JPH0429402B2 - - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a method of operating a centrifugal thin film dryer for treating waste liquid such as radioactive waste liquid, and in particular, relates to a method of operating a centrifugal thin film dryer for treating waste liquid such as radioactive waste liquid. This invention relates to a method of operating a thin film dryer.

(Prior art) A conventional centrifugal thin film dryer has a heat transfer surface formed on the inner surface of the main body that rotatably houses rotor blades, and heats the waste liquid supplied to this heat transfer surface to form a thin film. The thin film is scraped off by the rotary blade and discharged as an evaporation residue.

In this type of conventional centrifugal thin film dryer, the control device operates by keeping the supply amount of waste liquid and the rotational speed of the rotor constant, which are set according to the properties of the waste liquid to be treated such as radioactive waste liquid and the purpose of treatment. Most of the methods were designed to keep the amount of waste liquid supplied constant or to keep the temperature conditions of the heat transfer surface constant. Or, at most, the amount of waste liquid to be treated is controlled in order to obtain a constant concentration of evaporation residue.
For this reason, if the waste liquid to be treated adheres to the heat transfer surface and the rotor and these deposits gradually grow as solid matter, or if the waste liquid to be treated adheres to the heat transfer surface and the rotor blade, or if the waste liquid to be treated adheres to the heat transfer surface and the rotor, or if the waste liquid to be treated is In the case of something that changes in properties, the centrifugal force at a given rotation speed of the rotor;
These deposits cannot be easily removed by the scraping force exerted by the rotary blades on the heat transfer surface.

This may lead to a reduction in the heating ability of the heat transfer surface or generation of heat due to friction between the deposits and the rotor blade.

Furthermore, since a minute gap is provided between the outer end of the rotor blade and the heat transfer surface, the occurrence of deposits is unavoidable.

Therefore, in conventional centrifugal thin film dryers, in order to remove deposits from heat transfer surfaces, etc., the number of revolutions of the rotor blades is increased to increase the centrifugal force and scraping force of the rotor blades, which increases the power to remove deposits. We are trying to increase it.

(Problems to be Solved by the Invention) However, in such a method, if the scraping force becomes excessive, the waste liquid to be treated will be unevenly distributed over the required blades of the rotor, which may cause the entire rotor to lose its balance, overload, etc. I was invited.

For this reason, in conventional centrifugal thin film dryers, after a certain period of operation, operation is always stopped for a certain period of time, for example, about half a day, to remove deposits on the heat transfer surface, etc., and to clean the heat transfer surface, etc. There was a problem of low utilization rate.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for operating a centrifugal thin film dryer that increases the operating rate by minimizing the downtime.

[Structure of the invention]

(Means for Solving the Problems) The present invention forms a heat transfer surface on the inner surface of a main body that rotatably accommodates a rotor blade, heats the waste liquid supplied to the heat transfer surface to form a thin film, In a centrifugal thin film dryer that scrapes this thin film with the rotary blade and discharges it as an evaporation residue, when the temperature of the heat transfer surface or the evaporation residue exceeds a set value, or the load on the rotor blade exceeds the set value. When the value is exceeded,
The present invention is characterized in that the supply of the waste liquid and the rotation of the rotor blade are temporarily stopped, and then the rotor blade is rotated again and water is supplied to the heat transfer surface.

(Function) By operating the centrifugal thin film dryer, waste liquid is supplied along the heat transfer surface and heated.

As a result, a part of the waste liquid is evaporated, and the other part is formed as a thin film on the heat transfer surface as an evaporation residue, and this thin film is scraped off by the rotary blade and discharged in the form of slurry or powder.

During this period, some of the evaporation residue comes off the surface of the rotor blade and remains attached to the heat transfer insulation, etc., and gradually increases in thickness and grows, reducing the heating ability of the heat transfer surface, or Frictional heat between the outer end of the rotor blade and the deposits causes an increase in the temperature of the heat transfer surface and the discharged powder.

Furthermore, as deposits on heat transfer surfaces and the like grow, friction with the rotor blade increases, and the load on the rotor blade increases.

Therefore, when the temperature of the heat transfer surface or the discharged powder (evaporation residue) exceeds a set value, or the load on the rotor exceeds a set value, the supply of waste liquid and the rotation of the rotor are temporarily stopped.

For this reason, the evaporation residue held by the rotating rotor blades can be dropped by gravity to the discharge port below.

Thereafter, the rotor is rotated again and water is supplied to the heat transfer surface.

As a result, the heat transfer surface cools and contracts, so that the surface on which the deposits are attached is peeled off from the heat transfer surface.Furthermore, the deposits on the heat transfer surface are scraped off and removed by the rotary blades, and the transfer Hot surfaces and rotors are cleaned.

Therefore, there is no need to stop the operation of the centrifugal thin film dryer for a relatively long period of time to remove or clean the deposits adhering to the heat transfer surface, etc., and the operating rate of the centrifugal thin film dryer can be increased. .

