Carbon dioxide circulating energy storage system based on high-pressure heat exchange tank with injector / ejector and control method of carbon dioxide circulating energy storage system

Abstract

The invention discloses a carbon dioxide circulating energy storage system based on a high-pressure heat exchange tank with an ejector / ejector and a control method of the carbon dioxide circulating energy storage system. A high-pressure liquid CO2 storage tank and a heat storage tank are integrated on a cogeneration unit, a micro energy network or a new energy storage and consumption scene, so that high-density storage of cold / heat energy is realized; therefore, the peak regulation interval of the heat supply unit is effectively expanded, thermoelectric decoupling, deep grading and classification waste heat recovery and a temporary storage framework are achieved, and the comprehensive utilization rate and economical efficiency of energy are remarkably improved. On the basis, the flow guiding / jetting technology is applied to the high-pressure heat exchange tank, stirring and mixing of fluid in the tank are enhanced, a flowing dead zone is effectively eliminated, the problems of icing blockage and heat transfer resistance rising caused by local low temperature are fundamentally solved, meanwhile, stable regulation and control of system pressure, temperature and flow are achieved through a control method, and the system is suitable for large-scale popularization and application. And therefore, the gas-liquid heat and mass transfer efficiency is greatly enhanced, and efficient and stable operation of the carbon dioxide circulating energy storage system under the high-density energy storage condition is guaranteed.

Description

Technical Field

[0001] This invention relates to carbon dioxide cycle energy storage technology, and in particular to a carbon dioxide cycle energy storage system based on a high-pressure heat exchange tank with an ejector and its control method. Background Technology

[0002] To address issues such as low-temperature waste heat and pressure losses in coal-fired combined heat and power (CHP), the extensive utilization of high-grade energy in industrial production processes, and the mismatch between grid peak-shaving capacity and demand, existing technologies propose a liquid carbon dioxide energy storage system (LCES) with a cold regenerator and a cold accumulator, achieving improved operating time efficiency and... The efficiency is superior to that of traditional liquid air energy storage systems (LAES). However, this system does not make reasonable use of the heat generated by carbon dioxide compression and the cooling generated by expansion, nor does it consider coupling with thermal power plants. It has technical difficulties such as weak interaction between heat and electricity and steam pressure, low waste heat and pressure quality, rapid loss of gas work capacity, and serious underutilization of waste energy. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide a carbon dioxide circulating energy storage system and its control method based on a high-pressure heat exchange tank with an ejector. It couples a carbon dioxide energy storage system and a heat storage tank on the basis of a cogeneration unit, and at the same time utilizes the huge calorific value generated during the CO2 compression process and the cold energy and pressure during the expansion process to achieve heat and electricity decoupling, effectively expand the peak-shaving range of thermal power plants, and form a mode of heating and storing electricity at night and releasing and utilizing electrical energy during the day.

[0004] Technical Solution: To achieve the above objectives, the present invention provides a carbon dioxide circulating energy storage system based on a high-pressure heat exchange tank with an ejector. A high-pressure liquid storage tank is added between the high-pressure compressor and the high-pressure expander to store the high-pressure liquid CO2 compressed by the high-pressure compressor. During peak electricity demand periods, the CO2 is released to the high-pressure expander for expansion and work. Downstream of the high-pressure expander are a low-pressure liquid storage tank, an ejector high-pressure CO2 heat exchange tank, and a turbine generator system. The low-pressure liquid storage tank stores the expanded liquid CO2, which serves as the kinetic energy for the turbine generator. The ejector high-pressure CO2 heat exchange tank and turbine generator system include a turbine generator and a circulating heat exchange unit. The circulating heat exchange unit connects the low-pressure liquid storage tank and the turbine generator, forming a circulating path for power generation and heat exchange.

[0005] Preferably, the heat energy generated by the high-pressure compressor is stored in a heat storage tank for heating.

[0006] Preferably, the circulating heat exchange unit includes a CO2 heat exchange tank A, a CO2 heat exchange tank B, a water turbine, a heat exchanger, and a water tank. CO2 heat exchange tanks A and B each include an air inlet, an exhaust outlet, a pressure relief outlet, a water inlet, and a water outlet. CO2 heat exchange tanks A and B are connected to a low-pressure storage tank. A water turbine, a heat exchanger, and a water tank are connected in series between the water inlets of high-pressure CO2 heat exchange tank A and high-pressure CO2 heat exchange tank B, forming a first heat exchange path. A water turbine, a heat exchanger, and a water tank are connected in series between the water outlet of high-pressure CO2 heat exchange tank B and the water inlet of high-pressure CO2 heat exchange tank A, forming a second heat exchange path. The first and second heat exchange paths form a continuously flowing circulating water loop.

[0007] Preferably, the heat exchanger is a tubular heat exchanger based on tapered tubes and baffles with varying diameters.

[0008] Preferably, the low-pressure storage tank is connected to the air inlets of CO2 heat exchange tank A and CO2 heat exchange tank B via a pressure reducing valve and an air filling valve, respectively.

[0009] Preferably, the CO2 heat exchanger A and CO2 heat exchanger B are provided with an injection / jet device at their air inlets. The injection / jet device includes an ejector, a bypass pipe located at the throat of the ejector, and an auxiliary water pipe connected to and located below the bypass pipe. The ejector inlet is connected to the air outlet of the air filling valve, and the other end of the bypass pipe and the auxiliary water pipe are connected to the CO2 heat exchanger cavity.

