Catalytic element, hydrogen recombiner and working method of hydrogen recombiner

Abstract

The invention provides a catalytic element, a hydrogen recombiner and a working method of the hydrogen recombiner, and belongs to the technical field of hydrogen safety of nuclear energy industry departments. The catalytic element is in a water drop shape, a three-dimensional streamline solid structure of the catalytic element can be obtained by rotating a two-dimensional streamline by 360 degrees with the central axis as the axis, and the area of the bottom of the catalytic element is larger than that of the top of the catalytic element. The structural design of the catalytic element can effectively improve the hydrogen elimination performance and reduce the flow resistance, so that the comprehensive performance of the hydrogen recombiner is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrogen safety in the nuclear energy industry, and in particular relates to a catalytic element, a hydrogen recombiner and a working method of the hydrogen recombiner. Background Art

[0002] When a severe accident (LOCA accident) occurs in a pressurized water reactor, the zirconium alloy of the nuclear fuel assembly cladding will react with water vapor to produce and release a large amount of hydrogen into the containment.

[0003] The reaction formula of zirconium water reaction between zirconium alloy and water vapor is: Zr+2H 2 O→ZrO 2 +2H 2 ↑.

[0004] Hydrogen mixes with water vapor and air to form a flammable mixed gas. When the hydrogen concentration reaches the flammability limit, diffusion combustion, deflagration or detonation may occur, thereby destroying the integrity of the containment and causing radioactive substances to be released into the environment, causing irreversible damage to the public and the environment.

[0005] At present, countries around the world attach great importance to the behavior of hydrogen in the containment under severe accident conditions in nuclear power plants. As the main research hotspot, hydrogen mitigation measures are direct technical means to deal with potential hydrogen risks, and passive hydrogen removal technology has also become a research hotspot for hydrogen risk control technology in nuclear power plants. Among them, passive hydrogen recombiners have become widely used in nuclear power plants for severe accidents. Hydrogen removal equipment has the advantages of no need for external energy, rapid startup under low-concentration hydrogen conditions at room temperature, no moving parts, and passive continuous hydrogen removal. Passive hydrogen recombiners use precious metal catalysts covered on the surface of the catalytic element to cause hydrogen and oxygen to undergo catalytic oxidation reactions on its surface to produce water, and use the heat generated by the reaction to make the gas flow, produce a "chimney effect" inside the hydrogen recombiner device, and then form a natural cycle to maintain the continuous operation of the device. However, the structural design of the catalytic element in the passive hydrogen recombiner in the prior art needs to be improved in reducing gas flow resistance and improving hydrogen removal capacity. Summary of the invention

[0006] In view of this, in order to solve the problem that the structural design of the catalytic element in the passive hydrogen recombiner in the prior art needs to be improved in reducing gas flow resistance and improving hydrogen removal capacity, the present invention proposes a catalytic element, a hydrogen recombiner and a working method of the hydrogen recombiner.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A catalytic element is in the shape of a water drop, and the three-dimensional streamlined solid structure of the catalytic element can be obtained by rotating the two-dimensional streamline 360 ​​degrees with the central axis as the axis, and the area of ​​the bottom of the catalytic element is larger than the area of ​​the top.

[0009] As a preferred embodiment of the above-mentioned catalytic element, the outer surface of the catalytic element is smooth and fluent.

[0010] As a preferred embodiment of the above-mentioned catalytic element, the maximum thickness of the catalytic element is 0.2 to 3.0 times the length of the central axis.

[0011] As a preferred solution of the above-mentioned catalytic element, the distance between the position of maximum thickness of the catalytic element and the lowermost end is 10% to 85% of the length of the central axis.

[0012] As a preferred embodiment of the above-mentioned catalytic element, the angle between the top of the two-dimensional streamline and the central axis is a trailing edge angle, and the trailing edge angle is 5° to 85°.

[0013] The present invention also provides a hydrogen recombiner, comprising the above-mentioned catalytic element and a catalytic channel, wherein the catalytic channel has an inlet, a high reaction rate section, a chimney section and an outlet distributed in sequence, and the catalytic element is located in the high reaction rate section.

