outlet of the high-temperature regenerator is connected to a heater, the cooling side inlet of the high-temperature regenerator is connected to the cooling side outlet of the low-temperature regenerator, the cooling side inlet of the low-temperature regenerator is connected to the medium outlet of the pressurizing device, and the heating side outlet of the low-temperature regenerator is connected to a cooler.

Of these, it is preferable that the Rankine cycle system further includes a first three-way valve, a second three-way valve, and a compressor. It is preferable that the first three-way valve communicates with the compressor outlet, the cooling side outlet of the low-temperature regenerator, and the cooling side inlet of the high-temperature regenerator, respectively, and that the second three-way valve communicates with the compressor inlet, the heating side outlet of the low-temperature regenerator, and the heating side inlet of the cooler, respectively.

According to this technical proposal, by installing additional regenerators in the high-temperature regenerator and the low-temperature regenerator, the residual heat of the working medium flowing out from the operating device can be further utilized. In addition, the circulating medium flowing out from the low-temperature regenerator is branched, and a portion of it is compressed directly by the compressor without passing through the cooler, and then it is combined with the cooled and pressurized liquid circulating medium and then flowed into the heating device, thereby reducing the loss of the cold heat source in the Rankine cycle system and further improving the operating efficiency of the Rankine cycle system.

Among them, it is preferable that the operating device includes a first turbine, a second turbine, and a third turbine. It is preferable that the first turbine performs work to the outside by utilizing the change in the enthalpy value of the circulating medium in a supercritical state, the second turbine receives the circulating medium in a supercritical state from the first turbine and performs work to the outside by utilizing the phase transition of the circulating medium from the supercritical state to a gas state, and the third turbine receives the gas circulating medium from the second turbine and performs work to the outside by utilizing the change in the enthalpy value of the gas circulating medium.

According to this technical solution, by installing the operating device in the multi-stage turbine, the thermal energy transmitted to the circulating medium in the heater is fully converted into mechanical energy by the multi-stage turbine, improving the working efficiency of the entire circulation system. Among them, when the multi-stage turbine is a three-stage turbine, the circulating medium in the first turbine is maintained in a supercritical state, at this time, the density of the circulating medium is high, and the structure of the first turbine is more compact. After the circulating medium further expands adiabatically in the second turbine, it goes from the supercritical state to gas before entering the third turbine, and the residual heat of the circulating medium is further utilized in the third turbine, thereby increasing the working efficiency of the entire circulation system.

Among them, the circulating medium of the Rankine cycle system is preferably _CO2 .

According to this technical solution, currently _CO2 is mainly applied to the supercritical _CO2 (S- _CO2 ) Brayton cycle as the circulating medium, and the S- _CO2 Brayton cycle has many advantages such as high high-temperature heat source circulation efficiency, small compression energy loss, compact turbine device structure and small footprint, and low corrosiveness, and is one of the potential options for efficient power generation using residual heat from gas turbine exhaust gas. However, in the supercritical _CO2 (S- _CO2 ) Brayton cycle, the cold heat source temperature cannot be lowered below the _CO2 critical temperature (31.1°C), and this cold heat source temperature limits the working efficiency of the supercritical _CO2 (S- _CO2 ) Brayton cycle system.

Furthermore, the triple point of H ₂ O is 0.01°C and 610.75 Pa, and the temperature of its cooling end cannot be reduced to below 0°C. Also, the pressure of the triple point of H ₂ O is too low (less than 1 kPa), and it is an open circulation, so in order to reduce the pressure close to the triple point, it is necessary to use a vacuum pump to extract and perform work, and there is a limit to improving the circulation efficiency. On the other hand, the triple point of CO ₂ is -56.6°C and 0.52 MPa, and the temperature of the cold source can be reduced to a lower temperature, and the pressure of the triple point is above atmospheric pressure, the circulation form is a closed circulation, and there is no need to use a vacuum pump to evacuate, so that the entire circulation is above atmospheric pressure, and the infiltration of non-condensable gases into the low pressure part of the circulation is avoided. In this way, after combining and using good low-temperature cold sources, from a thermodynamic point of view, the circulation efficiency can be greatly improved.

Finally, since the corrosiveness of the CO ₂ circulating medium is much weaker than that of H ₂ O vapor, the corrosion resistance requirements for high-temperature component parts can be significantly relaxed.

