A high-pressure chemical looping coupled calcium cycle carbon dioxide capture system and application thereof

Abstract

The application relates to the technical field of CO2 capture, in particular to a high-pressure chemical chain coupled calcium cycle CO2 capture system and application thereof, and the capture system comprises a gas-fired power generation unit, a first waste heat power generation unit and a CO2 separation unit; the CO2 separation unit comprises a first air compressor, an air reactor, a first turbine, a carbonation tower and a calcining furnace. The calcium cycle is coupled with the chemical chain air reactor in a mode, high-concentration oxygen in tail flue gas of natural gas is used for oxidizing metal oxygen carriers in the air reactor, oxygen sources for the calcining furnace are provided, air originally required is replaced, the combined cycle is driven to work, the problem of flue gas preheating in the calcium cycle capture technology of natural gas flue gas is solved, the remaining oxygen in the flue gas is fully utilized, the CO2 concentration in the flue gas entering the carbonation tower is increased, and the capture energy consumption is reduced; and since part of the energy is used for driving the combined cycle, heat exchange loss can be effectively reduced, and the power output of the capture system is improved.

Description

Technical Field

[0001] This invention relates to the field of CO2 capture technology, and in particular to a high-pressure chemical chain coupled calcium cycle carbon dioxide capture system and its application. Background Technology

[0002] Carbon dioxide capture and storage is expected to become a key to mitigating CO2 emissions and reducing environmental impact. Among different CO2 capture technologies, post-combustion CO2 capture is the only end-of-pipe capture method that can reduce carbon emissions from stationary sources without changing industrial plants.

[0003] Among post-combustion CO2 capture technologies, the calcium cycle process is a promising low-energy CO2 capture technology with advantages such as wide availability of raw materials, high reactivity, and low cost. The calcium cycle process mainly consists of two processes: carbonation and calcination. However, both occur at relatively high reaction temperatures, resulting in significant waste heat. This includes waste heat released at 600-650℃ from the carbonation reaction and at 850℃ from the decarbonized flue gas products and calcination furnace products. Current research mainly uses steam circulation to absorb the waste heat from the calcium cycle, but the large temperature difference between the high-temperature waste heat and the main steam temperature leads to significant heat exchange losses. Furthermore, to avoid dilution of enriched CO2 by N2 in the air, the calcium cycle process typically employs oxygen-enriched combustion. However, the high-purity oxygen required for oxygen-enriched combustion consumes a large amount of air separation energy. All of these factors contribute to increased costs and decreased efficiency in practical applications, hindering the widespread adoption of this technology. Furthermore, when the calcium cycle process is used for flue gas capture at the tail end of a natural gas combined cycle, the carbonation furnace will require additional heat supply if flue gas preheating is not performed, which also poses a challenge to the application of calcium cycle technology in natural gas power plants.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a high-pressure chemical chain coupling calcium cycle carbon dioxide capture system and its application, aiming to solve the problems of large heat loss and high energy consumption in existing CO2 capture systems.

[0006] The technical solution of the present invention is as follows: A high-pressure chemical chain coupled calcium cycle carbon dioxide capture system includes: a gas-fired power generation unit, a first waste heat power generation unit that generates electricity using the flue gas discharged from the gas-fired power generation unit, and a CO2 separation unit that separates CO2 from the flue gas discharged from the first waste heat power generation unit. The CO2 separation unit includes: The first compressor is used to pressurize the flue gas discharged from the first waste heat power generation unit to form compressed flue gas; An air reactor, connected to the first compressor, is used to transfer oxygen from the compressed flue gas to a metal oxygen carrier to form metal oxides; the air reactor is loaded with a metal oxygen carrier and a carbon dioxide adsorbent. A first turbine is connected to the air reactor, and the oxygen-deficient flue gas from the outlet of the air reactor is used to drive the first turbine to do work. A carbonation tower is connected to the air reactor and the first turbine; the carbon dioxide adsorbent and the metal oxide in the air reactor are transferred to the carbonation tower to capture carbon dioxide in the oxygen-deficient flue gas from the outlet of the first turbine; A calcining furnace is connected to the carbonation tower and the air reactor; the product in the carbonation tower is transferred to the calcining furnace for reduction to form a reduction product, and the reduction product is returned to the air reactor. The high-pressure chemical loop coupled calcium cycle carbon dioxide capture system, wherein the metal oxygen carrier includes one or more of Fe, Cu, Co, Mn, and composite metal oxygen carriers; and / or, the carbon dioxide adsorbent is calcium oxide. In the high-pressure chemical loop coupled calcium cycle carbon dioxide capture system, the first compressor pressurizes the flue gas discharged from the first waste heat power generation unit to 1-15 bar to form compressed flue gas; the compressed flue gas enters the air reactor through a pipeline.

