JPH1119618A - Melt treating device of wet ash and melt treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the drying of wet ash without use of a fresh fuel and to greatly improve the fuel cost of a wet ash melt treating device by constituting this device in such a manner that part of the high-temp. waste gases discharged from a melting furnace of a melt treating section is utilized as a heat source for drying the wet ash. SOLUTION: The wet ash 20 collected from plural small-scale refuse incineration facilities is supplied from a hopper 21 by a feeder 21b into a hot air drying machine 21 where the ash is dried. Drying is executed in this hot air drying machine 21 by the hot air from a hot stove 22 at the time of starting of the melt treating device. Part of the waste gases C1 discharged from the melting furnace 1 are used as a heat source at the time of the stationary operation of the melt treating device. The waste gases C4 discharged from the drying machine 21 are subjected to dust removal by a bag filter device 24 and are then supplied to a secondary combustion device 5. TCDDs (2,3,7,8- tetrachlorodibenzo-p-dioxins) are pyrolyzed in this device. The dry ash 20a in the drying machine 21 is ejected to the inside of an ash bunker 26 through a magnetic separator 23 and is subjected to the melt treatment in the melting furnace 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for melting wet ash discharged from an incinerator of industrial waste or municipal solid waste, and a part of high-temperature exhaust gas from the melting furnace is converted into a wet ash. Melt treatment of wet ash that can be used as a heat source for drying, and the waste gas generated during drying of the wet ash is burned in a secondary combustion device, thereby saving energy and reducing dioxins while efficiently melting the wet ash. The present invention relates to an apparatus and a melting method.

[0002]

2. Description of the Related Art In recent years, in order to reduce the volume and harmlessness of incineration residues and fly ash discharged from incinerators such as industrial waste and municipal solid waste, attention has been focused on a melting treatment method of incineration residues and the like. It has been put to practical use in waste incineration facilities of larger scale. By melting and solidifying incineration residues, etc., the volume can be reduced to 1/2 to 1/3, and at the same time, elution of harmful substances such as heavy metals can be prevented, and road materials of molten slag and concrete aggregate can be used. This is because it is possible to reuse the material and extend the life of the final landfill site.

FIG. 2 shows an example of a melting apparatus for incineration residues and fly ash attached to a conventional refuse incineration facility. The incineration residues (dry ash) discharged from the refuse incinerator 30 are shown.
After removing metals 33 such as iron through a magnetic separator 32, the 31 is carried into an ash bunker 35 of a melting processor 34. The carried incineration residue 31 is supplied into the furnace by the pusher 35b through the hopper 35a of the surface melting furnace 35, and is sequentially melted from the surface layer of the incineration residue layer by the heat of combustion of the burner 35c, and flows down as molten slag 36.

[0004] The molten slag 36 that has dropped onto the slag conveyor 37 through the slag tap 35d of the melting furnace 35 is cooled by water here to become granulated slag 38, and is discharged to the outside. The high-temperature exhaust gas 39 from the melting furnace is emitted from the chimney to the atmosphere through an air preheater 40, a gas cooling chamber 41, and a bag filter device 42.

[0005] The melting treatment of incineration residues and fly ash includes a method of melting a material to be melted by electric energy such as an arc melting furnace, a plasma arc melting furnace, an electric resistance furnace, a surface melting furnace, a rotating melting furnace, and the like. There is a method in which a material to be melted is melted by the combustion energy of a fuel such as a coke bed furnace, and both methods are practically used. Among them, a melting treatment method using a surface melting furnace is most widely used. Further, in FIG. 2, reference numeral 44 denotes an induction blower, 45 denotes a push-in blower, 46
Is a water spray port, and 47 is a neutralizing agent supply port.

By the way, refuse incineration facilities equipped with the above-mentioned melting treatment apparatus for incineration residues are mainly limited to medium-sized or larger facilities, and most small-scale refuse incineration facilities are: Even now, the incineration residue that has been discharged is landfilled. However, in recent years, it has become increasingly difficult to secure final landfill sites for incineration residues, etc. As a result, even in small-scale incineration facilities, the volume of incineration residues to be discharged has been further reduced,
There is a strong demand for detoxification and effective use.

