Burner and ammonia mixed combustion boiler

Abstract

To provide a burner and an ammonia mixed combustion boiler capable of promoting combustion of ammonia and reducing generation of unburned ammonia.SOLUTION: A burner 10 includes: a first fuel flow passage L1 for supplying first fuel F1 of which combustion speed is higher than that of ammonia; a first air flow passage L2 for supplying first combustion air A1; an ammonia flow passage L3 for supplying ammonia F2; a second air flow passage L4 for supplying second combustion air A2; a first fuel ejection part 15 that ejects the first fuel F1; a first air ejection part 16 that ejects the first combustion air A1; an ammonia ejection part 17 that ejects the ammonia F2; and a second air ejection part 18 that ejects the second combustion air A2. The first fuel ejection part 15 is disposed upstream of the ammonia ejection part 17, and burns at least part of the first fuel F1 in a space surrounded by the ammonia flow passage L3.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a burner and an ammonia co-firing boiler.

Background Art

[0002] In order to protect the future from global warming, decarbonization (carbon neutral) has become a global trend. By replacing a part of hydrocarbon fuels such as natural gas and oil fuel used as fuels with ammonia that does not generate carbon dioxide, a reduction in carbon dioxide emissions is expected (see, for example, Patent Document 1). On the other hand, since ammonia has low flammability, there is a method of co-firing ammonia with a hydrocarbon fuel or hydrogen to stably burn ammonia. In Patent Document 2, an invention has been made to suppress incomplete combustion by specifying the ejection directions of the combustion flame of ammonia and the combustion flame of pulverized coal with respect to the flame of the pulverized coal fuel and ensuring the combustion time of ammonia.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Although ammonia does not generate carbon dioxide when burned, compared with other hydrocarbon fuels such as methane, which is the main component of city gas, it has the characteristics of a very slow combustion rate, a narrow flame retention range, and low flammability. Therefore, for example, when a hydrocarbon fuel and ammonia are supplied to a burner and co-fired, the combustion of the hydrocarbon fuel becomes unstable due to a decrease in the flame temperature of the hydrocarbon fuel caused by the influence of ammonia ejection, and there is a risk that the supplied ammonia is not completely burned and unburned ammonia is released into the atmosphere.

[0005] Accordingly, an object of the present invention is to provide a burner and an ammonia co-firing boiler that can promote the combustion of ammonia and reduce the generation of unburned substances of ammonia.

Means for Solving the Problems

[0006] The present invention includes a first fuel flow path that supplies a first fuel having a higher combustion rate than ammonia, a first air flow path that is disposed outside the first fuel flow path and supplies first combustion air, an ammonia flow path that is disposed outside the first air flow path and supplies ammonia, a second air flow path that is disposed outside the ammonia flow path and supplies second combustion air, a first fuel ejection part that is disposed at the tip of the first fuel flow path and ejects the first fuel that has flowed through the first fuel flow path, a first air ejection part that is disposed at the tip of the first air flow path and ejects the first combustion air that has flowed through the first air flow path, an ammonia ejection part that is disposed at the tip of the ammonia flow path and ejects the ammonia that has flowed through the ammonia flow path, and a second air ejection part that is disposed at the tip of the second air flow path and ejects the second combustion air that has flowed through the second air flow path. The first fuel ejection part is disposed upstream of the ammonia ejection part, and at least a part of the first fuel burns in a space surrounded by the ammonia flow path. The present invention relates to a burner.

[0007] Further, the first fuel is a gaseous fuel, and in the first fuel flow direction of the first fuel flow path, a first fuel flame retention part that serves as a flame retention part in the combustion of the first fuel ejected from the first fuel ejection part is provided downstream of the first fuel ejection part. The relationship between the inner diameter D of the first air flow path and the distance H from the tip of the first fuel flame retention part to the ammonia ejection part in the first fuel flow direction is preferably in the range of H:D = 3:2 to 3:4.

[0008] Further, the first fuel is a liquid fuel, and is disposed on the downstream side of the first fuel ejection portion in the first fuel flow direction of the first fuel flow path, and includes a first fuel flame retention portion that serves as a flame retention portion in the combustion of the first fuel ejected from the first fuel ejection portion. The relationship between the inner diameter D of the first air flow path and the distance H from the tip of the first fuel flame retention portion to the ammonia ejection portion in the first fuel flow direction is preferably in the range of H:D = 2:21 to 5:16.

[0009] Further, the ammonia ejection portion preferably ejects ammonia toward the outer edge portion of the flame formed by the combustion of the first fuel and the first combustion air.

[0010] The present invention also relates to an ammonia co-firing boiler including a burner and a combustion control unit that controls the burner, wherein the combustion control unit supplies the first fuel after starting the supply of the first combustion air and the second combustion air, and starts the supply of ammonia after a predetermined time has elapsed since the start of the combustion of the first fuel.

Advantages of the Invention

[0011] According to the present invention, it is possible to provide an ammonia co-firing burner and an ammonia co-firing boiler that promote the combustion of ammonia and reduce the generation of unburned substances of ammonia.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0013] (First Embodiment) Hereinafter, the burner and the ammonia co-firing boiler according to the first embodiment of the present invention will be described with reference to the drawings. The ammonia co-firing boiler device 1 of the present embodiment is a steam boiler that heats water to generate steam and supplies the steam to a load device (not shown). FIG. 1 is a longitudinal sectional view of the ammonia co-firing boiler device according to the first embodiment of the present invention. FIG. 2 is a longitudinal sectional view of the burner according to the first embodiment of the present invention.

