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, thermally decomposes part or all of the ammonia into nitrogen molecules and hydrogen molecules and burns the fuel gas in the state where the thermal decomposition has been performed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a burner.

Background Art

[0002] A burner that uses fuel gas and a supporting combustion gas is 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 oxidizer 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 an industrial furnace, 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] 2 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.

[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 that uses a fuel gas containing ammonia and a supporting combustion gas with an oxygen concentration of 30% or more, thermally decomposes some or all of the nitrogen molecules and hydrogen molecules of the ammonia, and burns the fuel gas in a state where the thermal decomposition has been performed.

[0010] [2] The burner according to [1], wherein the thermal decomposition of the ammonia is performed by performing heat exchange between the fuel gas and the combustion exhaust gas of the burner.

[0011] [3] The burner according to [2], further comprising a heat exchanger that performs the heat exchange between the fuel gas and the combustion exhaust gas of the burner.

[0012] [4] A fuel gas supply pipe that supplies the fuel gas and ejects it 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 that is provided so as to surround the fuel gas supply pipe on the radially outer side thereof, supplies the supporting combustion gas, and ejects it from a supporting combustion gas ejection hole at the tip.

[0013] [5] The burner according to [4], having a burner body with 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 × d1 At the position where it becomes d 1 <d 2 and {(D 1 -d 1 ) / D 1}×100 ≦ 20, the burner according to [4] or [5].

[0015] [7] The secondary fuel gas ejection holes are formed on the inner peripheral surface of the tip of the secondary fuel gas supply pipe, Let the inner diameter at the tip of the secondary fuel gas supply pipe be d 3 and the inner diameter at the position where the distance from the tip is L 2 be d 4 When 5×d 3 ≦L 2 ≦10×d 3 At the position where it becomes 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 secondary fuel gas supply pipe, Let the distance from the tip of the fuel gas supply pipe to the tip of the secondary fuel gas supply pipe be L 3 When 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 secondary fuel gas supply pipe, and a burner block having an opening in which the burner body is disposed, Let the maximum outer diameter of the secondary fuel gas supply pipe at the portion disposed in the opening be D 4 and the inner diameter at the tip of the opening be D 5 When D 4 ≦D 5 ≦1.1×D 4 and The tip of the secondary fuel gas supply pipe is located on the base end side of the tip of the opening, Let the distance from the tip of the opening to the tip of the secondary combustion gas supply pipe be L 4 When 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

Figure 5

Modes for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be illustrated 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 secondary combustion gas with an oxygen concentration of 30% or more, thermally decomposes some or all of the nitrogen molecules and hydrogen molecules of ammonia, and burns the fuel gas in a state where thermal decomposition has occurred.

[0021] According to the above configuration, by burning a fuel gas in a state where part or all of the ammonia is pyrolyzed with a supporting combustion gas having an oxygen concentration of 30% or more, it is possible to realize the burner 1 that can use ammonia in the fuel gas and ensure the radiation intensity and flame stability. The fuel gas is not particularly limited as long as it contains ammonia, but it is preferably mainly composed of ammonia in the state before pyrolysis (that is, the ammonia component exceeds 50% and is 100% or less). The supporting combustion gas is not particularly limited as long as the oxygen concentration is 30% or more, but it is preferably configured to use oxygen-enriched air so that the oxygen concentration in the supporting combustion gas is 30% or more.

[0022] The radiation intensity and flame stability of the burner 1 are related to the flame temperature and combustion speed, and the flame temperature and combustion speed are related to the oxygen concentration of the supporting combustion gas and the pyrolysis rate of ammonia in the fuel gas. For example, the relationship between the oxygen concentration of the oxidant (supporting combustion gas) and the adiabatic theoretical flame temperature of fossil fuel (methane) and ammonia is as shown in FIG. 3, and the relationship between the oxygen concentration of the oxidant (supporting combustion gas) and the combustion speed of fossil fuel (methane) and ammonia is as shown in FIG. 4. The relationship between the pyrolysis rate of ammonia and the adiabatic theoretical flame temperature and combustion speed of ammonia in the pyrolyzed state and the adiabatic theoretical flame temperature and combustion speed of fossil fuel (methane) is as shown in FIG. 5. As shown in FIGS. 3 to 4, ammonia has a lower flame temperature and combustion speed than fossil fuel. Also, as shown in FIG. 5, as the pyrolysis rate of ammonia increases, the adiabatic theoretical flame temperature and combustion speed of ammonia in the pyrolyzed state increase. For example, the combustion speed when the pyrolysis rate of ammonia is 65.5% is equivalent to the combustion speed when fossil fuel (methane) is burned in air, and the adiabatic theoretical flame temperature when the pyrolysis rate of ammonia is 89.4% is equivalent to the adiabatic theoretical flame temperature when fossil fuel (methane) is burned in air. 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 burning the fuel gas in a state where part or all of the ammonia has been pyrolyzed, it is possible to ensure sufficient radiation intensity and flame stability for practical use in an industrial furnace. The pyrolysis rate of ammonia during combustion is not particularly limited, but it may be, for example, 65.5% or more as described above, or 89.4% or more as described above.

