Combustion method for ammonia fuel hot rolling heating furnace
By adjusting the ammonia ratio and combustion-supporting gas in the combustion system of the ammonia fuel hot rolling furnace, the problems of unstable ammonia fuel combustion and nitrogen oxide emissions were solved, achieving safe and stable zero-carbon combustion and ultra-low emissions.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHONGQING CISDI THERMAL & ENVIRONMENTAL ENG CO LTD
- Filing Date
- 2023-06-20
- Publication Date
- 2026-05-15
AI Technical Summary
Ammonia fuel burns slowly, has a narrow ignition range, and is unstable in hot rolling furnaces, producing large amounts of nitrogen oxides, making it difficult to meet zero carbon emissions and pollutant emission standards.
A combustion system for an ammonia-fueled hot rolling furnace is designed. By combining a liquid ammonia storage tank, a combustion fan, a liquid ammonia gasification and distribution device, an ammonia cracking device, an SNCR denitrification device, an SCR denitrification device, a residual ammonia collection device, and a condensate collection device, the system regulates the proportion of ammonia and combustion-supporting gas under different operating conditions to achieve stable combustion and ultra-low nitrogen oxide emissions.
It achieves safe and stable combustion of ammonia fuel in hot rolling furnaces with zero carbon emissions, meeting heating process requirements while reducing nitrogen oxide emissions.
Smart Images
Figure CN116538499B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of energy conservation and emission reduction, and relates to a combustion method for an ammonia fuel hot rolling furnace. Background Technology
[0002] Against the backdrop of dual carbon emissions, a revolution in smelting processes is imminent for the steel metallurgical industry. Current hot rolling furnaces primarily use carbon-containing fuels generated during steel mill production. However, future technologies, whether short-process electric arc furnaces or hydrogen metallurgy, will inevitably lead to changes in the fuel used in hot rolling furnaces. Therefore, finding a carbon-free fuel to replace the existing fuels in hot rolling furnaces is urgently needed.
[0003] Ammonia combustion produces nitrogen and water, achieving zero carbon emissions. Compared to the high costs of hydrogen production, transportation, and storage at present, ammonia production, transportation, and storage are inexpensive, and it has extensive experience in other industrial applications, showing potential for large-scale application in hot rolling furnaces. However: as a fuel, ammonia has a low flame propagation speed and a narrow ignition range, and it can exhibit unstable combustion at lower temperatures, posing safety hazards; furthermore, ammonia contains nitrogen, and as a nitrogen-containing fuel, its combustion produces large amounts of nitrogen oxides, failing to meet government pollutant emission standards. Summary of the Invention
[0004] In view of this, the object of the present invention is to provide a combustion method for an ammonia fuel hot rolling furnace.
[0005] To achieve the above objectives, the present invention provides the following technical solution:
[0006] A combustion method for an ammonia fuel hot rolling furnace, and a combustion system for an ammonia fuel hot rolling furnace, including a liquid ammonia storage tank, a combustion fan, a liquid ammonia gasification and distribution device, an ammonia cracking device, a furnace body, an ammonia fuel burner, an SNCR denitrification device, an SCR denitrification device, a residual ammonia collection device, a condensate collection device, and a nitrogen collection device.
[0007] The liquid ammonia storage tank is connected to the liquid ammonia vaporization and distribution device. The outlet of the liquid ammonia vaporization and distribution device is divided into four paths. Three paths are connected to the SNCR denitrification device, the ammonia cracking device, and the SCR denitrification device, respectively. One path is connected to the ammonia fuel burner to form an ammonia fuel channel.
[0008] The combustion air blower is connected to the ammonia fuel burner to form a combustion gas channel;
[0009] Ammonia fuel burners are installed on the furnace body, and the SNCR denitrification device is assembled at the end of the furnace body. At the end of the furnace body, the ammonia cracking device or the short-circuit bypass pipeline of the ammonia cracking device is connected in sequence through the flue along the flue flow direction. Then, the gas flows through the liquid ammonia vaporization distribution device, the SCR denitrification device, and the residual ammonia collection device. After the residual ammonia collection device, the condensate collection device and the nitrogen collection device are connected to form a flue gas channel.
