A clean air separation gas combustion reactor system and operation method

Abstract

The invention discloses a clean air separation gas combustion reactor system and an operation method. The system consists of a compression device, an end-stage cooler, a heat storage tank, a cold box, a cryogenic expander, an expansion valve, a fractionation tower, a throttle valve, a reheater and a natural gas boiler. The operation method of the system is an air separation and combustion coupling method. The invention uses waste heat to assist in heating the gas, nitrogen and oxygen, thereby improving the inlet conditions of the natural gas boiler. The system can independently produce oxygen to ensure the normal operation of the natural gas boiler, and at the same time, nitrogen, a byproduct of air separation, is added to serve as reflux flue gas to achieve a clean combustion effect. The purpose of adding a heat storage tank and a reheater is to utilize the waste heat in the air separation process to heat the gas, nitrogen and oxygen entering the natural gas boiler to improve the combustion efficiency. The purpose of adding low-temperature fractionation air separation is to independently produce oxygen required for oxygen-enriched combustion of gas fuel, and nitrogen is used as reflux flue gas to improve the combustion efficiency, thereby meeting the different needs of users.

Description

Technical Field

[0001] The invention belongs to the technical field of clean combustion, and in particular relates to a clean air separation gas combustion reactor system and an operation method. Background Art

[0002] NOx is a collective name for various nitrogen oxides such as NO, NO2 and N2O. NOx produced by combustion is mainly NO. There are three mechanisms for the generation of NOx: fuel-NOx, thermal-NOx and prompt-NOx. In industrial boilers, thermal-NOx is the main source of nitrogen oxides. At present, most large burners use non-premixed combustion bottles, that is, the gas and air are not mixed in the burner, but the two air flows are mixed at the burner outlet through different jets, swirls, etc. to ignite and burn. This combustion rate depends on the mixing rate of air and gas, which is called diffusion-controlled combustion. According to the analysis of the NOx generation mechanism and the influence of the gas burner operating conditions on the NOx emission concentration, in order to achieve low NOx in gas boilers, emissions need to be designed from several main aspects: gas staging, air staging, staging combustion area, and flue gas reflow.

[0003] In order to achieve clean combustion of gas boilers, the technical route usually selected is the swirl primary and secondary air rich and thin combustion technology. Generally, the combustion air is artificially divided into two streams and sent into the furnace, forming two combustion zones in the furnace, namely oxygen-rich and fuel-rich. In order to effectively reduce the generation of nitrogen oxides, the method usually adopted is to generate an oxygen-poor fuel-rich space in the ignition area next to the burner outlet, which slows down the mixing process of the secondary air, maintains the efficient combustion of volatiles in a reducing atmosphere, reduces the emission of fuel nitrogen oxides, and especially effectively avoids the generation of thermal NOx.

[0004] The existing swirl primary and secondary air rich-lean combustion technology still has certain defects, including:

[0005] 1. After adopting this combustion technology, the heat loss of incomplete combustion is increased, causing the combustion area in the furnace to shift backward, resulting in a sudden increase in the smoke temperature at the furnace outlet, thereby greatly reducing the thermal efficiency of fuel combustion;

[0006] 2. The existing air staged combustion technology has limited sources of high-concentration oxygen, which is usually purchased from outside;

[0007] 3. The existing gas boilers have fast combustion reactions, high flame temperatures, and large fluctuations in flue gas recirculation volume, making them difficult to accurately determine.

