JP5336898B2 - Bubble type fluidized bed boiler and operation method thereof - Google Patents

Description

  The present invention relates to a fluidized bed boiler capable of preventing clinker and low melting point ash from adhering to a furnace inner wall of a fluidized bed boiler and a heat transfer tube downstream of the furnace, and a method for operating the fluidized bed boiler.

  Conventionally, fluidized bed boilers have been widely used as boilers for efficiently burning industrial waste such as wood, waste tires, RPF (Refused Paper & Plastic Fuel), or general waste such as municipal waste. In a fluidized bed boiler, a fluidized bed in which a fluidized medium is fluidized is formed inside the furnace, and fuel such as the above-mentioned waste is burned into the fluidized bed, and the combustion exhaust gas generated by combustion is burned. It is a device that recovers thermal energy with a heat transfer tube installed at the latter stage of the furnace and uses it for power generation or the like. In the fluidized bed boiler, there are a bubbling fluidized bed boiler and a circulating fluidized bed boiler depending on the fluidized form. Among these, the structure of a bubble-type fluidized bed boiler is shown in FIG.

  As shown in the figure, in the bubble fluidized bed boiler 100, the bottom of the furnace 101 is filled with the fluid medium 103, and the fluid medium 103 is fluidized by primary air introduced from the lower part of the furnace to form a fluidized bed. The fuel is burned by putting the fuel into the bed. The unburned component or pyrolysis gas contained in the exhaust gas introduces secondary air from the secondary air introduction nozzle 105 provided on the side wall of the furnace and burns it. The combustion exhaust gas generated by the combustion is heat-exchanged in a heat transfer tube group 102 such as a superheater or a economizer installed at the latter stage of the furnace, and the recovered heat energy is used for power generation or the like. The furnace 101 is also provided with a heat transfer tube, and heat energy is recovered here.

In such a fluidized bed boiler 100, for the purpose of preventing clinker formation in the fluidized bed and the inner wall of the furnace and stable combustion, the fluidized sand is extracted from the bottom of the furnace together with the non-combustible material accumulated in the fluidized bed to adjust the bed height. Some of them are equipped with a means or a means for putting cinnabar sand or incinerated ash having a certain particle size or less into a furnace through a particle size separation device 107. This prevents flow failure and furnace wall adhesion due to clinker generation, and maintains stable operation.
Patent Document 1 (Japanese Patent Laid-Open No. Hei 8-193712) is equipped with a non-combustible material discharge control device that extracts the non-combustible material deposited in the fluidized bed together with the fluidized medium from the bottom of the furnace, and maintains the bed height appropriately. A configuration for preventing poor flow due to clinker generation in the fluidized bed is disclosed.
Furthermore, in Patent Document 2 (Japanese Patent Laid-Open No. 2002-333122), sand having a high melting point such as a silica component or incinerated ash having a predetermined particle size or less selected by a particle size separator is put into a furnace. The structure which prevents the clinker adhering to a furnace wall by reducing the ratio of the alkali metal compound in incineration ash is disclosed.

JP-A-8-193712 JP 2002-333122 A

As described above, it is possible to prevent clinker from adhering to the furnace wall or the fluidized bed by extracting the noncombustible material from the fluidized bed and introducing the silica sand or incinerated ash containing a large amount of silica into the furnace. However, in the prior art, the purpose is to prevent the formation of clinker in the fluidized bed, and further, a treatment process for separating the particle size is required before the dredged sand or incinerated ash is put into the furnace.
In order to perform stable operation of a bubbling fluidized bed boiler, it is necessary to prevent low melting point ash from adhering not only to the fluidized bed of the furnace but also to the heat transfer tubes installed at the latter stage of the furnace. It is required to establish an operation method that does not increase maintenance. Conventionally, a configuration for preventing the generation of clinker in a heat transfer tube has not been proposed, and there has been a problem that heat transfer efficiency is reduced by the clinker adhering to the heat transfer tube.

  Therefore, in view of the problems of the prior art described above, the present invention prevents the low melting point ash from adhering not only to the inside of the furnace but also to the heat transfer tube group disposed at the latter stage of the furnace, and enables the bubbles to be continuously operated stably. It aims at providing a type | mold fluidized bed boiler and its operating method.