[0023] CH, the main component of common fossil fuels 4 (methane) and NH 3 (ammonia) when burned, the chemical formulas are compared as follows. (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 NH 3 is burned in oxygen.

[0024] CO 2 and H 2 O included in the right side of each equation are known as radioactive gases, and these gases contribute to the radiation performance of the combustion flame. Comparing each equation, the concentrations of each radioactive gas are as follows, and it can be seen that changing the oxidant from air to oxygen improves the radiation performance of the flame. However, in Equation (2), the concentration of CO 2 in the exhaust gas increases. Also, in Equation (3), CO 2The concentration is zero, and the concentration of the radioactive gas is greater than that in Equation (1). Furthermore, in Equation (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 for ammonia with a low flame temperature, it is effective to increase the oxygen concentration of the oxidant.

Table 1

[0025] The burner 1 performs thermal decomposition of ammonia by performing heat exchange between the fuel gas and the combustion exhaust gas of the burner 1. According to the above configuration, the fuel gas can be efficiently heated using the heat of the combustion exhaust gas of the burner 1 and then thermally decomposed.

[0026] Ammonia can be thermally decomposed into nitrogen molecules and hydrogen molecules at 400 °C or higher in a thermal equilibrium state. Therefore, it is preferable that the burner 1 is configured to perform thermal decomposition of ammonia by performing heat exchange between the fuel gas and the combustion exhaust gas of the burner at 400 °C or higher. The equation representing the thermal decomposition of ammonia is as follows. (5)NH 3 →0.5N 2 +1.5H 2

[0027] The burner 1 has a heat exchanger 6 that performs heat exchange between the fuel gas and the combustion exhaust gas of the burner 1. According to the above configuration, heat exchange can be efficiently performed by the heat exchanger 6.

[0028] The burner 1 has a fuel gas supply pipe 2a that supplies fuel gas (preferably without pre-mixing with oxygen) and discharges it from the fuel gas discharge holes 2a1 at the tip, and a fuel gas supply pipe 2a that surrounds the fuel gas supply pipe 2a (preferably the tip of the fuel gas supply pipe 2a as shown in the figure) on the radially outer side of 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). The burner 1 also has a combustion-supporting gas supply pipe 2b that supplies combustion-supporting gas (preferably without pre-mixing with fuel) and discharges it from the combustion-supporting gas discharge holes 2b1 at the tip. According to the above configuration, fuel gas discharged from the fuel gas discharge holes 2a1 and combustion-supporting gas discharged from the combustion-supporting gas discharge holes 2b1 can be supplied to the burner flame, so stable combustion of ammonia can be achieved 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.

[0029] The burner 1 has a burner body 2 with a double-pipe 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.

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

[0031] The fuel gas discharge holes 2a1 are formed on the inner peripheral surface at the tip of the fuel gas supply pipe 2a, and the inner diameter at the tip of the fuel gas supply pipe 2a is d 1Let the outer diameter be D 1 Let the inner diameter at the position where the distance from the tip is L 1 be d 2 When it is so, 5×d 1 ≦L 1 ≦10×d 1 At the position where this holds, d 1 <d 2 is the case, and {(D 1 -d 1 ) / D 1}×100≦20. According to the above configuration, 5×d 1 ≦L 1 ≦10×d 1 At the position where this holds, d 1 <d 2 is the case, so that the fuel gas flow path near the fuel gas ejection hole 2a1 becomes narrower toward the fuel gas ejection hole 2a1, and thus the supply pressure of the fuel gas increases toward the fuel gas ejection hole 2a1. As a result, the supply pressure of the fuel gas at the fuel gas ejection hole 2a1 is made uniform, and therefore the uniformity of the ejection amount of the fuel gas at the fuel gas ejection hole 2a1 can be improved. Also, since {(D 1 -d 1 ) / D 1}×100≦20, at the tip of the fuel gas supply pipe 2a, 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 becomes sufficiently small in practical use, and thus prompt 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.

