HIGH-EFFICIENCY STEAM POWER CYCLE SYSTEM FOR CASCADED UTILIZATION OF ENERGY

Abstract

A high-efficiency steam power cycle system for cascaded utilization of energy includes a steam cycle system and an organic working fluid Rankine cycle system. The steam cycle system includes a steam generator, a steam turbine, a condenser, and a separation device. The separation device is provided with a first outlet and a second outlet. An outlet of the steam generator, the steam turbine, the condenser, an inlet of the separation device, the first outlet, and an inlet of the steam generator are sequentially connected. The organic working fluid Rankine cycle system includes a heat exchanger; the heat exchanger is provided with a water-based absorbent inlet and a water-based absorbent outlet. The water-based absorbent outlet, an inlet of the condenser, the inlet of the separation device, the second outlet, and the water-based absorbent inlet are sequentially connected.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Chinese Patent Application No. 202411575070.X, filed on Nov. 6, 2024, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to the technical field of energy and power engineering, and particularly relates to a high-efficiency steam power cycle system for cascaded utilization of energy.

BACKGROUND

In the technical field of energy and power engineering, the steam Rankine cycle system plays a crucial role. This system converts thermal energy into mechanical energy to provide power for industrial production or for power generation, and constitutes a core component of modern energy conversion technology. The basic operating principle of the steam Rankine cycle system involves using water as a working fluid. The water is heated in a boiler to generate steam, the steam expands through a steam turbine to perform work, is then exhausted into a condenser to be condensed back into water, and is finally pumped back to the boiler, forming a closed cycle.

The thermal efficiency of the steam Rankine cycle system reflects the system's capability to convert thermal energy into mechanical energy and is a key indicator for measuring its performance. Existing steam Rankine cycle systems have low thermal efficiency, leading to substantial energy waste.

SUMMARY

The present disclosure provides a high-efficiency steam power cycle system for cascaded utilization of energy, aimed at solving the problem in the prior art where steam Rankine cycle systems have low thermal efficiency, leading to substantial energy waste.

The present disclosure provides a high-efficiency steam power cycle system for cascaded utilization of energy, including: a steam cycle system and an organic working fluid Rankine cycle system; the steam cycle system includes a steam generator, a steam turbine, a condenser, and a separation device; the separation device is provided with a first outlet and a second outlet; an outlet of the steam generator, the steam turbine, the condenser, an inlet of the separation device, the first outlet, and an inlet of the steam generator are sequentially connected; the organic working fluid Rankine cycle system includes a heat exchanger; the heat exchanger is provided with a water-based absorbent inlet and a water-based absorbent outlet; the water-based absorbent outlet, an inlet of the condenser, the inlet of the separation device, the second outlet, and the water-based absorbent inlet are sequentially connected; the separation device is configured to separate a mixed liquid discharged from the condenser into water and a water-based absorbent solution; the water flows to the steam generator through the first outlet, and the water-based absorbent solution flows to the heat exchanger through the second outlet.

According to the high-efficiency steam power cycle system for cascaded utilization of energy provided by the present disclosure, an outlet of the condenser is connected to the water-based absorbent inlet.

According to the high-efficiency steam power cycle system for cascaded utilization of energy provided by the present disclosure, the organic working fluid Rankine cycle system further includes an expansion turbine, the heat exchanger is further provided with an organic working fluid inlet and an organic working fluid outlet, and the organic working fluid outlet, the expansion turbine, and the organic working fluid inlet are sequentially connected; and the expansion turbine is configured to convert thermal energy into mechanical energy or electrical energy.

According to the high-efficiency steam power cycle system for cascaded utilization of energy provided by the present disclosure, the organic working fluid Rankine cycle system further includes a cooler, an inlet of the cooler is connected to an outlet of the expansion turbine, and an outlet of the cooler is connected to the organic working fluid inlet.

According to the high-efficiency steam power cycle system for cascaded utilization of energy provided by the present disclosure, the organic working fluid Rankine cycle system further includes a first pumping member, and the first pumping member is disposed between the outlet of the cooler and the organic working fluid inlet.

According to the high-efficiency steam power cycle system for cascaded utilization of energy provided by the present disclosure, the steam cycle system further includes a second pumping member, and the second pumping member is disposed between the first outlet and the steam generator.

According to the high-efficiency steam power cycle system for cascaded utilization of energy provided by the present disclosure, a regulating member is disposed between the outlet of the condenser and the water-based absorbent inlet or between the outlet of the condenser and the inlet of the separation device.

