Combustor

Abstract

To provide a combustor capable of generating the swirl flow of fuel gas and oxidizing gas in a combustion pipe while simplifying the construction and facilitating the machining of a gas introduction part which introduces the fuel gas and the oxidizing gas into the combustion pipe.SOLUTION: A combustor 4 includes a cylindrical combustion pipe 20 having one end opened and the other end to which a closing wall 23 is fixed, a gas introduction pipe 21 mounted to the combustion pipe 20 for introducing ammonia gas and air into the combustion pipe 20, and an ignition plug 22 for igniting the ammonia gas introduced into the combustion pipe 20. In the gas introduction pipe 21 at its end on the side which is connected to combustion pipe 20, a gas outlet part 21a is provided for delivering the ammonia gas and the air into the combustion pipe 20. The gas introduction pipe 21 is protruded toward the inside of the combustion pipe 20 with respect to an insertion hole 24 of the combustion pipe 20 in the tangential direction of an inner peripheral face 20b of the combustion pipe 20 so that the gas outlet part 21a is stored in the combustion pipe 20.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a combustor.

Background Art

[0002] As a conventional combustor, for example, a tubular flame burner as described in Patent Document 1 is known. The tubular flame burner described in Patent Document 1 includes a cylindrical combustion tube having a closed base end and an open tip end that forms a combustion chamber, a plurality of flat channels that supply combustion air to the combustion chamber, and a plurality of fuel gas supply channels that are connected to the flat channels and supply fuel gas to the combustion chamber. A plurality of slits that open along the axial direction of the combustion tube are formed on the side surface of the base end side of the combustion tube. The flat channels are connected to the slits and are wide along the width direction corresponding to the axial direction of the combustion chamber. The slits are configured to eject combustion air and fuel gas in a mixed state tangentially to the inner surface of the combustion chamber. When the mixed combustion air and fuel gas are ejected from the slits tangentially to the inner surface of the combustion chamber, the mixed gas swirls along the inner surface of the combustion chamber, and the fuel gas burns in a state where a swirling flame (tubular flame) is formed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above prior art, an ideal swirling flow of a mixed gas of fuel gas and combustion air (oxidizing gas) occurs in the combustion chamber, so that the fuel gas is easily burned. However, as a gas introduction part for introducing fuel gas and combustion air into the combustion chamber, it is necessary to form fine slits in the combustion tube. For this reason, the structure of the gas introduction part becomes complicated and the processing of the gas introduction part becomes difficult.

[0005] An object of the present invention is to provide a combustor that can generate a swirling flow of fuel gas and oxidizing gas within a combustion tube while simplifying the structure and facilitating the processing of a gas inlet section that introduces a fuel gas and an oxidizing gas into the combustion tube. [Means for solving the problem]

[0006] A combustor according to one embodiment of the present invention comprises a cylindrical combustion tube having an open end and a blocking wall fixed to the other end, a gas inlet tube attached to the combustion tube for introducing a fuel gas and an oxidizing gas into the combustion tube, and an ignition unit attached to the blocking wall for igniting the fuel gas introduced into the combustion tube by the gas inlet tube, the combustion tube being provided with an insertion hole into which the gas inlet tube is inserted, and the end of the gas inlet tube connected to the combustion tube being provided with a gas outlet portion for directing the fuel gas and the oxidizing gas into the combustion tube, the gas inlet tube protruding in a tangent direction to the inner surface of the combustion tube toward the inside of the combustion tube relative to the insertion hole so that the gas outlet portion is accommodated within the combustion tube.

[0007] In such a combustor, when the fuel gas and the oxidizing gas are introduced into the cylindrical combustion tube by the gas introduction tube, the mixed gas of the fuel gas and the oxidizing gas flows through the combustion tube toward the blocking wall. Then, the fuel gas in the mixed gas is ignited and burned by the ignition unit, and the combustion gas is generated. Then, the combustion gas flows to the open side of the combustion tube. Here, the gas introduction tube protrudes in the tangential direction of the inner peripheral surface of the combustion tube toward the inside of the combustion tube with respect to the insertion hole so that the gas outlet part is accommodated in the combustion tube. As a result, when the fuel gas and the oxidizing gas are introduced into the combustion tube, a swirling flow (tubular flow) of the fuel gas and the oxidizing gas is generated in the combustion tube. Therefore, the fuel gas is ignited in the swirling flow state, and a tubular flame is formed. In addition, when the gas introduction tube is attached to the combustion tube, it is sufficient to perform simple hole processing on the combustion tube to form an insertion hole, and insert the gas introduction tube into the insertion hole. This simplifies the structure and facilitates processing of the gas introduction part that introduces the fuel gas and the oxidizing gas into the combustion tube.

