JP4691710B2 - Electric melting furnace for waste vitrification - Google Patents

Description

  The present invention relates to an electric melting furnace for waste glass solidification treatment, and in particular, glass raw material is melted using Joule heat generated by energizing molten glass in the melting furnace, and waste is mixed into the molten glass. The present invention relates to an electric melting furnace for solidifying treatment. This melting furnace is suitable for use in vitrification treatment of various industrial wastes, particularly vitrification treatment of highly radioactive liquid waste.

  A conventional electric melting furnace for solidifying solid waste has a structure in which a furnace body and a melting tank are formed of refractory bricks in a refractory melting furnace, and one or more pairs of heat-resistant alloy electrodes are arranged in the melting tank. It is. In a metal melting furnace, one or several heating electrodes made of a heat-resistant alloy having the melting tank wall as a counter electrode are arranged in a cylindrical melting tank having a melting tank wall made of a heat-resistant alloy. is there.

  Such an electric melting furnace uses the fact that molten glass has conductivity, and is configured to heat and melt the glass by Joule heat generated by passing an electric current through the electrode to the molten glass in the melting tank. By supplying the radioactive liquid waste and the glass raw material from the upper part of the melting furnace onto the molten glass liquid surface, the molten glass is heated by the molten glass and heated, evaporated, and calcined. After mixing, it is discharged from the melting furnace, cooled and vitrified.

  Since the soundness of the refractory bricks and the metal material constituting the melting furnace depends on the temperature of the molten glass in contact with them, it is desirable that the temperature distribution of the molten glass in the melting furnace is uniform. For this reason, various electrode arrangements have been attempted according to the shape of the melting furnace, the amount of waste disposal, and the like.

  When processing highly radioactive liquid waste, the abnormal temperature rise of a furnace bottom part wall generate | occur | produces and the problem which a waste disposal capacity falls arises. This abnormal temperature rise phenomenon at the bottom wall of the furnace is due to the fact that platinum group elements such as Ru, Pd, and Rh contained in highly radioactive liquid waste form a conductive material that is hardly soluble in molten glass and has higher viscosity than molten glass. The reason is that the Joule heat generated is not sufficiently supplied to the upper surface of the molten glass because the electrode current is concentrated on the conductive deposit and the interelectrode current is concentrated on the conductive deposit.

  For example, for refractory melting furnaces, the Proceedings of the International Topical Meeting on Nuclear and Hazardous Waste Management was held in Pasco, Washington, USA, from September 11 to 15, 1988. SPECTRUM '88) (House Wiese, “Industrial Vitrification of highly radioactive liquid waste in Belgian Pamela Plant” described on page 75 of American Nuclear Society, Inc.) of High Level Liquid Waste with the PAMERA Plant in Belgium), a conductive material composed of platinum group elements with a normal electrical resistance value of 1/3 and a viscosity value 5 times the normal is 5cm thick at the bottom of the furnace. It is reported that the current-carrying characteristics changed due to the deposition on the glass, and the glass production rate decreased from 30 kg / hr to 20 kg / hr.

  In addition, Shin-ichiro Torata's “Development of Glass Melting Furnace for Tokai Vitrification Technology Development Facility” described on page 82 of the minutes of the meeting (Development of Glass Melter for PNC Tokai Vitrification In the Facility), several experiments using a laboratory-scale melting furnace with a bottom gradient showed that a 45 ° gradient was effective for discharging sediments composed of platinum group elements. It is reported that the effect was evaluated from the test results of a large-scale melting furnace with

  As for the metal melting furnace, the "Ninth Test of the Cylindrical Electrode Direct Current Melting Furnace Engineering Test Apparatus (JCEM-E9 Test)" (N8410 98-041), which is a public research result report of the Japan Atomic Energy Agency Despite obtaining good results for the extraction performance of platinum group elements in a metal melting furnace having a furnace bottom gradient of 45 °, the treatment capacity with simulated waste liquid containing platinum group elements is It was confirmed that it decreased by 20% or more from the result of the test using the simulated waste liquid not containing the element. This is considered to be mainly due to the movement of the heating current density distribution to the lower part due to the concentration of the conductive platinum group element in the molten glass being higher in the lower layer part in the upper layer part and lower layer part of the melting tank, It is reported.

Proceedings of the International Topical Meeting on Nuclear and Hazardous Waste Management SPECTRUM'88 American Nuclear Society, Inc. Cylindrical Electrode Direct Current Melting Furnace Engineering Test Unit 9th Test (JCEM-E9 Test)-High Radioactive Waste Liquid Solidification Research Report-February 1998 Tokai Works

  As described above, in the conventional melting furnace, a small amount of conductive material is deposited on the bottom or slope surface of the glass melting furnace, or the molten glass is formed at the lower part of the melting tank, although the bottom of the furnace has a gradient. When the concentration of the conductive substance in the inside is expected to be high and such a phenomenon occurs, the above-described phenomenon of abnormal electric conduction or a decrease in waste disposal capacity occurs.

