JP2022062717A - Combined combustion furnace, and combined combustion boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent emissivity of flame from decreasing upon combusting carbon fuel mixed with low carbon fuel.

SOLUTION: There is provided a combined combustion furnace comprising a furnace, a first burner that injects carbon fuel to the furnace to burn the same, and a second burner that injects low carbon fuel of a lower carbon concentration relative to the carbon fuel to the furnace to burn the same. The first burner injects the carbon fuel in such a manner that carbon fuel flame is formed in a closer vicinity of the furnace wall relative to low carbon fuel flame resulting from the combustion of the low carbon fuel.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a combined combustion furnace and a combined combustion boiler.

The following Patent Documents 1 and 2 disclose a boiler for combined combustion of pulverized coal and ammonia. In these boilers, in order to reduce carbon dioxide (CO ₂ ) emissions, in addition to the pulverized coal that has been conventionally used as fuel, ammonia, which is a hydrogen carrier, is burned as fuel.

Japanese Unexamined Patent Publication No. 2016-041990 Japanese Unexamined Patent Publication No. 2016-183640

By the way, as is well known, a boiler is a heat transfer device that mainly transfers heat generated in a fireplace to water to generate steam. The amount of heat Q that enters the water flowing through the water pipe of the furnace wall by radiant heat transfer is the following equation (1) with respect to the combustion gas temperature T _gas of the furnace, the furnace wall temperature T _wall , the emissivity ε of the flame, and the Stefan-Boltzmann constant σ. It is represented by. As shown by this equation (1), the boiler performance, that is, the heat collection performance of the boiler is proportional to the emissivity ε of the flame.
Q = σε (T _gas ⁴ -T _wall ⁴ ) (1)

On the other hand, it is known that the emissivity ε of the flame depends on the carbon concentration contained in the fuel. Therefore, when a low carbon fuel such as ammonia that does not contain carbon as a constituent element is mixed with a carbon fuel such as pulverized coal or coal and burned in a furnace, compared with the case where the carbon fuel is burned as a single fuel. Therefore, there is a concern that the radiation coefficient ε of the flame will decrease, and as a result, the heat collection performance of the boiler will decrease.

The present invention has been made in view of the above circumstances, and an object of the present invention is to suppress a decrease in the emissivity of a flame when burning a carbon fuel and a low carbon fuel at the same time.

In order to achieve the above object, in the present invention, as a first solution for a combined combustion furnace, a furnace, a first burner for injecting carbon fuel into the furnace for combustion, and carbon rather than the carbon fuel are used. It is equipped with a second burner that injects and burns a low carbon fuel having a low concentration into the furnace, and the first burner is closer to the furnace wall of the furnace than the low carbon fuel flame due to the combustion of the low carbon fuel. The means of injecting the carbon fuel so as to form a carbon fuel flame is adopted.

In the present invention, as the second solution for the combined combustion furnace, in the first solution, a plurality of the first burners are arranged around the second burner.

In the present invention, as a third solution relating to the combined combustion furnace, in the first solution, the first burner and the second burner inject the low carbon fuel from the inside and the low carbon fuel from the outside. It adopts the means of being a composite burner that injects carbon fuel.

In the present invention, as the fourth solution means for the combined combustion furnace, in any of the first to third solutions, the means that the carbon fuel is pulverized coal is adopted.

In the present invention, as a fifth solution relating to the combined combustion furnace, in any of the first to fourth solutions, the means that the low carbon fuel is ammonia is adopted.

In the present invention, as a solution for the boiler, a means for providing a combined combustion furnace according to any one of the first to fifth solutions is adopted.

According to the present invention, since the carbon fuel is injected so that the flame is generated closer to the furnace wall of the furnace than the flame caused by the combustion of the low carbon fuel, the flame in the case of burning the carbon fuel and the low carbon fuel at the same time is used. It is possible to suppress the decrease in radiation rate.

