Combined combustion furnace and combined combustion boiler

Abstract

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

Description

Technical Field

[0001] The present invention relates to a composite combustion furnace and a composite combustion boiler.

Background Art

[0002] Patent Documents 1 and 2 below disclose boilers that perform composite combustion of pulverized coal and ammonia. In these boilers, in order to reduce the emission amount of carbon dioxide (CO2), in addition to pulverized coal that has been conventionally used as a fuel, ammonia, which is a hydrogen carrier, is burned as a fuel.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, as is well known, a boiler is a heat transfer device that mainly transfers the heat generated in a furnace to water to generate steam. The amount of heat Q input to the water flowing through the water pipes on the furnace wall by radiative heat transfer is expressed by the following formula (1) in terms of 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. As shown by this formula (1), the performance of the boiler, that is, the heat absorption performance of the boiler, is proportional to the emissivity ε of the flame. Q = σε(T gas 4 - T wall 4 ) (1)

[0005] On the other hand, it is known that the emissivity ε of the flame described above depends on the carbon concentration in the fuel. Therefore, when a low-carbon fuel such as ammonia, which 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, the emissivity ε of the flame decreases compared to when the carbon fuel is burned as a single fuel. As a result, there are concerns that the heat acquisition performance of the boiler will decrease.

[0006] This invention has been made in view of the above circumstances, and aims to suppress the decrease in flame emissivity when carbon fuel and low-carbon fuel are burned simultaneously. [Means for solving the problem]

[0007] To achieve the above objective, the present invention provides a first solution relating to a combined combustion furnace, comprising a furnace, a first burner that injects and burns carbon fuel into the furnace, and a second burner that injects and burns low-carbon fuel, which has a lower carbon concentration than the carbon fuel, into the furnace, wherein the first burner injects the carbon fuel such that the carbon fuel flame is formed closer to the furnace wall than the low-carbon fuel flame produced by the combustion of the low-carbon fuel.

[0008] In the present invention, as a second solution relating to a combined combustion furnace, the first solution described above employs the method in which the first burner is arranged in multiple locations around the second burner.

[0009] In the present invention, as a third solution relating to a combined combustion furnace, the first solution described above employs the means that the first burner and the second burner are combined burners that inject the low-carbon fuel from the inside and the carbon fuel from the outside.

[0010] In the present invention, as a fourth solution relating to a combined combustion furnace, the method adopted is that, in any of the first to third solutions described above, the carbon fuel is pulverized coal.

[0011] In the present invention, as a fifth solution relating to a combined combustion furnace, the method adopted is that the low-carbon fuel is ammonia, as in any of the first to fourth solutions described above.

[0012] In this invention, as a solution related to the boiler, a means is adopted in which a combined combustion furnace according to any of the first to fifth solutions described above is provided. [Effects of the Invention]

[0013] According to the present invention, since the carbon fuel is injected in such a way that the flame is generated closer to the furnace wall than the flame generated by the combustion of the low-carbon fuel, it is possible to suppress the decrease in flame emissivity when carbon fuel and low-carbon fuel are burned simultaneously. [Brief explanation of the drawing]

[0014] [Figure 1] This is a front view showing the main components of a combined combustion furnace A and a boiler equipped with the combined combustion furnace A according to the first embodiment of the present invention. [Figure 2] This is a view along the line XX in Figure 1. [Figure 3] This is a first cross-sectional view showing the main components of a combined combustion furnace B and a boiler equipped with the combined combustion furnace B according to a second embodiment of the present invention. [Figure 4] This is a second cross-sectional view showing the main components of a combined combustion furnace B and a boiler equipped with the combined combustion furnace B according to a second embodiment of the present invention. [Figure 5] This is a third cross-sectional view showing the main components of a combined combustion furnace B and a boiler equipped with the combined combustion furnace B according to a second embodiment of the present invention. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] First, a combined combustion furnace A and a boiler equipped with the combined combustion furnace A according to the first embodiment of the present invention will be described with reference to Figures 1 and 2.