  One object of the present invention is to dispose of waste due to the biased current-heating characteristics of the molten glass in the melting tank due to the conductive material produced by the platinum group elements contained in the waste to be vitrified. It is to prevent the processing capacity from being lowered. Specifically, there is to prevent the bias of the heat generation part in the energization heating due to the distribution concentration of the conductive material in the lower layer part of the molten glass in the melting tank being larger than that in the upper layer part.

  Another object of the present invention is to further facilitate discharge of the conductive substance generated in the melting tank by the platinum group element contained in the waste to be vitrified to the outside of the melting tank. This is to prevent the adverse effect of energization caused by the conductive material layer deposited on the bottom of the melting tank.

  Another object of the present invention is to facilitate control of melting of the glass raw material in the melting tank and discharging / stopping of the molten glass.

  Another object of the present invention is to make it possible to reduce the cost of replacement parts, the replacement time, and the amount of demolition waste in the parts constituting the furnace body.

Basically, the present invention is electrically connected to the conical heat-resistant alloy furnace bottom wall by the conical heat-resistant alloy furnace bottom wall, the annular refractory brick vertical wall, and the annular refractory brick vertical wall. A melting space is formed by being surrounded by a cylindrical heat-resistant alloy vertical wall provided in an insulating manner, and the bottom wall of the cone-shaped heat-resistant alloy furnace forms the entire area of the lower conical side wall in the melting space. A melting tank configured; a supply port for supplying glass raw material and waste into the melting tank; a molten glass outlet for discharging molten glass containing waste in the melting tank; and the conical heat-resistant alloy furnace A heat-resistant alloy heating electrode suspended from the center of the melting tank with the bottom wall and a cylindrical heat-resistant alloy vertical wall as a counter electrode, the conical heat-resistant alloy furnace bottom wall, and an annular refractory brick Vertical wall and cylindrical heat-resistant alloy vertical wall And an air-cooling cooling means provided on the heat-resistant alloy heating electrode, and a first AC power supply device connected to apply an AC voltage between the conical heat-resistant alloy furnace bottom wall and the heat-resistant alloy heating electrode; And a second AC power supply device connected so as to apply an AC voltage between the cylindrical heat resistant alloy vertical wall and the heat resistant alloy heating electrode. A melting furnace,
More specifically, the inclined wall surface of the bottom wall of the conical heat-resistant alloy furnace is formed with a uniform gradient of 45 ° to 60 ° toward the molten glass outlet located in the center of the bottom, or the cone The inclined wall surface of the bottom heat-resistant alloy-made furnace bottom bath wall is formed with a gradient that changes stepwise or continuously from 45 ° to 90 ° toward the molten glass discharge port located at the center of the bottom,
In addition, an auxiliary heating device is disposed around the bottom wall of the conical heat-resistant alloy furnace and the molten glass discharge port,
Furthermore, the conical heat-resistant alloy furnace bottom wall, the annular refractory brick vertical wall, the cylindrical heat-resistant alloy vertical wall, the molten glass outlet, the heat-resistant alloy heating electrode and the auxiliary heating device are each independently It is configured as a replaceable independent part.

  The auxiliary heating device provided around the bottom wall of the conical heat-resistant alloy furnace heats the molten glass in the melting tank for a predetermined time before being discharged from the molten glass discharge port. The molten glass in the vicinity of the bottom wall of the conical heat resistant alloy furnace is further heated.

  The melting tank is provided with a stirring gas supply pipe and / or a mechanical stirring device for stirring the molten glass in the melting tank.

The electric melting furnace for waste vitrification configured as described above is composed of a glass raw material and waste supplied from a supply port into a melting tank, and a conical heat-resistant alloy furnace bottom wall and a cylindrical heat - resistant alloy vertical wall. And the three types of electrodes composed of heat-resistant alloy heating electrodes are heated by Joule heat generated by energizing the molten glass between these electrodes to change into molten glass containing waste.

Even if the conductive material distribution concentration in the lower layer part of the molten glass in the melting tank becomes larger than that in the upper layer part or the conductive substance is deposited on the bottom wall of the conical heat-resistant alloy furnace in the melting tank, the second Because the AC voltage applied between the vertical wall of the cylindrical heat - resistant alloy and the heating electrode made of the heat-resistant alloy can pass the necessary heating current to the upper layer of the molten glass in the melting tank. It is possible to increase the heat supply to the raw material by increasing the heat generation in the vicinity of the surface of the molten glass.

