Combustion equipment

Abstract

To provide a burner of a simple configuration capable of suitably burning fuel of a low calorific value such as ammonia fuel.SOLUTION: The burner comprises a combustion air pipe 3 to be supplied with preheated air for combustion, and a fuel nozzle 2 disposed in the combustion air pipe to eject the supplied fuel of a low calorific value to burn the fuel in the combustion air pipe, with a combustion air flow path 5 defined between the fuel nozzle and the combustion air pipe to heat the fuel of a low calorific value in the fuel nozzle using the air for combustion. A plurality of heat transfer fins 2c is attached to an outer circumferential surface 2b of the fuel nozzle in a manner of being positioned in the combustion air flow path.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention provides a combustion device that has a simple configuration and is capable of satisfactorily combusting a low calorific value fuel such as an ammonia fuel. [Background technology]

[0002] Patent Documents 1 to 4 are known regarding techniques for burning ammonia, which has attracted attention as a combustion fuel for reducing carbon dioxide emissions.

[0003] The "low flammable fuel combustion device" of Patent Document 1 has a primary air supply pipe provided on the outer periphery of a fuel supply pipe equipped with an outlet for spraying low flammable fuel, which guides primary combustion air forward in the feed direction of the fuel supply pipe while swirling it along the outer periphery of the fuel supply pipe, and a secondary air supply pipe provided on the outer periphery downstream in the feed direction of the primary air supply pipe, which guides secondary combustion air forward in the feed direction of the primary air supply pipe while swirling it along the outer periphery of the primary air supply pipe.

[0004] The "low flammability fuel combustion device" of Patent Document 2 is configured by providing a fuel supply pipe for supplying low flammability fuel in the center of an air guide pipe that guides combustion air, providing radial nozzles on the outer periphery of the tip of this fuel supply pipe for spraying the low flammability fuel toward the outer periphery, providing a primary combustion tube on the outer periphery of the fuel supply pipe downstream of the radial nozzles, providing inner swirl vanes between the outer periphery of the tip of the fuel supply pipe and the inner periphery of the primary combustion tube, and further providing outer swirl vanes between the outer periphery of the downstream tip of the primary combustion tube and the inner periphery of the air guide pipe.

[0005] The "premix burner device for low heating value gas fuel" of Patent Document 3 is a premix burner device that burns one or both of low and high heating value gas fuels, and is configured with a gas supply device that supplies high heating value gas and low heating value gas, a burner tube that receives the gas at a predetermined flow rate and introduces primary air to mix it with the gas flow, a burner head with a long and narrow rectangular trapezoidal cross section with the narrower width on the downstream side, a furnace formed with an opening having a side wall that is wider than the dimensions of the burner head and tapers in the same direction as the burner head, a means for inserting the burner head into the opening to support the burner device below the hearth, and a means for adjusting the vertical relative position of the burner head within the opening.

[0006] The "ultra-low calorific value gas combustion device" of Patent Document 4 is provided with a set of regenerative burner systems in a furnace body, which supply combustion air or treated gas or premixed gas and discharge combustion gas through a heat storage body, and switch the flow of the combustion exhaust gas and the combustion air or treated gas relative to the heat storage body to supply high-temperature combustion air or treated gas through the heat storage body heated by the combustion exhaust gas. The combustion air or treated gas, or premixed gas of both the combustion air and treated gas, is preheated to a high temperature with high temperature efficiency through direct heat exchange with the heat storage body for a short period of time before being supplied, and the heat required to maintain the flame is compensated for by the enthalpy possessed by the high-temperature combustion air or treated gas, or both the combustion air and treated gas, or the premixed gas, thereby stably burning combustible substances or odorous components in the treated gas with a low calorific value of 400 Kcal / Nm3 or less.