[0014] As shown in FIG. 1, the ammonia co-firing boiler device 1 includes a can body 30, a burner 10, and a control unit 70. The can body 30 includes a plurality of water pipes 40, a lower header 50, and an upper header 60. Further, a combustion chamber 32 surrounded by a plurality of water pipes 40 is formed inside the can body 30. In the present embodiment, the ammonia co-firing boiler device 1 ejects gaseous fuel and ammonia from the burner 10 and co-fires the gaseous fuel and ammonia in the combustion chamber 32. As the gaseous fuel, hydrogen can be used in addition to hydrocarbon gases such as city gas and LPG. In the present embodiment, LNG of city gas, which is a gaseous fuel, is used as the first fuel having a higher combustion rate than ammonia.

[0015] The can body 30 is configured in a cylindrical shape and constitutes the main part of the outer shape of the ammonia co-firing boiler device 1. The can body 30 is arranged such that the height direction is along the vertical direction. An exhaust port 31 is formed in the upper part of the peripheral surface of the can body 30.

[0016] A plurality of water pipes 40 are arranged to extend vertically inside the can body 30. As shown in FIG. 1, the plurality of water pipes 40 constitute an inner water pipe group 41 and an outer water pipe group 42 arranged outside the inner water pipe group 41. The inner water pipe group 41 is configured to be arranged in an annular shape such that the plurality of water pipes 40 are coaxial with the fuel ejection central axis X of the burner 10 described later. In the present embodiment, the water pipes 40 constituting the inner water pipe group 41 are arranged in contact with adjacent water pipes 40. Further, the lower parts of the plurality of water pipes 40 constituting the inner water pipe group 41 have a small diameter, and a gap is formed between adjacent water pipes 40 at this lower part.

[0017] The outer water pipe group 42 is configured to be arranged in an annular shape such that the plurality of water pipes 40 are coaxial with the fuel ejection central axis X of the burner 10. Further, the outer water pipe group 42 is arranged such that a predetermined space is formed between the outer water pipe group 42 and the inner water pipe group 41. In the present embodiment, the water pipes 40 constituting the outer water pipe group 42 are arranged in contact with adjacent water pipes 40. Further, the upper parts of the plurality of water pipes 40 constituting the outer water pipe group 42 have a small diameter, and a gap is formed between adjacent water pipes 40 at this upper part.

[0018] As shown in Fig. 1, the combustion chamber 32 is formed by a space surrounded by the inner water pipe group 41 inside the can body 30. In this combustion chamber 32, LNG and ammonia F2 as the first fuel F1 with a faster combustion rate than ammonia are ejected from the burner 10, and the LNG and ammonia F2 as the first fuel F1 are co - burned. The combustion gas generated by the co - combustion of the LNG and ammonia F2 as the first fuel F1 rises through the gap formed between adjacent water pipes 40 at the lower part of the inner water pipe group 41 from the combustion chamber 32 to the space formed between the inner water pipe group 41 and the outer water pipe group 42. Then, the combustion gas that has risen through the space formed between the inner water pipe group 41 and the outer water pipe group 42 flows through the gap formed between adjacent water pipes 40 at the upper part of the outer water pipe group 42 to the exhaust port 31 formed at the upper part of the can body 30, and is discharged to the outside through an exhaust pipe (not shown) connected to this exhaust port 31.

[0019] The high - temperature combustion gas generated by the co - combustion of the LNG and ammonia F2 as the first fuel F1 is rapidly cooled by contact with the water pipe 40. Due to the decrease in the combustion gas temperature, the combustion reaction stops, and the unburned substances are discharged as exhaust gas. In a boiler, it is required to complete combustion within a limited time (space) until the combustion gas contacts the water pipe and suppress the generation of unburned substances. In this embodiment, the inner water pipe group 41 constitutes a water - cooled wall that surrounds the flame formed by the fuel ejected from the burner 10 and the combustion air.

[0020] The burner 10 extends in the vertical direction of the ammonia co - combustion boiler device 1 and is arranged at the upper part of the can body 30. As shown in Figs. 1 and 2, this burner 10 of this embodiment includes a first fuel flow path L1, a first air flow path L2, an ammonia flow path L3, a second air flow path L4, and a mixing flow path L5. Also, the burner 10 includes a first fuel flow path pipe 11, a first air flow path pipe 12, an ammonia flow path pipe 13, and a second air flow path pipe 14. Further, the burner 10 includes a first fuel ejection unit 15 and a first fuel flame retention unit 26 that are disposed at the tip of the first fuel flow path L1 and eject LNG as the first fuel F1 that has flowed through the first fuel flow path L1; a first air ejection unit 16 that is disposed at the end of the first air flow path L2 and ejects the first combustion air A1 that has flowed through the first air flow path L2 at the tip of the first air flow path L2; an ammonia ejection unit 17 that is disposed at the tip of the ammonia flow path L3 and ejects ammonia F2 that has flowed through the ammonia flow path L3; a second air ejection unit 18 that is disposed at the tip of the second air flow path L4 and ejects the second combustion air A2 that has flowed through the second air flow path L4; and a swirling unit 20 that is disposed on the proximal end side of the second air flow path L4. Further, the burner 10 includes a first fuel inlet 21 for introducing LNG as the first fuel F1, an ammonia inlet 23 for introducing ammonia F2, a wind box 28, and a first combustion air inlet 22 for introducing the first combustion air A1. The second combustion air introduction unit for introducing the second combustion air A2 includes the swirling unit 20 and a second combustion air inlet 24, and the wind box 28 includes a combustion air inlet 29 for introducing the combustion air A0.

