JP7179518B2 - Method for inactivating metallic sodium - Google Patents

Description

The present invention relates to a method for inactivating metallic sodium.

A metallic sodium dispersion used as a reaction agent for dechlorinating and detoxifying PCBs is usually prepared by dispersing particulate metallic sodium in mineral oil. In some cases, metallic sodium adheres to and remains on equipment parts and the like that have been used for PCB dechlorination and detoxification treatment.

As a method for cleaning equipment parts to which metallic sodium adheres, Non-Patent Document 1 describes steam cleaning in air, steam cleaning in inert gas, alcohol cleaning, high-temperature oil cleaning, liquefied ammonia cleaning, and cleaning with a low-temperature alloy. , washing with cloth, etc., water washing, sandblasting, etc. are disclosed.

According to Non-Patent Document 1 and others, water vapor cleaning is the most common method for sodium cleaning. It is also effective when the storage tank has a shape that makes it difficult to take out sodium. However, it takes time when there is a lot of sodium. Sodium can also be blown off by steam and fall into a puddle, causing excessive reaction.
Alcohol used for alcohol cleaning reacts more slowly with metallic sodium than does water. It takes a long time when there is a large amount of metallic sodium. Alcohol is also flammable.

High-temperature oil washing is a method of mechanical washing with mineral oil at about 200°C. However, adequate cleaning is not possible.
The manual wiping method is not suitable for cleaning a large amount of sodium because it is wiped with a cloth moistened with a very small amount of water or alcohol. Heavy equipment is required due to work under an inert gas atmosphere.
In the method of deactivating by pouring water over it, it is difficult to control the amount of hydrogen generated. may become difficult to control.

In addition, Patent Document 1 discloses that the surface of a device on which metallic sodium adheres is washed in one step with a wet inert gas mixed with carbon dioxide gas under pressure fluctuations such as pressurization, atmospheric pressure, and reduced pressure. Disclosed is a method for treating metallic sodium remaining on the surface of equipment, which is characterized by converting the metallic sodium contained in the sodium carbonate into sodium carbonate and stabilizing it.

Patent document 2 is used in a sodium-using facility in which metallic sodium is used, and the constituent parts of the sodium-using facility to which metallic sodium is attached are washed with inert oil at a temperature higher than the melting point of sodium to remove the adhesion. Disclosed is a method for cleaning sodium-using equipment, characterized in that the removal of metallic sodium is carried out.

Patent Document 3 discloses a method for cleaning a member to be cleaned to which metallic sodium adheres, in which a cleaning liquid is stored in a cleaning container constituting a cleaning apparatus to provide a liquid phase, and the member to be cleaned to which metallic sodium adheres is provided in the liquid phase. and an inert gas is blown into a cleaning device for cleaning a member to be cleaned to which metallic sodium adheres, and the oxygen concentration in the cleaning device is reduced to the explosion limit concentration or less. Discloses a method for cleaning metallic sodium characterized by

US Pat. No. 5,301,000 discloses a method for deactivating sodium metal comprising soaking the sodium metal in an inert oil and then adding water to the inert oil to convert the sodium metal to caustic soda.

Patent Document 5 discloses a cleaning tank for storing equipment to be cleaned contaminated with sodium, a supply tank for supplying a cleaning liquid made of alcohol into the cleaning tank, and a cleaning liquid recovery tank communicating with the cleaning tank via a valve. a pump for supplying the cleaning liquid recovered in the recovery tank to the cleaning tank; a decompression pump for maintaining the pressure in the recovery tank; and an inert gas for supplying inert gas into the recovery tank. a supply tank, a waste liquid drain tank connected to the washing tank via a valve, and a valve and a pressure reducing pump to the recovery tank for treating hydrogen produced by reaction of the contaminated sodium with the washing liquid in the washing tank. an oxidation treatment unit for blowing air or a gas mixed with oxygen so that the concentration of treated hydrogen is 75% by volume or more, a cooler for recovering water from the treated gas, and this and a water drain tank for storing the water collected by the cooler is disclosed.

