JPH08285259A - Method and device for combustion of fluidized bed type waste incineration furnace - Google Patents

Abstract

PURPOSE: To suppress the sudden change of the combustion state, and at the same time, reduce the discharging quantities of unburned contents and dioxines in the exhaust gas by a method wherein the oxygen partial pressure of one of the fluidized bed parts of the fluidized bed is controlled to be lower than the other fluidized bed part, and waste is fed to the fluidized bed part of which the oxygen partial pressure is lower. CONSTITUTION: The oxygen partial pressure of a fluidization gas (branching exhaust gas) 21 for one of fluidized bed parts of a fluidized bed 3 of a fluidized bed type waste incineration furnace 1 is controlled to be lower than a fluidized gas (primary air) 6 of the other fluidized bed part by a controller valve 24, and waste is charged to the fluidized bed part of which the oxygen partial pressure is lower from a charging chute 2. Also, the flowing speed of a medium for the fluidized bed part on the oxygen partial pressure side is controlled by adjusting the flow rate of the branching exhaust gas 21, etc. By this method, the trash is dried prior to a combustion, and the variation of the combustion state is made small. Also, by reducing the flowing speed of the part of which the oxygen partial pressure is lower when the trash feeding quantity is increased, the combustion state can be kept stable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluidized bed type waste incinerator for incinerating waste such as municipal solid waste, and in particular, by providing the fluidized bed with a difference in oxygen partial pressure,
The present invention relates to a combustion method and apparatus for a fluidized bed waste incinerator suitable for reducing the emission of unburned components such as O and hydrocarbons and dioxins.

[0002]

2. Description of the Related Art In the conventional combustion method of a fluidized bed type waste incinerator, waste such as municipal waste (hereinafter referred to as garbage)
FIG. 8 shows an example of a fluidized bed type waste incinerator applied to the incineration process of the above. The waste is thrown into the fluidized bed type waste incinerator 1 from the charging chute 2 and the primary air which is the fluidized gas supplied from the wind box through the air diffuser 5 or the dispersion plate installed at the lower part of the fluidized bed 3 in the fluidized bed 3. 6, the fluid medium (medium)
As it is fluidized with it, it is volatilized and burned, and the unburned gas generated from the dust is mixed with the secondary air 7 supplied to the empty column section 4 in the empty column section 4 and burned. At this time, the blower 16
The amount of the secondary air supplied in (1) is controlled by the controller 18 and the control valve 19 according to the combustion state such as the brightness in the furnace.

The incombustibles mixed in the dust sink into the fluidized bed 3 as they are fluidized together with the fluidized medium, and are discharged from the incombustibles discharging device 8 installed at the bottom of the furnace. On the other hand, the exhaust gas 9 is cooled by the gas cooler 11 and then sent to the air preheater 12 to preheat the primary air 6,
Further, it is cooled to about 200 ° C. by the gas cooler 13, and slaked lime is blown into the flue 10 in order to remove HCl in the exhaust gas. The slaked lime reacts with HCl here to become CaCl ₂ , and the unreacted and reacted slaked lime is collected together with ash by the bag filter (ash collecting means) 14, and the cleaned exhaust gas is blown into the atmosphere from the chimney 15 by the blower 17. Is released to. The ash collected by the bag filter 14 is finally landfilled after stabilizing heavy metals and the like by an ash treatment device.

Generally, since garbage has a large amount of volatile components and has a very high burning rate, most of it is volatilized by the combustion heat generated by burning a part thereof and burned in the empty column portion as unburned gas. For this reason, the shape of the empty tower, the arrangement of the secondary air nozzle, and the mixing of the exhaust gas with the secondary air to increase the momentum of the secondary air, etc. Promotes mixing with secondary air. In addition, it is difficult to supply a fixed amount of waste because the properties such as water content and bulk density change significantly, and the combustion state also fluctuates greatly due to such changes in the properties and the supply amount. Even if the above is prevented, a large amount of unburned gas is discharged from the furnace outlet due to a temporary shortage of air in the empty column section and a decrease in combustion gas temperature due to excess air. In order to cope with such changes in the combustion state due to changes in the amount of supplied dust and its properties, the amount of secondary air is controlled by the brightness of the furnace, the image analysis results of the combustion state, and the like.