[0008] In summary, there is an urgent need for a new clean air separation gas combustion technology reactor system and an operating method thereof. Summary of the invention

[0009] The purpose of the present invention is to provide a new clean air separation gas combustion reactor system and operation method to solve one or more of the technical problems of the existing swirl primary and secondary air dense and dilute combustion technology, such as high flue gas temperature at the furnace outlet, single oxygen source and insufficient independence, large fluctuations in flue gas circulation volume and poor control, resulting in waste of resources. The present invention can make the high-concentration oxygen required for natural gas combustion independently produced by air separation equipment; can ensure a reasonable furnace combustion area and a suitable furnace outlet flue gas temperature through the coordination of primary and secondary air, dense and dilute fuel, pure oxygen and nitrogen; innovatively use nitrogen produced by air separation to replace circulating flue gas, reduce the combustion temperature in the furnace, and thus achieve the purpose of controlling nitrogen oxide emissions.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is:

[0011] A clean air separation gas combustion reactor system, comprising a compression device 1, a stage end cooler 2, a heat storage tank 3, a cold box 4, a cryogenic expander 5, a fractionating tower 6, a throttle valve 7, a reheater 8 and a natural gas boiler 9;

[0012] The final stage outlet of the compression device 1 is connected to the hot end inlet of the final stage cooler 2, the hot end outlet of the final stage cooler 2 is connected to the inlet of the cold box 4, the outlet of the cold box 4 is connected to the inlet of the cryogenic expander 5, the outlet of the cryogenic expander 5 is connected to the inlet of the lower kettle of the fractionation tower 6, the bottom outlet of the fractionation tower 6 is connected to the reflux liquid inlet of the upper part of the fractionation tower 6 through the throttle valve 7, the condensation side and evaporation side outlets of the condenser evaporator in the upper kettle of the fractionation tower 6 are respectively connected to the nitrogen inlet and the oxygen-enriched air inlet of the cold end of the reheater 8, and the introduced fuel gas flow is connected to the fuel gas inlet of the cold end of the reheater 8; the interstage outlet of the multi-stage compressor in the compression device 1 is connected to the inlet of the heat storage tank 3, the cold end outlet of the final stage cooler 2 is also connected to the inlet of the heat storage tank 3, the outlet of the heat storage tank 3 is connected to the hot end inlet of the reheater 8, and the nitrogen outlet, oxygen-enriched air outlet and fuel gas outlet at the cold end of the reheater 8 are connected to the burner inlet of the natural gas boiler 9.

[0013] The system uses the waste heat generated by the compression device 1 during the compression process and the waste heat generated by the heat exchange of the high-temperature and high-pressure airflow in the end-stage cooler 2 after the compression is completed to assist in heating the fuel gas, nitrogen and oxygen, thereby improving the inlet conditions of the natural gas boiler 9, and adding air separation by-product nitrogen to serve as reflux flue gas.

[0014] The compression device 1 is a 2-4 stage compressor equipped with an interstage cooling device, with a simple structure and a high pressure ratio; wherein air is directly introduced from the atmosphere at the inlet of the compression device 1; at the same time, the outlets between the compressors of each stage in the compression device 1 lead out the heat storage medium that exchanges heat with the surface of the compressed air to the heat storage tank 3 for heat storage, and the heat storage medium before heat exchange is in a state of normal temperature and pressure.

[0015] The end-of-stage cooler 2 uses the heat storage medium to exchange surface heat with high-temperature air, the air temperature is reduced, and the heat storage medium is heated and enters the heat storage tank 3 from the cold end outlet of the end-of-stage cooler 2 for storage;

[0016] The heat storage tank 3 receives the heat storage medium from the compression device 1 and the end-stage cooler 2, and introduces the heat storage medium into the reheater 8 from the lower outlet;

[0017] The reheater 8 is used to preheat the gas entering the natural gas boiler 9. The specific working principle is surface heat exchange. The heat in the heat storage medium introduced by the heat storage tank 3 is used to heat the nitrogen, oxygen-enriched air and fuel gas at the inlet of the reheater 8, and then the nitrogen outlet, oxygen-enriched air outlet and fuel gas outlet at the cold end of the reheater 8 are sent to the burner inlet of the natural gas boiler 9 for clean combustion;

