Compressed air and waste heat hybrid energy storage system and method based on the shaft of a mine near retirement

Abstract

A compressed air and waste heat mixed energy storage system and method based on a mine shaft that is about to be retired, the system: a thermal energy storage mechanism is installed inside the shaft, and there are multiple vertically distributed hollow cylindrical tubes in the thermal energy storage mechanism; the cylindrical tubes are connected by flanges, and the flanges are connected to the sieve tray inside; each cylindrical tube is filled with solid heat storage materials, and an insulation layer is provided on the outer wall; there is a gap between the insulation layer and the inside of the shaft, and multiple groups of support units are provided on the outer circumference of the thermal energy storage mechanism; a sealing cover plate is provided on the top of the shaft, and a through hole for connecting the air inlet pipe and the air outlet pipe with a valve is provided on the sealing cover plate; the method: the stress performance of the shaft during the compressed air charging and discharging cycle stage is studied; the compressed air energy storage model in the shaft is determined; the compressed air energy storage model is numerically simulated and optimized; the grid independence of the optimized compressed air energy storage model is verified. The present invention combines a compressed air energy storage system with a thermal energy storage system to achieve the simultaneous storage and use of compressed air and waste heat.

Description

Technical Field

[0001] The invention relates to a compressed air and waste heat mixed energy storage system and method based on a mine shaft near retirement, belonging to the technical field of deep earth energy storage. Background Art

[0002] As the proportion of renewable energy in electricity production increases, the demand for energy storage has become increasingly prominent. Due to the spatiotemporal intermittency and instability of renewable energy sources such as wind and solar energy, the balance between energy supply and demand has become a major challenge facing related fields. Traditional power systems need to rely on energy storage technology to compensate for the fluctuations of renewable energy and ensure the stability and reliability of power system supply. In this context, various large-scale energy storage technologies, including Compressed Air Energy Storage (CAES) and Thermal Energy Storage (TES), have become hot topics of current research.

[0003] In recent years, with the implementation of the coal capacity reduction policy and the pressure of dual carbon target environmental protection, a large number of resource-depleted and low-capacity coal mines have been forced to close and retire. The underground space and facilities left behind in these mines have huge potential for resource recycling and can be transformed for new purposes, such as the aforementioned energy storage system. Using the underground space and facilities left behind in mines that are about to retire as the storage structure of CAES can not only solve the problem that traditional CAES requires large-scale gas storage facilities, but also provide new employment and economic development opportunities for the revitalization of resource-depleted mining areas and cities. CAES, as an effective large-scale and long-term energy storage method, compresses and stores air when electricity demand is low, and releases compressed air to drive turbines to generate electricity when electricity demand is peak, ensuring the stability of power system supply. In the above process, CAES generates a large amount of heat energy in the process of compressing air, and this heat converted from electrical energy and mechanical energy is usually wasted. In order to improve the overall efficiency of the system, this part of the heat can be stored and used to heat the air in the release stage when needed, realizing the storage of compressed air energy and the storage of waste heat accompanying the energy release process, and synergistically improving the power generation efficiency. This technology is called a heat-free energy recovery adiabatic compressed air energy storage system. Compared with the traditional compressed air energy storage system, this improved technology has not yet been put into operation in actual demonstration projects. The biggest challenge it faces is how to ensure the coordinated design of compressed air energy storage and waste heat storage. Summary of the invention

[0004] The present invention provides a compressed air and waste heat hybrid energy storage system and method based on the shaft of a mine that is about to be retired. The system and method can combine a compressed air energy storage system with a thermal energy storage system to form an efficient hybrid energy storage system, realize the simultaneous storage and use of compressed air and waste heat, and fully utilize the resource potential of the mine that is about to be retired.

[0005] In order to achieve the above-mentioned purpose, the present invention provides a compressed air and waste heat hybrid energy storage system based on a shaft of a mine that is about to be retired, comprising a shaft of a mine that is about to be retired, wherein a heat energy storage mechanism is installed inside the shaft of the mine that is about to be retired, wherein the heat energy storage mechanism comprises a plurality of hollow cylindrical tubes, wherein the plurality of cylindrical tubes are arranged axially along the shaft of the mine that is about to be retired from top to bottom, and are coaxial with the shaft of the mine that is about to be retired; adjacent cylindrical tubes are connected by flanges, and a sieve tray is connected inside the flange; each cylindrical tube is filled with a solid heat storage material, and an insulation layer is provided on the outer wall; there is a gap between the insulation layer and the inside of the shaft of the mine that is about to be retired;

[0006] A plurality of groups of support units are arranged on the outer circumference of a heat storage mechanism formed by a plurality of hollow cylindrical tubes, each group of support units includes a plurality of support rods and an annular shaft wall seat, the shaft wall seat is arranged circumferentially along the inner wall circumference of the shaft of the mine to be retired, and each group of support rods is arranged at equal intervals along the outer circumference of the heat storage mechanism at the height thereof, one end of each support rod is connected to the outer wall of the cylindrical tube, and the other end is connected to the shaft wall seat at an angle downward;

[0007] A sealing cover plate is provided on the top of the shaft of the temporarily retired mine, and a through hole for connecting the air inlet pipe and the air outlet pipe is opened on the sealing cover plate, and valves are provided on the air inlet pipe and the air outlet pipe; one end of the air inlet pipe and the air outlet pipe are both connected to the interior of the shaft of the temporarily retired mine, the other end of the air inlet pipe is connected to one end of the compressor, and the other end of the compressor is connected to the electric motor; the other end of the air outlet pipe is connected to one end of the turbine, and the other end of the turbine is connected to the generator.

