JPS602687A - Refining device for sodium - Google Patents

Abstract

PURPOSE:To provide a titled device which removes simultaneously all the impurities contained in Na by the constitution in which positive and negative potentials are respectively impressed on the unrefined Na side and refined Na side facing each other with a solid electrolyte permitting passage of sodium positive ion as a boundary. CONSTITUTION:Unrefined Na 3 is fed from an unrefined Na vessel 4 into the unrefined Na side 20 of an impurity removing vessel 19 which is internally bisected by a solid electrolyte 18 consisting of beta''-alumina, etc. and allowing the selective transmission of Na ion. High purity Na is fed to the refined Na side 21. A positive potential is impressed on the unrefined Na isolated by the solid electrolyte and a negative potential on the refined Na respectively from a power source 5 via both vessels which are electrically insulated 22 from each other. Then the Na on the unrefined side becomes Na ion and migrates to the refined side through the electrolyte 18 where said ion is contained as refined Na 5 in a refined Na vessel 6.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] This invention relates to a device for removing impurities in IIumum, particularly for sodium-sulfur batteries, reagent-use sodium, and high-speed growth batteries where activation of impurities is a concern. Regarding IJum purification equipment (for products requiring high purity such as furnaces).

[Background of the invention]

Conventional sodium purification methods include cold trap methods and distillation methods. First, the cold trap method will be explained. The cold trap method is a method for removing impurities by utilizing the differences in impurity groups in IIium (depending on the temperature as shown in FIG. 1). Figure 2 shows a sodium purification device using the cold trap method. This device consists of a part for removing impurities, that is, a metal mesh 1.
'L'f? :, an unpurified sodium chloride container 4 that supplies unpurified sodium 3 to the impurity removal tank 2 and the impurity removal tank;
Purified sodium temperature 6 for storing purified sodium 5
Also, a control device 7 for controlling the sodium temperature in the valley container.
and a sodium flow rate side n device 8.

The impurities contained in the unrefined sodium 3 are removed from the cooled gold and mesh 1 when fed to the impurity removal tank 2.
can be incorporated into Fully curved mesh tends to increase flow resistance over time due to the build-up of impurities. Therefore, consideration is given to the mesh arrangement in the impurity removal tank one by one to prevent this, but in the cold trap method, as shown in Figure 1, it is possible to reduce the concentration of oxygen and hydrogen in the sodium. It is possible. For example, if the temperature of the impurity removal tank is controlled to 150C, the oxygen concentration will be 2.8
ppm VC excess hydrogen concentration can be reduced to 0.181)I)m. However, impurities other than oxygen and hydrogen contained in sodium, such as calcium, potassium, chlorine, and carbon, cannot be removed by the cold trap method.

As a purification apparatus for removing oxygen from sodium, a purification apparatus using zirconia as shown in FIG. 3 has also been considered (percentage patent application No. 1987-98729). Unrefined) +1 um 3 is introduced into the impurity removal tank 2 and exposed to the reducing agent 14 via the zirconia wall 13. When the IJium side is set to a negative potential and the reducing agent side is set to a positive potential, the zirconia wall allows only oxygen ions to pass through, making it unpurified.) The oxygen in the IJum goes to the reducing agent side. and can reduce the oxygen concentration in unpurified sodium. Although this method can also remove the acid oxides contained in sodium, it cannot remove impurities in sodium, such as calcium, potassium, chlorine, and carbon, as with the cold trap method described above. .

A distillation method can be considered as a method for removing impurities other than oxygen 2 and hydrogen. The purification principle is similar to general distillation methods, in which differences in vapor pressure are used to separate IJium and impurities. Figure 4 shows a sodium purification device using the distillation method. The distillation tank 16 is filled with unrefined sodium 3,
A cooling fin 17 that heats the sodium temperature to 500 to 600'C to evaporate the sodium and is incorporated into the cooling section.
The sodium vapor is condensed and introduced into the purified sodium container 6. The distillation method can remove impurities such as oxides, calcium, and carbon in 11um (which has a low boiling point). However, its vapor pressure is higher than that of sodium, and the amount of water (
It is difficult to remove potassium on the order of [Oppm]. Also, although this is an essential flaw in the distillation method, since the principle is to utilize the difference in vapor pressure, the impurity concentration can be reduced by O.
It cannot be done.

In the distillation method, it is necessary to raise the temperature to +1 um above 65 aac, which increases the energy required for sodium purification. Furthermore, in order to raise the temperature to a higher temperature, the dissolution of component elements and impurities from the container material of the distillation tank cannot be ignored. Moreover, it is difficult to make the overall size of the device compact.

