JPH084681B2 - Mixer settra extractor with perforated walls - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a mixer-settler extractor with a porous wall.

(Prior Art) Generally, a mixer-settler extractor is a mixer chamber that performs a mixing and stirring operation to extract a target substance in one liquid phase into another phase between two different liquid phases, and a mixer chamber connected to the mixer chamber for mixing and dispersing. It is composed of a settler chamber that separates the liquid phase into the original two liquids. This type of extractor has the advantage that extraction equilibrium is achieved relatively easily and the stage efficiency per unit is 95% or more in terms of extraction equilibrium achievement rate, because sufficient agitation is performed in the mixer chamber. ing. For this reason, the mixer-settler extractor has been used on a large scale especially for refining and reprocessing of nuclear fuel. It has a gravity type with the simplest structure, a pump type mixer-settler extractor with a large processing flow rate, and a high-speed centrifugal separation type. Mixer-settler extractors have been developed.

To use the mixer-settler as a multi-stage continuous extractor,
It is necessary to select the optimal type such as structure and operability. Generally speaking, it is difficult for the gravity type to have multiple stages, and the centrifugal type is often used as a pump type because the structure is too complicated.
However, the pump-type mixer-settler extractor has a drawback that the volume of the settler chamber is 3 to 10 times larger than that of the mixer chamber.

By the way, the increase in the amount of the extractor and the solvent contained therein causes the following problems particularly in the reprocessing of nuclear fuel. Specifically, the residence time in the extractor becomes longer and the organic solvent undergoes radiolysis, and the amount of nuclear fuel material retained in the device increases, so attention must be paid to the criticality safety, or There has been a problem such as an increase in the size of the shield that encloses the entire extraction device, which has been a cause of reducing the economical efficiency of the reprocessing plant using the mixer-settler. Also, in principle, the mixer-settler extraction method should be effective for the purpose of general chemical sample analysis and separation / preparation as well as the ion-exchange column method, but the large settler portion makes it a good separator. It reduces efficiency, which is why it is rarely used in reality.

In the conventional mixer-settler extractor, it passes over a partition plate that is partitioned between the mixer chamber and the settler chamber by overflow, or a window is opened in the partition plate, and this window serves as a passage for the mixed liquid. ing. In the extraction operation, first, two different phases such as an aqueous phase and an organic phase are supplied to the mixer chamber and mixed by a stirrer, and one phase is dispersed as droplets in the other phase to form a so-called dispersed phase. . Another role of agitation is to create a circulating flow in the mixer chamber. Since the extraction reaction proceeds while the dispersed phase is circulating in the mixer chamber, one method is to increase the rotation speed of the stirrer and increase the circulation flow rate in order to increase the extraction efficiency. When the number of revolutions of the stirrer becomes higher, the dispersed phase droplets become smaller, but when the dispersed phase droplets become too small, it takes longer for the droplets to aggregate and separate into the original two phases in the extractor. Overall efficiency is reduced. Furthermore, when the droplets become small and become an emulsified state, they do not easily return to the original two phases and flow out of the extractor as they are, making separation work impossible. Therefore, an appropriate stirring rotation speed is selected depending on the liquid-liquid phase separation ability of the settler chamber.

The formation of the dispersed phase by stirring is understood to be that the kinetic energy given to the fluid by stirring partially becomes surface energy to form droplets. Therefore, in order for the mixed solvent containing the dispersed phase to quickly return to the original two phases, it is important to quickly remove the kinetic energy of the dispersed phase and the surface energy of the liquid droplets that have come out of the mixer chamber.

In the conventional method, the dispersed phase directly brought the kinetic energy and surface energy obtained in the mixer chamber to the settler chamber,
It took time to release these energies in the settler chamber. That is, it was necessary to lengthen the retention time of the solvent in the settler chamber to secure the release time. If the residence time cannot be made sufficiently long, a so-called flooding phenomenon occurs in which the mixed dispersed phase does not separate into two phases and goes out of the extractor. This is the reason why the conventional mixer-settler extractor has a large settler volume. Conventionally, a baffle plate is placed in the settler chamber to suppress the spread of the dispersed phase, but the effect of the baffle plate is to accumulate the dispersed phase in a part of the settler chamber, and it is essentially the dispersed phase itself. It is known that it does not reduce the volume.

Next, the droplet size generated by the rotation of the stirrer in the mixer chamber is widely distributed from small to large, and the large droplet has a slow extraction equilibrium achievement rate, which is the rate-determining effect of the extraction reaction in the mixer chamber. Become. Further, if the number of revolutions of the stirrer is increased to eliminate large liquid droplets, very fine liquid droplets are generated and the extraction time is shortened, but there is a problem that it takes time to aggregate in the settler chamber.

