BOILER WITH MIXED FUEL COMBUSTION

Abstract

Boiler (1) which performs a mixed fuel combustion of a sulfur-containing fuel and ammonia as fuel, wherein the boiler (1) comprises: an oven (2) with a front wall (2b), a rear wall (2c) facing the front wall (2b) and a side wall (2d) connecting the front wall (2b) and the rear wall (2c); a burner (4) mounted on the front wall (2b) and the rear wall (2c) of the furnace (2); and an ammonia injection opening (2f) provided on the front wall (2b) and / or the rear wall (2c), characterized in that the ammonia injection opening (2f) is arranged in a horizontal direction closer to the side wall (2d) than the burner (4), so that the ammonia to be burned flows as fuel along an inner wall surface of the side wall (2d) in which the burner (4) is not mounted.

Description

Technical area

[0001] The present invention relates to a boiler having the preamble features of claim 1. Such a boiler is known, for example, from JP 2018-138 863 A. Similar boilers are known from US 5 681 158 A, JP 2019-86 188 A, and US 4 940 006 A. State of the art

[0002] The following Patent Document 1 discloses a complex energy system that burns an ammonia-containing fuel. To reduce carbon dioxide emissions, the complex energy system adds ammonia to natural gas, which serves as the main fuel, and burns the ammonia-containing fuel. State of the art documentPatent document

[0003] [Patent document 1] JP 2016- 32 391 A Summary of the inventionTechnical problem

[0004] When a substance containing sulfur, such as natural gas or pulverized coal, is burned as fuel, corrosive hydrogen sulfide (H2S) is generated. When a furnace is exposed to the generated hydrogen sulfide for a long period of time, corrosion of the furnace gradually progresses, and accordingly, it is necessary to conduct regular maintenance for a boiler. Especially when using a two-stage combustion process in which an unburned fuel is reburned in an upper part of the furnace, corrosion may progress because a reduction zone with a high fuel concentration is formed in a main combustion zone in a middle part of the furnace, and a large amount of hydrogen sulfide is generated in the main combustion zone.

[0005] The present invention has been conceived in view of the above-described problems, and an object thereof is to suppress corrosion of a furnace wall portion due to hydrogen sulfide in a boiler that performs mixed fuel combustion of a fuel containing a sulfur component and an ammonia fuel. Solution to the problem

[0006] To solve this problem, the present invention proposes a boiler having the features of claim 1.

[0007] The ammonia injection port may be configured to inject ammonia in a direction in which the burner injects fuel.

[0008] The ammonia injection opening can also be located on the side wall.

[0009] The furnace may include a hopper wall that narrows toward an outlet opening through which ash is discharged to the outside, and the ammonia injection opening may be configured so that the ammonia flows along an inner wall surface of the hopper wall. Effects of the invention

[0010] According to the present invention, a portion of the ammonia to be burned as fuel flows from the ammonia injection port along the inner wall surface of the wall portion where the burner is not mounted. Since the inner wall surface of the wall portion where the burner is mounted is maintained in a high oxygen concentration state by the combustion air injected from the burner and a high reduction region is less likely to form thereon, the hydrogen sulfide concentration of this inner wall surface is relatively low, and this inner wall surface is less likely to be corroded. On the other hand, since the oxygen concentration of the inner wall surface of the wall portion where the burner is not mounted is relatively low and the hydrogen sulfide concentration is relatively high, this inner wall is likely to be corroded.According to the present invention, the ammonia injected from the ammonia injection port is combusted near the inner wall surface of the wall portion where the burner is not mounted, and many OH radicals are generated near this inner wall surface. As a result, an oxidation reaction of hydrogen sulfide is promoted near the inner wall surface of the wall portion where the burner is not mounted, and thus, it is possible to suppress corrosion of this wall portion due to hydrogen sulfide. Therefore, according to the present invention, it is possible to prevent corrosion of the furnace wall portion due to hydrogen sulfide in the boiler that performs mixed fuel combustion of a fuel containing a sulfur component and an ammonia fuel. Short description of the drawings Fig. 1 is a schematic diagram showing a main part configuration of a boiler according to a first embodiment of the present invention. Fig. 2 is a schematic perspective view of a furnace showing the arrangement of a burner and an ammonia injection port included in the boiler according to the first embodiment of the present invention. Fig. 3 is a plan view including a side wall of a furnace included in a boiler according to a second embodiment of the present invention. Fig. 4 is a schematic perspective view of a furnace showing the arrangement of a burner and an ammonia injection port included in a boiler according to a third embodiment of the present invention. Description of the embodiments