It is a front view which shows the main part structure of the composite combustion furnace A which concerns on 1st Embodiment of this invention, and the boiler which comprises the composite combustion furnace A. It is an arrow view in the X-ray line of FIG. It is a 1st sectional view which shows the main part structure of the combined combustion furnace B which concerns on 2nd Embodiment of this invention, and the boiler which comprises the said combined combustion furnace B. It is a 2nd sectional view which shows the main part structure of the combined combustion furnace B which concerns on 2nd Embodiment of this invention, and the boiler which comprises the said combined combustion furnace B. It is a 3rd sectional view which shows the main part structure of the combined combustion furnace B which concerns on 2nd Embodiment of this invention, and the boiler which comprises the said combined combustion furnace B.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
First, the combined combustion furnace A according to the first embodiment of the present invention and the boiler including the combined combustion furnace A will be described with reference to FIGS. 1 and 2.

The boiler according to the first embodiment includes a fireplace 1, a heat exchange device 2, a plurality of burners M11 to M33, N11 to N33 (first burner and second burner), an ammonia supply device 3, and a pulverized coal supply device 4. Is provided as a key part. Of these plurality of components, a part (lower part) of the furnace 1 and a plurality of burners M11 to M33 and N11 to N33 constitute the combined combustion furnace A according to the first embodiment.

The furnace 1 is composed of a furnace wall provided vertically and in a tubular shape, and is a furnace body that burns fuel to generate combustion heat. In this fireplace 1, high-temperature combustion gas is generated by burning fuel. A flue (not shown) is provided in the subsequent stage of such a fireplace 1. The combustion gas is released into the atmosphere through the flue, but nitrogen oxides (NOx) and sulfides (SOx) are removed while passing through the flue. The bottom of such a fireplace 1 is provided with a discharge port 1a for discharging ash generated by combustion of fuel to the outside.

The heat exchange device 2 is composed of a plurality of heat transfer tubes provided on the upper part of the fireplace 1 and the furnace wall, and water is circulated inside. This heat exchange device 2 is a general term for heat exchange devices provided in a boiler such as a superheater and a reheater, and generates water vapor by exchanging heat of combustion contained in combustion gas with water in a heat transfer tube. Let me.

The plurality of burners M11 to M33 and N11 to N33 are two-dimensionally and opposed to each other in the lower part of the fireplace 1, and fuel is injected into the fireplace 1 to burn it. These plurality of burners M11 to M33 and N11 to N33 are all composite burners that inject ammonia (low carbon fuel) and pulverized coal (carbon fuel) into the furnace 1 as fuels, and also serve as the first burner in the present invention. The second burner.

Although not shown, the fireplace 1 is provided with an ignition device for igniting fuels (ammonia and pulverized coal) injected from a plurality of burners M11 to M33 and N11 to N33. The fuel (ammonia and pulverized coal) injected into the furnace 1 from the burners M11 to M33 and N11 to N33 are ignited and burned by the action of the ignition device.

The ammonia supply device 3 is one of the fuel supply devices for supplying ammonia as a low carbon fuel to the plurality of burners M11 to M33 and N11 to N33. The pulverized coal supply device 4 is the other fuel supply device that supplies pulverized coal as carbon fuel to the plurality of burners M11 to M33 and N11 to N33.

Here, the ammonia is a compound of hydrogen (H) and nitrogen (N) as shown by the molecular formula (NH ₃ ), and does not contain carbon (C) as a constituent atom. Although this ammonia (low carbon fuel) is known as a flame-retardant substance, it is a hydrogen carrier substance having three hydrogen atoms like methane (CH ₃ ). On the other hand, pulverized coal is a fossil fuel obtained by pulverizing coal to a size of about several micrometers, and is generally used as a fuel for boilers. That is, ammonia is a low carbon fuel having a lower carbon concentration than pulverized coal (carbon fuel).

The plurality of burners M11 to M33 and N11 to N33 will be described in more detail. In the combined combustion furnace A according to the first embodiment, one of a pair of furnace walls facing each other in a vertical posture in the lower part of the furnace 1. Nine burners M11 to M33 are provided on the furnace wall of the same, and nine burners N11 to N33 are also provided on the other furnace wall. Each of the nine burners M11 to M33 and N11 to N33 are provided in three stages in the vertical direction and in three rows in the horizontal direction, that is, in a two-dimensional shape.

