JP5836096B2 - Earthwork materials - Google Patents

Description

  The present invention relates to an earthwork material used as a backfill material or the like using sewage sludge incineration ash, and to an earthwork material in which the amount of harmful substances contained in the sewage sludge incineration ash is suppressed to a soil environment standard or less.

  Hundreds of thousands of tons of sewage sludge incineration ash is generated annually, and some of it is used for backfill soil, roadbed materials, or admixtures for concrete products, but most of it is industrial waste. It is disposed of in the ground or on the sea as an object. In the future, it will be necessary to maximize the effective use of sewage sludge incineration ash in order to respond to the social situation such as tightness of waste disposal sites and reduction of environmental burden. However, sewage sludge incineration ash has environmental safety issues such as elution of heavy metals and harmful substances. Specifically, the amount of elution of fluorine, boron, arsenic, and selenium is mainly determined by soil environment standards (environment agency notification). No. 46) is a hindrance to effective use. Table 1 shows the elution amounts of fluorine, boron, arsenic, and selenium specified in the soil environmental standards (Environment Agency Notification No. 46).

Conventionally, fluorine insolubilization techniques include the use of calcium salts such as slaked lime to produce sparingly soluble calcium fluoride, and the process in which aluminum hydroxide is produced using aluminum salts such as aluminum sulfate. There are known methods for adsorption and insolubilization, methods for adsorption and insolubilization of fluorine in the process of producing magnesium hydroxide using a magnesium salt such as magnesium sulfate. As a boron insolubilization technique, a method of adsorbing and insolubilizing boron by using an aluminum salt such as aluminum sulfate or using aluminum sulfate and slaked lime together is known. Arsenic insolubilization technologies include a method of adsorbing and insolubilizing arsenic in the process of producing aluminum hydroxide using aluminum salts such as aluminum sulfate, and iron hydroxide using ferric chloride and other iron salts. A method of adsorbing and insolubilizing arsenic in the process of generation is known. As an insolubilization technique of selenium, an adsorption / insolubilization method using an iron salt or the like is known.
However, in these methods, the effect of insolubilization is low, and it has been difficult to suppress the elution amounts of fluorine, boron, arsenic and selenium from the sewage sludge incineration ash to below the soil environmental standard.

  From this point of view, several methods for suppressing elution of harmful substances in industrial waste such as sewage sludge incineration ash have been proposed. For example, technologies for capturing and insolubilizing arsenic and hexavalent chromium with chelating agents such as dithiocarbamate or dithiocarbamate derivatives (Patent Documents 1 and 2), adding thiosulfate compounds to contaminated soil and incineration ash, and heating incineration ash By adding a cement or lime, which is a hydraulic binder, to the incineration ash, a technology related to a device that insolubilizes heavy metals such as arsenic and selenium contained in the incineration ash, etc. (Patent Document 3) Technology that suppresses the elution of fluorine and boron contained (Patent Document 4), Technology that suppresses elution of fluorine from industrial waste by adding powder such as calcium aluminate to industrial waste such as steelmaking slag (Patent Document 5), calcium oxides and / or calcium hydroxides in boron-containing combustion ash generated by burning coal, paper sludge, etc. , Calcium sulfate, alumina cement, a technique for suppressing elution of boron from combustion ash by adding water (Patent Document 6), an insolubilizer containing calcium aluminate and calcium silicate Is a method for insolubilizing fluorine and / or boron by mixing the solid material containing fluorine and / or boron, the insolubilizing agent and water, and then curing for a required period of time. Patent Document 7) Adds and mixes anti-elution agents containing pollutants containing aluminum sulfate, sodium thiosulfate and iron powder as essential components to contaminated soil and incinerated ash so that heavy metals such as arsenic and selenium Technology that suppresses the elution of elemental and fluorine (Patent Document 8), adding and mixing a solidifying material such as Portland cement and water to sewage sludge incineration ash After granulation by the rolling granulation method or compression granulation method, the elution of heavy metals such as arsenic is physically suppressed by forming an asphalt film using asphalt / water emulsion on the surface of the granulated product. The technique (patent document 9) to do is reported.

