JP4439716B2 - Removal method of dioxins in waste water - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating dioxin-containing wastewater that can efficiently and economically remove dioxins contained in wastewater from a vinyl chloride monomer production facility or the like.
[0002]
[Prior art]
Dioxins were designated as specific facilities and drainage standards were set by the enforcement of the Act on Special Measures against Dioxins. For this reason, methods for removing dioxins from wastewater are being investigated in various fields. Extraction and removal of dioxins in a general organic solvent (n-hexane, methanol, ethanol, benzene, toluene, etc.) as an effective means for removing dioxins from wastewater The method (Japanese Patent Laid-Open No. 2000-167531) is known. Recently, studies have been made on treatment methods such as ozone, hydrogen peroxide and other oxidizing agents or titanium dioxide, manganese dioxide and other supported catalysts and UV-based decomposition, supercritical water oxidation, and high-temperature decomposition. It is being put into practical use little by little. However, since the activated carbon adsorption method, the coagulation sedimentation method and the like are both separation and removal treatment methods, it is necessary to treat the activated carbon and the coagulation sediment after separation. In addition, a decomposition method combining an oxidizing agent or a catalyst with ultraviolet rays is effective for decomposing and removing dioxins, but the processing cost becomes very high. Furthermore, although supercritical water treatment and high temperature treatment methods are effective for small-scale wastewater treatment, there are problems such as high equipment costs and treatment costs, which are not suitable for large-scale wastewater treatment.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to efficiently and economically remove dioxins in waste water from a vinyl chloride monomer production facility or the like.
[0004]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the present inventors have effectively and economically removed dioxins in washing wastewater from vinyl chloride monomer production facilities and the like using ethane dichloride. As a result, the present invention has been completed.
[0005]
That is, the present invention provides (1) contacting a wastewater containing dioxins with ethane dichloride to extract dioxins, and supplying the extract containing the dioxins to a distillation column for separating high-boiling components. A method for removing dioxins from wastewater, characterized by recovering ethane dichloride from the waste water and collecting waste liquid containing dioxins discharged from the bottom of the tower (Claim 1), (2) dioxin recovered from the bottom of the tower The method of removing dioxins from waste water according to claim 1 (Claim 2), wherein the waste liquid containing the waste is incinerated in an incinerator , and (3) the waste water after extraction of dioxins is used as a steam stripper after collecting the supplied ethane dichloride, dioxins in the waste water according to claim 1 or 2, wherein the removal of dioxins slightly remained by supplying to the activated sludge treatment facility Removing method (claim 3), and (4) waste water containing dioxins, method for removing dioxins in the waste water effluent in which claims 1-3, wherein discharged from a vinyl chloride monomer production apparatus (claim 4 )
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described with reference to FIG. 1, taking a general wastewater treatment process of a vinyl chloride production facility as an example. The process waste water 1 is sent to the stripper 21, collects ethane dichloride 2 contained in a trace amount, and then is supplied to the activated sludge treatment process 23 through the neutralization process 22. Ethane dichloride 3 synthesized as a raw material for vinyl chloride is supplied to the cracking furnace 26 after removing the low boiling point component 4 by the low boiling point component distillation column 24 and the high boiling point component 5 by the high boiling point component distillation column 25. The low boiling point component 4 and the high boiling point component 5 removed by the distillation columns 24 and 25 are disposed of in an incinerator.
[0007]
Next, an example when the dioxin removal method of the present invention is carried out will be described with reference to FIG. As shown in FIG. 2, the process waste water 1 is supplied to the extraction tank 27 and mixed with ethane dichloride 6 to extract dioxins. After the separation, the dioxin-containing ethane dichloride 7 is used as a raw material for the vinyl chloride monomer after removing the high boiling point component by the high boiling point component distillation column 25. The wastewater 8 is supplied to the activated sludge treatment step 23 through the neutralization treatment step 22 after the ethane 2 chloride contained in a trace amount is collected by the stripper 21.
[0008]
The dioxins in the present invention are defined to include PCDDs (polychlorinated dibenzo-para-dioxins), PCDFs (polychlorinated dibenzofurans), and coplanar PCBs (polychlorinated biphenyls).
[0009]
