JPS6133201A - Thin film dryer - Google Patents

Abstract

PURPOSE:To avoid concentrating corroded parts to specific positions by branching a steam supply nozzle for heating to supply steam to different heights of a heating jacket. CONSTITUTION:A concd. waste radioactive liquid is supplied from a waste liquid supply nozzle 2 to a body 1 and the uniformly thin film thereof is formed on the inside surface 4 of the body by a waste liquid distributor 3. The heated steam is supplied from the steam supply nozzle 9 to the heating jacket 8 to heat the inside surface of the body. The liquid is concentrated and solidified and is discharged through a solid discharge port 12. The steam is discharged through a moisture take-out hole 11. The temp. distribution by the heating is changed by a selector valve 14 to move the highly corrosive parts where chlorine ions are concentrated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to membrane drying used, for example, in drying and pulverizing radioactive concentrated waste liquid of atomic couplants.

[Technical background of the invention and its problems]

Liquid radioactive waste generated at nuclear power plants is generally concentrated in an evaporative concentrator to reduce its volume, mixed with cement, solidified, and stored in drums. However, in this treatment method, radioactive concentrated waste liquid concentrated in an evaporative concentrator is solidified with cement, and the volume increases approximately twice by the addition of cement, creating a problem of storage space in drums. In order to solve this problem, in recent years, radioactive concentrated waste liquid concentrated using an evaporative concentrator has been used as II! A solidification processing system has been developed that greatly increases the volume reduction rate by drying powder in a dryer and solidifying it into plastic.

FIGS. 5 and 6 are diagrams showing the configuration of a conventional thin film dryer. In the figures, 1 is a cylindrical main body for drying and pulverizing radioactive concentrated waste liquid, which is a solution to be treated. A waste liquid supply nozzle 2 for supplying radioactive concentrated waste liquid into the main body 1 is attached above the main body 1.

The radioactive concentrated waste liquid supplied into the main body 1 from the waste liquid supply nozzle 2 is caused to flow down in the form of a liquid film along the inner surface 4 of the main body by a waste liquid distributor 3 provided at the waste liquid supply nozzle outlet in the main body 1. It has become. Further, a rotary shaft 6 having a plurality of blades 5 attached to its outer peripheral surface is rotatably provided within the main body 1.

The upper end of the rotating shaft 6 is connected to a drive device (not shown), and the blade 5 is rotated by rotation of the drive device. Further, the inner peripheral surface of the main body 1 is lined with a heat transfer member 7 made of Inconel 625, forming the inner surface 4 of the main body. A heating jacket 8 is formed on the outside of the heat transfer member 7, and the inner surface 4 of the main body is heated through the heat transfer member 7. A steam supply nozzle 9 is connected to the upper part of the heating jacket 8 to supply heated steam as a heating medium to the heating jacket 8. Further, a steam exhaust nozzle 10 is connected to the lower part of the heating jacket 8.
The steam inside is vented to the outside. In addition, a moisture outlet 11 is provided at the upper end of the main body 1 to take out the liquid component of the radioactive concentrated waste liquid evaporated by the heat of the heated steam.
A solid discharge port 12 is provided at the lower end to discharge solid components of the radioactive concentrated waste liquid dried by the heat of the heated steam. Note that 13 in the figure is a lower bearing of the rotating shaft 5.

In the above configuration, the radioactive concentrated waste liquid supplied into the main body 1 from the waste liquid supply nozzle 2 is distributed by the waste liquid distributor 3 so as to form a uniform liquid film on the internal surface 4 of the main body, and is distributed along the internal surface 4 of the main body. Flow down.

At this time, heating steam is supplied to the heating jacket 8 from the steam supply nozzle 9 to heat the inner surface 4 of the main body. As a result, the radioactive concentrated waste liquid flowing down the inner surface 4 of the main body in the form of a liquid film is
While a constant liquid film is maintained by the rotation of the blade 5, water gradually evaporates due to the heat of the heated steam, and eventually solid begins to precipitate, forming a two-phase state of solid and liquid. Finally, it becomes a solid state that contains some water. This solid adheres to the inner surface 4 of the main body, but is scraped off by the blade 5 that rotates together with the rotary shaft 6, and drops downward while drying along the inner surface 4 of the main body due to centrifugal force, and is released from the solid discharge port 12. be discharged. Further, the water evaporated at this time is discharged from the water outlet 11.

