JP2002054812A - Melting method of incinerated ash - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reliably and inexpensively prevent the formation of sulfide due to sulfur contained in incineration ash when melting incineration ash discharged from a refuse incinerator or the like. SOLUTION: When melting incineration ash to reduce its volume, converter slag generated in a steel making process is blended, and the converter slag is melted together with the incineration ash. At that time, the mixing amount of the converter slag was 100 to 15 per ton of the generated molten slag.
It is preferably 0 kg. Further, in the case where the incinerated ash to be melted is incinerated ash of combustible waste separated and collected, the effect can be further exhibited.

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 incinerated ash discharged from a garbage incinerator or the like.
The present invention relates to a melting treatment method capable of preventing formation of sulfide due to sulfur contained in incineration ash during melting treatment and producing a molten slag having a stable composition.

[0002]

2. Description of the Related Art In recent years, incineration ash discharged from refuse incinerators and the like is melted in a melting furnace such as an electric furnace in order to reduce the volume, and is turned into molten slag. It has come to be used as a building material. The melting treatment of this incinerated ash is performed in a reducing atmosphere,
In addition, since incineration ash generally contains a metal component, in the incineration ash melting process, the metal component in the incineration ash is melted and dropped, and a part of the metal oxide in the incineration ash is reduced. It melts and a molten metal layer is formed on the furnace bottom. The molten metal is discharged from the furnace continuously or intermittently, and the amount thereof is controlled so as not to become too large.

[0003] Further, incinerated ash also contains sulfur, and usually, the sulfur in the incinerated ash is dissolved in the molten slag produced by melting the incinerated ash and the above-mentioned molten metal, and is discharged outside the furnace. Is discharged. The sulfur dissolved in the molten slag and the molten metal is extremely stable, and adverse effects on the environment are avoided. However, the saturation concentration of sulfur in the molten slag and the molten metal is naturally determined, and the molten slag and the molten metal do not dissolve in excess of the saturation concentration. The saturation concentration of the molten slag is determined by a factor called sulfide-capacity determined from the composition of the molten slag, and the saturation concentration of the molten metal is about 1.6 to 2.0 mass% in a carbon-saturated reducing atmosphere. is there.

Therefore, when the sulfur content in the incineration ash becomes extremely large or when the amount of the molten metal becomes extremely small, the sulfur is dissolved in the molten slag and the molten metal and discharged. In the melting furnace, sulfides such as FeS and ZnS may be generated and separated and concentrated at the boundary between the molten slag layer and the molten metal layer at the bottom of the furnace due to the density difference. In this case, the generated sulfide is discharged together with the molten slag, and when the solidified slag is crushed or adjusted for use as a material, the sulfide is mixed into the slag and the quality of the slag is reduced. Problems arise.

[0005] Recently, the separation and collection of garbage has been advanced, and only combustibles are often incinerated in garbage incinerators, and the amount of metal in the incineration ash has been reduced. It is even more problematic.

[0006]

If the sulfur saturation concentration of the molten slag is increased, the formation of sulfide is suppressed. In order to increase the sulfur saturation concentration of the molten slag, that is, to increase the amount of sulfur dissolved in the molten slag, the sulfide-capacity is increased by a method such as increasing the basicity (CaO / SiO ₂ ) of the molten slag. The amount of CaO may be increased, but in this case, it is necessary to add CaO in quicklime or limestone, so that the cost is increased due to the addition of quicklime or limestone.

On the other hand, if the sulfur saturation concentration of the molten metal is increased, the formation of sulfide is suppressed, but this is difficult in actual operation. If the carbon concentration in the molten metal is reduced, the saturation concentration of sulfur increases, but in this case, it is necessary to increase the oxygen potential in the melting furnace, and as a result, reduction of harmful metals such as lead does not proceed. , Will remain in the molten slag. The purpose of the melting treatment of incinerated ash is not only to volatilize the harmful metal but also to discharge the harmful metal as a metal by setting the inside of the furnace to a reducing atmosphere, but this cannot be expected at all.

[0008] Further, if the incineration ash is mixed with a metal component such as iron scrap and subjected to a melting treatment, the amount of molten metal is increased and the generation of sulfides can be suppressed. And increase the cost due to the mixing of metals such as iron scrap.