[0011] An embodiment of a boiler according to the present invention will be described below with reference to the drawings. (First embodiment)

[0012] Fig. Fig. 1 is a schematic diagram showing a main part configuration of a boiler 1 of a first embodiment. As shown in Fig. 1, the boiler 1 comprises a furnace 2, a flue 3, burners 4, a two-stage combustion air supply unit 5, an ammonia supply unit 6 and a pulverized coal supply unit 7.

[0013] The furnace 2 is a furnace body configured to include a vertically and cylindrically arranged furnace wall and burn a fuel such as ammonia and pulverized coal to generate combustion heat. In the furnace 2, a high-temperature combustion gas is generated by the combustion of the fuel. Furthermore, a lower part of the furnace 2 is provided with an exhaust port 2a through which the ash generated by the combustion of the fuel is discharged to the outside.

[0014] Fig. Figure 2 is a schematic perspective view of the furnace 2, showing the arrangement of the burners 4 and the ammonia injection ports 2f (which will be described later). Fig. In Figure 2, a double circle indicates the location of burner 4, and a small single circle indicates the location of ammonia injection port 2f (described later). Additionally, a large single circle indicates the position of the two-stage combustion air connection 2g (described later).

[0015] As in Fig. 2, the furnace 2 in the present embodiment has a hollow shape having a rectangular shape in plan view, and includes a front wall 2b, a rear wall 2c, side walls 2d, and a hopper wall 2e as wall portions. The front wall 2b is a wall portion located at a front side of the furnace 2. The rear wall 2c is a wall portion located at a rear side of the furnace 2 and facing the front wall 2b. The side wall 2d is a wall portion connecting the front wall 2b and the rear wall 2c. In the present embodiment, two side walls 2d are provided such that one side wall 2d connects one end of the front wall 2b in a horizontal direction and one end of the rear wall 2c in the horizontal direction, and the other side wall 2d connects the other end of the front wall 2b in the horizontal direction and the other end of the rear wall 2c in the horizontal direction.The hopper wall 2e comprises inclined walls that narrow towards the outlet opening 2a and forms the lower part of the furnace 2.

[0016] Of the wall sections of the furnace 2, the front wall 2b and the rear wall 2c are wall sections on which the burners 4 are mounted. Of the wall sections of the furnace 2, the side walls 2d and the hopper wall 2e are wall sections on which the burner 4 is not mounted. In the boiler 1 of the present embodiment, a plurality of ammonia injection ports 2f, which inject the ammonia supplied from the ammonia supply unit 6 into the interior of the furnace 2, are provided on the front wall 2b and the rear wall 2c, which are the wall sections on which the burners 4 are mounted.

[0017] As in Fig. As shown in Figure 2, the ammonia injection ports 2f provided on the front wall 2b are located closer to the side wall 2d than the burners 4 provided on the front wall 2b. That is, viewed from a side wall 2d, the ammonia injection port 2f closest to the side wall 2d is located closer to the side wall 2d than the burner 4 closest to the side wall 2d. The ammonia injection port 2f injects the ammonia in an injection direction of the fuel injected from the burner 4 and causes the ammonia to flow along the inner wall surface of the side wall 2d. The ammonia injected from the ammonia injection port 2f is a part of the ammonia originally supplied to the burner 4 as fuel, and after being injected into the furnace 2, the ammonia is burned inside the furnace 2.As described above, in the boiler 1 of the present embodiment, the ammonia to be burned as fuel is injected from the ammonia injection port 2f along the inner wall surface of the side wall 2d on which the burner 4 is not provided.

[0018] Although the ammonia injection port 2f in Fig. 1 to conceptually indicate that the ammonia injection port 2f is provided in the furnace 2, the position of the ammonia injection port 2f in Fig. 1 does not show the position where the ammonia injection port 2f is actually provided. In fact, the ammonia injection port 2f, as shown in Fig. 2, arranged between the burner 4 and the side wall 2d in the horizontal direction.

