JP4363657B2 - Method and apparatus for stabilizing incineration fly ash - Google Patents

Description

  The present invention is a technology for stabilizing incineration fly ash, molten fly ash, incineration ash discharged from incineration plants such as municipal waste, industrial waste, sewage sludge, and processing metal contaminants, soil, and industrial waste. It is about.

  Incineration fly ash generated during the incineration of industrial waste and municipal waste is finally landfilled, but since these incineration fly ash contains heavy metals, after landfill treatment It must be fixed so that heavy metals are not eluted by rainwater. Regarding the immobilization of incineration fly ash, it is obliged to carry out any of the following methods: "Cement solidification method", "Extraction method with acid or other solvent", "Melting fixation", or "Chemical addition method". ing. Among these, the “drug addition method” has been studied in various ways because it is generally easier to handle and handle than other methods. The chemical addition method is a method in which a predetermined amount of water, a chemical and incineration fly ash are kneaded and reacted to fix harmful heavy metals. Examples of the drug used for this purpose include organic chelate heavy metal immobilizing agents that form chelate compounds with heavy metals to form stable immobilization products that are insoluble in water, and inorganic heavy metal immobilizing agents such as iron salts.

As the organic chelate heavy metal immobilizing agent, an alkali metal salt or a transition metal salt of a compound having two or more dialkyldithiocarbamic acid or dialkyldithiocarbamic acid groups in the molecule, specifically, diethyldithiocarbamic acid, N ₁ , N ₂ , There are potassium salts such as N ₃ , N ₅ -tetra (dithiocarboxy) tetraethylenepentamine, piperazine bisdithiocarbamic acid, sodium salts, zinc salts, iron salts and the like. Among the inorganic heavy metal fixing agents, iron salt-based ones include ferrous sulfates such as ferrous sulfate and ferrous chloride, ferrous sulfates such as polyiron sulfate, ferric chloride, and ferric sulfate. There are two iron salts. As a method for treating incineration fly ash using iron salt, ferrous salt and / or ferric salt is added to incineration fly ash to immobilize heavy metals, and reducing ferrous iron There has been proposed a method for efficiently immobilizing heavy metals such as hexavalent chromium, arsenic and selenium by adding a salt together with an inorganic flocculant such as a sulfate band. Since iron salt is cheaper than organic liquid chelating agents and has a very low ecological effect, it has a high utility value as a stabilizer for incineration fly ash.
JP 2004-209372 A JP-A-8-99075

  This invention makes it a subject to provide the novel stabilization method and apparatus of incineration fly ash which prevents the elution of heavy metals using a cheap and highly safe iron salt or organic chelate heavy metal fixing agent.

In order to solve the above problems, in the present invention, incineration fly ash, and a mixture of ferrous salt and ferric salt, ferrous iron (Fe2 +) with respect to ferrous iron (Fe2 +) + ferric iron (Fe3 +). The kneaded product obtained by kneading an iron salt or organic chelate heavy metal immobilizing agent having a molar ratio [Fe2 + / (Fe2 + Fe3 +)] of 0.2 to 1.0 and water, at a temperature of 40 to 150 ° C., relative It is a method for stabilizing incineration fly ash characterized by curing in contact with the atmosphere in an environment with a humidity of 40% or more.
In the stabilization method, the kneaded product is 0.5 to 4.0 in a molar ratio alkali content that NaOH-equivalent with respect to the iron salt (ferrous salt + ferric), the alkali content is It can alkali content der Rukoto obtained from the acid consumption of the eluate of the kneaded material (pH 8.3).
Moreover, in this invention, in the apparatus which stabilizes incineration fly ash, it is the 1st with respect to 1st iron (Fe2 +) + 2nd iron (Fe3 +) with a mixture of incineration fly ash and a ferrous salt and a ferric salt. A kneader for obtaining a kneaded product by kneading an iron salt or organic chelate heavy metal fixing agent having a molar ratio of iron (Fe2 +) [Fe2 + / (Fe2 + Fe3 +)] of 0.2 to 1.0 and water was obtained. The incinerator fly ash stabilization device is characterized by having a curing device equipped with heating, humidification and air blowing means for curing the kneaded material in an environment having a temperature of 40 to 150 ° C. and a relative humidity of 40% or more. is there.

