JP3091197B1 - Method and apparatus for reducing dioxins in garbage gasification and melting equipment with char separation method - Google Patents

Abstract

An object of the present invention is to reduce the amount of dioxins in fly ash and exhaust gas and improve the slag conversion rate of ash in a char separation type refuse gasification and melting apparatus. SOLUTION: By connecting a melting furnace 30 and a dedicated cooling tower 52 via a melting furnace exhaust gas conduit 36a, an exhaust gas from the melting furnace 30 is introduced into the cooling tower 52, cooled, and then cooled. While adding lime to the exhaust gas, it is introduced into the third bag filter 56 to remove the acidic gas components in the exhaust gas, and the dust having a low chloride concentration captured by the first bag filter 21 and captured by the cooling tower 22. The dust having a low chloride concentration is recycled to the melting furnace 30 and melted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to solid combustibles (hereinafter referred to as municipal solid waste, industrial waste, solid waste fuel (RDF), etc.).
(Collectively called garbage) is gasified in a gasifier (partial combustion)
Then, an unburned gas (pyrolysis gas) containing char (unburned carbon) and ash is introduced into a solid-gas separator to be separated into solid and gas, and the separated unburned gas is introduced into an unburned gas-fired boiler and separated. And equipment for reducing dioxins in fly ash and flue gas in a char separation type refuse gasification / melting system that introduces char and ash into a melting furnace. In a char separation garbage gasification and melting system, the cooled exhaust gas is introduced into a dedicated dust collector, and the dust collected by the dust collector is treated as managed waste. The present invention relates to a method and an apparatus for reducing dioxins.

[0002]

2. Description of the Related Art Conventionally, a garbage gasifying and melting apparatus using a char separation method is already known (for example, Japanese Patent No. 28954).
See No. 69 (especially FIG. 10). FIG. 3 shows an example of a conventional char separation type waste gasification and melting apparatus.
The refuse introduced into the fluidized-bed gasification furnace (partial combustion furnace) 10 partially burns at a low air ratio (for example, 0.15 to 0.4, desirably 0.2 to 0.3) and generates unburned gas. (Pyrolysis gas) and unburned ash containing char (unburned carbon). Unburned gas including unburned ash (char and ash) is separated from the freeboard 12 of the gasifier 10 by a solid-gas separator, for example,
It is introduced into the cyclone 14 and separated into unburned gas and unburned ash.

[0003] The separated unburned gas is introduced into an unburned gas combustion boiler 16 and burns to generate steam (steam). Then, the exhaust gas from the boiler 16 is introduced into an air preheater 18 to preheat the air. Exhaust gas from the air preheater 18 as combustion air and fluidized air is introduced into the cooling tower 20 and cooled. And after activated carbon and / or lime (for example, slaked lime) is added to the exhaust gas cooled by the cooling tower 20,
This exhaust gas is introduced into the bag filter 23, and when harmful components in the exhaust gas, for example, activated carbon and lime are added, acidic gas components such as dioxins and hydrogen chloride / sulfur oxide in the exhaust gas are removed. 24 is a superheater, 26 is a superheater or evaporator, and 28 is an evaporator.

[0004] The unburned ash (char and ash) separated by the cyclone 14 is introduced into the swirling melting furnace 30 to burn the char, and the ash is melted to form slag. 32 is a water tank. The mixture of fluidized medium (eg, sand), ash, and large incombustibles discharged from the bottom of the fluidized bed gasifier 10 is introduced into a classifier 34 such as a vibrating sieve, and the large incombustibles and ash are removed from the system. It is withdrawn and the fluid medium is recycled.

In the conventional char separation type waste gasification and melting apparatus shown in FIG. 3, in order to recover the sensible heat of the high temperature (for example, 1300 to 1400 ° C.) exhaust gas from the melting furnace 30, a melting furnace exhaust gas conduit 36 is provided. Is connected to the boiler 16. In this case, CaCl ₂ ,
Since fly ash containing a high concentration of chlorides such as KCl and NaCl and high concentration of hydrogen chloride are contained, chloride coating and corrosion of a heat transfer tube occur. Therefore, in order to prevent high-temperature corrosion of the superheater 24 in particular, the melting furnace exhaust gas conduit 36 is connected to the downstream side of the superheater 24.

