JP2002048322A - Melting processing method and melting processing furnace for waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a melting processing method and a melting processing furnace for waste in which upon directly melting waste the processing cost is reduced. SOLUTION: Air that is rich in air or oxygen from tuyeres 3, 4 at a single stage or a plurality of stages is blown into previously heat, dry, and thermally decompose waste, and thereafter alternating electric power is supplied to a heating coil 10 disposed on an outer periphery at a lower portion in the furnace, whereby a molded workpiece obtained by coating with ceramics graphite or cokes previously disposed at a lower portion in the furnace, or a molded workpiece obtained by blending carbon powder and ceramics, or a molded workpiece of electrically conductive ceramics is induction-heated to melt thermal decomposition residues in the waste.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to the melting of waste such as municipal solid waste, industrial waste, sludge, and waste produced by digging up waste landfilled at a final disposal site to produce slag. The present invention relates to a treatment method and a waste treatment furnace. The slag produced by the method of the present invention can be used for civil engineering materials, road pavement materials, concrete aggregates and the like.

[0002]

2. Description of the Related Art At present, most waste is treated by an incineration method, but the incineration method has a drawback that a disposal site for incinerated ash is required. Particularly in metropolitan areas, it is difficult to secure a disposal site for incinerated ash.Therefore, a method of further melting and reducing the volume of incinerated ash incinerated with waste, or reducing the volume by directly melting the waste There is a growing need for methods to do so.

[0003] As a method of melting incinerated ash of waste, a method of melting in an arc furnace and a method of melting by induction heating are disclosed in Japanese Patent Publication No. 4-81084 and Japanese Patent Application Laid-Open No. 11-211032.

A method for directly melting waste in a shaft furnace without incineration is disclosed in Japanese Patent Publication No. 60-11766. Further, a method of incinerating and melting waste by inductively heating a conductive melting container is disclosed in Japanese Patent Application Laid-Open No. H06-26,004.
No. 273951.

[0005]

However, the former method of melting incinerated ash requires two-stage treatment because the waste is once incinerated and then melted, and the incinerated ash discharged from the incinerator is cooled. Many facilities must be installed, such as a facility for transporting materials to the melting furnace.

Further, the latter method of directly melting in a shaft furnace has a problem that a fuel such as coke is required. In the method of inductively heating a conductive melting container, the heat transfer of the molten material is so bad that no heat is transmitted. Inevitably, the diameter of the container is limited, and the amount of waste that can be treated in a day is limited to several tons.

The present invention has been made to solve the above problems.
It is an object of the present invention to provide a melting treatment method suitable for the actual situation of waste discharged in large quantities, while reducing the processing cost in directly melting waste without incineration.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention reduces and combusts waste that has been charged by blowing air or oxygen-enriched air from single or multiple-stage tuyeres. Thus, the waste is preheated, gasified by dry pyrolysis, and the pyrolysis residue is graphite or coke previously placed in the lower part of the furnace by applying an alternating current to a heating coil installed on the outer periphery of the lower part of the furnace. A method and apparatus for subjecting a molded body coated with ceramics, a molded body formed by mixing carbon powder with ceramics, or a molded body of conductive ceramics to induction heating to melt-process pyrolysis residues of waste.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail.
The melting furnace is composed of a shaft furnace, and the furnace body forms a pre-tropical zone, a drying zone, a pyrolysis zone, and a melting zone from the upper part to the lower part, and the waste supplied from the upper part of the melting furnace passes through the furnace. In the process of descending, it is preheated, dried and thermally decomposed sequentially to gasify gasification components, and then the pyrolysis residue is melted at the furnace bottom. As a heating source for preheating, drying, and pyrolysis, air or oxygen-enriched air is blown in from the lower part of the furnace body, and combustible substances in waste are partially burned to reduce and burn. Rises inside the furnace to preheat, dry and pyrolyze the waste supplied from the furnace top.

