JP2013231555A - Centrifugal type thin film dryer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a centrifugal type thin film dryer capable of suppressing blocking accompanied by the drying and solidification of a waste liquid on the surface of liquid supply piping.SOLUTION: A centrifugal type thin film dryer includes: a hollow heat transfer barrel 11 having a heat transfer face for heating a treatment liquid; a treatment liquid inlet 16 for introducing the treatment liquid into the heat transfer barrel 11; a rotating shaft arranged in an axial center position of the heat transfer barrel 11; and blades radially provided at the rotating shaft and scraping off the powder of the treatment liquid generated on the heat transfer face by a concentration and drying. A pipe 41 allowing the treatment liquid to pass therein and composed of a water repellent material is arranged at the treatment liquid inlet 16.

Description

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

  One of the main objectives of wastewater treatment equipment is to measure volume reduction of wastewater. In particular, in a nuclear power plant where the waste storage space in the site is a problem, pulverization of residual solids obtained by evaporating the water in the concentrated effluent generated by using a dryer is performed. The powdered concentrated effluent is mixed with cement, solidified, mixed with plastic and solidified, granulated and pelletized, then solidified with sentiment or plastic and discarded.

  In addition, solid particle waste such as granular ion exchange resin, powder ion exchange resin, and filter aid that purify the condensate and waste water from the reactor are dehydrated and dried, and then mixed with cement and plastic to solidify. Processed and discarded.

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

  This centrifugal thin film dryer mainly has a vertically long cylindrical heat transfer cylinder with a heat transfer surface that evaporates and dries the drained water, and a rotating blade that scrapes off the waste liquid that has solidified and adheres to the heat transfer surface. Provided with a rotating shaft. In addition, a liquid supply pipe for supplying waste liquid is provided at the upper part of the heat transfer cylinder. The discharged liquid is supplied into the centrifugal thin film dryer from the supply pipe, and then touches the heat transfer surface heated to a predetermined temperature, and is solidified as the evaporation / drying of water proceeds. The rotating blade scrapes off the solidified waste liquid on the heat transfer surface to make it into powder, separates it, and drops it downward. The powdered effluent is finally discharged from a discharge port provided below the machine body.

  2. Description of the Related Art Conventionally, a technique for preventing sludge scaling generated on the inner surface of a heat transfer drum of a centrifugal thin film dryer and avoiding a decrease in heat transfer efficiency is known (see, for example, Patent Documents 2, 3, and 4).

JP-A 64-30601 JP 57-21901 A Japanese Patent Laid-Open No. 11-248353 JP 2011-33241 A

  The drainage liquid is supplied into the centrifugal thin film dryer via the 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 drainage. For this reason, before the waste liquid is supplied into the heat transfer cylinder, there is a problem that the waste liquid may be dried and solidified inside the liquid supply pipe and the liquid supply pipe may be blocked.

In order to solve this problem, it is conceivable to perform modification by adding an additive to the drainage to suppress the adhesion of the drainage 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 drainage 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 drainage or changing the shape of the supply pipe, and a practical solution cannot be obtained.

  Further, formation of a water-repellent film on the inner surface of the liquid supply pipe has been studied, but there is a problem in the resistance of the film, and further improvement has been desired.

  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 drainage on the surface of a 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 cylinder. A rotating shaft disposed at the axial center of the rotating shaft, and a blade that is provided radially on the rotating shaft and scrapes off the powder of the processing liquid generated on the heat transfer surface by concentration and drying. The inlet is provided with a pipe made of a water repellent material through which the processing liquid flows.

  According to the centrifugal thin film dryer according to the present invention, it is possible to suppress clogging associated with the drying and solidification of the drainage 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 expanded sectional view of the area | region II of the centrifugal thin film dryer of FIG. The principal part expanded sectional view of the expansion | extension pipe | tube shown in FIG. The principal part expanded sectional view which shows the other Example of the expansion | extension pipe | tube shown in FIG.

  Embodiments of the present invention will be described with reference to the accompanying drawings. In the present embodiment, the centrifugal thin film dryer according to the present invention is applied to an example used when performing a drying process in which a radioactive drainage generated during operation of a nuclear power plant is dried into a thin film and pulverized. To explain. In addition, this centrifugal thin film dryer can be applied also 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 ° C.) by supplying the heating steam supplied from the heating steam inlet 13.

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

  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 is opposed to the drainage inlet 16, and is provided so as to be rotatable integrally with the rotary shaft 19. The dispersion ring 21 reflects the drainage supplied from the drainage 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 cross-sectional view of region II of the centrifugal thin film dryer 1 of FIG.