[0007] On the other hand, in order to meet the above-mentioned demand, providing a melting treatment device in each of the small-scale incineration facilities has many problems in terms of economic efficiency. Therefore, there is a demand for a wide-area melting treatment facility that collects incineration residues and the like from a plurality of small-scale refuse incineration facilities and collects and collects them at one place.

[0008] However, in the case of the wide-area melting system, since it is not provided near the refuse incinerator unlike the conventional melting system shown in FIG. 2, incineration residues and the like are so-called dry ash. Therefore, it cannot be received by the melt processing apparatus in the form of ash, and is inevitably mixed with water or the like, and is carried in the form of wet ash for cooling and dust prevention.

It is, of course, technically possible to carry out the melting treatment of the carried wet ash as it is. But,
If the wet ash is directly melted as it is, the amount of fuel required for evaporating the water in the wet ash increases, the fuel ratio of the melting processor deteriorates, and the amount of high-temperature exhaust gas from the melting furnace increases. In addition, there is a problem that the exhaust gas treatment equipment becomes large and the equipment cost increases. Further, even when a separate dryer is provided to pre-dry the wet ash, the fuel ratio of the entire melt processing apparatus is not different from that of the direct melting processing at all, and the temperature at the time of drying the wet ash is not changed. Since the temperature range (around 300 ° C.) just overlaps the temperature range for synthesizing dioxins, there is a risk that dioxins may be produced, and there is a problem that a device for decomposing and removing these dioxins is required.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in a melt processing apparatus of a type which receives wet ash from a plurality of refuse incineration facilities. (2) that the fuel ratio of the melt processing apparatus deteriorates, and that the amount of exhaust gas increases, thereby increasing the cost of exhaust gas processing;
When the wet ash is dried as a pre-treatment, not only does the fuel ratio deteriorate, but also there is a risk that dioxins may be generated during the drying process. The present invention provides a wet ash melting apparatus and a melting method capable of efficiently melting incineration residues (moist ash) having a high water content while preventing a large increase in the amount of dioxins and the like. is there.

[0011]

According to a first aspect of the present invention, there is provided a wet ash melting processing apparatus comprising a wet ash drying processing section and a dry ash melting processing section, wherein the wet ash drying processing section includes a wet ash drying processing section. , A hot air dryer that dries wet ash by using a part of the high temperature exhaust gas from the melting furnace of the melting process as a heat source, an exhaust gas treatment device that treats the exhaust gas from the hot air dryer, and a melting process of the exhaust gas from the exhaust gas treatment device And a ventilator for supplying the secondary ash to the secondary combustion device. The melting unit for the dry ash, a melting furnace for heating and melting the dry ash from the drying unit, and a high-temperature exhaust gas from the melting furnace are discharged. High-temperature flue, reducing gas supply device for supplying reducing gas into high-temperature exhaust gas in the high-temperature flue, and secondary combustion device for burning high-temperature exhaust gas in a reducing atmosphere and exhaust gas from the hot-air dryer And high-temperature exhaust gas from the secondary combustion device A device for the temperature drop is for a basic configuration of the invention that was formed from the exhaust gas treatment apparatus for cleaning the exhaust gas from the secondary combustion apparatus moved down the temperature.

According to a second aspect of the present invention, there is provided an apparatus according to the first aspect, wherein the melting furnace is used as a surface melting furnace, the reducing gas is used as a natural gas, and the temperature of the exhaust gas from the secondary combustion device is lowered. An air preheater and a gas cooling device are provided in the secondary combustion device and a device for treating exhaust gas from the dryer is provided in the bag filter device.

According to a third aspect of the present invention, after the wet ash is dried by a dryer using high-temperature exhaust gas from the melting furnace as a heat source, the dry ash from the dryer is melted by the melting furnace. The basic structure of the present invention is to blow a reducing gas into a high-temperature exhaust gas from the furnace to make the high-temperature exhaust gas a reducing atmosphere, and to re-burn the high-temperature exhaust gas in the reducing atmosphere and the exhaust gas from the dryer in a secondary combustion device. It is assumed that.

