A geothermal energy adjustable generation system based on carbon dioxide working medium

Abstract

The application discloses a geothermal energy adjustable power generation system based on carbon dioxide working medium, which comprises a power generation well, a temperature and pressure adjusting device connected through a pipeline, a gas-liquid heat exchange device connected with the temperature and pressure adjusting device at one end and connected with a steam superheating device at the other end, a heat supply device and a turbine arranged on the steam superheating device, a power generation device connected with the turbine, the power generation device connected with the gas-liquid heat exchange device through a pressure adjusting device, a plunger pump connected with a recharging well at one end and connected with the gas-liquid heat exchange device through a refrigeration device at the other end. The system can further heat the carbon dioxide working medium after being converted into steam, thereby improving the temperature and pressure of the steam and the power generation efficiency of the turbine. Moreover, the output of the heat supply device is adjusted, the rotating speed of the turbine and the output power of the power generation device are adjusted, the adjustability of the power generation capacity is realized, and the defect of the vacancy of the technology in China is solved.

Description

Technical Field

[0001] This invention belongs to the field of geothermal energy cascade utilization technology, specifically relating to a geothermal energy adjustable power generation system based on carbon dioxide as the working fluid. Background Technology

[0002] Enhanced Geothermal Systems (EGS), also known as engineered geothermal systems or hot dry rock, are an important type of geothermal resource. Their development and utilization primarily involve power generation through water circulation for heat extraction. However, traditional EGS technology faces numerous problems when using water as the heat transfer medium, such as excessive water consumption and short-circuiting or blockage between geothermal wells. To address these issues, the use of supercritical CO2 as the heat transfer medium for power generation or heating is being explored.

[0003] Supercritical CO2 has unique physical properties such as low viscosity and high density, which gives it typical advantages in thermal reservoirs, such as good fluidity, high heat transfer efficiency, and low compressibility. Summary of the Invention

[0004] The purpose of this invention is to provide a geothermal energy adjustable power generation system based on carbon dioxide as the working fluid, so as to solve the technical defects in the practical application and promotion of existing technologies.

[0005] To achieve the above objectives, the present invention employs the following technical solution: A geothermal energy adjustable power generation system based on carbon dioxide as the working fluid, comprising: The power generation well is connected to a temperature and pressure regulating device via pipelines. A gas-liquid heat exchange device is connected at one end to the temperature and pressure regulating device and at the other end to a steam superheating device. The steam superheating device is equipped with a heating device and a turbine. The turbine is connected to a power generation device. The power generation device is connected to the gas-liquid heat exchange device through a pressure regulating device. The plunger pump is connected to the reinjection well at one end and to the gas-liquid heat exchange device at the other end via a refrigeration unit.

[0006] Furthermore, the temperature and pressure regulating device is a de-temperature and pressure reducing valve, which is used to de-temperature and reduce the pressure of the carbon dioxide working fluid output from the power generation well.

[0007] Furthermore, the gas-liquid heat exchange device and the steam superheating device are used to supplement the heat of the carbon dioxide working fluid.

[0008] Furthermore, the gas-liquid heat exchange device is a regenerator.

[0009] Furthermore, the steam superheating device is a reheater.

[0010] Furthermore, the pressure regulating device is used to regulate the system back pressure.

[0011] Furthermore, the refrigeration device is a refrigerator.

[0012] Furthermore, the heat source in the heating device is one of flue gas waste heat, industrial waste heat, or solar heat.

[0013] Furthermore, the power generation device is a generator.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. This system directly obtains geothermal resources through power generation wells and uses carbon dioxide as the working fluid for energy conversion. Carbon dioxide has excellent thermal conductivity and fluidity, enabling it to efficiently absorb and transfer geothermal energy. The temperature and pressure regulating device adjusts the temperature and pressure of the carbon dioxide working fluid to adapt to the subsequent energy conversion process, thereby improving the overall system's energy conversion efficiency. Secondly, the steam superheating device allows for further heating of the carbon dioxide working fluid after conversion into steam, increasing the steam temperature and pressure and enhancing the turbine's power generation efficiency. Furthermore, by adjusting the output of the heating device, the heating intensity in the steam superheating device can be flexibly controlled, thereby adjusting the turbine's speed and the power generation device's output power, achieving adjustable power generation and addressing the current technological gap in China.

