A plasma igniter cathode device

Abstract

A plasma igniter cathode device belongs to the field of plasma igniters and overcomes the defect of a high cathode ablation rate in the prior art. The plasma igniter cathode device of the present invention comprises a shell component (3) and a corrosion-resistant component (1) arranged at the core of the shell, and an arc-starting component (2) arranged between the shell component (3) and the corrosion-resistant component (1); the arc-starting component (2) is made of pure silver; the corrosion-resistant component (1) is made of pure hafnium, pure tungsten, or an alloy with any proportion of the two; and the shell component (3) is made of pure copper. The cathode structure of the present invention is divided into zones and acts in a synergistic manner, ensuring low ablation while not affecting conductivity and arc starting, thereby improving the service life of the cathode.

Description

Technical Field

[0001] The invention belongs to the field of plasma igniters, and in particular relates to a cathode device of a plasma igniter. Background Art

[0002] Research on plasma ignition technology began with the development of a plasma pulverized coal igniter in the United States in the 1970s. Its ignition mechanism relies on a high-temperature plasma jet emitted by a plasma generator to directly ignite the primary air pulverized coal, achieving cold air ignition. Compared to stable combustion in power plants and traditional fuel oil ignition methods, plasma ignition burners offer the advantages of low cost, environmental friendliness, high efficiency, and simplicity. Generally speaking, the operating and technical maintenance costs of plasma ignition are only 15% to 20% of those of heavy oil ignition, saving tens of millions of yuan in initial investment and commissioning costs for new power plants. Because no fuel is used during ignition, electrostatic precipitators can be deployed during the initial ignition phase, reducing the environmental pollution caused by large amounts of smoke and dust emissions. Furthermore, the use of a single fuel reduces the transportation and storage of fuel, improving the plant's environmental performance.

[0003] The air carrier plasma generator is composed of a coil, a cathode, an anode, etc., wherein the cathode material is made of a metal material with high electrical conductivity, high thermal conductivity and oxidation resistance. The anode is also made of a metal material with high electrical conductivity, high thermal conductivity and oxidation resistance, and they are all cooled by water to withstand the high temperature impact of the arc. When the cathode reaches the specified discharge distance, under the action of aerodynamic force and magnetic field, the device generates a stable arc discharge and generates plasma. A direct current is used to contact the arc under the condition of an air medium pressure of ~0.01MPa, and a DC air plasma with stable power is obtained under the control of a strong magnetic field. The plasma forms a local high temperature zone with a temperature T>5000K and a large temperature gradient in the central combustion tube of a specially designed burner. The coal powder particles are subjected to high temperature through the plasma "fire core" and are heated to 10 -3 Volatiles are released quickly within seconds, causing the coal powder particles to break and pulverize and regenerate volatile matter, thereby burning rapidly.

[0004] In a plasma igniter system, the cathode erosion rate is significantly greater than that of the anode, making it a key factor in determining igniter life. Cathode erosion is primarily a physical process, controlled by the plasma heat transfer process and primarily dependent on the heat load generated by the cathode spot. Common cathode materials include graphite rods, copper, and silver. Graphite rods have a high melting point and low cost, but are susceptible to oxidation failure during service and have relatively low resistance to high-temperature erosion. Silver has excellent electrical and thermal conductivity, but its low melting point and relatively high electron work function make it susceptible to ablation and perforation. Copper also has high electrical and thermal conductivity and high melting and boiling points, making it suitable as anode and cathode materials. However, prolonged exposure to high-temperature plasma can easily lead to oxidation and scale growth, compromising arc stability. Using inert gas to shield the electrodes reduces igniter power, limiting ignition to low-power operation for bituminous coal. This increases ignition costs for highly coalified anthracite coal and does not completely address cathode erosion under high-power operation. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defect of high cathode ablation rate in the prior art, thereby providing a plasma igniter cathode device.

[0006] To this end, the present invention provides the following technical solutions.

[0007] A plasma igniter cathode device comprises a shell component, a corrosion-resistant component arranged at a core of the shell, and an arc-starting component arranged between the shell component and the corrosion-resistant component;

[0008] The arc striking component is made of pure silver;

[0009] The corrosion-resistant component is pure hafnium, pure tungsten or an alloy of the two in any proportion;

[0010] The shell component is made of pure copper.

[0011] Furthermore, the top end of the arc striking assembly includes a circular surface at the center and a conical surface at the outside.