According to the high-efficiency steam power cycle system for cascaded utilization of energy provided by the present disclosure, the steam cycle system further includes a third pumping member, an inlet of the third pumping member is connected to the outlet of the condenser, and an outlet of the third pumping member is connected to the water-based absorbent inlet and the inlet of the separation device, respectively.

According to the high-efficiency steam power cycle system for cascaded utilization of energy provided by the present disclosure, the water-based absorbent solution includes a salt solution.

According to the high-efficiency steam power cycle system for cascaded utilization of energy provided by the present disclosure, the separation device includes a membrane distillation separation device.

In the high-efficiency steam power cycle system for cascaded utilization of energy provided by the present disclosure, under the condition of constant steam pressure within the condenser and unchanged work output from the steam turbine, supplying the water-based absorbent from the water-based absorbent outlet of the heat exchanger into the condenser can significantly increase the outlet temperature of the condenser. The mixed liquid at the condenser outlet, after being separated by the separation device, enters the heat exchanger to exchange heat with the organic working fluid. The thermal energy is transferred to the organic working fluid cycle system and is converted into mechanical energy or electrical energy, thereby enhancing the thermal efficiency of the system and improving the utilization rate of energy.

BRIEF DESCRIPTION OF THE DRAWINGS

To illustrate the technical solutions in the present disclosure or in the prior art more clearly, the following provides a brief introduction to the accompanying drawings required for describing the embodiments or the prior art. Obviously, the accompanying drawings in the following description show only some embodiments of the present disclosure. Persons of ordinary skill in the art may obtain other drawings based on these accompanying drawings without creative effort.

The accompanying figure is a schematic structural diagram of a high-efficiency steam power cycle system for cascaded utilization of energy according to the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

To make the objectives, technical solutions, and advantages of the present disclosure clearer, the following describes the technical solutions of the present disclosure clearly and completely with reference to the accompanying drawings in the present disclosure. Obviously, the described embodiments are only some, not all, embodiments of the present disclosure. Based on the embodiments in the present disclosure, all other embodiments obtained by persons of ordinary skill in the art without creative effort shall fall within the protection scope of the present disclosure.

In the description of the embodiments of the present disclosure, it should be noted that, unless otherwise explicitly specified and defined, the terms “connected” and “connection” should be understood broadly. For example, a connection may be a fixed connection, a detachable connection, or an integral connection; a connection may be a mechanical connection, an electrical connection, a direct connection, or a connection through an intermediate medium. Persons of ordinary skill in the art can understand the specific meanings of the foregoing terms in the embodiments of the present disclosure according to specific situations.

In the description of the embodiments of the present disclosure, it should be noted that the orientation or positional relationship indicated by the terms “center”, “longitudinal”, “transverse”, “upper”, “lower”, “front”, “rear”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inner”, “outer”, and the like is based on the orientation or positional relationship shown in the accompanying drawings. This is only for convenience of describing the embodiments of the present disclosure and simplifying the description, and does not indicate or imply that the mentioned apparatus or element must have a specific orientation or must be constructed and operated in a specific orientation. Therefore, the foregoing terms should not be understood as limitations to the embodiments of the present disclosure.

Furthermore, the terms “first” and “second” are used for descriptive purposes only, and should not be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined by “first” or “second” may explicitly or implicitly include one or more such features. In the description of the present disclosure, “a plurality of” means two or more, unless otherwise explicitly and specifically defined.

The following describes the embodiments of the present disclosure in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary, and are intended to explain the present disclosure, but should not be understood as limitations to the present disclosure.

The following disclosure provides many different embodiments or examples for implementing different structures of the present disclosure. To simplify the disclosure of the present disclosure, the following describes components and arrangements in specific examples. Certainly, these are only examples and are not intended to limit the present disclosure. In addition, the present disclosure may repeat reference numerals and/or letters in different examples. Such repetition is for the purpose of simplification and clarity, and does not indicate relationships between the various discussed embodiments and/or arrangements. Furthermore, the present disclosure provides examples of various specific processes and materials, but persons of ordinary skill in the art may recognize the applicability of other processes and/or the use of other materials.