According to a fourth aspect of the present invention, in the third aspect of the present invention, a part of the exhaust gas from the dryer is mixed into a high-temperature exhaust gas drawn from a melting furnace for a heat source of the dryer. Exhaust gas at a temperature near 600 ° C. is supplied to the dryer.

According to a fifth aspect of the present invention, in the third aspect of the present invention, the melting furnace is a surface melting furnace, the reducing gas is natural gas, and the exhaust gas from the dryer is filtered by a bag filter device. After the treatment, it is supplied to the secondary combustion device.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram showing a configuration of a wet ash melting apparatus according to an embodiment of the present invention. The melting processing apparatus is for drying incineration residues and fly ash having a high water content (hereinafter referred to as wet ash). A portion H and a melting portion M for melting wet ash after drying (hereinafter referred to as dry ash) are formed.

That is, in FIG. 1, 1 is a surface melting furnace, 2
Is a slag tap, 3 is a water seal conveyor device, 4 is a high temperature flue, 5 is a secondary combustion device, 6 is an air preheater, 7 is a gas cooling device, 8 is a bag filter device, 9 is a push blower, 10
Denotes an induction ventilator, 11 denotes a natural gas supply device, 12 denotes an auxiliary agent supply device, and 13 and 14 denote molten fly ash carry-out conveyors, and these form a melting processing section M for dry ash 20a.

In FIG. 1, reference numeral 21 denotes a hot air drier, 2
1a is a wet ash receiving hopper, 22 is a hot stove, 23 is a magnetic separator, 24 is a bag filter device, 25 is a conveyor, 26
Is an ash bunker, which forms a dry processing portion H for the wet ash 20.

Referring to FIG. 1, wet ash 20 collected from a plurality of small-scale refuse incineration facilities is supplied to wet ash receiving hopper 21a.
Is supplied into the hot-air dryer 21 by the feeder 21b through the so-called hot-air drying.
It is dried from 0% to about 5%.

The hot-air dryer 21 includes a hot-air stove 22, and the wet ash 20 is dried by hot air from the hot-air stove 22 when the melting processing apparatus is started. Further, at the time of steady operation of the melt processing apparatus, part of 1000 to 1200 ° C. in a high temperature exhaust gas C ₁ discharged from the surface melting furnace 1 to be described later is used as a heat source. That is, a part of the dryer hot exhaust gas C ₁ was pulled to 21 side by attracting blower 27c, a portion of the exhaust gas C ₄ from the dryer 21 (recycle gas)
Is supplied to the drier 21 to reduce the moisture content of the wet ash 20 to about 5% as described above. The structure of the dryer 21 may be of any type as long as it uses hot air as a heating source.

The dry ash 20a having a moisture content of about 5% discharged from the dryer 21 is converted into a metal material 28 by a known magnetic separator 23.
Is removed by the conveyor 25 together with the dust and the like from the bag filter device 24 into the ash bunker 26.

On the other hand, about 2
Exhaust gas C ₄ having a temperature of 00 ° C. is subjected to a process such as dust removal by a bag filter device 24, and a part of the exhaust gas C ₄ is recirculated to a dryer 21 by a circulating blower 27 b, and the remaining portion of the exhaust gas C ₄ is blown by a blower 27 a. It is supplied into the next combustion device 5. As a result, dioxins are contained in flue gas C ₄ becomes to be thermally decomposed at a high temperature of the secondary combustion unit within 5, dissipation to the outside of dioxins hardly occurs. In the present embodiment has used the bag filter apparatus 24 as the processing unit of the exhaust gas C ₄ from the dryer, the exhaust gas treatment device is a matter of course that may be other than the bag filter apparatus.

The dry ash 20a in the ash bunker 26 is:
It is conveyed into the hopper 1a of the surface melting furnace 1 by the conveyor 26a, and is sequentially supplied into the melting furnace 1 by the pusher 1b.