JP 1998-192870 A JP 2001-121133 A JP 2006-000746 A JP 2004-089816 A JP 2001-259570 A JP 2005-329343 A JP 2006-224025 A JP 2002-239522 A JP-A-1995-060222

However, these conventional techniques have problems such as using expensive components, requiring a large-scale device, requiring complicated granulation operations, and requiring long-term curing. This is only a means that can suppress the elution of only the harmful substances, and it cannot suppress the elution of the four kinds of harmful substances.
Therefore, the problem of the present invention is that the amount of elution of fluorine, boron and heavy metals (arsenic, selenium), which are harmful substances contained in sewage sludge incineration ash, is less than the soil environment standard in earthwork materials using sewage sludge incineration ash. An object of the present invention is to provide an economical and efficient prescription of earthwork materials that can be suppressed.

  Therefore, as a result of repeated studies, the present inventor, when using sewage sludge incineration ash containing fluorine, boron and heavy metals (arsenic, selenium) as an earthwork material, the sewage sludge incineration ash, calcium aluminate, aluminum sulfate In addition to lime and lime, a combination of alkali metal phosphates can suppress the amount of toxic substances released from the mixture obtained by mixing the earthwork material with water to below the soil environmental standards, and It has been found that the elution suppression effect is exhibited in a short time after the mixture is prepared. In addition, the present inventors have found that the addition of cement to the blending of the earthwork material further increases the effect of suppressing the elution of harmful substances, thereby completing the present invention.

That is, the present invention relates to the following [1] to [7].
[1] (A) Sewage sludge incinerated ash whose elution amount of one or more selected from fluorine, boron, arsenic and selenium exceeds soil environmental standards, (B) calcium aluminate, (C) aluminum sulfate, (D) Earthwork material containing lime and (E) alkali metal phosphate.
[2] (A) 0.2 to 2 parts by mass of calcium aluminate, (C) 0.1 to 1 parts by mass of aluminum sulfate, and (D) 0.05 to lime with respect to 100 parts by mass of sewage sludge incineration ash The earthwork material of [1] containing 10 to 10 parts by mass and (E) 0.01 to 0.1 parts by mass of an alkali metal phosphate.
[3] The earthwork material according to [1] or [2], wherein the main component of (B) calcium aluminate is amorphous 12CaO · 7Al ₂ O ₃ .
[4] The earthwork material according to any one of [1] to [3], wherein (E) the alkali metal phosphate is potassium phosphate.
[5] The earthwork material according to any one of [1] to [4], further containing cement.
[6] The earthwork material according to [5], wherein the cement is white Portland cement.
[7] The earthwork material according to any one of [1] to [6], wherein an elution amount of fluorine, boron, arsenic, and selenium is suppressed to a soil environmental standard or less.

  The earthwork material using the sewage sludge incineration ash of the present invention is less than the soil environment standard for the amount of elution of fluorine, boron and heavy metals (arsenic, selenium), which are harmful substances contained in the sewage sludge incineration ash, in an economical formulation. Environmental safety is high. And since the elution suppression effect is exhibited for a short time after mixing this earthwork material with water, it can be used for a backfill material etc., without having to provide the curing period after mixing long. Furthermore, since the earthwork material of the present invention maintains the elution suppression effect after mixing with water for a long period of time, the mixture can be stored for a long period of time, which is convenient when used as an admixture for cement products. Therefore, the present invention is an extremely useful technique for promoting effective use of sewage sludge incineration ash.

  The (A) sewage sludge incineration ash used in the earthwork material of the present invention has been subjected to incineration treatment to dehydrate, further reduce and stabilize sewage sludge. As harmful components, fluorine, boron, arsenic And at least one elution amount selected from selenium exceeds the soil environment standard (Environment Agency Notification No. 46). As the sewage sludge incineration ash, those having a maximum particle size of 1.2 mm or less are preferable.

The (B) calcium aluminate used in the earthwork material of the present invention is basically a substance obtained by heat-treating a CaO raw material and an Al ₂ O ₃ raw material. Calcium aluminate may be any hydrated active substance having a crystallized structure composed of CaO and Al ₂ O ₃ or a vitrified structure as a chemical component, and other chemicals in addition to CaO and Al ₂ O _3. A compound added with a component, a solid solution, a glassy substance, or a mixture thereof may be used. The former example _{12CaO · 7Al 2 O 3, CaO} · Al 2 O 3, 3CaO · Al 2 O 3, CaO · 2Al 2 O 3, CaO · 6Al 2 O 3 and the like, and as the latter example, 4CaO · include a _{3Al 2 O 3 · SO 3,} 11CaO · 7Al 2 O 3 · CaF 2, Na 2 O · 8CaO · 3Al 2 O 3 or the like. Preferably, since it is excellent in the elution suppression effect of harmful components, the main component is amorphous 12CaO · 7Al ₂ O _{3 in} which the clinker after heat treatment is rapidly cooled to a vitrification ratio of 90% or more. good. The fineness of calcium aluminate is preferably 2000 cm ² / g or more in terms of Blaine specific surface area.