To improve the thermal efficiency of a steam Rankine cycle system, the most direct method is to increase the maximum temperature or decrease the minimum pressure within the cycle system. The maximum temperature in the cycle system is limited by the heat source temperature and the temperature resistance of materials, making such an increase difficult to achieve. However, the minimum pressure in the cycle system is located at the condenser. Since the medium discharged from the steam turbine into the condenser is saturated steam, the minimum pressure is correlated with the minimum temperature. Therefore, reducing the medium pressure implies lowering the temperature, but the reduction of the medium temperature is limited by the ambient cold source temperature. Based on this, embodiments of the present disclosure propose generating electricity by utilizing the temperature difference between the minimum temperature of the cycle system and the ambient temperature, while keeping the maximum temperature and minimum pressure of the cycle system unchanged, thereby improving the thermal efficiency of the cycle system.

The high-efficiency steam power cycle system for cascaded utilization of energy according to the present disclosure is described below with reference to the accompanying figure.

The high-efficiency steam power cycle system for cascaded utilization of energy provided by embodiments of the present disclosure includes a steam cycle system 100 and an organic working fluid Rankine cycle system 200.

The steam cycle system 100 is a thermodynamic cycle system. The operating principle of the steam cycle system 100 is based on converting thermal energy into mechanical energy, which can subsequently be used for power generation or providing motive power. The steam cycle system 100 includes a steam generator 110, a steam turbine 120, and a condenser 130. An outlet of the steam generator 110 is fluidly connected to an inlet of the steam turbine 120. An outlet of the steam turbine 120 is fluidly connected to an inlet of the condenser 130. An outlet of the condenser 130 is fluidly connected to an inlet of the steam generator 110. The steam generator 110 heats water to generate high-temperature, high-pressure steam and supplies the high-temperature, high-pressure steam to the steam turbine 120. The high-temperature, high-pressure steam enters the steam turbine 120, expands to perform work, and drives the steam turbine 120 to rotate, thereby generating mechanical energy. This mechanical energy drives a generator or other mechanical device connected to the shaft of the steam turbine 120. During the passage of the steam through the steam turbine 120, the pressure and temperature of the steam gradually decrease. The low-pressure steam exhausted from the steam turbine 120 enters the condenser 130, where the low-pressure steam is cooled by cooling water or air to form condensate. The condensate is returned to the steam generator 110, completing the cycle.

A water-based absorbent, at the same temperature, exhibits a lower saturation vapor pressure than pure water; at the same saturation vapor pressure, the water-based absorbent has a higher temperature than pure water. To increase the temperature at the outlet of the condenser 130, embodiments of the present disclosure supply the water-based absorbent into the condenser 130. The water-based absorbent mixes with the low-pressure steam discharged from the steam turbine 120. Under the condition of a constant steam pressure within the condenser 130, the water-based absorbent significantly increases the water temperature inside the condenser 130, forming a water-based absorbent solution at a temperature higher than the ambient temperature. It is to be understood that low-pressure water vapor is present in the condenser 130. In embodiments of the present disclosure, the water-based absorbent may be formed by uniformly dissolving a salt with a certain concentration in water. This salt solution exhibits an absorption characteristic, namely, at the same temperature, the saturation vapor pressure of the salt solution is lower than that of pure water, and at the same saturation vapor pressure, the temperature of the salt solution is higher than that of pure water. The salt may be lithium bromide or other salts having similar characteristics.

The organic working fluid Rankine cycle system 200 includes a heat exchanger 210. The heat exchanger 210 is provided with a water-based absorbent inlet and a water-based absorbent outlet. In the heat exchanger 210, the water-based absorbent undergoes heat exchange with the organic working fluid in the organic working fluid Rankine cycle system. After heat exchange, the water-based absorbent enters the condenser 130.

The steam cycle system 100 includes two circulating loops: a steam loop and a water-based absorbent loop. To prevent the water-based absorbent from entering the steam loop, embodiments of the present disclosure provide a separation device 140 disposed between the condenser 130 and the steam generator 110. The separation device 140 is configured to separate the mixed liquid discharged from the condenser 130 into water and a water-based absorbent solution. Specifically, the separation device 140 is provided with an inlet, a first outlet 141, and a second outlet 142. The water-based absorbent outlet, the inlet of the condenser 130, the inlet of the separation device 140, the second outlet 142, and the water-based absorbent inlet are sequentially connected. The water-based absorbent undergoes heat exchange with the organic working fluid of the organic working fluid Rankine cycle system in the heat exchanger 210. After heat exchange, the water-based absorbent enters the condenser 130. Inside the condenser 130, the water-based absorbent mixes with the low-pressure steam discharged from the steam turbine 120, forming a mixed liquid comprising the water-based absorbent solution and water at a temperature higher than the ambient temperature. This mixed liquid enters the separation device 140 for separation. The water separated by the separation device 140 flows to the steam generator 110 through the first outlet 141 and enters the next cycle. The water-based absorbent solution separated by the separation device 140 enters the heat exchanger 210 through the second outlet 142. After heat exchange with the organic working fluid in the heat exchanger 210, the water-based absorbent solution re-enters the condenser 130. It is to be noted that the parameters of the water separated by the separation device 140 remain unchanged compared to the water formed within the condenser 130. In one embodiment, the separation device 140 is a membrane distillation separation device.

