Double-heat-storage type heating furnace and method for hydrogen-doped combustion of ammonia gas
By utilizing the waste heat of flue gas in a dual regenerative furnace to drive the cracking of ammonia to produce hydrogen, forming an ammonia-hydrogen mixed fuel, the problems of difficult ignition of ammonia combustion and high NOx emissions are solved, achieving stable combustion and low nitrogen emissions.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NORTHEASTERN UNIV CHINA
- Filing Date
- 2026-02-26
- Publication Date
- 2026-05-12
AI Technical Summary
Ammonia combustion in industrial furnaces and kilns presents challenges such as ignition difficulties, flame detachment, and flameout. Furthermore, while traditional regenerative combustion technology improves combustion stability, it leads to excessive NOx emissions, creating a contradiction between combustion stability and low nitrogen emissions.
A dual regenerative heating furnace system is adopted, which uses the waste heat of flue gas to drive the cracking of ammonia to produce hydrogen. By loading an ammonia decomposition catalyst in the regenerative chamber, an ammonia-hydrogen mixed fuel is formed. The waste heat of flue gas is recovered and the hydrogen content is controlled through a periodic reversing system, so as to achieve stable combustion and low nitrogen emissions.
It achieves stable combustion of ammonia fuel, reduces NOx emissions, improves energy efficiency, and requires no external hydrogen source or fossil fuel assistance. Its compact structure makes it easy to modify.
Smart Images
Figure CN122015508A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of regenerative heating furnaces, and particularly relates to a dual regenerative heating furnace and method for ammonia gas combustion with hydrogen. Background Technology
[0002] While hydrogen (H2) is a zero-carbon fuel, its low volumetric energy density and poor storage and transportation safety limit its large-scale industrial application. Ammonia (NH3), as a carbon-free energy carrier, has become a hot topic for replacing coal and gas fuels in energy-intensive industries such as metallurgy due to its high hydrogen content (17.7%), ease of liquefaction and storage (liquefaction occurs at room temperature and 9.2 bar), and complete industrial supply chain support. Furthermore, the combustion products of ammonia are only water and nitrogen, making it a key pathway to achieving zero-carbon emissions in industrial heating processes.
[0003] Using ammonia fuel in heating furnaces can significantly reduce carbon emissions in metallurgical enterprises. However, compared with traditional fuels such as natural gas, ammonia has poor combustion performance, limiting its direct application in industrial furnaces. Ammonia has an extremely high ignition temperature (651°C) and a flame propagation speed of only about 0.07 m / s, which is only 1 / 5 the speed of methane. Due to its difficulty in ignition, low calorific value, and narrow combustible range, pure ammonia combustion is prone to ignition difficulties, flame misfire, or even accidental flameout under the large space and high load conditions of industrial heating furnaces, making it difficult to maintain the continuity of the heating process and the uniformity of the temperature field.
[0004] To overcome the problem of unstable ammonia combustion, existing solutions involve adding high-calorific-value hydrocarbon fuels such as hydrogen or natural gas to increase combustion stability. This approach often requires the introduction of additional high-calorific-value fuels, leading to additional carbon emissions. For pure ammonia, a low-calorific-value fuel, the inventors propose using regenerative high-temperature air combustion (HTAC), a technology widely used in industry, to improve combustion reaction stability. HTAC recovers waste heat from flue gas through a heat regenerator, preheating the combustion aid or fuel to a high temperature and utilizing sensible heat to enhance reactivity, which can indeed improve the ignition performance of ammonia and stabilize the flame. However, for ammonia, a nitrogen-containing fuel (Fuel-N), the nitrogen element in the ammonia molecule is easily oxidized in the high-temperature, oxygen-rich environment created by HTAC, leading to an exponential increase in fuel-type NOx formation. Therefore, while traditional HTAC technology solves the ignition difficulty problem, it inevitably leads to severe NOx emission exceedances, creating a contradiction between "stable combustion" and "low NOx."
