JPH11192471A - Treatment of melted fly ash or incineration fly ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preventing the elution of heavy metals contained in fly ash into the environment at a low cost without increasing the treating volume and a method for surely decomposing dioxin in the fly ash at low equipment cost and running cost. SOLUTION: The melted fly ash generated from a melting furnace of the municipal refuse and/or industrial waste or the incineration ash generated from an incinerator are treated by this method. Namely, the pH of the melted fly ash or incineration fly ash 11 to be treated is measured in advance the melted fly ash or incineration fly ash 11 is heated to 580-800 deg.C when the pH is >=11.0 to control the pH of the treated fly ash 14 to pH 8.5 to <11.0 to prevent the elution of the heavy metals in the treated fly ash 11, and the dioxin contained in the treated fly ash 14 is decomposed at the same time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molten fly ash generated from a melting furnace or a fly ash generated from an incinerator, which prevents leaching of heavy metals contained therein and decomposes dioxin. And a dioxin decomposition method.

[0002]

2. Description of the Related Art In recent years, when municipal garbage and / or industrial waste is melted in a melting furnace or incinerated in an incinerator, hydrogen chloride or the like in exhaust gas generated from the melting furnace or incinerator is used. In order to adsorb and fix acidic components, a method of blowing slaked lime (Ca (OH) 2) into exhaust gas has been practiced. Such flue gas contains molten fly ash or incinerated fly ash (hereinafter simply referred to as fly ash) having a relatively small particle diameter in the calcined ash generated during the melting process or the incineration process. And are collected by a dust collector or the like. Fly ash is often landfilled at a final disposal site,
Fly ash contains harmful heavy metals such as lead and cadmium, and toxic dioxins, etc., which elute into the surroundings due to the action of rainwater or the like and become a factor that pollutes the environment. Methods for preventing the elution of heavy metals from fly ash include (1) melt solidification, (2) chemical treatment, (3) cement treatment, and (4)
Four methods of acid extraction are known. The melt-solidification method involves heating fly ash to its melting temperature and entrapping heavy metals in the molten slag.The chemical treatment involves chemically encapsulating heavy metals in chemicals as represented by the chelate method. It is. The cement treatment is a method in which fly ash is mixed with cement to be solidified, and the acid extraction method is a method in which fly ash is immersed in an acid to extract and remove heavy metals. On the other hand, as a method for decomposing dioxin in fly ash, for example, Japanese Patent Publication No. 6-388
According to Japanese Patent No. 63, fly ash is stored at 200 ° C. in an oxygen-deficient state.
It is said that heating at 550 ° C. to decompose polyhalogenated compounds containing dioxin. According to JP-A-8-303741, fly ash is reduced to 400 to
By heating to 550 ° C., harmful organic chlorine compounds such as dioxin can be decomposed. The publication,
Proceedings of the 5th Waste Management Research Conference (January 1994)
Published by Japan Society of Waste Management on 20th of October) 398-400, "Leaching characteristics of heavy metals in municipal solid waste incineration fly ash" (authored by Mitsui Engineering & Shipbuilding Co., Ltd.) and Die Breaker (fly ash heat dechlorination equipment) issued by Mitsui Engineering & Shipbuilding Co., Ltd. , As decomposition atmosphere conditions other than temperature,
For example, there is no description of a hypoxic state or the like.

[0003]

However, the above methods of melting and solidifying the fly ash, mixing the fly ash with a chemical and cement, or extracting the heavy metals in the fly ash by acid are all expensive. In addition, there is a problem that the volume after processing increases. In addition, slaked lime is often added as a neutralizing agent for acid gas in exhaust gas in municipal solid waste, etc., so it does not react during fly ash generated from melting furnaces or fly ash generated from incinerators. Ca
There is a problem that the O content is included and the pH when fly ash is immersed in water increases, which promotes the elution of heavy metals.
On the other hand, in the method of decomposing dioxin, in order to decompose in a state of oxygen deficiency, as described in JP-B-6-38863, air intrusion is prevented or
It is necessary to fill the processing apparatus with an inert gas such as nitrogen.
In any of these cases, in order to always maintain the oxygen-deficient state, the processing apparatus must be securely sealed.
Of course, the processing apparatus has a supply port and a discharge port for fly ash, and the structure of the supply and discharge device becomes complicated because it is necessary to secure airtightness while taking in and out the fly ash. Of course, in addition to that, the sealing structure of each part of the apparatus becomes large, so that the whole apparatus becomes considerably expensive. Also,
Of course, when using an inert gas, it is necessary to always replenish it.
The operating cost increases accordingly. In another non-hypoxic condition (hereinafter referred to as oxidizing atmosphere in air),
Although the heat treatment is performed at 400 to 550 ° C., according to an experiment conducted by the inventors in an oxidizing atmosphere in the air, as shown in Table 7 and FIG. A heating temperature of ° C. is not sufficient. The present invention has been made in view of the above circumstances, and a method for preventing heavy metal contained in fly ash from eluting into the environment at a low cost without increasing the processing volume, and a method for preventing heavy metal elution of fly ash, and equipment and operating costs. It is an object of the present invention to provide a method for decomposing fly ash, which can decompose dioxin at a low cost and reliably.

