JPH11128679A - Device for reducing dioxines of discontinuous combustion refuse incineration plant and reducing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the emission of dioxines in the start-up and shutdown of a discontinuous-combustion refuse incineration plant. SOLUTION: The waste gas from an incinerator 1 is introduced into a recombustion chamber 2, burned, then conducted to a dust removing equipment through a gas cooling equipment 3 consisting of a high-temp. air preheater 31, a heat exchanger 32 and a gas cooling chamber 33 and purified in this discontinuous-combustion refuse incineration plant. The dust removing equipment is composed of a bag filter 4 for normal operation and an auxiliary bag filter 5 used in the start-up, shutdown and normal operation, and the collected ash 94 shaken down from the auxiliary bag filter 5 in the start-up and shutdown is returned to the recombustion chamber 2 to thermally decompose the dioxines.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing dioxins contained in exhaust gas and collected ash in a refuse incineration facility for incinerating refuse such as general waste and industrial waste.

[0002]

2. Description of the Related Art Exhaust gas discharged from refuse incineration facilities contains toxic dioxins in addition to dust and acidic harmful gases. include.

The Ministry of Health and Welfare has established guidelines for controlling the emission of these dioxins, and measures combustion stabilization in incinerators on the basis of a full continuous combustion system, and the combustion gas can stay at 850 ° C. or higher for 2 seconds. In addition to providing a reburn chamber, we recommend using a bag filter with high dioxin removal capability in the exhaust gas treatment equipment, and recommending a burn-off method that does not leave unburned materials in the incinerator when the furnace is closed.

Further, the collected ash of the bag filter is required to be stabilized as a specially controlled waste.

[0005] Guidance according to the above guidelines can be complied with in the case of an all-incineration type incinerator with a large processing capacity and stable combustion, but the amount of waste and the number of personnel are small, and the operation is only performed for about 8 hours a day. There are many difficulties in the case of a mechanized batch furnace that cannot be used or a quasi-continuous combustion type incinerator that has a limit of 16 hours of operation. In particular, as a result of adopting the above-mentioned boil-off method, the furnace temperature in the next morning has dropped to 150 to 300 ° C. and the bag filter inlet temperature has dropped to 80 to 150 ° C. There are problems such as low temperature corrosion of the equipment and sticking of the neutralizing chemical reaction product to the filter cloth with high deliquescent.

Therefore, in the above-mentioned mechanized batch furnace or quasi-continuous combustion type, that is, a non-continuous combustion type waste incineration facility in which the furnace is closed for a predetermined time every day, the temperature in the incinerator rises and the temperature of the gas flowing into the bag filter rises to 130 ° C. During the start-up work until the temperature reaches the level and after the burning-out work where the heat source is lost, the exhaust gas is flown by bypassing the bag filter to prevent low-temperature corrosion of the bag filter and fixation of reaction products to the filter cloth. The method has been adopted, which has led to a situation in which dust and dioxins are released for a long time.

[0007] As a measure against bypass during the start-up work,
FIG. 6 shows a "bag filter for an incinerator" whose outline is shown in JP-A-6-79118.

That is, by providing a bag filter that does not spray slaked lime or a low-temperature filter LTF using an electric precipitator in the normal bypass flue BPL, dust in exhaust gas at low temperatures is not captured. During normal operation, the main bag filter MBF is operated by the switching valve COV.
And a normal filtration / neutralization operation is performed.

Although these bypass flue treatment methods are effective in preventing a bag filter from being damaged by low-temperature gas at the time of starting up and shutting down a non-continuous combustion type waste incineration plant, the present invention aims to reduce dioxins. Is a technology that is not available.

A typical example of an exhaust gas treatment method for removing dioxins is disclosed in Japanese Patent Application Laid-Open No. Hei 8-243341.
FIG. 7 shows a flow chart of an exhaust gas treatment process disclosed in Japanese Patent Application Laid-Open Publication No. H11-15095.

In FIG. 7, the exhaust gas from incinerator a is:
The temperature is reduced to about 150 ° C. by the temperature reducing device b, and the dust is removed by a dust removing facility c such as a bag filter or an electric dust collector.

Subsequently, a fresh adsorbent e made of activated carbon or slaked lime supplied from the adsorbent adding device d is added to the gas after the primary dust removal, and the gas is purified again by the subsequent bag filter f for purification. After that, it is released into the atmosphere from the chimney g.

