JP2001281393A - Treatment device for exhaust gas from mixed oxide fuel pellet sintering furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment device capable of efficiently cooling the exhaust gas of a sintering furnace with water, preventing the penetration of cooling water into the sintering furnace in the breakage of a cooling means, and further surely diluting the hydrogen concentration in the exhaust gas to an explosion lower limit concentration or lower. SOLUTION: This treatment device comprises an exhaust gas inlet pipe 2 having an outlet opening 2a for introducing exhaust gas into a vessel and discharging it upward in the upper part within the vessel; a dispersing plate 5 for changing the exhaust gas upward flow introduced into the vessel into a downward flow; the cooling means for cooling the exhaust gas downward flow in the vessel with water; an exhaust gas discharge pipe 3 provided in the lower part of the vessel to discharge the cooled exhaust gas into a glove box; and inert gas inlet pipes 8 and 8' for introducing an inert gas to the exhaust gas inlet pipe or the exhaust gas flow after cooled in the lower part of the vessel to dilute it. The exhaust gas is cooled to about 60 deg.C or lower, diluted to the explosion lower limit hydrogen concentration or less, and then exhausted into the globe box.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a pretreatment such as cooling prior to directing exhaust gas from a sintering furnace of plutonium / uranium mixed oxide (hereinafter abbreviated as "MOX") fuel pellets into a glove box. Therefore, the present invention relates to an exhaust gas treatment device interposed between a sintering furnace and a glove box.

[0002]

2. Description of the Related Art In a sintering furnace for MOX fuel pellets, diluted with an inert gas such as nitrogen to prevent oxidation of a material to be sintered and to obtain physical properties of a sintered material within product specifications. A hydrogen-containing gas having a hydrogen concentration of 4 to 8% is constantly flowing as an atmospheric gas. Further, since the inside of the sintering furnace is heated to about 1700 ° C., the exhaust gas of the hydrogen-containing gas flowing out of the sintering furnace has a high temperature of about 400 ° C. near the furnace outlet. Since high-temperature exhaust gas from a sintering furnace contains radioactive substances, the exhaust gas must be exhausted into a glove box.

When exhaust gas from an incinerator made of a high-temperature hydrogen-containing gas is directly introduced into a glove box, a transparent acrylic plate panel of the glove box or a rubber glove is burned by burning of combustible materials in the glove box. There is also a danger that the hydrogen-containing gas having a concentration exceeding the lower explosion limit, such as a hydrogen concentration of 4 to 8%, may come into contact with air and explode.

For this reason, water cooling is performed before exhausting high-temperature exhaust gas from the incinerator into the glove box.
Further, the exhaust gas is exhausted into a glove box and rapidly diffused and diluted, so that the hydrogen concentration of the hydrogen-containing gas is reduced to the explosion lower limit concentration or less. As a method of cooling the exhaust gas with water, a construction method of wrapping a water pipe around the exhaust gas pipe is adopted, and even if the water pipe is damaged, the cooling water enters the incinerator and contamination due to furnace damage That can be prevented.

[0005]

However, the method of winding a water pipe around the exhaust gas pipe has a drawback that the cooling efficiency is poor and the length of winding of the water pipe is long. Further, in this method, fumes (produced by thermal decomposition of organic substances such as lubricants and binders added to the raw material powder of MOX fuel pellets during thermal sintering) are gradually generated in the exhaust gas pipes. Although it is necessary to perform periodic cleaning because it accumulates on and adheres to the surface, there is a drawback that cleaning is difficult because the exhaust gas pipe is installed in the glove box.

When the exhaust gas is exhausted into a glove box and rapidly diffused and diluted so that the hydrogen concentration becomes lower than the lower explosive lower limit concentration, electric parts or the like serving as an ignition source are installed near the exhaust gas outlet. It is necessary to prevent fires and explosions by performing design management that does not require this, and as a result, there is a problem that this area becomes a dead space and reduces the space utilization rate in the glove box.

The present invention has been made in order to solve the problems in the prior art as described above, and it is possible to efficiently cool a high-temperature exhaust gas from a MOX fuel pellet incinerator with water and to use a cooling means. Provide an inexpensive, compact, easy-to-maintain and control exhaust gas treatment system that can prevent cooling water from entering the sintering furnace even if it is damaged, and can reliably dilute the hydrogen concentration in the exhaust gas below the lower explosion limit. It was done for the purpose of doing.