[0014] As a preferred solution of the above hydrogen recombiner, the bottom of the catalytic element is closer to the inlet of the catalytic channel than the top.

[0015] As a preferred solution of the above hydrogen recombiner, the gas flow around the catalytic element is stable and smooth, the flow field is evenly distributed, and no severe boundary layer separation phenomenon occurs.

[0016] The present invention further provides a working method of a hydrogen recombiner, using the above-mentioned hydrogen recombiner, comprising:

[0017] S1: Hydrogen and air enter the high reaction rate section from the inlet, and a catalytic reaction occurs on the outer surface of the catalytic element to generate water vapor and release heat;

[0018] S2: natural convection is formed in the chimney section;

[0019] S3: Water vapor flows out from the outlet.

[0020] As a preferred solution of the working method of the hydrogen recombiner, it further includes S0 before S1. S0: determining the arrangement angle and arrangement mode of the catalytic element in the high reaction rate section according to the required hydrogen removal capacity and the change of flow resistance.

[0021] Compared with the prior art, the catalytic element, hydrogen recombiner and working method of the hydrogen recombiner provided by the present invention have the following beneficial effects:

[0022] 1. The present invention provides a catalytic element, a hydrogen recombiner, and a working method of the hydrogen recombiner. In the catalytic element, based on the chemical characteristics of the hydrogen catalytic oxidation reaction and the structural characteristics of the passive hydrogen recombiner, the high catalytic reaction area is mainly concentrated in the upstream area of ​​the catalytic element, that is, the bottom of the catalytic element. After hydrogen enters the catalytic channel, it first contacts the bottom of the catalytic element. The catalytic element is in the shape of a water drop, and the area of ​​the bottom of the water drop-shaped catalytic element is larger than the area of ​​the top. Increasing the upstream area of ​​the bottom of the catalytic element in a limited space can effectively improve the hydrogen removal capacity of the catalytic element. Compared with other traditional catalytic element structures, it can make full use of the active sites of the catalyst and improve the utilization rate of the catalyst.

[0023] 2. The present invention provides a catalytic element, a hydrogen recombiner and a working method of the hydrogen recombiner. In the catalytic element, the catalytic element is in the shape of a water droplet, which can ensure that the incoming gas flows smoothly, the surrounding flow field is distributed stably and evenly, and there are no boundary layer separation and eddy current phenomena. The flow resistance of the water droplet-shaped catalytic element is much smaller than the flow resistance of the catalytic element with a traditional structure.

[0024] 3. The present invention provides a catalytic element, a hydrogen recombiner, and a working method of the hydrogen recombiner. In the catalytic element, the three-dimensional streamlined solid structure of the catalytic element is based on the rotation of the two-dimensional streamline, and is formed by rotating the two-dimensional streamline 360° around the central axis. When designing the catalytic element, the two-dimensional streamline is designed first, and the shape of the two-dimensional streamline directly affects the structure of the teardrop-shaped catalytic element. The shape of the two-dimensional streamline can be continuously changed by adjusting the corresponding parameters such as the maximum thickness, the position of the maximum thickness, the leading edge radius and the trailing edge angle, so as to select a more ideal teardrop-shaped structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0026] Figure 1 is a structural diagram of a catalytic element provided in a specific embodiment of the present invention;

[0027] Figure 2 It is a structural diagram of a hydrogen recombiner provided in a specific embodiment of the present invention.

[0028] In the figure:

[0029] 1. Two-dimensional streamlines; 2. Central axis; 3. Catalytic element; 4. Inlet; 5. High reaction rate section; 6. Chimney section; 7. Outlet. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely explain the technical solutions in the embodiments of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict, and the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0031] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0033] In the description of this embodiment, the terms "upper", "lower", "right" and other directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplified operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0034] See also Figure 1-2 To describe this embodiment, the present invention provides a catalytic element, a hydrogen recombiner and a working method of the hydrogen recombiner, wherein the catalytic element 3 is in the shape of a teardrop, and the three-dimensional streamlined solid structure of the catalytic element 3 can be obtained by rotating the two-dimensional streamline 1 360° with the central axis 2 as the axis, and the area of ​​the bottom of the catalytic element 3 is larger than the area of ​​the top.

