Ammonia catalytic combustion system and combustion control method

Abstract

The application discloses a kind of ammonia catalytic combustion system and combustion control method, its system includes combustion chamber, catalyst chamber, air chamber and feed pipe;Combustion chamber upper end is equipped with flue gas outlet, lower end surface is fixedly connected bearing plate;Catalyst chamber is installed in the inside of combustion chamber, and the inner wall of combustion chamber and the outer wall of catalyst chamber are enclosed to form combustion space;Catalyst bed is arranged in the inside of catalyst chamber, and a plurality of injection holes are formed in side wall;The inside of air chamber is air cavity, and air inlet is formed in lower end;The bearing plate is penetrated and formed with multiple groups of air flow holes;The feed pipe is inserted into air cavity from the bottom center of air chamber, vertically extends to the top of catalyst chamber, and the top outlet of feed pipe and the top cover between the top of catalyst chamber are reserved ventilation gap.The beneficial effects of the present application are that: combustion chamber, catalyst chamber, air chamber coaxial integrated nested structure, without independent external cracking device, external hydrogen supply system, whole machine height integration, reduce hardware investment and operation cost.

Description

Technical Field

[0001] This invention relates to the interdisciplinary field of clean energy technology and combustion engineering, specifically to an ammonia catalytic combustion system and combustion control method. Background Technology

[0002] Currently, seeking clean and sustainable energy alternatives to traditional fossil fuels has become a core issue in the energy sector. Ammonia (NH3), because its molecules do not contain carbon atoms and do not produce carbon dioxide (CO2) when burned, is hailed as a zero-carbon fuel. Furthermore, it is easily liquefied (it can be liquefied at -33.4℃ under normal pressure or about 0.8MPa at room temperature) for storage and transportation, possesses a mature global storage and transportation infrastructure, and has a relatively high energy density. Therefore, it is widely considered a highly promising hydrogen energy carrier and one of the mainstream alternative fuels of the future.

[0003] However, if ammonia is used directly as fuel in a combustion device, it will be subject to its inherent combustion defects, resulting in the following main problems: 1. High ignition temperature and low flame propagation speed: Ammonia has a high ignition temperature, usually above 650℃, but its laminar flame propagation speed is about 1 / 50 of that of hydrogen and 1 / 5 of that of methane, far lower than that of conventional gaseous fuels such as methane and hydrogen. This makes it difficult to ignite ammonia fuel directly, and the flame stability is poor, making it prone to flameout under load fluctuations; 2. Narrow combustible concentration range: The stable combustion equivalence ratio of the ammonia-air mixture is only 0.8~1.1, with a narrow combustible limit range. This requires extremely high precision in controlling the combustion conditions, further increasing the difficulty of stable combustion; 3. Challenges in controlling nitrogen oxide (NOx) emissions: Ammonia molecules themselves contain nitrogen, and under oxygen-rich or high-temperature combustion conditions, they easily generate large amounts of NOx through fuel-type and thermal pathways. If not effectively controlled, the emission levels may far exceed environmental standards.

[0004] To address the challenges of ammonia combustion, current mainstream industry solutions include two main technologies: ammonia-hydrogen premixed combustion and external ammonia cracking. Ammonia-hydrogen premixed combustion involves pre-mixing hydrogen and ammonia in a specific ratio, utilizing the high reactivity of hydrogen to improve the combustion performance of the mixed fuel. While this method effectively optimizes ammonia combustion, it requires a separate hydrogen supply system, such as a high-pressure hydrogen storage tank or on-site hydrogen production unit, leading to system complexity, high safety requirements, and significantly increased initial investment and operating costs. External ammonia cracking technology involves installing a separate ammonia cracking unit before the burner. This unit first converts some or all of the ammonia into hydrogen-containing gas through catalytic cracking (2NH3 → N2 + 3H2), and then the cracked mixture is fed into the burner for combustion. This method also faces challenges such as system complexity, large equipment footprint, slow response of the cracking unit, difficulty adapting to rapid load changes, and increased energy consumption.

[0005] Therefore, there is an urgent need to develop a low-cost, fast-start, and stable ammonia fuel catalytic combustion system and method that can operate under a wide load range. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing an ammonia catalytic combustion system and combustion control method, aiming to solve the problems of complex structure, high investment and operating costs in existing technologies.

[0007] The technical solution adopted in this invention is: an ammonia catalytic combustion system, comprising a combustion chamber, a catalyst chamber, an air chamber, and a feed pipe; The combustion chamber has a hollow cavity structure, with a flue gas outlet at the upper end and a support plate fixed to the lower end face of the combustion chamber. The catalyst chamber is installed inside the combustion chamber, and the inner wall of the combustion chamber and the outer wall of the catalyst chamber enclose an annular combustion space. The top of the catalyst chamber is covered with a top cover, and a catalyst bed filled with catalytic material is horizontally arranged inside the catalyst chamber. Several nozzles are opened on the side wall of the catalyst chamber below the catalyst bed, and the nozzles connect the inside of the catalyst chamber with the outer combustion space. The air chamber is located directly below the catalyst chamber; the interior of the air chamber is an air cavity, and the lower end of the air chamber has an air inlet communicating with the air cavity. The upper end of the air chamber is sealed and connected to the support plate; the support plate has multiple sets of air flow holes through it to connect the air cavity with the combustion space. The feed pipe enters the air chamber from the bottom center of the air chamber and extends vertically upward to the top of the catalyst chamber. A ventilation gap is reserved between the top outlet of the feed pipe 1 and the top cover of the catalyst chamber.