[0008] The gas introduction pipe may have a cross-sectional area such that when the mixed gas of the fuel gas and the oxidizing gas is introduced into the combustion pipe from the gas outlet portion, the flow velocity is 3 m / s to 25 m / s with respect to the flow rate of the mixed gas. In such a configuration, since the combustible range of the fuel gas with respect to the excess ratio of the oxidizing gas becomes wider, the fuel gas is more likely to burn stably.

[0009] The gas introduction pipe may have a circular cross-sectional shape, and the ratio of the inner diameter of the gas introduction pipe to the inner diameter of the combustion pipe may be 0.30 to 0.45. In such a configuration, especially when the flow rate of the fuel gas supplied into the combustion pipe is large, the combustible range of the fuel gas with respect to the excess ratio of the oxidizing gas becomes even wider. Therefore, the fuel gas is even more likely to burn stably.

[0010] The combustion pipe may have a main body portion and a tapered portion that tapers from the main body portion toward the closing wall. In such a configuration, in the vicinity of the ignition portion, the symmetry of the flow velocity of the mixed gas with respect to the axial direction of the combustion pipe is improved. Therefore, the fuel gas is even more likely to burn stably.

[0011] The insertion hole is provided in the main body portion, and the difference between the outer diameter radius of the base end of the tapered portion and the outer diameter radius of the tip of the tapered portion may be equal to or less than the inner diameter radius of the main body portion. In such a configuration, especially when the flow rate of the fuel gas supplied into the combustion pipe is large, the combustible range of the fuel gas with respect to the excess ratio of the oxidizing gas becomes even wider. Therefore, the fuel gas is even more likely to burn stably.

Advantages of the Invention

[0012] According to the present invention, it is possible to generate a swirling flow of the fuel gas and the oxidizing gas in the combustion pipe while simplifying the structure and facilitating the processing of the gas introduction portion for introducing the fuel gas and the oxidizing gas into the combustion pipe.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Mode for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and duplicate descriptions are omitted.

[0015] FIG. 1 is a schematic configuration diagram showing a reforming system including a combustor according to the first embodiment of the present invention. In FIG. 1, the reforming system 1 includes an ammonia gas supply source 2, an air supply source 3, the combustor 4 of the present embodiment, and a reformer 5.

[0016] The ammonia gas supply source 2 generates ammonia gas (NH3 gas) which is the fuel gas. Although not particularly shown in the drawings, the ammonia gas supply source 2 has an ammonia tank for storing ammonia in a liquid state and a vaporizer for vaporizing the liquid ammonia to generate ammonia gas.

[0017] The air supply source 3 generates air which is an oxidizing gas. As the air supply source 3, for example, a blower or the like is used.

[0018] The combustor 4 burns the ammonia gas generated by the ammonia gas supply source 2 to generate high-temperature combustion gas. The combustor 4 will be described in detail later.

[0019] The reformer 5 is connected to the combustor 4. The reformer 5 is connected to the combustor 4 directly or via a connecting pipe. The reformer 5 generates a reformed gas containing hydrogen by reforming the ammonia gas using the heat generated by burning the ammonia gas.

[0020] The reformer 5 has an ATR catalyst 5a. The ATR catalyst 5a is an autothermal reforming catalyst that burns ammonia gas with the heat of the combustion gas generated by the combustor 4 and reforms the ammonia gas by decomposing it into hydrogen with the combustion heat (self-heat) of the ammonia gas. The ATR catalyst 5a has, for example, a honeycomb structure.

[0021] The ATR catalyst 5a burns ammonia gas in a temperature range of about 200°C to 400°C, for example, and reforms ammonia gas in a temperature range higher than the combustion temperature of ammonia gas (for example, about 250°C to 500°C). As the ATR catalyst 5a, for example, a cobalt-based catalyst, a rhodium-based catalyst, a ruthenium-based catalyst, a palladium-based catalyst, or the like is used.