The conventional char separation type waste gasification and melting apparatus shown in FIG. 3 has the following advantages. (1) Since a fixed amount of char is supplied to the swirling melting furnace, stable melting operation can be performed. The lower calorific value of the char is usually 2,500 to 30, since all the water is separated to the unburned gas side.
It is relatively high at about 00 kcal / kg, and when the throughput of the furnace is increased to some extent, the ash can be melted using the combustion heat of the char. That is, self-heating can be performed. (2) By connecting the melting furnace exhaust gas conduit 36 to the downstream side of the superheater 24, the concentration of hydrogen chloride in the gas around the superheater is reduced, and the superheater outlet steam temperature can be set higher than before, thereby improving power generation efficiency. I do. (3) Since the total air ratio is as small as about 1.3 (the total air ratio when a normal combustion furnace is used without using a gasifier is 1.
8 or more), the amount of exhaust gas is reduced, and each device and piping can be made small and compact.

[0007]

However, in the configuration of the conventional char separation type waste gasification and melting apparatus shown in FIG. 3, the low temperature section of the boiler 16 and the inside of the air preheater 18 are known as the synthesis temperature of dioxins. 600-200 ° C
(Especially 500 to 300 ° C) and CaCl ₂ , KC
Since the chlorides such as 1 and NaCl have a high concentration and are melted and pass through in a state of high adhesion, the chlorides are unburned in the low-temperature portion of the boiler 16 and the heat transfer tubes and wall surfaces in the air preheater 18. It adheres and accumulates together with powders of copper, iron, etc., which are said to be catalysts for the production of substances and dioxins. The fact that dioxins are produced by the contact between the deposits and the exhaust gas containing hydrogen chloride for a sufficiently long time, because the concentration of dioxins at the furnace outlet in this temperature range becomes several times to several tens times, It is easily inferred and is a known fact. That is, it is widely known that dioxins are not instantaneously synthesized in exhaust gas, but are generated over a relatively long time in ash due to contact between exhaust gas and ash.

[0008] The exhaust gas discharged from the melting furnace 30 is a dirty gas from which a large amount of chloride precipitates when the hydrogen chloride concentration is high and the temperature decreases, although the gas amount is as small as about 10% of the total gas amount. is there. Therefore, when this melting furnace exhaust gas is introduced into the boiler 16 as shown in FIG. 3, there is a problem that dioxins are generated as described above. Further, in FIG. 3, dust trapped by the bag filter 23 and dust trapped by the cooling tower 20 have a high chloride concentration and are discarded. In this case, there is a problem that the slag conversion ratio of the ash becomes small. In order to increase the slag conversion rate of the ash, it is conceivable to recycle the dust to the melting furnace 30. In this case, however, a trouble in the dust transfer system (recycling system), the melting furnace 30, and the melting furnace exhaust gas conduit (duct) ) 36, boiler 16, air preheater 18,
Coating and corrosion troubles in the cooling tower 20, the exhaust gas duct at the boiler outlet, the exhaust gas duct at the air preheater outlet, the exhaust gas duct at the cooling tower outlet, and the like are more likely to occur.

The present invention has been made based on the above findings and has been made to solve the above-mentioned problems. An object of the present invention is to reduce contaminated gas discharged from a melting furnace by about 10% of the total gas. Introduced from the surface to a dedicated cooling tower (reducing tower), avoiding sharing the cooling tower for unburned gas combustion boiler exhaust gas occupying about 90% of the total gas amount, high HCl concentration,
And quenching the melting furnace exhaust gas containing fly ash containing a high concentration of chloride in the cooling tower below the synthesis temperature of dioxins,
Since the melting furnace exhaust gas cooled by the cooling tower contains fly ash with a high chloride concentration, this gas is introduced into a special dust collector (for example, a bag filter), and the collected dust is treated as managed waste. Accordingly, it is an object of the present invention to provide a method and an apparatus capable of reducing the generation of dioxins in fly ash and exhaust gas while suppressing the generation of dioxins in the exhaust gas system.

[0010] Another object of the present invention is to introduce an exhaust gas containing ash having a low chloride concentration, which is generated from an unburned gas combustion boiler, to another dust collector, and collect the collected dust in a cooling tower. Provided is a method and an apparatus for reducing dioxins in which slag is improved by recycling slag by recycling only dust collected by a dust collector together with waste dust to a melting furnace. Is to do.