The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a melting treatment method capable of reliably and inexpensively preventing the generation of sulfide by sulfur contained in incineration ash in the melting treatment of incineration ash discharged from a garbage incinerator or the like. That is.

[0010]

According to a first aspect of the present invention, there is provided a method for melting incinerated ash, which is used for melting and reducing the volume of incinerated ash.
It is characterized by mixing converter slag generated in the steel making process and melting the converter slag together with incineration ash.

According to a second aspect of the present invention, there is provided a method for melting incineration ash according to the first aspect, wherein the mixing amount of the converter slag is per ton of molten slag generated by melting the incineration ash and the converter slag. The weight is set to 100 to 150 kg.

A method for melting incinerated ash according to a third invention is characterized in that, in the first invention or the second invention, the incinerated ash is incinerated ash of combustible waste separated and collected. is there.

The converter slag generated in the steel making process has a high basicity (CaO / SiO ₂ ) of 3 to 5 and contains 20 to 30% by mass of FeO (hereinafter referred to as “%”).
On the other hand, the incineration ash discharged from a garbage incinerator or the like has a basicity of about 0.3 to 0.5, which is extremely low as compared with converter slag. In the present invention, such converter slag is melted together with the incineration ash, so that the basicity of the molten slag generated by mixing and melting the incineration ash and the converter slag increases, and as shown in FIG. The amount of sulfur dissolved in the slag increases. That is, when the basicity of the molten slag increases, the sulfide-capacity of the molten slag increases, the sulfur saturation concentration of the molten slag increases, and the generation of sulfide is suppressed. In addition, FIG.
It is a figure which shows the relationship between the basicity of a molten slag, and the distribution ratio of sulfur, The both are shown in the range of the shaded area of FIG. The distribution ratio shown in FIG. 1 is the ratio between the sulfur concentration in the molten slag and the sulfur concentration in the molten metal.

On the other hand, FeO in the converter slag is easily reduced by the reducing atmosphere in the melting furnace for melting the incineration ash to generate molten iron and increase the amount of molten metal in the furnace bottom. The amount of sulfur dissolved in the molten metal layer increases,
Sulfide formation is suppressed.

That is, by mixing the converter slag with the incineration ash and performing the melting treatment, the basicity of the generated molten slag increases and the amount of molten metal increases.
Since both have the action and effect of suppressing the formation of sulfide, the formation of sulfide due to the sulfur contained in the incineration ash is prevented in the furnace.

Converter slag may be effectively used for roadbed materials and the like, but it is difficult to use it as a material because of its high basicity, and is mainly used for landfills. Therefore,
Compared with other sulfide-inhibiting substances such as quicklime, limestone and iron scrap, it is much cheaper, and even if it is added and blended, the increase in melt processing cost can be reduced.

If the amount of converter slag is too small, the effect and effect of suppressing the formation of sulfide are small. On the other hand, if the amount is excessive, the total amount of molten slag increases, and The energy costs for the rise. Therefore, the present inventors changed the blending amount of converter slag to a range of up to 300 kg per ton of molten slag to be produced by using an electric resistance type melting furnace shown in Examples described later, We conducted a melting treatment test of incinerated ash from garbage and investigated the sulfur concentration in the molten metal and the sulfide formation. FIG. 2 shows the result of the investigation.

FIG. 2 is a diagram showing the relationship between the amount of converter slag and the sulfur temperature in the molten metal.
Are shown in the shaded area. As shown in FIG. 2, the unit consumption of converter slag is 100 tons of molten slag per ton.
At less than kg (hereinafter, referred to as “kg / ton”), the sulfur concentration of the molten metal was a saturated concentration of about 2%, and in this case, sulfide was generated at the interface between the molten slag and the molten metal. Basic unit of converter slag is about 100kg / to
At the time of n, the sulfur concentration in the molten metal starts to decrease.
In the range of the mixing basic unit exceeding 0 kg / ton, the sulfur concentration in the molten metal decreased with an increase in the mixing amount.

From these results, the converter slag was 100 k
It has been found that sulphide formation can be prevented by blending in a blending unit unit of g / ton or more. The upper limit of the amount of converter slag is not particularly limited, but is preferably 150 kg / ton or less in terms of the energy cost of melting.