[0008] Furthermore, a transparent inspection hatch is provided on the sealing cover plate.

[0009] Furthermore, the support units are arranged axially at equal intervals along the shaft of the mine to be retired, and their number is not less than the number of cylindrical tubes; and the support rods are I-beams.

[0010] Furthermore, the solid heat storage material filled inside each cylindrical tube is high melting point solid granite rock particles, and the particle size of the rock particles is larger than the sieve hole size of the sieve tray; the insulation layer arranged on the outer wall of each cylindrical tube is mineral rock wool, a low thermal conductivity insulation material.

[0011] Furthermore, the through hole opened on the sealing cover plate for connecting the air inlet pipe and the air outlet pipe is integrated, and a thermal energy storage mechanism sealing plate is provided above the sealing cover plate where the through hole is located. The lower end surface of the thermal energy storage mechanism sealing plate is attached to the upper end surface of the sealing cover plate, and a through hole is opened for the air inlet pipe and the air outlet pipe to pass through the interior of the thermal energy storage mechanism.

[0012] A method for storing energy based on a compressed air and waste heat mixed energy storage system in a mine shaft near retirement, comprising the following steps:

[0013] Step 1: Analyze the stress performance of the shaft of the mine to be retired during the compressed air charging and discharging cycle stage;

[0014] Step 2: Preliminarily determine the compressed air energy storage model in the shaft of the mine to be retired;

[0015] Step 3: Perform numerical simulation optimization on the compressed air energy storage model preliminarily determined in step 2;

[0016] Step 4: Verify the grid independence of the compressed air energy storage model optimized in step 3.

[0017] Furthermore, the specific process of step one is as follows:

[0018] (1-1) The weight of the heat storage mechanism is transferred to the shaft and rock mass of the retreating mine through each group of support rods and the shaft wall seat. The force on the shaft wall seat is: the self-gravity of the shaft wall seat and the single cylinder supported, the total gravity calculation value is taken, and the gravity forms a combined force N 1 ; Normal compressive stress on the bearing surface of the wellbore wall The combined force , is the angle between the pressure-bearing surface of the wellbore wall and the horizontal plane; the normal compressive stress of the pressure-bearing surface of the wellbore wall is Generates horizontal force, and the wellbore generates reaction force on the well wall ; Tangential stress between the bearing surface of the wellbore wall and the bedrock The combined force ;exist x and y Direction to establish the equilibrium equation:

[0019] (1);

[0020] Arranged:

[0021] (2);

[0022] Taking the bearing surface of the wellbore wall seat as the reference, the bearing area A of the wellbore wall seat per unit arc length within the circumference of the wellbore is:

[0023] , (3);

[0024] The stress on the bearing surface of the shaft wall must be less than the allowable strength of the surrounding rock of the shaft of the mine in the event of a mine withdrawal. , The size is affected by the surrounding rock type, hard and dense rock MPa, medium hard rock MPa, soft rock MPa; the normal compressive stress on the bearing surface of the wellbore wall is determined by equations (2) and (3): for:

[0025] (4);

[0026] Get the shaft wall width b The calculation formula is:

[0027] (5);

[0028] (1-2) When the mutual sliding between the pressure surface of the wellbore wall and the bedrock is small, the tangential stress between the pressure surface and the wall is approximately =0, according to formula (2):

[0029] (6);

[0030] Substituting formula (6) into formula (5) yields:

[0031] (7);

[0032] (1-3) When the force between the wellbore wall and the wellbore is small, it is approximately = 0, equation (5) degenerates into:

[0033] (8);

[0034] b The design critical value compromise is calculated using the following formula:

[0035] (9);

[0036] In the formula, the combined force N 1 The vertical pressure load per unit arc length along the outer perimeter of the shaft of the retreating mine is taken as the calculation standard, and the deadweight of the shaft wall is ignored and the following formula is used for calculation:

[0037] (10);

[0038] In the formula, is the vertical deadweight of the wellbore wall support, in MN; is the bulk density of a single cylinder in the thermal energy storage mechanism, in MN / m³; is the height of a single cylinder in the thermal energy storage mechanism, in m; is the outer radius of the cylindrical tube in the thermal energy storage mechanism; is the outer radius of the shaft of the mine to be retired, in m;

[0039] (1-4) Shaft wall seat height parametersh The calculation is done using the following formula:

[0040] (11);

[0041] In the formula, It is the shear strength of the wall base concrete, in MPa.

[0042] Furthermore, the specific process of step 2 is as follows:

[0043] (2-1) Determine the outer diameter, inner diameter, depth and volume of the shaft of the mine to be retired based on the gas storage working pressure and operating pressure difference required by the compressed air energy storage power station with installed capacity; use medium-temperature thermal storage compressed air energy storage technology to determine the temperature of the compressed air entering the first hollow cylinder of the thermal energy storage mechanism in the shaft of the mine to be retired, and determine the inflation time, mass flow rate, gas storage time, compressed air storage temperature, expansion release time and mass flow rate during a complete cycle of 24-hour system operation;

[0044] (2-2) According to the thermal energy storage mechanism, the compressed air temperature at the compressor outlet is gradually reduced to a level suitable for the safe operation of compressed air energy storage. At the same time, the compression waste heat is stored at a high temperature, and the compressed air is reheated in the exhaust stage to increase the temperature, so as to achieve the requirements of lowering the compression temperature and increasing the expansion temperature. The length, diameter, material, external insulation material and internal heat storage material of multiple hollow cylinders in the thermal energy storage mechanism are determined; the aspect ratio parameter of the cylinder is defined :

[0045] (12).