[0005] Therefore, the dilemma of poor ammonia combustion stability and high NOx emissions needs to be addressed urgently. Summary of the Invention
[0006] To address the shortcomings of existing technologies, this invention provides a dual regenerative heating furnace and method for ammonia-hydrogen blending combustion. It utilizes waste heat from flue gas to drive ammonia cracking to produce hydrogen, achieving stable combustion of ammonia-hydrogen mixed fuels and low nitrogen emissions, thereby realizing energy conservation and emission reduction in industrial furnaces and kilns.
[0007] A dual regenerative heating furnace for ammonia-hydrogen-blended combustion includes:
[0008] The regenerative burner system includes a fuel passage / flue gas passage and an air passage / flue gas passage, which are symmetrically arranged on both sides of the furnace body; a first regenerative chamber is provided in the fuel passage / flue gas passage, and the first regenerative chamber is filled with fuel passage regenerative material; a second regenerative chamber is provided in the air passage / flue gas passage, and the second regenerative chamber is filled with air passage regenerative material.
[0009] The gas supply system is connected to the fuel passage / flue gas passage and the air passage / flue gas passage via a reversing system, and is used to alternately supply ammonia fuel and combustion air;
[0010] The exhaust system is connected to the fuel passage / flue gas passage and the air passage / flue gas passage via a reversing system, and is used to alternately exhaust flue gas;
[0011] The first heat storage chamber is loaded with an ammonia decomposition catalyst layer, which is used to heat the fuel channel heat storage body and the ammonia decomposition catalyst layer by utilizing the waste heat of the flowing flue gas; after reversal, the flowing ammonia fuel is partially catalytically cracked to produce hydrogen, forming an ammonia-hydrogen mixed fuel.
[0012] The ammonia decomposition catalyst layer is loaded on the surface of the fuel channel heat storage body.
[0013] The catalyst in the ammonia decomposition catalyst layer includes at least one of noble metal catalysts, non-noble metal catalysts, bimetallic catalysts, carbide catalysts, or nitride catalysts.
[0014] The fuel channel heat storage body and the air channel heat storage body are made of honeycomb ceramic or ceramic heat storage balls.
[0015] The gas supply system includes an ammonia fuel supply pipeline and an air supply pipeline, which are connected to the corresponding fuel passage / flue gas passage and air passage / flue gas passage through an internal reversing valve and an external reversing valve, respectively.
[0016] A combustion control method for a dual regenerative heater based on the above-mentioned ammonia-hydrogen-blended combustion specifically includes the following steps:
[0017] S1: Heat storage stage: High-temperature flue gas flows through the fuel channel / flue gas channel and the air channel / flue gas channel, storing heat in the heat storage body;
[0018] S2: Cracking and Preheating Stage: Ammonia fuel flows through a heated fuel channel regenerator loaded with an ammonia decomposition catalyst layer, forming a high-temperature ammonia-hydrogen mixed fuel; at the same time, combustion air flows through a heated air channel regenerator and is preheated.
[0019] S3: Hydrogen-blended combustion stage: The preheated ammonia-hydrogen fuel mixture and combustion air enter the furnace chamber of the heating furnace for mixing and combustion.
[0020] S4: Cyclic Switching Stage: Through periodic switching of the reversing system, the fuel passage / flue gas passage and the air passage / flue gas passage alternately cycle between the functions of the fuel / air inlet passage and the flue gas outlet passage.
[0021] In step S2, the ammonia fuel feed rate is adjusted by the control system, and the ammonia cracking rate is adjusted by the switching frequency, so that the volume percentage of hydrogen in the mixed fuel entering the furnace is maintained between 10% and 25%.
[0022] In step S2, the ammonia-hydrogen mixed fuel is preheated to above 600°C.
[0023] During the switching process in step S4, when the fuel channel / flue gas channel, which was previously used as a fuel inlet channel, is switched to a flue gas outlet channel, the residual ammonia in the channel undergoes a selective non-catalytic reduction reaction with the nitrogen oxides in the high-temperature flue gas to reduce the concentration of nitrogen oxides in the flue gas.
[0024] The temperature of the flue gas discharged from the exhaust system is controlled below 150℃.
