JPH0213718A - Pulverized coal ignition torch - Google Patents

Abstract

PURPOSE:To eliminate the necessity of expensive inert gas such as argon gas, to simplify a structure and to reduce a size by employing air as operating gas, using a thermionic emission type electrode material which is not consumed with oxidation even in an oxidative atmosphere such as Hf, Zr, etc., as a cathode, and disposing an anode at a pulverized coal ignition flame side. CONSTITUTION:When a thermionic emission type electrode material such as Hf, Zr, etc., is employed near an arc generation point of a cathode 3, it is not consumed with oxidation even in an oxidative atmosphere such as air, etc. When a voltage is applied to the cathode 3, and anode nozzle 4, an arc is generated between both the electrodes. Pressurized air 9 as operating gas flows from an injection port 1a provided in an inner cylinder 1 into a gas passage 6 in this state, and injects from a hole 7. As a result, the arc generated between both the electrodes is stabilized at the position of a protrusion member 8 in which the anode point 10 of the arm is composed integrally with the nozzle 4 by the operation of the injected opening gas to form an arc plasma 11. Accordingly, the point 10 of the arc is exposed directly with a region in contact with mixture stream 12 of pulverized coal and the air, the coal is heated in contact with the plasma 10 of high temperature, and ignited.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pulverized coal ignition torch, and particularly to an ignition torch for easily igniting pulverized coal using a plasma flame.

[Conventional technology]

Conventionally, in addition to coal as the main fuel, three types of fuel have been used in general coal-fired boilers: heavy oil for startup and light oil for ignition. If coal is used as the burner fuel for starting and igniting, the fuel system becomes one system, and the fuel storage,
Supply equipment is significantly simplified. Therefore, as a means of achieving this goal, several attempts are underway to directly ignite pulverized coal with plasma.

FIG. 3 discloses Japanese Patent Publication No. 5B-1330, in which an arc ignition torch 31 is used to bring a plasma flame 32 into contact with a mixed flow 34 of pulverized coal and air ejected from a pulverized coal burner 33. , high temperature plasma flame 3
2 is a method of igniting pulverized coal.

Figure 4 shows the plasma ignition torch 3 used in Figure 3.
This figure shows the structure of No. 1. Basically, it is an eddy current stabilization type device, which consists of a pair of cylindrical non-consumable metal electrodes 35 and 36 facing each other, connected by an insulating bushing 37, and a plurality of gas inlet holes on the side. While introducing pressurized gas such as air through 38, a voltage is applied by a power source 40 between metal electrodes 35 and 36 to form an arc 39, thereby creating a high-temperature, high-speed plasma flame 32.

On the cathode 36 side, heat generation at the cold cathode generation point is large, -
If the electrode is left at a fixed point, the electrode will be immediately damaged by melting, so the external coil 41 forms a magnetic field to rotate the arc 39 at high speed inside the cylindrical cathode to stabilize it.

Because of this structure, a large current is required to obtain a stable arc, so in this example, the arc current is not clear, but the output is very large at 56 kW.

FIG. 5 is an example of a plasma torch for igniting pulverized coal disclosed in Japanese Patent Laid-Open No. 60-194211. Thermionic emission type W electrode 52 is used for the cathode, and Cu is used for the anode nozzle 53.

A plasma flame 57 is formed using air 54 as a working gas, but the Wt electrode 52 is significantly consumed in an oxidizing atmosphere. With a nozzle structure, W
Argon 56, an inert gas, is made to flow around the electrode 52.

When this torch is used, it is possible to form a stable arc even at relatively low currents, and it is said to work well at outputs of 1.5 kW or more.

However, the torch structure including the water cooling structure is complicated and expensive, and the shape is also large, making it difficult to reduce the diameter to 40 mm or less.

[Problem to be solved by the invention]

In the case of the conventional torch mentioned above, it requires a large amount of power,
There were problems such as the equipment becoming complicated and large and requiring an inert gas such as argon gas to prevent oxidation. .

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of conventional torches and to provide a small-sized pulverized coal ignition torch with the simplest structure and using air as an operating gas.

[Means to solve the problem]

The above purpose is to use air as the operating gas in an ignition device that ignites using plasma, and to use Hf, Z
This is achieved by using a thermionic emission type electrode material that does not suffer from oxidative consumption even in an oxidizing atmosphere such as R, and by placing the anode on the side of the pulverized coal ignition flame.

[Effect]

If a thermionic emission type electrode material such as Hf or Zr is used near the arc generation point of the cathode, it will function as a stable thermionic emission type cathode without being consumed by oxidation even in an oxidizing atmosphere such as air. . As a result, a stable arc plasma can be formed in an air atmosphere even at a low current, so there is no need to use expensive inert gas such as argon, and there is no need to use a large current to maintain the arc. Nor.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a sectional view showing an embodiment of the pulverized coal ignition torch of the present invention, and FIG. 2 is a side view of FIG. 1.

