JP2001151506A - Method of manufacturing calcium silicate based porous body formed by removing dioxins from waste incineration ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a calcium silicate based porous body increased in safety by eliminating the fear of the elution of harmful materials such as heavy metals or dioxins and formed by removing dioxins from waste incineration ash having high additional value. SOLUTION: The calcium silicate based porous body is synthesized by placing the waste incineration ash under an alkali condition with the coexistence of an oxidizing agent and after that, hydrothermally treating to decompose and remove the dioxins in the waste incineration ash.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses refuse incineration ash such as RDF incineration ash as a raw material, and dioxins in the ash are simultaneously decomposed and removed to be useful as a heat-resistant material, a fire-proof material, a sound-absorbing material, an adsorbent and the like. The present invention relates to a method for producing a calcium silicate-based porous body from refuse incineration ash.

[0002]

2. Description of the Related Art General waste is partially disposed of as landfill, but most of the waste is disposed of after landfill after incineration. However, when municipal solid waste is directly incinerated, the amount of dioxins generated is a problem, making it difficult to locate a final disposal site for landfill disposal of incinerated ash. Heretofore, as a method for removing dioxins from refuse incineration ash, in addition to a molten slag method, a method of decomposing and removing using a supercritical fluid (Japanese Unexamined Patent Publication No. 9-32)
No. 7478) has been invented.

[0003]

However, the above gazette technology requires a large amount of energy, requires a high pressure resistance of the apparatus because of using a supercritical fluid, and can use materials such as Hastelloy and Inconel which have high pressure resistance. There were great restrictions such as the need for special materials having corrosion resistance.
There was a problem that the apparatus became expensive and the energy consumption per incineration ash to be treated increased. Special attention had to be paid to driving safety. further,
In this method, the purpose is only to decompose dioxins, and no consideration is given to the effective use of incinerated ash after treatment. With the above problems (1) to (4), the method was not easy to use.

On the other hand, as a method of effectively utilizing garbage incineration ash, a method of forming into molten slag and using it for roadbed materials and concrete aggregates, a method of adjusting components, a method of molding and firing to form bricks, and a method of kneading with concrete. After that, a method of molding and solidifying into blocks, a method of using as a part of a raw material for cement production, and the like have been developed. However, according to these methods, (i) the price of the obtained product is low in spite of requiring a large amount of energy, and (ii) the elution of harmful components such as heavy metals and dioxins among the incinerated ash components. Currently, there is a problem in that the anxiety has not been resolved, and practical application has not progressed much. For these reasons, there is a need for the development of an effective use method that is safer and adds more value to the processed product.

[0005] The present invention solves the above-mentioned problems and eliminates the anxiety of elution of harmful components such as heavy metals and dioxins to enhance safety and to provide high added value by removing dioxins from incinerated ash. An object of the present invention is to provide a method for producing a calcium silicate-based porous body.

[0006]

In order to achieve the above object,
The gist of the present invention according to claim 1 is that, after placing incineration ash under alkaline conditions and coexisting with an oxidizing agent, dioxins in the incineration ash are decomposed and removed by hydrothermal treatment to remove calcium silicate. The present invention relates to a method for producing a calcium silicate-based porous body obtained by removing dioxins from waste incineration ash, which comprises synthesizing a porous body. The method for producing a calcium silicate-based porous body obtained by removing dioxins from refuse incineration ash according to the second aspect of the present invention is a method for producing a calcium silicate-based porous body at 100 ° C.
Hydrothermal treatment is performed under a saturated vapor pressure of 250 ° C. When the incineration ash is placed under alkaline conditions and an oxidizing agent is allowed to coexist with the ash, hydrothermal treatment decomposes dioxins. Dioxins are decomposed, and their chlorine remains in water and reacts with alkalis to render them harmless (eg, potassium chloride). In addition, harmful components of heavy metals in the incineration ash component are fixed by ion exchange with Ca ions which are crystal lattice ions, or are strongly alkaline components (for example, Ca (OH) ₂ ) released from a porous body. It reacts and co-precipitates as a hydroxide to stabilize and eliminate anxiety of elution. Further, Pb present in the incinerated ash is dissolved and removed in the hydrothermal treatment waste liquid by the hydrothermal treatment. Then, when the garbage incineration ash is placed under alkaline conditions and subjected to hydrothermal treatment in the presence of an oxidizing agent, a calcium silicate-based porous body having an adsorption ability for heavy metal ions and the like is obtained.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of a method for producing a calcium silicate-based porous body of the present invention by removing dioxins from refuse incineration ash will be described in detail.

