JP2011033241A - Centrifugal type thin film dryer - Google Patents

Abstract

A centrifugal thin film dryer capable of suppressing clogging associated with drying and solidification of waste liquid on the surface of a liquid supply pipe.
SOLUTION: A hollow heat transfer cylinder 11 having a heat transfer surface for heating a process liquid, a process liquid inlet 16 for introducing the process liquid into the heat transfer cylinder 11, and an axial center position of the heat transfer cylinder 11. A rotating shaft disposed on the rotating shaft, and a blade that radiates on the rotating shaft and scrapes off the powder of the processing liquid generated on the heat transfer surface by concentration and drying. An aqueous film 41 is formed.
[Selection] Figure 2

Description

  The present invention relates to a centrifugal thin film dryer applied to a waste liquid treatment facility and the like, and more particularly to a centrifugal thin film dryer that suitably suppresses blockage of a supply pipe due to a condensed matter.

  One of the main purposes of waste liquid treatment equipment is to measure volume reduction of waste liquid. In particular, in a nuclear power plant where the waste storage space in the premises is a problem, the residual solid content obtained by evaporating the water of the concentrated waste liquid generated by using a dryer is pulverized. The powdered concentrated waste liquid is mixed with cement, solidified, mixed with plastic, solidified, granulated, pelletized, then solidified with sentiment or plastic, and discarded.

  In addition, solid particle wastes such as granular ion exchange resins, powder ion exchange resins, and filter aids that purify reactor condensate and wastewater are solidified by dehydration and drying, and then mixed with cement and plastic. Processed and discarded.

  The waste liquid drying treatment is a very useful unit operation from the viewpoint of volume reduction of waste because the volume can be reduced to about 1/10. Conventionally, many centrifugal thin-film dryers are used for these drying processes (for example, refer patent document 1).

  This centrifugal thin film dryer mainly has a vertically long cylindrical heat transfer drum with a heat transfer surface that evaporates and dries the water in the waste liquid, and a rotating blade that scrapes off the waste liquid that has solidified and adheres to the heat transfer surface. With a rotating shaft. In addition, a liquid supply pipe for supplying waste liquid is provided at the upper portion of the heat transfer cylinder. After the waste liquid is supplied into the centrifugal thin film dryer from the liquid supply pipe, it touches the heat transfer surface heated to a predetermined temperature, and is solidified as the evaporation and drying of water proceeds. The rotating blade scrapes off the solidified waste liquid on the heat transfer surface, pulverizes and separates it, and drops it downward. The pulverized waste liquid is finally discharged from an outlet provided below the machine body.

  2. Description of the Related Art Conventionally, a technique is known that prevents scaling of sludge generated on the inner surface of a heat transfer drum of this centrifugal thin film dryer and avoids a decrease in heat transfer efficiency (see, for example, Patent Document 2).

JP-A 64-30601 Japanese Patent Laid-Open No. 11-248353

  The waste liquid is supplied into the centrifugal thin film dryer via a liquid supply pipe. Since this liquid supply pipe is provided in the upper part of the heat transfer cylinder, the temperature rises due to heat from the heat transfer surface for drying and solidifying the waste liquid. For this reason, before the waste liquid was supplied into the heat transfer cylinder, there was a problem that the waste liquid might dry and solidify inside the liquid supply pipe and the liquid supply pipe might be blocked.

  In order to solve this problem, it is conceivable to modify the waste liquid by adding an additive or the like to suppress the adhesion of the waste liquid to the inner surface of the liquid supply pipe. It is also conceivable to devise the shape of the liquid supply piping so that the waste liquid is difficult to dry and solidify.

  However, at the present stage, there has been a situation that a sufficient solution cannot be obtained by reforming the waste liquid or changing the shape of the supply pipe, and a practical solution cannot be obtained.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a centrifugal thin film dryer capable of suppressing clogging associated with drying and solidification of waste liquid on the surface of the liquid supply pipe.

  The centrifugal thin film dryer according to the present invention includes a hollow heat transfer cylinder having a heat transfer surface for heating the process liquid, a process liquid inlet for introducing the process liquid into the heat transfer cylinder, and the heat transfer. A rotary shaft disposed at the axial center of the cylinder, and a blade provided radially on the rotary shaft and scraping off the powder of the processing liquid generated on the heat transfer surface by concentration and drying. A water repellent film is formed on the surface of the liquid inlet.