[Purpose of the invention]

The object of the present invention is to address the shortcomings of conventional methods for removing impurities in 11 um. In order to solve problems such as ■ only specific elements among impurities can be removed and ■ difficulty in purifying purified sodium, we use a solid electrolyte that selectively permeates only sodium ions. An object of the present invention is to provide a sodium purification device that can remove all impurities at once.

[Summary of the invention]

The present invention makes it possible to remove impurities such as potassium, calcium, and oxygen contained in sodium by using a solid electrolyte that selectively transmits only sodium ions. As a result, it becomes possible to remove all impurities in Na)11um, and highly pure sodium can be obtained.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

The unrefined sodium 3 from the unrefined sodium container 4 is injected into the unrefined sodium side 20 of the impurity removal tank 19, which is internally divided into two parts by the solid electrolyte 18, and is purified on the opposite side via the solid electrolyte. ) Inject high purity sodium into the ram side 21. Then isolated with a solid electrolyte 7'1.
A positive potential is applied to the unpurified sodium, and a negative potential is applied to the purified sodium. Here, since sodium has electrical conductivity, voltage can be applied to both containers. According to the applied electric field, the sodium on the unrefined back side passes through the solid electrolyte as ions and moves to the refining side. The purified sodium is stored in a purified sodium container 6.

22 in FIG. 5 is an electrical insulator for insulating the positive electrode and the negative electrode.

In this device, β″-alumina is used as the solid electrolyte,
Its surface area was approximately 200 cm2. The temperature during sodium-IIium purification was 300 tl', and the applied voltage was 2.0 V.
In the case of the following, the amount of Sl-IJumN produced per unit time was changed by about 1 g/#. Note that the surface current density of β''-alumina at that time was 400 m4-.

Table 1 shows the analysis results of the purified sodium obtained in the experiment. For comparison, Table 1 also lists the analysis results of IJium, which was purified by the cold trap method. The analysis results show that the sodium purification method of the present invention suppresses the concentration of all impurity elements such as potassium and calcium, which the cold trap method did not have the purification ability to, below 0.1 ppm, which is the analytical detection limit in this experiment. was completed.

Table 1 ~ (i ppm: The analytical sensitivity is 0.1 plum, indicating that the concentration is below this detection limit.

Although the IJ alumina purification rate was about 1 g/mi, the surface current density of β"-alumina was increased,
If β''-alumina, which has a larger surface area, is used, the IJium purification speed can be easily achieved, which is about 10 times the current rate.
However, as long as the temperature is above the temperature at which sodium does not solidify (melting point 98C), the function of this embodiment will not be impaired. However, since the specific resistance of β"-alumina increases as the temperature decreases, energy loss due to Joule heat generation in β"-alumina increases when refined at low temperatures.

According to the above-described embodiment of the present invention, all of the impurity elements in Na)IJum can be purified, and all of the impurity elements in Na)IJium can be obtained with high purity in -times of operations.

FIG. 6 shows another embodiment of the present invention, which differs from FIG. 5 in that metal meshes are attached to both surfaces of the solid electrolyte to serve as electrodes 24. FIG. Purified sodium (1111
By providing an entertainment mesh electrode on the 21, it is no longer necessary to inject into the purified sodium side of the high-purity sodium chloride at the start of purification, so that the purity of the purified sodium is 1.1 and the functions of the present invention are fully demonstrated. can. In addition, the metal mesh electrode provided on the unrefined 1111120 not only facilitates the supply of unrefined sodium to the solid electrolyte surface, but also reduces the amount of IJium that remains during complete refining or when the refining is completed. It is effective. That is, due to the surface tension of /Ql sodium, unrefined sodium is transported through the mesh by capillary action and is efficiently supplied to the solid electrolyte. In this embodiment, a metal mesh was used; however, a carbon mesh, a graphite mesh, or other electrically conductive metal mesh may be used instead.

In the above example, n) When the amount of purified IIium increases, impurities adhere to the surface of the solid electrolyte, reducing the purification ability, and sometimes damage to the solid electrolyte, which is thought to be caused by impurities, is observed. . These causes limit the use of the solid electrolyte and limit the lifespan of the sodium purification apparatus of the present invention. Therefore, in the modified example shown in FIG. 7, a cold trap 25 was provided to supply unpurified IJium 3 to the impurity removal device 1p19, and rough purification was performed. By this method, most of the oxides in sodium can be removed, so the life of the solid electrolyte can be extended.