As a method for industrially producing a calcium silicate-based porous material by a hydrothermal treatment method, there is known a method of producing a building material having properties such as weight reduction, high strength, and moisture absorption / release properties by tobermorite or zonotolite. Manufacturing methods (Takeshi Mitsuda, "Utilization for building material systems", "Utilization of fine ceramics", Okawa Publishing (1986), pp. 208 to 229) are known. However, such a method generally requires operations such as pulverization and classification of raw materials, component adjustment, mixing, and the like as pretreatment, resulting in high cost products. Therefore, it cannot be said that producing a calcium silicate-based material from refuse incineration ash by the above-described method and effectively utilizing it is an excellent method from the viewpoint of cost. On the other hand, as a method for decomposing dioxins in incineration ash, a method of melting and converting into slag and a method of using a supercritical fluid have been proposed. The value is low, the latter requires high temperature and high pressure of about 374 ° C. and 22.1MP or more, and the materials used for manufacturing the apparatus have great restrictions and the cost is high. It has problems such as not being considered.

In order to solve such a problem, the present inventor added an oxidizing agent to refuse incineration ash such as RDF incineration ash and hydrothermally treated the refuse incineration ash, which enables simultaneous decomposition of dioxins. Of calcium silicate based porous material was developed. As a result, it is preferable to add an oxidizing agent such as hydrogen peroxide to refuse incineration ash such as RDF incineration ash and perform hydrothermal treatment under alkaline conditions (especially at a temperature of about 100 to 250 ° C. under a saturated vapor pressure). )), The dioxins are decomposed and removed, and at the same time, the crystalline portion of calcium silicate minerals such as tobermorite and CS-
It has been found that an amorphous portion such as H is mixed to form a porous calcium silicate hydrate based porous material having a large specific surface area. Then, it was confirmed that this porous body could be used as a heat-resistant material, a fire-proof material, a sound-absorbing material, an adsorbent, and the like.

[0010] The refuse incineration ash used in the present invention may be ash produced by directly burning general waste, but after adding calcium oxide or calcium hydroxide to the general waste, the solid waste (RDF) is formed. It is more preferable to use the ash generated when the ashed product is incinerated. This is because the calcium content increases and it is convenient to use as calcium silicate. It is more preferable to use incinerated ash in which RDF is incinerated in a fluidized bed furnace because the incinerated ash is uniformly generated. The refuse incineration ash is suspended in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide in the presence of an oxidizing agent such as hydrogen peroxide at 100 ° C.
Hydrothermal treatment is performed at a temperature of 250 ° C. under a saturated vapor pressure for several hours or more to synthesize a calcium silicate-based porous body. The resulting porous body can be effectively used as an adsorbent, a building material, or the like. The reason for setting the temperature of the hydrothermal treatment in the range of 100 ° C. to 250 ° C. (optimally around 180 ° C.) is that if the temperature is lower than 100 ° C., it is difficult for the reaction to proceed. This is because the mineral undergoes a phase transition and forms another crystal structure.

The concrete production method of the calcium silicate-based porous material of the present invention, from which dioxins are removed from incineration ash, and the evaluation test results of the calcium silicate-based porous material are shown below.

[Example 1] Here, according to the Japan Recycling Management System, RDF produced by adding several percent of calcium hydroxide to general waste and molding is produced when incinerated in a fluidized bed furnace. Use incineration ash. Then, an aqueous solution (1 N potassium hydroxide, 1.25 to 5.0% hydrogen peroxide) containing potassium hydroxide and hydrogen peroxide is added to the incinerated ash in a 20-fold amount (in terms of weight), and the incinerated ash is added. Put in suspension. Subsequently, 180-220 in an autoclave.
Hydrothermal treatment was performed at a saturated vapor pressure of 5 ° C. for 5 to 10 hours to oxidatively decompose dioxins and synthesize a calcium silicate porous material. Oxidative decomposition of dioxins and synthesis of calcium silicate-based porous material are performed under a saturated vapor pressure of 180 ° C.
Hydrothermal treatment for more than an hour suffices.