  According to the centrifugal thin film dryer according to the present invention, it is possible to suppress clogging accompanying the drying and solidification of the waste liquid on the surface of the liquid supply pipe and to improve the drying efficiency.

The fragmentary longitudinal cross-section which shows the whole structure of the centrifugal thin film dryer in this embodiment. The enlarged view of the area | region II of the centrifugal thin film dryer of FIG. The figure for demonstrating the definition of the contact angle with respect to a pure water.

  Embodiments of the present invention will be described with reference to the accompanying drawings. In this embodiment, the centrifugal thin film dryer according to the present invention is applied to an example used when performing a drying process in which radioactive waste liquid generated during operation of a nuclear power plant is dried into a thin film and pulverized. To explain. This centrifugal thin film dryer can also be applied to various waste liquid treatments generated from plant facilities such as industrial waste treatment facilities other than nuclear power plants.

  FIG. 1 is a partial longitudinal sectional view showing an overall configuration of a centrifugal thin film dryer in the present embodiment.

  The centrifugal thin film dryer 1 includes a heat transfer drum 11 having a hollow cylindrical shape. A heating jacket 12 is provided outside the heat transfer cylinder 11. The heating jacket 12 is provided with a heating steam inlet 13 protruding outside at an upper position and an evaporation drain discharge port 14 protruding outside at a lower position.

  The inner surface of the heat transfer cylinder 11 functions as a heat transfer surface 15 that is heated to a predetermined temperature. The heat transfer surface 15 is heated to a predetermined temperature (for example, about 170 degrees) by supplying the heating steam supplied from the heating steam inlet 13.

  The heat transfer cylinder 11 is provided with a waste liquid inlet 16 and an evaporating vapor outlet 17 at an upper position. The waste liquid inlet 16 is a pipe as a liquid supply port for introducing the waste liquid into the heat transfer cylinder 11. The evaporating vapor outlet 17 is a pipe serving as a discharge port for discharging evaporated vapor that is a part of the radioactive waste liquid (waste liquid). The heat transfer drum 11 is provided with a waste liquid dry powder discharge port 18 at the lower end position. The waste liquid dry powder discharge port 18 is configured as a conical cone and is a discharge port for discharging waste liquid dry powder generated by drying the waste liquid.

  A rotating shaft 19 is disposed in the hollow portion of the heat transfer cylinder 11. The rotary shaft 19 is configured in a shaft shape extending in the vertical direction in the figure, and is disposed at the axial center position of the heat transfer cylinder 11. The rotating shaft 19 is configured to be rotatable by a drive motor (not shown).

  The rotating shaft 19 is provided with a rotating blade 20 and a dispersion ring 21.

  The rotating blade 20 is rotatably mounted via a rotating blade mounting seat 22. The rotating blades 20 are arranged radially aligned in the axial direction and the circumferential direction of the rotating shaft 19. The tip of the rotary blade 20 is disposed opposite to the heat transfer surface 15 on the inner surface of the heat transfer drum 11 with a slight gap. The dispersion ring 21 is disposed so that the outer peripheral surface thereof faces the waste liquid inlet 16 and is provided so as to be rotatable integrally with the rotary shaft 19. The dispersion ring 21 reflects the waste liquid supplied from the waste liquid inlet 16 on the annular outer peripheral surface and disperses it on the heat transfer surface 15 in the centrifugal direction.

  FIG. 2 is an enlarged view of region II of the centrifugal thin film dryer 1 of FIG.

  The waste liquid inlet 16 of the centrifugal thin film dryer 1 includes a waste liquid inlet nozzle 31 and an extension pipe 32 as an intubation tube inserted into the waste liquid inlet nozzle 31. The waste liquid inlet nozzle 31 is integrally formed with the heat transfer cylinder 11 by welding or the like. The waste liquid inlet nozzle 31 is provided with an inlet nozzle flange 31a at the tip protruding outward from the heat transfer cylinder 11. An external piping flange portion 33a of an external piping 33 for supplying waste liquid is detachably connected to the inlet nozzle flange portion 31a by a bolt 35 and a nut 36.

  The extension pipe 32 is open at both ends, and has a configuration for supplying waste liquid supplied from the external pipe 33 side to the heat transfer cylinder 11 side. In addition, the extension pipe 32 has an extension pipe flange part 32a at an end part 32b opened to the external pipe 33 side. The elongated pipe flange portion 32a is nipped and fixed to the joint surface portion between the inlet nozzle flange portion 31a and the external piping flange portion 33a. The elongated pipe flange portion 32 a that is nipped and fixed is liquid-tightly and firmly fixed in the waste liquid inlet nozzle base 31.

