A multi-connection type carbon dioxide closed circulation formation heat exchange system

Abstract

The application relates to a multi-connection type carbon dioxide closed circulation stratum heat exchange system and relates to the field of stratum heat exchange technology equipment, which comprises a vertically arranged main pipe, a branch pipe is vertically arranged on the outer side of the main pipe, the bottom end of the branch pipe is fixedly connected with the side wall of the main pipe, the inside of the branch pipe is communicated with the inside of the main pipe, and multiple branch pipes are arranged on the outer side of the main pipe. The application has the effects of improving the heat exchange efficiency of the system and enhancing the operation flexibility of the system for heat extraction and heat supplement from the stratum.

Description

Technical Field

[0001] This application relates to the field of formation heat exchange technology and equipment, and in particular to a multi-connected closed-loop carbon dioxide formation heat exchange system. Background Technology

[0002] Driven by the need for low-carbon energy and environmental development, the construction of new energy sources is accelerating. Geothermal energy, as a type of new energy, is natural heat extracted from the Earth's crust. This energy originates from the Earth's internal lava and exists in the form of heat, and can be widely used in areas such as compressed carbon dioxide energy storage, agriculture, heating, and power generation. Currently, the development of shallow geothermal energy is relatively mature, mainly used for heating, hot spring therapy, and aquaculture. However, shallow geothermal energy has a low grade and requires a large extraction area, making it difficult to utilize in densely built-up areas or where higher grades are required.

[0003] Compared to shallow geothermal areas, mid-deep geothermal regions are less affected by surface temperature fluctuations, have higher temperatures, and exhibit larger geothermal gradients. Data shows that the geothermal gradient in mid-deep layers (2-8 km depth) is 3-6℃ per 100 meters, indicating that mid-deep strata contain considerable usable thermal energy, which can effectively compensate for the insufficiency of shallow geothermal energy.

[0004] However, current medium-deep buried pipe heat exchange systems, such as vertical well coaxial casing type, U-shaped well single pipe type and well groups composed of them, have problems such as low heat exchange efficiency, inflexible heat extraction and heat replenishment operation modes, insufficient inter-well linkage, and insufficient compatibility with external heat sources. Summary of the Invention

[0005] To improve the heat exchange efficiency of the system and enhance the operational flexibility of the system in extracting and replenishing heat from the formation, this application provides a multi-connected closed-loop carbon dioxide formation heat exchange system.

[0006] This application provides a multi-connected closed-loop carbon dioxide formation heat exchange system, which adopts the following technical solution:

[0007] A multi-connected closed-loop carbon dioxide formation heat exchange system includes a vertically arranged main pipe, with branch pipes vertically arranged on the outer side of the main pipe. The bottom end of the branch pipe is fixedly connected to the side wall of the main pipe, and the interior of the branch pipe is connected to the interior of the main pipe. Multiple branch pipes are arranged on the outer side of the main pipe.

[0008] Optionally, the branch pipe includes a vertical section, the bottom end of which is fixedly connected to a horizontal section, the vertical section and the horizontal section are in relative communication, and the horizontal section is fixedly connected to the side wall of the main pipe.

[0009] Optionally, the outer side of the main tube is covered with a first insulation layer.

[0010] Optionally, a circulating working fluid is injected into the branch pipe. The temperature of the circulating working fluid is lower than the temperature inside the formation. The low-temperature circulating working fluid is heated inside the formation and then flows into the main pipe.

[0011] Optionally, a second insulation layer is provided on the outside of the branch pipe.

[0012] Optionally, a circulating working fluid is injected into the main pipe. The temperature of the circulating working fluid is lower than the temperature inside the formation. After the circulating working fluid is heated inside the formation, it flows into the branch pipe.

[0013] Optionally, the circulating working fluid is liquid carbon dioxide.

[0014] Optionally, a third insulation layer is provided on the outer side of some of the multiple branch pipes, and a circulating working fluid is injected into the branch pipes without the third insulation layer. The temperature of the circulating working fluid is lower than the temperature inside the formation. After the circulating working fluid is heated inside the formation, it flows into the branch pipe with the third insulation layer.