[0021] The first fuel flow path L1 supplies LNG as the first fuel F1 having a higher combustion rate than ammonia. In the present embodiment, the first fuel flow path L1 is formed by a first fuel flow path pipe 11 that allows LNG as the first fuel F1 having a higher combustion rate than ammonia to flow therethrough. The first fuel ejection unit 15 is disposed upstream of the ammonia ejection unit 17 in the first fuel flow direction of the first fuel flow path L1. At least a part of the LNG ejected as the first fuel F1 from the first fuel ejection unit 15 is burned in the space surrounded by the ammonia flow path L3. That is, it is possible to secure a space in which at least a part of the LNG as the first fuel F1 is burned before being mixed with the ammonia F2. Thereby, by improving the flame retention property of the LNG as the first fuel F1 and stabilizing the combustion of the first fuel F1, the combustion of ammonia is promoted and the generation of unburned substances of ammonia can be suppressed.

[0022] The tip of the first fuel flow path pipe 11 has a conical shape. The first fuel injection part 15 is composed of fuel flow holes 27 which are a plurality of through holes formed on the conical peripheral surface of the tip of the first fuel flow path pipe 11. The first fuel flame holding part 26 has a frustum of a cone shape that expands toward the tip side, and a plurality of through holes are formed on the peripheral surface of the frustum of the cone as the first air injection part 16 from which the first combustion air A1 jets out. The plurality of through holes as the first air injection part 16 are formed in multiple rows spaced apart in the expanding direction. Also, the first combustion air A1 jets out from the gap between the frustum of the cone of the first fuel flame holding part 26 as the first air injection part 16 and the inner peripheral surface of the first air flow path pipe 12. The first fuel flame holding part 26 is arranged on the downstream side of the first fuel injection part 15 in the first fuel flow direction of the first fuel flow path L1, and serves as a flame holding part in the combustion of the LNG as the first fuel F1 jetted out from the first fuel injection part 15.

[0023] In the present embodiment, the base end side of the first fuel flame holding part 26 is connected to the tip side of the first fuel flow path pipe 11 in the first fuel flow direction of the first fuel flow path L1. Also, the tip of the first fuel flame holding part 26 is arranged on the downstream side of the first fuel injection part 15 and on the upstream side of the ammonia injection part 17 in the first fuel flow direction of the first fuel flow path L1.

[0024] The first air flow path L2 is arranged outside the first fuel flow path L1 and supplies the first combustion air A1. In the present embodiment, the first air flow path L2 is formed by the outer peripheral surface of the first fuel flow path pipe 11 forming the first fuel flow path L1, the frustum of the cone-shaped outer peripheral surface of the first fuel flame holding part 26, and the inner peripheral surface of the first air flow path pipe 12. Also, the downstream tip of the first air flow path L2 points to the position of the gap between the frustum of the cone of the first fuel flame holding part 26 and the inner peripheral surface of the first air flow path pipe 12 in the first fuel flow direction. The first combustion air A1 flows between the outer peripheral surface of the first fuel flow path pipe 11 and the inner peripheral surface of the first air flow path pipe 12, and then jets out from the through holes formed on the frustum of the cone-shaped peripheral surface of the first fuel flame holding part 26 as the first air injection part 16 and the gap between the frustum of the cone of the first fuel flame holding part 26 and the inner peripheral surface of the first air flow path pipe 12, is mixed with the LNG as the first fuel F1, and burns efficiently.

[0025] Figures 3 to 6 are diagrams showing the combustion test results of the burner 10 of the first embodiment. In FIGS. 3 and 4, in the burner 10 of the present embodiment, the relationship between the inner diameter D of the first air flow path L2 and the distance H from the tip of the first fuel flame retention part 26 to the ammonia ejection part 17 in the first fuel flow direction is shown for the case of H:D = 3:4, and the test results of co-combusting LNG as the first fuel F1 and ammonia F2 are shown. The co-combustion test was carried out under the conditions of an ammonia co-combustion rate of 40% and 50%. FIG. 3 is a diagram showing the relationship between the exhaust gas oxygen concentration and the exhaust gas carbon monoxide concentration in the combustion test of the burner 10 of the first embodiment. The vertical axis of the graph in FIG. 3 shows the relative value when based on the highest value of the exhaust gas carbon monoxide concentration at an ammonia co-combustion rate of 50%. The horizontal axis of the graph in FIG. 3 is the exhaust gas oxygen concentration [%]. As shown in FIG. 3, there was no sharp increase in the carbon monoxide concentration until the oxygen concentration was less than 1% in the case of an ammonia co-combustion rate of 50% and until the oxygen concentration was less than 1.5% in the case of an ammonia co-combustion rate of 40%. Note that the ammonia co-combustion rate indicates the ratio of the combustion amount (based on calorific value) of ammonia fuel in the combustion amount of the ammonia co-combustion boiler device 1.

[0026] FIG. 4 is a diagram showing the relationship between the exhaust gas oxygen concentration and the exhaust gas nitrous oxide concentration in the combustion test of the burner 10 of the first embodiment. The vertical axis of the graph in FIG. 4 shows the relative value when based on the highest value of the exhaust gas nitrous oxide concentration at an ammonia co-combustion rate of 50%. The horizontal axis of the graph in FIG. 4 is the exhaust gas oxygen concentration [%]. As shown in FIG. 4, when the exhaust gas oxygen concentration exceeds 4%, the exhaust gas nitrous oxide concentration increases rapidly. Also, LNG as the first fuel F1 burned well in the range of an exhaust gas oxygen concentration of 1.5% or more and 4% or less. Further, as the ammonia co-combustion rate increased from 40% to 50%, the increase in the exhaust gas carbon monoxide concentration shifted to the low oxygen concentration side.