[0008] According to the above scheme, the edge of the top cover extends radially outward to form an extension section, which protrudes from the outer cylindrical surface of the catalyst chamber.

[0009] According to the above scheme, a swirl structure is installed in the annular combustion space. The swirl structure is located below the nozzle and above the support plate. The swirl structure is generally disc-shaped and horizontally arranged. An assembly inner hole matching the outer wall of the support plate is opened in the center of the swirl structure. Several swirl blades are arranged around the circumference of the assembly inner hole. Adjacent swirl blades form a spiral swirl channel that is connected vertically.

[0010] According to the above scheme, the nozzle is inclined downward from the inside out, and the angle between the nozzle axis and the catalyst chamber axis is 50~70°.

[0011] According to the above scheme, electric heating elements are embedded in the side wall of the combustion chamber and the side wall of the catalyst chamber, respectively; multiple heat transfer enhancement rods are arranged circumferentially in the catalyst chamber. The heat transfer enhancement rods are radially designed, with one end in thermal contact with the side wall of the catalyst chamber and the other end extending into the catalyst bed.

[0012] According to the above scheme, the catalyst chamber is formed by connecting two sections, the lower section being the catalyst chamber base section and the upper section being the catalyst chamber elevation section; the top cover is assembled at the top of the catalyst chamber elevation section; both the catalyst chamber base section and the catalyst chamber elevation section form a connected annular catalytic reaction chamber, and the catalyst bed is arranged in the catalytic reaction chambers in the catalyst chamber base section and the catalyst chamber elevation section; a gas distribution area is provided at the top and bottom of the catalyst bed, and the nozzle is connected to the gas distribution area at the bottom.

[0013] According to the above scheme, the air inlet is connected to an external air supply pipeline, and an air flow meter is installed on the air supply pipeline; the feed pipe is connected to an external ammonia supply pipeline, and an ammonia flow meter is installed on the ammonia supply pipeline.

[0014] According to the above scheme, the ammonia catalytic combustion system is also equipped with a temperature sensor, a pressure sensor, a flue gas analyzer, and a PLC controller. Multiple temperature sensors are designed and arranged at the bottom, middle and top of the catalyst bed to detect the temperature at various locations in the catalyst bed. The pressure sensor is located at the bottom of the catalyst bed and is used to detect the pressure in the catalyst chamber. The detection end of the flue gas analyzer is located at the flue gas outlet at the top of the flue, and is used to detect the components of O2, NOx and unburned ammonia in the flue gas. Each of the temperature sensors, pressure sensors, flue gas analyzers, air flow meters, and ammonia flow meters is connected to the PLC controller, transmitting the detected real-time data to the PLC controller.

[0015] This invention also employs an ammonia catalytic combustion control method, which is based on the ammonia catalytic combustion system described above; the method is as follows: Outside air flows into the air chamber through the air inlet at the bottom of the air chamber, rises through the air flow holes on the support plate, and enters the annular combustion space of the combustion chamber after being formed by the swirling structure. Ammonia gas rises through the feed pipe to the top of the catalyst chamber and then flows downward through the catalyst bed to complete catalytic cracking. The cracked mixed gas is then injected downward into the combustion space through the side wall nozzles, where it mixes with the rising swirling air and undergoes combustion to generate flue gas. The PLC controller switches the system between high-pyrolysis operation mode and high-power operation mode according to external load commands and emission index requirements; When the system switches to high-cracking operation mode, the system is initially in a cold standby state at room temperature, and there is no medium flowing through the feed pipe; the electric heating element of the catalyst chamber is started, and the catalyst bed is uniformly preheated to the set target temperature within 5 to 10 minutes; When the temperature sensor in the middle of the catalyst bed detects that the catalyst bed temperature has reached the ignition threshold, air is first introduced to form an air swirling flow field, and then ammonia is introduced while controlling the ammonia-air equivalence ratio to a lean combustion condition of 0.8~1.0. The ammonia is catalytically cracked in the catalyst bed to generate a hydrogen-rich cracked mixed fuel gas, which is mixed with air and then combusted stably. After the combustion sustains a temperature rise, the electric heating element is turned off. After the system stabilizes, the catalyst bed space velocity is maintained at 8000 h⁻¹. - ¹~10000 h - ¹, The temperature is stable at 550℃~600℃; When the system switches to high-power operation mode, the PLC controller synchronously and gradually increases the ammonia and air flow rates within a set time, raising the catalyst bed space velocity from the initial value to the set value of 18000 h⁻¹. - ¹~20000 h - ¹; Part of the ammonia is cracked to generate highly active hydrogen to anchor the flame, while the remaining uncracked ammonia is mixed with swirling air and undergoes turbulent combustion in the combustion space to achieve 90% rated power operation.