[0015] 2. In the power generation well, the output carbon dioxide working fluid has a high temperature and pressure. The temperature and pressure of the working fluid can be effectively reduced by the desuperheating and pressure reducing valve to meet the operating requirements of the subsequent equipment, thereby protecting the equipment from damage caused by high temperature and high pressure.

[0016] 3. The gas-liquid exchange device can utilize the low-temperature heat of geothermal energy to heat the carbon dioxide working medium from a liquid state to a gaseous state, enabling it to enter a more efficient energy conversion state. The steam superheating device 4 further heats the gaseous carbon dioxide to a supercritical state or a higher superheated state, thereby improving its expansion efficiency and work capacity in the turbine.

[0017] 4. The regenerator can recover the heat energy from the low-temperature carbon dioxide working fluid discharged from other parts of the system and transfer it to the high-temperature carbon dioxide working fluid entering the system, which significantly improves the energy conversion efficiency of the system.

[0018] 5. The reheater can reheat low-pressure steam that has already done work to a superheated state, increasing its temperature and pressure, thereby increasing the steam's expansion and work capacity in the turbine, significantly improving the steam's thermal energy utilization efficiency, and enabling the system to generate more electricity.

[0019] 6. By adjusting the back pressure, the system can be ensured to operate stably under various working conditions, maintaining the normal operation of the equipment and extending its service life. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A schematic diagram of the structure of a geothermal energy adjustable power generation system based on carbon dioxide working fluid provided for this invention; Figure 2 A schematic diagram of summer operating parameters for a geothermal energy adjustable power generation system based on carbon dioxide working fluid, provided by the present invention; Figure 3 A schematic diagram of the winter pure electric mode operation parameters of the geothermal energy adjustable power generation system based on carbon dioxide working fluid provided by the present invention; Figure 4 A schematic diagram of the operating parameters for the winter power generation and heating modes of the adjustable geothermal power generation system based on carbon dioxide working fluid provided by the present invention. Figure 5 A flowchart of the geothermal energy adjustable power generation method based on carbon dioxide working fluid provided by the present invention; In the diagram: 1. Power generation well; 2. Temperature and pressure regulating device; 3. Gas-liquid heat exchange device; 4. Steam superheating device; 5. Heating device; 6. Turbine; 7. Power generation device; 8. Pressure regulating device; 9. Refrigeration device; 10. Plunger pump; 11. Recharge well. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0024] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0025] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention 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 the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0026] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0027] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0028] Enhanced Geothermal Systems (EGS), also known as engineered geothermal systems or hot dry rock, are an important type of geothermal resource. Their development and utilization primarily involve power generation through water circulation for heat extraction. However, traditional EGS technology faces numerous problems when using water as the heat transfer medium, such as excessive water consumption and short-circuiting or blockage between geothermal wells. To address these issues, the use of supercritical CO2 as the heat transfer medium for power generation or heating is being explored.

[0029] Supercritical CO2 has unique physical properties such as low viscosity and high density, which gives it typical advantages in thermal reservoirs, such as good fluidity, high heat transfer efficiency and low compressibility. Currently, EGS heat extraction + CO2 power generation systems have begun to be used internationally, but there are no relevant mature engineering cases in China, which makes it impossible for this technology to be practically applied and promoted.

[0030] To address the aforementioned technical deficiencies, the inventors have provided a geothermal energy adjustable power generation system based on carbon dioxide as the working fluid.