[0027] In FIGS. 5 and 6, in the burner 10 of the first embodiment, test results of co - firing LNG as the first fuel F1 and ammonia F2 when H:D = 3:2 are shown. The co - firing tests were carried out under conditions of ammonia co - firing ratios of 40% and 50%. FIG. 5 is a diagram showing the relationship between the exhaust gas oxygen concentration and the exhaust gas carbon monoxide concentration in the combustion test of the burner 10 of the first embodiment. The vertical axis of the graph in FIG. 5 shows the relative value based on the highest value of the exhaust gas carbon monoxide concentration at an ammonia co - firing ratio of 50%. The horizontal axis of the graph in FIG. 5 is the exhaust gas oxygen concentration [%]. As shown in FIG. 5, there was no sharp increase in the carbon monoxide concentration until the oxygen concentration was less than 1% in the case of an ammonia co - firing ratio of 50%, and until the oxygen concentration was less than 1.5% in the case of an ammonia co - firing ratio of 40%.

[0028] FIG. 6 is a diagram showing the relationship between the exhaust gas oxygen concentration and the exhaust gas nitrous oxide concentration in the combustion test of the burner 10 of the first embodiment. The vertical axis of the graph in FIG. 6 shows the relative value based on the highest value of the exhaust gas nitrous oxide concentration at an ammonia co - firing ratio of 50%. The horizontal axis of the graph in FIG. 6 is the exhaust gas oxygen concentration [%]. As shown in FIG. 6, when the exhaust gas oxygen concentration exceeds 4%, the nitrous oxide concentration increases rapidly. Also, as the ammonia co - firing ratio increases from 40% to 50%, the increase in the exhaust gas carbon monoxide concentration shifts to the low - oxygen - concentration side. As the distance H becomes longer, the mixing position of the secondary air moves to the downstream side of the burner 10, and a tendency for the exhaust gas carbon monoxide concentration to increase was recognized. However, in both the case of H:D = 3:4 and the case of H:D = 3:2, within the range of the exhaust gas oxygen concentration of 1.5% or more and 4% or less, the exhaust gas carbon monoxide concentration and the exhaust gas nitrous oxide concentration were within the allowable range.

[0029] From FIGS. 3 to 6, in the present embodiment, the relationship between the inner diameter D of the first air flow path L2 and the distance H from the tip of the first fuel flame - holding part 26 to the ammonia ejection part 17 in the first fuel flow direction is such that when the first fuel F1 is LNG as a gaseous fuel, it is preferable that H:D is in the range of 3:2 to 3:4. As a result, the first fuel injection part 15 is located upstream of the ammonia injection part 17 and burns only with LNG as the first fuel F1 before mixing with the ammonia F2, so that the inflammability retention of LNG as the first fuel F1 can be improved. In addition, since a part of the LNG as the first fuel F1 is mixed with and burns with the first combustion air A1 flowing out from the first air flow path L2, it has the effect of preheating the ammonia F2 and improving the combustibility of the ammonia F2.

[0030] The mixing flow path L5 is arranged downstream of the first fuel flow path L1 and the first air flow path L2, and the first fuel F1 and the first combustion air A1 flow through it. In the present embodiment, the mixing flow path L5 is formed by the conical outer peripheral surface of the tip of the first fuel flow path pipe 11, the frustum-shaped inner peripheral surface of the first fuel flame retention part 26, and the inner peripheral surface of the first air flow path pipe 12. Further, the mixing flow path L5 includes the downstream side from the position of the gap between the frustum shape of the first fuel flame retention part 26, which is the downstream tip of the first air flow path L2, and the inner peripheral surface of the first air flow path pipe 12 in the first fuel flow direction. Also, the mixing flow path L5 is a flow path in which the first fuel F1 ejected from the first fuel ejection part 15 and the first combustion air A1 ejected from the first air ejection part 16 are mixed. In the mixing flow path L5, a part of the LNG as the first fuel F1 and a part of the first combustion air A1 are mixed and burned efficiently. In addition, since a part of the LNG as the first fuel F1 burns after flowing out of the mixing flow path L5, excessive heating of the burner 10 can be prevented, and thermal deterioration of the burner 10 and the like can be suppressed.

[0031] The ammonia flow path L3 is arranged outside the first air flow path L2 and supplies the ammonia F2. In the present embodiment, the ammonia flow path L3 is formed by the outer peripheral surface of the first air flow path pipe 12 and the inner peripheral surface of the ammonia flow path pipe 13. The ammonia ejection part 17 ejects the ammonia F2 that has flowed through the ammonia flow path pipe 13 downward. More specifically, the ammonia ejection part 17 has an ammonia ejection path 19 that directs the ejection of the ammonia F2. In the present embodiment, the ammonia F2 is ejected in the direction in which the through hole of the ammonia ejection path 19 extends.

[0032] The ammonia injection part 17 injects ammonia F2 toward the outer edge of the flame formed by the combustion of LNG as the first fuel F1 and the first combustion air A1. Thereby, the mixing of the ammonia F2 with the combustion gas of the first fuel F1 and the second combustion air A2 is promoted, and the generation of unburned substances of ammonia can be further reduced.

[0033] Returning to FIG. 2, the second air flow path L4 is arranged outside the ammonia flow path L3 and supplies the second combustion air A2. In the present embodiment, the second air flow path L4 is formed by the outer peripheral surface of the ammonia flow path pipe 13 and the inner peripheral surface of the second air flow path pipe 14. The second air flow path pipe 14 has a turning part 20 for turning the second combustion air A2. In the present embodiment, the turning part 20 is arranged on the proximal end side of the second air flow path pipe 14. The second combustion air A2 is turned by the turning part 20 and ejected as a swirling flow centered on the fuel ejection central axis X from the second air ejection part 18.

