Carbon capture energy system without external energy input

Abstract

The application discloses a carbon capture energy system without external energy input, comprising: a compressed energy storage and release power generation unit, which is configured to store energy by compressing a first working medium and generate power by expanding the compressed first working medium; an absorption method carbon capture unit, which is configured to separate and capture CO2 in a flue gas stream by sequentially absorbing and resolving the CO2; an LNG cold energy utilization unit, which is configured to use cold energy generated by LNG gasification to deeply cool and liquefy the separated CO2 in the absorption method carbon capture unit, thereby generating liquid CO2; and a second power generation cycle unit, which is configured to recover compression heat generated in the compression process of the first working medium, perform secondary expansion power generation, and condense a second working medium circulating in the second power generation cycle unit by using cold energy generated by LNG gasification, so that the second working medium forms a closed cycle. The system can fully utilize compression heat, LNG cold energy and flue gas waste heat to achieve carbon capture.

Description

Technical Field

[0001] This application relates to the field of energy-saving carbon emission reduction and separation technology, and in particular to a carbon capture energy system that does not require external energy input. Background Technology

[0002] Traditional absorption carbon capture (ACC) systems have high energy and heat requirements, hindering their development in many scenarios. These systems typically require large amounts of high-temperature steam and external electricity to drive reboilers, pumps, and auxiliary equipment, resulting in high energy consumption and poor economic efficiency. Furthermore, natural gas power plants have high flue gas temperatures (300–500°C), but traditional systems do not adequately utilize waste heat from these gases, failing to maximize energy recovery. On the other hand, liquefied natural gas (LNG) vaporization releases a significant amount of cold energy (-162°C), which is poorly utilized in current technologies. Carbon dioxide, as a recyclable working fluid, can be compressed for energy storage and expanded for power generation between high and low pressure. However, the round-trip energy efficiency (RTE) of existing CO2 energy storage systems generally does not exceed 50%, limiting their engineering applications.

[0003] The thermal energy of flue gas itself is a high-quality energy source. By combining energy storage and LNG cold energy, a heat exchange network and energy consumption network of an integrated carbon capture system can be constructed, forming a carbon capture energy system that does not require external energy input, thus achieving the dual goals of efficient energy storage and carbon dioxide emission reduction.

[0004] Therefore, there is an urgent need in the field to provide a carbon capture energy system that does not require external energy input, which can make full use of compression heat, LNG cold energy and flue gas waste heat to achieve carbon capture. Utility Model Content

[0005] The purpose of this application is to provide a carbon capture energy system that does not require external energy input, which can make full use of compression heat, LNG cold energy and flue gas waste heat to achieve carbon capture.

[0006] This application provides a carbon capture energy system that requires no external energy input, comprising:

[0007] A compression energy storage and release power generation unit, wherein the compression energy storage and release power generation unit is configured to store energy by compressing a first working medium and release energy to generate electricity by expanding and compressing the first working medium;

[0008] An absorption carbon capture unit is configured to achieve CO2 separation and capture by sequentially absorbing and desorbing CO2 in a flue gas stream;

[0009] An LNG cold energy utilization unit is configured to use the cold energy generated by LNG vaporization to cryogenically liquefy the CO2 separated by the absorption carbon capture unit, thereby generating liquid CO2.

[0010] The second power generation cycle unit is configured to recover the heat of compression generated during the compression process of the first working fluid and perform secondary expansion power generation, and to condense the second working fluid circulating in the second power generation cycle unit through the cold energy generated by LNG gasification, so as to form a closed loop.

[0011] The heat from the flue gas is supplied to the compression energy storage and release power generation unit and the absorption carbon capture unit, respectively.

[0012] In another preferred embodiment, the temperature of the flue gas flow is 300-500°C.

[0013] Preferably, the absorption carbon capture unit and LNG cold energy cool and liquefy the captured CO2 to -78°C.

[0014] Preferably, the compression and expansion of the working fluid in the compression energy storage and release power generation unit can be single-stage or multi-stage.

[0015] In another preferred embodiment, the compression energy storage and release power generation unit includes a first compressor, a first heat exchanger, a high-pressure storage tank, a second heat exchanger, a first expander, and a low-pressure storage tank in fluid communication. The first compressor is configured to compress the first working fluid. In the second heat exchanger, the high-pressure first working fluid from the high-pressure storage tank absorbs heat from the flue gas flow. The first expander is used to expand the high-temperature, high-pressure first working fluid from the first heat exchanger, thereby generating electricity. The electrical energy generated by the first expander is used for all compressors and pumps in the system.