[0004]

According to the present invention, there is provided a semiconductor device comprising:
The method for treating molten fly ash or incinerated fly ash described above is a method for treating molten fly ash generated from a melting furnace for municipal waste and / or industrial waste or incinerated fly ash generated from an incinerator. The pH of the molten fly ash or incinerated fly ash to be measured is measured, and when the measured value is 11.0 or more, the molten fly ash or the incinerated fly ash is heated to 580 to 800 ° C. Is adjusted to 8.5 or more and less than 11.0 to prevent elution of heavy metals in the treated fly ash, and dioxin contained in the treated fly ash is also decomposed at the same time. The method for treating molten fly ash or incinerated fly ash according to claim 2 is characterized in that
Or a method of treating molten fly ash generated from a melting furnace of industrial waste, or incinerated fly ash generated from an incinerator, measuring the pH of the molten fly ash or incinerated fly ash to be treated in advance, When the measured value is less than 8.5 neutral or acidic, an alkali source is added in advance to adjust the pH of the molten fly ash or incinerated fly ash to 11.0 or more, and then the molten fly ash or incinerated Heat treatment of fly ash to 580-800 ° C, pH of treated fly ash
Is set to 8.5 or more and less than 11.0 to prevent elution of heavy metals in the treated fly ash, and dioxin contained in the treated fly ash is also decomposed. The method for treating molten fly ash or incinerated fly ash according to claim 3 is a method for treating molten fly ash generated from a melting furnace for municipal garbage and / or industrial waste or incinerated fly ash generated from an incinerator. After the molten fly ash or incinerated fly ash to be treated in advance is washed with water, the pH of the washed fly ash is measured, and when the measured value is 12.0 or more, the washed fly ash is heated to 580 to 800 ° C. Treated and treated fly ash p
H is set to 8.5 or more and less than 11.8 to prevent elution of heavy metals in the treated fly ash, and dioxin contained in the treated fly ash is also decomposed at the same time. The method for treating molten fly ash or incinerated fly ash according to claim 4 is a method for treating molten fly ash produced from a melting furnace for municipal waste and / or industrial waste or incinerated fly ash produced from an incinerator. Then, after washing the molten fly ash or incinerated fly ash to be treated in advance,
The pH of the washed fly ash is measured, and when the measured value is neutral or acidic, less than 8.5, an alkali source is added in advance to adjust the pH of the washed fly ash to 12.0 or more, and then the The washed fly ash is heat-treated at 580 to 800 ° C. to adjust the pH of the treated fly ash to 8.5 or more and less than 11.8, to prevent elution of heavy metals in the treated fly ash and to be included in the treated fly ash. Dioxin is also decomposed at the same time.

[0005] Melt fly ash is ash accompanying exhaust gas generated from a melting furnace when municipal waste and / or industrial waste is treated in a melting furnace. Or, when treating industrial waste in an incinerator, ash accompanying exhaust gas generated from the incinerator, and in each case, particles having a relatively small particle size discharged together with the exhaust gas were collected by a dust collector or the like. Consist of things. on the other hand,
The incineration ash that accumulates at the bottom of the incinerator is called main ash. The pH of the molten fly ash or incinerated fly ash (hereinafter, simply referred to as fly ash), and the pH of the intermediate fly ash and the final treated fly ash that have been treated with these fly ash are the Test Method No. 13 of the Notification of the Environment Agency Is a measured value of pH measured by the method defined in the above, obtained by immersing a predetermined amount of sample in a predetermined amount of water under predetermined conditions, and measuring the hydrogen ion concentration in the immersion liquid . Heat treatment of fly ash (alkaline fly ash) having a pH of 11.0 or more causes Ca (OH) 2 in fly ash
Dehydration reaction at about 580 ° C (1), formation reaction of calcium silicate of CaO and SiO2 ((2), (3),
(4)), formation reaction of Na2 O with SiO2 and Al2 O3 ((5) to (9)), K2 O with SiO2 and Al2
Formation reaction with O3 ((10) to (14)), MgO and C
A production reaction with aO and SiO2 occurs, and a stable compound is produced, so that a free alkali source (CaO,
Na2 O, K2 O, MgO) can be reduced.