[0046] Furthermore, the specific process of step three is as follows:

[0047] (3-1) Using ANSYS Fluent simulation software, the heat transfer numerical simulation of the operation process of the thermal energy storage mechanism was carried out and the heat transfer process was analyzed. Based on the simulation results, the model was optimized by adjusting the porosity of the solid heat storage material packed bed, the flow channel structure, the thickness of the insulation layer and the aspect ratio of the cylindrical tube;

[0048] (3-2) During the cooling and heating process of the compressed air fluid in the thermal energy storage mechanism of the mine shaft, the convective heat transfer follows the conservation of mass, momentum and energy equations. According to the User Guide of ANSYS Fluent software, the basic control equation is expressed as follows:

[0049] The mass conservation equation can also be expressed as a continuity equation in fluid mechanics, that is, the increase in the mass of a fluid microelement per unit time is equal to the net mass flowing into the microelement in the same interval of time. The differential expression of the mass conservation equation is as follows:

[0050] (13);

[0051] In the formula, t is the time item; is the Laplace operator, represents the dot product; is the density of compressed air; is the compressed air velocity vector; is the porosity of the solid heat storage material packed bed in the cylinder;

[0052] Momentum conservation means that the rate of change of momentum of the fluid in the microelement over time is equal to the sum of various external forces acting on the microelement. The momentum conservation equation is solved using the non-steady-state Reynolds averaged NS equation, which is expressed as follows:

[0053] (14);

[0054] In the formula, p is the air pressure; is the tangential stress tensor of the compressed air microelement; The external body force of the compressed air microelement; is the dynamic viscosity of compressed air; is a coefficient related to the packed bed parameters, and the calculation formula is as follows:

[0055] (15);

[0056] In the formula, is the average particle size of the solid heat storage material packed in the cylindrical drum;

[0057] According to the energy conservation equation, the energy equation of the heat transfer process is based on the assumption of local thermal equilibrium, and the porous medium heat and mass transfer theory is used for analysis. The calculation domain of the solid heat storage material packed bed in the cylindrical tube satisfies:

[0058] (16);

[0059] The computational domain of compressed air fluid satisfies:

[0060] (17);

[0061] In the formula, is the density of the solid heat storage material in the packed bed in the cylinder; is the total energy of the solid heat storage material packed in the cylindrical bed; are the thermal conductivity and corresponding temperature of the solid heat storage material packed in the cylindrical tube; are the thermal conductivity of compressed air and the corresponding temperature respectively; is the total energy of the compressed air fluid phase; are the fluid-solid convection heat transfer coefficient and heat transfer area, respectively; among them, the heat transfer area of ​​the porous medium in the solid packed bed The calculation is done using the following formula:

[0062] (18);

[0063] Convective heat transfer coefficient The calculation is as follows through its definition and the characteristic number correlation formula of the factors affecting the convective heat transfer coefficient:

[0064] (19);

[0065] The Ergun formula is used to calculate the pressure drop of compressed air passing through the packed bed in the cylindrical drum:

[0066] (20);

[0067] (3-3) The outer wall of the cylindrical tube in the thermal energy storage mechanism is an insulating surface, and the interior is a porous medium, that is:

[0068] (twenty one).

[0069] Furthermore, the specific process of step 4 is as follows:

[0070] (4-1) In ANSYS Fluent software, a thin layer structure is set by linking multilayer materials. The temperature dependence of compressed air and heat storage materials is set by custom functions UDF. The thermal conductivity of compressed air is the parameter under constant pressure. The custom function relationship between the thermal conductivity of 5Mpa compressed air and temperature is: y=0.0629x+26.717, x is temperature, unit is ℃; y is thermal conductivity, unit is m W·(m·K) –1 ;

[0071] (4-2) During the numerical model simulation calculation process, grid independence verification is performed to find the appropriate number of grids.

[0072] The present invention utilizes the shaft of a mine that is about to be retired as a place to store compressed air and thermal energy. By nesting a thermal energy storage mechanism inside the shaft of the mine that is about to be retired, a closed, high-pressure gas storage tank is formed, so that the compressed air energy storage system and the thermal energy storage system are combined to achieve the simultaneous storage and use of compressed air and waste heat. The thermal energy storage mechanism integrates and replaces the cooler, heat storage device, and reheater in the traditional compressed air energy storage system. The present invention effectively stores compressed air and the waste heat generated during its compression process, improves the overall efficiency of the system, provides a stable and reliable energy supply for the power grid, and promotes economic transformation in resource-depleted areas of mines that are about to be retired. At the same time, it reduces dependence on fossil fuels, reduces greenhouse gas emissions, and achieves both economic and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 It is a schematic diagram of the system structure of the present invention;

[0074] Figure 2 It is a partial cross-sectional schematic diagram of the system structure of the present invention;

[0075] Figure 3 It is a schematic diagram of the working principle of the system of the present invention;

[0076] Figure 4 It is a schematic diagram of a complete cycle process of the system operation in an embodiment of the present invention;

[0077] Figure 5 Schematic diagram of the temperature change process of the cooling and heating process in the embodiment of the present invention;

[0078] Figure 6 is a heat transfer numerical simulation model diagram in an embodiment of the present invention;

[0079] Figure 7 Schematic diagram of temperature distribution during the gas charging and discharging cycle in an embodiment of the present invention;

[0080] Figure 8 Schematic diagram of temperature change during the charging and discharging cycle in an embodiment of the present invention.

