JP4607005B2 - Waste liquid recycling method - Google Patents

Description

  The present invention relates to a waste liquid recycling method in which a waste liquid in which a solid component and a liquid component are mixed is separated into a solid component and a liquid component and reused respectively.

  As an example of a waste liquid in which a solid component and a liquid component are mixed, there is a waste coolant that is discharged when cutting or polishing an electronic component material such as a semiconductor wafer. In semiconductor wafer cutting processing and polishing processing, a coolant composed of hard material is added while cooling the semiconductor wafer by flowing a coolant, and the waste coolant is added to the liquid coolant as a solid component. This is a mixture of abrasives and semiconductor wafer processing waste (see Patent Document 1).

Conventionally, such waste coolant has been treated as industrial waste, which has been a problem because not only does this waste disposal cost enormous costs, but also the load on the environment increases.
Therefore, a waste liquid recycling method for separating the waste liquid generated in the semiconductor wafer cutting / polishing process into a solid component abrasive and processing waste and a liquid component coolant is proposed. (See Patent Document 2).

  In this waste liquid recycling method, solid sludge containing a large amount of solid components and liquid components are obtained by adding a diluent to the waste liquid containing a mixture of abrasives, processing waste, and coolant liquid to lower the viscosity, followed by centrifugation. And a distillation drying step for vaporizing the residual liquid component of the obtained solid sludge to dry powder the solid component, and this distillation drying includes a vibration drying device that heats the solid sludge while vibrating. It is used.

In this waste liquid recycling method, the solid component in the waste liquid can be separated and recovered from the coolant liquid, and the solid component thus obtained can be reused as, for example, a mold release agent. .
Japanese Patent Laid-Open No. 11-198816 JP 2003-225700 A

By the way, in the above-mentioned recycling method of waste liquid, first, solid waste having a solid component of, for example, about 85% is obtained by centrifuging the waste liquid. However, only by centrifugation, the solid component is contained in the separated liquid component. There is a possibility that it may be mixed in a minute amount, and there is a problem that it becomes impossible to effectively reuse the separated liquid component.
In addition, a vibration drying apparatus is used when drying solid sludge containing a large amount of solid components. This vibration drying device promotes the contact with the inner wall of the heated container by vibrating the solid sludge charged in the container and improves the drying efficiency. It was only moving and solid sludge could not be efficiently dried.

  The present invention has been made in view of the above circumstances, and it is possible to efficiently separate a waste liquid in which a liquid component and a solid component are mixed into a solid component and a liquid component, and to collect the liquid component with high purity. It aims at providing the recycling method of the waste liquid which can recycle | reuse both a solid component and a liquid component.

In order to achieve the above object, the present invention proposes the following means.
The invention according to claim 1 is a waste liquid recycling method in which a waste liquid in which a solid component and a liquid component are mixed is separated into the solid component and the liquid component, and the solid component and the liquid component are reused. A concentration step of evaporating the liquid component of the waste liquid using a thin film evaporator to produce a concentrated liquid of the solid component, and solid sludge obtained by centrifuging the waste liquid into the concentrated liquid A drying step for drying the mixed liquid using a stirring and drying device to obtain the solid component, and a collection step for liquefying and collecting the vaporized liquid component discharged in the concentration step and the drying step It is characterized by having.

  The waste liquid recycling method having this configuration includes a concentration step of generating a solid component concentrate using a thin film evaporator. The thin film evaporator has a cylindrical body, and inside this body is equipped with rotating blades that rotate at a high speed with a slight gap from the inner wall of the body, and the body is heated outside the body. A jacket to be placed is arranged. When waste liquid is supplied into the fuselage, a thin liquid film is formed in the slight gap between the rotary blade and the fuselage wall due to the centrifugal force generated by the rotation of the rotary blade, and the liquid component evaporates due to heating by contact with the fuselage wall. Thus, a concentrated liquid of the solid component is generated.

  In the drying step of drying the mixed solution obtained by adding solid sludge to the concentrated solution obtained in the concentration step, a stirring and drying device is used. This stirring / drying apparatus includes a cylindrical container and a stirring rotor that is rotatably inserted into the container and has stirring blades. In this stirring and drying apparatus, the mixed solution is supplied into a cylindrical container, and drying is performed while stirring the mixed solution with a stirring rotor.