(Example) Hereinafter, an example of the present invention will be described in Figures 1 to 4.
This will be explained with reference to the figures.

FIG. 2 shows the overall configuration of an embodiment of the present invention, in which a liquid supply pipe 20 and a water supply pipe 30 are both connected to the liquid supply nozzle 2 of the centrifugal thin film dryer main body 1.

The centrifugal thin film dryer main body 1 is constructed as shown in FIGS. 3 and 4, and has a rotary blade 4 rotatably and coaxially accommodated in a cylindrical main body body 3.

As shown in FIG. 4, the main body shell 3 has a double cylinder structure in which an inner cylinder 3b is housed coaxially within an outer cylinder 3a. A heating jacket 3c is connected to a heating source to vent heated steam, and an inner cylinder 3b is connected to the heating jacket 3c.
A heat transfer tube 5 having a heat transfer surface 5a that heats the waste liquid 21 to form a thin film as an evaporation residue is fitted inside the tube in close contact. The temperature of the heat transfer surface 5a is measured by a heat transfer surface thermometer 6.

The rotary blade 4 has a plurality of blades 4b fixed in the circumferential direction to the outer periphery of a rotating shaft 4a coaxially housed in the main body shell 3, and a plurality of blades 4b are fixed in the axial direction. A minute gap is set in the radial direction between each outer end of these blades 4b and the heat transfer surface 5a.

The upper end of the rotating shaft 4a is connected to the rotating shaft of a motor 7 located at the top of the main body 1, as shown in FIG. The load on the blade 4 can be detected.

Further, a ring-shaped distribution ring 9 fitted on the upper part of the rotating shaft 4a is arranged at almost the same height as the mounting position of the liquid supply nozzle 2, and the waste liquid spouted from the liquid supply nozzle 2 and the water supply are It is designed to be distributed almost uniformly in the circumferential direction.

A vapor discharge hole 10 is opened in the upper part of the main body shell 3 for discharging steam evaporated by heating a part of the waste liquid supplied to the heat transfer surface 5a. A discharge port 11 for discharging body-shaped evaporation residue is opened, and this discharge port 11
The temperature of the evaporation residue discharged is determined by the residue thermometer 12.
It is measured by

As shown in FIG. 2, the tip of the liquid supply pipe 20 connected to the liquid supply nozzle 2 of the main body 1 is connected to a waste liquid tank 22 that stores waste liquid 21 such as radioactive waste liquid. The waste liquid 21 is placed in the main body 1 on the way.
A liquid supply pump 23 for pressure-feeding the liquid to the liquid supply nozzle 2, and a control valve 24 and a stop valve 25 for controlling the amount of waste liquid 21 to be supplied are provided, respectively.

On the other hand, the tip of the water supply pipe 30 connected to the liquid supply nozzle 2 is connected to a water supply source 31 that stores water such as relatively low-temperature hot water. A water supply pump 32 for pressure feeding;
A water supply control valve 33 and a stop valve 34 are respectively provided to control the amount of water supplied.

Next, a method of operating the centrifugal thin film dryer constructed in this way will be explained with reference to FIG.

FIG. 1 shows time on the horizontal axis and the amount of waste liquid 21 supplied to the liquid supply nozzle 2 and the rotation speed of the rotor 4 on the vertical axis, and shows an example of the operating method of the present invention. .

That is, first, a waste liquid treatment operation is performed in which the waste liquid 21 is supplied to the liquid supply nozzle 2 of the main body 1 of the centrifugal thin film dryer and the rotary blade 4 is rotated.

As a result, when the temperature of the heat transfer surface 5a rises and the measured value of the heat transfer surface thermometer 6 exceeds the required set value, or when the measured value of the residue thermometer 12 exceeds the required set value, Alternatively, when the power load on the rotary blade 4 increases and the measured value of the ammeter 8 exceeds a required set value, the control operation is switched to. That is, the stop valve 25 of the liquid supply pipe 20 is completely closed to stop the supply of the waste liquid 21, and the rotation of the rotary blade 4 is continued for the required time.
For example, it is temporarily stopped for about 2 minutes.

Thereafter, the rotary blade 4 is rotated again, and then the stop valve 34 of the water supply pipe 30 is fully opened to supply water to the liquid supply nozzle 2. This water supply amount is determined by the water supply control valve 3.
3, the amount is increased in steps as shown in FIG. This allows a large amount of water to be supplied to the main body 1.
This is because if the powder is supplied all at once, the powdered evaporation residue in the main body 1 may contain water and become liquid.

Next, the operation of this embodiment will be described.

First, when performing a waste liquid treatment operation, the rotor blade 4 of the main body 1 is rotated, the stop valve 25 of the water supply pipe 20 is opened, and the waste liquid 21 is supplied to the liquid supply nozzle 2 of the main body 1.

As a result, the waste liquid 21 spouted into the main body 1 from the liquid supply nozzle 2 hits the outer peripheral surface of the rotating distribution ring 9, and then receives the centrifugal force of the rotating rotor blade 4 and hits the heat transfer surface 5a. Almost uniformly distributed.