[0018] The natural gas boiler 9 uses a swirl primary and secondary air concentration-lean burner, and the oxygen, nitrogen and fuel gas entering the natural gas boiler 9 are preheated by the reheater 8, and the graded pure oxygen and fuel gas are mixed at the inlet of the swirl primary and secondary air concentration-lean burner; the nitrogen by-product of air separation is sent to the center of the inlet of the swirl primary and secondary air concentration-lean burner to serve as the return flue gas;

[0019] The compression device 1, the end-stage cooler 2, the heat storage tank 3, and the reheater 8 constitute a heat storage subsystem, in which the heat storage medium is liquid heat transfer oil. The liquid heat transfer oil is in a closed-loop state in the heat storage subsystem, and a circulating pump is used to push the liquid heat transfer oil to work in each cooling device of the compression device 1; the specific amount of heat transfer oil and the flow rate between each cooling device need to be determined according to the system capacity.

[0020] The cold box 4 is specifically structured as a packed bed type cold storage device, which uses spherical granular stones as fillers to store and release cold energy, has an operating temperature range of -198°C to 30°C, and uses a multi-tank cold storage and a double-tank series operation mode; when releasing cold energy, it cools the high-pressure air from the final cooler 2, and the cold energy source is electric energy supplementary cooling;

[0021] The cryogenic expander 5 is used to liquefy low-temperature air. After the high-pressure and low-temperature air expands and works in the cryogenic expander 5, the temperature and pressure both drop. During the expansion process, part of the air is liquefied, and the outlet of the cryogenic expander 5 is a gas-liquid two-phase mixed air.

[0022] The fractionation tower 6 is used to separate air; liquid air is partially vaporized and rises in the lower kettle of the fractionation tower 6 to exchange heat and mass with the reflux liquid, and the remaining liquid air is mixed with the refluxed oxygen-rich liquid air, and enters the evaporation side of the condenser evaporator after throttling, and the nitrogen on the condensation side is cooled, heated and evaporated to become oxygen-rich air and led out; after the liquid nitrogen is cooled into liquid, a part of it is led out from under the top cover of the condenser evaporator as a product, and the other part is used as reflux liquid to exchange heat and mass with the rising gas;

[0023] The throttle valve 7 is used to reduce the temperature of the oxygen-enriched liquid air and increase the cooling energy of the oxygen-enriched liquid air.

[0024] In the air separation and combustion coupling method of a clean air separation gas combustion reactor system, the purified air is compressed in the compressor of the compression device 1, and heat exchanged and cooled in the interstage cooling device; the compressed high-temperature and high-pressure air enters the end-stage cooler 2, and performs surface heat exchange and cooling with the heat storage medium, and the high-temperature heat storage medium after heat exchange enters the heat storage tank 3 for storage;

[0025] The high-pressure air after heat exchange enters the cold box 4 for further deep cooling, and the temperature drops to below -100°C; the high-pressure and low-temperature air enters the cryogenic expander 5 for expansion and work, part of the air is liquefied, and part of the work is recovered at the same time, and the outlet of the cryogenic expander 5 is low-temperature gas-liquid two-phase mixed air;

[0026] After the gas-liquid mixed air at the outlet of the cryogenic expander 5 is sent to the lower kettle of the fractionation tower 6, and then further cooled by the throttle valve 7, the liquid air is separated in the fractionation tower 6, and the nitrogen product is drawn out on the condensation side of the condenser evaporator of the upper kettle of the fractionation tower 6, and the oxygen product is drawn out on the evaporation side;

[0027] The air enters the compression device 1 and is finally liquefied and separated into nitrogen and oxygen. The operating conditions of the many steps in the middle are not particularly limited. It only needs to obtain gas-liquid two-phase air after the cryogenic expander 5.

[0028] The nitrogen and oxygen flow drawn out of the distillation tower 6 and the fuel gas flow introduced from the outside are sent to the reheater 8 to exchange heat with the high-temperature heat storage medium introduced from the heat storage tank 3. After the various air flows are preheated, the graded pure oxygen is mixed with the fuel gas and sent to the burner inlet of the natural gas boiler 9 for rapid ignition and full combustion to improve the combustion efficiency. At the same time, nitrogen, a by-product of air separation, is added to the center of the burner inlet of the natural gas boiler 9 to serve as reflux flue gas, which has the effect of clean combustion, and finally improves the combustion efficiency of the natural gas boiler 9 and ensures the effect of clean combustion.