Here, the dust h collected in the dust removal facility c
Is collected in the ash treatment facility i, and the collected ash j mainly composed of the adsorbent collected by the bag filter f is regenerated by heating to 400 ° C. or more in a reducing atmosphere by the desorption / regeneration facility k. The regenerated adsorbent m is added upstream of the bag filter f.

As indicated by the two-dot chain line, there is also a method in which part or all of the collected ash j is returned to the upstream side of the dust removal equipment c. In either case, the effect of reducing the consumption of the fresh adsorbent e can be obtained. is there.

Further, the exhaust gas generated from the desorption / regeneration facility k is treated in the heavy metal treatment facility n.

[0016]

However, in the above-mentioned conventional exhaust gas treatment system, a dust removal facility is required twice, and a desorption / regeneration facility k for collecting ash and a heavy metal treatment facility n are required.
However, there is a problem that equipment costs and operating costs increase due to the complexity.

In the case of a general equipment arrangement in which a water injection type gas cooling chamber is provided in front and an air preheater and an air heater for preventing white smoke are provided, the air preheater and the air for preventing white smoke are used. Exhaust gas passing through the inside of the heater, etc.
Since the temperature is gradually lowered to around 70 ° C., the temperature condition matches the temperature at which dioxins are resynthesized, and high concentrations of dioxins arrive at the dust removal equipment.

Further, the bypass system shown in FIG. 6 does not take measures against dioxin, and the conventional technology shown in FIG. 7 does not have a bypass circuit for the full continuous combustion system. On the other hand, in the case of the non-continuous combustion method, as described above, all the equipment, including the incinerator, is destined to cool down when the furnace is closed. However, no consideration has been given to the phenomenon of resynthesizing in a low temperature range to produce a high concentration of dioxin.

For this reason, a large amount of dioxins is adsorbed particularly on the bag filter of the dust removing equipment c, and is discharged not only to the ash processing equipment i having no dioxin processing ability but also to be generated at the time of startup and shutdown. Due to easy low-temperature corrosion and deliquescence on the surface of the filter cloth, there is a problem in that the cost of maintaining the dust removal equipment c and the post-bag filter f as a whole increases.

[0020]

The dioxin reduction device of the non-continuous combustion type waste incineration plant according to the first aspect of the present invention is used every day when incinerating waste such as general waste and industrial waste. Exhaust gas discharged from a non-continuous combustion type waste incinerator that is closed for hours is guided to a bag filter through a reburning chamber and a gas cooling device, and a harmful gas neutralizing agent and a carbon-based adsorbent supplied to the bag filter. By this, soot and acid harmful gas and dioxins contained in exhaust gas,
In a discontinuous combustion type waste incineration facility configured to be filtered, neutralized, adsorbed and removed, the bag filter includes a sub-bag filter that is also used during start-up / down and during normal operation. The secondary bag filter is configured as two groups: a main bag filter for normal operation having a larger capacity than the filter, and a discharge means for discharging the collected ash of the auxiliary bag filter is connected to the reburning chamber via a switching means and a collected ash transfer mechanism. It was done.

According to a second aspect of the present invention, in the apparatus for reducing dioxins in a non-continuous combustion type waste incineration plant, the gas temperature reducing equipment includes a heat exchanger such as an air preheater for high temperature and an air heater for preventing white smoke. In this case, a water-injection type gas cooling chamber is provided after the vessel group.

According to a third aspect of the present invention, there is provided a method for reducing dioxins in a non-continuous combustion type waste incineration facility, wherein a non-consecutive furnace is closed for a predetermined time every day when incinerating waste such as general waste and industrial waste. Exhaust gas discharged from the combustion type waste incinerator is led to a bag filter through a reburning chamber and a gas temperature reducing facility, and harmful gases and dioxins supplied to the back filter are removed by filtration, neutralization and adsorption. A method for reducing dioxins in a discontinuous combustion type waste incineration facility configured as described above, wherein when starting up and shutting down by the above discontinuous combustion type waste incineration facility, exhaust gas is introduced only into the auxiliary bag filter and treated. The collected ash during this period is returned to the reburning chamber to reburn unburned materials and thermally decompose dioxins. During normal operation, the main bag filter and the auxiliary bag filter are used. It processes the exhaust gas and, collecting ash both the bag filter is intended to perform the stabilizing process in fed to the fly ash treatment apparatus.

In the method for reducing dioxins in a non-continuous combustion type waste incineration plant according to claim 4 of the present invention, the surface of the filter cloth of the auxiliary bag filter is set up before starting up and down operation. It is pre-coated with a carbon-based adsorbent and a harmful gas neutralizing agent necessary for the adsorption of dioxins generated during the shutdown operation.