[0010] Liquid ammonia is stored in a liquid ammonia storage tank and flows through a liquid ammonia vaporization distribution device, absorbing waste heat or electrical heat from the boiler flue gas and converting it into ammonia gas. After vaporization, the ammonia gas is divided into four streams. The first stream, with a flow rate of 'a', is connected to the ammonia fuel inlet of the ammonia fuel burner. The second stream, with a flow rate of 'b', is connected to the SNCR denitrification device. The third stream, with a flow rate of 'c', flows through the ammonia cracking device, absorbing waste heat or electrical heat from the flue gas and converting it into hydrogen and a small amount of nitrogen under the action of a catalyst before being connected to the hydrogen fuel inlet of the ammonia fuel burner. The fourth stream, with a flow rate of 'd', is connected to the SCR denitrification device. The flow rates of the four ammonia streams are controlled and regulated by valves according to the combustion control strategy.
[0011] Optionally, the combustion control strategy is:
[0012] 1) When the furnace temperature is below x℃, the proportions of the four streams of ammonia flowing out of the liquid ammonia vaporization distribution device satisfy the following relationship: a+b+c+d=100%, b=0%, c=15%~30%, d=0.1~0.35%; the ammonia cracking device absorbs electric heat to convert ammonia into a mixture of hydrogen and nitrogen for stable combustion; the value of d is adjusted according to the nitrogen oxide content of the flue gas.
[0013] 2) When the furnace temperature range is x℃~y℃, the proportions of the four streams of ammonia gas flowing out of the liquid ammonia vaporization distribution device meet the following relationship: a+b+c+d=100%, b=0%, c=0%, d=0.1%~0.35%; the value of d is adjusted according to the nitrogen oxide content of the flue gas.
[0014] 3) When the furnace temperature range is y℃~z℃, the proportions of the four streams of ammonia flowing out of the liquid ammonia gasification distribution device satisfy the following relationship: a+b+c+d=100%, b=0.1~0.35%, c=0%~99.9%, d=0%; the value of b is adjusted according to the nitrogen oxide content of the flue gas; the ammonia cracking device absorbs the waste heat or electric heat of the flue gas to convert ammonia into a mixture of hydrogen and nitrogen gas. The larger the value of c, the lower the system exhaust temperature and the more ammonia fuel is saved. The optimal value of c is determined by comparing the cost of the catalyst used in the ammonia cracking device with the cost of liquid ammonia.
[0015] x < y < z.
[0016] Optionally, the combustion-supporting gas is blown into the system by a blower and connected to the combustion-supporting gas inlet of the ammonia fuel burner.
[0017] Optionally, the combustion-supporting gas can be air, oxygen-enriched air, or pure oxygen, and the gas flow rate can be controlled and adjusted by valves according to the gas composition and the corresponding combustion control strategy.
[0018] Optionally, after the flue gas in the furnace is injected with ammonia to reduce nitrogen oxides through the SNCR denitrification device, it is discharged from the furnace body into the flue and flows sequentially through the ammonia cracking device or the short-circuit bypass pipeline of the ammonia cracking device, and then through the liquid ammonia gasification distribution device, the SCR denitrification device, and the residual ammonia collection device; the water in the flue gas is collected and stored by the condensate collection device; after the water is removed, only nitrogen in the flue gas flows into the nitrogen collection device for flue gas recirculation or direct discharge.
[0019] Optionally, the flue gas temperature is 850℃~1100℃ when it flows through the SNCR denitrification unit and 800℃~900℃ when it flows into the ammonia cracking unit.
[0020] Optionally, the furnace body is divided into a heat recovery section without heating, a preheating section, a heating section, and a soaking section. The preheating section, heating section, and soaking section are equipped with ammonia fuel burners, while the heat recovery section is not equipped with ammonia fuel burners or other heating equipment, so that the SNCR denitrification unit can operate at a suitable temperature.
[0021] Optionally, the ammonia fuel burner has a hydrogen fuel inlet, an ammonia fuel inlet, and a combustion-supporting gas inlet.
[0022] Optionally, x is in the range of 640℃~660℃, y is in the range of 930℃~980℃, and z is in the range of 1350℃~1450℃.
[0023] The beneficial effects of this invention are as follows:
[0024] This system achieves safe and stable combustion of ammonia fuel and ultra-low nitrogen oxide emissions from the hot rolling furnace by adjusting the proportions of ammonia involved in direct combustion, pyrolysis, SNCR, and SCR under different operating conditions. The final emission of the combustion system is nitrogen, thus achieving zero carbon emissions from the hot rolling furnace while meeting the heating process requirements.
[0025] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description
[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:
[0027] Figure 1 This is a schematic diagram of the system in Embodiment 1 of the present invention;
[0028] Figure 2 This is a schematic diagram of an ammonia fuel burner structure;
[0029] Figure 3 This is a schematic diagram of another type of ammonia fuel burner structure;
[0030] Figure 4 This is a schematic diagram of the system in Embodiment 2 of the present invention.