[0016] Preferably, the first expander provides more than 80% of the total power generation of the system to drive the compressor and pump and maintain the system without external power input.

[0017] Preferably, the first working medium is air or CO2.

[0018] Preferably, the compression energy storage and release power generation unit further includes a first throttle valve located downstream of the high-pressure storage tank and upstream of the first heat exchanger, and a second throttle valve located downstream of the low-pressure storage tank and upstream of the first compressor.

[0019] In another preferred embodiment, the absorption carbon capture unit includes a heat recovery device and a reboiler. The heat recovery device is in fluid communication with the second heat exchanger and is used to absorb the waste heat of the flue gas flow and provide the waste heat to the reboiler.

[0020] In another preferred embodiment, the pressure range of the high-pressure storage tank is 12.5 to 16.5 MPa, and the pressure range of the low-pressure storage tank is 2.8 to 4.0 MPa.

[0021] In another preferred embodiment, the second power generation cycle unit includes a first pump, a second expander, and a second generator. The first pump is used to pump a second working fluid to the first heat exchanger. In the first heat exchanger, the high-pressure second working fluid from the first pump exchanges heat with the high-temperature and high-pressure first working fluid from the first compressor, thereby obtaining a high-temperature and high-pressure second working fluid that flows into the second expander.

[0022] In another preferred embodiment, the second expander is used to expand the high-temperature and high-pressure second working fluid, thereby driving the second generator to generate electricity. The low-pressure second working fluid flowing out of the second expander also utilizes the cold energy generated by the vaporization of the LNG, and then is condensed and enters the first pump for circulation.

[0023] In another preferred embodiment, the LNG cold energy utilization unit includes a second pump and a third heat exchanger. The second pump pumps liquid LNG into the third heat exchanger, which is in fluid communication with the second expander. In the third heat exchanger, CO2 output from the absorption carbon capture unit exchanges heat with the low-pressure second working fluid from the second expander and the liquid LNG, thereby condensing the CO2 output from the absorption carbon capture unit into liquid CO2 and the low-pressure second working fluid from the second expander into a liquid low-pressure second working fluid.

[0024] Preferably, the LNG cold energy utilization unit further includes a second compressor and a first cooler. The second compressor is configured to compress the CO2 separated by the absorption carbon capture unit. The first cooler is located upstream of the third heat exchanger and downstream of the second compressor. The cooled CO2 flowing out of the first cooler enters the third heat exchanger for further liquefaction by LNG cold energy.

[0025] In another preferred embodiment, the third heat exchanger is also connected to the first pump of the second power generation cycle unit, and the liquid low-pressure second working fluid flows into the first pump for circulation.

[0026] In another preferred embodiment, the low-pressure first working fluid flowing out of the low-pressure storage tank flows into the first compressor to circulate in the compression energy storage and release power generation unit.

[0027] In another preferred embodiment, the compression energy storage and release power generation unit further includes a cold energy storage device located downstream of the first expander and upstream of the low-pressure storage tank. The cold energy storage device is in fluid communication with the first compressor and is located upstream of the first compressor. Through the cold energy storage device, the cold energy generated by the vaporization of the first working fluid is used to store the first working fluid in the low-pressure storage tank in a liquid form.

[0028] In another preferred embodiment, the absorption carbon capture unit includes a heat recovery device, an absorption tower, a lean liquid pump, a fourth heat exchanger, a mixer, a reboiler, a desorption tower, a gas-liquid separator, a condenser, a water replenishment tank, and an absorbent replenishment tank, for capturing, desorbing, and purifying CO2 from flue gas using a chemical absorption method.

[0029] In another preferred embodiment, the second heat exchanger and the heat recovery device are both connected to the flue gas flow and are used to provide the waste heat of the flue gas to the steam heating of high-pressure CO2 and the reboiler of the absorption carbon capture unit, respectively.

[0030] It should be understood that, within the scope of this utility model, the above-described technical features of this utility model and the technical features specifically described below (such as in the embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be described in detail here. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. It should be understood that the drawings described below are merely some implementation examples of this utility model, and those skilled in the art can obtain other implementation examples based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of a low-pressure gaseous energy storage process according to the first embodiment of this application;

[0033] Figure 2 This is a schematic diagram of a low-pressure liquid energy storage process according to the second embodiment of this application.

