JPH1147716A - Method and system for treating refuse incineration fly ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and system which enable the recovery of heavy metals from fly ash produced in a refuse incinerating apparatus by simple equipment, the utilization of the residue as a raw material for cement, and the extension of the life of disposal facilities by reducing the scale of reclamation. SOLUTION: In a fly ash treatment method, fly ash collected from exhaust gas from a refuse incinerator is extracted with water in extraction tanks 1, 2 and separated into filter cake and filtrate by separating means 6, 10, the obtained cake F is used as a part of raw materials for producing cement, and the filtrate from the separating means 6, 10 is treated chemically by heavy metal separating means 17, 18, 24, 28 to be separated into residual heavy metals and filtrate to recover heavy metals contained in the fly ash.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of treating incineration fly ash for treating fly ash generated from waste incineration equipment, and a treatment system suitable for carrying out the method. .

[0002]

2. Description of the Related Art As is well known, in a general waste incineration facility, a waste generated by the incineration of waste is collected together with exhaust gas by a cyclone, an electric dust collector, a cooling tower, or the like. Ash is generated. Here, fly ash is used to protect the incinerator by removing the soot and dust called incineration fly ash generated in the exhaust gas by the incineration of the waste itself and the chlorine component contained in the exhaust gas when incinerating the waste. Is a general term for dust and the like called lime fly ash generated by blowing slaked lime into the lime. The fly ash collected from the exhaust gas in this way contains silicon, calcium, and chlorine as main components, and contains a lot of low-boiling heavy metals such as zinc and lead. Therefore, due to the growing demand for environmental protection in recent years, for the treatment of this type of fly ash, especially for the stabilization of heavy metals, any of the melting method, cement solidification method, chemical treatment method and solvent elution method It is obliged to detoxify and landfill by such a method.

[0003]

However, as described above, the fly ash generated by incineration of refuse is mainly composed of silicon, calcium and the like. Unless the form has long-term stability like slag, the possibility of elution of heavy metals in the future cannot be denied. Further, if the fly ash is landfilled as it is by the above-mentioned processing method, the entire capacity becomes large, and there is a possibility that shortage of a processing plant may be caused at an early stage. Therefore, the present inventors have conducted intensive research on an effective processing method of fly ash by a method according to the above processing method,
First, the fly ash was extracted with water or acid, and the filter cake obtained by separating the fly ash was analyzed. As a result, the filter cake contained silicon and calcium as main components, and a small amount of zinc, lead or the like. Although it contains a boiling point heavy metal, there is no component that critically hinders its use as a cement raw material, and furthermore, after the filtrate is chemically treated, solid-liquid separation is performed, whereby zinc contained in the filtrate is removed. It has been found that residual heavy metals such as lead and lead can be recovered.

The present invention has been made based on such knowledge, and it has been found that heavy metals can be recovered from fly ash generated in refuse incineration facilities by simple equipment, and the residue can be recycled as a raw material for cement production. It is another object of the present invention to provide a method and a system for treating incineration fly ash, which makes it possible to extend the life of a treatment plant by reducing the amount of landfill treatment.

[0005]

According to a first aspect of the present invention, there is provided a method for treating fly ash from refuse incineration according to the present invention, wherein fly ash collected from flue gas in a refuse incinerator is extracted with water and filtered with a filter cake. Liquid and then use the obtained filter cake as a part of the raw material for cement production, and on the other hand, by chemically treating the filtrate to separate it into residual heavy metals and the filtrate, contained in the fly ash It is characterized by recovering heavy metals. At this time, the invention described in claim 2 is
The fly ash is characterized by being extracted with water, sedimented and separated, then further washed with water and separated by filtration to separate the filter cake and the filtrate.

According to a third aspect of the present invention, there is provided a waste incineration fly ash treatment system according to the present invention, wherein a fly ash collected from flue gas in a waste incinerator is extracted with water, and discharged from the extraction tank. Separating means for separating a filtered cake and a filtrate from the treated liquid containing the separated water and fly ash, a storage tank for storing the filtered cake separated by the separating means, and a residue obtained by chemically treating the filtrate. It is characterized by comprising heavy metal separation means for separating heavy metal and filtrate, and the invention according to claim 4, wherein the separation means is a thickener for sedimenting and separating the treatment liquid, And a filter press for filtering and separating the sediment from the thickener.

[0007] In the treatment system for refuse incineration fly ash according to claim 3 or 4 and the treatment method according to claim 1 or 2 using the same, fly ash collected from exhaust gas in a refuse incinerator is used. By water extraction and further separation, R ₂ O (= Na ₂ O + 0.658 * K ₂ O) is reduced to about 80
% And is separated into a filter cake containing a small amount of low-boiling heavy metals such as zinc and lead, and a filtrate mainly containing the low-boiling heavy metals. The filter cake thus separated does not impair the properties of the cement even if it is used as a cement raw material by mixing 1 to several percent with clinker. On the other hand, the filtrate was subjected to a chemical treatment to separate it into a residual heavy metal and a filtrate, whereby the heavy metal was recovered and treated by a non-ferrous metal separation and recovery step, and separated and rendered harmless. For water,
It can be drained as it is.

