JPH05329459A - Treatment of municipal waste incineration ash - Google Patents

Abstract

PURPOSE:To propose the treating method which recycles municipal waste incineration ashes as building materials without throwing away the incineration ashes for reclamation and eliminates the need for a place for discarding the incineration ashes. CONSTITUTION:The municipal waste incineration ashes are incorporated into a cementitious mixture formed by incorporating line into the desulfurization slurry of the exhaust gases discharged from a power plant, etc., and fly ashes, by which the building materials are formed. As a result, the municipal waste incineration ashes are effectively utilized together with the industrial waste of the other cementitious mixture as the building materials, such as subbase course materials. The need for preparing the place for throwing away the incineration ashes and the treatment cost are reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to incineration ash of refuse fly ash and bottom ash generated in an incinerator for municipal solid waste.
The present invention relates to a method in which waste collected from a thermal power plant is mixed with a substance containing a main component and is treated so that it can be reused.

[0002]

2. Description of the Related Art Conventionally, the incineration ash of the above-mentioned municipal waste may cause secondary pollution if it is directly buried and disposed of. Therefore, it is landfilled in an enclosed management type disposal site.
Wastewater generated there is also treated and released harmlessly.
Further, the harmful components in the flue gas generated in the thermal power plant and fly ash are recovered, and a suspension containing lime or limestone is mixed into this to obtain a cementitious mixture, which is a building filler, brick, etc. It has also been proposed to use it as a building material or a road basic material (Japanese Patent Publication No. 57-10057).

[0003]

[Problems to be Solved by the Invention] When the incineration ash of municipal solid waste is to be buried and discarded, it is necessary to successively prepare dumping sites. Since such treatment of municipal solid waste will be carried out locally, it is necessary to have sufficient places within the region where dumping can be continued for many years, but in urban areas where large amounts of municipal solid waste are generated, dumping sites are not possible. Can't be satisfied. In addition, since municipal waste contains harmful substances and may cause pollution, it is difficult to reuse it as it is.

It is an object of the present invention to propose a treatment method in which municipal waste incineration ash can be reused as a construction material without being discarded and a dumping place is unnecessary.

[0005]

In order to achieve the above object, the present invention comprises an aqueous suspension containing 30 to 90% by weight of solids, the solids being 0.25 to 70% by weight. Alkaline earth metal hydroxide, 10 to 99.5% by weight fly ash, and 0.25 to 70% by weight alkaline earth metal sulfite (a part of this sulfite being alkaline earth metal sulfite, Municipal waste incineration ash was mixed into a cementitious mixture consisting of It is preferable to mix 25 to 75% by dry weight of municipal waste incineration ash into the cementitious mixture.

[0006]

In the cementitious mixture, 25 to 75% by dry weight of municipal waste incineration ash is mixed and stirred to adjust the water content to form a mixture, which is crushed in the same manner as roadbed materials and embankment materials. The maximum dry density is greater than when only the cementitious mixture is tamped, the compressive strength increases over time, and the compressive strength of the cementitious mixture is almost the same, and no harmful substances elute, and civil engineering works It can be used as a material similar to general soil.

[0007]

[Example] The exhaust gas of a thermal power plant is introduced into a limestone slurry to obtain a slurry containing calcium sulfite and calcium sulfate, and after adding fly ash discharged together with the boiler exhaust gas, the water content thereof is adjusted, Mix cement with lime to obtain a cementitious mixture. An example of the composition is as follows. Water 20% CaSO ₃ 1 / 2H ₂ O + CaSO ₄ 2H ₂ O 25% Unreacted limestone (CaCO ₃ ) 12% Fly ash 40% Slaked lime (Ca (OH) ₂ ) 3% This cementitious mixture is incinerated with municipal solid waste. When dust fly ash and bottom ash generated in the furnace are mixed, no harmful substances are eluted from the incineration ash, and the incineration ash can be reused as a construction material such as a roadbed material without being buried and discarded.

[0008] The incineration ash of municipal solid waste and the above cementitious mixture have the physical properties shown in the following Tables 1 and 2 in the test by the soil test method, and the cement tester standard test method and the Environmental Agency Notification No. 13 In the test according to (4), it has the chemical properties shown in Tables 3 to 4 below. In these tables, municipal waste is analyzed by dividing it into waste fly ash FA generated above the incinerator and bottom ash BA generated below, and the cementitious mixture is coal ash fly ash F (hereinafter referred to as fly ash F). ,
(A fly ash) and a lime water slurry S containing calcium sulfite and calcium sulfate were separately analyzed. Table 1 shows the water content, specific gravity and particle size distribution, and Table 2 shows the results of the FA water content measurement test.
Is the chemical component analysis test result, and Table 4 is the dissolution test result.

