Flue Gas Recirculation Nitrogen-Free Combustion Coupled with Carbon Dioxide Capture Process System and Method

Abstract

The present invention discloses a flue gas recirculation nitrogen-free combustion coupled with carbon dioxide capture process system and method. A cooling section of a flue gas pre-cooling system, a cooling section of a first heat exchanger, a first separator, a blower, a cooling section of a second heat exchanger, a cooling section of a third heat exchanger, a molecular sieve adsorption tower, a refrigeration unit and a re-absorption tower are sequentially connected to the flue gas outlet of the boiler and burner system; two paths of CO2 in the re-absorption tower perform heat exchange, one path outputs liquid CO2, and the other path is sequentially connected to the heating section of the second heat exchanger and the heating section of the first heat exchanger; the nitrogen-containing non-condensable gas outlet of the re-absorption tower is sequentially connected to the heating section of the third heat exchanger and a pressure swing adsorption nitrogen removal system; an air separation system, a pressure swing adsorption nitrogen removal system and the heating section of the first heat exchanger are connected to the boiler and burner system through the heating section of the flue gas pre-cooling system. The present invention integrates the functions of oxy-fuel combustion, flue gas circulation and carbon dioxide capture and purification, and has the advantages of zero pollution emission and high efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas carbon dioxide capture and recovery, and particularly relates to a flue gas recirculation nitrogen-free combustion coupled carbon dioxide capture process system and method. Background Art

[0002] Climate change has a profound impact on the Earth's environment, which is a huge challenge faced by mankind. To address global climate change and achieve the sustainable development of human social civilization and the Earth's ecosystem, China has put forward the strategic background of carbon neutrality from a scientific perspective and proposed the goals of "carbon peak and carbon neutrality" based on the scientific basis of addressing climate change.

[0003] CCUS technology is a greenhouse gas emission reduction technology that can significantly reduce greenhouse gas emissions from the use of fossil fuels, covering four links: CO 2 capture, transportation, utilization, and storage. In the capture stage, high-concentration oxygen is currently mainly obtained through oxygen production technology to achieve flue gas recirculation of oxy-fuel combustion or capture and utilization of CO 2 after combustion. After capture, the CO 2 will be transported to a safe storage point for storage or reuse through transportation methods such as pipelines, tank trucks, or ships.

[0004] The core of carbon neutrality is to reduce or even eliminate CO 2 emissions. CCUS / CCS (carbon capture, utilization, and storage) can play an important role, and the carbon industry centered on CCUS / CCS will become an emerging industry under the goal of carbon neutrality. CCUS technology is the only means to significantly reduce greenhouse gas emissions from industrial processes. For the refining, gas power, cement, and steel industries, to achieve deep emission reduction during the production process, CCUS technology is essential and irreplaceable by renewable energy power and energy-saving technologies, which is crucial for China to implement the low-carbon development strategy and achieve green development.

[0005] Currently, no implementation of a flue gas recirculation nitrogen-free combustion coupled carbon dioxide capture process system has been found. Summary of the Invention

[0006] Aiming at the above problems existing in the prior art, the present invention provides a flue gas recirculation nitrogen-free combustion coupled carbon dioxide capture process system and method, which integrates the functions of oxy-fuel combustion, flue gas circulation, and carbon dioxide capture and purification, and has the advantages of zero pollution emission, high efficiency, and high economic benefits.

[0007] The present invention discloses a flue gas recirculation nitrogen-free combustion coupled with carbon dioxide capture process system, including: an air separation system, a pressure swing adsorption nitrogen removal system, a flue gas precooling system, a first heat exchanger, a second heat exchanger, a third heat exchanger, a first air cooler, a first separator, a blower, a compressor, a refrigeration unit, a reabsorption tower, and a boiler and burner system; wherein,

[0008] The flue gas outlet of the boiler and burner system is sequentially connected to the cooling section of the flue gas precooling system, the cooling section of the first heat exchanger, the first air cooler, the first separator, and the blower along the flowing direction of the flue gas. The first air outlet branch of the blower is sequentially connected to the compressor, the cooling section of the second heat exchanger, the cooling section of the third heat exchanger, the refrigeration unit, and the reabsorption tower along the flowing direction of the flue gas;

