JP3611314B2 - Plasma ash melting furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma ash melting furnace, and more particularly to an invention for preventing a side current of a plasma ash melting furnace that melts incinerated ash containing fly ash by high-temperature plasma generated from an electrode inserted in the furnace body.
[0002]
[Prior art]
Conventionally, incineration ash generated by incineration of municipal waste and industrial waste has been recovered as slag after being melted and solidified as a measure to prolong the life of the final disposal site and prevent secondary pollution. Incinerated ash collected as slag has no fear of leaching of harmful substances, and can be reused as civil engineering and building materials.
Among the melting furnaces for converting incinerated ash into slag, the plasma ash melting furnace shown in FIG. 9 is inserted from an iron furnace body 12 having a cylindrical shape, a refractory material 13 covering the inner wall of the furnace body, and a furnace lid. A main electrode 14 that hangs down and an electrode 34 that is inserted from the lower part of the furnace so as to face the main electrode 14.
[0003]
In the plasma ash melting furnace 11, the incinerated ash charged from the ash hopper 30 is transferred to the melting furnace 11 by the quantitative feeder 31, and the incinerated ash is connected to the main electrode 14 and the counter electrode 34 connected to the DC power source 32. It is introduced into the furnace in a plasma state by the arc 35 generated during the period. At this time, the inside of the furnace is maintained in a reducing atmosphere by an inert gas such as N ₂ gas supplied from the top of the furnace.
The molten slag 15 melted at a temperature of 1500 ° C. or higher by the plasma high-temperature gas flow is separated from the molten metal 16 and discharged from the discharge port to generate slag, which is reused for various purposes.
The exhaust gas generated in the ash melting furnace is reduced in temperature by cooling air, and sent to an exhaust gas treatment device (not shown) through a bag filter 38.
[0004]
However, incinerated ash that is melt-processed, especially fly ash, contains a large amount of salts with a relatively low melting point, so when it is melted at high temperatures, most of it is volatilized in the gas and adheres to the inner wall of the furnace. To do. Molten salts such as potassium chloride and sodium chloride attached in this way have high conductivity, and therefore there is a risk that side current will be generated due to poor insulation.
Further, the refractory 13 covered on the furnace wall is easily damaged and consumed due to the adhesion of the molten salt, and is used to support the refractory material from the low-resistance molten salt adhering to the furnace wall accompanying the damage and consumption. There is a problem in that the melting efficiency with respect to the molten slag is reduced due to conduction to the metal fitting.
[0005]
Therefore, in order to prevent the generation of a side current in the vicinity of the electrode, as shown in the enlarged view (b) of the D section of the schematic cross-sectional view (a) of the conventional plasma ash melting furnace of FIG. A method is adopted in which an insulating sleeve 16 is provided between the electrode 13 and the electrode 14, or a gap is provided between the electrode 14 and the furnace body. Further, in Japanese Patent Application Laid-Open No. 11-351541, the sealing gas is blown uniformly, and the clearance C between the insulating sleeve 16 and the main electrode 14 is increased toward the inside of the furnace, and even if molten salt adheres, it contacts the main electrode 14. The structure is such that it will not be done.
[0006]
Further, in order to prevent conduction due to adhesion of molten salt to the furnace inner wall, Japanese Patent Laid-Open No. 10-288231 discloses a cylindrical body in which an outer layer is made of an insulating refractory and an inner layer is made of a foam refractory. A method of sieving is proposed. Thus, by protecting an electrode with a cylindrical body, the corrosion of the electrode by molten salt and the short circuit between the electrodes or the molten salt adhering to the furnace wall can be prevented.
[0007]
[Problems to be solved by the invention]
However, in the above prior art, molten salt penetrates into the gap between the insulating sleeve and the electrode, so that sufficient insulation cannot be obtained, and the molten salt adheres to the clearance shape as disclosed in JP-A-11-351541. Even if it is formed so as not to be in contact with the main electrode, there is a possibility that the distance from the electrode becomes close due to the accumulation of molten salt and conduction is caused. Further, even when a tubular body surrounding the electrode is provided as disclosed in Japanese Patent Application Laid-Open No. 10-288231, the tubular body is significantly deteriorated and damaged by a high-temperature atmosphere around the electrode, and a problem remains in the durability of the tubular body.
In view of the problems of the prior art, the present invention is a plasma ash capable of preventing molten salt from entering the insulating gap with a simple structure and limiting adhesion of the molten salt to the furnace inner wall to prevent insulation failure. The purpose is to provide a melting furnace.
