JP7103781B2 - Fluidized bed furnace - Google Patents

Description

The present invention relates to a fluidized bed furnace and a method for operating the same.

Conventionally, a fluidized bed furnace equipped with a fluidized bed in which a fluidized medium filled in the lower part of the furnace is made to flow with a fluidized gas blown from the bottom of the furnace, and a low air ratio combustion of fuel (combustion object) is performed in the fluidized bed. Are known. Here, in the low air ratio combustion of the fuel, the air ratio of the fluidizing gas is set to a low air ratio of less than 1, and the fuel is partially burned to dry and thermally decompose the fuel and gasify it. Patent Documents 1 and 2 disclose this type of fluidized bed furnace.

The fluidized bed furnace of Patent Document 1 is composed of a fluidized bed portion and a freeboard portion located above the fluidized bed portion. In this fluidized bed furnace, a fluidized gas having an air ratio of 0.3 to 0.6 is supplied to the bottom of the fluidized bed, and dioxin having an air ratio of 0.4 to 0.7 is supplied near the surface of the fluidized bed. Combustion air for decomposition is supplied, and secondary air is supplied to the free board section. Then, in this fluidized bed furnace, partial combustion of fuel is performed in the fluidized bed section, and the generated gas and char generated in the fluidized bed section are burned in the freeboard section.

Further, the fluidized bed furnace of Patent Document 2 is composed of a fluidized bed portion, a freeboard portion located above the fluidized bed portion, and a post-combustion region located above the freeboard portion. Primary air with an air ratio of 1 or less is supplied to the bottom of the fluidized floor, and the freeboard is created with a highly oxidized atmosphere with an air ratio of 1.0 to 1.5 by the secondary air blown in, and the post-combustion region is The air ratio is set to 1.5 or more by the tertiary air blown. Then, in this fluidized bed furnace, partial combustion of fuel is performed in the fluidized bed section, the generated gas generated in the fluidized bed section is burned in the freeboard section, and the unburned gas component in the exhaust gas of the freeboard section is post-combusted. Burn in the area.

Japanese Unexamined Patent Publication No. 2014-40938 Japanese Unexamined Patent Publication No. 6-18017

As in Patent Documents 1 and 2, when partial combustion of fuel is performed in the fluidized bed, the proportion of unburned fuel (unburned char) in the fluidized bed increases, and the unburned char and its volatile matter increase. There is a risk of causing a rapid combustion reaction in the free board section and the subsequent combustion region.

When the surface layer portion of the fluidized bed portion is exposed to a high temperature due to a rapid combustion reaction, agglomeration may occur on the surface layer portion and the flow characteristics of the fluidized bed portion may deteriorate. Further, when the temperature inside the furnace becomes locally high due to a rapid combustion reaction, local deterioration of the furnace components such as the furnace wall occurs. For this reason, it is desirable to suppress a rapid combustion reaction in the freeboard section and the subsequent combustion region.

The present invention has been made in view of the above circumstances, and in a fluidized bed furnace provided with a fluidized bed section in which slow partial combustion of fuel is performed and a freeboard section provided above the fluidized bed section, the freeboard section is provided. It is an object of the present invention to provide a technique for suppressing a rapid combustion reaction in.

The fluidized bed furnace according to one aspect of the present invention is
A fluidized bed that burns fuel and
A freeboard section located above the fluidized bed section and
A fuel inlet for charging the fuel into the freeboard unit and
Secondary combustion gas for which the oxygen concentration is adjusted by the combustion exhaust gas generated in the freeboard section is blown into the freeboard section so as to suppress abnormal combustion of the fuel in the freeboard section. With a supply unit,
The gas to which the secondary combustion gas is blown into the secondary combustion gas supply unit toward a position downstream of the fuel input port of the free board unit and adjacent to the fuel input port. It includes the supply port.

According to the fluidized bed furnace having the above configuration, a local and rapid combustion reaction in the freeboard section is caused by blowing a secondary combustion gas containing combustion exhaust gas having a lower oxygen concentration than air into the freeboard section. It is suppressed. In addition, a secondary combustion gas containing combustion exhaust gas having a lower oxygen concentration than air is blown into the immediate downstream side of the fuel inlet, so that the freeboard portion, in particular, the fuel inlet and its surroundings is locally and locally. The rapid combustion reaction is suppressed.