[0011]

In order to achieve the above object, a method for reducing dioxins in a char separation type refuse gasification and melting apparatus according to the present invention is to supply refuse to a gasification furnace to gasify the refuse. The unburned gas containing char and ash was introduced from the gasifier into the solid-gas separator to separate it into solid and gas, and the solid-gas separated unburned gas was introduced into the unburned gas combustion boiler and burned to generate steam. Later, the exhaust gas from the boiler is introduced into the air preheater to preheat the air, the exhaust gas from the air preheater is introduced into the cooling tower and cooled, and then the cooled exhaust gas is sent to the first dust collector. After collecting the dust in the exhaust gas, the ash is added to the exhaust gas from the first dust collector and then introduced into the second dust collector while adding lime to remove the acidic gas component in the exhaust gas. 2 Exhaust gas from the dust collector is exhausted by an unburned gas combustion boiler induction fan. On the other hand, the char and ash separated into solid and gas are introduced into a melting furnace to burn the char and melt the ash into slag, and the exhaust gas from the melting furnace is introduced into a cooling tower to be cooled, and then cooled. While adding lime to the exhaust gas, the exhaust gas is introduced into a third dust collector to remove an acid gas component in the exhaust gas, and is disposed upstream (in front of) the first dust collector or / and the first dust collector and the second dust collector. Activated carbon is added to an exhaust gas conduit between the dust collector and the exhaust device to reduce dioxins (see FIGS. 1 and 2).

In this method, the dust having a low chloride concentration captured by the first dust collector or the dust having a low chloride concentration captured by the first dust collector and the cooling tower is supplied to the melting furnace (recycle). ) To be melted (FIG. 1,
(See FIG. 2). Thus, by recycling dust, the slag conversion rate of ash can be increased. Also,
The exhaust gas from the third dust collector is combined with the exhaust gas from the second dust collector and discharged by an unburned gas combustion boiler induction fan (see FIG. 1), or the exhaust gas from the third dust collector is melted by a melting furnace. The exhaust gas from the second dust collector can be configured to be discharged by an independent exhaust gas system separate from the exhaust gas from the second dust collector (see FIG. 2). In the latter case, there is an advantage that the furnace pressure of the melting furnace does not fluctuate and stable operation becomes possible. Activated carbon may be added to the upstream side (front side) of the third dust collector.

An apparatus for reducing dioxins in a char separation type refuse gasification / melting apparatus according to the present invention includes a gasification furnace for gasifying refuse in a reducing atmosphere, and a solid-gas separation connected to a gas outlet of the gasification furnace. Gas-fired boiler connected to the wake of the solid-gas separator via an unburned gas conduit, an air preheater connected to the boiler via an exhaust gas conduit, and an air preheater. A cooling tower connected via an exhaust gas conduit, a first dust collector connected to the cooling tower via a cooling exhaust gas pipe, and a first dust collector connected to the first dust collector via an exhaust gas pipe A second dust collector; lime supply means for adding lime connected to an exhaust gas conduit from the first dust collector;
An induction fan for an unburned gas combustion boiler provided downstream of the dust collector, and an exhaust gas upstream (in front of) the first dust collector or / and between the first dust collector and the second dust collector. A char separation type refuse gasification / melting apparatus comprising: activated carbon supply means provided in a conduit; and a melting furnace connected to a lower part of the solid-gas separator through a char / ash conveying means. A cooling tower is connected via a melting furnace exhaust gas conduit, a third dust collector is connected to the cooling tower via a cooling exhaust gas conduit, and lime supply means is connected to the cooling exhaust gas conduit. (See FIGS. 1 and 2).