On the other hand, in the melting zone, a molded body in which graphite or coke is coated with ceramics in advance, a molded body formed by mixing carbon powder with ceramics, or a molded body made of conductive ceramics is arranged in the lower part of the furnace body. Then, the pyrolysis residue is melted by the heat obtained by adding the heat of induction heating of the molded body and the heat raised in the process of turning the waste itself into the pyrolysis residue. The pyrolysis residue in this case includes non-combustible substances such as rubble, ceramics, bottles, and metals, in addition to the residue formed by the pyrolysis of combustibles. Electricity used for induction heating generates combustible pyrolysis gas by partially burning and reducing combustion of combustible substances in waste, and complete combustion in the secondary combustion furnace provided at the latter stage of the melting furnace, The electric energy recovered by the boiler and generator provided next is used.

By forming a molded body in which graphite or coke is coated with ceramics or a molded body in which carbon powder is mixed with ceramics, graphite or coke, which is a heating element, is consumed by contact with a combustion gas. Can be prevented. In the case of carbon powder, regular carbon or irregular carbon may be used. In addition, a conductive ceramic can be used as the heating element, and is less consumed by contact with the combustion gas. As the conductive ceramic, silicon carbide, molybdenum silicide, carbon, lanthanum chromite, or the like can be used.
Further, the ceramic to be coated with graphite or coke, or the ceramic to be mixed with the carbon powder may be a commercially available ceramic such as silicon carbide, alumina, magnesia, or a composite material of these, and naturally a conductive ceramic may be used. good. However, when conductive ceramics are used as the heating element, the electrical resistance changes depending on the temperature, and in many cases, the resistance tends to increase at low temperatures and decrease at high temperatures. Care must be taken because the heating may take some extra time.

[0012] and 0.008 m ³ or less of the mass as the shape of the molded body disposed below the furnace, by filling in the lower furnace, the role if melt and the unmelted material as grate not heating element only Is efficiently separated, so that a melt suitable for effective use can be produced. It is preferable that the lump has a shape close to a spherical shape because the voids can be uniform. It is not preferable to use a compact having a mass exceeding 0.008 m ³ , since end-burning components may be discharged from the voids.

[0013] As another shape of the molded body disposed in the lower part of the furnace, a prismatic shape is formed, and by stacking it in a lattice shape in the lower part of the furnace, it functions as a fire grate as described above, and the molten material and the unmolten material are separated. Since it separates efficiently, a melt suitable for effective use can be produced.

According to the present invention, since the molded body to be arranged is made conductive, the heated molded body is brought into direct contact with the pyrolysis residue and melts. And hundreds of tons of waste per day are possible. Further, since there is no heat generation in the container, wear of the refractory is small.

When the inside of the furnace is set to a reducing atmosphere, substances such as heavy metals are reduced and volatilized and transferred to the exhaust gas side. Therefore, according to the present invention, a safe melt can be produced by charging coke into the furnace, setting the furnace in a reducing atmosphere, and volatilizing heavy metals and the like into a melt containing very little harmful substance. Also, when using a ceramic containing carbon such as silicon carbide, if coke is charged into the furnace and the atmosphere is reduced,
There is no more wear. On the other hand, the heavy metals volatilized and moved to the exhaust gas side are finally collected in a dust collector in a state where they are more concentrated than the original waste, and yamamoto can be reduced.

In the conventional technology for inductively heating incinerated ash, since the incinerated ash of waste is targeted, the configuration inside the melting furnace is different from that of the present invention. In the prior art, since incinerated ash is melted, it is necessary to install an incinerator for incinerating waste separately. In the present invention, the waste can be directly melted in one process by providing a shaft portion having a pre-tropical zone, a drying zone, and a pyrolysis zone without incinerating the waste in an incinerator in advance. it can. In the prior art, air is supplied into the melting furnace to oxidize and burn the unburned portion of the incinerated ash.However, the present invention partially burns the waste to make the furnace a reducing atmosphere, By generating the pyrolysis gas, the gas can be easily and completely burned without auxiliary fuel in the secondary combustion furnace provided at the latter stage of the melting furnace, and as a result, electric energy is recovered by the boiler and generator provided next. It becomes possible. The present invention has an effect that the calorific value of the waste can be used directly and in the form of recovered electricity as a heat source for melting the waste.