[0024]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an outline of a dioxin reduction device of a discontinuous combustion type waste incineration plant according to the present invention, and FIG. 2 is a diagram showing gas, air, fly ash and water of the incineration plant. FIG. 4 is a schematic flowchart mainly showing the flow of FIG.

1 and 2, reference numeral 1 denotes an incinerator for incinerating refuse such as municipal waste and industrial waste, and a reburning chamber 2 installed on the incinerator 1 serves to reduce a gas flow in the downstream. After passing through the heating equipment 3, the main bag filter 4 and the sub bag filter 5
It is connected to a mixed flue, an induction ventilator and a chimney (not shown) through a dust removal facility composed of groups.

The incinerator 1 includes a vertical incinerator main body 11.
And a hopper 12 for supplying garbage, a dry grate 13,
Refuse support means 14 for supporting refuse during combustion at the bottom of the incinerator body 11, incineration ash discharge means 15 located below the refuse support means 14, and auxiliary combustion burner 16 for start-up and burning
, Furnace outlet 17 and furnace outlet 1 which are connection ports with the reburn chamber 2
It is constituted by an in-furnace thermometer 18 (see FIG. 2) and the like provided near 7.

The reburning chamber 2 is provided above the furnace outlet 17 and is a device for reburning the combustion gas 61 discharged from the incinerator 1 and the collected ash of the auxiliary bag filter 5 described later. A main body 21, a mixing plate 22 provided above the furnace outlet 17, a trapping ash supply mechanism 23 mounted on an upper part of the reburning chamber main body 21, and a reburn burner 2 for raising the temperature of the reburning chamber
4 and an elevated flue 25 connected to the outlet of the reburn chamber main body 21
And a recombustion chamber thermometer 26 (see FIG. 2).

The gas desuperheater 3 comprises a heat exchanger group 3 such as a high-temperature air preheater 31 and a white smoke prevention air heater.
2 and a downstream water injection type gas cooling chamber 33 are mainly connected.

Since the air preheater 31 and the heat exchanger group 32 exchange heat with the high-temperature reburn gas 62, the surface of the heat transfer tube is covered with an amorphous refractory material such as a silicon carbide material or a high alumina material, for example, to provide heat resistance. The temperature of the reburning gas 62 flowing through is reduced to a temperature-lowering gas 63, and the insufficient amount of temperature reduction is left to the subsequent gas cooling chamber 33.

On the other hand, as shown in FIG.
The normal-temperature air sent to the air preheater 31 is heated to supply the combustion air 35 to the incinerator 1 and the reburning air 36 to the reburning chamber 2. The normal-temperature air sent into the group 32 is used for raising the temperature of a clean gas (not shown) and for using residual heat such as heating and hot water supply. The gas cooling chamber 33 stores the temperature-reduced gas 6 exiting the heat exchanger group 32.
3 is a device for reducing the temperature of the subsequent main bag filter 4 to a temperature at which the removal efficiency of the main bag filter 4 is maximized. A plurality of direct pressure water injection nozzles 37 are provided on the upstream side, and a two fluid water injection nozzle 38 is provided on the downstream side.
It has.

The main bag filter 4 includes a filtration chamber 42 for suspending a plurality of filter cloths 41, a hopper chamber 44 provided with a discharge means 43 attached below the filtration chamber 42, and a filter chamber 42 located above the filtration chamber 42. Gas chamber 46 provided with a cleaning means 45
And the like (FIG. 1 shows three chambers).

The auxiliary bag filter 5 has the same structure as that of the main bag filter 4, that is, a filter chamber 52 for suspending a plurality of filter cloths 51, a hopper chamber 54 having discharge means 53, and a removing means 55. One section of the bag filter device, which is composed of a clean gas chamber 56 and the like, and in which a plurality of unit dust collecting mechanisms are normally assembled, is used as a sub-bag filter. The main bag filter 4 and the sub bag filter 5 configured as described above are connected to a flue base 73 disposed at the outlet of the heat exchanger group 33 via a flue and a clean duct group. .

The above-mentioned flue and clean duct group are composed of a main flue 7
4. Secondary flue 76, bypass flue 78, main cleaning duct 75
And a sub-cleaning duct 77.

The main flue 74 is connected to the flue base 73, has a main exhaust gas damper 74d, and introduces the exhaust gas 64 to the main bag filter 4 during normal operation.

The sub flue 76 is branched from the main flue 74 and has a sub exhaust gas damper 76d, and introduces the medium temperature exhaust gas 66 to the sub bag filter 5 at the time of starting and lowering operations.

