Coal chemical black water waste heat ORC power generation system

Abstract

The application discloses a coal chemical black water waste heat ORC power generation system, which comprises a low-pressure flash separation tank, a double-working medium storage tank, an evaporator, a temperature sensor and a controller. The double-working medium storage tank is internally partitioned into a first chamber and a second chamber, the first chamber is internally provided with a first evaporating working medium, and the second chamber is internally provided with a second evaporating working medium. The evaporator is provided with a first evaporating branch and a second evaporating branch in parallel, and the outlets of the first evaporating branch and the second evaporating branch are jointly connected to the inlet of a turbine expander. The temperature sensor is in signal connection with the controller, a first electromagnetic valve and a second electromagnetic valve. When the temperature of black water is higher than a preset threshold value, a black water discharge pipeline is in communication with the first chamber. When the temperature of black water is lower than the preset threshold value, the black water discharge pipeline is in communication with the second chamber. The controller dynamically adjusts the working medium selection according to real-time temperature data, ensures that the system always works at an optimal efficiency point, and improves the working stability of the turbine expander.

Description

Technical Field

[0001] This application belongs to the field of coal chemical waste heat recovery technology, specifically relating to a coal chemical black water waste heat ORC power generation system. Background Technology

[0002] In coal chemical processes such as coal gasification and coal liquefaction, high-temperature black water requires multi-stage flash evaporation to recover heat and reduce pollutant concentrations. Conventional processes employ a two-stage treatment: high-pressure flash evaporation and low-pressure flash evaporation. In the high-pressure flash evaporation stage, the black water temperature can reach over 150°C, generating medium-pressure steam that can be directly used to drive steam turbines for power generation or process heating, resulting in a high heat recovery rate. After low-pressure flash evaporation, the black water is further cooled to 80-130°C. The low-pressure steam generated in this stage has large temperature fluctuations and low grade due to the heat source, leading to low efficiency in traditional steam power generation systems. A large amount of waste heat is forced to be discharged through cooling towers, resulting in energy waste and thermal pollution.

[0003] To avoid wasting the waste heat of black water during the low-pressure flash evaporation stage, traditional technologies have proposed using Organic Rankine Cycle (ORC) power generation technology to recover this waste heat. This involves using low-boiling-point organic matter as the working fluid, which absorbs heat in a heat exchanger, evaporates into steam, and then drives a generator to produce electricity through turbine expansion. However, traditional ORC power generation units have the following problems in recovering black water waste heat: 1. Poor adaptability: Black water temperature fluctuates drastically due to production load. Traditional ORC systems use a single evaporation working fluid, which is prone to overpressure damage at high temperatures and insufficient vaporization at low temperatures, resulting in poor power generation. 2. Weak resistance to fouling: Black water after low-pressure flash evaporation still contains trace amounts of coal dust. Direct heat exchange can easily clog the evaporator channels, requiring frequent shutdowns for cleaning. Utility Model Content

[0004] This application provides a coal chemical black water waste heat ORC power generation system to solve the technical problems of poor adaptability to black water temperature fluctuations and weak anti-fouling ability of traditional ORC power generation systems used for black water waste heat absorption.

[0005] The technical solution adopted in this application is as follows:

[0006] An ORC (Organic Rechargeable Gas) power generation system for waste heat from coal chemical black water includes: a low-pressure flash separation tank, the outlet of which is connected to a black water discharge pipeline; a dual-working-fluid storage tank, internally divided into a first chamber and a second chamber, the first chamber containing a first evaporating working fluid and the second chamber containing a second evaporating working fluid, the boiling point of the first evaporating working fluid being higher than that of the second evaporating working fluid; and an evaporator with a first evaporation branch and a second evaporation branch connected in parallel, the inlet of the first evaporation branch connected to the first chamber via a first solenoid valve, and the inlet of the second evaporation branch connected to the first chamber via a second solenoid valve. The outlets of the first evaporation branch and the second evaporation branch are connected to the inlet of the turbine expander, which is connected to the second chamber. A temperature sensor is installed on the black water discharge pipe to detect the black water temperature. A controller is connected to the temperature sensor, the first solenoid valve, and the second solenoid valve. When the black water temperature is higher than a preset threshold, the first solenoid valve is opened and the second solenoid valve is closed, and the black water discharge pipe is connected to the first chamber. When the black water temperature is lower than the preset threshold, the second solenoid valve is opened and the first solenoid valve is closed, and the black water discharge pipe is connected to the second chamber.