  The extension pipe 32 is a pipe having a predetermined diameter smaller than that of the waste liquid inlet nozzle 31. The extension pipe 32 is detachably attached to the waste liquid inlet nozzle 31. The diameter of the extension pipe 32 is set in accordance with characteristics including the properties and flow rate of the waste liquid flowing through the extension pipe 32. Therefore, the extension pipe 32 is configured to be replaced with a pipe having an appropriate shape according to the waste liquid handled by the centrifugal thin film dryer 1. By making the extension tube 32 replaceable, it is possible to supply waste liquid in the centrifugal thin film dryer 1 according to the characteristics of the waste liquid, and to further increase the drying efficiency. In addition, the inner diameter of the waste liquid inlet nozzle 31 is set so that the extension pipe 32 having various outer diameters corresponding to the waste liquid can be accommodated, for example, larger than the inner diameter of the conventional waste liquid inlet nozzle 31. .

  A coating 41 is formed on the inner surface of the extension tube 32 from a material having water repellency. The film 41 preferably has a film thickness of 1 μm or more and 100 μm or less. By setting the film thickness of the film 41 to 1 μm or more, the surface of the elongated tube 32 can be uniformly covered by the film 41, and a rapid decrease in water repellency associated with partial exposure of the surface of the elongated tube 32 can be suppressed. it can. In addition, by setting the film thickness of the film 41 to 100 μm or less, the adhesion strength of the film 41 to the surface of the elongated tube 32 is maintained, and the oxidation resistance is reduced due to the occurrence of cracks in the film 41, and the film 41 is peeled off. Occurrence can be suppressed.

  The material constituting the film 41 preferably includes at least a fluororesin. Examples of the fluororesin include PTFE (polytetrafluoroethylene), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), ETFE (tetrafluoroethylene-ethylene). Copolymer) and the like can be applied. In particular, from the viewpoint of heat resistance and water repellency, PTFE is suitable for the fluororesin material constituting the film 41.

  Moreover, it is preferable that the material which comprises the membrane | film | coat 41 is a material which consists of a mixture with which metal powder was mixed in addition to the fluororesin. For example, nickel metal powder is preferably used as the metal powder. This is because the nickel metal powder is suitable for the material of the film 41 in terms of interaction with the fluororesin in addition to corrosion resistance and heat resistance.

  The coating 41 preferably contains 20% by volume or more and 80% by volume or less of metal powder, and the remainder is made of a fluororesin. By setting the ratio of the metal powder in the mixture material of the film 41 to 20% by volume or more, it is possible to sufficiently obtain wear characteristics and dimensional stability. Moreover, by setting the ratio of the metal powder in the material of the film 41 to 80% by volume or less, a decrease in water repellency and a decrease in the adhesion strength of the film 41 are suppressed, and a phenomenon such as peeling is prevented and a practical film 41 is obtained. Can be formed.

Further, the coating 41 of the elongated tube 32 preferably has a contact angle with respect to pure water of 90 degrees or more. Here, FIG. 3 is a figure for demonstrating the definition of the contact angle with respect to a pure water. The contact angle is defined by an angle θ formed between the tangent of the droplet and the film surface. Specifically, the contact angle is a value defined by the following formula. In the above formula, h represents the height of the droplet, and 2r represents the length of the side of the droplet in contact with the coating surface in FIG.
[Equation 1]
θ = 2 tan ⁻¹ (h / r)

  The reason why the contact angle of the film 41 with respect to pure water is 90 degrees or more is that it is a value suitable for obtaining the effect of suppressing the solid content of the dried and solidified waste liquid.

  Next, the effect | action at the time of the drying process driving | operation of the centrifugal thin film dryer 1 in this embodiment is demonstrated.

  Radioactive waste liquid generated during operation of the nuclear power plant and stored in a waste liquid storage tank (not shown) is supplied from the waste liquid inlet 16 into the heat transfer cylinder 11 at a constant flow rate. At this time, the rotary shaft 19 is rotated by a drive motor (not shown). Further, the heat transfer drum 11 is heated to, for example, 170 degrees by supplying steam to the heating jacket 12.

