Circulating fluidized bed boiler and method for producing fly ash

Abstract

To provide a circulation fluidized bed boiler and a method for producing fly ash capable of suppressing running cost incurred by exchange of an inner cylinder.SOLUTION: A circulation fluidized bed boiler includes: a furnace configured to burn fuel while causing a fluid material to flow; a cyclone to which combustion gas generated by the furnace is introduced and that is configured to separate powder and granular materials from the combustion gas; and an air exhaust part configured to discharge gas from which powder and granular materials have been separated by the cyclone as exhaust gas. The cyclone includes: an outlet part connected to the air exhaust part; an inner cylinder disposed at the outlet part so as to extend vertically while projecting toward the inner side of the cyclone; and a sealing member disposed at a gap between an inner peripheral surface of the air exhaust part or the outlet part and an outer peripheral surface of the inner cylinder and configured to inhibit flowing of exhaust gas at the gap.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a circulating fluidized bed boiler and a method for producing fly ash. [Background technology]

[0002] Patent Document 1 discloses a circulating fluidized bed boiler including a furnace and a cyclone. The furnace is configured to mix air and fuel with a fluidized material while fluidizing the fluidized material, thereby burning the fuel. Combustion gas generated by the combustion of fuel in the furnace is introduced into the cyclone. The cyclone is configured to separate relatively large granular material (e.g., powder or particles of the fluidized material) that accompanies the combustion gas by centrifugal separation, and return the separated material to the furnace. The combustion gas, together with relatively small dust particles that were not separated by the cyclone, is discharged downstream from the cyclone.

[0003] The cyclone includes a cyclone body having a cylindrical portion into which combustion gas is introduced, and a cylindrical inner cylinder located at the center of the cylindrical portion of the cyclone body. The cylindrical portion of the cyclone body is provided with an inner cylinder receiving portion facing inward. The metal inner cylinder has a plurality of outward protrusions arranged in the circumferential direction, which penetrate the peripheral wall of the inner cylinder and are attached by welding. The inner cylinder is supported by the cyclone body by placing the plurality of protrusions on the inner cylinder on the inner cylinder receiving portion of the cyclone body. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-020711 Summary of the Invention [Problem to be solved by the invention]

[0005] In the circulating fluidized bed boiler of Patent Document 1, the inner cylinder has a plurality of openings spaced apart in the circumferential direction (see paragraphs 0017, 0031, and 0035). The purpose of these openings is to prevent ash from accumulating between the protruding body of the inner cylinder and the inner cylinder receiving part of the cyclone body, and to relieve thermal stress at the welded part of the protruding body by allowing combustion gas to flow inside and outside the inner cylinder through the openings (see same reference).

[0006] However, when the combustion gas after centrifugal separation in the cyclone is discharged from the cyclone through the inner tube as exhaust gas, the high-temperature (e.g., approximately 850°C to 1000°C) exhaust gas flows through the opening, softening the area of ​​the inner tube where the exhaust gas flows. As a result, the pressure exerted by the exhaust gas on the inner tube can cause the area of ​​the inner tube near the softened portion to deform radially inward and outward. In this case, the overall outer shape of the inner tube becomes smaller, and there is a concern that when the circulating fluidized bed boiler is stopped and the inner tube cools, the protruding body of the inner tube may come off the inner tube holder of the cyclone body, causing the inner tube to fall from the cyclone body. Therefore, the inner tube must be replaced before it falls, which increases the frequency of inner tube replacement. This can increase running costs.

[0007] Therefore, the present disclosure describes a circulating fluidized bed boiler and a method for producing fly ash that can reduce the running costs associated with replacing the inner tube. [Means for solving the problem]

[0008] An example of a circulating fluidized bed boiler includes a furnace configured to burn fuel while fluidizing a fluidizing material, a cyclone configured to receive combustion gas generated in the furnace and separate particulate matter from the combustion gas, and an exhaust section configured to discharge gas obtained after the particulate matter has been separated in the cyclone as exhaust gas. The cyclone includes an outlet section connected to the exhaust section, an inner cylinder disposed in the outlet section so as to extend vertically while protruding toward the inside of the cyclone, and a sealing member disposed in a gap between the inner circumferential surface of the exhaust section or the outlet section and the outer circumferential surface of the inner cylinder and configured to obstruct the flow of exhaust gas in the gap. [Effects of the Invention]

