JP7403502B2 - Combustion furnace and boiler - Google Patents

Description

The present invention relates to combustion furnaces and boilers.

Patent Document 1 listed below discloses a composite energy system that burns fuel containing ammonia. This combined energy system burns natural gas, which is the main fuel, with ammonia added to it, with the aim of reducing carbon dioxide emissions.

Japanese Patent Application Publication No. 2016-032391

By the way, when ammonia is burned as part of the fuel, there is a concern that nitrogen oxides (NOx) contained in the combustion gas will increase. The above-mentioned background technology is aimed exclusively at reducing carbon dioxide emissions, and does not provide any solutions for reducing nitrogen oxides (NOx). When burning a carbon fuel such as natural gas and a nitrogen-containing fuel such as ammonia together, it is essential to suppress the increase in nitrogen oxides (NOx) from a practical standpoint.

The present invention has been made in view of the above-mentioned circumstances, and aims to suppress the increase in nitrogen oxides (NOx) when carbon fuel and nitrogen-containing fuel are combusted together.

In order to achieve the above object, the present invention provides, as a first solving means related to a combustion furnace, a furnace set to an air atmosphere lower than the theoretical air amount, and a carbon fuel and a nitrogen-containing fuel injected into the furnace. and a plurality of composite burners that inject the carbon fuel from a double cylinder provided concentrically around the shaft center, and inject the carbon fuel at a predetermined angle around the shaft center to the outside of the double cylinder. In this method, the nitrogen-containing fuel is injected from a plurality of single cylinders.

In the present invention, as a second solving means related to a combustion furnace, a furnace is provided with a furnace set to an air atmosphere lower than the theoretical air amount, and a plurality of composite burners that inject and burn carbon fuel and nitrogen-containing fuel into the furnace. The composite burner injects the nitrogen-containing fuel from a plurality of single cylinders provided at a predetermined angle around the shaft center, and injects the nitrogen-containing fuel from double cylinders provided concentrically further from the shaft center than the single cylinders. A method of injecting the carbon fuel is adopted.

In the present invention, as a third solution related to a combustion furnace, in the first or second solution, the composite burner injects the premixed carbon fuel and the nitrogen-containing fuel. adopt.

In the present invention, as a fourth solving means related to a combustion furnace, the carbon fuel is pulverized coal and the nitrogen-containing fuel is ammonia in any one of the first to third solving means. adopt.

In the present invention, the boiler is provided with a combustion furnace according to any one of the first to fourth solutions.

According to the present invention, it is possible to suppress an increase in nitrogen oxides (NOx) when carbon fuel and nitrogen-containing fuel are combusted together.

BRIEF DESCRIPTION OF THE DRAWINGS It is a front view which shows the main part structure of the combustion furnace A based on 1st Embodiment of this invention, and the boiler provided with the said combustion furnace A. FIG. 2 is a view taken along line XX in FIG. 1; FIG. 2 is a sectional view showing a main part configuration of a combustion furnace B and a boiler including the combustion furnace B according to a second embodiment of the present invention. FIG. 2 is a sectional view showing a main part configuration of a combustion furnace C and a boiler including the combustion furnace C according to a third embodiment of the present invention. It is a sectional view showing composition of a burner in a 3rd embodiment of the present invention.

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

The boiler according to the first embodiment includes a furnace 1, a heat exchange device 2, a plurality of burners M11 to M34 (24 in total), N11 to N34, a pulverized coal supply device 3, and an ammonia supply device 4 as main parts. There is. Note that among these plurality of components, a part (lower part) of the furnace 1 and the plurality of burners M11 to M34 and N11 to N34 constitute the combustion furnace A according to the first embodiment.

The furnace 1 is a furnace body configured with a vertical, cylindrical furnace wall that combusts fuel to generate combustion heat. In this furnace 1, high-temperature combustion gas is generated by burning fuel. A flue (not shown) is provided at the rear stage of such a furnace 1. The combustion gas is released into the atmosphere through the flue, and nitrogen oxides (NOx) and sulfides (SOx) are removed while passing through the flue. Incidentally, at the bottom of such a furnace 1, an outlet 1a is provided 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 and the furnace wall of the furnace 1, and water flows inside. This heat exchange device 2 is a general term for heat exchange devices installed in a boiler such as a superheater and a reheater, and generates steam by exchanging combustion heat of combustion gas with water in a heat transfer tube. let

A plurality of burners M11 to M34 (24 in total) and N11 to N34 are arranged two-dimensionally and facing each other in the lower part of the furnace 1, and inject fuel into the furnace 1 for combustion. That is, the 12 burners M11 to M34 are arranged orthogonally to one of the pair of opposing furnace walls in the furnace 1, and the remaining 12 burners N11 to N34 are arranged orthogonally to the other of the pair of furnace walls. There is. More specifically, the 12 burners M11 to M34 and the burners N11 to N34 are orthogonally arranged in three stages in the vertical direction and four stages in the horizontal direction at predetermined intervals.

