A dry hot rock heat utilization system based on carbon dioxide injection type heat pump

Abstract

The application refers to a dry hot rock heat utilization system based on a carbon dioxide ejector heat pump, comprising an ejector, a cooler, a pressure reducing device, an evaporator and a heat exchanger; the inlet of the ejector is connected to a production well, and the outlet of the ejector is connected to the cooler; the outlet of the cooler is connected to the first inlet of the heat exchanger and the inlet of the pressure reducing device respectively; the outlet of the pressure reducing device is connected to the inlet of the evaporator; the outlet of the evaporator is connected to the second inlet of the heat exchanger, and the outlet in the heat exchanger is connected to the suction port of the ejector; the application realizes efficient utilization of low-grade energy by injecting low-pressure vapor in the ejector, improves the heat extraction efficiency of the heat transfer fluid, does not need to increase pump power, and effectively reduces the energy consumption of the system. In addition, the working medium flows through the heat exchanger after flowing out of the evaporator, further reduces the temperature of the working medium to be injected into the underground, increases the enthalpy difference between the injection well and the production well, enhances the transportation and heat extraction capacity of the working medium, and improves the underground heat exchange effect of the dry hot rock.

Description

Technical Field

[0001] This invention relates to the field of dry hot rock thermal extraction technology, and in particular to a dry hot rock heat utilization system based on a carbon dioxide jet heat pump. Background Technology

[0002] Geothermal resources, particularly hot dry rock, are abundant and have great development potential. The mainstream method for extracting heat from hot dry rock is to establish an underground geothermal reservoir (EGS) system using hydraulic fracturing. Water is used as the heat extraction medium to absorb heat, and the water is then extracted to the surface through pumping, where it is used for heat exchange.

[0003] However, current geothermal utilization systems struggle to fully extract underground heat and transfer it to the surface. High-temperature underground heat is difficult to extract efficiently, consuming significant pump power and wasting substantial amounts of usable energy. Furthermore, the energy carried by the extracted working fluid in the geothermal reservoir is not fully utilized before being reinjected underground, resulting in low utilization rates of hot dry rock heat extraction. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the technical problem in the prior art that the energy in the hot dry rock is difficult to be extracted and utilized efficiently with low energy consumption during the heat extraction process of hot dry rock, thus causing energy loss.

[0005] This invention provides a dry hot rock heat utilization system based on a carbon dioxide jet heat pump, comprising: The system includes ejectors, coolers, pressure-reducing equipment, evaporators, heat exchangers, and pressurizing equipment. The circulating working fluid of the dry hot rock heat utilization system is CO2. The ejector has a working fluid inlet, an ejector fluid inlet, and a mixed fluid outlet. The outlet of the production well is directly connected to the working fluid inlet via a pipeline, and the mixed fluid outlet is connected to the inlet of the cooler. The outlet of the cooler forms a main reinjection branch and an ejector circulation branch, respectively. The main reinjection branch is connected to the first inlet of the heat exchanger, the first outlet of the heat exchanger corresponding to the first inlet is connected to the inlet of the pressurizing equipment, and the outlet of the pressurizing equipment is used to connect to the injection well. The ejector circulation branch is connected to the inlet of the heat exchange coil installed in the heat exchanger via the pressure reducing equipment and the evaporator in sequence, and the outlet of the heat exchange coil is connected to the ejector fluid inlet. High-temperature, high-pressure CO2 from the production well enters the ejector through the working fluid inlet, forming a low-pressure zone at the ejector fluid inlet. The CO2 in the ejector circulation branch is depressurized by the depressurization device and evaporated in the evaporator before flowing through the heat exchange coil to exchange heat with the CO2 in the reinjection main branch. After absorbing heat, it is ejected by the ejector. The CO2 in the reinjection main branch is cooled by heat exchanger and then transported to the injection well by the pressurization device.

[0006] Furthermore, the pressurizing device is a compressor.

[0007] Furthermore, the evaporator is one of the following: plate evaporator, shell-and-tube evaporator, tube-and-tube evaporator, finned-tube heat exchanger, or spiral plate evaporator.

[0008] Furthermore, the pressure-reducing device is an expander or a throttle valve.

[0009] Furthermore, the heat energy source for the evaporator can be air thermal energy, geothermal energy, solar energy, or low-temperature waste heat.

[0010] Furthermore, the compressor is one of a reciprocating compressor, a screw compressor, a scroll compressor, or a centrifugal compressor.

[0011] Furthermore, the connections between the ejector, cooler, pressure reducing equipment, evaporator, and heat exchanger are all pipeline connections.