[0012] Furthermore, 1 / 4 of the outer diameter of the circular surface at the top of the arc-striking component is ≤ the diameter of the circular surface at the top of the corrosion-resistant component is ≤ 1 / 2 of the outer diameter of the circular surface at the top of the arc-striking component.

[0013] Furthermore, the outer side of the top end of the shell component is set to a conical surface, and the bottom end of the conical surface of the arc striking component is connected with the top end of the conical surface of the shell component to form a slope.

[0014] Furthermore, the housing assembly, arc striking assembly, and corrosion-resistant assembly are coaxially arranged.

[0015] Furthermore, the shell component, arc striking component and corrosion-resistant component are connected by expansion joints.

[0016] Furthermore, a thread is provided on the outer bottom of the housing assembly.

[0017] Furthermore, the inner wall of the outer shell group is provided with a diameter-changing step.

[0018] Furthermore, at least one of the following conditions is met:

[0019] A. The purity of pure hafnium and pure tungsten shall not be less than 99.9wt%;

[0020] B. The sum of pure hafnium and pure tungsten in the alloy is not less than 99.9wt%;

[0021] C. The purity of pure silver is not less than 99.9%wt.

[0022] Furthermore, the purity of the pure copper is not less than 99.9 wt %.

[0023] Application of plasma igniter cathode device in power plant.

[0024] The technical solution of the present invention has the following advantages:

[0025] 1. The plasma igniter cathode device provided by the present invention includes a shell component and a corrosion-resistant component arranged at the core of the shell, and an arc-striking component arranged between the shell component and the corrosion-resistant component; the arc-striking component is made of pure silver; the corrosion-resistant component is pure hafnium, pure tungsten or an alloy with any proportion of the two.

[0026] The present invention provides an independent arc starting component made of pure silver between the shell component and the corrosion-resistant component, which is easier to stimulate electric charge and thus form an arc than the shell component and the corrosion-resistant component, thereby reducing the rate of shell burning.

[0027] The present invention designs a cathode structure with multiple coaxially arranged components. The outer shell assembly is made of pure copper, which not only has excellent thermal conductivity but is also easy to process and form. The arc starting assembly is made of pure silver, leveraging the high electronic work function of silver, facilitating arc starting and striking, and ensuring plasma stability. The corrosion-resistant assembly is made of pure hafnium, pure tungsten, or an alloy containing hafnium, tungsten, and their binary alloys in any proportion, leveraging the high melting points and strong corrosion resistance of hafnium, tungsten, and their binary alloys. This allows the cathode to withstand the cathode spot heat load, providing strong corrosion resistance and significantly reducing the ablation rate during plasma igniter operation. The cathode structure of the present invention utilizes partitioned loads and synergistic effects, ensuring low ablation while not affecting electrical conductivity and arc starting, thereby extending the cathode's service life.

[0028] 2. In the plasma igniter cathode assembly provided by the present invention, the diameter of the arc-starting component's top circular surface is 1 / 4 ≤ the diameter of the corrosion-resistant component's top circular surface ≤ 1 / 2 the diameter of the arc-starting component's top circular surface. Within this range, the electrode maintains excellent electrical conductivity, improves arc-starting efficiency, and enables rapid ignition. It also ensures that the cathode spot heat load falls as much as possible on the corrosion-resistant component, extending its service life.

[0029] 3. In the plasma igniter cathode assembly provided by the present invention, the outer top of the housing assembly is tapered, with the bottom of the arc-starting assembly's tapered surface connected to the top of the housing assembly's tapered surface, forming a slope. This slope maximizes protection for the pure copper housing assembly, as arc edge temperatures are high. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 1 is a schematic structural diagram of the cathode device of the plasma igniter of Example 1;

[0032] Figure 2 It is a schematic top view of the cathode device structure of the plasma igniter in Example 1.

[0033] Reference numerals:

[0034] 1-Corrosion-resistant component; 2-Arc striking component; 3-Housing component; 4-Thread; 5-Water cooling channel. DETAILED DESCRIPTION

[0035] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0036] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0037] Example 1

[0038] A plasma igniter cathode device, such as Figure 1 、 Figure 2As shown, it includes a shell component 3 and a corrosion-resistant component 1 arranged at the core of the shell, and an arc-striking component 2 arranged between the shell component 3 and the corrosion-resistant component 1; the components are coaxially arranged, the shell component 3 is expanded and connected to the arc-striking component 2, and the arc-striking component 2 is expanded and connected to the corrosion-resistant component 1.