[0009] According to the circulating fluidized bed boiler and the method for producing fly ash according to the present disclosure, it is possible to reduce the running costs associated with replacing the inner cylinder. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing an example of a circulating fluidized bed boiler. [Figure 2] FIG. 2 is a cross-sectional view showing the vicinity of an inner cylinder constituting the circulating fluidized bed boiler of the example of FIG. [Figure 3] FIG. 3 is a top view showing an inner tube constituting the circulating fluidized bed boiler of the example of FIG. [Figure 4] Figure 4(a) is a cross-sectional view that schematically shows how exhaust gas flows near the inner tube in the circulating fluidized bed boiler of the example of Figure 1, and Figure 4(b) is a cross-sectional view that schematically shows how exhaust gas flows near the inner tube when the circulating fluidized bed boiler of the example of Figure 1 does not include a sealing member. DETAILED DESCRIPTION OF THE INVENTION

[0011] In the following description, the same elements or elements having the same functions will be designated by the same reference numerals, and redundant explanations will be omitted. Note that in this specification, when referring to the top, bottom, right, and left of a figure, the directions of the reference numerals in the figure will be used as the reference.

[0012] [Circulating fluidized bed boiler overview] The configuration of a circulating fluidized bed boiler 1 will be described with reference to Figures 1 to 3. As shown in Figure 1, the circulating fluidized bed boiler 1 includes a furnace (fluidized bed reactor) 10, a cyclone 20, a heat exchanger 30, an exhaust section 40, a dust collector 50, and a chimney 60.

[0013] The furnace 10 is configured to mix air and fuel (e.g., coal, biomass, etc.) with fluidized material (e.g., coal ash, limestone, sand, etc.) while fluidizing the fluidized material, and combust the fuel. Examples of biomass include wood chips and coconut shells.

[0014] The furnace 10 includes a combustion chamber 11 that extends in the vertical direction and has a cylindrical shape, and a discharge line 12. A fuel supply port (not shown) for supplying fuel is provided in the middle of the combustion chamber 11 in the vertical direction. The combustion chamber 11 is filled with a fluid material. In the combustion chamber 11, the fluid material and the fuel supplied from the fuel supply port flow from bottom to top due to the fluidizing air introduced into the interior. While flowing in the combustion chamber 11, the fuel is mixed with NOx. X It is burned at around 830℃ to 900℃ to suppress the generation of CO₂.

[0015] The discharge line 12 extends between the upper part of the combustion chamber 11 and the upper part of a main body 21 of a cyclone 20 (described later) so as to connect them. The downstream end of the discharge line 12 is connected to the main body 21 so as to extend in a direction along the inner circumferential surface of the main body 21 (for example, a tangential direction). The discharge line 12 is configured to introduce the combustion gas G1 generated in the combustion chamber 11 into the cyclone 20. The combustion gas G1 reaches the cyclone 20 through the discharge line 12 while carrying with it powder and granular material having a relatively large particle size and dust having a relatively small particle size. The temperature of the combustion gas G1 may be, for example, about 850°C to 1000°C.

[0016] The powdered or granular materials include, for example, powder or particles of fluid material, cinders, gypsum, etc. The cinders include, for example, coal cinders (also called bottom ash or clinker ash). The dust includes, for example, soot and dust. The soot and dust includes, for example, coal soot and dust (also called fly ash), wood chip ash, coconut shell ash, etc.

[0017] The cyclone 20 includes a main body 21, an outlet 22, a discharge line 23, and an inner cylinder 70. The main body 21 extends in the vertical direction and has a cylindrical shape. The main body 21 is configured to separate powder and granular material accompanying the combustion gas G1 introduced through the discharge line 12 from the combustion gas G1 by centrifugal separation.

[0018] The outlet portion 22 extends in the vertical direction and has a cylindrical shape. The outlet portion 22 is disposed at the upper end of the main body 21 and is configured to discharge the combustion gas G1 that has been centrifuged in the main body 21 downstream as exhaust gas G2. Dust that has not been centrifuged in the main body 21 is accompanied by the exhaust gas G2.