  The drainage inlet 16 of the centrifugal thin film dryer 1 includes a drainage inlet nozzle 31 and an extension pipe 32 as an intubation inserted into the drainage inlet nozzle 31. It is composed of a double tube composed of the outer tube 42.

  The drainage inlet nozzle 31 is integrally formed by being joined to the heat transfer cylinder 11 by welding or the like. The drainage 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 drainage is detachably connected to the inlet nozzle flange portion 31a by bolts 35 and nuts 36.

  The extension pipe 32 is open at both ends, and has a configuration for supplying the 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 drainage inlet nozzle base 31.

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

  The extension pipe 32 is composed of a double pipe in which the inner pipe 41 is made of fluororesin and the outer pipe 42 is made of metal. The thickness of the inner tube 41 and the outer tube 42 is preferably 0.5 mm or more from the viewpoint of maintaining strength and preventing deformation, and 2 mm from the viewpoint of improving the workability by making the extension tube 32 more compact. The following is preferred.

  The material of the inner tube 41 constituting the inside of the double tube is preferably 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. From the viewpoint of heat resistance, water repellency, radiation resistance, and alkali resistance, PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) is particularly suitable for the fluororesin material constituting the inner tube 41.

  As a method of fixing the inner tube 41 to the outer tube 42, for example, a stopper is formed by overlay welding of stainless steel on the inner surface of the metal tube end portion (drainage drying portion inlet portion) of the outer tube 42. Yes. Conversely, a protrusion or a flange may be provided on the inner tube 41 side of the end portion (a portion away from the drainage drying unit inlet) 32b opened on the external pipe 33 side to serve as a stopper. Further, the inner tube 41 can be fixed in the outer tube 42 by applying an adhesive having excellent alkali resistance such as an inorganic adhesive between the inner surface of the outer tube 42 and the outer surface of the inner tube 41.

  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.

  A radioactive drainage generated during operation of the nuclear power plant and stored in a drainage storage tank (not shown) is supplied from the drainage 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 ° C. by supplying steam to the heating jacket 12.

  In the present embodiment, the radioactive drainage supplied to the centrifugal thin film dryer 1 is, for example, a sodium borate aqueous solution generated by neutralizing boric acid drainage with sodium hydroxide. In addition, the radioactive drainage supplied to the centrifugal thin film dryer 1 in the present embodiment is not limited to the drainage mainly composed of sodium borate, and other soluble and insoluble components are the main components. Even if it does, it is applicable.

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

  The radioactive drainage splashed on the heat transfer surface 15 flows down the heat transfer surface 15 by gravity. For this reason, a thin film of radioactive drainage is formed on the heat transfer surface 15. The radioactive drainage 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 drainage further flows down by gravity while being concentrated by evaporation of volatile components.

  The evaporating vapor derived from the radioactive drainage 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 drainage adhering to the heat transfer drum 11 in the form of 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 drainage dry powder discharge port 18. Discharged.

  Here, in the centrifugal thin film dryer 1, as the temperature of the heat transfer drum 11 heated by the steam rises, the temperature of the liquid supply pipe constituting the drainage inlet 16 is also raised. In addition, before the waste liquid is supplied to the heat transfer cylinder 11, 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 flow rate of the waste liquid cannot be supplied into the heat transfer cylinder 11. As a result, the drying efficiency of the centrifugal thin film dryer 1 is reduced.

  On the other hand, the centrifugal thin film dryer 1 in the present embodiment has an extension pipe 32 inserted in the drainage inlet nozzle base 31 constituting the drainage inlet 16 in order to prevent the above-described problems from occurring. The pipe 41 side is a double pipe made of fluororesin and the outer pipe 42 side is made of metal, which can prevent damage such as tearing due to drainage flow output, etc., and the supplied radioactive waste is condensed in the liquid supply pipe Adhering is suitably suppressed, and the drainage can be efficiently supplied into the heat transfer cylinder 11. Here, as a method of fixing the inner tube 41 made of fluororesin disposed inside the double tube to the metal tube on the outer tube 42 side, as shown in FIG. ) Was used to form the stopper 43 by overlay welding of stainless steel.

  Here, in order to confirm the effect of suppressing the adhesion of drainage due to the arrangement of the fluororesin inner pipe 41 inside the elongated pipe 32 inserted into the drainage inlet nozzle 31 as the drainage inlet 16, The test was carried out using a double pipe in which PFA as an inner pipe and stainless steel as an outer pipe were arranged. The thickness of each tube was 1 mm. A sodium borate aqueous solution was used as the drainage. The centrifugal thin film dryer 1 was continuously operated for 8 hours.