[0031] Figure reference numerals: 1. Liquid ammonia storage tank; 2. Combustion fan; 3. Liquid ammonia vaporization and distribution device; 4. Ammonia cracking device; 5. Furnace body; 6. Ammonia fuel burner; 61. Hydrogen fuel inlet for ammonia fuel burner; 62. Ammonia fuel burner ammonia fuel inlet; 63. Combustion gas inlet for ammonia fuel burner; 7. SNCR denitrification device; 8. SCR denitrification device; 9. Residual ammonia collection device; 10. Condensate collection device; 11. Nitrogen collection device; 12. Ammonia preheater; 13. Combustion gas preheater. Detailed Implementation
[0032] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.
[0033] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.
[0034] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.
[0035] Example 1
[0036] Please see Figures 1-3This invention includes a liquid ammonia storage tank 1, a combustion-supporting blower 2, a liquid ammonia vaporization and distribution device 3, an ammonia cracking device 4, a furnace body 5, an ammonia fuel burner 6, an SNCR denitrification device 7, an SCR denitrification device 8, a residual ammonia collection device 9, a condensate collection device 10, and a nitrogen collection device 11. The liquid ammonia storage tank 1 is connected to the liquid ammonia vaporization and distribution device 3. The outlet of the liquid ammonia vaporization and distribution device 3 splits into four paths: three paths are connected to the SNCR denitrification device 7, the ammonia cracking device 4, and the SCR denitrification device 8, respectively; and one path is connected to the ammonia fuel burner 6, forming an ammonia fuel channel. The combustion-supporting blower 2 is connected to the ammonia fuel burner 6, forming a combustion-supporting gas channel. Ammonia fuel burners 6 are installed on the furnace body 5. An SNCR denitrification device 7 is installed near the end of the furnace body 5 at a flue gas temperature of 850℃~1100℃. The end of the furnace body 5 is connected to the ammonia cracking device 4 or the ammonia cracking device short-circuit bypass pipeline through the flue along the flue gas flow direction. Then it flows through the liquid ammonia gasification distribution device 3, the SCR denitrification device 8, and the residual ammonia collection device 9. The residual ammonia collection device 9 is connected to the condensate collection device 10 and the nitrogen collection device 11 to form a flue gas channel. Liquid ammonia is stored in liquid ammonia storage tank 1 and flows through liquid ammonia vaporization distribution device 3, absorbing waste heat or electrical heat from the heating furnace flue gas to convert it into ammonia gas. After vaporization, the ammonia gas is divided into four streams. The first stream, with a flow rate of a, is connected to the ammonia fuel inlet of ammonia fuel burner 6. The second stream, with a flow rate of b, is connected to SNCR denitrification device 7. The third stream, with a flow rate of c, flows through ammonia cracking device 4, absorbing waste heat or electrical heat from the flue gas, and is converted into hydrogen and a small amount of nitrogen under the action of a catalyst before being connected to the hydrogen fuel inlet of ammonia fuel burner 6. The fourth stream, with a flow rate of d, is connected to SCR denitrification device 8. The flow rates of the four ammonia streams are controlled and regulated by valves according to the combustion control strategy. Combustion-supporting gas is blown into the system by blower 2 and connected to the combustion-supporting gas inlet of ammonia fuel burner 6. The combustion-supporting gas can be air, oxygen-enriched air, or pure oxygen, and the gas flow rate is controlled and regulated by valves according to the gas composition and the corresponding combustion control strategy. After the flue gas in the furnace passes through the SNCR denitrification unit 7 where ammonia is injected to reduce nitrogen oxides, it is discharged from the furnace body into the flue, flows through the ammonia cracking unit 4 or the ammonia cracking unit short-circuit bypass pipeline, and then flows through the liquid ammonia vaporization distribution unit 3, the SCR denitrification unit 8, and the residual ammonia collection unit 9. Water in the flue gas is collected and stored by the condensate collection unit 10. After the water is removed, only nitrogen remains in the flue gas, which flows into the nitrogen collection unit 11 for flue gas recirculation or direct discharge. The furnace body 5 is divided into a heat recovery section without heating, a preheating section, a heating section, and a soaking section. The preheating section, heating section, and soaking section are equipped with ammonia fuel burners, while the heat recovery section is not equipped with ammonia fuel burners or other heating equipment so that the SNCR denitrification unit can operate at a suitable temperature.The ammonia fuel burner 6 has a hydrogen fuel inlet 61, an ammonia fuel inlet 62, and a combustion-supporting gas inlet 63. In this embodiment: a low-nitrogen oxide gas flame-regulating burner disclosed in CN2379705Y is used, with its central air duct serving as the hydrogen fuel inlet 61, its gas duct serving as the ammonia fuel inlet 62, and its air inlet serving as the combustion-supporting gas inlet 63; and a dual-swirl flat flame burner disclosed in CN106122946B is used, with its central air duct serving as the hydrogen fuel inlet 61, its gas duct serving as the ammonia fuel inlet 62, and its main air duct serving as the combustion-supporting gas inlet 63.