The obtained calcium silicate-based porous material was washed with water, dried at 60 ° C. for one week, and analyzed for mineral composition and measured for dioxin content by an X-ray diffractometer. Analysis results of mineral composition by X-ray diffractometer
₂ O _2: 1.5%, in 1N KOH aqueous solution, under the suspension state, 220 ° C., illustrated in Figure 1 for the case of the obtained porous body by hydrothermal treatment of 10 hours. As can be seen from this result, the entire diffraction pattern including the peak caused by 1.1 nm tobermorite appearing at 2θ: 7.8 ° and the whole of the diffraction pattern were added with and without hydrogen peroxide during the hydrothermal treatment. It was found that hydrogen peroxide did not affect the hydrothermal treatment of the incinerated ash.

Table 1 shows an example of the decomposition results of dioxins.
Show. The decomposition rate of dioxin is H ₂O₂: 2.5%,
220N in 1N KOH aqueous solution under suspension
96.2 ° C. by hydrothermal treatment for 10 hours (porous body A in Table 1).
%, H₂O₂: 1.25% in 1N KOH aqueous solution
Hydrothermal treatment at 220 ° C for 10 hours under the state of spencer
(Porous body B in Table 1) 89.7%, H₂O₂: 2.5
%, 1N KOH aqueous solution under suspension, 22
55.5 by hydrothermal treatment at 0 ° C. for 5 hours (porous body C in Table 1)
%, H₂O₂: 2.5%, 1N KOH aqueous solution, suspension
Hydrothermal treatment at 180 ° C for 10 hours under pension condition (Table
And 16.2% for the porous body D).

[0015]

[Table 1]

The contents of the symbols shown in Table 1 are as follows. (1) Total PCDDs Total of polychlorodibenzoparadioxins (2) Total PCDFs Total of polychlorodibenzofurans (3) Total Coplanar PCBs Total of coplanar-picy-vibes (4) Total (PCDDs + PCDFs + Coplanar PCBs) Sum of polychlorodibenzoparadioxins, polychlorodibenzofurans and coplanar pieces

Although not shown in Table 1, from many experimental results, the removal rate of dioxins is increased by increasing the amount of added hydrogen peroxide and the duration of the hydrothermal treatment, and the dioxins in the incinerated ash are increased by the hydrothermal treatment. It was found that simultaneous decomposition can be effectively performed. In the present embodiment, hydrogen peroxide is used as the oxidizing agent, but another oxidizing agent (for example, potassium peroxodisulfate) can be used instead.

Example 2 A calcium silicate-based porous material obtained by hydrothermal treatment of RDF incinerated ash accompanied by simultaneous decomposition of dioxin has a large specific surface area (about 77 m ² /
g), its application as an adsorbent is expected. Therefore,
In order to examine the possibility, the adsorption ability to metal ions and orthophosphate ions was examined. Evaluation of the adsorption ability of the porous body was performed by placing 0.5 g of the porous body and 100 ml of a metal nitrate aqueous solution having a metal ion concentration of about 0.005 mol / l or an orthophosphate ion concentration of about 0.0004 mol / l in a 300 ml Erlenmeyer flask. Take 100 ml of aqueous solution,
A method of shaking at 5 ° C., collecting a sample solution at regular time intervals, and analyzing the concentration of metal ions or orthophosphate ions present in the solution was used. FIG. 2 illustrates the results of the measurement of the adsorption ability of the obtained calcium silicate-based porous material in the case of copper. From these experimental results, Cr (III), Co (I
I), Ni (II), Cu (II), Zn (II), Cd (II), Pb (II), Ag (I)
The metal ions such as 36 to 194 mg / g were adsorbed mainly by the ion exchange action with calcium ions.
Orthophosphate ion reacts with calcium ion to form hydroxyapatite,
It was found that 3 mg / g was adsorbed.