However, the burning rate and volatilization rate of the waste in the fluidized bed are very high, and when the waste is supplied to the fluidized bed waste incinerator, it is instantly combusted and most of it is volatilized, so that in the empty column section. The state of combustion of unburned gas changes abruptly under the influence of the amount and property of waste that fluctuates greatly. For this reason, there is a time delay in controlling the amount of secondary air, and when a large amount of dust is supplied at one time, unburned gas in an amount greater than that combustible with secondary air is generated. It is not possible to sufficiently cope with the suddenly changing combustion state, and as shown in FIG. 9, a large amount of unburned components represented by CO and dioxins are temporarily discharged.

Further, in a fluidized bed type waste incinerator in which exhaust gas is mixed with primary air and supplied to a fluidized bed in order to suppress NOx emission amount, the oxygen partial pressure of the primary air is lowered, so Although the combustion rate and volatilization rate are slightly reduced, the oxygen partial pressure is sufficient to burn the dust even with the primary air mixed with the exhaust gas, so even in this case, CO is temporarily represented by the variation in the dust supply amount. A large amount of unburned gas is discharged.

[0007]

In the conventional combustion method for a fluidized bed waste incinerator, when garbage is supplied to the fluidized bed waste incinerator, it is instantly burned and most of it is volatilized. Therefore, the combustion state of the unburned gas in the empty column part changes greatly due to the influence of the amount and property of the waste supply, and there is a time delay in the control of the secondary air amount, or the amount that can be burned with the secondary air. There has been a problem that a large amount of unburned components and dioxins are temporarily discharged, such as the generation of unburned gas as described above.

Further, since the oxygen partial pressure is sufficient to burn the dust even with the primary air mixed with the exhaust gas in order to suppress the NOx emission amount, a large amount of unburned fuel is temporarily generated due to the fluctuation of the dust supply amount. There was a problem that gas was discharged.

The object of the present invention is to incinerate a fluidized bed type waste incineration system capable of suppressing a rapid change in the combustion state and reducing the emissions of unburned components such as CO and hydrocarbons in exhaust gas and dioxins. It is an object of the present invention to provide a combustion method and apparatus for a furnace.

[0010]

In order to achieve the above object, a combustion method for a fluidized bed type waste incinerator according to the present invention comprises:
In the combustion method of a fluidized bed type waste incinerator in which fluidized gas is supplied to the fluidized bed to flow the medium and incinerate at least waste consisting of municipal waste, the oxygen partial pressure of one fluidized bed part of the fluidized bed Is controlled to be lower than that of the other fluidized bed portion, and the waste is supplied to one fluidized bed portion having a low oxygen partial pressure.

A configuration may be employed in which the fluid velocity of the medium in the fluidized bed portion having a low oxygen partial pressure is controlled according to the combustion state.

Further, in one fluidized bed portion having a low oxygen partial pressure,
The branched exhaust gas branched from the exhaust gas of the fluidized bed waste incinerator may be recirculated, and the primary air preheated by the exhaust gas may be supplied to the other fluidized bed portion having a high oxygen partial pressure.

Further, a waste heat boiler is attached to the fluidized bed type waste incinerator, and the steam generated in the waste heat boiler and used for the power generator is branched to one fluidized bed portion having a low oxygen partial pressure. The primary air preheated with a part of the steam generated in the waste heat boiler may be supplied to the other fluidized bed portion having a high oxygen partial pressure.

An oxygen enrichment device for separating the primary air preheated by the exhaust gas from the fluidized bed waste incinerator into oxygen-lean air and oxygen-enriched air is provided, and one of the fluidized bed parts with a low oxygen partial pressure is provided. It is also possible to supply oxygen-diluted air and supply oxygen-enriched air to the other fluidized bed portion having a high oxygen partial pressure.