[0034] In each of the attached figures, the markings are as follows:

[0035] 11-First Compressor

[0036] 12-First heat exchanger

[0037] 13-High-pressure storage tank

[0038] 14-First throttle valve

[0039] 15-Second heat exchanger

[0040] 16-First Expander

[0041] 17-Low-pressure storage tank

[0042] 18-Second Throttling Valve

[0043] 21-First Pump

[0044] 22-Second Expander

[0045] 31-Second Compressor

[0046] 32-First Cooler

[0047] 33-Second Pump

[0048] 34-Third heat exchanger

[0049] 41-Heat recovery device

[0050] 42-Absorption Tower

[0051] 43-Lean solution pump

[0052] 44-Fourth heat exchanger

[0053] 45-Mixer

[0054] 46-Reboiler

[0055] 47-Analysis Tower

[0056] 48-Gas-Liquid Separator

[0057] 49-Condenser

[0058] 50-Water Refill Tank

[0059] 51-Absorbent Replenishment Tank

[0060] 52-Second Cooler Detailed Implementation

[0061] Through extensive and in-depth research, the inventors have developed a carbon capture energy system that requires no external energy input. This integrated energy system combines energy storage (ES), liquefied natural gas (LNG) cold energy utilization, and absorption carbon capture technology, making it suitable for any high-energy-consumption CO2 capture scenario, such as natural gas combined cycle power plants. The system achieves efficient CO2 capture and liquefaction storage by recovering compression heat and flue gas waste heat, combined with absorption and LNG cold energy. The energy storage power round-trip efficiency reaches 70%, and the CO2 capture rate exceeds 99.5%. It is suitable for scenarios such as natural gas power plants, offering the advantages of high energy storage density and low carbon emissions. The system of this application can achieve CO2 capture without external energy input (e.g., electricity) under stable operating conditions.

[0062] In the following description, many technical details are presented to help the reader better understand this application. However, those skilled in the art will understand that the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0063] the term

[0064] As used herein, the terms "second power generation cycle unit" and "second power generation cycle loop" are used interchangeably;

[0065] As used herein, the terms “flue gas” and “flue gas flow” are used interchangeably;

[0066] This application has at least one of the following advantages:

[0067] (a) The system of this application utilizes compression heat recovery, LNG cold energy utilization and flue gas waste heat in a cascade manner, generates electricity by absorbing compression heat, and generates electricity by storing and releasing energy through compressed air CO2 and other media. That is, the first expander and the second expander generate electricity, which enables the system to capture CO2 in a stable state without external energy input. In other words, in a stable operating state, the entire system can achieve the entire process of compression, desorption, liquefaction and power generation without external energy (e.g. electrical energy) input.

[0068] Optionally, (b) the system of this application improves the energy round-trip efficiency (RTE) of the energy storage system to 70% through compression heat recovery, LNG cold energy utilization and flue gas waste heat cascade utilization;

[0069] Optionally, (c) a portion of the waste heat from the flue gas in this application provides heat to the reboiler of the stripping tower, thereby reducing the energy consumption of the carbon capture system;

[0070] Optionally, (d) the system integration of LNG cold energy and chemical absorption carbon capture technology in this application can achieve a CO2 capture rate of up to 99.5%, significantly reducing carbon emissions;

[0071] Optionally, (e) the system absorption carbon capture of this application has a wider range of applications than cryogenic carbon capture and can handle feed gas with lower CO2 content;

[0072] Optionally, (f) the system of this application adopts a dual-mode energy storage of liquid and gas (Example 1 and Example 2) to adapt to different engineering scenarios, with a maximum energy storage density of 58.17 kWh / m³. 3 ;

[0073] Optionally, (g) the system round-trip energy efficiency (RTE) of this application is 42.3% higher than that of conventional compressed energy storage systems;

[0074] Optionally, (h) the system of this application reduces reliance on renewable energy and is applicable to stationary carbon emission scenarios such as natural gas power plants.

[0075] A carbon capture energy system that requires no external energy input

[0076] The system includes:

[0077] A compression energy storage and release power generation unit, wherein the compression energy storage and release power generation unit is configured to store energy by compressing a first working medium and release energy to generate electricity by expanding and compressing the first working medium; preferably, the first working medium is air or CO2.