[0007] The power generation system described in this application also includes the following additional technical features:

[0008] The boiling point of the first evaporating working fluid is 30 to 40°C, and the boiling point of the second evaporating working fluid is 10 to 20°C.

[0009] The preset threshold is 100℃. When the black water temperature is ≥100℃, the first solenoid valve is opened, and when the black water temperature is <100℃, the second solenoid valve is opened.

[0010] The cross-sectional area of ​​the first evaporation branch is S1, and the cross-sectional area of ​​the second evaporation branch is S2, where 1.5S2≤S1≤2.5S2.

[0011] The black water discharge pipeline includes a first pipeline connected to the outlet and a second pipeline connected to the dual-working-medium storage tank. The first pipeline and the second pipeline are connected by a cyclone separator, which is used to filter black water impurities in the first pipeline.

[0012] The cyclone separator includes a tube body, the interior of which is hollow to form a separation chamber. The tube body includes a cylindrical section at the top and a conical section at the bottom. The cylindrical section has an inlet on its side that connects the first pipeline to the separation chamber. The top of the cylindrical section has an outlet. One end of the conical section is connected to the cylindrical section, and the other end extends away from the cylindrical section with a gradually decreasing cross-sectional area. The cyclone separator also includes an overflow pipe, one end of which is located inside the conical section, and the other end extends vertically and passes through the outlet to connect to the second pipeline.

[0013] The power generation system also includes a slag receiving bin, and the bottom of the conical section is provided with a slag discharge port, which is connected to the slag receiving bin.

[0014] The second pipeline is equipped with a ceramic membrane filter.

[0015] The inner walls of the first evaporation branch and the second evaporation branch are provided with a corrugated heat exchange layer, which is composed of multiple corrugated plates.

[0016] Due to the adoption of the above technical solution, the beneficial effects achieved by this application are as follows:

[0017] 1. The ORC power generation system of this application has a dual-working-fluid storage tank with independent first and second chambers, storing first and second evaporating working fluids with different boiling points, respectively. These chambers are connected to the first and second evaporation branches in the evaporator, respectively. Combined with a temperature sensor and controller, intelligent switching of the evaporating working fluid is achieved, significantly improving the ORC power generation system's adaptability to black water temperature fluctuations. In coal chemical production, the temperature of black water after low-pressure flash evaporation fluctuates drastically within the range of 80-130℃ depending on the production load. The temperature sensor can detect the black water temperature in the black water discharge pipe in real time. When the black water temperature is higher than the preset threshold of the ORC power generation system, the controller controls the first solenoid valve to open and the second solenoid valve to close. The first evaporating working fluid with a higher boiling point in the first chamber enters the first evaporation branch and evaporates, subsequently driving the turbine expander. Conversely, when the black water temperature is lower than the preset threshold of the ORC power generation system, the controller controls the first solenoid valve to close and the second solenoid valve to open. The second evaporating working fluid with a lower boiling point in the second chamber enters the second evaporation branch and evaporates, subsequently driving the turbine expander. Because the boiling point of the first evaporating working fluid is higher than that of the second, adaptive adjustment of the blackwater temperature is achieved. When the blackwater temperature is high, it reduces the probability of overheating caused by excessive vaporization of the working fluid; when the blackwater temperature is low, it ensures sufficient vaporization of the working fluid. This design enables the system to maintain stable power generation efficiency over a wide temperature range, solving the problem of poor adaptability in traditional ORC systems. The controller dynamically adjusts the working fluid selection based on real-time temperature data, ensuring that the system always operates at its optimal efficiency point, thus improving the operational stability of the turbine expander.

[0018] 2. As a preferred embodiment of this application, the first evaporating working fluid with a boiling point of 30 to 40°C has a moderate saturated vapor pressure under high-temperature conditions, which ensures sufficient working pressure to drive the turbine expander without causing the risk of system overpressure; while the second evaporating working fluid with a boiling point of 10 to 20°C can still maintain a high vaporization rate under low-temperature conditions, ensuring that the power generation system can still generate electricity stably under low load.