Further, a fluidized gas is supplied to the fluidized bed to fluidize the medium to incinerate at least a waste consisting of municipal waste,
In the combustion method of a fluidized bed type waste incinerator that cools the exhaust gas and reacts it with slaked lime and discharges it through the ash collecting means, an ash melting furnace is attached to the ash collecting means, and one of the fluidized beds The oxygen partial pressure of the fluidized gas in the bed part is controlled to be lower than that of the other fluidized bed part, and the ash melting furnace exhaust gas and waste are supplied to the one fluidized bed part with a low oxygen partial pressure to supply the oxygen partial pressure. The primary air preheated by the exhaust gas may be supplied to the other fluidized bed portion having a high temperature.

Further, the fluidized bed waste incinerator is configured to be used in the combustion method of any one of the fluidized bed waste incinerators described above.

[0017]

According to the present invention, the oxygen partial pressure of the fluidizing gas in one fluidized bed portion of the fluidized bed is controlled to be lower than that in the other fluidized bed portion, and the waste is supplied to one fluidized bed portion, so Combustion that occurs in the is suppressed and the refuse is first dried as it is fluidized with the fluid medium. Then, as the dried waste is fluidized, it is dispersed in a portion having a high oxygen partial pressure and burned. First, by drying the waste, fluctuations in the combustion state are reduced, and when the amount of supplied dust is increased, the flow velocity of the part with a low oxygen partial pressure is reduced, so that the part with a high oxygen partial pressure is reduced. A rapid increase in the amount of dispersed dust is prevented and the combustion state is stabilized.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, a combustion method for a fluidized bed waste incinerator in which a fluidized gas is supplied to a fluidized bed 3 to flow a medium to incinerate a waste consisting of at least municipal solid waste. The oxygen partial pressure of the fluidized gas (branched exhaust gas) 21 in one of the fluidized bed portions of 3 is controlled to be lower than that of the fluidized gas (primary air) 6 in the other fluidized bed portion by the controller 23 and the control valve 24. The waste is supplied from the charging chute 2 to the one fluidized bed portion having a low partial pressure. Then, the flow velocity of the medium (fluid medium) in the one fluidized bed portion having a low oxygen partial pressure is controlled by adjusting the flow rate of the branched exhaust gas 21 by the controller 23 and the control valve 24 in accordance with the combustion state, and the oxygen is controlled. The branched exhaust gas 21 branched from the exhaust gas of the fluidized bed waste incinerator 1 is recirculated to the one fluidized bed portion having a low partial pressure, and the primary air preheated with the exhaust gas is supplied to the other fluidized bed portion having a high oxygen partial pressure. 6 shall be supplied.

That is, as shown in FIGS. 1 and 2, the air diffuser is divided into an air diffuser 5a and an air diffuser 5b, and the oxygen partial pressure branched from the flue 10 to one air diffuser 5a close to the charging chute 2 is divided. 7 to 12% of the branched exhaust gas 21 is recirculated by the blower 16 via the dust collector 22, and the preheated primary air 6 is supplied to the other diffuser pipe 5b, so that the difference in oxygen partial pressure in the fluidized bed 3 is increased or decreased. Attach. The waste introduced into the fluidized bed waste incinerator 1 from the introduction chute 2 is dried as it is fluidized with the fluidized medium by the branched exhaust gas 21 supplied through the diffuser pipe 5a in the fluidized bed 3. After that, the primary air 6 supplied by the blower 16 via the air diffuser 5b is combusted as it is fluidized with the fluidized medium.

The unburned gas generated from the waste in the fluidized bed 3 is
In the empty column section 4, the air is mixed with the secondary air 7 supplied to the empty column section 4 via the control valve 19 controlled by the controller 18 by the blower 16 and burned. The exhaust gas 9 is water-cooled by the gas cooler 11 via the heat transfer body, and after the primary air 6 is preheated by the air preheater 12, a part thereof becomes the branched exhaust gas 21 branched from the flue 10 and dust is removed by the dust collector 22. It is refluxed to the fluidized bed 3 via the air diffuser 5a. The remaining exhaust gas is cooled to approximately 200 ° C by the gas cooler 13 and HC
Slaked lime is blown in to remove l. Unreacted and reacted slaked lime together with ash bag filter (ash collection means)
The clean exhaust gas collected in 14 is blower 17
Is discharged by the chimney 15 into the atmosphere.