[0010] Preferably, the jetting / ejector device comprises multiple sets, evenly arranged on the tank body of the CO2 heat exchanger, and the ejector inlets of all jetting / ejector devices are interconnected.

[0011] Preferably, the bypass pipe is equipped with a Tesla valve and a check valve, and the auxiliary water pipe is equipped with a check valve and a water pump.

[0012] The control method for the above-mentioned carbon dioxide cycle energy storage system described in this invention includes the following:

[0013] In the initial state, the first heat exchange passage, the second heat exchange passage, CO2 heat exchange tank A, and the water tank are filled with working fluid water. The filling rate of CO2 heat exchange tank A is 80%, and CO2 heat exchange tank B contains 0.5 MPa of gaseous CO2 at a temperature of 20°C.

[0014] Step 1: Open the upstream gas filling valve of CO2 heat exchanger A. The working fluid water in CO2 heat exchanger A is drawn to the throat of the ejector through the bypass pipe. It is then mixed evenly with the CO2 introduced from the low-pressure storage tank and injected into CO2 heat exchanger A.

[0015] Step 2: When the pressure inside CO2 heat exchanger A is balanced with the charging pressure, close the upstream air valve of CO2 heat exchanger A; at this time, the high-pressure CO2 inside CO2 heat exchanger A pushes the working fluid water into the first heat exchange passage and flows into CO2 heat exchanger B.

[0016] Step 3: When the pressure inside CO2 heat exchange tanks A and B is balanced, close the water valves between CO2 heat exchange tank A and the turbine unit, and between the water tank and CO2 heat exchange tank B, and at the same time open the vent valve of CO2 heat exchange tank A.

[0017] Step 4: When the back pressure of CO2 heat exchanger A is released, close the vent valve of CO2 heat exchanger A and open the upstream charging valve of CO2 heat exchanger B. The working fluid water in CO2 heat exchanger B is drawn to the throat of the ejector through the bypass pipe, and after being evenly mixed with the CO2 introduced from the low-pressure storage tank, it is charged into CO2 heat exchanger B.

[0018] Step 5: When the pressure inside CO2 heat exchanger B is balanced with the charging pressure, close the upstream air charging valve of CO2 heat exchanger B; at this time, the high-pressure CO2 inside CO2 heat exchanger B pushes the working fluid water to the second heat exchange passage and flows into CO2 heat exchanger A.

[0019] Step 6: When the pressures of high-pressure CO2 heat exchangers A and B are balanced, close the water valves between high-pressure CO2 heat exchanger A and the turbine unit, and between the water tank and high-pressure CO2 heat exchanger B, and open the vent valve of high-pressure CO2 heat exchanger B.

[0020] Step 7: Repeat steps 1 to 6 until the working fluid in the low-pressure storage tank is exhausted or the grid demand gradually decreases and returns to the off-peak period, then restart the compressor to compress and store energy.

[0021] Preferably, in the later stage of filling, when the pressure inside the CO2 heat exchange tank increases and the low pressure formed inside the ejector is insufficient to actively draw water from the tank, the water pump in the auxiliary water circuit is turned on to actively provide water to the ejector.

[0022] Beneficial Effects: This invention has the following advantages: 1. The invention integrates a high-pressure liquid CO2 storage tank and a heat storage tank between the compressor and the expander, realizing high-density storage of cold / heat energy. This effectively expands the peak-shaving range of the heating unit in the cogeneration coupled micro-energy network, achieving heat and power decoupling and waste heat recovery, and significantly improving the comprehensive energy utilization rate. 2. The high-pressure CO2 heat exchange tank and turbine system described in this invention form a circulation path for power generation and heat exchange between the low-pressure storage tank and the turbine, achieving deep waste heat recovery. On this basis, the high-pressure heat exchange tank is applied to enhance the mixing of fluids inside the tank, effectively eliminating flow dead zones and fundamentally avoiding the problems of icing blockage and soaring heat transfer resistance caused by local low temperatures. At the same time, the system pressure, temperature, and flow rate are stably regulated through control methods, thereby greatly enhancing the gas-liquid heat and mass exchange efficiency and ensuring the efficient and stable operation of the system under high-density energy storage conditions. Attached Figure Description

[0023] Figure 1 Diagram of a carbon dioxide cycle energy storage system;

[0024] Figure 2 Diagram of the high-pressure CO2 heat exchanger tank and turbine unit in a carbon dioxide circulating energy storage system;

[0025] Figure 3 Schematic diagram of a single inlet / jet device for a high-pressure CO2 heat exchanger;

[0026] Figure 4 Schematic diagram of multiple inlet / jet devices for a high-pressure CO2 heat exchanger;

[0027] Figure 5 This is a schematic diagram of the evolution of the jet charging flow state in the high-pressure CO2 heat exchanger in Example 4.

[0028] Figure 6 This is a schematic diagram of the internal structure of a tubular heat exchanger.

[0029] Figure 7 This is a schematic diagram of the tapered tube structure inside a tubular heat exchanger.

[0030] Figure 8 This is a schematic diagram of the internal perforated plate structure of a tubular heat exchanger.

