JPH11244809A - Melting method of incineration residue containing salt - Google Patents

Abstract

(57) [Problem] To provide a melting treatment method in which a molten salt layer is not generated, and a melting treatment method in which a slag in which a molten salt layer is not generated and chlorine elution is suppressed is obtained. SOLUTION: When charging an incineration residue containing salts into a melting furnace for melting treatment, a component adjusting material containing Ca and / or Mg is charged to adjust the components of the charge. Further, the melt that has been subjected to the melting treatment as described above is rapidly cooled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for melting incineration residues containing salts such as municipal waste incineration residues.

[0002]

2. Description of the Related Art In the disposal of incineration residues generated when municipal waste and industrial waste are incinerated, there is a case in which heavy metals are insolubilized. In addition, as it becomes difficult to obtain a final disposal site, it has become necessary to reduce the volume of incineration residues. For this reason, melting treatment has been performed as a treatment for insolubilizing heavy metals in the incineration residue and reducing the volume of the incineration residue itself.

[0003] The melting treatment of the incineration residue is performed by various methods.
5013, JP-A-7-77319, JP-A-60-646
In a method using an electric resistance type melting furnace as disclosed in Japanese Patent Publication No. 82, and a method using a high-frequency induction type melting furnace, the incineration residue is loaded on the melt while staying in the furnace. An operation of melting the molten steel is performed. At this time, when melting the incineration residue containing salts, the treatment is about 15 minutes.
Since it is carried out in a furnace maintained at about 00 ° C., sodium chloride (Na
Most of alkali metal chlorides such as Cl) and potassium chloride (KCl) volatilize, but salts such as calcium chloride (CaCl ₂ ) hardly volatilize and remain in the furnace. For this reason, the separation occurs while the molten material stays in the furnace, and is separated into a layer of molten slag mainly composed of oxide and a layer of molten salt composed of salts such as chloride. In this case, a molten slag layer is generated on the lower side, and a molten salt layer is generated on the upper side. The separated molten slag and molten salt are separated and discharged. After the molten slag is solidified, it is supplied to a purpose such as a roadbed material, and the molten salt contains harmful heavy metals.

[0004]

The above prior art has the following problems.

[0005] When a molten salt layer is formed in the furnace, the erosion of the refractory by the molten salt becomes severe at the site where the molten salt layer is formed, and the furnace inner wall must be repaired frequently. Further, among the above conventional techniques, in the method using an electric resistance melting furnace, a current is passed between electrodes immersed in the melt in the furnace, and the melt itself is heated by electric resistance heat at that time, and the furnace itself is heated. The melt inside is maintained at a predetermined temperature, but if the melt separates into a molten slag layer and a molten salt layer, the current flowing between the electrodes will flow to the molten salt layer with high electrical conductivity. As a result, the molten slag layer cannot be maintained at a predetermined temperature. For this reason,
The melting of the charged incineration residue becomes insufficient, and the viscosity of the molten slag increases, making it difficult to discharge the slag. As a result, the operation of the melting furnace cannot be continued.

Although most of the salts contained in the incineration residue are chlorides, when the incineration residue containing salts is melted by the above-mentioned conventional method, the molten slag and the salts are separated and discharged. Nevertheless, the obtained slag contains a large amount of chlorine, and a large amount of chlorine is eluted when the slag is subjected to a dissolution test. For this reason, the slag obtained by melting the incineration residue containing salts cannot be used as an aggregate for buildings or the like, and its use is limited to roadbed materials and the like.

[0007] As described above, when the incineration residue containing salts is melt-processed according to the above-mentioned conventional technique, the salts are liberated to form a molten salt layer, and this molten salt layer adversely affects equipment and operation. Problems arise and, furthermore, the slag produced tends to elute chlorine, which limits its use.

[0008] It is an object of the present invention to provide a melting treatment method in which a molten salt layer is not formed and a melting treatment method in which a slag in which a molten salt layer is not formed and elution of chlorine is obtained is obtained.

[0009]

Means for Solving the Problems In order to achieve the above object, in the first invention, when charging the incineration residue containing salts into a melting furnace and performing melting treatment, Ca and / or Mg is used.
The component adjustment material containing is charged, and the components of the charge are adjusted.

[0010] In the second invention, the melt melt-processed by the method according to the first invention is rapidly cooled.

Next, a description will be given of how the component adjusting material containing Ca and / or Mg is charged and the components of the charge are adjusted.