[0007] A technology for preheating combustion air is known from Patent Document 5. In the "method for protecting a recuperator in a radiant tube heating device" of Patent Document 1, a recuperator is inserted into a radiant tube to a position in the radiant tube where the tip of the recuperator does not protrude from the inner surface of the furnace wall, and a refractory member having a blocking part for blocking radiant heat from the radiant tube and a circulating part for circulating exhaust gas from the burner is disposed in the radiant tube on the inner side of the furnace than the tip of the recuperator, close to the tip of the recuperator but not in contact with it. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent Publication No. 2022-12927 [Patent Document 2] Patent No. 6906881 [Patent Document 3] Japanese Patent Application Publication No. 55-134214 [Patent Document 4] Japanese Patent Application Publication No. 6-241431 [Patent Document 5] JP 2011-94900 A Summary of the Invention [Problem to be solved by the invention]

[0009] Ammonia fuel and other low calorific value fuels are very difficult to burn. As a countermeasure, in Patent Document 1, combustion air is swirled around the outer periphery of a fuel supply pipe provided with an outlet for ejecting low combustible fuel, and is guided forward in the feed direction of the fuel supply pipe.

[0010] In Patent Document 2, a primary combustion tube is provided on the outer periphery downstream of the radial nozzle of the fuel supply pipe, and swirling blades are provided between the tip of the fuel supply pipe and the inner periphery of the primary combustion tube, and between the tip of the downstream side of the primary combustion tube and the inner periphery of the air guide pipe.

[0011] In Patent Document 3, preheated combustion air is introduced into a burner device that burns low calorific value gas fuel, and in Patent Document 4, combustion air is preheated before being supplied to a burner provided in an ultra-low calorific value gas combustion device.

[0012] If the combustion air is introduced while swirling along the outer periphery of the fuel supply pipe, or if swirling blades are provided to mix the low-heat-value fuel and the combustion air, the swirling of the combustion air will cause the flame to spread, making it difficult for the flame to reach far.

[0013] In addition, the burner structure is complicated, making manufacturing difficult and increasing costs.

[0014] When the combustion air is preheated and introduced while swirling around the outer periphery of the fuel supply pipe, there is a problem that it reacts violently with the fuel, resulting in excessive combustion.

[0015] The present invention has been devised in view of the above-mentioned problems in the conventional art, and has an object to provide a combustion device that has a simple configuration and is capable of satisfactorily combusting a low heating value fuel such as an ammonia fuel. [Means for solving the problem]

[0016] The combustion device according to the present invention comprises a combustion air pipe to which preheated combustion air is supplied, and a fuel nozzle provided inside the combustion air pipe for ejecting the supplied low heating value fuel and combusting it within the combustion air pipe, and is characterized in that a combustion air flow path is defined between the fuel nozzle and the combustion air pipe, for heating the low heating value fuel in the fuel nozzle with the combustion air.

[0017] The fuel nozzle may be provided with fins for heat transfer on an outer surface thereof, the fins being positioned in the combustion air flow path.

[0018] A baffle plate for narrowing the combustion air flow path is provided near the fuel ejection portion of the fuel nozzle.

[0019] The present invention is characterized in that a sleeve is provided in the combustion air flow passage around the outside of the baffle plate at a distance from the baffle plate, and causes the combustion air in the combustion air flow passage to flow straight along the combustion air pipe.

[0020] The combustion air tube is a radiant tube having a recuperator for preheating the combustion air.

[0021] The low heating value fuel is an ammonia fuel. Effect of the Invention

[0022] The combustion device according to the present invention has a simple configuration including a fuel nozzle that heats a low heating value fuel with preheated combustion air, and can satisfactorily combust a low heating value fuel such as ammonia fuel. [Brief description of the drawings]

[0023] [Figure 1] 1 is a side cross-sectional view showing a first embodiment of a combustion device according to the present invention. [Diagram 2] FIG. 4 is a cross-sectional view showing a second embodiment of a combustion device according to the present invention. [Diagram 3] 3 is a cross-sectional view of the combustion device shown in FIG. 2 as viewed from the front. [Figure 4] FIG. 4 is a cross-sectional view showing a third embodiment of a combustion device according to the present invention. [Diagram 5] FIG. 5 is a cross-sectional view of the combustion device shown in FIG. 4, as viewed from the front. [Figure 6] FIG. 5 is a diagram showing an example of a radiant tube burner incorporating the combustion device shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a combustion apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

[0025] As shown in FIG. 1, the combustion device 1 according to the first embodiment includes a fuel nozzle 2 that supplies a low calorific value fuel such as an ammonia fuel, and a combustion air pipe 3 that is disposed coaxially with the fuel nozzle 2 outside the fuel nozzle 2 and to which preheated combustion air is supplied.