[0031] Figure 9 This is a graph showing the changes in energy coefficient and heat rate of the carbon dioxide cycle energy storage system in Example 1;

[0032] Figure 10 This is a comparison chart of the peak-shaving capacity changes between the carbon dioxide cycle energy storage system in Example 1 and the existing system. Detailed Implementation

[0033] The technical solution of the present invention will be described in detail below with reference to the embodiments and accompanying drawings.

[0034] Example 1

[0035] like Figure 1 As shown, this embodiment provides a carbon dioxide cycle energy storage system including: a high-pressure compressor (with a matching motor), a high-pressure expander (with a matching generator), a high-pressure liquid storage tank of 16MPa, a low-pressure liquid storage tank of 6MPa, a high-temperature steam heat pump, an induced / jet high-pressure CO2 heat exchange tank and a turbine generator system, a gas-liquid separation device, an interstage heat exchanger, a twin-screw expander, and a CO2 capture device. When the CO2 capture device is running, it continuously captures and replenishes the CO2 in the carbon dioxide cycle energy storage system from the flue gas of the thermal power plant. It can also extract the CO2 in the carbon dioxide cycle energy storage system as fixed carbon dioxide and related chemical products.

[0036] The working principle of the carbon dioxide cycle energy storage system is as follows: At night, surplus electricity from the power plant drives the high-pressure compressor motor to compress gaseous CO2 into liquid CO2 at 16 MPa, which is then fed into the high-pressure storage tank. The liquid CO2 then expands at a relatively low flow rate through the high-pressure expander (generating electricity) to the low-pressure storage tank, achieving interstage cooling of the compressor. During this process, the compressor temperature gradually increases with the increase in pressure stage. According to numerical simulation results, the highest compressor temperature will exceed 120℃, and the low-pressure stage will be above 30℃. At the same time, the liquid CO2 needs to absorb heat to increase its enthalpy as it expands in the high-pressure expander.

[0037] Several sets of pulsating heat pipe heat exchangers (rapid start-up, no additional energy consumption) are installed at different pressure stages of the compressor and expander to complete interstage heat exchange between the high-pressure compressor and the high-pressure expander. The working fluid (water) in the high-temperature heat network of the interstage heat exchanger transfers the high-temperature heat from the high-pressure stage of the compressor to the thermal power plant's heat storage tank. The heat storage tank is designed with heat pipes as the framework and phase change material as the matrix, with a large heat capacity, enabling rapid heat storage and release. The heat in it can stably guarantee residential heating. In order to further improve the development and utilization space of low-temperature waste heat in the carbon dioxide cycle energy storage system and expand the forms of refined waste heat utilization, this embodiment adds a high-temperature rise, wide-range operating condition "pressurized boiling" steam heat pump in the process stage after the heat storage tank to produce high-quality steam (steam parameters >130℃, 0.17MPa) for direct energy supply to surrounding large-scale industrial users. In industrial parks where a steam pipeline network has been built, the steam produced by this system can be connected (or pressurized and connected) to achieve steam consumption and provide energy services to steam and heat-using enterprises.

[0038] During the day, when peak power consumption exceeds the maximum installed capacity of the thermal power plant, the high-pressure storage tank is opened to release high-pressure CO2 to drive the generator of the high-pressure expander for expansion, work, and heat exchange. Simultaneously, the low-pressure storage tank is opened, and CO2 enters the induction / jet high-pressure CO2 heat exchange tank and the turbine system to discharge lower-pressure CO2. This CO2 first passes through the printed circuit board heat exchanger (PCHE) for further heating and pressurization, then flows through the twin-screw expander (SE) for full expansion and work. The exhaust back pressure of the twin-screw expander is almost zero. The ambient temperature and pressure CO2 discharged from the SE can either flow out of the current cycle energy storage system or continue to participate in the next round of compression energy storage.

[0039] During daytime operation, CO2 absorbs a large amount of heat (releasing cold energy) to increase its enthalpy. This cold energy can be used to cool the steam turbine units, TRT (blast furnace gas residual pressure turbine power generation unit), compressors, and other heat-generating components in thermal power plants through a low-temperature cooling network to protect equipment and improve efficiency. A nighttime operating mode can also be activated simultaneously, which involves starting the high-pressure compressor and utilizing the low-temperature cooling of the expander.

[0040] The high-pressure CO2 heat exchanger tank and turbine system using induction / jet flow enables deep waste heat recovery. Without this system in the CO2 circulation energy storage system, the rate of CO2 heat absorption and expansion (temperature rise) would decrease, preventing the efficient conversion of internal energy into pressure potential energy and kinetic energy, thus affecting power generation. Furthermore, the twin-screw expander lacks the space and time for rapid heating, and air condensation easily leads to liquid buildup, causing significant damage to the expander blades due to liquid hammer. This results in the loss of substantial amounts of high-quality cold energy, pressure energy, and high-speed kinetic energy. Losses increase dramatically. Furthermore, the accelerated expansion of high-pressure CO2 during heat exchange in the PCHE (Polyhydrogen Chiller) leads to drastic pressure changes that can trigger vibrations and mechanical fatigue, greatly increasing the likelihood of equipment damage and leaks. Alternatively, current cogeneration CO2 energy storage systems commonly use exhaust steam extraction from the final stage of the medium-pressure cylinder to heat CO2, resulting in a severe mismatch between heating and extraction parameters and significant waste of steam's work potential (residual pressure).

