JP7752919B2 - Ammonia combustion equipment - Google Patents

Description

The present invention relates to an ammonia combustion facility that mixes ammonia with air and burns it. In particular, the facility is characterized by the fact that when ammonia is mixed with air and burned, the ammonia is sufficiently burned to prevent unburned ammonia from remaining, and NOx is prevented from being generated when the ammonia is burned.

Combustion equipment that mixes fuel with combustion air and burns it generally uses hydrocarbon fuels.

However, when hydrocarbon fuel is mixed with combustion air and burned in this manner, there is a problem in that a large amount of greenhouse gases such as carbon dioxide ( _CO2) is generated.

In recent years, there has been a demand for reducing greenhouse gases such as carbon dioxide (CO _{2 )} , and the use of fuels other than hydrocarbon fuels has been considered.

It has also been known for some time that ammonia can be used as a fuel, but ammonia has poorer flammability than hydrocarbon fuels, making it difficult to completely burn it, and unburned ammonia is likely to remain. Furthermore, if ammonia is burned vigorously to reduce the amount of unburned ammonia, the flame temperature increases, resulting in increased NOx emissions.

Patent Document 1 proposes that when ammonia, a low-combustibility fuel with poor combustibility as described above, is mixed with combustion air and burned, the combustibility of the ammonia is enhanced by selectively premixing the ammonia with combustion air.

However, even when selectively using ammonia, a low-combustibility fuel, premixed with combustion air in this way, there are still problems, such as the ammonia not being burned sufficiently, leaving unburned ammonia, or when burning it vigorously to reduce the amount of unburned ammonia, the flame temperature increases, resulting in increased NOx emissions.

Patent Document 2 also proposes that when burning sulfur-containing fuels such as natural gas and pulverized coal, ammonia is injected from an ammonia injection port along the inner wall surface of a wall section where no burner is installed, causing the ammonia to burn near the inner wall surface, thereby preventing the wall from being eroded by hydrogen sulfide generated by the combustion of the sulfur components.

However, the method disclosed in Patent Document 2 does not provide the effect of preventing unburned ammonia from remaining or increasing the amount of NOx generated when ammonia itself is combusted as described above.

JP 2016-130619 A Japanese Patent Application Laid-Open No. 2020-139700

The present invention aims to solve the above-mentioned problems in ammonia combustion equipment, which mixes ammonia with air and burns it.

In other words, the objective of the present invention is to ensure that ammonia is sufficiently burned when it is mixed with air and burned in an ammonia combustion facility such as the one described above, preventing unburned ammonia from remaining, and to prevent the generation of NOx during ammonia combustion.

In order to solve the above-mentioned problems, the ammonia combustion equipment according to the present invention is an ammonia combustion equipment in which ammonia is mixed with air and burned, and a guide pipe is provided on the outer periphery of the tip of the ammonia discharge pipe that discharges the ammonia, for guiding the ammonia discharged from the ammonia discharge pipe into a furnace, and air is introduced into the guide pipe through an air inlet between the ammonia discharge pipe and the guide pipe, and the ammonia and air are jetted radially into the furnace from a plurality of radial jets provided radially on the outer periphery of the tip of the guide pipe to be combusted, and an air introduction adjustment means is provided that sets the air ratio for burning ammonia in the range of 0.95 to 0.99 and adjusts the size of the air introduction part between the ammonia discharge pipe and the guide pipe .

The inventors conducted an experiment in which ammonia was mixed with air and burned, and investigated the relationship between the air ratio at which ammonia was burned, the amount of unburned ammonia that remains when ammonia is not fully burned, and the amount of NOx generated when ammonia is burned. As a result, as shown in Figure 1, it was found that as the air ratio decreases, the amount of NOx generated decreases and reaches zero, and at the same time, there is a point at which unburned ammonia, which was previously zero, begins to generate, i.e., a point at which both NOx generation and unburned ammonia generation approach zero.

Furthermore, experimental results showed that the point at which both NOx emissions and unburned ammonia emissions approach zero is when the air ratio for burning ammonia is in the range of 0.95 to 0.99. In Figure 1, Experiment A shows the changes in the amount of NOx and unburned ammonia generated when the air ratio for burning ammonia was 0.95, the lowest, while Experiment B shows the changes in the amount of NOx and unburned ammonia generated when the air ratio for burning ammonia was 0.99, the highest.

