JP5126974B2 - Induction heating melting furnace and induction heating method - Google Patents

Description

  The present invention relates to a melting furnace by induction heating and an induction heating method. More particularly, the present invention relates to a melting furnace by induction heating and an induction heating method suitable for use in vitrification of high-level radioactive liquid waste.

  As a glass melting furnace used for vitrification of high-level radioactive liquid waste, there is one that heats glass mixed with high-level radioactive liquid waste using Joule heat generated by energization (Non-patent Document 1). . This glass melting furnace is shown in FIG. A main electrode 102 is provided on the wall surface of the melting tank 101 to generate Joule heat by energizing the molten glass mixed with the high-level radioactive liquid waste. In addition, the heating by Joule heat generated by the main electrode 102 cannot raise the molten glass at the bottom of the melting tank 101 to a sufficient temperature. Therefore, the auxiliary electrode 103 is provided at a position lower than the main electrode 102, and the melting tank The molten glass at the bottom of 101 is energized to generate Joule heat for heating.

Ryohei Terai, “Melting Glass with Cooling Crucible”, [online], Material Integration vol.20 No10 (2007) p55-p59, [Search July 15, 2008], Internet <URL: http: // www. tic-mi.com/publ/essay/terai/0710terai.pdf>

  However, in the above glass melting furnace, the main electrode 102 and the auxiliary electrode 103 are used to heat the mixture of the high-level radioactive liquid waste and the glass, so that it is difficult to uniformly heat the entire mixture, In this mixture, temperature unevenness occurs, and the fluidity of the mixture partially deteriorates.

  The high-level radioactive liquid waste contains platinum group metal particles (hereinafter referred to as metal particles). Metal particles have a higher specific gravity than molten glass, and may precipitate and accumulate on the bottom of the furnace. However, the above glass melting furnace does not have means for actively preventing the precipitation and deposition of metal particles.

  An object of the present invention is to provide an induction heating melting furnace and an induction heating method capable of uniformly heating a conductive liquid. It is another object of the present invention to provide an induction heating melting furnace and an induction heating method capable of preventing precipitation and deposition of metal particles contained in a high-level radioactive liquid waste.

In order to achieve such an object, the induction heating melting furnace according to claim 1, a container for storing a mixture of high-level radioactive liquid waste and glass, a heating element provided in the container and capable of heating the mixture , comprising a heating device by changing the magnetic penetration distance of the electromagnetic field be generated by switching the frequency of the alternating current to the induction heating both of the heating element or heating elements and mixture used, the heating device, mixed by induction heating of the heating element A first heating step for indirectly heating the body, and a second heating for inductively heating both the heating element and the mixture by lowering the frequency of the alternating current than the first heating step to increase the magnetic penetration distance. is intended to implement the process, the first heating step, is shall be performed in the order of the second heating step.

The magnetic permeation distance δ of the electromagnetic field generated by the heating device is obtained by Equation 1.
<Equation 1>
δ = (2 / ωσμ) ^ (1/2)
Here, ω: angular frequency 2πf (f: frequency), σ: electrical conductivity, and μ: magnetic permeability.

That is, when the frequency f of the alternating current used is changed, the magnetic penetration distance δ of the electromagnetic field generated by the heating device changes. Since the distance between the mixture and the heating element from the heating device, that is, the magnetic penetration distance δ, is different, the induction heating target is switched between the case of the heating element and the case of the heating element and the mixture by changing the frequency f. be able to.

For example, the heating element is first induction-heated, and the mixture in the container is indirectly heated by the heat of the heating element. Thereafter, the frequency f of the alternating current used by the heating device is switched to inductively heat both the heating element and the mixture in the container. Conversely, after both the heating element and the mixture in the container are induction-heated by the heating device, the mixture may be indirectly heated by induction heating of the heating element. The mixture may be already liquid when it is put into the container, or it is solid when it is put into the container, but it may be melted by heating in the container to become liquid. Further, a mixture of such a solid and a liquid may be used.

Also, the melting furnace by induction heating according to claim 2, wherein the heating device is capable of generating an electromagnetic force for stirring the mixture in the mixing body. Therefore, the mixture can be stirred by generating an electromagnetic force in the mixture . At this time, when the mixture in contains impurities such as, for example, metal particles, a mixture with impurities contained therein can be agitated.