[0017]

As an example of the EXAMPLE 1 Waste melt processing, the advance graphite in the lower furnace are coated with ceramics, melting treatment apparatus was charged to furnace bottom a molded body of spherical volume of 0.0003 m ³ FIG. 1 shows the case where the melting process is performed.

The melting apparatus includes a shaft furnace 1, a waste charging apparatus 2, an upper tuyere 3, a lower tuyere 4, a shaft part 5,
It is composed of a bosh section 6, a furnace lower part 7, a gas discharge pipe 8, a slag discharge port 9, a heating coil 10, a high-frequency power supply 11, and a spherical molded body 12 in which graphite is coated with ceramics.

In FIG. 1, waste is loaded from a waste loading device 2 at the upper part of a shaft furnace 1. Municipal waste was disposed of as waste. Table 1 shows the properties of the melted municipal solid waste.

[0020]

[Table 1] The shaft furnace 1 is composed of a shaft portion 5, a bosh section 6, and a lower part 7 inside the furnace, and an upper tuyere 3 provided around the bosh section.
Air is supplied from a lower tuyere 4 provided around the lower part of the furnace.

The process 560 kg / h of waste graphite are each about 1% and 6% of the waste, 400 Nm ³ / h air from the upper tuyere 200 Nm ³ / h, from the lower tuyeres
Was supplied.

The waste and graphite charged into the melting furnace form a packed bed in the furnace, and the combustibles of the waste are burned by the air blown from the upper tuyere 3 and the lower tuyere 4.
The combustion gas rises in the melting furnace from the bottom of the furnace, and the waste is preheated, dried and thermally decomposed by the sensible heat of the combustion gas. Steam, pyrolysis gas and fine dust generated in the process of drying and pyrolysis of the waste are discharged from the gas discharge pipe 8.

On the other hand, the thermal decomposition residue of the waste is heated to a high temperature and descends to the lower part 7 in the furnace. An alternating current is passed from a high-frequency power supply 11 to a heating coil 10 installed on the outer periphery of the lower part of the furnace to induction-heat a molded body 12 coated with graphite filled in the lower part of the furnace with ceramics. The pyrolysis residue inside is brought into contact and melted. Pyrolysis residue is 130
It is heated from 0 ° C. to 1750 ° C. to be in a molten state, and discharged from the slag discharge port 9 to the outside of the furnace.

As the electric power for the induction heating, a gas generated by burning the gas discharged from the gas discharge pipe and generating steam by the boiler using the heat was used. This block diagram is shown in FIG. The exhaust gas discharged from the gas discharge pipe 8 burns unburned components in the exhaust gas in the secondary combustion chamber 14, generates steam in the boiler 15 with this heat, and generates electricity generated in the generator 20 by induction heating. Use as power. Boiler 15
After passing through the exhaust gas, the temperature of the exhaust gas is reduced by an exhaust gas cooler 16, dust is collected by a dust collector 17, and the
Discharged from

The molten slag discharged from the slag discharge port 9 is water-cooled into fine sand-like particles. Also,
Slag in the molten state contains molten metal,
Metal also becomes fine particles like slag. Slag is used as aggregate or civil engineering material for secondary concrete products such as interlocking blocks.

FIG. 4 shows a conventional shaft furnace type direct melting furnace of the prior art, and the same equipment as in FIG. 1 is designated by the same symbol.
When the same waste is treated by the conventional method, coke needs to be about 6% of the waste, and it is necessary to enrich oxygen in the lower tuyere of about 45 Nm ³ and to blow air. Needed to form a packed layer 19 of coke. Compared with this conventional method, the method of the present invention can reduce coke consumption and oxygen as shown in the embodiments.

