JP3457169B2 - How to treat incinerated fly ash - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for treating incinerated fly ash generated from a refuse incinerator for incinerating municipal waste, industrial waste, etc. It belongs to the technical field of incineration fly ash processing methods that enable reduction of fuel and effective utilization of incineration fly ash.

[0002]

2. Description of the Related Art Incinerator ash and incinerated fly ash are generated from a refuse incinerator that incinerates municipal waste and industrial waste. Further, the exhaust gas contains HCl, SO _x , and NO _x , and further contains heavy metals such as Cd and Pb. In Japan, the exhaust gas regulations of refuse incinerators have recently been strengthened, and the technology for removing HCl, SO _x , and NO _x has been developed, and the amount of harmful gas emitted from the chimney has become extremely small. However, these HCl, SO _x , NO _x
Is collected in the dust collector or adsorbed by the demineralizer in the electrostatic precipitator and discharged in the form of coexisting with heavy metals such as Cd and Pb. Further, in order to remove dioxins and the like in exhaust gas together with heavy metals, an electric dust collector and a bag filter are often used.

However, when the incineration fly ash collected by the above-mentioned electric dust collector or bag filter is landfilled without treating the incineration fly ash, for example, fresh water according to Notification No. 13 of the Environmental Agency was used. Dissolution test (By the way, Pb
Regulation value of 0.3 mg / l or less, regulation value of Cd is 0.3
It is below mg / l. ) Can not be cleared, the fact is that incineration fly ash is generally landfilled after being solidified with cement. However, in recent years, further reduction of the elution amount of harmful substances such as dioxins and heavy metals has been required in order to surely meet strict environmental standards, and incineration fly ash has been required to deal with the difficulty of securing landfill treatment sites. There is a demand for effective utilization.

An example of a device capable of easily reducing the elution amount of harmful substances is, for example, JP-A-5-15867.
The one disclosed in Japanese Patent Publication (Heating type ash processing device) is known. The heating ash treatment apparatus according to Conventional Example 1 heats incineration fly ash generated from a refuse incinerator to a temperature at which heavy metals are volatilized by a heat transfer body or a burner to decompose dioxins, and to remove heavy metals. By volatilizing and separating the separated volatile matter, the heavy metals can be easily and inexpensively separated, and the volatile matter and the non-volatile matter can be easily collected and treated.

[0005] Further, as a means for effective utilization, there is known one disclosed in, for example, Japanese Patent Publication No. 59-18344 (sintering method of fly ash granules). In the sintering method of the fly ash granulated product according to this conventional example 2, fly ash generated from a coal-fired boiler or the like, that is, raw pellets obtained by granulating incinerated fly ash is laminated on a moving grate to produce raw ash. A method of sintering while forming an air flow passing from the upper side to the lower side in the layer of pellets, more specifically, by preheating, drying, igniting, heat retaining and cooling the raw pellets on a moving grate, An artificial lightweight aggregate or the like is obtained as a calcined product.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention Conventional Example 1 or 2
Each of the incineration fly ash treatment technologies related to the above is considered to be useful as such. However, in the incineration fly ash treatment technology according to Conventional Example 1, harmful substances such as heavy metals and dioxins in the incineration fly ash are detoxified, but the incineration fly ash after firing treatment is landfilled. In addition to this, a huge amount of thermal energy is required to heat the incineration fly ash, which causes a problem of increasing the firing processing cost.

Further, according to the incineration fly ash processing technique of the second conventional example, since the incineration fly ash generated from the coal-fired boiler does not contain a large amount of heavy metals, the incineration fly ash is burned. There was no problem with regard to the amount of toxic substances eluted from the artificial lightweight aggregate obtained in this way. However, regarding fly ash generated by incineration of waste such as municipal waste,
Since it contains a large amount of harmful heavy metals and the necessary conditions for volatilizing low-boiling heavy metals cannot be obtained, it cannot be effectively used if the elution amount of heavy metals cannot be kept below the reference value. There was a problem. Of course, the low boiling heavy metals can be volatilized by adopting an external heating means, extending the firing time, etc., but this is not preferable because it causes an increase in fuel cost.

[0008] Therefore, the object of the present invention is to ensure that the heavy metals can be volatilized even in the case of incinerated fly ash of municipal waste or industrial waste that has a low energy cost and contains a large amount of heavy metals. It is to provide a method for treating incinerated fly ash that makes it possible to effectively utilize the incinerated fly ash by making it harmless.