JP-A-62-75396 JP 2007-254870 A Japanese Patent Application Laid-Open No. 2003-121593 WO2015/186637A1 JP-A-58-96300

"Safety Guidelines for Handling Liquid Sodium" Japan Atomic Energy Research Institute, pp.17-19, December 1968

An object of the present invention is to provide a method for inactivating metallic sodium.

As means for solving the above problems, the present invention including the following aspects has been completed.

[1] A method for inactivating metallic sodium, which comprises converting metallic sodium into a sodium alkoxide in a mixture of an inert oil and an alcohol having 4 to 8 carbon atoms.

[2] Soaking metallic sodium in an inert oil, and then adding an alcohol having 4 to 8 carbon atoms to the inert oil to convert the metallic sodium into a sodium alkoxide. Inactivation method.

[3] The inactivation method according to [1] or [2], wherein the alcohol is at least one selected from the group consisting of 1-pentanol, 1-hexanol, and 1-heptanol.
[4] The inactivation method according to any one of [1] to [3], further comprising adjusting the temperature during conversion to 0°C to 98°C.
[5] The deactivation method according to any one of [1] to [4], wherein the inert oil is insulating oil.
[6] The inactivation method according to any one of [1] to [5], further comprising purging with an inert gas.

According to the process of the present invention, metallic sodium can be completely converted to sodium alkoxide with a small amount of alcohol. Since the sodium alkoxide dissolves in the inert oil, the sodium alkoxide does not accumulate at the bottom of the cleaning tank, facilitating disposal.

One form of the method for inactivating metallic sodium of the present invention comprises converting metallic sodium to a sodium alkoxide in a mixture of an inert oil and an alcohol containing 4 to 8 carbon atoms.
Another form of the method for inactivating metallic sodium according to the present invention is to immerse metallic sodium in an inert oil, and then add an alcohol having 4 to 8 carbon atoms to the inert oil to to sodium alkoxide.

The inert oil used in the present invention is not particularly limited as long as it is used for storing metallic sodium. Examples of inert oils include hexane, cyclohexane, benzene, kerosene, decalin, transformer oil (trans oil described in JIS C 2320-1993), insulating oil, heavy oil (described in JIS K2205), liquid paraffin or cleaning oil ( Substitutes for chlorofluorocarbons, trichloroethane, kerosene, etc. include hydrocarbon-based solvents used for cleaning automobiles, electronic parts, and precision equipment. Among these, insulating oil is preferred.

Insulating oil is classified into type A and type B according to JIS standards.

Type A is classified into 1 to 7 types.
Type 1: Insulating oil containing mineral oil as a main component. There are No. 1 used for oil-filled capacitors and oil-filled cables, No. 2 and No. 3 used for oil-filled transformers and oil circuit breakers (excluding cold regions), and No. 4 used for large-capacity high-voltage transformers.
Type 2: Insulating oil containing alkylbenzene as a main component. Used in oil-filled capacitors and oil-filled cables. There are branched No. 1 (low viscosity) and No. 2 (high viscosity), linear No. 3 (low viscosity) and No. 4 (high viscosity).
Type 3: Insulating oil containing polybutene as a main component. Used in oil-filled capacitors and oil-filled cables. There are low viscosity No. 1, medium viscosity No. 2, and high viscosity No. 3.
Type 4: Insulating oil containing alkylnaphthalene as a main component. Used in oil-filled capacitors. There are No. 1 with low viscosity and No. 2 with high viscosity.
Class 5: Insulating oil containing alkyldiphenylalkane as a main component. Used in oil-filled capacitors. There are No. 1 with low viscosity and No. 2 with high viscosity.
Class 6: Insulating oil containing silicone oil as the main component. Used in oil-immersed transformers.
7th class: Mixed insulating oil of 1st class insulating oil and 2nd class insulating oil. There are No. 1 used for oil-filled capacitors and oil-filled cables, No. 2 and No. 3 used for oil-filled transformers and oil circuit breakers (excluding cold regions), and No. 4 used for large-capacity high-voltage transformers.

