Energy release method of carbon dioxide phase change energy storage system

Abstract

The invention discloses an energy release method of a carbon dioxide phase change energy storage system, which belongs to the technical field of carbon dioxide energy storage, and comprises the following steps: compressing, condensing and liquefying a carbon dioxide working medium, and storing the carbon dioxide working medium as liquid carbon dioxide; boosting and heating the liquid carbon dioxide, converting the liquid carbon dioxide into high-pressure dry gas, inputting the high-pressure dry gas into a power generation turbo expander to do work, and driving a power generator to generate power; and low-temperature carbon dioxide gas exhausted by the power generation turbo expander is returned to an inlet of the compression procedure, and totally-closed carbon dioxide working medium circulation is achieved. Through a multi-stage echelon heat management strategy, separated operation of the liquefaction energy storage unit and the power generation turbine unit and sealing integrated design, closed circulation of compression, liquefaction, storage, energy release and circulation is constructed, zero emission and sealing of a carbon dioxide working medium are achieved, stepped utilization of cold energy and heat energy in the system is achieved, and the energy utilization efficiency of the system is improved. And the overall energy efficiency is obviously improved.

Description

TECHNICAL FIELD

[0001] The application relates to an energy release method of a carbon dioxide phase change energy storage system and belongs to the technical field of carbon dioxide energy storage. BACKGROUND

[0002] With the intensification of environmental challenges worldwide and the continuous tension of traditional energy resources, the development and utilization of various renewable energies have been increasingly valued. Although clean energies such as solar energy and wind energy have great potential, their intermittency and volatility also bring severe challenges to the stable operation of power systems. Under this background, energy storage technology, as a key link for balancing energy supply and demand and improving the regulation capacity of power grids, plays an irreplaceable role. Effective energy storage and release methods not only enable the large-scale consumption of renewable energies, but also enhance the flexibility and reliability of power grids, promoting the transformation of energy structure to a low-carbon and sustainable direction. Among various energy storage technology routes, compressed air energy storage, as a physical energy storage method with large-scale and long-time energy storage capacity, has gradually shown its engineering feasibility and application prospect. During periods of excess power supply or low load, air is compressed using electric energy and stored in underground salt caverns, abandoned mines or high-pressure gas storage equipment; when power demand increases or the system is insufficiently powered, the stored compressed air is released and converted into electric energy through an expander set to be delivered to the power grid. Through this “charge-discharge” cycle, compressed air energy storage can effectively realize the time-space translation of electric energy, enhance the adaptability of renewable energy fluctuations in power systems, and thus promote the efficient use of energy and the safe and stable operation of the system. In recent years, liquefied air (carbon dioxide) energy storage has been widely used due to its high energy density, but there are still the following bottlenecks: high power consumption in the liquefaction stage, insufficient cold energy recovery, low round-trip efficiency of the system; unstable gasification in the energy release process, low-temperature corrosion of expander exhaust and difficulty in dryness control; single source of working medium, lack of negative carbon path. Therefore, there is an urgent need for a long-time energy storage technology with high energy density, wide geographical adaptability, efficient cold-heat coupling and negative carbon benefit. SUMMARY SUMMARY

[0003] The purpose of the present application is to provide an energy release method of a carbon dioxide phase change energy storage system, which realizes zero emission and sequestration of carbon dioxide working medium, realizes step-by-step utilization of cold and heat energy in the system, and significantly improves the overall energy efficiency through a multi-stage thermal management strategy, separate operation of liquefied energy storage units and power generation turbine units, and integrated design of sequestration.

[0004] To achieve the above purpose, the technical scheme of the present application is as follows.

[0005] In one aspect, the present application provides a method for energy release of a carbon dioxide phase change energy storage system, comprising the following steps:

[0006] Step S1, compressing and condensing and liquefying the carbon dioxide working medium to store as liquid carbon dioxide;

[0007] Step S2, pressurizing and heating the liquid carbon dioxide to convert it into high-pressure dry gas, which is input into a power generation turbine expander to drive a generator to generate electricity;

[0008] Step S3, returning the low-temperature carbon dioxide gas discharged from the power generation turbine expander to the inlet of the compression process to realize a fully closed carbon dioxide working medium circulation.

