JP5772349B2 - Glass melting furnace operation method - Google Patents

Description

The present invention relates to a method for operating a glass melting furnace installed in a high-level radioactive liquid waste vitrification facility.

  In general, high-level radioactive liquid waste that is generated at nuclear facilities is sent to the glass melting furnace of the high-level radioactive liquid waste glass solidification facility, treated as a glass solid, and then stored in the radioactive waste storage facility. Is done.

  In the vitrification facility, high-level radioactive waste liquid is mixed when melting the raw glass inside the glass melting furnace, and the molten glass mixed with the high-level radioactive waste liquid is poured into a canister (stainless steel container), A glass solidified body is formed by solidifying the molten glass.

  A conventional glass melting furnace includes, for example, a melting furnace body that is constructed of a refractory material such as a refractory brick so that a melting space is formed therein, and whose outer periphery is covered with a metal casing. The upper ceiling wall of the melting furnace body is provided with an inlet into which high-level radioactive liquid waste as a liquid to be treated and raw glass such as glass beads are charged, and in the middle in the vertical direction of the inner wall of the melting furnace body The main electrode for heating and melting the raw glass in the melting space by energization between each other is disposed oppositely, and at the lower end of the bottom portion that is narrowed downward in the melting furnace body, the main electrode and A bottom electrode is arranged to heat and melt the glass at the bottom in the melting space by energization between them. The flow-down hole formed in the bottom electrode is connected to a flow-down nozzle for extracting molten glass mixed with high-level radioactive waste liquid and injecting it into the canister. A high frequency induction heating coil is disposed. Further, an auxiliary electrode is disposed between the main electrode and the bottom electrode on the outer periphery of the portion that is shaped to squeeze below the inner wall of the melting furnace body.

  In the conventional glass melting furnace as described above, high-level radioactive liquid waste and raw glass are introduced from the inlet of the melting furnace main body, and first, a current is passed between the main electrodes and between the auxiliary electrodes to cause a joule of the molten glass therebetween. The high-level radioactive liquid waste and raw glass are sufficiently melted together by heat. Subsequently, current is passed between the main electrode and the bottom electrode to heat the glass on the bottom electrode by Joule heat. Thereafter, the flow nozzle that extends from the flow hole of the bottom electrode is heated by energizing the high-frequency induction heating coil for the nozzle to melt the solidified glass clogged therein and withdraw it downward. The molten glass in the main body is allowed to flow down into a canister set at the lower part thereof and hermetically accommodated as a glass solidified body.

  For example, Patent Document 1 shows a general technical level related to the glass melting furnace as described above.

JP 2002-249321 A

  By the way, the high-level radioactive liquid waste contains about 1% of platinum group elements such as ruthenium, palladium, rhodium, etc., but the platinum group elements are separated without melting into the glass in the melting furnace body. If the particles are small, they move in the same manner as glass, but if the particles are large, they tend to settle and deposit on the bottom of the melting furnace body as compared to the movement of the molten glass in the melting furnace body. In addition, since the platinum group element is conductive, when the concentration of the platinum group element in the glass at the bottom of the melting furnace sinks and becomes high, the metal is present there. And the electrical resistance of the glass becomes low, even if current is passed between the main electrode and the bottom electrode and current is passed through the glass, sufficient Joule heat cannot be obtained, and the viscosity of the glass does not decrease, There is a possibility that the glass at the bottom of the melting furnace main body cannot be made to flow down from the flow down nozzle.

  For this reason, the extraction angle of the platinum group element is improved by increasing the inclination angle of the portion that is narrowed downward in the melting furnace body from about 45 ° to about 60 °. This has been proposed by the inventors of the present invention. In one batch process in which the furnace bottom is heated to flow down the glass and then the furnace bottom is cooled, the molten glass mixed with the liquid to be treated has a constant weight ( For example, at the time of extracting 400 [kg]), the glass at the upper part of the melting furnace main body having a high temperature in the latter half of the flow of the molten glass (for example, at the time of extracting 200 [kg] in the latter half of the total 400 [kg]) As a result of analysis, it was found that the nozzle tends to reach the falling nozzle.

  Here, the flow-down nozzle has a function of stopping the flow of the molten glass, but the flow-down can be stopped when glass at a certain temperature (about 1000 [° C.]) or more reaches the flow-down nozzle. Disappear.

  However, since it is very difficult to change the structure of the falling nozzle in order to make it possible to stop the flowing of the molten glass, it is necessary to find a solution other than the flowing nozzle.