Air-cooled cooling means provided on the conical heat-resistant alloy furnace bottom wall, the annular refractory brick vertical wall, the cylindrical heat - resistant alloy vertical wall and the heat-resistant alloy heating electrode are used to increase the temperature of these walls and electrodes. Suppresses erosion of the material.

  The gradient of about 45-60 ° formed on the bottom wall of the cone-shaped heat-resistant alloy furnace, or the gradient changing to 45-90 °, causes platinum group elements contained in the waste to form a conductive material that is hardly soluble in glass. Also, the conductive material can be easily discharged out of the melting tank to prevent the conductive material from being deposited on the bottom wall and forming a layered material.

  An auxiliary heating device disposed around the bottom wall of the conical heat-resistant alloy furnace and the molten glass discharge port assists in controlling the melting of the glass raw material in the melting tank and the discharge / stop of the molten glass.

In addition, a conical heat-resistant alloy furnace bottom wall, an annular refractory brick vertical wall, a cylindrical heat - resistant alloy vertical wall, a molten glass discharge port, a heat-resistant alloy heating electrode, The auxiliary heating device allows for a reduction in the cost of replacement parts, replacement time and the amount of demolition waste.

The present invention is provided by electrically insulating from the bottom wall of the cone-shaped heat-resistant alloy furnace by the cone-shaped heat-resistant alloy furnace bottom wall, the annular refractory brick vertical wall, and the annular refractory brick vertical wall. A melting space is formed by being surrounded by a cylindrical heat-resistant alloy vertical wall, and the bottom wall of the conical heat-resistant alloy furnace is a melting tank configured to form the entire area of the lower conical side wall in the melting space . The cylindrical heat-resistant alloy vertical wall and the heat-resistant alloy independent from the first AC power source connected to apply an AC voltage between the conical heat-resistant alloy furnace bottom wall and the heat-resistant alloy heating electrode Included in the waste to be vitrified by the configuration in which the upper layer portion of the molten glass in the melting tank is energized by the second AC power supply device connected to apply an AC voltage between the heating electrodes. Platinum family Even if the distribution concentration of the conductive material in the lower layer part of the molten glass in the melting tank is larger than that in the upper layer part due to the conductive substance produced by the element, a sufficient current can be passed through the upper layer part. In this case, it is possible to prevent the bias of the heat generation portion in the case of the waste and to prevent the waste processing capacity from being lowered.

Also, the air-cooling cooling means provided on the conical heat-resistant alloy furnace bottom wall, the annular refractory brick vertical wall, the cylindrical heat - resistant alloy vertical wall, and the heat-resistant alloy heating electrode, Controls material erosion by suppressing temperature rise.

  In the present invention, the inclined wall surface of the bottom wall of the conical heat-resistant alloy furnace is formed with a uniform gradient of 45 ° to 60 ° toward the molten glass discharge port located at the bottom center, or the bottom center. Due to the platinum group elements contained in the waste to be vitrified by forming with a gradient that changes stepwise or continuously from 45 ° to 90 ° toward the molten glass outlet located in the section. The discharge of the conductive material generated in the melting tank to the outside of the melting tank is facilitated, and the adverse effect of electricity (abnormal heat generation) due to the conductive material layer deposited on the bottom wall of the conical heat-resistant alloy furnace is prevented. Can do.

  In the present invention, an auxiliary heating device is provided around the bottom wall of the conical heat-resistant alloy furnace and the molten glass discharge port, thereby melting the glass raw material in the melting tank and discharging / discharging the molten glass. Stop control can be easily realized. In particular, the molten glass is heated by heating the molten glass in the vicinity of the conical heat-resistant alloy furnace bottom wall in the melting tank by generating heat for a predetermined time before discharging the molten glass in the melting tank from the molten glass discharge port. It is possible to make the discharge smooth by reducing the viscosity.

The present invention further includes the above-mentioned conical heat-resistant alloy furnace bottom wall, annular refractory brick vertical wall, cylindrical heat - resistant alloy vertical wall, molten glass discharge port, heat-resistant alloy heating electrode, and auxiliary heating device, By configuring each as an independent part that can be replaced independently, it is possible to reduce the cost of replacement parts, the replacement time, and the amount of dismantling waste in the parts constituting the furnace body.