  In the present embodiment, the radioactive waste liquid supplied to the centrifugal thin film dryer 1 is, for example, a sodium borate-based aqueous solution generated by neutralizing boric acid waste liquid with sodium hydroxide. In addition, the radioactive waste liquid supplied to the centrifugal thin film dryer 1 in the present embodiment is not limited to the waste liquid mainly composed of sodium borate, but has other soluble and insoluble components as the main component. Even if it is a thing, it is applicable.

  The radioactive waste liquid introduced into the heat transfer cylinder 11 is attached to the dispersion ring 21 provided at the upper position of the rotary shaft 19 and in the vicinity of the waste liquid inlet 16, and is dispersed on the heat transfer surface 15 by centrifugal force. .

  The radioactive waste liquid scattered on the heat transfer surface 15 flows down the heat transfer surface 15 by gravity. For this reason, a thin film of radioactive waste liquid is formed on the heat transfer surface 15. The radioactive liquid waste formed in a thin film is supplied from the heating steam inlet 13 and heated by the steam flowing through the heating jacket 12 provided outside the heat transfer cylinder 11. The radioactive liquid waste further flows down by gravity while being concentrated by evaporation of volatile components.

  The evaporating vapor derived from the radioactive liquid waste is discharged from the evaporating vapor outlet 17 and processed by an evaporating vapor processing apparatus (not shown). Further, the drain generated by the evaporated vapor is discharged from the evaporated drain discharge port 14.

  The tip of the rotary blade 20 attached to the rotary shaft 19 rotates with a slight gap (for example, about 0.5 mm) from the heat transfer drum 11. The radioactive waste liquid adhering to the heat transfer drum 11 in a thin film is scraped off by the tip of the rotary blade 20 to become dry powder, descends in the centrifugal thin film dryer 1 and is discharged from the waste liquid dry powder discharge port 18. Is done.

  Here, in the centrifugal thin film dryer, as the temperature of the heat transfer cylinder heated by the steam rises, the temperature of the liquid supply pipe constituting the waste liquid inlet is also raised. In addition, before the waste liquid is supplied to the heat transfer cylinder, a phenomenon occurs in which the waste liquid is dried and solidified in the pipe due to the heat of the liquid supply pipe. Along with this, the inside of the liquid supply pipe is blocked by the dried and solidified waste liquid, and a sufficient amount of waste liquid cannot be supplied into the heat transfer cylinder. As a result, the drying efficiency of the centrifugal thin film dryer is reduced.

  On the other hand, the centrifugal thin film dryer 1 in the present embodiment is provided on the inner surface of the extension pipe 32 inserted in the waste liquid inlet nozzle 31 constituting the waste liquid inlet 16 in order to prevent the occurrence of the above-mentioned problems. It is possible to appropriately prevent the supplied radioactive waste from adhering as a condensate in the liquid supply pipe by performing a film treatment, and to efficiently supply the waste liquid into the heat transfer cylinder 11.

Here, in order to confirm the effect of suppressing the adhesion of the waste liquid by applying the film treatment to the inner surface of the elongated pipe 32 inserted into the waste liquid inlet nozzle 31 as the waste liquid inlet 16, PTFE as a fluororesin and a metal powder are used. A material composed of a mixture of nickel metal powders was subjected to a coating treatment on the inner surface of the elongated tube 32 using the ratio and film thickness shown in Table 1 below and tested. In each example and comparative example, a sodium borate aqueous solution was used as a waste liquid. In each example and comparative example, the centrifugal thin film dryer 1 was operated continuously for 8 hours.

  As a result, in the extension pipe 32 of the centrifugal thin film dryer 1 using the volume ratio and the film thickness of the mixtures shown in Comparative Examples 1 to 4, clogging due to drying and solidification of the waste liquid was observed. On the other hand, in the extension pipe 32 of the centrifugal thin film dryer 1 using the volume ratio and the film thickness of the mixture shown in Examples 1 to 5, no clogging due to drying and solidification of the waste liquid is observed, and a favorable drying process is performed. Was able to do.

  That is, it is preferable that the mixture material of the film 41 contains nickel metal powder (metal powder) in an amount of 20% by volume to 80% by volume, and the remainder is made of PTFE (fluororesin). Furthermore, the film 41 preferably has a film thickness of 1 μm or more and 100 μm or less. By configuring the film 41 as described above, drying and solidification in the supply pipe could be suitably suppressed.

