JP2003083517A - Waste plasma melting method and waste plasma melting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste plasma melting method and a waste plasma melting device suitable for it in which the number of maintenances can be decreased and the stable heating and plasma melting operation of waste can be carried out. SOLUTION: In the waste plasma melting method and the waste plasma melting device suitable for performing the waste plasma melting method, the plasma torch has a hollow part passing through the plasma torch and the hollow part is charged with plasma operating gas together with the plasma.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to melting treatment of incineration residue in a incinerator, fly ash, etc., and melted materials of waste such as steel-making reduced powder slag, dust collection dust, and crushed brick waste by plasma flame. And a plasma melting processing apparatus suitable for the method.

[0002]

2. Description of the Related Art Incineration residues discharged from municipal solid waste incinerators, such as particles, flakes, and lump wastes, are subjected to plasma melting treatment in a melting furnace in order to reduce their volume (to reduce the volume). ing. There are various types of heating sources used for the purpose of plasma melting treatment of waste, and plasma heating using a plasma torch as described in JP-A-9-72517 is one of them. This uses an inert gas plasma such as Ar as a heat source. The plasma torch to be used is supplied with an inert gas as plasma working gas, electric power and cooling water, and these are electrically and mechanically connected to each other. A metallic plasma torch having an electrically insulated structure is used.

Then, the waste is supplied from the outside of the plasma torch and melted. Plasma is in a high-energy state in which substances are ionized, and the plasma torch forms 20
Put the waste into a plasma flame of 00 to 2500 ° C (the flame generated by passing a plasma working gas such as air between the plasma generated between the electrodes) or install the waste at the bottom of the melting furnace. Turn on and melt with a plasma flame using a metal plasma torch.

Conventionally, a melting furnace using a plasma torch has an anode or a cathode inside the torch, depending on the arrangement of the electrodes, and the other electrode outside the torch (for example, the electrode provided at the bottom of the melting chamber). Having transfer
fer type, and a non-transfer having an anode and a cathode in one torch.
r: non-transition type, and two combined metal torch types in which a DC power source uses separate torches for the anode and cathode.

[0005]

At least the following problems are encountered in the conventional waste plasma melting treatment method using a metallic plasma torch and the waste plasma melting treatment method using a two-combination metal torch type plasma torch. 1
One or more is a problem. There are problems due to the complexity of the structure of the metal plasma torch, and in the case of the metal torch, there are problems of intermittent operation and electrode consumption.

First, a problem caused by the complexity of the structure of the metal plasma torch will be described. The waste heating / plasma melting treatment apparatus using the metal plasma torch is effective in achieving the high temperature, but the stability of the metal plasma torch used as a device is affected by various reasons. There are also issues to be addressed, and there is room for improvement as a waste treatment device. In other words, the main cause of lack of stability is the complexity of the structure of the metal plasma torch. As described above, the metal plasma torch has a structure for supplying an inert gas, electric power, and cooling water, and these are required to be electrically and mechanically insulated from each other, so that a complicated It becomes a structure. Evaporation of powdered material,
FIG. 5 is a reprint of the drawing described in Japanese Patent Application Laid-Open No. 11-288787, which is an invention relating to a thermal plasma device used for melting and melting radioactive waste, and the like, which is caused by the complexity of the metal plasma torch structure. Will be described.

In FIG. 5, a plasma torch 1 for generating a thermal plasma is, for example, a cylindrical member 16 formed of quartz glass, a gas ring 17 attached to the upper part of the cylindrical member 16, and a cylindrical member 16 outside the cylindrical member 16. The high frequency coil 18 and the like are arranged. The cylindrical member 16 has a double pipe structure, and is mounted between the upper flange 19 and the lower flange 20. A probe 21 is provided at the center of the gas ring 17. An opening is bored in the center of the probe 21 in the longitudinal direction, and the powder material to be processed is supplied from the powder supply unit (not shown) into the cylindrical member 16 through the opening together with the plasma working gas. Supplied. The lower flange 20 is mounted on the chamber 23 via a base lid 22. The cylindrical member 16, the gas ring 17, the high frequency coil 18, the upper flange 19, the lower flange 20, the probe 21, the base lid 22 and the like which are mounted on the chamber 23 are collectively referred to as a torch.