[0029] The air separation and combustion coupling method needs to achieve the air separation and combustion coupling relationship by controlling the air intake of the compression device 1 and the amount of gas input into the natural gas boiler 9: by controlling the air intake of the compression device 1, the nitrogen and oxygen flow rates finally obtained can be changed; and the amount of oxygen entering the natural gas boiler 9 needs to match the amount of gas entering the natural gas boiler 9 in pure oxygen combustion to achieve the purpose of sufficient combustion and clean combustion; that is, by controlling the air intake of the compression device 1 and the amount of gas entering the natural gas boiler 9, the combustion power of the natural gas boiler 9 can be controlled.

[0030] Compared with the conventional natural gas boiler clean combustion system, the air separation gas combustion reactor system of the present invention only needs to add a heat accumulator, a reheater, and a low-temperature fractionation air separation on the basis of the original natural gas boiler clean combustion system. These devices themselves have simple structures, low prices, and stable performance. Therefore, the air separation gas combustion reactor system is expected to achieve significant energy saving and economic benefits, and can achieve the following beneficial effects:

[0031] (1) The system enables the high-concentration oxygen required for natural gas combustion to be independently produced through an air separation unit.

[0032] (2) Able to ensure a reasonable combustion area in the furnace and appropriate furnace outlet smoke temperature through the coordination of primary and secondary air, concentrated and diluted fuel, pure oxygen and nitrogen.

[0033] (3) The heat energy of the heat storage medium and the high-pressure and high-temperature air surface can be used to heat the nitrogen, oxygen and fuel gas sent to the gas furnace, and the high-pressure air expansion work can be recovered, thereby saving energy and improving system efficiency.

[0034] (4) Innovatively use nitrogen produced by air separation to replace circulating flue gas, reduce the combustion temperature in the furnace and thus achieve the purpose of controlling nitrogen oxide emissions.

[0035] (5) The excess nitrogen and oxygen obtained from the air separation system can be sold as products, creating additional economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the structure of the system of the present invention. DETAILED DESCRIPTION

[0037] like Figure 1 As shown, a clean air separation gas combustion reactor system of the present invention is composed of a compression device 1, a stage end cooler 2, a heat storage tank 3, a cold box 4, a cryogenic expander 5, a fractionating tower 6, a throttle valve 7, a reheater 8 and a natural gas boiler 9;

[0038] The final stage outlet of the compression device 1 is connected to the hot end inlet of the final stage cooler 2, the hot end outlet of the final stage cooler 2 is connected to the inlet of the cold box 4, the outlet of the cold box 4 is connected to the inlet of the cryogenic expander 5, the outlet of the cryogenic expander 5 is connected to the inlet of the lower kettle of the fractionation tower 6, and then the bottom outlet of the fractionation tower 6 is connected to the reflux liquid inlet of the upper part of the fractionation tower 6 through the throttle valve 7, the condensation side and evaporation side outlets of the condenser evaporator in the upper kettle of the fractionation tower 6 are respectively connected to the nitrogen inlet and oxygen-enriched air inlet of the cold end of the reheater 8, and the introduced gas flow is connected to the gas inlet of the cold end of the reheater 8. The interstage outlet of the multi-stage compressor in the compression device 1 is connected to the inlet of the heat storage tank 3, the cold end outlet of the final stage cooler 2 is also connected to the inlet of the heat storage tank 3, and then the outlet of the heat storage tank 3 is connected to the hot end inlet of the reheater 8, and finally the nitrogen, oxygen-enriched air and gas outlets at the cold end of the reheater 8 are connected to the burner inlet of the natural gas boiler 9.