[0022] Note that instead of the ATR catalyst 5a, the reformer 5 may separately have a combustion catalyst for burning ammonia gas and a reforming catalyst for decomposing ammonia gas into hydrogen.

[0023] Further, the reforming system 1 includes air flow paths 6 and 7, throttle valves 8 and 9, ammonia gas flow paths 10 and 11, and injectors 12 and 13.

[0024] The air flow path 6 connects the air supply source 3 and the combustor 4. The air flow path 6 is a flow path through which the air generated at the air supply source 3 flows toward the combustor 4. The air flow path 7 connects the air supply source 3 and the reformer 5. The air flow path 7 is a flow path through which the air generated at the air supply source 3 flows toward the reformer 5.

[0025] The throttle valve 8 is disposed in the air flow path 6. The throttle valve 8 is a flow rate control valve that controls the flow rate of the air supplied to the combustor 4. The throttle valve 9 is disposed in the air flow path 7. The throttle valve 9 is a flow rate control valve that controls the flow rate of the air supplied to the reformer 5.

[0026] The ammonia gas flow path 10 connects the ammonia gas supply source 2 and the injector 12. The ammonia gas flow path 10 is a flow path through which the ammonia gas generated at the ammonia gas supply source 2 flows toward the injector 12. The ammonia gas flow path 11 connects the ammonia gas supply source 2 and the injector 13. The ammonia gas flow path 11 is a flow path through which the ammonia gas generated at the ammonia gas supply source 2 flows toward the injector 13.

[0027] The injector 12 is a fuel injection valve that injects ammonia gas toward the combustor 4. The injector 12 injects ammonia gas between the throttle valve 8 and the combustor 4 in the air flow path 6. For this reason, ammonia gas and air flow on the upstream side of the combustor 4 in the air flow path 6.

[0028] The injector 13 is a fuel injection valve that injects ammonia gas toward the reformer 5. The injector 13 injects ammonia gas between the throttle valve 9 and the reformer 5 in the air flow path 7. For this reason, ammonia gas and air flow on the upstream side of the reformer 5 in the air flow path 7.

[0029] The reformer 5 is connected to the hydrogen utilization device 15 via the reformed gas flow path 14. The reformed gas flow path 14 is a flow path through which the reformed gas generated by the reformer 5 flows toward the hydrogen utilization device 15.

[0030] The hydrogen utilization device 15 is a device that utilizes hydrogen contained in the reformed gas. Examples of the hydrogen utilization device 15 include an ammonia engine or an ammonia gas turbine using ammonia gas as fuel, or a fuel cell that generates electricity by chemically reacting hydrogen and oxygen in the air.

[0031] Figure 2 is a perspective view of the combustor 4. Figure 3 is a cross-sectional view of the combustor 4. Figure 4 is a cross-sectional view taken along line IV-IV of Figure 3. In Figures 2 to 4, the combustor 4 of the present embodiment is a tubular flame burner.

[0032] The combustor 4 includes a combustion tube 20, a gas introduction tube 21 that introduces ammonia and air into the combustion tube 20, and a spark plug 22 that ignites the ammonia gas introduced into the combustion tube 20 by the gas introduction tube 21.

[0033] The combustion tube 20 and the gas introduction tube 21 are formed of a metal material such as stainless steel that has corrosion resistance against ammonia gas. The combustion tube 20 and the gas introduction tube 21 have a cylindrical shape (circular cross-section). The circular cross-section means that the cross-section cut perpendicular to the axial direction of the combustion tube 20 and the gas introduction tube 21 is circular. The circular shape here includes not only a true circular shape but also an elliptical shape.

[0034] One end of the combustion tube 20 is open. That is, one end of the combustion tube 20 is an open end 20a. The other end of the combustion tube 20 is closed. A circular closing wall 23 is fixed to the other end of the combustion tube 20.

[0035] One end of the gas introduction pipe 21 is connected to the combustion tube 20. That is, one end of the gas introduction pipe 21 is the end on the side where the gas introduction pipe 21 is connected to the combustion tube 20. The other end of the gas introduction pipe 21 is connected to the above air flow path 6. The gas introduction pipe 21 is bent in a substantially L shape so as to extend along the axial direction of the combustion tube 20.