The chamber 23 is constructed so that it can be evacuated to an appropriate pressure by an evacuation device (not shown). The high frequency power supply 33 supplies high frequency power to the high frequency coil 18. In addition, in order to protect the chamber 23 from high temperature and keep the inside of the chamber 23 at high temperature, a fireproof heat insulating material 24 is arranged around the inner wall of the chamber 23. In the high-frequency induction thermal plasma device having such a configuration, the plasma working gas is supplied through the gas ring 17 of the plasma torch 1, and the high-frequency coil 18 is supplied with high-frequency power to form the thermal plasma in the plasma torch 1. To do. Then, the powder material to be processed is supplied into the thermal plasma together with the plasma working gas through the probe 21 to evaporate and melt the powder material. This evaporated and melted material is a substrate (not shown) in the chamber 23.
Adheres in a film on top.

Such a high-frequency induction thermal plasma device is used not only for film formation by vaporization and melting of the powder material, but also for melting radioactive waste, iron, etc., and decomposing CFCs. Plasma torch 1 for melting, dissolving and disassembling
This is due to the induction thermal plasma of about 10,000 degrees generated inside. Since the induction thermal plasma of about 10,000 degrees is generated in the plasma torch 1, the probe 21 and the gas ring 1 are
7. Cooling water is circulated inside the cylindrical member 16 and the base lid 22 so that they are not damaged by the radiant heat of the induction thermal plasma. As described above, when the metallic plasma torch 1 shown in FIG. 5 is used, it is expected that the structure for using the cooling water will be complicated. The circulation of cooling water will be described below.

In FIG. 5, reference numeral 25 is a circulating water tank containing cooling water, reference numeral 26 is a cooler, and reference numerals 27 and 28.
Is a pump. The pump 27 is a circulating water tank 25.
The cooling water inside is sucked, and the probe 21 and the gas ring 1
7, the cooling water is discharged to the introduction pipe 29 connected to the inside of the cylindrical member 16 and the base lid 22 at a discharge pressure of, for example, about 3 to 4 kgf / cm ² . Then, the cooling water that has passed through the inside of the probe 21, the gas ring 17, the cylindrical member 16 and the base lid 22 is returned to the circulating water tank 25 through the discharge pipe 30 connected to these inside. The pump 28 sucks the cooling water in the circulating water tank 25 and discharges it into a pipe 31 connected to the cooler 26. The cooling water cooled by the cooler 26 passes through the pipe 32 and is returned to the circulating water tank 25. In this way, the cooling water stored in the circulating water tank 25 is always cooled to a predetermined temperature, and the probe 21, the gas ring 17, the cylindrical member 16 and the base lid 22 are constantly cooled by the circulation of the cooling water. Will be chilled. The cooling water is also circulated to the high frequency power supply 33.

As described above with reference to FIG. 5, many problems are expected to occur in the conventional waste plasma melting treatment method using the metallic plasma torch. The details will be described below.

Since a large amount of cooling water exists inside the metallic plasma torch, it is necessary to always consider the risk of water leakage and, in the worst case, steam explosion. In addition to that,
It is also necessary to frequently maintain each component that constitutes the extremely complicated structure and the component that is consumed by use. A conventional metal plasma torch is composed of a large number of parts having respective functions, and in addition, a large amount of cooling water is required inside the torch. Therefore, it is necessary to perform frequent maintenance, and the maintenance itself is complicated and requires a lot of man-hours.

[0013] Further, it is easily affected by splashes of waste heat. In other words, since parts with various functions are exposed at the tip of the metal plasma torch, if splashes from waste adhere to such parts, electrical and mechanical insulation between parts will occur. Will be destroyed, resulting in problems such as abnormal discharge, blockage of the plasma working gas flow path, and disturbance of the gas flow. As a result, instability of the plasma flame, misfire, coolant leakage, and in the worst case, breakage of the plasma torch may result in non-ignition in which the plasma flame itself cannot be generated before that. Further, in the case of a metal plasma torch, the tip of the torch that generates plasma is heavily worn, and frequent plasma torch replacement is essential.

In the case of the conventional metal plasma torch, a pilot arc called a pilot arc is first generated inside the plasma torch and jetted from the tip of the torch. In this state, the tip of the torch is brought close to the molten metal surface to form an electric path with a pilot arc, and then a heating power supply voltage is applied to generate a plasma main arc. However, it is a fact that stable ignition has not been realized for the following reasons.

First, the frame shape of the pilot arc is sensitively influenced by the electrode shape at the tip of the plasma torch and the relative positional relationship. In other words, this is because the tip of the torch wears out with use, and especially when regular maintenance is important, if this is not enough, problems such as shortening of the pilot arc and deflection will occur. Therefore, the formation of an electric path with the surface of the molten metal cannot be performed completely.