[0009]

The present invention has been made in view of the above circumstances, and therefore, in order to solve the above problems, a method for treating incinerated fly ash according to claim 1 of the present invention is adopted. The means is a method for treating incineration fly ash, which comprises incinerating fly ash containing a large amount of heavy metals generated from an incinerator that incinerates municipal solid waste and industrial waste in a calcination furnace to obtain a calcined product. In addition, the crushed waste plastic obtained by crushing chlorine-containing waste plastic is mixed and mixed to be molded into a mixed molded product, and then the mixed molded product is fired.

[0010]

The means adopted by the method for treating incinerated fly ash according to claim 2 of the present invention is characterized in that, in the method for treating incinerated fly ash according to claim 1, the mixed molded product is granulated. .

[0012] The means adopted by the method for treating incinerated fly ash according to claim 3 of the present invention is the method for treating incinerated fly ash according to any one of claims 1 and 2, wherein the baking treatment is performed. It is characterized by spraying a gas onto an object to quench it.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A firing furnace for carrying out a method for treating incinerated fly ash according to the present invention is shown in FIG.
Will be described with reference to.

Reference numeral 1 shown in FIG. 1 is a firing furnace for firing incineration fly ash generated from an incinerator (not shown) for incinerating municipal waste and industrial waste. A firing burner 10 to which fuel is supplied from a fuel supply pipe 9 and combustion air is supplied from a combustion air supply pipe 8 is attached to the firing furnace 1. Further, a cooling air supply pipe 11 that supplies a gas for cooling the calcined product immediately after the calcining process, that is, a cooling air is connected to the side for discharging the calcined calcined product.

Further, in the firing furnace 1, incineration fly ash discharged from the incineration fly ash storage tank 2, crushed waste plastic discharged from the crushed waste plastic storage tank 3, and fine powder discharged from the pulverized coal storage tank 4. Charcoal is mixed by a mixer 5 to which water is supplied from a water supply pipe 6, and the kneaded product mixed by the mixer 5 is formed into granules by a granulator 7 and supplied as a mixed molded product. Has been done. In addition, the reason why the mixed molded product is granulated in this way is to improve the cooling rate of the baked product obtained by baking the mixed molded product by improving the air permeability of the cooling air. is there.

The granulated mixed molded product is fired in the firing furnace 1, and is forcibly and rapidly cooled by the cooling air supplied from the cooling air supply pipe 11 to be provided outside the furnace. The baked product 15 is placed in the processed product storage tank 14.
It is configured to be stored as. On the other hand, the exhaust gas discharged from the firing furnace 1 is processed by the wet exhaust gas processing device 12 and then discharged into the atmosphere through the exhaust gas discharge duct 13.

Hereinafter, a method of firing incineration fly ash in the firing furnace having the above-mentioned structure will be described. For example, when municipal solid waste or industrial waste is incinerated by a refuse incinerator such as a fluidized bed incinerator (not shown), incinerated ash and incinerated fly ash are generated. Out of the incineration ash generated from the refuse incinerator and the incineration fly ash, the incineration fly ash is collected by an electric dust collector or a bag filter. When the incineration fly ash thus collected is subjected to the firing treatment, first, a predetermined amount of pulverized waste plastic pulverized by a grinder (not shown) and having a particle size not larger than a predetermined size is mixed with the incineration fly ash collected. When crushed waste plastic is mixed,
A predetermined amount of pulverized coal is also mixed if necessary.

Then, the incinerated fly ash and the crushed waste plastic or the incinerated fly ash, the crushed waste plastic and the pulverized coal are mixed by the mixer 5, and the mixed product is granulated by the granulator 7 to be dried and dried. After that, it is put into the firing furnace 1 to be subjected to a firing treatment. Since the pulverized waste plastic burns as a fuel during the firing treatment in the firing furnace 1, the consumption of fuel such as heavy oil and electric power required for heating is reduced. Be reduced.

The heavy metals contained in the fired product granulated depending on the temperature during the firing process are volatilized and the dioxins are decomposed, so that the content of harmful substances in the fired product is reduced. Can be effectively reduced. Of course, the volatilized heavy metals are sent to the wet exhaust gas treatment device 12 together with the exhaust gas discharged from the firing furnace 1. Then, heavy metals are removed by the wet exhaust gas treatment device 12, and only clean exhaust gas with a low content of heavy metals is released into the atmosphere through the exhaust gas exhaust duct 13.