[0078] An absorption carbon capture unit is configured to achieve CO2 separation and capture by sequentially absorbing and desorbing CO2 in a flue gas stream;

[0079] An LNG cold energy utilization unit is configured to use the cold energy generated from LNG vaporization to cryogenically liquefy CO2 emitted from an absorption carbon capture unit, thereby generating liquid CO2. This cold energy is also used to condense the second working fluid circulating in a second power generation cycle unit.

[0080] The second power generation cycle unit is configured to recover the heat of compression generated during the compression process of the first working fluid and perform secondary expansion power generation, and to condense the second working fluid circulating in the second power generation cycle unit through the cold energy generated by LNG gasification, so as to form a closed loop.

[0081] The heat from the flue gas is supplied to the compression energy storage and release power generation unit and the absorption carbon capture unit, respectively.

[0082] Preferably, the second power generation cycle includes a first pump 21, a second expander 22, and a second generator. The second power generation cycle unit is configured to have the first pump pump a second working fluid to absorb the compression heat generated during the compression process of the first working fluid, and to drive the second generator to generate electricity through the second expander. The expanded second working fluid is further cooled and condensed using the cold energy generated by LNG vaporization, and the condensed second working fluid is returned to the first pump to form a cycle.

[0083] Preferably, the compressed energy storage and release power generation unit includes a high-pressure storage tank (HPT) 13 and a low-pressure storage tank 17. Preferably, the pressure range of the high-pressure storage tank (HPT) 13 is 12.5-16.5 MPa, and the pressure range of the low-pressure storage tank (LPT) 17 is 2.8-4.0 MPa.

[0084] Preferably, the absorption carbon capture unit and LNG cold energy cool and liquefy the captured CO2 to -78°C, with a CO2 capture rate of ≥99.5%.

[0085] Preferably, the compression energy storage and release power generation unit includes a first expander 16. The first expander 16 and the second expander 22 of the second power generation cycle unit are power generation units, and the generated electricity is used to supply the compressor and pump in the system. The first expander 16 provides no less than 80% of the power consumption of the system.

[0086] Preferably, the LNG cold energy utilization unit includes a third heat exchanger, in which the second working fluid circulating in the second power generation cycle unit (or the second power generation cycle loop) exchanges heat with the LNG cold energy and the CO2 output by the absorption carbon capture unit.

[0087] Preferably, the compression energy storage and release power generation unit includes a second heat exchanger 15 located upstream of the first expander 16 and downstream of the high-pressure storage tank 13. In the second heat exchanger 15, the flue gas exchanges heat with the high-pressure working fluid flowing out of the high-pressure storage tank 13. Preferably, the absorption carbon capture unit also includes a heat recovery device 41, which is connected to the first heat exchanger 15 and is used to absorb the waste heat of the flue gas. That is, the waste heat of the flue gas is recovered through the heat exchanger 3 to provide heat energy for the compression energy storage and release power generation unit. At the same time, another part of the waste heat of the flue gas serves as the heat source for the reboiler of the desorption tower of the absorption carbon capture unit, thereby reducing system energy consumption and making full use of the waste heat of the flue gas.

[0088] To make the objectives, technical solutions, and advantages of this utility model clearer, the embodiments of this utility model will be described in further detail below with reference to the accompanying drawings. It should be understood that these are merely examples provided to the reader of possible implementations of this utility model, and are not intended to limit the scope of this utility model.

[0089] Example

[0090] See Figure 1 and Figure 2 This application provides a carbon capture energy system that requires no external energy input. This system is an integrated energy system based on CO2 energy storage, LNG cold energy, and absorption carbon capture, including a compression energy storage and release power generation unit, an LNG cold energy utilization unit, an absorption carbon capture unit, and a second power generation cycle unit. The system achieves the entire process of compression, desorption, liquefaction, and expansion power generation through internal energy cycling, requiring no external energy input during steady-state operation.

[0091] The system includes a compression energy storage and release power generation unit for compressing and storing energy and generating electricity from working fluids such as air or CO2; an LNG cold energy utilization unit that distributes the cold energy from LNG gasification to the cold source of the CO2 liquefaction and second power generation cycle unit; an absorption carbon capture unit that captures CO2 from flue gas through chemical absorption; and a waste heat recovery system that recovers some of the waste heat from the flue gas during the compression energy storage and release power generation process of working fluids such as air or CO2, and recovers the remaining waste heat from the flue gas through the reboiler in the desorption tower during the capture of CO2 from the flue gas through chemical absorption.

