JPH0660915A - Disposal method for spent nas battery - Google Patents

Abstract

PURPOSE:To simply dispose a spent NaS battery without corroding a facility or generating a dangerous material. CONSTITUTION:The electrode cap of a spent NaS battery is cut, and an outer peripheral container and a solid electrolyte tube are broken. They are laid in an incinerator 6 spread with dry sand 7 with their opening sections faced downward, and they are burned at 700-1000 deg.C in the excess air having the air ratio (m) of 2.0-4.0. Sodium and sulfur are converted into neutral and safe Na2SO4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention treats the waste of a sodium-sulfur battery (referred to as NaS battery in this specification), which is expected to be put to practical use as a battery for electric power storage and a power source for electric vehicles. It is about how to do it.

[0002]

2. Description of the Related Art The NaS battery described above is provided with a β-alumina solid electrolyte tube inside an aluminum outer peripheral container, filled with metallic sodium as a cathode active material inside the outer peripheral container, and outside of the outer peripheral container. It has a structure in which sulfur which is an anode active material is filled between and. Such Na
Since the S battery has the ability to store a large amount of electric power, it is being used for an electric power storage system in electric power companies.

However, such a NaS battery gradually deteriorates during repeated charging / discharging.
It is expected that a large amount of used NaS batteries will be generated after 10 years. At present, the treatment technology of the used NaS battery has not been completed, and it is unavoidable to store it as it is. However, as described above, metallic Na and sulfur are contained in the NaS battery, and these are designated as dangerous substances by the Fire Service Law, so it is difficult to store a large amount.

Incidentally, the only prior art relating to the method of treating a used NaS battery is disclosed in Japanese Patent Laid-Open No. 3-88281. This method is a method in which sodium is first separated from a used NaS battery and then sulfur is incinerated and recovered as sulfuric acid. However, in this method, since it is necessary to first separate sodium from the NaS battery, the steps are complicated and simultaneous processing is not possible, and there is a problem that the facility is corroded by sulfuric acid mist when recovering sulfuric acid.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems and is capable of treating sodium and sulfur in a used NaS battery at the same time, and further corrodes equipment and generates dangerous substances. The present invention has been completed to provide a method for treating a used NaS battery that is free from the risk of

[0006]

The present invention made to solve the above-mentioned problems is to cut the electrode cap of a used NaS battery, destroy the outer container and the solid electrolyte tube, and dry it with dry sand. Place in a laid oven and place in excess air at 70
It is characterized by incineration at 0 to 1000 ° C.

[0007]

The present invention will be described in more detail below with reference to the illustrated embodiments. FIG. 1 is a cross-sectional view showing a used NaS battery, 1 is an outer container made of aluminum, 2 is a β-alumina solid electrolyte tube therein, 3 is a solid electrolyte tube 2
Metallic sodium, which is a cathode active material filled inside, is 4; sulfur, which is an anode active material filled outside the solid electrolyte tube 2, 5 is an electrode cap, and 8 is an electrode rod.

From this state of FIG. 1, first, the electrode cap 5 is cut as shown in FIG. 2, and then a large number of notches are made in the outer peripheral container 1 as shown in FIG. Further, a hole is made from the cut portion of the electrode cap 5 by a drill or the like until it reaches the cathode portion.
Finally, as shown in FIG. 4, the internal β-alumina solid electrolyte tube 2 is mechanically broken. A large number of NaS batteries thus pretreated are set inside the fixed bed type incinerator 6 with the openings facing downward as shown in FIG. Since sodium reacts with water, dry sand 7 is laid in the furnace.

Then, while the hot air of 900 to 1100 ° C. is sent by the preheater and the inside of the furnace is maintained at a negative pressure by sucking by the exhaust blower, the temperature inside the furnace is 700 to 1000 ° C., preferably 800 to 900 ° C. Incinerate as. At this time, the air ratio m =
The combustion is carried out under an excess of air of 2.0 to 4.0, preferably m = 2.5 to 3.5. As a result, sodium and sulfur react to generate stable neutral salt Na ₂ SO ₄ as incinerated ash, and at the same time SO _x gas is generated. It was confirmed by X-ray diffraction that the product of the present invention was Na ₂ SO ₄ . The incineration with the opening facing downward as described above is to facilitate the outflow of the contents of sodium and sulfur from the container.

If the air ratio m is less than 2.0, alkaline Na ₂ S is likely to be produced, and incineration ash cannot be landfilled. Conversely, if the air ratio m is larger than 4.0, it becomes uneconomical in terms of temperature maintenance and blower capacity. Also the temperature is 700
If the temperature is lower than ℃, the reaction rate becomes slow and Na ₂ S tends to remain due to incomplete combustion. On the other hand, if the temperature exceeds 1000 ° C, an explosive reaction occurs and it becomes difficult to maintain a negative pressure in the furnace, and sodium sulfite may be blown out of the furnace.

After holding under such conditions for about 4 hours, the burner of the preheater is stopped and the exhaust gas blower is operated for about 1 to 2 hours. The SO _x gas thus generated can be completely exhausted. The exhaust gas from the incinerator is NaOH.
Will be led to an alkaline scrubber using an aqueous solution of
The pH of the alkali scrubber is measured from time to time and the pH is 9
When it becomes below, add 20% NaOH to make pH more than 11,
Always keep the pH between 9-11. As a result, all the generated SO _x gas will be recovered as Na ₂ SO ₄ . The neutrality of the obtained incinerated ash was confirmed by the pH of the aqueous solution.

[0012]

As described above, according to the method for treating a used NaS battery of the present invention, it is possible to treat a used NaS battery in a simple process, and to remove sodium and sulfur in the NaS battery. It can be processed simultaneously to Na ₂ SO ₄ . Since this Na ₂ SO ₄ is a neutral substance, it can be landfilled as it is, and since sulfuric acid is not generated in the treatment step as in the conventional method, there is no possibility that the incinerator will be corroded. Therefore, according to the present invention, used NaS batteries can be safely processed in large quantities.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a used NaS battery.

FIG. 2 is a sectional view showing a state in which a cap of a used NaS battery is cut.

FIG. 3 is a cross-sectional view showing a state in which a peripheral container of a used NaS battery is cut out and a hole is formed from a cap portion.

FIG. 4 is a cross-sectional view showing a state in which a solid electrolyte tube of a used NaS battery is broken.

FIG. 5 is a cross-sectional view showing an incineration process.

[Explanation of symbols]

 1 Outer container 2 Solid electrolyte tube 3 Sodium 4 Sulfur 5 Cap 6 Incinerator 7 Dry sand 8 Electrode rod

Claims (1)

[Claims] 1. The electrode cap of a used NaS battery is cut, the outer container and the solid electrolyte tube are broken, and this is placed in a furnace covered with dry sand, and the temperature is 700 to 1000 ° C. under excess air.
A method for treating a used NaS battery, which comprises incineration at