That is, of the nine burners M11 to M33 and N11 to N33, three burners M11 to M13 and N11 to N13 are provided in the upper stage, and three burners M21 to M23 and N21 to N23 are provided in the middle stage, respectively. Three burners M31 to M33 and N31 to N33 are provided in the lower stage, respectively. Of these nine burners M11 to M33 and N11 to N33, three burners M11 to M31 and N11 to N31 are located on the right side when viewed from the outside of the furnace 1, and three burners each are located. M12 to M32 and N12 to N32 are located in the center, and three burners M13 to M33 and N13 to N33 are located on the left side, respectively.

The three burners M11 to M13 and N11 to N13 located in the upper row are all provided at the same height, and the three burners M21 to M23 and N21 to N23 located in the middle row are all provided at the same height. The three burners M31 to M33 and N31 to N33, which are located in the lower stage, are all provided at the same height. Further, three burners M11 to M31 and N11 to N31 located on the right side are provided in a row in the vertical direction, and three burners M12 to M32 and N12 to N32 located in the center are provided in a row in the vertical direction. The three burners M13 to M33 and N13 to N33 located on the left side are provided in a row in the vertical direction. That is, the nine burners M11 to M33 and N11 to N33, respectively, are arranged orthogonally to the vertical plane of the furnace 1.

Further, among the nine burners M11 to M33 and N11 to N33, the ones having the same code number are in a positional relationship facing each other. That is, the burner M11 and the burner N11 face each other in the same horizontal plane, the burner M12 and the burner N12 face each other in the same horizontal plane, the burner M13 and the burner N13 face each other in the same horizontal plane, and the burner M21 and the burner N21 face each other. Face each other in the same horizontal plane, the burner M22 and the burner N22 face each other in the same horizontal plane, the burner M23 and the burner N23 face each other in the same horizontal plane, and the burner M31 and the burner N31 face each other in the same horizontal plane. , The burner M32 and the burner N32 face each other in the same horizontal plane, and the burner M33 and the burner N33 face each other in the same horizontal plane.

Ammonia (low carbon fuel) is supplied from the ammonia supply device 3 to the nine burners M11 to M33 and N11 to N33 arranged on each furnace wall of the furnace 1 in this way, and fine powder is supplied from the pulverized coal supply device 4. Charcoal (carbon fuel) is supplied. The individual burners M11 to M33 and N11 to N33 are composite burners (first burner and second burner) that inject ammonia from the inside (center side) and pulverized coal from the outside (outer peripheral side). ..

For example, the individual burners M11 to M33 and N11 to N33 are formed in a triple tubular shape, and ammonia is supplied to the inner pipe, pulverized coal is supplied to the central pipe, and combustion air is supplied to the outer pipe. Therefore, in the furnace 1, as shown in the figure, for each of the burners M11 to M33 and N11 to N33, they are formed by burning pulverized coal around the ammonia flame Sa (low carbon fuel flame) formed by burning ammonia. A pulverized coal flame Sb (carbon fuel flame) is formed.

That is, in the burners M11 to M33 and N11 to N33 provided on the two facing furnace walls in the furnace 1, the pulverized coal flame Sb is generated closer to the furnace wall of the furnace 1 than the ammonia flame Sa due to the combustion of ammonia. Inject pulverized coal so as to. In other words, the burners M11 to M33 and N11 to N33 inject ammonia so that the ammonia flame Sa is farther from the furnace wall of the furnace 1 than the pulverized coal flame Sb.

Subsequently, the operation of the combined combustion furnace A and the boiler according to the first embodiment will be described in detail.
In the combined combustion furnace A and the boiler, ammonia is supplied from the ammonia supply device 3 to the burners M11 to M33 and N11 to N33, respectively, and pulverized coal is supplied from the pulverized coal supply device 4.

Then, ammonia and pulverized coal are injected into the fireplace 1 from the burners M11 to M33 and N11 to N33 and burned, so that combustion gas with combustion heat is generated in the fireplace 1. Then, the combustion gas rises in the furnace 1 and acts on the heat exchange device 2, so that the water is vaporized by the combustion heat of the combustion gas and steam is generated. The boiler supplies the steam generated in this way to an external device such as a generator. The combustion gas after heat exchange with the heat exchange device 2 is released from the fireplace 1 to the outside air via the flue.