As described above, a kneaded product obtained by adding a metal salt, particularly an iron salt or an organic chelate heavy metal fixing agent to incinerated fly ash is cured in an environment of 40 to 150 ° C. and a relative humidity of 40% or more. According to the method for stabilizing incineration fly ash characterized in that the following effects can be obtained.
(1) Reduction of drug usage (2) Improvement and stabilization of processing performance (3) Prevention of elution of difficult-to-process heavy metals such as hexavalent chromium, selenium, arsenic and antimony (4) Prevention of sticking between kneaded molded products, Prevention of dust generation

Hereinafter, various embodiments of the present invention will be described by taking incineration fly ash treatment as an example. The incineration fly ash which is a target in the present invention is not particularly limited, but is collected by incineration fly ash (EP, BF, multi-cyclone, etc.) discharged from incineration facilities for municipal waste, industrial waste, and sewage sludge. ).
The stabilization method of the present invention will be described with reference to FIG. 1 which is a schematic configuration diagram. Normally, dust 1 is filtered by a dust collector 2, and the incineration fly ash separated by the dust collector 2 is stored in a storage silo. 3 is saved. The incineration fly ash 5 is weighed from the storage silo 3 with a weight meter 4 and sent to the kneader 6 where humidified water from the humidified water tank 11 is added. At this time, the heavy metal fixing agent 12 is usually contained in the humidified water, and the humidified water containing the heavy metal fixing agent 12 is supplied to the kneader 6. The kneaded material that has come out of the kneader is sent to the treated ash pit 10 by the carry-out conveyor 9. Usually, the kneaded material which came out of the kneader is cured (dried and solidified) until it is carried out on the carry-out conveyor and in the ash pit.
The carry-out conveyor is also referred to as a curing conveyor, but is simply a conveyor for carrying the kneaded product from the kneader to the treatment ash pit.

In the conventional treatment, the kneaded product (or kneaded molded product) humidified at the time of kneading is merely brought into contact with the atmosphere on the carry-out conveyor or the treated ash pit and naturally dried, and is not focused on curing. That is, there was no process of positively applying humidity to the kneaded product under atmospheric contact and heat curing. The present invention actively performs curing.
As a result of intensive studies on a chemical treatment method for incineration fly ash using an iron salt or an organic chelate heavy metal fixing agent, the present inventors have obtained a kneaded product obtained by adding iron salt to incineration fly ash at a temperature of 40 to It was found that elution of heavy metals can be effectively suppressed by curing in an environment of 150 ° C. and a relative humidity of 40% or more, and the present invention has been completed. Target elements include harmful heavy metals such as lead, cadmium, mercury, chromium, arsenic, selenium, magnesium, aluminum, calcium, vanadium, manganese, cobalt, nickel, copper, zinc, tin, antimony, molybdenum, Examples thereof include boron and fluorine.

The present invention is not limited to the method for treating incinerated fly ash using iron salts, but also for treating incinerated fly ash using an organic chelate heavy metal immobilizing agent, and for contaminated soil and industrial waste such as metals. It can also be applied to processing.
Conventionally, as a heat treatment method for incineration fly ash, Hagenmeier type thermal decomposition technology has been proposed. This method is a technique aimed at decomposing dioxins by raising the temperature of incinerated fly ash to about 350 ° C. in an oxygen-free reactor (fly ash heater).
On the other hand, the present invention is a technique for immobilizing heavy metals by placing the kneaded material in an environmental condition of a temperature of 40 to 150 ° C. and a relative humidity of 40% or more under the coexistence conditions of air (oxygen). This is fundamentally different from the Hagenmeier method.

