JPH07217832A - Plasma melting apparatus - Google Patents

Abstract

PURPOSE:To separate and recover fine powder to be solidified and recovered after other substance is melted by melting the powder to be recovered from an incinerator for waste such as general refuse, etc., and recovering heavy metal by cooling and solidifying after vaporizing it. CONSTITUTION:The plasma melting apparatus comprises a molten pool 22 for storing a furnace bot,tom electrode 21 and a molten dust 23 at a lower part of a melting furnace 20, a torch electrode 24 provided at an upper part of the furnace 20, a plasma torch having a nozzle 25 for feeding fine powder 26 and heating plasma gas 28 to outside the electrode 24, and a power source 32 for generating a transfer type arc plasma 33 between the electrode 21 and the electrode 24. When the powder 26 is supplied to the furnace 20 together with the plasma gas, the powder 26 is melted at a high temperature by the plasma 33.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention melts fine powders collected from an incinerator for wastes such as general waste, collects heavy metals by cooling and solidifying after vaporization, and solidifies other substances after melting. The present invention relates to a plasma melting device for separating and collecting fine powders to be collected.

[0002]

2. Description of the Related Art In recent years, the amount of fine dust (dust collecting dust) generated as soot dust generated by incineration of waste such as general garbage has become extremely large. And this fine powder contains harmful substances such as heavy metals and dioxins with low melting point in the surface layer, and if this fine powder is landfilled as it is, there is a concern that it will affect the biological system. Heavy metals are melted at high temperature, heavy metals are vaporized by evaporation, etc. and then rapidly cooled and solidified, and other substances are cooled after melting and solidified into sand or blocks to be separated, and heavy metals are reused. , And sand-like or block-like solids of other substances are used for building materials and the like, and the study of fine powder treatment is underway.

As an example of a conventional apparatus for melting these fine powders, there is one using electric resistance as a heat source. That is, as shown in FIG. 3, a heating element 2 using electric resistance as a heat source is provided in the melting furnace 1 to heat and melt the fine powder material 4 supplied from the hopper 3 into the melting furnace 1 to form a bottom portion of the melting furnace 1. Are accumulated in the molten state. The accumulated melt 5 is taken into the recovery container 8 from the melt outlet 6 through the pipe 7, and the melt 5 is cooled and recovered as a glassy solid substance 9. On the other hand, the heavy metal 10 having a low melting point is vaporized in the above-mentioned melting process, vaporized and led out of the heating furnace 1 through the outlet 11 provided above.
It is rapidly cooled and solidified by the cooling unit 12 such as cooling air provided in the lead-out unit, and is recovered in the heavy metal recovery unit 13. The exhaust gas from which the heavy metal 10 has been collected is discharged by the blower fan 14 through the duct 15. Also, as another conventional example,
A gas burner may be used as a heat source, but it is omitted in principle because it is not much different from the above-mentioned melting device.

[0004]

However, the heating by such a heating element using electric resistance as a heat source is indirect heating, so that the thermal efficiency is low and the heating temperature is limited to a high temperature. There is a problem that an effective heating atmosphere cannot be selected depending on the property. Further, those using a gas burner as a heat source, in addition to the problems in the melting device using electric resistance as the heat source described above, there is a problem of exhaust gas treatment associated with combustion, these prior art various melting device of fine powder There was a problem. The present invention solves such a problem as a melting apparatus for fine powder, and provides a melting apparatus capable of improving thermal efficiency, raising the heating temperature, and selecting an effective heating atmosphere depending on the properties of the fine powder. To do.

[0005]

The plasma melting apparatus according to the present invention melts fine powders collected from an incinerator for waste such as general waste, and collects heavy metals by cooling and solidifying after vaporization, and other substances. Is a melting device for separating and recovering fine powder that is solidified and recovered after melting, with a furnace bottom electrode provided at the bottom of the melting furnace and a molten pool for accumulating the melt,
A torch electrode provided in the upper part of the melting furnace, a plasma torch including a fine powder and a plasma gas feeding nozzle for heating the fine powder on the outside of the torch electrode, and a transfer type between the furnace bottom electrode and the torch electrode. A power supply unit for generating arc plasma is provided, and when the fine powder is supplied to a melting furnace together with a heating plasma gas, the fine powder is melted at a high temperature by the transfer arc plasma. .