[0016] According to the above scheme, the PLC controller determines the working status of the catalyst online; when the catalyst bed activity is determined to be ineffective, the PLC controller immediately terminates the current high-cracking or high-power operation mode and switches to the pure ammonia diffusion combustion operation mode; simultaneously, the air-fuel ratio of the system is adjusted to the optimal range of 0.8 to 1.1 suitable for stable diffusion combustion of pure ammonia, the electric heating element of the catalyst chamber is started to assist in preheating, and the pure ammonia gas is preheated by the smoke entrainment of the flue gas in the flue gas recirculation zone, so that its temperature is raised above the ignition point.

[0017] The beneficial effects of this invention are as follows: 1. This invention adopts a coaxial integrated nested structure of combustion chamber, catalyst chamber, and air chamber. Ammonia gas flows upward through the feed pipe and then back through the built-in catalyst bed for in-situ cracking. The cracked mixture is directly burned in the annular combustion space. Compared with existing technologies, it does not require a separate external cracking device or an external hydrogen supply system. The entire machine is highly integrated, significantly reducing the equipment footprint and lowering hardware investment and maintenance costs. It solves the problems of complex structure, high investment and operating costs in existing technologies. Air flows upward through the flow holes of the support plate, and cracked ammonia gas is sprayed downward through the nozzles to form a counter-current flow field, which enhances the mixing uniformity and makes the combustion reaction more complete. Furthermore, the ammonia gas is forced to flow downward through the entire catalyst bed by the top cover, ensuring a stable ammonia cracking conversion rate and improving the inherent problems of difficult ammonia ignition and unstable flame. Low-NOx combustion can be achieved without additional hydrogen supply.

[0018] 2. In this invention, the top cover is designed with a radial extension section. After the high-temperature flue gas flows upward and impacts the extension section, it turns downward and forms a stable high-temperature flue gas recirculation zone in the center of the combustion chamber. This can continuously entrain high-temperature products to preheat the low-temperature ammonia-air mixture, reduce the ignition energy threshold, anchor the flame root, avoid flameout under low load and operating condition fluctuations, and improve combustion stability.

[0019] 3. The present invention designs a swirling structure, in which the swirling blades of the swirling structure form a spiral swirling channel. After the upward air flows through it, it gains tangential velocity and forms a high-intensity swirling field. Combined with the cracked gas injected by the downward tilting nozzle, the turbulent disturbance is enhanced, which greatly reduces the problem of uneven local concentration of the gas mixture, resulting in higher ignition reliability and more complete combustion. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of Example 1.

[0021] Figure 2 This is a schematic diagram showing the layout of the air chamber, catalyst chamber, combustion chamber, support platform, support plate, and feed pipe.

[0022] Figure 3 This is a schematic diagram of a vortex structure.

[0023] The components include: 1. Feed pipe; 2. Through-core sleeve; 3. Air chamber; 4. Support plate; 5. Air flow hole; 6. Swirl blades; 7. Swirl structure; 8. Combustion chamber; 9. Top cover; 10. Catalyst chamber heightened section; 11. Catalyst chamber base section; 12. Support platform; 13. Flue; 14. Flue gas analyzer; 15. Air cavity; 16. Air inlet; 17. Data acquisition instrument; 18. Air supply pipeline; 19. Air flow meter; 20. Ammonia supply pipeline; 21. Ammonia flow meter; 22. PLC controller; 23. Nozzle; 24. Assembly inner hole. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] In the description of the embodiments of this application, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application 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, they should not be construed as limitations on the embodiments of this application. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0027] In the embodiments of this application, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0028] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the embodiments of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples. Additionally, the term "a plurality of" indicates two or more.

[0029] like Figure 1 and Figure 2 The ammonia catalytic combustion system shown includes a combustion chamber 8, a catalyst chamber 3, an air chamber 3, and a feed pipe 1; The combustion chamber 8 has a hollow cavity structure, with a flue gas outlet at the upper end and a support plate 4 fixedly connected to the lower end face of the combustion chamber 8. The catalyst chamber is installed inside the combustion chamber 8, and the inner wall of the combustion chamber 8 and the outer wall of the catalyst chamber enclose an annular combustion space (i.e., the main reaction zone). The top of the catalyst chamber is provided with a top cover 9, and a catalyst bed filled with catalyst material is horizontally arranged inside the catalyst chamber. Several nozzles 23 are opened on the side wall of the catalyst chamber below the catalyst bed, and the nozzles 23 connect the inside of the catalyst chamber with the outer combustion space. The air chamber 3 is located directly below the catalyst chamber. The air chamber 3 is a cavity structure that is closed at the bottom and open at the top. The interior is an air chamber 15. An air inlet 16 communicating with the air chamber 15 is opened at the bottom of the air chamber 3. The upper port of the air chamber 3 is sealed and connected to the support plate 4. The support plate 4 has multiple sets of air flow holes 5 through it to connect the air chamber 15 with the combustion space. The feed pipe 1 enters the air cavity 15 from the bottom center of the air chamber 3 and extends vertically upward to the top of the catalyst chamber. A ventilation gap is reserved between the top outlet of the feed pipe 1 and the top cover 9 of the catalyst chamber.