[0036] The combustion tube 20 is provided with an insertion hole 24 having a circular cross-section into which the gas introduction pipe 21 is inserted. The insertion hole 24 is arranged at the central portion in the axial direction of the combustion tube 20. The insertion hole 24 is provided at a position such that the gas introduction pipe 21 is inserted into the combustion tube 20 in a tangential direction with respect to the inner peripheral surface 20b of the combustion tube 20.

[0037] A mixed gas of ammonia gas and air flows inside the gas introduction pipe 21. A gas outlet portion 21a for leading the mixed gas of ammonia gas and air into the combustion tube 20 is provided at one end of the gas introduction pipe 21. The gas introduction pipe 21 protrudes in a tangential direction with respect to the inner peripheral surface 20b of the combustion tube 20 toward the inside of the combustion tube 20 with respect to the insertion hole 24 so that the gas outlet portion 21a is accommodated in the combustion tube 20. Here, the tangential direction mentioned here includes not only the complete tangential direction but also the substantially tangential direction.

[0038] At this time, one end surface of the gas introduction pipe 21 that defines the gas outlet portion 21a is disposed at a position corresponding to a virtual surface M along the same radial direction of the combustion pipe 20 within the combustion pipe 20 (see FIG. 3). Thereby, since the mixed gas of ammonia gas and air is introduced into the combustion pipe 20 in a tangential direction of the inner peripheral surface 20b of the combustion pipe 20, a swirling flow (tubular flow) of the mixed gas is generated within the combustion pipe 20. Specifically, the mixed gas flowing in the axial direction of the gas introduction pipe 21 along the inner wall surface of the gas introduction pipe 21 passes through the gas outlet portion 21a and flows in the circumferential direction of the combustion pipe 20 along the inner wall surface of the combustion pipe 20. Therefore, compared with the case where one end surface of the gas introduction pipe 21 is connected to the outer peripheral surface of the combustion pipe 20 so that the gas outlet portion 21a of the gas introduction pipe 21 is not accommodated within the combustion pipe 20 (for example, the same structure as FIGS. 5 and 6), the swirling flow of the mixed gas is more likely to occur.

[0039] As described above, the gas introduction pipe 21 has a circular cross-sectional shape. The gas introduction pipe 21 has a cross-sectional area S such that when the mixed gas of ammonia gas and air is introduced into the combustion pipe 20 from the gas outlet portion 21b, the flow velocity (inlet flow velocity) is 3 m / s to 25 m / s with respect to the flow rate (L / min) of the mixed gas. The cross-sectional area S of the gas introduction pipe 21 is represented by the flow rate of the mixed gas / the inlet flow velocity of the mixed gas.

[0040] The spark plug 22 is attached to the radial center portion of the closing wall 23. The spark plug 22 is an ignition portion that ignites the ammonia gas introduced into the combustion pipe 20 to ignite the ammonia gas.

[0041] In such a combustor 4, when the mixed gas of ammonia gas and air is introduced into the combustion pipe 20 by the gas introduction pipe 21, the mixed gas becomes a swirling flow (see FIG. 3). At this time, a part of the mixed gas flows toward the closing wall 23 in a swirling flow state within the combustion pipe 20 (see FIG. 4). Then, when the mixed gas reaches the vicinity of the closing wall 23, the ammonia gas in the mixed gas is ignited by the spark plug 22 to form a tubular flame, and combustion gas is generated. The combustion gas flows toward the open end 20a of the combustion pipe 20 together with the remaining mixed gas (see FIG. 4).

[0042] When the reforming system 1 equipped with the combustor 4 as described above is started, the throttle valves 8, 9 and the injectors 12, 13 are opened, so that air flows through the air flow paths 6, 7 toward the combustor 4 and the reformer 5 respectively, and ammonia gas is injected from the injectors 12, 13 toward the combustor 4 and the reformer 5 respectively. Then, a mixed gas of ammonia gas and air is supplied to the combustor 4 and the reformer 5 respectively.