Further, another plasma melting apparatus according to the present invention melts fine powders collected from an incinerator for waste such as general waste, and collects heavy metals by cooling and solidifying after vaporization,
Other substances are solidified after melting and recovered.In a melting device for separating and recovering fine powder, a furnace bottom electrode provided in the lower part of the melting furnace, a melting pool for accumulating the melt, and an upper part of the melting furnace. The torch electrode is provided, the torch electrode protecting plasma gas feeding first nozzle is provided outside the torch electrode, and the fine powder and the heating plasma gas feeding second nozzle is provided outside the first nozzle. Plasma torch,
A torch electrode is provided between the furnace bottom electrode and the torch electrode to protect the torch electrode when the fine powder is supplied from the second nozzle to the melting furnace together with the heating gas. The working gas is supplied from the first nozzle to protect the torch electrode, while the fine powder is melted at a high temperature by the transfer arc plasma.

[0007]

FIG. 1 shows a first embodiment according to the present invention. FIG. 1 is a schematic view of a vertical cross section of a melting apparatus, in which 20 is a melting furnace and 21
Is a furnace bottom electrode provided at the bottom of the melting furnace 20, 22 is a molten pool in which molten dust 23 in which fine powder is melted is accumulated, and 24 is a tungsten provided at the top of the melting furnace 20. Torch electrode, 25 is torch electrode 2
4 is a torch nozzle formed in a cylindrical shape whose lower part is narrowed to the outside of 4, and the torch electrode 24 and the torch nozzle 25 are
It is formed as a plasma torch 31. Then, the torch nozzle 25 is supplied with the fine powder 26 and the heated plasma gas 28 from a supply pipe 30 connected to the feed port 27 of the fine powder 26 and the feed port 29 of the heated plasma gas 28. In addition, the torch nozzle 25 provided on the outer periphery of the torch electrode 24 supplies the fine powder 26 and the heated plasma gas 28 to the melting furnace 20 almost uniformly.
It is desirable to use a mesh-like dispersion filter or the like in the nozzle 25 portion to make it uniform.

Reference numeral 32 is a DC power source for generating a transfer arc plasma 33 between the furnace bottom electrode 21 and the torch electrode 24, 34 is an extraction pipe for extracting the molten dust 23 of the molten pool 22, and 35 is an extraction pipe 34. The amount of the molten dust 23 taken out is adjusted by a valve provided. Reference numeral 36 denotes a container that cools and solidifies the extracted molten dust 23 and stores the glass dust therein. A glass-like solid material 37 is collected in the container 36.
Reference numeral 38 is a duct for collecting exhaust gas containing vaporized low melting point heavy metal 39 which is generated in the process of melting the fine powder 26 or which is evaporated from the molten pool, and the duct 38 is provided with an exhaust gas cooling blower 40. The exhaust gas cooling unit 41 and the recovery unit 42 for recovering the heavy metal 39 are provided. Four
Reference numeral 3 is an exhaust gas emission unit.

Next, the operation and action of this apparatus will be described. The present invention is also one in which the fine powder 26 having a low melting point heavy metal attached to the surface is melted, and the heavy metal 44 and the molten dust 23 containing no heavy metal are cooled and separated into a glassy solid 37 for recovery. Before the voltage is applied between the furnace bottom electrode 21 and the torch electrode 24, the fine powder 26 and the heating plasma gas 28 are not supplied, the molten pool 22 does not have the molten dust 23, and the furnace bottom electrode 21 is exposed. In the operation of the melting apparatus, a DC voltage is applied to both electrodes, and nitrogen gas, for example, as heating plasma gas 28 is supplied to the melting furnace 1 from the heating plasma gas supply port 29 through the nozzle 25. As a result, transfer arc plasma is generated between the torch electrode 24 and the furnace bottom electrode 21. Next fine powder 2
6 is supplied from the feed port 27, is mixed with the heated plasma gas 28 by the supply pipe 30, and is supplied from the nozzle 25 to the melting furnace 20.
Is supplied to. The supplied fine powder 26 is heated by the nitrogen plasma flow, melts and evaporates, and melts the dust 2.
3 is sent to the furnace bottom electrode 21.

