JPS59189984A - Melt caking method for dust collector ash - Google Patents

Abstract

PURPOSE:To fixedly stabilize noxious metals existent in fly ash, by adding CaO and SiO2 to dust collector ash formed by burning general waste matter, etc. in a burning plant while adjusting CaO/SiO2 (by wt. ratio) below 1.2, and continuously melt caking said fly ash. CONSTITUTION:CaO and SiO2 are added to fly ash formed by burning general waste matter, etc. in a burning plant and collecting it with a dust collector, while adjusting CaO/SiO2 (by wt. ratio) below 1.2, and continuous melt caking treatment is performed to safely fix noxious metals existent in the fly ash and to remarkably reduce the volume of fly ash. It is important that the caked matter is in a glasified state to fix the heavy metals in the fly ash without exudation. For this purpose, it is necessary to hold CaO/SiO2 below 1.2. In addition, it is suitable to hold a melting temp. above 1,300 deg.C for continuously tapping molten matter.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for melting and solidifying collected machine ash generated when general waste such as household waste is incinerated in an incineration plant.

Dust collectors have different compositions depending on the type of garbage, incineration method, etc. A typical example is dust collectors generated from incinerators equipped with wet dehydrochlorination equipment (hereinafter referred to as fly 7).
Table 1 Composition of dust collector (hereinafter referred to as fly ash B) generated from an incinerator equipped with dry dehydrochlorination processing equipment The main components of both A and B are calcium oxide (Cab) and silicon dioxide (5i).
O2), mineral components of aluminum sesquioxide (A12o3), sodium oxide (Na20), potassium oxide (K2O), salt # (C1), gpH sulfur (804)
It consists of salts such as and cadmium (Cd
).

Contains heavy metals such as lead (Pb) and chromium (Cr).

The major difference between fly ashes A and B is the content of CaO, with fly ashes B containing more CaO.

This is done by injecting calcium hydroxide (Ca (OH)2) into an incinerator for dehydrochlorination treatment and hydrogen chloride (i((
,”7), the reaction product (C,a (,:
This is because the excess Ca (OH) 2 or the like is all collected in the dust collector.

Next, when these fly ashes were subjected to a dissolution test using embedding No. 13, as shown in Table 2, the solubility of fly ash A was as high as 27.4%, and in addition, Cd, r'b
, Cr is eluted.

Table 2 In addition, Fly7 Soci B also has a high solubility of 289%, and in this case, pXT is as high as 12.6. Although -cd, C, and r6+ are not eluted, a large amount of Pb is eluted.

As can be seen from the above, if fly ash is thrown away easily, it will cause secondary pollution.

In addition, as shown in Table 3, fly ragsaw is a fine powder that easily scatters, making it a very difficult waste to handle.

- Landfill sites, which are the final disposal sites for fly assemblies, are becoming increasingly difficult to secure as suitable sites are depleted year by year.

Particularly in urban areas, it is almost impossible to secure a location for these species. Furthermore, since the amount of municipal waste is increasing year by year, it is natural that the amount of fly ash discharged will also increase.

Due to these problems, the development of appropriate processing techniques for these fly ash is a major challenge for the technical field.

In order to solve this problem, conventional techniques have been proposed, such as ■ Solidification treatment method using binders such as concrete and asphalt ■ Solidification treatment method using plastics.

However, although both methods ① and ② can be expected to immobilize harmful heavy metals in fly assemblies to some extent,
Currently, the binder is expensive, and disadvantages such as increased weight and volume of the final solid product make commercialization difficult.

In view of the current situation, the present invention eliminates the above-mentioned drawbacks and fixes harmful heavy metals contained in fly ash by heating and melting the fly ash and solidifying it.
In addition to making it safer, the volume is significantly reduced. The company also confesses that the solidified material can be made into lumps to make it easier to handle, reuse or dispose of in a landfill, and at the same time provide an appropriate processing method for fly assemblies that can be processed continuously.

In other words, in the present invention, a certain amount of fly ash collected in a dust collector is mixed and homogenized, and then the S
A substance containing a large amount of io2 is added and mixed, homogenized, and continuously melted in an electric resistance furnace. At this time,
It is also possible to heat and melt using gas.

The above object is achieved by cooling the melt with water or air to melt and solidify the fly assembly.

A detailed explanation of the present invention follows. The melting point of this type of waste is correlated with CaO/5iO2 (weight ratio), so C+IO
It is economical to prepare S i02 in advance and melt it at as low a temperature as possible, and this is already well known.

Figure 1 shows the relationship between CaO/5iOz and melting point for fly ash. When CaO/SiO2 is 0.5, the melting point reaches its minimum point, and the melting point at this time is 1030°C. Therefore, considering only the melting point, CaO/8i0z is 0.5
However, in order to melt fly ash continuously, stably, and consistently in an electric resistance furnace, and to ensure the safety of the solidified product,
If the melting conditions are determined only by the melting point, this objective cannot be achieved. Rather, in order to determine melt negativity, the following three
Point 1 is important and essential.

% I K 11 contained in fly 7 sauce in solidified material
In order to immobilize the metal and make it safe so that it will not dissolve or elute, it is important that the solidified material is vitrified at °C.

By vitrification, heavy metals are bound into the network structure of the glass, stabilized, and no longer elute. However, if the heavy metals are not vitrified and remain sintered, they may contain crystalline metals. ..., heavy metals will be eluted in the elution test.