[0025] By employing the above technical solution, the present invention has at least the following beneficial effects:
[0026] This invention provides a dual regenerative heating furnace and method for ammonia-hydrogen co-combustion. It utilizes a regenerator to efficiently recover waste heat from high-temperature flue gas, preheating the fuel and combustion air, significantly reducing fuel consumption and improving system energy efficiency. Specifically, this invention uses ammonia as fuel, eliminating carbon dioxide emissions at the source. An ammonia decomposition catalyst is loaded onto the regenerator, and the sensible heat of the flue gas stored in the regenerator drives an endothermic cracking reaction of ammonia to produce hydrogen. By constructing an ammonia / hydrogen co-combustion system, the high reactivity of hydrogen enhances the stability of ammonia combustion and effectively suppresses the formation of nitrogen oxides. Specifically:
[0027] (1) The regenerative combustion technology used in this invention alternately switches air / fuel and flue gas, so that the flue gas flows through the heat storage body, recovering the sensible heat of the high-temperature flue gas to the maximum extent, and preheating the combustion air and ammonia fuel to a high temperature through the heat recovered by the heat storage body, while keeping the exhaust temperature below 150°C, maximizing the recovery of flue gas waste heat, and making the combustion temperature in the furnace more uniform.
[0028] (2) This invention solves the problem of poor combustion stability of ammonia fuel, achieving efficient and stable combustion without the need for an external hydrogen source: Existing technologies usually require an external hydrogen source or the use of fossil fuels to assist ignition in improving the combustion performance of ammonia, which increases the complexity and operating cost of the system. This invention integrates catalytic cracking function in the regenerator chamber, utilizing the waste heat of flue gas to convert part of the ammonia into highly active hydrogen. By using the extremely low ignition energy and extremely fast flame propagation speed of hydrogen (approximately 40 times that of ammonia) as an "ignition source" and "combustion stabilizer," the combustible limits of the mixed fuel are significantly broadened, fundamentally solving the problems of difficult ignition, easy flame miss, and flameout of pure ammonia fuel in industrial furnaces.
[0029] (3) This invention achieves cascaded energy utilization and thermochemical regeneration, significantly improving the system's thermal efficiency: Traditional regenerative furnaces can only recover the sensible heat of flue gas and are limited by the lower limit of flue gas temperature. This invention utilizes the strong endothermic characteristics of the ammonia decomposition reaction (2NH3+ΔH→N2+3H2) to convert low-grade flue gas waste heat into high-grade hydrogen chemical energy. This thermochemical regeneration process not only recovers heat but also increases the lower heating value of the fuel entering the furnace, further improving the system's theoretical thermal efficiency compared to traditional physical preheating methods, thus achieving deep cascaded energy utilization.
[0030] (4) When the reversing valve in this invention reverses, since there is residual ammonia in the channel, the high-temperature flue gas can remove part of the NOx in the flue gas under the condition that ammonia is a reducing agent, thereby further reducing nitrogen oxide emissions.
[0031] (5) The present invention has a compact structure and is easy to retrofit from old furnaces. The present invention integrates the catalytic cracking reactor and the regenerative heat exchanger into one space, eliminating the need for a large external cracking furnace or independent post-processing equipment, such as an SCR denitrification tower, which greatly reduces the floor space and facilitates low-cost green retrofitting of existing metallurgical regenerative heating furnaces. Attached Figure Description
[0032] Figure 1 A cross-sectional schematic diagram of a dual regenerative heating furnace for ammonia-hydrogen-blended combustion provided by the present invention;
[0033] Figure 2 A schematic diagram of the working principle of a dual regenerative heating furnace for ammonia-hydrogen-blended combustion provided by the present invention before and after the reversing valve switching.