[0034] The first fuel inlet 21 introduces LNG as the first fuel F1. Specifically, LNG as the first fuel F1 is sent into the first fuel inlet 21 from a first fuel supply part (not shown). The ammonia inlet 23 introduces ammonia F2. Specifically, ammonia F2 is sent into the ammonia inlet 23 from an ammonia supply part (not shown). The wind box 28 introduces the combustion air A0 from the combustion air inlet 29. Specifically, a duct extended from a blower (not shown) is connected to the combustion air inlet 29 of the wind box 28, and the combustion air A0 is sent through the duct from the blower. A part of the combustion air A0 sent into the wind box 28 is supplied as the first combustion air A1 to the first combustion air inlet 22. Also, a part of the combustion air A0 sent into the wind box 28 is supplied as the second combustion air A2 to the second combustion air inlet 24. The secondary combustion air A2 sent from the secondary combustion air inlet 24 forms a swirling flow in the swirling section 20 and flows through the secondary air flow path L4.

[0035] In the above burner 10, LNG as the first fuel F1 is ejected downward from the first fuel ejection section 15, and the first combustion air A1 ejected from the first air ejection section 16 is mixed with LNG as the first fuel F1. At least a part of the LNG as the first fuel F1 mixed with the first combustion air A1 burns stably in the space surrounded by the ammonia flow path L3. Specifically, at least a part of the LNG as the first fuel F1 mixed with the first combustion air A1 burns stably only with the LNG as the first fuel F1 in the space downstream of the first fuel flame retention section 26 and surrounded by the inner peripheral surface of the first air flow path pipe 12, and the inner peripheral surface of the first air flow path pipe 12 is heated by the flame of the LNG as the first fuel F1.

[0036] Also, ammonia F2 is ejected from the ammonia ejection section 17, and the secondary combustion air A2 that has become a swirling flow in the swirling section 20 is ejected from the secondary air ejection section 18. The ejected ammonia F2 is mixed with the secondary combustion air A2 and co - burned with the LNG as the first fuel F1 to promote combustion. Thereby, the burner 10 ejects LNG as the first fuel F1 with a combustion speed faster than that of ammonia, ejects the first combustion air A1 outside the LNG as the first fuel F1, ejects ammonia F2 outside the first combustion air A1, and ejects the secondary combustion air A2 outside the ammonia F2. By having such a configuration, the ammonia F2 can be stably burned.

[0037] Also, by arranging the first fuel ejection section 15 upstream of the ammonia ejection section 17, a space can be secured in which the LNG as the first fuel F1 burns before mixing with the ammonia F2. Thereby, by improving the flame retention property of the LNG as the first fuel F1 and stabilizing the combustion of the first fuel F1, the combustion of ammonia is promoted and the generation of unburned substances of ammonia can be suppressed. In addition, since at least a part of the LNG as the first fuel F1 burns before being mixed with the ammonia F2, the ammonia F2 can be mixed with a combustion gas having a low oxygen concentration and burned to suppress the generation of NOx. Also, on the downstream side of the first fuel flame retention part 26 in the ammonia flow path L3 and in the space surrounded by the inner peripheral surface of the first air flow path pipe 12, the inner peripheral surface of the first air flow path pipe 12 on the downstream side from the first fuel flame retention part 26 is heated by the LNG as the first fuel F1 that is ejected from the first fuel ejection part 15 and burns, and the ammonia F2 flowing through the ammonia flow path L3 can be heated. That is, the first air flow path pipe 12 on the downstream side from the first fuel flame retention part 26 can indirectly heat the ammonia F2 flowing through the ammonia flow path L3 by the combustion gas of the LNG, rather than by direct mixing of the combustion gas of the LNG and the ammonia F2, as an ammonia heating part of the burner 10. Thereby, the ammonia F2 can be burned more stably without causing instability of combustion due to a rapid temperature change of the combustion gas or the like, and the generation of unburned substances of ammonia can be reduced.

[0038] The control unit 70 controls the combustion of the ammonia co-firing boiler device 1. The control unit 70 is composed of an arithmetic processor such as a PLC (Programmable Logic Controller), a DSP (Digital Signal Processor), an FPGA (Field-Programmable Gate Array), etc. Various functions of the control unit 70 are realized, for example, by executing a predetermined software (program) stored in a storage unit (not shown). Various functions of the control unit 70 may be realized by the cooperation of hardware and software, or may be realized only by hardware (electronic circuit).

[0039] As shown in FIG. 1, the control unit 70 includes a combustion control unit 71. The combustion control unit 71 supplies the LNG as the first fuel F1 after starting the supply of the first combustion air A1 and the second combustion air A2, and starts the supply of the ammonia F2 after a predetermined time has elapsed since starting the combustion of the LNG as the first fuel F1. As a result, when the combustion of ammonia F2 starts, the burner 10 and the furnace interior are heated, and the generation of unburned matter of ammonia at the start of ammonia combustion can be suppressed. Further, since the secondary combustion air A2 is supplied when ammonia F2 is supplied, combustion at a predetermined air ratio can be achieved at the start of the supply of ammonia F2, and the generation of unburned ammonia can be suppressed.

[0040] According to the burner 10 and the ammonia co-firing boiler apparatus 1 of the present embodiment described above, the following effects can be obtained.