Type B is classified into 1 to 6 types IEC.
Class 1 IEC: Insulating oil whose main component is mineral oil. Class 1 IEC No. 1 used for oil-filled cables (Class I, Class II, Class III, compliant with IEC60465:1988), Class 1 IEC No. 2 used for oil-filled transformers and oil circuit breakers (Class I, Class II , Class III, corresponding to IEC60296:1982), and IEC No. 2A (Class IA, Class II A, Class III A, corresponding to IEC60296:1982), which is mineral oil added with an antioxidant.
Class 2 IEC: Insulating oil whose main component is alkylbenzene. Used in oil-filled capacitors and oil-filled cables. There are Class I, Class II and Class III. Corresponds to IEC60867:1993.
3 types IEC: Insulating oil whose main component is polybutene. Used in oil-filled capacitors and oil-filled cables. There are low-viscosity class I and high-viscosity class II (type I, type II). Corresponds to IEC60963:1988.
4 types IEC: Insulating oil whose main component is alkylnaphthalene. Used in oil-filled capacitors. Corresponds to IEC60867:1993.
Class 5 IEC: Insulating oil used in oil-filled capacitors. There are five types of IEC No. 1 containing methylpolyallylmethane as the main component and five types of IEC No. 2 containing alkyldiphenylethane as the main component. Corresponds to IEC60867:1993.
Class 6 IEC: Insulating oil whose main component is silicone oil. Used in oil-immersed transformers. Corresponds to IEC60836:1988.

The temperature during the conversion is preferably adjusted to 0 to 98°C, more preferably 0 to 60°C, still more preferably 0 to 40°C, from the viewpoint of reaction efficiency and safety.

Metallic sodium to which the method of the present invention is applied is not limited by its state. Examples include metallic sodium adhering to equipment and storage tanks, and degraded metallic sodium that has been oxidized in contact with air. The equipment includes mechanical equipment such as kneaders, pumps, and stirring blades, as well as pipes, valves, flanges, strainers, and the like that connect these mechanical equipment.

The amount of inert oil relative to metallic sodium is not particularly limited as long as the inert oil is in contact with metallic sodium. For example, when inactivating metallic sodium adhering to a device, the amount of oil can be such that the entire device to which metallic sodium adheres is immersed in the inert oil. When the metallic sodium adhering to the storage tank is to be inactivated, the amount can be adjusted so that the metallic sodium adhering to the inner surface of the storage tank is below the liquid surface of the inert oil.

The alcohols used in the present invention are alcohols having 4 to 8 carbon atoms. The alcohol preferably used in the present invention is compatible with the inert oil, specifically, completely dissolved in the inert oil at a volume ratio of 50:50 at room temperature. Further, the alcohol used in the present invention preferably has a solubility in water at 25° C. of 100 g/l or less, more preferably 80 g/l or less. Alcohol preferably used in the present invention is at least one selected from the group consisting of 1-pentanol, 1-hexanol, and 1-heptanol from the viewpoint of being able to suppress rapid reaction progress.

Reaction of alcohol (ROH) and Na produces sodium alkoxide (NaOR) and hydrogen (H ₂ ). By measuring the hydrogen gas concentration, the amount of hydrogen produced per hour can be calculated. For example, the hydrogen gas concentration can be measured in the exhaust line of the reservoir. The progress of the reaction can be grasped from the amount of hydrogen produced per hour. In order to improve safety, when the amount of hydrogen generated per hour is large, it is preferable to reduce the amount of alcohol added per hour. Specifically, it is preferable to adjust the addition amount of alcohol per hour while monitoring the hydrogen gas concentration in the exhaust so that the hydrogen gas concentration is less than 4 vol %. For example, the amount of alcohol added per hour is preferably 0.1 to 5 mol/hour, more preferably 0.5 to 4 mol/hour, and still more preferably 0.7 to 2 mol/hour, relative to 1 mol of Na. It is time.