[0034] in:
[0035] 1. Furnace chamber; 2. Furnace body; 3. Right fuel passage / flue gas passage; 4. Right air passage / flue gas passage; 5. Internal reversing valve; 6. External reversing valve; 7. Right fuel passage regenerator; 8. Right air passage regenerator; 9. Right catalyst; 10. Ammonia fuel inlet; 11. Internal flue gas outlet; 12. Air inlet; 13. External flue gas outlet; 14. Left fuel passage regenerator; 15. Left air passage regenerator; 16. Left catalyst; 17. Left fuel passage / flue gas passage; 18. Left air passage / flue gas passage; T hot First thermocouple; T cold Second thermocouple. Detailed Implementation
[0036] To better explain and facilitate understanding of the present invention, the technical solution and effects of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
[0037] like Figure 1 As shown, a dual regenerative heating furnace for ammonia-hydrogen blending combustion includes a furnace body, a regenerative burner system arranged in pairs on both sides of the furnace body, a gas supply system, and a flue gas exhaust system.
[0038] The furnace body is symmetrically equipped with a left fuel / flue gas channel 17 and a right fuel / flue gas channel 3 on its left and right sides. Both channels are hollow pipes, with one end connected to the furnace body 2 and the other end connected to an internal reversing valve 5 for an external fuel pipeline. Furthermore, a first right heat storage chamber is provided on the right fuel / flue gas channel 3, located between the internal reversing valve 5 and the connection point between the right fuel / flue gas channel 3 and the furnace body. The first right heat storage chamber is filled with a right fuel channel heat storage body 7. Similarly, a first left heat storage chamber is provided on the left fuel / flue gas channel 17, located between the internal reversing valve 5 and the connection point between the left fuel / flue gas channel 17 and the furnace body. The first left heat storage chamber is filled with a left fuel channel heat storage body 14. Temperature sensors are installed inside both the first right and first left heat storage chambers.
[0039] The furnace body is symmetrically equipped with a right air / flue gas channel 4 and a left air / flue gas channel 18 on its left and right sides. Both the right air / flue gas channel 4 and the left air / flue gas channel 18 are hollow pipes, with one end connected to the furnace body 2 and the other end connected to an external reversing valve 6 connected to an external air duct. Furthermore, a second right heat storage chamber is provided on the right air / flue gas channel 4, located between the external reversing valve 6 and the connection end between the right air / flue gas channel 4 and the furnace body. The second right heat storage chamber is filled with a right air channel heat storage body 8. Similarly, a second left heat storage chamber is provided on the left air / flue gas channel 18, located between the external reversing valve 6 and the connection end between the left air / flue gas channel 18 and the furnace body. The second left heat storage chamber is filled with a left air channel heat storage body 15.
[0040] Furthermore, the right fuel passage / flue gas passage 3 and the right fuel passage heat accumulator 7 on the right fuel passage / flue gas passage 3 are disposed on one side of the furnace body. Similarly, the right air passage / flue gas passage 4 and the right air passage heat accumulator 8 on the right air passage / flue gas passage 4 are disposed on the same side as the right fuel passage / flue gas passage 3, and are located outside the right fuel passage / flue gas passage 3 and the right fuel passage heat accumulator 7. Since the furnace body has a symmetrical structure, on the opposite side from the right fuel passage / flue gas passage 3, the left fuel passage / flue gas passage 17 and the left fuel passage heat accumulator 14 on the left fuel passage / flue gas passage 17 are disposed on one side of the furnace body, symmetrically arranged with the right fuel passage / flue gas passage 3 and the right fuel passage heat accumulator 7. Similarly, the left air passage / flue gas passage 18 and the left air passage heat storage body 15 on the left air passage / flue gas passage 18 are located on the same side as the left fuel passage / flue gas passage 17, and are located outside the left fuel passage / flue gas passage 17 and the left fuel passage heat storage body 14, while being symmetrically arranged with the right air passage / flue gas passage 4 and the right air passage heat storage body 8.
[0041] In this configuration, one inlet of the internal reversing valve 5 is an ammonia fuel inlet 10, and one outlet is an internal flue gas outlet 11. Similarly, one inlet of the external reversing valve 6 is an air inlet 12, and one outlet is an external flue gas outlet 13. Furthermore, the first right regenerator chamber is also equipped with a right ammonia decomposition catalyst layer, which is a filled right catalyst 9. The right catalyst 9 causes a portion of the ammonia gas entering through the ammonia fuel inlet 10 of the internal reversing valve 5 to decompose and produce hydrogen gas as it passes through the right fuel channel regenerator 7, thus enabling hydrogen-blended combustion of ammonia and increasing the combustion rate. Likewise, the first left regenerator chamber is also equipped with a left ammonia decomposition catalyst layer, which is a filled left catalyst 16. The left catalyst 16 causes a portion of the ammonia gas entering through the ammonia fuel inlet 10 of the internal reversing valve 5 to decompose and produce hydrogen gas as it passes through the left fuel channel regenerator 14, thus enabling hydrogen-blended combustion of ammonia and increasing the combustion rate.