[0019] 3. As a preferred embodiment of this application, the installation of a hydrocyclone separator significantly enhances the anti-fouling capability of the power generation system. Even after low-pressure flash evaporation treatment, coal chemical black water may still contain some solid particles. If these particles directly enter the evaporator, they will form scale on the heat exchange surface, reducing heat exchange efficiency and even causing blockage. The hydrocyclone separator utilizes the principle of centrifugal force to effectively remove solid particles from the black water, greatly reducing the risk of scaling in the subsequent evaporator. Secondly, this design optimizes the system's process layout. By placing the hydrocyclone separator between the first and second pipelines, a reasonable pretreatment process is formed: the black water first passes through the hydrocyclone separator to remove large particulate impurities before entering the subsequent evaporator for heat exchange. This process design ensures the purification effect without significantly affecting the heat recovery efficiency, effectively extending the service life of the power generation system. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0021] Figure 1 This is a schematic diagram of a coal chemical black water waste heat ORC power generation system according to one embodiment of this application;

[0022] Figure 2 This is a schematic diagram of a cyclone separator according to one embodiment of this application.

[0023] List of components and reference numerals:

[0024] 1. Low-pressure flash separator;

[0025] 2 Blackwater discharge pipes, 21 First pipe, 22 Second pipe;

[0026] 3 dual-fluid storage tanks, 31 first chamber, 32 second chamber;

[0027] 4 Evaporator, 41 First evaporation branch, 42 Second evaporation branch, 43 Black water flow channel;

[0028] 5. First solenoid valve;

[0029] 6. Second solenoid valve;

[0030] 7. Temperature sensor;

[0031] 8 controllers;

[0032] 9. Hydrocyclone separator, 91. Tube body, 911. Cylindrical section, 912. Conical section, 92. Separation chamber, 93. Inlet, 94. Outlet, 95. Overflow pipe, 96. Slag discharge port;

[0033] 10. Slag receiving bins;

[0034] 110 ceramic membrane filter;

[0035] 120 turbine expander. Detailed Implementation

[0036] To more clearly illustrate the overall concept of this application, a detailed explanation is provided below with reference to the accompanying drawings.

[0037] Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of this application is not limited to the specific embodiments disclosed below. It should be noted that, unless otherwise specified, the embodiments of this application and the features thereof can be combined with each other.

[0038] Furthermore, it should be understood in the description of this application that the terms "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0039] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0040] In this application, unless otherwise expressly specified and limited, the "above" or "below" of the second feature can mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. In the description of this specification, references to terms such as "an embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples.

[0041] like Figure 1As shown, a coal chemical black water waste heat ORC power generation system includes: a low-pressure flash separation tank 1, the outlet of which is connected to a black water discharge pipe 2; a dual-working-fluid storage tank 3, internally divided into a first chamber 31 and a second chamber 32, the first chamber 31 containing a first evaporating working fluid and the second chamber 32 containing a second evaporating working fluid, the boiling point of the first evaporating working fluid being higher than that of the second evaporating working fluid; and an evaporator 4, equipped with a first evaporation branch 41 and a second evaporation branch 42 connected in parallel, the inlet of the first evaporation branch 41 being connected to the first chamber 31 via a first solenoid valve 5, and the inlet of the second evaporation branch 42 being connected to... The second chamber 32 is connected via the second solenoid valve 6. The outlets of the first evaporation branch 41 and the second evaporation branch 42 are connected to the inlet of the turbine expander 120. The temperature sensor 7 is installed on the black water discharge pipe 2 to detect the black water temperature. The controller 8 is connected to the temperature sensor 7, the first solenoid valve 5, and the second solenoid valve 6. When the black water temperature is higher than a preset threshold, the first solenoid valve 5 is opened and the second solenoid valve 6 is closed, and the black water discharge pipe 2 is connected to the first chamber 31. When the black water temperature is lower than a preset threshold, the second solenoid valve 6 is opened and the first solenoid valve 5 is closed, and the black water discharge pipe 2 is connected to the second chamber 32.

