JPH0144897Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field This invention completely prevents backfire,
This invention relates to a flat burner for gas combustion that has good durability and can perform high-temperature combustion for a long period of time.

BACKGROUND ART In recent years, a burning wall as shown in FIGS. 2a and 2b has been known as a combustion device for all kinds of heating furnaces, instead of a burner.

Burning wall is also known as luminous wall, and luminous wall furnace was first developed in America as a gas combustion method.
As shown in Fig. 2 a and b, fuel gas G and combustion air A are mixed, the mixed gas is blown into the breathable refractory 1, and the mixture is combusted within the refractory 1, so that the furnace inner wall surface (bright flame surface) is maintained at the maximum temperature, and the objects to be heated in the furnace are heated by radiation heat transfer from the burning wall surface and convection heat transfer from the fuel gas.

The problem that the invention aims to solve In this case, the conventional burning wall surface is
If the temperature is kept at a high temperature of 0.degree. C. or higher, the wall heat conduction and internal combustion zone will move to the back side, and if left as is, it will reach the air mixture chamber 2, causing a backfire and damaging the device itself, which is a fatal flaw.

Therefore, the practical range of bright flame surface temperature of conventional burning walls remains at around 800 to 1000℃.
It has never been used in high-temperature industrial furnaces of 1200°C or higher.

In the conventional burning wall, as shown in the temperature distribution inside the bright flame wall shown in Figure 4, there is a temperature difference of 4T at about 10 mm from the bright flame surface (furnace inner surface) of 500 to 600°C, which occurs inside the burning wall. This resulted in large internal strains, lowering the structure and strength of the breathable refractory, and resulting in significant shortcomings in durability.

For this reason, the current situation is that the burning wall method is not employed at all in the fields of the steel industry, ceramic industry, and other high-temperature industries.

Means for Solving the Problems It is an object of the present invention to provide a flat burner for gas combustion that solves the above-mentioned drawbacks, completely prevents backup fire, has good durability, and is capable of continuously performing high-temperature combustion for a long period of time.

A specific example of the present invention will be explained based on the drawings.
In FIG. 1, the refractory layers 11 are arranged sequentially in the thickness direction of the furnace wall. That is, the refractory layer 11 includes, on the furnace inner surface 18 side, a Si ₃ N ₄ refractory or SiC refractory 21 that has good radiation when heated to red heat;
The middle part is made of Al ₂ O ₃ -SiO ₂ based castable or refractory brick 22, and the back side 16 is made of heat insulating castable, heat insulating brick or ceramic fiber sheet 23 for cutting off heat transfer from the refractory layer 11 to the air mixture chamber 12. are the constituent members.

The fuel gas G supplied to the air mixture chamber 12 of the gas combustion flat burner configured in this way
The dynamic pressure of the mixture of combustion air A and combustion air A is blocked by the shielding plate 14, suppressed, and uniformly dispersed. Then, the mixed gas detours to the gap between the inner circumferential surface of the mixture chamber 12 and the shielding plate 14 and passes through the refractory layer 1.
It reaches the air mixture chamber 12 on the 1 side, and the refractory layer 1
1 and uniformly supplied to a large number of thin tubes 13 penetrating the refractory 11. The mixed gas ejected onto the inner surface of the furnace burns in the form of a large number of very thin flames 35. Then, the furnace inner surface 18 of the refractory layer 11
The sides are red hot and radiate heat into the furnace.

The pore diameter of the capillary tube 13 is determined so that the discharge speed of the mixed gas can be maintained (adjusted) higher than the combustion propagation speed of the mixed gas. At this time, the mixed gas is uniformly supplied to the thin tube 13, making it easy to determine the hole diameter.

Even if the temperature on the furnace inner surface 17 side of the capillary tube 13 and the furnace inner surface 18 side of the refractory layer 11 becomes higher than the ignition temperature of the mixed gas, the back surface 15 side of the capillary tube 13 and the back surface 16 side of the refractory layer 11 will not reach the mixed gas. There is no risk of backfire as the water is cooled down. Further, the gap between the air mixture chamber 12 and the shielding plate 14 is made smaller than the cross-sectional area of the introduction pipe 19 that introduces the mixed gas into the air mixture chamber 12, thereby further increasing safety against backup fire.

