JP2002095933A - Treating method and device for smoke washing waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove dioxins, mercury, fluorine, etc., from smoke washing waste water in forms easy to be aftertreated. SOLUTION: Smoke washing waste water generated when exhaust gas of an incinerator is washed is introduced into a membrane separator 16 to membrane-separate the waste water into a concentrate of suspended solid containing dioxins and a permeate containing mercury and fluorine. The permeate is introduced into a mercury adsorption tower 12 and brought into contact with a carbon-based adsorbent to adsorb and remove mercury and fluorine dissolved in the permeate. The concentrate of suspended solid containing dioxins is returned to the incinerator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating harmful substances (dioxins, mercury, fluorine, etc.) in smoke exhaust water obtained by treating combustion exhaust gas.

[0002]

2. Description of the Related Art At present, a widely used method for treating smoke and wastewater is shown in FIG. In this conventional method, the smoke washing wastewater is introduced into a first coagulation tank 1 and a coagulation agent is added thereto.
The supernatant is introduced into the second flocculation tank 3 and the coagulation agent is charged. Then, the precipitate is precipitated in the second sedimentation tank 4, and then the supernatant is introduced into the sand filtration tower 6. 5 is a sludge dewatering machine. As described above, in the conventional method, first, the flocculating agent was charged, the suspended solids, fluorine, and the like were separated by flocculation precipitation and sand filtration, and then the mercury adsorption tower 7 filled with the chelating agent and the chelating agent were charged. This is a processing flow in which harmful heavy metals are adsorbed and removed in the heavy metal adsorption tower 8. In that case, the components of the apparatus were many, resulting in a rather complicated water treatment flow. In addition, the coagulated sediment also contains dioxins and mercury and heavy metals adsorbed on suspended solids, and there is a risk that mercury will be circulated and concentrated when returned to an incinerator for disposal. Further, in the case of disposal in a managed landfill or the like, there is a problem that the amount of sludge increases due to the addition of a flocculant, and the sludge disposal cost increases.

[0003] To solve these problems, Japanese Patent Laid-Open No.
JP-A-347548 describes a method for removing mercury in smoke wash effluent by sending the smoke wash effluent to a sand filtration tower and a chelating tower, and making the filter sand and the chelate resin have the same particle size. I have. However, no consideration is given to dioxins that may be mixed in the smoke-washing wastewater.

[0004]

The method described in the above publication has a certain effect in removing mercury, but cannot remove harmful substances such as dioxins and fluorine at the same time. The present invention has been made to solve the above problems, and an object of the present invention is to form dioxins, mercury, heavy metals, fluorine and other harmful substances contained in smoke-washing wastewater in a form that can be easily post-treated. It is an object of the present invention to provide a method and an apparatus for efficiently removing the same.

[0005]

Means for Solving the Problems Normally, trace amounts of various harmful substances, organic substances and coloring substances are highly likely to be mixed in the smoke washing drainage. Generally, it contains dioxins, mercury, various heavy metals, fluorine, organic substances and the like, and is removed in a form adsorbed by sludge and an adsorbent. In some cases, the removed material is disposed of in a managed landfill or returned to an incinerator for disposal. When disposed in an incinerator, there is an advantage that there is no new treatment cost, but if low-boiling metals such as mercury are mixed, there is a high possibility that enrichment will occur in the system due to circulation. Disposal by transport outside is indispensable.

In order to efficiently remove all harmful substances, it is necessary to separate components that can be returned to an incinerator for processing and components that have a possibility of circulating and condensing, and to perform appropriate processing for each. . Therefore, by making the membrane separation process the first step, the suspended solids containing dioxins, which can be treated in the incinerator, are completely separated and concentrated, so that they can be easily returned to the incinerator. I made it. In addition, since mercury and the like are adsorbed to the filtrate, dioxins are not contained in the waste adsorbent that needs to be discharged, thus solving many problems of the smoke washing drainage treatment.

In the method for treating smoked wastewater according to the present invention, the smoked wastewater obtained by washing the exhaust gas from an incinerator is introduced into a membrane separator to contain a concentrated liquid of suspended solids containing dioxins, mercury, fluorine and the like. It is configured to perform membrane separation with a permeate. In this method, it is preferable that the concentrated liquid of the suspended solid containing dioxins is returned to the incinerator to thermally decompose the dioxins.