In the high-efficiency steam power cycle system for cascaded utilization of energy provided by the embodiment of the present disclosure, under the condition of constant steam pressure within the condenser 130 and unchanged work output from the steam turbine 120, supplying the water-based absorbent from the water-based absorbent outlet of the heat exchanger 210 into the condenser 130 can significantly increase the outlet temperature of the condenser 130. The mixed liquid at the condenser 130 outlet, after being separated by the separation device 140, enters the heat exchanger 210 to exchange heat with the organic working fluid. The thermal energy is transferred to the organic working fluid cycle system and is converted into mechanical energy or electrical energy, thereby enhancing the thermal efficiency of the system and improving the utilization rate of energy.

In embodiments of the present disclosure, the outlet of the condenser 130 is connected to the inlet of the separation device 140 and the water-based absorbent inlet of the heat exchanger 210, respectively. Specifically, the water-based absorbent solution formed in the condenser 130 at a temperature higher than the ambient temperature is split into two streams: one stream enters the heat exchanger 210 to exchange heat with the organic working fluid, while the other stream enters the separation device 140 for separation. The water-based absorbent entering the heat exchanger 210 exchanges heat with the organic working fluid, and the water separated by the separation device 140 enters the steam generator 110 to commence a new cycle.

In embodiments of the present disclosure, this flow splitting reduces the separation pressure on the separation device 140 and also allows for adjustment of the medium flow rate within the steam cycle system. It should be noted that the water-based absorbent solution discharged from the outlet of the condenser 130 may be mixed with the water-based absorbent solution separated by the separation device 140 before entering the heat exchanger 210 for heat exchange with the organic working fluid.

In embodiments of the present disclosure, the flow rate of the stream directed from the condenser 130 to the heat exchanger 210 and the flow rate of the stream directed to the separation device 140 are not specifically limited and may be adjusted according to actual operating conditions. In one embodiment, a regulating member is disposed between the outlet of the condenser 130 and the water-based absorbent inlet of the heat exchanger 210 to regulate the flow rate that enters the heat exchanger 210 from the outlet of the condenser 130. Alternatively, a regulating member is disposed between the outlet of the condenser 130 and the inlet of the separation device 140 to regulate the flow rate that enters the separation device 140 from the outlet of the condenser 130.

As shown in the accompanying figure, the organic working fluid Rankine cycle system 200 in embodiments of the present disclosure further includes an expansion turbine 220. The heat exchanger 210 is further provided with an organic working fluid inlet and an organic working fluid outlet. The organic working fluid outlet, the expansion turbine 220, and the organic working fluid inlet are sequentially connected, forming the organic working fluid Rankine cycle system 200. The circulating medium of the organic working fluid Rankine cycle system 200 is the organic working fluid. The water-based absorbent outlet, the inlet of the condenser 130, the inlet of the separation device 140, the second outlet 142, and the water-based absorbent inlet are sequentially connected, forming a loop. The circulating medium of this loop is the water-based absorbent. The water-based absorbent enters the condenser 130 via the water-based absorbent outlet and the inlet of the condenser 130. Inside the condenser 130, the water-based absorbent mixes with water to form a water-based absorbent solution, resulting in a temperature increase. This water-based absorbent solution then enters the heat exchanger 210 either through the outlet of the condenser 130 or through the second outlet 142 of the separation device 140. Within the heat exchanger 210, the water-based absorbent solution exchanges heat with the organic working fluid, causing the organic working fluid to convert into high-temperature, high-pressure steam. The high-temperature, high-pressure steam enters the expansion turbine 220 and expands to perform work. This process converts the thermal energy carried by the high-temperature, high-pressure organic working fluid into mechanical energy or electrical energy, effectively utilizing the temperature difference and thereby improving the thermal efficiency of the system. After performing work in the expansion turbine 220, the organic working fluid is converted into a low-temperature, low-pressure gas and returns to commence a new cycle. The water-based absorbent, after exchanging heat with the organic working fluid, re-enters the condenser 130 to commence a new cycle. In embodiments of the present disclosure, the system may comprise a plurality of expansion turbines 220. The plurality of expansion turbines 220 may be arranged to form an expansion turbine train.