[0032] 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 Let the inner diameter at the position where the distance from the tip is L 2 be d 4 When it is so, 5×d 3 ≦L 2 ≦10×d 3 At the position where this holds, d 3 <d 4 is the case, and the tip of the fuel gas supply pipe 2a is located on the base end side with respect to 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 it is so, L 3<5×d 3 is satisfied. According to the above configuration, 5×d 3 ≦L 2 ≦10×d 3 At the position where this holds, d 3 <d 4 is satisfied, so the flow path of the supporting combustion gas becomes narrower toward the supporting combustion gas ejection hole 2b1. As a result, the supply pressure of the supporting combustion gas increases toward the supporting combustion gas ejection hole 2b1. Consequently, the supply pressure of the supporting combustion gas at the supporting combustion gas ejection hole 2b1 is equalized, and thus the uniformity of the ejection amount of the supporting combustion gas at the supporting combustion gas ejection hole 2b1 can be improved. Further, the tip of the fuel gas supply pipe 2a is located on the base end side with respect to the tip of the supporting combustion gas supply pipe 2b, and L 3 <5×d 3 is satisfied, so the mixing chamber 3 can be formed while suppressing the possibility of flashback, and thus even better flame stability due to even better mixing can be realized. In this embodiment, the fuel gas supply pipe 2a and the supporting combustion gas supply pipe 2b each extend linearly and parallel to the central axis O in the range where at least 0≦L 2 ≦10×d 3 holds.

[0033] The burner 1 includes a burner body 2 having a fuel gas supply pipe 2a and a supporting combustion gas supply pipe 2b, and a burner block 4 having an opening 4a in which the burner body 2 is disposed (preferably coaxially as shown in the figure). Let the maximum outer diameter of the supporting combustion gas supply pipe 2b at the portion disposed in the opening 4a be D 4 and the inner diameter at the tip of the opening 4a be d 5 . When this is the case, D 4 ≦d 5 ≦1.1×D 4 is satisfied, and the tip of the supporting combustion 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 supporting combustion gas supply pipe 2b be L 4 . When this is the case, 0.2≦{(d 5 / 2) 2 ×π}÷L 4 2 ≦0.5. According to the above configuration, D 4 ≦d 5 ≦1.1×D 4and the tip of the combustion-supporting gas supply pipe 2b is located on the base end side of the tip of the opening 4a, and 0.2 ≦ {(d 5 / 2) 2 × π} ÷ L 4 2 ≦ 0.5, the burner main body 2 can be protected from the radiant heat from the installation environment such as an industrial furnace while forming a good combustion chamber 5 by the opening 4a of the burner block 4. Note that the burner 1 is not limited to the configuration having the burner block 4, and for example, instead of or in addition to the burner block 4, it may have a water-cooled jacket. The opening 4a is configured as a circular through-hole in the present embodiment, but is not limited thereto.

[0034] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and the above-described embodiments can be variously modified without departing from the gist of the present invention.

Explanation of reference numerals

[0035] 1 Burner 2 Burner main 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 Fuel 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 L1 Distance L 2 Distance L 3 Distance L 4 Distance O Central axis

Claims

1. A burner that uses a fuel gas containing ammonia and a combustion supporting gas with an oxygen concentration of 30% or more, thermally decomposes a part or all of the ammonia into nitrogen molecules and hydrogen molecules, and combusts the fuel gas in the thermally decomposed state.

2. The burner according to claim 1 , wherein the thermal decomposition of the ammonia is carried out by heat exchange between the fuel gas and a combustion exhaust gas of the burner.

3. 3. The burner according to claim 2, further comprising a heat exchanger for effecting said heat exchange between said fuel gas and said burner flue gas.

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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