Here, in the combined combustion furnace A and the boiler according to the first embodiment, the burners M11 to M33 and N11 to N33 have ammonia and pulverized coal so that the pulverized coal flame Sb is formed around the ammonia flame Sa. Is injected into the furnace 1. As is well known, ammonia has lower flammability than pulverized coal and is generally hard to burn, but pulverized coal having excellent combustibility burns before ammonia, so that the surrounding of ammonia injected into the furnace 1 The pulverized coal flame Sb is formed by the combustion of the pulverized coal.

The pulverized coal flame Sb is formed by burning pulverized coal having a carbon concentration higher than that of ammonia, and therefore the brightness is higher than the brightness of the ammonia flame Sa. Further, since such a pulverized coal flame Sb is formed so as to surround the ammonia flame Sa having a relatively low brightness for each of the burners M11 to M33 and N11 to N33, the brightness is compared on the furnace wall of the furnace 1. The radiant heat from the high-targeted pulverized coal flame Sb is mainly irradiated.

That is, according to the first embodiment, when the ammonia and the pulverized coal are burned at the same time, the decrease in the emissivity of the flame in the furnace wall of the furnace 1 is suppressed as compared with the case where only the pulverized coal is burned as fuel. It is possible. Therefore, according to this first embodiment, it is possible to suppress a decrease in the heat collection performance of the boiler as compared with the case where only pulverized coal is burned as fuel.

[Second Embodiment]
Next, the combined combustion furnace B according to the second embodiment of the present invention and the boiler provided with the combined combustion furnace B will be described with reference to FIGS. 3 to 5. In FIGS. 3 to 5, the same components as those shown in FIGS. 1 and 2 described above are designated by the same reference numerals.

The combined combustion furnace B according to the second embodiment has the same components as the combined combustion furnace A according to the first embodiment, but has ammonia (low carbon fuel) for the burners M11 to M33 and N11 to N33, respectively. ) And the supply of pulverized coal (carbon fuel) are different from those of the combined combustion furnace A according to the first embodiment. The combined combustion furnace B includes an ammonia supply device 3 and a pulverized coal supply device 4 as in the combined combustion furnace A according to the first embodiment, but in FIGS. 3 to 5, the ammonia supply device 3 and the pulverized coal are provided. The supply device 4 is omitted for convenience.

As can be seen by comparing FIGS. 3 to 5, in the combined combustion furnace B according to the second embodiment, eight pulverized coals are injected around one burner M22 that injects ammonia on the furnace wall on one side. (Multiple) burners M11 to M21 and M23 to M33 are arranged. Further, on the other side of the furnace wall, eight (plural) burners N11 to N21 and N23 to N33 for injecting pulverized coal are arranged around one burner N22 for injecting ammonia.

That is, in this combined combustion furnace B, the burners M22 and N22 are the first burners in the present invention, and the burners M11 to M21, M23 to M33, N11 to N21 and N23 to N33 are the second burners in the present invention. be.

In such a combined combustion furnace B, as shown in FIG. 4, ammonia is injected from the two burners M22 and N22 to form an ammonia flame Sa in the furnace 1 at a position corresponding to the burners M22 and N22. To. Further, as shown in FIGS. 3 to 5, pulverized coal (carbon fuel) is injected from other burners M11 to M13, M21, M23, M31 to M33, N11 to N13, N21, N23, and N31 to N33. A pulverized carbon flame Sb is formed at positions corresponding to the burners M11 to M13, M21, M23, M31 to M33, N11 to N13, N21, N23, and N31 to N33 in the furnace 1.

That is, in this second embodiment, the pulverized coal flame Sb having a relatively high brightness is formed so as to surround the ammonia flame Sa having a relatively low brightness in both the facing furnace walls, so that the furnace wall of the furnace 1 has a relatively high brightness. Is mainly irradiated with radiant heat from the pulverized coal flame Sb. Therefore, according to such a second embodiment, the emissivity of the flame in the furnace wall of the furnace 1 when the ammonia and the pulverized coal are burned at the same time as in the combined combustion furnace A according to the first embodiment described above. It is possible to suppress the decrease in.