The bypass flue 78 is communicated from the flue base 73 to the main cleaning duct 75 and has a bypass damper 78d for supplying the low-temperature gas 68 at startup and after burning off.
It is discharged directly from the flue base 73 to the main cleaning duct 75.

The main cleaning duct 75 has a main cleaning gas damper 75d, and discharges the cleaning gas 65 from the main bag filter 4 during normal operation.

The sub-cleaning duct 77 is provided with a sub-cleaning gas damper 77d, and discharges the medium-temperature clean gas 67 from the sub-bag filter 5 to the main cleaning duct 75 at the time of starting and lowering operations.

The branch point of the bypass flue 78 and the secondary flue 7
One end of a pipe 81 for transporting a medicine is connected to a main flue 74 at the middle of the branch point of No. 6, and a chemical 82 for neutralizing an acidic harmful gas such as slaked lime is provided in the middle of the pipe 81.
And an adsorbent storage tank 85 for storing a carbon-based adsorbent 84 such as powdered activated carbon or activated coke, for example, are connected via discharge means.

Each powder discharged from the medicine storage tank 83 and the adsorbent storage tank 85 is pumped into the main flue 74 by transfer air 69 from a medicine blower 86 for sucking air at room temperature. A drug layer is formed on the surfaces of the filter cloths 41 and 51 of the bag filter 4 and the sub-bag filter 5.

Below the plurality of discharge means 43 of the main bag filter 4, a common discharge conveyor 47 is provided to neutralize collected ash collected by the main bag filter 4 during normal operation and acidic harmful gas. The main fly ash 91 from which the chemical layer adsorbed with dioxins has been dropped is discharged to a fly ash treatment device 92 for stabilization.

A switching means 57 is provided below the discharging means 53 of the auxiliary bag filter 5.
Captures the collected ash collected by the auxiliary bag filter 5 during the start-up / fall-down operation, and the auxiliary collected ash 93 that has dropped off the chemical layer that has adsorbed dioxins and neutralized the acidic harmful gas. While returning to the reburning chamber main body 21 via the ash collection transfer mechanism 58 and the supply mechanism 23, the auxiliary fly ash 94 dropped off in the same manner as the main bag filter 4 during normal operation can be switched to be sent to the discharge conveyor 47. It is configured.

Next, a description will be given of an exhaust gas treatment method from the initial startup to the final shutdown in the discontinuous combustion type waste incineration facility configured as described above.

The temperature inside the incinerator main body 11 at the start of operation varies depending on the structure of the incinerator and the shutdown time, as described above.
Since the temperature has dropped to 0 to 300 ° C.,
Thereby, the inside of the incinerator main body 11 in which only the incineration ash remains is heated to the refuse ignition temperature.

Next, flammable garbage for start-up, which is pre-sorted in a garbage storage (not shown), is supplied little by little from the hopper 12 onto the dry grate 13 and burned, so that the incinerator main body 11 is separated. The combustion gas generated by heating the inside
1 is sent out to the reburning chamber 2 through the furnace outlet 17, and the incinerated ash is discharged from the incinerated ash discharging means 15 through the refuse support plate 14 to the outside of the furnace at an appropriate time.

In the reburning chamber 2, the combustion gas 61 stirred and mixed by the mixing plate 22 is heated to 850 ° C. or more by the supplied high-temperature reburning air 36 and the flame of the reburning burner 24.
Under the high-temperature atmosphere, unburned carbons, which are precursors of dioxin generation, and unburned gases that cause odors are completely burned.

Simultaneously, the dioxins contained therein are also thermally decomposed into a reburn gas 62, and by raising the temperature of the air preheater 31 and the heat exchanger group 32 from the elevated flue 25, the reburn gas 62 is converted into the reburn gas. The temperature is reduced to a temperature at which no synthesis is performed, and the temperature is reduced to a temperature-lowering gas 63. The temperature is further reduced at once by passing through the gas cooling chamber 33 to a low-temperature gas 68. The main cleaning duct 75 passes from the flue base 73 to the bypass flue 78.
Sent to.