[0030] In this invention, outside air is introduced into the air chamber 3 through the air inlet 16, and flows upward through the air flow hole 5 of the support plate 4 into the combustion space of the combustion chamber 8; ammonia gas is transported to the top of the catalyst chamber through the feed pipe 1, and flows downward due to the obstruction of the top cover 9, passes through the catalyst bed to complete the catalytic pretreatment, and is then injected into the combustion space through the spray hole 23 on the side wall of the catalyst chamber, where it is fully mixed with the air introduced in front and undergoes a combustion reaction; the high-temperature flue gas generated by combustion is finally discharged to the outside through the flue 13 above the combustion chamber 8.

[0031] Preferably, the air inlet 16 is connected to an external air supply pipeline 18, and an air flow meter 19 is installed on the air supply pipeline 18; the feed pipe 1 is connected to an external ammonia supply pipeline 20, and an ammonia flow meter 21 is installed on the ammonia supply pipeline 20.

[0032] In this invention, the air flow rate entering the air chamber 3 is pre-adjusted using an air flow meter 19, and the ammonia flow rate entering the combustion chamber 8 is pre-adjusted using an ammonia flow meter 21, so that the final air-to-ammonia equivalence ratio is within the combustible range.

[0033] Preferably, a swirl structure 7 is installed in the annular combustion space, the swirl structure 7 is located below the nozzle 23 and above the support plate 4.

[0034] In this invention, the catalyst chamber is mounted on the support plate 4 via the support platform 12. The feed pipe 1 passes through the air chamber 3, the support plate 4, and the support platform 12 in sequence before entering the catalyst chamber and penetrating the catalyst bed. Specifically, the support platform 12 is a hollow structure with both ends open. The lower end of the support platform 12 is fixed to the support plate 4, and the upper end of the support platform 12 is connected and fixed to the lower end of the catalyst chamber. The swirl structure 7 is fixed to the outer periphery of the connection between the support platform 12 and the catalyst chamber.

[0035] In this invention, such as Figure 3 As shown, the swirl structure 7 is a fixed flow guide component, which is generally disc-shaped and horizontally arranged. The combustion space is located above the swirl structure 7. An assembly inner hole 24 is opened in the center of the swirl structure 7, which is matched with the outer wall of the catalyst chamber and the support platform 12. The swirl structure 7 is specifically assembled on the outer circumferential surface of the connection between the support platform 12 and the catalyst chamber. Several swirl blades 6 are arranged around the circumference of the assembly inner hole 24, and adjacent swirl blades 6 form a spiral swirl channel that is connected vertically. Air passage holes 5 that are connected vertically are also arranged in the area between the assembly inner hole 24 and the swirl blades 6. The air flowing upward from the support plate 4 is given tangential velocity after passing through the swirl channel, thereby forming a high-intensity swirl field. This design can optimize the airflow distribution and reduce the flow dead zone. In actual operation, the swirl intensity can be dynamically adjusted by adjusting the intake airflow.

[0036] Preferably, the nozzle 23 is inclined downward from the inside out, and the angle between the axis of the nozzle 23 and the axis of the catalyst chamber is 50~70°, preferably 60°.

[0037] In this invention, the direction closer to the catalyst chamber axis is defined as the inner direction, and the direction farther from the catalyst chamber axis is defined as the outer direction. The downward tilting design of the nozzle 23 allows the cracked mixed gas jet ejected downward from the catalyst chamber to form a countercurrent convergence with the upward swirling air, enhancing the turbulent mixing downstream of the nozzle 23 outlet and within the combustion space, and facilitating stable combustion at the flame root.

[0038] Example 1 This embodiment relates to an ammonia catalytic combustion system, which, in addition to the above structure, also includes the following configuration.

[0039] In this embodiment, the combustion chamber 8, air chamber 3, catalyst chamber, and support platform 12 are all cylindrical structures, arranged coaxially. The upper outer edge of the combustion chamber 8 and the upper outer edge of the air chamber 3 are each provided with a connecting flange. The air chamber 3 and the combustion chamber 8 are respectively connected to the central support plate 4 through corresponding connecting flanges. The catalyst chamber is sealed to the support plate 4. The combustion chamber 8, air chamber 3, catalyst chamber, and support plate 4 together form a whole. This design not only facilitates manufacturing, transportation, and on-site installation, but also ensures the structural integrity and long-term operational reliability of the system under high temperature and high pressure conditions. The feed pipe 1 enters the air chamber 3 through a through-core sleeve 2; the air chamber 3 and the support plate 4, as well as the air chamber 3 and the feed pipe 1, are all sealed connections.

[0040] In this embodiment, the edge of the top cover 9 extends radially outward to form an extension segment, which protrudes from the outer cylindrical surface of the catalyst chamber.