  Further, in the conventional glass melting furnace as described above, since the process of cooling the furnace bottom becomes long, the time required for one batch processing becomes very long, and improvement has been desired.

In view of such circumstances, the present invention can reliably stop the flow of molten glass without changing the structure of the flow nozzle, and can also shorten the time required for one batch process, thereby improving work efficiency. It is intended to provide a glass melting furnace operating method that can be achieved.

The present invention is a refractory melting furnace main body into which a liquid to be treated and a raw material glass containing a platinum group element are charged, and an electric current between them disposed opposite to an intermediate portion in the vertical direction of the inner wall of the main body of the melting furnace. A main electrode for heating and melting the raw glass in the main body of the melting furnace, and a main body of the melting furnace by being energized between the main electrode and disposed at the lower end of the bottom portion of the main body of the melting furnace that is narrowed downward. A bottom electrode for heating and melting the glass at the inner bottom, and a flow-down nozzle for dropping the molten glass that is suspended from the lower end of the bottom electrode and mixed with the liquid to be treated and injecting it into the canister,
A furnace heating process for raising the glass temperature at the bottom of the melting furnace body, and a molten glass in which the liquid to be treated is mixed from the flow nozzle by raising the glass temperature raised in the furnace heating process to a set temperature. An operation method of a glass melting furnace in which a batch process includes a glass flow process for extracting glass and a furnace bottom cooling process for reducing the glass temperature raised to a set temperature in the glass flow process,
A cooling jacket in which a cooling air flow passage is formed is disposed on the outer periphery of a portion of the melting furnace body that is narrowed downward, and the bottom heating is performed with respect to the cooling air flow passage of the cooling jacket. Supplying and circulating cooling air from the middle of the process, passing through the glass flow-down process, and stopping the supply of the cooling air in the middle of the furnace bottom cooling process. It is.

  According to the above means, the following operation can be obtained.

  As described above, the cooling air is supplied to the cooling air flow passage of the cooling jacket from the middle of the furnace bottom heating process and is circulated, and the cooling air is supplied in the middle of the furnace bottom cooling process through the glass flow down process. When the process is stopped, the furnace bottom heating step and the glass are performed even if the inclination angle of the portion of the melting furnace main body that is narrowed downward in order to improve the extractability of the platinum group element is larger than the conventional one. When a certain weight of the molten glass mixed with the liquid to be treated is extracted in a single batch process consisting of a flow-down process and a furnace bottom cooling process, the glass at the upper part of the melting furnace main body having a high temperature in the latter half of the flow of the molten glass is Since the cooling air is efficiently cooled by the cooling air supplied to the cooling air flow passage of the cooling jacket, it is avoided that the glass at a certain temperature or more in the falling nozzle reaches. It is, even in the current flow down the nozzle it is possible to reliably stop the stream of glass.

  Further, since the furnace bottom cooling process is shortened as compared with the conventional glass melting furnace, the time required for one batch process can be shortened.

According to the operation method of the glass melting furnace of the present invention, the flow of the molten glass can be reliably stopped without changing the structure of the flow nozzle, and the time required for one batch processing can be shortened. An excellent effect of improving efficiency can be achieved.

It is a whole schematic block diagram which shows the Example of the glass fusing furnace of this invention. (A) is a sectional side view showing a cooling jacket in the embodiment of the glass melting furnace of the present invention, (b) is a plan sectional view showing the cooling jacket in the embodiment of the glass melting furnace of the present invention, It is the IIb-IIb cross-section equivalent figure of a). It is a time chart which shows each process in the Example of the glass fusing furnace of this invention. It is a whole schematic block diagram which shows an example of the glass melting furnace which the present inventors developed previously. It is a time chart which shows each process in an example of the glass melting furnace which the present inventors developed before.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  1 to 3 show an embodiment of a glass melting furnace according to the present invention, which is constructed of a refractory material 2 such as a refractory brick so that a melting space 1 is formed therein, and has a metal outer periphery. A melting furnace main body 4 covered with a casing 3 is provided, and a high-level radioactive waste liquid 5 as a liquid to be treated and a raw glass 6 such as glass beads are charged into an upper ceiling wall of the melting furnace main body 4. And a main electrode 8 that heats and melts the raw glass 6 in the melting space 1 by energization between each other in the middle in the vertical direction of the inner wall of the melting furnace body 4. A bottom electrode 9 that heats and melts the glass in the inner bottom of the melting space 1 by energization with the main electrode 8 is disposed at the lower end of the bottom that is constricted in a conical shape, and the melting furnace body 4 Stray that receives refractory waste that has fallen off 10 Place, the high level radioactive liquid waste 5 from the center of the bottom electrode 9 are as extracting the molten glass is mixed.