[0015] Optionally, multiple branch pipes are connected in sequence to form a branch pipe sub-frame, with the main pipe located at the center point of the branch pipe sub-frame.

[0016] Optionally, a gap is left between the multiple branches.

[0017] In summary, this application includes at least one of the following beneficial technical effects:

[0018] 1. The radiation area of ​​the well casing for heat exchange with the formation has been expanded, especially the radiation area of ​​the horizontal casing in the deep high-temperature section. At the same time, carbon dioxide fluid working fluid with higher specific heat capacity and heat exchange capacity is used to improve the heat exchange efficiency of the system.

[0019] 2. A multi-pipe interconnected well pipe design was adopted to achieve multiple inlets / outlets for the working fluid. The outlet and inlet of the working fluid and its flow rate can be adjusted according to the differences and changes in formation temperature, which enhances the linkage between wells and realizes the operational flexibility of the system to extract and replenish heat from the formation.

[0020] 3. The multi-inlet / outlet design enables flexible access to external heat sources of different grades, enhancing the compatibility of the heat exchange system with external heat sources and improving the system's adaptability to different scenarios. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of a multi-connected closed-loop carbon dioxide formation heat exchange system according to an embodiment of this application.

[0022] Figure 2This is a top view of a multi-connected closed-loop carbon dioxide formation heat exchange system according to an embodiment of this application.

[0023] Explanation of reference numerals in the attached diagram: 1. Main pipe; 2. Branch pipe; 21. Vertical section; 22. Horizontal section. Detailed Implementation

[0024] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0025] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0026] Driven by the need for low-carbon energy and environmental development, the construction of new energy sources is accelerating. Geothermal energy, as a type of new energy, is natural heat extracted from the Earth's crust. This energy originates from the Earth's internal lava and exists in the form of heat, and can be widely used in areas such as compressed carbon dioxide energy storage, agriculture, heating, and power generation. Currently, the development of shallow geothermal energy is relatively mature, mainly used for heating, hot spring therapy, and aquaculture. However, shallow geothermal energy has a low grade and requires a large extraction area, making it difficult to utilize in densely built-up areas or where higher grades are required.

[0027] Compared to shallow geothermal areas, mid-deep geothermal regions are less affected by surface temperature fluctuations, have higher temperatures, and exhibit larger geothermal gradients. Data shows that the geothermal gradient in mid-deep layers (2-8 km depth) is 3-6℃ per 100 meters, indicating that mid-deep strata contain considerable usable thermal energy, which can effectively compensate for the insufficiency of shallow geothermal energy.

[0028] However, current medium-deep buried pipe heat exchange systems, such as vertical well coaxial casing type, U-shaped well single pipe type and well groups composed of them, have problems such as low heat exchange efficiency, inflexible heat extraction and heat replenishment operation modes, insufficient inter-well linkage, and insufficient compatibility with external heat sources.

[0029] To improve the heat exchange efficiency of the system and enhance the operational flexibility of the system in extracting and replenishing heat from the formation, this application provides a multi-connected closed-loop carbon dioxide formation heat exchange system.

[0030] The following is in conjunction with the appendix Figure 1-2 This application will be described in further detail.

[0031] This application discloses a multi-connected closed-loop carbon dioxide formation heat exchange system. (Refer to...) Figure 1 , Figure 2 A multi-connected closed-loop carbon dioxide formation heat exchange system includes a vertically arranged main pipe 1, and branch pipes 2 vertically arranged outside the main pipe 1. The bottom end of the branch pipe 2 is fixedly connected to and communicates with the bottom end of the main pipe 1. Multiple branch pipes 2 are arranged outside the main pipe 1, and the bottom ends of multiple branch pipes 2 are all connected to the bottom end of the main pipe 1. A gap is left between two adjacent branch pipes 2, and multiple branch pipes 2 are connected in sequence to form a branch pipe 2 distribution frame. The main pipe 1 is located at the center point of the branch pipe 2 distribution frame.

