Phase change power generation system based on the reuse of abandoned mines

Abstract

The present invention relates to resource recycling technology, specifically a phase change power generation system based on the recycling of abandoned mines, including a double-layer pressure-surge tank, a pneumatic turbine, a generator set and several groups of U-shaped phase change tubes; the U-shaped phase change tubes are distributed and buried in the side walls of the tunnel and in the ground, the double-layer pressure-surge tank is provided with an inner cavity and an outer cavity, the inner cavity stores high-temperature and high-pressure phase change medium and transports it to the pneumatic turbine to drive its blades to rotate and do work, the pneumatic turbine is connected to the main shaft of the generator set, and the generator set transmits the electric energy to the grid-connected device via a cable. The underground tunnel space is used as the layout space of the power generation equipment, and the characteristics of the phase change medium are used to absorb the formation temperature, and the free expansion forms a certain pressure as the power to drive the phase change medium circulation, without energy multi-stage conversion links and multi-stage transmission processes, and the energy effective utilization rate is significantly enhanced.

Description

Technical Field

[0001] The invention relates to resource recycling technology, in particular to a phase change power generation system based on the recycling of abandoned mines. Background Art

[0002] When a mine is abandoned, it will cause many harms to the environment. For example, the residual methane and other gas gases in the abandoned mine strata will continue to be released into the atmosphere, causing a greenhouse effect; in addition, the stratum stress of abandoned mines is unstable, which can easily lead to stratum subsidence, and even cause geological disasters such as landslides and ground subsidence, resulting in economic losses. A large amount of manpower and material resources are invested in the early stage of mine construction, and the economic added value is high. If the abandoned mines can be reused, it will save energy and reduce environmental disasters, and it is also a favorable way for human society to achieve long-term economic benefits. Taking into account the burial depth of abandoned mines and the changes in geothermal gradients, the reuse technology of geothermal resource mining for deep abandoned mines is an important technology with low economic cost, green environmental protection and sustainable development. It is also an important means to promote economic development, employment and sustainable development in mining areas.

[0003] In response to the problem of geothermal resource exploitation in abandoned mines, researchers from industry enterprises and scientific research institutes have proposed a variety of solutions, such as an abandoned mine geothermal-photothermal coupling power generation system and a power generation method thereof (CN114704343A), in which an underground water intake device is installed in the abandoned mine and pipelines are laid, and the working fluid is transmitted to a dual-working fluid heat exchanger through the surface solar thermal panels and the underground water intake device. The steam generated by the dual-working fluid heat exchanger is transported to the generator set for power generation, in order to achieve the reuse of the abandoned mine; an indirect heating device for abandoned mines and a method for heating using the device (CN111237849A), in which a heating pipeline consisting of an insulating inner tube and a heat-conducting outer tube is set in the abandoned mine and connected to a heat exchanger, and a prepared circulating heat-conducting fluid is injected into the heating pipeline, so as to indirectly obtain geothermal energy from the abandoned mine strata, and the flow of the circulating heat-conducting fluid is promoted by a circulating water pump to achieve heat exchange and utilization in the heat exchanger. A method for multi-stage in-situ power generation of deep geothermal resources based on the reuse of abandoned coal mines (CN118346552A), which injects a suitable working fluid into a circulating pipeline pre-buried in the goaf, and then uses the geothermal resources collected in the goaf to evaporate the organic circulating working fluid to generate steam to drive the in-situ generator set to achieve the power generation process.