For this reason , in the ammonia combustion equipment according to the present invention, in the ammonia combustion equipment in which ammonia is mixed with air and burned as described above , a guide pipe is provided on the outer periphery of the tip of the ammonia discharge pipe that discharges the ammonia, for guiding the ammonia discharged from the ammonia discharge pipe into a furnace, air is introduced into the guide pipe through an air inlet between the ammonia discharge pipe and the guide pipe, and the ammonia and air are jetted radially into the furnace from a plurality of radial jet ports provided radially on the outer periphery of the tip of the guide pipe to be combusted, with the air ratio for burning the ammonia being set in the range of 0.95 to 0.99.

As described above , when ammonia is discharged from the ammonia discharge pipe into a guide pipe provided on the outer periphery of the tip of the ammonia discharge pipe, air is introduced into the guide pipe through the air inlet between the ammonia discharge pipe and the guide pipe, and ammonia and air are jetted radially into the furnace from a plurality of radial jets provided radially on the outer periphery of the tip of the guide pipe for combustion, the flame spreads radially near the inner wall surface of the furnace. Therefore, even when ammonia with low flammability is jetted into the furnace and combusted, it is possible to prevent the flame from extending long into the furnace and directly hitting the workpiece in the furnace, thereby deteriorating the finish of the workpiece, as in the conventional case.

Furthermore, in this ammonia combustion facility, the air ratio for burning ammonia was set in the range of 0.95 to 0.99 as described above, and therefore the amount of unburned ammonia and NOx generated during combustion was also reduced.

In the ammonia combustion facility, when the ammonia and air introduced into the guide pipe as described above are jetted radially into the furnace from a plurality of radial jet ports provided radially on the outer periphery of the tip of the guide pipe for combustion, and the air ratio for burning the ammonia is adjusted to be in the range of 0.95 to 0.99 , an air introduction adjustment means is provided to adjust the size of the air introduction section between the ammonia discharge pipe and the guide pipe.

Furthermore, when adjusting the air ratio for burning ammonia to be in the range of 0.95 to 0.99 as described above, an air guide section that guides air into the furnace can be provided on the outer periphery of the guide tube, and the air guided into the furnace through the air guide section can be mixed with the ammonia and air that are jetted radially into the furnace from multiple radial jets provided on the outer periphery of the tip of the guide tube as described above, and then combusted. The amount of air guided into the furnace through the air guide section can also be adjusted using a guide air adjustment means.

In the ammonia combustion equipment of the present invention, the air ratio for burning ammonia is set to the range of 0.95 to 0.99, so that ammonia is sufficiently burned during combustion as described above, and it is possible to prevent unburned ammonia from remaining, and also to prevent NOx from being generated during ammonia combustion.

Furthermore, in the ammonia combustion equipment of the present invention, as described above, ammonia and air are combusted by being jetted radially into the furnace from a plurality of radial jets provided radially on the outer periphery of the tip of the guide tube. Therefore, even when ammonia, which has low flammability, is jetted into the furnace for combustion, the flame spreads radially near the wall of the furnace, preventing the flame from extending far into the furnace and directly hitting the material to be treated inside the furnace, which would result in poor finish of the material, as was the case in the past.

FIG. 1 is a diagram showing the relationship between the air ratio at which ammonia is combusted, the amount of unburned ammonia that remains without being sufficiently burned, and the amount of NOx generated during the combustion of ammonia in the ammonia combustion equipment of the present invention. FIG. 1 is a schematic explanatory diagram showing a state in which ammonia is discharged from an ammonia discharge pipe into a guide pipe provided on the outer periphery of the tip of the ammonia discharge pipe, air is introduced into the guide pipe through an air inlet between the ammonia discharge pipe and the guide pipe, and ammonia and air are jetted radially into a furnace from a plurality of radial jets provided radially on the outer periphery of the tip of the guide pipe, and burned, in an ammonia combustion facility according to an embodiment of the present invention. 3 is an explanatory cross-sectional view taken along line A-A, showing a state in which a guide section for guiding air into a furnace is provided on the outer periphery of a guide tube in the ammonia combustion equipment according to the embodiment shown in FIG. 2, and the amount of air guided into the furnace through the air guide section is adjusted by a guide air adjusting means.

