JP5807349B2 - Detoxification method for solid waste containing heavy metals - Google Patents

Description

  The present invention relates to a method for detoxifying solid waste containing heavy metals, and more specifically, a method for effectively insolubilizing and detoxifying harmful substances such as heavy metals contained in solid waste such as incineration ash. It is about.

  In recent years, recycling of incinerated ash discharged from lime boilers, biomass boilers, and the like as civil engineering materials has been studied. However, the incinerated ash contains heavy metals derived from lime and biomass fuel, and even if the content of these heavy metals satisfies the standards of the Soil Contamination Countermeasures Law, it exceeds the elution standards. May elute. Lime boiler ash and biomass boiler ash elute heavy metals such as lead and hexavalent chromium, and toxic substances such as arsenic, selenium, fluorine, and boron, but technology to insolubilize them safely has been established. The actual situation is not done.

  In addition, the use as civil engineering materials is mainly road base materials and aggregates, and the ash is not as it is, but it can be used as a compacted granulated material by kneading cement material and water. is necessary. Furthermore, in consideration of the possibility that roadbed materials and aggregates will be used again for other purposes after a few years, even if they are finely crushed, heavy metals and other harmful substances will not be eluted. It is necessary to.

In this way, when using ash containing heavy metals and other harmful substances as civil engineering materials, it must be solidified and granulated (solidification performance), and heavy metals and other harmful substances should not be eluted (heavy metals, etc.) Two points of insolubilization performance).
On the other hand, Patent Document 1 discloses a method for treating ash that insolubilizes lead, hexavalent chromium, arsenic, and selenium in ash using a heavy metal fixing agent.
Patent Document 2 discloses a method for solidifying and insolubilizing fluorine or boron in soil or incinerated ash in which cement material is mixed with soil or incinerated ash from which fluorine or boron is eluted.
However, these methods have a problem that it is difficult to satisfy the solidification performance and the insolubilization performance of heavy metals at the same time.

Japanese Patent No. 3271534 JP 2004-89816 A

  The present invention has been made under such circumstances, and effectively insolubilizes and detoxifies harmful substances such as heavy metals contained in solid waste such as incineration ash, It aims at providing the method which can be solidified and granulated.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that phosphoric acid and / or its salt, iron salt, cement and lime, and in some cases, solid waste containing heavy metals. It was found that the object can be achieved by adding a mineral acid and / or a mineral acid salt. The present invention has been completed based on such findings.

That is, the present invention provides the following (1) to (5).
(1) A solid waste detoxification method characterized by adding phosphoric acid and / or a salt thereof, an iron salt, cement and lime to a solid waste containing heavy metals.
(2) The solid waste detoxification method according to (1) above, wherein a mineral acid and / or a mineral acid salt is further added to the solid waste containing heavy metals.
(3) The method for detoxifying solid waste according to (2) above, wherein the solid waste containing heavy metals has an alkalinity (acid consumption at pH 8.3) of 20 mg / g (calcium carbonate equivalent) or more.
(4) The method for detoxifying solid waste according to the above (2) or (3), wherein the mineral acid and / or mineral acid salt is aluminum sulfate.
(5) The relationship between the alkalinity (mg / g) of the solid waste which uses quick lime as lime and contains heavy metals and the addition amount (mass%) of quick lime and aluminum sulfate with respect to the solid waste is as follows. The method for detoxifying a solid waste according to the above (4) that satisfies the formula (1).
[Alkalinity of solid waste (mg / g) × 0.027 + Amount of quicklime added (mass%) × 0.54] <Amount of added aluminum sulfate (mass%) <[Alkalinity of solid waste (mg / g) × 0.027 + amount of added quicklime (mass%) × 1.08] (1)

  According to the present invention, there is provided a method capable of effectively insolubilizing and detoxifying harmful substances such as heavy metals contained in solid waste such as incinerated ash, and solidifying and granulating the solid waste. can do.

  The solid waste detoxification method of the present invention (hereinafter also simply referred to as “detoxification method”) is a solid waste containing heavy metals (hereinafter also referred to as “heavy metal containing solid waste”), It is characterized by adding phosphoric acid and / or its salt, iron salt, cement and lime.