In order to solve the above problems, the present invention is a bubble fluidized bed boiler comprising a furnace filled with a fluid medium at the bottom, and a heat recovery device connected to the top of the furnace and provided with a heat transfer tube.
The furnace side wall is provided with secondary air introduction nozzles in a multi-stage shape in the vertical direction, and a position where the secondary air introduction nozzle exists in the lower stage region of the secondary air introduction nozzle and directly below. A replenishment medium supply port for supplying a replenishment medium made of a high melting point substance,
The air supply amount of the secondary air introduction nozzle of each stage is set so that the superficial velocity increases from the lower stage side to the upper stage side of the secondary air introduction nozzle, and is supplied from the supply medium supply port. The replenishment medium is transferred to the heat recovery device from above the furnace accompanied by combustion exhaust gas.

  In the present invention, the replenishment medium supplied from the replenishment medium supply port on the side wall of the furnace is blown upward by the secondary air introduced from the secondary air introduction nozzle immediately below the replenishment medium supply port, and further provided in a multistage shape. In addition, since the secondary air introduction nozzle is configured so that the superficial velocity increases from the lower stage side toward the upper stage side, the blown-up supply medium is reliably conveyed to the upper side of the furnace. And it will be conveyed with a combustion exhaust gas to the heat recovery apparatus installed in the latter stage of the furnace. Accordingly, the supply medium is included in the ash in the exhaust gas that passes through the heat recovery device, thereby increasing the proportion of the high melting point substance in the ash, thereby preventing the ash from melting and extending in the heat recovery device. Makes it possible to suppress the production of clinker. In addition, since a part of the supply medium supplied from the supply medium supply port falls to the bottom of the furnace, the ratio of the high-melting-point substance in the fluidized bed increases as described above, and the generation of clinker can be suppressed. .

As described above, according to the present invention, since the replenishment medium is transported to the heat recovery device side, it is possible to prevent low melting point ash from being generated on the heat transfer surface of the heat recovery device, maintain the heat transfer efficiency, and maintain the fluidized bed. It becomes possible to improve the reliability of continuous stable operation of the boiler. In addition, it is possible to establish stable operation conditions with a simple configuration without installing a dedicated particle size separation device, and cost and maintenance can be reduced. The replenishment medium is a fine particle having a high melting point equal to or higher than the combustion gas temperature. For example, silica sand, SiO ₂ , Al ₂ O ₃ or the like is used.

Furthermore, a plurality of the secondary air introduction nozzles are provided around the periphery of the furnace side wall,
On the supply line for supplying secondary air to the plurality of secondary air introduction nozzles, a damper for adjusting the air supply amount is provided,
The secondary air introduction nozzle located immediately below the replenishment medium supply port and the other secondary air introduction nozzles located at the same step height each have independent dampers, and these dampers are used for the replenishment. The secondary air introduction nozzle located immediately below the medium supply port is set to have a larger air supply amount than the other secondary air introduction nozzles.

  In this way, the secondary air introduction nozzles located at the same step height each have an independent damper, and the secondary air introduction nozzle located directly below the supply medium supply port is the other secondary air introduction nozzle. By setting the air supply amount to be larger, it is possible to reliably blow up the replenishment medium without changing the total amount of secondary air introduced into the furnace.

In addition, the air supply amount of the air introduction nozzle of each stage is set so that a part of the supply medium supplied from the supply medium supply port falls to the furnace bottom.
Thus, by setting the air supply amount so that a part of the replenishment medium falls to the furnace bottom, the replenishment medium is supplied to both the fluidized bed and the heat recovery device at the bottom of the furnace, and both the fluidized bed and the heat recovery device It is possible to prevent the formation of clinker and low melting point ash.