[0092] Specifically, the compression energy storage and release power generation unit includes a first compressor 11, a first heat exchanger 12, a high-pressure storage tank 13, a first throttle valve 14, a second heat exchanger 15, a first expander 16, a low-pressure storage tank 17, and a second throttle valve 18 in fluid communication, to realize the compression energy storage and release power generation of carbon dioxide; preferably, the compression and expansion of the working fluid can be single-stage or multi-stage.

[0093] The absorption carbon capture unit utilizes chemical absorption to sequentially absorb and desorb CO2 from flue gas to achieve CO2 separation and capture. The absorption carbon capture unit includes a heat recovery device 41, an absorption tower 42, a lean liquid pump 43, a fourth heat exchanger 44, a mixer 45, a reboiler 46, a desorption tower 47, a gas-liquid separator 48, a condenser 49, a water replenishment tank 50, an absorbent replenishment tank 51, and a second cooler 52.

[0094] The second heat exchanger 15 of the compression energy storage and release power generation unit and the heat recovery device 4 in the absorption carbon capture unit are used for flue gas waste heat recovery. The waste heat of the flue gas is recovered through the second heat exchanger 15 to provide heat energy for the compression energy storage and release power generation unit. At the same time, another part of the waste heat of the flue gas serves as the heat source for the reboiler 46 of the desorption tower 47 of the absorption carbon capture unit. The heat recovery device 41 of the absorption carbon capture unit is connected to the second heat exchanger 15. The heat recovery device 41 transfers the waste heat of the flue gas to the reboiler, thereby reducing system energy consumption and making full use of the waste heat of the flue gas.

[0095] The second power generation cycle unit includes a first pump 21, a second expander 22, and the second power generation cycle unit also utilizes the heat of compression of compressed air or CO2 from the first compressor 11 of the compression energy storage and release power generation unit and the LNG vaporization cold energy from the LNG cold energy utilization unit mentioned below.

[0096] The LNG cold energy utilization unit includes a second compressor 31, a first cooler 32, a second pump 33, and a third heat exchanger 34. The LNG vaporization cold energy is used by the third heat exchanger 34 to liquefy CO2 obtained from the absorption carbon capture unit, thereby outputting liquid CO2 from the third heat exchanger 34. The LNG vaporization cold energy is also used to drive the second expander 22 to generate electricity. In other words, the LNG cold energy is divided into two parts: one part is used as a cold source for the second power generation cycle unit, and the other part is used to liquefy CO2 obtained from the absorption carbon capture unit, which is beneficial for carbon sequestration.

[0097] The workflow of the system in this application

[0098] During the energy storage phase, the first compressor 11 of the compression energy storage and release power generation unit is used to compress air or CO2. Taking CO2 as an example, the high-temperature, high-pressure CO2 discharged from the first compressor 11 enters the first heat exchanger 12 and exchanges heat with the cold end medium of the first heat exchanger 12. The high-pressure liquid CO2 cooled by the first heat exchanger 12 enters the high-pressure storage tank 13 for storage. In one embodiment, the low-pressure CO2 is compressed to a supercritical state (16.5 MPa) through one or more stages.

[0099] The first heat exchanger 12 of the compression energy storage and release power generation unit has the function of reducing the temperature of CO2 to make it suitable for entering the high-pressure storage tank 13; the first heat exchanger 12 also has the function of recovering compression heat. Preferably, the compression heat is used to heat the high-pressure second working fluid pumped by the first pump 21 of the second power generation cycle unit before expansion, or to provide a heat source for other energy recovery mechanisms.

[0100] The first heat exchanger 12 is also connected to the second expander 22 of the second power generation cycle unit (second working fluid cycle loop, ORC cycle loop). In the first heat exchanger 12, the high-temperature, high-pressure CO2 from the first compressor 11 exchanges heat with the high-pressure liquid second working fluid pumped by the first pump 21 of the second power generation cycle unit. The high-temperature, high-pressure gaseous second working fluid flowing out of the first heat exchanger 12 flows into the second expander 22, which expands the high-temperature, high-pressure gaseous second working fluid, thereby driving the second generator to generate electricity. That is, the heat of compression generated by the first compressor 11 compressing air or CO2 is converted into electrical energy through the second power generation cycle unit.