[0031] The present invention will now be described in further detail with reference to the accompanying drawings: Firstly, such as Figure 1 As shown, this embodiment of the invention provides a geothermal energy adjustable power generation system based on carbon dioxide as the working fluid, including a power generation well 1, which is connected to a temperature and pressure regulating device 2 via pipeline; a gas-liquid heat exchange device 3, one end of which is connected to the temperature and pressure regulating device 2, and the other end of which is connected to a steam superheating device 4, which is equipped with a heating device 5 and a turbine 6, and the turbine 6 is connected to a power generation device 7, preferably a generator, which is connected to the gas-liquid heat exchange device 3 via a pressure regulating device 8; and a plunger pump 10, one end of which is connected to a reinjection well 11, and the other end of which is connected to the gas-liquid heat exchange device 3 via a refrigeration device 9. In application, the carbon dioxide working fluid absorbs heat in a deep fissure at a depth of 5,000 meters, and simultaneously, under the action of thermosiphon effect, is transported to the temperature and pressure regulating device 2 through the power generation well 1. The temperature and pressure regulating device 2 can then regulate the temperature and pressure of the carbon dioxide working fluid to adapt it to the subsequent energy conversion process, thereby improving the energy conversion efficiency of the entire system. After the temperature and pressure of the carbon dioxide working fluid are regulated, the gas-liquid heat exchange device 3 and the steam superheating device 4 work together to further heat the carbon dioxide working fluid after it is converted into steam, thereby increasing the temperature and pressure of the steam and increasing the power generation efficiency of the turbine 6. Finally, by adjusting the output of the heating device 5, the heating intensity in the steam superheating device 4 can be flexibly controlled, thereby adjusting the speed of the turbine 6 and the output power of the power generation device 7, achieving adjustable power generation. In this process, the gas-liquid heat exchange device 3 is not only used for preheating the carbon dioxide working fluid, but also connected to the power generation device 7 through the pressure regulating device 8, realizing energy recovery and recycling. The low-temperature carbon dioxide working fluid generated during power generation can be preheated by the gas-liquid heat exchange device 3 to improve energy utilization efficiency. The installation of the plunger pump 10 and the reinjection well 11 allows the carbon dioxide working fluid after system circulation to be reinjected underground, maintaining the sustainable use of geothermal resources. At the same time, the installation of the refrigeration device 9 can further reduce energy consumption during system operation and improve the overall energy efficiency ratio. In summary, this design successfully enabled geothermal energy generation based on carbon dioxide as the working fluid, filling a gap in the domestic application of this technology. Figure 1As shown, the temperature and pressure regulating device 2 is preferably a desuperheating and pressure reducing valve. Since the carbon dioxide working fluid output from the power generation well 1 is in a supercritical state with high temperature and pressure, directly sending the high-temperature and high-pressure working fluid into the subsequent heat exchange and power generation equipment may damage the equipment or reduce its service life. The installation of the temperature and pressure regulating device 2 can effectively reduce the temperature and pressure of the working fluid, making it meet the operating requirements of the subsequent equipment, thereby protecting the equipment from damage caused by high temperature and high pressure. At the same time, if a leak or accident occurs when the high-temperature and high-pressure carbon dioxide working fluid flows in the system, it may cause a safety accident. The temperature and pressure regulating device 2 can reduce this risk to a certain extent, because even if a leak occurs, the potential danger will be reduced accordingly because the temperature and pressure of the working fluid have been reduced. In addition, the temperature and pressure regulating device 2 not only reduces the temperature and pressure of the working fluid, but can also regulate the flow rate and state of the working fluid to a certain extent, making it better suited to the subsequent heat exchange and power generation process. By precisely controlling the temperature and pressure of the working fluid, the energy conversion process can be optimized and the power generation efficiency of the entire system can be improved. By pretreating the working fluid through the temperature and pressure regulating device 2, wear and failure rates of subsequent equipment can be reduced, thereby lowering system operating and maintenance costs. Furthermore, since the system can utilize geothermal energy more efficiently, it can also reduce power generation costs to some extent. Figure 1 As shown, furthermore, the gas-liquid heat exchange device 3 and the steam superheating device 4 are used to supplement the heating of the carbon dioxide working fluid; specifically, the gas-liquid heat exchange device 3 is preferably a regenerator, and the steam superheating device 4 is preferably a reheater. The gas-liquid heat exchange device 3 achieves heat exchange between gas and liquid through a high-vacuum sealed shell and tube, which has a highly efficient heat recovery effect. In the process of supplementing the heating of the carbon dioxide working fluid, waste heat resources can be fully utilized, improving energy utilization efficiency. At the same time, since the gas-liquid heat exchange device 3 adopts an anti-corrosion and anti-scaling design, the gas-liquid heat exchange device 3 can operate stably for a long time under harsh operating conditions, reducing maintenance costs. The steam superheating device 4 can further heat the saturated steam, making it superheated steam with a certain degree of superheat. This not only improves the quality of the steam, but also reduces the energy loss of the steam during transportation. As the steam temperature in the steam superheater increases, although the convective heat release effect of the steam on the tube wall will deteriorate, the overall heat transfer effect is still better than that of unsuperheated steam, which helps to achieve higher heat transfer efficiency in the process of supplementing the heating of the carbon dioxide working fluid. Figure 1As shown, the pressure regulating device 8 is preferably a valve, used to regulate the system back pressure. As a pressure regulating device 8, the valve can precisely control the back pressure in the system. By adjusting the valve opening, fine regulation of the back pressure can be achieved, keeping it within a preset range. This helps ensure stable system operation and avoids equipment failure or performance degradation caused by back pressure fluctuations. Furthermore, the valve can reduce energy loss caused by excessively high or low back pressure. Under excessively high back pressure, the system may need to consume more energy to overcome it; while under excessively low back pressure, it may lead to reduced system efficiency and energy waste. Adjusting the valve can keep the back pressure within the optimal range, thereby reducing energy loss. Figure 1 As shown, one end of the plunger pump 10 is connected to the reinjection well 11, and the other end is connected to the gas-liquid heat exchange device 3 through the refrigeration device 9. The refrigeration device 9 is preferably a refrigerator. Through the synergistic effect of the plunger pump 10, the refrigeration device 9 and the gas-liquid heat exchange device 3, the system can maintain a stable operating state. The efficient transmission of the plunger pump 10, the precise temperature control of the refrigeration device 9 and the efficient heat exchange of the gas-liquid heat exchange device 3 together constitute the stable foundation of the system.