  The recycling method of the waste liquid according to claim 2, wherein as the stirring and drying device, a cylindrical container and a plurality of stirrings that are rotatably inserted in the container and are provided at intervals in the axial direction and the circumferential direction. A stirring rotor having blades and a cylindrical floating rod inserted freely in the container, and when at least two of the plurality of stirring blades rotate the stirring rotor, A stirrer / dryer configured to have a flange portion that feeds the floating rod that is in contact with the inner peripheral surface so that a force directed inward in the radial direction of the stirring rotor is generated on the axis of the floating rod. It is characterized by that.

  In the waste liquid recycling method with this configuration, the stirring / drying device used in the drying step is provided with a floating rod inside the container, and is provided with a hook portion that allows the floating rod to float inside the container. Solid components and the like attached to the rotor and the inner wall of the container can be scraped off by the floating rod, and the rotation of the stirring rotor is not hindered by the adhesion of the solid components. Also, by moving the floating rod at the buttocks, it is possible to prevent the floating rod from pressing the inner peripheral surface of the container and causing abnormal noise and vibration when the floating rod is pushed up, and stirring and drying can be performed stably. Can do.

According to the first aspect of the present invention, since the thin film evaporator is used in the concentration step for evaporating and concentrating the liquid component of the waste liquid, the waste liquid can be brought into contact with the inner wall surface of the fuselage in a thin liquid film state. The heat transfer efficiency from the fuselage can be improved, and the waste liquid can be concentrated efficiently. In addition, since the liquid component is liquefied and then recovered, the liquid component is not mixed with the solid component, and the liquid component can be separated with high purity.
Moreover, since the stirring drying apparatus is used for the drying process of the liquid mixture of a concentrate and solid sludge, the liquid mixture can be dried efficiently. Also in this drying step, since the liquid component is vaporized and separated, the liquid component can be separated with high purity.

  According to the second aspect of the invention, since the stirring and drying can be performed stably without the solid component adhering to the stirring rotor and the inner wall of the container, the mixed liquid can be dried more efficiently. In particular, if the solid component is likely to be agglomerated, the agitation rotor may not be able to rotate due to the solid component adhering to the rotating body or the inner wall of the container, so use a stirrer / dryer equipped with a floating rod. Is preferred.

  As described above, according to the present invention, the waste liquid in which the liquid component and the solid component are mixed can be efficiently separated into the solid component and the liquid component, and the liquid component can be recovered with high purity. It is possible to provide a waste liquid recycling method that can be used.

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows an example of a waste coolant recycling method according to an embodiment of the present invention.
This recycling method 1 of the waste coolant W is to treat the waste coolant W in which an abrasive or processing waste is mixed in the coolant liquid (in this embodiment, the waste coolant W in which 1% of a solid component is mixed in the coolant liquid). is there.

First, the concentration process 2 which concentrates the solid component by evaporating the liquid component 2B of the waste coolant W using the thin film evaporator 10 is performed. A thin film evaporator 10 used in the concentration step 2 is shown in FIGS.
The thin film evaporator 10 includes a cylindrical body 11, a rotary blade 20 disposed inside the body 11, and a drive unit 26 that rotates the rotary blade 20.

  The body 11 includes a cylindrical body 12 that has a cylindrical shape, and side surface portions 13A and 13B that close openings at both ends of the cylindrical body 12. A waste coolant supply port 14 for supplying waste coolant W into the fuselage 11 is formed on one end side (left side in FIG. 2) of the fuselage 11, and a lower side is formed on the other end side (right side in FIG. 2) of the fuselage 11. A concentrate outlet 15 is formed through the wall, and a vapor outlet 16 is formed through the upper side wall. The vapor outlet 16 is equipped with a demister 16A that separates gas and liquid.

  Also, a jacket 17 is provided on the outer peripheral surface of the body 11 through which a fluid for heating the body 11 (high-temperature steam in this embodiment) flows from the one end side to the front side of the concentrate outlet 15. Yes. A steam inlet 18 through which high-temperature steam flows is provided at one end side of the jacket 17, and a drain outlet 19 penetrating the lower side wall surface is provided at the other end side of the jacket 17.