The Rankine cycle system further includes an external cold heat source, an external heat source, and an organic media Rankine cycle circuit, the organic media Rankine cycle circuit having an organic media heater and an organic media cooler, the external heat source flows through the heater and then enters the organic media heater, and the external cold heat source is preferably connected to the cooler and the organic media cooler, respectively.

According to this technical proposal, by adopting a circulation form that combines a Rankine cycle and an organic Rankine cycle, it is possible to achieve higher circulation efficiency. For the same heat source, when using the combined cycle system of the present invention, it is possible to achieve a greater amount of power generation and improve the energy utilization rate.

The temperature of the external cold source is preferably between -162°C and 0°C. According to this technical solution, the temperature of the gas circulation medium can be quickly lowered to near the triple point by using a relatively low-temperature cold source. In addition, a low temperature cold source is advantageous for improving the operating efficiency of the Rankine cycle system.

Preferably, the external heat source is a gas unit and the external cold source is liquefied natural gas.

According to this technical proposal, the gas unit is used as the heat source, that is, the excess heat (e.g., high-temperature fumes) generated by the gas unit is reused. In addition, since the temperature of the cold heat source of liquefied natural gas is about -162°C, the gas circulation medium can be quickly cooled to a saturated liquid near the triple point, and the low temperature of the cold heat source is advantageous for improving the operating efficiency of the Rankine cycle system. Furthermore, after the liquefied natural gas is introduced into the cooler as a cold heat source and heat exchanged with the circulation medium, it can be introduced into the gas unit as a 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 that the cold heat source material can be utilized to the maximum extent.

1 is a structural schematic diagram of a Rankine cycle system according to an embodiment of the present invention. FIG. FIG. 2 is a structural schematic diagram of a Rankine cycle system according to another embodiment of the present invention. FIG. 2 is a structural schematic diagram of a Rankine cycle system according to another embodiment of the present invention.

The present invention will be described in more detail with reference to the following specific examples and drawings. The content realized by the present invention is not limited to the following embodiments, and all of the various modifications, conversions, combinations and improvements made within the scope of knowledge possessed by a person skilled in the art based on the technical concept of the present invention fall within the scope of protection of the present invention.

Overall configuration. As shown in FIG. 1, the Rankine cycle system according to this embodiment includes a medium circuit formed by sequentially communicating a heater 1, an operating device 2, a regenerator 5, a cooler 3, and a pressurizing device 4. The circulating medium flows in a circulating manner inside the medium circuit, and specifically, the triple point temperature of the circulating medium is less than 0°C, and the triple point pressure of the circulating medium is higher than standard atmospheric pressure. The circulating medium absorbs thermal energy in the heater 1 and becomes a supercritical fluid, and then flows into the operating device 2, expands, and performs work, thereby converting the thermal energy into mechanical energy that is more easily utilized. The gaseous circulating medium that has passed through the operating device 2 enters the regenerator 5, where the residual heat of the circulating medium is reused, and then enters the cooler 3 to lower its temperature. After the gaseous circulating medium is cooled with a saturated liquid at a temperature T1 (Tgls<T1<Tgls+20°C) slightly higher than the triple point temperature Tgls of the circulating medium, the circulating medium enters the pressurizing device 4 and is pressurized. The pressurized liquid circulation medium enters the regenerator 5, absorbs the residual heat from the exhaust of the operating equipment, and then enters the heater 1 again to start a new circulation. In this way, thermal energy is repeatedly converted into mechanical energy.

In this embodiment, the structure of each apparatus or device is not limited. For example, in some embodiments, the operating apparatus 2 may be a rotary turbine, and in other embodiments, the operating apparatus 2 may be a cylinder apparatus having a transmission rod. Similarly, any simple substitution of the apparatus or device in the present invention, provided that it does not contradict the technical solution of the present invention, is not considered to exceed the scope of protection of the present invention.

In this embodiment, the regenerator 5 is a device for reusing residual heat from the operating device 2. That is, in this embodiment, a preferred embodiment of a Rankine cycle with the addition of the regenerator 5 has been described as an example, but as will be recognized by those skilled in the art, the Rankine cycle system according to the present invention may be configured without including a regenerator, by being connected in sequence by the heater 1, the operating device 2, the cooler 3, and the pressurizing device 4.

In this embodiment, first, since the triple point temperature of the circulating medium is lower than 0°C, a cold heat source medium with a lower temperature can be used. In addition, since the triple point pressure is higher than standard atmospheric pressure, there is no need to maintain a vacuum in the condenser, which saves energy while preventing outside air from entering the circulation system. In this way, after combining and using high-quality low-temperature cold heat sources, the circulation efficiency can be significantly improved using Carnot's theorem.