[0004] In summary, the current coordinated development process of abandoned mine reuse technology and geothermal resource exploitation technology mostly adopts the layout of different forms of pipelines and the injection of required working fluids, realizes the exploitation and transportation of geothermal resources through working fluid circulation, and transfers the heat carried by the working fluid to water or water vapor in the heat exchanger for power generation or other forms of secondary utilization. In this process, the working fluid injection link and the working fluid circulation link both require different forms of energy drive. Although the reuse technology of abandoned mines has been realized, there are many processes involved in the exploitation, transportation and conversion of geothermal resources. There is a multi-stage transfer process of heat, and there is also a process of converting thermal energy to potential energy; potential energy to kinetic energy and thermal energy, and then from thermal energy to kinetic energy and electrical energy, which is easy to cause heat dissipation. Since the burial depth of most mines is about 1,000 meters, the formation temperature is 45~60℃, the heat convection and heat transfer efficiency are relatively low, and the heat dissipation caused by the multi-stage conversion of energy is the main factor leading to the low actual exploitation efficiency of geothermal resources and the high cost of exploitation. Summary of the invention

[0005] In order to solve the above-mentioned problems of the cost, energy conversion technology, efficiency, etc. of energy recycling in abandoned mines, the present invention provides a phase change power generation system based on the recycling of abandoned mines, in which underground phase change medium is pre-buried in the abandoned mine stratum to generate heat convection with the stratum, and the phase change medium undergoes a phase change from liquid to gas, thereby causing pressure imbalance in the pipeline, and the pressure difference is used to drive the gaseous phase change medium to circulate, drive the turbine unit to operate, and then drive the generator set to generate electricity. During the whole process, the circulation of the phase change medium does not require external energy drive, but only relies on the pressure difference formed by its own phase transformation; and the process has no multi-stage transfer and conversion of energy, which improves the utilization efficiency of geothermal resources; during the operation of the entire system, there is no need for any external energy to drive the medium circulation, and there are no energy-consuming components and no pollutant emissions in any form. While being green and environmentally friendly, it also saves energy and improves the underground geothermal storage efficiency. The technical solutions adopted by the present invention are as follows:

[0006] A phase change power generation system based on the reuse of abandoned mines comprises a double-layer pressure-surge tank, a pneumatic turbine, a generator set and a plurality of groups of U-shaped phase change tubes; the U-shaped phase change tubes are distributed and buried in the side walls of the tunnel and in the ground; the double-layer pressure-surge tank is provided with an inner cavity and an outer cavity; the inner cavity stores high-temperature and high-pressure phase change medium and transports it to the pneumatic turbine to drive its blades to rotate and do work; the pneumatic turbine is connected to the main shaft of the generator set; the generator set transports the electric energy to a grid-connected device via a cable; the grid-connected device is installed outside the mine; the phase change medium is cooled and depressurized in the pneumatic turbine and then flows back to the outer cavity, and then transported back to the U-shaped phase change tube; the phase change medium absorbs the heat of the tunnel side walls and the ground in the U-shaped phase change tube, and is transported to the inner cavity of the double-layer pressure-surge tank after heating and pressure increase.

[0007] In the above-mentioned phase change power generation system based on the reuse of abandoned mines, the U-shaped phase change tube is U-shaped as a whole, including an inlet end and an outflow end. The inlet ends are respectively connected in parallel to the return pipeline, and the return pipeline is connected to the outer cavity to transport the phase change medium after cooling and pressure reduction; the outflow ends are respectively connected in parallel to the discharge pipeline, and the discharge pipeline is connected to the inner cavity to transport the high-temperature and high-pressure phase change medium.

[0008] In the above-mentioned phase change power generation system based on the reuse of abandoned mines, a two-way feedback pressure regulating valve I and a vortex tube are connected in sequence between each outflow end and the return pipeline, the valve outlet of the two-way feedback pressure regulating valve I is connected to the high-pressure inlet of the vortex tube, the high-pressure outlet of the vortex tube is connected to the return pipeline through a section of curved pipe, the cold end outlet of the vortex tube is connected to the inflow end, and a one-way valve is arranged between the two to prevent backflow.

[0009] The above-mentioned phase change power generation system based on the reuse of abandoned mines has a one-way valve installed on each inflow end and near the connection with the return pipeline, and a one-way valve installed on the discharge pipeline and near the connection with the U-shaped phase change tube; the U-shaped phase change tube is placed in a cement pier.