[0009] Optionally, in step S1, a multi-stage compressor is used to compress the carbon dioxide working medium to obtain dense-phase carbon dioxide;

[0010] The compressed carbon dioxide has a pressure of , a temperature of , and a density of at least .

[0011] Optionally, in step S1, the condensation and liquefaction includes:

[0012] The dense-phase carbon dioxide is sent into a molten salt heat exchanger for cooling, and the heat generated during the compression process is recovered and stored in a molten salt tank, and the temperature of the cooled carbon dioxide is , and the operating temperature of the molten salt tank is ;

[0013] The cooled carbon dioxide is passed into a heat transfer oil heat exchanger for cooling, and then adiabatically expanded through a liquefied expander to obtain liquid carbon dioxide and store it in a double-layer metal storage tank, the outlet temperature of the heat transfer oil heat exchanger is , the outlet temperature of the liquefied expander is , and the outlet pressure is .

[0014] Optionally, the carbon dioxide after the liquefied expander enters a gas-liquid separator, the liquefied carbon dioxide is pressurized by a low-temperature pump and stored in a double-layer metal storage tank, and the gaseous carbon dioxide that is not liquefied is returned to the inlet of the compressor;

[0015] The storage temperature of the double-layer metal storage tank is , and the storage pressure is .

[0016] Optionally, in the liquefaction process, the removed cold energy is used to prepare eutectic salt water ice slurry and store it in an ice slurry cold storage tank;

[0017] The prepared eutectic salt water ice slurry has a mass fraction of The phase change temperature is , the latent heat is not less than , and the ice slurry solid content is .

[0018] Optionally, in the step S2, the liquid carbon dioxide is pressurized by a low-temperature pump and then is introduced into the ice slurry storage tank to exchange heat with the eutectic salt water ice slurry, so as to realize supercooling.

[0019] The supercooled liquid carbon dioxide enters a gasifier and is heated by the molten salt delivered from a molten salt tank, so as to form high-pressure dry gas.

[0020] The outlet pressure of the low-temperature pump is , and the outlet temperature of the gasifier is .

[0021] Optionally, in the step S2, the power generation turbine expander is a three-stage series power generation turbine expander, and the outlet of each stage is injected with liquid carbon dioxide for internal cooling and reheating from a double-layer metal storage tank, and the three-stage series power generation turbine expander coaxially drives a generator to generate power.

[0022] Optionally, the mass flow of the liquid carbon dioxide injected into the outlet of each stage of the three-stage series power generation turbine expander is of the main flow.

[0023] The single-stage expansion ratio of the three-stage series power generation turbine expander is 3 to 4, the outlet pressure is , and the exhaust temperature is .

[0024] The generator is a permanent magnet generator, and the rotating speed is .

[0025] Optionally, in the step S3, the low-temperature carbon dioxide discharged from the power generation turbine expander is cooled by a heat conducting oil heat exchanger to cool heat conducting oil, and then flows through the ice slurry storage tank to further recover heat, and returns to the compressor inlet to mix with the enriched carbon dioxide and enters the next round of energy storage cycle.

[0026] Optionally, before the carbon dioxide is compressed in the step S1, the carbon dioxide is subjected to enrichment treatment, and the enriched carbon dioxide is adjusted to an atmospheric pressure state, mixed with the returned low-temperature carbon dioxide, and the enrichment process is operated at a pressure of .

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] The application realizes zero emission and sequestration of carbon dioxide working medium through the construction of a closed cycle of "compression-liquefaction-storage-energy release-cycle", greatly improves the energy utilization efficiency, and has environmental protection benefits. The system recovers compression heat from the molten salt tank for working medium heating, and recovers liquefaction cold energy from the ice slurry cold storage system for working medium supercooling, thereby reducing compression power consumption. Meanwhile, the power generation turbine adopts liquid carbon dioxide internal cooling and reheating technology, and recovers exhaust cold energy, greatly improving the overall energy efficiency of the system. The energy release stage adopts a three-stage series connection power generation turbine expander design, and the expansion process is stable without liquid knock risk. The application also adopts a liquefaction and power generation turbine split and multi-stage design, which gives the system the advantages of high energy density, fast response capability and flexible site selection, and provides a large-scale, sustainable and efficient energy storage solution for the power grid. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 An energy release method of the carbon dioxide phase change energy storage system provided by the embodiment of the application is shown in the figure. DETAILED DESCRIPTION