The circulating medium then reaches a supercritical state in the heating device, and since the circulating medium is denser when in a supercritical state and requires relatively fewer turbine stages to expand and perform work, the high pressure turbine device in this embodiment is much more compact than the turbine structure in a conventional steam Rankine cycle. Smaller turbine device volume translates into smaller plant area and more compact circulating flow.

Finally, since the temperature of the circulating medium in a supercritical state is higher than that of the gas circulating medium, according to Carnot's theorem, when the cold source provided by the cooler 3 is fixed, the circulating medium in the Rankine cycle system of the present invention can reach a higher initial temperature. In other words, the working efficiency of the Rankine cycle system of the present invention is higher than that of the conventional system.

Here, the circulating medium of the Rankine cycle system is preferably _CO2 .

In this embodiment, currently, _CO2 is mainly applied to the supercritical _CO2 (S- _CO2 ) Brayton cycle as the circulating medium. The S- _CO2 Brayton cycle has many advantages, such as high high-temperature heat source circulation efficiency, small compression energy loss, compact structure of the rotary turbine device, small footprint, and low corrosiveness, and is one of the potential options for efficient power generation using the residual heat of gas turbine exhaust gas. However, in the S- _CO2 Brayton cycle, the cold heat source temperature does not fall below the _CO2 critical temperature (31.1°C). This cold heat source temperature limits the working efficiency of the S- _CO2 Brayton cycle system.

In addition, the triple point of H ₂ O is 0.01°C, 610.75 Pa, and its cooling end temperature cannot be reduced to below 0°C, and the triple point pressure of H ₂ O is too low (less than 1 kPa), so the circulation form is open circulation, and therefore, in order to cool it to a pressure close to the triple point, it is necessary to use a vacuum pump to extract air and perform work, which increases extra energy consumption and limits the improvement of circulation efficiency. In contrast, the circulation form of CO ₂ is closed circulation, and there is no need to use a vacuum pump to evacuate, and the triple point of CO ₂ is -56.6°C, 0.52 MPa, so the temperature of the cold source can be reduced to a lower temperature, and the triple point pressure is above atmospheric pressure, which avoids the penetration of external condensable air into the circulation inside the condenser. In this way, after combining and using good low-temperature cold sources, from a thermodynamic point of view, the circulation efficiency can be greatly improved.

In addition, since the corrosiveness of the CO ₂ circulating medium is considerably weaker than that of H ₂ O vapor, the corrosion resistance requirements for high-temperature component members can be significantly relaxed.

Finally, the specific volume of the _CO2 circulation medium is much smaller than that of _H2O , which can greatly reduce the size of the operating device and save factory area.

The Rankine cycle device according to this embodiment is described in more detail below.

Heater. In this embodiment, the heater 1 may be any device capable of heating the circulating medium. Specifically, the heater 1 may be a heat exchanger that uses an external heat source 6 to heat the circulating medium. One end of the heat exchanger is used to introduce the external heat source 6, and the other end is used to introduce the circulating medium, so that the circulating medium absorbs the heat of the external heat source 6 through heat exchange, increases in temperature, and undergoes a phase transition. This makes it easier to do work later. The external heat source 6 is preferably solar energy, nuclear energy, fossil fuels, and the like. Furthermore, the external heat source 6 is preferably a gas unit. This allows the residual heat of high-temperature fumes after combustion in the gas unit to be reused, thereby saving resources.

Operating device 2. In this embodiment, the operating device 2 may be a device capable of converting thermal energy into mechanical energy by utilizing the work caused by the expansion of a circulating medium, for example, a cylinder structure that reciprocates a transmission rod by gas expansion, or a rotary turbine structure that performs work by gas expansion and rotation. This embodiment will be further described using an example in which the operating device 2 is a rotary turbine.

The rotary turbine preferably includes a first turbine 21, a second turbine 22, and a third turbine 23. The first turbine 21 performs work to the outside by utilizing the change in the enthalpy value of the circulating medium in a supercritical state. The second turbine 22 receives the circulating medium in a supercritical state from the first turbine 21, and performs work to the outside by expansion by utilizing the phase transition of the circulating medium from the supercritical state to a gas state. The third turbine 23 receives the circulating medium that is a gas from the second turbine 22, and performs work to the outside by utilizing the change in the enthalpy value of the gas circulating medium.

