JP2012254433A - Method for treating incineration ash containing fluorine and heavy metals - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating incineration ash containing fluorine and heavy metals, in which the incineration ash is treated so that the fluorine and the heavy metals contained in the incineration ash, that becomes a raw material of civil engineering materials such as a subbase material and a backfilling material to be utilized in a soil field, can be made below values set in the environmental quality standards for soil and so that the treated incineration ash can be used suitably even in such a winter season that cement is hardly hardened particularly.SOLUTION: In the case that the incineration ash contains at least one component of fluorine of >0.8 mg/L, hexavalent chromium of >0.05 mg/L and lead of >0.01 mg/L when subjected to the elution test method based on the 2003 announcement No.18 of the Environment Agency, clay soil, cement, a cold protecting agent and water are added to the incineration ash and an obtained mixture is kneaded and cured. As a result, the fluorine and the heavy metals can be insolubilized so that the amounts of the fluorine and the heavy metals to be eluted can become below the standard values even when the curing temperature is ≤10°C.

Description

The present invention relates to a method for treating fluorine and heavy metal-containing combustion ash. More specifically, in order to comply with the elution regulation values for fluorine and heavy metals, which are regulated substances under the Soil Contamination Countermeasures Law enacted in February 2003 by the Ministry of the Environment, the combustion ash containing them is treated as industrial waste. Clay soil not effectively used, cement, calcium chloride-based cryogen and water are kneaded and cured, so that the elution amount of fluorine contained in the combustion ash is 0.8 mg / L or less, hexavalent The present invention relates to a combustion ash treatment method in which the elution amount of chromium is 0.05 mg / L or less and the lead elution amount is 0.01 mg / L or less.

As part of measures to prevent global warming, boilers that use non-fossil fuels, such as waste tires, wood chips, and RPF, have been operating. However, the amount of combustion ash emitted from new energy boilers is much larger than that of fossil fuel boilers, and some of them are used as raw materials for cement, but they contain a large amount of chlorine and harmful substances derived from fuel. When it is contained, it is difficult to take it up as a cement raw material, and in many cases it is disposed of in landfills, and a detoxification treatment method is required for effective use, and many treatment methods are disclosed.
Among them, many treatment methods using cement have been disclosed, but the solidification of the cement does not proceed at low temperatures including cold regions, the curing effect is not sufficient, and the elution suppression of fluorine and other heavy metals is insufficient. There may be.

As a technique using cement, for example, a method is disclosed in which incinerated ash or molten fly ash is mixed with steel slag fine powder and fly ash together with water, and then mixed with an extrusion molding machine (Patent Document 1). However, this method takes 6 weeks or more after the mixture is molded in order to suppress elution. Or it requires steam curing or autoclave curing to shorten the curing period, it is too costly while ensuring the safety of the handling operator, in addition, it is limited by the grain size of steelmaking slag and fly ash used, etc. This shows one end of how difficult elution suppression is.

As a method to suppress the elution of heavy metals from soil, charcoal and incinerated ash, etc., solidified main agent mixed with granulated slag, dihydrate gypsum and slaked lime or cement and potassium chloride, magnesium chloride, sodium chloride, calcium chloride, ammonium chloride, carbonate Select 5 or more types from 10 types such as potassium, etc. and mix 1 or more types from 3 types such as citric acid to make a soil solidifying agent. Furthermore, the obtained soil solidifying agent and soil (Patent Document 2) discloses a technique for mixing and solidifying substances such as coals, charcoal, and porous materials (Patent Document 2). In particular, the lead elution amount shown in the examples is 0.03 mg / L, which exceeds the soil environmental standard value, and by adding various chemicals, sufficient elution suppression of fluorine and heavy metals in incineration ash is sufficient. It can not be expected.