[0010] In the above-mentioned phase change power generation system based on the reuse of abandoned mines, the U-shaped phase change tubes are provided with sedimentation troughs on the pipelines, wherein the sedimentation troughs of the U-shaped phase change tubes in the side walls of the tunnels are all protruding downward, and the sedimentation troughs of the U-shaped phase change tubes in the tunnel ground are all protruding towards the side close to the ground.

[0011] In the above-mentioned phase change power generation system based on the reuse of abandoned mines, the left side of the bidirectional feedback pressure regulating valve I is a valve inlet, and the right side is a valve outlet. A valve core, a spring and various cavity flow channels are arranged in the valve body; the valve core includes a rear plug, a connecting rod and a front plug connected in sequence, and the cavity flow channel includes an inlet cavity, a side flow channel, a main flow channel, a pressure reducing cavity, an outlet cavity and a feedback flow channel;

[0012] The rear plug is used to cooperate with the opening and closing of the valve inlet. A partition is installed on the rear plug to divide the inlet cavity into a rear cavity and a front cavity, and the partition can be moved with the plug; the rear cavity can be connected to the valve inlet, and the rear cavity is connected to the side flow channel, and the side flow channel is connected to the main channel, the pressure relief chamber and the outlet cavity in turn. The front plug is used to open and close the pressure relief chamber, and a spring is installed between the front plug and the valve body to form a flow channel for the phase change medium; the outlet cavity is connected to the feedback flow channel, and the feedback flow channel is connected to the front cavity to form a feedback channel of the valve body.

[0013] In the above-mentioned phase change power generation system based on the reuse of abandoned mines, a heat insulation layer is arranged on the outer surface of the inner cavity, the lower end of the inner cavity is the heat-carrying phase change medium inlet, and the upper end is the heat-carrying phase change medium outlet, the lower end of the outer cavity is the reflux medium inlet, and the upper end is the reflux medium outlet; the heat-carrying phase change medium outlet is connected to the turbine inlet of the pneumatic turbine through a pipeline and a two-way feedback pressure regulating valve II is arranged on the pipeline, and a pressure reducing valve, a one-way valve and a two-way feedback pressure regulating valve III are installed between the reflux medium outlet and the reflux pipeline; the two-way feedback pressure regulating valve II and the two-way feedback pressure regulating valve III have the same structure as the two-way feedback pressure regulating valve I.

[0014] In the above-mentioned phase change power generation system based on the reuse of abandoned mines, the phase change medium can be any one of R141b (dichloromonofluoroethane), R142b (monochlorodifluoroethane), R134a (tetrafluoroethane), and R600a (isobutane).

[0015] The beneficial effects of the present invention are as follows: the underground tunnel space is used as the layout space for power generation equipment, the characteristics of the phase change medium are used to absorb the formation temperature, and the free expansion forms a certain pressure as the driving force for the phase change medium circulation, and various valve bodies are used to cooperate with each other to form a pressure difference between the pipeline and the U-shaped phase change tube, thereby realizing the automatic replenishment of the phase change medium. The system has no other energy-consuming components, and the phase change medium absorbs the heat of the formation and expands freely to form a driving force, directly driving the turbine unit to generate electricity, without multi-stage energy conversion links and multi-stage transmission processes, and the effective energy utilization rate is significantly enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention;

[0017] Figure 2 A lateral schematic diagram of the arrangement of a U-shaped phase change tube in a lane according to an embodiment of the present invention;

[0018] Figure 3 It is a schematic diagram of the structure of a double-layer pressure-stabilizing tank according to an embodiment of the present invention;

[0019] Figure 4 This is a schematic structural diagram of a U-shaped phase change tube on a lane side wall according to an embodiment of the present invention;

[0020] Figure 5 This is a schematic diagram of the structure of a U-shaped phase change tube on the tunnel surface according to an embodiment of the present invention;

[0021] Figure 6 Schematic diagram of the structure of a bidirectional feedback pressure regulating valve according to an embodiment of the present invention.