[0041] Example 2

[0042] like Figure 2As shown, the high-pressure CO2 heat exchanger and turbine system provided in this embodiment includes: high-pressure CO2 heat exchanger A, high-pressure CO2 heat exchanger B, turbine, tubular heat exchanger, and water tank. CO2 heat exchanger A and high-pressure CO2 heat exchanger B each have an air inlet, an air outlet, a pressure relief port, a water inlet, and a water outlet. A low-pressure storage tank (-6MPa) is connected to the air inlet of high-pressure CO2 heat exchanger A and high-pressure CO2 heat exchanger B via a pressure reducing valve and an air inlet valve, respectively. The air outlet and pressure relief port of high-pressure CO2 heat exchanger A and high-pressure CO2 heat exchanger B are connected to a gas-liquid separation device via an air vent valve and a pressure relief valve, respectively. A turbine, tubular heat exchanger, and water tank are connected in series between the water inlet of high-pressure CO2 heat exchanger A and high-pressure CO2 heat exchanger B, forming the first heat exchange path (purple path). The water outlet of high-pressure CO2 heat exchanger B and the water inlet of high-pressure CO2 heat exchanger A are connected in series with a water turbine, a tubular heat exchanger, and a water tank, forming a second heat exchange path (grey path). The outlet of the gas-liquid separator is connected to the water tank.

[0043] The first heat exchange passage and the second heat exchange passage form a continuously flowing circulating water loop. The two high-pressure CO2 heat exchange tanks act as hubs and are connected in series with the water turbine, heat exchanger and water storage tank, so that the CO2 charging (heat exchange), work and discharge are coordinated with the water pressurization, cooling, work, heat exchange and reflux processes.

[0044] The pressure relief valves of high-pressure CO2 heat exchange tanks A and B automatically discharge high-pressure carbon dioxide from the tanks according to a set threshold, thereby reducing the pressure inside the tanks. The low-pressure storage tank, the high-pressure CO2 heat exchange tank (including the jet flow system), and the turbine unit system are connected by pressure reducing valves. These valves reduce and stabilize the dynamically fluctuating high input pressure at a constant, lower output pressure level, ensuring stable output pressure unaffected by changes in upstream input pressure or downstream flow demand. This guarantees that the CO2 parameters input to the high-pressure CO2 heat exchange tanks always meet the design range.

[0045] Based on the operational requirements of the thermal power plant / micro-energy park, the high-pressure CO2 heat exchanger A and high-pressure CO2 heat exchanger B have a diameter of 3.5m and a height of 7m. The tanks can withstand a high pressure of 7MPa. The injection pressure range of the inlet / ejector of high-pressure CO2 heat exchanger A and high-pressure CO2 heat exchanger B is 3-5MPa, and the exhaust pressure is 0.3-0.8MPa. The hot water temperature of the tubular heat exchanger is 35-45℃. The water flow pipe is made of F92.WB36 material and has a diameter of 40mm. The CO2 gas pipe (green passage) is made of F91 material and has a diameter of 30mm. The pipe wall is wrapped with an aerogel insulation layer.

[0046] The aforementioned piping system separates the pressureless, low-pressure hot water carried during the exhaust of the tubular heat exchanger, high-pressure CO2 heat exchanger A, and high-pressure CO2 heat exchanger B into a water tank via a gas-liquid separator. Driven by upstream high-pressure water, this water then supplies a second source of water through water pipes for the ejector heat exchange charging process in high-pressure CO2 heat exchanger A, thus matching the heat network and water network and forming a closed water cycle. The hot water for the heat exchangers originates from the hot end of the medium-temperature heat network in the cogeneration system and flows back to the intermediate-temperature heat network to cool other temperature-controlled components of the cogeneration generator unit.

[0047] In high-pressure CO2 heat exchanger tanks and turbine generator systems, if a high-pressure CO2 gas-liquid mixture is directly injected from a low-pressure storage tank into high-pressure CO2 heat exchanger tanks A and B, the mixing of the gas and liquid will be weakened due to surface tension and the viscous resistance of the saturated gas. This will affect the heat and mass transfer between the gas and liquid, making it impossible to quickly reach thermal stability and prolonging the cycle time. To meet different operating requirements, this invention provides two injection / jet devices, such as Embodiments 3 and 4, to achieve stable injection of liquid CO2 into high-pressure CO2 heat exchanger tanks A and B.

[0048] Example 3

[0049] like Figure 3 As shown, in this embodiment, the ejector / ejector device includes an ejector. The ejector inlet is equipped with a vortex pressure nozzle, which is connected to a low-pressure outlet pipe via a filling pipe. The ejector outlet is connected to the upper space of the high-pressure CO2 heat exchanger (A / B). The ejector throat is equipped with a bypass pipe, which communicates with the lower middle space of the high-pressure CO2 heat exchanger (A / B). The bypass pipe is equipped with a Tesla valve and a check valve. An auxiliary water pipe is also provided at the bottom of the high-pressure CO2 heat exchanger (A / B), and this auxiliary water pipe is connected to the bypass pipe. The auxiliary water pipe is equipped with a check valve and a water pump.