(1) Ca (OH) 2 → CaO + H 2 O (2) CaO + SiO 2 → CaO.SiO 2 (3) 2CaO + SiO 2 → 2CaO.SiO 2 (4) 3CaO + 2SiO 2 → 3CaO.2SiO 2 (5) Na 2 O + SiO 2 → Na 2 O.SiO 2 (6 Na2O + 2SiO2 → Na2O.2SiO2 (7) 2Na2O + SiO2 → 2Na2O.SiO2 (8) Na2O + Al2O3 + 6SiO2 → Na2O.
Al2 O3 .6SiO2 (9) Na2 O + Al2 O3 + 2SiO2 → Na2 O.
Al2 O3 .2SiO2 (10) K2 O + SiO2 → K2 O.SiO2 (11) K2 O + 2SiO2 → K2 O.2SiO2 (12) K2 O + 4SiO2 → K2 O.4SiO2 (13) K2O + Al2 O3 + 2SiO2 → K2 O.A
l2 O3 · 2SiO2 (14) K2 O + Al2 O3 + 6 SiO2 → K2 O · A
l2 O3 .6SiO2 If the heating temperature at the time of heat-treating the fly ash is lower than 580 DEG C., it becomes difficult to cause the reactions (1) to (14). Conversely, if the heating temperature of the fly ash is higher than 800 ° C., heavy metals, metal chlorides, etc. evaporate, causing secondary pollution, which requires an exhaust gas treatment, which is not preferable.

[0007] The p of the treated fly ash obtained by heat-treating the fly ash
If H is lower than 8.5, the elution amount of heavy metal ions such as lead increases. In addition, even if the pH of the treated fly ash becomes 11.0 or more, it becomes a factor to increase this elution amount. In the case of the treated fly ash obtained by heat-treating the washed fly ash, the pH value of the treated fly ash is lower than 8.5, and conversely, when the pH value of the treated fly ash is 11.8 or more, the concentration of heavy metal dissolved increases. Is not preferred.

The elution amount (elution concentration) of heavy metal eluted when the treated fly ash is submerged is as follows: (1) pH value obtained by immersing the treated fly ash in water and stirring; Determined by the concentration of the water-soluble chloride in it. (1) Elution of heavy metal components such as Pb, Cd, Zn, and Cr
The elution amount is highly dependent on the pH value, and the elution amount is determined by the pH value. (2) Due to the presence of water-soluble heavy metal chlorides such as lead chloride in fly ash, the solubility product of heavy metal oxides and hydroxides is increased, and the elution concentration of heavy metals is increased. The pH value of fly ash is CaO in the free state or
The pH value is determined by the concentration of Ca (OH) 2, and even if present in a small amount, the pH value indicates an alkalinity of 12 or more. For example, it is not an exaggeration to say that the elution amount of lead (Pb), which has a large pH dependence and is abundant in fly ash, is determined by this pH value.

According to the present invention, fly ash containing lime such as Ca (OH) 2 and CaO is heated in a specific temperature range to activate by a dehydration reaction (580 ° C. or more) of Ca (OH) 2. To generate CaO having a high concentration, thereby promoting the reaction of generating CaO and SiO2. In addition, alkali metal and alkaline earth metal oxides (Na2O, K2O,
(MgO etc.) becomes active, and a formation reaction with SiO2 etc. occurs. As a result, CaO, Na2 O, K2 O, MgO, etc., which are free alkali sources, are converted into SiO2, Al
It reacts with 2 O3 and the like, is captured and fixed, and can maintain the pH value when immersed in water in a predetermined range to prevent elution of heavy metals. In addition, after the fly ash is washed with water, heat treatment of the washed fly ash can further effectively prevent the elution of heavy metals from the treated fly ash. That is, since the water-soluble heavy metal chlorides and the like have been removed in advance by washing the fly ash with water, heat treatment of the dried or washed fly ash containing a small amount of water can further prevent the elution of heavy metals. Can be done

