An ammonia cracking reactor based on a TPMS structure and a preparation method thereof

Abstract

The application provides an ammonia cracking reactor based on a TPMS structure and a preparation method thereof, which comprises a reaction cavity and catalyst particles in the reaction cavity; the reaction cavity is a TPMS structure, the TPMS structure has a continuous and smooth three-dimensional periodic curved surface, forms a first flow channel and a second flow channel which are independent and through each other, the first flow channel is an ammonia cracking reaction flow channel, and the second flow channel is a heat exchange medium flow channel; the catalyst particles are distributed in the TPMS first flow channel, the catalyst particles are spherical or cylindrical particles, and the first flow channel can be filled according to the cracking rate requirement. The application has the advantages that the original equipment is solved from the defect of large size, efficient, stable and compact operation of the ammonia cracking reaction is realized, the exhaust heat of the gas turbine is used for heating the ammonia cracking, and energy is saved.

Description

Technical Field

[0001] This invention relates to the field of ammonia cracking reaction technology, and specifically to an ammonia cracking reactor based on TPMS structure and its preparation method. Background Technology

[0002] As an important part of the comprehensive governance of carbon dioxide emissions and the realization of energy transformation, the marine transportation industry has been given a net-zero emission target and plan by the International Maritime Organization (IMO) by 2050. Using green ammonia as the fuel for ship power systems to replace fossil fuels such as diesel or heavy oil is an effective solution. For ship power technology, gas turbine technology has natural advantages in ammonia combustion and pollution control. For green ammonia fuel, gas turbine power technology is the best choice. Marine gas turbine is a thermodynamic engine that uses continuously flowing gas as the working fluid. Through the cyclic process of air compression by the compressor, mixing and combustion in the combustion chamber, and expansion and work by the gas turbine, the chemical energy of the fuel is converted into mechanical work and electricity generation. Its core advantages are reflected in: (1) Power density and lightweight: The volume is only 1 / 3-1 / 5 of that of a diesel engine at the same power, and the weight is significantly reduced. It is particularly suitable for space-constrained ship designs, improving the ship's maneuverability and load-bearing capacity. (2) Rapid response and flexibility: Excellent low-temperature start-up performance, can reach full load within 1-2 minutes, and has a short switching time from cold standby to full load, suitable for emergency peak shaving or high dynamic scenarios. (3) Environmentally friendly and low-emission, meeting increasingly stringent ship emission standards. (4) Compact structure and automation: The transmission mechanism is simplified, facilitating monitoring, remote control, and full automation, significantly improving the engine room working environment, and supporting the integration of intelligent technologies such as digital twins. (5) Low vibration and low noise: Smooth operation with very few low-frequency noise components, making it a marine-friendly power technology. (6) The use of compound cycle technology allows ammonia gas turbines to perform thermoelectric conversion more efficiently (>48%). However, the combustion of ammonia as a fuel presents certain challenges. To better control ammonia combustion and reduce the generation of combustion byproducts, pretreatment of ammonia fuel is necessary. The main treatment method is cracking to generate a hydrogen-containing gaseous fuel mixture, which has better combustion characteristics, thus solving the technical problems of ammonia combustion.

[0003] Existing ammonia cracking equipment suffers from several major drawbacks: low heat exchange efficiency, easy catalyst deactivation, large weight and volume, insufficient resistance to high temperature and pressure, and inconvenient catalyst installation and maintenance. Since ammonia cracking requires a large amount of high-temperature heat, and gas turbine exhaust gas is characterized by its large volume and high temperature, this not only meets the heat energy required for cracking but also effectively utilizes the waste heat of the gas turbine, improving its efficiency. Therefore, gas turbine exhaust gas presents a significant opportunity for heat exchange cracking of ammonia. Summary of the Invention

[0004] This invention proposes an ammonia cracking reactor based on a TPMS structure and its preparation method. The ammonia gas channel and the flue gas channel for heating employ a novel geometric configuration, namely a TPMS (Triply Periodic Minimal Surface) heat transfer structure. Utilizing the TPMS geometry (specific surface area approximately 1500-3000 m² / m³), heat exchange efficiency can be significantly improved, while the weight and volume are far smaller than traditional reactors (specific surface area approximately 50-200 m² / m³). Its core lies in the near-wall heat transfer characteristics of TPMS: the continuous curved wall of TPMS can significantly shorten the heat diffusion path and enhance convective heat transfer to catalyst particles; simultaneously, it integrates catalyst installation processes to achieve efficient, stable, and compact operation of the ammonia cracking reaction, solving the problem of the bulky and cumbersome nature of conventional ammonia cracking reactors. This is particularly beneficial for site-constrained applications, such as marine applications, laying the foundation for efficient, compact, and zero-carbon power generation in gas turbine ammonia combined cycle power generation systems.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: An ammonia cracking reactor based on a TPMS structure, comprising: The reaction chamber is a TPMS structure with a continuous and smooth three-dimensional periodic surface, forming an independent and interconnected first flow channel and a second flow channel. The first flow channel is an ammonia cracking reaction channel, and the second flow channel is a heat exchange medium channel. Catalyst particles are distributed in the first channel of the TPMS. The catalyst particles are spherical or cylindrical and are filled according to the required cracking rate, and can fill the first channel completely.