The fluidized bed furnace according to another aspect of the present invention is
A fluidized bed that burns fuel and
A freeboard section located above the fluidized bed section and
A fuel inlet for charging the fuel into the freeboard unit and
Secondary combustion gas for which the oxygen concentration is adjusted by the combustion exhaust gas generated in the freeboard section is blown into the freeboard section so as to suppress abnormal combustion of the fuel in the freeboard section. With a supply unit,
The secondary combustion gas supply unit is used for the secondary combustion to the fuel supply path leading to the fuel inlet so that the secondary combustion gas is supplied from the fuel inlet in a state of being mixed with the fuel. It includes a gas supply pipe for secondary combustion that supplies gas .

According to the fluidized bed furnace having the above configuration, a local and rapid combustion reaction in the freeboard section is caused by blowing a secondary combustion gas containing combustion exhaust gas having a lower oxygen concentration than air into the freeboard section. It is suppressed. In addition, the fuel charged from the fuel inlet suppresses a local and rapid combustion reaction in and around the fuel inlet.

The fluidized bed furnace according to another aspect of the present invention is
A fluidized bed that burns fuel and
A freeboard section located above the fluidized bed section and
A fuel inlet for charging the fuel into the freeboard unit and
Secondary combustion gas for which the oxygen concentration is adjusted by the combustion exhaust gas generated in the freeboard section is blown into the freeboard section so as to suppress abnormal combustion of the fuel in the freeboard section. Supply department and
A tertiary combustion gas having an oxygen concentration adjusted by the combustion exhaust gas and having a higher oxygen concentration than the secondary combustion gas is placed downstream of the gas flow of the secondary combustion gas supply section of the free board section. It is provided with a gas supply unit for tertiary combustion that blows into.

According to the fluidized bed furnace having the above configuration, a local and rapid combustion reaction in the freeboard section is caused by blowing a secondary combustion gas containing combustion exhaust gas having a lower oxygen concentration than air into the freeboard section. It is suppressed. Moreover, the combustion of the combustible gas in the freeboard section can be slowed down by blowing the tertiary combustion gas containing the combustion exhaust gas having a lower oxygen concentration than air into the freeboard section.

In the flow bed furnace, the tertiary combustion gas supply unit supplies a tertiary combustion gas having a higher oxygen concentration toward the downstream side of the combustion gas flow, and is a plurality of stages of tertiary combustion gas dispersed in the combustion gas flow direction. It may include a supply port.

As a result, the tertiary combustion gas having a higher oxygen concentration is supplied to the downstream side of the flow of the combustion gas having a large amount of unburned combustion gas, so that the combustion of the combustible gas in the free board portion is slowed down and locally. Targeted and rapid combustion reaction can be suppressed.

In the fluidized bed furnace, the tertiary combustion gas supply unit has a temperature sensor that detects the temperature of the diffusion region of the tertiary combustion gas that has been blown in, and the combustion exhaust gas with respect to air based on the detection values of the temperature sensor. A control device that adjusts the oxygen concentration of the tertiary combustion gas so that the detected value of the temperature sensor is within a predetermined range by changing the mixing amount of the above may be included.

In this way, the oxygen concentration of the tertiary combustion gas is adjusted so that the temperature of the freeboard section is within a predetermined range, so that the combustion of the flammable gas in the freeboard section can be slowed down, and the combustion of the flammable gas can be slowed down. It is possible to suppress a local and rapid combustion reaction in the freeboard section.

According to the present invention, in a fluidized bed furnace provided with a fluidized bed section in which slow partial combustion of fuel is performed and a freeboard section provided above the fluidized bed section, a rapid combustion reaction in the freeboard section can be suppressed. can.

FIG. 1 is a block diagram showing a schematic configuration of a combustion system including a fluidized bed furnace according to an embodiment of the present invention. FIG. 2 is a diagram showing a schematic configuration of a fluidized bed furnace according to an embodiment of the present invention. FIG. 3 is an enlarged view of the fluidized bed portion of the fluidized bed furnace. FIG. 4 is an enlarged view of a fluidized bed portion of the fluidized bed furnace according to the first modification.

