JPH0461681B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method of operating a centrifugal thin film dryer for drying and separating radioactive waste liquid discharged from, for example, nuclear power generation equipment into evaporated components and non-evaporated components. [Technical Background of the Invention] Generally, a centrifugal thin film dryer has a heating jacket inside a cylindrical outer shell, and superheated steam is introduced into the heating jacket to heat the inner peripheral surface of the outer shell. configured to heat. In addition, such a centrifugal thin film dryer is equipped with a rotating shaft at the center of the outer shell, and the slurry-like waste liquid introduced into the outer shell by the centrifugal force of the rotating shaft is transferred to the inner circumferential surface of the outer shell. The structure is such that the non-evaporable components are dried and separated into evaporated components and non-evaporated components, and the non-evaporated components deposited in a thin film on the inner circumferential surface of the outer shell are scraped off by a rotary blade attached to the rotating shaft. By the way, if superheated steam is rapidly introduced into the heating jacket of such a centrifugal thin film dryer, excessive thermal stress is generated in the outer shell, and the outer shell may be damaged by the thermal stress. Therefore, conventionally, before treating the waste liquid in a centrifugal thin film dryer, superheated steam is gradually introduced into the heating jacket to preheat the outer shell to a predetermined temperature, and then the waste liquid is introduced into the outer shell. [Problems with the Background Art] However, according to this method, since the rotating shaft of the centrifugal thin film dryer is insulated from the outer shell by air, only the outer shell is heated immediately after preheating. This results in a clearance greater than the design value between the inner circumferential surface of the outer shell and the rotor blade. If waste liquid treatment is started in such a state, the thickness of the thin film formed on the inner peripheral surface of the outer shell will become thicker, and the properties of the non-evaporable components scraped off by the rotor blades will become unstable. A problem arises. For this reason, in the past, it was not possible to treat the waste liquid immediately after preheating, and the waste liquid was processed after the rotating shaft reached a predetermined temperature due to radiant heat from the outer shell, so there was a problem that the preheating time was long. [Object of the Invention] The present invention has been made based on the above points, and its purpose is to shorten the waiting time from startup to start of operation, and to make it possible to treat waste liquid even immediately after preheating. The object of the present invention is to provide a possible operating method for a centrifugal thin film dryer. [Summary of the Invention] That is, the present invention introduces superheated steam into a heating jacket formed in a cylindrical outer shell, introduces slurry-like waste liquid into the inner side of the outer shell, and introduces the waste liquid into the outer shell. The superheated steam is applied to the inner circumferential surface of the outer shell heated by the centrifugal force of a rotating shaft disposed at the center of the outer shell, and is dried and separated into evaporated components and non-evaporated components. When the centrifugal thin film dryer is started, the non-evaporable components adhering to the surface in a thin film form are scraped off with a rotary blade attached to the rotating shaft.
Preheating steam is introduced into the heating jacket, water or hot water is introduced into the outer shell, and the water or hot water introduced into the outer shell is evaporated to preheat the rotating shaft with the steam. It is something. [Embodiments of the Invention] Hereinafter, with reference to FIGS. 1 to 4, the first embodiment of the present invention will be described.