[0019] A support piece 24 protruding toward the radial center of the outlet portion 22 may be provided on the inner peripheral surface of the outlet portion 22. The support piece 24 may include one or more support pieces 24. When the support piece 24 includes one support piece 24, the support piece 24 may be annular or substantially C-shaped. When the support piece 24 includes multiple support pieces 24, the multiple support pieces 24 may be aligned in the circumferential direction on the inner peripheral surface of the outlet portion 22, as illustrated in FIGS. 2 and 3, or may be aligned in the circumferential direction at approximately equal intervals on the inner peripheral surface of the outlet portion 22. In the example of FIG. 3, eight support pieces 24 are aligned in the circumferential direction at approximately equal intervals on the inner peripheral surface of the outlet portion 22.

[0020] 1, the discharge line 23 extends between the lower part of the combustion chamber 11 and the heat exchanger 30 so as to connect them. The discharge line 23 is configured to introduce the powder and granular material separated by centrifugal separation in the main body 21 into the heat exchanger 30. The inner cylinder 70 will be described in detail later.

[0021] The heat exchanger 30 is configured to recover heat from the high-temperature (e.g., about 900°C) powder or granular material introduced through the discharge line 23, and return the powder or granular material after heat recovery (e.g., about 500°C) to the lower part of the combustion chamber 11. The heat recovered in the heat exchanger 30 may be used, for example, for power generation.

[0022] The exhaust section 40 extends between the outlet section 22 and the dust collector 50 so as to connect them. The exhaust section 40 has, for example, a cylindrical shape. The exhaust section 40 is configured to recover heat from the high-temperature exhaust gas G2 discharged from the cyclone 20 through the outlet section 22 and introduce the exhaust gas G2 after heat recovery into the dust collector 50. In order to recover heat from the exhaust gas G2, for example, a superheater and a coal economizer (not shown) may be provided midway through the exhaust section 40. The heat recovered in the exhaust section 40 may be used, for example, for power generation or the like.

[0023] The dust collector 50 is configured to collect dust (fly ash, etc.) accompanying the exhaust gas G2. The dust collector 50 may be a bag filter or an electrostatic precipitator. The fly ash collected in the dust collector 50 may be used as a cement raw material. The chimney 60 is configured to discharge the clean gas after the dust has been collected in the dust collector 50 into the atmosphere.

[0024] [Inner cylinder configuration] Next, the inner cylinder 70 will be described in detail with reference to Figures 2 and 3. The inner cylinder 70 is disposed in the outlet portion 22. The inner cylinder 70 is also called a vortex finder, and generates a centrifugal separation effect by causing the combustion gas G1 introduced into the main body 21 from the discharge line 12 to swirl around the outer periphery of the inner cylinder 70. The inner cylinder 70 may be made of metal.

[0025] The inner cylinder 70 includes a main body 71 and a protruding piece 72. The main body 71 is positioned inside the outlet portion 22 so as to extend in the up-down direction. The lower part of the main body 71 protrudes toward the inside of the main body 21.

[0026] The protruding piece 72 protrudes radially outward from the outer peripheral surface of the main body 71. The protruding piece 72 is configured to be supportable relative to the outlet section 22. In the example shown in FIGS. 2 and 3 , the protruding piece 72 is supported by the support piece 24 of the outlet section 22. At this time, taking into consideration thermal expansion of the inner cylinder 70 during operation of the circulating fluidized bed boiler 1, the outer peripheral surface of the protruding piece 72 is spaced apart from the inner peripheral surface of the exhaust section 40, and the outer peripheral surface of the main body 71 is spaced apart from the inner peripheral surface of the outlet section 22. That is, a gap D1 is formed between the outer peripheral surface of the protruding piece 72 and the inner peripheral surface of the exhaust section 40. A gap D2 (another gap) is formed between the outer peripheral surface of the main body 71 and the inner peripheral surface of the outlet section 22. Note that thermal expansion of the inner cylinder 70 during operation of the circulating fluidized bed boiler 1 may cause the outer peripheral surface of the main body 71 to abut against the tip of the support piece 24.

[0027] As illustrated in FIG. 2, a baffle member 80 may be attached to the lower end of the inner cylinder 70. In this case, the baffle member 80 is located below the gap D2, i.e., below the outlet portion 22. The baffle member 80 may be, for example, an annular plate-like body. The baffle member 80 may be made of metal (e.g., stainless steel). The baffle member 80 may be connected to the inner cylinder 70 by welding its inner peripheral edge to the outer peripheral surface of the main body 71.