[0043] When the mixed gas is introduced into the combustion tube 20 from the gas introduction pipe 21 in the combustor 4, the mixed gas flows through the combustion tube 20 as a swirling flow. And when the swirling mixed gas reaches the vicinity of the closing wall 23, the ignition plug 22 ignites, so that the ammonia gas in the mixed gas catches fire and burns. Specifically, as shown in the following formula, ammonia and oxygen in the air chemically react to generate high-temperature combustion gas (exothermic reaction). NH3+3 / 4O2→1 / 2N2+3 / 2H2O …(A)

[0044] The combustion gas flows through the combustion tube 20 toward the open end 20a and is supplied to the reformer 5. Then, the ATR catalyst 5a of the reformer 5 is heated by the heat of the combustion gas, and the temperature of the ATR catalyst 5a rises. And when the temperature of the ATR catalyst 5a reaches the combustible temperature, the ignition of the ignition plug 22 stops and at the same time the throttle valve 8 and the injector 12 are closed, so that the supply of air and ammonia gas to the combustor 4 stops. Thereby, the generation of the combustion gas by the combustor 4 is completed.

[0045] Also, when the temperature of the ATR catalyst 5a reaches the combustible temperature, the ammonia gas burns by the ATR catalyst 5a, so that the exothermic reaction of the above formula (A) occurs, and the temperature of the ATR catalyst 5a further rises due to the self-heat of the ATR catalyst 5a.

[0046] Then, when the temperature of the ATR catalyst 5a reaches the reformable temperature, ammonia gas is reformed by the ATR catalyst 5a. Specifically, as shown in the following formula, the decomposition reaction of ammonia occurs (endothermic reaction), and a reformed gas containing hydrogen is generated. The reformed gas flows through the reformed gas flow path 14 and is supplied to the hydrogen utilization device 15. NH3→3 / 2H2+1 / 2N2…(B)

[0047] FIG. 5 is a perspective view showing a combustor as a comparative example. FIG. 6 is a cross-sectional view of the combustor shown in FIG. 5. In FIGS. 5 and 6, the combustor 50 of this comparative example includes a cylindrical combustion tube 51 with one end open and the other end closed, four flat gas introduction members 52 for introducing ammonia and air into the combustion tube 51, and a spark plug 53 for igniting the ammonia gas introduced into the combustion tube 51.

[0048] Four slits 54 are formed at equal intervals along the circumferential direction in the combustion tube 51. The slits 54 extend in the axial direction of the combustion tube 51. Each gas introduction member 52 is fixed to the combustion tube 51 such that the gas outlet portion 52a communicates with the slit 54. The gas introduction member 52 is arranged to introduce ammonia and air in the tangential direction of the inner peripheral surface 51b of the combustion tube 51 in cooperation with the slit 54. Therefore, an ideal swirling flow of ammonia and air is formed.

[0049] However, in this comparative example, the gas introduction part for introducing ammonia gas and air into the combustion tube 51 is constituted by four flat gas introduction members 52. For this reason, it is necessary to form four fine slits 54 in the combustion tube 51. As a result, the structure of the gas introduction part becomes complicated and the processing of the gas introduction part becomes difficult. In addition, since the four gas introduction members 52 extend in all directions along the radial direction of the combustion tube 51, it leads to an increase in the size of the combustor 50.

[0050] In view of such problems, in the present embodiment, when ammonia gas and air are introduced into the cylindrical combustion tube 20 through the gas introduction pipe 21, the mixed gas of ammonia gas and air flows in the combustion tube 20 toward the closing wall 23. Then, the ammonia gas in the mixed gas is ignited and burned by the ignition plug 22, and combustion gas is generated. And the combustion gas flows to the open side of the combustion tube 20. Here, the gas introduction pipe 21 protrudes in the tangential direction of the inner peripheral surface 20b of the combustion tube 20 toward the inside of the combustion tube 20 with respect to the insertion hole 24 so that the gas outlet portion 21a is accommodated in the combustion tube 20. Thereby, when ammonia gas and air are introduced into the combustion tube 20, a swirling flow (tubular flow) of ammonia gas and air is generated in the combustion tube 20. Therefore, when the ammonia gas is ignited in a swirling flow state, a tubular flame is formed. Further, when attaching the gas introduction pipe 21 to the combustion tube 20, a simple hole machining may be performed on the combustion tube 20 to form the insertion hole 24, and the gas introduction pipe 21 may be inserted into the insertion hole 24. Thereby, regarding the gas introduction portion for introducing ammonia gas and air into the combustion tube 20, simplification of the structure and facilitation of processing are achieved. Furthermore, since the gas introduction pipe 21 is bent so as to extend along the axial direction of the combustion tube 20, the radial dimension of the combustor 4 is reduced, and miniaturization of the combustor 4 is achieved.