In this apparatus, it is preferable that the bottom of the first dust collector, or the bottom of the first dust collector and the bottom of the cooling tower, and the melting furnace are connected via a dust recycling pipe ( 1 and 2). Further, the exhaust gas conduit from the third dust collector may be combined with the exhaust gas conduit from the second dust collector upstream of the induction fan for the unburned gas combustion boiler (see FIG. 1), or the third dust collector may be used. An exhaust fan for the melting furnace is provided in the exhaust gas conduit from the vessel, and the exhaust gas from the third dust collector is discharged by an independent exhaust gas system separate from the exhaust gas from the second dust collector. (See FIG. 2). In some cases, activated carbon supply means is provided upstream (in front of) the third dust collector. In the above configuration, it is preferable that the gasification furnace be a fluidized bed gasification furnace, the melting furnace be a rotary melting furnace, and the first dust collector, the second dust collector, and the third dust collector be bag filters.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments and can be implemented with appropriate modifications. FIG. 1 shows an apparatus for reducing dioxins in a char separation type waste gasification and melting apparatus according to a first embodiment of the present invention. In the present embodiment, a fluidized-bed gasification furnace is used as the gasification furnace, a swirling melting furnace is used as the melting furnace,
Although the case where a bag filter is used as the dust collector, the second dust collector and the third dust collector is shown, other types of gasifiers,
It is also possible to use a melting furnace and a dust collector.

Reference numeral 10 denotes a fluidized-bed gasifier, and the gasifier 1
The solid-gas separator, for example, a cyclone 14 is connected to the free board 12. The fluidized-bed gasifier 10 is shown in FIG.
Although a diffuser type is shown in FIG. 1, it is of course possible to use an air distribution plate type. An unburned gas combustion boiler 16 is connected to the upper part (the downstream side) of the cyclone 14 via an unburned gas conduit 38, and an air preheater 18 is connected to the boiler 16 via an exhaust gas conduit 40. The cooling tower 22 is connected to 18 via an exhaust gas conduit 42. As the cooling tower 22, for example, a type that sprays water is used. The first bag filter 2 is connected to the cooling tower 22 through a cooling exhaust pipe 43.
Activated carbon supply means 78 for adding activated carbon (or activated coke) is connected to the temperature-reduced exhaust gas conduit 43. Further, the second bag filter 23 is connected to the first bag filter 21 via an exhaust gas conduit 80, and the activated carbon supply means 82 and the lime supply means 84 are connected to the exhaust gas conduit 80. Further, an unburned gas combustion boiler induction fan 49 is provided in the exhaust gas conduit 47 downstream of the second bag filter 23.

The swirl melting furnace 30 is connected to the lower part of the cyclone 14 via a char / ash conveying means 44, for example, a pipe provided with a discharger such as a rotary feeder. The swirling melting furnace 30 includes a substantially vertical pre-combustion section 46 for supplying char and ash, combustion air and, if necessary, an auxiliary fuel for pre-combustion, and the pre-combustion section 46 is connected in a tangential direction and substantially connected. A substantially cylindrical swirl melting part 48 installed in a horizontal direction,
It comprises a substantially vertical reburning section 50 connected to the swirling / melting section 48 and a slag cooling water tank 32 connected to the lower surface of the swirling / melting section 48 via a slag flow outlet.

A cooling tower 52 is connected to the reburning section 50 of the swirling melting furnace 30 through a melting furnace exhaust gas conduit 36a, and a third bag filter 56 is connected to the cooling tower 52 through a cooling exhaust gas conduit 54. A lime supply unit 58 for adding lime (eg, slaked lime) to the exhaust gas is connected to the cooling exhaust gas conduit 54. In some cases, activated carbon (or activated coke) may be added by providing activated carbon supply means 86. As the cooling tower 52, for example, a type that sprays water is used as in the case of the cooling tower 22.

Dust extraction pipe 60 from the bottom of cooling tower 22
The dust extraction pipe 88 from the bottom of the first bag filter 21 joins and is connected to the dust recycling pipe 64, and the dust recycling pipe 64 is connected to the pre-combustion section 46 of the rotary melting furnace 30. A dust extraction pipe 62 from the bottom of the second bag filter 23 is for extracting dust to the outside of the system. Further, the exhaust gas conduit 66 from the third bag filter 56 joins with the exhaust gas conduit 47 from the second bag filter 23, and the combined exhaust gas conduit 68 is connected to the unburned gas combustion boiler induction fan 49. Further, the dust extraction pipe 70 from the bottom of the cooling tower 52 and the third
A dust extraction pipe 72 from the bottom of the bag filter 56 is connected to a dust extraction pipe 74.