The best embodiment of the electric melting furnace for waste vitrification of the present invention is:
Cylindrical heat-resistant alloy furnace bottom wall, annular refractory brick vertical wall, and cylindrical refractory brick vertical wall, electrically insulated from the conical heat-resistant alloy furnace bottom wall. A melting space that is surrounded by a vertical wall made of a metal to form a melting space, and the bottom wall of the conical heat-resistant alloy furnace is formed to form the entire area of the lower conical side wall in the melting space; and the melting tank A supply port for supplying glass raw materials and waste, a molten glass discharge port for discharging molten glass containing waste in the melting tank, a furnace bottom wall made of the conical heat resistant alloy and a vertical shape made of a cylindrical heat resistant alloy Heat-resistant alloy heating electrode installed in the center of the melting tank so as to have a counter wall as a counter electrode, the bottom wall of the conical heat-resistant alloy furnace, the vertical wall of the annular refractory brick, and the cylindrical heat-resistant alloy Vertical wall and heat-resistant alloy heater An air-cooling type cooling means provided in the first heat source, a first AC power supply device connected to apply an AC voltage between the conical heat-resistant alloy furnace bottom wall and the heat-resistant alloy heating electrode, and the cylindrical heat-resistant alloy A second AC power supply device connected to apply an AC voltage between the vertical wall made of heat and the heating electrode made of the heat-resistant alloy,
The inclined wall surface of the conical heat-resistant alloy furnace bottom wall is formed with a uniform gradient of 45 ° to 60 ° toward the molten glass discharge port located at the bottom center, or the molten glass located at the bottom center. Formed with a gradient that changes stepwise or continuously from 45 ° to 90 ° towards the outlet,
An auxiliary heating device is disposed around the bottom wall of the conical heat-resistant alloy furnace and the molten glass outlet,
The conical heat-resistant alloy furnace bottom wall, the annular refractory brick vertical wall, the cylindrical heat-resistant alloy vertical wall, the molten glass outlet, the heat-resistant alloy heating electrode and the auxiliary heating device can be replaced independently. It is configured as an independent part.

  The melting tank is provided with a stirring gas supply pipe and / or a mechanical stirring device for stirring the molten glass in the melting tank.

  1 is a longitudinal front view of an electric melting furnace for waste vitrification in Example 1 of the present invention, FIG. 2 is a cross-sectional view taken along the line AA ′ in FIG. 1, and FIG. B 'arrow sectional drawing and FIG. 4 are flowcharts of waste vitrification processing operation.

  The melting tank 1 is configured to be surrounded by a conical heat-resistant alloy furnace bottom wall 2, an annular refractory brick vertical wall 3, and a cylindrical heat-resistant alloy vertical wall 4 to form a melting space. The circular refractory brick vertical wall 3 is positioned between the conical heat-resistant alloy furnace bottom wall 2 and the cylindrical heat-resistant alloy vertical wall 4 and functions to electrically insulate the two. Cooling jackets 5, 6, and 7 for circulating cooling air that is a cooling medium are provided in the respective part walls 2, 3, and 4. In addition, the conical heat-resistant alloy furnace bottom wall 2 forms an inclined wall surface that is narrowed by a 60 ° gradient toward the molten glass discharge port 8 located below the center portion thereof. Then, various refractory bricks 9 to 13 having heat insulation properties are arranged outside the respective part walls 2, 3, and 4, and the outer periphery thereof is covered with a metal casing 14 to constitute the entire furnace.

  The inclined wall surface in the bottom wall 2 of the cone-shaped heat-resistant alloy is formed on the wall surface of the bottom wall 2 of the cone-shaped heat-resistant alloy by forming a platinum group element contained in the waste into a hardly soluble conductive material in the molten glass. The conductive deposit that causes electrical damage by being deposited can be easily discharged together with the molten glass from the molten glass discharge port 8, and is formed with a uniform gradient of 45 ° to 60 °. Alternatively, it is desirable to form with a gradient such that the inclination angle changes stepwise or continuously from 45 ° to 90 °.

  Below the molten glass discharge port 8, a glass solidified body container (not shown) is installed so that it can be taken in and out.

  The disc-shaped refractory brick 9 located at the bottom of the furnace is inside the metal casing 14 to form a refractory brick bottom layer, and the molten glass discharge port 8 is formed at the center of the conical heat-resistant alloy. A space 9a for disposing an induction heating coil 15 that leads out of the furnace bottom wall 2 and controls the outflow of the molten glass by controlling the heating of the molten glass discharge port 8 (outflow / blocking); Furthermore, an auxiliary heating device 16 attached to the wall surface of the space 9a is provided. The auxiliary heating device 16 is configured using a heating resistor. Then, the outflow of the molten glass from the molten glass discharge port 8 is controlled by the induction heating coil 15 or the auxiliary heating device 16.