(Problems to be Solved by the Invention) The present invention has been made in view of the above circumstances, and an object thereof is to provide a mixer-settler extractor having a small settler volume, a short extraction time, and a high extraction efficiency. is there.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention is a pump-type mixer-settler extractor including a mixer chamber having an agitator and a settler chamber communicating with the mixer chamber. In, a mixer settra extractor with a porous wall in which a porous wall made of a porous material is formed in at least a part of the partition between the mixer chamber and the settler chamber, and the mixer-settler extraction with the porous wall It is also characterized in that the container is configured in multiple stages.

 Next, the principle of the present invention will be described.

If a partition wall made of an appropriate porous material is provided here without opening between the mixer chamber and the settler chamber, the porous wall will have an appropriate resistance to the flow of the two-phase liquid mixture containing the dispersed phase, and Unlike the baffle plate, it absorbs the kinetic energy of fluid.
Furthermore, the porous wall forms a thin channel inside it and thus has a large surface area, and while the dispersed phase droplets flow through this narrow channel, they collide with the surrounding wall and lose the surface energy of the droplet. As a result, they are aggregated into larger droplets. The absorption of kinetic energy and the agglomeration due to droplet collision described above are the main actions of the porous wall.

Further, as another function, there is a classification (sieving) function for the dispersed phase droplets on the porous wall. That is, among the liquid droplets reaching the porous wall surface in the mixer chamber, the liquid droplets having a cross section smaller than the pore cross-section of the surface immediately flow into the holes, while the liquid droplets having a cross-sectional area larger than the hole are , Or a part of which is divided and becomes a small particle size flows into the porous wall, and the rest returns to the mixer chamber and circulates. Therefore, in order to eliminate large droplets, it is not necessary to increase the rotational speed of the stirrer so much and extremely small droplets need not be formed.

Further, when the inside of the porous wall has a structure in which packed layers or porous plates are laminated, the dispersed mixed phase flows in the packed phase having a large surface area, so that the mixed contact of the two phases is promoted and the extraction is performed. It can be expected that the reaction proceeds rapidly like a packed column, as a side effect.

The pore size of the porous wall is important for the reasons mentioned above. If it is too large, it does not serve as a porous wall.

The porous wall structure of the present invention is the optimum condition found as a result of such studies. If the retention time is 1 minute or less, the droplets with a radius of 3 mm or less have reached the extraction equilibrium, so it is necessary that these be porous walls through which they can pass. That is, a hole having a radius of 3 mm or less or a cross-sectional area of about 30 mm ² or less is used. In the case of the extraction process in which the retention time in the mixer may be long, the diameter of the liquid droplet is also large, and thus the cross section of the porous wall hole is also large. For example, if the retention time is about 10 minutes, the maximum cross section of the droplet may be as large as 100 mm ² , and a hole of this size is effective. In the actual preparation of the porous wall, it is unavoidable that there is a distribution in the size of the beads as the raw material and the size of the pore diameter of the porous plate. The amount of beads or pores that deviate from the area described in the claims does not cause a significant deterioration in properties as long as the total cross-sectional area of those beads and pores is within 10% of the total cross-sectional area of all beads and pores, and it is acceptable to use. . However, in the case of small particle size glass beads, they are packed closely, so
The flow resistance of the liquid passing therethrough becomes large.

The material of the porous wall may be any material as long as it is physically and chemically stable to the solution and solvent with which it comes into contact. For example, stainless steel, ceramics, glass, fluorine resin, etc. are generally used. It is a material. In addition, various metal materials, carbon materials, organic plastic materials and the like can be used. Further, the perforated wall is formed by laminating one or more nets or cloth-like ones, and it is desirable that the mesh lattice spacing of each net or cloth is 10 mm or less on average.

By the way, although the result of introducing the porous wall into the mixer-settler extractor is shown in the example, the settler chamber which required a volume three times or more that of the conventional mixer chamber becomes smaller than the mixer chamber,
The volume of the apparatus including the settler chamber and the porous wall portion is about the same as or smaller than that of the mixer chamber. Further, the amount of the extraction treatment liquid retained in the porous wall portion and the settler chamber is about half the amount retained in the mixer chamber, and the solvent extraction becomes remarkably efficient. Furthermore, due to the decrease in the volume of the settler chamber, the residence time of the extract in the mixer-settler is shortened, and 0 per stage.
It will be possible to set it to about 5 to 1 minute. Therefore, a continuous extractor in which 10 to 20 mixer-settlers are connected can be operated very efficiently.

(Operation) According to the mixer-settler extractor with a porous wall of the present invention, the settler chamber becomes smaller than the mixer chamber, and the volume of the settler chamber is reduced, and the residence time of the extract in the mixer-settler is shortened and 10 to 20 stages are connected. The continuous extractor can be operated very efficiently.