[0028] When viewed from the top and bottom, the baffle member 80 overlaps the entire gap D2. That is, the outer peripheral edge of the baffle member 80 is located radially outward of the gap D2.

[0029] 2 and 3, a sealing member 90 may be disposed in the gap D1. That is, the sealing member 90 may be disposed between the inner circumferential surface of the exhaust section 40 and the protruding piece 72. In the example of FIGS. 2 and 3, the sealing member 90 is supported by the support piece 24. The presence of the sealing member 90 prevents the exhaust gas G2 from flowing from the main body 21 toward the exhaust section 40 from flowing through the gap D1.

[0030] The sealing member 90 may seal the entire gap D1 or may seal only a portion of the gap D1. In the former case, as illustrated in FIG. 3, the sealing member 90 has an annular shape, and the entire periphery of the inner cylinder 70 is covered by the sealing member 90.

[0031] The sealing member 90 may be composed of, for example, a base layer and a coating layer provided thereon. The base layer may be composed of, for example, refractory fiber. The coating layer may be composed of, for example, a castable refractory. In this case, the base layer (refractory fiber) may be first placed in the gap D1, and then the castable refractory mixed with water may be applied (for example, by pouring, troweling, spraying, etc.) onto the base layer.

[0032] As illustrated in Fig. 2, a sealing member 100 (another sealing member) may be disposed in the gap D2. That is, the sealing member 100 may be disposed below the protruding piece 72, between the inner circumferential surface of the outlet portion 22 and the outer circumferential surface of the main body 71. As illustrated in Fig. 2, the sealing member 100 may be located below the protruding piece 72 and above the baffle member 80. The presence of the sealing member 100 prevents the exhaust gas G2 from flowing through the gap D2 as it attempts to travel from the main body 21 toward the exhaust portion 40.

[0033] The sealing member 100 may seal the entire gap D2, or may seal only a portion of the gap D2. In the former case, the sealing member 90 has an annular shape, and the sealing member 100 covers the entire periphery of the inner cylinder 70. Note that the baffle member 80 may be attached to the inner cylinder 70 after the sealing member 100 is placed in the gap D2.

[0034] [Effect] As illustrated in FIG. 4(b), when the circulating fluidized bed boiler 1 does not include the sealing members 90 and 100, the high-temperature exhaust gas G2 flows through the gaps D1 and D2, causing the inner tube 70 to soften in particular in the region through which the exhaust gas flows. As a result, the pressure exerted by the exhaust gas G2 on the inner tube 70 can cause the softened portion of the inner tube 70 to deform radially inward and outward (see arrows Ar in FIG. 4(b)). In this case, the overall outer shape of the inner tube 70 becomes smaller. Therefore, when the circulating fluidized bed boiler 1 is stopped and the inner tube 70 cools, the protruding pieces 72 of the inner tube 70 may come off the support pieces 24 of the main body 21, potentially causing the inner tube 70 to fall off the main body 21. Therefore, the inner tube 70 must be replaced before it falls off, increasing the frequency of replacement of the inner tube 70. This can increase running costs.

[0035] As a countermeasure, it is conceivable to support the inner tube 70 using steel material (e.g., H-beam). Specifically, the steel material is fixed to the support pieces 24, and through-holes (e.g., rectangular holes) through which the steel material can pass are formed in the main body 71 of the inner tube 70. The steel material is then passed through the through-holes, whereby the inner tube 70 is supported by the cyclone 20 via the steel material and the support pieces 24. However, even in this case, deformation of the inner tube 70 progresses around the through-holes formed in the inner tube 70, and after a predetermined period of time (e.g., after about six to seven years), the deformation of the inner tube 70 becomes so severe that it may be necessary to replace the inner tube 70. This is presumably because the exhaust gas G2 passing through another gap D2 flows through the through-holes that are intended to pass the steel material, making it easier for deformation to progress around the through-holes.

[0036] In contrast, according to the above example, as illustrated in FIG. 4(a), the presence of the sealing members 90, 100 makes it difficult for the exhaust gas G2 to flow through the gaps D1, D2. As a result, the inner tube 70 is less likely to be softened by the exhaust gas G2, and the pressure acting on the inner tube 70 from the exhaust gas G2 as the exhaust gas G2 flows is reduced. Therefore, deformation of the outer shape of the inner tube 70 is suppressed, and the frequency of replacement of the inner tube 70 decreases. As a result, it is possible to suppress the running costs associated with replacing the inner tube 70.