[0042] During operation, the waste heat from the high-temperature flue gas discharged from the furnace chamber 1 of the heating furnace is used to heat the heat storage body. After reversal, the ammonia fuel flows through the preheated heat storage body and the ammonia decomposition catalyst layer, and the endothermic cracking reaction is driven by physical sensible heat to convert part of the ammonia fuel into highly active hydrogen gas, forming a high-temperature ammonia / hydrogen mixed fuel that is injected into the furnace chamber 1 of the heating furnace for combustion.
[0043] Preferably, the right fuel channel heat storage body 7, the left fuel channel heat storage body 14, the right air channel heat storage body 8, and the left air channel heat storage body 15 are made of the same material, using honeycomb ceramic heat storage body or ceramic heat storage ball as the carrier. The right catalyst 9 and the left catalyst 16 use the same type of catalyst, including but not limited to at least one of Ru (ruthenium) based catalyst, non-precious metal catalyst (such as Ni, Co, Fe, etc.), bimetallic catalyst (such as Ni-Co, Co-Re, Ni-Ru, etc.), and carbide / nitrogen oxide catalyst, which is loaded onto the surface of the carrier by impregnation or coating.
[0044] The aforementioned dual regenerative furnace for ammonia-hydrogen co-firing integrates flue gas waste heat recovery and ammonia cracking. Ammonia (NH3) is used as fuel, a potential zero-carbon fuel with high energy density and no direct carbon dioxide production during combustion. The technical logic of the entire solution is as follows: High-quality waste heat is recovered from the flue gas using a regenerator, and a portion of the ammonia undergoes a cracking reaction within the regenerator chamber via an internal catalyst: 2NH3 → N2 + 3H2. This process converts the recovered waste heat into the chemical energy of the fuel, producing highly reactive hydrogen (H2). The extremely low ignition temperature (470°C) and extremely fast flame velocity (2.91 m / s) of hydrogen serve as an ignition source to assist ammonia combustion. This design not only significantly broadens the flammability limit and enhances flame stability through ammonia-hydrogen co-firing, but also suppresses NOx formation in the high-temperature zone through the rational distribution of cracking products. The entire technical solution achieves a high degree of unity between energy cascade utilization, stable combustion, and deep emission reduction, providing reliable technical support for the large-scale industrial application of ammonia.
[0045] The specific method of using the above-mentioned dual regenerative heating furnace with ammonia-hydrogen blending combustion is as follows:
[0046] Before heating, first determine that the right fuel passage / flue gas passage 3 is the fuel inlet passage, the right air passage / flue gas passage is the air inlet passage, and the left fuel passage / flue gas passage 17 and the left air passage / flue gas passage 18 are the flue gas outlet passages. In this state, during operation, the heat storage body 14 in the left fuel passage and the heat storage body 15 in the left air passage are in the flue gas exhaust cycle, i.e., the heat absorption cycle, while the heat storage body 7 in the right fuel passage and the heat storage body 8 in the right air passage are in the heat release cycle.
[0047] S1: Heat storage stage:
[0048] High-temperature flue gas flows through the first right combustion chamber on the right fuel passage / flue gas passage 3 and the second right combustion chamber on the right air passage / flue gas passage 4, transferring heat to the right fuel passage heat accumulator 7 and the right air passage heat accumulator 8 respectively before being discharged.