(C) Aluminum sulfate used in the earthwork material of the present invention is a hydrate represented by Al ₂ (SO ₄ ) ₃ .nH ₂ O as a chemical component, or an anhydrous salt represented by Al ₂ (SO ₄ ) _3. Any of these may be used. Preferably, hydrates with n of 14 to 18 are preferable because they are excellent in the elution suppression effect of harmful components.

The (D) lime used for the earthwork material of the present invention is mainly composed of calcium oxide represented by CaO as a chemical component, or calcium hydroxide represented by Ca (OH) ₂ as a chemical component. Can be used, and may include both. Preferably, lime having a high content of calcium oxide is preferable because it has an excellent elution suppressing effect on harmful components. The fineness of lime is preferably 2000 cm ² / g or more as the Blaine specific surface area.

  As the (E) alkali metal phosphate used in the earthwork material of the present invention, a readily soluble salt such as sodium phosphate or potassium phosphate can be used. In this invention, a favorable elution inhibitory effect is acquired by a short curing period by mix | blending an alkali metal phosphate. As the alkali metal phosphate, potassium phosphate represented by the following formulas (1) to (3) is preferable, and dihydrogen phosphate represented by the following formula (2) because it is excellent in the effect of shortening the curing period. Potassium is more preferred.

K ₂ HPO ₄ (1)
KH ₂ PO ₄ (2)
K ₃ PO ₄ (3)

Examples of the cement used in the earthwork material of the present invention include Portland cement, mixed cement, special cement, and ecocement. Portland cement means normal Portland cement, early-strength Portland cement, ultra-early strong Portland cement, moderately hot Portland cement, sulfate-resistant Portland cement, white Portland cement, low heat Portland cement, and their low alkali type Portland cement. . Mixed cement refers to blast furnace cement, fly ash cement, silica cement and the like. Special cements include cement-based solidified materials, alumina cements, ultrafast cements, Auin-based cements, ultrafine particle cements, oil well cements, and the like. Eco-cement refers to cement manufactured using waste such as municipal waste incineration residue as the main raw material. Among these cements, white Portland cement is preferable, and white Portland cement contains almost no harmful heavy metals such as selenium and hexavalent chromium, and therefore can be particularly suitably used for the earthwork material of the present invention.

  The earthwork material of the present invention is 0.2 to 2 parts by weight of calcium aluminate, 0.1 to 1 part by weight of aluminum sulfate, 0.05 to 10 parts by weight of lime, 100 parts by weight of alkali metal phosphorus, based on 100 parts by weight of sewage sludge incineration ash. The content ratio of 0.01 to 0.1 parts by weight of acid salt is the amount of elution of fluorine, boron, arsenic and selenium contained in sewage sludge incineration ash below the soil environment standard (Environment Agency Notification No. 46) It is preferable from the point of the effect to suppress to this, and economical efficiency. The content of calcium aluminate, aluminum sulfate and lime is preferably in the above range from the viewpoint of the elution suppressing effect of harmful substances, and the elution suppressing effect even if the curing time is shortened by setting the lime content in the above range. Is preferable in that it is obtained. In addition, the content of the alkali metal phosphate is preferably in the above range from the viewpoint of shortening the curing time. It is preferable that the content (mass) of the alkali metal phosphate is about 1/40 to 1/10 that of calcium aluminate because a good elution suppressing effect can be obtained in a short curing period and it is economical.

  When cement is added to the earthwork material of the present invention, elution of fluorine, boron, arsenic and selenium contained in the sewage sludge incineration ash can be more effectively suppressed. Preferably, 0.5 to 10 parts by mass of cement is added to 100 parts by mass of sewage sludge incineration ash, and a more preferable mixing ratio is 2 to 5 parts by mass. When cement is blended, it is economical because a good elution preventing effect can be obtained even if the blending ratio of calcium aluminate, aluminum sulfate, lime, and alkali metal phosphate is small.