Next, the operation of the apparatus shown in FIG. 1 will be described. The refuse introduced into the fluidized-bed gasification furnace (partial combustion furnace) 10 partially burns at a low air ratio (for example, 0.15 to 0.4, desirably 0.2 to 0.3) and generates unburned gas. (Pyrolysis gas) and unburned ash containing char (unburned carbon). Unburned gas containing unburned ash (char and ash)
The gas is introduced into the cyclone 14 from the free board 12 of the gasifier 10 and separated into unburned gas and unburned ash. At this time,
Most of the chlorine content in the refuse (for example, 70 to 80 wt%) is converted into chlorides such as CaCl ₂ , KCl, and NaCl, contained in the ash, and separated from the lower part of the cyclone 14. In the unburned gas separated from the upper part of the cyclone 14, the remaining chlorine (eg, 20 to 30% by weight) in the refuse is included as chloride in the fly ash and HCl gas.

The separated unburned gas is supplied to an unburned gas conduit 38.
After passing through the unburned gas combustion boiler 16 and burning to generate steam (steam), the exhaust gas from the boiler 16 is introduced into the air preheater 18 through the exhaust gas conduit 40 to preheat the air. Exhaust gas from the air preheater 18 as combustion air and fluidized air is introduced into the cooling tower 22 through an exhaust gas conduit 42 and cooled. Then, after the activated carbon is added to the exhaust gas cooled in the cooling tower 22, the exhaust gas is introduced into the first bag filter 21, and dioxins in the exhaust gas are removed by the activated carbon. After activated carbon and lime (eg, slaked lime) are added to the exhaust gas from the first bag filter 21, the exhaust gas is introduced into the second bag filter 23, and dioxins in the exhaust gas are activated by the activated carbon, and chloride in the exhaust gas is activated by the lime. Acid gas components such as hydrogen and sulfur oxides are removed. Second bag filter 23
Purified exhaust gas from unburned gas combustion boiler induction fan 4
9 leads to the chimney. 24 is a superheater, 26 is a superheater or evaporator, and 28 is an evaporator. The air preheater 1
A part of the air preheated in 8 is supplied as fluidized air to the diffuser pipe of the fluidized bed gasifier 10, and the rest of the preheated air is used as combustion air in the pre-combustion unit 4 of the swirling melting furnace 30.
6. It is supplied to the reburn unit 50 and the boiler 16. Also,
The mixture of fluidized medium (eg, sand), ash, and large incombustibles discharged from the bottom of the fluidized bed gasifier 10 is introduced into a classifier 34 such as a vibrating sieve, and the large incombustibles and ash are removed from the system. The withdrawn fluid medium (eg, sand) is recycled.
The dust trapped by the cooling tower 22 and the first bag filter 21 has a low chloride concentration, and is recycled to the swirling melting furnace 30 by the dust recycling pipe 64 for melting treatment.
In the melting furnace 30, unburned components in the dust burn, and the dioxins are decomposed at a high temperature. The dust captured by the second bag filter 23 is discharged out of the system because it contains a high concentration of chloride and unreacted lime.

The unburned ash (char and ash) separated by the cyclone 14, the dust from the cooling tower 22 and the dust from the first bag filter 21 are supplied to the pre-combustion section 46 of the swirling melting furnace 30 by the combustion air. , Optionally with supplemental fuel, where most of the char is burned. Pre-combustion unit 4
The pre-combustion gas from 6 is introduced tangentially into the substantially cylindrical swirl / melt section 48, and a portion of the remaining char adheres to the peripheral wall and is captured and burned. Most of the ash (for example, 80
(About 90 wt%) is melted and turned into slag, which falls into the water tank 32 from the swirling melting portion 48, is cooled and turned into water-cooled slag, and is taken out by a discharger such as a conveyor. Exhaust gas from the swirling / melting unit 48 is introduced into the reburning unit 50, where air necessary for combustion is additionally supplied to complete combustion.

Since the inside of the swirling melting section 48 of the swirling melting furnace 30 is at a high temperature (for example, 1300 to 1400 ° C.), chlorides such as CaCl ₂ , KCl, and NaCl contained in the ash are decomposed to chlorine. The portion becomes HCl gas and moves into the exhaust gas. Therefore, the slag contains no chlorine or a trace amount of chlorine. As described above, high-concentration HCl is contained in the exhaust gas of the melting furnace, and ash that has not been slagged (for example, 10 to 20% by weight of the ash introduced into the swirling melting section 48) is fly ash. Included. When the gas temperature decreases, HCl reacts with Ca, K, Na and the like in fly ash, and CaCl ₂ , KCl,
Chloride such as NaCl is produced.

