JP3436112B2 - Melting equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for continuously heating and melting a material to be melted, and in particular, it continuously discharges radioactive waste generated by nuclear power generation, etc. The present invention relates to a device for melting and reducing volume.

[0002]

2. Description of the Related Art At present, a large amount of low-level radioactive waste is being generated by nuclear power generation and the like, and it is important to secure the storage and burial place for it. Under such circumstances, as a method for treating and disposing of radioactive waste, development of melting treatment with high volume reduction is being promoted in place of the cement solidification treatment method with low volume reduction. As a melting method, there is a high-frequency melting furnace in which a conductive heating element is filled in the furnace, but this type of melting furnace is, as described in (JP-A-4-17631), etc. A method is used in which a conductive heating element is filled, a high frequency is passed through an induction coil wound outside the furnace, the conductive heating element and the charged metal are heated, and molten metal is continuously taken out from the tap.

[0003]

However, in the above-mentioned high-frequency melting furnace of the conductive heating element-filling type, the heat generation density is highest near the furnace side wall due to the skin effect (1). Since the melted substance is easily melted, the viscosity of the melted substance is easily lowered, and (2). Since the porosity is highest in the region separated from the furnace side wall by the radius of the conductive heating element,
It is known that part of the melt flows down in the high porosity region near the furnace side wall and contacts the inner wall of the furnace. Further, as the melt flows down in the furnace, the melt gradually repeats contact with the conductive heating element and gradually expands its flow region. for that reason,
A part of the molten material melted in the upper part of the conductive heating element filling layer comes into contact with the furnace side wall refractory when flowing down in the furnace.

Refractory materials are generally physically and chemically eroded by contact with the melt. Since the corrosion rate of refractory materials controls the life of refractory materials and the frequency of repairs to the furnace, not only refractory materials with excellent corrosion resistance are adopted, but also the contact between the melt and the furnace side wall is suppressed from the perspective of the furnace structure, It is necessary to extend the life of the product. In particular, in the case of a furnace in which radioactive waste is melted, the effects of radiation on the human body of repair workers, a decrease in the facility utilization rate due to the shutdown of the melting furnace for repairs, an increase in the furnace maintenance costs due to repairs, etc. From the viewpoint, it is essential to reduce the repair frequency and extend the life of the furnace.

An object of the present invention is to suppress the contact of the melt flowing down in the furnace with the refractory material on the side wall of the furnace, thereby extending the life of the refractory material on the side wall of the furnace and reducing the frequency of repairing the furnace. It is to provide a melting device.

[0006]

The features of the first invention for achieving the above object are that a melting tank is provided, and an inlet for a material to be melted and a conductive heating element is provided in an upper portion of the melting tank. In a high-frequency melting furnace that has a melt discharge port at the bottom of the melting tank, a conductive heating element is laminated on the bottom inside the melting tank, and a high-frequency coil is provided outside the melting tank, The inner diameter of the furnace at the contact surface of the heating element filling layer and the melted material is smaller than that of the conductive heating element filling layer.

According to the first aspect of the invention, the inner diameter of the furnace at the contact surface of the conductive heating element packed layer and the material to be melted is made smaller than the inner diameter of the furnace at the conductive heating element packed layer. Since the melted material can be charged into the center of the furnace, it is prevented that the melted material is directly charged and melted on the vicinity of the furnace side wall of the conductive heating element-filled layer, which has the highest temperature, and does not come into contact with the furnace side wall. (2). Since the upper part of the high porosity region near the furnace side wall is blocked, it is possible to prevent the melt from flowing down near the furnace side wall and contacting with the furnace side wall. . For this reason,
It is possible to significantly suppress the erosion of the refractory due to contact with the melt. The amount of change in the inner diameter of the furnace closes the upper portion of the high porosity region near the side wall of the furnace, and therefore needs to be equal to or larger than the radius of the conductive heating element.

The second aspect of the present invention is that in the above melting apparatus, the inner diameter of the melting tank in the upper part of the conductive heating element-filled layer is made smaller toward the upper part.

According to the second aspect of the invention, since the inner diameter of the furnace in the upper part of the conductive heating element packing layer is made narrower toward the upper part, the melted material that is charged is caught by the side wall of the furnace and the charging into the furnace is disturbed. It is possible to prevent (hereinafter, referred to as “shelf-hanging”), and it is possible to smoothly perform the process of charging and melting the material to be melted into the furnace.

A third aspect of the present invention is that in the above melting furnace, the inner diameter of the conductive heating element packed bed is made narrower toward the top of the packed bed.

According to the third aspect of the present invention, the inner diameter of the furnace in the conductive heating element packed bed is made smaller toward the upper part of the packed bed, so that the effect of extending the life of the melting tank can be achieved. This is because the melted material melted at the contact surface of the conductive heating element filling layer and the melted material,
Even if the flow area expands while coming into contact with the conductive heating element and the flow area expands, the amount of contact between the furnace side wall and the melt is reduced because the furnace space expands by the amount of change in the furnace inner diameter in the conductive heating element packed bed. This is because it can be done.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram of a melting device that best illustrates the features of the present invention.