Furthermore, the organic working fluid Rankine cycle system 200 further includes a cooler 230. An inlet of the cooler 230 is connected to an outlet of the expansion turbine 220. An outlet of the cooler 230 is connected to the organic working fluid inlet of the heat exchanger 210. The cooler 230 is configured to cool the organic working fluid exiting the expansion turbine 220, forming a low-temperature, low-pressure organic working fluid. This low-temperature, low-pressure organic working fluid then enters the heat exchanger 210 through the organic working fluid inlet to exchange heat with the water-based absorbent before commencing a new cycle. The cooler 230 includes an air cooler, a water cooler, or similar devices.

In the present disclosure, the water-based absorbent is supplied into the condenser 130 via the heat exchanger 210. Inside the condenser 130, the water-based absorbent mixes with the low-pressure steam discharged from the steam turbine 120, thereby increasing the water temperature within the condenser 130 and forming a water-based absorbent solution at a temperature higher than the ambient temperature. This process establishes an energy cascade. The thermal energy is then transferred to the organic working fluid Rankine cycle system 200, either via the separation device 140 or directly through the heat exchanger 210, and is converted into mechanical energy or electrical energy, thereby improving the thermal efficiency of the overall system.

The organic working fluid Rankine cycle system 200 in embodiments of the present disclosure further includes a first pumping member 240. The first pumping member 240 is disposed between the outlet of the cooler 230 and the organic working fluid inlet of the heat exchanger 210. The first pumping member 240 increases the flow velocity of the fluid, reduces the thermal resistance of the fluid, and enables the liquid organic working fluid at the outlet of the cooler 230 to rapidly enter the heat exchanger 210, thereby improving the heat exchange efficiency of the heat exchanger 210. The first pumping member 240 may be an organic working fluid pump.

The steam cycle system 100 in embodiments of the present disclosure further includes a second pumping member 150. The second pumping member 150 is disposed between the first outlet 141 and the steam generator 110. The second pumping member 150 causes the water separated by the separation device 140 to rapidly enter the steam generator 110, thereby ensuring continuous water flow and efficient operation of the cyclic process. The second pumping member 150 further serves to reduce pressure losses and thermal losses in the overall system, thereby improving the efficiency of the entire system. The second pumping member 150 may be a feedwater pump.

The steam cycle system 100 further includes a third pumping member 160. An inlet of the third pumping member 160 is connected to the outlet of the condenser 130. An outlet of the third pumping member 160 is connected to the water-based absorbent inlet of the heat exchanger 210 and the inlet of the separation device 140, respectively. The third pumping member 160 rapidly distributes the low-temperature fluid (mixed liquid of water and the water-based absorbent) at the outlet of the condenser 130 to the heat exchanger 210 for heat exchange or to the separation device 140 for separation. The operation of the third pumping member 160 improves the thermal energy recovery efficiency, ensures stable operation of the system, and maximizes the utilization of thermal energy. The third pumping member 160 may be a condensate pump.

Embodiments of the present disclosure employ a water-based absorbent instead of pure water as the medium in the steam power cycle system. This water-based absorbent can be formed by uniformly dissolving a salt with a specific concentration in water. The resulting salt solution exhibits absorption characteristics, namely, at the same temperature, its saturation vapor pressure is lower than that of pure water, and at the same saturation vapor pressure, its temperature is higher than that of pure water. The condenser 130 adopts a mixed direct condensation structure. A concentrated salt solution is sprayed into the condenser 130 to directly contact the steam discharged from the steam turbine 120 for condensation, thereby forming a diluted salt solution. The diluted salt solution discharged from the condenser 130 is pressurized. A portion of the pressurized diluted salt solution is fed to a membrane distillation separation device to produce a concentrated salt solution and pure water. The pure water enters the steam generator 110 to generate high-temperature steam, which subsequently enters the steam turbine 120 to expand and perform work. The concentrated salt solution from the membrane distillation separation device is mixed with another portion of the diluted salt solution discharged from the condenser 130, forming a reconstituted concentrated salt solution. This reconstituted concentrated salt solution is cooled by the heat exchanger 210 and then sprayed back into the condenser 130. Simultaneously, the thermal energy is transferred through the heat exchanger 210 to the organic working fluid of the organic Rankine cycle system for power generation.