Further, the waste liquid 21 flows downward along the heat transfer surface 5a, and during this time it is heated, a part of it evaporates and is discharged from the vapor discharge hole 10, and the rest forms a thin film on the heat transfer surface 5a as an evaporation residue. do.

When the thickness of this thin film increases beyond the required thickness, it is scraped off by the rotating rotor blades 4, falls to the discharge port 11 below, and is discharged from the discharge port 11 in the form of slurry or powder. .

During this operation, if the evaporation residue of the waste liquid 21 adhering to the heat transfer surface 5a grows or increases the number of adhesion points, the heat transfer area of the heat transfer surface 5a will be reduced and the heating capacity will be reduced. By increasing the friction between these deposits and the rotor blade 4, the frictional heat is increased, and the temperature of the heat transfer surface 5a and the powdery evaporation residue is increased.

Further, due to the increase in friction between the rotor blade 4 and the deposits, the load on the rotor blade 4 increases, and the current applied to the motor 7 that drives the rotor blade 4 increases.

Therefore, the heat transfer surface thermometer 6 and the residue thermometer 12
When any of the measured values exceeds these set values, or when the measured value of the ammeter 8 exceeds the set value, the control operation is switched to as shown in FIG. 1.

That is, the stop valve 25 of the liquid supply pipe 20 is fully closed to stop the supply of the waste liquid 21, and the rotation of the rotary blade 4 is temporarily stopped for about two minutes, for example.

When the rotation of the rotor blade 4 stops, a part of the evaporation residue of the waste liquid 21 that has been carried around by each blade 4b of the rotor blade 4 falls to the discharge port 11 below due to its own weight.

After that, while rotating the rotor blade 4 again,
The stop valve 34 of the water supply pipe 30 is fully opened to supply water to the liquid supply nozzle 2. This water supply amount is determined by the water supply control valve 3.
3, the amount is increased in steps as shown in FIG.

The supplied water is ejected from the liquid supply nozzle 2 onto the outer circumferential surface of the rotating distribution pipe 9, receives the centrifugal force of the rotor blades 4, is dispersed onto the heat transfer surface 5a, and flows downward along the heat transfer surface 5a. do.

As a result, the heat transfer surface 5a is rapidly cooled and contracted by the supplied water, and the deposits are peeled off from the heat transfer surface 5a, and the rotor blades 4 scrape off the deposits.
Moreover, the heat transfer surface 5a and the rotor blade 4 are cleaned by the supplied water.

Therefore, the heating ability of the heat transfer surface 5a is restored.

After that, the stop valve 34 is closed without stopping the rotation of the rotor blade 4, and the supply of water is stopped, while
The stop valve 34 is opened, the waste liquid 21 is supplied to the liquid supply nozzle 2 again, and the waste liquid treatment operation is performed.

The above adjustment operation time was, for example, about 30 minutes when the waste liquid supply flow rate was 150/h.

Therefore, according to this embodiment, in order to remove the deposits on the heat transfer surface 5a and clean the heat transfer surface 5a, etc.,
There is no need to stop the operation of the main body 1, and the operating rate of the centrifugal thin film dryer can be improved.

It goes without saying that the operating method of the above embodiment may be configured to be automatically performed by a controller.

[Structure of the invention]

As explained above, in the present invention, water is supplied to the heat transfer surface to remove deposits during the operation of treating the waste liquid of the centrifugal thin film dryer. There is no need to stop operation to remove deposits, and the operating rate can be improved.

[Brief explanation of drawings]

Fig. 1 is a graph of one embodiment of the present invention, Fig. 2 is an overall configuration diagram of the centrifugal thin film dryer shown in Fig. 1, and Fig. 3 is a graph of an embodiment of the present invention.
The figure is a partially cutaway perspective view of the centrifugal thin film dryer main body shown in FIG. 2, and FIG. 4 is a longitudinal cross-sectional view showing the centrifugal thin film dryer main body shown in FIG. 2 with some parts omitted. 1... Centrifugal thin film dryer main body, 2... Liquid supply nozzle, 3... Main body shell, 4... Rotating blade, 5a... Heat transfer surface, 6... Heat transfer surface thermometer, 12... Residue thermometer ,
13...Ammeter.

Claims (1)

[Claims] 1. A heat transfer surface is formed on the inner surface of the main body that rotatably accommodates the rotor blade, the waste liquid supplied to the heat transfer surface is heated to form a thin film, and this thin film is applied by the rotor blade. In a centrifugal thin film dryer that scrapes and discharges as evaporation residue, when the temperature of the heat transfer surface or the evaporation residue exceeds a set value, or when the load on the rotor blade exceeds the set value, A method for operating a centrifugal thin film dryer, characterized in that the supply of the waste liquid and the rotation of the rotor blade are temporarily stopped, and then the rotor blade is rotated again and water is supplied to the heat transfer surface. 2. The method of operating a centrifugal thin film dryer according to claim 1, wherein the amount of water supplied is gradually increased.