In this embodiment, the operating device 2 is installed in a multi-stage turbine, so that the thermal energy transmitted to the circulating medium in the heater 1 is fully converted into mechanical energy by the multi-stage turbine, thereby improving the working efficiency of the entire circulation system. As will be recognized by those skilled in the art, the effect of performing work by the circulating medium in the operating device 2 can be achieved even if a single or other number of turbines are installed. These do not exceed the scope of protection of the present invention. Here, when the multi-stage turbine is a three-stage turbine, the circulating medium in the first turbine 21 is maintained in a supercritical state. At this time, the density of the circulating medium is high, the structure of the first turbine 21 is more compact, and the circulating medium further expands adiabatically in the second turbine 22 and turns from the supercritical state into gas before entering the third turbine 23, and the residual heat of the circulating medium is further utilized in the third turbine 23, thereby increasing the working efficiency of the entire circulation system.

Regenerator 5. In this embodiment, the regenerator 5 may be a device that has two flow paths, one for cold and one for hot, and exchanges heat between the media in the two flow paths. Specifically, the heating side inlet of the regenerator 5 is connected to the medium outlet of the operating device 2, the heating side outlet of the regenerator 5 is connected to the heating side inlet of the cooler 3, the cooling side inlet of the regenerator 5 is connected to the medium outlet of the pressurizing device 4, and the cooling side outlet of the regenerator 5 is connected to the heater 1.

In this embodiment, the gaseous circulating medium at the outlet of the operating device 2 enters the regenerator 5 and exchanges heat with the liquid circulating medium that has been cooled and compressed in the regenerator 5, so that the gaseous circulating medium is pre-cooled in the regenerator 5, and then introduced into the cooler 3 where it is cooled. The liquid circulating medium pressurized by the pressurizing device 4 is pre-heated in the regenerator 5 before entering the heater 1, thereby utilizing the residual heat of the circulating medium from the operating device 2, reducing the energy required by the heater 1 and the cooler 3, and improving the operating efficiency of the Rankine cycle system.

2, the regenerator 5 includes a high-temperature regenerator 51 and a low-temperature regenerator 52, the heating side inlet of the high-temperature regenerator 51 is connected to the medium outlet of the operating device 2, the heating side outlet of the high-temperature regenerator 51 is connected to the heating side inlet of the low-temperature regenerator 52, the cooling side outlet of the high-temperature regenerator 51 is connected to the cooling side inlet of the heater 1, the cooling side inlet of the high-temperature regenerator 51 is connected to the cooling side outlet of the low-temperature regenerator, and the cooling side inlet of the low-temperature regenerator 52 is connected to the medium outlet of the pressurizing device 4. The Rankine cycle system further includes a first three-way valve 91, a second three-way valve 92, and a compressor 8, the first three-way valve 91 is connected to the compressor 8 outlet, the cooling side outlet of the low-temperature regenerator 52, and the cooling side inlet of the high-temperature regenerator 51, respectively, and the second three-way valve 92 is connected to the compressor 8 inlet, the heating side outlet of the low-temperature regenerator 52, and the heating side inlet of the cooler 3, respectively.

As an example of operation, as shown in the Rankine cycle system in Figure 2, the circulating medium first enters the cooling side inlet of heater 1, the high-temperature exhaust gas from the gas unit enters the heating side inlet of heater 1, the two air flows exchange heat in the heat exchanger, the cooled fumes are discharged from the heating side outlet of the heat exchanger, and the heated circulating medium flows out from the cooling side outlet of the heat exchanger and continues to enter the operating device 2 to expand and perform work. The operating device 2 has three turbines, and 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 be heated, then enters the second turbine 22 and the third turbine 23, respectively, and expands again to perform work. The circulating medium at the outlet of the third turbine 23 enters the heating side of the high-temperature regenerator 51, where it exchanges heat with the circulating medium on the cooling side of the high-temperature regenerator 51 to lower its temperature. The circulating medium that has been cooled once again enters the heating side of the low-temperature regenerator 52, where it exchanges heat with the air flow on the cooling side of the low-temperature regenerator 52 to lower its temperature. Next, the circulating medium that has been cooled twice is branched into two by the second three-way valve 92. The circulating medium of the main branch is cooled to liquid by the cooler 3, enters the pressurizing device 4 to be pressurized, and then enters the low-temperature regenerator 52 again to be reheated and heated, and the circulating medium of the sub-branch directly enters the compressor 8 to be pressurized. Next, the two branches of circulating medium are merged by the first three-way valve 91 to become one air flow, which then enters the cooling side of the high-temperature regenerator 51 to reheat and raise its temperature, and then enters the heater 1 to absorb heat and continue the circulation process.