By the way, since the radioactive concentrated waste liquid supplied from the waste liquid supply nozzle 2 into the main body 1 is concentrated in advance in an evaporative concentrator, the concentration of radioactive concentrated waste liquid is 5. The waste liquid contains OOOppm of chlorine ions. On the other hand, the main body portion including the heating jacket 8 is heated to about 180° C. by the heat of the heating steam.

Therefore, the temperature of the inner surface 4 of the main body, on which the radioactive concentrated waste liquid flows down in the form of a liquid film, exceeds 100°C, and the chlorine ions exceed 5.0001)l)m, reaching a maximum of 17.0°C. OOOpp
It is a very harsh corrosive environment where it is concentrated to about 1000 yen.

Figure 4 is a diagram showing the corrosion resistance limit of Inconel 625.
In the figure, the horizontal axis represents chlorine ion once, and the vertical axis represents temperature. Inconel 625 is generally considered to have the best corrosion resistance in environments with temperature A and high chlorine ion concentration.
However, during the drying and powdering process, the temperature ranges from about 50℃ to about 160℃,
Chloride ion m degree is 5. Maximum i7 from oooppm. o
The part that comes into contact with the radioactive corrosion waste liquid concentrated to oo'ppm is in the region of high temperature and high chlorine ion concentration exceeding the corrosion resistance limit mA. Therefore, high temperature/high chlorine ion 1
It is expected that the specific area of the inner surface 4 of the main body that comes in contact with radioactive concentrated waste liquid will not have sufficient corrosion resistance even if it is lined with Inconel 625, which has excellent corrosion resistance, and that area will shorten the life of the entire device. There was a possibility that it would become something like that.

[Purpose of the invention]

The present invention was made in view of these circumstances, and its purpose is to prevent a specific area of the inner surface of the main body from being corroded in a short period of time, and to achieve a long life even in a severe corrosive environment with high temperature and high chlorine ion concentration. An object of the present invention is to provide a 7a membrane dryer with excellent corrosion resistance.

[Summary of the invention]

In order to achieve the above object, the present invention provides means for changing the temperature distribution on the inner surface of the main body over time, and moves the corroded area on the inner surface of the main body so as not to concentrate it in a specific area.

[Embodiments of the invention]

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

FIG. 1 is a longitudinal sectional view of a thin film dryer showing an embodiment of the present invention, in which the same parts as in FIG. 6 are designated by the same reference numerals.

In this embodiment, as a means for changing the temperature distribution on the inner surface 4 of the main body, the steam supply nozzle 9 is connected to the heating jacket 8 with branched supply ports 9a and 9b at different height positions, as shown in FIG. ing. In addition, a switching valve 14 is installed at each supply port 9a and 9b of the steam supply nozzle 9, and by operating these switching valves 14, the heating steam supply port can be switched to 9a or 9b. It has become. Note that the switching valve 14 may be operated either manually or automatically.

Next, the operation of this embodiment will be explained. In the process of drying and solidifying waste liquid, the most severe condition for corrosivity to the internal surface 4 of the main body is when the waste liquid is concentrated to the limit, that is, it is in a two-phase state where solid and liquid coexist, and it becomes completely solid. It has almost no corrosive properties. In this two-phase state, the chloride ion concentration is highest. Here, the operating state of the thin film dryer, that is, the heating temperature of the main body by steam, the heat transfer rate to the waste liquid, the supply speed of the waste liquid to the main body,
Assuming that the number of revolutions of the blade, the composition of the waste fluid, etc. are constant, the portion where the corrosion conditions are most severe will exist within a certain range in the vertical direction of the inner surface 4 of the main body.

FIG. 3 shows the temperature distribution on the inner surface of the main body during operation of the thin film dryer, and the dotted line 31 in the figure is the result of measuring the temperature on the inner surface of the main body during operation of the conventional thin film dryer. From this measurement result, conventionally, the area A that is highly corrosive during the evaporation drying process is limited to the upper part of the inner surface 4 of the main body.