[0081] In the figure: 1, mine shaft for retirement, 2, heat storage mechanism, 3, cylinder, 4, sieve tray, 5, solid heat storage material, 6, insulation layer, 7, support rod, 8, shaft wall seat, 9, sealing cover plate, 10, air inlet pipe, 11, air outlet pipe, 12, compressor, 13, electric motor, 14, turbine, 15, generator, 16, inspection hatch, 17, sealing plate of heat storage mechanism. DETAILED DESCRIPTION

[0082] The present invention will be further described below in conjunction with the accompanying drawings.

[0083] like Figures 1 to 3As shown, a compressed air and waste heat hybrid energy storage system based on a shaft of a mine that is about to be retired comprises a shaft of a mine that is about to be retired, wherein a heat storage mechanism 2 is installed inside the shaft of the mine that is about to be retired, wherein the heat storage mechanism comprises a plurality of hollow cylindrical tubes 3, wherein the plurality of cylindrical tubes 3 are axially arranged from top to bottom along the shaft of the mine that is about to be retired, and are coaxial with the shaft of the mine that is about to be retired; adjacent cylindrical tubes 3 are connected by flanges, and a sieve tray 4 is connected inside the flange; each cylindrical tube 3 is filled with a solid heat storage material 5, and an insulation layer 6 is provided on the outer wall; and there is a gap between the insulation layer 6 and the inside of the shaft of the mine that is about to be retired;

[0084] A plurality of groups of support units are arranged on the outer circumference of the heat storage mechanism 2 formed by a plurality of hollow cylindrical tubes 3, each group of support units includes a plurality of support rods 7 and an annular shaft wall seat 8, the shaft wall seat 8 is arranged circumferentially along the inner wall circumference of the shaft 1 of the retreating mine, and each group of support rods 7 is arranged at equal intervals along the outer circumference of the heat storage mechanism 2 at the height thereof, one end of each support rod 7 is connected to the outer wall of the cylindrical tube 3, and the other end is connected to the shaft wall seat 8 at an angle downward;

[0085] A sealing cover plate 9 is provided at the top of the shaft 1 of the mine to be retired. A through hole is opened on the sealing cover plate 9 for connecting an air inlet pipe 10 and an air outlet pipe 11. Both the air inlet pipe 10 and the air outlet pipe 11 are provided with valves. One end of the air inlet pipe 10 and the air outlet pipe 11 are connected to the interior of the shaft 1 of the mine to be retired, the other end of the air inlet pipe 10 is connected to one end of a compressor 12, and the other end of the compressor 12 is connected to an electric motor 13. The other end of the air outlet pipe 11 is connected to one end of a turbine 14, and the other end of the turbine 14 is connected to a generator 15.

[0086] In order to facilitate observation of the situation in the shaft 1 of the mine to be retired, a transparent inspection hatch 16 is provided on the sealing cover plate 9 .

[0087] In order to further improve the supporting stability of the support unit for the thermal energy storage mechanism 2, the support units are arranged axially along the shaft 1 of the retreating mine at equal intervals, and their number is not less than the number of cylindrical tubes 3; the support rod 7 is an I-beam.

[0088] As a preferred embodiment, the solid heat storage material 5 filled inside each cylindrical tube 3 is high melting point solid granite rock particles, and the particle size of the rock particles is larger than the sieve hole diameter of the sieve tray 4; the insulation layer 6 arranged on the outer wall of each cylindrical tube 3 is mineral rock wool, a low thermal conductivity insulation material.

[0089] As a preferred embodiment, the through hole opened on the sealing cover plate 9 for connecting the air inlet pipe 10 and the air outlet pipe 11 is integrated, and a thermal energy storage mechanism sealing plate 17 is provided above the sealing cover plate 9 where the through hole is located. The lower end surface of the thermal energy storage mechanism sealing plate 17 is arranged in contact with the upper end surface of the sealing cover plate 9, and a through hole is opened for the air inlet pipe 10 and the air outlet pipe 11 to pass through the interior of the thermal energy storage mechanism 2.

[0090] During the charging stage, the valve on the outlet pipe 11 is closed, and the valve on the inlet pipe 10 is opened. The excess trough or abandoned wind and abandoned light drive the motor to inhale air and compress it into high-temperature and high-pressure gas, which is then pumped into the thermal energy storage mechanism 2 by the compressor 12 through the inlet pipe 10 with a built-in valve. After the high-temperature and high-pressure air enters the system, it flows axially from top to bottom through the cylindrical tubes 3 in different thermal energy storage mechanisms 2. Each time it passes through a cylindrical tube 3, the compressed air exchanges heat with the heat storage material and transfers the heat to the multi-stage solid heat storage filling material. The compressed air generates a partial temperature drop, and the captured compression heat is stored in the thermal energy storage mechanism 2 (TES system). After the heat is absorbed, the high-pressure and normal-temperature air is finally injected into the closed shaft 1 of the mine to be retired. After reaching the set pressure, the valve on the inlet pipe 10 is closed, and the high-pressure and normal-temperature air is stored in the shaft 1 of the mine to be retired.