[0007] The high-pressure chemical chain coupled calcium cycle carbon dioxide capture system wherein the reaction pressure in the air reactor is 1-15 bar and the reaction temperature in the air reactor is 950-1100℃.

[0008] The high-pressure chemical chain coupled calcium cycle carbon dioxide capture system, wherein the reaction temperature in the carbonation tower is 600-650℃.

[0009] The high-pressure chemical chain coupled calcium cycle carbon dioxide capture system, wherein the reaction temperature in the calcining furnace is 900-950℃.

[0010] The high-pressure chemical loop coupled calcium cycle carbon dioxide capture system, wherein the gas-fired power generation unit includes: The second compressor is used to pressurize air to form compressed air; A combustion chamber, connected to the second compressor, is used to mix and burn natural gas with the compressed air; The second turbine is connected to the combustion chamber, and the flue gas from the outlet of the combustion chamber is used to drive the second turbine to do work.

[0011] The high-pressure chemical loop coupled calcium cycle carbon dioxide capture system, wherein the first waste heat power generation unit includes: a first waste heat boiler, a third turbine, a first condenser, and a first pump; The first waste heat boiler is connected to the second turbine; the first waste heat boiler forms a closed loop connection with the third turbine, the first condenser, and the first pump; the flue gas discharged from the first waste heat boiler enters the first compressor.

[0012] The high-pressure chemical loop coupled calcium cycle carbon dioxide capture system further includes a second waste heat power generation unit; the second waste heat power generation unit includes: a second waste heat boiler, a fourth turbine, a second condenser, and a second pump; The second waste heat boiler is connected to the carbonation tower and the calcining furnace; the second waste heat boiler forms a closed loop connection with the fourth turbine, the second condenser, and the second pump; the second waste heat boiler discharges decarbonized flue gas and CO2-rich gas.

[0013] Application of a high-pressure chemical chain coupled calcium cycle carbon dioxide capture system in the tail gas capture of natural gas power plants.