Therefore, according to the waste incineration fly ash treatment system and treatment method of the present invention, heavy metals are recovered from fly ash generated from the waste incineration facility by a simple facility such as water extraction, and the residue is dried. By doing so, it can be recycled as a part of the cement raw material. As a result,
In addition to the high cost, there is no need for complicated processing facilities requiring a great deal of time for operation management, and the processing medium is inexpensive water. In addition to being economical and capable of reducing the volume of the processing substance to be landfilled, it is possible to extend the life of the landfill site.

At this time, various systems using chemical or mechanical means are known as systems for separating the water-extracted treatment liquid. Is separated into the above-mentioned filter cake and the filtrate by sedimentation-separation of the water-extracted treatment liquid and further filtration separation, so that the above-mentioned separation treatment can be carried out by simple equipment such as a thickener and a filter press. In addition, since the filter cake is washed with water when it is separated by filtration, low boiling heavy metals such as zinc can be effectively separated from the filter cake.

[0010]

FIG. 1 shows an embodiment of a waste incineration fly ash treatment system according to the present invention. FIG.
In the figure, reference numeral 1 denotes a first extraction tank to which fly ash conveyed by a conveying means (not shown) and water for extraction are supplied, and a second extraction tank 2 is sequentially provided after the first extraction tank 1.
And a receiving tank 3 are provided. A thickener 6 is provided on the downstream side of the receiving tank 3 via a pump 4 and a delivery pipe 5. The thickener 6 is for sedimentation and separation of the treated water extracted from the water received from the receiving tank 3, and a sediment discharge pipe 7 connected to a lower part thereof is provided with a receiving tank 8.
And a pump 9 through which the sediment is filtered and separated by a filter press 10. Here, a washing water supply pipe 11 for washing the sediment is connected to the filter press 10. A telescopic conveyor 13 is provided below the filter press 10 for sequentially feeding the filter cake separated by filtration into a storage silo (storage tank) 12.

On the other hand, the supernatant water (filtrate) after sedimentation and separation in the thickener 6 is subjected to a chemical reaction from a transfer tank 16 by a receiving tank 14 and a pump 15 to a first reaction tank 17 for separating residual heavy metals. Second reaction tank 18
To be sent to And the first reaction tank 17
Is connected to a supply pipe 19 of iron chloride (FeCl ₂ ), and a second reaction tank 18 is provided with sodium hydrogen sulfide (NaH
The supply pipe 20 of S) is connected. The filtrate filtered and separated by the filter press 10 is also connected to the transfer pipe 16 via the receiving tank 21 and the pump 22 and is sent to the first reaction tank 17.

A thickener 24 for sedimenting and separating heavy metals from the chemically treated filtrate is disposed downstream of the discharge pipe 23 of the second reaction tank 18 and is connected to a lower portion thereof. The sediment discharge pipe 25 is guided via a receiving tank 26 and a pump 27 to a filter press 28 for filtering and separating the heavy metals. Below the filter press 28, heavy metals separated by filtration are stored in a silo 2
9 is provided with a charging conveyor 30 for charging. And the above-mentioned 1st reaction tank 17, 2nd reaction tank 18,
The thickener 24 and the filter press 28 constitute heavy metal separating means. The water separated by the filter press 28 and the thickener 24 is drained from the drain pipe 31 to the outside of the system.

Next, an embodiment of a processing method according to the present invention using the waste incineration fly ash processing system having the above configuration will be described with reference to FIG. First, fly ash is charged into the first extraction tank 1, and the extracted water is supplied and stirred, and then sent to the second extraction tank 2 and stirred to perform water extraction of the fly ash. Next, the obtained treated water is stored in the receiving tank 3, and then sent from the discharge pipe 5 to the thickener 6 by the pump 4, where it is settled and separated. Next, the sediment sedimented and separated in the thickener 6 is sent to the filter press 10 via the receiving tank 8 and the pump 9, washed with the washing water supplied from the washing water supply pipe 11, and separated by filtration. Then, the filter cake F thus obtained is sequentially charged into the storage silo 12 by the telescopic conveyor 13, and the storage silo 1 is appropriately charged.
2 and taken out to a transporting means (not shown), subjected to a separate drying treatment and the like, and then used as a part of cement raw material.