[0039] In this embodiment, the corrosion-resistant component 1 is pure hafnium, the purity of which is not less than 99.9 wt %. The melting point of metallic hafnium is 2227° C. It has strong corrosion resistance, can reduce the ablation rate of the imprinting device during the operation of the plasma igniter, and increase the service life of the cathode device.

[0040] The arc striking component 2 is made of pure silver with a purity of not less than 99.9 wt %. Pure silver facilitates arc starting and striking, ensuring plasma stability. Pure silver also has good plasticity and is easily expandable and connected to the pure copper housing component 3 .

[0041] The shell component 3 is made of pure copper, and the purity of the pure copper is not less than 99.9wt%.

[0042] The top of the arc-striking component 2 includes a circular surface in the center and a conical surface on the outside. 1 / 4 of the outer diameter of the circular surface at the top of the arc-striking component 2 ≤ the diameter of the circular surface at the top of the corrosion-resistant component 1 ≤ 1 / 2 of the outer diameter of the circular surface at the top of the arc-striking component 2.

[0043] The outer side of the top end of the shell component 3 is set to a conical surface, and the bottom end of the conical surface of the arc striking component 2 is connected with the top end of the conical surface of the shell component 3 to form a slope.

[0044] The upper end of the inner wall of the shell component 3 is provided with a reducing step for expansion connection with the arc striking component 2. The outer bottom of the shell component 3 is provided with a thread 4, which is threadedly connected to the cooling water channel of the plasma igniter, forming a water cooling channel 5 at the lower end of the inner part of the shell component 3.

[0045] Comparative Example 1

[0046] The plasma igniter cathode device of this comparative example is basically the same as that of Example 1, except that this comparative example does not include the arc striking component 2, and the arc striking component 2 and the corrosion-resistant component 1 in Example 1 are replaced by the material of the corrosion-resistant component 1 of an integrated structure.

[0047] Test example

[0048] The ablation rate test was performed on the cathode devices of Example 1 and Comparative Example 1: a pure copper component was used as the experimental anode, and the ablation rate test of the cathode device was performed using the unit area weighing method. The ablation time was 30 minutes, the plasma power supply current was 80A, the distance between the cathode and the anode was set to 2mm, and the swirl inlet pressure was 1.5MPa.

[0049] The test results show that the ablation amount of Example 1 of the present invention is 4.5g / mm 2, the ablation amount of comparative example 1 is 7.2g / mm 2 .

[0050] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A plasma igniter cathode device, characterized in that: It comprises a shell component (3), a corrosion-resistant component (1) arranged at the core of the shell, and an arc-starting component (2) arranged between the shell component (3) and the corrosion-resistant component (1); The arc striking component (2) is made of pure silver; The corrosion-resistant component (1) is made of pure hafnium, pure tungsten or an alloy containing the two in any proportion; The shell component (3) is made of pure copper; The top end of the arc striking component (2) comprises a circular ring surface at the center and a conical surface at the outside; 1 / 4 of the outer diameter of the circular ring surface at the top of the arc-starting component (2) ≤ the diameter of the circular ring surface at the top of the corrosion-resistant component (1) ≤ 1 / 2 of the outer diameter of the circular ring surface at the top of the arc-starting component (2); The outer side of the top end of the shell component (3) is configured as a conical surface, and the bottom end of the conical surface of the arc striking component (2) is connected to the top end of the conical surface of the shell component (3) to form a slope.

2. The plasma igniter cathode device according to claim 1, characterized in that: The housing component (3), the arc striking component (2), and the corrosion resistant component (1) are coaxially arranged.

3. The plasma igniter cathode device according to claim 2, characterized in that: The housing component (3), the arc striking component (2), and the corrosion resistant component (1) are connected by expansion joints.

4. The plasma igniter cathode device according to claim 1, characterized in that: The outer bottom of the housing component (3) is provided with a thread (4).

5. The plasma igniter cathode device according to claim 1, characterized in that: The inner wall of the housing component (3) is provided with a diameter-changing step.

6. The plasma igniter cathode device according to claim 1, characterized in that: At least one of the following conditions is met: A. The purity of pure hafnium and pure tungsten shall not be less than 99.9wt%; B. The sum of pure hafnium and pure tungsten in the alloy is not less than 99.9wt%; C. The purity of pure silver is not less than 99.9%wt.

7. The plasma igniter cathode device according to claim 1, characterized in that: The purity of pure copper is not less than 99.9wt%.

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