(Example) The Example of this invention is described with reference to drawings.

FIG. 1 (a) is a schematic configuration diagram of an embodiment of the present invention, in which the mixer-settler extractor 1 with a porous wall is shown.
Is composed of a mixer chamber 2, a settler chamber 3, and a porous layer 4 arranged between both chambers, and a mixer 5 is provided in the mixer chamber 2. In addition, nozzles 6a and 6b for inflowing different two-phase liquids are provided in the mixer chamber.
On the other hand, a nozzle 7a and a nozzle 7b for taking out the two liquids phase-separated are arranged in the settler chamber.

As the porous layer, spherical particles having a diameter of 1 cm or less, particles having a volume-equivalent volume thereof are packed in layers, or particles having this shape are sintered into a plate-like porous layer (first
Figure b), or one or more nets or cloths that are piled up, and the mesh grid spacing of each net or cloth is 10 on average.
A porous wall having a size of less than or equal to mm (Fig. 1c) or a plate or a thin film having at least one through hole having a cross-sectional area of 100 mm ² or less is used (Fig. 1). d) may be used.

FIG. 2 is a schematic configuration diagram of another embodiment of the present invention, which shows the case where uranium is purified using the porous wall mixer-settler extractor 1. Mixer room 2 has an effective volume of 10
, The settler chamber 3 has an effective volume 4 and is filled with glass beads 4a (average diameter 2 mm) in a thickness of 1 cm between them, and further in contact with it, large glass beads 4b (average diameter 5 mm) 1.3
A porous layer 4 filled with a thickness of cm is provided. A 3 mol / nitric acid aqueous solution containing hexavalent uranium (uranyl nitrate) at a concentration of 0.1 mol / n and an n-dodecane solvent containing 30% by weight of TBP were supplied to the mixer chamber 2 at a flow rate of 10 / min for both the aqueous solution and the solvent. The stirrer 5 in the mixer chamber 2 had a four-piece root length of 10 cm and a rotation speed of 500 rpm. Under this condition, the dispersed phase does not cause flooding and the aqueous solution and the solvent are separated into each phase from the settler chamber 3 and the extractor 1
Taken out. Further, in the single-stage extraction operation under these operating conditions, the extraction efficiency of uranium was 95%, and the processing time (retention time from entering the mixer chamber to leaving the settler chamber) was about 45 seconds.

FIG. 3 is a schematic configuration diagram in which the porous wall mixer-settler extractor 1 is provided in multiple stages.

The mixer-settler extractors 1A, 1B, 1C and 1D with porous walls are connected between four extractors via a pump 8 for transferring a two-phase liquid. Each mixer-settler extractor 1A, 1B, 1C, 1D consists of a mixer chamber 2A, 2B, 2C, 2D with an effective volume of 500 ml and a settler chamber 3A, 3B, 3C, 3D with an effective volume of 200 ml, and a 0.1 mm thick stainless steel between them. Five steel perforated plates (holes with a diameter of 0.2 mm are drilled on the entire surface) are stacked at 1 mm intervals and connected to them, and stainless steel plates with holes with a diameter of 1,2,3,4,5 mm The porous layers 4A, 4B, 4C and 4D are provided by laminating each one in this order at 1 mm intervals. 0.5mo to the first stage extractor 1A
It is supplied to the mixer chamber 2A at a flow rate of 3 mol / nitric acid aqueous solution containing l / uranyl nitrate (U 120 g /) at 500 ml / min., and the same amount is withdrawn from the settler chamber 3A by the pump 8, and the second stage extractor 1B Send to mixer room 2B. On the other hand, n-dodecane solvent containing 30V% of TBP is supplied to the 4th stage mixer chamber 2D at a flow rate of 500 ml / min, and the same amount is withdrawn from the 4th stage setter chamber 3D and is fed to the 3rd stage mixer chamber 2C. send. Thus, uranium was extracted by countercurrent contact using the four-stage mixer-settler extractor.

As a result, the uranium concentration of the aqueous solution discharged from the fourth-stage mixer-settler was 0.01g / = 10ppm, and the uranium concentration in the organic solvent discharged from the first-stage mixer-settler was 0.4mol /. . The extraction efficiency of uranium at each stage was as high as 95% of the equilibrium value.

FIG. 4 (a) is a schematic configuration diagram of another example in which the porous wall mixer-settler extractor of the present invention is used in multiple stages.
In this example, the mixer chamber 11 of the porous wall mixer-settler extractor 10 is provided with an agitator 15 and the settler chamber 12 is shown as a multistage continuous extractor having a transfer pump 14 built therein.