In the melting furnace by induction heating according to claim 3, the heating element and the heating device are provided on the outer periphery and the bottom of the container. Therefore, the mixture in the container can be heated from the outer periphery and the bottom of the container.

Furthermore, the induction heating method according to claim 4 is a method in which a heating element provided in a container for storing a mixture of high-level radioactive liquid waste and glass is induction-heated by a heating device provided outside the container. A first heating step for indirectly heating the mixture, and after heating the mixture by the first heating step, the magnetic permeation distance of the electromagnetic field generated by lowering the frequency of the alternating current used by the heating device is increased. And a second heating step of inductively heating the mixture in addition to the heating element.

Therefore, in the first heating step, the heating element is heated by the heating device, and the mixture in the container is heated by the heat of the heating element. Then, a 2nd heating process is performed and both the heat generating body and mixture in a container are induction-heated. As a result, the mixture is heated by the heat generated by the heating element and induction heating by the heating device. The mixture may be already liquid when it is put into the container, or it may be solid when it is put into the container, but it may be melted to become liquid by heating in the first heating step. Further, a mixture of such a solid and a liquid may be used.

In the induction heating method according to claim 5 , in the second heating step, induction heating of the mixture is performed while generating an electromagnetic force for stirring the mixture in the mixture by a heating device. Therefore, the mixture can be stirred by generating an electromagnetic force in the mixture . At this time, when the mixture in contains impurities such as, for example, metal particles, a mixture with impurities contained therein can be agitated.

Further, the induction heating method according to claim 6, wherein the glass after the solid glass is melted by first heating step is placed in a container in the form of solid, and performs the second heating step. The glass in the mixture is an insulator in a solid state, but has a conductivity in a molten state at a high temperature, and induction heating is possible. After the glass in the mixture is melted to become a conductive material by heating with the heating element, the frequency f of the alternating current used by the heating device is switched to inductively heat both the mixture and the heating element in the container.

In the melting furnace by induction heating according to claim 1 , the mixture of the high-level radioactive liquid waste and the glass is heated by the heating element in the container, or the heating element generates heat in the container and the electromagnetic field generated by the heating device. Since the mixture is heated, the mixture can be heated more uniformly than in the case where Joule heat is generated by energization by the electrodes as shown in FIG. 15 to heat the mixture in the container. Therefore, generation | occurrence | production of temperature nonuniformity can be prevented and it can prevent that a mixture becomes low temperature partially and fluidity | liquidity deteriorates.
In addition, even when the glass in the mixture is solid, the mixture can be stirred by generating electromagnetic force after it has become molten glass in the first heating step, so that the metal contained in the mixture Particles can be prevented from settling and depositing. Therefore, it becomes easy to discharge the metal particles together with the mixture.

In addition, in the melting furnace by induction heating according to claim 2, since the mixture can be stirred by generating electromagnetic force in the mixture , impurities such as metal particles are contained in the conductive liquid. In some cases this can be prevented from precipitating and depositing. Therefore, it becomes easy to discharge impurities together with the conductive liquid.

Moreover, in the melting furnace by induction heating according to claim 3, the mixture in the container can be heated from the outer periphery and the bottom of the container, so that the mixture can be heated more uniformly. Further, natural convection of the mixture by heating from the outer periphery and bottom of the container if it contains temperature variations and impurities of the mixture is effective to prevent settling and accumulation of impurities.

Furthermore, in the induction heating method according to claim 4 , the mixture can be heated by induction heating after melting the solid glass in the mixture to produce conductivity. Here, in the first heating step, the mixture in the container is heated by the heating element, and in the second heating step, the mixture in the container is heated by the heat generated by the heating element and the electromagnetic field generated by the heating device. As shown in FIG. 15, the mixture can be heated more uniformly than when the mixture in the container is heated by generating Joule heat by energization by the electrodes. Therefore, generation | occurrence | production of temperature nonuniformity can be prevented and it can prevent that a mixture becomes low temperature partially and makes fluidity | liquidity deteriorate.