[0014] Beneficial Effects: This invention provides a high-pressure chemical loop coupled calcium cycle carbon dioxide capture system and its application. The high-pressure chemical loop coupled calcium cycle carbon dioxide capture system includes: a gas-fired power generation unit, a first waste heat power generation unit that generates electricity using the flue gas discharged from the gas-fired power generation unit, and a CO2 separation unit that separates CO2 from the flue gas discharged from the first waste heat power generation unit. The CO2 separation unit includes: a first compressor for pressurizing the flue gas discharged from the first waste heat power generation unit to form compressed flue gas; and an air reactor connected to the first compressor for transferring oxygen in the compressed flue gas to a metal oxygen carrier to form a metal oxygen carrier. The system comprises: an oxide; an air reactor loaded with a metal oxygen carrier and a carbon dioxide adsorbent; a first turbine connected to the air reactor, wherein the oxygen-deficient flue gas from the air reactor outlet is used to drive the first turbine; a carbonation tower connected to the air reactor and the first turbine; the carbon dioxide adsorbent and the metal oxide in the air reactor are transferred to the carbonation tower to capture carbon dioxide from the oxygen-deficient flue gas from the first turbine outlet; and a calcining furnace connected to the carbonation tower and the air reactor; the product in the carbonation tower is transferred to the calcining furnace for reduction to form a reduction product, which is then returned to the air reactor. This invention employs a calcium cycle coupled with a chemical loop air reactor, utilizing the high concentration of flue gas from the tail end of natural gas to oxidize the metal oxygen carrier in the air reactor, providing an oxygen source for the calcining furnace, replacing the originally required air, and driving the combined cycle. This not only solves the problem of flue gas preheating in natural gas flue gas calcium cycle capture technology but also fully utilizes the remaining oxygen in the flue gas, increasing the CO2 concentration in the flue gas entering the carbonation tower and reducing capture energy consumption; simultaneously, it avoids the energy consumption of the air separation unit. Furthermore, since a portion of the energy is used to drive the combined cycle, replacing the traditional steam cycle, heat exchange losses can be effectively reduced and the power output of the capture system can be increased. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of a high-pressure chemical loop coupled calcium cycle carbon dioxide capture system according to the present invention; Figure 2 This is a process flow diagram of the application of the high-pressure chemical loop coupled calcium cycle carbon dioxide capture system in the tail gas capture of a natural gas power plant in Example 1. Figure 3 The process flow diagram of the natural gas calcium ring oxygen-enriched combustion and capture system in Comparative Example 1 is shown. Figure 4 The process flow diagram of the non-capture natural gas combined cycle power generation system in Comparative Example 2 is shown below. Explanation of reference numerals in the attached drawings: Gas-fired power generation unit 100, second compressor 101, combustion chamber 102, second turbine 103, first waste heat power generation unit 200, first waste heat boiler 201, third turbine 202, first condenser 203, first pump 204, CO2 separation unit 300, first compressor 301, air reactor 302, first turbine 303, carbonation tower 304, calcining furnace 305, second waste heat power generation unit 400, second waste heat boiler 401, fourth turbine 402, second condenser 403, second pump 404. Detailed Implementation

[0016] This invention provides a high-pressure chemical loop coupled calcium cycle carbon dioxide capture system and its application. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0017] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0018] like Figure 1 As shown, the present invention provides a high-pressure chemical chain coupled calcium cycle carbon dioxide capture system, comprising: a gas-fired power generation unit 100, a first waste heat power generation unit 200 for generating electricity using the flue gas discharged from the gas-fired power generation unit 100, and a CO2 separation unit 300 for separating CO2 from the flue gas discharged from the first waste heat power generation unit 200. The CO2 separation unit 300 includes: The first compressor 301 is used to pressurize the flue gas discharged from the first waste heat power generation unit 200 to form compressed flue gas. An air reactor 302 is connected to the first compressor 301 and is used to transfer oxygen in the compressed flue gas to a metal oxygen carrier to form metal oxides; the air reactor 302 is loaded with a metal oxygen carrier and a carbon dioxide adsorbent. A first turbine 303 is connected to the air reactor 302, and the oxygen-deficient flue gas at the outlet of the air reactor is used to drive the first turbine to do work. Carbonation tower 304 is connected to air reactor 302 and first turbine 303; carbon dioxide adsorbent and metal oxide in air reactor 302 are transferred to carbonation tower 304 to capture carbon dioxide in oxygen-deficient flue gas at the outlet of first turbine 303; The calcining furnace 305 is connected to the carbonation tower 304 and the air reactor 302; the product in the carbonation tower 304 is transferred to the calcining furnace 305 for reduction to form a reduction product, and the reduction product is returned to the air reactor 302.

[0019] In this embodiment, a calcium cycle and chemical loop air reactor coupling mode is adopted. First, the flue gas discharged from the first waste heat power generation unit 200 is pressurized by the first compressor 301 to form compressed air, which is then transported to the air reactor 302. The metal oxygen carrier in the air reactor 302 reacts with the oxygen in the compressed flue gas to form metal oxides and oxygen-deficient flue gas. The oxygen-deficient flue gas is then transported to the first turbine 303 to perform work, and the oxygen-deficient flue gas after performing work is then transported to the carbonate tower for CO2 capture. At the same time, the metal oxides in the air reactor... The product and carbon dioxide adsorbent are transported to the carbonation tower to capture CO2 in the oxygen-deficient flue gas using the carbon dioxide adsorbent therein; then the products (including metal oxides) in the carbonation tower are transported together to the calcining furnace 305, where the calcination reaction is heated by the exothermic oxidation reaction of natural gas with the metal oxides and the residual heat released by the air reactor 302, resulting in carbon dioxide adsorbent and metal oxygen carrier. Finally, the reduced carbon dioxide adsorbent and metal oxygen carrier are transported to the air reactor 302 to await the next cycle.