[0019] The flue 3 is connected to the upper part of the furnace 2 and discharges the combustion gas generated in the furnace 2 to the outside as exhaust gas. The flue 3 includes a horizontal flue 3a extending horizontally from the upper part of the furnace 2 and a rear flue 3b extending downward from an end portion of the horizontal flue 3a.

[0020] Although in Fig. 1, the boiler 1 includes a superheater mounted in the upper part or the like of the furnace 2. The superheater generates steam by heat exchange between the combustion heat generated in the furnace 2 and water. In addition, the boiler 1 may include a reheater, a fuel preheater, and an air preheater, although this is not the case in Fig. 1 is not shown.

[0021] The burners 4 are arranged on the wall sections in the lower part of the furnace 2. A plurality of the burners 4 are mounted in a circumferential direction of the furnace 2. In addition, although in Fig. 1, several burners 4 are also mounted in a height direction of the furnace 2. The burners 4 are arranged two-dimensionally in the lower part of the furnace 2 and are arranged to face each other and inject and burn the fuel. All burners 4 are compound burners that can inject the ammonia and pulverized coal as fuel into the furnace 2. Although in Fig. 1, the furnace 2 is equipped with an ignition device for igniting the fuel (ammonia and coal dust) blown into the furnace 2 by the burners 4. In addition, the boiler 1 has a combustion air supply unit that supplies combustion air to the burners 4, although this is not shown in Fig. 1 is not shown. The fuel (ammonia and coal dust) blown into the furnace 2 by each of the burners 4 is ignited and burned together with the combustion air by actuating the ignition device.

[0022] All burners 4 mounted in the boiler 1 do not necessarily have to be the previously described compound burners. For example, a single-burner configuration for burning coal with a single fuel may be adopted. However, the boiler 1 of the present embodiment is provided with at least one burner 4 capable of burning ammonia as fuel, so that the boiler 1 can perform mixed-fuel combustion of the ammonia and pulverized coal inside the furnace 2.

[0023] Here, ammonia (NH3) is a compound of hydrogen (H) and nitrogen (N), as expressed by a molecular formula, and does not contain carbon (C) as a constituent atom. In addition, ammonia (a low-carbon fuel) is known as a flame-retardant substance and is a hydrogen carrier substance with three hydrogen atoms, like methane (CH3). Coal dust is obtained by crushing the fossil fuel coal to a size of approximately a few micrometers and is typically used as fuel for boilers. This means that ammonia is a low-carbon fuel with a lower carbon concentration than coal dust (a carbon fuel).

[0024] The two-stage combustion air supply unit 5 is connected to the furnace 2 above the burner 4 and supplies two-stage combustion air to the furnace 2. The two-stage combustion air is supplied by the two-stage combustion air supply unit 5, and an unburned portion of the fuel not burned by the burner 4 is combusted by the two-stage combustion air. In this way, the heat collection performance of the boiler 1 can be improved and the unburned portion of the fuel contained in the exhaust gas can be reduced.

[0025] The ammonia supply unit 6 includes an ammonia supply source 6a, a burner supply section 6b, a connecting supply section 6c, and an ammonia supply control device 6d. The ammonia supply source 6a includes a tank that stores the ammonia. The ammonia supply source 6a does not necessarily have to be a component of the ammonia supply unit 6. That is, the ammonia supply unit 6 can draw the ammonia from the externally mounted ammonia supply source 6a.

[0026] The burner supply section 6b includes a burner supply line 6b1 connecting the ammonia supply source 6a and the burner 4, a total flow rate adjustment valve 6b2, and a burner supply rate adjustment valve 6b3 mounted in an intermediate portion of the burner supply line 6b1. The burner supply line 6b1 carries a portion of the ammonia supplied from the ammonia supply source 6a to be supplied to the burner 4. The total flow rate adjustment valve 6b2 regulates a total flow rate of the ammonia to be supplied from the ammonia supply source 6a to the burner supply line 6b1. The total flow rate of the ammonia is a flow rate of the ammonia to be burned as fuel. The burner supply amount adjusting valve 6b3 is arranged on the downstream side of the total flow amount adjusting valve 6b2 and controls a flow amount of the ammonia to be supplied to the burner 4.