In place of the molded body 12 in which graphite is coated with ceramics, a molded body in which coke is coated with ceramics, a molded body formed by mixing carbon powder with ceramics, or a molded body made of conductive ceramics is used. The same effect was obtained. Furthermore, charge coke into the furnace,
By changing the atmosphere in the furnace to a reducing atmosphere, the content of lead contained in the slag could be reduced to a very small amount of 18 mg / kg.

As wastes to be treated, waste in which incinerated ash was mixed with municipal waste and waste in which sludge was mixed with municipal waste were respectively treated. The same effects as described above were obtained.

EXAMPLE 2 FIG. 3 shows a melt processing apparatus in which prism-shaped compacts 13 previously coated with ceramics of graphite are stacked in a lattice at the lower part of the furnace, instead of the spheres filled in Example 1.

The waste is heated in the same manner as in the first embodiment to become a pyrolysis residue and goes down to the lower part 7 in the furnace. An alternating current is applied from a high-frequency power supply 11 to a heating coil 10 installed on the outer periphery of the lower part of the furnace to induce heating of a prism-shaped formed body 13 coated with ceramics stacked on the lower part of the furnace, thereby forming a high-temperature state. The pyrolysis residue of the waste is brought into contact with the body 13 and melted. The pyrolysis residue is heated from 1300 ° C. to 1750 ° C. to be in a molten state and discharged from the slag discharge port 9 to the outside of the furnace. As a result, the same effect as in Example 1 was obtained. In addition, instead of the molded body 13 coated with graphite ceramic, a molded body obtained by coating coke with ceramics, a molded body formed by mixing carbon powder with ceramics, or a molded body made of conductive ceramics is used in the same manner. The effect was obtained.

[0031]

According to the present invention, the following effects can be realized.

1) Compared with the method of melting incineration ash in an arc furnace or induction heating furnace after incineration of waste, the method of the present invention can directly melt waste, and the equipment configuration is simple and economical. . Furthermore, not only is the incineration ash unnecessary to be handled, but also the thermal efficiency is higher than the method of once cooling the incineration ash and melting it in an arc furnace.

2) When the waste is directly melted in a shaft furnace without incineration, in the present invention, a molded product obtained by coating graphite or coke with ceramics, a molded product obtained by mixing carbon powder with ceramics, or It is possible to reduce the fuel consumption and reduce or eliminate the oxygen enriched in the air blown from the tuyere by inductively heating the conductive ceramic molded body and melting the pyrolysis residue. . Further, the temperature of the molten slag can be easily adjusted by adjusting the power input amount of the induction heating.

3) As a heating method using electricity, there is a method such as energization heating. However, it is necessary to install electrodes through the furnace wall of the melting furnace, which complicates the structure and further replaces worn-out electrodes. However, induction heating does not have such a problem.

4) By charging coke into the furnace, the inside of the furnace can be made into a reducing atmosphere, similarly to the conventional shaft furnace, and heavy metals such as lead in the molten slag are volatilized and reduced. Therefore, when slag is used effectively, there is no concern about adverse effects on the environment. Accordingly, the present invention is a waste melting furnace having the advantages of using electricity while utilizing the advantages of a shaft furnace of reducing heavy metals in slag.

5) As the electric power for induction heating, there is no need to purchase power from the outside by generating electricity using the calorific value of the waste and effectively utilizing it.

6) By recycling the slag after the melting process, not only is the slag disposal site unnecessary, but also natural destruction by mining of natural sand can be prevented.

[Brief description of the drawings]

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

FIG. 2 is a diagram in which electric power can be supplied to a heating coil using waste heat of a melting furnace.

FIG. 3 is a diagram showing another embodiment of the present invention.