[0050] The vortex pressure nozzle enables the localized spiral acceleration of the high-pressure CO2 gas-liquid mixture, generating intense shear force atomization. At the nozzle, pressure and temperature decrease, while fluid volume and velocity increase, and pressure at the top of the tank rises. At this point, water from the bottom of the tank is "drawn" or "suctioned" through the Tesla valve pipeline to the throat of the conical ejector, achieving uniform mixing of the high-pressure CO2 gas-liquid mixture and water at the throat. This efficient heat exchange between the warm water and CO2 allows CO2 to rapidly increase its enthalpy (expansion work potential), avoiding safety hazards such as valve icing, blockage of the filling pipeline, and degradation of the mechanical properties of valve sealing devices caused by the rapid expansion and heat absorption of CO2 during continuous charging. The mixed, low-temperature water and CO2 are then injected into the high-pressure CO2 heat exchange tank as the working fluid for the next stage of the work process.

[0051] During the later stages of filling, when the pressure inside the high-pressure CO2 heat exchanger (A / B) increases and the low pressure formed inside the ejector is insufficient to actively draw water from the tank, the auxiliary water pump can be activated to actively provide water to the ejector. During this process, the pump power is dynamically adjusted based on the water flow rate in the bypass pipe to prevent excessive flow from affecting the liquid breaking efficiency within the ejector cavity, thereby maintaining the continuous operation of the entire ejection, mixing, and heat exchange process.

[0052] The charging process involves vigorous mixing (ejector atomization) and the working fluid water will reach or approach the dissolution saturation state at the current temperature and pressure in a very short time (much less than one cycle). Therefore, it can be assumed that the amount of CO2 dissolved in the working fluid water reaches a sustained saturation state after the first cycle. Subsequent processes do not need to consider the pressure fluctuation losses caused by dissolution and heat exchange, and the water and dissolved CO2 are regarded as a physically stable mixed working fluid.

[0053] Example 4

[0054] To further shorten the charging and heat exchange time of the high-pressure CO2 heat exchange tank (A / B) and break the local eddies and dead zones generated by a single-angle jet, this embodiment symmetrically installs several jet devices, as shown in Embodiment 3, in a ring-shaped area at the same height on the outer wall of the tank. Figure 4 As shown. All auxiliary water pipes of the inlet / jet devices are connected to a ring-shaped water supply header located at the bottom of the tank, below the bypass pipes. Each bypass pipe is connected to the ring-shaped water supply header. All air supply pipes of the inlet / jet devices are connected to a ring-shaped air supply header, which in turn connects to the main air supply pipe, reducing the number of sealing elements. By controlling the start / stop and flow rate of individual air supply pipes, a high degree of synchronization in the operating status of all inlet / jet devices connected in parallel is ensured at all times. During operation, corresponding valves are opened / closed synchronously to ensure a high degree of synchronization in the operating status of all inlet / jet devices connected in parallel at all times.

[0055] The inner walls of the air supply pipe, bypass pipe, auxiliary water supply pipe, and ring water supply header in the jetting device are all coated with a superhydrophobic coating, and the inner wall surfaces of all pipe connections are rounded.

[0056] To monitor the energy storage / release process within the high-pressure CO2 heat exchanger tank and the turbine unit system during operation, a pressure gauge is installed at the top of the high-pressure CO2 heat exchanger tank (A / B), and flow meters are installed on the charging pipe and venting pipe of the jet device, as well as on the pipeline connecting the high-pressure CO2 heat exchanger tank (A / B) to the turbine unit. Based on the flow meter data, the evolution of the jet charging flow state within the CO2 heat exchanger tank can be simulated, such as... Figure 5 As shown.

[0057] Example 5

[0058] The operating parameters of the circulating water in the high-pressure CO2 heat exchanger and turbine system fluctuate relatively, exhibiting periodic changes, with a maximum head of 510 m and an average head of 235 m. Therefore, this embodiment selects a horizontally arranged impulse turbine unit. This turbine has a relatively simple structure, with the main vulnerable parts being the nozzles (especially the nozzle needles and nozzle heads) and the runner. Inspection, replacement, or maintenance of these components does not require disassembling the entire unit or the large spiral casing, significantly reducing maintenance costs and downtime. The multi-nozzle characteristic of the impulse turbine unit is well-suited to the flow fluctuation conditions present in the high-pressure CO2 heat exchanger and turbine system.

[0059] Water head calculation formula: H=P / (ρg), H=5MPa / 1000(kg / m³) 3 ) / 9.81(m / s 2 =510m, Discharged water volume V out From 0 to 3V / 4 (initial water volume is 3V / 4), let a = V / 4, then the range of discharged water volume is 0 to 3a.

[0060] Pressure P and Discharged Water Volume V out The relationship is: P = 5a / (V) out +a), mean pressure P avg For P to V out The integral divided by the total discharged water volume yields the following result:

[0061] ,

[0062] H avg =P avg / (ρg)=235m.

[0063] Example 6

[0064] The circulating water in the high-pressure CO2 heat exchange tank and turbine system acts as a heat transport medium. After flowing through the turbine, it exchanges heat with the heating network and its temperature rises. When CO2 is charged again, the heat is transferred to the CO2, increasing the gas's enthalpy, expansion pressure and work potential.