[0008]
[Means for Solving the Problems]
Therefore, in order to solve the problem, the present invention described in claim 1
In a plasma ash melting furnace having a tubular electrode at the top of an iron furnace body whose inner wall is coated with a refractory material, and having an insulating sleeve disposed with a gap in the furnace penetration part of the electrode,
A configuration in which the insulating sleeve is expanded with a plurality of steps at an inclination angle so that a gap between the insulating sleeve and the electrode is directed into the furnace, and molten salt generated by ash melting flows down along the inclined surface; It is characterized by that.
In this invention, the upper inclined surface of the insulating sleeve is set to an angle that determines the flow path in the direction in which the inert gas sealing the gap diffuses without swirling, and the molten salt adhering to the lower inclined surface easily flows down. An angle. Thereby, even if the molten salt adheres to the insulating sleeve around the electrode, it flows down to the outside of the furnace, and sufficient insulation can be obtained.
[0009]
According to a second aspect of the present invention, the insulating sleeve is formed so as to protrude from the furnace wall around the insulating sleeve, so that the molten salt flowing down adheres to the furnace lid through the insulating sleeve and solidifies. Without falling on the molten slag and minimizing deposits.
Further, according to claim 3, the insulating sleeve is notched in a hollow cone shape so as to surround the electrode, and the lower portion thereof is notched in a hollow cone shape with a larger inclination angle than the cone, and is generated by ash melting. By adopting a configuration that prevents the molten salt from adhering to the insulating sleeve, the above effect can be realized with a simple structure.
[0010]
According to a fourth aspect of the present invention, there is provided a molten salt retracting portion formed by a lower inclined surface of the insulating sleeve having a gap between the furnace penetrating portions having an inclination angle of approximately 10 ° to 25 ° with respect to a horizontal direction. And a gas flow escape portion formed by an upper inclined surface having an inclination angle of less than about 2 ° with respect to the direction. This invention shows the most suitable angle of the inclined surface. By making the inclined surface the angle, the gas flow does not swirl on the upper inclined surface, and the molten salt smoothly flows on the lower inclined surface. run down.
[0011]
The invention according to claim 5 is a plasma ash melting furnace having a tubular electrode on the upper part of an iron furnace body whose inner wall is coated with a refractory material, and having an insulating sleeve disposed with a gap in the furnace penetration part of the electrode.
One or a plurality of molten salt evacuation parts are provided on the inner wall of the ash melting furnace side wall or the inner wall of the furnace lid, and the molten salt generated by ash melting flows down the furnace wall by the molten salt evacuation part. .
According to this invention, the adhesion of the molten salt can be minimized by providing the molten salt retracting portion on the furnace wall to which the molten salt easily adheres. Note that the furnace lid may be inclined downward toward the outer edge of the furnace, so that the molten salt flows down from the furnace center to the outside, so that the molten salt retracting portion works effectively.
[0012]
The invention according to claim 6 is the plasma ash melting furnace in which the furnace lid is inclined downward toward the outer edge of the furnace, wherein the molten salt retracting portion is provided on the furnace lid and has a step on the side wall of the furnace. It is the level | step-difference part or collar part which inclines so that it may have.
Furthermore, the invention according to claim 7 is characterized in that the molten salt retracting portion is a stepped portion or a flange portion provided at the upper portion of the inner wall of the furnace and having an enlarged diameter at the lower portion.
According to these inventions, the molten salt is limited to the molten salt retracting portion without adhering to the furnace side wall, and further, the molten portion is melted into the furnace lid by setting the angle of the stepped portion or the flange portion to an angle at which the molten salt drops. Salt adhesion is also minimized.
[0013]
In the invention according to claim 8, the support metal for joining the refractory material to the iron furnace body or the support metal for supporting various sensors penetrating the furnace lid is made of an insulating refractory such as ceramics. It is characterized by that.
As described above, since the molten salt depositing portion is limited by the molten salt retracting portion, by using an insulating refractory for the support metal only in the depositing portion, leakage from the support metal fitting due to consumption of the refractory is prevented. Therefore, it is possible to realize a device that is less likely to cause insulation failure at low cost. The insulating refractory is preferably made of alumina ceramics or the like.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.
1 is a schematic sectional view of a plasma ash melting furnace according to an embodiment of the present invention, FIG. 2 is an enlarged view of a portion A showing the upper part of the plasma ash melting furnace of FIG. 1, and FIG. 3 is an upper side wall of the plasma ash melting furnace of FIG. FIG. 3 is an enlarged view of part B showing the second embodiment. FIG. 3 is an enlarged view of part B showing the second embodiment.
[0015]
In FIG. 1, 11 is a plasma ash melting furnace body, 12 is an iron furnace body that forms the outer shell of the furnace body 11, and 13 is a refractory material that covers the inner wall of the furnace body 12, such as meteorite bricks and alumina castables. Etc. are formed. In this embodiment, the furnace lid of the melting furnace has a conical shape with the center portion protruding upward, and the inclination angle of the furnace lid is approximately 1 ° or more with respect to the horizontal direction. Such a shape can maintain the structural strength of the refractory and contribute to prevention of adhesion of the molten salt described later. Reference numeral 14 denotes a main electrode penetrating through the top of the ash melting furnace. In this embodiment, a tubular graphite electrode is used. Other configurations are substantially the same as those of the conventional plasma ash melting furnace described with reference to FIG.