[Combustion system 100 configuration]
First, the configuration of the combustion system 100 including the fluidized bed furnace 1 according to the embodiment of the present invention will be described. The combustion system 100 shown in FIG. 1 is a system that burns fuel (combustion target) such as coal, biomass, RDF, municipal waste, and industrial waste, and recovers the exhaust heat thereof.

The combustion system 100 includes a fluidized bed furnace 1 that burns fuel. The combustion exhaust gas system 3 of the fluidized bed furnace 1 is provided with a heat exchange device 31, a cyclone type dust collector 32, a bag filter 33, and an attraction blower 34 which is an attraction fan. Exhaust heat of the combustion exhaust gas of the flow bed furnace 1 is recovered by the heat exchange device 31, dust is separated by the cyclone type dust collector 32 and the bag filter 33, and a part of the dust is discharged to the outside of the system through a chimney (not shown) by the attraction blower 34. Will be done.

An exhaust gas recirculation system 4 is connected to the downstream side of the bug filter 33 of the combustion exhaust gas system 3. The exhaust gas recirculation system 4 is provided with a gas recirculation blower 40, and a part of the combustion exhaust gas of the combustion exhaust gas system 3 is returned to the flow bed furnace 1 by the gas recirculation blower 40. The combustion exhaust gas returned to the flow bed furnace 1 by the exhaust gas recirculation system 4 is used as a flow gas (primary combustion gas), a secondary combustion gas, and a tertiary combustion gas.

[Structure of fluidized bed furnace 1]
Next, the configuration of the fluidized bed furnace 1 according to the embodiment of the present invention will be described. The fluidized bed furnace 1 shown in FIG. 2 has a furnace body 10 provided with a combustion chamber including a fluidized bed portion 11 at the bottom of the furnace and a freeboard portion 12 above the fluidized bed portion 11, and an operation control device for controlling the operation of the fluidized bed furnace 1. It is equipped with 15. Below the freeboard portion 12, there is a throttle portion 13 in which the cross-sectional area of the gas passage is narrowed as compared with the remaining portion of the combustion chamber. In the freeboard section 12, the combustion gas flows from the bottom to the top, and a heat transfer tube constituting the heat exchange device 31 is installed in the flue connected to the upper part of the freeboard section 12.

FIG. 3 is an enlarged view of the fluidized bed portion 11. As shown in FIGS. 2 and 3, the fluidized bed portion 11 is filled with a fluidized bed 51 such as silica sand, and a fluidized gas supply device 52 that supplies fluidized gas to the fluidized bed 51 from the bottom thereof. An internal circulating fluidized bed is formed by partition walls 41, 42 that partition the fluidized bed 51 into three cells 61, 62, 63.

The first partition wall 41 partitions the lower portion of the furnace body 10 including the fluidized bed portion 11 into a combustion region 53 and a heat recovery region 54. The second partition wall 42 is provided in the heat recovery region 54 in the vicinity of the first partition wall 41 and in parallel with the first partition wall 41. The fluidized bed portion 11 is formed by the partition walls 41 and 42 between the first side wall 10a of the furnace body 10 and the first partition wall 41, the "combustion cell 61", the first partition wall 41 and the second partition wall 41. In three cells, a "circulation cell 62" formed between the partition wall 42 and a "heat collecting cell 63" formed between the second partition wall 42 and the second side wall 10b of the furnace body 10. It is partitioned. The heat collecting cell 63 is provided with a heat transfer tube 64 such as a superheater tube or an evaporator tube. Heat recovery is performed by the heat medium passing through the heat transfer tube 64.

Above the combustion region 53, a combustion chamber extending linearly in the vertical direction is formed. On the other hand, above the heat recovery area 54, a ceiling wall 43 that closes the upper part of the heat recovery area 54 is provided. The upper end of the first partition wall 41 is close to the ceiling wall 43, and an upper communication port serving as an unburned gas supply port 68 is formed between the upper end of the first partition wall 41 and the ceiling wall 43. The lower end of the first partition wall 41 is higher than the lower end of the second partition wall 42, whereby a lower communication port 55 through which the flow medium flows is formed below the first partition wall 41. Further, at the upper and lower portions of the second partition wall 42, communication ports 56 and 57 are formed in which the circulation cell 62 and the heat collecting cell 63 are communicated with each other and the flow medium is circulated.