[0091] During the exhaust phase, the valve on the air inlet pipe 10 is closed, and the valve on the air outlet pipe 11 is opened. The compressed air stored in the shaft 1 of the mine to be retired enters the solid heat storage material 5 of the multi-stage cylindrical tube 3 from bottom to top in the axial direction through the sieve tray 4 connected by the flange; the high-pressure and normal-temperature gas is heated step by step to become high-temperature and high-pressure gas that is easy to generate electricity, and then enters the turbine 14 through the air inlet pipe 10 with a built-in valve to drive the expander rotor to operate and generate electricity; as the compressed air temperature and pressure approach the atmosphere, it is discharged; the exhaust phase can continue until the air pressure accumulated in the shaft 1 of the mine to be retired reaches the set critical value. After this phase, if the material in the area of ​​the thermal energy storage mechanism 2 is still at a high temperature, after the exhaust phase, before the next inflation phase begins, each cylindrical tube 3 in the thermal energy storage mechanism 2 can be ventilated, inflated and cooled to restore the heat storage capacity of the solid heat storage material 5.

[0092] Example: The outer diameter of the mine shaft 1 is 10m, the inner diameter is 8m, the depth is about 1000m, the volume of the shaft is about 50000m3, the deadweight of each cylindrical tube 3 of the thermal energy storage mechanism 2 is 3.2MN, and the angle between the pressure surface of the shaft wall seat 8 and the horizontal plane is The geometric parameters of the wellbore wall seat 8 related to the wellbore surrounding rock are shown in Table 1:

[0093] Table 1 Wellbore wall seat design parameters

[0094] Surrounding rock Wall seat height / m Wall seat width / m sandstone 0.53 0.59 Fine sandstone, medium fissures 1.06 0.84 Mudstone, moderately fractured 2 1.03

[0095] By setting the gas storage working pressure of 5-10MPa and the operating pressure difference of about 5MPa, a compressed air energy storage power station with an installed capacity of about 100MW can be realized. The motor 13 of the compressed air energy storage system drives the compressor 12 to compress the air, and the exhaust temperature can reach up to 1000°C. The medium-temperature thermal storage compressed air energy storage technology adopted in this embodiment has a compressed air temperature of about 300°C entering the first cylindrical tube 3 of the wellbore thermal energy storage mechanism 2. In a complete cycle of 24-hour system operation, the inflation stage is 8 hours, the mass flow rate is about 30kg / s, the gas storage stage is 13 hours, the compressed air storage temperature is about 30°C, the expansion release stage is 3 hours, and the mass flow rate is about 90kg / s. Figure 4 As shown;

[0096] Setting the height of a single cylinder 3 of the wellbore thermal energy storage mechanism 2 m, aspect ratio , i.e. the outer radius of a single cylinder 3 m, 5 groups of single cylindrical tubes 3 are designed to be arranged in sequence from top to bottom along the axial direction of the wellbore; after passing through 5 levels of 500m cylindrical tubes 3, the approximately 300°C inlet compressed air is cooled to a surrounding rock temperature of approximately 30°C, and this sensible heat is stored in the solid heat storage material in the thermal energy storage mechanism 2. High-pressure and normal-temperature compressed air enters the storage space between the thermal energy storage mechanism 2 and the wellbore wall. During the expansion and release stage, the compressed air passes through the sieve holes from the storage space between the thermal energy storage mechanism 2 and the wellbore wall in reverse through 5 levels of 500m cylindrical tubes 3, taking away the heat stored in the solid heat storage material in the thermal energy storage mechanism 2, and reheating it to approximately 300°C. The temperature change design of the cooling and heating process of the 5-level 500m cylindrical tube 3 is as follows: Figure 5 As shown. In terms of structural materials, galvanized stainless steel is used to make the main structure of the cylinder 3, the exterior is made of low thermal conductivity insulation material mineral rock wool, and the internal heat storage material is designed to be high melting point solid granite rock particles, and the minimum particle size in the rock particle grading must be larger than the sieve hole diameter of the flange connection tray between the unit modules to ensure that the heat storage rock material in the cavity of the cylinder 3 is effectively supported by the flange tray;

[0097] The inlet of the wellbore is set as a velocity inlet and a temperature of 300°C according to the mass flow rate of compressed air and the geometric dimensions. The outlet is a pressure outlet, the relative pressure is set to 0Pa, and the temperature is 30°C. The interior is a porous medium, and the entire calculation area consists of two parts: the internal solid packed bed porous medium calculation domain and the solid calculation domain of the outer wall (galvanized stainless steel + insulation layer) of the thermal energy storage mechanism 2. All calculation domains use unstructured grids and ensure that the grid division is close to the actual physical scene. Near the contact surface, the grid needs to be locally refined to improve the calculation accuracy. For other porous medium rock areas that have little effect on the calculation results, a sparser grid can be used. Since the thickness of the outer wall of the thermal energy storage mechanism 2 and the insulation layer 6 is relatively thin, the thin layer structure is set by linking multi-layer materials in ANSYS Fluent, which can not only ensure the accuracy of the numerical simulation, but also reduce the demand for computing resources and simulation time;