In this embodiment, the regenerator 5 is further provided with a high-temperature regenerator 51 and a low-temperature regenerator 52, which allows the residual heat of the working medium flowing out of the operating device 2 to be further utilized. The circulating medium flowing out of the low-temperature regenerator 52 is branched, and a portion of it is compressed directly by the compressor 8 without passing through the cooler 3, and then merges with the cooled and compressed liquid circulating medium before being passed through the heating device, thereby reducing the loss of the cold heat source in the Rankine cycle system and further improving the operating efficiency of the Rankine cycle system.

In this embodiment, the cooler 3 may be any device capable of cooling the circulating medium. Specifically, the cooler 3 may be a heat exchanger that cools the circulating medium using an external cold source 7, with one end of the heat exchanger being used to introduce the external cold source and the other end being used to introduce the circulating medium, so that the gas circulating medium has its own heat absorbed by the external cold source through heat exchange, and its temperature is reduced to near its triple point. This facilitates subsequent heat absorption. It also increases the temperature difference between the cooling end and the heating end of the Rankine cycle, improving circulation efficiency.

The temperature of the external cold heat source is -162°C to 0°C. Using a relatively low-temperature cold heat source allows the gas circulation medium to be cooled quickly and sufficiently to near the triple point, and the low cold source temperature is advantageous for improving the operating efficiency of the Rankine cycle system. The external cold heat source 7 is preferably liquefied natural gas. The cold source temperature of liquefied natural gas is about -162°C, which is advantageous for improving the operating efficiency of the Rankine cycle system. Furthermore, after heat exchange with the circulation medium in the cooler 3, the liquefied natural gas can continue to be introduced into the gas unit as fuel, and the generated high-temperature fumes can be used as the external heat source 6, so that recycling of the high-quality external cold heat source material, liquefied natural gas, can be realized.

Pressurizing device 4. In this embodiment, the pressurizing device 4 may be a liquid booster pump. Specifically, the pressurizing device 4 pressurizes the saturated liquid circulating medium that flows out of the cooler 3 and has a temperature near the triple point of the circulating medium. Since the pressure of the circulating medium is close to its triple point, the energy that is converted by the circulating medium expanding in the operating device 2 and performing work in the primary Rankine cycle system is utilized as much as possible.

As shown in FIG. 3, the Rankine cycle system further includes an organic media Rankine cycle circuit, which includes an organic media heater 1a and an organic media cooler 3a, and the external heat source 6 flows through the heater 1 and then enters the organic media heater 1a. The external cold heat source 7 is preferably connected to the cooler 3 and the organic media cooler 3a.

Furthermore, the organic media Rankine cycle may include other devices in the Rankine cycle system. As shown in FIG. 3, the organic media Rankine cycle further includes an organic media operating device 2a, an organic media pressurizing device 4a, and an organic media regenerator 5a. The flow mechanism of the circulating medium in the organic media Rankine cycle is the same as the flow mechanism of the Rankine cycle system according to the present invention, so a description thereof will be omitted here.

In this embodiment, a circulation form that combines a Rankine cycle and an organic Rankine cycle is adopted, thereby achieving higher circulation efficiency. When the combined cycle system of the present invention is applied to the same heat source, a larger amount of power can be generated and the energy utilization rate can be improved.

The Rankine cycle method applied to the Rankine cycle system according to this embodiment includes a heating step of providing an external heat source 6 and a circulating medium, and heating the circulating medium with the external heat source 6 to raise its temperature to a supercritical state; an operating step of causing the circulating medium in a supercritical state to perform work on the outside and change into a gas close to the triple point pressure of the circulating medium; a cooling step of providing an external cold heat source 7, and cooling and lowering the gas circulating medium with the external cold heat source 7 to obtain a saturated liquid circulating medium that is lower than 0°C and close to the triple point temperature; and a compression step of pressurizing the liquid circulating medium.

It will be recognized by those skilled in the art that the specific technical features in each embodiment can be adaptively divided or merged. The division or merging of the specific technical features does not cause the technical solution to deviate from the principles of the present invention, and therefore all divided or merged technical solutions are within the scope of protection of the present invention.