The flow gas supply device 52 supplies the flow gas whose flow rate is adjusted independently to each of the combustion cell 61, the circulation cell 62, and the heat collection cell 63. At the bottom of each cell of the combustion cell 61, the circulation cell 62, and the heat collecting cell 63, one or more air diffusers 80 having a large number of air outlets opened toward the side are provided. Each air diffuser 80 is arranged below the lower ends of the first partition wall 41 and the second partition wall 42. However, the flow gas supply device 52 replaces the air diffuser pipe 80 with a wind box arranged at the bottom of each cell 61, 62, 63 and a gas dispersion plate provided so as to close the upper part of the wind box. It may be provided (all are not shown).

The air diffuser pipe 80 is connected to each cell 61, 62, 63 by a header, and each header is provided with flow rate adjusting means 81a, 82a, 83a such as a damper (or valve) and a flow meter 81b, 82b, 83b. Gas supply pipes 81, 82, 83 are connected. To the flow gas supply pipe 81 connected to the air diffuser pipe 80 arranged at the bottom of the combustion cell 61 and the flow gas supply pipe 82 connected to the air diffuser pipe 80 arranged at the bottom of the circulation cell 62. Air is supplied by the indentation blower 79. Further, the exhaust gas recirculation system 4 is connected to the flow gas supply pipe 83 connected to the air diffuser pipe 80 arranged at the bottom of the heat collecting cell 63.

The operation control device 15 supplies each flow gas based on the detection values of the temperature sensor (not shown) that detects the temperature of the combustion cell 61 and the heat collection cell 63 in the flow layer 51 and the flow meters 81b, 82b, 83b and the like. The flow rate adjusting means 81a, 82a, 83a are operated so as to adjust the flow rate of the flow gas of the pipes 81, 82, 83. Air is blown out as a flowing gas from the bottoms of the combustion cell 61 and the circulation cell 62, and combustion exhaust gas is blown out as a flowing gas from the bottom of the heat collecting cell 63.

Here, the superficial velocity of the fluidized gas in the combustion cell 61 is larger than the superficial velocity of the fluidized gas in the heat collecting cell 63, and the superficial velocity of the fluidized gas in the circulating cell 62 is that of the combustion cell 61. The flow rate of the fluidized gas is adjusted so as to be larger than the superficial velocity of the fluidized gas and the superficial velocity of the fluidized gas in the heat collecting cell 63. As a result, the flow medium of the combustion cell 61 moves to the circulation cell 62 through the lower communication port 55 of the first partition wall 41, and the flow medium of the circulation cell 62 passes through the upper communication port 56 of the second partition wall 42. A flow of the flow medium is generated so as to move to the heat collection cell 63 and the flow medium of the heat collection cell 63 circulates to the combustion cell 61 and the circulation cell 62 through the lower communication port 57 of the second partition wall 42. By such circulation of the fluid medium, the heat energy of the fluid medium that has become hot in the combustion cell 61 is taken out in the heat collecting cell 63, and the fluid medium whose temperature has decreased is returned to the combustion cell 61. , The temperature rise of the flow medium of the combustion cell 61 is suppressed.

In the freeboard portion 12, a fuel inlet 65 is opened in the first side wall 10a, which is immediately above the surface layer portion of the fluidized bed portion 11 during operation. The fuel inlet 65 is located on the upstream side of the flow of combustion gas with respect to the throttle portion 13. Fuel is supplied to the fuel inlet 65 by a fuel supply device (not shown). The fuel charged into the furnace from the fuel inlet 65 falls to the upper part of the combustion cell 61 of the fluidized bed portion 11.

In the free board section 12, an unburned gas supply port 68 is opened in the furnace wall on the downstream side of the flow of combustion gas from the fuel inlet 65 and around the throttle section 13. From the unburned gas supply port 68, the air-fuel mixture of air and combustion exhaust gas is blown into the fluidized bed 51 from the air diffuser pipe 80 arranged in the fluidized bed 51 of the heat recovery region 54 and passed through the fluidized bed 51. , Blow out as a secondary combustion gas.

In the free board section 12, a plurality of stages of tertiary combustion gas supply ports 69 are opened in the furnace wall on the downstream side of the combustion gas flow from the unburned gas supply port 68. The plurality of stages of the tertiary combustion gas supply ports 69 are dispersed at a plurality of height positions, in other words, dispersed in the flow direction of the combustion gas. Flow rate adjusting means 88 and 89 such as dampers (or valves) are provided in the air supply path to each tertiary combustion gas supply port 69 and the combustion exhaust gas supply path. Further, a temperature sensor 70 is provided on the furnace wall included in the diffusion region of the tertiary air blown out from the tertiary combustion gas supply port 69.