Example 3 The calcium silicate-based porous body obtained by hydrothermal treatment of RDF incinerated ash has pores, a large specific surface area (about 77 m ² / g), and is lightweight. It is considered to be useful as a raw material such as a heat-resistant material, a fireproof material, and a sound-absorbing material. Then, the moldability was examined. The moldability of the porous body, after adding the porous body as it is or water or water glass aqueous solution as a binder,
The test was performed by applying a pressure of 127.4 kg / cm ² for 1 minute. Table 2 shows the results. From the experimental results,
The compression strength, bulk density and specific surface area of the molded product were 76.4 kg / cm ² , 0.
68 g / cm ³ and 72.9 m ² / g, and 25%
239.7 kg for a molded body with 50 v / w% added water glass
/ Cm ² , 0.88 g / cm ³ and 44.7 m ² /
g, indicating that a molded product having sufficient properties for use as a building material or the like can be obtained. Generally, if the compressive strength of the molded body exceeds 50 kg / cm ² , it can be used as a wall material.

[0020]

[Table 2]

Thus, it can be seen that the calcium silicate-based porous material obtained by hydrothermal synthesis of the refuse incineration ash according to the present invention has a greatly reduced content of dioxins as compared with the incineration ash as the raw material. Was. The porous body has a low bulk density, a large specific surface area, and has properties such as moisture absorption / desorption, adsorption, and water permeability. Therefore, compared to conventional roadbed materials, it has high added value such as building materials and adsorbents. It can be used for various purposes. For example, it was found that when used as an adsorbent, it has an adsorbing ability for metal ions, orthophosphate ions, and the like. This porous body has good moldability, and a good molded body is obtained as it is or after adding water or an aqueous solution of water glass as a binder, followed by pressure molding, and its compressive strength is also about 76.4 kg / cm ^2. From the above, it was found that it can be used for building materials and the like.

In the present invention, the present invention is not limited to the embodiment described above, and various modifications can be made within the scope of the present invention depending on the purpose and application. The type of incinerated ash, the type and concentration of the alkaline aqueous solution and the oxidizing agent, and the like can be appropriately selected according to the application.
The term "under the saturated vapor pressure" under the saturated vapor pressure of 100C to 250C in the present invention includes the supersaturated vapor pressure or the superheated state.

[0023]

As described above, the method of the present invention for producing a calcium silicate-based porous material from incineration ash, which enables simultaneous decomposition of dioxins, does not require any special operation or equipment, and can be oxidized during hydrothermal treatment. By simply adding the agent, the content of dioxins in the obtained porous body can be significantly reduced. Dioxins can be decomposed by hydrothermal treatment under a saturated vapor pressure of about 200 ° C., and energy consumption per incineration ash to be treated can be reduced as compared with the conventional dioxin removal method. Furthermore, the synthesized calcium silicate-based porous material has properties such as moisture absorption / release properties, adsorptivity, water permeability, etc., and has a variety of high value-added heat-resistant materials, fire-resistant materials, sound-absorbing materials, adsorbents, etc. Available for use. For example, 127.4k
When molded for 1 minute at a pressure of g / cm ² , the moldability is good and the compressive strength is 76.4 to 239.7 kg / cm ^2.
And a lightweight (bulk density of 0.68 to 0.8)
8 g / cm ³ ) is considered to be useful as a functional building material. This molded article is porous and has a wide specific surface area (72.9 to 44.7 m ² / g), and when used as an adsorbent, adsorbs transition metal ions, heavy metal ions, orthophosphate ions, and the like. Show noh. As described above, the present invention can simultaneously achieve the effective use of garbage incineration ash and the removal of dioxins, which are currently decisive, and are extremely useful because they can solve the problem of effective use of waste and the dioxin problem at once. .

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction pattern diagram of a calcium silicate-based porous material obtained by a production method of the present invention.

FIG. 2 is a graph showing a measurement result of a copper ion adsorption ability of a calcium silicate-based porous material obtained by the production method of the present invention.

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Claims (2)

[Claims] 1. A method for synthesizing a calcium silicate-based porous body by placing dirt incineration ash under alkaline conditions and coexisting with an oxidizing agent, followed by hydrothermal treatment to decompose and remove dioxins in the dirt incineration ash. A method for producing a calcium silicate-based porous body by removing dioxins from refuse incineration ash. 2. The method for producing a calcium silicate-based porous material according to claim 1, wherein the dioxins are removed from the incinerated refuse ash according to claim 1, which is subjected to hydrothermal treatment under a saturated vapor pressure of 100 ° C. to 250 ° C.