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 combined combustion furnace and a combined combustion boiler. [Background technology]

[0002] The following Patent Documents 1 and 2 disclose boilers that perform combined combustion of pulverized coal and ammonia. In these boilers, in order to reduce carbon dioxide (CO2) emissions, ammonia, which is a hydrogen carrier, is burned as fuel in addition to pulverized coal, which has traditionally been used as fuel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-041990 A [Patent Document 2] JP 2016-183640 A Summary of the Invention [Problem to be solved by the invention]

[0004] As is well known, a boiler is a heat transfer device that generates steam by transferring heat generated in a furnace mainly to water. The amount of heat Q that enters the water flowing through the water tubes in the furnace wall by radiation is expressed as the combustion gas temperature T gas , furnace wall temperature T wall , the flame emissivity ε, and the Stefan-Boltzmann constant σ are expressed by the following equation (1). As equation (1) shows, the boiler performance, that is, the boiler's heat absorption performance, is proportional to the flame emissivity ε. Q = σε(T gas 4 -T wall 4 ) (1)

[0005] On the other hand, it is known that the flame emissivity ε 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 flame emissivity ε is lower than when the carbon fuel is burned as a single fuel, and as a result, there is a concern that the heat absorption performance of the boiler will be reduced.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and has as its object to suppress a decrease in flame emissivity when a carbon fuel and a low carbon fuel are burned simultaneously. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the present invention provides a first solution relating to a combined combustion furnace, which includes a furnace, a first burner for injecting carbon fuel into the furnace and burning it, and a second burner for injecting low-carbon fuel having a lower carbon concentration than the carbon fuel into the furnace and burning it, and the first burner injects the carbon fuel so that a carbon fuel flame is formed closer to the furnace wall than the low-carbon fuel flame produced by burning the low-carbon fuel.

[0008] The present invention employs, as a second solution relating to a combined combustion furnace, the above-mentioned first solution, in which a plurality of the first burners are arranged around the second burner.

[0009] The present invention adopts a third solution relating to a combined combustion furnace, which is the above-mentioned first solution, in which 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] The present invention employs, as a fourth solution relating to a combined combustion furnace, any one of the first to third solutions, in which the carbon fuel is pulverized coal.

[0011] The present invention employs a fifth solution relating to a combined combustion furnace, which is any one of the first to fourth solutions, in which the low-carbon fuel is ammonia.

[0012] The present invention employs a solution relating to a boiler in which the combined combustion furnace is provided with any one of the first to fifth solutions described above. Effect of the Invention

[0013] According to the present invention, the carbon fuel is injected so that the flame is generated closer to the furnace wall than the flame produced by the combustion of the low-carbon fuel, thereby making it possible to suppress the decrease in the emissivity of the flame when the carbon fuel and the low-carbon fuel are burned simultaneously. [Brief description of the drawings]

[0014] [Figure 1] 1 is a front view showing the configuration of a main part of a combined combustion furnace A according to a first embodiment of the present invention and a boiler equipped with the combined combustion furnace A. FIG. [Diagram 2] FIG. 2 is a view taken along line XX in FIG. [Diagram 3] FIG. 1 is a first cross-sectional view showing the configuration of a main part of a combined combustion furnace B according to a second embodiment of the present invention and a boiler equipped with the combined combustion furnace B. [Figure 4] 2 is a second cross-sectional view showing the configuration of a main part of a combined combustion furnace B according to a second embodiment of the present invention and a boiler equipped with the combined combustion furnace B. FIG. [Diagram 5] FIG. 11 is a third cross-sectional view showing the configuration of a main part of a combined combustion furnace B according to a second embodiment of the present invention and a boiler equipped with the combined combustion furnace B. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [First embodiment] First, a combined combustion furnace A according to a first embodiment of the present invention and a boiler equipped with the combined combustion furnace A will be described with reference to Figs.