[0041] (1) The burner 10 of the present embodiment includes a first fuel passage L1 that supplies LNG as a first fuel F1 having a combustion speed faster than that of ammonia, a first air passage L2 that is disposed outside the first fuel passage L1 and supplies the primary combustion air A1, an ammonia passage L3 that is disposed outside the first air passage L2 and supplies ammonia F2, a second air passage L4 that is disposed outside the ammonia passage L3 and supplies the secondary combustion air A2, a first fuel ejection portion 15 that is disposed at the tip of the first fuel passage L1 and ejects LNG as the first fuel F1 that has flowed through the first fuel passage L1, a first air ejection portion 16 that is disposed at the tip of the first air passage L2 and ejects the primary combustion air A1 that has flowed through the first air passage L2, an ammonia ejection portion 17 that is disposed at the tip of the ammonia passage L3 and ejects ammonia F2 that has flowed through the ammonia passage L3, and a second air ejection portion 18 that is disposed at the tip of the second air passage L4 and ejects the secondary combustion air A2 that has flowed through the second air passage L4. The first fuel ejection portion 15 is disposed upstream of the ammonia ejection portion 17, and at least a part of the LNG as the first fuel F1 burns in the space surrounded by the ammonia passage L3. As a result, by providing a configuration in which LNG as a first fuel having a combustion speed faster than that of ammonia is ejected, the primary combustion air A1 is ejected outside the first fuel F1, ammonia F2 is ejected outside the primary combustion air A1, and the secondary combustion air A2 is ejected outside the ammonia F2, ammonia can be stably combusted. Also, by arranging the first fuel injection part 15 upstream of the ammonia injection part 17, a space can be secured where the LNG as the first fuel F1 burns before mixing with the ammonia F2. Thereby, the inflammability retention of the LNG as the first fuel F1 can be improved, the ammonia co-combustion can be stabilized, and the generation of unburned ammonia can be suppressed. Also, since at least a part of the LNG as the first fuel F1 burns before mixing with the ammonia F2, the ammonia F2 can suppress the generation of NOx by mixing with and burning in a combustion gas with a low oxygen concentration. Also, in the ammonia flow path L3 downstream of the first fuel flame retention part 26, the inner peripheral surface of the first air flow path pipe 12 is heated by the LNG as the first fuel F1 that is ejected from the first fuel injection part 15 and burns, and the ammonia F2 flowing through the ammonia flow path L3 can be heated. Thereby, the ammonia F2 can be made to burn more stably, and the generation of unburned ammonia can be reduced.

[0042] (2) The burner 10 described in (1) is such that the first fuel F1 is a gaseous fuel, and in the first fuel flow direction of the first fuel flow path L1, it is arranged downstream of the first fuel injection part 15, and includes a first fuel flame retention part 26 that serves as a flame retention part in the combustion of the gaseous fuel (LNG) as the first fuel F1 ejected from the first fuel injection part 15. The relationship between the inner diameter D of the first air flow path L2 and the distance H from the tip of the first fuel flame retention part 26 to the ammonia injection part 17 in the first fuel flow direction is such that H:D is in the range of 3:2 to 3:4. Thereby, the first fuel injection part 15 is located upstream of the ammonia injection part 17, and since only the LNG as the first fuel F1 burns before mixing with the ammonia F2, the inflammability retention of the LNG as the first fuel F1 can be improved. Also, since a part of the LNG as the first fuel F1 burns after the first combustion air A1 flows out from the first air flow path L2, excessive heating of the burner 10 can be prevented, and thermal deterioration of the burner 10 and the like can be suppressed. Also, there is an effect of preheating the ammonia F2 and improving the combustibility of the ammonia F2.

[0043] (3) The burner 10 described in (1) or (2) is configured such that the ammonia ejection part 17 ejects ammonia F2 toward the outer edge of the flame formed by the combustion of LNG as the first fuel F1 and the first combustion air A1. Thereby, the mixing of the ammonia F2 with the combustion gas of the first fuel F1 and the second combustion air A2 is promoted, and the generation of unburned ammonia can be further reduced.

[0044] (4) The ammonia co-firing boiler apparatus 1 including the burner 10 described in (1) to (3) is provided with a combustion control unit 71 that controls the burner 10. The combustion control unit 71 supplies LNG as the first fuel F1 after starting the supply of the first combustion air A1 and the second combustion air A2, and starts the supply of ammonia F2 after a predetermined time has elapsed since the start of the combustion of the LNG as the first fuel F1. Thereby, at the start of the combustion of ammonia F2, the burner 10 and the furnace interior are heated, and the generation of unburned ammonia at the start of ammonia combustion can be suppressed. Further, since the second combustion air A2 is being supplied at the time of the supply of ammonia F2, there is no fluctuation in the amount of combustion air at the start of the supply of ammonia F2, and combustion can be performed at a predetermined air ratio, suppressing the generation of unburned ammonia.

[0045] (Second Embodiment) Next, the burner 10 of the second embodiment will be described with reference to FIGS. 7 to 9. FIG. 7 is a longitudinal sectional view of the burner 10 according to the second embodiment of the present invention. In the present embodiment, A heavy oil, which is a liquid fuel, is used as the first fuel F1 having a higher combustion rate than ammonia. In the present embodiment, except for the first air ejection part 16A, the first fuel ejection part 15A, and the baffle plate 26A, the configuration is the same as that of the burner 10 of the first embodiment, and thus the same reference numerals are given and the description thereof is omitted.