  The cylindrical refractory brick 10 is inside the metal casing 14 and forms a refractory brick outer peripheral layer on the refractory brick 9. The lower refractory brick 11 disposed in the lower portion inside the cylindrical refractory brick 10 forms a refractory brick lower inner peripheral layer supporting the outer periphery of the conical heat resistant alloy furnace bottom wall 2. The lower refractory brick 11 includes an auxiliary heating device 17 on its inner peripheral wall surface.

  The auxiliary heating device 17 is configured by using a resistance heating element or an induction heating coil, and the glass raw material (solidified glass) charged into the melting tank 1 is made of the conical heat resistant alloy furnace bottom wall 2 and the heat resistant alloy. Used for start-up operation for heating to a temperature at which a molten state that can be energized by three types of electrodes constituted by the vertical wall 4 and the heat-resistant alloy heating electrode 18 is used, and for adjusting the temperature of the lower layer portion of the molten glass 24 in the melting tank 1 To do.

  In particular, the auxiliary heating device 17 has a temperature distribution of the molten glass 24 in the melting tank 1 even if a current-carrying adverse effect due to an increase in the concentration of the conductive material in the lower layer portion of the molten glass 24 in the melting tank 1 occurs. Auxiliary heating for optimizing the temperature of the molten glass 24 can be realized, thereby facilitating operational control such as the flow of the molten glass 24 and the production of uniform waste-containing glass.

The auxiliary heating devices 16 and 17 are connected so that power is supplied from an external power supply device (not shown). The lead wires from the auxiliary heating devices 16 and 17 to the external power supply device are not shown in the drawings, but heat-resistant insulated conductors are used, and the lead wires from the auxiliary heating device 16 are refractory bricks forming the space 9a. 9 and is installed so that it can be detached from the lower side together with the auxiliary heating device 16, and the lead wire from the auxiliary heating device 17 is extended upward along the inner walls of the refractory bricks 11 and 12 to be refractory. diverted to the outside by passing the bricks 13, it placed so as to be detachable from above with the auxiliary heating device 17.
Also, the upper refractory brick 12 which is arranged inside the upper portion of the cylindrical refractory bricks 10, the refractory bricks to hold a periphery of the annular refractory brick vertical wall 3 and a cylindrical heat-resistant alloy vertical wall 4 An upper inner peripheral layer is formed.

  The disc-shaped refractory brick 13 located at the ceiling of the furnace body is fitted inside the cylindrical refractory brick 10 and placed on the upper end of the upper refractory brick 12 to form a refractory brick upper cover layer. The disc-shaped refractory brick 13 is provided with a heating electrode through-hole 13a installed through the heating electrode 18 made of a heat-resistant alloy and other means around the through-hole in the center of the disc-shaped refractory brick 13. With through-holes.

  The heating electrode 18 made of heat-resistant alloy penetrates through the heating electrode through hole 13a of the refractory brick 13 so that the heat-resistant alloy furnace bottom wall 2 and the heat-resistant alloy vertical wall 4 are positioned as counter electrodes. Install it hanging on the part. The heat-resistant alloy heating electrode 18 is installed so that it can be moved to an arbitrary height in the bathtub 1. The heating electrode 18 made of a heat-resistant alloy is provided with a cooling passage 18 a inside, and is configured to circulate the cooling air supplied from the cooling air inlet 19 and discharge it from the cooling air outlet 20. Further, a plurality of such heat-resistant alloy heating electrodes 18 may be installed.

  The refractory brick 13 further includes a waste supply port 21 and a glass raw material supply port 22 for supplying waste and glass raw material to be processed into the melting tank 1 from the upper part of the melting tank 1, and during waste processing. A waste gas outlet 23 for discharging the generated waste gas, a stirring air supply pipe 25 for supplying stirring air into the melting tank 1 (molten glass 24) in order to stir the molten glass 24 in the melting tank 1, and A mechanical stirrer 26 is passed through. The stirring air can be changed to another gas.

  The conical heat-resistant alloy furnace bottom wall 2, the annular refractory brick vertical wall 3, the cylindrical heat-resistant alloy vertical wall 4, and the molten glass discharge port in the waste glass solidification electric melting furnace configured as described above. 8. Inductive heating coil 15, heat-resistant alloy heating electrode 18, and auxiliary heating devices 16 and 17 are independent component structures so that they can be independently detached and replaced sequentially from the top or bottom of the melting furnace. As a result, it is possible to reduce the cost of replacement parts, the replacement time, and the amount of demolition waste.