On the other hand, the generated sodium alkoxide dissolves in the inert oil without precipitating, so it can be removed from the system together with the discharge of the inert oil. Sludge and the like may be generated due to impurities. Solids such as sludge can be washed away with inert oil or the like.

EXAMPLES Next, the present invention will be described more specifically by showing examples. However, the examples are not intended to limit the scope of the invention.

The following inert oils were used in the examples.
Insulating oil G: color L 0.5 (ASTM), density 0.8790 g/cm ³ (15°C), kinematic viscosity 44.86 mm ² /g (0°C), 8.250 mm ² /g (40°C);2. 230 mm ² /g (100°C), pour point -32.5°C, flash point 144°C (PM), oxidation less than 0.01 mgKOH/g, water content 7 ppm, JIS C2320 Class 1 No. 2 compliant product

Example 1
100 g of insulating oil G and 1 g of metallic sodium were placed in a 300 ml glass flask, and the solution was purged with nitrogen gas while stirring at 200 rpm. To this, while supplying nitrogen gas at 100 ml/min, the temperature was maintained in the range of 21 to 25 ° C., and 1-pentanol was added dropwise for 1 hour and stopped dropping for 1 hour repeatedly to obtain metallic sodium. was converted to sodium alkoxide. The maximum concentration of hydrogen contained in the discharged nitrogen gas was 0.76%. The dropwise addition of 5 mol of 1-pentanol was able to completely deactivate 1 mol of sodium metal.

Example 2
Metal sodium was converted to sodium alkoxide in the same manner as in Example 1, except that 1-pentanol was changed to 1-butanol. Dropwise addition of 5 mol of 1-butanol was able to completely deactivate 1 mol of metallic sodium.

Example 3
Metal sodium was converted to sodium alkoxide in the same manner as in Example 1 except that 1-pentanol was changed to 1-hexanol. The dropwise addition of 5 mol of 1-hexanol was able to completely deactivate 1 mol of metallic sodium.

Example 4
Metal sodium was converted to sodium alkoxide in the same manner as in Example 1, except that 1-pentanol was changed to 1-heptanol. The dropwise addition of 10 mol of 1-heptanol was able to completely deactivate 1 mol of metallic sodium.

Example 5
Metal sodium was converted to sodium alkoxide in the same manner as in Example 1, except that 1-pentanol was changed to 1-octanol. The dropwise addition of 10 mol of 1-octanol was able to completely deactivate 1 mol of metallic sodium.

Comparative example 1
Metal sodium was converted to sodium alkoxide in the same manner as in Example 1, except that 1-pentanol was changed to methanol. The maximum concentration of hydrogen contained in the discharged nitrogen gas was 0.45%. The temperature of the liquid sometimes reached 27°C. Although 10 mol of methanol was added dropwise to 1 mol of metallic sodium, about 0.67 g of metallic sodium remained in the flask.

Claims (5)

reacting the sodium metal soaked in the inert oil with an alcohol to convert the sodium metal to a sodium alkoxide;
the inert oil is an oil inert to metallic sodium used for storing metallic sodium;
alcohol is at least one selected from the group consisting of 1 -pentanol, 1-hexanol, and 1-heptanol;
A method for inactivating metallic sodium. Soaking metallic sodium in an inert oil, then adding an alcohol to the inert oil to react the metallic sodium with the alcohol to convert the metallic sodium to a sodium alkoxide;
the inert oil is an oil inert to metallic sodium used for storing metallic sodium;
alcohol is at least one selected from the group consisting of 1 -pentanol, 1-hexanol, and 1-heptanol;
A method for inactivating metallic sodium. The inactivation method according to claim 1 or 2 , further comprising adjusting the temperature during conversion to 0°C to 98°C. The deactivation method according to any one of claims 1 to 3 , wherein the inert oil is insulating oil. A method according to any one of claims 1 to 4 , further comprising purging with an inert gas during conversion.