[0032] Branch pipe 2 includes a vertically arranged vertical section 21, and a horizontal section 22 is horizontally arranged at the bottom end of the vertical section 21. The vertical section 21 and the horizontal section 22 are fixedly connected, and the connection between the vertical section 21 and the horizontal section 22 is smoothly transitioned. One end of the horizontal section 22 is fixedly connected to and communicates with the vertical section 21, and the other end of the horizontal section 22 is fixedly connected to and communicates with the bottom end of the side wall of the main pipe 1. This allows the space inside the branch pipe 2 to communicate with the space inside the main pipe 1, and multiple branch pipes 2 can also communicate with each other through the interior of the main pipe 1.

[0033] In some embodiments, branch pipe 2 serves as a cryogenic working fluid injection pipe, and main pipe 1 serves as a high-temperature working fluid return pipe. The cryogenic working fluid is injected through branch pipe 2, undergoes heat exchange within the formation, and the resulting high-temperature working fluid enters the main pipe 1 and is then discharged from it. A first insulation layer can be fitted onto the outside of the main pipe 1, and this first insulation layer is fixedly connected to the main pipe 1 to insulate it.

[0034] In a specific embodiment, this system is used for the thermal energy utilization of compressed carbon dioxide storage and building heating. The ground outlet of the pipeline is connected to a low-temperature heat pump system. A low-temperature fluid working medium at a certain temperature is introduced into each branch pipe 2 at a certain speed, allowing the fluid working medium to flow through the vertical part 21 and the horizontal part 22 of each branch pipe 2, causing it to be heated by the ground and collect at the bottom of the main pipe 1, and then flow out through the insulated main pipe 1. The high-temperature fluid flowing out of the main pipe 1 is introduced into the heat pump system and used as a heat source for the heat pump evaporator. The high-temperature fluid is cooled down by the heat pump and restored to a low-temperature fluid, which is then introduced into the branch pipe 2 for a new round of heating. This cycle is repeated to form a closed-loop system for extracting heat from the medium-deep ground temperature, providing a stable heat source for the heat pump system, thereby providing a continuous heat supply for the discharge section of the compressed carbon dioxide system and the building heating system.

[0035] In another specific embodiment, this system is used for a multi-energy complementary heating system. The ground outlet of the pipe is connected to the heat pump heating system. Unlike the above embodiment, in this embodiment, the working fluid flowing into each branch pipe 2 can come from different energy systems, such as the heating fluid from a solar thermal collector system, the heating fluid from a municipal solid waste fuel heating system, or the heating fluid from a sewage heat exchange source. The carbon dioxide working fluid, after heat exchange with these different heat sources, flows through each branch pipe 2, carrying the same fluid at different temperatures, into the ground for heat exchange, and then flows into the heat pump system through the main pipe 1. This not only slows down the rate of geothermal energy loss and reduces the geothermal burden, but also facilitates the design of the heat pump heating system and achieves comprehensive utilization of multiple energy sources.

[0036] In another specific embodiment, the system is used for power generation. Taking a dual-cycle power generation system (organic working fluid Rankine cycle system) as an example, the ground outlet of the pipeline is connected to the dual-cycle power generation system. A low-temperature working fluid at a certain temperature is introduced into each branch pipe 2 at a certain speed, allowing the working fluid to flow through the vertical part 21 and the horizontal part 22 of each branch pipe 2. The fluid is heated by the ground and reaches a certain temperature, undergoing a phase change to generate steam, which collects at the bottom of the main pipe 1 and then flows out through the insulated main pipe 1. The steam flowing out of the main pipe 1 is introduced into the power generation system, driving the turbine to rotate, which in turn drives the generator to generate electricity. After the steam is depressurized by the turbine, it returns to a low-temperature fluid and is then introduced into the branch pipe 2 for a new round of heating and evaporation. This cycle repeats, forming a closed-loop system for medium-deep geothermal heat extraction, providing a continuous and stable supply of steam to the power generation system. When using this system for power generation, a large geothermal extraction depth is required to ensure a sufficiently high temperature for the working fluid to evaporate.

[0037] In other embodiments, the main pipe 1 serves as a cryogenic working fluid injection pipe, and the branch pipe 2 serves as a high-temperature working fluid return pipe. The cryogenic working fluid is injected from the main pipe 1, undergoes heat exchange within the formation, and the resulting high-temperature working fluid enters the branch pipe 2 and is then discharged from it. A second insulation layer can be fitted onto the outside of the branch pipe 2, and this second insulation layer is fixedly connected to the branch pipe 2 to insulate it.