[0027] The connecting supply section 6c includes a connecting supply line 6c1 connected to the ammonia injection port 2f of the furnace 2, and a connecting supply amount adjustment valve 6c2 mounted in an intermediate portion of the connecting supply line 6c1. One end of the connecting supply line 6c1 is connected to the burner supply line 6b1 between the total flow rate adjustment valve 6b2 and the burner supply amount adjustment valve 6b3. That is, the connecting supply line 6c1 connects the burner supply section 6b and the ammonia injection port 2f, receives a portion of the ammonia from the burner supply section 6b, and supplies the portion of the ammonia to the ammonia injection port 2f. The connecting supply amount adjustment valve 6c2 controls the flow rate of the ammonia injected from the ammonia injection port 2f.

[0028] The ammonia supply control device 6d controls the total flow rate adjustment valve 6b2, the burner supply rate adjustment valve 6b3, and the terminal supply rate adjustment valve 6c2 to adjust an opening degree of the total flow rate adjustment valve 6b2, an opening degree of the burner supply rate adjustment valve 6b3, and an opening degree of the terminal supply rate adjustment valve 6c2. The ammonia supply control device 6d adjusts the opening degree of the total flow rate adjustment valve 6b2 based on an external command or the like, thereby controlling the total flow rate of ammonia sucked from the ammonia supply source 6a.

[0029] Furthermore, the distribution of ammonia sucked from the ammonia supply source 6a and supplied to the burner 4 and the ammonia injection port 2f is determined by the opening degree of the burner supply amount adjusting valve 6b3 and the opening degree of the terminal supply amount adjusting valve 6c2. That is, the burner supply amount adjusting valve 6b3 and the terminal supply amount adjusting valve 6c2 constitute a mechanism (distribution adjusting mechanism 6b4) for adjusting a distribution ratio of ammonia between the burner 4 and the ammonia injection port 2f. The ammonia supply control device 6d adjusts the distribution ratio of ammonia to the burner 4 and the ammonia injection port 2f by controlling the distribution adjusting mechanism 6b4 including the burner supply amount adjusting valve 6b3 and the terminal supply amount adjusting valve 6c2.

[0030] The pulverized coal supply unit 7 is connected to the burner 4, crushes the coal into pulverized coal, and supplies the pulverized coal to the burner 4. The pulverized coal supply unit 7 includes, for example, a mill that crushes the coal to a particle size of about a few micrometers to obtain pulverized coal, and a coal feeder that supplies the pulverized coal generated by the mill to the burner 4. The pulverized coal supply unit 7 may be configured to supply the pulverized coal directly from the mill to the burner 4 without providing the coal feeder.

[0031] In the boiler 1 of the present embodiment, ammonia is supplied from the ammonia supply unit 6 to the burner 4, and pulverized coal is supplied from the pulverized coal supply unit 7 to the burner 4, thereby forming a flame through the burner 4 using ammonia and pulverized coal as fuel. In addition, two-stage combustion air is supplied into the furnace 2 through the two-stage combustion air supply unit 5, and the unburned fuel contained in the combustion gas is burned. The combustion gas generated by the combustion of the fuel flows from the lower part to the upper part of the furnace 2 and is discharged to the outside through the flue 3. Furthermore, in the boiler 1 of the present embodiment, the ammonia injected from the ammonia injection port 2f of the furnace 2 flows along the inner wall surface of the side wall 2d and is burned near the inner wall surface of the side wall 2d.

[0032] In the boiler 1 of the present embodiment, the inner wall surfaces of the front wall 2b and the rear wall 2c, on which the burners 4 are mounted, are maintained in a high oxygen concentration state by the combustion air blown from the burner 4, and a high reduction region is less likely to form thereon. Therefore, the hydrogen sulfide concentration near the inner wall surfaces of the front wall 2b and the rear wall 2c is relatively lower than the hydrogen sulfide concentration near the inner wall surface of the side wall 2d, thereby making the inner wall surfaces of the front wall 2b and the rear wall 2c less likely to corrode.