[0008]

That is, according to the present invention, M
An exhaust gas treatment device for an OX fuel pellet sintering furnace includes a container having a detachable lid on a top thereof; exhaust gas from the mixed oxide fuel pellet sintering furnace is introduced into the container, and discharged upward at an upper portion of the container. An exhaust gas introduction pipe having an outlet opening for causing the exhaust gas to be introduced into the vessel from the outlet opening of the exhaust gas introduction pipe, and a dispersion plate provided in the vicinity of the exhaust gas introduction pipe exit opening for changing an upward flow of the exhaust gas into a downward flow. A cooling means for water-cooling the downward flow of the exhaust gas in the container; and an exhaust gas discharge pipe provided at a lower portion of the container for discharging the cooled exhaust gas into the glove box.

The structure of the exhaust gas treatment apparatus described above is such that the exhaust gas discharge pipe is connected to a glove box in an inert gas atmosphere and used, but is connected to a glove box not in an inert gas atmosphere. In the case of an exhaust gas treatment device that performs, an inert gas introduction pipe that opens into the exhaust gas introduction pipe is provided to dilute the exhaust gas with the inert gas,
Alternatively, an inert gas introduction pipe that opens into the cooled exhaust gas flow that flows through the lower part of the vessel is provided, and the cooled exhaust gas is diluted with the inert gas so that the hydrogen concentration in the exhaust gas is reduced to the explosion lower limit concentration or less. There is a need to.

[0010] In a preferred embodiment of the present invention, the dispersion plate has a cap shape with a downward edge, and surrounds the outside of the exhaust gas outlet opening at a distance, and the lower end of the downward edge has an exhaust gas introduction end. It is covered so as to be below the pipe outlet opening. Further, below the outlet opening of the exhaust gas discharge pipe, a tray for receiving the cooling water leaked from the cooling means and a detecting means for detecting a water level in the tray are provided.

Further, as the cooling means, a structure in which cooling water flows through a plurality of pipes disposed through the inside of the container, or a structure in which cooling water flows through a cooling jacket provided on the wall of the container is adopted. Can be.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to preferred embodiments shown in the drawings. The exhaust gas treatment apparatus shown in FIG. 1 has a container 1 having a detachable lid 1a at the top, an exhaust gas introduction pipe 2 connected to a lower part of the container side wall, and a lower part of the container side wall opposite to the exhaust gas introduction pipe 2. And a cooling means 4 disposed in the container. The cooling means 4 in the embodiment of FIG. 1 has a structure similar to that of a heat exchanger for flowing cooling water through a plurality of pipes 4a disposed through the inside of the container 1, and exhaust gas flows between the cooling water pipes 4a. It is designed to be cooled when passing through.

The exhaust gas introduction pipe 2 extends through the lower part of the side wall of the container 1 and extends upward and opens at the upper part in the container. In the vicinity of the outlet opening 2a of the exhaust gas introduction pipe 2, a dispersion plate 5 for changing the upward flow of the exhaust gas introduced into the container from the outlet opening 2a into a downward flow is provided. The dispersing plate 5 in the embodiment of FIG. 1 has a cap shape with a downward edge 5a, surrounds the outside of the outlet opening 2a at intervals, and the lower end of the downward edge 5a is lower than the outlet opening 2a. Is covered.

Below the outlet opening 3a of the exhaust gas discharge pipe 3, a tray 6 for receiving the leaked water when the cooling water leaks from the cooling means 4, and a detecting means 7 for detecting the water level in the tray 6 are provided. It is arranged.

The exhaust gas treatment apparatus of the present invention having the above-described structure is interposed between a MOX fuel pellet sintering furnace (not shown) and a glove box GB, and the exhaust gas from the sintering furnace is provided. Is introduced from the exhaust gas introduction pipe 2 into the container 1, and the exhaust gas after the treatment in the container 1 is
It is discharged from the exhaust gas discharge pipe 3 into the glove box GB.

The operation of the exhaust gas treatment device will be described below. Exhaust gas from the MOX fuel pellet sintering furnace is introduced into the vessel 1 through an exhaust gas introduction pipe 2 and discharged into the upper part of the vessel through an outlet opening 2a. At this time, the exhaust gas is released as an upward flow, but hits the dispersion plate 5 and is discharged downward,
The cooling means 4 is cooled while passing between the cooling water pipes 4a. The cooled exhaust gas is supplied to the exhaust gas discharge pipe 3 at the bottom of the container.
Is discharged into the glove box GB. The dotted arrows in FIG. 1 indicate the flow of exhaust gas in the apparatus.