  Japanese Patent Publication No. 61-47154 discloses a method in which waste containing a heavy metal is mixed with an alkali in the presence of an iron salt and then kept at a temperature of less than 300 ° C. In Japanese Patent No. 3176162, A method is disclosed in which water and divalent iron are added, and then the flue gas is added to the mixture, and the pH is set to 7.0 to 11.5 and the temperature is set to 30 to 99 ° C. However, in these methods, the humidity of the atmosphere in contact with the object to be processed is not defined at all. This invention newly discovered that the heavy metal fixation effect became high by processing the humidity of the atmosphere which contacts a to-be-processed object as the range of this invention. By treating the humidity of the atmosphere in contact with the object to be processed as the scope of the present invention, the effect of fixing the heavy metal is increased as a result of preventing rapid drying of the object to be processed and promoting the ferritization reaction. Guessed. Even when the amount of water in the workpiece is large, the heat treatment alone causes rapid drying of the surface layer of the workpiece, resulting in insufficient ferrite and uniform treatment. Ferrite ratio does not increase.

In the present invention, a kneaded product obtained by adding iron salt and water to incinerated fly ash is actively ferritized by adjusting the curing conditions, thereby exhibiting the effect of fixing heavy metals and preventing heavy metal elution.
Moreover, even if it suppresses heavy metal elution using this organic chelate heavy metal fixing agent, heavy metal fixation and a heavy metal elution prevention effect can be exhibited by adding the curing of this invention.
In other words, even if iron salt is not added to incineration fly ash, ferritization and curing with iron salts such as iron compounds and iron chlorides in incineration fly ash make it difficult to dissolve calcium compounds, calcium carbonate, copper, etc. Solidification action by hydroxides other than iron such as zinc and manganese becomes stronger, and it becomes possible to fix heavy metals and prevent heavy metal elution.
About curing temperature, it is 40-150 degreeC, Preferably it is 60-100 degreeC. If it is less than 40 degreeC, stabilization as a ferrite compound of the heavy metals in a kneaded material will be slow, and practical use will be difficult. If it exceeds 150 ° C., the surface of the kneaded material is rapidly dried, and the effect of fixing heavy metals is reduced.

Below, a specific example is demonstrated and demonstrated about a curing device. As shown in FIG. 2, a curing device including a blower, a heating device, and a humidifying device can be installed between the kneader and the treated ash pit. The curing device is not a simple drying device, but is for stabilizing heavy metals in the kneaded material as a ferrite compound while passing through this device. That is, there is a big difference that heavy metals can be stabilized and fixed by curing with this apparatus, while heavy metals are likely to be eluted from the treated product by simple drying.
FIG. 3 shows a schematic diagram of a hopper type curing apparatus. The kneaded product is stored in a hopper that includes a watering device for humidification and an air diffuser. If necessary, air, warmed air, warmed humidified air can be sent from the diffuser. Moreover, it can sprinkle from the watering apparatus for humidification as needed.
Furthermore, the curing device main body (hopper) can be kept warm and heated. If the kneaded material itself has heat and the temperature is 60 ° C. or higher, it is only necessary to keep the curing device warm without heating. A nozzle spray for watering can be provided in the watering device for humidification to spray water continuously or intermittently. As heating and humidified air, water vapor generated by passing a high-temperature gas such as incineration exhaust gas through water can be used. Furthermore, warm water can be sprayed from the humidifying watering device. Moreover, the heat retention and heating of the curing device body (hopper) can be indirectly performed by introducing incineration exhaust gas or hot water into a jacket provided on the outer wall of the hopper.