[Heavy metal-containing solid waste]
There is no restriction | limiting in particular as heavy metal containing solid waste to which the detoxification method of this invention is applied. For example, incineration ash, deposits, deposits, deposits, bricks generated during dismantling work of incinerator equipment such as garbage incinerators, etc. Examples include dust collecting plates, filter cloths, flue components, sludge, and wastewater treatment residue.
These solid wastes generally contain lead, hexavalent chromium, arsenic, selenium, cadmium, mercury, fluorine, boron, and the like as heavy metals.
The detoxification method of the present invention is preferably applied to a heavy metal-containing solid waste having an alkalinity (acid consumption at pH 8.3) of 20 mg / g (calcium carbonate equivalent) or more.
Here, the alkalinity is an index indicating the remaining state of the alkali component of the heavy metal-containing solid waste. Specifically, the acid consumption by the method described below is expressed in terms of calcium carbonate (mg-CaCO ₃ / G-solid waste).
(Measurement method of acid consumption)
Solid waste was crushed and 1 g was collected, 1000 mL of demineralized water was added thereto and stirred for 1 hour, 50 mL of the stirred solution was collected, 0.02 N-H at pH 8.3 using phenolphthalein as an indicator. Titrate with ₂ SO ₄ solution.

[Additives]
In the detoxification method of the present invention, phosphoric acid and / or a salt thereof, iron salt, cement and lime, and optionally a mineral acid and / or a mineral acid as an additive to the heavy metal-containing solid waste. Salt is added.

Examples of phosphoric acid include orthophosphoric acid, hypophosphorous acid, metaphosphorous acid, pyrophosphorous acid, orthophosphorous acid, hypophosphoric acid, metaphosphoric acid, pyrophosphoric acid, triphosphoric acid, and condensed phosphoric acid. Examples of the phosphate include sodium salts, potassium salts, primary phosphates and secondary phosphates of these phosphoric acids.
Among these phosphoric acids and / or salts thereof, orthophosphoric acid and salts thereof, polyphosphoric acid and salts thereof, metaphosphoric acid and salts thereof, pyrophosphoric acid and salts thereof from the viewpoint of detoxifying solid waste containing heavy metals. , Condensed phosphoric acid and salts thereof are preferable, orthophosphoric acid (H ₃ PO ₄ ), monosodium dihydrogen phosphate (NaH ₂ PO ₄ ), disodium monohydrogen phosphate (Na ₂ HPO ₄ ), condensed phosphoric acid More preferred.
Examples of the iron salt include ferrous chloride and ferrous sulfate, and ferrous chloride is preferable from the viewpoint of detoxifying solid waste containing heavy metals.

Examples of the cement include resource circulation type eco-cement manufactured using waste such as Portland cement, mixed cement, special cement, magnesia cement, and municipal waste incineration residue as a main raw material.
Examples of Portland cement include ordinary Portland cement, early-strength Portland cement, ultra-high-strength Portland cement, moderately hot Portland cement, sulfate-resistant Portland cement, white Portland cement, low heat Portland cement, and low alkali type Portland cement. Can be mentioned.
Examples of the mixed cement include blast furnace cement, fly ash cement, silica cement, and the like. Depending on the amount of blast furnace slag, blast furnace cement is classified as A type (5-30%), B type (30-60%), C type ( 60% or more), which can be appropriately selected and used.
Examples of the special cement include cement-based solidified material, alumina cement, ultrafast cement, auin cement, ultrafine cement, and oil well cement.
Among these cements, Portland cement and blast furnace cement are preferable, and blast furnace cement is more preferable from the viewpoint of detoxifying solid waste containing heavy metals.

Examples of lime include quick lime and / or slaked lime.
In addition, the mineral acid and / or mineral acid salt is used to adjust the alkalinity of the solid waste when the heavy metal-containing solid waste having a high alkalinity is targeted. Examples of the mineral acid and / or mineral acid salt include hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, and salts thereof. In these, a sulfuric acid and / or a sulfate are preferable, and a sulfate is more preferable.
Examples of the sulfate include sodium sulfate, potassium sulfate, calcium sulfate, magnesium sulfate, ferrous sulfate, ferric sulfate, and aluminum sulfate. Aluminum sulfate is particularly preferable.
Each said additive chemical | medical agent can be used individually by 1 type or in combination of 2 or more types.