Further, since fly ash is heated at a high temperature of 580 ° C. or more in an oxidizing atmosphere in the air, an effect of decomposing dioxin and rendering it harmless is also obtained. Also, recently, powder adsorbents such as activated coke and activated carbon have been blown to adsorb dioxins in exhaust gas, and the fly ash generated may contain such activated coke and activated carbon. The presence or absence of ignition of these activated coke and activated carbon is greatly affected not only by the ambient temperature but also by the surrounding environment, such as the deposition state and the state of ventilation, but according to experiments by the inventors, at the current heating temperature of 580 ° C. or more, It has been confirmed that ignition and combustion can be ensured even in a short time. Usually, the powder adsorbent is injected in an amount of about 3% with respect to the amount of fly ash, so that assuming that all of the fire ignites to CO2, the temperature of the fly ash rises by about 100 ° C.
(The heat transfer efficiency was assumed based on the above experimental results.) Therefore, the amount of heat for heating can be reduced accordingly. Also, naturally, a large amount of dioxin is adsorbed and captured in this powder adsorbent,
These dioxins are similarly decomposed and rendered harmless by the heating of the fly ash.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. FIG. 1 is an explanatory view of a fly ash treatment device 10 to which a method for treating molten fly ash or incinerated fly ash according to a first embodiment of the present invention is used. Alternatively, a high-temperature processing furnace 15 for heating the fly ash 11 in a nitrogen gas to obtain the treated fly ash 14 is provided. The method for treating molten fly ash or incinerated fly ash according to the first embodiment of the present invention will be described below. The fly ash 11 is fed into the high-temperature processing furnace 15 without using the nitrogen gas 13 or using the nitrogen gas, and is heated at a predetermined heating temperature of 580 to 800 ° C. for a predetermined heating time, for example, 15 to 240.
The heated fly ash 14 can be obtained by heating for minutes.

The heating time varies depending on the heating method such as indirect heating or direct heating, the structure of the heating device, the heating capacity, and the like. In short, it is set by how to raise the temperature of all the fly ash to be treated within a predetermined temperature range. For example, the heat treatment time can be shortened by stirring the fly ash during the heat treatment.

Recently, slaked lime is blown into exhaust gas from a melting furnace or an incinerator in order to remove acidic gas in the exhaust gas, so that fly ash generated is almost always alkaline. In some incinerators, slaked lime is not injected, so fly ash is acidic or neutral fly ash. In the case of an acidic fly ash having a pH value of about 6 to 8 or a neutral fly ash of less than 8.5, the elution concentration of heavy metals when these are immersed in water increases. Accordingly, when the pH value of the fly ash 11 is so low, an alkali source, for example, Ca (OH) 2,
About 10 wt% is mixed, and once the pH value is shifted to the alkali side of 11.0 or more, the same heat treatment is performed to adjust the pH value of the treated fly ash to a range of 8.5 to 11.0. And the elution of heavy metals can be prevented. Further, even when the pH value of the fly ash 11 to be treated is about 6 to 8 when the fly ash 11 is previously washed with water, the alkali source is similarly mixed with the fly ash 11 and once the pH value is 12.0 or more. After being shifted to the alkali side, the pH value is adjusted to 8.5 to 1 by heat treatment.
By reducing the content to the range of 1.8, elution of heavy metals can be effectively prevented. Hereinafter, Examples 1 to 3 will be specifically described with reference to tables.

Example 1 Table 2 shows that fly ash 11 having the composition shown in Table 1 was prepared at 300 ° C., 400 ° C., 500 ° C., 600 ° C., and 7 ° C.
The relationship between the pH value of the treated fly ash obtained by heating each at a heating temperature of 00 ° C. for 15 minutes and the heavy metal elution concentration is shown. FIG. 2 is a graph showing these relationships.

[0015]

[Table 1]

[0016]

[Table 2]

As shown in Table 2 and FIG. 2, when the heating temperature is around 600 ° C., the pH value sharply decreases, and the elution concentration of heavy metals (Pb, Zn, Cd) also sharply decreases. You can see that. This is, as described above, Ca (O
This is because the free CaO component promoted the formation reaction with SiO2 and the like when the dehydration reaction temperature of H) 2 exceeded 580 ° C. Here, the heat treatment temperature is preferably 60 in consideration of large fluctuations in the components of fly ash and uneven burning during the heat treatment.
The temperature is preferably set to 0 ° C. or higher.