At this time, the temperature of the low-temperature gas 68 is measured by a flue thermometer 79 (see FIG. 2) provided in the flue base 73, and the main and sub-bag filters 4 due to low-temperature corrosion and deliquescence are measured.
If the temperature is 130 ° C. or higher at which adverse effects on No. 5 can be avoided,
The gas path is switched from the bypass flue 78 to the sub-flue 76, and the heated intermediate-temperature exhaust gas 66 flows through the sub-bag filter 5. On the surface of the filter cloth 51 of the auxiliary bag filter 5,
A precoat layer having a sufficient thickness is formed by the neutralizing agent 82 and the carbon-based adsorbent 84.
The dust, acidic harmful gas contained therein, and a small amount of dioxins resynthesized after the pyrolysis are filtered, neutralized, and adsorbed by the precoat layer to form a medium-temperature clean gas 67.
, And is discharged to the cleaning duct 75 via the sub-cleaning duct 77.

The temperature of the reburn gas 62 in this state is
Reburning chamber thermometer 2 provided near the outlet of reburning chamber main body 21
After confirming in step 6, if the temperature is stably maintained at 850 ° C. or higher, the operation is switched to the normal operation using general waste.

At the time of switching, first, the precoat layer on the surface of the filter cloth 51 of the auxiliary bag filter 5 and the trapped ash
The sub-collected ash 93 that has been dropped and dropped is retained on the collected ash transfer mechanism 58 via the discharging means 53 and the switching means 57, and a pre-coat layer having a normal thickness is formed on the surface of the filter cloth 51. Let it reform.

If the combustion state in the incinerator 1 is stabilized by the measurement of the in-furnace thermometer 18, the retained ash 93 collected by the ash is collected by the ash collection mechanism 58 and the supply mechanism 23. It is sent to the reburn chamber 2 and reburned.

In normal operation, the amount of exhaust gas 64 is increased by incinerating the rated amount of general waste.
Subsequent to the main bag filter 4, the auxiliary bag filter 5 in which the precoat layer is reformed is brought into operation.

At this time, since the main bag filter 4 has a pre-coated layer formed in advance similarly to the above-mentioned sub-bag filter 5, the exhaust gas 64 is filtered, neutralized and filtered by the main and sub-bag filters 4 and 5. It is absorbed and becomes a clean gas 65,
The air is discharged from the chimney from the main and sub-cleaning ducts 75 and 77 to the atmosphere via an inducible ventilator (not shown).

If this normal operation is continued and the differential pressure between the inside and outside of the filter cloths 41 and 51 or the concentration of the harmful gas in the clean gas 65 exceeds a specified value by a group of detectors (not shown), After the pre-coat layer and the collected ash on each filter cloth surface are removed by 55, the pre-coat layer is re-formed on each filter cloth surface with the neutralizing agent 82 and the carbon-based adsorbent 84, so that the normal filtration operation can be performed. Return.

During this normal operation, the combustion state of the incinerator 1 is relatively stable, and the pyrolysis of dioxins and their precursors in the incinerator 1 and the reburn chamber 2 is completely performed (the toxicity of dioxins). Equivalent: hereinafter abbreviated as DXQ = about 1 ng
−TEQ / Nm ³ ), and the temperature of the cooling gas 63 at the outlet of the heat exchanger group 32 is 550 to 650 ° C. at which there is no risk of dioxin resynthesis.
In order to lower the temperature to around 170 ° C at once, exhaust gas 64
Dioxin resynthesis can be almost completely inhibited (DXQ <2
ng-TEQ / Nm ³ ), DXQ <0.1 ng-T in the clean gas 65 by adsorption with the main and sub bag filters 4 and 5
It is easy to achieve EQ / Nm ³ .

Therefore, the main fly ash 91 dropped from the main bag filter 4 and the sub fly ash 94 dropped from the sub bag filter 5 during the normal operation are provided with 1/10 to 1/5 of the conventional system.
Since the dioxins are contained only to the extent, the supply amount of the carbon-based adsorbent 84 is not only small, but also the stabilization treatment in the fly ash treatment device 92 becomes easy.

However, the secondary trapping ash 93 discharged from the secondary bag filter 5 at the time of start-up / fall-down is obtained by processing the exhaust gas during the period when the entire incineration facility is relatively low temperature and unstable, and Even if the thermal decomposition is performed inside, the dioxins are re-synthesized in the gas temperature-reducing facility 3 and are likely to be adsorbed in the secondary trapping ash 93.

Accordingly, the secondary trapping ash 93 containing the carbon-based adsorbent 84 adsorbing dioxins on the surface of the filter cloth 51 is returned to the reburning chamber 2 when the combustion state is stabilized during normal operation, and the dioxins are thermally decomposed. And a carbon-based adsorbent 84;
The unburned matter in the collected ash is burned to reduce the amount of fly ash in the exhaust gas 64.

