Plasma torch, plasma furnace and working method of plasma furnace

Abstract

The invention provides a plasma torch, a plasma furnace and a working method of the plasma furnace, and aims to solve the technical problem of radioactive leakage when radioactive wastes are treated. The plasma torch comprises an anode tube which is internally provided with an anode material, one end of the anode tube is a nozzle, the other end of the anode tube is a connecting part, and the connecting part is provided with a working gas channel; one end of the cathode rod is movably arranged in the connecting part, the cathode rod is made of a cathode material, and a gap exists between the end part of the cathode rod and the anode material; the driving end of the driving part is in power connection with the cathode rod, and the driving part is used for driving the cathode rod to move into the anode tube; the cathode of the plasma power supply is electrically connected with the cathode rod, and the anode is electrically connected with the anode material; and the output end of the gas supply device is communicated with the working gas channel. According to the plasma torch, the cathode rod is made to move in the connecting part through the driving piece, the distance between the cathode rod and the anode material is reduced, and therefore radioactive leakage caused by cathode material replacement is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of radioactive waste disposal, and in particular to a plasma torch and a plasma furnace and a working method of the plasma furnace. Background Art

[0002] With the rapid development of the nuclear power industry, the amount of radioactive waste generated during the operation and decommissioning of nuclear power plants has increased year by year, and the demand for disposal has also increased accordingly. The development of relevant radioactive waste treatment technologies has become a top priority.

[0003] Compared with traditional treatment technologies, plasma gasification and molten glass solidification technology has the advantages of wide application range, fast reaction speed, low secondary pollution, small amount of tail gas and compact equipment. It can realize the decomposition and gasification combustion of radioactive waste, high-temperature melting of inorganic waste and solidification process of radioactive nuclides in one system, greatly reducing the volume of waste and obtaining a stable final waste body.

[0004] The mainstream plasma technology for radioactive waste disposal on the market currently uses nitrogen (or air) as a plasma carrier, which produces a high-temperature plasma jet after ionization, pyrolyzes, gasifies and melts the radioactive waste, and finally forms a glass solid body, solidifying the radionuclides and harmful heavy metals in the glass body to achieve volume reduction and harmless treatment.

[0005] During this process, due to the high temperature and high enthalpy characteristics of the plasma arc itself, some harmful nuclides, such as Cs-137, can easily volatilize into the flue gas under high temperature conditions. In addition, the cathode, the core component of the plasma torch, has a short life. In the process of treating radioactive waste, there is a problem of needing to replace the cathode midway, which increases the risk of radioactive leakage. Summary of the invention

[0006] In view of the technical problem of radioactive leakage when replacing the cathode midway during the process of treating radioactive waste, the present invention provides a plasma torch, wherein a connecting portion is arranged at the end of an anode tube, and a cathode rod is movably arranged in the connecting portion; then, when the distance between the end of the cathode rod and the anode material increases, the cathode rod is moved in the connecting portion by a driving member to reduce the distance between the cathode rod and the anode material, thereby avoiding radioactive leakage caused by replacing the cathode material.

[0007] The technical solution of the present invention is:

[0008] A plasma torch comprising:

[0009] An anode tube, in which an anode material is arranged, one end of the anode tube is a nozzle, and the other end is a connecting part, and the connecting part is provided with a working gas channel;

[0010] A cathode rod, one end of which is movably disposed in the connecting portion, the cathode rod is made of cathode material, and there is a gap between the end of the cathode rod and the anode material;

[0011] A driving member, a driving end of which is connected to the cathode rod in power and used to drive the cathode rod to move into the anode tube;

[0012] A plasma power supply, the negative electrode of which is electrically connected to the cathode rod, and the positive electrode of which is electrically connected to the anode material;

[0013] A gas supply device, the output end of which is communicated with the working gas channel.

[0014] Optionally, one end of the cathode rod is provided with an external thread, and the other end is provided with a threaded hole, and the plasma torch further comprises a plurality of spare cathode rods.