Since the composition of the incinerated ash is not constant, if the amount of the converter slag is fixed, the sulfur concentration in the molten metal may increase to the saturation concentration. Therefore, in order to prevent this, it is preferable to periodically analyze the sulfur concentration in the discharged molten metal and change the blending amount of the converter slab so that the sulfur concentration of the molten metal does not become a saturated concentration. .

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 3 is a schematic diagram showing one example of a melting furnace used in the present invention.

As shown in FIG. 3, an electric resistance type melting furnace 1 for melting incineration ash has a furnace body 2 for melting incineration ash therein, and a furnace lid 3 for covering an upper portion of the furnace body 2. Is provided. The furnace body 2 has an outer shell made of an iron shell 8 and a refractory 9 is applied inside thereof.
A tap 6 for discharging 0 and a tap 7 for discharging molten slag 11 are provided. The discharge of the molten metal 10 from the tap hole 6 and the discharge of the molten slag 11 from the slag port 7 may be performed continuously or intermittently. In the case of intermittent discharge, the tap hole 6 and the slag port 7 are closed with a mud material (not shown) when not discharging.

The furnace lid 3 has an outer shell made of an iron shell 8 and a refractory 9 is applied inside the furnace shell.
Two electrodes 4 are arranged. The tip of each electrode 4 is movable up and down into the furnace body 2.
Each of the electrodes 4 is connected to a power supply device (not shown), so that a current flows between the electrodes 4. or,
A charging chute 5 for charging incineration ash and converter slag into the furnace body 2 is disposed on the ceiling of the furnace lid 3. still,
Although three electrodes 4 are provided in FIG. 3, the number of the electrodes 4 is not limited to three, and may be one as long as a current flows through the charge in the furnace body 2. Moreover, even if it is two or more, any number may be sufficient.

A method for melting incinerated ash according to the present invention using the electric resistance type melting furnace 1 having the above-described configuration will be described below.

The incineration ash discharged from a refuse incinerator or the like, in particular, the incineration ash generated when combustible waste is incinerated is charged into the furnace body 2 through the charging chute 5. The converter slag generated in the steelmaking process is charged into the furnace body 2 via the charging chute 5. At that time, as described above, the unit consumption of the converter slag is preferably 100 to 150 kg / ton, and therefore, the unit consumption of the converter slag is 100 kg / ton.
It is preferable to adjust the incineration ash and converter slag cut-out device (not shown) so that the incineration ash and the converter slag are set to 150 kg / ton, and charge the incineration ash and the converter slag into the furnace body 2 at the same time.

By charging the incineration ash and the converter slag in this way, the distribution of the incineration ash and the converter slag in the furnace body 2 is made uniform, and the melting process can be performed smoothly. The converter slag is obtained by solidifying and crushing what is generated during the blowing of the molten steel in the converter, and its size is not particularly limited, and may be any size. Further, the incineration ash and the converter slag are preliminarily mixed, and the resulting mixture is placed in a furnace body 2.
It may be charged inside.

When a current flows through the electrodes 4, a current flows between the electrodes 4, and the unmelted material 12 composed of a mixture of incineration ash and converter slag is heated by Joule heat and melts to form a molten slag 11. However, as in the start of heating, the furnace body 2
When only the unmelted material 12 is present in the inside, the current is extremely difficult to flow and the unmelted material 12 is not heated. It is necessary to keep the electrical connection between them.
When the molten slag 11 is formed, a current flows through the molten slag 11, so that the tip of the electrode 4 is immersed in the molten slag 11, and the unmelted material 12 is continuously heated and melted by the Joule heat of the molten slag 11. . In this state, the carbon material as a current-carrying material is unnecessary, but the carbon material is continuously or intermittently charged into the furnace body 2 as necessary in order to make the atmosphere in the furnace body 2 a reducing atmosphere. I do.