[0009]

[Table 1]

[0010]

[Table 2]

[0011]

[Table 3]

[0012]

[Table 4]

As shown in Tables 1 and 2, the refuse fly ash FA of municipal waste incineration ash has a large amount of fine particles of 74 μm or less, like the fly ash F, and corresponds to silt in the classification of soil. The specific gravity of FA and BA particles is smaller than that of cement (specific gravity about 3.16) or soil (specific gravity about 2.7),
It is about the same as F. Further, the measurement of the water content of FA may not be required unless oven drying is performed for at least one week after water addition. For general soil and F, oven drying takes about 1 day. B
A has a smaller fine grain content (74 μm or less) than FA, and corresponds to sandy soil in soil classification. The specific gravity of BA particles is smaller than that of cement or soil and is almost the same as FA or F.

As can be seen from Table 3, the chemical constituents of FA are much smaller in SiO ₂ and Al ₂ O ₃ than in F and CaO,
It is characterized by a large amount of SO _{3 and} high unburned content. Also, F
The pH of A is not as alkaline as F. In the dissolution test, as shown in Table 4, cadmium, hexavalent chromium, and total mercury were detected, although the standard values were not exceeded. In particular,
Compared to F, it tends to contain more hexavalent chromium. The chemical composition of BA shows the same tendency as that of FA, but SiO ₂
And Al ₂ O ₃ are less and the pH is more alkaline than FA, but slightly lower than F. No harmful substances were detected in the BA dissolution test.

When such incinerated municipal waste incineration ash is mixed in the cementitious mixture at a rate of 25 to 75% by dry weight and the water content is adjusted, it becomes a soil-like construction material that can be compacted, and is used from a thermal power plant. The generated waste and municipal waste incineration ash can be recycled into civil engineering materials at the same time.

In a thermal power plant using domestically produced coal, CaSO ₃ 1 / 2H ₂ O + CaSO ₄ 2H ₂ O and unreacted limestone (CaCO
₃ ) Total dry weight% and fly ash dry weight%
And are 1: 3, and these CaSO ₃ 1 / 2H ₂ O + CaSO ₄ 2H ₂ O
2% slaked lime is mixed with the total weight of unreacted limestone (CaCO ₃ ) and fly ash, and the balance is water cementitious mixture (raw material A). The following 6 types of samples were prepared by mixing the waste fly ash FA (raw material B) and the bottom ash BA (raw material C), and various tests were conducted to examine whether the samples are suitable as construction materials. A sample prepared by adding 2% of slaked lime to FA was prepared for comparison of solidification characteristics when preparing this sample. The sample used for this test was prepared by a mixing method in which the raw materials, which were weighed so as to have a blending ratio, were put in a soil mixer and stirred for 3 minutes, and then predetermined water was added, followed by stirring for 3 minutes. did. A sample of the resulting mixture was immediately tested. Details of the samples and tests are as follows. Sample 1: 25% raw material A and 75% raw material B by dry weight%
Was prepared by the above mixing method. Sample 2: 50% raw material A and 50% raw material B in dry weight%
Was prepared by the above mixing method. Sample 3: 75% raw material A and 25% raw material B in dry weight%
Was prepared by the above mixing method. Sample 4: 25% raw material A and 75% raw material C in dry weight%
Was prepared by the above mixing method. Sample 5: 50% of raw material A and 50% of raw material C by dry weight
Was prepared by the above mixing method. Sample 6: 75% of raw material A and 25% of raw material C by dry weight
Was prepared by the above mixing method. Sample 7: 2% slaked lime was added to 100% of the raw material B in terms of dry weight, and the mixture was prepared by the above mixing method. These samples were tested for compaction and solidification characteristics and elution test based on the soil test method. The test of compaction characteristics, when each sample is used as a roadbed material or embankment material, knows whether it can be constructed in the same manner as general soil, and to what extent the water content ratio should mix raw materials A, B and C. It is carried out for the purpose of obtaining the optimum water content ratio and the maximum dry density of the composition from the relationship between the water content ratio of the sample and the dry density. In general,
Although soil strength and durability increase in proportion to dry density,
Since the dry density also changes depending on the water content, it is necessary to obtain the relationship between the water content and the dry density by this test.
At the time of construction, it is usual to adjust the soil to the optimum water content ratio and run it many times with heavy machinery to make it highly dense. The solidification property is evaluated by a uniaxial compression test, and a mixture of raw materials A, B or C is produced at the optimum water content ratio obtained from the compaction property test, and immediately after the production, a maximum of 5 cm in diameter and 10 cm in height is obtained in a mold. The specimen was obtained by compacting to a dry density, sealed in a vinyl bag, and cured in a thermostatic chamber at 20 ° C. to a prescribed age, and then tested. Uniaxial compression test is JIS A
According to 1216, the test was conducted on the 7th and 28th days. The elution test was carried out to investigate the elution suppressing effect of the raw material A when the municipal waste incineration ash was mixed with the raw material A (cementitious mixture) to form a mixture, and this mixture was used on land. The test was conducted in accordance with the dissolution test method applied to landfill of industrial waste (Environmental Agency Notification No. 13B). The sample was crushed from a uniaxial test specimen of 28 days of age and tested with a particle size range of 0.5 to 5.0 mm. However, the test items excluded the items in which elution was not observed even with the raw materials. The results of the compaction characteristics test are shown in Table 5 below. Samples 1 to 3 mixed with FA have compaction characteristics similar to soil, and the compaction characteristics have a small difference depending on the mixing ratio and the maximum dry density. And the optimum water content is about the same as the raw material A (cementitious mixture). Further, as compared with BA, the optimum water content ratio was small and the maximum dry density was large. Samples 4 to 6 mixed with BA also have compaction characteristics similar to the soil, and although the compaction characteristics differ little depending on the blending ratio, the maximum dry density is smaller and the optimum water content ratio is higher than FA. It was found that BA affects the compaction property of raw material A more than FA.