[0041] In this embodiment, within the catalyst chamber, ammonia gas is delivered to the bottom of the top cover 9 via the feed pipe 1 and then deflected downwards, uniformly distributed circumferentially into the annular catalyst bed for catalytic cracking, generating cracked mixed combustion gas. This cracked mixed combustion gas is injected into the combustion space through the nozzles 23 on the sidewall of the catalyst chamber, where it mixes and burns with air in the area below the top cover 9. The high-temperature flue gas generated by combustion flows upwards, but is deflected by the radial extension of the top cover 9, with some flue gas flowing downwards to form a stable flue gas recirculation zone. This recirculation zone continuously entrains high-temperature combustion products to the flame root, fully preheating the newly introduced low-temperature mixed gas, effectively increasing the initial temperature of the combustible mixture and reducing ignition energy consumption. Simultaneously, relying on the synergistic flame stabilization effect of the top cover 9 and the flue gas recirculation, the flame root is reliably anchored, significantly enhancing the flame's resistance to disturbances. This allows the unit to maintain stable combustion even under low-load operation and significant fluctuations in operating conditions, preventing flameout failures, reducing cold start energy consumption, and improving the overall system's thermal efficiency and operational reliability.

[0042] In this embodiment, to overcome the challenge of high ignition temperature of ammonia catalyst (typically 300-450℃), electric heating elements are embedded inside the side walls of combustion chamber 8 and catalyst chamber, respectively; the electric heating elements are silicon molybdenum rods or high-temperature resistant heating wires. During system cold start-up, the electric heating elements are activated to uniformly and indirectly preheat the catalyst bed, rapidly raising the catalyst bed temperature to the catalyst ignition threshold. This preheating method enables rapid and stable cold start-up of the device and avoids catalyst sintering and activity decay caused by localized high temperatures, ensuring a smooth transition from cold standby to normal combustion conditions.

[0043] In this embodiment, the catalyst chamber is mounted above the swirl structure 7. The catalyst chamber is formed by connecting two sections: the lower section is the catalyst chamber base section 11, and the upper section is the catalyst chamber elevation section 10. The top cover 9 is mounted on the top of the catalyst chamber elevation section 10. Both the catalyst chamber base section 11 and the catalyst chamber elevation section 10 form interconnected annular catalytic reaction chambers. The catalyst bed is arranged within the catalytic reaction chambers of the catalyst chamber base section 11 and the catalyst chamber elevation section 10. Gas distribution zones are provided at the top and bottom of the catalyst bed, and the nozzle 23 is connected to the gas distribution zone at the bottom. The catalyst chamber base section 11 is directly exposed in the main reaction combustion space of the combustion chamber 8, serving as the core heating surface, and can efficiently absorb combustion heat through both thermal radiation and convection heat transfer. The catalyst chamber elevation section 10 is located above the catalyst chamber base section 11, which not only increases the catalyst loading height but, more importantly, acts as an extended heating surface, increasing the heat exchange contact area with the high-temperature flue gas and continuously transferring heat to the upper part of the catalyst bed. This structural design of the catalyst chamber enables uniform heat distribution along the axial direction of the catalyst bed, completely improving the temperature gradient between the upper and lower parts of the catalyst bed that is common in traditional structures, and solving the defect of incomplete ammonia cracking caused by the low temperature at the upper part of the catalyst bed.

[0044] In this embodiment, multiple enhanced heat transfer rods are arranged circumferentially within the catalyst chamber. These rods are radially designed, with one end in thermal contact with the side wall of the catalyst chamber (the combustion space is outside the catalyst chamber), and the other end extending into the catalyst bed. The enhanced heat transfer rods are made of high thermal conductivity materials (such as graphite, silicon carbide, or specific high-temperature alloys). These rods actively and rapidly transfer the high-intensity heat from the lower combustion space to the central and upper parts of the catalyst bed. This design, with heat transferred from below to above and radially uniform temperature, significantly improves the temperature uniformity within the catalyst bed compared to the traditional method relying solely on wall conduction. It also significantly accelerates the system's preheating speed, shortens start-up time, and effectively reduces the cold zone effect within the catalyst bed, ensuring that ammonia from bottom to top undergoes cracking at the optimal temperature. This substantially improves the overall cracking efficiency and the stability of hydrogen yield.

[0045] In this embodiment, the catalyst bed is filled with a highly active ammonia cracking catalyst, which may be nickel-based, ruthenium-based, or nickel-ruthenium composite catalyst materials. Ammonia gas is fed upwards through the feed pipe 1 at the bottom center to the top of the catalyst chamber, and then turns back downwards, penetrating the entire annular catalyst bed. During the downward movement of the ammonia gas, it is heated uniformly and undergoes a cracking reaction (2NH3→N2+3H2) under the catalytic action of the catalyst, generating hydrogen-rich cracked mixed fuel gas.

[0046] In this embodiment, as Figure 1 As shown, a temperature sensor, a pressure sensor, a flue gas analyzer 14, and a PLC controller 22 are also added. Multiple temperature sensors can be designed and arranged at the bottom, middle and top of the catalyst bed to detect the temperature at various locations in the catalyst bed. The pressure sensor is located at the bottom of the catalyst bed (i.e., at the inlet) to detect the pressure in the catalyst chamber and to detect whether there is blockage in the catalyst. The detection end of the flue gas analyzer 14 is arranged at the flue gas outlet at the top of the flue duct 13, and is used to detect components such as O2, NOx and unburned ammonia (NH3) in the flue gas; Each of the temperature sensors, pressure sensors, flue gas analyzer 14, air flow meter 19, and ammonia flow meter 21 is connected to the PLC controller 22, transmitting the detected real-time data to the PLC controller 22; the PLC controller 22 receives the real-time data and executes different control strategies based on this data.