[0012] The advantage of this application compared to the prior art is that the dry hot rock heat utilization system based on a carbon dioxide jet heat pump mentioned in this application includes: an ejector, a cooler, a pressure reducing device, an evaporator, and a heat exchanger; the inlet of the ejector is used to connect to the production well, and the ejector nozzle is connected to the cooler; the outlet of the cooler is connected to the first inlet of the heat exchanger and the inlet of the pressure reducing device respectively; the outlet of the pressure reducing device is connected to the inlet of the evaporator; the outlet of the evaporator is connected to the second inlet of the heat exchanger, and the outlet of the heat exchanger is connected to the ejector nozzle; the outlet of the heat exchanger is connected to the inlet of the pressure increasing device.

[0013] The heat transfer medium of the dry hot rock utilization system mentioned in this application is CO2. First, high-temperature and high-pressure CO2 vapor from the production well is ejected through an ejector, forming a low-pressure zone at the ejector's inlet. Low-pressure CO2 vapor from the heat exchanger coil is then ejected. The high-temperature and high-pressure CO2 gas from the production well and the low-pressure CO2 vapor from the heat exchanger are mixed and discharged from the ejector's nozzle. After being cooled by a cooler, part of it directly enters the heat exchanger. The remaining CO2 working fluid is depressurized by a depressurization device and then enters the evaporator. The evaporator uses air heat energy, geothermal energy, solar energy, or low-temperature waste heat to evaporate the CO2 vapor. After being discharged from the evaporator, it enters the heat exchanger coil and exchanges heat with the working fluid of the heat exchanger. The working fluid temperature of the heat exchanger is further reduced and then enters the ejector through the inlet.

[0014] This application utilizes the high-temperature, high-pressure characteristics of steam in hot dry rock. On one hand, it incorporates a jet heat pump into the hot dry rock heat utilization system. By using high-pressure steam from the production well to eject low-pressure steam from the evaporator, and leveraging the high-pressure characteristics of the working fluid in the production well, it achieves efficient utilization of low-grade energy. This eliminates the need for excessive pumping power to extract the underground working fluid, improving the working fluid's transport capacity and reducing overall system energy consumption. On the other hand, by adding a heat exchange device for the working fluid after depressurization by the depressurization equipment, the temperature of the working fluid at the injection well inlet is further reduced, increasing the enthalpy difference between the injection and production wells. This enhances the heat extraction and transport capacity of the working fluid, reduces the energy consumption of the pressurization equipment, and improves the underground heat exchange effect of the hot dry rock, achieving the goal of efficient and stable system operation. Attached Figure Description

[0015] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0016] Figure 1 This is a schematic diagram of a dry hot rock heat utilization system based on a carbon dioxide jet heat pump mentioned in this invention.

[0017] 1. Ejector; 2. Cooler; 3. Pressure reducing equipment; 4. Evaporator; 5. Heat exchanger; 6. Pressurization equipment. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0019] Reference Figure 1 As shown, the present invention provides a dry hot rock heat utilization system based on a carbon dioxide jet heat pump, comprising: 1. Injector; 2. Cooler; 3. Pressure reducing device; 4. Evaporator; 5. Heat exchanger; 6. Pressurizing device; Specifically, the inlet of ejector 1 is used to connect to the production well, and the outlet of ejector 1 is connected to cooler 2; the outlet of cooler 2 is connected to the first inlet of heat exchanger 5 and the inlet of pressure reducing device 3 respectively; the outlet of pressure reducing device 3 is connected to the inlet of evaporator 4; the outlet of evaporator 4 is connected to the second inlet inside heat exchanger 5, the outlet of heat exchange coil inside heat exchanger 5 is connected to the ejector port of ejector 1; and the outlet of heat exchanger 5 is connected to the inlet of pressurizing device 6.

[0020] For example, the first inlet of the heat exchanger 5 is the inlet of the heat exchanger 5, and the second inlet inside the heat exchanger 5 is the inlet of the heat exchange coil inside the heat exchanger 5.

[0021] In this technical solution, the connection between the ejector 1, cooler 2, pressure reducing device 3, evaporator 4, heat exchanger 5, and pressurizing device 6 is all pipeline connection.

[0022] In this application, the heat transfer medium of the hot dry rock utilization system is CO2; for example, the heat transfer medium can be supercritical CO2. Using supercritical CO2 as the working medium for hot dry rock development can reduce water consumption, reduce pipe scaling and corrosion, and supercritical CO2 as a heat extraction medium has stronger convection and higher extraction efficiency than H2O, and also has the additional benefit of "carbon storage".