[0039] The air separation and combustion coupling method of the clean air separation gas combustion reactor system of the present invention is as follows:

[0040] The purified air is compressed in the compressor of the compression device 1 and heat-exchanged in the interstage cooling device. The pressure of the air at the outlet of the final compressor of the compression device 1 is 8 MPa and the temperature is 350°C. The compressed high-temperature and high-pressure air enters the final cooler 2 and exchanges heat with the heat storage medium on the surface to cool it down. After the heat exchange, the temperature of the high-pressure air is reduced from 350°C to 46°C. The high-temperature heat storage medium after the heat exchange enters the heat storage tank 3 for storage.

[0041] The high-pressure air after heat exchange enters the cold box 4 for further deep cooling, and the temperature drops from 46°C to -150°C; the high-pressure and low-temperature air enters the cryogenic expander 5 for expansion and work, and the pressure drops from 8MPa to 0.688MPa, and the temperature drops from -150°C to -168.7°C. Part of the air is liquefied, and part of the work is recovered at the same time. The outlet of the cryogenic expander 5 is a low-temperature gas-liquid two-phase mixed air;

[0042] After the gas-liquid mixed air at the outlet of the cryogenic expander 5 is sent to the lower kettle of the fractionation tower 6, and then further cooled by the throttle valve 7, the liquid air is separated in the fractionation tower 6, and the nitrogen product can be drawn out on the condensation side of the condenser evaporator of the upper kettle of the fractionation tower 6, and the oxygen product can be drawn out on the evaporation side;

[0043] There are no special restrictions on the operating conditions of the many steps from the time the air enters the compression device 1 to the final liquefaction and separation into nitrogen and oxygen. It is only necessary to obtain gas-liquid two-phase air after the cryogenic expander 5.

[0044] The nitrogen and oxygen flow drawn out from the distillation tower 6 and the fuel gas flow introduced from the outside are sent to the reheater 8 to exchange heat with the high-temperature heat storage medium introduced from the heat storage tank 3. After each gas flow is preheated to 100°C, the graded pure oxygen is mixed with the fuel gas and sent to the natural gas boiler 9 for rapid ignition and full combustion to improve the combustion efficiency. At the same time, nitrogen, a by-product of air separation, is added to the natural gas boiler 9 to serve as reflux flue gas, which has the effect of clean combustion, and finally improves the combustion efficiency of the natural gas boiler and ensures the effect of clean combustion.

[0045] The air separation and combustion coupling method described above needs to achieve the air separation and combustion coupling relationship by controlling the air intake of the compression device 1 and the amount of fuel gas input into the natural gas boiler 9: by controlling the air intake of the compression device 1, the nitrogen and oxygen flow rates finally obtained can be changed; and the amount of oxygen entering the natural gas boiler 9 needs to match the amount of fuel gas entering the natural gas boiler 9 in pure oxygen combustion to achieve the purpose of sufficient combustion and clean combustion; that is, by controlling the air intake of the compression device 1 and the amount of fuel gas entering the natural gas boiler 9, the combustion power of the natural gas boiler 9 can be controlled.

[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A clean air separation gas combustion reactor system, characterized in that: It is composed of a compression device (1), a final cooler (2), a heat storage tank (3), a cold box (4), a cryogenic expander (5), a fractionating tower (6), a throttle valve (7), a reheater (8) and a natural gas boiler (9); The final stage outlet of the compression device (1) is connected to the hot end inlet of the final stage cooler (2), the hot end outlet of the final stage cooler (2) is connected to the inlet of the cold box (4), the outlet of the cold box (4) is connected to the inlet of the cryogenic expander (5), the outlet of the cryogenic expander (5) is connected to the inlet of the lower kettle of the fractionation tower (6), the bottom outlet of the fractionation tower (6) is connected to the reflux liquid inlet of the upper part of the fractionation tower (6) through a throttle valve (7), the condensation side and evaporation side outlets of the condenser evaporator in the upper kettle of the fractionation tower (6) are respectively connected to the reheater (8). ) the nitrogen inlet at the cold end is connected to the oxygen-enriched air inlet, and the introduced fuel gas flow is connected to the fuel gas inlet at the cold end of the reheater (8); the interstage outlet of the multi-stage compressor in the compression device (1) is connected to the inlet of the heat storage tank (3), the cold end outlet of the end-stage cooler (2) is also connected to the inlet of the heat storage tank (3), the outlet of the heat storage tank (3) is connected to the hot end inlet of the reheater (8), and the nitrogen outlet, oxygen-enriched air outlet and fuel gas outlet at the cold end of the reheater (8) are connected to the burner inlet of the natural gas boiler (9).