[0008] The method of the present invention is also directed to a method of introducing smoke-cleaning wastewater obtained by cleaning exhaust gas from an incinerator into a membrane separator to concentrate a suspended solid containing dioxins and a permeate containing mercury and fluorine. It is characterized in that the permeate is introduced into a mercury adsorption tower and brought into contact with a carbon-based adsorbent to adsorb and remove mercury, fluorine, organic components and coloring components dissolved in the permeate. . In this method, it is preferable that the concentrated liquid of the suspended solid containing dioxins is returned to the incinerator to thermally decompose the dioxins.

It is preferable that the liquid subjected to the adsorption treatment in the mercury adsorption tower is introduced into a heavy metal adsorption tower and brought into contact with a chelating agent (chelate resin) to remove heavy metals in the liquid. Further, the mercury adsorption tower and the heavy metal adsorption tower may be backwashed with the chelated liquid.

[0010] As the carbon-based adsorbent, it is preferable to use charcoal of organic matter, sludge or livestock waste. In particular,
It is preferable to use a carbide containing sulfur and calcium salts as the carbon-based adsorbent. Further, it is preferable to use sewage sludge carbide as the carbide. It is preferable to use a microfiltration membrane or an ultrafiltration membrane in the membrane separation step. In this case, the pore size of the microfiltration membrane or ultrafiltration membrane is 1 to 0.001.
μm, preferably 0.6 to 0.005 μm.

[0011] The smoke-cleaning wastewater treatment apparatus according to the present invention introduces washing wastewater obtained by washing exhaust gas from an incinerator, and concentrates a suspended solid containing dioxins (concentrated liquid containing solids), mercury, fluorine and the like. A membrane separator for membrane separation into a permeate containing water, a mercury adsorption tower filled with a carbon-based adsorbent for introducing a permeate to adsorb and remove mercury and fluorine, and introducing an adsorbed liquid And a heavy metal adsorption tower filled with a chelating agent (chelate resin) for removing heavy metals.

In this smoke washing wastewater treatment apparatus, it is preferable that the membrane separator and the incinerator are connected via a return line for a concentrated liquid of suspended solids containing dioxins. Further, it is preferable to provide a washing water tank for storing a part of the treatment water of the heavy metal adsorption tower, and to connect the washing water tank to the mercury adsorption tower and the heavy metal adsorption tower via a backwash line. .

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method and apparatus for treating smoke and wastewater according to the present invention will be described in detail with reference to the drawings, in comparison with conventional methods and apparatuses. Although the actual processing flow may vary depending on various conditions of the incineration plant, a general flow of the smoke-washing wastewater treatment is as shown in FIG. 4 described above. The smoke washing wastewater passes through a first flocculation tank 1 and a first sedimentation tank 2, and also a second flocculation tank 3 and a second sedimentation tank 4, to separate suspended solids and components that can be removed by flocculation by sedimentation. The settled sludge is dewatered by the sludge dewatering machine 5, and the dewatered cake is taken out of the system. On the other hand, the treated water subjected to coagulation and sedimentation in two stages is led to a sand filtration tower 6 to remove suspended matter that cannot be removed by sedimentation separation.
Through the heavy metal adsorption tower 8, the water is discharged out of the system as treated water.
9 is a backwash water tank.

FIG. 1 shows an apparatus for carrying out a method for treating smoke and wastewater according to a first embodiment of the present invention. In the present embodiment, the smoke washing wastewater first enters the smoke washing wastewater tank 10 and is mixed with the backwashing wastewater at the time of backwashing of the subsequent mercury adsorption tower 12 and heavy metal adsorption tower 14, and then the membrane separator provided with the membrane 17 is provided. 16 is sent. The concentrated liquid of suspended solids containing dioxins separated and concentrated by the membrane separator 16 is sent directly to the incinerator via the return line 18 for processing. On the other hand, the filtrate (permeate) from the membrane separator 16 removes mercury dissolved in the liquid in the mercury adsorption tower 12 and then adsorbs and removes various heavy metals dissolved in the heavy metal adsorption tower 14. And discharged out of the system as treated water. A part of the treated water is stored in the backwash water tank 20, and the mercury adsorption tower 1 is passed through the backwash lines 22 and 24.
2. Used when backwashing the heavy metal adsorption tower 14.