[0016] The boiler according to this first embodiment includes, as main components, a furnace 1, heat exchange equipment 2, a plurality of burners M11 to M33, N11 to N33 (the first burner and the second burner), an ammonia supply device 3, and a pulverized coal supply device 4. Among these plurality of components, a part (lower part) of the furnace 1 and the plurality of burners M11 to M33, N11 to N33 constitute the composite combustion furnace A according to the first embodiment.

[0017] The furnace 1 is composed of a furnace wall provided vertically and cylindrically, and is a furnace body that burns fuel to generate combustion heat. In this furnace 1, high-temperature combustion gas is generated by the combustion of fuel. A flue (not shown) is provided at the rear stage of such a furnace 1. The combustion gas is discharged into the atmosphere through the flue, and nitrogen oxides (NOx) and sulfides (SOx) are removed while passing through the flue. In addition, a discharge port 1a for discharging ash generated by the combustion of fuel to the outside is provided at the bottom of such a furnace 1.

[0018] The heat exchange equipment 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 is flowing inside. This heat exchange equipment 2 is a general term for heat exchange equipment provided in a boiler, such as a superheater and a reheater, and generates steam by heat-exchanging the combustion heat of the combustion gas with the water in the heat transfer tubes.

[0019] The plurality of burners M11 to M33, N11 to N33 are arranged two-dimensionally and oppositely at the lower part of the furnace 1, and inject fuel into the furnace 1 to burn it. These plurality of burners M11 to M33, N11 to N33 are all composite burners that inject ammonia (low-carbon fuel) and pulverized coal (carbon fuel) into the furnace 1 as fuel, and are the first burner and the second burner in the present invention.

[0020] Although not shown in the diagram, the furnace 1 is equipped with an ignition device that ignites the fuel (ammonia and pulverized coal) injected from multiple burners M11-M33 and N11-N33. The fuel (ammonia and pulverized coal) injected into the furnace 1 from each of the burners M11-M33 and N11-N33 is ignited and combusted by the action of the ignition device.

[0021] Ammonia supply device 3 is one fuel supply device that supplies ammonia as a low-carbon fuel to the multiple burners M11-M33 and N11-N33. Pulverized coal supply device 4 is the other fuel supply device that supplies pulverized coal as a carbon fuel to the multiple burners M11-M33 and N11-N33.

[0022] Here, ammonia, as shown by its molecular formula (NH3), is a compound of hydrogen (H) and nitrogen (N), and does not contain carbon (C) as a constituent atom. Although ammonia (a low-carbon fuel) is known as a flame retardant, it is a hydrogen carrier substance that, like methane (CH3), has three hydrogen atoms. On the other hand, pulverized coal is made by crushing coal, a fossil fuel, to a size of a few micrometers, and is commonly used as fuel for boilers. In other words, ammonia is a low-carbon fuel with a lower carbon concentration than pulverized coal (a carbon fuel).

[0023] To further explain the above-mentioned multiple burners M11-M33 and N11-N33, in the combined combustion furnace A according to this first embodiment, of the pair of furnace walls that face each other in a vertical position at the bottom of the furnace 1, nine burners M11-M33 are provided on one furnace wall, and nine burners N11-N33 are provided on the other furnace wall. Each of the nine burners M11-M33 and N11-N33 is arranged in three rows vertically and three columns horizontally, that is, in a two-dimensional manner.

[0024] Specifically, of the nine burners M11-M33 and N11-N33, three burners M11-M13 and N11-N13 are located on the upper level, three burners M21-M23 and N21-N23 are located on the middle level, and three burners M31-M33 and N31-N33 are located on the lower level. Furthermore, of these nine burners M11-M33 and N11-N33, three burners M11-M31 and N11-N31 are located on the right side when viewed from the outside of furnace 1, three burners M12-M32 and N12-N32 are located in the center, and three burners M13-M33 and N13-N33 are located on the left side.