[0009] The first CO outlet of the reabsorption tower 2 branch outlet discharges liquid low-temperature CO 2 The second CO outlet of the reabsorption tower 2 branch is connected to the heating section of the second heat exchanger. The outlet of the heating section of the second heat exchanger and the second air outlet branch of the blower are incorporated into the heating section of the first heat exchanger; The nitrogen-containing non-condensable gas outlet at the top of the reabsorption tower is sequentially connected to the heating section of the third heat exchanger and the pressure swing adsorption nitrogen removal system;

[0010] The outlet of the air separation system, the outlet of the pressure swing adsorption nitrogen removal system, and the outlet of the heating section of the first heat exchanger are incorporated into the inlet of the heating section of the flue gas precooling system. The outlet of the heating section of the flue gas precooling system and the fuel are incorporated into the boiler and burner system.

[0011] As a further improvement of the present invention, it further includes: a second air cooler;

[0012] The second air cooler is connected between the compressor and the cooling section of the second heat exchanger.

[0013] As a further improvement of the present invention, it further includes: a second separator and a molecular sieve adsorption tower;

[0014] The second separator and the molecular sieve adsorption tower are sequentially arranged between the cooling section of the third heat exchanger and the refrigeration unit.

[0015] As a further improvement of the present invention, it further includes: a fourth heat exchanger and a J-T throttle refrigeration valve;

[0016] The first CO outlet of the reabsorption tower 2 branch is connected to the cooling section of the fourth heat exchanger. The outlet of the cooling section of the fourth heat exchanger discharges liquid low-temperature CO 2 ; The second CO outlet of the reabsorption tower2 The branch is successively connected with the J-T throttle refrigeration valve, the heating section of the fourth heat exchanger, and the heating section of the second heat exchanger.

[0017] The present invention also discloses a flue gas recirculation nitrogen-free combustion coupled with carbon dioxide capture process method, including:

[0018] The oxygen-rich air at the outlet of the air separation system, the high-concentration CO 2 formed by the recirculation flue gas at the outlet of the pressure swing adsorption nitrogen removal system and the recirculation flue gas at the outlet of the first heat exchanger is heated by exchanging heat with the flue gas in the flue gas precooling system, and then enters the boiler and burner system together with the fuel;

[0019] The fuel and the heated mixed combustion-supporting gas heat the medium to be heated in the boiler and burner system, and the flue gas generated after the fuel combustion is precooled by exchanging heat with the mixed combustion-supporting gas in the flue gas precooling system;

[0020] The precooled flue gas successively enters the first heat exchanger for heat exchange and temperature reduction, the first air cooler for air cooling and temperature reduction, and the first separator for gas-liquid separation. The gas phase after gas-liquid separation is extracted by a blower and pressurized once;

[0021] A part of the gas after the first pressurization enters the compressor for secondary pressurization. The high-temperature flue gas after the secondary pressurization successively enters the second air cooler for air cooling and temperature reduction, the second heat exchanger for heat exchange and temperature reduction, the third heat exchanger for heat exchange and temperature reduction, the second separator for gas-liquid separation, and the molecular sieve adsorption tower for removing saturated water in the flue gas;

[0022] The dehydrated flue gas enters the refrigeration unit for temperature reduction, and then the low-temperature flue gas enters the heavy absorption tower for gas-liquid mass transfer separation; the nitrogen-containing non-condensable gas at the top after separation successively enters the third heat exchanger for heat exchange and temperature increase, and the pressure swing adsorption nitrogen removal system for nitrogen removal, and high-concentration CO 2 is obtained for use as the mixed combustion-supporting gas; 2 The bottom liquid CO 2 is divided into two streams after passing through the bottom reboiler. One stream enters the J-T throttle refrigeration valve for throttling and temperature reduction. The CO 2 after throttling and temperature reduction successively enters the fourth heat exchanger for heat exchange and temperature increase, the second heat exchanger for heat exchange and temperature increase, and then is mixed with the other part of the gas after the first pressurization and enters the first heat exchanger for heat exchange and temperature increase, and the recirculation flue gas for use as the mixed combustion-supporting gas is obtained; the other stream of liquid CO 2 enters the fourth heat exchanger for heat exchange and temperature reduction, and then the liquid low-temperature CO

[0023] As a further improvement of the present invention, it further includes:

[0024] The liquid phase separated by the first separator, the liquid phase separated by the second separator, and the liquid phase adsorbed by the molecular sieve adsorption tower enter the water treatment system.