Of these 24 burners M11 to M34 and N11 to N34 in total, 20 burners M11 to M24 and N11 to N34 are dedicated to pulverized coal that is injected into the furnace 1 using only pulverized coal (carbon fuel) as fuel. It is a burner (burner exclusively for carbon fuel), and corresponds to the first burner in the present invention. In addition, the remaining (four) burners M31 to M34 are all ammonia-only burners (nitrogen-containing fuel-only burners) that inject only ammonia (nitrogen-containing fuel) into the furnace 1, and are the second burners in the present invention. equivalent to a burner.

Although not shown, the furnace 1 is provided with an ignition device that ignites fuel (ammonia or pulverized coal) injected from a plurality of burners M11 to M34 and N11 to N34. Fuel (ammonia or pulverized coal) injected into the furnace 1 from each of the burners M11 to M34 and N11 to N34 is ignited and combusted by the action of the ignition device.

The pulverized coal supply device 3 is a fuel supply device that supplies pulverized coal to the above-mentioned 20 burners M11 to M24 and N11 to N34 (burners dedicated to pulverized coal). This pulverized coal supply device 3 is equipped with a coal mill for each stage of the 20 burners M11 to M24 and N11 to N34, and is supplied to the 20 burners M11 to M24 and N11 to N34 via the coal mill. Supply pulverized coal. That is, this pulverized coal supply device 3 includes a total of five coal mills, and each coal mill pulverizes coal to produce pulverized coal.

Among these five coal mills, the first coal mill supplies pulverized coal to four burners M11 to M14 forming one stage, and the second coal mill also forming one stage. The pulverized coal is supplied to four burners M21 to M24, the third coal mill supplies pulverized coal to four burners N11 to N14, which also constitute one stage, and the fourth coal mill also supplies pulverized coal to four burners N11 to N14, which also constitute one stage. Pulverized coal is supplied to four burners N21 to N24 that constitute a stage, and the fifth coal mill supplies pulverized coal to four burners N31 to N34 that also constitute one stage.

The ammonia supply device 4 is a fuel supply device that supplies ammonia to the four burners M31 to M34 (burners dedicated to ammonia charcoal) described above. Note that ammonia is a compound of hydrogen (H) and nitrogen (N), as shown by the molecular formula (NH3), and does not contain carbon (C) as a constituent atom. In addition, although this ammonia is known as a flame-retardant substance, it is a hydrogen carrier substance that has three hydrogen atoms, similar to methane (CH ₃ ), and is a nitrogen-containing substance that burns relatively well in a specified high-temperature environment. It's fuel.

Next, the operation of the combustion furnace A and the boiler according to the first embodiment will be explained in detail. In this combustion furnace A and boiler, pulverized coal is supplied from the pulverized coal supply device 3 to 20 burners M11 to M24 and N11 to N34 (burners dedicated to pulverized coal), and pulverized coal is supplied to 4 burners M31 to M34 (burners dedicated to ammonia coal). ) is supplied with ammonia from an ammonia supply device 4.

Then, pulverized coal is injected into the furnace 1 from 20 burners M11 to M24 and N11 to N34 (burners dedicated to pulverized coal) and burned, and pulverized coal is injected into the furnace 1 from four burners M31 to M34 (burners dedicated to ammonia charcoal). Ammonia is injected into the tank and combusts. As a result, in the furnace 1, as shown in FIGS. 1 and 2, a pulverized coal flame Sa is formed by burning pulverized coal, and an ammonia flame Sb is formed by burning ammonia.

Here, the air atmosphere in the furnace 1 is maintained in a state lower than the theoretical air amount. That is, each burner M11 to M34 and N11 to N34 injects pulverized coal or ammonia into the furnace 1, but at the same time supplies a certain amount of combustion air into the furnace 1. The amount of combustion air supplied is set such that the amount of air in the space containing the pulverized coal flame Sa and the ammonia flame Sb in the furnace 1 is lower than the theoretical amount of air. In FIGS. 1 and 2, an area in the furnace 1 where the air amount is lower than the theoretical air amount is defined as an air shortage area Sk.