FIG. 4 shows a schematic view of a kiln type curing device. The kneaded material on the conveying device (conveyor) is sent to a kiln type curing device equipped with a warming / humidifying device (comprising a warming heater, air or humidified air or warmed humidified air discharging device, steam piping, etc.). . Since there is an opening, air necessary for ferritization can be supplied by natural ventilation. Moreover, air, warm air, and warm humid air can be sent as needed. As heating and humidified air, water vapor generated by aeration of exhaust gas discharged from an incineration facility or the like may be used. The heating / humidifying device may be provided in the entire conveying device, or may be provided only in the front stage portion of the conveying device. Before and after the curing device is in an open state, air may be naturally ventilated, or in order to improve the ventilation of the curing device, forced ventilation such as a ventilation port or an exhaust fan or a blower device may be provided at the outlet of the curing device. it can.
Although the shape of the kneaded material supplied to this apparatus is not specifically limited, In order to improve curing efficiency, a diameter of 1 to 10 mm, a length of 1 to 30 mm are preferable for pellets, and a diameter of 1 to 10 mm is preferable for granules. Further, the kneaded product may be pulverized and supplied to the apparatus before curing. The type of the kneading machine is not particularly limited, and a vibration mixer, a bread granulator, a biaxial bench kneader mixer, or the like can be used as appropriate.

When ferrous salt and ferric salt are added to incinerated fly ash containing alkali, as shown in the following formula (3) in addition to the reactions shown in the following formulas (1) and (2) Magnetite (Fe ₃ O ₄ ) is produced.
xM ²⁺ + (3-x) Fe ²⁺ + 6OH ⁻ → M _x Fe _(3-x) (OH) ₆ (1)
xM 2 ⁺ + yFe ³ +2 (x + 3 / 2y) OH ⁻ → MxFey (OH) _{2 (x + 3 / 2y)} (2)
Fe ²⁺ + 2Fe ³⁺ + 4OH ⁻ → Fe ₃ O ₄ + 2H ₂ (3)
[Wherein M represents a heavy metal such as Pb, Cd, Hg, or Zn. ]
This magnetite has an extremely large heavy metal trapping action, and a part of Fe is replaced with another metal, thereby generating a kind of ferrite having a stable heavy metal elution suppressing ability.

Moreover, when ferrous salt is added to incinerated fly ash containing an alkali component, a kind of ferrite having a stable heavy metal elution suppressing ability is generated by the following two-stage reaction.
Neutralization reaction: xM ²⁺ + (3-x) Fe ²⁺ + 6OH ⁻ → M _x Fe _(3-x) (OH) ₆ (1)
Oxidation reaction: M _x Fe _(3-x) (OH) ₆ +1/2 O ₂ → M _x Fe _(3-x) O ₄ + 3H ₂ O (4)
The ferritization reaction is an oxidation reaction that occurs in an alkaline region, and is accelerated under high temperature and high humidity conditions in the presence of oxygen. Although there are various theories on the ferritization reaction, a hydroxide (MxFe _(3-x) (OH) ₆ ) in which Fe (OH) ₂ or Fe ²⁺ is partially substituted with heavy metal (M ²⁺ ) is observed from the surface. It is thought that it is oxidized to produce ferrite. In the case of a mixture of ferrous hydroxide and ferric hydroxide, the ferrous hydroxide is oxidized to iron oxyhydroxide (FeOOH) by temperature, humidity, and oxygen. It is considered that ferric iron reacts to produce a heavy metal ferrite compound.

Methods for treating acidic exhaust gas such as hydrogen chloride (HCl) and sulfur oxide (SOx) generated during incineration are roughly classified into dry / semi-dry treatment or wet treatment. The dry / semi-dry treatment is a system in which slaked lime or slaked lime slurry is blown into the front stage of the dust collector, the acidic gas is removed by reaction, and the fly ash is collected by the dust collector. On the other hand, the wet process is a system in which exhaust ash is collected by a dust collector and the exhaust gas is washed with an alkaline liquid such as caustic soda (NaOH). The alkali content of incinerated fly ash is compared with the dry and semi-dry process. Lower. For this reason, the alkalinity of the incinerated fly ash varies greatly depending on the exhaust gas treatment method.
The reaction formulas (1) to (4) are reactions that easily proceed under alkaline conditions. In the present invention, the alkali content is (i) the alkali content in the incineration fly ash, or (ii) the alkali content added in the kneading step and the alkali content in the incineration fly ash, and the content is The molar amount of alkali content converted to NaOH is 0.5 to 4.0, more preferably 2.0 to 4.0 as the molar ratio with respect to the molar amount of the iron salt.