[0015] Optionally, a cathode base is provided at one end of the anode tube, and the connecting portion is located on the cathode base.

[0016] Optionally, a sealing component is also provided on the cathode base.

[0017] Optionally, the anode tube is a metal tube for constraining the arc provided inside one side of the nozzle.

[0018] Optionally, a liquid cooling channel is provided on the anode tube, and the liquid cooling channel covers the metal tube.

[0019] In view of the technical problem that some harmful nuclides can easily volatilize into flue gas under high temperature conditions, the present invention provides a plasma furnace including a plasma torch, by adding an air duct between the plasma torch and the plasma furnace, and passing airflow into the air duct to form wall-adhering wind, so that the wall-adhering wind is ejected from around the nozzle to wrap the plasma flame, thereby preventing the high-temperature flame from contacting the volatile nuclides for a short time, thereby preventing some harmful nuclides from volatilizing into the flue gas.

[0020] A plasma furnace comprises a plasma torch, wherein an air duct is arranged between the plasma torch and the plasma furnace.

[0021] Optionally, swirl blades are provided in the air duct.

[0022] A method for operating a plasma furnace comprises the following steps:

[0023] S10, the gas supply device sprays working gas and causes cooling liquid to flow in the liquid cooling channel;

[0024] S20, introducing a swirling airflow into the plasma furnace through an air duct;

[0025] S30, using a high frequency voltage to trigger a plasma arc between the cathode rod and the anode material;

[0026] S40, starting the driving member to drive the cathode rod to move into the anode tube, and maintaining a certain distance between the end of the cathode rod and the anode material.

[0027] Optionally, in step S20, the gas flowing in the air duct is the same as the working gas;

[0028] In the step S30, the ablation state of the cathode rod end is monitored in real time. If the distance between the cathode rod end and the anode material is greater than 3 mm, step S40 is implemented.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] A connecting portion is provided at the end of the anode tube, and a cathode rod is movably provided in the connecting portion. Then, when the distance between the end of the cathode rod and the anode material increases, the cathode rod is moved in the connecting portion by a driving member to reduce the distance between the cathode rod and the anode material, thereby avoiding radioactive leakage caused by replacement of the cathode material.

[0031] By adding an air duct between the plasma torch and the plasma furnace and passing air into the air duct, wall-adhering wind is formed, and the wall-adhering wind is ejected from around the nozzle to wrap the plasma flame, preventing the high-temperature flame from contacting volatile nuclides for a short time, thereby avoiding the volatilization of some harmful nuclides into the flue gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 is a schematic diagram of the structure of a plasma torch;

[0034] Figure 2 is a schematic diagram of the structure of a plasma furnace;

[0035] Figure 3 This is a schematic diagram of the plasma furnace working process;

[0036] Figure 4 is a schematic diagram of the structure of the driving member;

[0037] Figure 5 Schematic diagram of the structure of the cathode base.

[0038] Reference numerals:

[0039] 100, plasma torch; 110, anode tube; 120, cathode rod; 130, driving member; 140, plasma power supply; 150, gas supply device; 160, anode material; 170, cathode base; 180, sealing assembly;

[0040] 111. metal tube; 112. liquid cooling channel;

[0041] 131. servo motor; 132. driving wheel; 133. gear;

[0042] 171, embedded groove; 172, working gas channel; 173, bolt hole;

[0043] 181, sealing ring; 182, bolt; 183, pressure plate;

[0044] 200. Plasma furnace; 210. Air duct. DETAILED DESCRIPTION

[0045] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0046] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplicity and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0047] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0048] Embodiment 1:

[0049] See also Figure 1This embodiment discloses a plasma torch, including an anode tube 110, a cathode rod 120, a driving member 130, a plasma power supply 140 and a gas supply device 150. The anode tube 110 is provided with an anode material 160, and one end of the cathode rod 120 is connected to one end of the anode tube 110. By electrically connecting the cathode rod 120 and the anode material 160 to the negative electrode and the positive electrode of the plasma power supply 140 respectively, an arc is generated in the anode tube 110, and the motor in the anode tube 110 is blown out from the nozzle through the gas supply device 150. After the cathode rod 120 is ablated, the cathode rod 120 is driven by the driving member 130 to move into the anode tube 110.