[0042] The ORC power generation system of this application has a dual-working-fluid storage tank 3 with two independent chambers, a first chamber 31 and a second chamber 32, which store a first evaporation working fluid and a second evaporation working fluid with different boiling points, respectively. These chambers are connected to the first evaporation branch 41 and the second evaporation branch 42 in the evaporator 4, respectively. With the help of a temperature sensor 7 and a controller 8, intelligent switching of the evaporation working fluid is achieved, significantly improving the adaptability of the ORC power generation system to black water temperature fluctuations. In coal chemical production, the temperature of the black water after low-pressure flash evaporation fluctuates drastically within the range of 80-130℃ depending on changes in production load. Temperature sensor 7 can detect the blackwater temperature in blackwater discharge pipe 2 in real time. When the blackwater temperature is higher than the preset threshold of the ORC power generation system, controller 8 controls the first solenoid valve 5 to open and the second solenoid valve 6 to close. The first evaporating medium with a higher boiling point in the first chamber 31 enters the first evaporation branch 41 and evaporates under heat, subsequently driving the turbine expander 120 to work. Conversely, when the blackwater temperature is lower than the preset threshold of the ORC power generation system, controller 8 controls the first solenoid valve 5 to close and the second solenoid valve 6 to open. The second evaporating medium with a lower boiling point in the second chamber 32 enters the second evaporation branch 42 and evaporates under heat, subsequently driving the turbine expander 120 to work. Because the boiling point of the first evaporating medium is higher than that of the second evaporating medium, adaptive adjustment of the blackwater temperature is achieved. When the blackwater temperature is high, the probability of overheating caused by excessive vaporization of the working medium can be reduced; when the blackwater temperature is low, sufficient vaporization of the working medium can be ensured. This design enables the system to maintain stable power generation efficiency over a wide temperature range, solving the problem of poor adaptability in traditional ORC systems. The controller 8 dynamically adjusts the working fluid selection based on real-time temperature data to ensure that the system always operates at the optimal efficiency point, thereby improving the working stability of the turboexpander 120.

[0043] Specifically, the evaporator 4 has a black water channel 43 in the middle. The black water after low-pressure flash evaporation enters the black water channel 43 of the evaporator 4 through the black water discharge pipe 2, flows over the heat exchange surface, and is discharged after cooling. The first evaporation branch 41 and the second evaporation branch 42 are located on both sides of the black water channel 43. Preferably, the evaporator 4 adopts a plate or shell-and-tube heat exchange structure. The black water channel 43 is separated from the first evaporation branch 41 and the second evaporation branch 42 by metal walls, and heat is transferred through the metal walls. The black water channel 43 is independent of the first evaporation branch 41 and the second evaporation branch 42 and is not connected to them.

[0044] In a preferred embodiment of this application, the boiling point of the first evaporating medium is 30 to 40°C, and the boiling point of the second evaporating medium is 10 to 20°C.

[0045] The first evaporating medium, with a boiling point of 30 to 40°C, has a moderate saturated vapor pressure under high-temperature conditions, which ensures sufficient working pressure to drive the turbine expander without causing the risk of system overpressure. The second evaporating medium, with a boiling point of 10 to 20°C, can still maintain a high vaporization rate under low-temperature conditions, ensuring that the power generation system can still generate electricity stably under low load.

[0046] Preferably, the first evaporating medium is pentane, and the second evaporating medium is R245fa.

[0047] As a preferred embodiment of this implementation, the preset threshold is 100°C. When the black water temperature is ≥100°C, the first solenoid valve 5 is opened, and when the black water temperature is <100°C, the second solenoid valve 6 is opened.

[0048] The temperature of blackwater after low-pressure flash evaporation fluctuates between 80-130℃ during normal production, but drops to 80-100℃ during low-load or nighttime operation. Setting the switching threshold to 100℃ falls precisely at the boundary between these two typical operating ranges, ensuring the power generation system operates at its optimal state in most situations. Furthermore, due to the measurement fluctuations in blackwater temperature, setting the threshold too close to the normal operating temperature could lead to frequent switching of the working fluid during small temperature fluctuations, affecting operational stability. The 100℃ setting maintains a sufficient safety distance from the typical operating temperature, ensuring the stability and reliability of the control system and significantly reducing wear on actuators such as the first solenoid valve 5 and the second solenoid valve 6. Moreover, the 100℃ threshold maximizes the overall energy efficiency of the system. When the blackwater temperature is above 100℃, using a high-boiling-point working fluid yields higher heat-to-work conversion efficiency; conversely, when the temperature is below 100℃, switching to a low-boiling-point working fluid avoids efficiency degradation due to insufficient vaporization.

[0049] As another preferred embodiment of this implementation, such as Figure 1 As shown, the cross-sectional area of ​​the first evaporation branch 41 is S1, and the cross-sectional area of ​​the second evaporation branch 42 is S2, where 1.5S2≤S1≤2.5S2.