[0023] In one feasible implementation, the CO2 working fluid is ejected from the ejector 1 to the cooler 2. After passing through the cooler 2, at least a portion of the CO2 working fluid enters the heat exchanger 5 for heat exchange and is then injected into the injection well via the pressurization device 6. The remaining CO2 working fluid is depressurized by the depressurization device 3 and then enters the evaporator 4 for evaporation, and then enters the heat exchanger 5 for heat exchange before entering the ejector 1. The above description is merely exemplary, and this application does not limit the state of CO2 during the heat exchange process.

[0024] A jet heat pump is a heat pump system that uses jet technology to achieve heating and cooling. It heats or cools by controlling the gas flow from the ejector. The working principle of a jet heat pump is based on a thermodynamic cycle process. Compared with traditional heat pumps, jet heat pumps have advantages such as high efficiency, stability, and energy saving. They can quickly respond to different load demands and provide stable temperature and humidity control. Furthermore, jet heat pumps can use natural refrigerants, avoiding environmental pollution and safety risks.

[0025] This application incorporates a jet heat pump into a dry hot rock heat utilization system. By using the high-pressure steam from the extraction well to eject the low-pressure steam from the evaporator 4, and utilizing the high-pressure characteristics of the working fluid in the extraction well, it achieves efficient utilization of low-grade energy. This eliminates the need for excessive pumping power to extract the underground working fluid, improves the working fluid's transport capacity, and reduces the overall energy consumption of the system.

[0026] In this technical solution, the CO2, after heat exchange in heat exchanger 5, re-enters ejector 1 and is ejected. The ejected CO2 can then re-enter the heat exchange cycle, thus achieving the recycling of the working fluid. Furthermore, by adding a heat exchanger for heat exchange with the depressurized working fluid in depressurization device 3, the temperature of the working fluid at the injection well inlet is further reduced, increasing the enthalpy difference between the injection and production wells. This enhances the heat extraction and transport capacity of the working fluid, reduces the energy consumption of pressurization device 6, improves the underground heat exchange efficiency of hot dry rock, and achieves the goal of efficient and stable system operation.

[0027] like Figure 1As shown, high-temperature and high-pressure CO2 vapor from the production well is ejected through the ejector, forming a low-pressure zone at the ejector's inlet. This zone then draws in low-pressure CO2 vapor from the heat exchanger coil of heat exchanger 5. The high-temperature and high-pressure CO2 gas from the production well and the low-pressure CO2 vapor from heat exchanger 5 mix and are discharged from the ejector's outlet. After being cooled in cooler 2, a portion of the CO2 working fluid directly enters heat exchanger 5. The remaining CO2 working fluid is depressurized by depressurization device 3 and then enters evaporator 4. The evaporator uses air thermal energy, geothermal energy, solar energy, or low-temperature waste heat to evaporate the CO2 vapor. After being discharged from evaporator 4, the CO2 vapor enters the heat exchanger coil of heat exchanger 5 and exchanges heat with the working fluid of heat exchanger 5. This further reduces the temperature of the working fluid in heat exchanger 5 before it is drawn into the ejector.

[0028] This application discloses a dry hot rock heat utilization system based on a carbon dioxide jet heat pump, mainly composed of an ejector 1, a cooler 2, a pressure-reducing device 3, an evaporator 4, a heat exchanger 5, a pressurizing device 6, an injection well, and a production well. The system incorporates an ejector 1 at the production wellhead. Utilizing the high temperature and pressure characteristics of steam in the dry hot rock, low-pressure steam is ejected through the ejector 1 to achieve efficient utilization of low-grade energy, improving the efficiency of the production well without requiring additional pump power, thus effectively reducing system energy consumption. The working fluid flows from the evaporator 4 through the heat exchanger 5, further reducing the temperature of the working fluid to be injected underground. This increases the enthalpy difference between the injection well and the production well, enhancing the transport and heat extraction capacity of the working fluid, improving the underground heat exchange effect of the dry hot rock, and increasing the overall system efficiency.

[0029] In this technical solution, the dry hot rock utilization system also includes: Pressurization device 6 is used to pressurize the CO2 after heat exchange in heat exchanger 5 and inject it into the injection well.

[0030] This application uses pressurizing equipment 6 to pressurize CO2 after heat exchange in heat exchanger 5 and inject it into the injection well, thereby further improving work efficiency. Modern pressurizing equipment 6 is made of advanced technology and high-quality materials, has reliability and durability, can operate stably for a long time, and reduces maintenance and repair costs.

[0031] In this technical solution, the pressurizing device 6 is a compressor.

[0032] In other embodiments, the pressurizing device 6 is a high-pressure pump. Here, high pressure has two aspects: one is that the CO2 itself has a relatively high pressure, and the other is that a high pressure head is required.