[0006] Furthermore, the TPMS structure of the reaction chamber is selected from one or a combination of the three mainstream biomimetic TPMS cell configurations: Gyroid, Diamond, and Primitive.

[0007] Gyroid (G, spiral shape, biomimetic butterfly scales) is a spiral-twisting dual-channel system where fluids continuously split and converge, resulting in spontaneous strong turbulence and optimal heat transfer and pressure drop balance.

[0008] Diamond (D type, biomimetic lattice skeleton) has a three-dimensional interconnected mesh structure, the strongest structural rigidity, high pressure resistance (50 bar + adapted for ammonia cracking), and the highest heat transfer coefficient, but its flow resistance is relatively large, making it the first choice for high temperature and high pressure heat exchangers.

[0009] Primitive (P Schwarz-P, straight-through type) has a near-straight through-flow channel, with the lowest pressure drop and smooth flow, making it suitable for low-pressure gas heat exchange and waste heat recovery.

[0010] TPMS has an ultra-high specific surface area: the specific volume heat exchange area can reach 1500~3000m² / m³, which is 3~8 times that of plate-fin heat exchangers. For the same heat exchange capacity, the volume is reduced by 20%~55% and the weight is reduced by 12%~18%.

[0011] Since the heat source for the reaction comes from the waste heat of the flue gas through the heat exchange of the TPMS, and the heat required for ammonia cracking is about 10 times the heat required to raise the temperature of ammonia by 50 degrees, the design of the TPMS structure is particularly important. It must not only meet the heat exchange requirements for ammonia cracking, but also allow the ammonia enough time to crack in order to achieve the best results.

[0012] Furthermore, the first flow channel is provided with an inlet area and a main reaction area in sequence along the ammonia flow direction. The length of the inlet area is 20% to 30% of the total length of the reaction chamber, and the length of the main reaction area is 70% to 80% of the total length of the reaction chamber.

[0013] Furthermore, the first flow channel and the second flow channel are arranged in counter-current, cross-flow, or vertical flow configurations.

[0014] A method for preparing an ammonia cracking reactor based on a TPMS structure includes the following steps: S1) Establish a data model based on flue gas flow rate, pressure parameters and temperature parameters, and design and derive a suitable TPMS structure based on catalyst characteristics. The specific structure can be one or a combination of Gyroid type, Diamond type, Primitive type. S2) Using 3D printing technology, a reaction chamber with the TPMS structure designed in step S1) is printed to form an independent first flow channel and second flow channel; S3) The reaction chamber of the TPMS structure is filled with catalyst particles, and the gradient distribution of catalyst concentration is achieved by controlling the particle concentration, size and density; S4) After assembly, it undergoes sealing treatment and airtightness testing.

[0015] Further, during the assembly in step S4), the catalyst particles are first loaded into the first flow channel according to the set density, then filter screens are installed at both ends of the first flow channel, and then the ammonia inlet and cracked gas outlet of the first flow channel and the flue gas inlet and flue gas outlet of the second flow channel are installed on the pressure-bearing outer layer.

[0016] Compared with the prior art, the present invention has the following advantages: To overcome the technical pain points of existing ammonia cracking equipment, such as low heat exchange efficiency, easy catalyst deactivation, large size, insufficient high temperature and high pressure resistance, and inconvenient catalyst installation and maintenance, this patented technology proposes an ammonia cracking reactor based on a TPMS structure and its preparation method. Its core lies in combining the microscale triple curved surface enhancement advantages of TPMS with efficient heat exchange and integrating the catalyst installation process. This not only solves the problem of the original equipment's large size, but also achieves efficient, stable, and compact operation of the ammonia cracking reaction. At the same time, it utilizes the exhaust heat of the gas turbine to heat the ammonia cracking, which saves energy and lays a solid foundation for improving the efficiency of the gas turbine. This lays the foundation for realizing efficient, compact, and zero-carbon power generation of a gas turbine ammonia combined cycle power generation system. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the TPMS structure of the present invention.