In the preceding paragraph, it was described that a large amount of salts was contained in the slag obtained by subjecting the incineration residue containing salts to melting treatment. (Dissolution) was examined in detail. First, for a large number of slags obtained by melting municipal waste incineration residues,
Composition analysis was performed to examine the relationship between the slag composition and the chlorine content in the slag. The result is shown in FIG. In FIG. 3, the vertical axis shows the chlorine content (wt%) in the slag, and the horizontal axis shows the slag component ratio (mol / mol) expressed by (Ca + Mg) / (Si + Al). Also, in the figure, the points marked with Δ indicate the results when the molten salt was not released during melting, and the points marked with Δ indicate the results when the molten salt was released.

As shown in this figure, (Ca + Mg) / (Si
+ Al) as the component ratio increases, the amount of chlorine dissolved in the slag tends to increase. And
The points indicated by the mark (■) are the results when the molten salt was released at the time of melting, and indicate that the slag generated under these conditions was in a state where chlorine was saturated. That is, the chlorine content at the point indicated by the symbol ■ is the saturated chlorine concentration at that component ratio.

[0014] Then, regarding the result of only the mark, (Ca
Looking at the relationship between the component ratio of slag represented by (+ Mg) / (Si + Al) and the chlorine content, as shown in the figure, they both correspond almost linearly. For this reason, the upper section divided by this straight line is an area where molten salt is generated during melting, and the lower section is an area where molten salt is not generated.

The above straight line is represented by the following equation (1). Y = 2.5X−0.75 (1) where, Y: Saturated chlorine concentration of slag X: Component ratio of incineration residue expressed by (Ca + Mg) / (Si + Al) (mol / mol) In the equation (1), Is different from the display in FIG. 3 in which X is shown as the component ratio of the incineration residue and shows the relationship between the slag composition and the chlorine content in the slag, but the component ratio is (Ca + Mg) / (Si + Al) In the case represented by the formula, most of the components such as Ca, Mg, Si, and Al contained in the incineration residue move into the slag, so that the component ratio of the slag and the component ratio of the incineration residue are substantially the same. You can think. Therefore, for convenience, in formula (1), X is the component ratio of the incineration residue.

As described above, the relationship between the component ratio of the incineration residue and the chlorine content of the slag is clarified.
If the components of the incineration residue are adjusted, the operation can be performed in a state where no molten salt is generated.

The chlorine contained in the incineration residue is mainly derived from chlorides such as NaCl, KCl, and CaCl _2. Of these, the chlorine derived from NaCl and KCl is less than the melting temperature of the incineration residue. Most are volatilized and do not remain in the melt. Further, chlorine derived from CaCl ₂ remains without volatilizing. For this reason, most of the chlorine remaining in the melt is in the form of CaCl ₂ . Thus, Na and K contained in the incineration residue
Cl corresponding to the sum of the equivalents of NaCl, KC
Since Cl volatilizes in the form of l, Cl remaining in the molten slag can be obtained by the following equation (2).

Y = y ₀ − (Na + K) × 3.55 (2) where y: chlorine content (wt%) remaining in the slag y ₀ : chlorine content (wt%) of incineration residue Na: incineration Sodium content of the residue (mol / kg) K: Potassium content of the incineration residue (mol / kg) Therefore, the value of the chlorine content y remaining in the slag obtained by the equation (2) is obtained by the equation (1). If the saturated chlorine concentration Y of the slag is not more than the value of the saturated chlorine concentration Y, that is, if the relation between Y and y is Y ≧ y, the salts in the incineration residue are not released as molten salts, Dissolve.

The component adjusting material added to adjust the component ratio of the slag represented by (Ca + Mg) / (Si + Al) is a substance containing either Ca and Mg or Ca and Mg, and , Slaked lime, limestone powder, dolomite and the like, or a mixture thereof, steel slag, concrete waste, and the like can be used.

As described above, by adjusting the component ratio of the incineration residue, chlorine can be dissolved in the molten slag without releasing the molten salt, but depending on the conditions for cooling and solidifying the slag. However, the dissolution of chlorine dissolved in the slag differs greatly. The effect of the cooling conditions on the chlorine elution will be described with reference to FIGS.

FIGS. 4 and 5 show the results of a dissolution test performed on slag obtained by melting the incineration residue under the melting conditions under which the molten salt is liberated, in accordance with the soil environment criteria (Notification No. 46 of the Environment Agency). FIG. 4 shows the chlorine elution concentration of the slag obtained by leaving and cooling the molten slag, and FIG. 5 shows the chlorine elution concentration of the slag obtained by rapidly cooling the molten slag. According to this result, the chlorine elution concentration after quenching is lower than the upper limit (0.02%) of the chloride ion content in the JIS standard (R5210) for Portland cement,
It was a good value. However, the chlorine elution concentration when left to cool slowly was significantly high.