[0046] The burner 10 includes a first fuel ejection part 15A and a baffle plate 26A disposed at the tip side of the first fuel flow path pipe 11, and a first air ejection part 16A. The baffle plate 26A is in the shape of a disc having a circular opening at the center through which the first fuel F1 ejected from the first fuel ejection part 15A passes. The baffle plate 26A is fixed to the tip of the first fuel flow path pipe 11 by a support member. Further, the tip of the baffle plate 26A is disposed on the downstream side of the first fuel ejection part 15A and on the upstream side of the ammonia ejection part 17 in the first fuel flow direction of the first fuel flow path L1. Combustion air supply holes or slits are appropriately provided on the plate surface of the baffle plate 26A.

[0047] The first combustion air A1 flows between the outer peripheral surface of the first fuel flow path pipe 11 and the inner peripheral surface of the first air flow path pipe 12 and passes through the combustion air supply holes or slits of the baffle plate 26A. Thereby, a vortex of the first combustion air A1 is formed on the downstream side of the baffle plate 26A. Thereby, a stable flame-holding state of the A heavy oil as the first fuel F1 can be formed, and a good combustion state can be continuously maintained.

[0048] FIG. 8 and FIG. 9 are diagrams showing the combustion test results of the burner 10 of the second embodiment. FIG. 8 is a diagram showing the relationship between the exhaust gas oxygen concentration and the exhaust gas carbon monoxide concentration in the combustion test of the burner 10 of the second embodiment. The vertical axis of the graph in FIG. 8 shows the relative value when the self-reference value of the exhaust gas carbon monoxide concentration is set to 1. The horizontal axis of the graph in FIG. 8 is the exhaust gas oxygen concentration [%]. In FIG. 8, in the burner 10 of the present embodiment, the relationship between the inner diameter D of the first air flow path L2 and the distance H from the tip of the baffle plate 26A to the ammonia ejection part 17 in the first fuel flow direction is shown for the three conditions of H:D = 1:13.9, 1:4.6, and 1:3.5. The test results of burning the A heavy oil as the first fuel F1 are shown. As shown in FIG. 8, the A heavy oil as the first fuel F1 burns well in the range of the exhaust gas oxygen concentration of 3% or more and 7% or less. Further, on the high oxygen concentration side of the exhaust gas oxygen concentration, the exhaust gas carbon monoxide concentration reaches the self-reference value at 7.6% for H:D = 1:13.9, 9% for H:D = 1:4.6, and 8.5% for H:D = 1:3.5.

[0049] FIG. 9 is a diagram showing the relationship between H:D and the exhaust gas oxygen concentration at which the exhaust gas carbon monoxide concentration rapidly increases in the combustion test of the burner 10 of the second embodiment. In FIG. 9, the horizontal axis of the graph indicates the distance H from the tip of the first fuel flame retention part 26 to the ammonia injection part 17 (the inner diameter D of the first air flow path is fixed at a predetermined value), and the solid black circles shown in the graph indicate the exhaust gas oxygen concentration at which the exhaust gas carbon monoxide concentration rapidly increases in FIG. 8. The vertical axis of the graph in FIG. 9 is the exhaust gas oxygen concentration [%]. The relationship between the length of the distance H shown in FIG. 9 and the exhaust gas oxygen concentration at which the exhaust gas carbon monoxide concentration rapidly increases can be approximated by a quadratic function. From the approximate curve of this quadratic function, when H:D is from 1:10.5 to 1:3.1, the exhaust gas oxygen concentration at which the exhaust gas carbon monoxide concentration rapidly increases is estimated to be 8% or more, and it is preferable that H:D is from 2:21 to 5:16. Further, when a margin of 0.3% is added to the exhaust gas oxygen concentration, from FIG. 9, H:D becomes from 1:8.8 to 1:3.3, and it is more preferable that H:D is from 2:17 to 3:10.

[0050] From FIGS. 8 and 9, in the present embodiment, regarding the relationship between the inner diameter D of the first air flow path L2 and the distance H from the tip of the baffle plate 26A in the first fuel flow direction to the ammonia injection part 17, when the first fuel F1 is a liquid fuel, it is preferable that H:D is in the range of 2:21 to 5:16. Thereby, the first fuel injection part 15A is located upstream of the ammonia injection part 17 and burns only with the A heavy oil as the first fuel F1 before mixing with the ammonia F2, so that the flame retention property of the A heavy oil as the first fuel F1 can be improved. Further, since a part of the A heavy oil as the first fuel F1 burns after the first combustion air A1 flows out from the first air flow path L2, it has the effect of preheating the ammonia F2 and improving the combustibility of the ammonia F2. In addition, excessive heating of the burner 10 can be prevented, and thermal deterioration of the burner 10 and the like can be suppressed.

[0051] (5)(1), (3) to (4) The burner 10 described has a first fuel F1 that is a liquid fuel and is arranged on the downstream side of the first fuel ejection part 15 in the first fuel flow direction of the first fuel flow path L1. It has a first fuel flame retention part 26 that serves as a flame retention part in the combustion of the liquid fuel (A heavy oil) as the first fuel F1 ejected from the first fuel ejection part 15. The relationship between the inner diameter D of the first air flow path L2 and the distance H from the tip of the first fuel flame retention part 26 to the ammonia ejection part 17 in the first fuel flow direction is such that H:D is in the range of 2:21 to 5:16. As a result, the first fuel ejection part 15 is located upstream of the ammonia ejection part 17 and burns only with A heavy oil as the first fuel F1 before mixing with ammonia F2. Therefore, the flame retention property of A heavy oil as the first fuel F1 can be improved. Also, a part of A heavy oil as the first fuel F1 burns after the first combustion air A1 flows out from the first air flow path L2, so it has the effect of preheating ammonia F2 and improving the combustibility of ammonia F2. Also, excessive heating of the burner 10 can be prevented, and thermal deterioration of the burner 10 can be suppressed.