The hole diameter of the thin tube 13 is preferably 1 to 10 mm; if it is less than 1 mm, the combustion power will be too small; if it exceeds 10 mm, it will be the same as a conventional single tube burner, but the risk of backfire will increase, and the back pressure of the mixed gas supply will be kept high. Therefore, the supply amount is limited to large quantities.

The cross-sectional shape of the thin tube 13 is circular, oval, square,
It can be any polygonal shape, but it is generally circular,
Use metal (SUS, heat-resistant metal, etc.) or ceramic (Si ₃ N ₄ , SiC, Al ₂ O _3, etc.).

With the above-mentioned technical configuration, compared to the breathable refractories used in conventional burning walls, it has a denser structure, higher strength, and better durability against rapid heating and cooling temperature cycles. Ceramic fiber sheet has good durability against rapid heating and cooling temperature cycles.

There is also an embodiment in which the periphery of the opening of the thin tube 13 on the furnace inner surface 18 of the refractory layer 11 is formed into a concave portion concentric with the hole (not shown). The cross-sectional shape of the concave part is circular;
Oval, rectangular, polygonal, etc. are all suitable. flame 3
There is an advantage that the radiant heat of No. 5 is easily transmitted to the furnace inner surface 18 of the refractory layer 11.

Next, a specific example of the present invention will be shown.

Gas combustion flat burner specifications Fuel gas: LPG (combustion propagation velocity (temperature 50℃) 0.55 m/sec) Supply amount: LPG 3Nm ³ /H, Air 73.5Nm ³ /H Back pressure 360mmAq Flat burner area: 400mm x 400mm = 0.16 ^m2 refractory layer thickness: {Si ₃ N ₄ system or SiC system refractory 10
mm, Al ₂ O ₃ -SiO ₂ series castable 50 mm, insulation castable 10 mm} Number of capillary tubes: 360 Capillary tube material: SUS Capillary dimensions: Inner diameter 2 mmφ Gas flow velocity in capillary tube: 18.7 m/sec Shield plate dimensions: 396 mm x 396 mm Shield plate material :SS41 Furnace inner surface temperature: 1200℃ Back surface temperature: 41℃ Another specific example (not shown) in which the periphery of the opening of the thin tube 13 of the above specific example is made into a concave portion is as follows: Furnace inner surface temperature: 1300℃ (recess size (diameter: 5 mmφ, depth: 5 mm) In both specific examples, stable high-temperature combustion was achieved within the range of mixed gas supply amount of 60 Nm ³ /N (gas flow rate in capillary tube 14.7 m/sec) to 240 Nm ² /N.

Effects of the invention According to the invention as described above, there are the following effects.

(1) Backfire can be completely prevented, durability is good, and high-temperature combustion can be carried out continuously for a long period of time.

(2) If the refractory layer is made by pouring castable refractories, large-sized ones can be made.

(3) The required heating conditions can be easily designed by changing the size of the tubes and the density of the distribution.

(4) Si ₃ N ₄ refractory brick or SiC with good radiation
It was possible to use refractory bricks, increasing efficiency and saving energy.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical cross-sectional view showing an embodiment of the gas combustion flat burner of the present invention, and FIG. 2 is a schematic cross-sectional view of a conventional burning wall, where a is a general type and b is a modified type. FIG. 3 is a graph showing the temperature distribution within the luminous flame wall of a burning wall with a conventional structure. In the figure, 11... refractory layer, 12... air mixture chamber, 13... thin tube, 14... shielding plate, 16...
...Back surface, 18...Furnace inner surface, 22...Al ₂ O ₃ −SiO ₂
Castable or refractory brick, 23...Insulating material.

Claims (1)

[Scope of utility model registration request] Si ₃ N ₄ refractory or SiC refractory 21 on the furnace inner surface 18 side, Al ₂ O ₃ -SiO ₂ castable or refractory brick 22 in the middle, and heat insulating material 2 on the back side 16.
3 as a constituent member, and a large number of thin tubes 13 are embedded in the back surface 16 of the refractory layer 11,
This is a flat burner for gas combustion in which an air mixture chamber 12 is provided and a shielding plate 14 is attached inside the air mixture chamber 12.