[0032] This embodiment also provides a method for adjustable geothermal power generation based on carbon dioxide as the working fluid. The method is implemented using the adjustable geothermal power generation system based on carbon dioxide as described above. Figure 5 As shown, it includes: S101. Obtain carbon dioxide working fluid and perform desuperheating and depressurization operations; exemplarily, the carbon dioxide working fluid absorbs heat in a deep fissure at a depth of 5,000 meters, and is simultaneously obtained through power generation well 1 under the action of thermosiphon effect. The carbon dioxide working fluid obtained from power generation well 1 is in a supercritical state with high temperature and high pressure; to meet the system operation requirements, the supercritical carbon dioxide working fluid with high temperature and high pressure is transported to temperature and pressure regulating device 2, and the temperature and pressure regulating device 2 is used to desuperheat and depressurize the supercritical carbon dioxide working fluid with high temperature and high pressure to the pressure that the turbine can withstand; with the enthalpy of the working fluid remaining constant, it is recommended that the pressure be adjusted to 26 MPa and the temperature to 170°C. S102. The de-cooled and depressurized carbon dioxide working fluid is reheated to improve its work-capacity. For example, the de-cooled and depressurized carbon dioxide working fluid is reheated through a gas-liquid heat exchanger 3 and a steam superheater 4 to improve its work-capacity while preventing the turbine's final stage from entering the two-phase region. During the reheating process, from... Figure 1 As can be seen, the heating device 5 provides heat to the steam superheating device 4, and the heat source in the heating device 5 can be one of the following: flue gas waste heat, industrial waste heat or solar heat.

[0033] S103. Power generation using the reheated carbon dioxide working fluid; exemplarily, the reheated carbon dioxide working fluid enters the power generation device 7 through the turbine 6 to generate electricity. During the power generation process, the pressure regulating device 8 is used to regulate the system back pressure. The system's power generation and reheating are as follows: Figure 2 As shown.