Further, as described above, the metal plasma torch is composed of a large number of parts having respective functions,
The tips are the parts where they are exposed. If splashes from the molten metal adhere to such parts, the mutual electrical
Problems such as mechanical insulation failure will occur and the function of the plasma torch will not be achieved. In order to avoid this, it is necessary to adjust the tip of the torch so that it does not come too close to the surface of the molten metal, but it may be uncertain to secure the electric path in the pilot arc.

As described above, since a large amount of cooling water is supplied to the inside of the conventional metal torch, in order to avoid the risk of water leakage or steam explosion due to damage to the torch, this also requires the torch tip to be on the molten metal surface. This is the reason why stable ignition and securing of electric circuit for pilot arc were difficult.

On the other hand, the slag is often suspended on the upper surface of the waste for various reasons, and it is necessary to dispose the slag during the plasma melting process. Depending on the molten state (melting temperature) and composition, this slag may not have electrical conductivity. In this case, it is necessary to secure the electric path with the molten metal surface by the pilot arc, so it is especially necessary to It will be difficult to secure it.

Next, in the case of the two-piece metal torch type, problems of intermittent operation and electrode consumption will be described. As a characteristic of the plasma generation phenomenon in both the anode torch of the twin metal twin torch and the electrode torch of the cathode torch, the plasma on the anode side into which electrons enter is more unstable than the plasma on the cathode side from which electrons are emitted. Therefore,
For example, when the melting furnace is started, that is, when the plasma is started, when the temperature is raised, or when the conditions inside the melting furnace change significantly such as when the material to be melted (for example, incinerated ash) is initially charged, maintain the generation of the plasma arc on the anode side. However, there is a problem in that driving becomes intermittent and driving becomes intermittent. Further, the tip of the electrode of the anode torch into which the electrons rush is heated more than that of the cathode torch from which the electrons are emitted. Therefore, there is a problem in that the tip of the anode torch becomes hot and the consumption of the electrode becomes severe.

Therefore, an object of the present invention is to provide a waste plasma melting method and a waste plasma melting processing apparatus suitable for the method, which can reduce the number of maintenance steps and can perform stable heating and plasma melting processing operation of waste. And

[0021]

As a result of a review of the plasma torch, the present inventor has found that the plasma torch to be used has a hollow portion, and the hollow portion is incinerated in an incinerator which is a non-processed object together with the plasma working gas. By charging residue, fly ash, etc., and waste such as steel-reduced powder slag, dust collection dust, and brick crushed material, the processed material can surely pass through the plasma flame and be melted securely. It was found that the amount of internally generated dust can be reduced. In addition, it was found that by forming the plasma flame generation part with graphite, plasma melting treatment of the waste can be achieved with stable operation with less consumption of the torch electrode and failure.

The present invention comprises the following means. The reference numerals in the parentheses () are added for reference. [Means 1] In the method for plasma-dissolving a waste (6) heated by a plasma torch (1), the plasma torch (1) has a hollow portion (2) penetrating inside the plasma torch, and the hollow portion ( A waste plasma melting treatment method characterized in that the waste (6) and the plasma working gas (7) are charged into 2).

[Means 2] The waste plasma melting treatment method according to [Means 1], wherein the plasma flame (12) generation portion of the plasma torch (1) is formed of graphite.

[Means 3] A melting furnace (3) comprising a plasma torch (1) having a hollow portion (2) penetrating the inside thereof, and a counter electrode (4) disposed at the bottom so as to face the plasma torch (1). ), A moving means (5) for varying the relative distance between the counter electrode (4) and the plasma torch (1), and a waste material (6) and a plasma working gas (7) in the hollow portion (2). A waste plasma melting treatment apparatus comprising a feeding means (8) to be charged and a power source (9) having one end connected to the plasma torch (1) and the other end connected to the counter electrode (4).

[Means 4] The plasma flame (12) generation portion of the plasma torch (1) is made of graphite [Means 3]
The waste plasma melting treatment apparatus described in 1.

[Means 5] The waste plasma melting treatment apparatus according to [Means 3] or [Means 4] in which a gasification combustion chamber (34) is added.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION The effect of providing a hollow portion penetrating the inside of the plasma torch in the plasma torch and charging waste and plasma working gas into the hollow portion will be described below. First, by throwing the waste material into the hollow portion, the directly processed material can be thrown into the high temperature plasma flame. Therefore, as in the case of supplying a processed material such as powder from the outside to the flame tip as in the past, the powder processed material or the processed material is treated by the plasma gas flow, the updraft in the furnace, the furnace dust collection gas flow, etc. The dust particles that adhere to the object do not fly up and scatter, and the amount of auxiliary dust collected by the dust collector is also small. Further, since the processed material passes through the high temperature flame, it is surely melted.