[0051] By the way, when ammonia gas and air are introduced into the combustion tube 20 through the gas introduction pipe 21, a swirling flow of the mixed gas of ammonia gas and air is generated. However, when the mixed gas swirls in the combustion tube 20, the mixed gas interferes with the gas introduction pipe 21, so that the symmetry of the flow velocity of the mixed gas with respect to the axial direction of the combustion tube 20 may be broken in the vicinity of the ignition plug 22. In this case, as shown in FIG. 7, it affects the combustible range of ammonia gas with respect to the air excess ratio λ.

[0052] In FIG. 7, the combustion amount of ammonia gas is proportional to the flow rate of ammonia gas. The air excess ratio λ corresponds to the composition of the mixed gas of ammonia gas and air. The air excess ratio λ = 1 is the stoichiometric (theoretical air-fuel ratio at which the fuel is completely burned) state. The air excess ratio λ>1 is the lean (air excess) state. The air excess ratio λ<1 is the rich (fuel excess) state.

[0053] In the present embodiment, the gas introduction pipe 21 has a cross-sectional area S such that the intrusion flow velocity when the mixed gas is led out from the gas outlet portion 21b into the combustion pipe 20 is 3 m / s to 25 m / s with respect to the flow rate of the mixed gas of ammonia gas and air. In this case, as shown by the solid lines P1 and P2 in FIG. 7, compared with the case where the cross-sectional area S of the gas introduction pipe 21 does not satisfy the above conditions (see the broken lines Q1 and Q2), the combustible range of ammonia gas becomes wider overall on the lean side. The solid line P1 and the broken line Q1 indicate the combustion limit values on the lean side. The solid line P2 and the broken line Q2 indicate the combustion limit values on the rich side. Therefore, the combustible range of ammonia gas is the region between the solid lines P1 and P2 and the region between the broken lines Q1 and Q2. At this time, the cross-sectional area S of the gas introduction pipe 21 is about 80 mm 2 is. The distance X (see FIG. 4) from the central axis of the gas introduction pipe 21 to the closing wall 23 is 10 mm to 100 mm.

[0054] Thus, according to the present embodiment, since the combustible range of ammonia gas with respect to the air excess ratio λ becomes wider, ammonia gas is likely to burn stably. Therefore, the combustion performance of the combustor 4 is improved.

[0055] FIG. 8 is a cross-sectional view showing a combustor according to the second embodiment of the present invention, and is a view corresponding to FIG. 4. In FIG. 8, the combustor 4A of the present embodiment includes a combustion pipe 20, a gas introduction pipe 21, and a spark plug 22, similarly to the above-described first embodiment.

[0056] In this embodiment, compared with the above-described first embodiment, the ratio of the inner diameter R2 of the gas introduction pipe 21 to the inner diameter R1 of the combustion pipe 20 (inner diameter R2 of the gas introduction pipe 21 / inner diameter R1 of the combustion pipe 20) is larger. Specifically, the ratio of the inner diameter R2 of the gas introduction pipe 21 to the inner diameter R1 of the combustion pipe 20 is 0.30 to 0.45.

[0057] Also, in this embodiment, similar to the above-described first embodiment, the gas introduction pipe 21 has a cross-sectional area S such that when the mixed gas of ammonia gas and air flows at a flow rate (L / min), the intrusion flow velocity when the mixed gas is introduced into the combustion pipe 20 from the gas outlet portion 21b (see FIG. 3) is 3 m / s to 25 m / s.

[0058] In such a case, as shown by the solid lines P1 and P2 in FIG. 9, compared with the case where the ratio of the inner diameter R2 of the gas introduction pipe 21 to the inner diameter R1 of the combustion pipe 20 and the cross-sectional area S of the gas introduction pipe 21 do not satisfy the above conditions (see the broken lines Q1 and Q2), the combustible range of the ammonia gas becomes wider on the lean side as a whole, and particularly when the flow rate of the ammonia gas supplied into the combustion pipe 20 is large, the combustible range of the ammonia gas becomes wider on the rich side. At this time, the cross-sectional area S of the gas introduction pipe 21 and the distance X (see FIG. 4) from the central axis of the gas introduction pipe 21 to the closing wall 23 are the same as those in the above-described first embodiment.