[0047] In this embodiment, the outer wall of the catalyst chamber is provided with an interface for installing a temperature sensor, located below the swirl structure 7. This temperature sensor is connected to the PLC controller 22 and is used to detect the temperature of the combustion zone. The leads of each temperature and pressure sensor are led out and connected to the PLC controller 22 via a data acquisition unit 17. All sensors, their connections, and functions are existing technologies.

[0048] Example 2 This embodiment provides a method for controlling the catalytic combustion of ammonia, which is based on the catalytic combustion system described in Embodiment 1.

[0049] In the cold start phase of this embodiment, the PLC controller 22 collects real-time temperature signals from multiple points in the catalyst bed, dynamically adjusts the output power of the electric heating element inside the side wall of the catalyst chamber, as well as the air intake flow rate, ammonia intake flow rate and ammonia-air ratio, so as to promote uniform and rapid heating of the catalyst bed and drive the system to smoothly switch from the cold start state to the self-sustaining combustion state.

[0050] In this embodiment, the PLC controller 22 has three preset operating modes: high-cracking, high-power, and pure combustion. The high-cracking operating mode increases the hydrogen production from ammonia cracking by matching low space velocity with the optimal catalytic reaction temperature, achieving ultra-low NO. xCombustion; the high-power operation mode appropriately increases the space velocity, coordinating catalytic cracking and space combustion to meet the high thermal power output requirements; the pure ammonia diffusion combustion operation mode is a backup operation mode, which completes pure ammonia diffusion combustion by adjusting the air-fuel ratio and swirl intensity. The PLC controller 22 can automatically switch the operation mode according to external load commands and real-time flue gas emission indicators, and dynamically optimize parameters such as air-fuel ratio and swirl intensity to ensure that the system continuously maintains the optimal combustion conditions in each mode. For the pure combustion operation mode, the PLC controller 22 identifies abnormal operation signals such as catalyst activity decay, bed temperature distortion, and flameout in real time. If an abnormal signal is detected, the operating parameters are corrected in real time or the system is switched to the pure combustion operation mode to ensure continuous and stable heating of the system and improve the system's fault tolerance and safety redundancy.

[0051] A method for controlling the catalytic combustion of ammonia, the method being implemented based on the catalytic combustion system described in Example 1; the method is as follows: Outside air flows into the air chamber 15 through the air inlet 16 at the bottom of the air chamber 3, rises through the air flow holes 5 on the support plate 4, and enters the annular combustion space of the combustion chamber 8 after being formed by the swirling structure 7. Ammonia gas rises through the feed pipe 1 to the top of the catalyst chamber and then flows downward through the catalyst bed to complete catalytic cracking. The cracked mixed gas is then injected downward into the combustion space through the side wall nozzles 23, where it mixes with the rising swirling air and undergoes combustion to generate flue gas. The flue gas is discharged from the flue gas outlet at the top of the combustion chamber 8. At the same time, some of the flue gas flows back to the root of the flame, thereby enhancing preheating, ignition, and flame stabilization. The PLC controller 22 switches the system between high-pyrolysis operation mode and high-power operation mode according to external load commands and emission index requirements; When the system switches to high-cracking operation mode, the system is initially in a cold standby state at room temperature, and there is no medium flowing through the feed pipe 1. The electric heating element of the catalyst chamber is started, and the catalyst bed is uniformly preheated to the set target temperature within 5 to 10 minutes. During the preheating process, the catalyst chamber base section 11 is heated first due to its good thermal conductivity and small heat capacity, and the heat is rapidly transferred radially through the enhanced heat transfer rod. The catalyst chamber heightened section 10 receives radiative and convective heat through its large wall area. When the temperature sensor in the middle of the catalyst bed detects that the catalyst bed temperature has reached the ignition threshold (usually 400℃), air is first introduced to form a stable swirling flow field, and then ammonia is introduced while controlling the ammonia-air equivalence ratio to a lean combustion condition of 0.8~1.0. The ammonia is catalytically cracked in the catalyst bed to generate a hydrogen-rich cracked mixed fuel gas, which is mixed with air and then combusted stably. After the combustion sustains a temperature rise, the electric heating element is turned off. After the system stabilizes, the catalyst bed space velocity is maintained at 8000 h⁻¹. - ¹~10000 h -¹, the temperature is stabilized at 550℃~600℃, with ammonia catalytic cracking reaction as the main process, and stable combustion and ultra-low NO are achieved by utilizing hydrogen-rich cracked mixed fuel gas. x emission; When the system switches to high-power operation mode, this mode starts with a high-cracking operation mode at 40% of rated power, requiring the thermal power to be increased to 90% of the rated power. After receiving the load increase command, the PLC controller 22 performs smooth control through its built-in algorithm, synchronously and gradually increasing the ammonia and air flow rates within a set time (2-3 minutes), and reducing the catalyst bed space velocity from the initial value (8000 h⁻¹) to... - ¹~10000 h - ¹) Increase to the set value (18000 h) - ¹~20000 h - ¹); During the variable load process, the heat storage characteristics of the catalyst chamber collective section and the catalyst chamber heightened section 10, together with the enhanced heat transfer rod, work together to equalize the temperature, effectively buffering the bed cooling effect caused by the rapid increase in flow rate, and ensuring the stability of the bed catalytic activity; the system enters the mixing mode, some ammonia is cracked to generate highly active hydrogen to anchor the flame, and the remaining uncracked ammonia is fully mixed with the large flow of swirling air, and strong turbulent combustion occurs in the combustion space, ultimately achieving high-load stable operation at 90% of the rated power, taking into account both high power output and good combustion conditions; the PLC controller 22 finely adjusts the air-fuel ratio according to the real-time feedback of O2 content from the flue gas analyzer 14 to ensure complete combustion and good emission characteristics.