[0025] As a further improvement of the present invention,

[0026] In the flue gas precooling system, the flue gas is cooled from 150°C to 180°C to 110°C to 130°C;

[0027] In the first heat exchanger, the flue gas is cooled to 85°C to 105°C;

[0028] In the first air cooler, the flue gas is cooled to 30°C to 40°C;

[0029] In the second air cooler, the flue gas is cooled to 30°C to 40°C;

[0030] In the third heat exchanger, the flue gas is cooled to 20°C to 25°C;

[0031] In the refrigeration unit, the flue gas is cooled to -30°C to -25°C.

[0032] As a further improvement of the present invention,

[0033] In the blower, it is pressurized once to 8 kPag;

[0034] In the compressor, it is pressurized twice to 3 MPag.

[0035] As a further improvement of the present invention, in the molecular sieve adsorption tower, the water content in the dehydrated flue gas is less than 0.1%.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] The present invention adopts the method of oxy-fuel combustion, which can improve the combustion efficiency of the boiler, and increase the CO concentration in the flue gas through the flue gas circulation cooling equipment, 2 concentration, improve the capture and recovery efficiency of CO, 2 and produce CO by-products while achieving zero carbon emissions, which is conducive to the realization of the carbon neutrality goal and can improve the economic benefits of enterprises. 2 Brief Description of the Drawings

[0038] Figure 1 It is a schematic structural diagram of a flue gas recirculation nitrogen-free combustion coupled carbon dioxide capture process system disclosed in an embodiment of the present invention.

[0039] In the figure:

[0040] 1-1, Air separation system; 1-2, Pressure swing adsorption nitrogen removal system; 2, Flue gas precooling system; 3-1, First heat exchanger; 3-2, Second heat exchanger; 3-3, Third heat exchanger; 3-4, Fourth heat exchanger; 4-1, First air cooler; 4-2, Second air cooler; 5-1, First separator; 5-2, Second separator; 6, Blower; 7, Compressor; 8, Molecular sieve adsorption tower; 9, Refrigeration unit; 10, Reabsorption tower; 11, J-T throttle refrigeration valve; 12, Boiler and burner system; A, Heated medium; B, Water; C, Nitrogen. Detailed implementation manners

[0041] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0042] The present invention will be further described in detail below with reference to the accompanying drawings:

[0043] As Figure 1 shown, the present invention provides a flue gas recirculation nitrogen-free combustion coupled carbon dioxide capture process system, which is characterized by comprising: an air separation system 1-1, a pressure swing adsorption nitrogen removal system 1-2, a flue gas precooling system 2, a first heat exchanger 3-1, a second heat exchanger 3-2, a third heat exchanger 3-3, a fourth heat exchanger 3-4, a first air cooler 4-1, a second air cooler 4-2, a first separator 5-1, a second separator 5-2, a blower 6, a compressor 7, a molecular sieve adsorption tower 8, a refrigeration unit 9, a reabsorption tower 10, a J-T throttle refrigeration valve 11 and a boiler and burner system 12; wherein,

[0044] The air separation system 1-1, the pressure swing adsorption nitrogen removal system 1-2, the first heat exchanger 3-1, the flue gas precooling system 2 and the boiler and burner system 12 constitute an oxy-fuel combustion unit, and the oxy-fuel combustion unit is used to increase the oxygen content in the combustion-supporting gas. Oxy-fuel combustion can give full play to the performance of the fuel, reduce the heat loss caused by incomplete combustion, improve the boiler thermal efficiency, and at the same time provide sufficient fuel calorific value margin for the recirculation of CO 2 2.