  As shown in FIG. 1, the bottom electrode 9 has a conical electrode portion 9d in which a conical space 9c is formed in the center of the disc portion 9b, and a bottom electrode 9 hanging from the lower end of the conical electrode portion 9d. It has a configuration in which a molten glass mixed with high-level radioactive waste liquid 5 is integrally formed with a flow-down nozzle 12 for extracting and injecting the molten glass into the canister 11.

  As shown in FIG. 1, a high frequency induction heating coil 14 as a heating means is disposed on the outer periphery of the conical electrode portion 9d in the bottom electrode 9, and a nozzle as a heating means is provided on the outer periphery of the falling nozzle 12. A high-frequency induction heating coil 15 is disposed.

  An indirect heating device 16 that constantly heats the interior of the melting space 1 is disposed above the melting furnace body 4, and a middle auxiliary electrode 17 is provided in the constricted shape in the melting furnace body 4. The lower auxiliary electrode 18 is disposed between the main electrode 8 and the bottom electrode 9. Cooling air flow passages 8a and 17a through which cooling air flows are formed inside the main electrode 8 and the middle auxiliary electrode 17, respectively.

  In the case of the present embodiment, as shown in FIGS. 2A and 2B, the cooling air flow is provided inside the outer periphery of the portion of the melting furnace main body 4 that is conically narrowed downward. A cooling jacket 19 in which a passage 19 a is formed is disposed between the main electrode 8 and the bottom electrode 9 and between the middle auxiliary electrode 17 and the lower auxiliary electrode 18.

  In the glass melting furnace in the present embodiment, as shown in FIG. 3, a furnace bottom heating step for raising the glass temperature at the bottom of the melting furnace body 4 and a glass temperature raised in the furnace bottom heating step are further set. A glass flow-down step for extracting the molten glass mixed with the high-level radioactive waste liquid 5 as the liquid to be treated from the flow-down nozzle 12 by raising the temperature, and a furnace bottom for lowering the glass temperature raised to the set temperature in the glass flow-down step The cooling process is repeated as one batch process, and cooling air is supplied and circulated from the middle of the furnace bottom heating process to the cooling air flow passage 19a of the cooling jacket 19, and the glass flowing process is performed. The supply of the cooling air is stopped in the middle of the furnace bottom cooling step.

  Incidentally, as shown in FIG. 3, the indirect heating device 16 is always operated, and the energization between the main electrodes 8 and the energization between the middle auxiliary electrodes 17 are always performed to constantly heat the inside of the molten space 1, thereby the molten glass temperature. Is maintained at a temperature exceeding 1000 [° C.].

  The high-frequency induction heating coil 14 is always energized, while the main electrode 8 and the bottom electrode 9 are energized from the middle of the furnace bottom heating process to the middle of the glass flow process. The high-frequency induction heating coil 15 is energized during the glass flow-down process, whereby the furnace bottom glass temperature gradually rises in the furnace bottom heating process and continues to rise in the glass flow-down process, and in the furnace bottom cooling process. It is supposed to decrease.

  As described above, cooling air is supplied and circulated from the middle of the furnace bottom heating process to the cooling air flow passage 19a of the cooling jacket 19, and after passing through the glass flow down process, the cooling air in the middle of the furnace bottom cooling process. When the supply is stopped, the inclination angle of the portion that is narrowed downward in the melting furnace main body 4 in order to improve the extractability of the platinum group element is about 60 °, which is conventionally about 45 °. Even if it is made large, the molten glass mixed with the high-level radioactive waste liquid 5 as the liquid to be treated in a single batch process consisting of the furnace bottom heating process, the glass flow down process, and the furnace bottom cooling process has a constant weight (for example, 400 [kg]), when the molten glass flows out in the latter half (at the time of withdrawal of 200 [kg] in the latter half of the total 400 [kg]) Since the glass is efficiently cooled by the cooling air supplied to the cooling air flow passage 19a of the cooling jacket 19, the glass at a certain temperature (for example, about 1000 [° C.]) or more in the flowing nozzle 12 reaches the glass. Such a situation can be avoided, and even the current flow nozzle 12 can reliably stop the flow of glass.