As a method for detoxifying and solidifying incinerated ash, a cement-based solidifying agent (cement, sodium lignin sulfonate, sodium tripolyphosphate, zirconium, soda is added to 100 parts by mass of a mixture of 100 parts by mass of incinerated ash and 10 to 30 parts by mass of sand. 15 to 30 parts by mass of a mixture of ash / calcium chloride and ferrous oxide) and 7 to 15 parts by mass of the synthetic emulsion resin solution with respect to the mixture of incineration ash, sand and cement-based auxiliary agent, and molded. The method of curing is patented (Patent Document 3). The described solidifying agent is combined with six kinds of chemicals other than cement, and the manufacturing process is complicated. However, as described in the text of the literature in comparison of the effects of the examples and comparative examples, the presence or absence of elution of heavy metals is only the difference depending on the presence or absence of the synthetic emulsion, so the elution inhibitor is only the synthetic emulsion. Can be easily read.
Moreover, in any literature, the prescription of elution suppression is performed on normal temperature or the conditions heated.

In this way, it is said that technology that can suppress elution of fluorine and heavy metals in combustion ash below the soil environmental standard value is not easy, but further elution suppression technology under winter curing conditions where the use of cement is restricted There was nothing.
JP 1999-165144 A JP 2005-272510 A Japanese Patent No. 3077644

The problem to be solved by the present invention is to make fluorine and heavy metals from combustion ash used as a raw material for civil engineering materials used in the field of soil such as roadbed materials and backfill materials to be below the soil environmental standard value. This is a treatment method that can be suitably used even in winter when cement solidification is difficult to proceed.

In order to solve the above-mentioned problems, a method for achieving suppression of elution of fluorine and heavy metals from combustion ash by adding clayey soil such as combustion ash and silt, cement and a cryogen, including the following inventions To do.
(1) Elution amount is 0.8mg / L of fluorine and 0.05mg / L of hexavalent chromium as heavy metals and 0.01mg / L of lead when dissolved by the dissolution test method based on Notification No. 18 of 2003 Environment Agency Fluorine that is insolubilized so that the amount of elution becomes less than the standard value by curing and curing clay ash, cement, cryogen and water to the combustion ash containing components that exceed at least one of the above And method for treating heavy metal-containing combustion ash.
(2) The treatment method for fluorine and heavy metal-containing combustion ash according to (1), wherein the curing condition is 10 ° C. or less.
(3) The method for treating fluorine and heavy metal-containing combustion ash according to (1) or (2), wherein the clayey soil is a silt main body composed of 0.004 to 0.06 millimeters.
(4) The fluorine and heavy metal according to any one of (1) to (3), wherein the cryogen is added in an amount of 1 to 10 parts by mass in terms of solid content with respect to 100 parts by mass of the solid content of the mixture of combustion ash and cement. Of processing ash containing combustion ash.
(5) The cryogen is a calcium chloride cryogen, and 1.0 to 5 parts by mass of calcium chloride in the calcium chloride cryogen is mixed with 100 parts by mass of the solid content of the combustion ash and cement. (1) The processing method of fluorine and heavy metal containing combustion ash of any one of (4).

The combustion ash treatment method of the present invention is a method that can suppress the elution amount of fluorine and heavy metals below the soil environmental standard value, and can suppress elution even in winter when the temperature is low.

Hereinafter, the present invention will be described in detail.
In order to detoxify and effectively use fluorine and heavy metal-containing combustion ash, the present inventors conducted extensive research on clay soil and cement, and various cement admixtures. By doing so, it was found that there is an effect of suppressing elution of fluorine and heavy metals at the same time even under winter curing conditions.
As combustion ash used in the present invention, solid fuel such as coal, biomass fuel such as wood chips and bark, waste fuel such as RPF, RDF, and waste tires, waste paper, black liquor, paper sludge activated sludge, etc. Combustion ash generated when combusting physical biomass, and more specifically, fly ash captured by a cyclone electrostatic precipitator (EP), bag filter, etc. The agglomeration is not particularly limited.
The combustion ash may be combustion ash obtained by burning fuel or waste selected from one or more kinds, and even if a plurality of combustion ash is mixed, it can also be used as a raw material combustion ash.