[0037] The working principle of this embodiment is as follows:
[0038] This system achieves safe and stable combustion of ammonia fuel and ultra-low nitrogen oxide emissions from the hot rolling furnace by adjusting the proportions of ammonia involved in direct combustion, pyrolysis, SNCR, and SCR under different operating conditions. The final emission of the combustion system is nitrogen, thus achieving zero carbon emissions from the hot rolling furnace while meeting the heating process requirements.
[0039] From start-up to furnace temperature below 652℃: The furnace temperature is below the ignition point of ammonia, requiring the burners to provide a pilot flame to stabilize ammonia combustion. At this time, the flue gas temperature is below the 800℃~900℃ required by the ammonia cracking unit. The ammonia cracking unit operates electrically, cracking 15%~30% of the incoming ammonia into hydrogen and a small amount of nitrogen, which are then fed into the burners as pilot flame fuel to ensure stable ammonia combustion. At this time, the flue gas temperature is below the 850℃~1100℃ required by the SNCR unit, and the combustion of nitrogen-containing ammonia produces a large amount of nitrogen oxides. At this time, the ammonia supply to the SNCR unit is shut off, and the ammonia supply to the SCR unit at the end of the flue is turned on, using selective catalytic denitrification to treat the nitrogen oxides in the flue gas.
[0040] When the furnace temperature is above 652℃ to 950℃: the furnace temperature is already above the ignition point of ammonia, and stable combustion of ammonia can be achieved without a pilot flame; at this point, the flue gas temperature before the ammonia cracking unit is just within the catalyst's active temperature range, but stable combustion of hydrogen fuel without a pilot flame is no longer required, so the ammonia supply to the ammonia catalytic unit can be shut off; at this point, the flue gas temperature is below the 850℃~1100℃ temperature required by the SNCR unit, and the combustion of nitrogen-containing ammonia produces a large amount of nitrogen oxides, so the ammonia supply to the SNCR unit is shut off, and the ammonia supply to the SCR unit at the end of the flue is turned on, using selective catalytic reduction to treat the nitrogen oxides in the flue gas.
[0041] When the furnace temperature is above 950℃ to 1400℃, ammonia can burn stably. The flue gas temperature before the ammonia cracking unit also reaches the catalyst's active temperature range. Ammonia cracking requires heat absorption. The higher the cracking ratio, the more waste heat from the flue gas is recovered and utilized, the higher the exhaust temperature, and the more ammonia fuel is saved. However, this will also consume more ammonia cracking catalyst. It is necessary to evaluate the cost of catalyst use and the cost of liquid ammonia and adjust the ammonia cracking ratio accordingly. When the temperature at the end of the furnace reaches the suitable reaction temperature for SNCR, the SCR ammonia supply at the end of the flue is shut off, and the selective non-catalytic reduction method is used to treat nitrogen oxides in the flue gas.
[0042] Example 2
[0043] Please see Figure 4 The present invention includes a liquid ammonia storage tank 1, a combustion-supporting blower 2, a liquid ammonia vaporization and distribution device 3, an ammonia cracking device 4, a furnace body 5, an ammonia fuel burner 6, an ammonia fuel burner hydrogen fuel inlet 61, an ammonia fuel burner ammonia fuel inlet 62, an ammonia fuel burner combustion-supporting gas inlet 63, an SNCR denitrification device 7, an SCR denitrification device 8, a residual ammonia collection device 9, a condensate collection device 10, a nitrogen collection device 11, an ammonia preheater 12, and a combustion-supporting gas preheater 13.