Further, in the induction heating method according to claim 5 , since the mixture can be stirred by generating electromagnetic force in the mixture , when impurities such as metal particles are contained, this precipitates and deposits. Can be prevented. Therefore, it becomes easy to discharge impurities together with the mixture .

In the induction heating method according to claim 6 , the mixture can be heated by induction heating after melting the solid glass in the mixture to produce conductivity. Here, in the first heating process, the mixture in the container is indirectly heated by the heating element, and in the second heating process, the mixture in the container is heated by the heat generated by the heating element and the electromagnetic field generated by the heating device. Therefore, as shown in FIG. 15, the mixture can be heated more uniformly than when the mixture in the container is heated by generating Joule heat by energization by the electrodes. Therefore, it is possible to prevent the occurrence of temperature unevenness, to prevent the mixture from partially becoming low temperature and to deteriorate the fluidity, and to smoothly fill the mixture into the vitrification container from the flow nozzle. be able to.

  Hereinafter, the configuration of the present invention will be described in detail based on the best mode shown in the drawings.

  FIG. 1 shows an example of an embodiment of a melting furnace by induction heating according to the present invention. This melting furnace includes a container 2 for storing a conductive liquid 1, a heating element 3 provided in the container 2 and capable of heating the conductive liquid 1, and a magnetic permeation distance of an electromagnetic field generated by switching the frequency of an alternating current used. A heating device 4 for induction heating the heating element 3 or both the heating element 3 and the conductive liquid 1 by changing δ is provided.

  In the present embodiment, a glass melting furnace used for vitrifying a high-level radioactive liquid waste will be described as an example of a melting furnace by induction heating. However, you may apply to melting furnaces other than a glass melting furnace. In a glass melting furnace that vitrifies high-level radioactive waste liquid, the conductive liquid 1 is a mixture of high-level radioactive waste liquid and glass (hereinafter referred to as mixture 1). The glass is solid when it is put into the container 2 and is then melted by heating in the container 2. However, liquid molten glass may already be placed in the container 2 when it is placed in the container 2. The high-level radioactive liquid waste contains metal particles 10 such as platinum group particles such as ruthenium and palladium.

  The container 2 is formed of a heat-resistant brick such as ceramics or the like. The top plate 2a of the container 2 is provided with a supply port 5 for introducing the mixture 1 of high-level radioactive waste liquid and glass and an exhaust gas port 6 for letting off the exhaust gas. Further, a flow-down nozzle 8 is provided on the bottom plate 2 b of the container 2. The flow-down nozzle 8 is provided with a valve (not shown). A glass solidification container (not shown) is placed below the flow-down nozzle 8. By covering the top of the container 2 with the top plate 2a, it is possible to prevent heat dissipation, prevent a temperature drop, and facilitate the temperature management in the container 2.

  The heating element 3 has, for example, a bottomed cylindrical shape and is provided so as to overlap the inner surface of the container 2. However, the shape of the heating element 3 is not limited to the bottomed cylindrical shape. For example, when there is no need to heat from the bottom of the container 2, a cylindrical shape without a bottom may be used. Further, in consideration of ease of manufacture, the cylindrical portion 3a and the bottom portion 3b may be separated. Further, the cylindrical portion 3a may be an integral cylindrical body as shown in FIG. 9, for example, but may be divided in the axial direction as shown in FIG. 10, for example, as shown in FIG. May be divided, or may be divided in the circumferential direction as shown in FIG. 12, or may have other shapes. Manufacturing is facilitated by dividing the cylindrical portion 3a. Further, the bottom 3b may be an integral disk-shaped member as shown in FIG. 13, for example, but may have a shape in which the outer peripheral portion and the inner peripheral portion are connected by a plurality of connecting portions as shown in FIG. Other shapes may be used. The heating element 3 is made of, for example, silicon carbide, molybdenum disilicide or the like. However, the material of the heating element 3 is not limited to these, and may be a metal such as Inconel, for example. The thickness of the heating element 3 is such that the magnetic field generated by the heating device 4 can pass through. Specifically, for example, it is preferably about 10 mm. A protective layer 7 that prevents corrosion by the mixture 1 is provided on the inner peripheral surface of the heating element 3. The protective layer 7 is, for example, a ceramic coating layer having a thickness of several mm. However, the protective layer 7 is not limited to the ceramic coating layer, and the thickness is not limited to several mm.