[0026] That is, this combustion device 1 comprises a combustion air pipe 3 to which preheated combustion air is supplied, and a tubular fuel nozzle 2 that is provided inside the combustion air pipe 3 and sprays the supplied low heating value fuel for combustion within the combustion air pipe 3. Between the fuel nozzle 2 and the combustion air pipe 3, a combustion air flow path 5 is defined and formed, which heats the low heating value fuel in the fuel nozzle 2 with the combustion air.

[0027] The fuel nozzle 2 is made of a material having good thermal conductivity, such as a heat-resistant metal, for example, stainless steel.

[0028] The fuel nozzle 2 is provided with a fuel ejection portion 2a, which ejects low heating value fuel into the interior of the combustion air pipe 3, at the downstream tip in the flow direction of the low heating value fuel and combustion air (hereinafter referred to as the flow direction).

[0029] A plurality of radially or annularly protruding heat transfer fins 2c are provided on the outer circumferential surface 2b of the fuel nozzle 2 at appropriate intervals in the length direction (flow direction) of the fuel nozzle 2 and positioned in the combustion air flow path 5. The fins 2c are not necessarily provided.

[0030] The combustion air pipe 3 has an inner surface 3a arranged with a gap between it and the outer surface 2b of the fuel nozzle 2. A combustion air flow path 5 is defined in the section between the inner surface 3a of the combustion air pipe 3 and the outer surface 2b of the fuel nozzle 2, from the fuel ejection part 2a, which is the tip of the fuel nozzle 2, to the attachment base 2d of the combustion air pipe 3, which is the base end on the opposite side.

[0031] The combustion air pipe 3 extends downstream of the fuel nozzle 2 in the flow direction.

[0032] A fuel nozzle 2 protrudes to the outside on the upstream side from the combustion air pipe 3, and a flow rate adjustment valve 4 for adjusting the flow rate of low calorific value fuel to the fuel nozzle 2 is provided.

[0033] Preheated combustion air is supplied to the combustion air pipe 3. The combustion air flows through a combustion air flow passage 5 outside the fuel nozzle 2, and flows toward the downstream side of the fuel ejection portion 2a.

[0034] In the combustion device 1 according to the first embodiment, the fuel nozzle 2 for the low heat generating fuel is made of a material with good thermal conductivity, and preheated combustion air is supplied into the combustion air pipe 3. This combustion air is circulated through the combustion air flow path 5. Therefore, the low heat generating fuel in the fuel nozzle 2 is heated by the heated combustion air through the fuel nozzle 2, making it easier to combust.

[0035] In particular, ammonia (NH3) is decomposed into nitrogen and hydrogen, and the hydrogen makes it highly combustible.

[0036] That is, ammonia, which is a low calorific value fuel inside the fuel nozzle 2, is easily decomposed into hydrogen and nitrogen, and can be combusted satisfactorily.

[0037] Since the combustion air pipe 3 extends downstream of the fuel nozzle 2, the heated low heating value fuel ejected from the fuel ejection portion 2a is mixed with the preheated combustion air, thereby generating a flame F using the low heating value fuel.

[0038] The combustion air pipe 3 is disposed on the outer periphery of the fuel nozzle 2 with a gap between it and the outer periphery 2b of the fuel nozzle 2, so that the combustion air flows in the same direction as the injection direction of the low calorific value fuel.

[0039] As a result, the direction in which the flame F caused by combustion spreads is the same as the flow direction of the low heat value fuel and the combustion air, and the flame F can be made to travel in a straight line and reach farther than, for example, when the combustion air is supplied in a swirling manner.

[0040] Fins 2c are provided on the outer peripheral surface 2b of the fuel nozzle 2 and are located in the combustion air flow path 5. The fins 2c increase the surface area of ​​the fuel nozzle 2 and improve the heat transfer performance, thereby efficiently raising the temperature of the low heating value fuel and promoting the decomposition of ammonia if the fuel is ammonia.

[0041] A combustion device 1 according to the second embodiment is shown in Figures 2 and 3. Figure 2 is a cross-sectional view taken along line AA in Figure 3.