As the clay soil used in the present invention, a soil mainly composed of silt is used. Silt is an intermediate size between sand and clay and is generally called fine sand. In geology and petrology, 1/16 to 1/256 mm (about 0.004 to 0.06 mm), and in soil science, 0.002 to 0.02 mm, which is smaller than 1/256 mm. Is classified as mud and sand larger than 1/16 mm as sand. In the present invention, those having a size of 1/16 to 1/256 mm are effectively used as silt. However, there are not many cases in which silt is strictly fractionated even in the industry where it is generated, and the actual situation is that the sediment settled in the sedimentation basin after the sand is collected is disposed of. In view of such circumstances, even if particles having a particle size other than the silt are included, they can be suitably used in the present invention.

Examples of the cement used in the present invention include blast furnace cement, which are classified into A type, B type, and C type according to the blending of blast furnace slag with Portland cement, but are not particularly limited.
In the present invention, blending of cement is essential, but the blending amount is expressed as a ratio from the total solid content of combustion ash, clayey soil, and cement, and the cement is selected between 10 to 60% by mass. If the blending ratio is less than 10% by mass, the contribution ratio to the solidification by the cement is small, and the difference in the cryoprotective effect becomes unclear. On the other hand, a cement content exceeding 60% by mass is not economically preferable because it has an effect on solidification but leads to an increase in cost.

In the present invention, the cryoprotectant to be used is one that promotes the hydration reaction of cement and may be one that is generally commercially available, one that is commercially available as an antifreeze agent, and the shape may be either solid or liquid. A liquid is more preferable for uniform stirring and shortening the kneading time of the rope, and it is commercially available using an inorganic nitrogen compound, calcium chloride, calcium sulfate, sodium nitrite, calcium nitrite, calcium nitrate or the like as the main component. Among them, the calcium chloride-based cryoprotectant has a large amount of chloride ions, and has been recognized to be harmful to iron, but it is relatively inexpensive and easy to handle. It can be used suitably.
The cryoprotectant is preferably added in an amount of 1 to 10 parts by mass in terms of solids with respect to 100 parts by mass in total of solids of combustion ash and cement. If it is less than 1 part by mass, it does not contribute to the promotion of the hydration reaction of the cement and the elution suppression effect is not manifested. Moreover, even if it adds exceeding 10 mass parts, an effect will stop and it is economically unpreferable.
When treating with combustion ash and cement, clayey soil, and calcium chloride cryoprotectant, the calcium chloride content in the calcium chloride cryoprotectant is 1.0 to 100 parts by mass with respect to a total of 100 parts by mass of combustion ash and cement solids. Add 5 parts by weight, particularly preferably 1 to 3 parts by weight. Calcium chloride-based cryoprotectant is added as a part of the added water, and the adjusted water is reduced and added in consideration of that amount.

Moreover, although water required for a hydration reaction is provided with cement, the treated water which added the chemical separately for the purpose of removing impurities, such as general water, industrial water, or factory waste water, can also be used conveniently.

If the amount of water to be added is extremely large, the hydration reaction takes time and the strength decreases, and if it is extremely small, solidification after curing such that sufficient hydration reaction does not proceed and solidification becomes difficult. It is known to affect the strength of goods. However, in general, as a precaution when adding a cryoprotectant, when the cryoprotectant is a liquid product, the contained moisture is converted as a part of the added water. Furthermore, there are many examples where the maximum water-cement ratio (W / C ratio) is generally described as about 50% in the instruction manual for the cryoprotectant, but in the present invention, silt is included and combustion ash is contained. Since it is rich in water absorption, it does not necessarily match the above-mentioned general water cement ratio. One of the unique features of the present invention is that the combustion ash is included so that the water retention performance is excellent and the stable hydration reaction proceeds.For example, the amount of water is easy to handle after kneading. The amount necessary for the hydration reaction may be adopted within a common sense range.

In the present invention, dry combustion ash and cement are mixed in advance so as to be uniformly dispersed, and then clay soil containing moisture, calcium chloride-based cryogen and necessary moisture are added, and all materials are mixed and kneaded. It is preferable to carry out. However, it is not necessary to perform these in separate apparatuses, and it is preferable to knead them using a known mixing / kneading apparatus.