[0045] The pressure swing adsorption nitrogen removal system 1-2, the flue gas precooling system 2, the first heat exchanger 3-1, the second heat exchanger 3-2, the third heat exchanger 3-3, the fourth heat exchanger 3-4, the first air cooler 4-1, the second air cooler 4-2, the first separator 5-1, the second separator 5-2, the blower 6 and the compressor 7 constitute the flue gas recirculation unit. The flue gas recirculation unit means that the flue gas passes through the CO captured by the carbon dioxide capture system 2 Mixes with the oxygen-rich air from the air separation system upstream of the combustion-supporting gas duct of the boiler burner, and then enters the furnace through the burner to burn with the fuel; its main function is to reduce NO X generation, CO 2 As a diluent, it can more effectively reduce NO X concentration, while reducing the excess air coefficient and improving the combustion efficiency. At the same time, to avoid that a part of the low-temperature recycled gas introduced into the burner due to flue gas recirculation reduces the temperature of the flue gas in the furnace, changes the heat distribution between the furnace and each heating surface, and affects the boiler efficiency, multiple heat exchangers are set in the whole cycle of flue gas to perform multi-stage heat exchange, while increasing the cycle temperature, reducing the temperature of the exhaust gas, and reducing the load of the flue gas dehydration equipment.

[0046] The second separator 5-2, the molecular sieve adsorption tower 8, the refrigeration unit 9, the reabsorption tower 10, the J-T throttle refrigeration valve 11 and the fourth heat exchanger 3-4 constitute the CO 2 purification unit, CO 2 The purification unit is used for deep dehydration of the flue gas, further cooling and liquefying the dehydrated CO 2 and separating it through adsorption mass transfer in the absorption tower to increase the concentration of liquid-phase CO 2 and obtain a CO 2 product meeting the commercial standards.

[0047] Specifically:

[0048] The inlet of the air separation system 1-1 of the present invention is placed in the air or connected to an air source. The outlet of the air separation system 1-1, the outlet of the pressure swing adsorption nitrogen removal system 1-2, and the outlet of the heating section of the first heat exchanger 3-1 are merged into the inlet of the heating section of the flue gas precooling system 2. The outlet of the heating section of the flue gas precooling system 2 is merged with the fuel into the boiler and burner system 12.

[0049] The flue gas outlet of the boiler and burner system 12 of the present invention is sequentially connected with the cooling section of the flue gas precooling system 2, the cooling section of the first heat exchanger 3-1, the first air cooler 4-1, the first separator 5-1 and the blower 6 along the flow direction of the flue gas. The first air outlet branch of the blower 6 is sequentially connected with the compressor 7, the second air cooler 4-2, the cooling section of the second heat exchanger 3-2, the cooling section of the third heat exchanger 3-3, the second separator 5-2, the molecular sieve adsorption tower 8, the refrigeration unit 9 and the reabsorption tower 10 along the flow direction of the flue gas.

[0050] The first CO outlet branch of the reabsorption tower 10 of the present invention 2 is connected to the cooling section of the fourth heat exchanger 3-4, and liquid low-temperature CO exits from the outlet of the cooling section of the fourth heat exchanger 3-4 2 ; The second CO outlet branch of the reabsorption tower 10 2 is successively connected with a J-T throttle refrigeration valve 11, the heating section of the fourth heat exchanger 3-4, and the heating section of the second heat exchanger 3-2. The outlet of the heating section of the second heat exchanger 3-2 and the second air outlet branch of the blower 6 are merged into the heating section of the first heat exchanger 3-1; The nitrogen-containing non-condensable gas outlet at the top of the reabsorption tower 10 is successively connected with the heating section of the third heat exchanger 3-3 and the pressure swing adsorption nitrogen removal system 1-2.

[0051] As Figure 1 shown, the present invention provides a flue gas recirculation nitrogen-free combustion coupled with carbon dioxide capture process method, including:

[0052] Step 1, The mixed auxiliary combustion gas formed by the oxygen-rich air at the outlet of the air separation system 1-1, the high-concentration CO at the outlet of the pressure swing adsorption nitrogen removal system 1-2 2 and the recirculation flue gas at the outlet of the first heat exchanger 3-1 is heated by exchanging heat with the boiler flue gas in the flue gas precooling system 2 and then enters the boiler and burner system 12 to burn together with the fuel; Among them, the air separation system 1-1 separates nitrogen and oxygen in the air by using the selective adsorption performance of its high-efficiency solid adsorbent for nitrogen and oxygen, and the separated oxygen concentration is above 90%.