At this time, if the amount of waste supplied decreases, the controller 2
3 and the control valve 24 reduce the amount of recirculation of the branch exhaust gas 21, and when the amount of dust supply increases, the controller 23 and the control valve 24 gradually increase the amount of supply of the branch exhaust gas 21 to a certain amount during normal operation. By doing so, the flow rate of the medium in the fluidized bed portion having a low oxygen partial pressure is controlled. The rapid increase in the amount of waste supply occurs after the amount of waste supply decreases due to clogging of the dust collector, etc.Therefore, when the amount of waste supply decreases, the flow rate of the medium is reduced to increase the amount of waste supply rapidly. Even so, it is possible to suppress the dispersion of dust and suppress a rapid change in combustion. Moreover, since the amount of gas in the furnace decreases when the amount of refuse supplied decreases, it is possible to prevent the temperature of the empty column portion from decreasing due to the decrease in the amount of heat generation. In addition, the amount of unburned gas generated in the empty column section from the fluidized bed depends on the flow rate of the fluidized bed section where the oxygen partial pressure is low. The control of quantity becomes effective.

Next, the operation of the fluidized bed will be described. As shown in FIG. 3, a fluidized bed portion (a fluidized bed portion) 3a in which the oxygen partial pressure is lowered to the extent that dust does not ignite, and a fluidized bed portion (the other fluidized bed portion) in which the oxygen partial pressure is increased to an extent that dust is sufficiently burned (the other The fluidized bed 3 is divided into (fluidized bed portion) 3b, the oxygen partial pressures are made higher and lower, and the refuse to be incinerated is supplied to the fluidized bed portion 3a having a low oxygen partial pressure, so that the refuse first flows with the fluidized medium. It is mainly dried as it is liquefied. If the whole fluidized bed 3 has such a low oxygen partial pressure, almost no dust is burned, but a portion of the fluidized bed 3 where the oxygen partial pressure is as high as air is formed, and thus the dried waste As they are fluidized, they are dispersed in the fluidized bed portion 3b having a high oxygen partial pressure and burned. Since the property of waste is greatly affected by the change in water content and the change in property is reduced by drying, the property of waste is stabilized and the fluctuation of the combustion state is reduced by first drying the waste. In addition, by decreasing the fluidization speed of the fluidized bed portion 3a having a low oxygen partial pressure when the amount of waste supplied increases, the fluidized bed portion 3b having a high oxygen partial pressure is obtained.
It is possible to prevent a rapid increase in the amount of dust dispersed in the air and stabilize the combustion state.

According to the present invention, the flow velocity of the fluidized bed portion having a low oxygen partial pressure is controlled in combination with the amount of secondary air to control the unburned gas emission amount represented by CO as shown in FIG. A temporary increase can be suppressed. Further, even when the fluidizing speed of the fluidized bed is increased, a rapid change in the combustion state can be suppressed, so that the amount of unburned components such as CO and hydrocarbons in the exhaust gas and the amount of dioxins can be reduced.

Another embodiment of the present invention will be described with reference to FIG. This is an example of using steam generated from a power generation facility as a fluidized gas having a low oxygen partial pressure when the power generation facility is provided. A waste heat boiler 25 is installed in connection with the outlet of the fluidized bed waste incinerator 1, and the exhaust gas 9 heats water 26 in the waste heat boiler 25 to generate steam 27, and then cools it with a gas cooler 13. And bug filter 14
It is rendered harmless and discharged from the stack 15. Waste heat boiler 2
The steam 27 generated in 5 is sent to the power generator 28, used for power generation, returned to water by the condenser 29, and supplied to the waste heat boiler 25. The steam 30 branched from the outlet of the power generation device 28 is supplied to one fluidized bed portion of the fluidized bed 3 via the diffuser pipe 5a, and part of the steam 27 is preheated to the other fluidized bed portion via the diffuser pipe 5b. The generated primary air 6 is supplied to stably burn the waste.