  The heating element 3 is provided corresponding to the entire range of the peripheral wall 2c and the bottom plate 2b of the container 2, for example. However, it is not necessarily provided corresponding to the entire range of the peripheral wall 2 c and the bottom plate 2 b, and may be provided in a range necessary for heating the mixture 1. The heating device 4 is provided in a range necessary for heating the heating element 3.

  The heating device 4 is, for example, an induction heating coil, and is provided on both the outer periphery and the bottom of the container 2 in this embodiment. However, it is not necessary to provide the heating device 4 on both the outer periphery of the container 2 and the bottom of the container 2, and if it is possible to sufficiently heat the mixture 1, either heating device 4 may be omitted. good. For example, a water-cooled copper coil can be used as the induction heating coil. However, you may use things other than a water-cooled copper coil. In addition, the code | symbol 9 is a water channel which circulates cooling water in the figure. Moreover, although the coil which has an iron core may be used as an induction heating coil, use of the coil which does not have an iron core is also possible. That is, the iron core may be unnecessary depending on the distance between the iron core and the object to be heated and the frequency of the alternating current. In general, the iron core increases the magnetic flux, but the magnetic flux may be difficult to reach when the object to be heated is slightly separated, and the energy loss (iron loss) increases as the frequency of the alternating current increases. Therefore, the presence or absence of the iron core is determined in consideration of these. In addition, although the induction heating coil of this embodiment has an iron core, description of the iron core is abbreviate | omitted in drawing.

The magnetic permeation distance δ of the lines of magnetic force generated by the heating device 4 is obtained by Equation 2.
<Equation 2>
δ = (2 / ωσμ) ^ (1/2)
Here, ω: angular frequency 2πf (f: frequency), σ: electrical conductivity, and μ: magnetic permeability.

  That is, when the frequency f of the alternating current to be used is changed, the magnetic permeation distance δ of the magnetic lines B1 and B2 generated by the heating device 4 changes. Since the distances of the mixture 1 and the heating element 3 from the heating device 4 are different, the object of induction heating is switched between the mixture 1, the mixture 1 and the heating element 3 by changing the frequency f. (FIGS. 2 and 3, FIG. 6 and FIG. 7). For example, when the heating element 3 is made of metal and has a thickness of 10 mm, the frequency f is 10 KHz, the magnetic penetration distance δ is about 5 mm, the frequency f is 1 KHz, and the magnetic penetration distance δ is about 16 mm. By changing to 1 KHz, the object of induction heating can be switched from the heating element 3 only to the heating element 3 and the mixture 1.

  In the present embodiment, the heating device 4 is also used as an electromagnetic force generating means for generating an electromagnetic force F that stirs the mixture 1 in the mixture 1. Therefore, the induction heating coil as the heating device 4 uses a three-phase AC coil suitable for generating a moving magnetic field.

  A heating device 4 provided on the outer periphery of the container 2 (hereinafter referred to as a heating device 4A when distinguished from the heating device 4 at the bottom of the container 2) is shown in FIGS. The heating device 4A is provided so as to surround the peripheral wall 2c. The three-phase AC coil that is the heating device 4A is a combination of AX, BY, and CZ, and each coil 4a is connected in pairs, and the winding directions of the A, B, and C coils 4a are the same. The winding directions of the X, Y, and Z coils 4a are the same, and the winding directions of the A, B, and C coils 4a and the X, Y, and Z coils 4a are reversed. Here, the number of turns is determined so as to satisfy the condition of (magnetic field strength) = (number of turns) × (current). Moreover, the electric current sent through each coil 4a is calculated | required from (current) = (voltage) / (impedance).

  Each coil 4a is arranged in the order of A → Z → B → X → C → Y → A →... → Y toward the upper side of the container 2 in the axial direction, and the phase difference of each coil 4a is 60 degrees. For example, as shown in FIGS. 4A and 4B, when A is 0 degrees, Z is 60 degrees, B is 120 degrees, X is 180 degrees, C is 240 degrees, and Y is 300 degrees. When a three-phase alternating current for generating electromagnetic force is supplied to the heating device 4A from a power source (not shown), for example, as shown by an arrow in FIG. 3, the magnetic lines B1 are formed around the coil 4a and the peripheral wall 2c of the container 2 and the heating element. 3a, the protective layer 7, and the mixture 1 are generated, and a moving magnetic field upward in the axial direction of the container 2 is formed by a change in the current flowing through each coil 4a.