The melting furnace exhaust gas containing high concentration HCl and fly ash containing high concentration chloride is supplied to the melting furnace exhaust gas conduit 3.
6a, into the cooling tower 52, quenching the exhaust gas from the melting furnace by means of water spraying, etc. to melt the chloride, thereby increasing the adhesiveness and the dioxin generation temperature.
Rapidly pass through a temperature range of 200 ° C (especially 500 to 300 ° C).

After lime (eg, slaked lime) is added to the exhaust gas cooled by the cooling tower 52, the exhaust gas
Introduced to bag filter 56, hydrogen chloride in exhaust gas
Acid gas components such as sulfur oxides are removed. In addition, since a trace amount of dioxins may be generated, activated carbon (or activated coke) may be supplied simultaneously with lime for this measure. This makes it possible to effectively suppress the generation of dioxins in a flue gas treatment system containing a fly ash having a high HCl concentration and a high chloride content. Therefore, dioxins in dust (fly ash) captured by the cooling tower 52 and dust (including fly ash) captured by the third bag filter 56 can be reduced, and the third bag filter 56 Dioxins in exhaust gas from wastewater can be reduced.

The purified exhaust gas from the third bag filter 56 is sent together with the purified exhaust gas from the second bag filter 23 to the chimney by the unburned gas combustion boiler induction fan 49. Since the chloride concentration of the dust captured by the cooling tower 52 and the third bag filter 56 is high, these dusts are treated as controlled waste. The dioxins in the exhaust gas discharged from the cooling tower 22 are adsorbed by the activated carbon charged in front of the first bag filter 21, and
It is also adsorbed and / or adhered to dust and collected by the first bag filter 21. The activated carbon to which the dioxins are adsorbed and the dust to which the dioxins are adsorbed or / and adhered are introduced into the melting furnace 30 and adsorbed or / or adsorbed by high-temperature combustion.
And the attached dioxins are completely decomposed. Therefore, as a whole system, dioxins can be reliably reduced and removed. Activated carbon is charged before the first bag filter 21 or the second bag filter 23.
, Or both.

FIG. 2 shows a dioxin reducing device in a char separation type refuse gasification and melting apparatus according to a second embodiment of the present invention. In the first embodiment shown in FIG. 1, the exhaust gas from the melting furnace that has exited the dedicated cooling tower 52 passes through a dedicated third bag filter 56, and is shared with the exhaust gas from the unburned gas combustion boiler 16 by an induction fan. It is led to the chimney via 49. Regarding the induction fan 49 for the unburned gas combustion boiler, since the furnace pressure of the gasification furnace (partial combustion furnace) 10 into which the refuse is charged fluctuates with the fluctuation of the refuse input amount, The induction fan 49 is controlled to suppress fluctuations in the furnace pressure of the gasification furnace 10. If the induction fan 49 for the gasification furnace 10 and the unburned gas combustion boiler 16 is also used as a fan for the melting furnace 30, when the supply amount of refuse changes, the rotation speed of the induction fan 49 changes and the melting furnace The pressure in 30 fluctuates, causing disturbances in operating stability. In order to prevent this, in the present embodiment, as shown in FIG. 2, after the exhaust gas of the melting furnace 30 is passed through a dedicated third bag filter 56, an induction fan 76 for the melting furnace is provided, and the gasification furnace is provided. The exhaust gas of the fuel cell 10 and the unburned gas combustion boiler 16 is configured to be guided to a chimney by an exhaust gas system independent of the exhaust gas. Other configurations and operations are the same as those in the first embodiment.

[0028]