  According to this centrifugal thin film dryer 1, the temperature of the waste liquid inlet 16 is formed by forming a water-repellent film on the inner surface of the liquid supply pipe constituting the waste liquid inlet 16 that supplies the waste liquid to the centrifugal thin film dryer 1. Dry solidification of the waste liquid accompanying the rise can be suitably suppressed. For this reason, the centrifugal thin film dryer 1 can suitably perform the waste liquid drying process without reducing the drying efficiency.

  Further, the clogging can be suppressed by forming the coating 41 on the pipe, and the effect can be obtained simply and efficiently compared to the modification of the waste liquid or the change of the shape of the liquid supply pipe.

  The centrifugal thin film dryer 1 according to the present embodiment is configured such that an extension pipe 32 that can be replaced according to the characteristics of the waste liquid is inserted inside the liquid supply pipe (waste liquid inlet nozzle 31) of the waste liquid inlet 16. An example in which a heavy pipe is formed and the coating 41 is formed on the inner surface of the elongated pipe 32 has been described. However, the pipe on which the film 41 is formed is not limited to the extension pipe 32, and in the case of a liquid supply pipe constituted by a single pipe without the extension pipe 32, a film is formed on the inner surface of the liquid supply pipe. May be.

  Further, when the extension tube 32 is inserted, the extension tube 32 is formed not only on the inner surface of the extension tube 32 but also on the outer surface of the extension tube 32 and the inner surface of the waste liquid inlet nozzle 31. It is possible to prevent the waste liquid that has circulated from the liquid from adhering and depositing on the waste liquid inlet nozzle 31.

DESCRIPTION OF SYMBOLS 1 Centrifugal thin film dryer 11 Heat transfer drum 12 Heating jacket 13 Heating steam inlet 14 Evaporating drain outlet 15 Heat transfer surface 16 Waste liquid inlet 17 Evaporating steam outlet 18 Waste liquid dry powder outlet 19 Rotating shaft 20 Rotating blade 21 Dispersion ring 22 Rotating blade mounting seat 31 Waste liquid inlet nozzle 31a Inlet nozzle flange 32 Extension pipe 32a Extension pipe flange 32b End 33 External piping 33a External piping flange 35 Bolt 36 Nut 41 Film

Claims (11)

A hollow heat transfer cylinder having a heat transfer surface for heating the treatment liquid;
A treatment liquid inlet for introducing the treatment liquid into the heat transfer cylinder;
A rotating shaft disposed at the axial center of the heat transfer cylinder;
A blade provided radially on the rotating shaft, and scraping off the powder of the treatment liquid generated on the heat transfer surface by concentration and drying;
A centrifugal thin film dryer, wherein a water-repellent film is formed on the surface of the treatment liquid inlet. The treatment liquid inlet is a tube base formed integrally with the heat transfer cylinder, and an internal tube inserted in a removable manner with respect to the tube base.
The centrifugal thin film dryer according to claim 1, wherein the water repellent film is formed on an inner surface of the inner tube. The treatment liquid inlet is a tube base formed integrally with the heat transfer cylinder, and an internal tube inserted in a removable manner with respect to the tube base.
2. The centrifugal thin film dryer according to claim 1, wherein the water-repellent coating is formed on an inner surface and an outer surface of the inner tube and an inner surface of the nozzle. The centrifugal thin film dryer according to any one of claims 1 to 3, wherein the water repellent coating has a contact angle with respect to pure water of 90 degrees or more. The centrifugal thin film dryer according to any one of claims 1 to 4, wherein the water repellent coating includes at least a fluororesin. 6. The centrifugal thin film dryer according to claim 5, wherein the fluororesin is PTFE (polytetrafluoroethylene). The centrifugal thin film dryer according to claim 5, wherein the water repellent film further contains a metal powder. 8. The centrifugal thin film dryer according to claim 7, wherein the water repellent coating is composed of 20% by volume or more and 80% by volume or less of the metal powder, and the rest is composed of a fluororesin. The centrifugal thin film dryer according to claim 7 or 8, wherein the metal powder is nickel metal powder. The centrifugal thin film dryer according to any one of claims 1 to 9, wherein the water-repellent coating has a film thickness of 1 µm to 100 µm. The centrifugal thin film dryer according to any one of claims 1 to 10, wherein the treatment liquid is a radioactive waste liquid generated in a nuclear power plant.

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