In the above, (i) the alkali content of incineration fly ash can be expressed as the alkali amount determined from the acid consumption (pH 8.3) of the eluate of incineration fly ash. The acid consumption (pH 8.3) can be determined according to JIS K 0 102 15.2 (1998). (Ii) The alkali component added in the kneading step is an alkali component derived from the chemical added in the kneading step.
As a method for determining the total amount of alkalis in (i) incineration fly ash or (ii) alkalis added in the kneading step and alkalis in incineration fly ash, an eluate of incineration fly ash or kneaded material is prepared, It is preferable to measure the acid consumption (pH 8.3) for the eluate. In the present invention, an alkali component important for obtaining a sufficient effect is not an alkali component derived from a bicarbonate but an alkali component derived from a hydroxide or a carbonate. Examples of the alkali content index include acid consumption (pH 4.8) and pH in addition to the acid consumption (pH 8.3). Both methods include an index including an alkali content derived from bicarbonate. It is. Therefore, (i) the alkali content of the incinerated fly ash or (ii) the total amount of the alkali component added in the kneading step and the alkali content of the incinerated fly ash, prepare the eluate of the incinerated fly ash or the kneaded product, By measuring the acid consumption (pH 8.3) of the eluate and determining the addition rate of the iron salt, a more stable and reliable treatment can be performed.

  As the iron salt, any iron salt such as ferrous sulfate such as ferrous sulfate and ferrous chloride, and ferric salt such as polyiron sulfate, ferric chloride, and ferric sulfate can be used. It is preferable that the iron salt is a mixture of a ferrous salt and a ferric salt, and the molar ratio of the ferrous iron to the ferrous iron + ferric iron is in the range of 0.2 to 1.0. Further, the amount of humidified water added at the time of kneading is usually 20 to 40% by weight (against fly ash), but can be appropriately adjusted depending on the state of the kneaded product. If the water content is excessive, the fluidity is increased, and problems such as sticking of the kneaded molded products that do not solidify occur. In addition, when the water content is too low, not only the ferritization becomes insufficient, but also solidification does not occur and the processed product is scattered, and the original purpose of preventing the processed product from being scattered cannot be achieved. The water content with respect to the incinerated fly ash in the present invention is preferably 20 to 40% by weight, and can prevent sticking between the kneaded molded products and dust generation.

As the organic chelate heavy metal immobilizing agent, any known immobilizing agent can be used. Alkali metal salts or transition metal salts of compounds having two or more dialkyldithiocarbamic acid or dialkyldithiocarbamic acid groups in the molecule, specifically, is _{diethyldithiocarbamate, N 1, N 2, N} 3, N 5 - tetra (dithiocarboxy) tetraethylenepentamine, potassium salts such as piperazine bis dithiocarbamate, sodium salts, zinc salts, etc. are preferably used iron it can.
Further, the curing period according to the present invention varies depending on the properties of the incinerated fly ash and the curing conditions and is not generally determined, but is preferably cured for 10 minutes to 24 hours. Further, after curing the kneaded product according to the present invention, it may be further naturally dried, or may be forcedly heated and dried.
According to the present invention, difficult-to-process heavy metals such as hexavalent chromium, arsenic, and selenium, which have been difficult with conventional processing, can be efficiently immobilized, so that elution of heavy metals from incineration fly ash is reliably prevented. It is possible.