Since this system uses a plasma heat source, the amount of gas supplied is much smaller than that of the fuel combustion system. Therefore, the amount of exhaust gas treated by the gas entering the furnace interior can be small, and the dust collector facility cost, maintenance cost such as replacement of the furnace cloth, and post-treatment cost of the supplementary dust collection dust can be reduced. For example, JP-A-7-331353
In the melting furnace described in Japanese Patent Publication, a steelmaking waste, heavy oil, and oxygen are charged in a heavy oil-oxygen burner torch, but in this type of melting furnace, the heat source is heat of fuel and heat of oxidation reaction, so the amount of oxygen supplied And the amount of exhaust gas is large.

Exhaust gas amounts of the heavy oil-oxygen burner system and the plasma heat source system used in the present invention will be compared below. In the heavy oil-oxygen burner system, the amount of oxygen supplied for complete combustion of fuel is 2.25 Nm ³ / kg per kg of A heavy oil for combustion, and the combustion product gas at that time is 23.9 Nm ³ / kg, and the calorific value is It is about 10,000 kcal / kg. Therefore 1
The amount of combustion exhaust gas per 0000 Kcal is 23.9 Nm ³ .
Actually, CO ₂ , SOx, Nox gas, etc. due to combustion and oxidation of elements such as C, S, N contained in the treated product are also added to this, but for comparison, only the A heavy oil is used. Only the flue gas of combustion is compared and discussed below.

On the other hand, in the case of the plasma heat source system according to the present invention, the plasma gas supply amount is 68 N in the air plasma system.
m ³ / hr. Since the torch output range is 60 to 300 kW and normally operates at 100 kW, even if the improvement without water cooling is ignored and the electric-heat energy effective conversion rate is 50%, the calorific value at that time is 100 kw × 3600 × 0.5 × 860 Kcal. / Kwh = 1
It is 54800000 kcal / hr. Therefore, the supplied plasma gas amount per 10000 kcal of calorific value is 0.005 Nm ³ . Therefore, in comparison of the amount of exhaust gas generated during heat generation by both methods, the plasma heating method of the present invention is significantly less. As a result, it is possible to reduce the amount of exhaust gas to be treated, reduce the dust collector equipment cost, maintenance costs such as furnace cloth replacement, and the auxiliary dust collection dust post-treatment cost.

In addition, in the present invention, the waste is directly charged into the high temperature plasma flame by charging the waste into the hollow portion. At that time, the plasma heat source system in which the amount of gas supplied at the same time is significantly small By combining the above, it is possible to reduce the falling speed of the waste. As a result, it becomes possible to secure a long time for the waste to pass through the high temperature flame, and the waste can be more surely melted as compared with the case where the fuel combustion method is applied.

Next, the effect of using graphite as the material of the plasma torch having a hollow will be described. The melting point of graphite in vacuum or in an inert atmosphere is 3700 ° C, which is the highest melting point. Therefore, graphite itself has a plasma temperature of 2000-25
It has the property of not melting even at a high temperature of 00 ° C. By using this graphite, it is theoretically possible to prevent melting and consumption of the plasma torch. Actually, even if the plasma working gas is an inert argon gas, a nitrogen gas, or a reducing gas, there is no exhaustion.

When actually used in a melting furnace, the torch is consumed even though the graphite has a high melting point. It is not that the graphite is melted and consumed but that the torch is chemically reacted with the atmospheric gas or the processed material at a high temperature. The graphite torch is exhausted. This is because oxygen cannot be completely eliminated in a practical processing furnace. There is also oxygen contained in the processed material. Therefore, in a furnace having an oxidizing atmosphere such as air, graphite C reacts with oxygen to generate carbon dioxide gas C.
It becomes O ₂ and the electrodes are consumed.

A reducing atmosphere is preferable to suppress the consumption of graphite, but the amount of consumption is practically no problem if the oxidizing atmosphere is a low oxygen atmosphere. The degree of wear varies depending on not only the atmosphere gas in the furnace but also the element of the processed material. That is, the degree of plasma torch wear varies depending on the rate at which the treated material chemically reacts with graphite, the physical properties of the produced compound, and the melting point, but it is much less expensive than a metal torch and is economical. Further, since the torch tip does not need to be cooled, the torch structure can be simplified and the maintainability can be significantly improved. Maintenance-free is also possible.