An example will be explained. FIG. 1 is a diagram schematically showing an apparatus for carrying out the operating method of a centrifugal thin film dryer according to this embodiment, and reference numeral 1 in the figure is a storage tank for storing waste liquid 2. In FIG. A centrifugal thin film dryer 4 is connected to this storage tank 1 via a waste liquid pipe 3. Waste liquid piping 3
A waste liquid pump 5 and a waste liquid control valve 6 are sequentially inserted from the storage tank 2 side, and the waste liquid pump 5 forces the waste liquid 2 in the storage tank 1 into the centrifugal thin film dryer 4 . Further, a waste liquid flow rate detector 7 and an on-off valve 8 are inserted into the waste liquid pipe 3. A waste liquid control device 9 controls the waste liquid control valve 6, and this waste liquid control device 9 adjusts the opening degree of the waste liquid control valve 6 based on the flow rate detection signal s7 from the waste liquid flow rate detector 7. Therefore, the flow rate of waste liquid supplied to the centrifugal thin film dryer 4 is controlled. In addition to the waste liquid line, a water (or hot water) line is connected to the centrifugal thin film dryer 4 . In this embodiment, a case will be described in which water is supplied. That is, the reference numeral 11 in the figure is a water supply pipe, and this water supply pipe 11 includes a water supply pump 12, a water supply control valve 13,
A water supply flow rate detector 14 and an on-off valve 15 are inserted in this order. The water supply control valve 13 is the water supply control device 16
controlled by That is, the water supply control device 16
adjusts the opening degree of the water supply control valve 13 based on the detection signal s14 from the water supply flow rate detector 14, thereby adjusting the water supply flow rate supplied to the centrifugal thin film dryer 4 . Further, the water supply pipe 11 and the waste liquid pipe 3 are connected via a pipe 17.
An on-off valve 18 is inserted in 7. Next, the configuration of the centrifugal thin film dryer 4 will be explained with reference to FIGS. 2 and 3. FIG. 2 is a partially cutaway perspective view of the centrifugal thin film dryer 4 , and FIG. 3 is a longitudinal sectional view. Code 21 in the figure
is a cylindrical body (outer body), and a rotating shaft 22 is accommodated within this cylindrical body 21 . A plurality of rotary blades 23 are attached to this rotary shaft 22 at equal intervals in the axial direction. The cylindrical body 21 has a double-walled structure, and a heating jacket 24 is formed thereon, and the inner peripheral surface of the cylindrical body 21 serves as a heat transfer surface 25. Heated steam is supplied into the heating jacket 24,
The inside of the cylinder 21 is heated from the outside. A liquid supply nozzle 26 for introducing the waste liquid 2 from the waste liquid line or water from the water supply line into the upper part of the cylinder 21 is connected. A distribution ring 27 is arranged within the cylinder 21 at the same position in the axial direction as the liquid supply nozzle 26 . This distribution ring 27 directs the waste liquid 2 or water introduced from each liquid supply nozzle 26 to the heat transfer surface 25.
Let it flow down evenly along the A vapor outlet 28 is connected above the liquid supply nozzle 26 of the cylindrical body 21, and the evaporated waste liquid 2 is discharged through the vapor outlet 28. On the other hand, a discharge port 29 is formed at the lower end of the cylindrical body 21, and the evaporation residue of the waste liquid 2 is discharged through the discharge port 29. Next, the driving method will be explained. First, before introducing the waste liquid 2 into the centrifugal thin film dryer 4 and performing a waste liquid treatment operation, water is introduced into the centrifugal thin film dryer 4 and a warm-up operation is performed for a predetermined period of time. In other words, in the past, the dryer 4 was warmed up only from the outside using an external heating method, but in this embodiment, the dryer 4 was warmed up from the inside in addition to the external heating method. This warms up the engine by heating it. This will be explained in detail below. That is, the on-off valve 8 is closed and water is supplied via the water supply pipe 11. At that time, it is also possible to open the on-off valve 18 and supply hot water from two directions. The water thus supplied is distributed via the liquid supply nozzle 26 and the distribution ring 27, and at the same time adheres to the heat transfer surface 25 as a result of the centrifugal force of the rotor 23 acting thereon. It is then heated by the heat from the heating jacket 24 and evaporates into steam. As a result, the inside of the centrifugal thin film dryer 4 is heated evenly from the inside. The water supply flow rate at this time is set in advance and stored in the water supply control device 16. The water supply control device 16 adjusts the opening degree of the water supply control valve 13 based on the water supply flow rate detection signal s14 from the water supply flow rate detector 14, and controls the water supply flow rate to a set water supply flow rate. The situation is shown in the middle diagram a in FIG. In addition, Fig. 4 shows time changes on the horizontal axis and on the vertical axis the steam temperature in the heating jacket 24, the rotation speed of the rotating shaft 22, and the flow rate of liquid supplied (water or waste liquid). It is. After performing the warm-up operation for a predetermined time in this manner, the on-off valve 15 is closed to stop the supply of water. Next, the on-off valve 8 is opened and the waste liquid 2 stored in the storage tank 1 is supplied to the centrifugal thin film dryer 4 by the waste liquid pump 5. The waste liquid 2 is supplied by the on-off valve 18 in the same way as the water supply.