[0065] To address the characteristics of small heat exchange temperature difference and high circulating water velocity at the heating network, this embodiment employs a tubular heat exchanger based on tapered tubes and baffles with varying diameters, such as... Figure 6 As shown. The structure of a tapered tube is based on a corrugated tube with the addition of straight-edge sections, which are tangent to the crests and troughs of the corrugations, as shown. Figure 7 As shown, the improved design increased the average convective heat transfer coefficient by 5%–20% and reduced the pressure drop by 4.6%–20%. Figure 8The diagram shows the orifice plate with different diameters used in this embodiment. The shell-side fluid flows through the gap between the large orifice and the heat exchange tube, while the small orifice acts as a support for the tube bundle. This transforms the flow of fluid along the transverse direction of the tube bundle in traditional shell heat exchangers into the flow along the longitudinal direction of the tube bundle, reducing pressure drop, minimizing "flow dead zones," and effectively preventing fluid-induced vibration. It has advantages such as simple processing, low cost, and uniform wall-attached jet formation.

[0066] Example 7

[0067] This embodiment provides an operation control method for high-pressure CO2 heat exchanger A and high-pressure CO2 heat exchanger B based on an induction / jet device, including the following:

[0068] In the initial state, the first heat exchange passage, the second heat exchange passage, the high-pressure CO2 heat exchange tank A, and the water tank are filled with working fluid water. The filling rate of the high-pressure CO2 heat exchange tank A is 80%, and only 0.5 MPa of gaseous CO2 remains in the high-pressure CO2 heat exchange tank B at a temperature of 20°C.

[0069] Step 1: CO2 (high-pressure gas-liquid mixture) in the low-pressure storage tank is injected into the high-pressure CO2 heat exchanger A through an injection / jet device. Under the combined effect of the Bernoulli effect and the high pressure at the top of the tank, water in the high-pressure CO2 heat exchanger A is drawn into the throat of the ejector through a bypass pipe connected to the perimeter of the tank, where it is uniformly mixed with CO2. During the filling process, the water in the tank undergoes violent agitation, which allows for rapid heat exchange with CO2, causing most of the water vapor to condense and creating space (pressure reduction) to continue accommodating CO2.

[0070] Step 2: When the pressure inside the high-pressure CO2 heat exchanger A is balanced with the charging pressure (above 5MPa), close the charging valve of the high-pressure CO2 heat exchanger A to terminate the CO2 injection into the high-pressure CO2 heat exchanger A.

[0071] At this time, the high-pressure CO2 inside the high-pressure CO2 heat exchange tank A pushes the working water into the first heat exchange passage. The working water passes through the turbine unit, the tubular heat exchanger and the water tank in succession, and finally flows into the high-pressure CO2 heat exchange tank B.

[0072] Step 3: When the pressure inside high-pressure CO2 heat exchange tanks A and B is roughly balanced, close the water valves between high-pressure CO2 heat exchange tank A and the turbine unit, and between the water tank and high-pressure CO2 heat exchange tank B. At the same time, open the exhaust valve of high-pressure CO2 heat exchange tank A, and discharge the CO2 in tank A to the twin-screw expander after being separated by the gas-liquid separation device to continue to cool down, depressurize and expand to do work.

[0073] Step 4: When the high-pressure CO2 heat exchanger A is close to the exhaust back pressure, close its exhaust valve and open the charging valve of the high-pressure CO2 heat exchanger B to charge high-pressure CO2 into the high-pressure CO2 heat exchanger B (this step has the same effect as step 1).

[0074] Step 5: When the pressure inside CO2 heat exchanger B is balanced with the charging pressure, close the upstream air charging valve of CO2 heat exchanger B; at this time, the high-pressure CO2 inside CO2 heat exchanger B pushes the working fluid water to the second heat exchange passage and flows into CO2 heat exchanger A.

[0075] Step 6: When the pressures of high-pressure CO2 heat exchangers A and B are balanced, close the water valves between high-pressure CO2 heat exchanger A and the turbine unit, and between the water tank and high-pressure CO2 heat exchanger B, and open the vent valve of high-pressure CO2 heat exchanger B.

[0076] Step 7: Repeat steps 1 to 6 until the working fluid in the low-pressure storage tank is exhausted or the grid demand gradually decreases and returns to the off-peak period, then restart the compressor to compress and store energy.

[0077] Example 7

[0078] In this embodiment, some device performance indicators in the system described in Example 1 are calculated, and the process is as follows:

[0079] Steam turbine unit of a combined heat and power (CHP) unit:

[0080]

[0081] In the formula: the values ​​of the main steam mass flow rate before and after the change of operating conditions are q and q, respectively. m,1 q m,0 The values ​​of the regulating stage pressure before and after the change of operating conditions are p. 01 p0, the values ​​of the steam turbine exhaust pressure before and after the change of operating conditions are p g1 p g The values ​​of the regulating stage temperature before and after the change of operating conditions are T, respectively. 01 、T0.

[0082] The isentropic efficiency of the compressor stage is:

[0083]

[0084] In the formula: h0 is the inlet specific enthalpy of the stage, h1 is the actual outlet specific enthalpy of the stage, h 1s The isentropic outlet specific enthalpy is given. The compressor's adiabatic efficiency and power consumption are as follows:

[0085]

[0086] Where: h c,i (i) represents the specific enthalpy of the inlet working fluid at stage i, kJ / kg; h c,s (i) represents the enthalpy of the i-th stage outlet working fluid during isentropic compression, kJ / kg; h c,o (i) represents the actual enthalpy of the i-th stage outlet compression, kJ / kg; P c The power consumption of the compressor unit is kW; N is the number of compressor units; qc The working fluid flow rate of the compressor is kg / s.