[0016] The boiler according to the first embodiment includes as its main components a furnace 1, a heat exchanger 2, a plurality of burners M11 to M33, N11 to N33 (first burners and second burners), an ammonia supplying device 3, and a pulverized coal supplying device 4. Among these multiple components, a part (lower part) of the furnace 1 and the multiple burners M11 to M33, N11 to N33 configure the combined combustion furnace A according to the first embodiment.

[0017] The furnace 1 is a furnace body that is composed of a vertical, cylindrical furnace wall and burns fuel to generate combustion heat. In this furnace 1, high-temperature combustion gas is generated by burning the fuel. A flue (not shown) is provided at the rear 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. An exhaust port 1a is provided at the bottom of such a furnace 1 to discharge ash generated by the combustion of the fuel to the outside.

[0018] The heat exchanger 2 is composed of multiple heat transfer tubes installed on the upper part or furnace wall of the furnace 1, and water flows inside. This heat exchanger 2 is a general term for heat exchangers installed in a boiler, such as a superheater or reheater, and generates steam by exchanging the combustion heat of the combustion gas with the water in the heat transfer tubes.

[0019] A plurality of burners M11 to M33, N11 to N33 are arranged two-dimensionally and facing each other in the lower part of the furnace 1, and inject and combust fuel into the furnace 1. All of these burners M11 to M33, N11 to N33 are composite burners that inject ammonia (low carbon fuel) and pulverized coal (carbon fuel) as fuel into the furnace 1, and serve as the first and second burners of the present invention.

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

[0021] The ammonia supplying device 3 is one of the fuel supplying devices that supplies ammonia as a low-carbon fuel to the burners M11 to M33, N11 to N33. The pulverized coal supplying device 4 is the other of the fuel supplying devices that supplies pulverized coal as a low-carbon fuel to the burners M11 to M33, N11 to N33.

[0022] Here, the above-mentioned 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, this ammonia (low-carbon fuel) is known as a flame-retardant substance, but is a hydrogen carrier substance having three hydrogen atoms like methane (CH3). On the other hand, pulverized coal is a fossil fuel that has been pulverized to a size of about several micrometers, and is generally used as a fuel for boilers. In other words, ammonia is a low-carbon fuel with a lower carbon concentration than pulverized coal (carbon fuel).

[0023] To explain the burners M11-M33 and N11-N33 in more detail, in the combined combustion furnace A according to the first embodiment, nine burners M11-M33 are provided on one of a pair of furnace walls that face each other in parallel in a vertical position in the lower part of the furnace 1, and similarly nine burners N11-N33 are provided on the other furnace wall. Each of the nine burners M11-M33 and N11-N33 is provided in three stages in the vertical direction and three rows in the horizontal direction, that is, two-dimensionally.

[0024] That is, of the nine burners M11-M33 and N11-N33, three burners M11-M13 and N11-N13 are provided in the upper stage, three burners M21-M23 and N21-N23 are provided in the middle stage, and three burners M31-M33 and N31-N33 are provided in the lower stage. Moreover, 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 the 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, N11-N13 located at the top are all provided at the same height, the three burners M21-M23, N21-N23 located at the middle are all provided at the same height, and the three burners M31-M33, N31-N33 located at the bottom are all provided at the same height. The three burners M11-M31, N11-N31 located on the right side are all provided in a vertical line, the three burners M12-M32, N12-N32 located in the center are all provided in a vertical line, and the three burners M13-M33, N13-N33 located on the left side are all provided in a vertical line. That is, the nine burners M11-M33, N11-N33 are each arranged perpendicular to the vertical plane of the furnace 1.

[0026] Moreover, among the nine burners M11 to M33 and N11 to N33, those having the same reference numerals are positioned opposite each other. That is, the burners M11 and N11 face each other in the same horizontal plane, the burners M12 and N12 face each other in the same horizontal plane, the burners M13 and N13 face each other in the same horizontal plane, the burners M21 and N21 face each other in the same horizontal plane, the burners M22 and N22 face each other in the same horizontal plane, the burners M23 and N23 face each other in the same horizontal plane, the burners M31 and N31 face each other in the same horizontal plane, the burners M32 and N32 face each other in the same horizontal plane, and the burners M33 and N33 face each other in the same horizontal plane.