2. A clean air separation gas combustion reactor system as claimed in claim 1, characterized in that: The system uses waste heat generated by the compression device (1) during the compression process and waste heat generated by heat exchange of the high-temperature and high-pressure airflow in the end-stage cooler (2) after compression to assist in heating the fuel gas, nitrogen and oxygen, thereby improving the inlet conditions of the natural gas boiler (9), and at the same time adding air separation by-product nitrogen to serve as reflux flue gas.

3. A clean air separation gas combustion reactor system as claimed in claim 1, characterized in that: The compression device (1) is a 2-4 stage compressor equipped with an interstage cooling device, has a simple structure and a high pressure ratio; air is directly introduced from the atmosphere at the inlet of the compression device (1); at the same time, the outlets between the compressors of each stage in the compression device (1) lead out the heat storage medium that exchanges heat with the surface of the compressed air to the heat storage tank (3) for heat storage, and the heat storage medium before the heat exchange is in a state of normal temperature and pressure.

4. A clean air separation gas combustion reactor system as claimed in claim 1, characterized in that: The end-of-stage cooler (2) uses the heat storage medium to exchange heat with the high-temperature air on the surface, the air temperature is reduced, and the heat storage medium is heated and enters the heat storage tank (3) for storage through the cold end outlet of the end-of-stage cooler (2); The heat storage tank (3) receives the heat storage medium from the compression device (1) and the end-stage cooler (2), and introduces the heat storage medium into the reheater (8) from the lower outlet; The reheater (8) is used to preheat the gas entering the natural gas boiler (9). The specific working principle is surface heat exchange. The heat in the heat storage medium introduced by the heat storage tank (3) is used to heat the nitrogen, oxygen-enriched air and fuel gas at the inlet of the reheater (8). The nitrogen outlet, oxygen-enriched air outlet and fuel gas outlet at the cold end of the reheater (8) are then sent to the inlet of the burner of the natural gas boiler (9) for clean combustion. The natural gas boiler (9) uses a swirl primary and secondary air concentration-lean burner, preheats the oxygen, nitrogen and fuel gas entering the natural gas boiler (9) through a reheater (8), and performs graded pure oxygen and fuel gas mixing at the inlet of the swirl primary and secondary air concentration-lean burner; nitrogen, a byproduct of air separation, is sent to the center of the inlet of the swirl primary and secondary air concentration-lean burner to serve as reflux flue gas; The compression device (1), the final cooler (2), the heat storage tank (3), and the reheater (8) constitute a heat storage subsystem, wherein the heat storage medium is liquid heat transfer oil. The liquid heat transfer oil is in a closed loop state in the heat storage subsystem, and is driven by a circulation pump to work in each cooling device of the compression device (1); the specific amount of the heat transfer oil and the flow rate between each cooling device need to be determined according to the system capacity.