In the furnace 1, pulverized coal and ammonia are burned to generate combustion gas accompanied by combustion heat. Then, when this combustion gas rises in the furnace 1 and acts on the heat exchange device 2, water is vaporized by the combustion heat of the combustion gas and water vapor is generated. The boiler supplies the steam generated in this way to external equipment such as a generator. Note that the combustion gas after heat exchange with the heat exchange device 2 is released from the furnace 1 to the outside air via a flue.

Here, in the combustion furnace A and the boiler according to the first embodiment, since pulverized coal and ammonia are burned in the air-deficient region Sk described above, ammonia atoms (N) generated by thermal decomposition of ammonia (NH ₃ ) is suppressed from combining with oxygen atoms (O) generated by the thermal decomposition of oxygen (O ₂ ) in the air to become nitrogen monoxide (NO), and combining with other ammonia atoms (N) to form ammonia The molecule becomes (N ₂ ).

That is, in the air shortage region Sk, the reaction expressed by the following equation (1) is suppressed, and the reaction expressed by the following equation (2) becomes active. For example, the amount of air in the air deficit region Sk is approximately 0.8 to 0.9 when expressed as an index called excess air ratio.
_NH3 +5/ _4O2 →NO+3/ _2H2O (1)
NH ₃ + 3/4O ₂ → 1/2N ₂ + 3/2H ₂ O (2)

According to the first embodiment, since pulverized coal (carbon fuel) and ammonia (nitrogen-containing fuel) are combusted in the air shortage region Sk where the air amount is lower than the theoretical air amount, pulverized coal (carbon fuel) It is possible to suppress the increase in nitrogen oxides (NOx) such as nitrogen monoxide (NO) when ammonia and ammonia (nitrogen-containing fuel) are burned together.

[Second embodiment]
Next, a combustion furnace B according to a second embodiment of the present invention and a boiler including the combustion furnace B will be described with reference to FIG. 3. In FIG. 3, the same components as those shown in FIGS. 1 and 2 described above are given the same reference numerals.

This combustion furnace B has the same components as the above-mentioned combustion furnace A, but uses a plurality of (24) mixed fuels in which pulverized coal (carbon fuel) and ammonia (nitrogen-containing fuel) are premixed. It is injected into the furnace 1 from burners M11 to M34 and N11 to N34. That is, the pulverized coal supply device 3 and the ammonia supply device 4 in this combustion furnace B supply a mixed fuel of pulverized coal (carbon fuel) and ammonia (nitrogen-containing fuel) to all burners M11 to M34 and N11 to N34. supply

According to the second embodiment, a mixed flame Sc is formed in the furnace 1 by burning the mixed fuel. Since this mixed flame Sc is formed in the air-deficient region Sk similarly to the combustion furnace A described above, the reaction of the above equation (1) is suppressed, and the reaction of the above equation (2) becomes active. Therefore, according to the second embodiment, similarly to the first embodiment, it is possible to suppress the increase in nitrogen oxides (NOx) such as nitric oxide (NO).

[Third embodiment]
Finally, a combustion furnace C according to a third embodiment of the present invention and a boiler equipped with the combustion furnace C will be described with reference to FIGS. 4 and 5. In FIG. 3, the same components as those shown in FIGS. 1 and 2 described above are given the same reference numerals.

A plurality of (24) burners P11 to P34 and Q11 to Q34 in this combustion furnace C are composite burners that individually inject individually received pulverized coal and ammonia into the furnace 1. That is, the pulverized coal supply device 3 in this combustion furnace C supplies pulverized coal to all burners P11 to P34 and Q11 to Q34, and the ammonia supply device 4 supplies ammonia to all burners P11 to P34 and Q11 to Q34. supply

In such a combustion furnace C, a composite flame Sd is formed by burning pulverized coal and ammonia individually or as a mixture in the furnace 1. Since this composite flame Sd is formed in the air-deficient region Sk like the combustion furnaces A and B mentioned above, the reaction of the above equation (1) is suppressed, and the reaction of the above equation (2) becomes active. Therefore, according to the third embodiment, similarly to the first and second embodiments, it is possible to suppress the increase in nitrogen oxides (NOx) such as nitric oxide (NO).