[0049] S2: Cracking and Preheating Stage
[0050] Ammonia fuel enters the right fuel channel / flue gas channel 3 from the ammonia fuel inlet 10. When the ammonia fuel passes through the right fuel channel heat storage body 7, it absorbs the residual heat of the right fuel channel heat storage body 7. It is not only preheated by the right fuel channel heat storage body 7, but also some of the ammonia gas is decomposed into hydrogen gas by the right catalyst 9, achieving the effect of hydrogen blending and obtaining ammonia-hydrogen mixed fuel. At the same time, the ammonia-hydrogen mixed fuel is preheated to above 600°C.
[0051] S3: Hydrogen-infused combustion stage:
[0052] Combustion air enters the right air passage / flue gas passage 4 through air inlet 12, and is preheated as it passes through the right air passage heat storage body 8. The preheated ammonia-hydrogen fuel mixture and combustion air simultaneously enter the furnace chamber 1 of the furnace body 2. The preheated ammonia-hydrogen fuel mixture contacts the preheated combustion air at the furnace opening and undergoes mixed combustion. The high-temperature flue gas formed after combustion is discharged through the left fuel passage / flue gas passage 17 and the left air passage / flue gas passage 18. As the high-temperature flue gas flows through the left fuel passage heat storage body 14 and the left air passage heat storage body 15, it transfers heat to these bodies, ensuring full utilization of the residual heat in the high-temperature flue gas. Low-temperature flue gas is discharged through the inner flue gas outlet 11 and the outer flue gas outlet 13.
[0053] S4: Cyclic switching: The working state of the heat storage chamber is switched periodically by the internal reversing valve 5 and the external reversing valve 6.
[0054] After the switch, the left fuel / flue gas passage 17 becomes the fuel inlet passage, the left air / flue gas passage 18 becomes the air inlet passage, and the right fuel / flue gas passage 3 and right air / flue gas passage 4 become the flue gas outlet passages. In this state, during operation, the right fuel passage heat storage body 7 and the right air passage heat storage body 8 are in the flue gas exhaust cycle (i.e., the heat absorption cycle), while the left fuel passage heat storage body 14 and the left air passage heat storage body 15 are in the heat release cycle. This results in periodic reversal of combustion, and the state of the heat storage bodies switches periodically accordingly. Specifically:
[0055] After a period of time, the inner reversing valve 5 and the outer reversing valve 6 turn, and ammonia fuel enters the furnace chamber 1 of the furnace body 2 from the left fuel channel / flue gas channel 17. Combustion air enters the furnace chamber 1 from the left air channel / flue gas channel 18, and flue gas is discharged from the right fuel channel / flue gas channel 3 and the right air channel / flue gas channel 4.
[0056] Through periodic reversing combustion, ammonia fuel passes through the right fuel channel heat storage body 7 or the left fuel channel heat storage body 14 after being preheated at high temperature, and air passes through the right air channel heat storage body 8 or the left air channel heat storage body 15 after being preheated at high temperature, thus recovering the waste heat in the flue gas.
[0057] Among them, combined Figure 2 As shown, when the internal reversing valve 5 and the external reversing valve 6 switch, the ammonia fuel inlet channel changes from the right fuel channel / flue gas channel 3 to the left fuel channel / flue gas channel 17, and the combustion air inlet channel changes from the right air channel / flue gas channel 4 to the left air channel / flue gas channel 18. Ammonia fuel enters the furnace through fuel channel 17, and combustion air enters the furnace chamber through the left air channel / flue gas channel 18. At this time, the right fuel channel / flue gas channel 3 and the right air channel / flue gas channel 4 serve as flue gas outlet channels, and the flue gas produced after combustion is discharged from the right fuel channel / flue gas channel 3 and the right air channel / flue gas channel 4, respectively. At this time, there is still ammonia gas in the right fuel channel / flue gas channel 3 and the right air channel / flue gas channel 4 that has not been completely purged by the flue gas, and the flue gas temperature is very high. Ammonia gas, acting as a reducing agent, can react with NOx in the flue gas to generate non-toxic and non-polluting N2, CO2, and H2O, i.e., selective non-catalytic reduction (SNCR) denitrification. When the internal reversing valve 5 and the external reversing valve 6 switch again, the working process and principle remain the same. The left fuel passage / flue gas passage 17 and the left air passage / flue gas passage 18 serve as flue gas discharge channels, and the flue gas produced after combustion is discharged from the left fuel passage / flue gas passage 17 and the left air passage / flue gas passage 18, respectively. At this time, there is still ammonia gas in the left fuel passage / flue gas passage 17 and the left air passage / flue gas passage 18 that has not been completely purged by the flue gas, and the flue gas temperature is very high. Ammonia gas, as a reducing agent, can react with NOx in the flue gas to generate non-toxic and non-polluting N2, CO2, and H2O. Through this method, the concentration of nitrogen oxides in the flue gas is further reduced.
