Burner

Abstract

To provide a burner that uses ammonia as fuel and can secure radiation intensity and flame stability.SOLUTION: A burner uses fuel gas containing ammonia and combustion supporting gas of which oxygen concentration is 30% or greater and temperature is equal to or higher than a threshold value that is 100°C.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a burner.

Background Art

[0002] Burners that use fuel gas and supporting combustion gas are known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In industrial furnaces such as metal heating furnaces, glass melting furnaces, and aluminum melting furnaces, it is common to use a burner that burns fuel with an oxidizing agent as a heat source. As the fuel, various fossil fuels such as solid fuels such as pulverized coal, liquid fuels such as kerosene or heavy oil, or gaseous fuels such as natural gas or LPG are used. In industrial furnaces, the object to be heated is heated by the radiant heat transfer of the flame obtained by burning the fuel.

[0005] 2 When using fossil fuels, a large amount of CO will be contained in the combustion exhaust gas. Therefore, in recent years, it has been proposed to use ammonia.

[0006] Although ammonia has the characteristic that it does not generate CO even when burned, on the other hand, since it does not contain carbon, there are problems such as a decrease in the radiant intensity of the flame or instability of the flame due to a slow combustion rate. 2

[0007] Therefore, an object of the present invention is to provide a burner that uses ammonia as fuel and can ensure radiant intensity and flame stability.

Means for Solving the Problems

[0008] One aspect of the present invention is as follows.

[0009] [1] A burner using a fuel gas containing ammonia and a supporting combustion gas having an oxygen concentration of 30% or more and a temperature equal to or higher than a threshold value of 100°C.

[0010] [2] The burner according to [1], wherein the supporting combustion gas is heated to a temperature equal to or higher than the threshold value by exchanging heat with the combustion exhaust gas of the burner.

[0011] [3] The burner according to [2], further comprising a heat exchanger for heating the supporting combustion gas to a temperature equal to or higher than the threshold value by heat exchange with the combustion exhaust gas of the burner.

[0012] [4] A fuel gas supply pipe for supplying the fuel gas and ejecting the fuel gas from a fuel gas ejection hole at the tip, A burner according to any one of [1] to [3], further comprising a supporting combustion gas supply pipe provided so as to surround the fuel gas supply pipe on the radially outer side thereof, for supplying the supporting combustion gas and ejecting the supporting combustion gas from a supporting combustion gas ejection hole at the tip.

[0013] [5] The burner according to [4], having a burner body having a double pipe structure formed by the fuel gas supply pipe and the supporting combustion gas supply pipe.

[0014] [6] The fuel gas ejection hole is formed on the inner peripheral surface of the tip of the fuel gas supply pipe, When the inner diameter at the tip of the fuel gas supply pipe is d 1 and the outer diameter is D 1 and the inner diameter at a position where the distance from the tip is L 1 is d 2 , then 5×d 1 ≦L 1 ≦10×d 1 and at this position, d 1 <d2 and {(D 1 -d 1 ) / D 1}×100≦20, the burner according to [4] or [5].

[0015] [7] The pilot gas ejection hole is formed on the inner peripheral surface of the tip of the pilot gas supply pipe. Let the inner diameter at the tip of the pilot gas supply pipe be d 3 , and when the inner diameter at a position where the distance from the tip is L 2 is d 4 , 5×d 3 ≦L 2 ≦10×d 3 at the position where d 3 <d 4 and the tip of the fuel gas supply pipe is located on the base end side of the tip of the pilot gas supply pipe, when the distance from the tip of the fuel gas supply pipe to the tip of the pilot gas supply pipe is L 3 , L 3 <5×d 3 The burner according to any one of [4] to [6].

