Combined combustion furnace and combined combustion boiler

Abstract

To suppress a decrease in flame emissivity when a low-carbon fuel is mixed with a carbon fuel and burned. [Solution] The system comprises a furnace, a first burner that injects carbonaceous fuel into the furnace and burns it, and a second burner that injects low-carbon fuel with a lower carbon concentration than the carbonaceous fuel into the furnace and burns it, and the first burner injects the carbonaceous fuel so that a carbonaceous fuel flame is formed closer to the furnace wall than the low-carbon fuel flame produced by combustion of the low-carbon fuel.

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, 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] Japanese Patent Application Laid-Open No. 2016-041990 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-183640 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 heat transfer is multiplied by 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 shown in equation (1), the boiler performance, i.e., the boiler's heat absorption capacity, 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 decreases compared to when the carbon fuel is burned alone, and as a result, there is a concern that the heat absorption performance of the boiler may decrease.

[0006] The present invention has been made in view of the above circumstances, and aims 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 comprises a furnace, a first burner that injects carbonaceous fuel into the furnace and burns it, and a second burner that injects low-carbon fuel having a lower carbon concentration than the carbonaceous fuel into the furnace and burns it, and the first burner injects the carbonaceous fuel so that a carbonaceous fuel flame is formed closer to the furnace wall than the low-carbon fuel flame produced by combustion of the low-carbon fuel.

[0008] The present invention employs, as a second solution relating to a combined combustion furnace, the solution of the 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 same as the 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, a solution in which, in any one of the first to third solutions, the carbonaceous fuel is pulverized coal.

[0011] The present invention employs, as a fifth solution relating to a combined combustion furnace, 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 according to any one of the first to fifth solutions is provided. [Effects 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 generated 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 explanation 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. [Figure 2] FIG. 2 is a view taken along the line XX in FIG. 1. [Figure 3] 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. FIG. [Figure 4] 10 is a second cross-sectional view showing the configuration of the main parts 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. [Figure 5] 10 is a third cross-sectional view showing the configuration of the main parts of the combined combustion furnace B according to the second embodiment of the present invention and the boiler equipped with the combined combustion furnace B. FIG. DETAILED DESCRIPTION OF THE INVENTION

[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. 1 and 2. FIG.

[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 supply device 3, and a pulverized coal supply device 4. Of these components, a part (lower part) of the furnace 1 and the plurality of burners M11 to M33, N11 to N33 constitute a combined combustion furnace A according to the first embodiment.

[0017] The furnace 1 is a furnace body composed of vertical, cylindrical furnace walls 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 downstream of the 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 outlet 1a is provided at the bottom of the furnace 1 to discharge ash generated by the combustion of fuel to the outside.

[0018] The heat exchanger 2 is made up of multiple heat transfer tubes installed on the upper part or furnace wall of the furnace 1, and water flows through it. This heat exchanger 2 is a general term for heat exchangers installed in boilers, such as superheaters and reheaters, 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 at the bottom of the furnace 1, and inject and burn fuel into the furnace 1. All of these burners M11 to M33, N11 to N33 are combined burners that inject ammonia (low carbon fuel) and pulverized coal (carbon fuel) as fuel into the furnace 1, and serve as both the first burner and the second burner in the present invention.

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

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

[0022] Here, as indicated by the molecular formula (NH3), ammonia is a compound of hydrogen (H) and nitrogen (N) and does not contain carbon (C) as a constituent atom. Although ammonia (low-carbon fuel) is known as a flame-retardant substance, it is a hydrogen carrier substance with three hydrogen atoms, similar to methane (CH3). Meanwhile, pulverized coal is a fossil fuel made by pulverizing coal to a size of about several micrometers, and is commonly used as a boiler fuel. In other words, ammonia is a low-carbon fuel with a lower carbon concentration than pulverized coal (carbon fuel).