[0058] As a preferred embodiment, this example also includes a control system. The ammonia fuel flow rate is adjustable, and the ammonia cracking rate is adjusted by controlling the reversing frequency to maintain the hydrogen volume percentage entering the furnace 1 between 10% and 25%. A crack-free baseline model is pre-stored in the control system. This model is used to calculate the theoretical sensible heat drop based on the current ammonia fuel flow rate and the inlet and outlet temperature difference of the furnace 1. Due to the endothermic effect of cracking, the actual temperature drop rate will be greater than the theoretical sensible heat drop rate, and the difference between the two is proportional to the amount of ammonia participating in the reaction. A first thermocouple T is installed at the high-temperature end of each ammonia fuel regenerator, i.e., on the side closest to the furnace 1. hot A second thermocouple T is installed at the low-temperature end of the heat storage body, that is, on the side near the ammonia fuel inlet. cold First thermocouple T hotSecond thermocouple T cold Electrically connected to the control system. The control system receives the aforementioned first thermocouple T. hot Second thermocouple T cold The signal is used to adjust and control the switching frequency of the reversing valve through preset conditions. Specifically, in this embodiment, the theoretical sensible heat drop calculated by the non-pyrolysis benchmark model based on the preset ammonia fuel flow rate is 3.0℃ / s ± 0.5℃ / s, which meets the temperature drop range of 4.5℃ / s to 7.5℃ / s required for hydrogen pyrolysis rate. If the thermocouple detects that the temperature of the heat storage body drops below 4.5℃ / s, the calculated heat absorption is mainly sensible heat with very little chemical heat absorption. In this case, the reversing frequency is reduced by the control system, i.e., the reversing cycle is extended. Extending the reversing cycle allows the heat storage body to accumulate more heat during the flue gas stage, increasing the peak temperature; at the same time, it increases the residence time of ammonia fuel at the high-temperature end, thereby increasing the pyrolysis rate and ensuring stable flame. If the thermocouple detects that the temperature drop rate of the heat storage body exceeds 10℃ / s, the calculated chemical heat absorption is too large. This means that the pyrolysis rate is too high, producing too much hydrogen, which may lead to excessively high combustion temperature and the production of a large amount of thermal NOx. In this case, the reversing frequency is increased by the control system, i.e., the reversing cycle is shortened. Shortening the commutation cycle prevents the regenerator from being heated to extremely high peak temperatures, and the rapid passage of ammonia fuel through the high-temperature end reduces the residence time, thereby suppressing the cracking rate and controlling combustion in a low-NOx mode.
[0059] Although primarily relying on thermal calculations, the heat storage medium may age or accumulate ash during long-term operation, leading to changes in heat transfer efficiency. Therefore, the control system is periodically (e.g., every 24 hours) or in a pre-set commissioning mode, calibrated and corrected in conjunction with NOx emissions from the flue outlet to eliminate system errors.
[0060] The ammonia-hydrogen co-firing dual regenerative heater provided by this invention achieves low NOx emissions through the following two points: First, it utilizes the ammonia cracking reaction to absorb a portion of the sensible heat of the flue gas and convert it into chemical energy, thereby reducing the initial physical temperature of the fuel entering the furnace and weakening the peak temperature of thermal NOx; Second, it utilizes the H2 and unreacted NH3 generated by cracking to form a reducing atmosphere at the flame root or jet center, where amino free radicals can reduce the generated NOx to N2 (NH2+NO→N2+H2O).