On the other hand, the supernatant water separated by the thickener 6 and the filtered water filtered and separated by the filter press 10 are sent from the transfer pipe 16 to the first reaction tank 17 by pumps 15 and 22, respectively. 19 Co-precipitation treatment with iron hydroxide is performed to recover heavy metals such as As and Cr, which are difficult to recover due to addition of iron chloride.
After being sent to 8 and subjected to sulfuration treatment for recovering general heavy metals by sodium hydrogen sulfide added from the supply pipe 20, it is sent from the discharge pipe 23 to the thickener 24. In the thickener 24, the heavy metal separated by the chemical treatment settles, and is sent from a lower part of the thickener 24 to a filter press 28 by a pump 27 and filtered, so that the heavy metal M is stored from the charging conveyor 30. It is collected in the silo 29 and separately processed in a non-ferrous metal separation and collection step. In addition, the wastewater from which the heavy metal M is collected and can be discharged to the outside of the system is drained from the thickener 24 and the filter press 28 via the drain pipe 31.

As described above, according to the waste incineration fly ash treatment system and the treatment method using the same, the heavy metal M is recovered from the fly ash generated from the waste incineration facility by a simple method such as water extraction. Since the residue can be recycled as a part of the cement raw material by drying or the like, the cost is high, and there is no need for a processing facility that requires labor for operation management, and the processing medium is inexpensive water. Therefore, the fly ash can be treated with simple equipment, which is economical. Moreover, since part of the fly ash is used as a cement raw material and only the part recovered as other heavy metals needs to be landfilled, etc., the volume of the processing substance to be landfilled can be reduced. The life of the factory can be extended.

In particular, as a system for separating a water-extracted treatment liquid, a thickener 6 and a filter press 10 are used. The water-extracted treatment liquid is separated by sedimentation with a thickener 6 and further separated by filtration with a filter press 10. Since the filter cake is separated into the filter cake and the filtrate, the separation treatment can be performed by a simple and easy-to-maintain facility. Since the filter cake is washed with washing water, low-boiling heavy metals such as zinc can be separated from the filter cake.

[0017]

As described above, according to the third or fourth aspect,
According to the waste incineration fly ash treatment system and the treatment method according to claim 1 or 2, the heavy metal is recovered from the fly ash generated from the waste incineration facility by simple equipment such as water extraction. Since the residue can be recycled as a part of the cement raw material by drying treatment or the like, it is not necessary to use a treatment facility that is expensive and requires time and labor for operation management, and the treatment medium is inexpensive water. Because of this, the above fly ash can be treated with simple equipment, so that it is economical, and at the same time, the volume of the treatment substance to be landfilled can be reduced, so that the life of the landfill is extended. It becomes possible.

In particular, according to the second or fourth aspect of the present invention, the separation treatment can be performed by simple equipment such as a thickener and a filter press, and at the time of filtration and separation, the filter cake is washed with water. Therefore, an effect that a low boiling heavy metal such as cadmium can be easily separated from the filter cake can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a waste incineration fly ash treatment system according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st extraction tank 2 2nd extraction tank 6 thickener 7 sediment discharge pipe 10 filter press 11 washing water supply pipe 12 storage silo (storage tank) 17 1st reaction tank 18 2nd reaction tank 24 thickener 28 filter press 29 storage silo 31 drainage pipe

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hidefumi Kamiishi 355 Karimachi, Hodogaya-ku, Yokohama-shi, Yokohama No. 1 Chiyoda Kako Construction Co., Ltd. 2-12-1, Chiyoda Chemical Construction Co., Ltd. (72) Inventor Taisuke Oshima 2-12-1, Tsurumi Chuo, Tsurumi-ku, Yokohama Kowa Seiko Co., Ltd., 46, Nakahara 46, Tobata-ku 25 over 24 Aso Cement Co., Ltd. in

Claims (4)

[Claims] 1. A fly ash collected from an exhaust gas in a refuse incinerator is extracted with water to separate it into a filter cake and a filtrate, and the obtained filter cake is used as a part of a raw material for cement production. And a method for treating refuse incineration fly ash, comprising recovering heavy metals contained in the fly ash by chemically treating the filtrate to separate the residual heavy metal and the filtrate. 2. The refuse according to claim 1, wherein the fly ash is extracted with water, then sedimented and separated, then further washed with water and separated by filtration to separate the filter cake and the filtrate. How to treat incinerated fly ash. 3. An extraction tank for water-extracting fly ash collected from flue gas in a refuse incinerator, and a treatment liquid containing water and fly ash sent from the extraction tank is converted into a filter cake and a filtrate. It is characterized by comprising a separating means for separating, a storage tank for storing the filter cake separated by the separating means, and a heavy metal separating means for chemically treating the filtrate to separate it into a residual heavy metal and a filtrate. Waste incineration fly ash processing system. 4. The incineration of refuse according to claim 3, wherein said separation means comprises a thickener for sedimenting and separating the treatment liquid, and a filter press for filtering and separating sediment from the thickener. Fly ash processing system.