Here, as each of the burners P11 to P34 and Q11 to Q34 (composite burner) in the third embodiment, one having the structure shown in FIG. 5 can be exemplified. For example, the composite burner Ra shown in FIG. 5(a) is formed into a substantially cylindrical shape as a whole, and pulverized coal is injected from a double cylinder r1 provided concentrically around the axis. Ammonia is injected from six single cylinders r2 provided at angles of 60 degrees around the axial center on the outside of the cylinder. That is, this composite burner Ra injects pulverized coal from the inside relatively close to the shaft center, and injects ammonia from the outside relatively far from the shaft center.

On the other hand, the composite burner Rb shown in FIG. 5(b) is formed into a substantially cylindrical shape as a whole, and includes a double cylinder r3 that is farther from the axis than the single cylinder r2 in place of the double cylinder r1, Pulverized coal is injected from this double cylinder r3. That is, this composite burner Rb injects ammonia from the inside relatively close to the shaft center, and injects pulverized coal from the outside relatively far from the shaft center.

On the other hand, the composite burner Rc shown in FIG. 5(c) has a generally cylindrical shape as a whole, injects ammonia from a single cylinder r4 including the axis, and is provided concentrically on the outside of this single cylinder r4. Pulverized coal is injected from the double cylinder r5. That is, this composite burner Rc injects ammonia from the inside relatively close to the shaft center, and injects pulverized coal from the outside relatively far away. Note that the tip of the single cylinder r4 in this composite burner Rc is not a simple opening, but is provided with a disk in which a plurality of injection holes are formed.

Note that the present invention is not limited to the above-described embodiments, and the following modifications may be considered, for example.
(1) In each of the above embodiments, pulverized coal, which is a type of carbon fuel, is used as a fuel, and ammonia, which is a type of nitrogen-containing fuel, is used as a fuel, but the present invention is not limited thereto. Low-carbon fuels other than pulverized coal may be used, and nitrogen-containing fuels other than ammonia may be used. For example, natural gas may be used as the carbon fuel.

(2) In each of the above embodiments, the present invention is applied to combustion furnaces A to C of a boiler, but the present invention is not limited thereto. The present invention is applicable to combustion furnaces other than boilers as long as they are equipped with one or more burners.

(3) In each of the above embodiments, a total of 24 burners M11 to M34, N11 to N34, P11 to P34, and Q11 to Q34 are provided in the lower part of the furnace 1, but the present invention is not limited thereto. The number of burners in the present invention may be other than 24, and the arrangement may not be orthogonal. For example, the burners may be provided concentrically.

(4) Although the configuration of the composite burner was illustrated in the third embodiment, the composite burner in the present invention is not limited to this.

A, B, C Combustion furnace M11~M34, N11~N34 Burner (dedicated burner)
P11~P34, Q11~Q34 Burner (compound burner)
Sa Pulverized coal flame Sb Ammonia flame Sc Mixed flame Sd Composite flame 1 Furnace 2 Heat exchange equipment 3 Pulverized coal supply device 4 Ammonia supply device

Claims (4)

a furnace set to an air atmosphere lower than the theoretical air amount;
A plurality of composite burners having circular injection holes and injecting carbon fuel and nitrogen-containing fuel into the furnace for combustion,
The composite burner injects the carbon fuel from a double cylinder provided concentrically around the shaft center, and injects the nitrogen-containing fuel from a plurality of single cylinders provided outside the double cylinder at a predetermined angle around the shaft center. inject,
The amount of air in the air deficit region, which is a region where the amount of air is lower than the theoretical air amount in the furnace, is about 0.8 to 0.9 when expressed as an index called excess air ratio.
A combustion furnace characterized by: a furnace set to an air atmosphere lower than the theoretical air amount;
a plurality of composite burners that inject carbon fuel and nitrogen-containing fuel into the furnace and burn them;
The composite burner injects the nitrogen-containing fuel from at least one single cylinder provided at or around the axial center, and injects the nitrogen-containing fuel from a double cylinder provided concentrically farther from the axial center than the single cylinder. inject fuel,
The air amount in the air deficiency region, which is a region where the air amount is lower than the theoretical air amount in the furnace, is about 0.8 to 0.9 when expressed as an index called excess air ratio,
A plurality of the single cylinders are provided at a predetermined angle around the axial center,
A combustion furnace characterized by: The combustion furnace according to claim 1 or 2 , wherein the carbon fuel is pulverized coal and the nitrogen-containing fuel is ammonia. A boiler comprising the combustion furnace according to any one of claims 1 to 3 .

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