As shown in Figure 1, fly ash becomes vitrified in the range where CaO/5i02 is 1.2 or less, which is
It can be easily measured using a line diffraction device. In other words, a safe solidified product can be obtained by adding the substances listed in Table 4 to the fly flier in advance, adjusting the CaO/SiO2 ratio to 1.2 or less, and then melting it.

Secondly, it is economical to operate the electric resistance furnace continuously day and night, and for this purpose it is necessary to continuously tap the molten material.

The possibility of continuous pouring is determined by the viscosity of the melt, but if the viscosity is set to 50
This becomes possible if the value is set to 0 poise or less.

Figure 2 shows the relationship between CaO/5i02 and viscosity at 1200.

The results when measured at 1300 and 1400°C are shown.

As is clear from this, the higher the temperature (I see, and at the same temperature, the larger CaO/5iOz is, the lower the viscosity is.
CaO/5 whose viscosity is 500 poise or less at a temperature of 0°C
i02 is 061-0.92, 0.49 or more, respectively.
If the melting temperature is 1200℃ or higher, the appropriate Ca
O/5iOz 'Nu range is narrow and CaO/SiO2
It is not suitable because the change in viscosity is large. Therefore, it is desirable to adjust the cao/S 102 to 0.49 or higher and the melting temperature to 1300°C or higher.
Become.

Thirdly, it is important that electric resistance furnaces operate stably under appropriate mechanical control. As is well known, VC electric resistance furnaces are heated by the heat of the current flowing between the electrodes in the molten material, so if the change in resistance of the molten material is minimized, the current will flow stably and it will be easy to control. .

Therefore, Fig. 3 shows the relationship between CaO/Si02 and specific resistance.
The results were measured at 300°C and 1400°C.

According to this, at 1,000-1,200℃, CaO/5
It can be seen that iOz in the range of 0.2 to 1.2 is not suitable because the change in specific resistance is large. Also 1,300℃, 1
, even at 400°C, CaO/5iOz is 0.2 to 0.
The range of CaO/5iOz of 6.5 to 1.2 is not suitable because the rate of change in specific resistance is large.

3A has been described about the essential melting conditions, which can be summarized as follows.

That is, by adding the substances listed in Table 4 to fly ash, Ca
O/5iOz is set to 0.5 to 1.0 in advance,
If it is melted at a temperature of 1300°C or higher, stable melting is possible and the object of the present invention can be achieved.However, in reality, changes over time in the composition of fly ash or changes in the composition of the substances in Table 4 are taken into consideration. Then, CaO/5iOz is 0.
It is desirable to adjust it to 7 to 0.8.

The arrows indicate examples of the present invention.

Example 1 Fly ash in Table 5, A has CaO/5iOz of 0.5
9, so without adjusting CaO/SiO2,
When the product was placed in an electric resistance furnace and melted at 1300° C., continuous melting was achieved in good condition, and the molten solids shown in Table 5 were obtained.

When this was subjected to the dissolution test in Table 5, Table 6, based on the embedding No. 13 test, good results as shown in Table 6 were obtained.

The volume reduction rate at this time was about 85%.Example 2 Fly Ash BK Table 4 Shirasu was added (Fly Ash L Niji 5 S = 2:1) to make CaO/8 i'02
Example 1 (Table 7) Note: CaO/5i was prepared by mixing fly ash B with shirasu.
It was placed in an electric resistance furnace and continuously melted under the same conditions as Mome, where Oz was set to 0.70.

As a result, continuous melting was possible in good conditions as shown in Table 7 □
A solidified product was obtained. When this was subjected to an elution test based on the embedding No. 13 test, good results as shown in No. 8 were obtained. The volume reduction rate at this time is approximately .

It was 80%.

Cab/s of fly ash discharged as above
If +02 is in the range of 05 to 1.0, leave it as is; if it is in a range other than this, that is, CaO/5IOz is 1.0, add the substances shown in Table 4. Adjust CaO/5i02 to 05-10 and heat to 1300℃
By melting and solidifying the fly ash in the above manner, fly ash can be processed very easily and economically, and the solidified product is safe and the volume can be greatly reduced.

Furthermore, since the solidified product can be obtained in the form of a lump, it is easy to handle, and it is also possible to dispose of it in a landfill or use it effectively. Therefore, the present invention can be said to be an extremely excellent method for treating fly ash.

[Brief explanation of drawings]

FIG. 1 shows the relationship between CaO/5i02 (weight ratio) and EA NoiX in fly ash. FIG. 2 shows the relationship between CaO/5iOz (weight ratio) and viscosity in the fly assembly. Figure 3 shows CaO/810 in fly ash.
2 shows the relationship between (weight ratio) and specific resistance.

Claims (1)

[Claims] 1) CdO/
A method for melting and solidifying ash collector ash, characterized by adjusting S:;02<weight ratio) to 1.2 or less and melting it.0 2) 4? The method for melting and solidifying a dust collector according to claim 1 is characterized in that -)/S:r02 (weight ratio) of the dust collector is adjusted in advance to 0.5 to 1.0 before melting. A melting and solidification treatment method for dust collectors. 3) A method for melting and solidifying a dust collector according to claim 1, characterized in that the melting temperature is 1300° C. or higher. 4) A method for melting and solidifying a dust collector according to claim 1, wherein the viscosity of the melt is 500 poise or less. 5) In the method for melting and solidifying a dust collector according to claim 1, the substance for adjusting C1C1/S+Osr (weight ratio) is whitebait, Kira, Kira clay, or pearlite. 4.Using at least one or two or more of bentonite, river sand, urban dust, incineration ash, and waste glass at the same time? The melting and solidification treatment method of the dust collector configuration described as e.