[0020] Specifically, this invention utilizes natural gas tail gas to oxidize the metal oxygen carrier in the air reactor, replacing the originally required air, and drives the combined cycle to perform work. This not only solves the problem of flue gas preheating in natural gas flue gas calcium ring capture technology, but also makes full use of the remaining oxygen in the flue gas, increasing the carbon dioxide concentration in the flue gas entering the carbonation tower and reducing capture energy consumption. Furthermore, compared to the traditional oxygen-enriched combustion calcium cycle process, the use of metal oxides to provide oxygen to the fuel in the calciner avoids the energy consumption of the air separation unit caused by directly separating oxygen from the air. Moreover, since a portion of the energy is used to drive the combined cycle, replacing the traditional steam cycle, heat exchange losses can be effectively reduced, and the power output of the capture system can be increased.

[0021] In some embodiments, the metal oxygen support includes one or more of Fe, Cu, Co, Mn, and composite metal oxygen supports; and / or, the carbon dioxide adsorbent is calcium oxide. Let the metal oxygen support be Me. When the compressed flue gas enters the air reactor 302, Me reacts with oxygen in the compressed flue gas to form metal oxides. The main chemical reaction that occurs is... The main chemical reaction between calcium oxide and CO2 is that calcium oxide reacts with carbon dioxide to form calcium carbonate, thereby capturing CO2 in the flue gas and obtaining decarbonized flue gas.

[0022] In some embodiments, the first compressor 301 pressurizes the flue gas discharged from the first waste heat power generation unit 200 to 1-15 bar to form compressed flue gas; the compressed flue gas enters the air reactor 302 through a pipeline.

[0023] Specifically, in the CO2 separation unit 300, the metal oxygen carrier Me and the carbon dioxide adsorbent together serve as the circulating medium of the CO2 separation unit; the flue gas discharged from the first waste heat power generation unit 200 is pressurized to 1-15 bar by the first compressor 301 and then enters the air reactor 302. In the air reactor 302, the compressed flue gas reacts with the metal oxygen carrier Me, transferring oxygen from the compressed flue gas to the metal oxygen carrier to generate metal oxide MeO; subsequently, the oxygen-deficient flue gas enters the first turbine 303 to perform work, and the oxygen-deficient flue gas after performing work then enters the carbonation tower 304; in the carbonation tower 304, the carbon dioxide adsorbent separates CO2 from the flue gas, and the generated product is sent to the calcining furnace 305 for regeneration, regenerating the carbon dioxide adsorbent and CO2-rich gas.

[0024] In some embodiments, the reaction pressure in the air reactor is 1-15 bar, and the reaction temperature in the air reactor is 950-1100°C. The medium entering the air reactor 302 is calcium oxide and a metal oxygen support, wherein under these conditions only the metal oxygen support Me participates in the reaction, and the main chemical reaction that occurs is... .

[0025] In some embodiments, the reaction in the carbonation tower is carried out at atmospheric pressure, and the reaction temperature in the carbonation tower is 600-650°C; the medium entering the carbonation tower consists of calcium oxide and MeO, of which only CaO participates in the reaction, and the main reaction that occurs is... .

[0026] In some embodiments, the reaction in the calcining furnace is carried out at atmospheric pressure, and the reaction temperature in the calcining furnace is 900-950°C; the medium entering the calcining furnace 305 is CaCO3 and MeO, and CaCO3 and MeO participate in the reaction simultaneously in the calcining furnace, with the main chemical reaction being... and .