[0022] In the figure: 1 is the top of the coal seam, 2 is the shaft, 3 is the tunnel, 4 is the bottom of the coal seam, 5 is a double-layer pressure-stabilizing tank, 6 is a pneumatic turbine, 7 is a generator set, 8 is a grid-connected device, 9 is a U-shaped phase change tube, 10 is a discharge pipeline, 11 is a return pipeline, 12 is a two-way feedback pressure regulating valve I, 13 is a vortex tube, 14 is a pressure reducing valve, 15 is a two-way feedback pressure regulating valve II, 16 is a two-way feedback pressure regulating valve III, 51 is an inner cavity, 52 is an outer cavity, 53 is a heat-carrying phase change medium inlet, 54 is a heat-carrying phase change medium outlet, 55 is a return medium inlet, 56 is Reflux medium outlet, 61 is the turbine inlet, 62 is the turbine outlet, 91 is the inflow end, 92 is the outflow end, 93 is the sedimentation tank, 94 is the elbow, 95 is the cement pier, 1201 is the rear plug, 1202 is the partition, 1203 is the connecting rod, 1204 is the front plug, 1205 is the spring, 1206 is the side flow channel, 1207 is the main flow channel, 1208 is the pressure reduction chamber, 1209 is the outlet chamber, 1210 is the feedback flow channel, 1211 is the valve inlet, 1212 is the valve outlet, 1213 is the rear chamber, and 1214 is the front chamber. DETAILED DESCRIPTION

[0023] The technical contents of the present invention are explained in detail below in conjunction with the accompanying drawings. The following embodiments are all illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical terms used have the same meanings as those commonly understood by those skilled in the art to which the present application belongs. It should be noted that the terms used are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application.

[0024] Taking a large number of deep mines in the central and western regions of my country as an example, under the influence of geothermal gradient, the temperature of the rock strata where these deep mines are located is between 40 and 60 degrees Celsius all year round, which is a valuable geothermal resource. Using the underground space of deep mines and the temperature of the rock strata where they are located to carry out underground power generation technology is a beneficial way to reuse deep abandoned mines.

[0025] The main structure of the abandoned mine is the coal seam top 1, the shaft 2, the tunnel 3 and the coal seam bottom 4. This embodiment is a phase change power generation system based on the reuse of abandoned mines. Figure 1As shown, it is mainly arranged in the tunnel 3, including a double-layer pressure-stabilizing tank 5, a pneumatic turbine 6 (such as a steam turbine), a generator set 7 and a plurality of groups of U-shaped phase change tubes 9. The U-shaped phase change tubes 9 are buried in the side walls and the ground of the tunnel 3, and contain a phase change medium. The phase change medium is heated and pressurized by heat exchange with the side walls and the ground, thereby driving the entire system to complete energy conversion. The inner cavity 51 of the double-layer pressure-stabilizing tank 5 is a high-temperature and high-pressure phase-change medium, which is transported to the pneumatic turbine 6 to drive its blades to rotate and do work. The transmission shaft of the pneumatic turbine 6 is connected to the main shaft of the generator set 7 through a coupling, an anti-reverse bearing joint, etc., to convert mechanical energy into electrical energy. The generator set 7 transports the electrical energy to the grid-connected device 8 via a cable. The grid-connected device 8 is installed outside the well; the phase-change medium is cooled and reduced in pressure in the pneumatic turbine 6 (most of it is a low-temperature and low-pressure gas, and less is a liquid), and then flows back to the outer cavity 52 of the double-layer pressure-stabilizing tank 5, and then transported to the U-shaped phase change tube 9. The phase-change medium absorbs the heat from the side walls of the tunnel 3 and the ground in the U-shaped phase change tube 9, and is transported to the inner cavity 51 of the double-layer pressure-stabilizing tank 5 after heating and increasing the pressure. This cycle completes energy collection.

[0026] The temperature of the phase change medium is selected according to the well depth and the water temperature of the geothermal layer. The boiling point of the phase change medium should be lower than the mining temperature of the geothermal layer. The phase change medium can be any one of R141b dichloromonofluoroethane, R142b monochlorodifluoroethane, R134a tetrafluoroethane, R600a isobutane, etc.

