JP3184963B2 - Separation and recovery method for organic chlorine-based solvents - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for separating and recovering an organic chlorine-based solvent contained in water or gas.

[0002]

2. Description of the Related Art In order to separate and recover an organic chlorinated solvent (for example, trichloroethylene, tetrachloroethylene, etc.) contained in water, the organic chlorinated solvent is adsorbed on activated carbon, separated from water, and then separated. A method is known in which steam is brought into contact with activated carbon to desorb the organochlorine solvent. Further, even in the case of an organic chlorine-based solvent contained in a gas, steam is used for desorption after adsorbing it on activated carbon. However, in the case of such a conventional method, since high-temperature steam is used for desorption of the organic chlorine-based solvent from the activated carbon to which the organic chlorine-based solvent has been adsorbed, the organic chlorine-based solvent is degraded due to hydrolysis or water content. However, there was a problem such as mixing in the collected material.

[0003]

SUMMARY OF THE INVENTION The present invention provides a method for efficiently separating and recovering an organic chlorinated solvent contained in water or gas without causing its deterioration and without containing water. Is the subject.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, according to the present invention, an adsorption step of contacting an organic chlorine-based solvent contained in water with activated carbon and adsorbing the organic chlorine-based solvent to activated carbon together with water, and an activated carbon adsorbing the organic chlorine-based solvent and water. An extraction step of contacting with supercritical carbon dioxide to extract the organochlorine solvent and water, a dehydration step of separating and removing water with a drying agent from the supercritical carbon dioxide from which the organochlorine solvent and water are extracted, A method for separating and recovering an organic chlorine-based solvent contained in water, comprising a step of condensing the organic chlorine-based solvent in a pure form by decompression and cooling from supercritical carbon dioxide containing an organic chlorine-based solvent. Is done. Further, according to the present invention, an adsorption step in which an organic chlorine-based solvent contained in a gas is brought into contact with activated carbon to adsorb the organic chlorine-based solvent to activated carbon, and the activated carbon adsorbed with the organic chlorine-based solvent is converted to supercritical carbon dioxide An extraction step of extracting the organic chlorinated solvent by contacting the organic chlorinated solvent with carbon or subcritical carbon dioxide, and decompressing and cooling the organic chlorinated solvent from supercritical carbon dioxide or subcritical carbon dioxide containing the organic chlorinated solvent. A method for separating and recovering an organic chlorine-based solvent contained in a gas, comprising a step of condensing in a pure form.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The organic chlorine-based solvent to be separated in the present invention includes, for example, chlorine-based solvents such as trichloroethylene and tetrachloroethylene, and compounds containing chlorine and fluorine such as freon. From metals, machinery, electronic component manufacturing factories, cleaning factories, etc., wastewater and gas containing such organic chlorine-based solvents are generated. According to the present invention, the organic chlorine-based solvent contained in the wastewater and gas is removed from these wastewater and gas. It can be efficiently separated and collected without causing its alteration and without containing water.

In order to preferably separate and recover the organic chlorine-based solvent contained in water according to the present invention, first, the organic chlorine-based solvent contained in water is brought into contact with activated carbon, and the organic chlorine-based solvent is adsorbed on the activated carbon. The concentration of the organic chlorinated solvent in the water is usually 0.1 to 1000 mg / l, especially 10 to 1 mg / l.
000 mg / l. Various types of conventionally known activated carbon can be used, and the shape thereof can be powdery or granular. Examples of the method of contacting the water with the activated carbon include various conventionally known methods, for example, a method of flowing water through an activated carbon packed tower, and a method of charging and stirring activated carbon in water. The amount of activated carbon used may be appropriately selected according to the concentration of the organic chlorine-based solvent contained in the water and the amount of treated water. Then, the activated carbon having adsorbed the organic chlorinated solvents and water in contact with supercritical CO ₂ or subcritical CO _2, the organochlorine capacity agent and water adsorbed thereto from the activated carbon supercritical CO ₂ or nitrous Extract to critical CO ₂ . In this extraction process, the extraction conditions are supercritical conditions or subcritical conditions of CO ₂ , that is, conditions near a critical point. Under such conditions, the temperature is from 25C to 100C, preferably from 35C to 50C. The pressure is 60 kg / cm ²
５００500 kg / cm ² , preferably 80 kg / cm ² ２2
00 kg / cm ² . Although water is removed from the supercritical or subcritical CO ₂ fluid immediately after extraction by a desiccant,
In this case, as a desiccant for removing water, a usual desiccant such as silica gel, calcium chloride, or zeolite can be used as it is.