[0035] Based on the chemical characteristics of hydrogen catalytic oxidation reaction and the structural characteristics of the passive hydrogen recombiner, the high catalytic reaction area is mainly concentrated in the upstream area of ​​the catalytic element 3, that is, the bottom of the catalytic element 3. After hydrogen enters the catalytic channel, it first contacts the bottom of the catalytic element 3. The catalytic element 3 is in the shape of a water drop, and the area of ​​the bottom of the water drop-shaped catalytic element 3 is larger than the area of ​​the top. Increasing the upstream area of ​​the bottom of the catalytic element 3 in a limited space can effectively improve the hydrogen removal capacity of the catalytic element 3. Compared with other traditional catalytic element 3 structures, it can make full use of the active sites of the catalyst and improve the utilization rate of the catalyst.

[0036] Moreover, the catalytic element 3 is in the shape of a water droplet, which can ensure that the incoming gas flows smoothly, the surrounding flow field is distributed stably and evenly, and there are no boundary layer separation and eddy current phenomena. The flow resistance of the water droplet-shaped catalytic element 3 is much smaller than the flow resistance of the catalytic element 3 with a traditional structure.

[0037] The three-dimensional streamlined solid structure of the catalytic element 3 is based on the rotation of the two-dimensional streamline 1, and is formed by rotating the two-dimensional streamline 1 360° around the central axis 2. When designing the catalytic element 3, the two-dimensional streamline 1 is designed first, and the shape of the two-dimensional streamline 1 directly affects the structure of the teardrop-shaped catalytic element 3. The shape of the two-dimensional streamline 1 can be continuously changed by adjusting corresponding parameters such as the maximum thickness, the position of the maximum thickness, the leading edge radius and the trailing edge angle, thereby selecting a more ideal teardrop-shaped structure.

[0038] Therefore, the structural design of the catalytic element 3 can effectively improve the hydrogen removal performance and reduce the flow resistance, thereby improving the comprehensive performance of the hydrogen recombiner.

[0039] Optionally, the outer surface of the catalytic element 3 is smooth and fluent, so that the surrounding airflow can flow smoothly.

[0040] Optionally, the maximum thickness of the catalytic element 3 is 0.2 to 3.0 times the length of the central axis 2. The maximum thickness of the catalytic element 3 is where the two-dimensional streamline 1 is farthest from the central axis 2. The farthest distance between the two-dimensional streamline 1 and the central axis 2 is 0.2 to 3.0 times the length of the central axis 2.

[0041] Optionally, the distance between the position of maximum thickness of the catalytic element 3 and the lowermost end is 10% to 85% of the length of the central axis 2 .

[0042] Optionally, the angle between the top of the two-dimensional streamline 1 and the central axis 2 is the trailing edge angle, and the trailing edge angle is 5° to 85°. The leading edge radius of the two-dimensional streamline 1 should be determined according to the specific size of the water drop-shaped catalytic element 3.

[0043] The present invention also provides a hydrogen recombiner, such as Figure 2As shown, the hydrogen recombiner includes the above-mentioned catalytic element 3 and a catalytic channel, which has an inlet 4, a high reaction rate section 5, a chimney section 6 and an outlet 7 distributed in sequence, and the catalytic element 3 is located in the high reaction rate section 5. Hydrogen enters from the inlet 4 and undergoes a catalytic reaction at the bottom of the water drop-shaped catalytic element 3, while generating water vapor and releasing a large amount of heat, and forms natural convection in the chimney section 6, and then flows out from the outlet 7, and then enters from the inlet 4 with the newly absorbed hydrogen. Due to the use of the water drop-shaped catalytic element 3, the flow resistance can be reduced, the natural convection can be strengthened, and the ability to absorb hydrogen can be increased, thereby improving the hydrogen removal efficiency.

[0044] Optionally, the bottom of the catalytic element 3 is closer to the inlet 4 of the catalytic channel than the top. After entering the catalytic channel, the hydrogen first contacts the bottom of the catalytic element 3, and the high catalytic reaction area is mainly concentrated in the upstream area of ​​the catalytic element 3, that is, the bottom of the catalytic element 3.