[0033] On the other hand, since the inner wall surface of the side wall 2d, on which the burner 4 is not mounted, is far from the burner 4, the oxygen concentration is likely to be relatively lower and the hydrogen sulfide concentration is likely to be relatively higher near the inner wall surface of the side wall 2d. In the boiler 1 of the present embodiment, the ammonia injected from the ammonia injection port 2f is burned near the inner wall surface of the side wall 2d, and many OH radicals are generated near the inner wall surface of the side wall 2d. As a result, an oxidation reaction of hydrogen sulfide is promoted near the inner wall surface of the side wall 2d, and thus, it is possible to prevent corrosion of the side wall 2d due to the hydrogen sulfide.That is, according to the boiler 1 of the present embodiment, it is possible to suppress the corrosion of the wall portion of the furnace 2 due to the hydrogen sulfide in a case of performing mixed fuel combustion of the fuel containing the sulfur component and the ammonia fuel.

[0034] Furthermore, the boiler 1 of the present embodiment includes, as wall portions, the front wall 2b in which the burner is mounted, the rear wall 2c in which the burner 4 is mounted and which is arranged to be opposite to the front wall 2b, and the side wall 2d which connects the front wall 2b and the rear wall 2c and on which the burner 4 is not mounted, wherein the ammonia injection ports 2f are provided on both the front wall 2b and the rear wall 2c, and the ammonia injection port 2f is arranged closer to the side wall 2d in the horizontal direction than the burner 4. Therefore, it is possible to reliably form a region having a high concentration of OH radicals between the flame formed by the burner 4 and the side wall 2d, and it is possible to more reliably prevent the corrosion of the side wall 2d.

[0035] Furthermore, in the boiler 1 of the present embodiment, the ammonia injection port 2f injects ammonia in the direction in which the burner 4 injects fuel. Therefore, it is possible to prevent a flow of ammonia injected from the ammonia injection port 2f from intersecting with a flow of fuel injected from the burner 4, and it is possible to prevent the flow of fuel injected from the burner 4 from being obstructed by the ammonia injected from the ammonia injection port 2f. (Second embodiment)

[0036] Next, a second embodiment of the present invention will be described. In the description of the present embodiment, the same elements as in the first embodiment will be omitted or simplified.

[0037] Fig. Fig. 3 is a plan view showing the side wall 2d of the furnace 2 included in a boiler of the present embodiment. As shown in Fig. As shown in Fig. 3, in the present embodiment, the ammonia injection port 2f is mounted on the side wall 2d in addition to the front wall 2b and the rear wall 2c. The ammonia injection port 2f mounted on the side wall 2d is located at a substantially central portion in the horizontal direction (forward / backward direction) connecting the front wall 2b and the rear wall 2c, and injects the ammonia along the inner wall surface of the side wall 2d at a low flow rate.

[0038] The forward / backward center part is located far away from the ammonia injection ports 2f provided on the front wall 2b and the rear wall 2c. Therefore, there is a possibility that the ammonia injected from the ammonia injection ports 2f provided on the front wall 2b and the rear wall 2c cannot reach the forward / backward center part. Since the ammonia injection port 2f is mounted on the side wall 2d in the present embodiment, the ammonia can flow along a larger area of ​​the inner wall surface of the side wall 2d, and it is possible to prevent the side wall 2d from corroding over a larger area. Therefore, according to the boiler of the present embodiment, since the ammonia injection port 2f is provided on the side wall 2d, the side wall 2d can be prevented from corroding over a larger area. (Third embodiment)

[0039] Next, a third embodiment of the present invention will be described. In the description of the present embodiment, the same elements as in the first embodiment will be omitted or simplified.

[0040] Fig. Fig. 4 is a schematic perspective view with the furnace 2 showing an arrangement of the burners 4 and the ammonia injection ports 2f in a boiler of the present embodiment. As shown in Fig. As shown in Fig. 4, according to the present embodiment, a plurality of ammonia injection ports 2f are provided on the hopper wall 2e on which the burner 4 is not mounted. The ammonia injection port 2f provided on the hopper wall 2e injects the ammonia along an inner wall surface of the hopper wall 2e.