In the case of the plasma torch used in the present invention,
It suffices to cool only the electrode (torch) gripping portion, and there is no need for a structure that allows cooling water to pass through the plasma torch, particularly the torch tip portion where plasma flame is generated. This is because it is a plasma torch that uses graphite that does not melt even in a high temperature range due to arc generation. Further, since the structure of the torch itself is simplified by omitting the structure for supplying the cooling water, the maintenance of the plasma torch is basically unnecessary, and for example, only the consumption amount due to oxidation of the graphite torch or the like may be added.

In addition, since it becomes unnecessary to supply cooling water to the plasma torch, the thermal efficiency can be improved. In the case of the conventional metal torch, tens of percent of the input power may be wasted by supplying the cooling water to the torch, but with the plasma melting treatment method of the present invention, this heat amount is effectively input to heating. can do. More specifically, generally, the plasma thermal energy balance of input electric energy is as follows: electric cable loss 6%, torch tip cooling loss 40.
%, Temperature rise in the surrounding atmosphere of the flame 49%, heat of fusion of the processed material in the plasma flame 5% (for example, literature Proceeding
of ATTAC '88, Osaka, (May, 1988, Proceedings of International Symposium hosted by the Society of High Temperature Society of Japan, p113-p118)). This method does not require cooling, and the heat loss equivalent to 40% due to this cooling water can be effectively converted into heat and the thermal efficiency can be improved.

When a graphite plasma torch is used, for example, the tip of the electrode can be immersed in a slag floating on the molten metal surface or the upper portion of the molten metal, stable ignition is possible, and an electric circuit is secured by a pilot arc. Is unnecessary. In other words, the basic structure of the plasma torch used in the present invention is only to provide an inert gas flow path such as Ar for plasma formation in a graphite material having a predetermined torch appearance shape, and to provide a cooling water flow path. Since it is not necessary, there is no need to worry about abnormal electric discharge or cooling water leakage due to droplet adhesion, which is a concern in the conventional metal plasma torch in which parts having various functions are exposed at its tip.

Specifically, after applying a heating power supply voltage to a graphite plasma torch, the tip portion is immersed in a slag floating on the molten metal surface or the molten metal upper portion, and immediately after that, it is drawn and floated on the molten metal surface or the molten metal upper portion. A plasma flame can be generated by maintaining an appropriate distance from the slag surface. According to this, the electric path is surely secured, and stable ignition of the plasma main arc is possible.

From the side of the power supply unit associated with the plasma melting treatment equipment, in the case of the conventional metal plasma torch,
In order to avoid the misfire of the plasma main arc due to the reasons mentioned above, it is necessary to set the voltage of the heating transformer maximum tap to be high, which enhances the electrical insulation of the metal plasma torch body and the plasma device as a whole. There is a need. On the other hand, in the case of the graphite plasma torch used in the present invention, the torch can be immersed and the electric path can be secured securely, so that the transformer voltage can be set low.

The significance of using the graphite plasma torch in the waste plasma melting treatment method and apparatus according to the present invention has been described above. The entire plasma torch does not necessarily have to be graphite, and at least the portion where the plasma flame is generated may be graphite. Next, the operation of the waste plasma melting treatment method and apparatus according to the present invention will be described with reference to the drawings.

The case of activating the waste plasma melting treatment apparatus according to the present invention will be described with reference to FIG. Figure 1 (a)
1 shows a waste plasma melting treatment apparatus according to the present invention.
A graphite plasma torch 1 having a hollow portion 2 is arranged in a melting furnace 3, and a power source 9 is connected to the counter electrode 4. As shown in FIG. 1B, a plasma working gas 7, for example, nitrogen gas is supplied into the melting furnace 3 to increase the oxygen concentration to 2%.
As described below, the plasma torch 1 is lowered to contact the counter electrode 4. Then, the fusion power is supplied from the power source 9 to the plasma torch 1. As shown in FIG. 1 (c), the plasma torch 1 is raised again to the preparatory arc position which is about 5 to 10 mm above the counter electrode 4, and the counter electrode 4 and the plasma torch 1 are moved.
A plasma flame 12 is generated between and. When the plasma flame 12 is interrupted, the plasma torch 1 is lowered again to contact the counter electrode 4, and then the plasma torch 1 is raised again to generate the plasma flame 12.