The following examples illustrate the invention.
The test method is as follows.
(1) Sample

(2) Heavy metal dissolution test 100 g of fly ash, 30 g of water and a predetermined amount of chemicals were added to a 500 mL plastic beaker, kneaded for about 5 minutes using a spatula, made into a clay, and then 10 minutes to 48 under predetermined conditions. Cured for hours. Thereafter, the sample was pulverized to 5 mm or less, and a heavy metal dissolution test was conducted based on the Environmental Agency Notification No. 13 test method.
(3) Additives Ferrous chloride solution: Fe content 10% by weight (manufactured by Wako Pure Chemical Industries, reagent grade 1, prepared by dissolving ferrous chloride tetrahydrate in distilled water)
Polyiron solution: Fe content 5.2% by weight (manufactured by Nippon Steel Mining)
Organic chelate heavy metal immobilizing agent: N ₁ , N ₂ , N ₃ , N ₅ -tetra (dithiocarboxy) tetraethylenepentamine sodium salt 50 wt% solution

Example 1
The drug is ferrous chloride solution, and the molar ratio of ferrous iron (Fe ²⁺ ) to ferrous iron + ferric iron (Fe ²⁺ + Fe ³⁺ ) [Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ )] Table 2 shows the test results for the sample A when is 1.0 (ie, Fe ³⁺ is 0). When the molar ratio of the alkali amount (mol as NaOH) obtained from the acid consumption (pH 8.3) to ferrous iron + ferric iron (Fe ²⁺ + Fe ³⁺ ) is compared under the condition of 3.4, the curing temperature is When it is 40-150 degreeC and relative humidity is 40% or more, the elution density | concentration of lead satisfy | filled the landfill standard value (0.3 mg / L) (No. 1-3, 6-7, 13-18) . When air-dried at a curing temperature of 20 ° C. and a relative humidity of 40% (No. 20), when heated to 100 ° C. or higher but the relative humidity is less than 40% (No. 9-12, 21), a relative humidity of 84% When the curing temperature was 20 ° C. (No. 19), the lead elution concentration exceeded the landfill reference value (0.3 mg / L).
Further, even when the curing temperature is 40 to 150 ° C. and the relative humidity is 40% or more, the acid consumption (pH 8.3) with respect to ferrous iron + ferric iron (Fe ²⁺ + Fe ³⁺ ) was obtained. When the molar ratio of alkali amount (molas NaOH) was 5.1 (No. 4), the elution concentration of lead exceeded the landfill reference value (0.3 mg / L). As for the curing time, the elution concentration of lead tended to be suppressed when the time was 0.5 h or more compared with 0.15 h (No. 13 to 18).

Example 2
Table 3 shows the results of testing for sample A using ferrous chloride solution and polyiron solution as chemicals, with a curing time of 1 hour, a curing temperature of 100 ° C., and a relative humidity of 80%.
In a molar ratio of the first iron to ferrous + ferric ^{(Fe 2+ + Fe 3+) (} Fe 2+) ^{[Fe 2+ / (Fe 2+ + Fe} 3+) ] is 0.2 to 1.0 Yes, the molar ratio of the alkali amount (mol as NaOH) determined from the acid consumption (pH 8.3) to the ferrous iron + ferric iron (Fe ²⁺ + Fe ³⁺ ) is in the range of 0.5 to 4.0. In some cases (No. 3-5, 8-9, 12-13), the elution concentration of lead satisfied the landfill standard value (0.3 mg / L), but ferrous iron + ferric iron (Fe ²⁺ + Fe ³⁺ ) when the molar ratio [Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ )] of ferrous iron (Fe ²⁺ ) is 0 or 0.1 (No. 1, 2, 6) or ferrous iron When the molar ratio of the alkali amount (mol as NaOH) obtained from the acid consumption (pH 8.3) to + ferric iron (Fe ²⁺ + Fe ³⁺ ) is 0.3 or 5.0 (No. 7, 10 , 11, 14), the elution concentration of lead exceeded the landfill reference value (0.3 mg / L).

