JP3918182B2 - Method for separating inorganic components in electrical insulating oil - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for dehalogenating and treating an organic halogen compound such as a polychlorinated biphenyl (hereinafter abbreviated as PCB) with a basic alkali metal compound.
[0002]
[Prior art]
A method of dehalogenating an organic halogen compound with an alkali metal dispersion in an organic solvent is described in JP-A-49-82570. However, more specifically, there are few reports of post-treatment methods for reusing and effectively utilizing decontaminated electrical insulating oil (hereinafter also referred to as oil), and the development of a more efficient reprocessing method is desired. It was.
[0003]
It is desired that the electrical insulating oil that has been decontaminated is effectively used as a fuel oil or the like. The high concentration of inorganic components in the treated oil hinders stable and efficient operation of the combustion furnace. Furthermore, since there is a view that residual chlorine ions cause dioxins and the like to be generated by combustion, a method for separating inorganic components from the treated oil is an important technique.
[0004]
In general, as a method for separating inorganic components such as alkali metal hydroxides in oil, there is a method of separating oil and water and then separating the liquid. In cases where wastewater treatment is difficult or there are restrictions on the amount of wastewater stored, a method of separating inorganic components in a solid state is desirable. In addition, depending on the degree of oxidation of the electrical insulating oil (JIS C 2101), the water washing operation may produce tar-like substances that appear to be a deteriorated component of the oil near the water layer or the interface between the water layer and the oil layer. In some cases, the reaction vessel or the like must be cleaned. It has been desired to develop a method for separating inorganic components in oil that does not generate such a tar-like product and can separate inorganic components in a solid state.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for efficiently separating and removing inorganic components in decontaminated oil in a method for dehalogenating and decomposing an electrically insulating oil contaminated with an organic halogen compound with a basic alkali metal compound or the like. And
[0006]
[Means for Solving the Problems]
The present invention relates to a method for separating inorganic components remaining in an electrical insulating oil when the organic halogen compound contained is dehalogenated and decomposed with an alkali metal or a basic alkali metal compound. The alkali metal compound is converted into an alkali metal hydroxide, and then solidified and removed by blowing carbon dioxide into electric insulating oil in the presence of 0.2 to 1.6 mol of water with respect to 1 mol of the alkali metal hydroxide. This is a method for separating inorganic components in electrical insulating oil.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The organic halogen compounds in the present invention are harmful organic halogen compounds such as PCB, dioxins, dibenzofurans having halogen, polychlorinated benzene, and methylene chloride.
[0008]
Examples of the alkali metal include sodium, potassium, lithium, rubidium, and cesium. Examples of the basic alkali metal compound include sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, and cesium hydroxide. Alkali metal hydroxides such as alkali metal hydroxides, sodium methoxide, sodium ethoxide, sodium propoxide, sodium butoxide, potassium methoxide, t-butoxypotassium, lithium aluminum hydride, sodium hydride A compound.
[0009]
Examples of the alkali metal hydroxide include sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, and cesium hydroxide.
[0010]
Examples of the electrical insulating oil include paraffinic oil, alkylbenzene oil, and the like, for example, trans oils defined in JIS C2320, 1, 2, 4, 5, 7, etc., and mixtures thereof, Including those deteriorated.
[0011]
Inorganic components to be separated include alkali metal halides produced from alkali metal or basic alkali metal compounds and organic halogen compounds used in dehalogenation decomposition, residual alkali metal or basic alkali metal compounds, used alkali metals or A hydrolyzate of a basic alkali metal compound, such as sodium chloride, potassium chloride, sodium hydroxide, potassium hydroxide, and the like.
[0012]
The dehalogenation decomposition reaction needs to be performed under conditions under which the target organic halogen compound is dechlorinated, but this depends on the alkali metal or basic alkali metal compound used. In order to satisfactorily separate the inorganic components in the oil, it is desirable that the chemical reaction between the oil and the alkali metal or basic alkali metal compound hardly occur. When a metal sodium dispersion which is an alkali metal is used, the reaction temperature is 30 ° C. or higher and 150 ° C. or lower, and usually 40 ° C. or higher and 100 ° C. or lower.