[0030] The technical solutions of the application will be described in detail below with reference to the drawings and specific embodiments. It should be understood that the embodiments of the application and the specific features in the embodiments are detailed descriptions of the technical solutions of the application, rather than limitations of the technical solutions of the application. In the case of no conflict, the technical features in the embodiments of the application and the embodiments can be combined with each other.

[0031] It should be noted that the term "and / or" is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which means that there are three cases of A alone, A and B together, and B alone. In addition, the character " / " generally represents an "or" relationship between the associated objects before and after it.

[0032] Embodiment 1

[0033] This embodiment introduces an energy release method of a carbon dioxide phase change energy storage system, as shown in Figure 1 The method comprises the following steps:

[0034] Step S1, compressing and condensing and liquefying carbon dioxide working medium, and storing it as liquid carbon dioxide;

[0035] Step S2, pressurizing and heating the liquid carbon dioxide, converting it into high-pressure dry gas, and inputting it into a power generation turbine expander to drive a generator to generate electricity;

[0036] Step S3, returning the low-temperature carbon dioxide gas discharged from the power generation turbine expander to the inlet of the compression process to realize working medium circulation.

[0037] Through the above scheme, the application realizes the "energy storage-storing-releasing carbon negative" closed loop, and the following industrial grade equipment needs to be equipped, and all equipment parameters are as follows:

[0038] Compressor: centrifugal multi-stage compressor (4 stages) is selected, inlet pressure is normal pressure, and outlet pressure is , rated power is 2.5 MW.

[0039] Salt heat exchanger: a tube-shell heat exchanger is selected, heat exchange area is 120 square meters, and pressure is 12 MPa.

[0040] Salt tank: a vertical carbon steel storage tank (with rock wool insulation layer) is used, volume is 500 cubic meters, operating temperature is , and the molten salt is Mixed salt.

[0041] Conduction oil heat exchanger: a plate heat exchanger is selected, heat exchange area is 80 square meters, and design temperature is 150 DEG C.

[0042] Liquefied expander: a radial turbine expander is selected, inlet pressure is 8 MPa, outlet pressure is , and design rotating speed is .

[0043] Eutectic salt water ice slurry preparation device: a scraper type ice slurry generator is selected, refrigerant is R410A, and raw material is Aqueous solution.

[0044] Ice slurry storage tank: a horizontal stainless steel tank (with PU insulation layer) is selected, volume is 300 cubic meters, and design temperature is .

[0045] Vacuum metal storage tank: a double-layer 304 stainless steel vacuum tank (sand is filled in the interlayer) is selected, volume is 800 cubic meters, design pressure is 3.0 MPa, and daily evaporation rate is less than or equal to 0.3%.

[0046] Low-temperature pump: a plunger type low-temperature liquid pump (double cylinder) is selected, inlet pressure is , outlet pressure is , and flow rate is 50 cubic meters / hour.

[0047] Gasifier: a shell and tube gasifier (heat exchange medium is molten salt) is selected, heat exchange area is 200 square meters, and outlet temperature is .

[0048] Three-stage series power generation turbine expander: an axial flow turbine (3 stages) is selected, single-stage expansion ratio is 3 to 4, total expansion ratio is 36, and the rotor is shared with the generator.

[0049] Permanent magnet generator: a high-speed permanent magnet synchronous generator is selected, rated rotating speed is , rated power is 10 MW, efficiency is greater than or equal to 97%, and AC / DC / AC conversion is connected to the grid.

[0050] Enrichment device: hollow fiber membrane separation assembly (polyimide membrane), treatment capacity 1000 Nm³ / h, operating pressure .

[0051] Step S1 is the energy storage stage, which is completed at night from 22:00 to 6:00 the next day (low electricity consumption), consuming low-pressure Convert to liquid storage, recover heat and cold at the same time, including the following steps:

[0052] S11, dense phase carbon dioxide preparation:

[0053] Use centrifugal multi-stage compressor to inhale from two main sources , including industrial tail gas after enrichment treatment and low-temperature returned by the system closed cycle.

