JP3399619B2 - Flame detector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame detecting device used for determining the presence or absence of a flame in a boiler furnace, for example, and more particularly to a material of a frame rod in the flame contact type flame detecting device.

[0002]

2. Description of the Related Art FIG. 5 shows the structure of a conventionally known pulverized coal burner or heavy oil burner for a boiler. In this figure, 1 is an atomizer, 2 is an igniter, and 3 is a flame contact type flame detection device, and these devices are held in a state of being inserted into the ignition burner 4. 5 is a fuel injection part set at the tip of the atomizer 1, 6 is fuel injected from the fuel injection part 5, 7 is a frame rod holding part provided at the tip of the flame contact type flame detection device 3, 8 Is a frame rod whose one end is held through the holding portion 7, 9 is a control power source of the flame contact type flame detection device 3, and 10 is a resistance detector of the flame contact type flame detection device 3.

The frame rod 8 detects whether or not the fuel 6 injected from the atomizer 1 is ignited by detecting an ionic current, and one end of the frame rod 8 is penetratingly held by a cylindrical holding portion 7. The tip portion is set to a position slightly (usually several cm) protruding from the opening of the ignition burner 1. For flame detection by the flame rod 8, a voltage is applied between the fuel injection unit 5 and the flame rod 8 by the current from the control power source 9, and the resistance detector 10 detects a difference between the fuel injection unit 5 and the flame rod 8. This is done by measuring the electrical resistance between them. That is, the jetted fuel 6 before ignition does not show conductivity, but the flame after ignition shows conductivity due to the ion current, so that the change in electrical resistance between the fuel injection part 5 and the frame rod 8 before and after ignition is suppressed. The presence or absence of ignition can be detected by measuring.

Since the tip of the frame rod 8 is inserted into the flame, a high degree of heat resistance, thermal shock resistance, oxidation resistance, high temperature creep strength and the like are required. Conventionally, in consideration of these points, a ceramic rod is used as the frame rod 8.

[0005]

By the way, the frame rod 8 attached to a boiler furnace or the like is not only heated to a high temperature, but is also heated to a high temperature under a significantly uneven temperature distribution as shown in FIG. Be heated. That is, the middle portion of the frame rod 8 has a low temperature because the unignited fuel 6 is injected, whereas the tip portion has a high temperature because it comes into contact with the flame, and the base end of the frame rod 8 has a high temperature. The side is also heated by the radiant heat in the furnace and becomes higher in temperature than the intermediate part. For this reason, a large thermal stress acts on the frame rod 8, and a ceramic frame rod having high brittleness is likely to cause a breakage accident.

Further, in the frame rod 8 attached to a coal-fired boiler or the like, as shown in FIG. 7A, the slag 1 is provided at a portion protruding from the opening of the ignition burner 1.
It is easy for 1 etc. to attach, and the frame rod 8 in a high temperature atmosphere
Since a large amount of weight is applied to the frame rod, a frame rod made of ceramics having high brittleness is likely to cause a breakage accident as shown in FIG. 7B.

As described above, the conventional flame detecting device has a problem in reliability because the thermal and mechanical external forces acting on the frame rod are not sufficiently taken into consideration.

The present invention has been made in view of such a point, and its purpose is excellent in heat resistance, thermal shock resistance, oxidation resistance, high temperature creep strength, thermal deformation resistance and resistance to mechanical external force. Another object is to provide a flame detection device.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above problems.
In order to solve the problem, a flame detector that detects the ion current of the flame
In the flame detection device provided with a head, as the frame rod, Ri Do from sintered alloy ferritic Fe-Cr-Al composition, the surface roughness used as a 3μm or less trough
I configured it. The present invention also solves the above problems.
Therefore, a frame rod that detects the ion current of the flame is provided.
In the flame detection device, as the frame rod
Ferrite-based Fe-Cr-Al composition sintered alloy
Using things, and fixed to the holding part via a shear pin for cutting with a constant force which is determined the frame rod advance
It was configured to do.

[0010]

Since the ferritic Fe-Cr-Al composition sintered alloy is basically a metal, it is excellent in resistance to thermal shock and mechanical shock, and the frame rod thus manufactured has a ceramic frame. Less likely to cause a cutting accident like a rod.

Further, this sintered alloy (especially 20 to 25%)
Cr, 3 to 8% Al) is excellent in heat resistance and oxidation resistance, as can be seen from the fact that it is generally used as a heat generating material. Its heat resistant temperature is 1400 ° C, and JI
It is about 300 ° C higher than the SUS310S specified in S, and even if it is used as a frame rod for a boiler, it can withstand the operating conditions sufficiently.

Further, this sintered alloy causes remarkable coarsening of the crystal grain size in a high temperature range as shown by the solid line in FIG.
Compared with the Fe-Cr-Al-based cast alloy shown by the broken line in FIG. 8, the crystal grain size in the high temperature range is remarkably large. Since the creep rate is almost inversely proportional to the square of the crystal grain size,
The sintered alloy according to the present application is excellent in creep resistance even when compared with similar cast alloys. The frame rod thus formed is not easily thermally deformed even when exposed to a high temperature flame, and can exhibit stable performance for a long period of time.