[0098] During the simulation, the thermal physical parameters of compressed air, the heat storage material in the cylinder 3 of the thermal energy storage mechanism 2, and the outer wall of the thermal energy storage mechanism 2 are very important. The compressed air and the heat storage material adopt a custom function (UDF) to set their temperature dependence. The thermal conductivity of compressed air considers the parameters under a constant pressure of 5.0 MPa, as shown in Table 2:

[0099] Table 2 Thermal conductivity of air at different temperatures under constant pressure of 5.0 MPa

[0100] Air temperature / °C <![CDATA[Thermal conductivity / mW·(m·K) –1 > 20 28 40 29.23 60 30.48 80 31.73 100 32.99 120 34.26 140 35.53 160 36.79 180 38.05 200 39.3 220 40.54

[0101] Considering granite rock granular material with a density of 2700 kg / m³ as heat storage material, its thermophysical parameters are set as shown in Tables 3 and 4. The thermophysical parameters of the outer wall of the thermal energy storage mechanism 2, 10 mm galvanized stainless steel (thermal conductivity 55 W / (m·K)) and 0.1 m thick insulation material (thermal conductivity 0.045 W / (m·K)), are considered unchanged:

[0102] Table 3 Thermal conductivity of granite heat storage granular materials

[0103] Granite temperature / °C <![CDATA[Thermal conductivity / W·(m·K) –1 > 0 2.2 200 1.75

[0104] Table 4 Specific heat capacity of granite heat storage granular materials

[0105] Granite temperature / °C <![CDATA[Specific heat capacity / J·(kg·K) –1 > 100 830 150 870 200 920

[0106] In the numerical model calculation process, the mesh quality has a great influence on the accuracy and reliability of the simulation results. Generally speaking, the smaller the mesh unit size and the more units there are, the more accurate the calculation results are. However, if the number of meshes is too dense, the computer performance requirements will be higher, which will increase the amount of computer calculations and extend the calculation cycle; at the same time, for Fluent analysis software, the denser the mesh, the better the convergence. However, if the mesh quality is too sparse, although the amount of calculation is reduced, the calculation results deviate from the actual results and the error is too large. Therefore, in order to minimize the impact of the number of meshes on the calculation results, mesh independence verification is often performed in simulation calculations to find the appropriate number of meshes. The mesh independence of the above numerical model is verified, with a 7mm unit length mesh as a reference. The parameters for different mesh sizes are shown in Table 5:

[0107] Table 5 Grid size parameters of numerical model

[0108] Unit length / mm Grid quantity Number of nodes Relative error / % 5 6122555 6143282 3.97 7 5328026 5346849 - 10 3000050 3014562 4.96 20 750018 757261 9.85 50 120126 122911 12.89 100 30000 31460 13.55

[0109] From the analysis of the numerical simulation calculation results of different mesh sizes, when a 20 mm unit mesh length is selected and the total number of meshes is about 750,000, the calculation result error is about 10%, which can meet the engineering error requirements and reduce the calculation time and cost to a certain extent. Therefore, in this embodiment and the related numerical simulation calculation process, a 20 mm unit mesh is used, and the mesh is appropriately encrypted at the TES outer wall and the insulation layer 6 and the interface.

[0110] The present invention conducts a heat transfer numerical simulation analysis on the storage and use process of the thermal energy storage mechanism 2 (TES). The TES thermal storage design technical scheme, the temperature distribution and the change curve of the charging and discharging cycle process are shown in the following figure. Figure 6 , Figure 7 and Figure 8 As shown in the figure. It can be seen from the figure that during a single charging and discharging cycle, the temperature of the TES system gradually increases from the inlet to the outlet during the charging stage, and the closer to the inlet, the greater the temperature rise rate and the temperature value; on the contrary, during the exhaust stage, the temperature of the entire TES system gradually decreases. However, during a single charging and discharging cycle, the temperature of the TES system after exhaust is higher than that before charging, indicating that the TES should be ventilated and cooled after a single or multiple charging and discharging cycles to restore the heat storage capacity of the heat storage material; during a single charging and discharging cycle, a vertical temperature layer will appear in the TES system, affecting the heat transfer process of the TES system for gas storage and discharge, and there is a step-type hysteresis phenomenon in the temperature rise and fall during the charging and discharging process of different unit modules; the pressure drop △P of the TES system generally does not exceed 5000Pa; the aspect ratio parameter of the TES unit module affects the pressure drop and heat transfer. In order to reduce the pressure drop, the aspect ratio should be reduced, but in order to improve the heat transfer effect of the gas storage and discharge process, the aspect ratio can be increased, and it should be noted that there is a certain critical value for the aspect ratio, and the balance between pressure drop and heat transfer needs to be sought.