  In addition, the surroundings of the conical heat-resistant alloy furnace bottom wall 2, the refractory brick vertical wall 3 and the heat-resistant alloy vertical wall 4 constituting the melting tank 1 are preliminarily stacked various refractory bricks having heat insulation properties. Since the structure is surrounded by 9 to 13 and covered with a metal casing 14, it is excellent in maintaining its structure and strength, and further having excellent strength, corrosion resistance, fire resistance, heat insulation, and sufficient strength. Can be realized.

  The three types of electrodes constituted by the conical heat-resistant alloy furnace bottom wall 2, the heat-resistant alloy vertical wall 4 and the heat-resistant alloy heating electrode 18 heat the molten glass 24 to a required temperature in the melting tank 1. The size is sufficient to energize the molten glass 24 so that it can be used.

  A direct energization heating power supply device for energizing the molten glass 24 so that the molten glass 24 is energized and heated uniformly by heating the molten glass 24 in the melting tank 1 with the three kinds of electrodes is a conical heat-resistant device. A first AC power supply device 27 connected so as to apply an AC voltage between the bottom wall 2 of the alloy furnace and the heat-resistant alloy heating electrode 18, and an AC current between the heat-resistant alloy vertical wall 4 and the heat-resistant alloy heating electrode 18. A second AC power supply device 28 connected to apply a voltage is provided. The first alternating current power supply device 27 and the second alternating current power supply device 28 are configured as electrically independent power supply devices, each capable of performing desired energization control by constant power control, constant current control, constant voltage control, or the like. To be configured.

  The lead lines from the conical heat-resistant alloy furnace bottom wall 2 and the heat-resistant alloy vertical wall 4 to the first AC power supply device 27 and the second AC power supply device 28 are not shown in the figure, but they are heat resistant. An insulated conductor is used, and the lead wire from the conical heat-resistant alloy furnace bottom wall 2 is led out to the outside by extending upward along the inner wall of the refractory brick 12 and penetrating the refractory brick 13. It is installed so that it can be attached and detached together with the bottom wall 2 of the furnace, and the leader line from the vertical wall 4 made of heat-resistant alloy is drawn upward from the upper end of the vertical wall 4 made of heat-resistant alloy and penetrates the refractory brick 13. It leads out and installs so that it can be attached or detached from the upper part with the vertical part wall 4 made from a heat-resistant alloy.

  In the electric melting furnace configured as described above, the molten glass in the melting tank 1 is applied by the AC voltage applied from the first AC power supply device 27 between the conical heat-resistant alloy furnace bottom wall 2 and the heat-resistant alloy heating electrode 18. The current flowing in the flow 24 mainly flows through the lower layer portion of the molten glass 24 in the melting tank 1 so as to generate Joule heat in the portion, and from the second AC power supply 28 to the vertical wall 4 made of heat-resistant alloy. The current flowing in the molten glass 24 in the melting tank 1 by the AC voltage applied between the heat-resistant alloy heating electrodes 18 mainly passes through the upper layer part of the molten glass 24 in the melting tank 1 and generates Joule heat in the part. To flow like.

  In addition, the induction heating coil 15 and the auxiliary heating devices 16 and 17 are connected to a power supply device (not shown) so that power feeding can be controlled individually, and the cooling jackets 5, 6, and 7 are respectively It connects with a cooling medium supply apparatus (illustration omitted) so that supply of a cooling medium can be controlled separately.

  In the conventional metal melting furnace, the mixed distribution concentration of the conductive platinum group elements in the molten glass 24 is higher in the lower layer portion in the upper layer portion and the lower layer portion in the melting tank, so that the heating current density distribution becomes lower layer portion. The waste treatment capacity is reduced due to the biased electric heating.

  However, in the first embodiment, the current path between the heat resistant alloy vertical wall 4 and the heating electrode 18 is mainly the upper layer of the molten glass 24 independently of the current path between the heat resistant alloy furnace bottom wall 2 and the heating electrode 18. Since it is formed in the portion, the heating current density in the vicinity thereof is increased to generate a large Joule heat generation in the portion, so that heat supply to the glass raw material and waste put near the surface of the molten glass 24 The waste treatment capacity can be improved.

  Further, by arranging the vertical part wall 4 made of heat-resistant alloy so as to extend above the surface of the molten glass 24, the heat of the high-temperature molten glass 24 is efficiently transmitted to the upper space in the melting tank 1 and melted. It is possible to improve the heating efficiency of the glass raw material and waste by supplying heat to the glass raw material and waste from the upper surface of the glass raw material and waste thrown near the surface of the glass 24. This improves the waste disposal capacity.

  Thus, the improvement of the waste processing capability realized by efficiently heating the molten glass 24, the glass raw material, and the waste in the melting tank 1 enables downsizing of the melting furnace.