[0027] The nine burners M11 to M33, N11 to N33 thus arranged on each furnace wall of the furnace 1 are supplied with ammonia (low carbon fuel) from an ammonia supplying device 3, and pulverized coal (carbon fuel) from a pulverized coal supplying device 4. Each of the burners M11 to M33, N11 to N33 is a composite burner (first burner and second burner) that injects ammonia from the inside (center side) and pulverized coal from the outside (outer periphery side).

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

[0029] That is, each of the burners M11-M33, N11-N33 provided on 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 generated by combustion of ammonia. In other words, each of the burners M11-M33, N11-N33 injects ammonia so that the ammonia flame Sa is farther 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 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 an ammonia supplying device 3 to each of the burners M11 to M33 and N11 to N33, and pulverized coal is supplied from a pulverized coal supplying device 4.

[0031] Ammonia and pulverized coal are injected from each of the burners M11-M33 and N11-N33 into the furnace 1 and burned, generating combustion gas accompanied by combustion heat in the furnace 1. This combustion gas rises in the furnace 1 and acts on the heat exchanger 2, causing water to vaporize due to the combustion heat of the combustion gas, generating steam. The boiler supplies the steam thus generated to an external device such as a generator. The combustion gas after heat exchange with the heat exchanger 2 is discharged from the furnace 1 to the outside air via the flue.

[0032] Here, in the combined combustion furnace A and boiler according to the first embodiment, each of the burners M11-M33 and N11-N33 injects ammonia and pulverized coal into the furnace 1 so that a pulverized coal flame Sb is formed around the ammonia flame Sa. As is well known, ammonia has lower combustibility than pulverized coal and is generally difficult to burn, but the pulverized coal, which has excellent combustibility, burns prior to ammonia, and 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 having a higher carbon concentration than ammonia, and therefore has a higher brightness than the ammonia flame Sa. Moreover, such pulverized coal flame Sb is formed in each of the burners M11 to M33 and N11 to N33 so as to surround the ammonia flame Sa having a relatively low brightness, so that the furnace wall of the furnace 1 is mainly irradiated with radiant heat from the pulverized coal flame Sb having a relatively high brightness.

[0034] That is, according to the first embodiment, when ammonia and pulverized coal are burned simultaneously, it is possible to suppress a decrease in the emissivity of the flame on the furnace wall of the furnace 1, compared to the case where only pulverized coal is burned as fuel. Therefore, according to this first embodiment, it is possible to suppress a decrease in the heat absorption performance of the boiler, compared to the case where only pulverized coal is burned as fuel.

[0035] Second Embodiment Next, a combined combustion furnace B according to a 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 components as those shown in Figures 1 and 2 above are denoted by the same reference numerals.

[0036] 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 the supply of ammonia (low carbon fuel) and pulverized coal (carbon fuel) to each of the burners M11 to M33 and N11 to N33 is different from that of the combined combustion furnace A according to the first embodiment. The combined combustion furnace B has an ammonia supply device 3 and a pulverized coal supply device 4 like 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 Figs. 3 to 5 for convenience.

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

[0038] 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.

[0039] In such a combined combustion furnace B, as shown in Fig. 4, ammonia is injected from two burners M22 and N22, thereby forming an ammonia flame Sa at a position corresponding to the burners M22 and N22 in the furnace 1. Also, as shown in Figs. 3 to 5, pulverized coal (carbon fuel) is injected from the other burners M11 to M13, M21, M23, M31 to M33, N11 to N13, N21, N23, and N31 to N33, thereby forming a pulverized coal flame Sb at a position 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.