  The rotary blade 20 disposed inside the body 11 has a columnar shaft portion 21, which is disposed such that the axis of the shaft portion 21 coincides with the axis of the cylindrical body 12. One end side and the other end side of the projection protrude from the side surface portions 13A and 13B. One end side of the shaft portion 21 is rotatably supported by a driven bearing portion 22 provided outside the one end side surface portion 13A of the body 11, and the other end side of the shaft portion 21 is the other end side of the body 11. The main bearing portion 23 provided outside the side surface portion 13B is rotatably supported. A pulley 27 is provided on the other end side of the shaft portion 21 protruding from the main bearing portion 23, and the pulley 27 is connected to a motor 29 via a belt 28. The pulley 27, the belt 28, the motor 29, Constitutes the drive unit 26.

On one end side of the outer peripheral surface of the shaft portion 21, there are a plurality of support columns 24 extending in the radial direction of the shaft portion 21 and reaching the vicinity of the inner peripheral surface 12A of the body 11 (cylindrical body 12) in the circumferential direction (this embodiment). In the embodiment, six are provided as shown in FIG. The rotary blade 20 has a cylindrical blade portion 25 formed so as to connect the most radially outer portion of the column portion 24, and the axis of the cylinder formed by the cylindrical blade portion 25 and the axis of the cylindrical body 12 Are formed to match.
In addition, as shown in FIG. 2, the cylindrical blade portion 25 is formed in a portion where the jacket 17 is disposed from one end side of the body 11, and from the portion where the concentrate outlet 15 is formed to the other end side. In other words, the cylindrical blade portion 25 is not formed, and only the shaft portion 21 is arranged.

In the thin film evaporator 10, high-temperature steam is supplied from the steam inlet 18 of the jacket 17, and the cylindrical body 12 of the body 11 is heated. The high-temperature steam becomes water (liquid) when the cylindrical body 12 is deprived of heat, and is discharged from the drain outlet 19 formed on the lower wall surface on the other end side of the jacket 17.
Further, the rotary blade 20 is rotated around the axis of the shaft portion 21 by the drive unit 26, and in the portion where the cylindrical blade portion 25 is provided, the inner peripheral surface of the cylindrical body 12 of the body 11 and the outer periphery of the cylindrical blade portion 25. A slight gap S is formed between the surfaces.

When the waste coolant W is supplied into the body 11 from the waste coolant supply port 14, the waste coolant W is thin in the gap S between the inner peripheral surface of the cylindrical body 12 and the outer peripheral surface of the rotating cylindrical blade portion 25. Will be formed. The waste coolant W thus formed into a thin liquid film comes into contact with the cylindrical body 12 heated by high-temperature steam, and the liquid component 2B in the waste coolant W is evaporated and vaporized, and the solid component is concentrated. The concentrated liquid 2A is produced. Here, in this embodiment, in this concentration step 2, the liquid component 2B occupying 50% of the waste coolant W is evaporated, and the concentrated liquid 2A is 49% of the liquid component of the original waste coolant W, solid. It is supposed to contain 1% of the component.
The produced concentrated liquid 2 </ b> A is taken out from the concentrated liquid outlet 15 formed on the lower side wall surface on the other end side of the body 11, and the vaporized liquid component 2 </ b> B is discharged from the vapor outlet 16.

Next, a drying step 3 is performed by drying the mixed solution obtained by adding solid sludge to the concentrated solution 2A obtained in the concentration step 2 using the stirring and drying device 30 to obtain a dried product 3A made of solid components. A stirring and drying apparatus 30 used in the drying step 3 is shown in FIGS.
As shown in FIGS. 7 and 8, the agitation / drying device 30 includes a cylindrical container 31, an agitation rotor 40 that is rotatably disposed in the container 31, and an idle movement that is freely disposed in the container 31. Rod 50.

The container 31 includes a container body 33 that is horizontally placed on a base and has side walls 32A and 32B provided at both ends, and a jacket (not shown) that is provided so as to cover the outer periphery of the container body 33. .
The container body 33 has a cylindrical shape, and a raw material inlet 34 for supplying the concentrate 2A and solid sludge is provided at the upper part of one end (right side in FIG. 4). A production outlet 35 for producing a dry product 3A obtained by drying a mixture of the concentrated liquid 2A and the solid sludge is provided. In addition, a bag filter 36 connected to a vacuum device (not shown) is provided at the upper part of the center of the container body 33.