  The use of the earthwork material of the present invention is not particularly limited, and can be effectively used as an embedding material for cement products such as embankment material, backfill material, backing material, soil improvement material, road material, and concrete. Moreover, it does not specifically limit about the manufacturing method of the earthwork material of this invention, A general manufacturing method can be used. Since the earthwork material of the present invention exhibits an elution suppression effect in a short time after mixing with water, it can be used without the need for a long curing period. For example, when used as a backfill material, a bread mixer on site The earthwork material of the present invention can be mixed with water using a general mixer such as a forced biaxial mixer or the like, and a backfilling operation can be performed immediately after processing into a slurry or block mixture. In addition, since the earthwork material of the present invention maintains an elution suppressing effect for a long time after mixing with water, the mixture can be stored for a long time and used as an admixture for cement products as appropriate.

  EXAMPLES Next, an Example is given and this invention is demonstrated still in detail.

(A) Sewage sludge incineration ash Two types of sewage sludge incineration ash having a maximum particle size of 1.2 mm or less were used. Table 2 shows the amount of fluorine, boron, arsenic, and selenium eluted from the sewage sludge incineration ash according to Environment Agency Notification No. 46.

(B) Calcium aluminate Quicklime (powder reagent) having a CaO content of 97% by mass as a CaO raw material, and Ban earth shale (Al ₂ O ₃ content of 88% by mass, Fe ₂ O ₃ content of 1% by mass) as an Al ₂ O ₃ raw material %), hematite and (Al ₂ O ₃ content of 3 mass%, Fe ₂ O ₃ content of 93 wt%) was used as Fe ₂ O ₃ raw material, mixed according to the formulation shown in Table 3, 1550 ± an electric furnace Heated at 50 ° C. for 2 hours. After heating, a clinker that was naturally cooled (slowly cooled) in the furnace to near room temperature and a clinker that was taken out of the furnace from around 1550 ° C. and immediately cooled with blown compressed air were obtained. For these clinker, the abundance of the generated crystal phase is quantified by powder X-ray diffraction, the remaining phase is regarded as the glass phase, the glass phase generation amount is calculated, and the vitrification rate of the clinker is calculated from the ratio (mass ratio) with the clinker total amount. Was calculated. This value is shown in Table 3. These clinkers were pulverized with a ball mill to a specific surface area of 5000 ± 500 cm ² / g.

(C) Aluminum sulfate 14-18 hydrate (abbreviation: ALS): Powder reagent manufactured by Kanto Chemical Co., Inc. (D) Calcium oxide (abbreviation: CAO): Powder reagent manufactured by Kanto Chemical Co., Inc. (E) Dipotassium hydrogen phosphate (abbreviation) : PK): Kanto Chemical Co., Inc. Powder Reagent (F) Ordinary Portland Cement (abbreviation: OPC): Taiheiyo Cement (F) White Portland Cement (abbreviation: WPC): Taiheiyo Cement “White Cement”

  The materials used were blended in the proportions shown in Table 4 to obtain the earthwork material of the present invention and the earthwork material of the comparative product.

(Measurement of elution amount)
600 g of water was added to 1000 g of the earthwork material shown in Table 4 and mixed for 3 minutes with a mortar mixer to prepare a mixture. The mixture is sealed in a plastic bag and cured at a temperature of 20 ° C. After the curing period of 3, 6, and 24 hours, elution of fluorine, boron, arsenic, and selenium is performed in accordance with the Environmental Agency Notification No. 46. The amount was measured. Table 6 shows the measurement results of the elution amount. The mixture is sealed in a plastic bag and cured at a temperature of 20 ° C. for 24 hours, and then the mixture is taken out from the plastic bag and stored in an environment at a temperature of 20 ° C. and a humidity of 60%. The amount of fluorine, boron, arsenic and selenium eluted was measured by a method according to Notification No. 46. Table 7 shows the measurement results of the elution amount.
[Measurement method of elution volume according to Environmental Agency Notification No. 46]
(1) Roughly crush the sample after curing for a predetermined period, collect and mix the sieve 2 mm passage.
(2) Weigh 50 g of sample in a 1000 mL capacity plastic container, add 500 g of solvent (adjusted to pH 6.1 by adding 0.5 mol hydrochloric acid to 1 L of pure water), and shaker (number of shakes 200 times / Shake for 6 hours.
(3) After allowing the polycontainer to stand for 30 minutes, the supernatant of the sample solution is filtered through a membrane filter having a pore diameter of 0.45 μm to obtain a test solution.
(4) The components of the collected test solution are measured by the method shown in Table 5.