In FIG. 1, an inlet 4 for the material to be melted and the conductive heating element is provided in the upper portion of the melting tank 2, and an outlet 5 for the molten material is provided in the lower portion of the melting tank to continuously perform the melting process. To do. Further, the conductive heating element 1 serving as a heat source is laminated on the bottom of the melting tank to melt the material to be melted put in the furnace.
The conductive heating element 1 and the high frequency coil 3 for inductively heating the material to be melted are installed outside the furnace side wall. Also,
In order to make the inner diameter of the contact surface of the conductive heating element filling layer and the melted material smaller than the inner diameter of the conductive heating element filling layer by the radius of the conductive heating element or more, (1). It is possible to prevent the material to be melted from being directly injected into the vicinity of the side wall of the dissolution tank of the body-filled layer and to dissolve it, and it is possible to suppress contact between the melted material and the side wall of the dissolution tank (2). It is possible to block the upper part of the high porosity region near the furnace side wall in the tank to prevent the melt from flowing near the melting tank side wall and coming into contact with the melting tank side wall. Thereby, the corrosion of the refractory due to the contact between the melt and the side wall of the melting tank can be significantly suppressed.

Further, since the inner diameter of the melting tank of the conductive heating element packed layer is made narrower toward the upper part of the packed layer, the melt flows down in the melting tank while being in contact with the conductive heating element, and the flow region is widened. However, if the spread is less than the amount of change in the inner diameter of the conductive heating element-filled layer, contact between the melt and the side wall of the melting tank can be avoided, and the life of the furnace can be extended.

Further, since the tubular refractory material 6 is slightly tapered inversely, the shelving can improve the prevention performance. Furthermore, if the surface of the cylindrical refractory material 6 is smooth, the effect of preventing shelving can be expected, and it is possible to facilitate the introduction and melting of the material to be melted.

Further, if the cylindrical refractory 6 is electrically conductive, for example, when melting a material to be melted containing water such as concrete, the conductive cylindrical refractory 6 is heated by induction to remove the contained water. It is possible to prevent steam explosion. Further, since the melt is preheated and kept warm in the conductive cylindrical refractory, there is an advantage that the melting efficiency in the melting region is improved. Of course, even if the cylindrical refractory material is made of an insulating material, it is possible to sufficiently obtain the effect of suppressing the flow of the molten material near the furnace side wall and extending the life of the furnace side wall refractory material.

The replenishment of the conductive heating element 1 reduced during the operation of the furnace is usually carried out by putting it into the furnace together with the material to be melted, but when the conductive heating element 1 is reduced or the height of the packed bed is high. In the case of a significant decrease, the tubular refractory 6 and the conductive heating element 1 are all pulled up, the conductive heating element 1 is charged and refilled, and then the tubular refractory 6 is inserted.
For pulling up and inserting the tubular refractory 6, after the temperature inside the furnace has dropped, hang a crane on the metal fitting attached to the upper part of the tubular refractory 6 or at least three points at equal intervals in the center of the tubular refractory. Make a hole and wire the crane.

Since the tubular refractory material 6 is inserted into the upper part of the conductive heating element filling layer in the melting tank, the tubular refractory material 6 can be easily attached and detached, and the repair / repair in the furnace can be easily performed. It is possible to improve the maintenance performance and the workability of the refilling work of the conductive heating element 1. A metal fitting 9 is attached to the upper part of the tubular refractory 6 so that it can be easily pulled out of the furnace, or
It has a structure in which holes are opened at 20 ° intervals and can be pulled up by a crane.

In addition, when the cylindrical refractory 6 is inserted into the furnace or pulled out of the furnace, a space between the furnace side wall refractory and the cylindrical refractory is provided so as not to contact and damage the melting tank side wall refractory. Make a gap in. As a method of supporting the cylindrical refractory in the furnace,
A method of placing directly on the conductive heating element filled in the furnace, or a method of projecting a plurality of protrusions or ring-shaped protrusions 7 inside the melting tank as shown in FIG. 1 and placing the cylindrical refractory 6 thereon, It is fixed by the method of joining and fixing a steel frame placed in a solid refractory and a metal disk installed above the melting tank.

FIG. 2 shows that in the melting apparatus shown in FIG. 1, the cylindrical refractory 6 is integrated with the melting tank 2, and the upper part of the filling layer of the conductive heating element 1 in the melting tank is overhanged to the inside. The inner diameter of the contact surface between the packed bed and the material to be melted is made smaller than the inner diameter of the furnace of the packed bed of the conductive heating element by the radius of the conductive heating element 1 or more. Therefore, like the melting apparatus of FIG. 1, (1). It is possible to prevent the melted material from being directly charged and melted in the vicinity of the side wall of the melting tank in the conductive heating element filling layer that reaches the maximum temperature. It is possible to suppress the contact between the melt and the side wall. (2). The upper part of the high porosity region near the furnace side wall is closed to prevent the melt from flowing down near the melt tank side wall and contacting the melt tank side wall. It is possible to prevent. Thereby, the corrosion of the refractory due to the contact between the melt and the side wall of the melting tank can be significantly suppressed.
The overhanging length of the side wall of the melting tank is equal to or larger than the radius of the conductive heating element as in the melting device of FIG.