Here, the cooling of the cooling gas 63 in the gas cooling chamber 33 from the latter stage of the start-up process to the normal operation is performed by the direct pressure water injection nozzle 37 on the upstream side and the two-fluid water injection nozzle 38 on the downstream side. Since the complete evaporation type automatic control is performed by the linkage of the above, there is no possibility that the non-evaporated water flows into the dust removing device side to impair the processing performance and the like.

When such a normal operation is performed and the incineration of a predetermined amount of waste is completed, the supply of the waste is stopped and the auxiliary burner 1 is turned off.
6 is ignited, and the burning operation is performed until the debris on the dry grate 13 and the debris support means 14 is completely turned into ash.

As a result, if the flame combustion due to the volatile components in the refuse ends and the combustion shifts to fixed combustion using the fixed carbon, the operation is switched to the independent operation of the auxiliary bag filter 5 to filter the residual gas.
Perform neutralization and adsorption.

Thereafter, when the amount of generated residual gas is reduced and the temperature of the flue base 73 falls below a specified value, the operation is switched to the bypass operation and brought into a standstill state in order to avoid low-temperature corrosion and deliquescence.

The outline of the operation procedure during this time is shown in FIGS.
This will be described with reference to the flowchart of FIG.

FIG. 3 is a chart showing a temperature raising and rising step, FIG. 4 is a chart showing a normal operation step, and FIG. 5 is a chart showing a falling step.
The temperature displayed is a standard value. [Temperature Raising Step] First, at the start of operation, since the temperature of all the facilities including the inside of the incinerator main body 11 has been lowered, the auxiliary burner 16 and the reburn burner 24 are ignited, so that the inside of the incinerator 1 and the inside of the reburn chamber 2 , The temperature of all the facilities that have been in the bypass operation since the previous day is increased (step S ₁ ), and the burner heating is continued until the measured value of the in-furnace thermometer 18 exceeds 400 ° C. (step S ₁ ). ₂ ). [Start-up process] In the state where the temperature in the incinerator 1 is 400 ° C. or more, if flammable refuse for startup is supplied little by little, the refuse is immediately ignited and combustion starts in the incinerator 1. ,
In addition to heating the inside of the incinerator main body 11 and accelerating the temperature rise of the reburning chamber 2 and the gas temperature reducing equipment 3 (step S ₃ ), a large amount of low-temperature synthesized on the surface of the filter cloth 51 of the auxiliary bag filter 5. A precoat layer is formed with the carbon-based adsorbent 84 and the normal amount of the neutralizing agent 82 increased to cope with dioxins (step S ₄ ).

As a result of the above-mentioned temperature raising operation, when the inlet temperature of the flue base 73, that is, the sub bag filter 5, which has been lowered to 100 ° C. or less, exceeds 130 ° C. at which gas can pass (step S ₅ ). The auxiliary exhaust gas damper 76d and the auxiliary clean gas damper 77d are opened and the bypass damper 78d is closed,
The gas is passed from the auxiliary flue 76 to the auxiliary bag filter 5, and the pre-coat layer filters, neutralizes and adsorbs the intermediate-temperature exhaust gas 66 at the time of start-up to form the intermediate-temperature clean gas 67.
Discharged 7 (Step S _6).

In this state, the supply amount of the starting waste is gradually increased.
Increase (step S₇), A re-combustion chamber that was easily fluctuated at first
Continue until the outlet temperature exceeds 850 ° C (step
S ₈).

At this point, the dust generated by the combustion of
Ioxins and unburned substances are completely pyrolyzed, reducing gas temperature
Medium temperature exhaust gas 66 after temperature reduction in facility 3 is passed to sub bag filter 5
Therefore, it is in a state where it is purified, and the start-up operation is completed.
The process proceeds to the normal operation process 4 (step A). [Normal operation process] First, the inside of the incinerator
Put general waste in predetermined amount (Step S ₉), Combustion is cheap
If set, the auxiliary burner 16 and the reburn burner 24 are stopped.
Stop (Step S_Ten). In addition, the auxiliary burner 16 and the
If the combustion becomes unstable during combustion, the combustion burner 24
I do.

Since the supply amount of the refuse increases and the discharge amount of the combustion gas 61 and the exhaust gas 64 also increases, the main exhaust gas damper 74 d
And the main cleaning gas damper 75d is opened, and the secondary exhaust gas damper 7 is opened.
By closing the 6d and secondary cleaning gas damper 77d, from the secondary bag filter 5 switches the driving system in the main bag filter 4 (step S _11), enters the normal operation while the precoat layer formation (step S _12).