[0050] This optimized cross-sectional area ratio significantly improves the overall performance of evaporator 4. Since high-boiling-point working fluids typically operate in a higher temperature range, a larger heat exchange area is required to ensure sufficient vaporization; while low-boiling-point working fluids typically have a larger latent heat of vaporization, requiring sufficient residence time. Through differentiated cross-sectional area design, both working fluids can achieve optimal vaporization performance under their respective operating conditions.

[0051] As a preferred embodiment of this application, such as Figure 1 , Figure 2As shown, the black water discharge pipeline 2 includes a first pipeline 21 connected to the outlet 94 and a second pipeline 22 connected to the dual working medium storage tank 3. The first pipeline 21 and the second pipeline 22 are connected by a hydrocyclone separator 9, which is used to filter black water impurities in the first pipeline 21.

[0052] The inclusion of cyclone separator 9 significantly enhances the pollution resistance of the power generation system. Even after low-pressure flash evaporation, coal chemical black water may still contain some solid particles. If these particles directly enter evaporator 4, they will form scale on the heat exchange surface, reducing heat exchange efficiency and even causing blockage. Cyclone separator 9 utilizes centrifugal force to effectively remove solid particles from the black water, greatly reducing the risk of scaling in the subsequent evaporator 4. Secondly, this design optimizes the system's process layout. By placing cyclone separator 9 between the first pipe 21 and the second pipe 22, a reasonable pretreatment process is formed: black water first passes through cyclone separator 9 to remove large particulate impurities before entering the subsequent evaporator 4 for heat exchange. This process design ensures purification effectiveness without significantly impacting heat recovery efficiency, effectively extending the service life of the power generation system.

[0053] As a preferred embodiment of this implementation, such as Figure 2 As shown, the cyclone separator 9 includes a tube body 91, which is hollow inside to form a separation chamber 92. The tube body 91 includes a cylindrical section 911 at the top and a conical section 912 at the bottom. The cylindrical section 911 has an inlet 93 on its side that connects the first pipeline 21 to the separation chamber 92. The cylindrical section 911 has an outlet 94 at its top. One end of the conical section 912 is connected to the cylindrical section 911, and the other end extends away from the cylindrical section 911 with a gradually decreasing cross-sectional area. The cyclone separator 9 also includes an overflow pipe 95, one end of which is located inside the conical section 912, and the other end extends vertically and passes through the outlet 94 to connect with the second pipeline 22.

[0054] The combined design of the cylindrical section 911 and the conical section 912 optimizes the separation efficiency. By dividing the tube body 91 into the upper cylindrical section 911 and the lower conical section 912, a stable swirling flow field is formed in the cylindrical section 911, while the centrifugal force is enhanced in the conical section 912 through its gradually decreasing cross-sectional area. In particular, placing the inlet 93 at a tangential position on the side of the cylindrical section 911 ensures that a strong swirling flow is immediately formed after the black water enters, improving the initial separation effect. One end of the overflow pipe 95 is located inside the conical section 912, and the other end extends to the outlet 94. This design ensures that only fully separated black water can enter the overflow pipe 95, which helps to improve the filtration effect of the cyclone separator 9.

[0055] Specifically, the inlet 93 is tangentially oriented towards the cylindrical section 911. Figure 2Curve X schematically illustrates the flow path of the black water. After entering the separation chamber 92 through the inlet 93, the black water spirals along the pipe wall and forms a high-speed rotating vortex. Under the action of centrifugal force, denser solid particles or heavy phase components are thrown towards the wall and move downwards along the conical wall of the conical section 912, while the less dense pure black water gathers towards the central axis region of the pipe body 91, forming an upward vortex near the central axis, and is discharged through the overflow pipe 95 at the top.

[0056] As a preferred example in this embodiment, such as Figure 2 As shown, the power generation system also includes a slag receiving bin 10, and a slag discharge port 96 is provided at the bottom of the conical section 912, which is connected to the slag receiving bin 10.

[0057] The slag receiving bin 10 and slag discharge port 96 enable continuous discharge of solid waste, eliminating the need for periodic slag removal by the hydrocyclone 9. Furthermore, an automatic slag discharge valve is installed at the slag discharge port 96. When solid waste accumulates to a certain level, the automatic slag discharge valve opens to discharge the waste. By setting up the slag receiving bin 10 and cooperating with the automatic slag discharge valve, continuous discharge of solid waste can be achieved, ensuring long-term stable operation of the system. In particular, placing the slag discharge port 96 at the bottom of the conical section 912 allows for natural settling and discharge of the slag by gravity, optimizing the structural design of the hydrocyclone 9.