As an embodiment aimed at extending the life of the solid electrolyte as shown in the above modification, it is also possible to completely utilize the purified zirconia gold shown in Fig. 3 instead of the cold tiger (10) tube. In the possible examples described above, unrefined sodium was supplied to the solid electrolyte surface in a liquid state, but in the example shown in FIG. 7, unrefined sodium was supplied in a vapor state.

If unpurified sulfur is supplied in liquid form, the sixth
As shown in the figure, even if it is made of crude N, only oxygen can be removed, so impurities in sodium, such as calcium and carbon, will adhere to the surface of the solid electrolyte, and the period during which it can be used for refining the solid electrolyte will be limited. It had the disadvantage of shrinking the fields. If IJium is supplied as vapor to the solid electrolyte, impurities with low vapor pressure contained in the unrefined sodium will be removed, making it possible to extend the life of the solid electrolyte.

The operating state shown in FIG. 8 will be explained. unrefined) +7um3
For example, the heater 9 is supplied to the impurity removal tank 26.
It is heated to 5 [On at f'L, becomes saturated steam, and is supplied to the inner surface of the solid electrolyte 18. The sodium supplied is
It is condensed by the metal mesh electrode 24 (11) installed on the surface of the solid electrolyte, and by the voltage 15 applied to the inner and outer surfaces of the solid electrolyte, it becomes sodium ions and passes through the homogeneous electrolysis)'gJ, forming purified sodium on the outside. stored on the side. Purified sodium is transferred to the purified sodium container 6 as necessary.1. Ru.

(further removed in the impurity removal tank 26) l) As the rum purification progresses, impurities with a saturation solubility or higher accumulate on the unrefined sodium side, and for example, sodium oxide and the like become precipitates. Therefore, a high concentration impurity removal container 27 is provided to remove these precipitates.

Similarly, in the above embodiment, β''-alumina was used as the isoelectrolyte, but the effects of the present invention will not be impaired if β''-alumina and borax glass are materials that selectively permeate sodium ions.

Furthermore, regarding the shape of the solid electrolyte, although plate-like and cylindrical shapes were used in the examples, it goes without saying that other shapes may be used without impairing the effects of the present invention.

〔Effect of the invention〕

(12) By using solid electrolyte gold that selectively permeates only sodium ions to purify impurities in sodium,
n) All the impurities contained in 11um? can be removed and high purity IJium is obtained.

[Brief explanation of drawings]

Figure 1 shows the solubility of oxygen and hydrogen in sodium.
Figure 2 is an explanatory diagram of a IIium purification apparatus using the conventional cold trap method, Figure 3 is an explanatory diagram of a sodium purification apparatus using zirconia, and Figure 4 is an explanatory diagram of a sodium purification apparatus using a distillation method. Fig. 5 is an explanatory diagram of a sodium purification apparatus of the present invention using β''-alumina kumquats, Fig. 6 is an explanatory diagram of a l-IIium purification apparatus in which metal mesh electrodes are provided in the same way as shown in Fig. 5, and Fig. 7 The figure is an explanatory diagram of a sodium purification apparatus that is the apparatus of Figure 6 attached with a sodium crude purification apparatus using a cold trap method, and Figure 8 is an explanatory diagram of a sodium purification apparatus that supplies sodium completely in a gaseous state to a solid electrolyte.1 ...Gold mesh, 2,19.26...Impurity removal (13) tank, 3...Unrefined sodium, 4...Unrefined sodium container, deceased...#g sodium sodium 6... - Refined sodium container, 7... Temperature control device, 8... Flow rate control device, 9... Heater, 1... Heater or cooling fin, 11... Stop valve, 12... Leak pulp , 13... Zirconia, 14... Reducing agent, 1
5... Denso, 16... Distillation tank, 17... Cooling fin, 18... Solid electrolyte, 20... IIk in unrefined sodium 21... Purified sodium side, 22...
Electrical insulation, 23...Pressure adjustment pressure, 24...Metal mesh 5JL25...Cold trap, (14) Fig. 2

Claims (1)

[Claims] 1. Is there a positive potential on the IJium side? , a sodium purification device characterized by applying a negative potential to the purified sodium side. 2. Claim 1) A sodium purification apparatus characterized in that the IJium purification apparatus is provided with mesh electrodes on the inner and outer surfaces of a solid electrolyte. 3. A sodium purification apparatus according to claim 1, characterized in that unrefined (unrefined) IJium is supplied to a solid electrolyte through the entire crude purification apparatus. 4. A sodium refining apparatus according to claim 1, characterized in that unrefined sodium is supplied to the solid electrolyte in a vapor state.