5. A clean air separation gas combustion reactor system as claimed in claim 1, characterized in that: The cold box (4) is specifically structured as a packed bed type cold storage device, which uses spherical granular stones as fillers to store and release cold energy, has an operating temperature range of -198°C to 30°C, and uses a multi-tank cold storage and a double-tank series connection mode for operation; when releasing cold energy, it cools the high-pressure air from the final cooler (2), and the cold energy source is electric energy supplementary cooling; The cryogenic expander (5) is used to liquefy low-temperature air; after the high-pressure and low-temperature air expands and performs work in the cryogenic expander (5), both the temperature and pressure drop; during the expansion process, part of the air is liquefied, and the outlet of the cryogenic expander (5) is a mixture of gas and liquid phases; The fractionation tower (6) is used to separate air; liquid air is partially vaporized and rises in the lower kettle of the fractionation tower (6) to exchange heat and mass with the reflux liquid, and the remaining liquid air is mixed with the refluxed oxygen-rich liquid air, and enters the evaporation side of the condenser evaporator after throttling, and the nitrogen on the condensation side is cooled, heated and evaporated to become oxygen-rich air and led out; after the liquid nitrogen is cooled into liquid, a part of it is led out from under the top cover of the condenser evaporator as a product, and the other part is used as the reflux liquid to exchange heat and mass with the rising gas; The throttle valve (7) is used to reduce the temperature of the oxygen-enriched liquid air and increase the cold energy of the oxygen-enriched liquid air.

6. The air separation and combustion coupling method of a clean air separation gas combustion reactor system according to any one of claims 1 to 5, characterized in that: The purified air is compressed in the compressor of the compression device (1) and is cooled by heat exchange in the interstage cooling device; the compressed high-temperature and high-pressure air enters the end-stage cooler (2) and is cooled by surface heat exchange with the heat storage medium; the high-temperature heat storage medium after heat exchange enters the heat storage tank (3) for storage; The high-pressure air after heat exchange enters the cold box (4) for further deep cooling, with the temperature dropping to below -100°C; the high-pressure and low-temperature air enters the cryogenic expander (5) for expansion and work, part of the air is liquefied, and part of the work is recovered at the same time, and the outlet of the cryogenic expander (5) is low-temperature gas-liquid two-phase mixed air; The gas-liquid mixed air at the outlet of the cryogenic expander (5) is sent to the lower kettle of the fractionation tower (6), and then further cooled by the throttle valve (7). The liquid air is separated in the fractionation tower (6), and the nitrogen product is drawn out on the condensation side of the condenser evaporator of the upper kettle of the fractionation tower (6), and the oxygen product is drawn out on the evaporation side; The air enters the compression device (1) and is finally liquefied and separated into nitrogen and oxygen. The operating conditions of the many steps in between are not particularly limited. It is only necessary to obtain gas-liquid two-phase air after the cryogenic expander (5); The nitrogen gas and oxygen flow drawn out of the fractionation tower (6) and the fuel gas flow introduced from the outside are sent to the reheater (8) to exchange heat with the high-temperature heat storage medium introduced from the heat storage tank (3). After the various gas flows are preheated, the graded pure oxygen is mixed with the fuel gas and sent to the burner inlet of the natural gas boiler (9) to ignite quickly and burn fully, thereby improving the combustion efficiency. At the same time, nitrogen gas, a by-product of air separation, is added to the center of the burner inlet of the natural gas boiler (9) to serve as reflux flue gas, thereby achieving the effect of clean combustion, thereby ultimately achieving the effect of improving the combustion efficiency of the natural gas boiler (9) and ensuring clean combustion.

7. The air separation and combustion coupling method according to claim 6 is characterized in that: It is necessary to achieve the air separation and combustion coupling relationship by controlling the air intake of the compression device (1) and the amount of fuel gas input into the natural gas boiler (9): by controlling the air intake of the compression device (1), the nitrogen and oxygen flow rates finally obtained are changed; and the amount of oxygen entering the natural gas boiler (9) needs to match the amount of fuel gas entering the natural gas boiler (9) in pure oxygen combustion to achieve the purpose of full combustion and clean combustion; that is, by controlling the air intake of the compression device (1) and the amount of fuel gas entering the natural gas boiler (9), the combustion power of the natural gas boiler (9) is controlled.

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