[0037] According to the above example, the sealing members 90, 100 can be disposed in the gaps D1, D2 so as to cover the entire periphery of the inner cylinder 70. In this case, the presence of the sealing members 90, 100 makes it even more difficult for the exhaust gas G2 to flow through the gaps D1, D2. This makes it possible to reduce the running costs associated with replacing the inner cylinder 70.

[0038] According to the above example, the sealing member 90 can be disposed in the gap D1 between the inner circumferential surface of the exhaust section 40 and the protruding piece 72. In this case, the outlet section 22 that supports the protruding piece 72 also supports the sealing member 90. Therefore, no separate member is required to support the sealing member 90. This makes it possible to simplify the structure of the circulating fluidized bed boiler 1.

[0039] According to the above example, the sealing member 100 can be disposed in the gap D2 between the inner circumferential surface of the outlet portion 22 and the outer circumferential surface of the main body 71. In this case, the presence of the sealing member 100 makes it difficult for the inner cylinder 70 to deform in its radial direction. This makes it possible to reduce the running costs associated with replacing the inner cylinder 70. During operation of the circulating fluidized bed boiler 1, the exhaust gas G2 flows upward toward the outlet portion 22, and an upward force of the exhaust gas G2 acts on the sealing member 100, making it difficult for the sealing member 100 to fall off.

[0040] According to the above example, the baffle member 80 that overlaps the entire gap D2 when viewed from the top and bottom can be provided on the inner cylinder 70. In this case, when the exhaust gas G2 is discharged from the outlet 22, the presence of the baffle member 80 makes it even more difficult for the exhaust gas G2 to flow through the gap D2 between the inner circumferential surface of the outlet 22 and the outer circumferential surface of the inner cylinder 70. Therefore, it is possible to reduce the running costs associated with replacing the inner cylinder 70.

[0041] According to the above example, the sealing member 90 may include a base layer made of refractory fiber and a coating layer made of castable refractory provided thereon. In this case, the refractory fiber prevents the exhaust gas G2 from flowing through the gap D1, and the castable refractory prevents the refractory fiber from being lifted by the exhaust gas G2. This allows the sealing member 90 to remain in the gap D1 for a long period of time.

[0042] 2, the cyclone 20 was constructed in a state in which the entire gap D1 was sealed with a sealing member 90 composed of a base layer and a coating layer provided thereon, and the circulating fluidized bed boiler 1 was actually operated for one year. As a result, it was confirmed that deformation of the inner cylinder 70 was significantly suppressed compared to when the sealing member 90 was not provided.

[0043] [Variations] The disclosure in this specification should be considered to be illustrative in all respects and not restrictive. Various omissions, substitutions, modifications, etc. may be made to the above examples without departing from the scope and spirit of the claims.

[0044] (1) The sealing members 90 and 100 may be disposed between the inner cylinder 70 and the inner circumferential surface of the exhaust unit 40 or the inner circumferential surface of the outlet unit 22 .

[0045] (2) The sealing members 90, 100 may be made of cinders or soot and dust. In this case, cinders or soot and dust generated during operation of the circulating fluidized bed boiler 1 can be used as the sealing members 90, 100. This makes it possible to form the sealing members 90, 100 at low cost. Note that the cinders or soot and dust placed in the gaps D1, D2 as the sealing members 90, 100 may be those that have naturally accumulated in the gaps D1, D2 during operation of the circulating fluidized bed boiler 1, or may be those that an operator has filled in the gaps D1, D2 before operation of the circulating fluidized bed boiler 1.

[0046] [Other examples] Example 1. An example of a circulating fluidized bed boiler includes a furnace configured to burn fuel while fluidizing a fluidizing material, a cyclone configured to receive combustion gas generated in the furnace and separate particulate matter from the combustion gas, and an exhaust section configured to discharge the gas obtained after the particulate matter is separated in the cyclone as exhaust gas. The cyclone includes an outlet section connected to the exhaust section, an inner cylinder disposed in the outlet section so as to extend vertically while protruding toward the interior of the cyclone, and a sealing member disposed in the gap between the inner circumferential surface of the exhaust section or outlet section and the outer circumferential surface of the inner cylinder and configured to obstruct the flow of exhaust gas through the gap. In this case, the presence of the sealing member makes it difficult for exhaust gas to flow through the gap between the inner circumferential surface of the exhaust section or outlet section and the outer circumferential surface of the inner cylinder. This makes it less likely for the inner cylinder to be softened by the exhaust gas, and reduces the pressure acting on the inner cylinder from the exhaust gas as it flows. This suppresses deformation of the outer shape of the inner cylinder, thereby reducing the frequency of inner cylinder replacement. As a result, it is possible to reduce the running costs associated with replacing the inner cylinder.