As shown in FIGS. 5 to 8, the agitation rotor 40 includes an agitation rotor body 41 whose outer shape is cylindrical, and a plurality of agitation blades 42 provided in the axial direction and the circumferential direction of the agitation rotor 40. It can be rotated in the direction of arrow A by a drive source (not shown) provided outside the container 31.
In addition, a flow path (not shown) through which high-temperature steam as a heat medium can be introduced is formed inside the stirring rotor body 41.

  As shown in FIGS. 5 and 6, the plurality of stirring blades 42 are provided on the circumferential surface of the stirring rotor body 41, on the intersection of the spiral locus and the linear locus on the circumferential surface of the stirring rotor body 41. The rotor body 41 is provided with an interval in the axial direction and the circumferential direction. This spiral trajectory is arranged so as to be in the direction of the arrow A shown in FIG. 5 or FIG. 6 from both ends of the stirring rotor body 41 toward the substantially center of the stirring rotor body 41. Further, the linear trajectories are arranged so as to be equidistant in the circumferential direction at four locations on the circumferential surface of the stirring rotor body 41 parallel to the axis of the stirring rotor body 41. A circle whose axis is arranged parallel to the axis of the agitating rotor body 41 between the agitating blade 42 arranged on the linear locus and the agitating blade 42 arranged on another adjacent linear locus. A columnar floating rod 50 is provided.

  As shown in FIGS. 5 and 6, the stirring blade 42 has a plate shape formed so as to gradually become thinner from the proximal end connected to the stirring rotor body 41 toward the radially outer tip of the stirring rotor body 41. The member has a trapezoidal cross section. The stirring blades 42 are formed such that when the stirring rotor 40 rotates in the direction of arrow A, the radially outer end of the stirring rotor 40 on the front surface 42a in the rotation direction is perpendicular to the rotation direction. Has been. In addition, on the outer side in the radial direction of the stirring rotor 40 on the surface 42b on the rear side in the rotational direction of the stirring blade 42, one side close to the center of the stirring rotor body 41 is positioned forward in the rotational direction with respect to the other side. The rear surface 42b in the rotational direction is inclined so as to face the center of the stirring rotor body 41.

  Further, the stirring blade 42 is hollow and is connected to the flow path of the stirring rotor body 41. As a result, the high-temperature steam flowing through the stirring rotor main body 41 also flows into the stirring blade 42, and the stirring blade 42 is heated. Further, a flange member 43 is provided at the tip of at least one stirring blade 42 among the plurality of stirring blades 42 provided on the same linear locus.

  The flange member 43 is a plate-like member and is provided on any one of the side surfaces of the stirring blade 42 in the axial direction of the stirring rotor 40. Further, the flange member 43 has a trapezoidal shape formed so that the width thereof gradually decreases from the tip, which is one end on the radially outer side of the stirring rotor 40, toward the radially inner side. When the stirring rotor 40 rotates in the A direction, the gutter member 43 causes the floating rod 50 that is in contact with the inner peripheral surface 33A of the container main body 33 to face radially outward of the stirring rotor 40 rather than in the rotating direction. Instead, the floating rod 50 is sent out so as to scoop so that a force directed inward in the radial direction of the stirring rotor 40 is generated on the axis of the floating rod 50.

  In the stirring and drying device 30, the liquid mixture of the concentrated liquid 2A and the solid sludge is dried as follows. First, high-temperature steam as a heat medium is introduced into the stirring rotor body 41. Thereby, the some stirring blade 42 is heated with the high temperature steam which distribute | circulates an inside. Moreover, the container main body 33 is heated by introducing high-temperature water vapor as a heat medium into a jacket provided on the outer peripheral surface of the container main body 33. Further, the inside of the container 31 is depressurized by a vacuum device connected to the bag filter 36. In this state, the stirring rotor 40 is rotated in the direction of arrow A.

  Then, the concentrated liquid 2 </ b> A and the solid sludge are supplied into the container 31 from the raw material inlet 34. The supplied concentrated liquid 2A and solid sludge are mixed and placed on the inner peripheral surface 33A on the lower side of the container body 33, and are stirred by the rotation of the stirring rotor 40. Moreover, the liquid mixture of the concentrated liquid 2A and the solid sludge is dried by contacting the stirring blade 42 heated by the high-temperature steam and the inner peripheral surface 33A of the container body 33. At this time, the solid component of the mixed solution may become agglomerated in the middle of stirring and drying the mixed solution and adhere to the stirring blade 42 or the inner peripheral surface 33A of the container body 33.