[0052] In this invention, the catalytic cracking temperature of the catalyst is usually 300-450℃, the target preheating temperature is 400℃-450℃, preferably 450℃, and the specific setting value should be determined according to the actual ignition temperature of the catalyst used.

[0053] In this method, the PLC controller 22 collects real-time operating data such as bed temperature and flue gas composition throughout the process, and determines the catalyst's working status online. When the temperature difference between the inlet and outlet of the catalyst bed decreases and deviates from the minimum threshold, the temperature distribution uniformity of the catalyst bed is abnormal and exceeds the set threshold, and the ammonia escape concentration in the flue gas exceeds the standard, the system determines that the catalyst bed activity has failed. The PLC controller 22 immediately terminates the current high-cracking or high-power operation mode and automatically switches to the pure ammonia diffusion combustion operation mode. Simultaneously, the air-fuel ratio of the system is adjusted to the optimal range of 0.8 to 1.1, preferably 0.9, suitable for stable diffusion combustion of pure ammonia. The electric heating element of the catalyst chamber is activated as needed for auxiliary preheating, and air swirl is generated by the swirl structure 7. The powerful air swirl and the top cover 9 work together to establish a stable high-temperature flue gas recirculation zone in the center of the combustion chamber 8. This recirculation zone can effectively entrain high-temperature flue gas and fully preheat the pure ammonia gas flow from the feed pipe 1, raising its temperature above the ignition point, thereby achieving stable ignition and combustion of pure ammonia. Although this mode has higher emissions, it ensures uninterrupted operation of the system under abnormal conditions, demonstrating the system's robustness; at the same time, it issues fault warning signals to achieve uninterrupted safe operation of equipment and improve the system's operational redundancy and reliability.

[0054] In this invention, the PLC controller 22 collects real-time data on exhaust O2 and NO through the flue gas analyzer 14. x Based on the detected ammonia escape concentration, closed-loop control is implemented to dynamically adjust the air-fuel ratio and suppress pollutant generation and ammonia escape.

[0055] In this invention, after receiving a shutdown command, the system first cuts off the ammonia supply and continuously introduces room temperature nitrogen to cool and purge the catalyst bed and combustion chamber 8. After the overall temperature of the equipment drops to a safe threshold, the system closes the inlet valve and cuts off the power supply to complete the orderly shutdown, thus avoiding problems such as catalyst aging and equipment thermal deformation caused by high temperature shutdown.

[0056] The catalytic combustion system and control method described in this invention have high technological maturity and wide application scenarios due to their core advantages in stable ignition, stable combustion under wide load, low NOx emissions and intelligent control. They provide advanced and reliable combustion technology solutions for deep decarbonization in many high-energy-consuming fields, and their application prospects are mainly reflected in industrial heat treatment, distributed energy, marine power and other fields.

[0057] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0058] Finally, it should be noted that the above are merely preferred embodiments of this application and are not intended to limit this application. Although this application has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. However, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An ammonia catalytic combustion system, characterized in that, Includes the combustion chamber, catalyst chamber, air chamber, and feed pipe; The combustion chamber has a hollow cavity structure, with a flue gas outlet at the upper end and a support plate fixed to the lower end face of the combustion chamber. The catalyst chamber is installed inside the combustion chamber, and the inner wall of the combustion chamber and the outer wall of the catalyst chamber enclose an annular combustion space. The top of the catalyst chamber is covered with a top cover, and a catalyst bed filled with catalytic material is horizontally arranged inside the catalyst chamber. Several nozzles are opened on the side wall of the catalyst chamber below the catalyst bed, and the nozzles connect the inside of the catalyst chamber with the outer combustion space. The air chamber is located directly below the catalyst chamber; the interior of the air chamber is an air cavity, and the lower end of the air chamber has an air inlet communicating with the air cavity. The upper end of the air chamber is sealed and connected to the support plate; the support plate has multiple sets of air flow holes through it to connect the air cavity with the combustion space. The feed pipe enters the air chamber from the bottom center of the air chamber and extends vertically upward to the top of the catalyst chamber. A ventilation gap is reserved between the top outlet of the feed pipe and the top cover of the catalyst chamber.

2. The ammonia catalytic combustion system as described in claim 1, characterized in that, The edge of the top cover extends radially outward to form an extension section, which protrudes from the outer cylindrical surface of the catalyst chamber.