Further, since the pressure inside the main body 1 at this time is around 1 atm, the temperature does not reach much higher than 100° C. in the range where moisture is present and evaporated. Therefore, in order to prevent problems caused by corrosion, area A, which is in a highly corrosive environment, should be moved downward at certain times to reduce the time each area is exposed to the corrosive environment.
It becomes possible to extend the life of that part.

A solid line 32 shown in FIG. 3 is the result of measuring the temperature of the inner surface 4 of the main body when heated steam is supplied to the heating jacket 8 from the supply port 9b in this embodiment. As is clear from this measurement result, the area A, which had been highly corrosive in the past, has moved downward (the area indicated by - in the figure), and that area has become a non-corrosive environment as shown in Figure 4. There is.

In this way, in this embodiment, the steam supply nozzle 9 is branched to provide steam supply ports 9a and 9b at different positions in the height direction of the heating jacket 8, and these supply ports 9a and 9b are appropriately controlled by the switching valve 14. By switching to , the harsh corrosive environment will not be concentrated in a specific area, making it possible to extend the life of the entire device.

FIG. 2 is a diagram showing another embodiment of the present invention, in which the inner surface 4 of the main body
A plurality of heaters 21 are installed at different heights within the heating jacket 8 as a means for changing the temperature distribution. In this way, the same effects as in the above embodiment can be obtained even if a plurality of heaters 21 are used and the heaters 21 are operated appropriately to change the temperature distribution on the inner surface 4 of the main body over time.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, since a means for changing the temperature distribution on the surface of the main body over time is provided, it is possible to prevent a specific region of the inner surface of the main body from being corroded in a short period of time.・IIL with excellent corrosion resistance and long life even in severe corrosive environments with high chlorine ion concentration! Dryer can be provided.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of an all dryer showing one embodiment of the present invention, Fig. 2 is a longitudinal sectional view of a thin film dryer showing another embodiment of the invention, and Fig. 3 is a conventional thin film dryer. 4 is a diagram showing the temperature distribution on the inner surface of the main body during operation of the thin film dryer according to the present invention, FIG. 4 is a diagram showing the corrosion resistance of Inconel 625, and FIG. 5 is the internal structure of a conventional thin film dryer. FIG. 6 is a vertical cross-sectional view. DESCRIPTION OF SYMBOLS 1... Main body, 2... Waste liquid supply nozzle, 3... Waste liquid distributor, 4... Inner surface of main body, 5... Blade, 6...
...Rotating shaft, 7...Heat transfer member, 8...Heating jacket, 9...Steam supply nozzle, 10...Steam discharge nozzle, 11...Moisture extraction port, 12...Solid content Vent,
14...Switching valve, 21...Heater. Applicant's representative Patent attorney Takehiko Suzue Figure 1, Figure 2, Figure 3] uu 150 200 Temperature s ("c) Figure 4 C1 - Concentration (ppm)

Claims (3)

[Claims] (1) A cylindrical body, a to-be-treated solution supply nozzle that supplies a to-be-treated solution containing solids into this body, and a to-be-treated solution supplied from this to-be-treated solution supply nozzle along the inner surface of the main body. a waste liquid distributor that causes the liquid to flow down in the form of a film; a rotating shaft that is rotatably provided within the main body and has a plurality of blades on the outer circumferential surface; and a heating jacket that is formed on the outer periphery of the main body and heats the inner surface of the main body. A heating medium supply nozzle that supplies a heating medium to the heating jacket; a heating medium discharge nozzle that discharges the heating medium supplied to the heating jacket from the heating medium supply nozzle; a water extraction port for extracting the liquid component of the solution to be treated that has been evaporated by the heating medium; a solid content outlet provided at the lower end of the main body for discharging the solid component of the solution to be processed that has been dried by the heat of the heating medium; A thin film dryer characterized by comprising: means for changing the temperature distribution over time. (2) The temperature changing means is a heating medium supply port consisting of a heating medium supply nozzle having a plurality of supply ports at different positions in the height direction of the heating jacket, and a switching valve provided at each supply port in this nozzle. The thin film dryer according to claim 1, characterized in that it is a switching mechanism. (3) The thin film dryer according to claim 1, wherein the temperature changing means is a plurality of heaters built into a heating jacket.