Claims

1. An energy storage method based on a compressed air and waste heat hybrid energy storage system in a mine shaft near retirement, characterized in that: The steps include: Step 1: Analyze the stress performance of the shaft of the mine (1) during the compressed air charging and discharging cycle stage; Step 2: preliminarily determine the compressed air energy storage model in the shaft of the mine to be retired (1); Step 3: Perform numerical simulation optimization on the compressed air energy storage model preliminarily determined in step 2; Step 4: Verify the grid independence of the compressed air energy storage model optimized in step 3; The specific process of step one is as follows: (1-1) The weight of the heat storage mechanism (2) is transferred to the shaft (1) and the rock mass of the impending mine through each group of support rods (7) and the shaft wall seat (8). The force applied to the shaft wall seat (8) is as follows: the self-gravity of the shaft wall seat (8) and the supported single cylindrical tube (3), the total gravity calculated value, and the gravity forming a resultant force N 1 ; Normal compressive stress on the pressure-bearing surface of the wellbore wall seat (8) The combined force , is the angle between the pressure-bearing surface of the wellbore wall seat (8) and the horizontal plane; the normal compressive stress on the pressure-bearing surface of the wellbore wall seat (8) Generates horizontal force, and the wellbore generates reaction force on the well wall ; Tangential stress between the bearing surface of the wellbore wall seat (8) and the bedrock The combined force ;exist x and y Direction to establish the equilibrium equation: （1）； Arranged: （2）； Taking the pressure-bearing surface of the wellbore wall seat (8) as a reference, the pressure-bearing area A of the wellbore wall seat (8) per unit arc length within the circumference of the wellbore is: ， （3）； The stress on the bearing surface of the shaft wall seat (8) must be less than the allowable strength of the surrounding rock of the shaft (1) of the mine to be retired. , The size is affected by the surrounding rock type, hard and dense rock MPa, medium hard rock MPa, soft rock MPa; The normal compressive stress on the pressure-bearing surface of the wellbore wall seat (8) is determined by equations (2) and (3): for: (4); Get the width of the shaft wall seat (8) b The calculation formula is: (5); (1-2) When the sliding between the bearing surface of the wellbore wall seat (8) and the bedrock is small, the tangential stress between the bearing surface and the wall seat is approximately =0, according to formula (2): （6）； Substituting formula (6) into formula (5) yields: （7）； (1-3) When the force between the wellbore wall seat (8) and the wellbore is small, it is approximately = 0, equation (5) degenerates into: （8）； b The design critical value compromise is calculated using the following formula: ， （9）； In the formula, the combined force N 1 The vertical pressure load per unit arc length along the outer perimeter of the shaft (1) of the retreating mine is taken as the calculation standard, and the deadweight of the shaft wall seat (8) is ignored and the following formula is used for calculation: （10）； In the formula, is the vertical deadweight supported by the wellbore wall seat (8), in MN; is the bulk density of a single cylindrical tube (3) in the thermal energy storage mechanism (2), in units of MN / m³; is the height of a single cylindrical tube (3) in the thermal energy storage mechanism (2), in meters; is the outer radius of the cylindrical tube (3) in the thermal energy storage mechanism (2); is the outer radius of the shaft of the temporary mine (1), in meters; (1-4) Shaft wall seat (8) Height parameters h The calculation is done using the following formula: （11）； In the formula, It is the shear strength of the wall base concrete, in MPa.

2. The energy storage method according to claim 1, characterized in that: The specific process of step 2 is as follows: (2-1) Determine the outer diameter, inner diameter, depth and volume of the shaft (1) of the mine to be retired based on the gas storage working pressure and operating pressure difference required by the compressed air energy storage power station with installed capacity; determine the temperature of the compressed air entering the first hollow cylinder (3) of the medium-temperature heat storage mechanism (2) of the shaft (1) of the mine to be retired using medium-temperature heat storage compressed air energy storage technology, and determine the inflation time, mass flow rate, gas storage time, compressed air storage temperature, expansion release time and mass flow rate during a complete cycle of 24-hour system operation; (2-2) According to the thermal energy storage mechanism (2), the temperature of the compressed air at the outlet of the compressor (12) is gradually reduced to a level suitable for the safe operation of the compressed air energy storage, and at the same time, the waste heat of compression is stored at a high temperature, and the compressed air is heated again in the exhaust stage to increase the temperature, so as to achieve the requirements of reducing the compression temperature and increasing the expansion temperature. The length, diameter, material, external insulation material and internal heat storage material of the multiple hollow cylindrical tubes (3) in the thermal energy storage mechanism (2) are determined; and the aspect ratio parameters of the cylindrical tubes (3) are defined. : （12）。 3. The energy storage method according to claim 2, characterized in that: The specific process of step three is as follows: (3-1) using simulation software to perform numerical heat transfer simulation on the operation process of the thermal energy storage mechanism (2) and analyze the heat transfer process, and based on the simulation results, optimizing the model by adjusting the porosity of the solid heat storage material filling bed, the flow channel structure, the thickness of the insulation layer (6) and the aspect ratio of the cylindrical tube (3); (3-2) During the cooling and heating process of the compressed air fluid in the shaft of the mine (1) thermal energy storage mechanism (2), the convective heat transfer follows the conservation of mass, momentum and energy equations. According to the User Guide of the simulation software, the basic control equation is expressed as follows: The differential expression of the mass conservation equation is as follows: （13）； In the formula, t is the time item; is the Laplace operator, represents the dot product; is the density of compressed air; is the compressed air velocity vector; is the porosity of the solid heat storage material packed bed in the cylindrical tube (3); The momentum conservation equation is solved using the unsteady-state Reynolds averaged NS equation, which is expressed as follows: （14）； In the formula, p is the air pressure; is the tangential stress tensor of the compressed air microelement; The external body force of the compressed air microelement; is the dynamic viscosity of compressed air; and is a coefficient related to the packed bed parameters, and the calculation formula is as follows: （15）； In the formula, is the average particle size of the solid heat storage material in the packed bed in the cylindrical tube (3); According to the energy conservation equation, the energy equation of the heat transfer process is based on the assumption of local thermal equilibrium and the porous medium heat and mass transfer theory is used to analyze the calculation domain of the solid heat storage material packed bed in the cylindrical tube (3): （16）； The computational domain of compressed air fluid satisfies: （17）； In the formula, is the density of the solid heat storage material in the packed bed in the cylindrical tube (3); is the total energy of the solid heat storage material packed in the cylindrical tube (3); are respectively the thermal conductivity and the corresponding temperature of the solid heat storage material packed in the cylindrical tube (3); are the thermal conductivity of compressed air and the corresponding temperature respectively; is the total energy of the compressed air fluid phase; are the fluid-solid convection heat transfer coefficient and heat transfer area, respectively; among them, the heat transfer area of ​​the porous medium in the solid packed bed The calculation is done using the following formula: （18）； Convective heat transfer coefficient The calculation is as follows through its definition and the characteristic number correlation formula of the factors affecting the convective heat transfer coefficient: （19）； The Ergun formula is used to calculate the pressure drop of compressed air passing through the packed bed in the cylindrical tube (3): （20）； (3-3) The outer wall of the cylindrical tube (3) in the thermal energy storage mechanism (2) is an insulating surface, and the interior is a porous medium, that is: （21）。 4. The energy storage method according to claim 3, characterized in that: The specific process of step 4 is as follows: (4-1) In the simulation software, a thin layer structure is set by linking multilayer materials. The temperature dependence of compressed air and heat storage materials is set by custom functions. The thermal conductivity of compressed air is the parameter under constant pressure. (4-2) During the numerical model simulation calculation process, grid independence verification is performed to find the appropriate number of grids.