[0016] [8] A burner body having the fuel gas supply pipe and the pilot gas supply pipe, and a burner block having an opening in which the burner body is disposed, when the maximum outer diameter of the pilot gas supply pipe at the portion disposed in the opening is D 4 and the inner diameter at the tip of the opening is D 5 , D 4 ≦D 5 ≦1.1×D 4 and the tip of the pilot gas supply pipe is located on the base end side of the tip of the opening, when the distance from the tip of the opening to the tip of the pilot gas supply pipe is L 4 ​ 0.2 ≦ {(D 5 / 2) 2 × π} ÷ L 4 2 ≦ 0.5, the burner according to any one of [4] to [7].

Advantages of the Invention

[0017] According to the present invention, it is possible to provide a burner that uses ammonia as a fuel and can ensure radiation intensity and flame stability.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be exemplified with reference to the drawings.

[0020] As shown in FIGS. 1 to 2, in one embodiment of the present invention, the burner 1 uses a fuel gas containing ammonia and a supporting combustion gas having an oxygen concentration of 30% or more and a temperature equal to or higher than a threshold value of 100°C.

[0021] According to the above configuration, since the oxygen concentration of the supporting combustion gas is 30% or more and the temperature of the supporting combustion gas is equal to or higher than the threshold value (100°C), it is possible to realize the burner 1 that uses ammonia as the fuel gas and can ensure radiation intensity and flame stability.

[0022] The radiant intensity of the burner 1 and the stability of the flame are related to the flame temperature and the combustion rate, and the flame temperature and the combustion rate are related to the oxygen concentration and the temperature of the supporting combustion gas. For example, the relationship between the oxygen concentration of the oxidizer (supporting combustion gas) and the adiabatic theoretical flame temperature of fossil fuel (methane) and ammonia is as shown in Figure 3, and the relationship between the oxygen concentration of the oxidizer (supporting combustion gas) and the combustion rate of fossil fuel (methane) and ammonia is as shown in Figure 4. Thus, ammonia has a lower flame temperature and combustion rate than fossil fuel. Also, the flame temperature and the combustion rate increase as the temperature of the supporting combustion gas rises. In view of the above, it has been found that by setting the oxygen concentration of the supporting combustion gas to 30% or more and the temperature to the threshold value or more, sufficient radiant intensity and flame stability for practical use in an industrial furnace can be ensured.

[0023] CH, which is the main component of common fossil fuels 4 (methane) and NH 3 (ammonia) are compared as follows when considering their combustion chemical formulas. (1) CH 4 + 2O 2 + 8N 2 → CO 2 + 2H 2 O + 8N 2 (2) CH 4 + 2O 2 → CO 2 + 2H 2 O (3) NH 3 + 0.75O 2 + 3N 2 → 1.5H 2 O + 3.5N 2 (4) NH 3 + 0.75O 2 → 1.5H 2 O + 0.5N 2 Equation (1) is the case when CH 4 is burned in air. Equation (2) is the case when CH 4 is burned in oxygen. Equation (3) is the case when NH 3 is burned in air. Equation (4) is the case when NH3 when it is burned in oxygen.

[0024] CO contained in the right side of each formula 2 and H 2 O are known as radioactive gases, and these gases contribute to the radiation performance of the combustion flame. Comparing each formula, the concentration of each radioactive gas is as follows, and it can be seen that the radiation performance of the flame is improved by changing the oxidant from air to oxygen. However, in formula (2), the concentration of CO 2 in the exhaust gas increases. Also, in formula (3), the concentration of CO 2 is zero, and the concentration of the radioactive gas is higher than that in formula (1). Furthermore, in formula (4) where the oxidant is changed from air to oxygen, the concentration of the radioactive gas is further improved. Therefore, it can be seen that increasing the oxygen concentration of the oxidant is effective for ammonia with a low flame temperature.

Table 1

[0025] The fuel gas is not particularly limited as long as it contains ammonia, but it is preferably mainly composed of ammonia (that is, the ammonia component exceeds 50% and is 100% or less). The component of the supporting combustion gas is not particularly limited as long as the oxygen concentration is 30% or more, but it is preferable that the supporting combustion gas uses oxygen-enriched air and the oxygen concentration in the supporting combustion gas is 30% or more.