This can be done from two directions by opening the valve. The waste liquid 2 supplied to the centrifugal thin film dryer 4 is introduced into the cylindrical body 21 through the liquid supply nozzle 26, and the heat transfer surface 25 is formed into a thin film by the uniform dispersion effect of the dispersion ring 27 and the centrifugal force of the rotor blades 23. It flows down in a shape.
At this time, it is heated through the heating jacket 24 and evaporated. The steam is then discharged through the vapor outlet 28, and the evaporation residue of the waste liquid 2 adhering to the heat transfer surface 25 is removed by the scraping action of the rotary blades 23, and becomes slurry or powder and is discharged from the outlet 29.
more excreted. Note that the supply amount of the waste liquid 2 is set in advance in consideration of the properties of the waste liquid 2, etc., and is stored in the waste liquid control device 9. The waste liquid control device 9 adjusts the opening degree of the waste liquid control valve 6 based on the waste liquid flow rate detection signal s7 from the waste liquid flow rate detector 7, and controls the waste liquid flow rate to be a preset waste liquid flow rate. This state is shown by the line b in FIG. The waste liquid treatment operation is then carried out continuously. According to this embodiment, the following effects can be achieved. That is, when water is introduced into the cylinder body 21 of the centrifugal thin film dryer 4 before starting the waste liquid treatment operation, the water introduced into the cylinder body 21 is transferred to the rotating shaft 22.
The inner peripheral surface (heat transfer surface 25) of the cylindrical body 21 due to the centrifugal force of
The rotating shaft 22 can be preheated by the steam because it becomes steam. Therefore, compared to the case where the rotating shaft 22 is preheated by radiant heat from the cylindrical body 21, the rotating shaft 22 can be preheated to a predetermined temperature in a shorter time, and immediately after preheating, the inner peripheral surface of the cylindrical body 21 and the rotation Since a clearance greater than the design value does not occur between the blade 23 and the blade 23, waste liquid can be treated even immediately after warming up. Next, a second embodiment will be explained. The apparatus used in this second embodiment is the same as the apparatus used in the first embodiment, and its explanation will be omitted. In this second embodiment, as shown by lines c and d in FIG. 5, after the warm-up operation is completed, the water supply is gradually reduced and at the same time, the waste liquid 2 is gradually supplied, until the water supply flow rate reaches zero. This is done so that the flow rate of the waste liquid reaches a predetermined amount when the flow rate reaches a predetermined amount. Similarly to FIG. 4, FIG. 5 is a diagram showing changes over time in steam temperature, rotational speed, and feed liquid flow rate. First, water is supplied to the centrifugal thin film dryer 4 via the water supply control valve 13 with the on-off valve 18 closed. The supplied water is introduced into the cylinder 21 through the liquid supply nozzle 26 and flows down on the heat transfer surface 25 in the form of a thin film due to the uniform distribution action of the dispersion ring 27 and the centrifugal force action of the rotor 23. and heating jacket 24
It is heated through and evaporates. The inside of the centrifugal thin film dryer 4 is uniformly heated from inside by the steam generated at that time. Note that the water supply flow rate at this time is set in advance and stored in the water supply control device 16. The water supply control device 16 adjusts the opening degree of the water supply control valve 13 based on the water supply flow rate detection signal s14 from the water supply flow rate detector 14, and controls the water supply flow rate to a preset water flow rate. Next, after a predetermined period of warm-up operation, the water supply control valve 13 is gradually closed, the water supply flow rate is gradually reduced, and the waste liquid 2 is gradually supplied. Then, when the water supply control valve 13 is fully closed and the water supply flow rate