[0017]

[Table 5]

The results of the uniaxial compression test for knowing the solidification characteristics are shown in Table 6 below. According to this test, the specimens prepared from Samples 1 to 3 of the mixture of FA showed almost no strength development in any formulation, but showed a tendency that the strength slightly increased at 28 days of age. When the proportion of FA is 25% or more, FA seems to hinder the solidification reaction of raw material A. The change in volume of the specimen shows an expansion tendency, and the expansion amount is quite large. These tendencies are more pronounced than BA. The specimens prepared from Samples 4 to 6 of the mixture of BA exhibited strength development in any of the blends. Regarding the strength, there is almost no difference due to the difference in the composition on the 7th day of the material age, but on the 28th day of the material age, the higher the amount of the raw material A, the higher the strength and the larger the increase in the strength. BA does not inhibit the solidification reaction of the raw material A, but is not considered to promote the reaction. Further, the volume change of the BA specimen has an expansion tendency like the FA, but
It was smaller than A and about the same as raw material A.

[0019]

[Table 6]

The dissolution test was carried out only on samples 1-3 of the FA mixture. The results are shown in Table 7 below. Samples 4-6 of the BA mixture were not run because there was no elution of harmful substances from the BA itself as seen in Table 4. In this dissolution test, as shown in Table 4, cadmium, hexavalent chromium, and total mercury, which were eluted by FA alone, were not eluted from Samples 1 to 3. This is considered to be the effect of suppressing the elution due to the chemical reaction of the raw material A. On the other hand, lead is eluted from these samples 1 to 3. However, it is considered that lead was eluted from F (coal ash fly ash) in raw material A, indicating that the coal ash used this time exceeds the reference value in Table 4.
Particularly noteworthy is that lead was not eluted in Sample 1 containing 75% FA. PH of these samples 1-3
Shows a high alkalinity, and the higher the mixing ratio of the raw material A, the higher.

[0021]

[Table 7]

The mixture obtained by mixing the raw material B or C with the raw material A has the same compaction property as that of the soil, and the water content ratio thereof is not much different from that of the raw material A alone, and can be produced as a mixture relatively easily. It can be used as a construction material for embankments and roadbeds. Originally, hazardous substances are eluted from the garbage fly ash of municipal waste, so the problem of secondary pollution will occur if it is not buried in a controlled disposal site, but mixing of the raw material A eliminates the elution of harmful substances. , Waste can be reused safely. It is also possible to mix the raw materials A and B or C in a ratio exceeding the above ratio.

[0023]

As described above, according to the present invention, the alkaline earth metal hydroxide of the suspension, the fly ash, and the alkaline earth metal sulfite (a part of this sulfite is alkaline earth metal sulfite). May be), by mixing the incineration ash of municipal waste with a cementitious mixture consisting of
A mixture that can be used as a construction material with compaction characteristics in which the elution of harmful substances from the incinerated ash is suppressed is obtained, and it is effective together with industrial waste obtained at thermal power plants, etc. without burying the municipal waste incinerated ash. It is possible to use, there is no need to prepare a disposal site for the incinerated ash, and the processing cost can be reduced.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C04B 11/30

Claims (2)

[Claims] 1. An aqueous suspension containing 30 to 90% by weight of solids, wherein the solids are 0.25 to 70% by weight of alkaline earth metal hydroxide and 10 to 99.5% by weight. Incinerating municipal solid waste incineration ash into a cementitious mixture of fly ash and 0.25 to 70% by weight of alkaline earth metal sulfite (some of this sulfite may be alkaline earth metal sulfite) A method for treating municipal waste incineration ash, which is characterized by being used as a construction material. 2. The cementitious mixture in the range of 25 to 75.
The method for treating municipal waste incineration ash according to claim 1, wherein dry weight% of the municipal waste incineration ash is mixed.