The surface melting furnace 1 has exactly the same structure as that of the conventional surface melting furnace, and melts the material (dry ash) in the melting furnace 1 by burning fuel B such as kerosene from the fuel supply device 11. 20a) is melted to form a molten slag 15.
Further, the formed molten slag 15 flows down along the surface of the layer 20a to be melted, and falls from the slag tap 2 onto the water sealing conveyor device 3 to become granulated slag 16 and is carried out to the outside. go.

That is, the fuel supply device 11 includes a supply portion 11b for reducing gas such as natural gas and a supply portion 11c for fuel B such as kerosene, and is ejected from the burner 17 in the surface melting furnace 1. fuel B is, the complete combustion by the supply of the combustion air a ₁ from the air preheater 6 (air ratio of approximately 1.1), and heating and melting the melts (Inuihai) 20a.

The high-temperature exhaust gas C ₁ generated by the combustion of the fuel B such as kerosene has a temperature of 1000 to 1200 ° C., and passes from the lower part of the melting furnace 1 through the high-temperature flue 4 to the lower part of the secondary combustion device 5. Is discharged to Further, a part of the high-temperature exhaust gas C ₁ is withdrawn from below the melting furnace 1 to be used as a heat source of the hot-air dryer 21 as described above,
Sent to the side.

This high-temperature exhaust gas C ₁ contains a relatively large amount of NOx because the combustion in the melting furnace 1 is a high-temperature combustion. When O ₂ is 12%, the NOx concentration becomes about 200 ppm. ing.

On the other hand, the dioxins in the high temperature exhaust gas C ₁ are almost completely decomposed by high heat when the combustion is stable because the inside of the melting furnace 1 is high temperature combustion. The concentration of dioxins is negligible. However, when the unburned matter (combustible component) contained in the dried ash 20a, which is the material to be melted, greatly changes, the combustion state in the melting furnace 1 may temporarily become an incomplete combustion state. Under such conditions, CO and dioxins are generated, and the temperature of dioxins in the high-temperature exhaust gas may increase.

A natural gas inlet 11a is provided at the entrance of the high-temperature flue 4 or at the center thereof.
Natural gas from the reducing gas supply unit 11b of the fuel supply device 11 is blown into the hot exhaust gas C ₁ than 1a. As a result, the high-temperature exhaust gas C ₁ becomes a reducing atmosphere, and the NOx is reduced and removed through the following reaction.

The mechanism of removing NOx by blowing natural gas is as follows. CnHm + O ₂ → Cn'Hm '+ CO + H ₂ O NO + Cn'Hm' → Cn "Hm" + N ₂ + CO + H ₂
O or NO + Cn'Hm '→ Cn "Hm" + HNi + CO + H
₂ O The gas flow rate of the high-temperature exhaust gas C _{1 in} the high-temperature flue 4 is set to 5 to 6 m / sec, and the residence time is set to about 1 sec or more, so that the above-mentioned NOx decomposition reaction is sufficiently performed. It is considered to be.

The high-temperature flue gas C ₂ after the natural gas is blown into the high-temperature flue 4 to form a reducing atmosphere to remove NOx continues to enter the secondary combustion device 5.
Here, the combustion air A ₂ is blown, so that secondary combustion is performed together with the exhaust gas C ₄ from the dryer 20.

Since the temperature of the high-temperature exhaust gas C ₂ at the inlet of the secondary combustion device 5 is about 1000 ° C. or more,
The secondary combustion device 5 does not require an auxiliary combustion device. Also, the high-temperature exhaust gas C ₂ and the dryer exhaust gas C in the secondary combustion device 5
The secondary combustion of No. ₄ is combustion in which the air ratio is suppressed to about 1.2 to 1.3, so that the generation of NOx is almost negligible. Furthermore, the residence time of the high-temperature exhaust gas C _{2 in} the secondary combustion device 5 is set to about 2 seconds or more. By remaining at a temperature of about 900 ° C. for about 2 seconds, the high-temperature exhaust gas C ₂ remains in the high-temperature exhaust gas C ₂ . The dioxins that have been burned will be almost completely thermally decomposed.