(Example 2) Example 2 shown in Table 3 is another experimental example using fly ash 11 having the composition shown in Table 1 as in Example 1 described above. The treatment time was changed to 15 minutes, 40 minutes, and 60 minutes, respectively, and the relationship between the pH value and the lead elution concentration of the treated fly ash obtained by heat treatment in this manner is shown.

[0019]

[Table 3]

In this case, the pH value of the fly ash 11 is 12.4.
1. Although the lead elution concentration was 359 ppm, the pH value of the treated fly ash was lowered to 10.47 to 10.67, and the lead elution concentration was set to environmental standards (0.3 pp at the landfill site).
m or less) can be suppressed to 0.1 to 0.17 ppm, which satisfies the following condition. Also, it can be seen that the pH value and the elution value are stable even when the heating time is lengthened.

(Example 3) Next, Table 4 shows an example of the components of acidic fly ash generated when slaked lime is not blown into the exhaust gas of an old incinerator. As shown in (1) of Table 5, the pH value of the fly ash when not subjected to the heat treatment is as low as 6.23, and the elution concentration of lead is 31 ppm, which is much higher than the environmental standard. On the other hand, as shown in (2) of Table 5, when 5 wt% of Ca (OH) 2 is added to fly ash, the pH value is 12.53, and the Pb elution concentration is as high as 122 ppm.
However, as shown in (3) of Table 5, this was carried out at 600 ° C. for 2 hours.
If heat treatment is performed at 0 minutes, the pH value becomes 10.68, and P
b The elution concentration can be 0.15 ppm, which is lower than the environmental standard.

[0022]

[Table 4]

[0023]

[Table 5]

Next, Example 4 concerning dioxin decomposition
Is shown. (Example 4)

[0025]

[Table 6]

[0026]

[Table 7]

Table 7 shows fly ash having the composition shown in Table 6 at 450 ° C.
The dioxin concentration of the treated fly ash obtained by performing the heat treatment in an oxidizing atmosphere in the air at a heating temperature of 550 ° C. and 650 ° C. for 30 minutes each is shown. FIG. 3 is a graph showing these relationships. By the way, in the “Guidelines on Prevention of Dioxin Generation Related to Waste Disposal / Issued in January 1997 (hereinafter referred to as new guidelines)”, the total emission of dioxins generated from waste treatment facilities is 5 μg-
TEQ / garbage ton is set as a reference value, and the concentration of each emission to achieve it is calculated as follows on the assumption of an incinerator. (1) Exhaust gas 5000 Nm3 / garbage ton x 0.1 ng-TEQ / Nm3 = 0.5 g-TEQ / garbage ton (2) Incineration ash 150 kg / garbage ton x 0.01 ng / g-TEQ = 1.5 g-TEQ / garbage ton (3) Fly ash 30 kg / garbage ton × 0.1 ng / g-TEQ = 3.0 μg-TEQ / garbage ton Total 5.0 μg-TEQ / garbage ton

Now, referring to Table 7 and FIG.
Although it is 0.1 ng / g-TEQ which is exactly the same as the above calculated value at ℃, depending on the composition of the fly ash, this value changes up and down. In some cases, it is not satisfactory. Therefore, a heating temperature of 550 ° C. is insufficient for dioxin decomposition, and a higher temperature is required. According to FIG. 3, the dioxin concentration sharply decreases after the heating temperature exceeds 550 ° C., and decreases to 0.05 ng / g-TEQ at 580 ° C. Thus, it can be seen that, even in an oxidizing atmosphere in the air, heating to 580 ° C. or more can reliably decompose dioxin even if the difference in the degree of reduction depending on the type of fly ash is considered. Considering the above-described heat treatment of heavy metals, in order to prevent heavy metal elution of fly ash and to simultaneously decompose dioxin, the heating temperature should be 580 ° C.
The above is necessary. FIG. 4 is an explanatory view of a fly ash processing apparatus 20 to which a method for processing molten fly ash or incinerated fly ash according to the second embodiment of the present invention is used.
Is a mixer 22 having a stirring blade for mixing the fly ash 21 and water, and the suspended water washed by the mixer 22 is separated into a washed fly ash 23 and a treated water 24, and the treated water 24 is separated. A filtration device 26 for supplying to the water treatment equipment 25;
3 is subjected to a heat treatment in an atmosphere containing no nitrogen gas or in a nitrogen gas to obtain a processing fly ash 28.
have.