Further, the supply medium supply port is means for supplying fuel into the furnace in addition to the supply medium.
Thus, by using the existing fuel supply means as the supply medium supply port, there is no need to newly provide a supply medium supply port.
Furthermore, the replenishment medium has a smaller diameter than the fluid medium.
By making the diameter of the replenishment medium smaller than the fluid medium fluidized in the fluidized bed at the bottom of the furnace, the replenishment medium can be reliably blown up by the secondary air and reliably conveyed to the heat recovery device.
Moreover, the control apparatus which adjusts the opening degree of the said damper and adjusts the air supply amount of the secondary air introduction nozzle of each said stage is provided.
This is provided with a control device for controlling the damper opening degree at least for each stage. The control device may be configured to individually control a plurality of secondary air introduction nozzles provided in each stage.

In addition, fuel is introduced into a fluid medium flowing at the bottom of the furnace, combustion exhaust gas generated by combustion of the fuel is guided from the upper part of the furnace to a heat recovery device, and combustion exhaust gas is disposed by a heat transfer tube disposed in the heat recovery device. In the operation method of a fluidized bed boiler that recovers heat from
Secondary air introduction nozzles are arranged in a multistage shape in the vertical direction on the furnace side wall of the furnace, so that the superficial velocity is increased from the lower stage side toward the upper stage side. While adjusting the opening of the damper that adjusts the air supply amount of the secondary air introduction nozzle,
A replenishment medium supply port is disposed in a lower stage region of the secondary air introduction nozzle and at a position immediately below the secondary air introduction nozzle, and a replenishment medium made of a high melting point substance is introduced into the furnace from the replenishment medium supply port. It is characterized by supplying.

In the present invention, since the replenishment medium is conveyed to the heat recovery device side, low melting point ash can be prevented from being generated on the heat transfer surface of the heat recovery device, heat transfer efficiency is maintained, and continuous stable operation of the fluidized bed boiler is achieved. It becomes possible to improve the reliability. In addition, it is possible to establish stable operation conditions with a simple configuration without installing a dedicated particle size separation device, and cost and maintenance can be reduced.
In addition, the secondary air introduction nozzles located at the same step height each have an independent damper, and the secondary air introduction nozzle located directly below the supply medium supply port has more air than the other secondary air introduction nozzles. By setting the supply amount to be large, it is possible to reliably blow up the replenishment medium without changing the total amount of secondary air introduced into the furnace.

Further, by setting the air supply amount so that a part of the replenishment medium falls to the furnace bottom, the replenishment medium is supplied to both the fluidized bed and the heat recovery device at the bottom of the furnace, and the clinker in both the fluidized bed and the heat recovery device. It is possible to prevent the generation of low melting point ash.
Further, by using the existing fuel supply means as a supply medium supply port, it is not necessary to newly provide a supply medium supply port.
Furthermore, by making the diameter of the replenishment medium smaller than the fluid medium, the replenishment medium can be reliably blown up by the secondary air and reliably conveyed to the heat recovery device.

It is a sectional side view of the furnace with which the fluidized bed boiler which concerns on the Example of this invention is provided. It is a sectional side view showing the whole fluidized bed boiler composition concerning the example of the present invention. It is the schematic which shows the furnace inner wall surface of the fluidized bed boiler which concerns on the Example of this invention. It is a sectional side view of the conventional fluidized bed boiler.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.
The embodiment according to the present invention is applied to a bubble fluidized bed boiler, and waste such as general waste or industrial waste, or fuel such as RDF or coal is used as the fuel.

As shown in FIG. 2, the bubble type fluidized bed boiler 1 of the present embodiment includes a furnace 2 that combusts injected fuel, and a heat recovery device 4 that is connected to the upper part of the furnace 2 by a flue 3. Prepare.
The heat recovery device 4 has a configuration in which a heat transfer tube group 40 is installed on an exhaust gas passage extending from the flue 3, and in FIG. The structure which arrange | positioned the container 42 and the economizer 43 is shown. The configuration of the heat transfer tube group 40 is not limited to this, and the heat transfer tubes may be disposed on the furnace wall or the like. The combustion exhaust gas generated in the furnace 2 is heat-exchanged when passing through the heat transfer tube group 40 of the heat recovery device 4, and the thermal energy of the exhaust gas is recovered.