Here, when the stirring blade 42 shifts from the vertically downward state to the horizontal state, the floating rod 50 is pushed up along the inner peripheral surface 33 </ b> A of the container body 33 while being supported by the stirring blade 42. At this time, the floating rod 50 drops the solid component adhering to the inner peripheral surface 33A of the container body 33 while moving.
Here, the stirring blade 42 pushes up the floating rod 50 along the inner peripheral surface 33A of the container body 33, but the gutter member 43 is arranged in the radial direction of the stirring rotor 40 along the axis of the floating rod 50 as the stirring rotor 40 rotates. Send it out in a way that generates inward force. That is, it is avoided that the floating rod 50 is pressed toward the inner peripheral surface 33 </ b> A of the container main body 33 by the flange member 43.

Next, when the stirring blade 42 shifts from the horizontal state to the vertically upward state, the floating rod 50 moves along the front surface 42a in the rotational direction of the stirring blade 42 from the radially outer side of the stirring rotor 40 to the axis of the stirring rotor 40. Move towards. At this time, the floating rod 50 drops the solid component adhering to the front surface 42a in the rotational direction of the stirring blade 42 while moving.
Thereafter, when the stirring blade 42 shifts from the vertically upward state to the horizontal state, the stirring rod 40 moves from the axis of the stirring rotor 40 along the surface 42b on the rear side in the rotation direction of the stirring blade 42 disposed in the front in the rotation direction. 40 moves radially outward and contacts the inner peripheral surface 33A of the container body 33. At this time, the floating rod 50 drops the solid component adhering to the surface 42b on the rear side in the rotation direction of the stirring blade 42 while moving.

Subsequently, when the stirring blade 42 shifts from the horizontal state to the vertically downward state, the floating rod 50 moves downward along the inner peripheral surface 33 </ b> A of the container body 33 while being supported by the stirring blade 42. At this time, the floating rod 50 drops the solid component adhering to the inner peripheral surface 33A of the container body 33 while moving.
When the stirring blade 42 shifts from the vertically downward state to the horizontal state, the floating rod 50 is left at the bottom of the inner peripheral surface 33A of the container body 33, but as described above, the stirring blade located behind the rotation direction. 42 is pushed up along the inner peripheral surface 33 </ b> A of the container main body 33.

In this way, by drying the mixed liquid of the concentrated liquid 2A and the solid sludge while stirring, a dry product 3A in which the solid components are dried is obtained and produced from the production outlet 35. The liquid product 3A is almost free of liquid components, and is composed of 1% solid component of the original waste coolant W and solid component of solid sludge.
The liquid component 3B removed by drying is discharged out of the container 31 through the bag filter 36.

  Next, the recovery / liquefaction step 4 for recovering and liquefying the liquid component 2B discharged in the concentration step 2 and the liquid component 3B discharged in the drying step 3 will be described. Both the liquid component 2B discharged in the concentration step 2 and the liquid component 3B discharged in the drying step 3 exist in a gas state. In the recovery / liquefaction step 4, these gases are recovered and cooled to liquefy and recover the liquid components 2B and 3B that have become gases. The recovered coolant liquid 4A is composed of 99% of the liquid component of the original waste coolant W and does not contain any solid component.

  In the recycling method 1 of the waste coolant W according to the present embodiment, the thin film evaporator 10 is used in the concentration step 2 for concentrating solid components, and the inside of the body 11 heated with the waste coolant W in a thin liquid film state. Since it can be made to contact 12 A of surrounding surfaces, evaporation of the liquid component 2B is accelerated | stimulated and solid component can be concentrated efficiently. In addition, since the heating and evaporation of the liquid component 2B are performed in a short time, it is possible to prevent deterioration due to the heat of the coolant that is the liquid component 2B.

In addition, the stirring / drying device 30 is used in the drying step 3 for drying the mixed liquid of the concentrated liquid 2A and the solid sludge, the mixed liquid can be sufficiently stirred, and the mixed liquid can be efficiently dried. . Further, since the floating rod 50 is provided inside the container 31 of the stirring and drying device 30, when the solid component adheres to the stirring rotor 40 and the inner peripheral surface 33A of the container 31 while the mixed liquid is being dried, The solid component can be scraped off by the floating rod 50, and the rotation of the stirring rotor 40 is not hindered, so that the mixed liquid can be reliably and efficiently dried.
In addition, since the stirring / drying device 30 is provided with the eaves member 23 for allowing the floating rod 50 to move freely in the container 31, the floating rod 50 presses the inner peripheral surface 33A of the container 31 when the floating rod 50 is pushed up. Thus, abnormal noise and vibration can be prevented, and stirring and drying can be performed stably.