[0059] Thus, according to this embodiment, particularly when the flow rate of the ammonia gas supplied into the combustion pipe 20 is large, the combustible range of the ammonia gas with respect to the air excess ratio λ becomes wider. Therefore, the ammonia gas burns more stably and easily.

[0060] FIG. 10 is a cross-sectional view showing a combustor according to the third embodiment of the present invention, and is a view corresponding to FIG. 4. In FIG. 10, the combustor 4B of this embodiment includes a combustion pipe 30, the above-described gas introduction pipe 21, and an ignition plug 22.

[0061] One end of the combustion tube 30 is an open end 30a. A closing wall 33 is fixed to the other end of the combustion tube 30. The combustion tube 30 has a main body portion 31 with a diameter that is equal throughout in the axial direction, and a tapered portion 32 that tapers from this main body portion 31 toward the closing wall 33. The tapered portion 32 is disposed on the other end side of the combustion tube 30 relative to the main body portion 31. An insertion hole 24 (see FIGS. 2 and 3) into which the gas introduction pipe 21 is inserted is provided in the main body portion 31.

[0062] The difference Δr between the outer diameter radius Ra of the proximal end 32a of the tapered portion 32 and the outer diameter radius Rb of the distal end 32b of the tapered portion 32 is equal to or less than the inner diameter radius Rc of the main body portion 31. The outer diameter radius Ra of the proximal end 32a of the tapered portion 32 is equal to the outer diameter radius of the main body portion 31. The inner diameter radius Rc of the main body portion 31 is the difference between the outer diameter radius of the main body portion 31 and the thickness of the main body portion 31. The closing wall 33 is fixed to the distal end 32b of the tapered portion 32. The outer diameter radius Rb of the distal end 32b of the tapered portion 32 is approximately equal to the radius of the closing wall 33.

[0063] Similar to the first embodiment described above, the gas introduction pipe 21 has a cross-sectional area S such that when the mixed gas of ammonia gas and air is introduced into the combustion tube 30 from the gas outlet portion 21b (see FIG. 3), the intrusion flow velocity is 3 m / s to 25 m / s with respect to the flow rate (L / min) of the mixed gas.

[0064] In such an embodiment, the combustion tube 30 has a tapered portion 32 that tapers from the main body portion 31 toward the closing wall 33. For this reason, the symmetry of the flow velocity of the mixed gas with respect to the axial direction of the combustion tube 30 is improved in the vicinity of the ignition plug 22. Therefore, the ammonia gas burns more stably and easily.

[0065] Also, in this embodiment, the insertion hole 24 is provided in the main body portion 31, and the difference Δr between the outer diameter radius Ra of the proximal end 32a of the tapered portion 32 and the outer diameter radius Rb of the distal end 32b of the tapered portion 32 is equal to or less than the inner diameter radius Rc of the main body portion 31.

[0066] In such a case, as shown by the solid lines P1 and P2 in FIG. 11, when the combustion tube 30 does not have the tapered portion 32 and the cross-sectional area S of the gas introduction tube 21 does not satisfy the above conditions (see the broken lines Q1 and Q2), the combustible range of the ammonia gas becomes wider on the lean side as a whole, and particularly when the flow rate of the ammonia gas supplied into the combustion tube 30 is large, the combustible range of the ammonia gas becomes wider on the rich side. At this time, the cross-sectional area S of the gas introduction tube 21 and the distance X from the central axis of the gas introduction tube 21 to the closing wall 23 (see FIG. 4) are the same as those in the first embodiment above. Further, the difference Δr between the outer diameter radius Ra of the base end 32a of the tapered portion 32 and the outer diameter radius Rb of the tip end 32b of the tapered portion 32 is, for example, 3 mm to 10 mm. The length H of the tapered portion 32 is, for example, 10 mm to 70 mm. The length H of the tapered portion 32 is the length from the base end 32a of the tapered portion 32 to the tip end 32b (closing wall 33) of the tapered portion 32.