  By forming an upward moving magnetic field by the heating device 4A, a current flowing in the circumferential direction is generated at a position in the vicinity of the container 2 of the mixture 1, that is, a position where the magnetic force line B1 penetrates in the radial direction. For example, a current from the back side to the near side in the figure is generated at the P1 position in FIG. 3, and a current from the near side to the back side in the figure is generated at the P2 position. Due to the moving magnetic field and the current generated in the mixture 1, an upward electromagnetic force F1 is generated from Fleming's left-hand rule. Although the direction of the current generated in the mixture 1 is reversed depending on the location, the winding directions of the A, B, C coil 4a and the X, Y, Z coil 4a are also reversed, so that the electromagnetic A force F1 is generated. This electromagnetic force F1 is generated at a position relatively close to the container 2, and drives the mixture 1 at a position relatively close to the container 2 and the metal particles 10 included therein upward.

  A heating device 4 provided at the bottom of the container 2 (hereinafter referred to as a heating device 4B when distinguished from the heating device 4A on the outer periphery of the container 2) is shown in FIGS. The heating device 4 </ b> B is configured by an AC coil, and is provided so as to face the bottom surface of the bottom plate 2 b of the container 2 and to be arranged along the circumferential direction so as to surround the falling nozzle 8. In the present embodiment, the heating device 4B at the bottom of the container 2 also inductively heats the heating element 3 or both of the heating element 3 and the mixture 1 and generates an electromagnetic force F2 in the same manner as the heating apparatus 4A on the outer periphery of the container 2. The mixture 1 and the metal particles 10 included therein are driven (electromagnetic stirring).

  In the present embodiment, three-phase AC coils 4b, 4c, and 4d are used as the heating device 4B. However, AC coils other than the three-phase AC coils 4b, 4c, and 4d may be used. Four sets of three-phase AC coils 4b, 4c and 4d are provided. However, the number of sets of the three-phase AC coils 4b, 4c, and 4d is not limited to four. The coils 4b, 4c, and 4d for each phase are arranged so as to be shifted by 30 degrees, for example. In the present embodiment, since the three-phase AC coils 4b, 4c, 4d are arranged at the bottom of the container 2, each coil 4b, 4c, 4d is shaped like a fan and spaced from each adjacent coil. 4b, 4c and 4d are arranged. The phase difference between the coils 4b, 4c and 4d is 120 degrees.

  In FIG. 7, a symbol with “•” in a circle means that a current flows from the back side toward the near side in the drawing. Moreover, the symbol which described x in (circle) means that the electric current is flowing toward the back | inner side from the near side with respect to drawing. Here, the number of turns of each of the coils 4b, 4c, and 4d is determined so as to satisfy the condition of (magnetic field strength) = (number of turns) × (current). Further, the current flowing through each of the coils 4b, 4c, 4d is obtained from (current) = (voltage) / (impedance).

  When a three-phase AC current is supplied to the heating device 4B from a power source (not shown), for example, as indicated by an arrow B2 in FIG. . The magnetic field line B2 is generated for each coil, but a rotating magnetic field directed toward one side in the circumferential direction of the container 2 is formed by the phase difference of each coil, the direction of the current flowing through each coil, and the change thereof.

  By forming a circumferential rotating magnetic field by the heating device 4B, a current flowing in the radial direction along the bottom plate 2b is generated at a position near the bottom plate 2b, that is, a position where the magnetic lines of force B2 penetrate in the radial direction. For example, at the position P3 in FIG. 7, a current from the back side to the near side in the figure is generated, and at the position P4, a current from the near side to the back side in the figure is generated. Due to the rotating magnetic field and the current generated in the mixture 1, an electromagnetic force F2 is generated in the circumferential direction along the bottom of the container 2 from Fleming's left-hand rule. The direction of the current generated in the mixture 1 is reversed depending on the location, but the direction of the magnetic force line B2 is also reversed, so that the electromagnetic force F2 in the same circumferential direction is always generated. This electromagnetic force F2 is generated in the mixture 1 and drives the mixture 1 and the metal particles 10 included in the mixture 1 in the circumferential direction.