Since the main component of the slag is ceramics, if the frame rod is metalized and made different from the slag, the amount of slag attached to the frame rod can be reduced and the increase in weight acting on the frame rod can be reduced. This also prevents the frame rod from being damaged and reduces creep deformation. Especially, the surface roughness of the frame rod is 3
When the thickness is less than or equal to μm, a phenomenon in which the slag is rooted on the surface of the frame rod, that is, a so-called anchor effect is suppressed, so that the adhesion and deposition of the slag on the frame rod can be significantly reduced.

[0014]

1 and 2 show the construction of a flame detection device according to an embodiment. FIG. 1 is a partially sectional side view of a flame detection device according to an embodiment, and FIG. 2 is a front view seen from the frame rod side. In these drawings, reference numeral 21 is a frame rod according to the present invention, and reference numeral 22 is a frame rod 2.
1 shows a shear pin for fixing 1 to the holding portion, and other portions corresponding to those in FIG. 4 have the same reference numerals.

The frame rod 21 is made of ferrite Fe.
It is made of a sintered alloy having a —Cr—Al composition, and its surface is surface-finished so that the surface roughness is 3 μm or less.

As shown in FIG. 1, the shear pin 21 includes a through hole 21a formed in the frame rod 21 and a holding portion 7.
The frame rod 21 is attached to the holding portion 7 by penetrating through the through hole 7a formed in the. Sharpin 2
As 2, a material having an arbitrary material and strength can be used as long as it can be relatively easily cut with a predetermined constant force, but in consideration of price, easiness of manufacturing, etc., Aluminum is particularly preferable, and one that is cut when the frame rod 21 is pulled by a force of about 20 kg in the axial direction is particularly preferable in order to prevent the frame rod 21 from falling off during mounting.

The other parts are the same as those of the flame detecting device according to the conventional example, and the description thereof will be omitted. As shown in FIG. 3, the flame detection device of this example is inserted into an ignition burner 4 together with an atomizer 1 and an igniter 2, and is used for flame detection and the like in a boiler furnace.

FIG. 4 shows the effect of the flame detecting apparatus according to this embodiment in comparison with the flame detecting apparatus according to the comparative example.

As is apparent from this figure, the flame detection device SU having a frame rod made of SiC ceramics, SU
A flame detection device including a frame rod made of S310S,
All of the flame detection devices provided with a frame rod made of Fe-Cr-Al-based cast alloy have heat resistance, thermal shock resistance,
At least one of high-temperature creep strength, mechanical strength, and slag adhesion is evaluated as having a problem in durability, or not applicable depending on use conditions, whereas ferrite-based Fe-Cr It can be seen that the flame detection device of the present invention provided with a frame rod made of a sintered alloy of -Al composition is very good for all evaluation items and is effective for improving the durability of the frame rod.

Further, in the flame detecting device of this embodiment, since the frame rod 21 is attached to the holding portion 7 by the shear pin 22, even if the frame rod 21 is deformed by high temperature creep, it can be easily pulled out from the holding portion 7. Therefore, maintenance of the flame detection device is easy. In addition, since the flame detection device of this example has a simple structure and the frame rod 21 is made of an inexpensive metal material,
There is also an effect that it can be provided at low cost.

[0021]

As described above, according to the present invention,
It is possible to increase the heat resistance, thermal shock resistance, high temperature creep strength and mechanical strength of the frame rod with an inexpensive material, and also to reduce the slag adhesion, so it is highly reliable with little damage, missing or malfunction. It is possible to provide a flame detecting device at low cost.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a flame detection device according to an embodiment.

FIG. 2 is a front view of the flame detection device according to the embodiment seen from the frame rod side.

FIG. 3 is a partial cross-sectional view showing a state in which the flame detection device according to the embodiment is incorporated into an ignition burner.

FIG. 4 is a table showing the effects of the embodiment.

FIG. 5 is a partial cross-sectional view showing the structure of a conventionally known ignition burner.

FIG. 6 is a graph showing a temperature distribution in the axial direction of a frame rod.

FIG. 7 is a partial cross-sectional view showing a state where the slag is attached to the frame rod and a state where the frame rod is cut off.

FIG. 8 is a graph showing a change in crystal grain size of a metal material forming a frame rod with temperature rise.

[Explanation of symbols]

3 Flame contact type flame detector 7 Frame rod holder 9 Control power supply 10 Resistance detector 21 frame rod 22 Sharpin

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Osamu Okada               6-9 Takaracho, Kure-shi, Hiroshima Babcock Sun               Standing Kure Factory (72) Hideki Nakazaki, the inventor               6-9 Takaracho, Kure-shi, Hiroshima Babcock Sun               Standing Kure Factory                (56) References JP-A-60-89746 (JP, A)                 JP-A-5-280734 (JP, A)

Claims (2)

(57) [Claims] 1. A flame detection apparatus which includes a flame rod for detecting the ion current of the flame, as the flame rod, Ri Do from sintered alloy ferritic Fe-Cr-Al composition, the surface roughness is less 3μm A flame detection device characterized by using a thing. 2. A flamero for detecting an ion current of a flame.
In a flame detection device equipped with a
Sintered alloy of ferritic Fe-Cr-Al composition
And the frame rod in advance.
Holds via shear pin that cuts with a specified constant force
A flame detection device characterized by being fixed to a section .