[0016]
The plasma ash melting furnace 11 applies a DC voltage between the main electrode 14 connected to the DC power source shown in FIG. 9 and the furnace bottom electrode 34 to generate a plasma arc and sequentially supply it from the ash hopper. Melt incineration ash to make slag. At this time, the Joule heat based on the electric resistance of the molten slag 15 is also utilized and the molten state is maintained.
A large amount of low melting point salts are contained in the slag 15 which is in a molten state by the plasma high-temperature gas flow generated by the main electrode 14, and these are vaporized and vaporized to form a molten salt 23 as a furnace lid. Adhere to and condense.
[0017]
FIG. 2 is an enlarged view of part A in FIG. 1, and an insulating sleeve 16 is disposed in the furnace 14 through the electrode 14 through a gap, from which a sealing gas such as N ₂ gas enters the furnace. Have been supplied. The gap between the insulating sleeve 16 and the main electrode 14 is expanded with an inclination angle in two stages toward the furnace. At this time, the lower inclined surface 16a has an inclination angle α = approximately 10 ° to 25 °, preferably approximately 20 ° with respect to the horizontal direction, and the lower inclined surface 16b has an inclination angle β = approximately less than 2 ° with respect to the vertical direction, Preferably, the angle is approximately 2 °.
[0018]
Further, the insulating sleeve 16 is configured to protrude from the furnace wall around the sleeve. The projecting portion has a projecting length capable of maintaining durability even in a high temperature atmosphere.
According to this embodiment, when the sealing gas is introduced into the furnace without being swirled by the upper inclined surface 16b, and the volatilized molten salt 23 is adhered to the insulating sleeve 16 by the lower inclined surface 16a. However, it can flow down the inclined surface and flow down to the furnace bottom to prevent insulation failure.
[0019]
FIG. 3 shows a first embodiment of an enlarged view of part B of FIG. 1, and FIG. 4 shows a second embodiment.
In this embodiment, a molten salt evacuation portion is provided at the upper portion of the furnace side wall, and in the first embodiment, a step portion 17 is provided on the upper portion of the side wall of the refractory 13 covered by the iron furnace body 12 and flows down after being attached to the furnace lid. The molten salt 23 is dripped at the stepped portion 17, and the second embodiment is provided with a trough 18 inclined toward the furnace center on the upper side wall of the refractory 13, as in the first embodiment. The molten salt 23 is configured to flow down from the trough 18.
With such a configuration, the molten salt that has been volatilized and adhered to the furnace lid flows down the inclined furnace lid and falls into the molten slag by the stepped portion 17 or the trough 18, so that adhesion of the molten salt to the furnace wall can be prevented. .
[0020]
Next, an ash melting furnace provided with a supporting metal member inserted in the furnace body will be described with reference to FIGS.
FIG. 5 is a schematic cross-sectional view when an insulating metal support is inserted into the furnace wall of the plasma ash melting furnace according to the embodiment of the present invention. FIG. 6 is a diagram showing sensors on the upper part of the plasma ash melting furnace according to the embodiment of the present invention. FIG. 7 is a schematic cross-sectional view of an insulating support hardware used in the present embodiment.
As shown in FIG. 5, the support hardware 22 is used for penetrating and joining the furnace body 12 and the refractory 13, and a plurality of support hardware is used for an integrated furnace.
[0021]
Examples of the support metal 22 include a screw-type support metal 22A as shown in FIG. 7A, and a Y-type support metal as shown in FIG. 7B. These support hardwares 22 are preferably highly insulating and durable, such as ceramic support tiles.
However, since the support hardware 22 is expensive, as shown in FIG. 5, for example, in the case of an ash melting furnace equipped with a rod 18, the molten salt does not adhere to the furnace side wall due to the rod 18, so The insulating refractory material may be used only for the support metal member 22 inserted into the metal plate. As described above, by insulating the support metal member 22, even when the refractory material 13 is consumed, the iron furnace body 12 and the molten salt 23 are not in direct contact with each other, and current conduction can be prevented.
[0022]
In addition, as shown in FIG. 6, it is preferable to insert an insulating fiber and an insulating support metal 22 in a place where the molten salt is easily condensed between the stepped portions 19 provided in the furnace lid, and further, By providing the insulating sleeve 16 having the two-step inclined surface, the adhesion of the molten salt to the refractory can be minimized, and the generation of the side current can be almost surely prevented.