[0026] The supporting combustion gas is heated to above the threshold value by exchanging heat with the combustion exhaust gas of burner 1. According to the above configuration, the supporting combustion gas can be efficiently heated by utilizing the heat of the combustion exhaust gas of burner 1.

[0027] The burner 1 has a fuel gas supply pipe 2a that supplies fuel gas (preferably without pre-mixing with oxygen) and ejects it from the fuel gas ejection holes 2a1 at the tip, and a fuel gas supply pipe 2a (preferably the tip of the fuel gas supply pipe 2a as shown in the figure) is surrounded radially outside the fuel gas supply pipe 2a (preferably, as shown in the figure, a combustion-supporting gas flow path is formed between the outer peripheral surface of the fuel gas supply pipe 2a and the inner peripheral surface of the combustion-supporting gas supply pipe 2b that is spaced apart from the outer peripheral surface over the entire circumference). It is provided with a combustion-supporting gas supply pipe 2b that supplies combustion-supporting gas (preferably without pre-mixing with fuel) and ejects it from the combustion-supporting gas ejection holes 2b1 at the tip. According to the above configuration, since fuel gas ejected from the fuel gas ejection holes 2a1 and combustion-supporting gas ejected from the combustion-supporting gas ejection holes 2b1 can be supplied to the burner flame, stable combustion of ammonia can be realized while suppressing flashback. The fuel gas supply pipe 2a preferably surrounds the central axis O of the combustion-supporting gas supply pipe 2b as shown in the figure, and more preferably is provided coaxially with the combustion-supporting gas supply pipe 2b as shown in the figure. The inner peripheral surface and outer peripheral surface of the fuel gas supply pipe 2a at the tip of the fuel gas supply pipe 2a and the inner peripheral surface and outer peripheral surface of the combustion-supporting gas supply pipe 2b at the tip of the combustion-supporting gas supply pipe 2b are circular in this embodiment, but are not limited thereto.

[0028] The burner 1 has a burner body 2 with a double-tube structure composed of a fuel gas supply pipe 2a and a combustion-supporting gas supply pipe 2b. According to the above configuration, radiation intensity and flame stability can be ensured with a simple structure.

[0029] The burner 1 has a heat exchanger 6 that heats the combustion-supporting gas to a threshold value or higher by heat exchange with the combustion exhaust gas of the burner 1. According to the above configuration, the heat exchanger 6 can efficiently heat the combustion-supporting gas.

[0030] The heat exchanger 6 is provided upstream of the secondary combustion gas supply pipe 2b. According to the above configuration, the secondary combustion gas before being supplied to the secondary combustion gas supply pipe 2b is heated to a threshold value or higher by the heat exchanger 6, so that the radiation intensity and the flame stability can be ensured well. In this case, the burner 1 may be configured to have a combustion exhaust gas path 7 for supplying combustion exhaust gas to the heat exchanger 6 and a secondary combustion gas path 8 for supplying the secondary combustion gas heated by the heat exchanger 6 to the burner body 2 (secondary combustion gas supply pipe 2b).

[0031] The effect of ensuring the radiation intensity and the flame stability increases as the temperature of the secondary combustion gas increases. The upper limit threshold value of the temperature of the secondary combustion gas is not particularly limited from the viewpoint of ensuring the radiation intensity and the flame stability. However, when using a metal heat exchanger 6, for example, it is 800 °C in consideration of the durability of the material of the heat exchanger 6 and the performance of the heat exchanger 6.