[0041] According to the boiler of the present embodiment, the ammonia injected from the ammonia injection port 2f provided on the hopper wall 2e flows along the inner wall surface of the hopper wall 2e and is burned near the inner wall surface of the hopper wall 2e, thereby forming a region with a high concentration of OH radicals near the inner wall surface of the hopper wall 2e. Therefore, the oxidation reaction of hydrogen sulfide near the inner wall surface of the hopper wall 2e is promoted, and it is possible to suppress corrosion of the hopper wall 2e. As described above, according to the boiler of the present embodiment, it is possible to prevent not only the side wall 2d but also the hopper wall 2e from being corroded by the hydrogen sulfide.

[0042] Although embodiments of the present invention will be described with reference to the accompanying drawings, the present invention is not limited to the above embodiments.

[0043] According to the first embodiment and the third embodiment, as shown in the Fig. 2 and Fig. 4, for example, a configuration is assumed in which another ammonia injection port 2f is not mounted between the ammonia injection ports 2f arranged at the same height. However, the present invention is not limited to this. For example, in a case where it is necessary to further improve the corrosion resistance of the front wall 2b and the rear wall 2c, one or more ammonia injection ports 2f may be arranged between the ammonia injection ports 2f arranged at the same height.

[0044] Furthermore, in the above-described embodiment, a configuration is adopted in which the two-stage combustion air is supplied to the upper part of the furnace 2. However, the present invention can also be applied to a boiler that does not supply the two-stage combustion air.

[0045] Furthermore, in the above-described embodiment, the boiler performing mixed fuel combustion of pulverized coal and ammonia as fuel was described. However, the present invention is not limited to this. For example, a configuration in which mixed combustion of natural gas and ammonia is performed, or a configuration in which mixed combustion of heavy oil or light oil and ammonia is performed, may be adopted. That is, the present invention is applicable to a boiler performing mixed fuel combustion of sulfur-containing fuel and ammonia. Industrial applicability

[0046] The present invention is applicable to a boiler that performs mixed fuel combustion of a fuel containing a sulfur component and ammonia as fuel. List of reference symbols 1 boiler 2 ovens 2a Outlet opening 2b Front wall (wall section) 2c Rear wall (wall section) 2d side wall (wall section) 2nd funnel wall (wall section) 2f Ammonia injection port 2g Two-stage combustion air connection 3 deduction 3a Horizontal deduction 3b Rear trigger 4 burners 5 Two-stage combustion air supply unit 6 Ammonia supply unit 6a Ammonia supply source 6b Burner supply section 6b1 burner supply line 6b2 Total flow adjustment valve 6b3 Burner supply quantity adjustment valve 6b4 Distribution adjustment mechanism 6c Connection supply section 6c1 connecting supply line 6c2 Connection supply quantity adjustment valve 6d Ammonia supply control device 7 Coal dust supply unit

Claims

[1] Boiler (1) which carries out mixed fuel combustion of a sulphur-containing fuel and ammonia as fuel, the boiler (1) comprising: an oven (2) having a front wall (2b), a rear wall (2c) facing the front wall (2b) and a side wall (2d) connecting the front wall (2b) and the rear wall (2c); a burner (4) mounted on the front wall (2b) and the rear wall (2c) of the furnace (2); and an ammonia injection opening (2f) provided on the front wall (2b) and / or the rear wall (2c), characterized by , that the ammonia injection opening (2f) is arranged closer to the side wall (2d) than the burner (4) in the horizontal direction, so that the ammonia to be burned flows as fuel along an inner wall surface of the side wall (2d) in which the burner (4) is not mounted. [2] A boiler (1) according to claim 1, wherein the ammonia injection port (2f) is configured to inject the ammonia in a direction in which the burner (4) injects the fuel. [3] Boiler (1) according to claim 1 or 2, wherein the ammonia injection port (2f) is further mounted on the side wall (2d). [4] Boiler (1) according to one of claims 1 to 3, wherein the furnace (2) comprises a hopper wall (2e) which narrows towards an outlet opening (2a) through which ash is discharged to the outside, and the ammonia injection port (2f) is configured so that the ammonia flows along an inner wall surface of the funnel wall (2e).

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