The present invention is not limited to each of the above embodiments, and for example, the following modifications can be considered.
(1) In each of the above embodiments, pulverized coal is adopted as the carbon fuel and ammonia is adopted as the low carbon fuel, but the present invention is not limited thereto. As long as the carbon concentration of the low carbon fuel is lower than that of the carbon fuel, a fuel other than pulverized coal may be adopted as the low carbon fuel, or a fuel other than ammonia may be adopted as the low carbon fuel. For example, when pulverized coal is adopted as the carbon fuel, biomass, methane, or hydrogen may be adopted as the low carbon fuel. Further, for example, biomass may be adopted as the carbon fuel, and ammonia or hydrogen may be adopted as the low carbon fuel.

(2) In each of the above embodiments, the case where the present invention is applied to the combined combustion furnaces A and B of the boiler has been described, but the present invention is not limited thereto. The present invention can be applied to other than boilers as long as it is a combined combustion furnace provided with a plurality of burners arranged in a two-dimensional manner.

(3) In each of the above embodiments, nine burners M11 to M33 and N11 to N33 are provided on the furnace walls facing each other in parallel at the lower part of the furnace 1, but the present invention is not limited thereto. The number of the plurality of burners in the present invention may be other than 9, and the arrangement may not be orthogonal as long as it is arranged in a two-dimensional manner. For example, they may be provided concentrically.

(4) In each of the above embodiments, the injection speed of pulverized coal and / or ammonia injected from the burners M11 to M33 and N11 to N33 is not mentioned, but for example, the injection speed of ammonia is made larger than the injection speed of pulverized coal. By setting, the ammonia flame Sa may be formed on the inner side (center side) of the furnace 1 with respect to the pulverized coal flame Sb.

(5) In each of the above embodiments, burners M11 to M33 and N11 to N33 for injecting pulverized coal or / and ammonia are provided on the two facing wall surfaces of the furnace 1, but the present invention is not limited thereto. For example, fuel injection holes are provided at the corners (4 places) of the fireplace in the vertical direction and at predetermined intervals, and fuel is injected from these fuel injection holes to the furnace wall at a predetermined injection angle to inside the fireplace. By adopting a fuel injection form that forms a swirling flow and setting the injection angle of ammonia to be larger than the injection angle of pulverized coal in this fuel injection form, the ammonia flame is placed inside the pulverized coal flame (on the center side of the fireplace). It may be formed.

(6) In each of the above embodiments, burners M11 to M33 and N11 to N33 for injecting pulverized coal or / and ammonia are provided on the two facing wall surfaces of the furnace 1, but the present invention is not limited thereto. For example, only the burner that injects ammonia may be arranged on the wall surface orthogonal to the above two wall surfaces. Further, in a boiler having an air supply port for two-stage combustion above the burner (downstream side of the gas flow) in the fireplace, ammonia may be injected from this air supply port.

(7) In the first embodiment, the individual burners M11 to M33 and N11 to N33 are formed into a triple tubular shape, but the present invention is not limited thereto. As the structure of the burners M11 to M33 and N11 to N33, a double tubular structure is sufficient.

A, B Combined combustion furnace M11 to M33, N11 to N33 Burner Sa Ammonia flame Sb Microcharcoal flame 1 Fireplace 2 Heat exchange equipment 3 Ammonia supply device 4 Microcoal supply device

Claims (6)

With a fireplace
A first burner that injects carbon fuel into the fireplace and burns it,
It is equipped with a second burner that injects a low carbon fuel having a lower carbon concentration than the carbon fuel into the fireplace and burns it.
The first burner is a composite combustion characterized in that the carbon fuel is injected so that the carbon fuel flame is formed closer to the furnace wall of the furnace than the low carbon fuel flame due to the combustion of the low carbon fuel. Furnace. The combined combustion furnace according to claim 1, wherein a plurality of the first burners are arranged around the second burner. The composite combustion furnace according to claim 1, wherein the first burner and the second burner are composite burners that inject the low carbon fuel from the inside and the carbon fuel from the outside. The combined combustion furnace according to any one of claims 1 to 3, wherein the carbon fuel is pulverized coal. The combined combustion furnace according to any one of claims 1 to 4, wherein the low carbon fuel is ammonia. A boiler comprising the combined combustion furnace according to any one of claims 1 to 5.

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