[0032] The fuel gas ejection holes 2a1 are formed on the inner peripheral surface of the tip of the fuel gas supply pipe 2a. Let the inner diameter at the tip of the fuel gas supply pipe 2a be d 1 and the outer diameter be D 1 and the inner diameter at the position where the distance from the tip is L 1 be d 2 . When 5×d 1 ≦L 1 ≦10×d 1 , d 1 <d 2 and {(D 1 -d 1 ) / D 1}×100≦20. According to the above configuration, since at the position where 5×d 1 ≦L 1 ≦10×d 1 , d 1 <d 2 , the flow path of the fuel gas becomes narrower toward the fuel gas ejection holes 2a1 in the vicinity of the fuel gas ejection holes 2a1, so that the supply pressure of the fuel gas increases toward the fuel gas ejection holes 2a1. As a result, the supply pressure of the fuel gas at the fuel gas ejection holes 2a1 is equalized, and thus the uniformity of the ejection amount of the fuel gas at the fuel gas ejection holes 2a1 can be improved. Also, {(D 1 -d 1 ) / D1 By being 100×{([[ID=]] 1 ÷[[ID=]] 1 )}≤20, the distance between the outer peripheral surface of the fuel gas flow path and the inner peripheral surface of the secondary combustion supporting gas flow path at the tip of the fuel gas supply pipe 2a becomes sufficiently small in practical use, so that rapid mixing of the fuel gas and the secondary combustion supporting gas can be achieved. Therefore, good flame stability due to good mixing can be realized.

[0033] The secondary combustion supporting gas ejection holes 2b1 are formed on the inner peripheral surface at the tip of the secondary combustion supporting gas supply pipe 2b. Let the inner diameter at the tip of the secondary combustion supporting gas supply pipe 2b be d 3 and the inner diameter at a position where the distance from the tip is L 2 be d 4 . When 5×d 3 ≤L 2 ≤10×d 3 , d 3 <d 4 . The tip of the fuel gas supply pipe 2a is located on the base end side of the tip of the secondary combustion supporting gas supply pipe 2b. Let the distance from the tip of the fuel gas supply pipe 2a to the tip of the secondary combustion supporting gas supply pipe 2b be L 3 . When L 3 <5×d 3 , according to the above configuration, since d 3 ≤L 2 ≤10×d 3 and d 3 <d 4 , the flow path of the secondary combustion supporting gas becomes narrower toward the secondary combustion supporting gas ejection holes 2b1, so the supply pressure of the secondary combustion supporting gas increases toward the secondary combustion supporting gas ejection holes 2b1. As a result, the supply pressure of the secondary combustion supporting gas at the secondary combustion supporting gas ejection holes 2b1 is equalized, and the uniformity of the ejection amount of the secondary combustion supporting gas at the secondary combustion supporting gas ejection holes 2b1 can be improved. Also, since the tip of the fuel gas supply pipe 2a is located on the base end side of the tip of the secondary combustion supporting gas supply pipe 2b and L 3 <5×d 3 , the mixing chamber 3 can be formed while suppressing the possibility of flashback, so that better flame stability due to even better mixing can be realized. In this embodiment, the fuel gas supply pipe 2a and the secondary combustion supporting gas supply pipe 2b each extend linearly in parallel to the central axis O in the range where at least 0≤L 2 ≤10×d 3 .

[0034] The burner 1 has a burner body 2 having a fuel gas supply pipe 2a and a combustion-supporting gas supply pipe 2b, and a burner block 4 having an opening 4a in which the burner body 2 is arranged (preferably coaxially as shown in the figure). The maximum outer diameter of the combustion-supporting gas supply pipe 2b at the portion arranged in the opening 4a is D 4 Let the inner diameter at the tip of the opening 4a be d 5 When D 4 ≦d 5 ≦1.1×D 4 That is, the tip of the combustion-supporting gas supply pipe 2b is located on the base end side with respect to the tip of the opening 4a. Let the distance from the tip of the opening 4a to the tip of the combustion-supporting gas supply pipe 2b be L 4 When 0.2≦{(d 5 / 2) 2 ×π}÷L 4 2 ≦0.5. According to the above configuration, since D 4 ≦d 5 ≦1.1×D 4 That is, the tip of the combustion-supporting gas supply pipe 2b is located on the base end side with respect to the tip of the opening 4a, and 0.2≦{(d 5 / 2) 2 ×π}÷L 4 2 ≦0.5, a good combustion chamber 5 can be formed by the opening 4a of the burner block 4, and the burner body 2 can be protected from radiant heat from the installation environment such as an industrial furnace. Note that the burner 1 is not limited to the configuration having the burner block 4. For example, instead of or in addition to the burner block 4, a configuration having a water-cooled jacket may be used. The opening 4a is configured as a circular through-hole in the present embodiment, but is not limited thereto.