[0023] To explain the plurality of burners M11 to M33, N11 to N33 in more detail, in the combined combustion furnace A according to the first embodiment, nine burners M11 to 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 to N33 are provided on the other furnace wall. Each of the nine burners M11 to M33, N11 to N33 is arranged in three rows in the vertical direction and three columns 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 on the upper tier, three burners M21-M23 and N21-N23 are provided on the middle tier, and three burners M31-M33 and N31-N33 are provided on the lower tier. 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 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 on the upper level are all provided at the same height, the three burners M21-M23, N21-N23 located on the middle level are all provided at the same height, and the three burners M31-M33, N31-N33 located on the lower level are all provided at the same height. The three burners M11-M31, N11-N31 located on the right side are arranged in a vertical row, the three burners M12-M32, N12-N32 located in the center are also arranged in a vertical row, and the three burners M13-M33, N13-N33 located on the left side are also arranged in a vertical row. That is, the nine burners M11-M33, N11-N33 are arranged perpendicular to the vertical plane of the furnace 1.

[0026] Furthermore, among the nine burners M11 to M33 and N11 to N33, those having the same reference numerals 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] Ammonia (low carbon fuel) is supplied from the ammonia supply device 3 to the nine burners M11 to M33, N11 to N33 arranged on each furnace wall of the furnace 1, and pulverized coal (carbon fuel) is supplied from the pulverized coal supply device 4. Each of the burners M11 to M33, N11 to N33 is a combined 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 to M33 and N11 to 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, in the furnace 1, as shown in the figure, for each of the burners M11 to M33 and N11 to 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, the burners M11 to M33 and N11 to N33 provided on two opposing furnace walls of the furnace 1 inject pulverized coal so that the pulverized coal flame Sb generated by the combustion of ammonia is closer to the furnace wall of the furnace 1 than the ammonia flame Sa. 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.

[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 supply device 3 to each of the burners M11 to M33 and N11 to N33, and pulverized coal is supplied from a pulverized coal supply device 4.

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

[0032] Here, in the combined combustion furnace A and boiler according to the first embodiment, each of the burners M11 to M33 and N11 to 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 superior combustibility, burns before the ammonia, and as a result, 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. Furthermore, 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, which has a relatively low brightness, and therefore the furnace wall of the furnace 1 is mainly irradiated with radiant heat from the pulverized coal flame Sb, which has 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 when 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 when 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. This combined combustion furnace B has an ammonia supply device 3 and a pulverized coal supply device 4, just 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 Figures 3 to 5 for convenience.

[0037] 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 of the present invention, and the burners M11 to M21, M23 to M33, N11 to N21, and N23 to N33 are the second burners of 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. In addition, 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, 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 brightness is formed on both opposing furnace walls so as to surround an ammonia flame Sa with a relatively low brightness, and therefore radiant heat from the pulverized coal flame Sb is mainly irradiated onto the furnace walls of the furnace 1. Therefore, according to this second embodiment, as with the combined combustion furnace A according to the first embodiment described above, it is possible to suppress a decrease in the emissivity of the flame on the furnace walls of the furnace 1 when simultaneously burning ammonia and pulverized coal.

[0041] The present invention is not limited to the above-described embodiments, and the following modifications are possible. (1) In 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 to this. 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. Furthermore, 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 combined combustion furnaces A and B of boilers, but the present invention is not limited to this. The present invention can be applied to any combined combustion furnace other than boilers as long as it has multiple burners arranged two-dimensionally.

[0043] (3) In the above embodiments, nine burners M11 to M33 and N11 to N33 are provided on each of the parallel opposing 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 does not have to be orthogonal as long as they are arranged two-dimensionally. For example, they may be arranged concentrically.

[0044] (4) In the above embodiments, no mention is 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 the above embodiments, burners M11 to M33 and N11 to N33 that inject 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 configuration may be adopted in which fuel injection holes extending in the vertical direction and spaced at predetermined intervals are provided at the corners (four locations) 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 inside the furnace, and in this fuel injection configuration, the injection angle of ammonia is set larger than the injection angle of pulverized coal, thereby forming an ammonia flame inside the pulverized coal flame (toward the center of the furnace).