[0042] As shown in the figure, the combustion device 1 of the second embodiment is provided with a baffle plate 7 that is located near the fuel ejection portion 2a of the fuel nozzle 2 of the combustion device 1 of the first embodiment and is provided around the entire outer peripheral surface 2b to narrow the combustion air flow path 5, and a sleeve 8 that is provided around the outside of the baffle plate 7 in the combustion air flow path 5 at a distance from the baffle plate 7 towards the combustion air pipe 3 and causes the combustion air in the combustion air flow path 5 to move straight along the combustion air pipe 3.

[0043] The sleeve 8 is provided in the length direction of the combustion air tube 3 and the fuel nozzle 2 with a gap between the sleeve 8 and both the outer circumferential surface 2 b of the fuel nozzle 2 and the inner circumferential surface 3 a of the combustion air tube 3 .

[0044] The sleeve 8 is provided, via a spacer 9, on the outer circumferential surface 7a of a baffle plate 7, the one end 8a of which is on the upstream side in the flow direction and is provided in the fuel nozzle 2.

[0045] The other downstream end 8 b of the sleeve 8 extends downstream of the fuel ejection portion 2 a of the fuel nozzle 2 .

[0046] In the illustrated example, the spacers 9 interposed between the inner peripheral surface 8c of the sleeve 8 and the outer peripheral surface 7a of the baffle plate 7 are disposed at four positions at equal intervals in the circumferential direction of the baffle plate 7.

[0047] Between the baffle plate 7 and the sleeve 8 and between the spacers 9 adjacent in the circumferential direction, a gap S that connects the combustion air flow path 5 to the inside of the sleeve 8 is formed.

[0048] Between the sleeve 8 and the combustion air pipe 3, a flow passage 6 is formed through which combustion air flows from the combustion air flow passage 5 in the longitudinal direction of the combustion air pipe 3.

[0049] The combustion air flowing through the combustion air flow passage 5 flows outside the fuel nozzle 2, and the flow velocity of the combustion air is reduced by the baffle plate 7 in the range defined from the baffle plate 7 to the mounting base 2d.

[0050] This allows the time for heating the low heating value fuel to be extended, and the temperature can be raised to a higher level, making the low heating value fuel easier to burn.

[0051] Moreover, the combustion air is divided into the gap S and the flow passage 6, and is circulated toward the downstream side of the fuel ejection portion 2a.

[0052] A spark plug 10 for igniting fuel is provided on the baffle plate 7 and faces inwardly into the sleeve 8.

[0053] In the combustion device 1 of the second embodiment, a baffle plate 7 is provided on the tip (fuel ejection portion 2a) side of the fuel nozzle 2, protruding from the outer peripheral surface 2b of the fuel nozzle 2. The baffle plate 7 extends the heating time of the low heating value fuel by the combustion air flowing inside the combustion air pipe 3 (combustion air flow path 5), making it easier to combust the low heating value fuel.

[0054] In particular, in the case of ammonia fuel, the decomposition into hydrogen and nitrogen can be promoted.

[0055] Therefore, the low calorific value fuel can be more reliably burned slowly rather than rapidly, and can be burned well.

[0056] A sleeve 8 is provided around the outside of the baffle plate 7, and combustion air can be circulated from the combustion air flow path 5 through both the inner gap S of this sleeve 8 and the outer flow path 6. The combustion air flowing through the gap S burns a low calorific value, and the flow of the combustion air flowing through the flow path 6 and out to the downstream side of the sleeve 8 makes the flame F go in a straight line, allowing it to reach a greater distance.

[0057] A combustion device 1 according to a third embodiment is shown in Figures 4 and 5. Figure 4 is a cross-sectional view taken along line BB in Figure 5.

[0058] In the second embodiment of the combustion device 1, an example has been described in which only a spark plug 10 is provided on the baffle plate 7. However, in the third embodiment of the combustion device 1, the baffle plate 7 is provided with a through hole 7b that allows combustion air to flow from the combustion air passage 5 toward the inside of the sleeve 8.

[0059] By providing the through hole 7b, the amount of combustion air given to the low calorific value fuel can be increased, and the flow rate can be adjusted by changing the size of the through hole 7b.

[0060] In the combustion device 1 according to the third embodiment, the preheating of the combustion air can be ensured with a simple structure.

[0061] An example of a method for supplying preheated combustion air to the combustion device 1 is shown in FIG.