  In the present embodiment, a single-phase alternating current is used for induction heating of the heating element 3 or both of the heating element 3 and the mixture 1, and electromagnetic forces F1 and F2 for stirring the mixture 1 (electromagnetic stirring) are used. When it is generated, a three-phase alternating current is used. A three-phase AC current may be used instead of a single-phase AC current for induction heating, but it is suitable to use an AC current with a higher frequency than that used for electromagnetic stirring for induction heating. In the form, a single-phase alternating current is used for induction heating. When both induction heating and electromagnetic stirring are performed simultaneously, a single-phase alternating current for induction heating and a three-phase alternating current for generating electromagnetic force are simultaneously supplied to the heating device 4. That is, when the heating element 3 is induction-heated, a high-frequency single-phase alternating current is used, and when both the mixture 1 and the heating element 3 are induction-heated, a medium-frequency single-phase alternating current is used. When generating electromagnetic forces F1 and F2 for stirring, a low-frequency three-phase alternating current is used. And when performing the induction heating and electromagnetic stirring of the mixture 1 simultaneously, a medium frequency single phase alternating current and a low frequency three phase alternating current are used simultaneously.

  Next, the induction heating method will be described. In the induction heating method, the heating element 3 provided in the container 2 for storing the mixture 1 of high-level radioactive liquid waste and solid glass is induction-heated by the heating device 4 provided outside the container 2, and the heating element 3 generates heat. After the fixed glass is melted by the first heating step for indirectly heating the mixture 1 and the first heating step, the frequency of the alternating current used by the heating device 4 is changed to change the heating element 3 and the mixture 1. And a second heating step for induction heating. Here, although the case where the above-mentioned glass melting furnace is used is demonstrated, you may implement the said induction heating method using things other than this. In addition to vitrification of the high-level radioactive liquid waste, an induction heating method may be used.

  FIG. 8 shows the induction heating method of this embodiment. With the valve (not shown) of the flow-down nozzle 8 closed, the mixture 1 of solid glass and high-level radioactive liquid waste is put into the container 2 from the supply port 5 (step S21). However, glass may be in a molten state. In this case, the first heating step can be omitted. In addition, it is not always necessary to put both the solid glass and the high-level radioactive liquid waste from the same supply port 5. The glass supply port and the high-level radioactive liquid waste supply port are separately provided to separate the glass and the high-level radioactive liquid waste. May be put separately.

  After putting the mixture 1 of solid glass and high-level radioactive liquid waste into the container 2, the heating element 3 is induction-heated by the heating device 4 (first heating step: step S22). For example, the heating element 3 is heated to, for example, about 1000 ° C. using a high-frequency alternating current having a value of about 10 K to 100 KHz. By this heating, the solid glass in the mixture 1 is heated and melted to become conductive molten glass. Heating is performed using both the heating device 4A on the outer periphery of the container 2 and the heating device 4B on the bottom of the container 2.

  After the solid glass melts and becomes conductive, both the mixture 1 and the heating element 3 are induction-heated by the heating device 4 (second heating step: step S23). For example, the mixture 1 and the heating element 3 are induction-heated using an alternating current having a medium frequency of about 1 K to 10 KHz, and the mixture 1 is heated to about 1200 ° C. Heating is performed using both the heating device 4A on the outer periphery of the container 2 and the heating device 4B on the bottom of the container 2.

  In the present embodiment, induction heating of the mixture 1 is performed while generating electromagnetic forces F1 and F2 for stirring the mixture 1 in the mixture 1 by the heating device 4 in the second heating step. That is, a single-phase alternating current for induction heating is supplied to the heating device 4 and at the same time, a three-phase alternating current for electromagnetic stirring is supplied. For example, a low-frequency three-phase alternating current of the order of 100 Hz is supplied. In this embodiment, since the conductive liquid is the glass mixture 1, a low-frequency three-phase alternating current of, for example, 100 Hz order is supplied as a three-phase alternating current for electromagnetic stirring. The frequency of the alternating current is not limited to the order of 100 Hz, and is appropriately determined according to the type of the conductive liquid. For example, when the conductive liquid is a liquid metal, it is possible to use a three-phase alternating current having a commercial frequency such as 50 Hz or 60 Hz.