Ammonia combustion equipment according to an embodiment of the present invention will now be described in detail with reference to the accompanying drawings. Note that the ammonia combustion equipment according to the present invention is not limited to the embodiment shown below, and can be modified as appropriate within the scope of the invention.

In the ammonia combustion facility according to the embodiment of the present invention, as shown in FIG. 2, an ammonia discharge pipe ₂₀ for discharging ammonia NH3 is inserted into the center of a support plate 12b supported by supports 12a attached to mounting members 11 provided on an outer wall surface 10a of a furnace 10.

Furthermore, in the mounting member 11, a guide pipe 30 for guiding ammonia _NH3 discharged from the ammonia discharge pipe 20 into the furnace 10 is attached to the center of a protruding portion 11a that is provided so as to protrude outward in a concave shape from the outer wall surface 10a of the furnace 10, so as to be located on the outer periphery of the tip of the ammonia discharge pipe 20, and a plurality of radiation nozzles 31 are provided on the outer periphery of the tip of the guide pipe 30 that is led into the furnace 10, in the radial direction.

In the ammonia combustion equipment of this embodiment, a threaded portion 22 is provided on the outer periphery of the ammonia discharge pipe 20, and an air introduction adjustment means 40 is provided that engages with the threaded portion 22 on the outer periphery of the ammonia discharge pipe 20, rotates, and moves in the axial direction of the ammonia discharge pipe 20. The air introduction adjustment means 40 adjusts the size of the air introduction section S1 between the ammonia discharge pipe 20 and the guide pipe 30.

In addition, the inner diameter of the discharge port 21 at the tip of the ammonia discharge pipe 20 is tapered toward the direction in which the ammonia NH ₃ is ejected, so that the ammonia NH ₃ introduced into the ammonia discharge pipe 20 is ejected forcefully from the contracted discharge port 21 into the guide pipe 30.

In addition, by combining this with a diffuser structure in which the inner diameter of the flow path 33 within the guide tube 30 gradually contracts in the flow direction and then expands again, an ejector effect is created, allowing for even more powerful ejection.

When ammonia NH ₃ is forcefully sprayed into the guide pipe 30 from the discharge port 21 of the ammonia discharge pipe 20 in this manner, air is sucked into the space between the ammonia discharge pipe 20 and the guide pipe 30 through the air inlet S1, and the sucked air is mixed with the ammonia NH ₃ sprayed into the guide pipe 30 and is guided to the tip of the guide pipe 30, and is sprayed in a radial direction near the inner wall surface 10 b of the furnace 10 from the plurality of radial spray ports 31 provided on the outer periphery of the tip of the guide pipe 30.

In addition, in the ammonia combustion equipment of this embodiment, an air guide section 32 that guides air into the furnace 10 is provided on the outer periphery of the guide pipe 30, and as a guide air adjustment means for adjusting the amount of air guided to the air guide section 32, multiple inlet holes 51 that guide air to the air guide section 32 are provided in the protruding section 11a of the mounting member 11, and air adjustment holes 53 are provided in a ring-shaped rotating plate 52 that rotates in contact with the surface of the protruding section 11a, corresponding to each inlet hole 51 provided in the protruding section 11a.

To adjust the amount of air introduced into the furnace 10 through the air guide section 32, as shown in Figure 3, the rotating plate 52 is rotated to change the area of communication between the inlet hole 51 in the protruding section 11a and the air adjustment hole 53 in the rotating plate 52, thereby adjusting the amount of air introduced into the air guide section 32 through the inlet hole 51 and the air adjustment hole 53. In this way, an appropriate amount of air is supplied into the furnace 10 through the air guide section 32.