5 in the arc plasma 33 in the melting furnace 20.
000 to 10000 ℃ high temperature and several times more viscous than its surroundings, arc plasma 3
The fine powder 26 in 3 reaches the furnace bottom electrode 21 without diffusing to the periphery. At least the surface of the fine powder substance 26 that has reached the furnace bottom electrode 21 is in a molten state, adheres to the surface of the furnace bottom electrode 21 and is melted, and does not scatter as fine powder. The fine powder 26 supplied into the melting furnace 20 is successively accumulated in the furnace bottom in a molten state by the arc plasma to form a molten pool 22. The low melting point heavy metal evaporates and vaporizes in the process of heating and melting the fine powder 26 in the arc plasma 33 and in the process of heating the molten dust 23 in the molten pool 22. At this time, the temperature of the molten pool 22 is from 1300 ° C. to 1500 ° C. where the fluidity of the molten dust 23 can be secured, and the arc plasma 3
The heat output of No. 3, that is, the output voltage of the power supply 32 can be adjusted and increased.

In the heating state by the arc plasma 33, the flow rate of the heating plasma gas 28 is reduced, and the gas is allowed to stay in the melting furnace 1 at 1000 ° C. or higher until the dioxy vaporized and separated from the molten dust 23 is decomposed. The exhaust gas containing the heavy metal 39 vaporized thereafter is exhausted to the exhaust gas cooling unit 4
Introduced in 1. The cooling air blown by the exhaust gas cooling blower 40 rapidly cools the temperature to 300 ° C. or lower. Therefore, the vaporized heavy metal 39 is solidified, and chlorine generated by the decomposition of dioxin is recovered by the recovery unit 42 without generating dioxin again. Heavy metal 3
The exhaust gas from which 9 has been removed is discharged from the exhaust gas discharge unit 43 to the atmosphere. By heating the exhaust gas in the nitriding atmosphere of the melting furnace 20, almost no NOx is generated.

Next, another embodiment of the present invention will be described with reference to FIG. In addition, FIG. 2 is also a schematic view of a vertical cross section of the melting device.
The same parts as those in FIG. 1 are denoted by the same reference numerals. First mentioned above
The difference from the above embodiment is that a nozzle for feeding a gas for protecting the torch electrode 24 is further provided between the torch electrode 24 and the torch nozzle 25. That is, reference numeral 45 is a nozzle (first nozzle) formed in a cylindrical shape with its lower portion being narrowed outside the torch electrode 24, and this nozzle 45 is connected to a feed port 47 of a plasma gas 46 for electrode protection. Argon gas, for example, is supplied from the pipe 48. The plasma gas 46 for protecting the electrode is also supplied to the nozzle 45.
It is desirable to use a mesh-like dispersion filter or the like at the nozzle 45 so as to make it uniform so that the gas is supplied almost uniformly into the melting furnace 1 through the torch electrode 24. A nozzle 49 (second nozzle) is provided outside the nozzle 45 (first nozzle) and has a cylindrical shape with a narrowed lower portion. Then, the second nozzle 49 is provided with a feed port 27 for the fine powder 26 and a heated plasma gas 28.
The fine powder 26 and the heated plasma gas 28 pass through the supply pipe 30 connected to the feed port 29 of the melting furnace 20.
Is supplied to. The torch electrode 24 and the first nozzle 4
5 and the second nozzle 49 are formed as a plasma torch 50.

The operation and action of this embodiment are affected by supplying the electrode protecting plasma gas 46 to the first nozzle 45 to supply the torch electrode 24 as the heating plasma gas 28, for example, nitrogen gas. It protects against receiving. After the electrode protecting plasma gas 46 is supplied from the first nozzle 45, or at the same time, the heating plasma gas 28 is supplied to the torch electrode 24.
A nitrogen / argon plasma flow is generated between the furnace bottom electrode 21 and the furnace bottom electrode 21, and the fine powder 26 supplied thereafter is heated by the arc plasma 50 by the nitrogen / argon plasma flow, and the molten dust 23 is melted / vaporized and the molten dust 23 is heated in the furnace. Bottom electrode 21
Sent to. As described above, in the second embodiment, the torch electrode 24 is protected from the heating plasma gas 28, and the nozzle 49 (second nozzle) for supplying the heating plasma gas 28 is used.
The nozzle 45 (first nozzle) for supplying the electrode protecting plasma gas 46 is provided inside the nozzle.
Therefore, even if the heating plasma gas 33 selected depending on the properties of the fine powder 26 adversely affects the torch electrode 24, it is protected by the electrode protecting plasma gas 46, and therefore the length of the torch electrode 24 is increased. The life can be extended.