The secondary combustor hot gas C ₃ after being secondary combustion in the 5, has a flue gas C ₃ which had been throat decompose N low and殆also dioxins NOx concentration,
It is continuously introduced from the secondary combustion device 5 to the air preheater 6,
After the heat recovery here, it is sent to the gas cooling device 7. In the air preheater 6, fresh air is supplied at about 35%.
0 preheated to ° C., is used as combustion air A ₂ of the combustion air A ₁ and secondary combustion apparatus 5 of the surface melting furnace 1. Also, 2
Combustion air A ₂ is supplied to the next combustion apparatus 5 is controlled by the exhaust gas oxygen concentration from the oxygen concentration detector 18 which is provided on the outlet side of the secondary combustion unit 5. Furthermore, the gas cooling device 7, is sprayed cold water into the flue gas C ₃ from the water injection port 19, which cool the flue gas C ₃ is performed by.

Exhaust gas C cooled to about 200 ° C. in the gas cooling device 7 is dust-removed and desalted by a bag filter device, and then emitted to the atmosphere through a chimney (not shown). An auxiliary agent supply device 12 is connected to the gas inlet side of the hug filter device 8.
By supplying an auxiliary agent such as Ca (OH) ₂ from a to the exhaust gas C ₃ , an absorbent layer such as an acid gas, SOx, and dust is formed on the outer surface of the filter medium of the bag filter device 8. Further, the dust (melted fly ash) from the bag filter device 8 is solidified as a chemical and rendered harmless.

In the embodiment shown in FIG. 1, a surface melting furnace is used as a melting furnace. However, any type of melting furnace capable of completely thermally decomposing dioxins in high-temperature exhaust gas can be used. Of course, a melting furnace may be used. Further, in the embodiment of FIG. 1, the gas supplied to the high-temperature exhaust gas is natural gas as described later. Can be used in place of natural gas. Furthermore,
In the embodiment of FIG. 1, the bag filter devices 8 and 24 are used as the exhaust gas treatment device. Of course, it may be possible.

[0036]

According to the present invention, a part of the high-temperature exhaust gas discharged from the melting furnace 1 of the melting section M is used as a heat source for drying the wet ash 20, so that no new fuel is used. The wet ash can be dried, and the fuel ratio of the wet ash melting treatment device can be greatly improved. Further, even if dioxin is generated in the dryer, the exhaust gas is burned at a high temperature in the secondary combustion device, so that it is almost thermally decomposed.
Furthermore, dioxins generated during drying and remaining in the dry ash are decomposed during high-temperature combustion in the melting furnace, so that dioxins in high-temperature exhaust gas from the melting furnace are reduced. In addition, in the present invention, the capacity of the exhaust gas treatment equipment is almost the same as the capacity of the conventional dry ash melting treatment, which is sufficient. There is no increase in capacity of the exhaust gas treatment device.

In the present invention, a reducing gas is blown into the high-temperature exhaust gas in a high-temperature flue, which is a discharge passage of the high-temperature exhaust gas from the melting furnace, to reduce and decompose NOx containing the high-temperature exhaust gas as a reducing atmosphere. By recombusting the high-temperature exhaust gas with reduced NOx, dioxins remaining in the high-temperature exhaust gas are decomposed and removed. As a result, both NOx and dioxin can be removed at the same time without having to provide a dedicated removal device to remove both, so that equipment costs and melt processing costs can be significantly reduced, and environmental pollution can be further reduced. It can be effectively prevented.

Further, in the present invention, (a) a highly efficient N
(2) Even if CO is generated due to fluctuations in unburned components in the material to be melted (wet ash), CO is burned by secondary combustion, so that unburned gas is (C) Since the dioxins are decomposed by the secondary combustion, many effects such as the dioxins in the collected dust are significantly reduced. The present invention is an invention having excellent practical utility as described above.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a configuration of a wet ash melting apparatus according to an embodiment of the present invention.