[0013]
A known method can be applied to the method of converting the remaining alkali metal or basic alkali metal compound into an alkali metal hydroxide. For example, an alkali metal hydroxide can be obtained by reacting a basic alkali metal compound with water. In addition, when the reaction between an alkali metal or basic alkali metal compound and water rapidly proceeds and causes a problem in operation, alcohols such as methanol, ethanol, isopropanol, butanol, and mixtures thereof, and alkali metals or bases It is also possible to react with water after reacting the basic alkali metal compound. It is also possible to mix a compound that makes the reaction mild in water, such as sodium hydroxide, potassium hydroxide, alcohols and the like. Of course, when an alkali metal hydroxide is used as the alkali metal or basic alkali metal compound, this operation is unnecessary.
[0014]
The amount of water that coexists in the alkali metal hydroxide and the electrical insulating oil is 0.2 to 1.6 mol, more preferably 0.4 mol, per mol of the alkali metal hydroxide in terms of molar ratio. From 1.3 to 1.3 moles. If the amount of water to be coexisted is too small, the reaction between the alkali metal hydroxide and carbon dioxide gas will not proceed easily, and if it is too much, water containing inorganic components will be mixed in the filtrate and the inorganic components will be sufficiently filtered. It becomes impossible to separate.
[0015]
The amount of carbon dioxide gas blown into the electrical insulating oil is determined by the amount of alkali metal hydroxide to be reacted. In order to completely convert the alkali metal hydroxide to the alkali metal carbonate, an amount of carbon dioxide gas of equimolar or more with respect to the alkali metal hydroxide is required. In order to advance the reaction with carbon dioxide quickly, it is possible to apply methods such as increasing the blowing amount of carbon dioxide, increasing the gas-liquid interface area, and increasing the pressure of carbon dioxide in the reaction vessel. The reaction temperature is not particularly limited, but should be within a temperature range where thermal decomposition of the insulating oil and solidification at a low temperature does not occur. For the stirring of the electrical insulating oil during the reaction, a general stirring device such as a stirring blade can be used. The stirring speed is not particularly limited, but it is possible to increase the gas-liquid interface area and shorten the reaction time by performing sufficient stirring. The reaction product of alkali metal hydroxide and carbon dioxide is mainly alkali metal hydrogen carbonate, which is less soluble in water than alkali metal hydroxide and suspended in electrical insulating oil. It becomes a crystal.
[0016]
As a method for removing the inorganic component suspended in the electrical insulating oil, a general method such as filtration or centrifugation can be used.
[0017]
【Example】
Examples are described below, but the present invention is not limited thereto.
[0018]
Example 1
Charge 250ml of heat-degraded trans oil (oxidation degree TVA = 0.9mgKOH / g) into a 300ml reaction vessel and dissolve 100mg of KC400 (condenser contents) which is PCB with an average chlorine addition number of 4 with stirring (190rpm) After flowing nitrogen gas and heating to 50 ° C., 14.8 g of a metal sodium dispersion liquid (Na concentration: 10%) prepared using trans oil as a solvent was dropped. After holding at 50 ° C. for 2 hours, the PCB concentration was analyzed by a gas chromatograph with an ECD detector, and it was confirmed that the PCB was completely decomposed. Subsequently, 2 g of water was added dropwise over 1 hour to decompose the remaining metallic sodium. While the whole reaction solution is air-cooled, carbon dioxide gas is blown into the solution at a flow rate of 50 ml / min for 2 hours using a glass ball filter G1, and sodium hydroxide, which is a hydrolyzate of metallic sodium, is reacted with carbon dioxide gas. It was. At this time, the internal pressure of the reaction vessel was atmospheric pressure. The trans oil in which the inorganic component was suspended in a crystalline state was filtered through a filter paper (5C, 9 cm) to separate the suspended component from the trans oil. The solid collected by filtration impregnated with oil was 10 g, and the amount of oil recovered was 260 ml. The solid content collected by filtration was washed with 100 ml of hexane, filtered, air-dried, and the weight was measured to find 6.58 g. When the degree of oxidation of the recovered trans oil was examined by the method of JIS C 2101, it was 0.3 mgKOH / g. When the concentration of sodium in the oil was measured by a combination of extraction with water and atomic absorption analysis, it was 0.1 ppm or less. When the chlorine ion concentration in the oil was determined by a combination of extraction with water and titration with a silver nitrate solution, the chlorine ion concentration in the oil was 200 ppm before filtration and 1 ppm or less after filtration.