  The heating device 4A on the outer periphery of the container 2 generates an electromagnetic force F1 that drives the mixture 1 at a position relatively close to the peripheral wall 2c of the container 2 upward. The mixture 1 driven upward by the electromagnetic force F1 and the metal particles 10 included in the mixture are reversed near the liquid surface and lowered near the center of the container 2, and then reversed near the bottom 3b and along the peripheral wall 2c. Rise. Thus, the mixture 1 and the metal particle 10 contained in it are stirred. The heating device 4B at the bottom of the container 2 generates an electromagnetic force F2 that drives the mixture 1 and the metal particles 10 in the circumferential direction at the bottom 3b in the container 2. Thereby, the mixture 1 and the metal particle 10 in the inner bottom part of the container 2 are rotated in the circumferential direction and stirred. Thus, in this invention, since the mixture 1 in the container 2 can be stirred by the two heating devices 4A and 4B, the metal particles 10 contained in the high-level radioactive waste liquid of the mixture 1 are suspended. Precipitation and accumulation can be prevented. However, since the electric conductivity of the molten glass of the mixture 1 is smaller than the electric conductivity of the metal particles 10, the electromagnetic force acting on the metal particles 10 is larger than the electromagnetic force acting on the molten glass of the mixture 1. .

  In the present invention, the heating element 3 is induction-heated in the first heating step, and the mixture 1 is heated by the heat. In the second heating step, the heating of the heating element 3 and induction heating of the mixture 1 are performed. Since heating is performed by induction heating using a coil, the mixture 1 can be heated in a wide range, and the entire mixture 1 can be heated uniformly. That is, when the Joule heating is performed by the main electrode or the auxiliary electrode as shown in FIG. 15, so-called so-called point heating is likely to be partial heating, but the heating by the heating element 3 or the induction heating coil is not performed as in the present invention. The so-called surface heating is suitable for heating the mixture 1 in a wide range, and it is easy to uniformly heat the entire mixture 1.

  In the present embodiment, the heating device 4 and the heating element 3 are provided on both the outer periphery and the bottom of the container 2, so that the mixture 1 can be naturally convected by heating from both the side surface and the bottom surface of the container 2. it can. The natural convection of the mixture 1 caused by heating from the side and bottom surfaces of the container 2 eliminates the temperature unevenness of the mixture 1 and prevents sedimentation / deposition of the metal particles 10. That is, even when electromagnetic stirring by the heating device 4 is not performed, temperature unevenness of the mixture 1 and settling / deposition of the metal particles 10 can be prevented. When electromagnetic stirring is performed, the temperature of the mixture 1 can be prevented. Unevenness and sedimentation / deposition of the metal particles 10 can be prevented even better.

  Thereafter, when the valve of the flow-down nozzle 8 is opened, the mixture 1 in the container 2 is discharged from the flow-down nozzle 8 and filled in the vitrification container (step S24). Since the metal particles 10 are dispersed in the mixture 1, the metal particles 10 are also filled together in the vitrification container. Since the mixture 1 is uniformly heated by the heating device 4 and there is no temperature unevenness, the mixture 1 can be smoothly filled into the vitrification container from the flow nozzle 8. At this time, after the heating device 4 is stopped, the mixture 1 and the metal particles 10 may be discharged from the flow-down nozzle 8 before being cooled, or the mixture 1 and the metal may be left in a state where the heating device 4 is operated. The particles 10 may be discharged from the falling nozzle 8.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in the above description, the heating device 4 is provided on both the outer periphery and the bottom of the container 2, but it is not necessarily provided on both, and may be provided only on either one.

  In the above description, the electromagnetic force for stirring the mixture 1 is generated in the second heating step. However, the electromagnetic force for stirring the mixture 1 may not be generated. Further, it is not always necessary to generate the electromagnetic force for stirring the mixture 1 in all of the second heating process, and for example, the electromagnetic force may be generated only in the latter stage of the second heating process.