The five subbag filters whose gas passage has been stopped (step S ₁₃ ) remove the precoat layer and the collected ash adhering to the surface of the filter cloth 51 (step S ₁₄ ), and discharge means 53 and switching means 57 allowed to stay on the collecting ash transport mechanism 58 via (step S _15), the filter cloth 51 surface to form a precoat layer by the neutralizing agent 82 and the carbonaceous adsorbent 84 (step S ₁₆₎ After that, the auxiliary exhaust gas damper 76d
And the sub-cleaning gas damper 77d are opened, and the parallel operation with the main bag filter 4 is started.

[0071] Vice collected ash is retained in the step S ₁₅ 9
3 confirms that the combustion state in the incinerator 1 is stable at more than 850 ° C. (step S ₁₇ ), and is returned to the reburning chamber main body 21 by the trapping ash transfer mechanism 58 and the supply mechanism 23. , rendered harmless by being re-burned with combustion gas 61 (step S _18).

[0072] On the other hand, in step S _12, the main bag filter 4 lines entering the normal operation by dust burning a predetermined amount,
If the continuation of the operation reaches the removal conditions, the precoat layer and the collected ash on the surface of the filter cloth 41 are removed, and then the precoat layer is formed again to perform the filtration, neutralization and adsorption treatment of the exhaust gas 64 (step). S _19).

Here, the dropped pre-coat layer and the collected ash become the main fly ash 91 and fly from the discharge conveyor 47 together with the sub-fly ash 94 dropped from the sub-bag filter 5 which has entered the parallel operation. It is sent to the ash processing device 92 and is subjected to a stabilization process (step S ₂₀ ).

The above incineration-filtration / neutralization / adsorption-removal-
By repeating a series of steps of the precoat layer forming, end normal operation has finished waste incineration operations a predetermined amount (step S _21), moves to the fall process of FIG. 5 (step B). [Fall point Step] First, the supply of the waste after the waste layer thickness on the drying grate 13 and refuse supporting means 14 is operated to be thinner stopped (step S _22), and ignite the auxiliary burner 16, incinerated waste in the furnace 1 performs operation Ri baked make every焚切until the ashes (step S _23).

As a result, if the flame inside the furnace due to the burning of the volatile components in the refuse is no longer visible (step S ₂₄ ), it is determined that the combustion has shifted from the flame combustion to the combustion, and the auxiliary burner 1
6 extinguished (step S _25), closes the main exhaust gas damper 74d and the main cleaning gas damper 75d, the main bag filter 4
To pause the system, the operation of the sub bag filter 5 strains only (step S _26).

The main bag filter 4 in which the gas flow is stopped is
To払落collected ash and precoat layer by the normal operation (step S _27), processing stabilize Shuhihai 91 (step S _28).

[0077] In the above step S sub bag filter 5 lines become isolated operation by _26, continue to filtration, neutralization and adsorption of medium temperature exhaust gas 66 by noticed combustion to lose weight was decreased gradually (step S _29), the flue base If the temperature falls below 130 ° C. (step S ₃₀ ), the bypass operation is switched to the bypass operation by opening the bypass damper 78 d and the auxiliary exhaust gas damper 76 d and the auxiliary clean gas damper 77 d (step S ₃₁ ), and the low-temperature gas 68 is released. To prevent adverse effects on dust removal equipment.

Thereafter, in order to treat the middle-temperature exhaust gas 66, the pre-coat layer and the collected ash of the sub-bag filter 5 in which the content of dioxins is increased are removed to form the sub-collected ash 93, and the collected ash transfer mechanism Switching means 57 switched to 58 side
Is stored on the collected ash transfer mechanism 58 (step _S32 ), and the entire operation is completed.

The incinerator 1 and the reburning chamber 2 in this description
The shape of the gas degassing equipment 3 is not limited to the shape shown in FIG.
Although one damper is provided on both the flue side and the clean duct side, one of them may be omitted.

Although the method of forming the chemical layer has been described in all of the precoat method, the exhaust gas entrainment method may be employed during the normal operation, and the cleaning operation in steps S ₂₇ and S ₃₂ in FIG. Not only at the end, but also before passing the gas on the next day, it has been described that the transfer air 69 of each medicine sucks the normal temperature air. However, a part of the clean gas 65 may be branched and sucked.

[0081]

As described above, according to the present invention, a method in which a sub-bag filter is used only when a large amount of dioxins are generated, and both a main and sub bag filter is used in a period where a small amount of dioxins is generated. Therefore, equipment costs can be reduced as compared with the conventional two-stage configuration type.