The temperature of the exhaust gas guided from the sintering furnace to the exhaust gas introducing pipe 2 is not always constant in the state of the inside of the sintering furnace, but may reach about 400 ° C. near the furnace outlet. Such high-temperature exhaust gas is cooled to 60 ° C. or lower, preferably 30 ° C. or lower by the cooling means 4 in the processing apparatus, and then discharged from the exhaust gas discharge pipe 3 into the glove box GB. Thus, it is possible to prevent structural members such as panels and gloves in the glove box GB from being damaged by the high-temperature exhaust gas.

At the end of the sintering reaction, the hydrogen concentration of the hydrogen-containing gas exhausted from the sintering furnace is equal to or higher than the lower explosion limit concentration of about 4 to 8%, which is almost the same as when supplying the gas to the sintering furnace. Therefore, it is necessary to dilute this to less than the lower explosive lower limit concentration of 3% or less. The exhaust gas treatment apparatus having the above-described structure is of a type used by being connected to a glove box having an inert gas atmosphere. By exhausting the gas into the glove box, it is possible to dilute the hydrogen concentration to a concentration equal to or lower than the lower explosive lower limit concentration, thereby preventing the glove box from being damaged by a fire or explosion.

In the event that the cooling water pipe 4a is damaged and the cooling water leaks, the leaked water accumulates in the tray 6 from the lower part of the container 1 through the exhaust gas discharge pipe outlet opening 3a. Tray 6
When the water accumulated in the cooling water reaches a predetermined water level, the water level detector 7 detects the water level, whereby the breakage of the cooling water pipe 4a can be detected. The exhaust gas discharge pipe 3 is provided at the lower part of the vessel 1 in order to ensure that the water leaking from the cooling water pipe 4a is discharged from the exhaust gas discharge pipe 3, whereby the leak water enters the sintering furnace. Thus, the furnace can be prevented from being damaged. Further, the dispersing plate 5 surrounds the outside of the exhaust gas introduction pipe outlet opening 2a, and the lower end of the downward edge 5a is formed at the outlet opening 2a.
By being covered below, it is possible to prevent leakage water from the cooling water pipe 4a from flowing back into the sintering furnace through the exhaust gas introduction pipe 2.

When the exhaust gas treatment apparatus of the present invention is used by connecting it to a glove box that is not in an inert gas atmosphere, the hydrogen concentration of the exhaust gas is diluted with the inert gas to the explosion lower limit concentration or less in the apparatus. There is a need. In this case, as shown in FIG. 1, an inert gas introduction pipe 8 is inserted and opened in the middle of the exhaust gas introduction pipe 2, and an inert gas is introduced from here to dilute the exhaust gas with the inert gas. . Since the exhaust gas composed of the hydrogen-containing gas may explode when mixed with an appropriate amount of air, the exhaust gas may be diluted before the exhaust gas comes into contact with the air. For this reason, the cooled exhaust gas may be diluted with an inert gas, and as shown by a dashed line in FIG.
The cooled exhaust gas can also be diluted with an inert gas by opening into the cooled exhaust gas flow that flows through the lower part. As the inert gas, nitrogen gas, argon gas, carbon dioxide gas or the like can be used, but from the viewpoint of cost, nitrogen gas is the cheapest.

In the exhaust gas from the MOX fuel pellet sintering furnace, fumes due to the thermal decomposition of organic substances added to the raw material of the pellets are slightly mixed and adhere to the cooling water pipe 4a of the exhaust gas treatment device. I do. If the amount of adhesion increases, the cooling efficiency decreases, so it is necessary to periodically clean the inside of the apparatus. In the apparatus of the present invention, since the lid 1a provided on the top of the container 1 is detachable, the inside of the container can be easily cleaned by removing the lid 1a.

FIG. 2 shows another embodiment of the exhaust gas treatment apparatus of the present invention. The same members as those in the apparatus of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The cooling means differs from the apparatus of FIG. That is, the cooling means shown in FIG. 2 has a structure in which the side wall of the container 1 is a cooling jacket 4b, and cooling water flows through the jacket 4b. In addition, container 1
When the longitudinal length of the container 1 is long, or when the space between the cooling jacket 4a and the exhaust gas introduction pipe 2 at the center of the container is large, the cooling efficiency of the exhaust gas decreases. By providing the extending cooling fins 9 (represented by dotted lines), the cooling efficiency can be increased.