[0044] Liquid ammonia storage tank 1 is connected to liquid ammonia vaporization distribution device 3. The outlet of liquid ammonia vaporization distribution device 3 is split into four branches, which are respectively connected to ammonia preheater 12, SNCR denitrification device 7, ammonia cracking device 4, and SCR denitrification device 8. The outlet of ammonia preheater 12 is connected to ammonia fuel burner 6, forming an ammonia fuel channel. Combustion fan 2 is connected to combustion gas preheater 13. The outlet of combustion gas preheater 13 is connected to burner 6, forming a combustion gas channel. Burner 6 is installed on furnace body 5. Near the end of furnace body 5, SNCR denitrification device 7 is installed. At the end of furnace body 5, along the flue gas flow direction, ammonia cracking device 4, combustion gas preheater 13, ammonia preheater 12, liquid ammonia vaporization distribution device 3, SCR denitrification device 8, and residual ammonia collection device 9 are connected in sequence through flue. After residual ammonia collection device 9, condensate collection device 10 and nitrogen collection device 11 are connected, forming a flue gas channel. Liquid ammonia is stored in liquid ammonia storage tank 1 and flows through liquid ammonia vaporization distribution device 3, absorbing waste heat or electrical heat from the heating furnace flue gas to convert it into ammonia gas. After vaporization, the ammonia gas is divided into four streams. The first stream, with a flow rate of a, flows through ammonia preheater 12 to absorb waste heat from the flue gas and then enters the ammonia fuel inlet of ammonia fuel burner 6. The second stream, with a flow rate of b, enters the SNCR denitrification device 7. The third stream, with a flow rate of c, flows through ammonia cracking device 4 to absorb waste heat or electrical heat from the flue gas and is converted into hydrogen and a small amount of nitrogen under the action of a catalyst before entering the hydrogen fuel inlet of ammonia fuel burner 6. The fourth stream, with a flow rate of d, enters the SCR denitrification device 8. The flow rates of the four ammonia streams are controlled and regulated by valves according to the combustion control strategy. Combustion-supporting gas is blown into the system by fan 2. It flows through combustion-supporting gas preheater 13 to absorb waste heat from the flue gas and then enters the combustion-supporting gas inlet of ammonia fuel burner 6. The combustion-supporting gas can be air, oxygen-enriched air, or pure oxygen, and the gas flow rate is controlled and regulated by valves according to the gas composition and the corresponding combustion control strategy. After the flue gas in the furnace passes through the SCR denitrification device 8 and is injected with ammonia to reduce nitrogen oxides, it is discharged from the furnace body into the flue and flows sequentially through the ammonia cracking device 4, the combustion gas preheater 13, the ammonia preheater 12, the liquid ammonia vaporization distribution device 3, the SCR denitrification device 8, and the residual ammonia collection device 9. The water in the flue gas is collected and stored by the condensate collection device 10 for other uses or direct discharge. After the water is removed, only nitrogen in the flue gas flows into the nitrogen collection device 11 for flue gas recirculation or direct discharge.
[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A combustion method for an ammonia fuel hot rolling furnace, characterized in that, A combustion system for an ammonia fuel hot rolling furnace is provided, comprising a liquid ammonia storage tank (1), a combustion fan (2), a liquid ammonia vaporization distribution device (3), an ammonia cracking device (4), a furnace body (5), an ammonia fuel burner (6), an SNCR denitrification device (7), an SCR denitrification device (8), a residual ammonia collection device (9), a condensate collection device (10), and a nitrogen collection device (11). The liquid ammonia storage tank (1) is connected to the liquid ammonia vaporization distribution device (3). The outlet of the liquid ammonia vaporization distribution device (3) is divided into four paths. Three paths are connected to the SNCR denitrification device (7), the ammonia cracking device (4), and the SCR denitrification device (8), respectively. One path is connected to the ammonia fuel burner (6) to form an ammonia fuel channel. The combustion blower (2) is connected to the ammonia fuel burner (6) to form a combustion gas channel; Ammonia fuel burner (6) is installed on the furnace body (5), and SNCR denitrification device (7) is assembled at the end of the furnace body (5). The end of the furnace body (5) is connected to the ammonia cracking device (4) or the short-circuit bypass pipeline of the ammonia cracking device (4) through the flue along the flue gas flow direction, and then through the liquid ammonia vaporization distribution device (3), SCR denitrification device (8), and residual ammonia collection device (9). The residual ammonia collection device (9) is connected to the condensate collection device (10) and the nitrogen collection device (11) to form a flue gas channel. Liquid ammonia is stored in a liquid ammonia storage tank (1), flows through a liquid ammonia vaporization distribution device (3), absorbs waste heat or electric heat from the heating furnace flue gas, and is converted into ammonia gas; after vaporization, the ammonia gas is divided into 4 streams. The first stream with a flow rate of a is connected to the ammonia fuel inlet of the ammonia fuel burner (6), the second stream with a flow rate of b is connected to the SNCR denitrification device (7), the third stream with a flow rate of c flows through the ammonia cracking device (4) to absorb waste heat or electric heat from the flue gas, is converted into hydrogen and a small amount of nitrogen under the action of a catalyst, and is then connected to the hydrogen fuel inlet of the ammonia fuel burner (6), and the fourth stream with a flow rate of d is connected to the SCR denitrification device (8); the flow rates of the four streams of ammonia gas are controlled and adjusted by valves according to the combustion control strategy. The combustion control strategy is as follows: 1) When the furnace temperature is below x℃, the proportions of the 4 streams of ammonia flowing out of the liquid ammonia vaporization distribution device (3) satisfy the following relationship: a+b+c+d=100%, b=0%, c=15%~30%, d=0.1~0.35%; the ammonia cracking device (4) absorbs electric heat and converts ammonia into a mixture of hydrogen and nitrogen for stable combustion; the value of d is adjusted according to the nitrogen oxide content of the flue gas. 2) When the furnace temperature range is x℃~y℃, the proportions of the four streams of ammonia flowing out of the liquid ammonia vaporization distribution device (3) satisfy the following relationship: a+b+c+d=100%, b=0%, c=0%, d=0.1%~0.35%; the value of d is adjusted according to the content of nitrogen oxides in the flue gas. 3) When the furnace temperature range is y℃~z℃, the proportion of the four streams of ammonia flowing out of the liquid ammonia gasification distribution device (3) satisfies the following relationship: a+b+c+d=100%, b=0.1~0.35%, c=0%~99.9%, d=0%; the b value is adjusted according to the nitrogen oxide content of the flue gas; the ammonia cracking device (4) absorbs the waste heat or electric heat of the flue gas and converts the ammonia into a mixture of hydrogen and nitrogen. The larger the c value, the lower the flue gas temperature of the system and the more ammonia fuel is saved. The optimal c value is determined by comparing the cost of the catalyst used in the ammonia cracking device (4) with the cost of liquid ammonia. x < y < z.
2. The combustion method of the ammonia fuel hot rolling furnace according to claim 1, characterized in that, The combustion-supporting gas is blown into the combustion-supporting gas inlet of the ammonia fuel burner (6) by the combustion-supporting blower (2).
3. The combustion method of the ammonia fuel hot rolling furnace according to claim 1, characterized in that, The combustion-supporting gas is air, oxygen-enriched air, or pure oxygen, and the gas flow rate is controlled and regulated by valves according to the gas composition and the corresponding combustion control strategy.
4. The combustion method of the ammonia fuel hot rolling furnace according to claim 1, characterized in that, After the flue gas in the furnace passes through the ammonia injection denitrification device (7) to inject ammonia to reduce nitrogen oxides, it is discharged from the furnace body into the flue and flows through the ammonia cracking device (4) or the short-circuit bypass pipeline of the ammonia cracking device (4). Then it flows through the liquid ammonia gasification distribution device (3), the SCR denitrification device (8), and the residual ammonia collection device (9). The water in the flue gas is collected and stored by the condensate collection device (10). After the water is removed, only nitrogen is left in the flue gas and flows into the nitrogen collection device (11) for flue gas circulation or direct discharge.
5. The combustion method of the ammonia fuel hot rolling furnace according to claim 1, characterized in that, The flue gas flows through the ammonia injection denitrification device (7), which is installed at the end of the furnace body (5) at a furnace temperature of 850℃~1100℃.
6. The combustion method of an ammonia fuel hot rolling furnace according to claim 1, characterized in that, The furnace body is divided into a heat recovery section without heat supply, a preheating section, a heating section and a homogenizing section. The preheating section, the heating section and the homogenizing section are equipped with ammonia fuel burners (6). The heat recovery section is not equipped with ammonia fuel burners (6) or other heating equipment so that the ammonia injection denitrification device (7) can operate at a suitable temperature.
7. The combustion method for an ammonia fuel hot rolling furnace according to claim 1, characterized in that, The ammonia fuel burner (6) is provided with a hydrogen fuel inlet (61), an ammonia fuel inlet (62), and a combustion-supporting gas inlet (63).
8. The combustion method of an ammonia fuel hot rolling furnace according to claim 1, characterized in that, x is in the range of 640℃~660℃, y is in the range of 930℃~980℃, and z is in the range of 1350℃~1450℃.