In the present invention, ethane dichloride, which is usually used as a raw material for producing vinyl chloride monomer, is used as an extraction solvent. It is of course possible to use the method.
[0010]
The extraction temperature is not particularly limited, but it is preferable to operate at normal temperature economically.
[0011]
The mixing mass ratio of the waste water and the extract is appropriately selected in the range of 100: 2 to 100: 100 weight ratio in consideration of the amount of ethane dichloride dissolved in the waste water.
[0012]
The extraction apparatus is not particularly limited as long as the apparatus can sufficiently mix waste water and ethane dichloride. For example, a batch type stirring and mixing type extraction tank or a continuous line mixing type extraction tank is used.
[0013]
The ethane dichloride used in the extraction can be recovered by supplying it to a distillation column that separates the high-boiling components. For example, in the embodiment shown in FIG. 2, the low-boiling components in the previous step are separated. You may supply to a distillation column (FIG. 2:24).
[0014]
【Example】
EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples. In the actual plant, dioxins purified by distillation are substantially free of dioxins, and dioxins separated and removed in high-boiling components are incinerated and made harmless. I have confirmed that.
[0015]
In the examples, the measurement and display method of the concentration of dioxins is as follows.
(Measurement of dioxin concentration)
This was performed based on JIS K 0312.
(Dioxin concentration display method)
The indication of the concentration of dioxins was expressed as an equivalent toxic amount [pg-TEQ / L] using a toxicity equivalent coefficient (WHO-1997-TEF) for the actual concentration [pg / L].
Example 1
A standard substance of dioxin was added to the mixed water of acid washing wastewater, alkali washing wastewater, and incinerator wastewater in the vinyl chloride monomer production process, and wastewater having an equivalent toxicity amount of 1000 pg-TEQ / L was prepared. 1 L of ethane dichloride (drainage: ethane dichloride = 100: 100) was mixed at 25 ° C. for 10 minutes with a shaker with respect to 1 L of this waste water, and after separation, the concentration of dioxins in the aqueous layer was measured. . As a result, the concentration of dioxins in the waste water was 0.8 pg-TEQ / L, and 99.92% could be removed.
(Example 2)
A standard substance of dioxin was added to the mixed water of acid washing wastewater, alkali washing wastewater, and incinerator wastewater in the vinyl chloride monomer production process, and wastewater having an equivalent toxicity amount of 1000 pg-TEQ / L was prepared. To 10 L of this wastewater, 0.2 L of ethane dichloride (drainage: ethane dichloride = 100: 2) is mixed at 25 ° C. for 10 minutes with a shaker, and after separation, the concentration of dioxins in the aqueous layer is determined. It was measured. As a result, the concentration of dioxins in the waste water was 1.2 pg-TEQ / L, and 99.88% could be removed.
[0016]
【The invention's effect】
As described above, according to the present invention, washing waste water from a specific facility such as a vinyl chloride monomer facility can be brought into contact with ethane dichloride to extract dioxins, and thereafter, for example, ethane dichloride is recovered and vinyl chloride is recovered. If it is used as a raw material for monomers, dioxins can be detoxified more efficiently and economically.
[Brief description of the drawings]
FIG. 1 is a block flow of general vinyl chloride process wastewater. FIG. 2 is a block flow illustrating a method for removing dioxins in one embodiment of the present invention.
1: Process wastewater 2: Ethane dichloride 3: Ethane dichloride 4: Low boiling point component (to incinerator)
5: High boiling point component (to incinerator)
6: Ethane dichloride 7: Dioxin-containing ethane dichloride 8: Waste water 21: Stripper 22: Neutralization process 23: Activated sludge treatment process 24: Low boiling component distillation tower 25: High boiling component distillation tower 26: EDC cracking furnace 27 : Extraction tank

Claims (4)

The waste water containing dioxins is contacted with ethane dichloride to extract dioxins, and the extract containing the dioxins is supplied to a distillation tower for separating high-boiling components, and ethane dichloride is recovered from the top of the tower. A method for removing dioxins in waste water , comprising collecting waste liquid containing dioxins discharged from the bottom . The method for removing dioxins in waste water according to claim 1, wherein the waste liquid containing dioxins recovered from the bottom of the tower is incinerated in an incinerator to render it harmless. After drainage after dioxins extracted supplied to the steam stripper to recover ethane dichloride, according to claim 1 or 2, wherein the removal of dioxins slightly remained by supplying to the activated sludge treatment facility How to remove dioxins in waste water. The method for removing dioxins in wastewater according to claim 1 , wherein the wastewater containing dioxins is wastewater discharged from a vinyl chloride monomer production apparatus.

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