[0025] The three burners M11-M13 and N11-N13 located in the upper section are all at the same height, the three burners M21-M23 and N21-N23 located in the middle section are all at the same height, and the three burners M31-M33 and N31-N33 located in the lower section are all at the same height. Furthermore, the three burners M11-M31 and N11-N31 located on the right side are arranged in a single row vertically, the three burners M12-M32 and N12-N32 located in the center are arranged in a single row vertically, and the three burners M13-M33 and N13-N33 located on the left side are arranged in a single row vertically. In other words, the nine burners M11-M33 and N11-N33 are arranged perpendicular to the vertical plane of the furnace 1.

[0026] Furthermore, among the nine burners M11-M33 and N11-N33, those with the same number in their designation are positioned opposite each other. That is, burner M11 and burner N11 face each other in the same horizontal plane, burner M12 and burner N12 face each other in the same horizontal plane, burner M13 and burner N13 face each other in the same horizontal plane, burner M21 and burner N21 face each other in the same horizontal plane, burner M22 and burner N22 face each other in the same horizontal plane, burner M23 and burner N23 face each other in the same horizontal plane, burner M31 and burner N31 face each other in the same horizontal plane, burner M32 and burner N32 face each other in the same horizontal plane, and burner M33 and burner N33 face each other in the same horizontal plane.

[0027] In this manner, the nine burners M11-M33 and N11-N33, arranged on each furnace wall of the furnace 1, are supplied with ammonia (low-carbon fuel) from the ammonia supply device 3 and pulverized coal (carbon fuel) from the pulverized coal supply device 4. Each of the individual burners M11-M33 and N11-N33 is a composite burner (first burner and second burner combined) that injects ammonia from the inside (center side) and pulverized coal from the outside (outer circumference side).

[0028] For example, each burner M11-M33 and N11-N33 is formed in a triple-tube shape, with ammonia supplied to the inner tube, pulverized coal supplied to the central tube, and combustion air supplied to the outer tube. Therefore, as shown in the figure, within the furnace 1, for each burner M11-M33 and N11-N33, an ammonia flame Sa (low-carbon fuel flame) formed by the combustion of ammonia is surrounded by a pulverized coal flame Sb (carbon fuel flame) formed by the combustion of pulverized coal.

[0029] In other words, each burner M11-M33 and N11-N33, located on the two opposing furnace walls of the furnace 1, injects pulverized coal so that the pulverized coal flame Sb is generated closer to the furnace wall of the furnace 1 than the ammonia flame Sa produced by the combustion of ammonia. To put it another way, each burner M11-M33 and N11-N33 injects ammonia so that the ammonia flame Sa is further away from the furnace wall of the furnace 1 than the pulverized coal flame Sb.

[0030] Next, the operation of the combined combustion furnace A and boiler according to this first embodiment will be described in detail. In this combined combustion furnace A and boiler, ammonia is supplied to each burner M11-M33 and N11-N33 from the ammonia supply device 3, and pulverized coal is supplied from the pulverized coal supply device 4.

[0031] Then, ammonia and pulverized coal are injected into the furnace 1 from each of the burners M11-M33 and N11-N33 and burned, generating combustion gases with combustion heat inside the furnace 1. These combustion gases then rise inside the furnace 1 and act on the heat exchanger 2, causing water to vaporize due to the combustion heat and generate steam. The boiler supplies the steam generated in this way to external equipment such as generators. The combustion gases that have exchanged heat with the heat exchanger 2 are then released into the outside air from the furnace 1 via the flue.

[0032] In the combined combustion furnace A and boiler according to this first embodiment, burners M11 to M33 and N11 to N33 inject ammonia and pulverized coal into the furnace 1 such that a pulverized coal flame Sb is formed around an ammonia flame Sa. As is well known, ammonia has lower flammability than pulverized coal and is generally difficult to burn, but because the highly flammable pulverized coal burns before the ammonia, a pulverized coal flame Sb is formed around the ammonia injected into the furnace 1 by the combustion of the pulverized coal.