[Addition amount of additive]
In the detoxification method of the present invention, the amount of the drug added to the heavy metal-containing solid waste can be appropriately determined in consideration of the degree of detoxification. The amount of phosphoric acid and / or salt thereof and iron salt is usually about 1 to 20% by mass, preferably 1 to 10% by mass, and the amount of cement is usually 1 to 100% by mass with respect to the solid waste. The amount of lime is usually 1 to 50% by mass, preferably 1 to 30% by mass.
Moreover, when targeting heavy metal containing solid waste with high alkalinity, it is preferable to adjust a alkalinity by adding a mineral acid and / or a mineral salt. For example, when quicklime is used as lime and aluminum sulfate is used as a mineral salt, it is determined by the following formula (1) from the alkalinity of the solid waste and the amount of quicklime to be added.
[Alkalinity of solid waste (mg / g) × 0.027 + Amount of quicklime added (mass%) × 0.54] <Amount of added aluminum sulfate (mass%) <[Alkalinity of solid waste (mg / g) × 0.027 + amount of added quicklime (mass%) × 1.08] (1)
In addition, when adding aluminum sulfate as 27 mass% aluminum sulfate aqueous solution, it determines with the following formula | equation (2) which converted the said Formula (1).
[Alkalinity of solid waste (mg / g) × 0.1 + Amount of quicklime added (mass%) × 2] <Amount of added 27 mass% aluminum sulfate aqueous solution (mass%) <[Alkalinity of solid waste ( mg / g) × 0.1 + addition amount of quicklime (mass%) × 4] (2)

In the detoxification method of the present invention, water is added to the solid waste, and the amount of the water is usually 10 to 200% by mass, preferably 20 to 100% with respect to the solid waste. % By mass.
Thus, the granulated solid formed by adding a predetermined amount of each of the above-mentioned additive chemicals and water to the solid waste and kneading the heavy solids and other harmful substances after curing for about one day. Although insolubilization and solidification strength of the substance can be obtained, it is preferable to cure for as long as possible for 3 days or longer.

  According to the solid waste detoxification method of the present invention, harmful substances such as heavy metals (lead, hexavalent chromium, arsenic, etc.) contained in solid waste such as incinerated ash discharged from lime boilers and biomass boilers, etc. Selenium, fluorine, boron, etc.) can be effectively insolubilized and detoxified, and the solid waste can be solidified and granulated, suppressing the elution of the harmful substances and being usable as civil engineering materials. .

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
In addition, the elution amount and cone index of each component in each example were measured by the following methods.

(1) Elution amount of each component After kneading the fly ash of the biomass boiler and the chemicals, curing for 1 day, pulverizing to 2mm or less, and carrying out the elution test according to Notification No. 46 of the Environment Agency in 1991 The elution amount of each component was measured.
In addition, the elution reference value of each component is as follows.
Lead: 0.01 mg / L or less, Hexavalent chromium: 0.05 mg / L or less Fluorine: 0.8 mg / L or less, Boron: 1.0 mg / L or less (2) Cone index (kN / m ² )
The solid index is measured by using a Yamanaka corn penetrometer for solids after a day of curing, which is formed into a cube of about 5 cm by mixing fly ash from a biomass boiler and chemicals. The strength of was determined. The cone index is over 800 kN / m ² .

Example 1 and Comparative Examples 1 to 4
Orthophosphoric acid, iron salt, cement and lime were added in the proportions shown in Table 1 to the fly ash of a biomass boiler having an alkalinity (calcium carbonate equivalent) of 25 mg / g from which heavy metals are eluted. The results are shown in Table 1. In addition, the result of untreated ash is also shown in Table 1 as a control.

From Table 1, it can be seen that:
Lead, hexavalent chromium and fluorine were eluted from the control untreated ash exceeding the standard values. On the other hand, in Example 1, as a result of kneading with water and four agents of orthophosphoric acid, ferrous chloride, blast furnace type B cement and quick lime, all the standard values can be cleared, and the cone index is 800 kN / m. ^It was higher than ² .
In Comparative Example 1, as a result of kneading with two components of orthophosphoric acid and ferrous chloride and water, lead and hexavalent chromium could be insolubilized, but the others could not be insolubilized and solidified.
In Comparative Example 2, even when blast furnace Type B cement was added to Comparative Example 1, it could not be sufficiently insolubilized, and the cone index was 260 kN / m ² , and sufficient solidification performance was not obtained.
In Comparative Example 3, as a result of using only blast furnace type B cement as a chemical, heavy metals could not be insolubilized, but the cone index was higher than 800 kN / m ² and the solidification performance was sufficient.
In Comparative Example 4, as a result of using three agents of orthophosphoric acid, ferrous chloride, and quicklime as chemicals, boron insolubilization was good, but heavy metals and fluorine could not be insolubilized, and the corn index was also 550 kN / m ² was insufficient.

Examples 2 and 3
As a result of adding orthophosphoric acid, iron salt, cement and lime to the fly ash of a biomass boiler with an alkalinity (calcium carbonate equivalent) of 56 mg / g from which heavy metals are eluted, and in addition to the above, Further, the results of adding aluminum sulfate in the proportions shown in Table 2 are shown in Table 2. In addition, the result of untreated ash is also shown in Table 2 as a control.