[0101] After the high-temperature and high-pressure gaseous second working fluid expands in the second expander 22, its pressure and temperature decrease, becoming a low-pressure second working fluid. This low-pressure second working fluid enters the third heat exchanger 34, where it exchanges heat with the LNG cold energy provided by the LNG cold energy utilization unit, causing the second working fluid to condense into a liquid and be drawn back into the first pump 21 to enter the next cycle. This second working fluid can be a refrigerant.

[0102] The carbon capture unit is used to absorb and desorb CO2 in flue gas sequentially using chemical absorption to achieve CO2 separation and capture. The CO2 discharged from the carbon capture unit enters the second compressor 31. The high-temperature and high-pressure gaseous CO2 obtained by the second compressor 31 enters the first cooler 32. The first cooler 32 cools the high-temperature and high-pressure gaseous CO2. The high-pressure gaseous CO2 discharged from the first cooler 32 enters the third heat exchanger 34. In the third heat exchanger 34, the high-pressure gaseous CO2 is further cooled by the low-temperature LNG gas pumped to the third heat exchanger 34 via the second pump 33, forming high-pressure liquid CO2. This high-pressure liquid CO2 can be stored in the high-pressure storage tank 13 of the compression energy storage and release power generation unit or transported.

[0103] In other words, in the third heat exchanger 34, the second working fluid, the high-pressure CO2 discharged from the first cooler 32, and the cold energy of LNG exchange heat. The third heat exchanger 34 is the key coupling device of this system.

[0104] The third heat exchanger 34 has the second working fluid steam discharged from the expander 1 and the high-pressure CO2 discharged from the first cooler 32 on one side, and LNG cold energy (-162℃) on the other side. The triple heat exchange process of the third heat exchanger 34 is as follows:

[0105] 1) LNG cold energy provides a low-temperature cold source for the condensation of the second working fluid. Specifically, the superheated steam discharged from the second expander 22 exchanges heat with the LNG cold energy, causing the second working fluid to gradually condense into a liquid. 2) LNG cold energy cools the CO2 discharged from the second compressor 31. The high-pressure CO2 discharged from the second compressor 31 requires deep cooling before entering the liquefaction section. LNG cold energy handles a portion of this cooling load. A cascaded heat exchange occurs between the three fluids in heat exchanger 4, maximizing overall energy efficiency. The structure of heat exchanger 4 ensures that the second working fluid is ultimately completely condensed into a liquid and returned to the first pump 21, while the CO2 from the first cooler 32 is deep-cooled and liquefied, reaching a temperature of -78°C. LNG cold energy is utilized efficiently, improving cold energy utilization efficiency.

[0106] During the energy release phase (expansion power generation phase), the CO2 stored in the high-pressure storage tank 13 enters the second heat exchanger 15 after the flow rate is controlled by the first throttle valve 14. At this time, the CO2 is a high-pressure, low-temperature liquid CO2. The heat source of the second heat exchanger 15 comes from the high-temperature flue gas, such as 300-500℃. The second heat exchanger 15 performs a heating function on the high-pressure, low-temperature liquid CO2, raising the CO2 temperature to the high temperature required by the first expander 16, that is, recovering the high-grade waste heat in the flue gas and improving the system energy efficiency.

[0107] The high-pressure CO2, after being heated and vaporized, enters the first expander 16. The first expander 16 expands the high-pressure CO2 to drive the first generator, producing electrical energy. The first expander 16 is the main power generation unit of the system, undertaking most of the energy storage and release output, accounting for more than 80% of the total power generation of the system. The output energy is used to drive the various compressors and pumps of the system. The expanded CO2 pressure drops rapidly, becoming a low-pressure working fluid. The expanded CO2 flows into the low-pressure storage tank 17. Preferably, the pressure range of the low-pressure storage tank (LPT) 17 is between 2.8 and 4.0 MPa. The low-pressure CO2 flowing out of the low-pressure storage tank 14 returns to the suction port of the first compressor after the flow rate is controlled by the second throttle valve 18, entering the next round of compression, thus forming a complete cycle.

[0108] The second heat exchanger 15 is also connected to the heat recovery device 4 in the absorption carbon capture unit. The heat recovery device 4 is connected to the reboiler 46 and provides waste heat from the flue gas to the reboiler 46. The heat recovery device 4 is also connected to the absorption tower 42. Thus, the absorption carbon capture unit absorbs and desorbs CO2 from the flue gas sequentially through equipment such as the lean liquid pump 43, the fourth heat exchanger 44, the mixer 45, the reboiler 46, the desorption tower 47, the gas-liquid separator 48, the condenser 49, the water replenishment tank 50, the absorbent replenishment tank 51, and the second cooler 52 to obtain CO2.