[0034] During summer operation, since the temperature in northern China is generally around 25℃, the back pressure drops to 7MPa, and the pressure regulating device 8 is fully open. The carbon dioxide working fluid first passes through the gas-liquid heat exchange device 3 for heat exchange, and then enters the temperature and pressure regulating device 2. At the same time, the carbon dioxide working fluid entering the temperature and pressure regulating device 2 is reheated to reduce its temperature before entering the refrigeration device 9, thereby achieving energy saving. In the process of using the refrigeration device 9 for cooling and energy saving, cooling and condensation can also be achieved through air cooling or ambient temperature water cooling, and the heat of the circulating water is removed through the cooling tower. The condensed carbon dioxide enters the plunger pump 10 for pressurization, and then is injected into the reinjection well 11 to recycle by absorbing heat from the geothermal environment. In this process, the carbon dioxide working fluid undergoes a transcritical thermodynamic cycle.

[0035] During winter operation, the installation of the steam superheater 4 is cancelled, and the industrial waste heat in the heating unit 5 is prioritized for heating rather than for supplementary power generation. Figure 3 The figure shows the operating parameters of the system in pure power generation mode under winter conditions. Supercritical carbon dioxide working fluid flows directly from power generation well 1 through temperature and pressure regulating device 2 and gas-liquid heat exchange device 3 into turbine 6 for power generation. During this process, pure power generation or power generation / heating modes can be designed according to user needs. In pure power generation mode, the cold energy of winter is fully utilized to reduce back pressure and increase power generation. However, attention must be paid to the superheat after turbine operation when the pressure drops to a low level. In this case, the back pressure can be appropriately increased or appropriate supplemental heating can be applied before turbine 6 to ensure the superheat after turbine operation.

[0036] When users have heating needs, the back pressure is increased by adjusting the opening of the pressure regulating device 8 after the turbine, and heating is provided to users through the gas-liquid heat exchange device 3. Finally, the heating is pumped into the reinjection well 11 by the plunger pump 10. The back pressure varies depending on the amount of heat supplied, and the power generation and heat supply change accordingly. Increasing the back pressure reduces power generation while increasing the heating output. Detailed calculations of the changes in heat supply and power generation with back pressure are attached. Figure 4 As shown.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the invention.

Claims

1. A geothermal energy adjustable power generation system based on carbon dioxide as the working fluid, characterized in that, include: The power generation well (1) is connected to a temperature and pressure regulating device (2) via a pipeline. The gas-liquid heat exchange device (3) is connected at one end to the temperature and pressure regulating device (2) and at the other end to a steam superheating device (4). The steam superheating device (4) is equipped with a heating device (5) and a turbine (6). The turbine (6) is connected to a power generation device (7). The power generation device (7) is connected to the gas-liquid heat exchange device (3) through a pressure regulating device (8). A plunger pump (10) is connected at one end to a reinjection well (11) and at the other end to a gas-liquid heat exchange device (3) via a refrigeration device (9).

2. The geothermal energy adjustable power generation system based on carbon dioxide working fluid according to claim 1, characterized in that, The temperature and pressure regulating device (2) is a de-temperature and pressure reducing valve, which is used to de-temperature and reduce the pressure of the carbon dioxide working fluid output from the power generation well (1).

3. The geothermal energy adjustable power generation system based on carbon dioxide working fluid according to claim 1, characterized in that, The gas-liquid heat exchange device (3) and the steam superheating device (4) are used to supplement the heat of the carbon dioxide working fluid.

4. The geothermal energy adjustable power generation system based on carbon dioxide working fluid according to claim 3, characterized in that, The gas-liquid heat exchange device (3) is a regenerator.

5. The geothermal energy adjustable power generation system based on carbon dioxide working fluid according to claim 3, characterized in that, The steam superheating device (4) is a reheater.

6. The geothermal energy adjustable power generation system based on carbon dioxide working fluid according to claim 1, characterized in that, The pressure regulating device (8) is used to regulate the system back pressure.

7. The geothermal energy adjustable power generation system based on carbon dioxide working fluid according to claim 1, characterized in that, The refrigeration device (9) is a refrigerator.

8. The geothermal energy adjustable power generation system based on carbon dioxide working fluid according to claim 1, characterized in that, The heat source in the heating device (5) is one of the following: flue gas waste heat, industrial waste heat or solar heat.

9. The geothermal energy adjustable power generation system based on carbon dioxide working fluid according to claim 1, characterized in that, The power generation device (7) is a generator.

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