  As a result, the extension tube made of only stainless steel was clogged by drying and solidifying the drainage. On the other hand, in the extension pipe 32 of the centrifugal thin film dryer 1 using a double pipe in which PFA which is a kind of fluororesin is arranged in the inner pipe and stainless steel is arranged in the outer pipe, the clogging due to the dry solidification of the drainage is not caused. It was not seen and a good drying process could be performed.

  That is, by using a double pipe in which a fluorine resin such as PFA is disposed in the inner pipe and a metal such as stainless steel is disposed in the outer pipe, drying and solidification in the supply pipe can be suitably suppressed.

  According to this centrifugal thin film dryer 1, the temperature of the drainage inlet 16 is set by disposing the fluororesin in the inner pipe of the liquid supply pipe constituting the drainage inlet 16 that supplies the drainage to the centrifugal thin film dryer 1. It is possible to suitably suppress the drying and solidification of the drainage liquid accompanying the rise. For this reason, the centrifugal thin film dryer 1 can suitably perform the drainage treatment without reducing the drying efficiency.

  Moreover, blockage can be suppressed by forming the inner pipe 41 with respect to the piping, and an effect can be obtained simply and efficiently as compared with the modification of the drainage or the change of the shape of the liquid supply piping.

  The centrifugal thin film dryer 1 according to the present embodiment includes an extension pipe 32 that can be replaced according to the characteristics of the drainage, inside the liquid supply pipe (drainage inlet nozzle base 31) of the drainage inlet 16. The example in which the pipe 41 is a PFA and the outer pipe 42 is a stainless steel double pipe has been described. However, the pipe in which the inner pipe 41 is formed is not limited to the extension pipe 32, and in the case of a liquid supply pipe constituted by a pipe that does not have the extension pipe 32, a water repellent material is formed inside the liquid supply pipe. A tube may be placed.

  Further, in the case where there is a possibility that the inner pipe 41 may be scraped off by the dry powder derived from the drainage or the rotating structure at the end portion (the drainage drying unit inlet) in the extension pipe 32, it is shown in FIG. As described above, it is possible to delete the inner tube 41 only at the end portion where the phenomenon may occur so that only the outer tube 42 is provided.

  In this case, there is a possibility that a deposit accompanying the drying and solidification of the drainage liquid may be generated at the end portion. Can get enough.

DESCRIPTION OF SYMBOLS 1 Centrifugal thin film dryer 11 Heat transfer cylinder 12 Heating jacket 13 Heating steam inlet 14 Evaporating drain outlet 15 Heat transfer surface 16 Drainage inlet 17 Evaporating steam outlet 18 Drained liquid powder outlet 19 Rotating shaft 20 Rotating blade 21 Dispersion ring 22 Rotating blade mounting seat 31 Drainage 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 Inner pipe 42 Outer pipe 43 Stopper

Claims (8)

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 pipe made of a water-repellent material is disposed in the treatment liquid inlet through which the treatment liquid flows. The treatment liquid inlet is composed of a nozzle formed integrally with the heat transfer cylinder, and an intubation tube that is detachably inserted into the nozzle.
The inner tube is a double tube composed of an inner tube and an outer tube, wherein the inner tube is composed of a water repellent material, and the outer tube is composed of metal and holds the inner tube. The centrifugal thin film dryer according to claim 1.   The centrifugal thin film dryer according to claim 2, wherein only the outer tube is disposed at the end of the inner tube in the treatment liquid outlet side.   4. The centrifugal thin film dryer according to claim 3, wherein a stopper for the inner tube is formed by overlay welding of stainless steel on the inner surface of the outer tube end portion on the treatment liquid outlet side of the inner tube.   The centrifugal thin film dryer according to any one of claims 1 to 4, wherein the water repellent material is a fluororesin.   The fluororesin includes PTFE (polytetrafluoroethylene), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), ETFE (tetrafluoroethylene-ethylene). 6. The centrifugal thin film dryer according to claim 5, wherein the centrifugal thin film dryer is a member selected from a copolymer.   The centrifugal thin-film dryer according to any one of claims 2 to 6, wherein the metal constituting the outer tube is stainless steel.   The centrifugal thin film dryer according to any one of claims 1 to 7, wherein the treatment liquid is a radioactive drainage generated in a nuclear power plant.

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