[0040] That is, in this second embodiment, a pulverized coal flame Sb with a relatively high luminance is formed on both opposing furnace walls so as to surround an ammonia flame Sa with a relatively low luminance, so that the radiant heat from the pulverized coal flame Sb is mainly irradiated onto the furnace wall of the furnace 1. Therefore, according to such a second embodiment, as with the combined combustion furnace A according to the above-mentioned first embodiment, when ammonia and pulverized coal are burned simultaneously, it is possible to suppress a decrease in the emissivity of the flame on the furnace wall of the furnace 1.

[0041] The present invention is not limited to the above-described embodiments, and the following modifications are possible. (1) In each of the above embodiments, pulverized coal is used as the carbon fuel and ammonia is used 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 used as the low-carbon fuel, and a fuel 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. Also, 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 present invention has been described as being applied to the combined combustion furnaces A and B of the boiler, but the present invention is not limited thereto. The present invention can be applied to any combined combustion furnace other than the boiler as long as it is equipped with a plurality of burners arranged two-dimensionally.

[0043] (3) In the above embodiments, nine burners M11 to M33, N11 to N33 are provided on each of the parallel facing furnace walls in the lower part of the furnace 1, but the present invention is not limited to this. The number of burners in the present invention may be other than nine, and the arrangement may not be an orthogonal arrangement as long as they are arranged two-dimensionally. For example, they may be arranged in a concentric circle.

[0044] (4) In each of the above embodiments, no mention was made of the injection speed of the pulverized coal and / or ammonia injected from the burners M11 to M33 and N11 to N33. However, for example, by setting the injection speed of ammonia to be higher than the injection speed of the pulverized coal, 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, the burners M11 to M33 and N11 to N33 for injecting pulverized coal and / or ammonia are provided on two opposing wall surfaces of the furnace 1, but the present invention is not limited to this. For example, a fuel injection form may be adopted in which fuel injection holes extending in the vertical direction and spaced at predetermined intervals are provided at the corners (four places) of the furnace, and fuel is injected from these fuel injection holes at a predetermined injection angle toward the furnace wall to form a swirling flow in the furnace, and in this fuel injection form, the injection angle of ammonia is set larger than the injection angle of pulverized coal to form an ammonia flame inside the pulverized coal flame (toward the center of the furnace).

[0046] (6) In each of the above embodiments, the burners M11-M33 and N11-N33 for injecting pulverized coal and / or ammonia are provided on the two opposing wall surfaces of the furnace 1, but the present invention is not limited to this. For example, only the burners for injecting ammonia may be disposed on a wall surface perpendicular to the above two wall surfaces. In addition, in a boiler having an air supply port for two-stage combustion 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, the individual burners M11 to M33 and N11 to N33 are formed in a triple tubular shape, but the present invention is not limited to this. The structure of the burners M11 to M33 and N11 to N33 is sufficient as long as it is double tubular. [Explanation of symbols]

[0048] A, B Combined combustion furnace M11~M33, N11~N33 burners Sa Ammonia flame Sb pulverized coal flame 1 Furnace 2 Heat exchange equipment 3. Ammonia supply unit 4 Pulverized coal supply device

Claims

1. The furnace and a first burner for injecting and burning carbonaceous fuel into the furnace; 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 in the second burner is set larger than the injection angle of the carbon fuel in the first burner so that a low-carbon fuel flame from the low-carbon fuel is formed closer to the center of the furnace than the carbon fuel flame caused by the combustion of the carbon fuel.

2. 2. The combined combustion furnace according to claim 1, wherein a plurality of the first burners are arranged around the second burner.

3. 2. The combined combustion furnace according to claim 1, wherein the first burner and the second burner are combined burners that inject the low-carbon fuel from the inside and inject the high-carbon fuel from the outside.

4. 4. The combined combustion furnace according to claim 1, wherein the carbon fuel is pulverized coal.

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

6. A boiler comprising the combined combustion furnace according to any one of claims 1 to 5.

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