[0027] Specifically, the oxygen required in the calcining furnace is provided by MeO, that is, MeO plays the role of transferring oxygen and reacting with the fuel input into the calcining furnace to provide energy for the regeneration reaction of CaCO3 in the calcining furnace; the energy required by the calcining furnace is provided by the combustion of fuel (natural gas CH4) and the heat released by the air reactor 302.

[0028] In some embodiments, the CO2 separation unit 300 needs to be replenished with new carbon dioxide adsorbent and oxygen carrier in a timely manner to maintain the activity of the carbon dioxide adsorbent and metal oxygen carrier. This operation is carried out in the calcining furnace. At the same time, excess metal oxygen carrier and carbon dioxide adsorbent are removed from the calcining furnace.

[0029] In some embodiments, the gas-fired power generation unit 100 includes: The second compressor 101 is used to pressurize air to form compressed air; Combustion chamber 102, connected to the second compressor, is used to mix and burn natural gas with the compressed air; The second turbine 103 is connected to the combustion chamber, and the flue gas discharged from the combustion chamber is used to drive the second turbine to do work.

[0030] Specifically, in the gas-fired power generation unit 100, natural gas enters the combustion chamber 102 and mixes with the compressed air pressurized by the second compressor 101, and combustion takes place in the combustion chamber 102; the high-temperature and high-pressure flue gas discharged from the combustion chamber 102 drives the second turbine 103 to do work, and the high-temperature and high-pressure flue gas at the outlet of the second turbine 103 continues to enter the first waste heat power generation unit 200.

[0031] In some embodiments, the first waste heat power generation unit 200 includes: a first waste heat boiler 201, a third turbine 202, a first condenser 203, and a first pump 204; The first waste heat boiler 201 is connected to the second turbine 103; the first waste heat boiler 201 forms a closed loop connection with the third turbine 202, the first condenser 203, and the first pump 204; the flue gas discharged from the first waste heat boiler 201 enters the first compressor 301.

[0032] Specifically, in the first waste heat power generation unit 200, the flue gas discharged from the second turbine 103 enters the first waste heat boiler 201 to heat the water in the first waste heat boiler. After being heated into steam, it enters the third turbine 202 to do work. The low-temperature steam at the outlet of the third turbine 202 enters the first condenser 203 to condense into water. Then it is pressurized and sent back to the first waste heat boiler 201 through the first pump 204 to absorb heat and start the next cycle.

[0033] In some embodiments, the high-pressure chemical loop coupled calcium cycle carbon dioxide capture system further includes a second waste heat power generation unit 400; the second waste heat power generation unit 400 includes: a second waste heat boiler 401, a fourth turbine 402, a second condenser 403, and a second pump 404. The second waste heat boiler 401 is connected to the carbonation tower 304 and the calcining furnace 305; the second waste heat boiler 401 forms a closed loop connection with the fourth turbine 402, the second condenser 403 and the second pump 404; the second waste heat boiler 401 discharges decarbonized flue gas and CO2-rich gas.

[0034] Specifically, the CO2-rich gas generated by the calcining furnace, the decarbonized flue gas generated by the carbonation tower, and the waste heat released by the carbonation tower are fed into the second waste heat boiler 401 to heat the water in the second waste heat boiler. After being heated into steam, the steam enters the fourth turbine 402 to do work. The low-temperature steam at the outlet of the fourth turbine 402 enters the second condenser 403 and is condensed into water. It is then pressurized and sent back to the second waste heat boiler 401 through the second pump 404 to absorb heat and start the next cycle. The decarbonized flue gas, whose heat has been absorbed by the second waste heat boiler 401, is discharged into the atmosphere. The CO2-rich gas can be pressurized and sent underground for storage, or it can be used as a raw material to produce other products.

[0035] In some embodiments, the first turbine 303 is a gas turbine; the second turbine 103 is a gas turbine; the third turbine 202 is a steam turbine; and the fourth turbine 402 is a steam turbine.

[0036] In addition, the present invention also provides an application of a high-pressure chemical chain coupled calcium cycle carbon dioxide capture system in the tail gas capture of natural gas power plants.