As examples of equipment, known mixing and stirring devices such as a Nikko dash mixer, drum mixer, tilting cylinder mixer, ribbon mixer, Eirich intensive mixer, and Pelegaia mixer can be suitably used. Moreover, about stirring time, since it has the characteristics in stirring ability with an apparatus, it does not dare prescribe, but it is about 1 to 15 minutes as a standard.

The present invention has an elution suppression effect even when the curing temperature after kneading is low. Curing is performed outdoors without heating in a house or room even in winter when the temperature is 10 degrees or less. Even under curing conditions of 10 ° C or higher, the addition of a cold-resistant agent accelerates the cement hydration reaction and has the effect of suppressing elution of fluorine and heavy metals. Less. Although it depends on the application, when it is used as a recycled roadbed material, it is cured and solidified in a shape that facilitates pulverization after solidification. The curing period is approximately 1 to 28 days, preferably 7 days to 14 days.

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples. Unless otherwise indicated, the following combustion ash was used as the combustion ash, and silt having the following particle size distribution was used. Moreover, unless otherwise indicated, the addition rate of the chemical | medical agent in an Example and a comparative example is shown by the mass% as a ratio of total solid content, such as combustion ash and cement. Further, details regarding the processing are shown in Example 1, and major changes are shown in order to clarify the difference between the other examples and the comparative example.

Combustion ash (1) properties Combustion ash was used as the combustion filter ash collected from the bag filter of a fluidized bed furnace using 50 parts by mass of waste tires, 25 parts by mass of wood raw materials such as waste materials, and 25 parts by mass of papermaking sludge as fuel. Moreover, the elution amounts of fluorine and heavy metals in combustion ash were measured and listed in Table 1.

Characteristics of combustion ash (2) Combustion ash was used as the combustion ash from the bag filter collection combustion ash of a fluidized bed furnace using 48 parts by mass of waste tires, 32 parts by mass of wood raw materials such as waste materials, and 20 parts by mass of papermaking sludge as fuel. Moreover, the elution amounts of fluorine and heavy metals in combustion ash were measured and listed in Table 1.

After pulverization in a silt particle size distribution quarry, the residue classified as a product was precipitated in a sedimentation basin and concentrated, and used as a raw silt.
When the particle size of the silt was measured using a laser diffraction scattering type particle size distribution measuring device (Microtrac_MT-3300EX), the average particle size was 11.44 μm, 62 μm or more was 5.6%, and 3.9 μm or less was 28.0. % Content.

(A) Dissolution test method The dissolution test was conducted in accordance with the Ministry of the Environment Notification No. 18 of 2003. That is, after sufficiently air-drying the sample, 50 g of a non-metallic sieve having a mesh opening of 2 mm was taken into a 1,000 mL polyethylene container with a lid, and 500 mL of pure water (pH 5.8 to 6.3) was added. In addition, a sample solution was prepared. This sample solution was shaken continuously for 6 hours at room temperature and atmospheric pressure using an industrial waste elution shaker (manufactured by Taitec Corporation) (shaking width: 4 to 5 cm, vibration frequency: 200 times / min). Next, the sample solution after shaking was allowed to stand for 30 minutes, and then centrifuged at about 3,000 rpm for 20 minutes. The supernatant was filtered through a membrane filter having a pore size of 0.45 μm, the filtrate was taken, the amount required for quantification was measured, and this was used as a test solution.

(B) Method for Measuring Fluorine The test solution was quantified with an ion chromatograph (ICS-2000 / manufactured by Nippon Dionex Co., Ltd.) (34.2 of JIS K 0102, Table 6 with Water Quality Environmental Standard Notification).

(C) Method for measuring hexavalent chromium The test solution was quantified by diphenylcarbazide absorptiometry (JIS K 0102 65.2.1).

(D) Method for measuring lead The test solution was quantified by ICP mass spectrometry (JIS K 0102 54.4).