[0023]

As can be seen from the above description, according to the present invention, it is possible to provide an exhaust gas treatment apparatus which is small in size, has a very simple structure, is inexpensive, easy to maintain, has few failures, and has high safety. it can. In particular, if the improvement of safety is specifically described, the following effects can be obtained.

(1) The exhaust gas from the sintering furnace is made to flow downward in the apparatus, cooled through a water-cooled cooling means, and then exhausted from an exhaust gas discharge pipe provided below the apparatus into the glove box. As a result of efficient and effective cooling, damage to the glove box structural material due to high-temperature exhaust gas can be prevented. Also, even if the cooling water leaks from the cooling means, it flows out from the exhaust gas discharge pipe below the device, preventing the leaked water from entering the sintering furnace and reliably preventing contamination caused by damage to the furnace. it can.

(2) An inert gas is introduced from the inert gas introduction pipe into the apparatus, and the hydrogen concentration of the exhaust gas is diluted to below the lower explosion limit concentration and then exhausted into the glove box. It is possible to prevent damage to the box and contamination caused by leakage of the radioactive substance generated outside the box outside the glove box.

(3) By disposing the dispersion plate so as to cover the vicinity of the outside of the exhaust gas introduction pipe outlet opening, even if the cooling water leaks from the cooling means in the apparatus, the leaked water passes through the exhaust gas introduction pipe. To prevent backflow into the sintering furnace, thereby preventing damage to the sintering furnace due to leakage water.

(4) By providing a tray for receiving leaked water below the outlet opening of the exhaust gas discharge pipe and a water level detecting means in the tray, it is possible to easily and quickly detect a leak due to breakage of a cooling water pipe in the apparatus. .

(5) Since the lid at the top of the apparatus is detachable, the inside of the apparatus can be easily cleaned, and the adhering matter adhering to the cooling water piping and the like can be periodically removed to prevent a decrease in cooling performance.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an embodiment of an exhaust gas treatment apparatus of the present invention.

FIG. 2 is a schematic sectional view showing another embodiment of the exhaust gas treatment apparatus of the present invention.

[Explanation of symbols]

 1: Container 1a: Lid 2: Exhaust gas introduction pipe 2a: Exhaust gas introduction pipe outlet opening 3: Exhaust gas discharge pipe 3a: Exhaust gas exhaust pipe exit opening 4: Cooling means 4a: Cooling water pipe 4b: Cooling jacket 5: Dispersion plate 5a: Downward Edge 6: Leaked water tray 7: Water level detecting means 8, 8 ': Inert gas introduction pipe GB: Glove box

Claims (7)

[Claims] A container having a detachable lid on a top thereof; and an outlet opening for introducing exhaust gas from a mixed oxide fuel pellet sintering furnace into the container and discharging the exhaust gas upward at an upper portion in the container. An exhaust gas introduction pipe; a dispersion plate provided near the exhaust gas introduction pipe exit opening for changing an upward flow of the exhaust gas introduced into the vessel from an exit opening of the exhaust gas introduction pipe to a downward flow; An exhaust gas treatment device for a mixed oxide fuel pellet sintering furnace, comprising: a cooling means for water-cooling the mixture; and an exhaust gas discharge pipe provided at a lower portion of the container for discharging the cooled exhaust gas into the glove box. 2. The exhaust gas treatment apparatus according to claim 1, further comprising an inert gas introduction pipe opened in the exhaust gas introduction pipe, whereby the exhaust gas is diluted with the inert gas. 3. An inert gas introduction pipe which opens into a cooled exhaust gas flow flowing through a lower portion of the vessel, whereby the cooled exhaust gas is diluted with the inert gas. The exhaust gas treatment device according to claim 1. 4. The dispersion plate has a cap shape with a downward edge, surrounds the outside of the exhaust gas introduction pipe outlet opening at intervals, and has a lower end of the downward edge at the exhaust gas introduction pipe exit opening. The exhaust gas treatment device according to any one of claims 1 to 3, wherein the exhaust gas treatment device is covered so as to be lower. 5. Under the outlet opening of the exhaust gas discharge pipe,
The exhaust gas treatment apparatus according to any one of claims 1 to 4, further comprising a tray for receiving the cooling water leaked from the cooling unit, and a detection unit for detecting a water level in the tray. 6. The cooling device according to claim 1, wherein the cooling means has a structure in which cooling water flows through a plurality of pipes disposed through the inside of the container. Exhaust gas treatment equipment. 7. The exhaust gas treatment apparatus according to claim 1, wherein the cooling means has a structure in which cooling water flows in a cooling jacket provided on the container wall.