[Operation method of fluidized bed furnace 1]
Here, an operation method of the fluidized bed furnace 1 having the above configuration will be described. In the fluidized bed furnace 1, low air ratio combustion is performed in the fluidized bed portion 11. More specifically, the air ratio (that is, the primary air ratio) of the combustion cell 61 of the fluidized floor portion 11 and the fuel input while setting the total air ratio of the fluidized floor portion 11 and the free board portion 12 to a value larger than 1. The amount of fluidized air and secondary combustion gas supplied to the combustion cell 61 and / or its so that the air ratio (secondary air ratio) around the mouth 65 is a low air ratio of less than 1. The air content is adjusted. Desirably, the primary air ratio is lower than the secondary air ratio. For example, when the total air ratio of the fluidized bed portion 11 and the free board portion 12 is 1.2, the primary air ratio may be 0.4 and the secondary air ratio may be 0.8.

In the fluidized floor portion 11 in a reducing atmosphere with a low oxygen concentration, a flammable pyrolysis gas and a pyrolysis residue are produced by the slow drying and thermal decomposition of the fuel. The thermal decomposition residue and the unburned residue of the fuel are the bottom of the combustion cell 61, and the furnace is provided from the outlet 72 of the flow medium and the incombustible material provided at an intermediate position between the first side wall 10a and the first partition wall 41. It is discharged to the outside. The thermally decomposed gas generated in the fluidized floor portion 11 is burned by the secondary combustion gas, the unburned portion in the combustion gas is completely burned by the tertiary combustion gas, and the combustion exhaust gas is discharged to the combustion exhaust gas system 3. To.

In the combustion cell 61 of the fluidized bed furnace 1 according to the above configuration, since the fuel is burned at a low air ratio, the unburned portion (unburned char) of the fuel in the combustion cell 61 is compared with the case where the air ratio is 1 or more. The ratio is large. When the primary air ratio is 0.4 as in the above example, the ratio of unburned char in the combustion cell 61 is particularly high as compared with the case where the conventional air ratio is about 0.8 to 0.9. growing.

The unburned char of the combustion cell 61 may move from the combustion cell 61 to the heat collecting cell 63 due to the circulation of the fluid medium. However, it is not desirable that a combustion reaction occurs in the heat collecting cell 63.

Therefore, in the flow bed furnace 1, the combustion exhaust gas having an oxygen concentration lower than that of air is used as the flow gas of the heat collection cell 63, and the heat collection cell 63 is further reduced in air as compared with the combustion cell 61 and the circulation cell 62. By setting the ratio, the combustion reaction of the unburned char in the heat collecting cell 63 is suppressed.

Further, if the proportion of fly ash containing unburned char and the volatile content of unburned char increases in the freeboard section 12, a rapid combustion reaction may occur in the freeboard section 12. When a rapid combustion reaction occurs in the freeboard portion 12 close to the fluidized bed 51 of the fluidized bed portion 11, the surface layer portion of the fluidized bed portion 11 is exposed to a high temperature, agglomeration occurs in the surface layer portion, and the fluidized bed portion 11 There is a risk that the flow characteristics of the Further, if a sudden combustion reaction occurs in the freeboard section 12, explosive expansion of air may occur, impairing the stability of the furnace operation, or deteriorating the furnace body 10.

Therefore, the fluidized bed furnace 1 includes a secondary combustion gas supply unit 86 that blows a secondary combustion gas whose oxygen concentration is adjusted by the combustion exhaust gas generated by the free board unit 12 into the free board unit 12, and is free of charge. The air ratio of the upstream portion of the board portion 12 is suppressed to less than 1. The secondary combustion gas supply unit 86 blows a secondary combustion gas containing combustion exhaust gas having a lower oxygen concentration than air into the freeboard unit 12, and a local and rapid combustion reaction in the freeboard unit 12 Abnormal combustion is suppressed.