[0037] In this embodiment, applying the high-pressure chemical chain coupled calcium cycle carbon dioxide capture system to the tail gas capture of natural gas power plants can reduce heat exchange losses, increase the power output of the capture system, and reduce the energy consumption required for capturing carbon dioxide.

[0038] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention.

[0039] Example 1 This embodiment provides an application of a high-pressure chemical loop coupled calcium cycle carbon dioxide capture system in the tail gas capture of a natural gas power plant, and its process flow diagram is as follows: Figure 2 As shown, the high-pressure chemical chain coupled calcium cycle carbon dioxide capture system includes a gas-fired power generation unit, a waste heat power generation unit, and a CO2 separation unit; wherein the gas-fired power generation unit includes a compressor, a combustion chamber, and a gas turbine; the waste heat power generation unit includes a waste heat boiler, a steam turbine, a condenser, and a pump; and the CO2 separation unit includes a compressor, an air reactor, a gas turbine, a carbonation tower, and a calcining furnace.

[0040] In the gas-fired power generation unit, natural gas enters the combustion chamber and mixes with air pressurized by the compressor, where combustion takes place. The high-temperature, high-pressure flue gas at the combustion chamber outlet drives the gas turbine to perform work. The high-temperature flue gas from the turbine outlet continues to enter the waste heat boiler, heating feedwater to generate steam, which then drives the turbine to perform work. In the waste heat power generation unit, the flue gas from the turbine outlet enters the waste heat boiler to heat the feedwater, turning it into steam, which then enters the turbine to perform work. The low-temperature steam at the turbine outlet enters the condenser and condenses into water, which is then pressurized and sent back to the waste heat boiler to absorb heat, starting the next cycle. In the CO2 separation unit, the metal oxygen carrier Me and the carbon dioxide adsorbent CaO are used together as the circulating medium. The captured flue gas is first pressurized to 1-15 bar by the compressor and then enters the air reactor. In the air reactor, the pressurized flue gas reacts with the metal oxygen carrier Me, transferring oxygen from the flue gas to the metal oxygen carrier to generate metal oxide MeO. Subsequently, the oxygen-deficient flue gas enters the turbine to perform work, and the oxygen-deficient flue gas then enters the carbonation tower. In the carbonation tower, CaO separates CO2 from the flue gas, and the CaO reacts with CO2 to produce CaCO3. The generated CaCO3 is then sent to the calcination furnace for regeneration, producing CaO and CO2-rich gas. The decarbonized flue gas and heat from the carbonation tower, along with the CO2-rich gas generated in the calcination furnace, enter the waste heat boiler to heat the feedwater. After being heated into steam, the steam enters the turbine to do work. The low-temperature steam at the turbine outlet enters the condenser and condenses into water. It is then pressurized and sent back to the waste heat boiler to absorb heat, starting the next cycle. The decarbonized flue gas, whose heat has been absorbed by the waste heat boiler, is discharged into the atmosphere, while the CO2-rich gas is pressurized and sent underground for storage.

[0041] Comparative Example 1 This comparative example provides a natural gas calcium ring oxygen-enriched combustion capture system, the process flow diagram of which is shown below. Figure 3As shown, it includes a gas-fired power generation unit, a waste heat boiler power generation unit, and a CO2 separation unit. Compared with Example 1, Comparative Example 1 uses an air separation unit to provide pure oxygen to the calcining furnace and does not include an air reactor. Meanwhile, the power plant flue gas is first heated by the outlet stream of the carbonation tower before being sent back into the carbonation tower for decarbonization; the rest of the process is similar.

[0042] Comparative Example 2 This comparative example provides a capture-free natural gas combined cycle power generation system, the process flow diagram of which is as follows: Figure 4 As shown, it includes a gas-fired power generation unit and a waste heat boiler power generation unit. After the gas and air are burned, the flue gas drives the gas turbine to do work. After doing work, the flue gas releases heat in the waste heat boiler to heat water, generating steam to drive the turbine to do work. The low-temperature flue gas is directly discharged into the atmosphere.