[0052] (Variant form) As described above, the preferred embodiments of the burner and the ammonia co - combustion boiler device according to the present invention have been explained. However, the present invention is not limited to the above - described embodiments and can be appropriately changed.

[0053] The swivel part 20 is arranged on the base end side of the second air flow path pipe 14, but is not limited to this. The swivel part 20 may be arranged on the tip end side of the second air flow path pipe 14. Even in such a burner 10, the co - combustion of the second combustion air A2 and ammonia F2 can be promoted, and the generation of unburned substances of ammonia can be suppressed.

[0054] Alternatively, by installing the swirler as the swivel unit 20 on the base end side, in the middle, or the tip end side of the first air flow path pipe 12, swirl may be imparted to the first combustion air A1. Also, swirl may be imparted to the first combustion air A1 by the shape of the wind box. The swirl of the first combustion air A1 promotes the combustion of the first fuel and also promotes the co-combustion of ammonia F2, and can suppress the generation of unburned substances of ammonia.

[0055] In the above-described embodiment, the burner 10 is applied to a boiler (for example, a small once-through boiler, a small-scale once-through boiler, etc., a marine water-tube boiler, a marine composite boiler, etc. in the case of a ship) in which the can body 30 is composed of a plurality of water pipes 40, a lower header 50, and an upper header 60, and includes a combustion chamber 32 surrounded by the plurality of water pipes 40. By applying the burner 10 to these boilers in which the combustion amount is controlled according to the variation of the required load, the generation of unburned substances accompanying the start / stop of the burner combustion and the change in the combustion amount can be effectively suppressed, and the combustion can be stabilized. Moreover, not limited to these boilers, the burner according to the present invention may be applied to a smoke tube boiler in which a plurality of pipes through which combustion gas burned in a combustion furnace flows are arranged in water, and steam is generated by performing heat exchange between the plurality of pipes and water. Also, the burner according to the present invention may be applied to a furnace without a water-cooled wall such as a heating furnace or an incinerator. Further, in addition to a boiler that generates steam, the burner according to the present invention can also be applied to a hot water boiler or a heat medium boiler in which a heat medium is circulated through a heat transfer pipe.

[0056] Note that since the present invention promotes the use of ammonia that does not emit carbon dioxide as a fuel, for example, it can contribute to Goal 7 of the Sustainable Development Goals (SDGs) led by the United Nations, "Ensure access to affordable, reliable, sustainable and modern energy".

Explanation of Reference Numerals

[0057] 1 Ammonia co-combustion boiler device 10 Burner 15 First fuel injection part 16 First air injection part 17 Ammonia ejection section 18 Second air ejection section 19 Ammonia ejection path 26 First fuel flame retention section 71 Combustion control section L1 First fuel flow path L2 First air flow path L3 Ammonia flow path L4 Second air flow path H Distance from the tip of the first fuel flame retention section 26 to the ammonia ejection section 17 D Inner diameter of the first air flow path L2 X Fuel ejection central axis

Claims

1. A first fuel flow path that supplies a first fuel having a combustion speed faster than ammonia, A first air flow path that is disposed outside the first fuel flow path and supplies first combustion air, An ammonia flow path that is disposed outside the first air flow path and supplies ammonia, A second air flow path that is disposed outside the ammonia flow path and supplies second combustion air, A first fuel ejection part that is disposed at the tip of the first fuel flow path and ejects the first fuel that has flowed through the first fuel flow path, A first air ejection part that is disposed at the tip of the first air flow path and ejects the first combustion air that has flowed through the first air flow path, An ammonia ejection part that is disposed at the tip of the ammonia flow path and ejects the ammonia that has flowed through the ammonia flow path, A second air ejection part that is disposed at the tip of the second air flow path and ejects the second combustion air that has flowed through the second air flow path, Comprising, The first fuel ejection part is disposed upstream of the ammonia ejection part, and at least a part of the first fuel burns in a space surrounded by the ammonia flow path, a burner.

2. The first fuel is a gaseous fuel, In the first fuel flow direction of the first fuel flow path, it is disposed downstream of the first fuel ejection part, and includes a first fuel flame retention part that serves as a flame retention part in the combustion of the first fuel ejected from the first fuel ejection part, The relationship between the inner diameter D of the first air flow path and the distance H from the tip of the first fuel flame retention part to the ammonia ejection part in the first fuel flow direction is such that H:D is in the range of 3:2 to 3:4, The burner according to claim 1.

3. The first fuel is a liquid fuel, In the first fuel flow direction of the first fuel flow path, it is disposed downstream of the first fuel ejection part, and includes a first fuel flame retention part that serves as a flame retention part in the combustion of the first fuel ejected from the first fuel ejection part, The relationship between the inner diameter D of the first air flow path and the distance H from the tip of the first fuel flame retention part to the ammonia ejection part in the first fuel flow direction is such that H:D is in the range of 2:21 to 5:16, The burner according to claim 1.

4. The ammonia ejection part ejects ammonia toward the outer edge of the flame formed by the combustion of the first fuel and the first combustion air, The burner according to claim 1.

5. The burner according to any one of claims 1 to 4, A combustion control unit that controls the burner, Comprising, The combustion control unit supplies the first fuel after starting the supply of the first combustion air and the second combustion air, and starts the supply of ammonia after a lapse of a predetermined time after starting the combustion of the first fuel. It is an ammonia co-firing boiler.

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