FIG. 2 is a system diagram showing a configuration of a melting apparatus for incineration residues and fly ash provided in a conventional refuse incineration facility.

[Explanation of symbols]

H is a wet ash drying section, M is a dry ash melting section, A ₁ ·
A ₂ is the combustion air, B is the fuel, C ₁ · C ₂ · C ₃ hot exhaust gas, C ₄ Driers exhaust gas 1 is melting furnace, 1a hopper, 1b are pushers, 2 slag tap, 3 Water seal conveyor device, 4 is a high temperature flue, 5 is a secondary combustion device, 6 is an air preheater, 7 is a gas cooling device, 8 is an exhaust gas treatment device (bag filter device), 9 is a forced air blower, 10 is an induced draft. Machine, 11 is a natural gas supply device, 11a is a natural gas inlet, 12 is an auxiliary agent supply device, 12a is an auxiliary agent inlet, 13 ·
14 is an ash discharge conveyor, 15 is a molten slag, 16 is a granulated slag, 17 is a burner, 18 is an oxygen concentration detector of exhaust gas, 19 is a water injection port, 20 is a high moisture content combustion residue and fly ash (wet ash). ), 20a are combustion residue and fly ash (dry ash) after drying,
21 is a hot air dryer, 21a is a wet ash receiving hopper, 21b
Is a feeder, 22 is a hot stove, 23 is a magnetic separator, 24 is a bag filter device, 25 is a conveyor, 26 is an ash bunker, 26a is a conveyor, 27a, 27b and 27c are blowers, and 28 is a metal material.

Claims (5)

[Claims] 1. A wet ash melting treatment apparatus comprising a wet ash drying treatment part and a dry ash melting treatment part, wherein the wet ash drying treatment part is a high-temperature exhaust gas from a melting furnace of the melting treatment part. A hot air dryer that dries wet ash using part of the heat as a heat source, an exhaust gas treatment device that treats exhaust gas from the hot air dryer, and a ventilator that sends exhaust gas from the exhaust gas treatment device to the secondary combustion device in the melting processing section A melting furnace for heating and melting the dry ash from the drying section, a high-temperature flue for discharging high-temperature exhaust gas from the melting furnace, and a high-temperature flue gas in the high-temperature flue. A reducing gas supply device for supplying a reducing gas into the high-temperature exhaust gas, and burning the high-temperature exhaust gas as the reducing atmosphere and the exhaust gas from the hot-air dryer 2
A wet combustion device comprising a secondary combustion device, a device for lowering the temperature of the high-temperature exhaust gas from the secondary combustion device, and an exhaust gas treatment device for purifying the exhaust gas from the secondary combustion device having the lowered temperature. Ash melting equipment. 2. A device for lowering the temperature of exhaust gas from a secondary combustion device, an air preheater and a cooling device, and a secondary combustion device and a dryer. 2. The wet ash melting treatment device according to claim 1, wherein the treatment device for the exhaust gas from the ash is a bag filter device. 3. The wet ash is dried by a dryer using the high-temperature exhaust gas from the melting furnace as a heat source, and then the dry ash from the dryer is melted by the melting furnace and reduced into the high-temperature exhaust gas from the melting furnace. A high-temperature exhaust gas in a reducing atmosphere by blowing a neutral gas, and the secondary combustion device is used to re-burn the high-temperature exhaust gas in the reducing atmosphere and the exhaust gas from the dryer in a secondary combustion device. . 4. A part of the exhaust gas from the dryer is mixed into a high-temperature exhaust gas drawn from a melting furnace for a heat source of the dryer, and the heating exhaust gas having a temperature of about 600 ° C. is supplied to the dryer. The method for melting wet ash according to claim 3, wherein 5. The method according to claim 1, wherein the melting furnace is a surface melting furnace, the reducing gas is natural gas, and the exhaust gas from the dryer is processed by a bag filter device and then sent to a secondary combustion device. Item 4. A method for melting wet ash according to Item 3.