[0043] In Example 1 and Comparative Examples 1-2, the gas turbine model was PG9171E, the gas turbine pressure ratio was 11.8, the natural gas input mass flow rate was 7.4 kg / s, the air input mass flow rate was 403.7 kg / s, the compressor pressure ratio was 11.8, and the gas turbine inlet temperature was 1100℃. The waste heat boiler power generation unit was dual-pressure, with a high pressure of 61 bar and a low pressure of 6 bar, and the main steam temperature was 527℃. The operating conditions for the carbonation reaction were: temperature 650℃ and pressure at atmospheric pressure; the operating conditions for the calcination reaction were: temperature 900℃ and pressure at atmospheric pressure; and the operating conditions for the air reactor were: temperature 950℃ and pressure 7 bar. The CO2 concentration in the flue gas was 3-5%, the CO2 capture rate was 90%, and the volume fractions of each component in the input natural gas were: CH4 - 79.75%, C2H6 - 9.68%, C3H8 - 4.45%, C4H... 10 -2.37%, CO2 -2.92%, N2 -0.83%, lower heating value 49.44 MJ / kg.

[0044] The performance of the systems in Example 1 and Comparative Examples 1-2 was statistically analyzed, and the data are shown in Table 1: Table 1. Comparison of system performance data between Example 1 and Comparative Examples 1-2

[0045] *Energy efficiency = (Electricity output - Electricity input) / Natural gas input The results show that the high-pressure chemical loop coupled calcium cycle carbon dioxide capture system of Example 1 is a significant improvement over the natural gas calcium ring oxy-fuel combustion capture system of Comparative Example 2. In the system provided in Example 1, the outlet gas from the air reactor is used to drive the combined cycle, increasing the output of the gas unit compared to the system of Comparative Example 1. Furthermore, by avoiding the air separation unit, the power consumption of air separation is saved, increasing the output of the steam power generation unit compared to the oxy-fuel combustion system. The efficiency penalty of Example 1 decreased from 9.1 percentage points in Comparative Example 1 to 5.2 percentage points. Therefore, the high-pressure chemical loop coupled calcium cycle carbon dioxide capture system provided in Example 1 can provide a highly efficient CO2 capture solution for flue gas capture in natural gas power plants.

[0046] In summary, this invention provides a high-pressure chemical loop coupled calcium cycle carbon dioxide capture system and its application. The high-pressure chemical loop coupled calcium cycle carbon dioxide capture system includes: a gas-fired power generation unit, a first waste heat power generation unit that generates electricity using the flue gas discharged from the gas-fired power generation unit, and a CO2 separation unit that separates CO2 from the flue gas discharged from the first waste heat power generation unit. The CO2 separation unit includes: a first compressor for pressurizing the flue gas discharged from the first waste heat power generation unit to form compressed flue gas; and an air reactor connected to the first compressor for capturing oxygen in the compressed flue gas to form metallic oxygen. The system comprises: an air reactor containing a metal oxide carrier and a carbon dioxide adsorbent; a first turbine connected to the air reactor for performing work on the oxygen-deficient flue gas discharged from the air reactor; a carbonation tower connected to the air reactor and the first turbine; the carbon dioxide adsorbent and the metal oxide in the air reactor being transferred to the carbonation tower, and the oxygen-deficient flue gas after the work performed by the first turbine entering the carbonation tower; and a calcining furnace connected to the carbonation tower and the air reactor; the product in the carbonation tower being transferred to the calcining furnace for reduction to form a reduction product, and the reduction product being returned to the air reactor. This invention employs a coupled mode of calcium cycle and chemical loop air reactor. It utilizes the high concentration of flue gas from the tail end of natural gas to oxidize the metal oxygen carrier in the air reactor, providing an oxygen source for the calciner, replacing the previously required air, and driving the combined cycle. This not only solves the problem of flue gas preheating in natural gas flue gas calcium cycle capture technology, but also fully utilizes the remaining oxygen in the flue gas, increasing the CO2 concentration in the flue gas entering the carbonation tower and reducing capture energy consumption; simultaneously, it avoids the power consumption of the air separation unit. Furthermore, since a portion of the energy is used to drive the combined cycle, replacing the traditional steam cycle, heat exchange losses can be effectively reduced, and the power output of the capture system can be increased.