[0007] By the above-mentioned extraction treatment with supercritical CO ₂ or subcritical CO ₂ , the organic chlorinated solvent and water contained in the activated carbon are extracted into supercritical CO ₂ and water is removed by a desiccant. Supercritical CO containing organic chlorine solvent
₂ or subcritical CO ₂ can condense and separate the organic chlorine-based solvent by reducing the pressure and cooling. The pressure for condensing the organic chlorine solvent is from atmospheric pressure to 30 kg / cm.
² , the cooling is 0 ° C or less, preferably -10 ° C to -80 ° C.
° C. The separated organic chlorinated solvent is recovered and reused. In the case of the present invention, the organic chlorinated solvent is separated and recovered from water without contacting with high-temperature steam or the like, so that it is not subjected to a reaction such as hydrolysis and contains no water, and its quality is high. is there.

In order to separate and recover the organic chlorine-based solvent contained in the gas according to the present invention, first, the organic chlorine-based solvent contained in the gas is brought into contact with activated carbon, and the organic chlorine-based solvent is adsorbed on the activated carbon. The concentration of the organic chlorinated solvent in the gas is usually 1 to 50,000 mg / m ³ , particularly 5 to 20 mg / m ³ .
000 mg / m ³ . Various types of conventionally known activated carbon can be used, and the shape thereof can be powdery or granular. Examples of the method of contacting the gas with the activated carbon include various conventionally known methods, for example, a method of flowing a gas through an activated carbon packed column. The amount of activated carbon used may be appropriately selected according to the concentration of the organic chlorine-based solvent contained in the gas and the amount of the gas to be treated. Then, the activated carbon having adsorbed the organic chlorinated solvents in contact with the supercritical CO ₂ or subcritical CO _2, the organochlorine capacity agent adsorbed thereto from the activated carbon in the supercritical CO ₂ or subcritical CO ₂ Let it be extracted. In this extraction process, the extraction condition is CO ₂
Supercritical or subcritical conditions, that is, conditions near the critical point. Under these conditions, the temperature is 25 ° C
To 100 ° C, preferably 35 ° C to 50 ° C. The pressure is ^{760kg / cm 2 ~500kg / cm 2} , preferably ^{80kg / cm 2 ~200kg / cm 2} .

The organic chlorine-based solvent contained in the activated carbon is extracted into supercritical CO ₂ or subcritical CO ₂ by the above-described extraction treatment with supercritical CO ₂ or subcritical CO _2. Supercritical CO ₂ or subcritical CO containing
₂ , the organic chlorine-based solvent can be condensed and separated by decompression and cooling. The pressure for condensing the organic chlorine-based solvent is from atmospheric pressure to 30 kg / cm ² , and the cooling temperature is 0 kg / cm ^2.
° C or lower, preferably from -10 ° C to -80 ° C. The separated organic chlorinated solvent is recovered and reused. In the case of the present invention, the organic chlorine-based solvent is separated and recovered from the gas without contacting with high-temperature steam or the like, so that it does not undergo a reaction such as hydrolysis and contains no water and has a high quality. It is.

[0010]

Next, the present invention will be described in more detail with reference to examples.