Next, a method for treating molten fly ash or incinerated fly ash according to a second embodiment of the present invention will be described. First, fly ash 2 collected from a melting furnace or an incinerator (not shown)
The water-soluble chlorides such as lead chloride, sodium chloride, potassium chloride and calcium chloride in the fly ash 21 are eluted by stirring and washing the mixture 1 and water with the mixer 22 for a predetermined time, for example, 10 to 30 minutes. Processed material (processed fly ash 28)
Elution of heavy metals when immersed in water can be effectively suppressed. Next, the treatment liquid mixed by the mixer 22 is filtered by a filtration device 26, and the washed fly ash 23, which is a solid content, is removed.
Into the high-temperature processing furnace 29, in an atmosphere in which nitrogen gas is not used, or in an atmosphere in which nitrogen gas is used, at a predetermined heating temperature of 580 to 800 ° C. for a predetermined time, for example, 15 to 2 hours.
The heated fly ash 28 can be obtained by heating for 40 minutes, preferably for 20 to 180 minutes. Note that the atmosphere in the heat treatment may be a oxidizing atmosphere in air, an inert gas atmosphere in nitrogen gas, or a reducing atmosphere such as hydrogen gas. On the other hand, after the treated water 24 separated and discharged from the filtration device 26 is properly treated in the water treatment facility 25,
It is designed to be discharged out of the system.

As described above, in the method for treating molten fly ash or incinerated fly ash according to the second embodiment, a predetermined temperature is applied to the washed fly ash 23 which has been subjected to a water washing treatment and from which water-soluble heavy metal chlorides and the like have been removed. Since the heat treatment under the conditions is performed, the elution of heavy metal when the heat-treated fly ash 28 is immersed in water or the like can be more effectively suppressed. Example 5 will be described.

(Example 5) In Example 5 of Table 8, fly ash 21 having the composition shown in Table 1 was washed and dehydrated in advance in the same manner as in Example 1 to obtain washed fly ash 23. The data of the treated fly ash 28 obtained by setting the same heating temperature as in Example 2 at 600 ° C. and changing the heating time to 15 minutes and 40 minutes, respectively, are shown. In this case, the pH value of the washed fly ash 23 was 12.53, and the lead elution concentration was 47.7 pp.
m, the pH value of the treated fly ash 28 was changed to 11.52.
It can be seen that the lead elution concentration can be suppressed to 0.1 to 0.18 ppm, which satisfies environmental standards, while reducing the concentration to 11.65 ppm.

[0032]

[Table 8]

The embodiment of the present invention has been described above.
The present invention is not limited to these embodiments, and all changes in conditions without departing from the gist are within the scope of the present invention. For example, in the present embodiment, the method of adjusting the pH value of fly ash by adding slaked lime as an alkali source has been described, but it is also possible to use CaO or the like other than slaked lime.

[0034]

According to the method for treating molten fly ash or incinerated fly ash according to the present invention, the fly ash having a specific pH value is heat-treated to a predetermined temperature to adjust the pH value of the treated fly ash to a predetermined range. In this way, CaO, Na2 O, K2 O, MgO, etc., which are the alkali sources released in the fly ash, are converted into SiO2, Al
Stabilize by reacting with 2 O3 etc. Thereby, an increase in pH value when immersed in water can be suppressed, and elution of heavy metals contained in the treated fly ash can be prevented. The methods of adding chemicals and cement to fly ash to prevent the elution of heavy metals and the method of extracting heavy metals from fly ash with an acid solution are both costly and increase the volume after treatment. Thus, elution of heavy metals contained in the processing fly ash can be prevented at low cost and without increasing the processing volume. In particular, in the method for treating molten fly ash or incinerated fly ash according to the third and fourth aspects, since the fly ash is washed in advance with water, water-soluble heavy metal chlorides and the like are removed, and the elution of heavy metals is more effectively prevented. Is achieved. On the other hand, fly ash 58 in the heavy metal elution prevention treatment
Even under heating at 0 ° C. or higher, even under an oxidizing atmosphere in the air, dioxin is found to have a fly ash concentration of 0.1 ng / g-T in the total emission reference value indicated in the “New Guidelines”.
Because it is surely reduced to a level significantly below the EQ,
Special structure for oxygen deficiency (reducing atmosphere)
No device is required, and the device is inexpensive. Further, the cost of an inert gas or the like is not required.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a method for treating molten fly ash or incinerated fly ash according to a first embodiment of the present invention.