[0047] Example 2: In the circulating fluidized bed boiler of Example 1, the sealing member may be disposed in the gap so as to cover the entire periphery of the inner tube. In this case, the presence of the sealing member makes it even more difficult for the exhaust gas to flow through the gap between the inner circumferential surface of the exhaust section or outlet section and the outer circumferential surface of the inner tube. This makes it possible to reduce the running costs associated with replacing the inner tube.

[0048] Example 3: In the circulating fluidized bed boiler of Example 1 or Example 2, the inner cylinder may include an annular protruding piece that protrudes outward from the outer peripheral surface of the inner cylinder and is configured to be supportable by the exhaust section or the outlet section, and the sealing member may be disposed between the inner peripheral surface of the exhaust section or the outlet section and the protruding piece. In this case, the exhaust section or the outlet section that supports the protruding piece also supports the sealing member. Therefore, a separate member for supporting the sealing member is not required. This makes it possible to simplify the structure of the circulating fluidized bed boiler.

[0049] Example 4: In the circulating fluidized bed boiler of Example 3, the cyclone may further include another sealing member disposed in another gap between the inner circumferential surface of the outlet portion and the outer circumferential surface of the inner cylinder below the protruding piece of the inner cylinder, and configured to obstruct the flow of exhaust gas in that gap. In this case, the presence of the another sealing member makes it even more difficult for exhaust gas to flow through the gap between the inner circumferential surface of the outlet portion and the outer circumferential surface of the inner cylinder. In addition, the placement of the another sealing member on the outer circumferential surface of the inner cylinder makes it less likely for the inner cylinder to deform in its radial direction. This makes it possible to reduce the running costs associated with replacing the inner cylinder.

[0050] Example 5: In any of the circulating fluidized bed boilers of Examples 1 to 4, the cyclone may further include a baffle member located lower than the gap toward the inner cylinder, and the baffle member may protrude outward from the outer peripheral surface of the inner cylinder so as to overlap the entire gap when viewed from the top-bottom direction. In this case, when exhaust gas is discharged from the outlet, the presence of the baffle member makes it even more difficult for the exhaust gas to flow through the gap between the inner peripheral surface of the outlet and the outer peripheral surface of the inner cylinder. This makes it possible to reduce the running costs associated with replacing the inner cylinder.

[0051] Example 6: In any of the circulating fluidized bed boilers of Examples 1 to 5, the sealing member may include a base layer made of refractory fiber and a coating layer made of castable refractory material provided on the base layer. In this case, the refractory fiber prevents exhaust gas from flowing through the gap between the inner circumferential surface of the exhaust port or outlet port and the outer circumferential surface of the inner tube, and the castable refractory material prevents the refractory fiber from being lifted up by the exhaust gas. Therefore, it is possible to maintain the sealing member disposed in the gap for a long period of time.

[0052] Example 7: In the circulating fluidized bed boiler of any one of Examples 1 to 6, the plugging member may contain cinders or soot and dust. In this case, the cinders or soot and dust generated during operation of the circulating fluidized bed boiler can be used as the plugging member. This makes it possible to produce the plugging member at low cost.