  The operation of the waste glass solidification treatment electric melting furnace configured as described above will be described with reference to FIG.

Step S 1
A glass raw material is introduced into the melting tank 1 from the glass raw material supply port 22, and the auxiliary heating device 17 is made to function so that the glass raw material in the melting tank 1 can be heated by applying current to the glass raw material to generate heat. When the molten glass is heated up to a state and becomes a molten glass state that can be energized and heated, the AC power supply devices 27 and 28 function to make the conical heat resistant alloy furnace bottom wall 2, the heat resistant alloy vertical wall 4, and the heat resistant alloy heating electrode 18. The Joule heat generated in the molten glass 24 is generated by energizing the molten glass 24 with the three types of electrodes configured as described above, and the molten glass 24 is heated by the Joule heat.

Step S 2
The highly radioactive liquid waste and the glass raw material are continuously charged from the waste supply port 21 and the glass raw material supply port 22 onto the surface of the molten glass 24 in the melting tank 1.

Step S 3
The conical heat-resistant alloy furnace bottom wall 2 and the AC heat-resistant alloy furnace 27 and 28 are heated by the AC power supply devices 27 and 28 so that the highly radioactive liquid waste and the glass raw material charged in the melting tank 1 can be heated to a predetermined temperature. Generation of Joule heat in the molten glass 24 by controlling the current flowing in the molten glass 24 in the melting tank 1 from three kinds of electrodes constituted by the vertical wall 4 made of the heat resistant alloy and the heating electrode 18 made of the heat resistant alloy. Thus, the temperature distribution of the molten glass 24 is made to have the desired characteristics, the stirring air is supplied into the molten glass 24 from the stirring air supply pipe 25 and the mechanical stirring device 26 is operated to stir the molten glass 24. Then, the waste gas generated in the melting tank 1 is discharged from the waste gas outlet 23 to the outside of the furnace to heat the radioactive liquid waste and the glass raw material to be melted through the process of temperature rising, water evaporation, and calcination. Gala And the mixed state with. During this time, the molten glass discharge port 8 is maintained at a temperature at which the glass does not melt (the molten glass 24 solidifies).

  In such heating, the conical heat-resistant alloy furnace bottom wall 2, the annular refractory brick vertical wall 3, the heat-resistant alloy vertical wall 4 and the heat-resistant alloy heating electrode 18 are provided with cooling jackets 5, 6, 7 and By appropriately cooling the coolant through the cooling passage 18a, overheating is suppressed and the erosion rate is reduced.

Specifically, this heating and cooling method is, for example,
(1) While the vertical wall 4 made of refractory bricks is being cooled, the molten glass 24 between the cooled heat-resistant alloy vertical wall 4 and the cooled heat-resistant alloy heating electrode 18 is heated by heating and the bottom wall of the heat-resistant alloy furnace 2 is cooled,
(2) The molten glass 24 between the cooled heat-resistant alloy vertical wall 4 and the cooled heat-resistant alloy heating electrode 18 is energized and heated by the auxiliary superheater 17 without cooling the heat-resistant alloy furnace bottom wall 2. To
(3) The molten glass 24 between the cooled heat-resistant alloy vertical wall 4 and the cooled heat-resistant alloy heating electrode 18 is energized and heated and the cooled heat-resistant alloy furnace bottom wall 2 and the cooled heat-resistant alloy heating electrode 18 are heated. Heating the molten glass 24 between
Such a method can be selected as appropriate.

  When the liquid level of the molten glass 24 in the melting tank 1 approaches a predetermined value and reaches a predetermined value after a predetermined time and reaches a predetermined time before discharging, an auxiliary heating device is added in addition to the energization heating. 17 is operated to increase the amount of heating to the molten glass 24 in the melting tank 1 and further heat the molten glass 24 in the vicinity of the conical heat-resistant alloy furnace bottom wall 2 in the melting tank 1. Control is performed to reduce the viscosity of the molten glass 24 to achieve smooth discharge.

Step S 4
In such a heating state, the processing is branched by detecting whether or not the liquid level of the molten glass 24 in the melting tank 1 has reached a predetermined value by continuous supply of waste and glass raw material. The detection of the liquid level is realized by a method of installing a detection sensor (not shown) in the melting tank 1 or a method of estimating from the amount of waste and glass raw material introduced.

Step S 5
The molten glass discharge port 8 is heated by the induction heating coil 15 and / or the auxiliary heating device 16 to melt the solidified glass in the molten glass discharge port 8, so that the molten glass 24 in the melting tank 1 is discharged from the molten glass. It is possible to flow out through the outlet 8.