After it was confirmed that the counter electrode 4 below the plasma torch 1 started to be melted by the plasma flame 12, the plasma torch 1 was lifted up to a heating arc position about 50 mm above the counter electrode 4 and the plasma flame was generated. Continuing, the gas atmosphere in the counter electrode 4 and the melting furnace 3 is heated and the temperature is raised.

In the waste plasma melting treatment method according to the present invention, since graphite is used for the plasma torch 1, the type and composition of the plasma working gas 7 is not limited when the plasma flame 12 is generated, and as a result, the plasma atmosphere is generated. Can be operated not only in a reducing atmosphere but also in an oxidizing atmosphere,
The possibility of waste treatment can be expanded. The oxidizing atmosphere does not hinder the treatment of wastes with a high organic content.

When raising the temperature of the plasma melting treatment apparatus,
This will be described with reference to FIG. With the plasma torch 1 in contact with the counter electrode 4 and the plasma flame 12 generated between the plasma torch 1 and the counter electrode 4 at the heating arc position, melting of the counter electrode 4 expands. For example, the voltage of the plasma torch at this time is 100 to several hundreds V and the current is 1000A.

The furnace atmosphere temperature measured by a thermometer (not shown) is 900 ° C. to 1000 ° C. (900 ° C. is a temperature at which particles, flakes, and waste 6 are melted, 100
(0 ° C. or higher is a temperature at which the furnace wall refractory is easily burnt out), the counter electrode 4 immediately below the plasma torch 1 begins to melt, and thus the clearance between the plasma torch 1 and the counter electrode 4 begins to occur and the plasma flame 12 It is in an unstable state that occurs or does not occur. Therefore, the plasma torch 1 rises by several mm, and the plasma flame 12 is generated between the counter electrode 4 and the plasma torch 1. At this time, when the plasma flame 12 is continued, the plasma torch 1 further rises to the preparatory arc position which is about 5 to 10 mm above the counter electrode 4.

After this plasma flame 12 confirms the spread of melting of the counter electrode 4 below the plasma torch 1, the plasma torch 1 is raised to a heating arc position about 50 mm above the counter electrode 4 to raise the plasma flame 12. The gas atmosphere in the counter electrode 4 and the melting furnace (3) is continuously heated and heated. For example, the voltage of the plasma torch at this time is 100 to several 100V, and the current is 1000 to 1300A.
Then, the temperature of the atmosphere in the furnace is maintained at about 1000 ° C.

Particles, flakes,
A case where the massive waste 6 is charged will be described with reference to FIGS. When the voltage of the plasma torch 1 is 100 to several hundreds V, the current is 1000 to 1300 A, the ambient temperature in the melting furnace 3 is about 1000 ° C., and the counter electrode 4 is melted over the entire area, the supply means 8 is used to make hollow graphite. Particles, flakes, and lump waste 6 are charged into the hollow portion 2 of the plasma torch 1 together with the plasma working gas 7, and are supplied onto the counter electrode 4. As shown in FIG. 1E, molten metal 11 is accumulated at the bottom of the melting furnace 3 by the molten metal of the counter electrode 4 and the molten metal in the waste 6, and the molten slag 1 is formed on the molten metal 11.
0 covers. The molten slag 10 is supplied by a supply means (not shown).
The waste 6 is partially melted and added.

When relatively low temperature particles, flakes, and lump waste 6 are put on the melted counter electrode 4, the temperature of the counter electrode 4 is temporarily lowered, and the molten slag 10 is also localized. Since it is not generated, the plasma flame voltage drops and becomes unstable. The ambient temperature in the furnace is maintained at about 1000 ° C., and then the plasma torch at the heating arc position rises to the molten plasma position about 100 mm above the counter electrode. When the plasma flame 12 is continued, the temperature of the atmosphere inside the furnace is maintained at about 1000 ° C., and the particles, flakes, and lump waste 6 are continuously charged.

When the plasma flame 12 is interrupted, the introduction of particles, flakes, and lump waste 6 is stopped. Then, after the plasma torch 1 descends and comes into contact with the counter electrode 4, only the plasma torch 1 rises from the preparation arc position to the heating arc position to generate the plasma flame 12, and the furnace atmosphere temperature is maintained at about 1000 ° C. . For example, the voltage of the plasma torch 1 at this time is a voltage at which the arc changes into plasma and is usually 100 V or more, and the current is 300 to 1000 A.