The secondary trapping ash containing a large amount of dioxins is thermally decomposed in a reburning chamber, and the fly ash treatment device is used to process only fly ash containing a small amount of dioxins during normal operation. In addition, the equipment is not only simplified, but also there is no need to separately install a desorption / regeneration facility for collected ash or a heavy metal processing apparatus.

Furthermore, the secondary trapping ash of the secondary bag filter at the time of startup and shutdown, which has a high risk of generating dioxins, is not only thermally decomposed in the reburning chamber but also reduced in gas when the combustion in the incinerator is stabilized. Danger of re-synthesis of dioxins by installing a heat exchanger group such as an air preheater for high temperature and an air heater for preventing white smoke, and a water injection type gas cooling chamber in the configuration of the heating equipment. Because the temperature range is avoided, the dioxin content at the entrance of the dust removal device is greatly reduced, and the emission of dioxins can be reduced by using a small amount of carbon-based adsorbent.

In addition, damage to the bag filter due to adsorption treatment of high-concentration dioxins and low-temperature corrosion and deliquescent phenomenon are as follows.
It is limited to only small-capacity sub-bag filters, and large-capacity main bag filters are on the safe side, so that repair work costs can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an outline of a non-continuous combustion type refuse incineration facility provided with a measure against dioxins according to the present invention.

FIG. 2 is a schematic flow diagram mainly showing flows of gas, air, fly ash, and water in an incineration facility.

FIG. 3 is a chart showing a temperature raising and start-up process.

FIG. 4 is a chart showing a normal operation process.

FIG. 5 is a chart showing a falling-down process.

FIG. 6 is a diagram showing an outline of a conventional incinerator bag filter used as a bypass measure during a start-up operation.

FIG. 7 is an exhaust gas treatment process diagram showing a typical example of a conventional exhaust gas treatment method for removing dioxins.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Incinerator 2 Reburning chamber 3 Gas de-heating equipment 31 Air preheater 32 Heat exchanger group 33 Gas cooling chamber 4 Main bag filter 5 Secondary bag filter 53 Discharge means 57 Switching means 82 Agent for neutralizing acidic harmful gas (in harmful gas 84) Carbon-based adsorbent

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F23J 15/06 F23J 15/00 K

Claims (4)

[Claims] When incinerating garbage such as general waste and industrial waste, exhaust gas discharged from a non-continuous combustion type incinerator that is closed every day for a predetermined time is supplied to a reburning chamber and a gas cooling facility. Guided through the bag filter, the harmful gas neutralizing agent and the carbon-based adsorbent supplied to the bag filter, filter and neutralize and adsorb soot and acidic harmful gases and dioxins contained in the exhaust gas. In the non-continuous combustion type waste incineration facility configured to remove, the bag filter includes a sub-bag filter that is also used during start-up / down and during normal operation, and a normal operation having a larger capacity than the sub-bag filter. And a discharge means for discharging the collected ash of the sub-bag filter is connected to the reburning chamber via a switching means and a collected ash transfer mechanism. Dioxins reduction apparatus of continued combustion waste incineration facility. 2. The gas de-heating apparatus is provided with a heat exchanger group such as a high-temperature air preheater and a white smoke prevention air heater, and a water injection gas cooling chamber after the heat exchanger group. The apparatus for reducing dioxins in a non-continuous combustion type waste incineration plant according to claim 1, wherein: 3. When incinerating waste such as municipal waste and industrial waste, exhaust gas discharged from a non-continuous combustion type incinerator that is closed every day for a predetermined time is supplied to a reburning chamber and a gas de-heating facility. A method for reducing dioxins in a non-continuous combustion type waste incineration facility configured to remove, by filtering, neutralizing and adsorbing, harmful gases and dioxins supplied to the bag filter through a bag filter. At the time of start-up and shut-down by the discontinuous combustion type waste incineration facility, exhaust gas is introduced and processed only in the auxiliary bag filter, and the collected ash during the period is returned to the reburning chamber, and unburned During the normal operation, exhaust gas is processed by the main bag filter and the auxiliary bag filter, and the collected ash from both bag filters is sent to the fly ash treatment device. And stable Dioxins method of reducing non-continuous combustion type waste incineration plants, which comprises carrying out the process. 4. A carbon-based adsorbent necessary for adsorbing dioxins generated during the start-up / fall-down operation before the start-up / fall-down operation, The method for reducing dioxins in a non-continuous combustion type waste incineration plant according to claim 3, wherein the method is pre-coated with a gas neutralizing agent.