reaches zero, the flow rate of the waste liquid 2 is set to a predetermined flow rate. At this time, as is clear from FIG. 5, the liquid supply flow rate is always constant. Note that the waste liquid flow rate is set in consideration of the properties of the waste liquid 2, etc., and is stored in the waste liquid control device 9. Then, the opening degree of the waste liquid control valve 6 is adjusted by the waste liquid control device 9 to obtain the target flow rate. Thereafter, waste liquid treatment operation will be carried out continuously. The treatment of the waste liquid 2 is the same as in the first embodiment, and its explanation will be omitted. As described above, according to the second embodiment, it is possible to not only achieve the same effects as the first embodiment, but also to provide a smoother operating state. That is, if the waste liquid 2 is supplied after a while after the water supply is stopped, the interior of the dryer 4 will be in a dry state because the dryer 4 is always heated via the heating jacket 24. Therefore, even if waste liquid 2 is supplied in such a state, it is predicted that stable operating conditions cannot be obtained. In the case of the first embodiment, this problem is avoided by supplying the waste liquid 2 immediately after completely stopping the supply of water. On the other hand, in the case of this second embodiment, a constant fluid (water, waste liquid, or a mixture of both) is always supplied into the centrifugal thin film dryer 4, and from the viewpoint of so-called wettability. Since the inside of the dryer 4 is always in a wet state, a stable operating state can be provided. [Effects of the Invention] As detailed above, the present invention introduces water or hot water into the outer shell when starting up the centrifugal thin film dryer, evaporates the introduced water or hot water, and turns the rotating shaft into steam. This prevents the clearance between the inner circumferential surface of the outer shell and the rotor blade from becoming larger than the design value immediately after preheating, reducing the waiting time from startup to start of operation. , it is possible to provide a method for operating a centrifugal thin film dryer that can process waste liquid even immediately after preheating.

[Brief explanation of the drawing]

1 to 4 are diagrams showing a first embodiment of the present invention, FIG. 1 is a diagram showing the configuration of a centrifugal thin film dryer and peripheral equipment, and FIG. 2 is a partially cutaway diagram of the centrifugal thin film dryer. 3 is a vertical cross-sectional view of the centrifugal thin film dryer, FIG. 4 is a diagram showing changes over time in steam temperature, rotation speed of the rotating shaft, and liquid supply flow rate, and FIG.
It is a figure which shows the time change of the steam temperature, the rotation speed of a rotating shaft, and the supply liquid flow rate in the case of Example. 2... Waste liquid, 3... Waste liquid piping, 4 ... Centrifugal thin film dryer, 11... Water supply piping, 21... Cylindrical body, 22
... Rotating shaft, 23 ... Rotating blade, 25 ... Heat transfer surface.

Claims (1)

[Claims] 1 Superheated steam is introduced into a heating jacket formed in a cylindrical outer shell, and a slurry-like waste liquid is introduced into the inner side of the outer shell, and the waste liquid is transferred to a rotating jacket disposed in the center of the outer shell. attached to the inner peripheral surface of the outer shell heated by the superheated steam due to the centrifugal force of the shaft, and dried and separated into evaporated components and non-evaporated components;
At the time of starting the centrifugal thin film dryer, which scrapes off the non-evaporable components adhering to the inner circumferential surface of the outer shell in the form of a thin film with the rotary blades attached to the rotating shaft, preheating steam is introduced into the heating jacket and the outer shell is removed. A method for operating a centrifugal thin film dryer, characterized in that water or hot water is introduced into the outer shell, the water or hot water introduced into the outer shell is evaporated, and the rotating shaft is preheated with steam.