Here, in the ammonia combustion equipment of this embodiment, as described above, ammonia NH _{3 is injected into the guide pipe 30 from the discharge port 21 of the ammonia discharge pipe 20, and air is sucked between the ammonia discharge pipe 20 and the guide pipe 30 through the air introduction section S1. While the air is mixed with the ammonia NH 3 in} the guide pipe 30, the ammonia NH ₃ and air are injected radially into the furnace 10 from a plurality of radial jets 31 provided on the outer periphery of the tip of the guide pipe 30 along the inner wall surface 10b of the furnace 10, and an appropriate amount of air is supplied into the furnace 10 through the air guide section 32 on the outer periphery side of the guide pipe 30. With this air added, the ammonia NH ₃ is combusted at an air ratio in the range of 0.95 to 0.99.

In this way, as shown in FIG. 1, the amount of unburned ammonia (NH ₃₎ generated during combustion and the amount of NOx generated can be reduced. In particular, when the air ratio for burning ammonia (NH ₃₎ is set to about 0.97, the amount of unburned ammonia generated and the amount of NOx generated can be significantly reduced.

Furthermore, in the ammonia combustion equipment of this embodiment, as described above, ammonia _NH3 and air are jetted radially into the furnace 10 from the plurality of radial jets 31 provided on the outer periphery of the tip of the guide pipe 30 along the inner wall surface 10b of the furnace 10, and an appropriate amount of air is supplied into the furnace 10 through the air guide section 32 on the outer periphery of the guide pipe 30 to combust the ammonia _NH3 . Therefore, the flame spreads radially near the inner wall surface 10b of the furnace 10, preventing the flame from extending too far into the furnace 10. When a workpiece (not shown) is heat-treated in the furnace 10, it is possible to prevent the flame from directly hitting the workpiece, thereby preventing the finish of the workpiece from being poor.

In the ammonia combustion equipment of this embodiment, as described above, ammonia _NH3 and air Air are jetted radially into the furnace 10 along the inner wall surface 10b of the furnace 10 from the plurality of radial jet ports 31 provided on the outer periphery of the tip of the guide pipe 30, but the ammonia combustion equipment of the present invention is not limited to the above.

For example, although not shown, a mixture of ammonia NH ₃ and air may be sprayed into the furnace from the tip of a spray pipe (not shown). In this case, too, if the ammonia NH ₃ is burned at an air ratio in the range of 0.95 to 0.99 as described above, the amount of unburned ammonia NH ₃ and the amount of NOx generated during combustion can be reduced.

10: Furnace 10a: Outer wall surface 10b: Inner wall surface 11: Mounting member 11a: Protrusion 12a: Support 12b: Support plate 20: Ammonia discharge pipe 21: Discharge port 22: Threaded portion 30: Guide pipe 31: Radiation nozzle 32: Air guide portion 33: Flow path 40: Air introduction adjustment means 51: Inlet hole 52: Rotating plate 53: Air adjustment hole Air: Air _NH3 : Ammonia S1: Air introduction portion

Claims (3)

In an ammonia combustion facility for burning ammonia mixed with air, a guide pipe is provided on the outer periphery of the tip of the ammonia discharge pipe that discharges the ammonia, for guiding the ammonia discharged from the ammonia discharge pipe into a furnace; air is introduced into the guide pipe through an air inlet section between the ammonia discharge pipe and the guide pipe; and the ammonia and air are jetted radially into the furnace from a plurality of radial jets provided radially on the outer periphery of the tip of the guide pipe to combust the ammonia, wherein the air ratio for burning the ammonia is set in the range of 0.95 to 0.99, and air introduction adjustment means is provided for adjusting the size of the air introduction section between the ammonia discharge pipe and the guide pipe . 2. The ammonia combustion facility according to claim 1 , wherein an air guide section for guiding air into the furnace is provided on the outer periphery of the guide pipe, and the air guided into the furnace through the air guide section is mixed with the ammonia and air jetted radially into the furnace from a plurality of radial jets provided on the outer periphery of the tip of the guide pipe along the inner wall surface of the furnace, and combusted, with an air ratio for burning the ammonia in the range of 0.95 to 0.99. 3. The ammonia combustion facility according to claim 2 , further comprising an air guide adjusting means for adjusting the amount of air guided into the furnace through said air guide section.