[0053] Step 2, The fuel and the heated mixed auxiliary combustion gas heat the heated medium A in the boiler and burner system 12, and the boiler flue gas generated after the fuel combustion is precooled by exchanging heat with the mixed auxiliary combustion gas in the flue gas precooling system 2; Among them, the boiler flue gas is cooled from 150°C to 180°C to 110°C to 130°C in the flue gas precooling system 2. The flue gas precooling system 2 can heat the mixed combustion-supporting gas, promote the premixing of the combustion-supporting agent and the fuel, improve the combustion efficiency, and at the same time can precool the flue gas, make full use of energy, reduce the load of subsequent equipment, and improve economic benefits.

[0054] Step 3, The precooled flue gas successively enters the first heat exchanger 3-1 for heat exchange and cooling, the first air cooler 4-1 for air cooling and cooling, and the first separator 5-1 for gas-liquid separation. The gas phase after gas-liquid separation is extracted by the blower 6 and pressurized once; Among them, the flue gas is cooled to 30°C to 40°C in the first air cooler 4-1. At this time, part of the saturated water in the flue gas condenses and precipitates, and gas-liquid separation is carried out in the first separator 5-1. The separated liquid phase (water B) is uniformly sent to the water treatment system, and the blower 6 extracts the gas phase and pressurizes it to 8 kPag.

[0055] Step 4: A part of the gas after primary pressurization enters the compressor 7 for secondary pressurization. The hot flue gas after secondary pressurization sequentially enters the second air cooler 4-2 for air cooling and temperature reduction, the second heat exchanger 3-2 for heat exchange and temperature reduction, the third heat exchanger 3-3 for heat exchange and temperature reduction, the second separator 5-2 for gas-liquid separation, and the molecular sieve adsorption tower 8 for removing saturated water in the flue gas. Among them, in the second air cooler 4-2, the flue gas is cooled to 30°C to 40°C; in the third heat exchanger 3-3, the flue gas is cooled to 20°C to 25°C; in the compressor 7, it is secondarily pressurized to 3MPag; in the molecular sieve adsorption tower 8, the water content in the dehydrated flue gas is less than 0.1%, providing guarantee for the next stage of flue gas cooling and purification; a large amount of condensed water B separated by the second separator 5-2 and the saturated water B adsorbed by the molecular sieve adsorption tower 8 enter the water treatment system.

[0056] Step 5: The dehydrated flue gas enters the refrigeration unit 9 for temperature reduction, and then the low-temperature flue gas enters the reabsorption tower 10 for gas-liquid mass transfer separation. Among them, in the refrigeration unit 9, the flue gas is cooled to -30°C to -25°C.

[0057] Step 6: The nitrogen-containing non-condensable gas at the top after gas-liquid mass transfer separation sequentially enters the third heat exchanger 3-3 for heat exchange and temperature increase, and the pressure swing adsorption nitrogen removal system 1-2 for removing nitrogen gas C, obtaining high-concentration CO for use as a mixed auxiliary combustion gas 2 , and returns to the burner inlet for continuous circulation.

[0058] Step 7: The bottom liquid CO after gas-liquid mass transfer separation 2 is divided into two streams after passing through the bottom reboiler. One of them enters the J-T throttle refrigeration valve 11 for throttle cooling. The CO after throttle cooling 2 sequentially enters the fourth heat exchanger 3-4 for heat exchange and temperature increase, the second heat exchanger 3-2 for heat exchange and temperature increase, and then is mixed with the other part of the gas after primary pressurization and enters the first heat exchanger 3-1 for heat exchange and temperature increase, obtaining the recycled flue gas for use as a mixed auxiliary combustion gas, and returns to the burner inlet for continuous circulation; the other stream of liquid CO 2 enters the fourth heat exchanger 3-4 for heat exchange and temperature reduction, and then the liquid low-temperature CO 2 is exported as a by-product; among them, the other part of the gas after primary pressurization returns to the first heat exchanger 3-1 to exchange heat with the boiler flue gas, and at the same time participates in combustion as a recycle gas, increasing the CO 2 concentration in the flue gas and improving the capture and recovery efficiency of CO 2 .