  From the results shown in Table 6, all the earthwork materials of the present invention have a curing period of 24 hours or less, and the amount of fluorine, boron, arsenic, and selenium released is less than the specified value of the soil environment standard (Environment Agency Notification No. 46). You can see that In addition, among the earthwork materials of the present invention, the earthwork materials excluding the present invention 1, 2, 3, 9, 14, and 20 have an elution amount of fluorine, boron, arsenic, and selenium with a curing period of 3 hours. It can be seen that the elution suppression effect is exhibited in a short time. On the other hand, it can be seen that the earthwork materials (comparative products 1 to 10) shown as comparative examples are inferior to the earthwork material of the present invention, and that the amount of elution is particularly large when the curing period is within 6 hours. In the comparative materials 6 and 10, the elution amount of fluorine when the curing period is 24 hours is suppressed to less than the soil environment standard, but the elution amount of boron, arsenic, and selenium exceeds the soil environment standard. Therefore, its performance is insufficient to suppress the elution of sewage sludge incineration ash.

  From the results shown in Table 6, the earthwork material of the present invention using crystalline calcium aluminate (CA-1) (present inventions 1 and 14) was formulated using amorphous calcium aluminate (CA-2). The amount of fluorine, boron, arsenic and selenium eluted is larger than that of the earthwork material of the present invention having the same ratio (Inventions 4 and 15), and it is preferable that the calcium aluminate is amorphous. Recognize.

  From the results shown in Table 6, the earthwork material of the present invention (invention 9) using ordinary Portland cement (OPC) is the earthwork material of the present invention having the same blending ratio (invention 9) using white Portland cement (WPC). Compared with 12), the amount of elution of selenium is larger, and it can be seen that white Portland cement is preferable as the cement.

  From the results of Table 6, it can be seen that, in the earthwork material of the present invention, when the amount of lime is increased, the elution suppression effect is improved. Moreover, in the earthwork material of this invention, when the compounding quantity of a phosphate is increased, it turns out that the elution inhibitory effect improves, and even if a curing time is short, the elution amount can be restrained small.

  From the results of Table 7, the earthwork material of the present invention (invention products 4, 5, 11, 12, 17, 18, 23, 25, 26) shown as examples is 1 in an environment of temperature 20 ° C. and humidity 60%. It can be seen that the amount of fluorine, boron, arsenic, and selenium eluted after the storage for months is kept below the standard value of the soil environment standard (Environment Agency Notification No. 46). On the other hand, comparative products 6 and 9 among the earthwork materials shown as comparative examples have an elution amount of fluorine, boron, arsenic, and selenium exceeding the soil environmental standards (Environment Agency Notification No. 46). The amount of elution increased before storage (when it was cured at 20 ° C. for 24 hours). Further, in Comparative product 10, the elution amounts of fluorine, boron, arsenic, and selenium were slightly lower than before storage, but the elution amounts of boron, arsenic, and selenium still exceeded the soil environmental standards.

Claims (8)

(A) Sewage sludge incineration ash with at least one elution amount selected from fluorine, boron, arsenic and selenium exceeding soil environmental standards, (B) calcium aluminate, (C) aluminum sulfate, (D) lime and ( E) An earthwork material containing an alkali metal phosphate and containing 0.01 to 0.1 part by mass of (E) an alkali metal phosphate with respect to 100 parts by mass of (A) sewage sludge incineration ash . (A) 0.2 to 2 parts by mass of calcium aluminate, (C) 0.1 to 1 part by mass of aluminum sulfate and ( D) 0.05 to 10 parts by mass of lime with respect to 100 parts by mass of sewage sludge incineration ash The earthwork material of Claim 1 containing a part . The earthwork material according to claim 1 or 2, wherein the main component of (B) calcium aluminate is amorphous 12CaO · 7Al ₂ O ₃ .   (E) The earthwork material according to any one of claims 1 to 3, wherein the alkali metal phosphate is potassium phosphate.   Furthermore, the earthwork material in any one of Claims 1-4 containing a cement.   The earthwork material according to claim 5, wherein the cement is white Portland cement.   The earthwork material according to any one of claims 1 to 6, wherein an elution amount of fluorine, boron, arsenic, and selenium is suppressed to a soil environmental standard or less. (A) The sewage sludge incineration ash is one or more elution amounts selected from fluorine and boron, and one or more elution amounts selected from arsenic and selenium exceeds the soil environment standard. The earthwork material according to any one of 7 above.