[0014]

As described above, the present invention can heat a fine powder in an arc plasma and in a molten pool at a high temperature, can melt it with high efficiency, and, depending on the nature of the fine powder, a plasma gas for heating. By selecting, the heating atmosphere can be controlled to be oxidized, nitrided or inert. In addition, by lowering the flow rate of plasma gas, it is possible to reduce gas costs, improve thermal efficiency by reducing exhaust gas loss, and decompose dioxin by prolonging the residence time in the high temperature melting furnace, thus reducing pollution. In addition, the rapid cooling device can be simplified. By reducing the flow rate of the plasma gas and increasing the arc plasma length, increasing the residence time of fine powder in the arc plasma,
The surface of the fine powder is sufficiently melted and evaporated, and the separation and decomposition of dioxin adhering to the surface layer and the evaporation of heavy metals can be promoted. Further, the surface of the fine powder is melted and the landing on the furnace bottom is ensured. In addition, the exhaust gas cooling unit rapidly increases to 30
By cooling below 0 ° C, the heavy metals with a low melting point in the exhaust gas are solidified and recovered without regenerating dioxin, and the molten dust contains some heavy metals, but is suitable for disposal and use after melting. By solidifying it into a suitable shape, it becomes possible to render the dust harmless, recycle it, reduce its volume, etc., and exert an excellent effect as a melting device for treating fine powder.

[Brief description of drawings]

FIG. 1 is a schematic view of a vertical cross section of a melting apparatus showing an embodiment of the present invention.

FIG. 2 is a schematic view of a vertical cross section of a melting device showing another embodiment of the present invention.

FIG. 3 is a schematic diagram of a vertical cross section of a conventional melting device.

[Explanation of symbols]

 1,20 Melting furnace 2 Heating element 3 Hopper 4,26 Fine powder 5,23 Melting dust 6 Melting dust outlet 7,34 Melting dust extracting pipe 8,36 Melting dust collecting container 9,37 Sandy solid matter of molten dust 10 Exhaust gas outlet 11,41 Exhaust gas cooling part 12,42 Heavy metal recovery part 13 Blower fan 14,43 Exhaust gas discharge part 21 Furnace bottom electrode 22 Molten pool 24 Torch electrode 25 Torch nozzle 27 Fine powder feed port 28 Heating plasma gas 29 Heated plasma gas feed port 30 Supply pipe 31, 51 Plasma torch 32 Power supply 33,50 Arc plasma 35 Valve 38 Duct 39 Low melting point heavy metal 40 Cooling blower 44 Heavy metal 45 First nozzle 46 Electrode protection plasma gas 47 Electrode protection Plasma gas delivery port 48 Electrode protection plasma Magus supply pipe 49 Second nozzle

Claims (4)

[Claims] 1. A fine powder collected from an incinerator for waste such as general refuse is melted, heavy metals are recovered by cooling and solidification after vaporization, and other substances are solidified after melting and separated. In a melting apparatus for recovery, a furnace bottom electrode and a molten pool provided in the lower part of the melting furnace, a torch electrode provided in the upper part of the melting furnace, and a fine powder and a plasma gas for heating are supplied to the outside of the torch electrode. A plasma torch consisting of an inlet nozzle and a power source for generating a transfer arc plasma between the furnace bottom electrode and the torch electrode were provided, and the fine powder was supplied to the melting furnace together with the heating plasma gas. At this time, the plasma melting apparatus is characterized in that the fine powder is melted at a high temperature by the transfer arc plasma. 2. Separation of fine powder recovered by melting fine powder collected from an incinerator for waste such as general waste, cooling and solidification after vaporization, and solidifying and collecting other substances after solidification In a melting apparatus for recovery, a furnace bottom electrode provided in a lower part of a melting furnace and a molten pool for accumulating a molten material, a torch electrode provided in an upper part of the melting furnace, and a torch electrode protection provided outside the torch electrode. First for plasma gas delivery
A plasma torch including a nozzle and a second nozzle for feeding a fine powder and a plasma gas for heating to the outside of the first nozzle; and a transfer arc plasma generated between the furnace bottom electrode and the torch electrode. A power supply unit, and when supplying the fine powder together with the heating plasma gas from the second nozzle to the melting furnace, while supplying the torch electrode protection gas from the first nozzle to protect the torch electrode, A plasma melting apparatus, characterized in that fine powder is melted at a high temperature by the transfer arc plasma. 3. The plasma melting apparatus according to claim 1, wherein an argon gas, a nitrogen gas, a hydrogen gas, a mixed gas of these, or air is used as the heating plasma gas. 4. The plasma melting apparatus according to claim 2, wherein argon gas or nitrogen gas is used as the plasma gas for protecting the torch electrode.