The furnace 2 is filled with a fluid medium 50 at the bottom. Further, a primary air nozzle 24 is provided at the bottom of the furnace, the fluid medium 50 is fluidized by the primary air 51 introduced from the primary air nozzle 24, and the fluidized bed 22 is formed at the bottom of the furnace.
A fluid medium extraction unit 26 is provided at the bottom of the furnace, and a fluid medium 52 containing an incombustible material is appropriately extracted from the fluid medium extraction unit 26. The fluid medium 52 containing the incombustible material extracted here is removed from the incombustible material 53 by the incombustible material separator 27, and then the fluid medium 54 is appropriately returned to the furnace 2.

  As shown in FIG. 1, secondary air introduction nozzles 31, 32, and 33 are provided on the side wall of the furnace 2 in a multistage shape in the vertical direction. These secondary air introduction nozzles 31, 32 and 33 are referred to as a secondary air introduction nozzle group 30. Although FIG. 1 shows a configuration in which the secondary air introduction nozzle group 30 has three stages, the number of stages is not limited to this. Further, dampers 46, 47, and 48 are provided on the air introduction lines for introducing the secondary air 56 to the secondary air introduction nozzles 31, 32, and 33, respectively. The dampers 46, 47, 48 are adjusted in opening so that the amount of secondary air 56 supplied to the secondary air introduction nozzles 31, 32, 33 is adjusted. Moreover, you may provide the control apparatus 49 which adjusts the opening degree of a damper for every secondary air introduction nozzle 31,32,33 of each stage. The control device 49 may be configured to individually adjust a plurality of dampers.

  Further, the amount of air introduced from the secondary air introduction nozzle group 30 is set so that the superficial velocity increases from the lower stage side to the upper stage side of the secondary air introduction nozzles 31, 32, 33, respectively. 47, 48. Preferably, the superficial velocity in the vicinity of the lowermost secondary air introduction nozzle 31 is 1 to 2 m / s, the superficial velocity in the vicinity of the middle secondary air introduction nozzle 32 is 2 to 3 m / s, and the secondary in the uppermost stage. The air supply amount of each secondary air introduction nozzle 31, 32, 33 is set so that the superficial velocity in the vicinity of the air introduction nozzle 33 is about 3 to 4 m / s. At this time, other conditions including the amount of primary air supplied from the lower part of the furnace are also taken into consideration. Preferably, the air ratio of the nozzles in each part is 0.5 to 0.7 for the primary air nozzle 24, 0.7 to 0.9 for the lower secondary air introduction nozzle 31, and the secondary air introduction nozzle for the middle stage. 32 may be set to 1.0 to 1.2, and the upper secondary air introduction nozzle 33 may be set to 1.2 to 1.5.

Further, a supply medium supply port 35 is provided on the side wall of the furnace 2. The replenishment medium supply port 35 is installed at a position where the secondary air introduction nozzle exists in the lower stage region of the secondary air introduction nozzle group 30 and immediately below. As a specific example, as shown in FIG. 3, the lowermost secondary air introduction nozzle 31 is located between the lowermost secondary air introduction nozzle 31 and the intermediate secondary air introduction nozzle 32 and immediately below the supply medium supply port 35. Installed at the location where is located. A plurality of supply medium supply ports 35 may be installed.
From this supply medium supply port 35, a supply medium 55 made of a high melting point material is supplied into the furnace 2. It is preferable that the replenishment medium 55 is always supplied during the operation of the fluidized bed boiler 1. The replenishment medium 55 is a fine particle having a high melting point equal to or higher than the combustion gas temperature. For example, silica sand, SiO ₂ , Al ₂ O ₃ or the like is used.

The diameter of the supply medium 55 is, for example, 800 μm or less on average. The diameter of the replenishment medium 55 is preferably smaller than the diameter of the fluid medium 50 of the fluidized bed 22, so that the replenishment medium 55 can be reliably blown upward.
Further, the replenishment media 55 having different diameters may be mixed. In this case, a replenishment medium having a particle diameter equal to or larger than that of the fluid medium 50 and a replenishment medium having a particle diameter smaller than that of the fluid medium 50 are mixed. For example, the replenishment medium 55 of 800 μm or less and the replenishment medium 55 of 800 μm or more are mixed at a predetermined ratio. Thereby, a part of the replenishment medium 55 can be blown up above the furnace and conveyed to the heat recovery device 4, and the other can be dropped onto the fluidized bed 22 at the bottom of the furnace.