FIG. 2 shows fly ash having the composition shown in Table 1 at 300 ° C., 400 ° C.,
500 ° C, 600 ° C, 700 ° C
5 is a graph showing the relationship between the treatment fly ash pH value, the lead elution concentration, and the heating temperature obtained by heating for 5 minutes.

FIG. 3 shows fly ash having the composition shown in Table 6 at 450 ° C., 550 ° C.,
FIG. 4 is a graph showing the relationship between the dioxin concentration of the treated fly ash and the heating temperature obtained by performing the heat treatment in an oxidizing atmosphere in the air at a heating temperature of 650 ° C. for 30 minutes.

FIG. 4 is an explanatory view of a fly ash processing apparatus to which a method for processing molten fly ash or incinerated fly ash according to a second embodiment of the present invention is applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Fly ash processing apparatus 11 Fly ash 13 Nitrogen gas 14 Processing fly ash 15 High temperature processing furnace 20 Fly ash processing apparatus 21 Fly ash 22 Mixer 23 Washing fly ash 24 Treated water 25 Water treatment equipment 26 Filtration device 28 Treated fly ash 29 High temperature Processing furnace

Continued on the front page (72) Inventor Hidemi Kosano 46-59, Ohara Nakahara, Tobata-ku, Kitakyushu-shi, Fukuoka New (72) Inventor Morihiro Nagata 46-59, Nakahara Oaza, Tobata-ku, Kitakyushu-shi, Fukuoka Nippon Steel Corporation Engineering Business Unit (72) Inventor Isao Arimitsu 46-59 Ohara Nakahara, Tobata-ku, Kitakyushu-shi, Fukuoka New Nippon Steel Corporation Engineering Business Unit

Claims (4)

[Claims] 1. A method for treating fly ash generated from a melting furnace for municipal garbage and / or industrial waste, or fly ash generated from an incinerator, comprising: PH of incinerated fly ash
When the measured value is 11.0 or more, the molten fly ash or incinerated fly ash is heated to 580 to 800 ° C., and the pH of the treated fly ash is set to 8.5 or more and less than 11.0. A method for treating molten fly ash or incinerated fly ash, comprising preventing elution of heavy metals in the treated fly ash and simultaneously decomposing dioxin contained in the treated fly ash. 2. A method for treating fly ash generated from a melting furnace for municipal garbage and / or industrial waste, or fly ash generated from an incinerator, comprising: PH of incinerated fly ash
If the measured value is less than 8.5 neutral or acidic, an alkali source is added in advance to adjust the pH of the molten fly ash or incinerated fly ash to 11.0 or higher, and then the The fly ash or incinerated fly ash is heat-treated at 580 to 800 ° C. to adjust the pH of the treated fly ash to 8.5 or more and less than 11.0 to prevent elution of heavy metals in the treated fly ash, A method for treating molten fly ash or incinerated fly ash, wherein dioxin contained therein is simultaneously decomposed. 3. A method for treating molten fly ash generated from a melting furnace for municipal garbage and / or industrial waste or incinerated fly ash generated from an incinerator, wherein the molten fly ash or the incinerated material to be treated in advance is provided. After the fly ash is washed with water, the pH of the washed fly ash is measured. If the measured value is 12.0 or more, the washed fly ash is heated to 580 to 800 ° C. to adjust the pH of the treated fly ash to 8.5. A method for treating molten fly ash or incinerated fly ash, wherein the content is less than 11.8 to prevent elution of heavy metals in the treated fly ash and to simultaneously decompose dioxin contained in the treated fly ash. 4. A method for treating fly ash generated from a melting furnace for municipal garbage and / or industrial waste or fly ash generated from an incinerator, wherein said fly ash or incineration to be treated in advance is provided. After the fly ash is washed with water, the pH of the washed fly ash is measured. If the measured value is less than 8.5, which is neutral or acidic, an alkali source is added in advance to adjust the pH of the washed fly ash to 12.0 or more. After that, the washed fly ash is heated to 580 to 800 ° C.
H is set to 8.5 or more and less than 11.8 to prevent the elution of heavy metals in the treated fly ash and to simultaneously decompose dioxin contained in the treated fly ash. Ash treatment method.