[0020]

EXAMPLE Next, a method of treating incinerated fly ash according to an example of the present invention will be described. First, municipal waste and industrial waste were supplied to a refuse incinerator for incineration, and incineration fly ash generated during incineration was collected by an electric dust collector or a bag filter. The incinerated fly ash thus collected is crushed into waste plastic to obtain crushed waste plastic having a particle size of 0.5 mm or less.
Wt% was mixed and mixed by the mixer 5, and the mixture was granulated by the granulator 7 to form a granular mixed molded product having an average particle size of 10 mm. There are two types of waste plastic mixed in incineration fly ash: polystyrene (hereinafter referred to as PS) and polyvinyl chloride (hereinafter referred to as PVC), and two types of granular mixed molding individually mixed into incineration fly ash. Each of the products was baked at 1000 ° C. for 30 minutes.

According to the incineration fly ash treatment method of the present invention, the firing temperature of 1000 ° C. can be achieved without supplying electric power or fuel such as heavy oil to the firing furnace as in the conventional example. I was able to. That is, since the mixing ratio of the crushed waste plastic to the incineration fly ash is set so that the baking temperature of 1000 ° C. can be achieved, the mixing ratio of the crushed waste plastic and the baking temperature are not limited. The firing temperature of the incinerated fly ash may be controlled in the temperature range of 800 to 1300 ° C in consideration of the durability of the firing furnace and the effect of removing harmful substances.

By the way, if the calcined product is kept at a temperature of 300 to 600 ° C. for a long time, the thermally decomposed dioxins are resynthesized. Therefore, in order to prevent the re-synthesis of dioxins, the cooling air is supplied from the cooling air supply pipe 11 to the calcined product immediately after the calcining (the temperature of the granular calcined product is 600 ° C. or more) and the spraying is performed. Then, it was rapidly cooled to obtain granular fired product 1 (containing crushed waste plastic with PS) and fired product 2 (containing crushed waste plastic with PVC).

The content of heavy metals in the thus-obtained granular calcined products 1 and 2 is shown in Table 1 in comparison with the content of heavy metals in incinerated fly ash. Incidentally, in order to confirm the difference from the forced cooling, the fired product 3 obtained by natural cooling without blowing cooling air (PVC mixed as crushed waste plastic) is also shown in Table 1. Shown in. The heavy metal content test is 127
It was done based on.

[0024]

[Table 1]

According to Table 1 above, for example, 1 kg / kg
PS mixed with incineration fly ash containing 500 mg of Pb
400 in the baked product 1 obtained by mixing and forcibly cooling
In the case of the baked product 2 obtained by mixing and mixing PVC with mg, and forcibly cooling, mix PVC with 200 mg again,
In addition, the calcined product 3 obtained by natural cooling has a content of 350 mg, which is less than the content reference value of 600 mg in the "Soil Contamination Investigation / Countermeasure Guideline for Heavy Metals", and other heavy metals Hg. , Cr, As, Cu, Zn are all reduced in content. It can be understood that the reason why the content of heavy metals in the calcined product is reduced is that the heavy metals are volatilized by the calcining treatment.

Further, as described above, the content of heavy metals is smaller in the calcined product 2 than in the calcined product 1. Such a difference in the content of heavy metals is due to the presence or absence of chlorine (hereinafter referred to as Cl) contained in the crushed waste plastic mixed in the incineration fly ash, as is well understood from the above description. . In other words, it has been suggested that Cl promotes volatilization of heavy metals, and in particular, in order to remove heavy metals from incinerator fly ash containing a large amount of heavy metals, PVC containing Cl may be mixed and mixed. It turns out to be extremely effective.

Next, the physical properties of the thus-calcined products 1 to 3 were examined. Their physical properties are shown in Table 2.

[Table 2] According to Table 2 above, all of the fired products 1 to 3 are excellent in crush strength and have physical properties that can be utilized as a recycled material such as an artificial lightweight aggregate as in the case of Conventional Example 2. Understands well.

By the way, even if the physical properties of the calcined product are excellent as described above, if the elution amount of heavy metals does not satisfy the soil environmental standard, these calcined products are used as resources such as artificial lightweight aggregates. Since it cannot be utilized as a resource, a dissolution test of heavy metals was conducted to investigate whether it could be utilized as a resource. The results of the dissolution test for heavy metals are shown in Table 3.
As shown in.

Lead or its compound is JISK01.
02 (54.2), cadmium or a compound thereof according to JIS K0102 (55.2), and mercury or a compound thereof according to Environmental Agency Notification No. 59 (Appendix 4). Hexavalent chromium compounds are analyzed by JISK0102 (65.2) and arsenic or its compounds are determined by the Environmental Agency Notification No. 5
Selenium was analyzed by the analysis method based on No. 9 (Appendix 2), and selenium was analyzed by the analysis method based on Environmental Agency Notification No. 59 (Appendix 2).