[0109] CO2 discharged from the absorption carbon capture unit enters the second compressor 31. The high-temperature, high-pressure gaseous CO2 obtained by the second compressor 31 enters the first cooler 32, which cools the high-temperature, high-pressure gaseous CO2. The high-pressure gaseous CO2 discharged from the first cooler 32 enters the third heat exchanger 34. In the third heat exchanger 34, the low-temperature LNG gas pumped to the third heat exchanger 34 by the second pump 33 is further cooled to form high-pressure liquid CO2. This high-pressure liquid CO2 can be stored in the high-pressure storage tank 13 of the compression energy storage and release power generation unit or transported.

[0110] exist Figure 1 and Figure 2 In this embodiment, the flue gas temperature is 300-500°C. After passing through the heat recovery device 41, the temperature is reduced to room temperature of 30°C and enters the absorption carbon capture unit. Finally, the high-purity CO2 that comes out of the gas-liquid separator 48 downstream of the desorption tower 47 has a temperature of 40°C. It is then cooled to -78°C by LNG at -164°C to achieve CO2 capture.

[0111] Figure 1 and Figure 2 A schematic diagram of a low-pressure gaseous energy storage process and two embodiments of low-pressure liquid energy storage are provided.

[0112] exist Figure 1In the embodiment of low-pressure gaseous energy storage, the process is as detailed above, with the low-pressure storage tank (LPT) at a pressure of 2.8 MPa and a temperature of 13°C, where CO2 is stored in a gaseous state.

[0113] Energy storage stage: CO2 is compressed to 16.5MPa in two stages, and the heat of compression is transferred to the second power generation cycle unit (or ORC cycle loop) second expander 22 for power generation through the first heat exchanger 12;

[0114] Energy release stage: Liquid CO2 is heated to 110°C by the second heat exchanger 15 to drive the first expander 16 to generate electricity. Waste heat from the exhaust gas is recovered by the heat recovery device 41 and used in the reboiler 46 of the absorption carbon capture unit. That is, the waste heat from the flue gas provides heat for the high-pressure, low-temperature liquid CO2, and at the same time provides heat for the reboiler 46 of the carbon capture and stripping tower.

[0115] exist Figure 2 In the embodiment of low-pressure liquid energy storage, with Figure 1 The difference in this embodiment is the addition of a cold energy storage device 19 (CSD). The CSD is located downstream of the first expander 16 and upstream of the low-pressure storage tank 17. The low-pressure, low-temperature first working fluid flowing from the first expander 16 flows into the CSD, and then into the low-pressure storage tank 17. The first working fluid flowing from the low-pressure storage tank 17 flows into the CSD through a second throttle valve 18, and then into the CSD. The first working fluid flowing from the CSD flows into the first compressor 11. In the CSD, the cold energy generated by the vaporization of CO2 in the CSD allows the low-pressure, low-temperature first working fluid from the first expander 16 to be stored in a liquid state in the low-pressure storage tank 17. That is, the CSD utilizes the cold energy generated by the vaporization of CO2 to maintain liquid storage. The low-pressure storage tank (LPT) has a pressure of 3.0 MPa and a temperature of -5°C, storing CO2 in a liquid state. The remaining processes are consistent with Embodiment 1. Efficiency increased to 59.30%.

[0116] In this invention, all directional indicators (such as up, down, left, right, front, back, etc.) are only used to explain the relative positional relationship and movement of each component in a specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0117] It should be noted that in this patent application, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this patent application, if it refers to performing an action according to an element, it means performing the action at least according to that element, including two cases: performing the action only according to that element, and performing the action according to that element and other elements. Expressions such as "multiple," "repeatedly," and "various" include two, two times, two kinds, and more than two, more than two times, and more than two kinds.

[0118] All documents mentioned in this application are considered to be incorporated in their entirety into the disclosure of this application so that they can serve as a basis for modifications if necessary. Furthermore, it should be understood that after reading the foregoing disclosure of this application, those skilled in the art can make various alterations or modifications to this application, and these equivalent forms also fall within the scope of protection claimed in this application.