[0027] Specific, combined Figure 1 , Figure 2 , Figure 4 and Figure 5 The U-shaped phase change tube 9 is U-shaped as a whole and is placed in the cement pier 94. There are multiple groups arranged in the side wall and ground of the tunnel 3. During installation, the temperature, heat flux density and formation water flow rate of the abandoned mine wall and the ground heat extraction stratum are first tested to optimize the drilling diameter, drilling depth and hole density; according to the actual depth of the abandoned mine, support characteristics, rock structure strength and wall and ground stability, the side wall and ground curing method of the tunnel 3 is selected. It can be based on the layout of the steel skeleton, and cement mortar with relatively good thermal conductivity is used for grouting and curing. After the waste is cured, holes are drilled in the side wall and the ground to install the U-shaped phase change tube 9. The cement used in the cement pier 95 should have good thermal conductivity and waterproofness, and the length of the cement pier 95 should be consistent with the drilling depth.

[0028] Each U-shaped phase change tube 9 includes an inflow end 91 and an outflow end 92. The inflow end 91 is connected in parallel to the return pipe 11, which is connected to the outer cavity 52 of the double-layer pressure-regulating tank 5 to transport the phase change medium after cooling and pressure reduction. The outflow end 92 is connected in parallel to the discharge pipe 10, which is connected to the inner cavity 51 of the double-layer pressure-regulating tank 5 to transport the high-temperature and high-pressure phase change medium. The overall flow direction of the phase change medium is from the U-shaped phase change tube 9 in the ground of the lane 3 to the U-shaped phase change tube 9 in the side wall, combined with Figure 2The outflow ends 92 of the U-shaped phase change tubes 9 in the side walls of the tunnel 3 are collected in the discharge pipeline 10 and then transported to the double-layer pressure-stabilizing tank 5 through the pipeline above the tunnel 3.

[0029] Furthermore, a two-way feedback pressure regulating valve Ⅰ12 and a vortex tube 13 are sequentially connected between each outflow end 92 and the return line 11. The valve outlet 1212 of the two-way feedback pressure regulating valve Ⅰ12 is connected to the high-pressure inlet of the vortex tube 13. The high-pressure outlet of the vortex tube 13 is connected to the return line 11 through a section of elbow pipe. The two-way feedback pressure regulating valve Ⅰ12 allows a weak pressure to be stored in the U-shaped phase change tube 9. This pressure value is determined by the starting pressure of the vortex tube 13. The cold end outlet of the vortex tube 13 is connected to the inflow end 91 and a one-way valve is set between the two to avoid backflow. The starting pressure of the one-way valve here is consistent with the starting pressure of the two-way feedback pressure regulating valve Ⅰ12. In order to prevent the pressure fluctuation of the gas-liquid coexistence state from causing backflow and causing the entire system to fail, a one-way valve is installed on each inflow end 91 and near the connection with the return line 11, and a one-way valve is installed on the discharge line 10 and near the connection with the U-shaped phase change tube 9. When the two-way feedback pressure regulating valve Ⅰ12 is started, the pressure of the U-shaped phase change tube 9 is slightly reduced due to the outflow of the phase change medium, and the one-way valve is opened, and the low-temperature gaseous medium or liquid medium is added to the U-shaped phase change tube 9 through the return line 11 to provide circulation power for thermal expansion. When the phase change medium flows through the vortex tube 13, high-speed rotation and separation will occur, forming two kinds of cold and hot airflows. The high-temperature airflow enters the discharge line 10 through the high-pressure outlet of the vortex tube 13, and according to the properties of the phase change medium, the cold airflow in the vortex tube 13 will flow into the inlet end 91 through its cold end outlet in the form of a liquid phase medium. In this embodiment, the working range of the vortex tube 13 can be selected from 0.3~1.0MPa.