The operation of the fluidized bed boiler 1 will be described below.
First, the fuel introduced into the furnace 2 burns in the fluidized bed 22 in which the fluidized medium 50 is fluidized, and unburned components and pyrolysis gas in the combustion exhaust gas generated by the combustion are provided on the furnace side wall. Combustion is performed by the secondary air 56 introduced from the secondary air introduction nozzle group 30. At this time, the supply medium 55 is supplied into the furnace 2 from the supply medium supply port 35. The replenishment medium 55 may be supplied from the outside, or may be supplied from the fluid medium extraction unit 26 to supply the fluid medium 54 from which incombustible substances have been removed. A part of the supply medium 55 supplied into the furnace 2 from the supply medium supply port 35 is blown up by the secondary air 56 introduced from the secondary air introduction nozzle 31 directly below the supply medium supply port 35, and further the secondary air. 56 is set so that the superficial velocity increases from the lower stage side to the upper stage side of the secondary air introduction nozzles 31, 32, 33, so that the replenishment medium 55 blown up is located above the furnace 2. And is conveyed to the heat recovery device 4 along with the exhaust gas through the flue 3.

In the heat recovery device 4, the exhaust gas passes with the ash including the replenishment medium 55, and heat exchange is performed in the superheaters 41 and 42 and the economizer 43, respectively, and the thermal energy of the exhaust gas is recovered. The recovered thermal energy is used for power generation and the like.
Since the ash in the exhaust gas that passes through the heat recovery device 4 contains the replenishment medium 55 made of a high-melting-point material, the proportion of the high-melting-point material increases, and the low-melting-point material melts to form a low-melting-point ash on the heat transfer surface. Generation can be prevented.
Since the main component of the adhering ash is an alkali metal salt such as sodium or potassium having a low melting point, the higher the concentration of the alkali metal salt in the ash, the easier the low melting point ash is produced. For this reason, the ash is melted in the heat recovery device 4 by reducing the alkali metal salt concentration in the ash, that is, by increasing the ratio of high melting point substances such as SiO ₂ and Al ₂ O ₃ contained in the ash. Thus, it is possible to prevent the low melting point ash from being generated. In addition, clinker generation in the fluidized bed 22 can be prevented by the replenishment medium 55 that has fallen into the fluidized bed 22 without being blown up by the secondary air 56.

  As described above, according to the present embodiment, since the replenishment medium 55 is transported to the heat recovery device 4 side, generation of low melting point ash on the heat transfer surface of the heat recovery device 4 can be prevented, and heat transfer efficiency can be maintained. Thus, the reliability of the continuous stable operation of the fluidized bed boiler 1 can be improved. In addition, it is possible to establish stable operation conditions with a simple configuration without installing a dedicated particle size separation device, and cost and maintenance can be reduced.

Further, in the present embodiment, as shown in FIG. 3, the secondary air introduction nozzle 31a located immediately below the supply medium supply port 35 and the other secondary air introduction nozzle 31b located at the same step height are independent of each other. Each of the secondary air introduction nozzles 31a located immediately below the supply medium supply port 35 is opened so that the air supply amount is larger than that of the other secondary air introduction nozzles 31b. It is preferable to adjust the degree.
In this way, the secondary air introduction nozzles 31 located at the same step height have their respective independent dampers, and the secondary air introduction nozzle 31a located directly below the supply medium supply port 35 is the other secondary air. By setting the air supply amount to be larger than the air introduction nozzle 31b, the replenishment medium 55 can be reliably blown up without changing the total amount of secondary air introduced into the furnace 2.