Claims

1. A carbon capture energy system that requires no external energy input, characterized in that, include: A compression energy storage and release power generation unit, wherein the compression energy storage and release power generation unit is configured to store energy by compressing a first working medium and release energy to generate electricity by expanding and compressing the first working medium; An absorption carbon capture unit is configured to separate and capture CO2 by sequentially absorbing and desorbing CO2 in a flue gas stream. An LNG cold energy utilization unit is configured to use the cold energy generated by LNG vaporization to cryogenically liquefy the CO2 separated by the absorption carbon capture unit, thereby generating liquid CO2. as well as The second power generation cycle unit is configured to recover the heat of compression generated during the compression process of the first working fluid and perform secondary expansion power generation, and to condense the second working fluid circulating in the second power generation cycle unit through the cold energy generated by LNG gasification, so as to form a closed loop. The heat from the flue gas is supplied to the compression energy storage and release power generation unit and the absorption carbon capture unit, respectively.

2. The system as described in claim 1, characterized in that, The compression energy storage and release power generation unit includes a first compressor (11), a first heat exchanger (12), a high-pressure storage tank (13), a second heat exchanger (15), a first expander (16), and a low-pressure storage tank (17) in fluid communication. The first compressor (11) is configured to compress the first working fluid. In the second heat exchanger (15), the high-pressure first working fluid from the high-pressure storage tank (13) absorbs the heat from the flue gas flow. The first expander (16) is used to expand the high-temperature and high-pressure first working fluid from the second heat exchanger (15) to generate electricity. The electrical energy generated by the first expander (16) is used for all compressors and pumps in the system.

3. The system as described in claim 2, characterized in that, The absorption carbon capture unit includes a heat recovery device (41) and a reboiler (46). The heat recovery device (41) is in fluid communication with the second heat exchanger (15). The heat recovery device (41) is used to absorb the waste heat of the flue gas flow and provide the waste heat to the reboiler (46).

4. The system as described in claim 2, characterized in that, The pressure range of the high-pressure storage tank is 12.5~16.5 MPa, and the pressure range of the low-pressure storage tank is 2.8~4.0 MPa.

5. The system as described in claim 2, characterized in that, The second power generation cycle unit includes a first pump (21), a second expander (22) and a second generator. The first pump (21) is used to pump the second working fluid to the first heat exchanger (12). In the first heat exchanger (12), the high-pressure second working fluid from the first pump (21) exchanges heat with the high-temperature and high-pressure first working fluid from the first compressor (11), and the resulting high-temperature and high-pressure second working fluid flows into the second expander (22).

6. The system as described in claim 5, characterized in that, The LNG cold energy utilization unit includes a second pump (33) and a third heat exchanger (24). The second pump (33) is used to pump liquid LNG into the third heat exchanger (24). The third heat exchanger (24) is in fluid communication with the second expander (22). In the third heat exchanger (24), the CO2 output from the absorption carbon capture unit exchanges heat with the low-pressure second working fluid from the second expander (22) and the liquid LNG, so that the CO2 output from the absorption carbon capture unit is condensed into liquid CO2, and the low-pressure second working fluid from the second expander (22) is condensed into liquid low-pressure second working fluid.

7. The system as described in claim 6, characterized in that, The third heat exchanger (24) is also connected to the first pump (21) of the second power generation cycle unit, and the liquid low-pressure second working fluid flows into the first pump (21) for circulation.

8. The system as described in claim 2, characterized in that, The low-pressure first working fluid flowing out from the low-pressure storage tank (17) flows into the first compressor (11) to circulate in the compression energy storage and release power generation unit.

9. The system as described in claim 2, characterized in that, The compression energy storage and release power generation unit also includes a cold energy storage device (19), which is located downstream of the first expander (16) and upstream of the low-pressure storage tank (17). The cold energy storage device (19) is in fluid communication with the first compressor (11) and is located upstream of the first compressor (11). Through the cold energy storage device (19), the cold energy generated by the vaporization of the first working fluid is used to store the first working fluid in the low-pressure storage tank (17) in liquid form.

10. The system as claimed in claim 1, characterized in that, The absorption carbon capture unit includes a heat recovery device (41), an absorption tower (42), a lean liquid pump (43), a fourth heat exchanger (44), a mixer (45), a reboiler (46), a desorption tower (47), a gas-liquid separator (48), a condenser (49), a water replenishment tank (50), and an absorbent replenishment tank (51), and is used to capture, desorb, and purify CO2 from flue gas by chemical absorption.

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