[0018] Figure 2 This is a schematic diagram of the ammonia cracking reactor structure of the present invention. Detailed Implementation

[0019] The embodiments of the present invention will now be described in further detail with reference to the accompanying drawings.

[0020] like Figure 1 , 2 As shown, an ammonia cracking reactor based on a TPMS structure includes a reaction chamber and catalyst particles within it. The reaction chamber is a TPMS structure with a continuous, smooth, three-dimensional periodic surface, forming an independent but interconnected first and second flow channels. The first flow channel is the ammonia cracking reaction channel, and the second flow channel is the heat exchange medium channel. The catalyst particles are distributed in the first TPMS flow channel, and the catalyst particles are spherical or cylindrical, filling the first flow channel according to the required cracking rate.

[0021] The TPMS structure of the reaction chamber is selected from one or a combination of the three mainstream biomimetic TPMS cell configurations: Gyroid, Diamond, and Primitive.

[0022] The first flow channel has an ammonia inlet and a cracked gas outlet at its two ends, respectively, and the second flow channel has a flue gas inlet and a flue gas outlet at its two ends, respectively.

[0023] The technical solution of the present invention is applied to a practical project, as described in detail below.

[0024] I. Basic Operating Conditions 1. Medium conditions High-temperature flue gas: flow rate 8 kg / s, 590℃, pressure drop limit 3000 Pa; Raw material ammonia: flow rate 0.32 kg / s, 450℃, 50 bar, pressure drop limit 1 bar; Process objective: Ruthenium-based catalyst, ammonia cracking conversion rate ≥90%.

[0025] 2. Thermodynamics and Heat Accounting At a pressure of 50 bar and a temperature of 520℃, the conversion rate just meets the standard, with the optimal operating range being 520~540℃; the heat from the high-temperature flue gas just meets the total heat requirement of 846kW for ammonia heating and cracking reaction, and the average countercurrent heat transfer temperature difference is 46.9K, indicating sufficient heat exchange conditions.

[0026] II. Core Technology Solution of TPMS Ammonia Cracker 1. Bilaterally differentiated TPMS porous structure (3D printing) Flue gas side: Primitive type TPMS, with high porosity and smooth flow, with a flue gas pressure drop of only 468Pa, far below the limit, and has almost no impact on the gas turbine back pressure; Ammonia reaction side: Gyroid high specific surface area TPMS has a larger specific surface area, which is suitable for particulate ruthenium-based catalysts, resulting in higher heat exchange and catalytic efficiency.

[0027] 2. Equipment Structure and Manufacturing It adopts an asymmetric plate and frame countercurrent stacking structure, and the material is Inconel 625 high-temperature alloy. The TPMS core is formed by metal 3D printing (SLM), and after vacuum stress relief annealing, it is filled with ruthenium-based particulate catalyst. The overall size of the machine is 1288×1600×533mm, the total weight is about 1380kg, and the total heat exchange area is 1044㎡.

[0028] 3. Advantages of catalysis and fluidity The TPMS porous structure is used to pack the particulate catalyst. Compared with the traditional tubular particulate packing structure, it has a regular and transparent flow channel, lower pressure drop, better heat exchange effect with wall adhesion, higher utilization rate of precious metal catalyst, and is less prone to local accumulation and pulverization of catalyst due to vibration. With a catalyst volume of 0.30m³ and a space velocity of 5000h⁻¹, it can stably achieve an ammonia cracking rate of over 90%.

[0029] 4. Compliance with key performance standards The flue gas pressure drop is 468 Pa and the ammonia side pressure drop is only 0.01 bar. Both pressure drops are significantly lower than the design limit, with sufficient safety margin.

[0030] III. Comparison of TPMS Ammonia Cracker and Traditional Shell-and-Tube Heat Exchanger Table 1 shows a technical comparison between the TPMS ammonia cracker and the traditional shell-and-tube heat exchanger.