As the filtration membrane, for example, a pore size of 1 to 0.0
A microfiltration membrane or ultrafiltration membrane of 01 μm, preferably 0.6-0.005 μm is used. If the pore size of the microfiltration membrane exceeds the upper limit of the above range, suspended solids containing dioxins cannot be removed, and most of the dioxins in the smoke washing drainage will flow out in the subsequent stage. On the other hand, when it is less than the lower limit of the above range, the apparatus becomes large because a high filtration pressure is required or sufficient permeation cannot be obtained. The mercury adsorption tower 12 is filled with a carbon-based adsorbent, for example, a carbide containing sulfur and calcium salts. A permeate containing mercury (mainly mercury chloride), fluorine and heavy metals is introduced into the mercury adsorption tower 12, and the mercury is adsorbed and removed as mercury sulfide,
Fluorine is adsorbed and removed as calcium fluoride. 26
Is a used carbide extraction line. The heavy metal adsorption tower 14 is filled with a chelating agent (chelating resin). A liquid containing a heavy metal is introduced into the heavy metal adsorption tower 14 to remove the heavy metal. Reference numeral 28 denotes a used chelating agent extraction line.

In this embodiment, the process is extremely simplified, as is apparent from a comparison between FIG. 4 and FIG. Also, since most of the dioxins are present in the suspended solids by completely separating the suspended solids by the membrane 17, most of the dioxins contained in the smoke wash effluent must be returned to the incinerator. Can be processed. Also,
Dioxins do not adhere to mercury and heavy metals that are adsorbed and separated in the subsequent stage at a high concentration, and therefore, it is possible to prevent post-treatment from becoming difficult.

[0017]

EXAMPLES Examples are shown below to further clarify the features of the present invention. Example 1 Table 1 shows examples of the most important step of the present invention in the membrane separation step.
Shown in Analysis of the membrane filtrate was performed using GB10, a microfiltration membrane.
This is a value obtained by analyzing a solution obtained by filtering a stock solution of smoke washing drainage using 0R (product number, pore size: 0.6 μm). From the analysis results of the membrane filtrate, it was found that most of the dioxins adhered to the suspended solids and could be separated with high efficiency by membrane treatment.
On the other hand, it was found that most of the mercury was dissolved and could be transferred to the subsequent step without being separated by the membrane treatment.

[0018]

[Table 1]

Example 2 A sewage sludge was heated to about 500 ° C. in an oxygen-free atmosphere to pulverize the sludge charcoalized to 75 μm or less, and then to a predetermined concentration (100 mg-Hg / L and 1 mg).
-Hg / L), and suspended in a mercury chloride solution adjusted to have an amount of adsorption. FIG. 2 shows the results as an adsorption isotherm, and FIG. 3 shows the measurement results of the change with time of the adsorption.

Example 3 A sewage sludge was carbonized by heating the sewage sludge to about 500 ° C. in an oxygen-free atmosphere to be pulverized to 75 μm or less, and then suspended in a fluorine solution adjusted to a predetermined concentration. The amount of adsorption was measured, and the results are shown in Table 2.
It is expected that increasing the amount of sludge carbide will further reduce fluorine.

[0021]

[Table 2]

[0022]

As described above, the present invention has the following effects. (1) It is possible to efficiently separate harmful substances in the smoke washing wastewater by a very simplified process called a membrane separation process. That is, all of the suspended solids containing dioxins can be separated into a concentrate in the membrane separation step and a permeate containing mercury, fluorine, and the like. (2) A concentrated solution of a suspended solid containing dioxins is
It can be returned to the incinerator without any treatment and processed. (3) Since the flow does not include the coagulation sedimentation step, the amount of generated sludge is small and the disposal cost can be drastically reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a flow of a smoke washing wastewater treatment apparatus according to a first embodiment of the present invention.

FIG. 2 is a graph showing an adsorption isotherm of mercury by sludge carbide.

FIG. 3 is a graph showing the change over time of adsorption of mercury by sludge carbide.