It is considered that the difference between the concentration of chlorine eluted in the case of rapid cooling and that in the case of slow cooling is caused by the following reasons. First, when the molten slag is cooled and solidified, when gradually cooled, chlorine (Cl) and Na, K, Ca, etc. are combined while ions are moving in the molten slag, and Na
Salts such as Cl, KCl, and CaCl ₂ precipitate. The salts not only adhere to the surface of the slag mass, but also exist in the slag cracks and internal voids. For this reason, when the slag is pulverized, a part of the salts is eluted.

On the other hand, when quenched, chlorine rapidly solidifies, so that chlorine is uniformly fixed in the amorphous structure at the atomic level. For this reason, this slag is crushed,
Even when leached with water, the elution of chlorine is suppressed to a small amount.

[0024]

FIG. 1 is a diagram showing an example of an embodiment according to the present invention. In advance, for the incineration residue containing salts and component conditioning materials, perform a predetermined component analysis,
The addition amount of the component adjusting material to the incineration residue is calculated based on the calculated values obtained by the formulas (1) and (2). Then, a predetermined amount of the incineration residue containing salts and a predetermined amount of the component adjusting material selected from quick lime, slaked lime, limestone powder, dolomite, or a mixture thereof, or steel slag, concrete waste, and the like are sent to the component adjusting step 10. Mix. The incineration residue whose components have been adjusted is charged into, for example, an electric resistance melting furnace 20. In the melting furnace 20, the electrodes 21 are immersed in the melt of the incineration residue that has already been melted, and electricity is generated between the electrodes to generate electric resistance heat, thereby heating the melt. The incineration residue charged into the furnace is heated and melted by the heat transfer from the melt. This melt stays in the furnace for about 10 to 20 hours and is then discharged. During that time, each component is separated by a difference in specific gravity and separated into a molten slag layer 40 and a molten metal layer 41. On this occasion,
If the components are adjusted based on the values calculated by the formulas (1) and (2), the salts dissolve in the molten slag without releasing and forming a molten salt layer.

Although the molten slag and the molten metal are separated and discharged, the molten slag is sent to the cooling step 30. In this step, a process of rapidly cooling to a transition temperature (about 700 to 800 ° C.) at which the molten slag becomes amorphous is performed.
As the treatment method, if a method of putting molten slag into a water tank or flowing water to directly contact the molten slag with water is employed, the molten slag can be efficiently cooled rapidly. Alternatively, the molten slag may be rapidly cooled by blowing it off together with pressurized air to cool it. Also, the molten slag is discharged into a water-cooled metal mold or metal gutter,
Indirect cooling may be used.

The slag quenched as described above has a very small amount of chlorine eluted and can be used as an aggregate for construction.

FIG. 2 is a diagram showing another example of the embodiment according to the present invention. In FIG. 2, the portions described in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In this embodiment, the component adjusting step is not provided, and the incineration residue and the component adjusting material are separately charged. According to this method, the input amount of the component adjusting material can be changed successively in accordance with the fluctuation of the incineration residue, so that it is effective to apply it to the case of treating incineration residue having a large fluctuation of the component.

[0028]

Example (Comparative Example 1) Fly ash and incinerated ash (analytical values are shown in Table 1) collected when slaked lime was blown into the flue of an incinerator for municipal solid waste to remove hydrogen chloride, The fly ash 1 was mixed at a ratio of incineration ash 4 to prepare a mixture A of incineration residues.
About this mixture A, the composition was calculated from the analysis value of the mixed fly ash and incineration ash, and based on this composition, (Ca + Mg)
The composition ratio of / (Si + Al) was determined. Further, the value of the saturated chlorine concentration Y of the slag and the value of the chlorine content y remaining in the slag were determined by the formulas (1) and (2) based on the above composition and component ratio. These values are shown in Table 2. As shown in Table 2, the mixture A has (Y-y) of -0.56 (negative value), indicating that the mixture A forms a molten salt layer upon melting.

In fact, when the mixture A was charged into the electric resistance type melting experimental furnace at a supply rate of 1 t / h and was continuously melted, the formation of a molten salt layer was recognized as the operation time passed. When the process was continued, the current drifted to the molten salt layer occurred, and an abnormal increase in the current value appeared, which hindered the operation. Table 3 shows the analysis values of the discharged slag.

(Example 1) Mixture A of incineration residue prepared in Comparative Example 1 was mixed with quicklime at a ratio of 100: 12 to prepare mixture B of incineration residue. About this mixture B,
The composition was calculated from the analysis values of the mixed fly ash, incineration ash, and quicklime, and based on this composition, (Ca + Mg) / (Si + A
The component ratio of 1) was determined. Further, based on the above composition and component ratio, the saturated chlorine concentration Y of the slag is calculated by the equations (1) and (2)
And the value of the chlorine content y remaining in the slag were determined.
These values are shown in Table 2. According to this table, (Y−y)
Is +0.17 (positive value), which indicates that the mixture B does not form a molten salt layer upon melting.