As described above, the present invention has the following effects. (1) High HCl concentration, CaCl ₂ , KC
1, Exhaust gas from the melting furnace containing fly ash containing high concentrations of chlorides such as NaCl is introduced into the boiler, air preheater, cooling tower, first dust collector and second dust collector without using it. After being introduced into a cooling tower and cooled, lime is added and treated by a dedicated third dust collector, so that the chloride concentration in the ash is high and the molten fly ash with high adhesion is provided. Is prevented from creating an environment (atmosphere) where dioxins are easily synthesized by depositing and accumulating on heat transfer tubes and wall surfaces in boilers and air preheaters, so that dioxins in fly ash and exhaust gas can be reduced. Reduction can be achieved. (2) As described in (1) above, since chloride coating in the boiler and the air preheater is suppressed, troubles such as clogging of the equipment and reduction in the amount of heat recovery are reduced, and stable operation is continued. Can be. (3) As described in (1) above, the melting furnace exhaust gas was introduced into a dedicated cooling tower without being introduced into a boiler, an air preheater, a cooling tower, a first dust collector and a second dust collector. After that, since the treatment is performed by the dedicated third dust collector, it is possible to reduce the corrosion caused by hydrogen chloride in the boiler, the air preheater, and the like. (4) The ash slag conversion rate can be increased by recycling the dust captured by the cooling tower and the first dust collector to the melting furnace. In this case, since the chloride concentration of the dust to be recycled is low, troubles in the dust transport system and coating / corrosion troubles in the melting furnace, duct, and cooling tower are minor, and there is little ash adhesion. In addition, generation of dioxins is suppressed, leading to improvement in maintainability. (5) Since dust adsorbing and / or adhering dioxins captured by the first dust collector is supplied to the melting furnace,
Dioxins are completely thermally decomposed by high-temperature combustion in a melting furnace, and dioxins can be reliably reduced as a whole system. In particular, when activated carbon is added upstream (in front of) the first dust collector, activated carbon adsorbing dioxins and dust adsorbing or / and adhering dioxins are captured and supplied to the melting furnace, and the high temperature is supplied to the melting furnace. Since dioxins are completely thermally decomposed by combustion, dioxins can be more reliably reduced as a whole system. (6) Since the melting furnace exhaust gas containing high concentration HCl and fly ash containing high concentration chloride is introduced into the cooling tower and cooled, the generation of dioxins is suppressed. (7) When an induction fan for the melting furnace is installed to make the exhaust gas system independent of the exhaust gas from the gasifier and the unburned gas combustion boiler, mutual interference is eliminated, and the furnace pressure in the melting furnace does not fluctuate and is stable. Operation is possible.

[Brief description of the drawings]

FIG. 1 is a systematic schematic configuration diagram of a dioxin reducing device in a char separation type waste gasification / melting device according to a first embodiment of the present invention.

FIG. 2 is a systematic schematic configuration diagram of an apparatus for reducing dioxins in a char separation type waste gasification / melting apparatus according to a second embodiment of the present invention.

FIG. 3 is a systematic schematic configuration diagram showing an example of a conventional char separation type waste gasification and melting apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Fluidized bed gasifier 12 Free board 14 Cyclone 16 Unburned gas combustion boiler 18 Air preheater 20, 22 Cooling tower 21 First bag filter 23 Second bag filter 24 Superheater 26 Superheater or evaporator 28 Evaporator 30 Swirling melting furnace 32 Water tank 34 Classifier 36, 36a Melting furnace exhaust gas conduit 38 Unburned gas conduit 40 Exhaust gas conduit from boiler 42 Exhaust gas conduit from air preheater 43 Reduced temperature exhaust gas conduit 44 Char / ash conveying means 46 Pre-combustion unit 47 Exhaust gas conduit from second bag filter 48 Swirling / melting unit 49 Induction fan for unburned gas combustion boiler 50 Reburning unit 52 Cooling tower 54 Cooling exhaust gas conduit 56 Third bag filter 58, 84 Lime supply means 60, 62, 70, 72, 88 Dust extraction pipe 64 Dust recycling pipe 66 Third bag filter Exhaust gas conduit 74 dust out of the system discharge pipe 76 melting furnace for induction fan 78,82,86 activated carbon supply means 80 exhaust gas conduit from the first bag filter

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-11-267456 (JP, A) JP-A-11-30411 (JP, A) JP-A-11-281021 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) F23J 15/00 B09B 3/00 302 F23G 5/027 F23G 5/16 F23J 1/00

Claims (11)