[0033] In this technical solution, the evaporator 4 is one of a plate evaporator, a shell-and-tube evaporator, a finned tube heat exchanger, or a spiral plate evaporator. The heat energy source for the evaporator 4 is air thermal energy, geothermal energy, solar energy, or low-temperature waste heat.

[0034] Evaporator 4 has a large surface area and good heat transfer performance, which can quickly absorb heat from the outside and evaporate the refrigerant to achieve the effect of cooling or heating.

[0035] Evaporator 4 can regulate the cooling or heating effect by controlling the flow and temperature of the refrigerant, providing a stable temperature output. Evaporator 4 utilizes the phase change process of the refrigerant for heat exchange, effectively recovering and utilizing energy. Compared to traditional direct heating or cooling methods, evaporator 4 achieves highly efficient energy conversion, improving energy utilization and thus reducing energy consumption and environmental pollution.

[0036] In this technical solution, the pressure-reducing device 3 is an expander or a throttle valve. The pressure-reducing device 3 can reduce high-pressure fluids or gases to a lower, safer pressure range, thereby ensuring the stable operation and safety of the system. It achieves pressure reduction by limiting the flow cross-sectional area of ​​the fluid or gas; compared to other methods, it has less energy loss, thus achieving energy-saving and environmentally friendly effects.

[0037] In this technical solution, the compressor includes: a reciprocating compressor, a screw compressor, a scroll compressor, or a centrifugal compressor. The compressor offers advantages such as energy saving, automation, and remote control, further improving the efficiency of the heat exchange cycle.

[0038] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

[0039] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0040] In this invention, unless otherwise explicitly 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 or an electrical 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 invention according to the specific circumstances.

[0041] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that they are in indirect contact through an intermediate medium. Furthermore, "above," "over," or "on top" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," or "beneath" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0042] In the description of this specification, the terms "one embodiment," "some embodiments," "embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. 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 may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0043] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A dry hot rock heat utilization system based on a carbon dioxide jet heat pump, characterized in that, include: The system includes an ejector, a cooler, a pressure-reducing device, an evaporator, a heat exchanger, and a pressurizing device, wherein the circulating working fluid of the dry hot rock heat utilization system is CO2; The ejector has a working fluid inlet, an ejector fluid inlet, and a mixed fluid outlet. The outlet of the production well is directly connected to the working fluid inlet via a pipeline, and the mixed fluid outlet is connected to the inlet of the cooler. The outlets of the coolers form a main reinjection branch and an ejector circulation branch, respectively. The reinjection main branch is connected to the first inlet of the heat exchanger, the first outlet of the heat exchanger corresponding to the first inlet is connected to the inlet of the pressurizing device, and the outlet of the pressurizing device is used to connect to the injection well; The ejector circulation branch is connected to the inlet of the heat exchange coil installed in the heat exchanger via the pressure reducing device and the evaporator in sequence, and the outlet of the heat exchange coil is connected to the ejector fluid inlet. High-temperature, high-pressure CO2 from the produced well enters the ejector through the working fluid inlet, forming a low-pressure zone at the ejector fluid inlet. The CO2 in the ejector circulation branch is depressurized by the depressurization device and evaporated in the evaporator before flowing through the heat exchange coil to exchange heat with the CO2 in the reinjection main branch. After absorbing heat, it is ejected by the ejector. The CO2 in the reinjection main branch is cooled by the heat exchanger and then transported to the injection well by the pressurization device.

2. The dry hot rock heat utilization system based on a carbon dioxide jet heat pump according to claim 1, characterized in that, The pressurizing device is a compressor.

3. The dry hot rock heat utilization system based on a carbon dioxide jet heat pump according to claim 1, characterized in that, The evaporator is one of the following: plate evaporator, shell-and-tube evaporator, tube-and-tube evaporator, finned-tube heat exchanger, or spiral plate evaporator.

4. A dry hot rock heat utilization system based on a carbon dioxide jet heat pump according to claim 1, characterized in that, The pressure-reducing device is an expander or a throttle valve.

5. A dry hot rock heat utilization system based on a carbon dioxide jet heat pump according to claim 1, characterized in that, The heat source for the evaporator is air heat energy, geothermal energy, solar energy, or low-temperature waste heat.

6. A dry hot rock heat utilization system based on a carbon dioxide jet heat pump according to claim 2, characterized in that, The compressor is one of a piston compressor, screw compressor, scroll compressor, or centrifugal compressor.

7. A dry hot rock heat utilization system based on a carbon dioxide jet heat pump according to claim 1, characterized in that, The ejector, the cooler, the pressure reducing device, the evaporator, the heat exchanger, and the pressurizing device are all connected by pipelines.

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