[0067] Thus, according to this embodiment, particularly when the flow rate of the ammonia gas supplied into the combustion tube 30 is large, the combustible range of the ammonia gas with respect to the air excess ratio λ becomes wider. Therefore, the ammonia gas burns more stably and easily.

[0068] Note that the present invention is not limited to the above embodiment. For example, in the above embodiment, one gas introduction tube 21 is attached to the combustion tube 20 or the combustion tube 30, but the number of the gas introduction tubes 21 is not particularly limited to one, and a plurality of them may be provided. For example, as shown in FIG. 12, two gas introduction tubes 21 may be attached to the combustion tube 20. In this case, two insertion holes 24 are provided in the combustion tube 20 so as to be separated from each other by 180 degrees in the circumferential direction. Then, the gas introduction tubes 21 project in the tangential direction of the inner circumferential surface 20b of the combustion tube 20 toward the inside of the combustion tube 20 with respect to each insertion hole 24 so that the gas outlet portions 21a are accommodated in the combustion tube 20.

[0069] Further, in the above embodiment, the gas introduction tube 21 has a cylindrical shape (circular cross-sectional shape), but it is not particularly limited to such a form. For example, in the first and third embodiments above, the shape of the gas introduction tube 21 may be a rectangular tube shape (square cross-sectional shape) or the like.

[0070] Also, in the above embodiment, the closing walls 23 and 33 are fixed to the other ends (the ends opposite to the open ends) of the combustion tubes 20 and 30, but are not particularly limited to such a form, and the closing walls 23 and 33 may be fixed in the vicinity of the other ends of the combustion tubes 20 and 30. The main point is that the closing walls 23 and 33 may be fixed to the other end sides of the combustion tubes 20 and 30.

[0071] Also, the burners 4, 4A, and 4B of the above embodiment are provided in the reforming system 1, but the present invention may also be applied to systems other than the reforming system.

[0072] Also, in the above embodiment, ammonia gas is used as the fuel gas, but the present invention is also applicable to a burner that uses a hydrocarbon gas or the like as the fuel gas.

[0073] Also, in the above embodiment, air is used as the oxidizing gas, but the present invention is also applicable to a burner that uses oxygen as the oxidizing gas.

Explanation of Reference Numerals

[0074] 4, 4A, 4B... burners, 20... combustion tubes, 20b... inner peripheral surface, 21... gas introduction pipe, 21a... gas outlet portion, 22... ignition plug (ignition portion), 23... closing wall, 24... insertion hole, 30... combustion tube, 31... main body portion, 32... tapered portion, 32a... base end, 32b... tip end, 33... closing wall, S... cross-sectional area, R1, R2... inner diameters, Ra, Rb... outer diameter radii, Rc... inner diameter radius, Δr... difference.

Claims

1. A cylindrical combustion tube having one end open and a closing wall fixed to the other end side, a gas introduction pipe attached to the combustion tube for introducing ammonia and an oxidizing gas into the combustion tube, and an ignition part attached to the closing wall for igniting the ammonia introduced into the combustion tube by the gas introduction pipe. The combustion tube is provided with an insertion hole into which the gas introduction pipe is inserted. A gas outlet part for leading the ammonia and the oxidizing gas into the combustion tube is provided at the end of the gas introduction pipe on the side connected to the combustion tube. The gas introduction pipe protrudes in a tangential direction of the inner peripheral surface of the combustion tube toward the inside of the combustion tube with respect to the insertion hole so that the gas outlet part is accommodated in the combustion tube. The ignition part is attached to the radial center part of the closing wall. The combustion tube has a main body part and a tapered part that tapers from the main body part toward the closing wall. The insertion hole is provided in the main body part. A combustor in which the difference between the outer diameter radius of the base end of the tapered part and the outer diameter radius of the tip of the tapered part is equal to or less than the inner diameter radius of the main body part.

2. The combustor according to claim 1, wherein the gas introduction pipe has a cross-sectional area such that when the mixed gas of ammonia and the oxidizing gas is led into the combustion tube from the gas outlet part, the flow velocity is 3 m / s to 25 m / s with respect to the flow rate of the mixed gas.

3. The gas introduction pipe has a circular cross-sectional shape. The combustor according to claim 2, wherein the ratio of the inner diameter of the gas introduction pipe to the inner diameter of the combustion tube is 0.30 to 0.45.

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