This mixture B was charged into an electric resistance type melting experimental furnace at a supply rate of 1 t / h, and was continuously melted. 12
The operation was continuously performed for 0 hours, but no formation of a molten salt layer was observed in the melting furnace, and no abnormality in increasing the current value occurred.

Then, the discharged slag is put into a water tank,
It was quenched. Table 3 shows the analysis values of the obtained slag.

Next, the slag was subjected to a dissolution test in accordance with a method for judging soil environmental standards (Notification No. 46 of the Environment Agency). In this dissolution test, the slag was pulverized to a size of less than 2 mm, added with a 10-fold amount of purified water, shaken for 6 hours, separated by filtration, and analyzed for the chlorine concentration in the eluate. The chlorine elution concentration from the slag was 2 mg / l.
This value is based on Portland cement JIS standard (R52
10) The upper limit of the chloride ion content (0.02
%) Converted to a chlorine elution concentration in an elution test (10 mg).
/ L), which is a good value that is significantly lower than (/ l).

Comparative Example 2 Fly ash and incinerated ash having the compositions shown in Table 1 were mixed in a ratio of fly ash 1: incinerated ash 2 to prepare a mixture C of incineration residues. For this mixture C, Example 1
And the composition and (Ca + Mg) / (Si + A)
The component ratio of 1), the value of the saturated chlorine concentration Y of the slag, and the value of the chlorine content y remaining in the slag were determined. Table 2 shows these values.
Shown in As shown in this table, the mixture C has (Y−y) −
2.10 (negative value), which was expected to generate a molten salt layer during melting.

Then, when the mixture C was charged into the electric resistance type melting experimental furnace and melted in the same manner as in Example 1, a molten salt layer was formed and the current value was reduced as in Comparative Example 1. Abnormality that increased significantly occurred, and operation was hindered. Table 3 shows the analysis values of the discharged slag.

(Example 2) Mixture D was prepared by mixing quicklime with the mixture B of the incineration residue prepared in Comparative Example 2 at a ratio of 100: 38. About this mixture D, similarly to the case of Example 1, composition and (Ca + Mg) / (Si + A
The component ratio of 1), the value of the saturated chlorine concentration Y of the slag, and the value of the chlorine content y remaining in the slag were determined. Table 2 shows these values.
Shown in As shown in this table, (Y−y) is +0.89 (positive value), and this value indicates that the mixture D does not form a molten salt layer upon melting.

This mixture D was charged into an electric resistance type melting experimental furnace at a supply rate of 1 t / h, and was continuously melted. 12
The operation was continuously performed for 0 hours, but no formation of a molten salt layer was observed in the melting furnace, and no abnormality in increasing the current value occurred.

Then, the discharged slag is put into a water tank,
It was quenched. Table 3 shows the analysis values of the obtained slag.

Next, a dissolution test was conducted in the same manner as in Example 1. The chlorine elution concentration in this elution test was 3 mg / l, which was a good value as in the case of Example 1.

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

[Table 3]

[0043]

According to the present invention, a component adjusting material containing Ca and / or Mg is charged and the components of the charge are adjusted to a range where a molten salt layer is not formed in the furnace. No troubles on facilities or operation caused by the generation of waste.

Further, according to the present invention, since the discharged molten slag is rapidly cooled, elution of chlorine from the slag is suppressed. For this reason, a slag having an extremely low chlorine elution concentration can be obtained, and the slag can be used for various purposes such as aggregate for construction.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an embodiment according to the present invention.

FIG. 2 is a diagram showing another example of the embodiment according to the present invention.

FIG. 3 is a diagram showing the relationship between slag composition and chlorine content in slag.

FIG. 4 is a diagram showing a relationship between a component ratio of slag and a chlorine elution concentration when a molten slag is gradually cooled.

FIG. 5 is a diagram showing the relationship between the component ratio of slag and the chlorine elution concentration when the molten slag is rapidly cooled.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Component adjustment process 20 Electric resistance melting furnace 21 Electrode 22 Molten slag outlet 23 Molten metal outlet 30 Cooling process 40 Molten slag layer 41 Molten metal layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FIF23J 1/00 B09B 3/00 ZAB

Claims (2)

[Claims] 1. When charging an incineration residue containing salts into a melting furnace for melting treatment, a component adjusting material containing Ca and / or Mg is charged to adjust the components of the charge. For melting incineration residues containing salts. 2. A method for melting incineration residues containing salts, the method comprising: quenching the melt processed by the method according to claim 1.