FIG. 6 shows another embodiment in which a fluidized gas having different oxygen partial pressures is supplied by using an oxygen enrichment device. An oxygen enrichment device 39 for separating the primary air preheated by the exhaust gas of the fluidized bed waste incinerator 1 into the oxygen lean air 41 and the oxygen enriched air 40 is provided, and the primary air 6 preheated by the air preheater 12 is provided. An oxygen enrichment device 39 using an oxygen enrichment film, etc.
Is separated into oxygen-enriched air 40 having an oxygen partial pressure of 25% or more and oxygen-diluted air 41 having an oxygen partial pressure of 15% by the fluidized bed 3
Oxygen-diluted air 41 is supplied to one fluidized bed portion having a low oxygen partial pressure via the diffuser pipe 5a, and oxygen-enriched air is supplied to the other fluidized bed portion having a high oxygen partial pressure via the diffuser pipe 5b. 40
Is a structure for supplying waste gas, and this structure enables stable combustion of dust.

Further, FIG. 7 shows a case where an ash melting furnace is installed side by side.
Another example of utilizing ash melting furnace exhaust gas as a fluidizing gas having a low oxygen partial pressure will be described. Fluidized gas is supplied to the fluidized bed 3 to flow a medium, incinerate at least waste consisting of municipal waste, and cool the exhaust gas to react with slaked lime and via ash collecting means (bug filter) 14. In the combustion method of a fluidized bed type waste incinerator for discharging, an ash melting furnace 33 is attached to the ash collecting means 14, and the oxygen partial pressure of one fluidized bed portion of the fluidized bed 3 is controlled from the other fluidized bed portion. The ash melting furnace exhaust gas 3 is provided in one fluidized bed portion of the fluidized bed 3 which is controlled to be low and has a low oxygen partial pressure.
5, the waste is supplied from the charging chute 2, and the primary air 6 preheated by the exhaust gas 9 is supplied to the other fluidized bed portion having a high oxygen partial pressure. That is, the ash collected by the bag filter 14 is supplied from the ash storage hopper 32 to the ash melting furnace 33, and is heated by the burner 34 to become molten slag. The melting furnace exhaust gas 35 having an oxygen partial pressure of 3 to 6% is water-cooled by a gas cooler 36 via a heat transfer body,
After the dust is removed by the dust collector 37, the dust is supplied to the fluidized bed 3 through the air diffuser 5a. According to this embodiment, the dust can be stably burned in the same manner as described above.

Furthermore, as another embodiment of the present invention, a fluidized bed waste incinerator is used in the combustion method of any one of the fluidized bed waste incinerators.

[0028]

According to the present invention, the oxygen partial pressure of one fluidized bed portion of the fluidized bed is controlled to be lower than that of the other fluidized bed portion, and the waste is supplied to one fluidized bed portion, so that the rapid flow rate is reduced. It is possible to suppress fluctuations in the combustion state, reduce the amount of unburned matter and dioxins in the exhaust gas, and achieve stable combustion.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an example of a fluidized gas supply structure shown in FIG.

3 is a vertical cross-sectional view showing an example of a fluidized gas supply structure shown in FIG.

FIG. 4 is a diagram showing a time-dependent change in CO concentration in exhaust gas discharged from the example of FIG.

FIG. 5 is a configuration diagram showing another embodiment of the present invention.

FIG. 6 is a configuration diagram showing another embodiment of the present invention.

FIG. 7 is a configuration diagram showing another embodiment of the present invention.

FIG. 8 is a diagram showing a conventional technique.

FIG. 9 is a diagram showing a time-dependent change in CO concentration in exhaust gas discharged by a conventional technique.