[0030] A settling tank 93 is provided on the pipeline of the U-shaped phase change tube 9. However, depending on the installation position, the settling tank 93 of the U-shaped phase change tube 9 in the side wall of the lane 3 and in the ground is slightly different. The settling tank 93 of the U-shaped phase change tube 9 in the side wall is all convex downward. This is because the phase change medium is mainly present at the bottom of the U-shaped phase change tube 9. When a gas plug occurs, the gas-liquid two-phase mixed medium flows forward. When it flows through the settling tank 93, the cross-sectional area increases. Under the pressure and its own gravity, the surface tension of the liquid phase medium is difficult to maintain its flow state, so it flows into the settling tank 93. The settling tank 93 of the U-shaped phase change tube 9 in the ground is all convex near the left and right sides of the ground. When a gas plug occurs, the gas-liquid two-phase mixed medium flows up and down. Therefore, it will be enriched in the settling tank 93 under the gravity of the liquid phase medium itself, which does not affect the normal circulation of the gas phase medium in the U-shaped phase change tube 9.

[0031] Specifically, Figures 1 to 3As shown, the double-layer pressure-stabilizing tank 5 is a double-layer tank structure, the inner tank forms an inner cavity 51, which is used to store the heat-carrying phase-change medium from the U-shaped phase-change tube 9 to increase the pressure of the inner cavity 51, and the space between the inner and outer tanks forms an outer cavity 52, which is used to store the phase-change medium after cooling and depressurization from the pneumatic turbine 6 and transport it back to the U-shaped phase-change tube 9 through the return pipe 11. The outer surface of the inner cavity 51 is provided with a heat-insulating layer, the lower end of the inner cavity 51 is a heat-carrying phase-change medium inlet 53, and the upper end is a heat-carrying phase-change medium outlet 54, the lower end of the outer cavity 52 is a reflux medium inlet 55, and the upper end is a reflux medium outlet 56, and flange joints are provided at each inlet and outlet to ensure sealing and connection reliability. The heat-carrying phase-change medium outlet 54 is connected to the turbine inlet 61 of the pneumatic turbine 6 via a pipeline, and a two-way feedback pressure regulating valve II 14 is arranged on the pipeline. A pressure reducing valve 15, a one-way valve and a two-way feedback pressure regulating valve III 16 are installed between the reflux medium outlet 56 and the reflux pipeline 11. The reflux medium is stored and buffered in the outer cavity 52 to slow down the flow rate, and at the same time, the pressure in the outer cavity 52 is gradually increased.

[0032] The pressure reducing valve 15 is used to prevent the impact of high-pressure and high-speed airflow from causing pipeline vibration and impact on system components. The starting pressure of the pressure reducing valve 15 should be higher than the starting pressure of the one-way valve here, and the starting pressure of the one-way valve here is consistent with the two-way feedback pressure regulating valve III 16. The starting pressure of the one-way valve here is higher than the starting pressure of the one-way valves in other pipelines. When the enrichment pressure of the phase change medium in the outer cavity 52 is higher than the starting pressure of the pressure reducing valve 15, the pressure reducing valve 15 opens, and the phase change medium flows into the U-shaped phase change tube 9 through the reflux pipeline 11. When the internal pressure of the pressure-resistant U-shaped phase change tube 9 is lower than the pressure of the reflux pipeline 11, the phase change medium will be automatically replenished into the pressure-resistant U-shaped phase change tube 9 by the reflux pipeline 11 under the drive of the pressure difference.

[0033] The two-way feedback pressure regulating valve I12, two-way feedback pressure regulating valve II14 and two-way feedback pressure regulating valve III16 have the same structure, but the working pressure is different, so the two-way feedback pressure regulating valve I12 is taken as an example for structural description. The left side of the two-way feedback pressure regulating valve I12 is a valve inlet 1211, and the right side is a valve outlet 1212. The valve body is provided with a valve core, a spring 1205 and various cavity flow channels. Figure 6 As shown, the valve core includes a rear plug 1201, a connecting rod 1203 and a front plug 1204 connected in sequence, and the cavity and flow channel mainly include an inlet cavity, a side flow channel 1206, a main flow channel 1207, a decompression cavity 1208, an outlet cavity 1209 and a feedback flow channel 1210. The valve core moves under the action of a spring 1205 and fluid pressure to realize the opening and closing of the bidirectional feedback pressure regulating valve Ⅰ12 to regulate the pressure. The "front" here is established by the direction of the phase change medium flow, and the opposite direction is "back".