  For reference, FIG. 4 is an overall schematic configuration diagram showing an example of a glass melting furnace previously developed by the present inventors. In the figure, the parts denoted by the same reference numerals as those in FIG. The basic structure is the same as that shown in FIG. 1 except that the auxiliary electrode 17 ′ is connected to the main electrode 8 and the bottom electrode 9 in a conical shape in the melting furnace body 4. A cooling air flow passage 17a 'through which the cooling air is circulated is formed inside the auxiliary electrode 17' and the cooling air is circulated inside the bottom electrode 9 A path 9h is formed.

  In the glass melting furnace previously developed by the present inventors shown in FIG. 4, as shown in FIG. 5, a furnace bottom heating step for raising the glass temperature at the bottom of the melting furnace body 4, and the furnace bottom The glass temperature raised in the heating step is further raised to a set temperature, and the glass flow-down step for extracting the molten glass mixed with the high-level radioactive waste liquid 5 as the liquid to be treated from the flow-down nozzle 12 and the glass flow-down step are set. The furnace bottom cooling process for lowering the glass temperature raised to the temperature is repeated as one batch process, and cooling air is supplied to the cooling air flow passage 9h of the bottom electrode 9 from the beginning of the furnace bottom cooling process. The supply of the cooling air is stopped in the middle of the furnace bottom cooling process.

  Incidentally, as shown in FIG. 5, the indirect heating device 16 is always operated, the energization between the main electrodes 8 and the energization between the auxiliary electrodes 17 ′ are always performed, and the inside of the molten space 1 is constantly heated, thereby melting glass. The temperature is maintained at a temperature exceeding 1000 [° C.], which is the same as the time chart shown in FIG.

  Further, the energization between the main electrode 8 and the bottom electrode 9 is performed from the beginning of the furnace bottom heating process to the middle of the glass flow process, and the energization to the high frequency induction heating coil 15 for the nozzle is performed in the glass flow process. As a result, the furnace bottom glass temperature gradually rises in the furnace bottom heating process, continues to rise in the glass flow-down process, and decreases in the furnace bottom cooling process. This is the same as the time chart shown in FIG.

  However, as apparent from comparison between FIG. 5 and FIG. 3, in the time chart shown in FIG. 5, the furnace bottom cooling process becomes very long, and accordingly, the time required for one batch processing becomes long. In the time chart shown in FIG. 3, since the furnace bottom cooling process is shortened, the time required for one batch process can be shortened.

  Thus, the flow of the molten glass can be stopped reliably without changing the structure of the flow-down nozzle 12, the time required for one batch process can be shortened, and the work efficiency can be improved.

In addition, the operating method of the glass melting furnace of this invention is not limited only to the above-mentioned Example, Of course, various changes can be added within the range which does not deviate from the summary of this invention.

DESCRIPTION OF SYMBOLS 1 Melting space 2 Refractory 3 Casing 4 Melting furnace main body 5 High level radioactive waste liquid (processed liquid)
6 Raw glass 7 Input port 8 Main electrode 9 Bottom electrode 12 Flowing nozzle 19 Cooling jacket 19a Cooling air flow passage

Claims (1)

A melting furnace body made of a refractory to which a liquid to be treated and a raw material glass containing a platinum group element are charged, and an inner wall of the melting furnace body disposed opposite to each other in the vertical direction inside the melting furnace body by energizing each other. A main electrode that heats and melts the raw glass of the glass, and a glass at the bottom of the inner portion of the melting furnace body that is disposed at the lower end of the bottom portion that has a shape that narrows downward in the main body of the melting furnace and is energized between the main electrode A bottom electrode that heats and melts, and a falling nozzle that draws from the lower end of the bottom electrode and draws the molten glass mixed with the liquid to be treated and injects it into the canister,
A furnace heating process for raising the glass temperature at the bottom of the melting furnace body, and a molten glass in which the liquid to be treated is mixed from the flow nozzle by raising the glass temperature raised in the furnace heating process to a set temperature. An operation method of a glass melting furnace in which a batch process includes a glass flow process for extracting glass and a furnace bottom cooling process for reducing the glass temperature raised to a set temperature in the glass flow process,
A cooling jacket in which a cooling air flow passage is formed is disposed on the outer periphery of a portion of the melting furnace body that is narrowed downward, and the bottom heating is performed with respect to the cooling air flow passage of the cooling jacket. A method for operating a glass melting furnace, comprising supplying and circulating cooling air from the middle of the process, stopping the supply of the cooling air in the middle of the furnace bottom cooling process through the glass flow-down process.

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