[0030]

[Table 3] According to Table 3 above, all of lead, cadmium, hexavalent chromium, arsenic, and selenium clear the soil environmental standard, and any of the calcined products can be utilized as recyclable materials such as artificial lightweight aggregates. Suggests.

Even if these calcined products have a content of heavy metals that can be effectively utilized as a recyclable material such as an artificial lightweight aggregate and have physical characteristics, if they contain a high concentration of dioxins. Since it cannot be effectively utilized, it was investigated how much dioxins in the calcined product were reduced by the calcining treatment. The results of the investigation are shown in Table 4 in which incinerated fly ash and burned products 1 to 3 are compared. In addition, T shown in the bottom column of this Table 4
EQ (Int.) Is a toxicity equivalent conversion value of dioxins.

[Table 4] According to Table 4 above, in the calcined products 1 and 2 that were forcibly cooled after the calcining process, dioxins were significantly reduced. Therefore, since the content of dioxins is small, the calcined products 1 and 2 can be fully utilized as a resource product such as an artificial lightweight aggregate. However, since the concentration of dioxins in the calcined product 3 naturally cooled after the calcining treatment is higher than the concentration of dioxins in the calcined products 1 and 2, effective use of the calcined product 3 Is left with challenges.

As described above, the method for treating incineration fly ash according to the present invention is effective in utilizing the incineration fly ash by mixing and mixing the waste plastic to be landfilled or incinerated with the incineration fly ash and firing the mixture. It is the one that was offered. Therefore, when burning incineration fly ash, the crushed waste plastic is used as a fuel, which significantly reduces the fuel consumption for firing incineration fly ash and also eliminates harmful substances such as heavy metals and dioxins. Since it can be effectively removed, and the obtained fired product can be used as a recycled material such as an artificial lightweight aggregate, it is not necessary to perform landfill treatment as in Conventional Example 1. , The incineration fly ash is advantageous in terms of the burning treatment cost of the incineration fly ash, and even if the incineration fly ash contains a large amount of heavy metals generated by incineration of waste such as municipal waste as in the conventional example 2, the standard value is obtained. There is an extremely excellent effect that the following can be achieved.

In the above, when PVC is used as the waste plastic mixed in the incineration fly ash for the firing treatment,
The results are described in comparison with the case of using PS . However, other waste plastics such as polyvinyl chloride
Since redene and the like can also be used, the scope of the technical idea of the present invention is not limited by the above-described embodiments.

[0034]

As described above, the claims 1 and 2 of the present invention are as follows .
According to the incineration fly ash treatment method according to 2 or 3 , the crushed waste plastic mixed and mixed with the incineration fly ash serves as fuel, so that fuel consumption for firing treatment is reduced and heavy metals, dioxins, etc. are reduced. It is possible to effectively remove harmful substances and to use the obtained calcined product as a recycled material such as artificial lightweight aggregate. It is extremely effective in improving the effective utilization of ash.

[Brief description of drawings]

FIG. 1 is a schematic configuration explanatory diagram of a firing furnace for carrying out a method for treating incinerated fly ash according to the present invention.

[Explanation of symbols]

1 ... Baking furnace 2 ... Incineration fly ash storage tank 3 crushed waste plastic storage tank 4 ... Pulverized coal storage tank 5 ... Mixer 6 ... Water supply pipe 7 ... Granulator 8 ... Combustion air supply pipe 9 ... Fuel supply pipe 10 ... Burning burner 11 ... Cooling air supply pipe 12 ... Exhaust gas treatment device 13 ... Exhaust gas exhaust duct 14 ... Firing processed material storage tank 15 ... Firing product

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-10-202221 (JP, A) JP-A-4-131174 (JP, A) JP-A-8-182983 (JP, A) JP-A-6- 136458 (JP, A) JP-B-63-33433 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) B09B 3/00

Claims (3)

(57) [Claims] 1. A method for treating incineration fly ash, comprising incinerating fly ash containing a large amount of heavy metals generated from an incinerator that incinerates municipal solid waste and industrial waste in a calcination furnace to obtain a calcined product. A method for treating incinerated fly ash, which comprises mixing crushed waste plastic obtained by crushing chlorine-containing waste plastic with fly ash to form a mixed molded product, and then firing the mixed molded product. 2. The method for treating incinerated fly ash according to claim 1, wherein the mixed molded product is granulated. 3. The method according to claim 1, wherein a gas is blown to the baked product to quench it.
The method for treating incinerated fly ash as described in one item.