[0033] This pulverized coal flame Sb is formed by the combustion of pulverized coal, which has a higher carbon concentration than ammonia, and therefore its brightness is higher than that of the ammonia flame Sa. Furthermore, since this pulverized coal flame Sb is formed in each of the burners M11-M33 and N11-N33 so as to surround the ammonia flame Sa, which has a relatively low brightness, the furnace wall of furnace 1 is mainly irradiated by radiant heat from the pulverized coal flame Sb, which has a relatively high brightness.

[0034] In other words, according to the first embodiment, when burning ammonia and pulverized coal simultaneously, it is possible to suppress the decrease in flame emissivity at the furnace wall of the furnace 1 compared to when burning only pulverized coal as fuel. Therefore, according to this first embodiment, it is possible to suppress the decrease in the heat recovery performance of the boiler compared to when burning only pulverized coal as fuel.

[0035] [Second Embodiment] Next, a combined combustion furnace B according to the second embodiment of the present invention and a boiler equipped with the combined combustion furnace B will be described with reference to Figures 3 to 5. In Figures 3 to 5, the same reference numerals are used for components that are the same as those shown in Figures 1 and 2 described above.

[0036] The combined combustion furnace B according to this second embodiment has the same components as the combined combustion furnace A according to the first embodiment, but the supply of ammonia (low-carbon fuel) and pulverized coal (carbon fuel) to each burner M11 to M33 and N11 to N33 differs from that of the combined combustion furnace A according to the first embodiment. This combined combustion furnace B is equipped with an ammonia supply device 3 and a pulverized coal supply device 4, similar to the combined combustion furnace A according to the first embodiment, but the ammonia supply device 3 and the pulverized coal supply device 4 are omitted in Figures 3 to 5 for convenience.

[0037] As can be seen by comparing Figures 3 to 5, in the combined combustion furnace B according to this second embodiment, on one side of the furnace wall, eight (or more) burners M11 to M21 and M23 to M33 that inject pulverized coal are arranged around one burner M22 that injects ammonia. On the other side of the furnace wall, eight (or more) burners N11 to N21 and N23 to N33 that inject pulverized coal are arranged around one burner N22 that injects ammonia.

[0038] In other words, in this combined combustion furnace B, burners M22 and N22 are the first burners in this invention, and burners M11 to M21, M23 to M33, N11 to N21, and N23 to N33 are the second burners in this invention.

[0039] In such a combined combustion furnace B, as shown in Figure 4, ammonia is injected from two burners M22 and N22, forming an ammonia flame Sa at positions corresponding to burners M22 and N22 within the furnace 1. Additionally, as shown in Figures 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, forming a pulverized coal flame Sb at positions corresponding to burners M11 to M13, M21, M23, M31 to M33, N11 to N13, N21, N23, and N31 to N33 within the furnace 1.

[0040] In other words, in this second embodiment, a relatively bright pulverized coal flame Sb is formed on both opposing furnace walls so as to surround the relatively low-brightness ammonia flame Sa, and the furnace walls of the furnace 1 are mainly irradiated with radiant heat from the pulverized coal flame Sb. Therefore, according to this second embodiment, similar to the combined combustion furnace A according to the first embodiment described above, it is possible to suppress the decrease in flame emissivity on the furnace walls of the furnace 1 when burning ammonia and pulverized coal simultaneously.

[0041] It should be noted that the present invention is not limited to the embodiments described above, and the following modifications are possible, for example. (1) In the above embodiments, pulverized coal was used as the carbon fuel and ammonia as the low-carbon fuel, but the present invention is not limited thereto. It is sufficient that the carbon concentration of the low-carbon fuel is lower than that of the carbon fuel, and fuels other than pulverized coal may be used as the low-carbon fuel, and fuels other than ammonia may be used as the low-carbon fuel. For example, when pulverized coal is used as the carbon fuel, biomass, methane, or hydrogen may be used as the low-carbon fuel. Alternatively, for example, biomass may be used as the carbon fuel and ammonia or hydrogen may be used as the low-carbon fuel.