[Explanation of symbols]

 1 fluidized bed waste incinerator 2 input chute 3 fluidized bed 3a fluidized bed part with low oxygen partial pressure 3b fluidized bed part with high oxygen partial pressure 4 empty tower part 5 diffuser pipe 5a diffuser pipe 5b diffuser pipe 6 primary air 7 2 Next air 8 Incombustibles discharge device 9 Exhaust gas 10 Flue 11 Gas cooler 12 Air preheater 13 Gas cooler 14 Bag filter 15 Chimney 16 Blower 17 Induced blower 18 Controller 19 Control valve 20 Valve 21 Branch exhaust gas 22 Dust collector 23 Controller 24 Control valve 25 Waste heat boiler 26 Water 27 Steam 28 Power generator 29 Condenser 30 Steam 32 Ash storage hopper 33 Ash melting furnace 34 Burner 35 Ash melting furnace exhaust gas 36 Gas cooler 37 Dust collector 39 Oxygen enricher 40 Oxygen enriched air 41 Oxygen lean air

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiromichi Fujiwara 6-9 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Co., Ltd. Kure Factory

Claims (7)

[Claims] 1. A combustion method for a fluidized bed waste incinerator in which a fluidized gas is supplied to a fluidized bed to flow a medium to incinerate a waste consisting of at least municipal solid waste. Combustion in a fluidized bed waste incinerator, characterized in that the oxygen partial pressure of the bed portion is controlled to be lower than that of the other fluidized bed portion, and the waste is supplied to the one fluidized bed portion having a low oxygen partial pressure. Method. 2. The combustion method for a fluidized bed waste incinerator according to claim 1, wherein the fluidization velocity of the medium in one fluidized bed portion having a low oxygen partial pressure is controlled according to the combustion state. Combustion method for fluidized bed waste incinerator. 3. The combustion method for a fluidized bed waste incinerator according to claim 1, wherein a branched exhaust gas branched from the exhaust gas of the fluidized bed waste incinerator is provided in one fluidized bed portion having a low oxygen partial pressure. And a primary air preheated with the exhaust gas is supplied to the other fluidized bed portion having a high oxygen partial pressure, to burn the fluidized bed waste incinerator. 4. The combustion method for a fluidized bed waste incinerator according to claim 1 or 2, wherein a waste heat boiler is attached to the fluidized bed waste incinerator, and one of the fluidized bed parts having a low oxygen partial pressure is attached. ,
Supplying branched steam that is generated in the waste heat boiler and used in the power generation device, to the other fluidized bed portion with high oxygen partial pressure, the primary air preheated with a part of the steam generated in the waste heat boiler. A method for combustion in a fluidized bed waste incinerator, which comprises: 5. The combustion method for a fluidized bed waste incinerator according to claim 1 or 2, wherein primary air preheated with exhaust gas from the fluidized bed waste incinerator is converted into oxygen-lean air and oxygen-enriched air. A separate oxygen-enriching device is provided, the oxygen-diluted air is supplied to one fluidized bed portion having a low oxygen partial pressure, and the oxygen-enriched air is supplied to the other fluidized bed portion having a high oxygen partial pressure. Combustion method of fluidized bed type waste incinerator characterized. 6. A fluidized gas is supplied to a fluidized bed to flow a medium, incinerate at least waste consisting of municipal waste, cool the exhaust gas to react with slaked lime, and discharge via ash collection means. In the combustion method of a fluidized bed waste incinerator, an ash melting furnace is attached to the ash collecting means, and the oxygen partial pressure of the fluidized gas in one fluidized bed portion of the fluidized bed is adjusted to the other fluidized bed portion. It is controlled to be lower, the ash melting furnace exhaust gas is supplied to the one fluidized bed portion having a low oxygen partial pressure, and the waste is supplied to the other fluidized bed portion having a high oxygen partial pressure, and the exhaust gas is supplied to the other fluidized bed portion. A combustion method for a fluidized bed waste incinerator, which is characterized by supplying preheated primary air. 7. A fluidized bed waste incinerator, which is used in the combustion method of a fluidized bed waste incinerator according to any one of claims 1 to 6.