Further, in the concentration step 2 and the drying step 3, the coolant that is the liquid components 2B and 3B is vaporized and discharged, and the solid components are not mixed by recovering and liquefying the vaporized liquid components 2B and 3B. A highly pure coolant liquid 4A can be obtained.
The coolant liquid 4A obtained by the recycling method 1 of the waste coolant W according to the present embodiment has high purity and can be reused as the coolant liquid again. In addition, the solid product dry product 3A is in a state where abrasives and processing waste are mixed, but can be reused as an abrasive during roughing before finishing or as a mold release agent. .
As described above, according to the present embodiment, the waste coolant W can be efficiently separated into the dry product 3A as a solid component and the coolant liquid 4A as a liquid component, and the coolant 4A can be recovered with high purity and is a solid component. Both the dried product 3A and the coolant 4A can be reused.

In this embodiment, the recycling method for waste coolant in which abrasives and processing waste are mixed in the coolant liquid has been described. However, the present invention is not limited to this, and the liquid component and the solid component of other waste liquid are separated. It may be a recycling method.
Further, the recycling method for treating the waste coolant in which 1% of the solid component is mixed in the coolant liquid has been described. However, the present invention is not limited to this, and the waste liquid in which the solid component is mixed to such an extent that it can be charged into the thin film evaporator. If it is.

  Further, concentration and drying may be performed in a state in which a decompression means is provided in a thin film evaporation apparatus used in the concentration process and a stirring and drying apparatus used in the drying process to decompress the body. In this case, it is preferable because the liquid component can be evaporated at a lower temperature than when it is performed at atmospheric pressure, concentration and drying can be performed more efficiently, and alteration of the liquid component due to heat can be prevented.

It is process drawing which shows the process of the recycling method of the waste coolant which is embodiment of this invention. It is side surface sectional drawing of the thin film evaporator used in the concentration process of FIG. It is XX sectional drawing in FIG. It is a side surface fragmentary sectional view of the stirring drying apparatus used at the drying process of FIG. It is a side view of the stirring rotor with which the stirring drying apparatus shown in FIG. 4 was equipped. It is an expanded view which shows the arrangement | positioning state of the stirring blade provided in the stirring rotor of FIG. It is YY sectional drawing in FIG. It is YY sectional drawing in the state which rotated the stirring rotor of FIG.

Explanation of symbols

1 Waste coolant recycling method (Waste liquid recycling method)
2 Concentration step 2A Concentrate 3 Drying step 3A Dry product (solid component)
4 Collection / liquefaction process (collection process)
4A Coolant liquid (liquid component)
DESCRIPTION OF SYMBOLS 10 Thin film evaporator 30 Stirrer / dryer 31 Container 33A Inner peripheral surface 40 Stirring rotor 42 Stirring blade 43 Scissor member (saddle part)
50 Idle rod W Waste coolant (waste liquid)

Claims (2)

A waste liquid in which a solid component and a liquid component are mixed is separated into the solid component and the liquid component, and the waste liquid is recycled by reusing the solid component and the liquid component, respectively.
A concentration step in which the liquid component of the waste liquid is evaporated using a thin film evaporator to produce a concentrate of the solid component, and a mixture obtained by adding solid sludge obtained by centrifuging the waste liquid to the concentrate A drying step of drying the liquid using a stirring and drying device to obtain the solid component, and a concentration step and a recovery step of liquefying and recovering the vaporized liquid component discharged in the drying step. A recycling method for waste liquid.   The stirring and drying device includes a cylindrical container, a stirring rotor that is rotatably inserted in the container and has a plurality of stirring blades provided at intervals in the axial direction and the circumferential direction, and the container. And a cylindrical floating rod inserted freely so that at least two of the plurality of stirring blades are in contact with the inner peripheral surface of the container when the stirring rotor is rotated. On the other hand, the waste liquid recycling method according to claim 1, further comprising a flange portion that feeds the axis of the floating rod so that a force directed radially inward of the stirring rotor is generated.

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