Further, since the inner diameter of the melting tank for the conductive heating element-filled layer is made narrower toward the upper portion of the packing layer, the melt is in contact with the conductive heating element 1 in the melting tank as in the melting apparatus shown in FIG. Even if the flow area spreads and the flow area is widened, contact between the melt and the side wall of the melting tank can be avoided if the amount is less than the amount of change in the inner diameter in the conductive heating element packed bed, and the life of the furnace is increased. It can be extended.

Further, since the upper part of the conductive heating element filling layer in the melting tank is slightly inversely tapered, it is possible to improve the shelving prevention performance. Reverse taper angle is 0
30 degrees is preferred. Furthermore, if the surface of the cylindrical refractory material is smooth, the effect of preventing shelving can be expected, and the molten material can be charged and the melting process can be facilitated.

Since the cylindrical refractory is integrated with the melting tank and the upper part of the filling layer of the conductive heating element 1 in the melting tank is overhanging inside, the cylindrical refractory is different from the melting device of FIG. There is no need to remove and install refractories. Therefore, when pulling up, it does not come into contact with the melting tank and is not damaged, and since it is not necessary to attach the metal fittings 9 for lifting or fixing, holes, projections, etc., it is possible to simplify the furnace structure. .

[0024]

According to the first aspect of the invention, in the melting tank, the inner diameter of the melting tank at the contact surface of the conductive heating element packed layer and the material to be melted is made smaller than the melting tank inner diameter at the conductive heating element packed layer. Therefore, (1). It is possible to prevent the melted material from being directly charged and melted on the vicinity of the furnace side wall in the conductive heating element packed bed, which reaches the maximum temperature, and contact with the side wall of the melting tank. ,
(2). The upper part of the high porosity region near the furnace side wall can be closed to prevent the melt from flowing down near the furnace side wall and contacting the furnace side wall, and the effect of extending the life of the melting tank can be achieved. Is.

According to the second aspect of the invention, since the inner diameter of the melting tank in the upper part of the conductive heating element packing layer is made narrower toward the upper part, the shelving prevention performance can be improved, and the molten material can be charged and melted. The processing can be facilitated.

According to the third aspect of the invention, since the inner diameter of the melting layer of the conductive heating element-filled layer in the melting tank is made narrower toward the upper portion of the filling layer, the melt is kept in contact with the conductive heating element in the melting tank. Even if the flow area spreads and the flow area expands, contact between the melt and the furnace side wall can be avoided and the life of the furnace can be extended if the amount is less than the inner diameter change amount in the conductive heating element packed bed. It is possible to

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a melting device that is an embodiment of the present invention.

FIG. 2 is a sectional view of a melting apparatus shown as another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Conductive heating element, 2 ... Melting tank, 3 ... High frequency induction coil, 4 ... Inlet for melted material and conductive heating element, 5 ... Melt outlet, 6 ... Cylindrical refractory, 7 ... Tube -Shaped refractory support protrusions, 8 ... Cylindrical refractory support metal fittings, 9 ... Cylindrical refractory lifting metal fittings.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiaki Matsuo 7-2 Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Electric Power & Electric Development Division (72) Inventor Masasho Matsuda Saiwaicho, Hitachi City, Ibaraki Prefecture 3-1-1, Hitachi Ltd., Hitachi factory (72) Inventor, Kiyotaka Ueda 3-1-1, Saiwaicho, Hitachi, Ibaraki Hitachi, Ltd. Hitachi factory (56) Reference: JP-A-4-17631 (JP, A) JP-A-50-75977 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G21F 9/30 551 C22B 9/16 B01J 19/00

Claims (3)

(57) [Claims] 1. A melting tank is provided, an inlet for a material to be melted and a conductive heating element is provided in an upper portion of the melting tank, and an outlet for the molten material is provided in a lower portion of the melting tank. In a high-frequency melting furnace in which a conductive heating element is laminated on the bottom and a high-frequency coil is provided outside the melting tank, the furnace inner diameter at the contact surface of the conductive heating material-packed layer and the melted material is changed to conductive heating. A melting device characterized in that it is made thinner than the inner diameter of the furnace in the body packed bed. 2. The melting apparatus according to claim 1, wherein an inner diameter of the furnace above the conductive heating element packing layer is made smaller toward the upper part of the furnace. 3. The melting apparatus according to claim 2, wherein the inner diameter of the furnace in the conductive heating element packing layer is made narrower toward the upper part of the packing layer.