EXAMPLE 1 A glass column having an inner diameter of 10 mm was filled with 10 g of activated carbon (CAL charcoal, CAL charcoal 20-30 mesh).
A 100 mg / l aqueous solution of trichloroethylene (TCE) was flowed at 100 ° C. at a temperature of 20 ° C. and at a flow rate of 3 ml / min. At this time, the treated water concentration was equal to the raw water concentration.
Take out the adsorbed activated carbon and remove it at 35 ° C and 2 mmHg
Dried for minutes. The TCE and water contained in the activated carbon were 33% by weight based on the weight of the dried activated carbon. The activated carbon was taken into an extraction cell, and supercritical carbon dioxide at a temperature of 35 ° C. and a pressure of 100 kg / cm ² was flowed into the cell. The fluid after extraction is passed through an absorption tube containing silica gel and
The pressure and pressure were reduced to -30 ° C. and kg / cm ² , and TCE was condensed and recovered. When the infrared absorption spectrum of the TCE thus recovered was observed, it was confirmed that the TCE contained no altered substance or water.

Example 2 An experiment was conducted in the same manner as in Example 1 except that 300 liters of a 50 mg / l aqueous solution of tetrachloroethylene was used instead of TCE, and similar results were obtained.

Example 3 In Example 1, instead of supercritical carbon dioxide, a temperature of 2 was used.
The experiment was conducted in the same manner except that subcritical carbon dioxide at 5 ° C. and a pressure of 70 kg / cm ² was used. Also in this case, TC
E could be separated and recovered with high purity.

Example 4 10 g of activated carbon (manufactured by Calgon, CAL charcoal 20-30 mesh) was filled in a glass column having an inner diameter of 10 mmφ.
Air containing 500 mg / m ³ of trichloroethylene (TCE) was heated at a temperature of 20 ° C. and a flow rate of 500 ml / min for 10 m.
³ shed. Next, the adsorbed activated carbon was taken out, and the TCE contained in the activated carbon was measured. As a result, it was found to be 31% by weight based on the weight of the activated carbon. The activated carbon was taken into an extraction cell, and supercritical carbon dioxide at a temperature of 35 ° C. and a pressure of 100 kg / cm ² was flowed into the cell. Fluid 4 after extraction is 10k
The TCE was condensed and recovered by cooling under reduced pressure to -30 ° C. and g / cm ² . When the infrared absorption spectrum of the TCE thus recovered was observed, it was confirmed that the TCE contained no altered substance or water.

[0015]

According to the present invention, an organic base solvent contained in water or a gas can be efficiently separated and recovered in a pure form without any alteration and without containing water. .

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-61-254289 (JP, A) JP-A-51-61484 (JP, A) JP-A-1-242621 (JP, A) JP-A-6-254 63308 (JP, A) JP-A-5-15749 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C02F 1/26 B01D 11/00-12/00 C02F 1/28 C02F 1/74 101

Claims (2)

(57) [Claims] 1. An adsorption step in which an organic chlorinated solvent contained in water is brought into contact with activated carbon to adsorb the organic chlorinated solvent on activated carbon together with water; An extraction step of extracting the organochlorine solvent and water by contacting with carbon or subcritical carbon dioxide,
A dehydration step of separating and removing water with a desiccant from the supercritical carbon dioxide or subcritical carbon dioxide obtained by extracting the organochlorine solvent and water, and from the supercritical carbon dioxide or subcritical carbon dioxide containing the organochlorine solvent, A method for separating and recovering an organic chlorine-based solvent contained in water, comprising a step of condensing the organic chlorine-based solvent in a pure form by decompression and cooling. 2. An adsorption step in which an organic chlorinated solvent contained in a gas is brought into contact with activated carbon to adsorb the organic chlorinated solvent to activated carbon; An extraction step of extracting the organic chlorinated solvent by contacting the organic chlorinated solvent with supercritical carbon dioxide or subcritical carbon dioxide containing the organic chlorinated solvent; A method for separating and recovering an organic chlorine-based solvent contained in a gas, comprising a step of condensing with an organic solvent.