[0031] Table 1 Overall size 1.10 m³ 2.97 m³ TPMS reduces the size by 63% compared to shell-and-tube type. Equipment weight 1380 kg 3538.46 kg TPMS reduces weight by 61% compared to shell-and-tube systems. Structural compactness 950 m² / m³ Approximately 348 m² / m³ TPMS is 63% more compact than shell-and-tube type. Total heat exchange area 1044 m² (heat transfer coefficient 65 W / (m²・K)) 2821.62 ㎡ (under the same heat load) For the same heat exchange capacity, shell-and-tube designs require 63% more heat exchange area. Flue gas side pressure drop 468 Pa Approximately 2800 Pa (close to the upper limit of 3000 Pa) The pressure drop of a shell-and-tube type is 6 times that of a TPMS, resulting in a significant increase in resistance. ammonia side pressure drop 0.01 bar 0.8~0.9 bar The pressure drop of shell-and-tube systems is nearly 100 times that of TPMS, resulting in a significant increase in energy consumption. Catalyst packing volume 0.30 m³ 0.81 m³ For the same cracking efficiency, shell-and-tube catalysts require 63% more catalyst, resulting in a significant increase in cost. GHSV airspeed 5000 h⁻¹ Approximately 1840 h⁻¹ Shell-and-tube catalytic converters experience a 63% decrease in space velocity and lower catalytic efficiency. Core manufacturing processes SLM metal 3D printing TPMS porous core Conventional tube bundle bending + welding 3D printing is fast and precise. Catalyst form Gyroid channel filled with ruthenium-based particle catalyst The tube is filled with ruthenium-based particulate catalyst. For the same cracking efficiency, shell-and-tube catalysts require 63% more catalyst, resulting in a significant increase in cost. Operational stability Uniform temperature field, no catalyst loss Large local temperature differences can easily lead to pulverization and loss due to prolonged rinsing. Unit cost of the main body Core 3D printing has high unit cost. Tube bundle processing is mature, and the unit price of the body is lower. TPMS 3D printing has a slightly higher unit price. Supporting civil engineering / scaffolding investment Small footprint and low supporting costs The equipment is large and requires high overall investment. The supporting integrated investment in shell-and-tube type projects will increase by approximately 60% or more. In summary, for high-temperature and high-pressure ammonia cracking scenarios, the TPMS integrated reactor is superior to traditional shell-and-tube reactors in all aspects, including volume, weight, heat exchange, catalytic performance, and fluid resistance. Only the cost of a single 3D-printed core is higher, making it suitable for operating conditions with high requirements for equipment compactness, system energy consumption, and catalytic stability.

[0032] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the concept of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An ammonia cracking reactor based on a TPMS structure, characterized in that: include: The reaction chamber is a TPMS structure with a continuous and smooth three-dimensional periodic surface, forming an independent and interconnected first flow channel and a second flow channel. The first flow channel is an ammonia cracking reaction channel, and the second flow channel is a heat exchange medium channel. Catalyst particles are distributed in the first channel of the TPMS. The catalyst particles are spherical or cylindrical and are filled according to the required cracking rate, and can fill the first channel completely.

2. The ammonia cracking reactor based on TPMS structure according to claim 1, characterized in that: The TPMS structure of the reaction chamber is selected from one or a combination of the three mainstream biomimetic TPMS cell configurations: Gyroid, Diamond, and Primitive.

3. The ammonia cracking reactor based on TPMS structure according to claim 2, characterized in that: The first flow channel is provided with an inlet area and a main reaction area in sequence along the ammonia flow direction. The length of the inlet area is 20% to 30% of the total length of the reaction chamber, and the length of the main reaction area is 70% to 80% of the total length of the reaction chamber.

4. An ammonia cracking reactor based on a TPMS structure according to claim 1 or 2, characterized in that: The first flow channel and the second flow channel are arranged in counter-current, cross-flow, or vertical flow configurations.

5. A method for preparing an ammonia cracking reactor based on a TPMS structure, characterized in that... Includes the following steps: S1) Establish a data model based on flue gas flow rate, pressure parameters and temperature parameters, and design and derive a suitable TPMS structure based on catalyst characteristics. The specific structure can be one or a combination of Gyroid type, Diamond type, Primitive type. S2) Using 3D printing technology, a reaction chamber with the TPMS structure designed in step S1) is printed to form an independent first flow channel and second flow channel; S3) The reaction chamber of the TPMS structure is filled with catalyst particles, and the gradient distribution of catalyst concentration is achieved by controlling the particle concentration, size and density; S4) After assembly, sealing treatment and airtightness testing are performed.

6. The method for preparing an ammonia cracking reactor based on a TPMS structure according to claim 5, characterized in that: In step S4), during assembly, the catalyst particles are first loaded into the first flow channel according to the set density, then filter screens are installed at both ends of the first flow channel, and then the ammonia inlet and cracked gas outlet of the first flow channel and the flue gas inlet and flue gas outlet of the second flow channel are installed on the pressure-bearing outer layer.

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