Among the free board portions 12, in the vicinity of the fuel inlet 65, there is a particularly large amount of unburned matter in the gas due to the fine powder and its volatile matter soared from the fuel injected into the furnace from the fuel inlet 65. Therefore, the secondary combustion gas supply unit 86 directs the secondary combustion gas toward a position downstream of the fuel input port 65 of the free board unit 12 and adjacent to the fuel input port 65. The unburned gas supply port 68 to be blown is included. The "position adjacent to the fuel inlet 65" is around the fuel inlet 65, and is particularly unburned in the gas due to the fine powder soared from the fuel input from the fuel inlet 65 and its volatile matter. It is a part with many. As a result, the secondary combustion gas containing the combustion exhaust gas having a lower oxygen concentration than the air is blown into the immediate downstream side of the fuel inlet 65, and is locally localized in the free board portion 12, particularly the fuel inlet 65 and its surroundings. Moreover, a rapid combustion reaction is suppressed.

In the present embodiment, the secondary combustion gas is blown from the unburned gas supply port 68 toward the throttle portion 13 on the immediately downstream side of the flow of the combustion gas of the fuel input port 65. The secondary combustion gas blown from the unburned gas supply port 68 into the free board section 12 contains a large amount of combustion exhaust gas whose oxygen concentration is further lowered by passing through the heat collecting cell 63, so that the fuel is input more effectively. It is expected that the combustion reaction in and around the mouth 65 will be suppressed.

Further, in the flow bed furnace 1, the tertiary combustion gas whose oxygen concentration is adjusted by the combustion exhaust gas is blown into the downstream side of the combustion gas flow from the unburned gas supply port 68 of the free board section 12. The supply unit 87 is provided. In this way, the tertiary combustion gas containing the combustion exhaust gas having a lower oxygen concentration than the air is blown to the downstream side of the flow of the combustion gas from the unburned gas supply port 68 of the free board unit 12, so that the free board unit 12 Combustion of the flammable gas in the above can be slowed down, and a local and rapid combustion reaction can be suppressed. The tertiary combustion gas has a higher oxygen concentration than the secondary combustion gas.

The tertiary combustion gas supply unit 87 includes a plurality of stages of tertiary combustion gas supply ports 69 dispersed in the flow direction of the combustion gas, a temperature sensor 70 for detecting the temperature of the diffusion region of the blown tertiary combustion gas, and a temperature. The operation control device 15 for adjusting the oxygen concentration of the tertiary combustion gas based on the detected value of the sensor 70 is included. The temperature of the diffusion region of the tertiary combustion gas blown out from each tertiary combustion gas supply port 69 is detected by the temperature sensor 70, and the operation control device 15 determines each tertiary combustion so that the detected temperature falls within a predetermined range. The oxygen concentration of the tertiary combustion gas blown from the combustion gas supply port 69 is adjusted.

Specifically, the operation control device 15 adjusts the oxygen concentration of the tertiary combustion gas by changing the mixing ratio of air and combustion exhaust gas by changing the opening degree of the flow rate adjusting means 88 and 89. When the temperature detected by the temperature sensor 70 at a certain location exceeds a predetermined range, the operation control device 15 maintains the flow rate of the tertiary combustion gas at a predetermined flow rate and supplies the tertiary combustion gas to that location. Open the flow rate adjusting means 88, 89 so that the oxygen concentration of the gas decreases and, when the detected temperature falls below a predetermined range, the oxygen concentration of the tertiary combustion gas supplied to the location increases. Adjust the degree.

From the plurality of stages of the tertiary combustion gas supply port 69 dispersed in the flow direction of the combustion gas, the tertiary combustion gas having a higher oxygen concentration is supplied toward the downstream side of the flow of the combustion gas. That is, the tertiary combustion gas having a higher oxygen concentration is supplied toward the downstream side of the flow of the combustion gas having a large unburned content of the combustion gas. As a result, the combustion of the flammable gas in the freeboard unit 12 is slowed down, and a local and rapid combustion reaction can be suppressed.

Although the preferred embodiment of the present invention has been described above, the present invention may include modified details of the specific structure and / or function of the above embodiment without departing from the spirit of the present invention. ..