[0045] Optionally, the gas flow around the catalytic element 3 is stable and smooth, the flow field is evenly distributed, and no severe boundary layer separation phenomenon occurs.

[0046] The present invention further provides a working method of a hydrogen recombiner, using the above-mentioned hydrogen recombiner, comprising:

[0047] S0: According to the required hydrogen removal capacity and the change of flow resistance, the arrangement angle and arrangement mode of the catalytic element 3 in the high reaction rate section 5 are determined. The parameters of the two-dimensional streamline 1 of the catalytic element 3, the arrangement angle and arrangement mode of the catalytic element 3 in the catalytic channel, the active site density of the catalyst and the catalytic material, etc. can be adjusted according to actual needs to cope with different hydrogen removal capacity and flow resistance changes.

[0048] S1: Hydrogen and air enter the high reaction rate section 5 from the inlet 4, and undergo a catalytic reaction on the outer surface of the catalytic element 3, generating water vapor and releasing heat. Hydrogen mainly undergoes a catalytic reaction in the upstream area of ​​the catalytic element 3, that is, at the bottom of the catalytic element 3.

[0049] S2: Natural convection is formed in the chimney section 6. The use of a water drop-shaped catalytic element 3 can reduce flow resistance and enhance natural convection.

[0050] S3: Water vapor flows out from outlet 7. After flowing out, it will enter again from inlet 4 with the newly absorbed hydrogen.

[0051] Obviously, the embodiments of the present invention disclosed above are only used to help illustrate the present invention. The embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. According to the content of this specification, many modifications and changes can be made. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that technicians in the relevant technical field can understand and use the present invention well. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A catalytic element, characterized in that: The catalytic element (3) is in the shape of a water drop. The three-dimensional streamlined solid structure of the catalytic element (3) can be obtained by rotating the two-dimensional streamline (1) by 360° with the central axis (2) as the axis. The area of ​​the bottom of the catalytic element (3) is larger than the area of ​​the top.

2. The catalytic element according to claim 1, characterized in that: The outer surface of the catalytic element (3) is smooth and fluent.

3. The catalytic element according to claim 1, characterized in that: The maximum thickness of the catalytic element (3) is 0.2 to 3.0 times the length of the central axis (2).

4. The catalytic element according to claim 1, characterized in that: The distance between the position of the maximum thickness of the catalytic element (3) and the lowermost end is 10% to 85% of the length of the central axis (2).

5. The catalytic element according to claim 1, characterized in that: The angle between the top of the two-dimensional streamline (1) and the central axis (2) is the trailing edge angle, and the trailing edge angle is 5° to 85°.

6. A hydrogen recombiner, characterized in that: It comprises the catalytic element (3) as described in any one of claims 1 to 5, and also comprises a catalytic channel, wherein the catalytic channel has an inlet (4), a high reaction rate section (5), a chimney section (6) and an outlet (7) distributed in sequence, and the catalytic element (3) is located in the high reaction rate section (5).

7. The hydrogen recombiner according to claim 6, characterized in that: The bottom of the catalytic element (3) is closer to the inlet (4) of the catalytic channel than the top.

8. The hydrogen recombiner according to claim 6, characterized in that: The gas flow around the catalytic element (3) is stable and smooth, the flow field is evenly distributed, and no boundary layer separation occurs.

9. A method for operating a hydrogen recombiner, characterized in that: The hydrogen recombiner according to any one of claims 6 to 8 comprises: S1: Hydrogen and air enter the high reaction rate section (5) from the inlet (4), and a catalytic reaction occurs on the outer surface of the catalytic element (3), generating water vapor and releasing heat; S2: Natural convection is formed in the chimney section (6); S3: Water vapor flows out from the outlet (7).

10. The operating method of the hydrogen recombiner according to claim 9, characterized in that: Before S1, S0 is also included. S0: according to the required hydrogen removal capacity and the change of flow resistance, the arrangement angle and arrangement mode of the catalytic element (3) in the high reaction rate section (5) are determined.

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