[0062] FIG. 6 shows, for example, a case in which the combustion device 1 of the third embodiment is used in a radiant tube burner 12 having a recuperator 11 that preheats the combustion air with high-temperature combustion exhaust gas.

[0063] In the radiant tube burner 12, the combustion device 1 is incorporated with a radiant tube 12a as a combustion air tube 3.

[0064] A heat exchange chamber 13 is provided inside the radiant tube 12a on the exhaust side of the radiant tube 12a, and a combustion air supply pipe 14 is provided inside the chamber 13.

[0065] Combustion air supplied from the combustion air supply pipe 14 is preheated in the chamber 13 , turns around at the tip of the chamber 13 , passes through a flow path 16 , and flows toward the combustion device 1 .

[0066] In the combustion device 1, a flame F is generated by a combustion reaction with the low calorific value fuel, and the flame F becomes combustion exhaust gas and flows toward the recuperator 11.

[0067] When the combustion exhaust gas flows outside the chamber 13, it exchanges heat with the combustion air from the combustion air supply pipe 14, thereby preheating the combustion air.

[0068] When the radiant tube burner 12 is started, the temperature inside the radiant tube 12a is low, making it difficult for the recuperator 11 to sufficiently preheat the combustion air.

[0069] Therefore, when starting the radiant tube burner 12, it is preferable to generate a flame F using a hydrocarbon fossil fuel such as city gas to increase the temperature inside the radiant tube 12a, obtain high-temperature combustion exhaust gas, and then switch to a low-calorific value fuel.

[0070] For this reason, in the illustrated example, the fuel nozzle 2 of the combustion device 1 is provided with switching valves 15a, 15b in order to initially supply fossil fuel and then switch to a fuel with a low calorific value.

[0071] FIG. 6 shows the case where the combustion device 1 according to the third embodiment is applied, but it goes without saying that the combustion devices 1 according to the first and second embodiments may also be applied to configure a radiant tube burner 12.

[0072] As described above, the present invention can make a difficult-to-burn, low-heat-value fuel more combustible with a simple structure.

[0073] In the case of ammonia fuel, hydrogen can be obtained by decomposition at high temperatures, making it easy to burn even if the fuel has a low calorific value.

[0074] Furthermore, the above-described embodiment is for the purpose of facilitating understanding of the present invention, and is not intended to limit the present invention. The present invention can be modified or improved without departing from the spirit of the present invention, and it goes without saying that the present invention includes equivalents thereof. [Explanation of symbols]

[0075] 1 Combustion equipment 2 Fuel nozzle 2a Fuel injection part 2b Outer surface 2c Fins 2d Mounting base 3 Combustion air pipe 3a Inner surface 4. Flow Control Valve 5 Combustion air passage 6 Flow Path 7 Baffle Plate 7a Outer surface 7b through hole 8 Sleeve 8a One end of the sleeve (upstream side) 8b Other end of sleeve (downstream side) 8c Inner surface 9 Spacer 10 Spark plug 11 Recuperator 12 Radiant tube burner 12a Radiant Tube 13. Chamber 14 Combustion air supply pipe 15a, 15b Switching valve 16 Flow Path F flame S void

Claims

1. a combustion air pipe to which preheated combustion air is supplied; a fuel nozzle provided inside the combustion air tube for ejecting a supplied low heating value fuel and combusting it within the combustion air tube; A combustion air flow path is defined between the fuel nozzle and the combustion air pipe, for heating the low heating value fuel in the fuel nozzle with combustion air, a baffle plate that narrows the combustion air flow path is provided near the fuel ejection portion of the fuel nozzle, a sleeve is provided in the combustion air flow passage around the outer periphery of the baffle plate at a distance from the baffle plate, and causes the combustion air in the combustion air flow passage to flow straight along the combustion air pipe; A combustion device characterized in that the baffle plate is provided with a spark plug for igniting fuel and a through hole for allowing combustion air to flow out, facing inward of the sleeve.

2. 2. The combustion apparatus according to claim 1, wherein the fuel nozzle has an outer surface provided with fins for heat transfer positioned in the combustion air flow path.

3. 3. The combustion apparatus according to claim 1, wherein the combustion air pipe is a radiant tube having a recuperator for preheating the combustion air.

4. 3. The combustion apparatus according to claim 1, wherein the low calorific value fuel is an ammonia fuel.

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