[0047] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A high-pressure chemical loop coupled calcium cycle carbon dioxide capture system, characterized in that, include: A gas-fired power generation unit, a first waste heat power generation unit that generates electricity using the flue gas discharged from the gas-fired power generation unit, and a CO2 separation unit that separates CO2 from the flue gas discharged from the first waste heat power generation unit. The CO2 separation unit includes: The first compressor is used to pressurize the flue gas discharged from the first waste heat power generation unit to form compressed flue gas; An air reactor, connected to the first compressor, is used to transfer oxygen from the compressed flue gas to a metal oxygen carrier to form metal oxides; the air reactor is loaded with a metal oxygen carrier and a carbon dioxide adsorbent. A first turbine is connected to the air reactor, and the oxygen-deficient flue gas from the outlet of the air reactor is used to drive the first turbine to do work. A carbonation tower is connected to the air reactor and the first turbine; the carbon dioxide adsorbent and the metal oxide in the air reactor are transferred to the carbonation tower to capture carbon dioxide in the oxygen-deficient flue gas from the outlet of the first turbine; A calcining furnace is connected to the carbonation tower and the air reactor; the product in the carbonation tower is transferred to the calcining furnace for reduction to form a reduction product, and the reduction product is returned to the air reactor.

2. The high-pressure chemical loop coupling calcium cycle carbon dioxide capture system according to claim 1, characterized in that, The metal oxygen support includes one or more of Fe, Cu, Co, Mn, and composite metal oxygen supports; and / or, the carbon dioxide adsorbent is calcium oxide.

3. The high-pressure chemical loop coupling calcium cycle carbon dioxide capture system according to claim 1, characterized in that, The first compressor pressurizes the flue gas discharged from the first waste heat power generation unit to 1-15 bar to form compressed flue gas; the compressed flue gas enters the air reactor through a pipeline.

4. The high-pressure chemical loop coupling calcium cycle carbon dioxide capture system according to claim 1, characterized in that, The reaction pressure in the air reactor is 1-15 bar, and the reaction temperature in the air reactor is 950-1100℃.

5. The high-pressure chemical loop coupling calcium cycle carbon dioxide capture system according to claim 1, characterized in that, The reaction temperature in the carbonation tower is 600-650℃.

6. The high-pressure chemical loop coupled calcium cycle carbon dioxide capture system according to claim 1, characterized in that, The reaction temperature in the calcining furnace is 900-950℃.

7. The high-pressure chemical loop coupling calcium cycle carbon dioxide capture system according to claim 1, characterized in that, The gas-fired power generation unit includes: The second compressor is used to pressurize air to form compressed air; A combustion chamber, connected to the second compressor, is used to mix and burn natural gas with the compressed air; The second turbine is connected to the combustion chamber, and the flue gas from the outlet of the combustion chamber is used to drive the second turbine to do work.

8. The high-pressure chemical loop coupled calcium cycle carbon dioxide capture system according to claim 7, characterized in that, The first waste heat power generation unit includes: a first waste heat boiler, a third turbine, a first condenser, and a first pump; The first waste heat boiler is connected to the second turbine; the first waste heat boiler forms a closed loop connection with the third turbine, the first condenser, and the first pump; the flue gas discharged from the first waste heat boiler enters the first compressor.

9. The high-pressure chemical loop coupling calcium cycle carbon dioxide capture system according to claim 1, characterized in that, The high-pressure chemical loop coupled calcium cycle carbon dioxide capture system also includes a second waste heat power generation unit; the second waste heat power generation unit includes: a second waste heat boiler, a fourth turbine, a second condenser, and a second pump; The second waste heat boiler is connected to the carbonation tower and the calcining furnace; the second waste heat boiler forms a closed loop connection with the fourth turbine, the second condenser, and the second pump; the second waste heat boiler discharges decarbonized flue gas and CO2-rich gas.

10. An application of the high-pressure chemical loop coupling calcium cycle carbon dioxide capture system as described in any one of claims 1-9 in the capture of exhaust gas from natural gas power plants.

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