In the figure, each mixer chamber 11 has a capacity of 150 ml and a settler chamber 1
2 is a volume of 50 ml, the part of the porous wall 13 placed between them is 5
It has a volume of 0 ml. The outlet of each settler chamber pump is a three-way valve, and the extracted liquid separated in the settler chamber 12 is sent to the next stage or sent out of the extractor as a treated liquid. Each mixer chamber 11 is supplied with the extraction liquid from the adjacent settler chamber 12 and has an inlet 16 for supplying the extraction liquid from the outside. With these inlets and outlets, the extraction liquid can be exchanged or the composition of the solution can be changed at any stage. Three 200 mesh stainless nets were stacked at 4 mm intervals between the mixer chamber 11 and the settler chamber 12, and a plate made by sintering stainless beads having a total diameter of 2 layers was inserted between the nets. Further, a plate having a thickness of 8 mm obtained by sintering graphite beads having a diameter of 4 mm is attached to the exit side of the porous wall composed of the mesh and the beads.

Next, a specific example in which uranium and thorium are separately extracted by using the above-mentioned multistage continuous extractor will be described with reference to FIG. 4 (b).

50 ml / min of NHO ₃ aqueous solution containing uranium and thorium at a concentration of 0.1 mol / min was added to the extractor at one end of this multistage continuous extraction device.
, And dodecane containing 30% TBP at a flow rate of 50 ml at the other 10th stage to perform countercurrent extraction. However, the TBP organic phase is once taken out of the extractor in the sixth step, and new 30% TBP / n dodecane is supplied again at a flow rate of 50 ml / min in the fifth step.
Concentrated nitric acid is added to the sixth stage at a flow rate of 10 ml / min.
In FIG. 4 (b), the flow of the extract is indicated by the arrow. As a result of these operations, 0.1 mol / uranium extracted organic phase was obtained from the 1st stage outlet, and 0.1 mol / uranium was extracted from the 6th stage outlet.
An organic phase obtained by extracting thorium was obtained.

[Effects of the Invention] As described above, according to the present invention, the retention time of the extract in the mixer-settler extractor is shortened due to the decrease in the volume of the settler chamber, so that the continuous extractor connected in multiple stages operates very efficiently. It has the excellent effect of being able to.

[Brief description of drawings]

FIG. 1 (a) is a schematic sectional view of an embodiment of the present invention, and FIGS. 1 (b) to (d) are perspective views of another example of the porous layer of FIG. 1 (a), and FIG. Is a schematic configuration diagram of another embodiment of the present invention,
FIG. 4 is a schematic configuration diagram in which the mixer-settler extractors of the present invention are connected in multiple stages, FIG. 4 (a) is another schematic configuration diagram in which the mixer-settler extractors of the present invention are connected in multiple stages, and FIG. 4 (b) is the same diagram. It is a figure which shows the flow of the extract of (a). 1,1A ~ 1D, 10 ... Mixer with a porous wall Setra extractor 2, 2A ~ 2D, 11 ... Mixer chamber 3, 3A ~ 3D, 12 ... Setra chamber 4, 4A ~ 4D, 13 ... Porous wall 5, 15 …… Stirrer 8,14 …… Pump

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masakazu Ota 1-1-7 Uchisaiwaicho, Chiyoda-ku, Tokyo Inside Nihon Nuclear Power Co., Ltd. (72) Inventor Junichi Taga 1-1-1, Shibaura, Minato-ku, Tokyo Toshiba Corporation Head Office

Claims (6)

[Claims] 1. A mixer-settler extractor comprising a mixer chamber having an agitator and a settler chamber communicating with the mixer chamber, wherein a porous wall made of a porous material is formed at a partition between the mixer chamber and the settler chamber. A mixer-settler extractor with a porous wall characterized in that 2. The porous wall is formed by layer-filling spherical particles having a diameter of 1 cm or less, or particles volumetrically equivalent thereto, or by sintering particles of this shape into a plate shape. The mixer-settler extractor with a porous wall according to item 1. 3. The method according to claim 1, wherein the perforated wall is formed by laminating one or more mesh-like or cloth-like ones, and the mesh lattice spacing of each mesh or cloth is 10 mm or less on average. Mixer settler extractor with porous walls. 4. The porous wall has a plate or thin film shape and a cross-sectional area of
The mixer-settler extractor with a porous wall according to claim 1, wherein at least one sheet having a large number of through holes of 100 mm ² or less is used. 5. The mixer-settler extractor with a porous wall according to claim 1, wherein the porous wall is a combination of the porous materials according to claims 2 to 4. 6. A mixer-settler extraction with a porous wall in which a mixer chamber having a stirrer, a settler chamber communicating with the mixer chamber, and a partition wall between the mixer chamber and the settler chamber is formed with a porous wall made of porous material. A mixer-settler extraction device with a porous wall, characterized in that the vessel is configured in multiple stages.