Claims
1. A dual regenerative heating furnace for ammonia-hydrogen-blended combustion, characterized in that, include: The regenerative burner system includes a fuel passage / flue gas passage and an air passage / flue gas passage, which are symmetrically arranged on both sides of the furnace body; a first regenerative chamber is provided in the fuel passage / flue gas passage, and the first regenerative chamber is filled with fuel passage regenerative material; a second regenerative chamber is provided in the air passage / flue gas passage, and the second regenerative chamber is filled with air passage regenerative material. The gas supply system is connected to the fuel passage / flue gas passage and the air passage / flue gas passage via a reversing system, and is used to alternately supply ammonia fuel and combustion air; The exhaust system is connected to the fuel passage / flue gas passage and the air passage / flue gas passage via a reversing system, and is used to alternately exhaust flue gas; The first heat storage chamber is loaded with an ammonia decomposition catalyst layer, which is used to heat the fuel channel heat storage body and the ammonia decomposition catalyst layer by utilizing the waste heat of the flowing flue gas; after reversal, the flowing ammonia fuel is partially catalytically cracked to produce hydrogen, forming an ammonia-hydrogen mixed fuel.
2. The dual regenerative heating furnace for ammonia-hydrogen blending combustion according to claim 1, characterized in that: The ammonia decomposition catalyst layer is loaded on the surface of the fuel channel heat storage body.
3. The dual regenerative heating furnace for ammonia-hydrogen-blended combustion according to claim 1, characterized in that: The catalyst in the ammonia decomposition catalyst layer includes at least one of noble metal catalysts, non-noble metal catalysts, bimetallic catalysts, carbide catalysts, or nitride catalysts.
4. The dual regenerative heating furnace for ammonia-hydrogen-blended combustion according to claim 1, characterized in that: The fuel channel heat storage body and the air channel heat storage body are made of honeycomb ceramic or ceramic heat storage balls.
5. A dual regenerative heating furnace for ammonia-hydrogen-blended combustion according to claim 1, characterized in that: The gas supply system includes an ammonia fuel supply pipeline and an air supply pipeline, which are connected to the corresponding fuel passage / flue gas passage and air passage / flue gas passage through an internal reversing valve and an external reversing valve, respectively.
6. A combustion control method for a dual regenerative heating furnace with ammonia-hydrogen blending combustion according to any one of claims 1 to 5, characterized in that, Specifically, the following steps are included: S1: Heat storage stage: High-temperature flue gas flows through the fuel channel / flue gas channel and the air channel / flue gas channel, storing heat in the heat storage body; S2: Cracking and Preheating Stage: Ammonia fuel flows through a heated fuel channel regenerator loaded with an ammonia decomposition catalyst layer, forming a high-temperature ammonia-hydrogen mixed fuel; at the same time, combustion air flows through a heated air channel regenerator and is preheated. S3: Hydrogen-blended combustion stage: The preheated ammonia-hydrogen fuel mixture and combustion air enter the furnace chamber of the heating furnace for mixing and combustion. S4: Cyclic Switching Stage: Through periodic switching of the reversing system, the fuel passage / flue gas passage and the air passage / flue gas passage alternately cycle between the functions of the fuel / air inlet passage and the flue gas outlet passage.
7. The combustion control method according to claim 6, characterized in that: In step S2, the ammonia fuel feed rate is adjusted by the control system, and the ammonia cracking rate is adjusted by the switching frequency, so that the volume percentage of hydrogen in the mixed fuel entering the furnace is maintained between 10% and 25%.
8. The combustion control method according to claim 6, characterized in that: In step S2, the ammonia-hydrogen mixed fuel is preheated to above 600°C.
9. The combustion control method according to claim 6, characterized in that: During the switching process in step S4, when the fuel channel / flue gas channel, which was previously used as a fuel inlet channel, is switched to a flue gas outlet channel, the residual ammonia in the channel undergoes a selective non-catalytic reduction reaction with the nitrogen oxides in the high-temperature flue gas to reduce the concentration of nitrogen oxides in the flue gas.
10. The combustion control method according to claim 6, characterized in that: The temperature of the flue gas discharged from the exhaust system is controlled below 150℃.