[0038] In other embodiments, some of the branch pipes 2 can serve as cryogenic working fluid injection pipes, while the remaining branch pipes 2 and the main pipe 1 serve as high-temperature working fluid return pipes. A third insulation layer is fitted outside the high-temperature working fluid return pipes. The cryogenic working fluid is injected from the branch pipes 2 without the third insulation layer. The cryogenic working fluid exchanges heat inside the formation. The high-temperature working fluid formed after heat exchange enters the branch pipes 2 and the main pipe 1 with the third insulation layer and is then discharged.

[0039] In this application, branch pipe 2 and main pipe 1 can be used as low-temperature working fluid injection section or high-temperature working fluid return section according to different actual needs, so as to realize flexible extraction and replenishment of formation heat, thereby improving the sustainability of formation efficient heat exchange.

[0040] In some embodiments, the working fluid inside the branch pipe 2 and the main pipe 1 can be selected as liquid carbon dioxide fluid. In actual engineering implementation, other heat exchange working fluids, such as water or low-boiling-point organic working fluids, can also be used according to specific needs.

[0041] In this application, the term "multiple" refers to at least two or more, unless otherwise expressly defined. The terms "installed," "connected," "linked," and "fixed," etc., should be interpreted broadly. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "linked" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is 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.

Claims

1. A multi-connected closed-loop carbon dioxide formation heat exchange system, characterized in that: It includes a vertically arranged main pipe (1), and a branch pipe (2) is vertically arranged on the outside of the main pipe (1). The bottom end of the branch pipe (2) is fixedly connected to the side wall of the main pipe (1). The inside of the branch pipe (2) is connected to the inside of the main pipe (1). Multiple branch pipes (2) are arranged on the outside of the main pipe (1).

2. The multi-connected closed-loop carbon dioxide formation heat exchange system according to claim 1, characterized in that: The branch pipe (2) includes a vertical part (21), and a horizontal part (22) is fixedly connected to the bottom end of the vertical part (21). The vertical part (21) and the horizontal part (22) are in relative communication, and the horizontal part (22) is fixedly connected to the side wall of the main pipe (1).

3. The multi-connected closed-loop carbon dioxide formation heat exchange system according to claim 1, characterized in that: The outer side of the main tube (1) is covered with a first insulation layer.

4. The multi-connected closed-loop carbon dioxide formation heat exchange system according to claim 3, characterized in that: The working fluid is injected into the branch pipe (2). The temperature of the working fluid is lower than that of the formation. After the working fluid is heated inside the formation, it flows into the main pipe (1).

5. The multi-connected closed-loop carbon dioxide formation heat exchange system according to claim 1, characterized in that: The outer side of the branch pipe (2) is fitted with a second insulation layer.

6. The multi-connected closed-loop carbon dioxide formation heat exchange system according to claim 5, characterized in that: The circulating working fluid is injected into the main pipe (1). The temperature of the circulating working fluid is lower than the temperature inside the formation. After the circulating working fluid is heated inside the formation, it flows into the branch pipe (2).

7. The multi-connected closed-loop carbon dioxide formation heat exchange system according to claim 4 or 6, characterized in that: The circulating working fluid is liquid carbon dioxide.

8. The multi-connected closed-loop carbon dioxide formation heat exchange system according to claim 1, characterized in that: A third insulation layer is provided on the outside of some of the multiple branch pipes (2). A circulating working fluid is injected into the branch pipe (2) without the third insulation layer. The temperature of the circulating working fluid is lower than the temperature inside the formation. After the circulating working fluid is heated inside the formation, it flows into the branch pipe (2) with the third insulation layer.

9. The multi-connected closed-loop carbon dioxide formation heat exchange system according to claim 1, characterized in that: Multiple branch pipes (2) are connected in sequence to form a branch pipe (2) distribution frame, and the main pipe (1) is located at the center point of the branch pipe (2) distribution frame.

10. The multi-connected closed-loop carbon dioxide formation heat exchange system according to claim 1, characterized in that: A gap is left between the multiple branch pipes (2).

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