[0054] After 4-stage compression of the compressor, the outlet parameters are stable: pressure 9 MPa (inside ), temperature 150°C (inside ), density 780 kg / m³ (≥ ), forming a supercritical dense phase state, then directly sent to the molten salt heat exchanger.

[0055] S12, cooling and heat recovery

[0056] Dense phase (9 MPa, 150°C) enters the tube side of the molten salt heat exchanger, and the shell side is passed through the low-temperature molten salt (80°C) sent from the molten salt tank, and the is cooled by countercurrent heat exchange.

[0057] After heat exchange, the temperature drops to 65°C, and the temperature of the molten salt after absorbing heat rises to 120°C (inside ), and is sent back to the molten salt tank for storage by the molten salt pump, completing the compression heat recovery.

[0058] The heat recovered in this step can meet the main needs of the subsequent energy release stage of gasification, and additional energy consumption is reduced.

[0059] S13, cooling, liquefaction, and storage

[0060] Pass the cooled (65°C, 9Mpa) into the tube side of the heat transfer oil heat exchanger, and the shell side is passed through low-temperature heat transfer oil (10°C), and is further cooled to 10°C (inside ).

[0061] The cooled It is fed into a liquefied expander for adiabatic expansion, where the pressure drops to 4.5 MPa and the temperature drops to -2℃. (Inside), at this time The vast majority is liquefied, and after passing through a gas-liquid separator, it becomes liquid. A very small amount of unliquefied gaseous material was placed in a vacuum metal storage tank with thermal insulation properties. Return to compressor inlet.

[0062] Among them, by activating a plunger-type cryogenic pump, the liquid output from the liquefied expander is... (4.5MPa, ) boosted to 2.3MPa ( (Inside), it is sent into a double-walled vacuum metal storage tank.

[0063] S14, Cold Energy Utilization

[0064] During the liquefaction process, the removed cold energy is transferred to the scraped-plate ice slurry generator via a refrigerant to produce eutectic brine ice slurry from a 12wt% NaCl aqueous solution: the ice will undergo a phase change at -8℃. Internal heat, latent heat 82kJ / kg (≥75kJ / kg), solid content 30% (Inside), stored in an ice slurry storage tank for later use.

[0065] S2, Energy Release Phase

[0066] S21, pressurization, subcooling and vaporization

[0067] Using a cryogenic pump to transfer liquid (2.3MPa, -8℃) pressurization, followed by subcooling in an ice slurry storage tank: liquid Countercurrent heat exchange with -8℃ ice slurry lowers the temperature to -5℃, preventing boiling before subsequent vaporization.

[0068] supercooled liquid The hot molten salt (120°C) from the molten salt tank enters the tube side of the shell-and-tube vaporizer and flows through the shell side, where it becomes liquid after heat exchange. Completely vaporized into high-pressure dry gas, the vaporizer outlet parameters are 14MPa and 40℃. (Inside), no liquid residue (to prevent turbine liquid hammer).

[0069] S22, Expansion Work and Power Generation

[0070] High-pressure dry gas (14MPa, 40℃) enters a three-stage series-connected turbine expander to perform work expansion:

[0071] Stage 1 expansion: Inlet 14MPa → Outlet 4.7MPa (expansion ratio 3), outlet temperature -5℃. At this time, 3% of the main flow rate of liquid is drawn from the vacuum metal storage tank. (Independent small flow cryogenic pump precision control, flow sensor + PLC synchronous regulation of liquid injection time and turbine speed), inject 1st stage outlet for internal cooling and reheating, temperature rises to 15℃.

[0072] 2nd stage expansion: inlet 4.7MPa→outlet 1.6MPa (expansion ratio 3), outlet temperature -18℃, inject 3% liquid internal cooling and reheating again, temperature rises to 8℃.

[0073] 3rd stage expansion: inlet 1.6MPa→outlet 0.15MPa (expansion ratio 3.2), outlet temperature -30℃ (internal), 3rd stage outlet dryness detection is 0.97 (≥0.96).