This pulverized coal ignition torch consists of an inner cylinder 1, a cathode 2, an outer cylinder 3, and an anode with four nozzles. The inner cylinder 1 is made of Cu and has a cylindrical shape, and a part thereof is provided with a plurality of ejection holes 1a that are opened in the circumferential direction. The inner cylinder 1 is connected to a negative output terminal of an arc power source (not shown). A cylindrical cathode 2 is fixed to the tip of the inner cylinder 1 with screws.

This cathode 2 has a hemispherical tip, and a cathode tip member 2a is embedded in the center of the hemisphere (the axial tip of the cathode 2). It is effective for the cathode tip member 2a to be made of a material that is not easily consumed by oxidation in an oxidizing atmosphere such as air and functions as a stable thermionic emission type.

Examples of such materials include Hf and Zr.

An outer cylinder 3 is arranged around the outer circumference of the inner cylinder 1 at a predetermined distance from the inner cylinder 1 via an insulating member 5, and the outer cylinder 3 has a cylindrical shape with a hemispherical inner wall surface at the tip. The anode nozzle 4 is fixed with a screw.

As described above, a gas flow path 6 is formed between the inner cylinder 1 and the cathode 2 and the outer cylinder 3 and the anode nozzle 4. The outer cylinder 3 is connected to a positive output terminal of an arc power source (not shown) and is grounded.

Further, a hole 7 is formed in the anode nozzle 4, and a plate-shaped protrusion member 8 having a thickness in the circumferential direction of the torch is integrally formed from the inner wall surface of the hole 7.

Next, the operation of the pulverized coal ignition torch constructed as described above will be explained.

When a voltage is applied to the cathode 3 and the anode nozzle 4, an arc is generated between the two electrodes. In this state, pressurized air as a working gas indicated by 9 in the figure flows into the gas flow path 6 from the jet port 1a provided in the inner cylinder 1. Then, the working gas in the gas flow path 6 is ejected from the hole 7. As a result, the arc generated between the two electrodes is caused by the action of the working gas ejected from the hole 7.
The anode point 10 of the arc is stabilized at the position of the protrusion member 8 integrally constructed with the anode nozzle 4, and the arc plasma 11
form.

Therefore, the anode point 10 of the arc is directly exposed to the area in contact with the mixed flow 12 of pulverized coal and air.
The pulverized coal comes into contact with the high-temperature arc plasma 10, is heated, and is ignited. However, since the cathode 1 is placed inside the anode nozzle 4, and air 9, which also serves as a cooling agent, is constantly flowing out even when not ignited, the cathode 1 is exposed to the polluted external combustion atmosphere. It never happens.

With this structure, the cathode l can form an arc surrounded by clean air without being exposed to the mixed flow 12 of pulverized coal and air, so it is protected from contamination and wear. Ru.

Next, the cathode 2 is made of Cu with a diameter of 6 mm, and the cathode tip member 1a is
A Hf with a diameter of 2 mm and a length of 4 mm was buried as a
The anode nozzle 4 was fixed to an inner cylinder 1 with a diameter of 2 mm and a diameter of 2 mm, and a hole 7 with a diameter of 1.6 mm was provided in the anode nozzle 4. and,
It was operated at an air flow rate of 151/min, an arc current of 20A, an arc voltage of 120cm, and an electrical input of 2.4kW.

As a result, pulverized coal could be stably ignited using a plasma flame, and contamination and wear of the cathode could be prevented.

〔Effect of the invention〕

According to the present invention, only air is used as the operating gas, there is no need for expensive inert gas such as argon, and there is no need for a water-cooled structure. Therefore, the structure can be extremely simple and the size can be reduced.

In addition, it is only necessary to feed electricity and compressed air to the torch, making it possible to provide an extremely practical plasma ignition torch.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of a pulverized coal ignition torch according to the present invention, FIG. 2 is a side view of FIG. 1, FIG. 3 is a schematic configuration diagram of a conventional pulverized coal ignition torch, and FIG. FIG. 5 is a sectional view of a conventional pulverized coal ignition torch. 1...Inner cylinder, 1a...Blowout hole, 2...
...Cathode, 2a...Cathode tip member, 3...
...Outer cylinder, 4...Anode nozzle, 5...
...Insulating member, 6... Air flow path, 7...
- Hole, 8... Projection member, 9... Working gas (air), IO... Arc anode point, 11...
...Arc plasma, 12...Mixed flow of pulverized coal and air. Agent Patent Attorney Masaru Nishimoto −

Claims (2)

[Claims] (1) The area near the arc generation point of the cathode is constructed of a thermionic emission type electrode material that does not undergo oxidative consumption in an oxidizing atmosphere, and this cathode is surrounded by an anode nozzle via a flow path of air as a working gas, A pulverized coal ignition torch characterized in that an anode projection member for forming an anode arc anode point is formed near a hole provided in the anode nozzle and near a region of a mixed flow of pulverized coal and air. . (2) The pulverized coal ignition torch according to claim 1, wherein the electron-emitting electrode material is made of Hf or Zr.