[0087] Assuming the temperature difference between the inlet and outlet of the working fluid in the heat exchanger is ΔT, we divide it into k equal time steps to derive the corresponding difference equation. Then, the heat released by CO2 on the high-pressure compressor side during the kth time step is:

[0088]

[0089] In the formula: q h,CO2 Let c be the mass flow rate of the working fluid during the kth equal time interval. p,CO2 (k) represents the isobaric specific heat capacity of CO2 in the high-pressure compressor during the kth equal time interval, T CO2,O (k) and T CO2,i (k) represents the CO2 inlet / outlet temperature of the kth compressor segment.

[0090] The heat absorbed by CO2 on the high-pressure expander side is:

[0091]

[0092] In the formula: q s,CO2 c is the CO2 mass flow rate. p,CO2 T is the isobaric specific heat capacity of CO2. CO2,O (k) and T CO2,i (k) represents the CO2 inlet / outlet temperature of the kth expansion unit.

[0093] The corresponding heat absorption of the cold flow in the heating network during the kth time interval is:

[0094] Q xew (k)=Q he (k)-Q se (k).

[0095] Further employing the energy utilization coefficient η r The system is evaluated using the heat rate q. The energy utilization coefficient is the ratio of the total electrical energy generated to the total energy consumed within one energy storage and release cycle.

[0096]

[0097] In the formula: P el The generator output is D0, which is the main steam flow rate. r D is the reheat steam flow rate. s For heating steam extraction flow rate, h0 is the main steam specific enthalpy, h fw For boiler feedwater specific enthalpy, h r For the specific enthalpy of reheat steam inlet, h r,1 For the exhaust enthalpy of the high-pressure cylinder, h s For the exhaust enthalpy of the intermediate-pressure cylinder, hs,1 Enthalpy of return water for heating.

[0098]

[0099] In the formula: P c For the power consumed by the compressor, P el P represents the generating capacity of the unit. e Q represents the generator power of the energy storage system. fw Q represents the heat absorbed by the boiler feedwater per unit time. r This refers to the heat absorbed by reheated steam per unit time.

[0100] The performance of the carbon dioxide cycle energy storage system in Example 1 can be evaluated using the above index formulas, such as... Figure 9 As shown, with the increase in carbon dioxide mass flow rate, the power of both the expander and compressor increases, leading to higher efficiency of the coupled energy storage system. This results in a slight increase in the energy utilization coefficient during both the non-heating and heating seasons. The average energy utilization coefficient of this system is 46.5%, and the heat rate is 7380 kJ / (kW·h), representing improvements of 3.5% and 4.3% respectively compared to existing thermal power plants.

[0101] like Figure 10 As shown, its heat and power load regulation area is enclosed by ABCDE. Under a certain heat load, the peak-shaving range of the unit is the difference between the maximum and minimum electrical load under that heat load. From point E to point D, as the heat load demand increases, the heating steam extraction flow rate must be increased, resulting in a decrease in the steam intake of the low-pressure cylinder, a reduction in the working steam, and a decrease in power generation. However, in order to meet the continued increase in heat load, while increasing the heating steam extraction flow rate, the minimum steam intake of the low-pressure cylinder must be ensured, which requires increasing the main steam flow rate. Therefore, the power generation in section BC increases. It can be further seen that with the gradual addition of energy storage, the strong coupling between heating and power generation in the cogeneration unit is weakened, and the peak-shaving range (the difference between the upper and lower lines / maximum and minimum power generation / y value of the same type of line) continues to expand. The constructed CO2 compression energy storage system coupled with the power supply and heating system balances the load fluctuations of the power grid and the heating network under the large-scale grid connection of new energy sources, and meets the applicability and reliability of multi-energy complementarity under a large operating range.

[0102] This system also includes a liquid CO2 energy storage system (energy density 7.5 kW·h / m³). 3 The system includes a 30MW·h energy storage system (with a maximum exhaust pressure of 6MPa in the low-pressure tank) and a hot water thermal energy storage system (with a heat storage capacity of 12MW·h and a maximum heating power of 50MW). The hot water energy storage system allows the existing thermal power plant system to meet a larger heating load, while the liquid carbon dioxide compression energy storage system significantly upgrades the existing electrical energy storage capacity of the thermal power plant. Simultaneously, existing thermal power units can achieve high-quality thermoelectric decoupling, increasing the peak-shaving range of the heating units by 37.2%.

Claims

1. A carbon dioxide circulating energy storage system based on a high-pressure heat exchanger with an ejector, characterized in that, A high-pressure liquid storage tank is added between the high-pressure compressor and the high-pressure expander to store the high-pressure liquid CO2 compressed by the high-pressure compressor. During peak electricity demand periods, the CO2 is released to the high-pressure expander to expand and perform work. Downstream of the high-pressure expander, there is a low-pressure liquid storage tank, an induction / jet high-pressure CO2 heat exchange tank, and a turbine generator system. The low-pressure liquid storage tank is used to store the liquid CO2 after expansion and work, which serves as the kinetic energy for the turbine generator to generate electricity. The induction / jet high-pressure CO2 heat exchange tank and turbine generator system include a turbine generator and a circulating heat exchange unit. The circulating heat exchange unit connects the low-pressure liquid storage tank and the turbine generator, forming a circulating path for power generation and heat exchange.