Example 3
Table 4 shows the results of the test for sample B using ferrous chloride solution and polyiron solution as chemicals, with a curing time of 1 hour, a curing temperature of 100 ° C., and a relative humidity of 80%.
In a molar ratio of the first iron to ferrous + ferric ^{(Fe 2+ + Fe 3+) (} Fe 2+) ^{[Fe 2+ / (Fe 2+ + Fe} 3+) ] is 0.2 to 1.0 Yes, the molar ratio of the alkali amount (mol as NaOH) determined from the acid consumption (pH 8.3) to the ferrous iron + ferric iron (Fe ²⁺ + Fe ³⁺ ) is in the range of 0.5 to 4.0. In some cases (No. 3, 4, 6-8), the elution concentration of lead satisfied the landfill reference value (0.3 mg / L). When the molar ratio of the alkali amount (mol as NaOH) obtained from the acid consumption (pH 8.3) to ferrous iron + ferric iron (Fe ²⁺ + Fe ³⁺ ) was 0.4 (No. 5, 9, 11, 13) or 4.7 to 4.8 (No. 10, 12, 14), the elution concentration of lead satisfies the landfill standard value (0.3 mg / L). could not. Further, when the molar ratio of the first iron to ferrous + ferric ^{(Fe 2+ + Fe 3+) (} Fe 2+) ^{[Fe 2+ / (Fe 2+ + Fe} 3+) ] is 0 (No. 1, 2) also exceeded the landfill reference value (0.3 mg / L).

Example 4
Table 5 shows the test results of sample C using ferrous chloride solution and polyiron solution as chemicals, with a curing time of 1 hour, a curing temperature of 100 ° C., and a relative humidity of 80%.
In a molar ratio of the first iron to ferrous + ferric ^{(Fe 2+ + Fe 3+) (} Fe 2+) ^{[Fe 2+ / (Fe 2+ + Fe} 3+) ] is 0.2 to 1.0 Yes, the molar ratio of the alkali amount (mol as NaOH) determined from the acid consumption (pH 8.3) to the ferrous iron + ferric iron (Fe ²⁺ + Fe ³⁺ ) is in the range of 0.5 to 4.0. In some cases, the elution concentration of hexavalent chromium satisfied the landfill reference value (1.5 mg / L) (No. 1-3, 7-12). Ferrous + ferric when the molar ratio of (Fe ²⁺ + Fe ³⁺⁾ first iron to (Fe ^{2+) [Fe 2+ / (Fe 2+ + Fe} 3+) ] is 0 (No.4) Or when the molar ratio of the alkali amount (mol as NaOH) determined from the acid consumption (pH 8.3) with respect to ferrous iron + ferric iron (Fe ²⁺ + Fe ³⁺ ) is 5.0 to 5.1 ( No. 13 to 15), the elution concentration of hexavalent chromium exceeded the landfill reference value (1.5 mg / L).

Example 5
Table 6 shows the test results of sample D using ferrous chloride solution and polyiron solution as chemicals, with a curing time of 1 hour, a curing temperature of 100 ° C., and a relative humidity of 80%.
In a molar ratio of the first iron to ferrous + ferric ^{(Fe 2+ + Fe 3+) (} Fe 2+) ^{[Fe 2+ / (Fe 2+ + Fe} 3+) ] is 0.2 to 1.0 Yes, when the molar ratio of the alkali amount (mol as NaOH) determined from the acid consumption (pH 8.3) to ferrous iron + ferric iron (Fe ²⁺ + Fe ³⁺ ) is in the range of 0.5-4 (Nos. 1-3, 7-9, 11-12), the elution concentration of selenium satisfied the landfill reference value (0.3 mg / L).
When the molar ratio of the first iron to ferrous + ferric ^{(Fe 2+ + Fe 3+) (} Fe 2+) ^{[Fe 2+ / (Fe 2+ + Fe} 3+) ] is 0 (No.4~ 6) or when the molar ratio of the alkali amount (mol as NaOH) determined from the acid consumption (pH 8.3) to ferrous iron + ferric iron (Fe ²⁺ + Fe ³⁺ ) is 5.0 (No. 6). 13 to 15), the elution concentration of selenium exceeded the landfill reference value (0.3 mg / L).