Under conditions of constant steam pressure within the condenser 130 and unchanged work output from the steam turbine 120, this configuration significantly increases the water temperature inside the condenser 130. The organic working fluid Rankine cycle system 200 then facilitates cascaded utilization of the energy from this high-temperature water, thereby increasing the overall thermal efficiency of the steam power cycle system. Embodiments of the present disclosure make full use of the mature steam Rankine cycle system and the organic working fluid Rankine cycle system 200. Based on an existing power plant's steam Rankine cycle system, only minor modifications are required for implementation. Equipment such as the steam turbine 120, the steam generator 110, and the second pumping member 150 requires no alterations. Equipment such as the condenser 130 and the third pumping member 160 requires only component-level material substitutions to accommodate the change of medium from water to the water-based absorbent (e.g., a salt solution). The implementation is achieved by adding one set of the organic working fluid Rankine cycle system 200 and one set of the membrane distillation separation device.

It should be finally noted that the above embodiments are merely intended to illustrate the technical solutions of the present disclosure, but not to construe them as limitations. Although the present disclosure has been described in detail with reference to the foregoing embodiments, persons of ordinary skill in the art should understand that they may still make modifications to the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features therein. However, these modifications or substitutions do not make the essence of the corresponding technical solutions depart from the spirit and scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. A high-efficiency steam power cycle system for cascaded utilization of energy, comprising: a steam cycle system and an organic working fluid Rankine cycle system; wherein

the steam cycle system comprises a steam generator, a steam turbine, a condenser, and a separation device, the separation device is provided with a first outlet and a second outlet; and an outlet of the steam generator, the steam turbine, the condenser, an inlet of the separation device, the first outlet, and an inlet of the steam generator are sequentially connected;

the organic working fluid Rankine cycle system comprises a heat exchanger, the heat exchanger is provided with a water-based absorbent inlet and a water-based absorbent outlet; and

the water-based absorbent outlet, an inlet of the condenser, the inlet of the separation device, the second outlet, and the water-based absorbent inlet are sequentially connected; and

the separation device is configured to separate a mixed liquid discharged from the condenser into water and a water-based absorbent solution; and the water flows to the steam generator through the first outlet, and the water-based absorbent solution flows to the heat exchanger through the second outlet.

2. The high-efficiency steam power cycle system for cascaded utilization of energy according to claim 1, wherein an outlet of the condenser is connected to the water-based absorbent inlet.

3. The high-efficiency steam power cycle system for cascaded utilization of energy according to claim 2, wherein the organic working fluid Rankine cycle system further comprises an expansion turbine, the heat exchanger is further provided with an organic working fluid inlet and an organic working fluid outlet, and the organic working fluid outlet, the expansion turbine, and the organic working fluid inlet are sequentially connected; and

the expansion turbine is configured to convert thermal energy into mechanical energy or electrical energy.

4. The high-efficiency steam power cycle system for cascaded utilization of energy according to claim 3, wherein the organic working fluid Rankine cycle system further comprises a cooler, an inlet of the cooler is connected to an outlet of the expansion turbine, and an outlet of the cooler is connected to the organic working fluid inlet.

5. The high-efficiency steam power cycle system for cascaded utilization of energy according to claim 4, wherein the organic working fluid Rankine cycle system further comprises a first pumping member, and the first pumping member is disposed between the outlet of the cooler and the organic working fluid inlet.

6. The high-efficiency steam power cycle system for cascaded utilization of energy according to claim 1, wherein the steam cycle system further comprises a second pumping member, and the second pumping member is disposed between the first outlet and the steam generator.

7. The high-efficiency steam power cycle system for cascaded utilization of energy according to claim 1, wherein a regulating member is disposed between the outlet of the condenser and the water-based absorbent inlet or between the outlet of the condenser and the inlet of the separation device.

8. The high-efficiency steam power cycle system for cascaded utilization of energy according to claim 1, wherein the steam cycle system further comprises a third pumping member, an inlet of the third pumping member is connected to the outlet of the condenser, and an outlet of the third pumping member is connected to the water-based absorbent inlet and the inlet of the separation device, respectively.

9. The high-efficiency steam power cycle system for cascaded utilization of energy according to claim 1, wherein the water-based absorbent solution comprises a salt solution.

10. The high-efficiency steam power cycle system for cascaded utilization of energy according to claim 1, wherein the separation device comprises a membrane distillation separation device.