Further, as shown in FIG. 1, each of the dampers 46, 47, 48 so that a part of the supply medium 55 supplied from the supply medium supply port 35 is blown upward and the other supply medium 55 falls to the furnace bottom. It is preferable to adjust the air supply amount of the secondary air introduction nozzles 31, 32, 33 of each stage. As a result, the replenishment medium 55 is supplied to both the fluidized bed 22 and the heat recovery device 4 at the bottom of the furnace, and it is possible to prevent the generation of clinker and low melting point ash in both the fluidized bed 22 and the heat recovery device 4. .
Furthermore, it is preferable to supply the replenishment medium 55 using the existing fuel supply means provided in the furnace 2, thereby eliminating the need to newly provide the replenishment medium supply port 35.
Furthermore, as shown in FIG. 3, the secondary air introduction nozzle 31a located immediately below the replenishment medium supply port 35 is installed to be inclined upward, and the other secondary air introduction nozzle 31b is installed to be inclined downward. You may make it do. Thereby, the replenishment medium 55 is easily blown up.

DESCRIPTION OF SYMBOLS 1 Fluidized bed boiler 2 Furnace 4 Heat recovery apparatus 22 Fluidized bed 26 Fluidized medium extraction part 30 Secondary air introduction nozzle group 31, 32, 33 Secondary air introduction nozzle 35 Supply medium supply port 40 Heat transfer tube group 41, 42 Superheater 43 Eco-saving device 46, 47, 48 Damper 49 Control device 51 Primary air 55 Supply medium 56 Secondary air

Claims (7)

In a bubble fluidized bed boiler comprising a furnace filled with a fluidized medium at the bottom, and a heat recovery device connected to the top of the furnace and provided with a heat transfer tube,
The furnace side wall is provided with secondary air introduction nozzles in a multi-stage shape in the vertical direction, and a position where the secondary air introduction nozzle exists in the lower stage region of the secondary air introduction nozzle and directly below. A replenishment medium supply port for supplying a replenishment medium made of a high melting point substance,
The air supply amount of the secondary air introduction nozzle of each stage is set so that the superficial velocity increases from the lower stage side to the upper stage side of the secondary air introduction nozzle, and is supplied from the supply medium supply port. A bubble type fluidized bed boiler in which the replenishment medium is accompanied by combustion exhaust gas and conveyed from above the furnace to the heat recovery device. A plurality of the secondary air introduction nozzles are provided around the periphery of the furnace side wall,
On the supply line for supplying secondary air to the plurality of secondary air introduction nozzles, a damper for adjusting the air supply amount is provided,
The secondary air introduction nozzle located immediately below the replenishment medium supply port and the other secondary air introduction nozzles located at the same step height each have independent dampers, and these dampers are used for the replenishment. 2. The bubble type according to claim 1, wherein the secondary air introduction nozzle located immediately below the medium supply port is set to have a larger air supply amount than the other secondary air introduction nozzle. Fluidized bed boiler.   The air supply amount of the air introduction nozzle of each stage is set so that a part of the supply medium supplied from the supply medium supply port falls to the furnace bottom. Bubble type fluidized bed boiler.   3. The bubble fluidized bed boiler according to claim 1, wherein the supply medium supply port is means for supplying fuel into the furnace in addition to the supply medium.   The bubble-type fluidized bed boiler according to claim 1 or 2, wherein the supply medium has a diameter smaller than that of the fluidized medium.   The bubble type fluidized bed boiler according to claim 2, further comprising a control device that adjusts an opening of the damper to adjust an air supply amount of the secondary air introduction nozzle of each stage. Fuel is introduced into a fluid medium flowing at the bottom of the furnace, and the combustion exhaust gas generated by the combustion of the fuel is led from the upper part of the furnace to the heat recovery device, and the heat from the combustion exhaust gas is heated by a heat transfer tube disposed in the heat recovery device. In the operation method of the fluidized bed boiler to be recovered,
Secondary air introduction nozzles are arranged in a multistage shape in the vertical direction on the furnace side wall of the furnace, so that the superficial velocity is increased from the lower stage side toward the upper stage side. While adjusting the opening of the damper that adjusts the air supply amount of the secondary air introduction nozzle,
A replenishment medium supply port is disposed in a lower stage region of the secondary air introduction nozzle and at a position immediately below the secondary air introduction nozzle, and a replenishment medium made of a high melting point substance is introduced into the furnace from the replenishment medium supply port. An operation method of a fluidized bed boiler, characterized by being supplied.

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