[0050] Specifically, the anode tube 110 is a tubular structure with two ends connected, and a tubular anode material 160 is disposed inside the anode tube 110. The anode material 160 is generally a copper alloy. One end of the anode tube 110 is a nozzle, and the other end is a connecting portion, and a working gas channel 172 is also disposed on the connecting portion.

[0051] The cathode rod 120 is a rod-shaped structure, and the cathode rod 120 is made of special materials, such as cerium-tungsten alloy, hafnium alloy, silver alloy, etc.

[0052] During the installation process, the distance between one end of the cathode rod 120 disposed in the connection portion and the end of the anode material 160 is 2-3 mm.

[0053] The driving end of the driving member 130 is connected to the cathode rod 120 in a power connection.

[0054] The output end of the gas supply device 150 is connected to the working gas channel 172, and the working gas is usually an inert gas or compressed air.

[0055] The working principle of this embodiment is to set a connecting part at the end of the anode tube 110, and movably set the cathode rod 120 in the connecting part. Then, when ablation occurs at the end of the cathode rod 120, resulting in an increase in the distance between it and the end of the anode material 160, the cathode rod 120 is driven to move in the connecting part by the driving member 130 to reduce the distance between the cathode rod 120 and the end of the anode material 160, thereby maintaining the normal operation of the plasma torch 100, thereby avoiding radioactive leakage caused by replacing the cathode material.

[0056] Preferably, one end of the cathode rod 120 is provided with an external thread, and the other end is provided with a threaded hole. The plasma torch 100 also includes a plurality of spare cathode rods 120, which can be called spare rods. When the cathode rod 120 installed in the connecting part is severely ablated and is about to be completely ablated, the spare rod is connected to the cathode rod 120 by thread matching, so that the cathode rod 120 can be lengthened, thereby greatly improving the life of the cathode by several times or even dozens of times, greatly improving the durability, and reducing the risk of radioactive leakage caused by cathode replacement in actual nuclear power engineering projects.

[0057] In one specific embodiment:

[0058] A cathode base 170 is disposed at one end of the anode tube 110. The cathode base 170 is a hollow structure, and the middle of the cathode base is a connecting portion for inserting the cathode rod 120. In addition, a sealing assembly 180 is also disposed on the cathode base 170.

[0059] By setting the cathode base 170, it is convenient to install the working gas channel 172 and the sealing assembly 180. By setting the sealing assembly 180, the four sides of the cathode rod 120 can be compressed and sealed, which can not only effectively isolate the internal and external connections of the anode tube 110, but also fix the working position of the cathode rod 120 to ensure its normal operation.

[0060] Preferably, the cathode base 170 is a hollow cylindrical structure, and a plurality of bolt holes 173 are provided on the circumference of the cathode base 170. The sealing assembly 180 includes a sealing ring 181 made of an insulating flexible material (such as a boron nitride fiber reinforced composite material), and bolts 182 for squeezing the sealing ring 181, and the bolts 182 match the bolt holes 173 on the cathode base 170.

[0061] In addition, if Figure 5 As shown, an inner groove 171 is provided on the inner side wall of the cathode base 170, and a sealing ring 181 is located in the inner groove 171. An arc-shaped pressing plate 183 is also provided in the inner groove 171, and the pressing plate 183 contacts the end of the bolt 182. When the cathode rod 120 is installed in the connecting portion, the pressing plate 183 is pressed by the bolt 182, and then the sealing ring 181 is pressed by the pressing plate 183, so as to achieve the sealing of the cathode rod 120 in the circumferential direction. The purpose of providing the pressing plate 183 is to ensure that the pressure of the sealing ring 181 on the cathode rod 120 in the circumferential direction is balanced.