[0059] The advantages of the present invention are as follows:

[0060] 1. In the carbon capture process of the present invention, the flue gas is deeply dehydrated, so that the water content in the flue gas is greatly reduced, ensuring the subsequent carbon dioxide circulation combustion efficiency, improving the quality of the carbon dioxide by-product, and at the same time effectively reducing the regeneration cost of the pressure swing adsorption system;

[0061] 2. The present invention uses a flue gas precooling system to heat the combustion-supporting gas, promote the premixing of the combustion promoter and the fuel, and improve the combustion efficiency;

[0062] 3. The present invention adopts a flue gas circulation process to increase the CO concentration in the boiler, effectively solve the generation of NO, and improve the CO capture efficiency; 2 concentration, effectively solve the generation of NO X generation, improve the CO 2 capture efficiency;

[0063] 4. The boiler combustion process system of the present invention realizes full-closed operation without NO and CO emissions, which is beneficial to environmental protection and reduces the greenhouse effect; X and CO 2 emissions, which is beneficial to environmental protection and reduces the greenhouse effect;

[0064] 5. The present invention adopts a deep dehydration and cooling process for flue gas to obtain liquefied CO by-products and improve economic benefits. 2 by-products and improve economic benefits.

[0065] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A flue gas recirculation nitrogen-free combustion coupled with carbon dioxide capture process system, characterized in that, it includes: an air separation system, a pressure swing adsorption nitrogen removal system, a flue gas precooling system, a first heat exchanger, a second heat exchanger, a third heat exchanger, a first air cooler, a first separator, a blower, a compressor, a refrigeration unit, a reabsorption tower, a boiler and a burner system, a fourth heat exchanger, and a J-T throttle refrigeration valve; wherein, the flue gas outlet of the boiler and burner system is sequentially connected to the cooling section of the flue gas precooling system, the cooling section of the first heat exchanger, the first air cooler, the first separator, and the blower along the flow direction of the flue gas. The first air outlet branch of the blower is sequentially connected to the compressor, the cooling section of the second heat exchanger, the cooling section of the third heat exchanger, the refrigeration unit, and the reabsorption tower along the flow direction of the flue gas; The first CO outlet of the reabsorption tower 2 branch outlet for liquid cryogenic CO 2 , the second CO outlet of the reabsorption tower 2 branch is connected to the heating section of the second heat exchanger, and the outlet of the heating section of the second heat exchanger and the second air outlet branch of the blower are merged into the heating section of the first heat exchanger; the nitrogen-containing non-condensable gas outlet at the top of the reabsorption tower is successively connected to the heating section of the third heat exchanger and the pressure swing adsorption nitrogen removal system; the outlet of the air separation system, the outlet of the pressure swing adsorption nitrogen removal system, and the outlet of the heating section of the first heat exchanger are merged into the inlet of the heating section of the flue gas precooling system, and the outlet of the heating section of the flue gas precooling system and the fuel are merged into the boiler and burner system; The first CO outlet of the reabsorption tower 2 branch is connected to the cooling section of the fourth heat exchanger, and liquid low-temperature CO exits from the outlet of the cooling section of the fourth heat exchanger 2 ; The second CO outlet of the reabsorption tower 2 branch is successively connected with the J-T throttle refrigeration valve, the heating section of the fourth heat exchanger, and the heating section of the second heat exchanger.

2. The flue gas recirculation nitrogen-free combustion coupled with carbon dioxide capture process system according to claim 1, characterized in that, it further includes: a second air cooler; the second air cooler is connected between the compressor and the cooling section of the second heat exchanger.

3. The flue gas recirculation nitrogen-free combustion coupled with carbon dioxide capture process system according to claim 1, characterized in that, it further includes: a second separator and a molecular sieve adsorption tower; the second separator and the molecular sieve adsorption tower are sequentially arranged between the cooling section of the third heat exchanger and the refrigeration unit.