[0023]
【The invention's effect】
As described above, according to the present invention, the upper inclined surface of the insulating sleeve is set to an angle that determines the flow path in the direction in which the inert gas sealing the gap diffuses without swirling, and the lower inclined surface is attached. By setting the angle at which the molten salt flows down, even if the molten salt adheres to the insulating sleeve around the electrode, it flows down to the outside of the furnace and sufficient insulation can be obtained.
Further, by causing the insulating sleeve to protrude from the surrounding refractory material, the molten salt flowing down flows down on the molten slag without adhering to the furnace lid through the insulating sleeve and solidifying, and the deposits can be minimized.
Furthermore, by providing a molten salt retreating part such as a stepped part or a soot on the furnace wall part where the molten salt is likely to adhere, the molten salt can flow down and the amount of adhesion can be reduced. By using an insulating material such as ceramics for the support metal, generation of side current can be prevented almost certainly.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a plasma ash melting furnace according to an embodiment of the present invention.
FIG. 2 is an enlarged view of a part A showing the upper part of the plasma ash melting furnace of FIG.
FIG. 3 is an enlarged view of part B showing a first embodiment of the upper side wall of the plasma ash melting furnace of FIG. 1;
FIG. 4 is an enlarged view of part B showing a second embodiment of the upper side wall of the plasma ash melting furnace of FIG.
FIG. 5 is a schematic cross-sectional view when an insulating support metal is inserted into the furnace wall of the plasma ash melting furnace according to the embodiment of the present invention.
FIG. 6 is a cross-sectional view of the main part when sensors are inserted into the upper part of the plasma ash melting furnace according to the embodiment of the present invention.
FIG. 7 is a schematic sectional view of an insulating support metal used in the present embodiment.
FIG. 8 is a schematic cross-sectional view (a) of a conventional plasma ash melting furnace, and an enlarged view of a D part (b).
FIG. 9 is an overall configuration diagram of a conventional plasma ash melting furnace.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Melting furnace 12 Iron skin 13 Refractory material 14 Electrode 15 Molten ash 16 Insulating sleeve 16a Lower inclined surface 16b Upper inclined surface 17 Refractory material step 18 Refractory material ridge 19 Step 20 Insulating material 21 Fiber 22 Support metal object 22A, 22B Ceramic support metal 23 Molten salt

Claims (8)

In a plasma ash melting furnace having a tubular electrode at the top of an iron furnace body whose inner wall is coated with a refractory material, and having an insulating sleeve disposed with a gap in the furnace penetration part of the electrode,
A structure in which the insulating sleeve is expanded with a plurality of steps at an inclination angle so that a gap between the insulating sleeve and the electrode is directed into the furnace, and molten salt generated by ash melting flows down along the inclined surface; A plasma ash melting furnace characterized by that. The plasma ash melting furnace according to claim 1, wherein the insulating sleeve is formed so as to protrude from a furnace wall around the insulating sleeve. The insulation sleeve is cut out in a hollow conical shape so as to surround the electrode, and the lower portion thereof is cut out in a hollow conical shape with an inclination angle larger than that of the cone so that the molten salt generated by ash melting adheres to the insulating sleeve. 3. The plasma ash melting furnace according to claim 1, wherein the plasma ash melting furnace is configured to prevent. The gap between the furnace penetrating portions is a molten salt retracting portion formed by the lower inclined surface of the insulating sleeve having an inclination angle of approximately 10 ° to 25 ° with respect to the horizontal direction, and an inclination angle of less than approximately 2 ° with respect to the vertical direction. The plasma ash melting furnace according to claim 1, further comprising a gas flow escape portion formed by an upper inclined surface. In a plasma ash melting furnace having a tubular electrode at the top of an iron furnace body whose inner wall is coated with a refractory material, and having an insulating sleeve disposed with a gap in the furnace penetration part of the electrode,
One or a plurality of molten salt retracting portions are provided on the inner wall of the ash melting furnace side wall or the inner wall of the furnace lid, and the molten salt generated by ash melting flows down the furnace wall by the molten salt retracting portion. Plasma ash melting furnace. A plasma ash melting furnace in which the furnace lid is inclined downward toward the outer edge of the furnace, wherein the molten salt evacuation part is provided on the furnace lid and is inclined so as to have a step on the side wall of the furnace. The plasma ash melting furnace according to claim 5, wherein the plasma ash melting furnace is a part. 6. The plasma ash melting furnace according to claim 5, wherein the molten salt retracting portion is a stepped portion or a flange portion provided at an upper portion of the inner wall of the furnace and having a lower portion expanded in diameter. The support metal for joining the refractory material to the iron furnace body or the support metal for supporting various sensors penetrating the furnace lid is made of an insulating refractory such as ceramics. Plasma ash melting furnace.

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