Example 6
Table 7 shows the results of testing using the organic chelate heavy metal immobilizing agent as a drug for sample A.
When the addition rate of the organic chelate heavy metal immobilizing agent is 3 w / w% and the curing time is 24 hours, the elution concentration of lead is 0.10 mg / L when the temperature is 30 ° C. and the relative humidity is 40%. (No. 2), No. 2 cured under the curing conditions of the present invention (temperature 40 to 150 ° C., relative humidity 40% or more). 4-6 and no. In 9, it was suppressed to 0.05 mg / L or less.

Example 7
Table 8 shows the results of testing using the organic chelate heavy metal immobilizing agent as a drug for sample C.
When the addition rate of the organic chelate heavy metal immobilizing agent is 3 w / w% and the curing time is 24 hours, the elution concentration of hexavalent chromium is 1.2 mg / L when the temperature is 30 ° C. and the relative humidity is 60%. (No. 2), the No. 2 cured under the curing conditions of the present invention (temperature 40 to 150 ° C., relative humidity 40% or more). 3-5 and no. In 7-10, it was suppressed to 1.1 mg / L or less.

Example 8
Table 9 shows the results of testing using the organic chelate heavy metal immobilizing agent as a drug for sample D.
When the rate of addition of the organic chelate heavy metal immobilizing agent is 3 w / w% and the curing time is 24 hours, the elution concentration of selenium is 0.8 mg / L when the temperature is 30 ° C. and the relative humidity is 60%. (No. 2), No. 2 cured under the curing conditions of the present invention (temperature 40 to 150 ° C., relative humidity 40% or more). 3-5 and no. 7 was suppressed to 0.7 mg / L or less. Similarly, when the addition rate of the organic chelate heavy metal immobilizing agent is 3 w / w% and the curing time is 24 hours, the elution concentration of antimony is 0.3 mg / L when the temperature is 30 ° C. and the relative humidity is 60%. (No. 2), No. 2 cured under the curing conditions of the present invention (temperature 40 to 150 ° C., relative humidity 40% or more). 3-5 and no. 7 was suppressed to 0.1 mg / L or less.

The schematic block diagram explaining the stabilization method of this invention. The schematic block diagram explaining the setting position of a curing device. The schematic block diagram of a hopper type curing apparatus. It is a schematic block diagram of a kiln type curing device, (a) Front view, (b) AA sectional view of an AA curing device.

Explanation of symbols

  1: Dust, 2: Bag filter (dust collector), 3: Storage silo, 4: Weight scale, 5: Fly ash, 6: Kneading machine, 9: Unloading conveyor, 10: Treated ash pit, 11: Humidified water tank, 12 : Heavy metal fixing agent

Claims (3)

The molar ratio of the incineration fly ash, a mixture of ferrous salt and the ferric salt, ferrous for ferrous (Fe ²⁺⁾ + ferric (Fe ³⁺⁾ (Fe ²⁺⁾ [Fe ^{2 +} / (Fe ²⁺ + Fe ³⁺ )] is 0.2 to 1.0, and a kneaded product obtained by kneading water with an organic chelate heavy metal fixing agent and a temperature of 40 to 150 ° C., A method for stabilizing incinerated fly ash, comprising curing in contact with the atmosphere in an environment having a relative humidity of 40% or more. The kneaded product is 0.5 to 4.0 in a molar ratio alkali content that NaOH-equivalent with respect to the iron salt (ferrous salt + ferric), the alkali component is eluted kneaded product the method for stabilizing incineration fly ash according to claim 1, wherein the alkali quantity der Rukoto obtained from acid consumption of the liquid (pH 8.3). In an apparatus for stabilizing incineration fly ash, incineration fly ash and a mixture of ferrous salt and ferric salt, ferrous iron against ferrous iron (Fe ²⁺ ) + ferric iron (Fe ³⁺ ) ( An iron salt or organic chelate heavy metal fixing agent having a molar ratio [Fe ²⁺ ) [Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ )] of 0.2 to 1.0 and water are kneaded and kneaded. And a curing device equipped with a heating, humidifying and blowing means for curing the obtained kneaded material in an environment having a temperature of 40 to 150 ° C. and a relative humidity of 40% or more. Ash stabilization device.

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