[0034] The rear plug 1201 is used to cooperate with the opening and closing of the valve inlet 1211. The rear plug 1201 is equipped with a partition 1202 to divide the inlet cavity into a rear cavity 1213 and a front cavity 1214. The partition 1202 can move with the plug 1201. The rear cavity 1213 can be connected to the valve inlet 1211, and the rear cavity 1213 is connected to the side flow channel 1206. The side flow channel 1206 is connected to the main flow channel 1207, the pressure relief cavity 1208 and the outlet cavity 1209 in sequence. The front plug 1204 is used to open and close the pressure relief cavity 1208. The spring 1205 is installed between the front plug 1204 and the valve body to form a circulation channel for the phase change medium; the outlet cavity 1209 is connected to the feedback flow channel 1210, and the feedback flow channel 1210 is connected to the front cavity 1214 to form a feedback channel of the valve body.

[0035] The phase change medium is enriched at the valve inlet 1211. When the pressure is higher than the pressure of the spring 1205, the phase change medium squeezes the valve core to move rightward to flow into the rear chamber 1213, and then passes through the side channel 1206, the main channel 1207, the pressure reduction chamber 1208, and the outlet chamber 1209 to the valve outlet 1212. The radial dimension of the pressure reduction chamber 1208 is larger than the radial dimension of the main channel 1207, which is used to increase the cross-sectional area, reduce the flow rate, and avoid the impact of the high-speed phase change medium on the valve body. A small amount of phase change medium in the outlet chamber 1209 flows into the front chamber 1214 through the feedback channel 1210. When there is a pressure difference between the rear chamber 1213 and the front chamber 1214, the partition 1202 moves, thereby adjusting the opening size of the rear plug 1201 and the valve inlet 1211 to achieve feedback regulation.

[0036] The above are only preferred implementations of the present application. It should be pointed out that for ordinary technicians in this technical field, several changes or improvements can be made without departing from the principles of the present application. These changes or improvements should also be regarded as the scope of protection of the present application.

Claims

1. A phase change power generation system based on the reuse of abandoned mines, characterized by: It comprises a double-layer pressure-stabilizing tank (5), a pneumatic turbine (6), a generator set (7) and a plurality of groups of U-shaped phase change tubes (9); The U-shaped phase change tubes (9) are distributed and buried in the side walls of the tunnel (3) and in the ground. The double-layer pressure-stabilizing tank (5) is provided with an inner cavity (51) and an outer cavity (52). The inner cavity (51) stores high-temperature and high-pressure phase change medium and transports it to the pneumatic turbine (6) to drive its blades to rotate and perform work. The pneumatic turbine (6) is connected to the main shaft of the generator set (7). The generator set (7) transports the electric energy to the grid-connected device (8) via a cable. The grid-connected device (8) is installed outside the well. The phase change medium is cooled and depressurized in the pneumatic turbine (6) and then flows back to the outer cavity (52). Thereafter, it is transported back to the U-shaped phase change tube (9). The phase change medium absorbs heat from the side walls of the tunnel (3) and the ground in the U-shaped phase change tube (9). After being heated and pressurized, it is transported to the inner cavity (51) of the double-layer pressure-stabilizing tank (5). The U-shaped phase change tube (9) is U-shaped as a whole, and comprises an inflow end (91) and an outflow end (92); the inflow end (91) is respectively connected in parallel to a return pipeline (11), and the return pipeline (11) is connected to the outer cavity (52) to transport the phase change medium after cooling and pressure reduction; the outflow end (92) is respectively connected in parallel to a discharge pipeline (10), and the discharge pipeline (10) is connected to the inner cavity (51) to transport the high-temperature and high-pressure phase change medium; A two-way feedback pressure regulating valve I (12) and a vortex tube (13) are sequentially connected between each outflow end (92) and the return pipeline (11); the valve outlet (1212) of the two-way feedback pressure regulating valve I (12) is connected to the high-pressure inlet of the vortex tube (13); the high-pressure outlet of the vortex tube (13) is connected to the return pipeline (11) via a curved pipe; the cold end outlet of the vortex tube (13) is connected to the inflow end (91), and a one-way valve is provided between the two to prevent backflow.