[0074] Turbine expander and permanent magnet generator share a rotor (rotating speed stabilized at 15000r / min), drive generator to output high frequency electric energy, converted by AC / DC / AC converter to 380V / 50Hz power frequency electric, directly connected to grid (no need for gear box speed up and step-up transformer), actual measured power generation power is stabilized at 10MW.

[0075] S3, cold energy recovery and closed cycle

[0076] Low temperature (0.15MPa, -30℃) discharged by turbine expander, first flows through shell side of heat transfer oil heat exchanger, cools heat transfer oil from 10℃ to 5℃ (to provide low temperature heat transfer oil for next day step S13).

[0077] Subsequently, low temperature continues to flow through shell side of ice slurry cold storage tank, further recovers cold energy (decreases ice slurry temperature from -8℃ to -10℃), and its own temperature rises to 5℃.

[0078] 5℃ final returns to compressor inlet, mixes with enriched industrial tail gas , enters next round of energy storage cycle, realizes 100% closed cycle of working medium (no emission).

[0079] In step S1, before compressing carbon dioxide, also includes enriching treatment of carbon dioxide, enriched carbon dioxide is adjusted to atmospheric pressure state by pressure, mixed with returned low temperature carbon dioxide;

[0080] Enrichment process operating pressure is .

[0081] (1) Industrial tail gas treatment and enrichment

[0082] Select industrial by-product tail gas (such as low concentration The tail gas is sent into the enrichment device (such as a hollow fiber membrane separation device, an amine absorption device, etc.) after being pretreated (removing dust, acid impurities, etc.) to meet the requirements of the subsequent enrichment device. Enrichment device (such as hollow fiber membrane separation device, amine absorption device, etc.);

[0083] The enrichment device is operated at an appropriate operating pressure (such as , which is adjusted according to the type of enrichment technology selected), and the separation of carbon dioxide from other components (such as nitrogen and oxygen) is achieved by physical or chemical methods. After enrichment, the purity needs to meet the requirements of the system working fluid cycle (to avoid impurities affecting equipment operation or reducing cycle efficiency).

[0084] After enrichment, the is adjusted to match the pressure of the compressor inlet, mixed with the low-temperature returned from the energy release stage, and sent together into the compressor inlet to supplement the loss of working fluid during the cycle.

[0085] (2) Carbon negative accounting;

[0086] During system operation, the amount of carbon negative depends on the actual enrichment treatment capacity of industrial by-products , the sealing efficiency of the system closed cycle and the energy consumption balance of the energy storage and release stage.

[0087] According to the actual operation parameters of the system (such as release power, energy storage power consumption, and enrichment device processing capacity), the net sealing amount per day / period can be calculated, and the technology potential of "electricity-storage-carbon negative integration" can be achieved.

[0088] In summary, the present application realizes zero emission and sealing of carbon dioxide working fluid through a fully closed working fluid cycle, and has certain environmental benefits. The system recovers compression heat from the molten salt tank for working fluid heating, and uses the ice slurry cold storage system to recover liquefied cold energy for working fluid supercooling, reducing compression power consumption. At the same time, the power turbine adopts liquid carbon dioxide internal cooling and reheating technology, and recovers exhaust cold energy, greatly improving the overall energy efficiency of the system. The energy release stage adopts a three-stage series connection turbine expander design, and the expansion process is stable without liquid knock risk. The present application also adopts a separate and multi-stage design of liquefaction and power turbine, which gives the system high energy density, fast response capability and flexible site selection advantages, providing a large-scale, sustainable and efficient energy storage solution for the power grid.

[0089] ​​The embodiments of the present application are described above with reference to the accompanying drawings, but the present application is not limited to the above-described specific embodiments, and the above-described specific embodiments are merely illustrative, but not restrictive, and a person of ordinary skill in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims, and these all belong to the protection of the present application.