4. A flue gas recirculation nitrogen-free combustion coupled with carbon dioxide capture process method based on the flue gas recirculation nitrogen-free combustion coupled with carbon dioxide capture process system according to any one of claims 1 to 3, characterized in that, it includes: The oxygen-rich air at the outlet of the air separation system and the high-concentration CO at the outlet of the pressure swing adsorption nitrogen removal system 2 After the mixed combustion-supporting gas formed by the oxygen-rich air at the outlet of the air separation system, the high-concentration CO at the outlet of the pressure swing adsorption nitrogen removal system and the recycled flue gas at the outlet of the first heat exchanger is heated up by exchanging heat with the flue gas in the flue gas precooling system, it enters the boiler and burner system together with the fuel; the fuel and the heated mixed auxiliary combustion gas heat the heated medium in the boiler and burner system, and the flue gas generated after the fuel combustion exchanges heat and is precooled with the mixed auxiliary combustion gas in the flue gas precooling system; the precooled flue gas sequentially enters the first heat exchanger for heat exchange and cooling, the first air cooler for air cooling and cooling, and the first separator for gas-liquid separation. The gas phase after gas-liquid separation is drawn out by the blower and pressurized once; a part of the gas after being pressurized once enters the compressor for secondary pressurization. The high-temperature flue gas after secondary pressurization sequentially enters the second air cooler for air cooling and cooling, the second heat exchanger for heat exchange and cooling, the third heat exchanger for heat exchange and cooling, the second separator for gas-liquid separation, and the molecular sieve adsorption tower to remove the saturated water in the flue gas; The dehydrated flue gas enters the refrigeration unit for temperature reduction, and then the low-temperature flue gas enters the heavy absorption tower for gas-liquid mass transfer separation; the nitrogen-containing non-condensable gas at the top after separation enters the third heat exchanger for heat exchange and temperature increase in sequence, and then enters the pressure swing adsorption nitrogen removal system for nitrogen removal, obtaining high-concentration CO used as mixed auxiliary combustion gas 2 ; the liquid CO at the bottom after separation 2 is divided into two streams after passing through the reboiler at the bottom of the tower. One of them enters the J-T throttle refrigeration valve for throttle temperature reduction. After throttle temperature reduction, the CO 2 enters the fourth heat exchanger for heat exchange and temperature increase in sequence, then enters the second heat exchanger for heat exchange and temperature increase, and then mixes with another part of the gas after primary pressurization and enters the first heat exchanger for heat exchange and temperature increase, obtaining the recycled flue gas used as mixed auxiliary combustion gas; the other stream of liquid CO 2 enters the fourth heat exchanger for heat exchange and temperature reduction, and then the liquid low-temperature CO 2 is exported as a by-product.

5. The flue gas recirculation nitrogen-free combustion coupled with carbon dioxide capture process method according to claim 4, characterized in that, it further includes: the liquid phase separated by the first separator, the liquid phase separated by the second separator, and the liquid phase adsorbed by the molecular sieve adsorption tower enter the water treatment system.

6. The flue gas recirculation nitrogen-free combustion coupled with carbon dioxide capture process method according to claim 4, characterized in that, in the flue gas precooling system, the flue gas is cooled from 150°C to 180°C to 110°C to 130°C; In the first heat exchanger, the flue gas is cooled to 85°C to 105°C; In the first air cooler, the flue gas is cooled to 30°C to 40°C; In the second air cooler, the flue gas is cooled to 30°C to 40°C; In the third heat exchanger, the flue gas is cooled to 20°C to 25°C; In the refrigeration unit, the flue gas is cooled to -30°C to -25°C.

7. The process method of flue gas recirculation nitrogen-free combustion coupled with carbon dioxide capture according to claim 4, characterized in that, In the blower, it is pressurized once to 8 kPag; In the compressor, it is pressurized twice to 3 MPag.

8. The process method of flue gas recirculation nitrogen-free combustion coupled with carbon dioxide capture according to claim 4, characterized in that, In the molecular sieve adsorption tower, the water content in the dehydrated flue gas is less than 0.1%.

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