5. The energy storage method based on the compressed air and waste heat hybrid energy storage system in the shaft of a mine to be retired according to claim 1, characterized in that: The energy storage system comprises a shaft of a mine to be retired (1), wherein a heat storage mechanism (2) is installed inside the shaft of the mine to be retired (1), wherein the heat storage mechanism (2) comprises a plurality of hollow cylindrical tubes (3), wherein the plurality of cylindrical tubes (3) are arranged axially from top to bottom along the shaft of the mine to be retired (1), and are coaxial with the shaft of the mine to be retired (1); adjacent cylindrical tubes (3) are connected via flanges, and a sieve tray (4) is connected inside the flange; each cylindrical tube (3) is filled with a solid heat storage material (5), and an outer wall is provided with a heat insulation layer (6); and there is a gap between the heat insulation layer (6) and the inside of the shaft of the mine to be retired (1); A plurality of groups of support units are provided on the outer circumference of a heat storage mechanism (2) formed by a plurality of hollow cylindrical tubes (3), each group of support units comprising a plurality of support rods (7) and an annular shaft wall seat (8), the shaft wall seat (8) being arranged circumferentially along the inner wall circumference of a shaft (1) of a mine to be retired, each group of support rods (7) being arranged at equal intervals along the outer circumference of the heat storage mechanism (2) at the height thereof, one end of each support rod (7) being connected to the outer wall of the cylindrical tube (3), and the other end being connected to the shaft wall seat (8) in a downwardly inclined manner; A sealing cover plate (9) is provided at the top of the shaft (1) of the mine to be retired. A through hole for connecting an air inlet pipe (10) and an air outlet pipe (11) is provided on the sealing cover plate (9). The air inlet pipe (10) and the air outlet pipe (11) are both provided with valves. One end of the air inlet pipe (10) and the air outlet pipe (11) are both in communication with the interior of the shaft (1) of the mine to be retired. The other end of the air inlet pipe (10) is connected to one end of a compressor (12). The other end of the compressor (12) is connected to an electric motor (13). The other end of the air outlet pipe (11) is connected to one end of a turbine (14). The other end of the turbine (14) is connected to a generator (15).

6. The energy storage method of the compressed air and waste heat hybrid energy storage system based on the shaft of a mine to be retired according to claim 5 is characterized in that: The sealing cover plate (9) is provided with a transparent inspection hatch (16).

7. The energy storage method based on the compressed air and waste heat hybrid energy storage system in the shaft of a mine to be retired according to claim 5 or 6, characterized in that: The support units are arranged at equal intervals along the axial direction of the shaft (1) of the mine to be retired, and their number is not less than the number of the cylindrical tubes (3); and the support rods (7) are I-beams.

8. The energy storage method based on the compressed air and waste heat hybrid energy storage system in the shaft of a mine to be retired according to claim 5 or 6, characterized in that: The solid heat storage material (5) filled inside each cylindrical tube (3) is high melting point solid granite rock particles, the particle size of the rock particles being larger than the sieve hole size of the sieve hole tray (4); the thermal insulation layer (6) provided on the outer wall of each cylindrical tube (3) is a low thermal conductivity thermal insulation material mineral rock wool.

9. The energy storage method based on the compressed air and waste heat hybrid energy storage system in the shaft of a mine to be retired according to claim 5, characterized in that: The through hole formed on the sealing cover plate (9) for connecting the air inlet pipe (10) and the air outlet pipe (11) is integrally connected, and a heat storage mechanism sealing plate (17) is provided above the sealing cover plate (9) at the location of the through hole. The lower end surface of the heat storage mechanism sealing plate (17) is arranged in contact with the upper end surface of the sealing cover plate (9), and a through hole is formed for the air inlet pipe (10) and the air outlet pipe (11) to pass through the interior of the heat storage mechanism (2).

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