When Example 2 and Example 3 are compared, Example 3 to which aluminum sulfate is added is superior in insolubilizing ability of lead and hexavalent chromium to heavy metals and fluorine. The cone index was all over 800 kN / m ² .

In Example 3, from the data of solid waste alkalinity 56 mg / g, quick lime addition amount 5 mass% and 27 mass% aluminum sulfate solution 10 mass% (2.7 mass% as aluminum sulfate), formula (2) Is as follows.
[Alkalinity of solid waste (mg / g) × 0.1 [56 × 0.1 = 5.6] + Quicklime (mass%) × 2 [5 × 2 = 10]] = 15.6 <27 mass % Aluminum sulfate aqueous solution (mass%) 20 <[alkalinity of solid waste (mg / g) × 0.1 [56 × 0.1 = 5.6] + quick lime (mass%) × 4 [5 × 4 = 20]] = 25.6

Examples 4-6
As a result of adding orthophosphoric acid, iron salt, cement and lime to the fly ash of a biomass boiler having an alkalinity (calcium carbonate equivalent) of 160 mg / g from which heavy metals are eluted, and in addition to the above, Furthermore, the result of adding aluminum sulfate at the ratio shown in Table 3 is shown in Table 3. In addition, the result of untreated ash is also shown in Table 3 as a control.

From Table 3, it can be seen that:
In Example 4 to which no aluminum sulfate solution was added and Example 5 to which 10% by mass of aluminum sulfate solution (2.7% by mass as aluminum sulfate) was added, insolubilization of lead, hexavalent chromium and fluorine was insufficient. On the other hand, in Example 6 to which 30% by mass of aluminum sulfate solution (8.1% by mass as aluminum sulfate) was added, insolubilization of lead and fluorine was sufficient, and it was not sufficient for hexavalent chromium. Further, the effect of insolubilization was observed as compared with Example 4 and Example 5. The cone index was more than 800 kN / m ^{2 in} all examples.

From the data of Examples 5 and 6, Equation (2) is as follows.
<Example 5>
[Alkalinity of solid waste (mg / g) × 0.1 [160 × 0.1 = 16] + Quicklime (mass%) × 2 [5 × 2 = 10]] = 26> 27 mass% aluminum sulfate aqueous solution (Mass%) 10 <[alkalinity of solid waste (mg / g) × 0.1 [160 × 0.1 = 16] + quick lime (mass%) × 4 [5 × 4 = 20]] = 36
<Example 6>
[Alkalinity of solid waste (mg / g) × 0.1 [160 × 0.1 = 16] + Quicklime (mass%) × 2 [5 × 2 = 10]] = 26 <27 mass% aluminum sulfate ( Mass%) 30 <[alkalinity of solid waste (mg / g) × 0.1 [160 × 0.1 = 16] + quick lime (mass%) × 4 [5 × 4 = 20]] = 36

  The solid waste detoxification method of the present invention is a hazardous material such as heavy metals (lead, hexavalent chromium, arsenic, selenium, selenium, etc.) contained in solid waste such as incinerated ash discharged from lime boilers and biomass boilers. Fluorine, boron, etc.) can be effectively insolubilized and rendered harmless, and the solid waste can be solidified and granulated, so that elution of the harmful substances can be suppressed and used as civil engineering materials.

Claims (4)

A solid waste detoxification method comprising adding phosphoric acid and / or a salt thereof, an iron salt, cement and lime to a solid waste containing heavy metals ,
The amount of the phosphoric acid and / or salt thereof and the iron salt is 1 to 20% by mass, the amount of the cement is 1 to 100% by mass, and the amount of the lime is 1 to 50% with respect to the solid waste. %, A method for detoxifying solid waste . The solid waste detoxification method according to claim 1 , wherein the solid waste containing heavy metals has an alkalinity (acid consumption at pH 8.3) of 20 mg / g (calcium carbonate equivalent) or more. The method of detoxifying the relative solid waste, further solid waste according to claim 1 or 2 you added aluminum sulfate. The relationship between the alkalinity (mg / g) of the solid waste containing quick metal and containing heavy metals and the addition amount (mass%) of quick lime and aluminum sulfate to the solid waste is expressed by the following formula (1 The solid waste detoxification method according to claim 3 , wherein
[Alkalinity of solid waste (mg / g) × 0.027 + Amount of quicklime added (mass%) × 0.54] <Amount of added aluminum sulfate (mass%) <[Alkalinity of solid waste (mg / g) × 0.027 + amount of added quicklime (mass%) × 1.08] (1)