[0062] In another specific embodiment:

[0063] Anode tube 110 is a nozzle having a metal tube 111 for arc confinement inside one side, and the metal tube 111 is made of copper. A liquid cooling channel 112 is provided inside anode tube 110, and liquid cooling channel 112 covers metal tube 111. By providing liquid cooling channel 112 and passing coolant into the liquid cooling channel, the metal tube 111 can be cooled.

[0064] In this embodiment, copper is selected as the metal tube 111 for confining the arc, mainly because copper has the comprehensive advantages of good electrical conductivity and thermal conductivity as well as low cost.

[0065] In another specific embodiment:

[0066] See also Figure 4 The driving member 130 includes a servo motor 131 and a pair of driving wheels 132, wherein the output shaft of the servo motor 131 is connected to the two driving wheels 132, there is a gap between the two driving wheels 132, and the axes of the two driving wheels 132 are parallel to each other, and the two driving wheels 132 rotate on the same plane. The two driving wheels 132 rotate at the same speed and in opposite directions under the drive of the servo motor 131.

[0067] Generally, two mutually meshing gears 133 with the same parameters are installed on the output shaft of the servo motor 131 , so that the output shaft of the servo motor 131 is coaxially connected to one of the gears 133 , and the requirement of two driving wheels 132 is achieved through the two gears 133 .

[0068] During the installation process, the two driving wheels 132 are respectively located on both sides of the cathode rod 120 and generate clamping force on the cathode rod 120 from both sides, so that under the driving action of the servo motor 131, the cathode rod 120 can be directly driven to approach the anode material 160.

[0069] Embodiment 2:

[0070] See also Figure 2 This embodiment discloses a plasma furnace, including the plasma torch 100 described in the first embodiment. Specifically, the plasma torch 100 is installed above the furnace body of the plasma furnace 200, and the furnace body is insulated with high temperature resistant and corrosion resistant refractory materials.

[0071] When the plasma torch 100 works normally, the high-temperature plasma flame outputted melts the radioactive waste in the furnace body to form a molten pool. The radioactive waste in the molten pool is melted by the high-temperature plasma flame to form a glass body.

[0072] During the melting process, some harmful radionuclides (Cs-137, I-131, Sr-90, Co-60, etc.) are effectively solidified inside the vitreous body. Professional leaching tests can verify that the harmful radionuclides will not cause radiation damage from inside the vitreous body to the outside.

[0073] In one specific embodiment:

[0074] An air duct 210 is provided at the installation position between the plasma torch 100 and the furnace body. The air duct 210 is wrapped around the plasma torch 100, and the two ends of the air duct 210 are respectively located outside and inside the furnace body, and one end of the air duct 210 is connected to the output end of the fan.

[0075] By adding an air duct 210 between the plasma torch 100 and the furnace body and passing air flow into the air duct 210, wall-adhering wind is formed, and the wall-adhering wind is ejected from around the nozzle to wrap the plasma flame, preventing the high-temperature flame from contacting volatile nuclides for a short time, thereby avoiding the volatilization of some harmful nuclides into the flue gas and improving safety.

[0076] Preferably, swirl blades are provided in the air duct 210, and the wall-adhering wind passes through the swirl blades and is ejected from around the nozzle to form a swirl airflow. The wall-adhering wind swirl structure allows the plasma torch 100 to be installed on the furnace body to protect the refractory material from being burned by the high-temperature plasma flame.

[0077] Embodiment three:

[0078] like Figure 3 As shown, this embodiment discloses a working method of a plasma furnace 200, which is based on the plasma furnace 200 in the second embodiment. Specifically, the following steps are included:

[0079] S10, the gas supply device 150 sprays working gas and causes cooling liquid to flow in the liquid cooling channel 112;

[0080] S20, introducing a swirling airflow into the plasma furnace 200 through the air duct 210, wherein the gas flowing in the air duct 210 is the same as the working gas;

[0081] S30, using a high frequency voltage to trigger a plasma arc between the cathode rod 120 and the anode material 160;

[0082] S40 , starting the driving member 130 to drive the cathode rod 120 to move into the anode tube 110 , and maintaining a certain distance between the end of the cathode rod 120 and the anode material 160 .