FIG. 4 is a diagram of a conventional direct melting furnace.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Shaft furnace 2 Waste charging device 3 Upper tuyere 4 Lower tuyere 5 Shaft part 6 Morning glory part 7 Furnace lower part 8
Gas discharge pipe 9 Slag discharge port 10 Heating coil 11 High frequency power supply 12 Molded body 13 Molded body 14 Secondary combustion chamber
15 Boiler 16 Exhaust gas cooler 17 Dust collector 18 Chimney
19 Coke packed bed 20 Generator

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F23G 5/46 ZAB F27B 1/00 4K045 F27B 1/00 1/16 4K056 1/16 1/20 4K061 1 / 20 F27D 11/06 Z F27D 11/06 17/00 101A 17/00 101 C22B 9/02 // C22B 9/02 B09B 3/00 303K (72) Inventor Hidemi Kosano 46-59 Nakahara, Tohara-ku, Kitakyushu New F-term in the Engineering Division of Nippon Steel Corporation (Reference) CA21 CA24 4D004 AA02 AA46 AB03 AC08 BA02 CA12 CA24 CA27 CA29 CA42 CB02 CB32 CB33 4K001 BA24 DA06 HA01 4K045 AA01 BA10 G B05 GB12 GC01 4K056 AA05 AA19 BA01 BB01 BB07 CA20 DA13 DA39 4K063 AA04 AA06 AA12 BA13 CA01 FA34

Claims (8)

[Claims] 1. A waste is charged into a shaft furnace, and air or oxygen-enriched air is blown from one or a plurality of tuyeres at a lower part of the furnace to reduce and burn the charged waste. In the method of sequentially preheating, drying, pyrolyzing and gasifying the waste charged in the furnace in the section, and then melting and processing the pyrolysis residue of the waste, graphite or coke is preliminarily coated with ceramics in the lower part of the furnace. A molded body coated with, or a molded body formed by mixing carbon powder with ceramics, or a molded body of conductive ceramics is arranged, and the thermally decomposed residue of the waste is obtained by induction heating the molded body. A method for melting waste, comprising melting. 2. The method for melting waste according to claim 1, wherein coke is charged into the furnace to make the furnace a reducing atmosphere, and harmful substances such as heavy metals are volatilized into a harmless melt. A method of melting and processing waste. 3. The method according to claim 1, wherein the gasified gas is discharged from a shaft furnace and then burnt, and the heat is used to generate electric power. A method for melting waste. 4. A shaft having a waste charging device at the furnace top, a pre-tropical zone, a drying zone, and a pyrolysis zone inside the furnace, and a single-stage or multiple-stage tuyere below the furnace body. In a furnace-type waste melting furnace, a molded body obtained by coating graphite or coke with ceramics, a molded body formed by mixing carbon powder with ceramics, or a molded body made of conductive ceramics is disposed in the lower part of the furnace. A waste melting furnace characterized in that a heating coil for supplying an alternating current for induction heating of a formed body is provided on an outer periphery of a lower part of the furnace. 5. The waste melting furnace according to claim 4,
Moldings graphite or coke arranged in the lower furnace are coated with a ceramic, or moldings were formed by mixing the ceramic and carbon powder, or a molded body of a conductive ceramic, and 0.008 m ³ or less of the volume of the mass A waste melting furnace characterized in that the lower part of the furnace is filled. 6. The waste melting furnace according to claim 4, wherein a graphite or coke disposed at a lower part in the furnace is coated with ceramics, a molded body formed by mixing carbon powder with ceramics, or a conductive body. A waste melting furnace characterized in that the formed body of the conductive ceramics has a prismatic shape and is stacked in a lattice shape at a lower portion in the furnace. 7. The waste melting furnace according to claim 4,
A waste melting furnace characterized in that a coke charging device is installed at the furnace top. 8. The waste melting furnace according to claim 4,
A boiler and a generator for generating electricity by using the waste heat of the melting furnace are provided at a stage subsequent to the melting furnace, and electricity generated by the generator can be supplied to a heating coil installed on an outer periphery of a lower portion of the melting furnace. A waste melting furnace characterized by the above-mentioned.