2. The carbon dioxide cycle energy storage system according to claim 1, characterized in that, The heat energy generated by the high-pressure compressor is stored in a heat storage tank for heating.

3. The carbon dioxide cycle energy storage system according to claim 1, characterized in that, The circulating heat exchange unit includes CO2 heat exchange tank A, CO2 heat exchange tank B, a water turbine, a heat exchanger, and a water tank. CO2 heat exchange tank A and CO2 heat exchange tank B include an air inlet, an exhaust outlet, a pressure relief outlet, a water inlet, and a water outlet. CO2 heat exchange tank A and CO2 heat exchange tank B are connected to a low-pressure storage tank. A water turbine, a heat exchanger, and a water tank are connected in series between the water inlets of high-pressure CO2 heat exchange tank A and high-pressure CO2 heat exchange tank B to form a first heat exchange path. A water turbine, a heat exchanger, and a water tank are connected in series between the water outlet of high-pressure CO2 heat exchange tank B and the water inlet of high-pressure CO2 heat exchange tank A to form a second heat exchange path. The first heat exchange path and the second heat exchange path form a continuously flowing circulating water loop.

4. The carbon dioxide cycle energy storage system according to claim 3, characterized in that, The heat exchanger is a tubular heat exchanger based on tapered tubes and baffles with varying diameters.

5. The carbon dioxide cycle energy storage system according to claim 3, characterized in that, The low-pressure storage tank is connected to the air inlets of CO2 heat exchange tank A and CO2 heat exchange tank B via a pressure reducing valve and an air filling valve, respectively.

6. The carbon dioxide cycle energy storage system according to claim 4, characterized in that, The CO2 heat exchanger A and CO2 heat exchanger B are equipped with a flow guide / jet device at their air inlets. The flow guide / jet device includes an ejector, a bypass pipe located at the throat of the ejector, and an auxiliary water pipe connected to and located below the bypass pipe. The ejector inlet is connected to the air outlet of the air filling valve, and the other end of the bypass pipe and the auxiliary water pipe are connected to the CO2 heat exchanger cavity.

7. The carbon dioxide cycle energy storage system according to claim 5, characterized in that, The jetting / ejector system comprises multiple sets, evenly arranged on the body of the CO2 heat exchanger, with the ejector inlets of all jetting / ejector systems connected.

8. The carbon dioxide cycle energy storage system according to claim 5, characterized in that, The bypass pipe is equipped with a Tesla valve and a check valve, and the auxiliary water pipe is equipped with a check valve and a water pump.

9. A control method applied to the carbon dioxide cycle energy storage system of claim 8, characterized in that, Includes the following: In the initial state, the first heat exchange passage, the second heat exchange passage, CO2 heat exchange tank A, and the water tank are filled with working fluid water. The filling rate of CO2 heat exchange tank A is 80%, and CO2 heat exchange tank B contains 0.5 MPa of gaseous CO2 at a temperature of 20°C. Step 1: Open the upstream gas filling valve of CO2 heat exchanger A. The working fluid water in CO2 heat exchanger A is drawn to the throat of the ejector through the bypass pipe. It is then mixed evenly with the CO2 introduced from the low-pressure storage tank and injected into CO2 heat exchanger A. Step 2: When the pressure inside CO2 heat exchanger A is balanced with the charging pressure, close the upstream air valve of CO2 heat exchanger A; at this time, the high-pressure CO2 inside CO2 heat exchanger A pushes the working fluid water into the first heat exchange passage and flows into CO2 heat exchanger B. Step 3: When the pressure inside CO2 heat exchange tanks A and B is balanced, close the water valves between CO2 heat exchange tank A and the turbine unit, and between the water tank and CO2 heat exchange tank B, and at the same time open the vent valve of CO2 heat exchange tank A. Step 4: When the back pressure of CO2 heat exchanger A is released, close the vent valve of CO2 heat exchanger A and open the upstream charging valve of CO2 heat exchanger B. The working fluid water in CO2 heat exchanger B is drawn to the throat of the ejector through the bypass pipe, and after being evenly mixed with the CO2 introduced from the low-pressure storage tank, it is charged into CO2 heat exchanger B. Step 5: When the pressure inside CO2 heat exchanger B is balanced with the charging pressure, close the upstream air charging valve of CO2 heat exchanger B; at this time, the high-pressure CO2 inside CO2 heat exchanger B pushes the working fluid water to the second heat exchange passage and flows into CO2 heat exchanger A. Step 6: When the pressures of high-pressure CO2 heat exchangers A and B are balanced, close the water valves between high-pressure CO2 heat exchanger A and the turbine unit, and between the water tank and high-pressure CO2 heat exchanger B, and open the vent valve of high-pressure CO2 heat exchanger B. Step 7: Repeat steps 1 to 6 until the working fluid in the low-pressure storage tank is exhausted or the grid demand gradually decreases and returns to the off-peak period, then restart the compressor to compress and store energy.

10. The control method according to claim 9, characterized in that, During the later stages of filling, when the pressure inside the CO2 heat exchanger increases and the low pressure formed inside the ejector is insufficient to actively draw water from the tank, the water pump in the auxiliary water circuit is turned on to actively provide water to the ejector.

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