3. The ammonia catalytic combustion system as described in claim 2, characterized in that, A swirling structure is installed in the annular combustion space. The swirling structure is located below the nozzle and above the support plate. The swirling structure is disc-shaped and horizontally arranged. An assembly inner hole is opened in the center of the swirling structure. Several swirling blades are arranged around the assembly inner hole in a circumferential direction. Adjacent swirling blades form a spiral swirling channel that is connected vertically.

4. The ammonia catalytic combustion system as described in claim 3, characterized in that, The nozzle is inclined downward from the inside out, and the angle between the nozzle axis and the catalyst chamber axis is 50~70°.

5. The ammonia catalytic combustion system as described in claim 4, characterized in that, Electric heating elements are embedded in the side walls of the combustion chamber and the catalyst chamber, respectively. Multiple heat transfer enhancement rods are arranged circumferentially in the catalyst chamber. The heat transfer enhancement rods are radially designed, with one end in thermal contact with the side wall of the catalyst chamber and the other end extending into the catalyst bed.

6. The ammonia catalytic combustion system as described in claim 5, characterized in that, The catalyst chamber is formed by connecting two sections, the lower section being the catalyst chamber base section and the upper section being the catalyst chamber elevation section. The top cover is assembled at the top of the catalyst chamber elevation section. Both the catalyst chamber base section and the catalyst chamber elevation section form interconnected annular catalytic reaction chambers, and the catalyst bed is arranged in the catalytic reaction chambers in both sections. Gas distribution zones are provided at the top and bottom of the catalyst bed, and the nozzles are connected to the gas distribution zones at the bottom.

7. The ammonia catalytic combustion system as described in claim 6, characterized in that, The air inlet is connected to an external air supply pipeline, which is equipped with an air flow meter; the feed pipe is connected to an external ammonia supply pipeline, which is equipped with an ammonia flow meter.

8. The ammonia catalytic combustion system as described in claim 7, characterized in that, The ammonia catalytic combustion system is also equipped with a temperature sensor, a pressure sensor, a flue gas analyzer, and a PLC controller. Multiple temperature sensors are designed and arranged at the bottom, middle and top of the catalyst bed to detect the temperature at various locations in the catalyst bed. The pressure sensor is located at the bottom of the catalyst bed and is used to detect the pressure in the catalyst chamber. The detection end of the flue gas analyzer is located at the flue gas outlet at the top of the flue, and is used to detect the components of O2, NOx and unburned ammonia in the flue gas. Each of the temperature sensors, pressure sensors, flue gas analyzers, air flow meters, and ammonia flow meters is connected to the PLC controller, transmitting the detected real-time data to the PLC controller.

9. A method for controlling the catalytic combustion of ammonia, the method being implemented based on the ammonia catalytic combustion system of claim 8; characterized in that, The method is as follows: Outside air flows into the air chamber through the air inlet at the bottom of the air chamber, rises through the air flow holes on the support plate, and forms a swirling airflow after passing through the swirling structure, entering the annular combustion space of the combustion chamber. Ammonia gas rises from the feed pipe to the top of the catalyst chamber and then flows downward through the catalyst bed to complete catalytic cracking. The cracked mixed gas is then injected downward into the combustion space through the side wall nozzles, where it mixes with the upward swirling air and undergoes combustion to generate flue gas. The PLC controller switches the system between high-pyrolysis operation mode and high-power operation mode according to external load commands and emission index requirements; When the system switches to high-cracking operation mode, the system is initially in a cold standby state at room temperature, and there is no medium flowing through the feed pipe; the electric heating element of the catalyst chamber is started, and the catalyst bed is uniformly preheated to the set target temperature within 5 to 10 minutes; When the temperature sensor in the middle of the catalyst bed detects that the catalyst bed temperature has reached the ignition threshold, air is first introduced to form an air swirling flow field, and then ammonia is introduced while controlling the ammonia-air equivalence ratio to a lean combustion condition of 0.8~1.

0. The ammonia is catalytically cracked in the catalyst bed to generate a hydrogen-rich cracked mixed fuel gas, which is mixed with air and then combusted stably. After the combustion sustains a temperature rise, the electric heating element is turned off. After the system stabilizes, the catalyst bed space velocity is maintained at 8000 h⁻¹. - ¹~10000 h - ¹, The temperature is stable at 550℃~600℃; When the system switches to high-power operation mode, the PLC controller synchronously and gradually increases the ammonia and air flow rates within a set time, raising the catalyst bed space velocity from the initial value to the set value of 18000 h⁻¹. - ¹~20000 h - ¹; Part of the ammonia is cracked to generate highly active hydrogen to anchor the flame, while the remaining uncracked ammonia is mixed with swirling air and undergoes turbulent combustion in the combustion space to achieve 90% rated power operation.

10. The ammonia catalytic combustion control method as described in claim 9, characterized in that, The PLC controller determines the catalyst's operating status online. When it determines that the catalyst bed has failed to function, the PLC controller immediately terminates the current high-cracking or high-power operation mode and switches to the pure ammonia diffusion combustion operation mode. Simultaneously, it adjusts the system's air-fuel ratio to the optimal range of 0.8 to 1.1 for stable diffusion combustion of pure ammonia, starts the electric heating element in the catalyst chamber for auxiliary preheating, and uses the flue gas recirculation zone to entrain the pure ammonia gas flow, raising its temperature above the ignition point.

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