Additionally, terms such as "first" and "second" are for descriptive purposes only and cannot be understood to indicate or imply the relative importance or number of the indicated technical features. Thus, a feature qualified as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "plurality" means two or more, unless otherwise specified.

The technical solution of the present invention has been described above based on several embodiments shown in the drawings, but it is obvious to those skilled in the art that the scope of protection of the present invention is not limited to these specific embodiments. On the premise that it does not deviate from the principle of the present invention, those skilled in the art may make equivalent modifications or substitutions to the relevant technical features, and all such modified or substituted technical solutions are included within the scope of protection of the present invention.

1: Heater, 2: Operating device, 21: First turbine, 22: Second turbine, 23: Third turbine, 3: Cooler, 4: Pressurizing device, 5: Regenerator, 51: High temperature regenerator, 52: Low temperature regenerator, 6: External heat source, 7: External cold heat source, 8: Compressor, 91: First three-way valve, 92: Second three-way valve, 1a: Organic media heater, 2a: Organic media operating device, 3a: Organic media cooler, 4a: Organic media pressurizing device, 5a: Organic media regenerator.

Claims (7)

A Rankine cycle system including a medium circuit formed by sequentially communicating a heater, an operating device, a cooler, and a pressurizing device, and a circulating medium flows through the medium circuit,
The operating device includes a first turbine that performs work to the outside by utilizing a change in the enthalpy value of the circulating medium in a supercritical state, and a second turbine that receives the circulating medium in a supercritical state from the first turbine and performs work to the outside by utilizing a phase transition of the circulating medium from a supercritical state to a gas state.
a third turbine that receives the circulating medium, which is a gas, from the second turbine and performs work on an external device by utilizing a change in enthalpy value of the circulating medium, wherein a triple point temperature of the circulating medium is less than 0° C., and a triple point pressure of the circulating medium is higher than standard atmospheric pressure,
the circulating medium exiting the heater is in a supercritical state;
The circulating medium flowing out from the operating device is a gas,
the circulating medium flowing out of the cooler is a saturated liquid, a temperature T1 is 0°C to 20°C higher than a triple point temperature Tgls of the circulating medium, and a pressure P1 of the circulating medium flowing out of the operating device is equal to a saturated vapor pressure of the circulating medium at the temperature T1. 2. The Rankine cycle system according to claim 1,
the medium circuit includes a reproducer;
a heating side inlet of the regenerator connected to a medium outlet of the operating device, a heating side outlet of the regenerator connected to a heating side inlet of the cooler, a cooling side inlet of the regenerator connected to a medium outlet of the pressurizing device, and a cooling side outlet of the regenerator connected to the heater. 3. The Rankine cycle system according to claim 2,
The regenerator comprises a high-temperature regenerator and a low-temperature regenerator,
A heating side inlet of the high-temperature generator communicates with a medium outlet of the operating device, a heating side outlet of the high-temperature generator communicates with a heating side inlet of the low-temperature generator, a cooling side outlet of the high-temperature generator communicates with the heater, and a cooling side inlet of the low-temperature generator communicates with a medium outlet of the pressurizing device,
The Rankine cycle system includes a first three-way valve, a second three-way valve, and a compressor,
the first three-way valve is connected to an outlet of the compressor, a cooling side outlet of the low-temperature regenerator, and a cooling side inlet of the high-temperature regenerator, respectively; and the second three-way valve is connected to an inlet of the compressor, a heating side outlet of the low-temperature regenerator, and a heating side inlet of the cooler, respectively. The Rankine cycle system according to any one of claims 1 to 3,
The Rankine cycle system is characterized in that the circulating medium is CO2. The Rankine cycle system according to any one of claims 1 to 3,
The Rankine cycle system includes an external cold source, an external heat source, and an organic media Rankine cycle circuit;
the organic media Rankine cycle circuit includes an organic media heater and an organic media cooler;
the external heat source flows through the heater and then enters the organic media heater;
the external cold source is in communication with the cooler and the organic medium cooler, respectively. 6. The Rankine cycle system according to claim 5,
The Rankine cycle system is characterized in that the temperature of the external cold source is -162°C to 0°C. 6. The Rankine cycle system according to claim 5,
1. A Rankine cycle system, comprising: a gas unit; and an external cold source that is a liquefied natural gas storage tank.

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