[0083] Among them, in the step S30, the voltage between the cathode rod 120 and the anode material 160 is about 15KV. After the arc is successfully started, a high-temperature plasma arc is generated between the anode material 160 and the cathode rod 120. The arc is ejected from the nozzle under the action of the working gas to form a high-temperature plasma flame with a flame temperature of 2000-3000°C.

[0084] In step S30, the ablation state of the end of the cathode rod 120 needs to be monitored in real time. If the end of the cathode rod 120 is ablated too much and the gap between the cathode rod 120 and the anode material 160 cannot meet the arc starting condition (the gap is greater than 3 mm), step S40 is implemented.

[0085] In the process of implementing step S40, it is necessary to first loosen the sealing assembly 180 so that the cathode rod 120 has the freedom to move along its length direction, and then start the driving member 130 to drive the cathode rod 120 to move into the connecting part. When the distance between the end of the cathode rod 120 and the end of the anode material 160 is between 2-3mm, stop the driving member 130 and tighten the sealing assembly 180 to ensure no leakage.

[0086] This working method can ensure that the gap between the cathode rod 120 and the anode material 160 is always maintained within a set range (2-3 mm), so that the plasma torch 100 can always work normally without stopping the power supply or manually replacing the cathode.

[0087] The above-mentioned embodiments only express the specific implementation of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A plasma torch, characterized in that: include: An anode tube, in which an anode material is arranged, one end of the anode tube is a nozzle, and the other end is a connecting part, and the connecting part is provided with a working gas channel; A cathode rod, one end of which is movably arranged in the connecting portion, the cathode rod is made of cathode material, and there is a gap between the end of the cathode rod and the anode material; A driving member, a driving end of which is connected to the cathode rod in power and used to drive the cathode rod to move into the anode tube; A plasma power supply, the negative electrode of which is electrically connected to the cathode rod, and the positive electrode of which is electrically connected to the anode material; A gas supply device, the output end of which is communicated with the working gas channel.

2. The plasma torch according to claim 1, characterized in that One end of the cathode rod is provided with an external thread, and the other end is provided with a threaded hole. The plasma torch also includes a plurality of spare cathode rods.

3. The plasma torch according to claim 1, characterized in that A cathode base is provided at one end of the anode tube, and the connecting portion is located on the cathode base.

4. The plasma torch according to claim 3, characterized in that A sealing component is also provided on the cathode base.

5. The plasma torch according to claim 1, characterized in that The anode tube is a metal tube for constraining the arc, which is arranged inside one side of the nozzle.

6. The plasma torch according to claim 5, characterized in that The anode tube is provided with a liquid cooling channel, and the liquid cooling channel covers the metal tube.

7. A plasma furnace comprising the plasma torch according to any one of claims 1 to 6, wherein an air duct is provided between the plasma torch and the plasma furnace.

8. The plasma furnace according to claim 7, characterized in that: The air duct is provided with swirl blades.

9. A method for operating a plasma furnace, characterized in that: The following steps are involved: S10, the gas supply device sprays working gas and causes cooling liquid to flow in the liquid cooling channel; S20, introducing a swirling airflow into the plasma furnace through an air duct; S30, using a high frequency voltage to trigger a plasma arc between the cathode rod and the anode material; S40, starting the driving member to drive the cathode rod to move into the anode tube, and maintaining a certain distance between the end of the cathode rod and the anode material.

10. The plasma furnace according to claim 9, characterized in that: In the step S20, the gas flowing in the air duct is the same as the working gas; In the step S30, the ablation state of the cathode rod end is monitored in real time. If the distance between the cathode rod end and the anode material is greater than 3 mm, step S40 is implemented.

Images