2. The phase change power generation system based on abandoned mine reuse according to claim 1 is characterized in that: A one-way valve is installed on each inflow end (91) near the connection with the return pipeline (11), and a one-way valve is installed on the discharge pipeline (10) near the connection with the U-shaped phase change tube (9); the U-shaped phase change tube (9) is placed in the cement pier (94).

3. The phase change power generation system based on abandoned mine reuse according to claim 1 is characterized in that: The U-shaped phase change tube (9) is provided with a sedimentation trough (93) on the pipeline, wherein the sedimentation trough (93) of the U-shaped phase change tube (9) in the side wall of the tunnel (3) is protruding downward, and the sedimentation trough (93) of the U-shaped phase change tube (9) in the ground of the tunnel (3) is protruding in the direction close to the ground.

4. The phase change power generation system based on abandoned mine reuse according to claim 1 is characterized in that: The bidirectional feedback pressure regulating valve I (12) has a valve inlet (1211) on the left side and a valve outlet (1212) on the right side, and a valve core, a spring (1205) and cavity flow channels are arranged in the valve body; the valve core comprises a rear plug (1201), a connecting rod (1203) and a front plug (1204) which are connected in sequence, and the cavity flow channels comprise an inlet chamber, a side flow channel (1206), a main flow channel (1207), a pressure reducing chamber (1208), an outlet chamber (1209) and a feedback flow channel (1210); The rear plug (1201) is used to cooperate with the opening and closing valve inlet (1211). A partition (1202) is installed on the rear plug (1201) to divide the inlet cavity into a rear cavity (1213) and a front cavity (1214). The partition (1202) can be moved behind the plug (1201); the rear cavity (1213) can be connected to the valve inlet (1211), and the rear cavity (1213) is connected to the side flow channel (1206), and the side flow channel (1206) is connected in sequence. The valve body comprises a main flow channel (1207), a pressure reducing chamber (1208) and an outlet chamber (1209); a front plug (1204) is used to open and close the pressure reducing chamber (1208); a spring (1205) is installed between the front plug (1204) and the valve body, thereby forming a flow channel for the phase change medium; the outlet chamber (1209) is connected to a feedback flow channel (1210), and the feedback flow channel (1210) is connected to the front chamber (1214), thereby forming a feedback channel of the valve body.

5. The phase change power generation system based on abandoned mine reuse according to claim 1 is characterized in that: The outer surface of the inner cavity (51) is provided with a heat insulating layer. The lower end of the inner cavity (51) is a heat carrier phase change medium inlet (53), and the upper end is a heat carrier phase change medium outlet (54). The lower end of the outer cavity (52) is a return medium inlet (55), and the upper end is a return medium outlet (56). The heat carrier phase change medium outlet (54) is connected to the turbine inlet (61) of the pneumatic turbine (6) via a pipeline, and a two-way feedback pressure regulating valve II (14) is provided on the pipeline. A pressure reducing valve (15), a one-way valve, and a two-way feedback pressure regulating valve III (16) are installed between the return medium outlet (56) and the return pipeline (11). The two-way feedback pressure regulating valve II (14) and the two-way feedback pressure regulating valve III (16) have the same structure as the two-way feedback pressure regulating valve I (12).

6. The phase change power generation system based on abandoned mine reuse according to claim 1 is characterized in that: The phase change medium can be any one of R141b, R142b, R134a, and R600a.

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