Example 1
Add 2,134 g of blast furnace B cement (equivalent to 38.8 mass% solids) to the burned ash (1) with an absolute dry mass of 1,166 g (equivalent to 21.2 mass% solid content) and add an Eirich intensive mixer (( The mixture was mixed for 1 minute as a pre-stirring using Nippon Eirich Co. Next, a total of 3,880 g of silt having a solid content concentration of 56.7% is added in consideration of the moisture brought into the silt (solid content of 40% by mass). ) 275 g of Bose) and 534 g of adjusted water were added and kneading was carried out for 2 minutes. The blending ratio of these raw materials and the mass% of the additives are shown in Table 2. After 7 days of solidification and curing period (age) at 5 ° C, a solid sample was subjected to a dissolution test in accordance with Notification No. 18 of the Ministry of the Environment in 2003. As shown in Table 3, fluorine, lead, hexavalent The amount of elution of any element of chromium was below the soil environmental standard value.

Example 2
The treatment was performed in the same manner as in Example 1 except that the amount of the adjusted water was 369 g (Table 2). As shown in Table 3, the elution amounts of fluorine, lead, and hexavalent chromium from the solidified sample with a age of 7 days under 5 ° C. curing were below the soil environment standard value.

Example 3
1,746 g of blast furnace B cement was added to the burning ash (1) having an absolute dry mass of 954 g, and mixed for 1 minute as preliminary stirring using an Eirich intensive mixer. Next, 1,800 g of silt having a solid content concentration of 56.7% was added in consideration of the moisture brought into the silt, 0.45 g of AE agent, calcium nitrite-based cryoprotectant (Poztec 99, manufactured by BASF Pozzolith Co., Ltd.) 225 g and 297 g of adjusted water were added and kneading was carried out for 2 minutes (Table 2). After 7 days of solidification and curing period (age) at 5 ° C, the solidified sample was subjected to a dissolution test according to Notification No. 18 of the Ministry of the Environment in 2003. As shown in Table 3, fluorine, hexavalent chromium and lead The amount of elution was below the soil environmental standard value.

Example 4
Add 8,800 g of blast furnace B cement to burned ash (2) with an absolute dry mass of 6,600 g, then add 13,200 g of silt with a solid concentration of 50%, and use calcium chloride (35% calcium chloride solution) as a cryogen. 1,100 g of Tokuyama Co., Ltd.) and 2,367 g of conditioned water were added, and kneading was carried out for 2 minutes using a biaxial dash 200N mixer (Nikko Co., Ltd.). The blending ratio of these raw materials and the mass% of the additives are shown in Table 4. After 7 days of solidification and curing period (age) at 5 ° C, a dissolution test was conducted on the solidified sample according to Notification No. 18 of the Ministry of the Environment in 2003. As shown in Table 5, fluorine, hexavalent chromium and lead The amount of elution was below the soil environmental standard value.

Example 5
The treatment was performed in the same manner as in Example 4 except that 1,987 g of calcium chloride-based cryoprotectant and 909 g of adjusted water were added (Table 4). After 7 days of solidification and curing period (age) at 5 ° C., the solidified sample was subjected to a dissolution test according to Ministry of the Environment Notification No. 18 of 2003. As shown in Table 5, fluorine and hexavalent chromium, The amount of lead elution was below the soil environmental standard.

Example 6
The treatment was performed in the same manner as in Example 4 except that the solidification curing temperature after the kneading treatment was set to 26 ° C. assuming the summer (Table 4). After 7 days of solidification curing period (age) at 26 ° C., a dissolution test was conducted on the solidified sample according to the Ministry of the Environment Notification No. 18 of 2003. As shown in Table 5, fluorine and hexavalent chromium, The amount of lead elution was below the soil environmental standard.