Claims

1. A method for energy release from a carbon dioxide phase change energy storage system, characterized in that, Includes the following steps: Step S1: Compress and condense the carbon dioxide working fluid, and store it as liquid carbon dioxide; Step S2: Pressurize and heat the liquid carbon dioxide to convert it into high-pressure dry gas, which is then fed into the power generation turbine expander to drive the generator to generate electricity. Step S3: Return the low-temperature carbon dioxide gas discharged from the power generation turbine expander to the inlet of the compression process to achieve a fully enclosed carbon dioxide working fluid cycle.

2. The energy release method of the carbon dioxide phase change energy storage system according to claim 1, characterized in that, In step S1, a multi-stage compressor is used to compress the carbon dioxide working medium to obtain dense phase carbon dioxide; The pressure of the compressed carbon dioxide is The temperature is The density is at least .

3. The energy release method of the carbon dioxide phase change energy storage system according to claim 2, characterized in that, In step S1, the condensation and liquefaction includes: The dense-phase carbon dioxide is fed into a molten salt heat exchanger for cooling, while the heat generated during compression is recovered and stored in a molten salt tank. The temperature of the cooled carbon dioxide is [temperature value missing]. The operating temperature of the molten salt tank is ; The cooled carbon dioxide is passed through a heat transfer oil heat exchanger for further cooling, and then adiabatically expanded in a liquefied expander to obtain liquid carbon dioxide, which is then stored in a double-walled metal storage tank. The outlet temperature of the heat transfer oil heat exchanger is [temperature missing]. The outlet temperature of the liquefied expander is Export pressure is .

4. The energy release method of the carbon dioxide phase change energy storage system according to claim 3, characterized in that, The carbon dioxide that passes through the liquefied expander enters the gas-liquid separator. After being pressurized by a cryogenic pump, the liquefied carbon dioxide is stored in a double-walled metal storage tank, while the unliquefied gaseous carbon dioxide returns to the compressor inlet. The storage temperature of the double-walled metal storage tank is: Storage pressure is .

5. The energy release method of the carbon dioxide phase change energy storage system according to claim 4, characterized in that, During the liquefaction process, the removed cold energy is used to prepare eutectic brine ice slurry and stored in ice slurry storage tanks; The prepared eutectic brine ice slurry was of mass fraction It is made from an aqueous solution of sodium chloride, with a phase transition temperature of Latent heat not less than The solid content of ice slurry is .

6. The energy release method of the carbon dioxide phase change energy storage system according to claim 5, characterized in that, In step S2, a cryogenic pump is used to pressurize liquid carbon dioxide and then introduce it into an ice slurry storage tank to exchange heat with eutectic brine ice slurry to achieve subcooling. The supercooled liquid carbon dioxide enters the vaporizer, where it is heated by molten salt transported through the molten salt tank to form high-pressure dry gas. The outlet pressure of the cryogenic pump is The vaporizer outlet temperature is .

7. The energy release method of the carbon dioxide phase change energy storage system according to claim 6, characterized in that, In step S2, the power generation turbine expander is a three-stage power generation turbine expander connected in series. Liquid carbon dioxide is injected from a double-walled metal storage tank at each stage outlet for internal cooling and reheating, and coaxially drives the generator to generate electricity.

8. The energy release method of the carbon dioxide phase change energy storage system according to claim 7, characterized in that, The mass flow rate of liquid carbon dioxide at each stage outlet of the three-stage series-connected power generator turbine expander is the mainstream flow rate. ; The single-stage expansion ratio of the three-stage series-connected power generator turbine expander is 3 to 4, and the outlet pressure is... The exhaust temperature is ; The generator is a permanent magnet generator with a rotational speed of [missing information]. .

9. The energy release method of the carbon dioxide phase change energy storage system according to claim 8, characterized in that, In step S3, the low-temperature carbon dioxide discharged from the generator turbine expander is cooled by the heat transfer oil heat exchanger, then flows through the ice slurry cold storage tank to further recover heat, and returns to the compressor inlet to mix with the enriched carbon dioxide and enter the next energy storage cycle.

10. The energy release method of the carbon dioxide phase change energy storage system according to claim 9, characterized in that, Before compressing the carbon dioxide in step S1, the process includes enriching the carbon dioxide. The enriched carbon dioxide is then pressurized to atmospheric pressure and mixed with the returned low-temperature carbon dioxide. The operating pressure of the enrichment process is... .

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