Then, similarly to the above, the plasma torch 1 rises from the preparation arc position to the heating arc position, and the plasma flame 12 is generated. Then, the operation shifts to normal operation. The length of the plasma flame 12 on the plasma torch 1 side during this operation is controlled by a potentiometer (not shown) attached to the plasma torch 1 based on the potential difference detected between the plasma torch 1 and the counter electrode 4. The potential difference at this time is
It is a total value of the potential in the molten slag 10 and the plasma flame 12 potential (approximately equal to the plasma flame length).

Finally, the case where the operation is stopped will be described. Melt slag (molten ash) and a part of the melted counter electrode are discharged by tilting the melting furnace, etc., then turn off the power and melt each plasma torch in order to prevent sticking to the counter electrode. It should be raised about 100 mm or more above the surface of the pond.

In the waste plasma melting treatment apparatus according to the present invention, a twin torch (single-phase transfer) type, a triple torch having an electric neutral point type counter electrode (4) at the bottom of the melting furnace (3). (Three-phase transfer)
Any one of a system and a system in which the number of torches is multiplied by N (N is an integer of 2 or more) can be selected and adopted as needed.

In the waste plasma melting treatment apparatus according to the present invention, the plasma working gas (7) contains not only an inert gas such as Ar and nitrogen but also an oxidizing gas such as air and a reducing gas.
It can be selected and used according to the melt processed product. For example, if it is possible to perform more detoxifying melting processing by oxidizing and melting the processed material, an oxidizing plasma working gas is used. Also, if the particle size of the processed material is large and it is necessary to increase the heat generation amount, increase the heat generation amount for oxidation by using an oxidizing plasma gas such as air.
It is also possible to make it easy to melt. More specifically, for example, in the case of a treated product containing toxic hexavalent chromium, it is possible to detoxify and melt by using a reducing gas. In this case, it is also possible to use the reducing gas as a plasma working gas. .

Generally, the flow rate of the plasma working gas is smaller than the amount of gas generated from the in-furnace processed product, and the reaction of the molten processed product after passing through the plasma torch is promoted in the subsequent in-furnace atmosphere. The furnace atmosphere is adjusted to an oxidizing or reducing atmosphere. The oxidizing atmosphere can be easily made by inflowing air, but the reducing atmosphere increases the CO concentration by introducing a reduction treatment material together, or introducing CO, which is a reducing gas, into the furnace, or by steaming gasification in a low oxygen atmosphere. Things are possible. It is also possible to install the plasma torch vertically and introduce the processed material into the plasma flame at the tip of the torch together with the plasma working gas at a substantially free fall velocity, but in this case, the flame passage time becomes short. Lengthening the flame passage time,
To accelerate the oxidation or reduction reaction in the flame, if the torch is installed tilted, the falling speed becomes slower.
The reaction time in the flame can be extended.

(Embodiment 1) FIG. 2 shows an embodiment of a waste plasma melting treatment apparatus according to the present invention. A plasma torch 1 made of graphite is vertically movable in the melting furnace 3, and the plasma torch 1 forms an electric circuit having a gap between a counter electrode 4 and a power source 9. The moving means 5 moves the plasma torch 1 up and down. In FIG. 2, the plasma torch 1
Although a case where the melting furnace 3 is moved up and down is shown in the drawing, it is sufficient if the displacement is relatively performed, so that the melting furnace 3 may be moved up and down with the plasma torch 1 fixed. The molten metal 1 at the bottom of the melting furnace 3
1 is formed by being melted by the heat generated by the plasma discharge of the counter electrode 4, but an appropriate amount may be provided at the bottom of the melting furnace 3 from the beginning.

(Embodiment 2) FIG. 3 shows another embodiment of the waste plasma melting treatment apparatus according to the present invention. The melting furnace 3 is formed as a substantially closed container, and a dust collector 13 is provided at the upper opening of the melting furnace 3. Further, the molten metal 11 is supplied from the molten metal discharge port 14, and the molten slag 10 is supplied from the molten slag discharge port 15.
Of the melting furnace 3 can be discharged without tilting.

FIG. 4 shows another embodiment in which a gasification combustion chamber 34 is further added to the above-described waste plasma melting treatment apparatus according to the present invention so as to facilitate the treatment of dioxins. As a measure against dioxin in the exhaust gas, dioxins are decomposed at high temperature in the gasification combustion chamber 34, and the exhaust gas is then rapidly cooled in an exhaust gas treatment device to prevent re-synthesis of dioxins and a fly ash and soot are collected by a dust collector.