FIG. 4 is a schematic configuration diagram showing an example of a flow of a conventional smoke washing wastewater treatment device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Smoke washing drainage tank 12 Mercury adsorption tower 14 Heavy metal adsorption tower 16 Membrane separator 17 Membrane 18 Return line 20 Backwash water tank 22, 24 Backwash line 26 Spent carbon extraction line 28 Spent chelating agent extraction line

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C02F 1/44 ZAB C02F 1/44 ZABK 1/58 1/58 M 1/62 1/62 D Z // B01J 20/20 B01J 20/20 D (72) Inventor Kazuyoshi Takagaki 1-1, Kawasaki-cho, Akashi-shi, Hyogo Kawasaki Heavy Industries, Ltd. Inside Akashi Plant (72) Inventor Masakazu Sawai 1-1-1, Higashi-Kawasaki-cho, Chuo-ku, Kobe-shi No. 3 Kawasaki Heavy Industries, Ltd.Kobe Head Office (72) Inventor Hiromasa Kusuda 1-3-1 Higashi Kawasaki-cho, Chuo-ku, Kobe City Kawasaki Heavy Industries, Ltd.Kobe Head Office (72) Inventor Kozo Yano Higashi Kawasaki, Chuo-ku, Kobe City 1-3-3 Kawasaki Heavy Industries, Ltd. Kobe Head Office F-term (reference) 4D006 GA06 GA07 KA02 KA72 KB12 KB30 KD03 KD09 KD19 KE12Q KE12R KE13Q KE13R MA22 PB08 PB20 PB70 4D024 AA04 AB11 AB18 BA01 BA03 BA11 BB06 BC01 CA01 DB03 DB04 DB05 4D025 AA09 AB21 AB22 AB23 AB24 AB25 AB26 BA17 BB07 CA05 DA03 DA05 4D038 AA08 AB40 AB63 AB73 BA04 BB06 BB09 4G066 AA04B AA05B AA32 CA

Claims (14)

[Claims] 1. Introducing smoke-washing wastewater from exhaust gas from an incinerator into a membrane separator to perform membrane separation into a concentrated liquid of suspended solids containing dioxins and a permeated liquid containing mercury, fluorine, and the like. A method for treating smoke-washing wastewater, characterized in that: 2. The method according to claim 1, wherein the concentrated liquid of suspended solids containing dioxins is returned to the incinerator. 3. A smoke-cleaning wastewater obtained by cleaning exhaust gas from an incinerator is introduced into a membrane separator, and is subjected to membrane separation into a concentrated liquid of suspended solids containing dioxins and a permeated liquid containing mercury, fluorine, and the like.
A method for treating sewage wastewater, comprising introducing a permeated liquid into a mercury adsorption tower and bringing it into contact with a carbon-based adsorbent to adsorb and remove mercury and fluorine dissolved in the permeated liquid. 4. The method according to claim 3, wherein the concentrated liquid of the suspended solids containing dioxins is returned to the incinerator. 5. The method according to claim 3, wherein the liquid subjected to the adsorption treatment is introduced into a heavy metal adsorption tower and brought into contact with a chelating agent to remove heavy metals in the liquid. 6. The method according to claim 3, wherein the mercury adsorption tower and the heavy metal adsorption tower are backwashed with the chelated liquid. 7. The method according to claim 3, wherein the carbon-based adsorbent is an organic substance, a sludge, or a char of livestock waste. 8. The method according to claim 3, wherein the carbon-based adsorbent is a carbide containing sulfur and calcium salts. 9. The carbide as claimed in claim 7, wherein the carbide is sewage sludge carbide.
Or the method for treating wastewater of smoke washing according to 8. 10. The method according to claim 1, wherein a microfiltration membrane or an ultrafiltration membrane is used in the membrane separation step. 11. The microfiltration membrane or ultrafiltration membrane having a pore size of 1
The method according to claim 10, wherein the thickness is from 0.001 µm to 0.001 µm. 12. A membrane separator for introducing a washing wastewater obtained by washing exhaust gas from an incinerator and performing membrane separation into a concentrated liquid of a suspended solid containing dioxins and a permeated liquid containing mercury, fluorine and the like. A mercury adsorption tower filled with a carbon-based adsorbent for adsorbing and removing mercury and fluorine by introducing a permeate, and a heavy metal adsorption filled with a chelating agent for removing heavy metals by introducing an adsorbed solution A smoke washing wastewater treatment device comprising a tower. 13. The smoke washing wastewater treatment apparatus according to claim 12, wherein the membrane separator and the incinerator are connected via a return line for a concentrated liquid of suspended solids containing dioxins. 14. A washing water tank for storing a part of the treated water of the heavy metal adsorption tower, and the washing water tank is connected to the mercury adsorption tower and the heavy metal adsorption tower via a backwash line. Or the smoke washing wastewater treatment apparatus according to 13.