[0058] As another preferred embodiment of this implementation, such as Figure 2 As shown, a ceramic membrane filter 110 is installed in the second pipeline 22.

[0059] Although the hydrocyclone separator 9 can remove most large particles, a small number of tiny particles may still remain in the water. The ceramic membrane filter 110 provides a second layer of filtration for the black water, further reducing solid waste residue in the second pipeline 22. In addition, the ceramic membrane has the characteristics of high temperature resistance, corrosion resistance, and high mechanical strength, making it particularly suitable for treating high-temperature and corrosive media such as coal chemical black water, and it has a long service life.

[0060] In a preferred embodiment of this application, the inner walls of the first evaporation branch 41 and the second evaporation branch 42 are provided with a corrugated heat exchange layer, which is composed of multiple corrugated plates.

[0061] The corrugated heat exchange layer enhances the heat exchange area of ​​the first evaporation branch 41 and the second evaporation branch 42, which helps to improve heat exchange efficiency.

[0062] For any parts not mentioned in this application, existing technologies may be used or referenced.

[0063] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0064] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A coal chemical black water waste heat ORC power generation system, characterized in that, include: A low-pressure flash separator, the outlet of which is connected to a black water discharge pipe; A dual-working-fluid storage tank, wherein the interior of the dual-working-fluid storage tank is divided into a first chamber and a second chamber, the first chamber contains a first evaporating working fluid, and the second chamber contains a second evaporating working fluid, wherein the boiling point of the first evaporating working fluid is higher than the boiling point of the second evaporating working fluid; The evaporator has a first evaporation branch and a second evaporation branch connected in parallel. The inlet of the first evaporation branch is connected to the first chamber through a first solenoid valve, and the inlet of the second evaporation branch is connected to the second chamber through a second solenoid valve. The outlets of the first evaporation branch and the second evaporation branch are connected to the inlet of the turboexpander. A temperature sensor is installed on the blackwater discharge pipe to detect the temperature of the blackwater; The controller is connected to the temperature sensor, the first solenoid valve, and the second solenoid valve. When the black water temperature is higher than a preset threshold, the first solenoid valve is opened and the second solenoid valve is closed. The black water discharge pipe is connected to the first chamber. When the black water temperature is lower than the preset threshold, the second solenoid valve is opened and the first solenoid valve is closed. The black water discharge pipe is connected to the second chamber.

2. The power generation system according to claim 1, characterized in that, The boiling point of the first evaporating working fluid is 30 to 40°C, and the boiling point of the second evaporating working fluid is 10 to 20°C.

3. The power generation system according to claim 2, characterized in that, The preset threshold is 100℃. When the black water temperature is ≥100℃, the first solenoid valve is opened, and when the black water temperature is <100℃, the second solenoid valve is opened.

4. The power generation system according to claim 2, characterized in that, The cross-sectional area of ​​the first evaporation branch is S1, and the cross-sectional area of ​​the second evaporation branch is S2, where 1.5S2≤S1≤2.5S2.

5. The power generation system according to claim 1, characterized in that, The black water discharge pipeline includes a first pipeline connected to the outlet and a second pipeline connected to the dual-working-medium storage tank. The first pipeline and the second pipeline are connected by a cyclone separator, which is used to filter black water impurities in the first pipeline.

6. The power generation system according to claim 5, characterized in that, The cyclone separator includes a tube body, the interior of which is hollow to form a separation chamber. The tube body includes a cylindrical section at the top and a conical section at the bottom. The cylindrical section has an inlet on its side that connects the first pipeline to the separation chamber. The top of the cylindrical section has an outlet. One end of the conical section is connected to the cylindrical section, and the other end extends away from the cylindrical section with a gradually decreasing cross-sectional area. The cyclone separator also includes an overflow pipe, one end of which is located inside the conical section, and the other end extends vertically and passes through the outlet to connect to the second pipeline.

7. The power generation system according to claim 6, characterized in that, The power generation system also includes a slag receiving bin, and the bottom of the conical section is provided with a slag discharge port, which is connected to the slag receiving bin.

8. The power generation system according to claim 5, characterized in that, The second pipeline is equipped with a ceramic membrane filter.

9. The power generation system according to claim 1, characterized in that, The inner walls of the first evaporation branch and the second evaporation branch are provided with a corrugated heat exchange layer, which is composed of multiple corrugated plates.

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