[0053] Example 8. A method for producing fly ash is a method for producing fly ash using any of the circulating fluidized bed boilers of Examples 1 to 7, and includes burning fuel while fluidizing a fluidizing material in a furnace, introducing the combustion gas produced in the furnace into a cyclone to separate particulate matter from the combustion gas, discharging the gas from which the particulate matter has been separated in the cyclone as exhaust gas through an outlet and an exhaust section, and recovering fly ash accompanying the exhaust gas in a dust collector. In this case, the same effects as those of Example 1 can be obtained. [Explanation of symbols]

[0054] 1...circulating fluidized bed boiler, 10...furnace, 20...cyclone, 22...outlet section, 40...exhaust section, 50...dust collector, 70...inner tube, 71...main body, 72...projecting piece, 80...baffle member, 90...sealing member, 100...sealing member (another sealing member), D1...gap, D2...gap (another gap), G1...combustion gas, G2...exhaust gas

Claims

1. a furnace configured to combust fuel while fluidizing a fluid material; a cyclone configured to receive the combustion gas generated in the furnace and separate powder and granular material from the combustion gas; an exhaust section configured to discharge, as exhaust gas, gas obtained after the powder or granular material has been separated in the cyclone, The cyclone is an outlet portion connected to the exhaust portion; an inner cylinder disposed at the outlet portion so as to protrude toward the inside of the cyclone and extend in the vertical direction; a sealing member disposed in a gap between an inner circumferential surface of the exhaust portion or the outlet portion and an outer circumferential surface of the inner cylinder, and configured to obstruct the flow of the exhaust gas in the gap, the inner cylinder includes an annular protruding piece that protrudes outward from an outer circumferential surface of the inner cylinder and is configured to be supportable by the exhaust portion or the outlet portion, the sealing member is disposed between an inner circumferential surface of the exhaust portion or the outlet portion and the protruding piece, The cyclone further includes another sealing member that is arranged in another gap between the inner surface of the outlet portion and the outer surface of the inner cylinder below the protruding piece of the inner cylinder and is configured to obstruct the flow of the exhaust gas in the another gap.

2. The cyclone further includes a baffle member located on a lower end side of the inner cylinder relative to the gap, 2. The circulating fluidized bed boiler according to claim 1, wherein the baffle member protrudes outward from the outer peripheral surface of the inner cylinder so as to overlap the entire gap when viewed from above.

3. The sealing member is a base layer made of fire-resistant fibers; 3. The circulating fluidized bed boiler according to claim 1, further comprising: a coating layer provided on the base layer and made of a castable refractory material.

4. A furnace configured to burn fuel while fluidizing a fluid material; a cyclone configured to receive the combustion gas generated in the furnace and separate powder and granular material from the combustion gas; an exhaust section configured to discharge, as exhaust gas, gas obtained after the powder or granular material has been separated in the cyclone, The cyclone is an outlet portion connected to the exhaust portion; an inner cylinder disposed at the outlet portion so as to protrude toward the inside of the cyclone and extend in the vertical direction; a sealing member disposed in a gap between an inner circumferential surface of the exhaust portion or the outlet portion and an outer circumferential surface of the inner cylinder, and configured to obstruct the flow of the exhaust gas in the gap, The cyclone further includes a baffle member located on a lower end side of the inner cylinder relative to the gap, The baffle member protrudes outward from the outer peripheral surface of the inner cylinder so as to overlap the entire gap when viewed from above and below.

5. A furnace configured to burn fuel while fluidizing a fluid material; a cyclone configured to receive the combustion gas generated in the furnace and separate powder and granular material from the combustion gas; an exhaust section configured to discharge, as exhaust gas, gas obtained after the powder or granular material has been separated in the cyclone, The cyclone is an outlet portion connected to the exhaust portion; an inner cylinder disposed at the outlet portion so as to protrude toward the inside of the cyclone and extend in the vertical direction; a sealing member disposed in a gap between an inner circumferential surface of the exhaust portion or the outlet portion and an outer circumferential surface of the inner cylinder, and configured to obstruct the flow of the exhaust gas in the gap, The sealing member is a base layer made of fire-resistant fibers; a coating layer provided on the base layer and made of castable refractory material.

6. The circulating fluidized bed boiler according to any one of claims 1 to 5, wherein the sealing member is disposed in the gap so as to cover the entire periphery of the inner cylinder.

7. The circulating fluidized bed boiler according to any one of claims 1 to 6, wherein the sealing member includes cinders or soot and dust.

8. A method for producing fly ash using the circulating fluidized bed boiler according to any one of claims 1 to 7, burning the fuel while fluidizing the fluid material in the furnace; introducing the combustion gas generated in the furnace into the cyclone to separate powder and granular material from the combustion gas; Discharging the gas obtained after the powder or granular material has been separated in the cyclone as exhaust gas through the outlet portion and the exhaust portion; and recovering fly ash accompanying the exhaust gas in a dust collector.

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