[0035] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

Explanation of reference numerals

[0036] 1 Burner 2 Burner body 2a Fuel gas supply pipe 2a1 Fuel gas ejection hole 2b Combustion-supporting gas supply pipe 2b1 Combustion-supporting gas ejection hole 3 Mixing chamber 4 Burner block 4a Opening 5 Combustion chamber 6 Heat exchanger 7 Combustion exhaust gas path 8 Combustion-supporting gas path d 1 Inner diameter d 2 Inner diameter d 3 Inner diameter d 4 Inner diameter d 5 Inner diameter D 1 Outer diameter D 2 Outer diameter D 3 Outer diameter D 4 Outer diameter L 1 Distance L 2 Distance L 3 Distance L 4 Distance O Central axis

Claims

1. A burner using a fuel gas containing ammonia and a combustion supporting gas having an oxygen concentration of 30% or more and a temperature equal to or higher than a threshold value of 100°C.

2. The burner according to claim 1 , wherein the combustion supporting gas is heated to above the threshold value by heat exchange with a combustion exhaust gas of the burner.

3. 3. The burner according to claim 2, further comprising a heat exchanger for heating the combustion supporting gas above the threshold value by heat exchange with the combustion exhaust gas of the burner.

4. a fuel gas supply pipe through which the fuel gas is supplied and the fuel gas is ejected from a fuel gas ejection hole at the tip of the fuel gas supply pipe; 2. The burner according to claim 1, further comprising a combustion-supporting gas supply pipe provided radially outside the fuel gas supply pipe so as to surround the fuel gas supply pipe, for supplying the combustion-supporting gas and ejecting the gas from a combustion-supporting gas ejection hole at a tip thereof.

5. 5. The burner according to claim 4, further comprising a burner body having a double-pipe structure including said fuel gas supply pipe and said combustion-supporting gas supply pipe.

6. the fuel gas ejection hole is formed on an inner circumferential surface of the tip of the fuel gas supply pipe, The inner diameter of the fuel gas supply pipe at the tip is d １ The outer diameter is D １ The distance from the tip is L １ The inner diameter at the position where ２ When I said that, 5×d １ ≦L １ ≦10×d １ At the position where １ <d ２ and {(D １ -d １ ) / D １ 5. The burner according to claim 4, wherein:}×100≦20.

7. the combustion supporting gas ejection hole is formed on the inner peripheral surface of the tip of the combustion supporting gas supply pipe, The inner diameter of the tip of the combustion supporting gas supply pipe is d ３ The distance from the tip is L ２ The inner diameter at the position where ４ When I said that, 5×d ３ ≦L ２ ≦10×d ３ At the position where ３ <d ４ and the tip of the fuel gas supply pipe is located closer to the base end than the tip of the combustion assisting gas supply pipe, The distance from the tip of the fuel gas supply pipe to the tip of the combustion supporting gas supply pipe is L ３ When I said that, L ３ <5×d ３ 5. The burner according to claim 4, wherein:

8. a burner body having the fuel gas supply pipe and the combustion supporting gas supply pipe; a burner block having an opening in which the burner body is disposed; The maximum outer diameter of the combustion supporting gas supply pipe at the portion disposed at the opening is D ４ The inner diameter at the tip of the opening is D ５ When I said that, D ４ ≦D ５ ≦1.1×D ４ and The tip of the combustion supporting gas supply pipe is located on the base end side of the tip of the opening, The distance from the tip of the opening to the tip of the combustion supporting gas supply pipe is L ４ When I said that, 0.2≦{(D ５ / 2) ２ ×π}÷L ４ ２ 5. The burner of claim 4, wherein the ratio of the stoichiometric ratio of the burner to the total stoichiometric ratio is ≦0.5.

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