Step S 6
The molten glass 24 in the melting tank 1 flows out through the molten glass discharge port 8 and is poured into a glass solidified body container (not shown).

Step S 7
The processing is branched by detecting whether or not the amount of the molten glass 24 discharged from the molten glass discharge port 8 has reached a predetermined amount. This detection is realized by measuring a decrease amount of the molten glass 24 in the melting tank 1 or an amount of the molten glass 24 injected into the vitrified container.

Step S 8
When the amount of the molten glass 24 discharged from the molten glass discharge port 8 reaches a predetermined amount, the outflow of the molten glass 24 from the molten glass discharge port 8 is stopped. This outflow stop stops heating of the molten glass discharge port 8 by the induction heating coil 15 and / or the auxiliary heating device 16, and the temperature of the molten glass discharge port 8 is solidified by the molten glass 24 in the molten glass discharge port 8. This is achieved by preventing the outflow.

It is a vertical front view of the electric melting furnace for waste vitrification processing in Example 1 of the present invention. It is A-A 'arrow sectional drawing in FIG. It is a B-B 'arrow sectional view in Drawing 1. It is a flowchart of a waste vitrification processing operation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Melting tank, 2 ... Conical heat-resistant alloy furnace bottom wall, 3 ... Annular refractory brick vertical wall, 4 ... Cylindrical heat-resistant alloy vertical wall, 8 ... Molten glass outlet, 18 ... Heat-resistant alloy made Heating electrode, 21 ... waste supply port, 22 ... glass raw material supply port, 24 ... molten glass, 27 ... first AC power supply device, 28 ... second AC power supply device.

Claims (7)

Cylindrical heat-resistant alloy furnace bottom wall, annular refractory brick vertical wall, and cylindrical refractory brick vertical wall, electrically insulated from the conical heat-resistant alloy furnace bottom wall. A melting space that is surrounded by a vertical wall made of a metal to form a melting space, and the bottom wall of the conical heat-resistant alloy furnace is formed to form the entire area of the lower conical side wall in the melting space; and the melting tank A supply port for supplying glass raw materials and waste, a molten glass discharge port for discharging molten glass containing waste in the melting tank, a furnace bottom wall made of the conical heat resistant alloy and a vertical shape made of a cylindrical heat resistant alloy Heat-resistant alloy heating electrode installed in the center of the melting tank so as to have a counter wall as a counter electrode, the bottom wall of the conical heat-resistant alloy furnace, the vertical wall of the annular refractory brick, and the cylindrical heat-resistant alloy Vertical wall and heat-resistant alloy heater An air-cooling type cooling means provided in the first heat source, a first AC power supply device connected to apply an AC voltage between the conical heat-resistant alloy furnace bottom wall and the heat-resistant alloy heating electrode, and the cylindrical heat-resistant alloy A waste glass solidification electric melting furnace comprising a second AC power supply device connected so as to apply an AC voltage between a vertical wall made of heat and a heating electrode made of the heat-resistant alloy.   The disposal according to claim 1, wherein the inclined wall surface of the bottom wall of the cone-shaped heat-resistant alloy furnace is formed with a uniform gradient of 45 ° to 60 ° toward the molten glass outlet located in the center of the bottom. Electric melting furnace for solidifying glass.   In Claim 1, the inclined wall surface of the conical heat-resistant alloy furnace bottom bath wall is formed with a gradient that changes stepwise or continuously from 45 ° to 90 ° toward the molten glass outlet located in the center of the bottom. An electric melting furnace for waste vitrification treatment characterized by   4. The electric melting for waste glass solidification treatment according to claim 1, wherein an auxiliary heating device is disposed around the bottom wall of the conical heat-resistant alloy furnace and the molten glass discharge port. Furnace.   In claim 4, the conical heat-resistant alloy furnace bottom wall, the annular refractory brick vertical wall, the cylindrical heat-resistant alloy vertical wall, the molten glass discharge port, the heat-resistant alloy heating electrode and the auxiliary heating device, An electric melting furnace for waste vitrification, which is configured as an independent part that can be replaced independently.   5. The auxiliary heating device provided around the bottom wall of the conical heat-resistant alloy furnace according to claim 4, wherein the auxiliary heating device generates heat for a predetermined time before discharging the molten glass in the melting tank from the molten glass discharge port. An electric melting furnace for waste vitrification treatment, wherein the molten glass in the vicinity of the bottom wall of the conical heat-resistant alloy furnace in the tank is further heated.   The waste according to claim 1, wherein a stirring gas supply pipe and / or a mechanical stirring device for stirring the molten glass in the melting tank is provided in the melting tank. Electric melting furnace for vitrification treatment.

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