[0046] (6) In the above embodiments, burners M11 to M33 and N11 to N33 that inject 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, only the burners that inject ammonia may be arranged on a wall surface perpendicular to the two wall surfaces. Also, in a boiler configured such that the furnace is provided with an air supply port for two-stage combustion above the burners (downstream of the gas flow), 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 device 4 Pulverized coal supply device

Claims

1. The furnace and a plurality of burners; each of the plurality of burners is a composite burner that injects low-carbon fuel from the inside and carbon-fuel fuel from the outside, thereby forming a carbon-fuel flame by combustion of the carbon fuel around a low-carbon fuel flame by combustion of the low-carbon fuel, and combustion air is supplied from outside the carbon fuel; the carbonaceous fuel is pulverized coal; The low-carbon fuel is a fuel that does not contain carbon as a constituent atom.

2. The furnace and a plurality of burners; each of the plurality of burners is a composite burner that injects low-carbon fuel from the inside and carbon-fuel fuel from the outside, thereby forming a carbon-fuel flame by combustion of the carbon fuel around a low-carbon fuel flame by combustion of the low-carbon fuel, and combustion air is supplied from outside the carbon fuel; the carbon fuel is pulverized coal; A combined combustion furnace in which the low-carbon fuel has a lower combustibility than the carbon fuel.

3. The furnace and A boiler having a combined combustion furnace including a plurality of burners, each of the plurality of burners is a composite burner that injects low-carbon fuel from the inside and carbon-fuel fuel from the outside, thereby forming a carbon-fuel flame by combustion of the carbon fuel around a low-carbon fuel flame by combustion of the low-carbon fuel, and combustion air is supplied from outside the carbon fuel; The low-carbon fuel is a fuel that does not contain carbon as a constituent atom.

4. The furnace and A boiler having a combined combustion furnace including a plurality of burners, each of the plurality of burners is a composite burner that injects low-carbon fuel from the inside and carbon-fuel fuel from the outside, thereby forming a carbon-fuel flame by combustion of the carbon fuel around a low-carbon fuel flame by combustion of the low-carbon fuel, and combustion air is supplied from outside the carbon fuel; The low-carbon fuel has a lower combustibility than the carbon fuel.

5. The furnace and a carbon fuel burner for injecting carbon fuel into the furnace; a low-carbon fuel burner that injects low-carbon fuel into the furnace; a plurality of the carbon-fuel burners are arranged around the low-carbon fuel burner, so that a carbon-fuel flame resulting from combustion of the carbon-fuel fuel surrounds a low-carbon fuel flame resulting from combustion of the low-carbon fuel; the carbon fuel is pulverized coal; The low-carbon fuel is a fuel that does not contain carbon as a constituent atom.

6. The furnace and a carbon fuel burner for injecting carbon fuel into the furnace; a low-carbon fuel burner that injects low-carbon fuel into the furnace; a plurality of the carbon-fuel burners are arranged around the low-carbon fuel burner, so that a carbon-fuel flame resulting from combustion of the carbon-fuel fuel surrounds a low-carbon fuel flame resulting from combustion of the low-carbon fuel; the carbon fuel is pulverized coal; the low-carbon fuel is less combustible than the carbon fuel; A combined combustion furnace in which a plurality of carbon fuel burners are arranged around the low-carbon fuel burner, so that only the carbon fuel burners are arranged on the bottom side of the furnace.

7. A combined combustion furnace as described in Claim 5, wherein multiple carbon fuel burners are arranged around the low-carbon fuel burner, so that only the carbon fuel burners are arranged on the bottom side of the furnace.

8. A combined combustion furnace described in any one of claims 5 to 7, wherein the carbon fuel burners are arranged in multiple numbers around the low-carbon fuel burner in at least two dimensions.

9. A combined combustion furnace as described in any one of claims 1, 2, 5 to 8, wherein the low-carbon fuel is ammonia.

10. A boiler as described in claim 3 or 4, wherein the low-carbon fuel is ammonia.

11. A boiler comprising the combined combustion furnace according to any one of claims 1, 2, and 5 to 9.

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