(57) [Claims] Claims: 1. Waste is supplied to a gasification furnace to be gasified,
The unburned gas containing char and ash was introduced from the gasifier into the solid-gas separator to separate it into solid and gas, and the solid-gas separated unburned gas was introduced into the unburned gas combustion boiler and burned to generate steam. Later, the exhaust gas from the boiler is introduced into the air preheater to preheat the air, the exhaust gas from the air preheater is introduced into the cooling tower and cooled, and then the cooled exhaust gas is sent to the first dust collector. After collecting the dust in the exhaust gas, the ash is added to the exhaust gas from the first dust collector and then introduced into the second dust collector while adding lime to remove the acidic gas component in the exhaust gas. 2 The exhaust gas from the dust collector is discharged by an unburned gas combustion boiler induction fan, and the char and ash separated into solid and gas are introduced into a melting furnace to burn the char and melt the ash into slag, which is then melted. The exhaust gas from the furnace is introduced into the cooling tower for cooling, and then the cooled exhaust gas is discharged. While adding lime to the waste gas, it is introduced into the third dust collector to remove the acidic gas component in the exhaust gas, and the upstream side of the first dust collector or / and the first dust collector and the second dust collector are connected to each other. A method for reducing dioxins in a char separation type refuse gasification / melting apparatus, characterized in that activated carbon is added to an exhaust gas pipe between the two to reduce dioxins. 2. The char separation refuse gas according to claim 1, wherein the dust captured by the first dust collector or the dust captured by the first dust collector and the cooling tower is supplied to a melting furnace to be melted. A method for reducing dioxins in a chemical melting device. 3. The gas separation method according to claim 1, wherein the exhaust gas from the third dust collector is combined with the exhaust gas from the second dust collector and discharged by an induction fan for an unburned gas combustion boiler. A method for reducing dioxins in a melting device. 4. The char separation system according to claim 1, wherein the exhaust gas from the third dust collector is discharged by an induction fan for the melting furnace in an independent exhaust gas system separate from the exhaust gas from the second dust collector. A method for reducing dioxins in waste gasification and melting equipment. 5. The method for reducing dioxins in a char separation type refuse gasification / melting apparatus according to claim 1, wherein activated carbon is added upstream of the third dust collector. 6. A gasifier for gasifying refuse in a reducing atmosphere, a solid-gas separator connected to a gas outlet of the gasifier, and an unburned gas conduit downstream of the solid-gas separator. An unburned gas-fired boiler connected through an air preheater connected to the boiler via an exhaust gas conduit, a cooling tower connected to the air preheater via an exhaust gas pipe, and the cooling tower A first dust collector connected to the first dust collector via an exhaust gas conduit, a second dust collector connected to the first dust collector via an exhaust gas conduit, and an exhaust gas conduit from the first dust collector. Lime supply means for adding lime connected thereto, an unburned gas combustion boiler induction fan provided downstream of the second dust collector, and an upstream side of the first dust collector and / or the first dust collector Activated carbon supply means provided in an exhaust gas conduit between the air and the second dust collector; And a melting furnace connected through a means. A char separation type refuse gasification / melting apparatus, comprising: a cooling tower connected to the melting furnace via a melting furnace exhaust gas pipe; 3. A dioxin reducing apparatus in a char separation type refuse gasification / melting apparatus, wherein a third dust collector is connected to the cooling gas exhaust pipe, and lime supply means is connected to the cooling exhaust pipe. 7. The char separation type refuse according to claim 6, wherein the bottom of the first dust collector, or the bottom of the first dust collector, the bottom of the cooling tower, and the melting furnace are connected via a dust recycling pipe. Dioxin reduction equipment in gasification and melting equipment. 8. The char separation system according to claim 6, wherein the exhaust gas conduit from the third dust collector is joined to the exhaust gas conduit from the second dust collector upstream of the induction fan for the unburned gas combustion boiler. Equipment for reducing dioxins in waste gasification and melting equipment. 9. An exhaust fan for a melting furnace is provided in an exhaust gas conduit from the third dust collector, and the exhaust gas from the third dust collector is separated by an independent exhaust gas system separate from the exhaust gas from the second dust collector. 8. The dioxin reducing device in the char separation type refuse gasification / melting device according to claim 6 or 7, wherein the device is configured to discharge the gas. 10. The apparatus for reducing dioxins in a char separation type refuse gasification and melting apparatus according to claim 6, wherein activated carbon supply means is provided upstream of the third dust collector. 11. The gasifier is a fluidized bed gasifier, the melting furnace is a rotary melting furnace, and the first dust collector, the second dust collector, and the third dust collector are bag filters. An apparatus for reducing dioxins in a char separation type refuse gasification / melting apparatus according to any one of 6 to 10.