  Further, in the above description, the high-level radioactive liquid waste and glass mixture 1 is taken as an example of the conductive liquid 1, but the heating target is not limited to this, and the conductive liquid has conductivity and can be inductively heated. If it is a fluid, it will not specifically limit. For example, a metal such as iron or aluminum, or a non-metal, which has a certain degree of electrical conductivity, or a material whose electrical conductivity increases as the temperature rises, such as glass, may be used as a heating target. Also, for example, when uniform heating is required as much as possible by melting or refining a metal such as iron or aluminum, or when it is desired to suppress the temperature rise of the container 2 or the heating element 3, the impurities are uniformly distributed in the conductive liquid 1. It is suitable for use in cases where it is desired to increase the mechanical strength of a material by mixing specific impurities (for example).

It is sectional drawing which shows an example of embodiment of the glass melting furnace of this invention. It is sectional drawing which shows the heating apparatus of a container outer periphery, and shows the mode of the generation | occurrence | production of the magnetic force line in a 1st heating process. It is sectional drawing which shows the heating apparatus of a container outer periphery, and shows the mode of the generation | occurrence | production of the magnetic force line in a 2nd heating process. It is a figure for demonstrating the three-phase alternating current coil which is a heating apparatus, (A) is a figure which shows the phase difference, (B) is a figure which shows electrical arrangement | positioning. It is a top view which shows the heating apparatus of a container bottom part. It is sectional drawing which shows the heating apparatus of a container bottom part, and shows the mode of the generation | occurrence | production of the magnetic force line in a 1st heating process. It is sectional drawing which shows the heating apparatus of a container bottom part, and shows the mode of generation | occurrence | production of the magnetic force line in a 2nd heating process. It is a flowchart which shows an example of embodiment of the glass melting method of this invention. It is a perspective view which shows the 1st modification of the cylindrical part of a heat generating body. It is a perspective view which shows the 2nd modification of the cylindrical part of a heat generating body. It is a perspective view which shows the 3rd modification of the cylindrical part of a heat generating body. It is a top view which shows the 4th modification of the cylindrical part of a heat generating body. It is a top view which shows the 1st modification of the bottom part of a heat generating body. It is a top view which shows the 2nd modification of the bottom part of a heat generating body. It is sectional drawing of the conventional glass melting furnace.

Explanation of symbols

1 Mixture of high-level radioactive liquid waste and glass 2 Container 3 Heating element 4 Heating device F1, F2 Electromagnetic force for stirring the mixture and metal particles contained in it

Claims (6)

A container for storing a mixture of high-level radioactive liquid waste and glass, a heating element provided in the container and capable of heating the mixture, and changing a magnetic penetration distance of an electromagnetic field generated by switching a frequency of an alternating current to be used. A heating device that induction-heats the heating element or both the heating element and the mixture, and the heating device induction-heats the heating element to indirectly heat the mixture. And the second heating step of inductively heating both the heating element and the mixture by lowering the frequency of the alternating current from that of the first heating step to increase the magnetic permeation distance. the first heating step, the melting furnace by induction heating, characterized that you performed in the order of the second heating step. The heating apparatus, melting furnace by induction heating according to claim 1, characterized in that it is capable of generating electromagnetic force to stir the mixture in the mixing body.   The melting furnace by induction heating according to claim 1, wherein the heating element and the heating device are provided on an outer periphery and a bottom of the container. A heating element provided in a container for storing a mixture of high-level radioactive liquid waste and glass is induction-heated by a heating device provided outside the container, and the mixture is indirectly heated by the heat generated by the heating element. After heating the mixture by the heating step 1 and the first heating step, the magnetic penetration distance of the electromagnetic field generated by lowering the frequency of the alternating current used by the heating device is increased and added to the heating element. And a second heating step of induction heating the mixture. 5. The induction heating method according to claim 4, wherein in the second heating step, induction heating of the mixture is performed while generating an electromagnetic force for stirring the mixture in the mixture by the heating device. . The induction heating method according to claim 4, wherein the glass is placed in the container in a solid state, and the second heating step is performed after the solid glass is melted by the first heating step .

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