[0042] (2) In the above embodiments, the case in which the present invention is applied to the combined combustion furnaces A and B of a boiler has been described, but the present invention is not limited thereto. The present invention can be applied to a combined combustion furnace other than a boiler, as long as it has a plurality of burners arranged in two dimensions.

[0043] (3) In each of the above embodiments, nine burners M11 to M33 and N11 to N33 are provided on parallel, opposing furnace walls at the bottom of the furnace 1, but the present invention is not limited thereto. The number of burners in the present invention may be other than nine, and the arrangement does not have to be orthogonal as long as they are arranged in a two-dimensional manner. For example, they may be arranged in concentric circles.

[0044] (4) In each of the above embodiments, the injection speed of pulverized coal and / or ammonia injected from burners M11-M33 and N11-N33 was not mentioned, but for example, by setting the ammonia injection speed to be greater than the pulverized coal injection speed, the ammonia flame Sa may be formed further back (towards the center) of the furnace 1 than the pulverized coal flame Sb.

[0045] (5) In each of the above embodiments, burners M11 to M33 and N11 to N33 are provided to inject pulverized coal and / or ammonia onto two opposing walls of the furnace 1, but the present invention is not limited thereto. For example, a fuel injection configuration may be adopted in which fuel injection holes are provided at the corners (four locations) of the furnace, extending vertically and spaced at predetermined intervals, and fuel is injected from these fuel injection holes into the furnace wall at a predetermined injection angle to form a swirling flow inside the furnace. In this fuel injection configuration, the injection angle of ammonia may be set to be greater than the injection angle of pulverized coal to form an ammonia flame inside the pulverized coal flame (towards the center of the furnace).

[0046] (6) In each of the above embodiments, burners M11-M33 and N11-N33 for injecting pulverized coal and / or ammonia are provided on two opposing walls of the furnace 1, but the present invention is not limited thereto. For example, only burners for injecting ammonia may be placed on a wall perpendicular to the two walls. Also, in a boiler configuration in which an air supply port for two-stage combustion is provided above the burners (downstream of the gas flow) in the furnace, ammonia may be injected from this air supply port.

[0047] (7) In the first embodiment described above, the individual burners M11 to M33 and N11 to N33 were formed in a triple-tubular shape, but the present invention is not limited thereto. The structure of the burners M11 to M33 and N11 to N33 can be any double-tubular shape. [Explanation of Symbols]

[0048] A and B combined combustion furnaces M11~M33, N11~N33 Burner Sa Ammonia flame Sb pulverized coal flame 1 Furnace 2 Heat exchange equipment 3. Ammonia supply system 4 Pulverized coal supply device

Claims

1. A fire pit and A first burner that injects carbon fuel into the furnace and burns it, The system includes a second burner that injects and burns a low-carbon fuel into the furnace, A combined combustion furnace characterized in that the injection angle of the low-carbon fuel with respect to the furnace wall in the second burner is set to be greater than the injection angle of the carbon fuel with respect to the furnace wall in the first burner, such that a low-carbon fuel flame is formed on the central side of the furnace than a carbon fuel flame formed by the combustion of the carbon fuel.

2. The composite combustion furnace according to claim 1, characterized in that a plurality of the first burners are arranged above and below the second burners.

3. The combined combustion furnace according to claim 1 or 2, characterized in that the carbon fuel is pulverized coal.

4. The combined combustion furnace according to any one of claims 1 to 3, characterized in that the low-carbon fuel is ammonia.

5. A boiler characterized by comprising a combined combustion furnace as described in any one of claims 1 to 4.

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