For example, in the flow bed furnace 1 according to the above embodiment, the secondary combustion gas is blown from the unburned gas supply port 68 into the free board section 12, but in addition to / instead of this, the secondary combustion gas is fuel. It may be supplied from the fuel inlet 65 in a state of being mixed with. In this case, as shown in FIG. 4, the secondary combustion gas supply unit 86 reaches the fuel inlet 65 so that the secondary combustion gas is supplied from the fuel inlet 65 in a state of being mixed with the fuel. The fuel chute purge gas supply pipe 67 for supplying the secondary combustion gas to the supply path 66 is included. As a result, since the fuel is charged into the freeboard unit 12 together with the secondary combustion gas, it is possible to suppress a local and rapid combustion reaction in and around the fuel input port 65.

1: Flow bed furnace 3: Combustion exhaust gas system 4: Exhaust gas recirculation system 10: Furnace body 10a: First side wall 10b: Second side wall 11: Flow bed part 12: Free board part 13: Squeeze part 15: Operation control device 31 : Heat exchange device 32: Cyclone type dust collector 33: Bug filter 34: Attracting blower 40: Gas recirculation blower 41: First partition wall 42: Second partition wall 43: Ceiling wall 51: Flow layer 52: Gas supply device for flow 53: Combustion region 54: Heat recovery region 55, 56, 57: Communication port 61: Combustion cell 62: Circulation cell 63: Heat collection cell 64: Heat transfer tube 65: Fuel inlet 66: Fuel supply path 67: Fuel chute purge gas supply Pipe 68: Unburned gas supply port 69: Gas supply port for tertiary combustion 70: Temperature sensor 72: Extraction outlet 79: Push-in blower 80: Air diffuser pipe 81, 82, 83: Gas supply pipe for flow 81a, 82a, 83a: Flow rate Adjusting means 81b, 82b, 83b: Flow meter 86: Secondary combustion gas supply unit 87: Tertiary combustion gas supply unit 88, 89: Flow rate adjusting means 100: Combustion system

Claims (5)

A fluidized bed that burns fuel and
A freeboard section located above the fluidized bed section and
A fuel inlet for charging the fuel into the freeboard unit and
Secondary combustion gas for which the oxygen concentration is adjusted by the combustion exhaust gas generated in the freeboard section is blown into the freeboard section so as to suppress abnormal combustion of the fuel in the freeboard section. With a supply unit,
The secondary combustion gas supply unit blows the secondary combustion gas toward a position downstream of the fuel input port of the free board unit and adjacent to the fuel input port. Including gas supply port,
Fluidized bed furnace. A fluidized bed that burns fuel and
A freeboard section located above the fluidized bed section and
A fuel inlet for charging the fuel into the freeboard unit and
Secondary combustion gas for which the oxygen concentration is adjusted by the combustion exhaust gas generated in the freeboard section is blown into the freeboard section so as to suppress abnormal combustion of the fuel in the freeboard section. With a supply unit,
The secondary combustion gas supply unit is used for the secondary combustion to the fuel supply path leading to the fuel inlet so that the secondary combustion gas is supplied from the fuel inlet in a state of being mixed with the fuel. Fuel chute to supply gas, including purge gas supply pipe,
Fluidized bed furnace. A fluidized bed that burns fuel and
A freeboard section located above the fluidized bed section and
A fuel inlet for charging the fuel into the freeboard unit and
Secondary combustion gas for which the oxygen concentration is adjusted by the combustion exhaust gas generated in the freeboard section is blown into the freeboard section so as to suppress abnormal combustion of the fuel in the freeboard section. Supply department and
A tertiary combustion gas having an oxygen concentration adjusted by the combustion exhaust gas and having a higher oxygen concentration than the secondary combustion gas is placed downstream of the gas flow of the secondary combustion gas supply section of the free board section. Equipped with a gas supply unit for tertiary combustion that blows into
Fluidized bed furnace. The tertiary combustion gas supply unit includes a plurality of stages of tertiary combustion gas supply ports dispersed in the gas flow direction, which supplies the tertiary combustion gas having a higher oxygen concentration toward the downstream side of the gas flow.
The fluidized bed furnace according to claim 3. The tertiary combustion gas supply unit changes the mixing amount of the combustion exhaust gas with respect to air based on the temperature sensor that detects the temperature of the diffusion region of the tertiary combustion gas that has been blown in and the detection value of the temperature sensor. This includes a control device that adjusts the oxygen concentration of the tertiary combustion gas so that the detected value of the temperature sensor is within a predetermined range.
The fluidized bed furnace according to claim 3 or 4.

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