As described above, the waste plasma melting treatment apparatus according to the present invention can be used as a gasification melting furnace by further adding the gasification combustion chamber 34. In order to gasify, it is necessary to burn the processed product as a combustible gas such as CO (eg, steaming in a low oxygen atmosphere at 300 to 450 ° C.), and a burning element (for example, carbon It must be waste, including organic matter that it contains. Municipal waste contains organic matter, and CO gas that is gasified in the initial steaming state reacts with blower air (oxygen) in the gasification combustion chamber 34 and burns at a high temperature.

Since incineration ash containing a large amount of inorganic substances is difficult to gasify with ash alone, it is necessary to mix and charge with other trash for gasification. Ashes alone are melted by plasma, but can be melted without being necessarily gasified. Gasification has the advantage that complete combustion of flue gas and dioxin decomposition can be performed without a secondary burner, increasing the amount of heat in the furnace. A plasma melting treatment device as a practical energy-saving system including exhaust gas treatment can be made. If the purpose is limited to melting and solidifying slag, it can be carried out without gasification.

The waste plasma melting treatment method and apparatus using the graphite plasma torch according to the present invention have been described above. However, the technical idea of the present invention is not limited to graphite, but other than metallic plasma torches having physical properties (electrical conductivity, heat resistance) similar to graphite, such as conductive sialon. It can also be deployed.

[0061]

According to the present invention, it is possible to provide a waste plasma melting treatment method and a waste plasma melting treatment apparatus suitable for it, which can reduce the number of maintenance steps and can perform stable heating and plasma melting treatment operation of waste. .

[Brief description of drawings]

FIG. 1 is a principle diagram of a waste plasma melting treatment method according to the present invention.

FIG. 2 is a waste plasma melting treatment apparatus 1 according to the present invention.
It is a figure which shows an Example.

FIG. 3 is a diagram showing another embodiment of the waste plasma melting treatment apparatus according to the present invention.

FIG. 4 is a diagram showing another embodiment in which a gasification combustion chamber is added to the waste plasma melting treatment apparatus according to the present invention.

FIG. 5 is a diagram showing a conventional waste plasma melting treatment apparatus.

[Explanation of symbols]

1 plasma torch, 2 hollow part, 3 melting furnace, 4 counter electrode, 5 moving means, 6 waste, 7 plasma working gas, 8 supplying means, 9 power source, 10 molten slag, 1
1 molten metal, 12 plasma flame, 13 dust collector,
14 Molten Metal Discharge Port, 15 Molten Slag Discharge Port, 16
Cylindrical member, 17 gas ring, 18 high frequency coil, 1
9 upper flange, 20 lower flange, 21 probe, 22 base lid, 23 chamber, 24 fireproof heat insulating material, 25 circulating water tank, 26 cooler, 27, 28
Pump, 29 introduction pipe, 30 discharge pipe, 31, 32
Tube, 33 high frequency power supply, 34 gasification combustion chamber,

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05B 7/18 B09B 3/00 303L // C22B 7/00 ZAB F term (reference) 3K061 AA16 AB03 AC01 AC03 BA05 BA05 CA14 DA12 DA18 DA19 DB11 NB02 NB23 3K084 AA04 AA08 AA12 BA07 4D004 AA36 AA37 AA43 AB07 AC08 CA28 CA29 CA43 CB31 4K001 BA12 BA14 DA01 GA16 GB12

Claims (5)

[Claims] 1. A method for melting waste plasma by heating with a plasma torch, wherein the plasma torch has a hollow portion penetrating the inside of the plasma torch, and the plasma working gas is charged into the hollow portion together with the waste. Characteristic waste plasma melting treatment method. 2. The waste plasma melting treatment method according to claim 1, wherein the plasma flame generation portion of the plasma torch is formed of graphite. 3. A plasma torch having a hollow portion penetrating the inside thereof, a melting furnace having a counter electrode provided at the bottom so as to face the plasma torch, and a relative distance between the counter electrode and the plasma torch is variable. Moving means, supply means for charging the hollow portion with waste and plasma working gas,
A waste plasma melting treatment apparatus comprising: a plasma torch having one end and a power source having the other end connected to the counter electrode. 4. The waste plasma melting treatment apparatus according to claim 3, wherein the plasma flame generating portion of the plasma torch is made of graphite. 5. The waste plasma melting treatment apparatus according to claim 3, further comprising a gasification combustion chamber.