Comparative Example 1
2,134 g of blast furnace B cement was added to the burned ash (1) having an absolute dry mass of 1,166 g, and mixed for 1 minute as preliminary stirring using an Eirich intensive mixer. Next, 3,880 g of silt having a solid content concentration of 56.7% (40% of the total mass of the solid content) was added, 1,015 g of adjusted water was added, and kneading was performed for 2 minutes. The blending ratio of these raw materials and the mass% of the additives are shown in Table 2. After the solidification curing period (age) at 5 ° C for 7 days, the elution test was conducted on the solidified sample in accordance with Notification No. 18 of the Ministry of the Environment in 2003. Although it was below the environmental standard value, the hexavalent chromium elution amount was 0.067 mg / L and the lead elution amount was 0.011 mg / L, which exceeded the soil environmental standard value.

Comparative Example 2
The treatment was performed in the same manner as in Comparative Example 1 except that 275 g of black liquor (20% solid content concentration) after kraft cooking and 520 g of adjusted water were added as lignin components (Table 2). After 7 days of solidification and curing period (age) at 5 ° C, the solidified sample was subjected to a dissolution test according to Notification No. 18 of the Ministry of the Environment in 2003. However, the elution amount of fluorine was 0.84 mg / L and the elution amount of lead was 0.012 mg / L, which exceeded the soil environmental standard values (Table 3).

Comparative Example 3
The treatment was performed in the same manner as in Comparative Example 1 except that 1,015 g of artificial seawater was added instead of 1,015 g of adjusted water (Table 2). After 7 days of solidification and curing period (age) at 5 ° C, the solidified sample was subjected to a dissolution test according to Notification No. 18 of the Ministry of the Environment in 2003. The amount of lead eluted was below the soil environmental standard value. However, the elution amounts of fluorine and hexavalent chromium were 0.81 mg / L and 0.054 mg / L, respectively, exceeding the soil environment standard values (Table 3).

Comparative Example 4
Add 8,800 g of blast furnace B cement to burned ash (2) with an absolute dry mass of 6,600 g, then add 13,200 g of silt with a solid content concentration of 50% (30% of the total mass of solid content), and adjust water 4,180 g was added, and kneading was performed for 2 minutes using a biaxial dash 200N type mixer (manufactured by Nikko Corporation). The blending ratio of these raw materials and the mass% of the additives are shown in Table 4. After 7 days of solidification curing period (age) at 5 ° C, the solidified sample was subjected to a dissolution test in accordance with Notification No. 18 of the Ministry of the Environment in 2003. As shown in Table 5, fluorine and hexavalent chromium Although the elution amount was not more than the soil environment standard value, the lead elution amount was 0.014 mg / L, which exceeded the soil environment standard value.

As is clear from comparing Examples 1 to 6 and Comparative Examples 1 to 4, fluorine and heavy metals derived from combustion ash are eluted below the soil environmental standard value even under winter curing conditions and summer conditions. Through the course of one year, it has become possible to safely use it as a civil engineering material in the field of soil such as recycled roadbed materials and backfill materials.

Claims (5)

Elution amount is 0.8 mg / L of fluorine and 0.05 mg / L of hexavalent chromium as heavy metals and 0.01 mg / L of lead when eluted by the dissolution test method based on Notification No. 18 of the Environment Agency in 2003 Fluorine and heavy metals that are insolubilized so that the amount of elution falls below the standard value by curing and curing clay ash, cement, cryogen and water to the combustion ash containing components exceeding the above items Of processing ash containing combustion ash. 2. The method for treating fluorine and heavy metal-containing combustion ash according to claim 1, wherein the curing condition is 10 [deg.] C. or less. The method for treating fluorine and heavy metal-containing combustion ash according to claim 1 or 2, wherein the clay soil is mainly composed of silt composed of 0.004 to 0.06 millimeters. The fluorine- and heavy metal-containing combustion ash according to any one of claims 1 to 3, wherein the cryoprotectant is added in an amount of 1 to 10 parts by mass in terms of solid content with respect to 100 parts by mass of the mixture solid content of combustion ash and cement. Processing method. The cold-resistant agent is a calcium chloride-based cold-resistant agent, and 1.0 to 5 parts by mass of calcium chloride in the calcium chloride-based cryogen is mixed with 100 parts by mass of the solid content of the combustion ash and cement. The processing method of fluorine and heavy metal containing combustion ash of any one of -4.