[0019]
Example 2
Charge 250ml of heat-degraded trans oil (oxidation degree TVA = 0.9mgKOH / g) into a 300ml reaction vessel and dissolve 100mg of KC400 (condenser contents) which is PCB with an average chlorine addition number of 4 and stir (190rpm) After flowing nitrogen gas and heating to 50 ° C., 31.3 g of a metal sodium dispersion liquid (Na concentration: 10%) prepared using trans oil as a solvent was dropped. After holding at 50 ° C. for 2 hours, the PCB concentration was analyzed by a gas chromatograph with an ECD detector, and it was confirmed that the PCB was completely decomposed. Subsequently, 5 g of water was added dropwise over 1 hour to decompose the remaining metallic sodium. While the whole reaction solution is air-cooled, carbon dioxide gas is blown into the solution at a flow rate of 50 ml / min for 2 hours using a glass ball filter G1, and sodium hydroxide, which is a hydrolyzate of metallic sodium, is reacted with carbon dioxide gas. It was. At this time, the internal pressure of the reaction vessel was atmospheric pressure. The trans oil in which the inorganic component was suspended in a crystalline state was filtered through a filter paper (5C, 9 cm) to separate the suspended component from the trans oil. The solid collected by filtration impregnated with oil was 18.6 g, and the amount of oil recovered was 280 ml. The solid content collected by filtration was washed with 150 ml of hexane, filtered, air-dried, and the weight was measured to find 12.2 g. When the degree of oxidation of the recovered trans oil was examined by the method of JIS C 2101, it was 0.35 mgKOH / g. When the concentration of sodium in the oil was measured by a combination of extraction with water and atomic absorption analysis, it was 0.1 ppm or less. When the chlorine ion concentration in the oil was measured by a method combining extraction with water and titration with a silver nitrate solution, the chlorine ion concentration in the oil was 198 ppm before filtration and 1 ppm or less after filtration.
[0020]
Comparative Example 1
Charge 500 ml of heat-degraded trans oil (oxidation degree TVA = 0.29mgKOH / g) into a 1000 ml reaction vessel, dissolve 200 mg of KC400 (condenser contents), which is a PCB with an average chlorine addition number of 4, and stir (190 rpm) ), Flowing nitrogen gas and heating to 50 ° C., and then dropwise adding 29 g of a metal sodium dispersion liquid (Na concentration 10%) prepared using trans oil as a solvent. After aging for 2 hours, 3 g of water was added dropwise over 1 hour to decompose the remaining metallic sodium. Thereafter, 50 ml of water was added over 15 minutes. After stirring for 30 minutes, the stirring was stopped and the mixture was left standing. As a result, a high-viscosity black tar-like product was formed at the interface between the aqueous layer and the aqueous layer and the oil layer, and partly adhered to the inner wall of the reaction vessel.
[0021]
【The invention's effect】
It is possible to efficiently separate and remove the inorganic components in the oil which has been dehalogenated and decomposed with a basic alkali metal compound or the like without causing a tar-like substance that hinders the post-treatment operation.

Claims (1)

In a method for separating inorganic components remaining in an electrical insulating oil when the organic halogen compound contained is dehalogenated and decomposed with an alkali metal or a basic alkali metal compound, the alkali metal or the basic alkali metal compound in the electrical insulating oil is It is characterized by being made into an alkali metal hydroxide and then solidified by blowing carbon dioxide into electric insulating oil in the presence of 0.2 to 1.6 moles of water per mole of alkali metal hydroxide. To separate inorganic components in electrical insulating oil.