As the unmelted material 12 in which the incineration ash and the converter slag are mixed, a molten slag 11 is formed. At the same time, part of the metal oxide in the incineration ash and Fe in the converter slag
O is reduced by the carbon material, and a molten metal 10 is formed at the bottom of the furnace body 2. During the melting process, the molten metal 10 and the molten slag 11 are continuously or intermittently discharged from the tap hole 6 and the slag port 7 so that the amount of the molten metal staying in the furnace body 2 is within a predetermined range. During this period, incinerated ash and converter slag are charged into the furnace body 2 continuously or intermittently through the charging chute 5 so that the unmelted material 12 always exists in the furnace body 2. I do. Then, the discharged molten slag 11 is solidified, crushed if necessary, and is effectively used for civil engineering and building materials.

By melting the incineration ash in this way, the sulfur contained in the incineration ash dissolves in the molten metal 10 and the molten slag 11 without forming sulfide in the furnace body 2 and Is discharged. As a result, when the molten slag 11 is used as a material, deterioration of the quality of the molten slag 11 due to sulfide is prevented beforehand, and the molten slag 11 can be used in a wide range of fields.

The melting furnace for melting the incineration ash is not limited to the above-mentioned electric resistance melting furnace 1, and the heating source is as follows.
The present invention can be applied to plasma heating, arc heating, burner heating, or even induction heating according to the above.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following is an explanation of an embodiment in which incinerated ash of combustible waste separated from incombustible substances such as metal and glass is melted by the method of the present invention using an electric resistance melting furnace shown in FIG. I do.

The composition of the converter slag used was CaO = 52
%, SiO ₂ = 14%, FeO = 25%, and the basicity was 3.7. This converter slag was blended at a ratio of 100 kg to 900 kg of incineration ash, and melted in an electric resistance melting furnace. Then, the melting process was continued while intermittently discharging the molten metal and the molten slag in the furnace, and a melting process of a total of 20 tons of incinerated ash was performed.

As a result, the composition of the resulting molten slag is CaO = 23%, SiO ₂ = 45%, and the basicity is 0.5%.
1, and about 50 kg of molten metal was produced per ton of molten slag produced. The sulfur concentration of the molten metal was 1.8%, and did not increase to the saturation concentration of 2.0%. From this result, it was determined that no sulfide was generated in the furnace. Also, from the result of solidifying the discharged molten slag, crushing it to 50 mm or less and examining the presence or absence of sulfide adhesion, no sulfide adhesion was observed, and it was confirmed that sulfide was not finally generated. It could be confirmed.

On the other hand, as a comparison, a test for melting only the above incinerated ash was also conducted. In this case, the composition of the molten slag was CaO = 19%, SiO ₂ = 48%, the basicity was 0.40, and about 30 kg of molten metal was produced per ton of the produced molten slag. . The sulfur temperature of the molten metal was 2.0% saturated, and it was confirmed that sulfides were mixed in the discharged molten slag.

As described above, by subjecting the incineration ash of combustible waste to the melting treatment using the melting treatment method according to the present invention, the basicity of the molten slag can be increased and the amount of the molten metal can be increased. It was found that it was possible to prevent the formation of sulfide by sulfur contained in the incineration ash.

[0036]

According to the present invention, when melting incinerated ash to reduce its volume, converter slag generated in the steel making process is blended.
Since the converter slag is melted together with the incineration ash, the basicity of the generated slag increases and the amount of molten metal increases, making it possible to prevent the formation of sulfides due to the sulfur contained in the incineration ash. Become. As a result, the quality deterioration of the molten slag due to the sulfide is prevented, the molten slag can be used in a wide range of fields, and an industrially beneficial effect is brought.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the basicity of molten slag and the sulfur distribution ratio.

FIG. 2 is a diagram showing the relationship between the amount of converter slag and the sulfur temperature in the molten metal.

FIG. 3 is a schematic view showing one example of a melting furnace used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric resistance melting furnace 2 Furnace 3 Furnace lid 4 Electrode 5 Charging chute 6 Tap hole 7 Slag port 8 Iron shell 9 Refractory 10 Molten metal 11 Molten slag 12 Unmelted material

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C22B 7/00 B09B 3/00 ZAB 7/04 303L 303D (72) Inventor Keisuke Nakahara Chiyoda-ku, Tokyo 1-2-1 Marunouchi Nihon Kokan Co., Ltd. F-term (reference) 3K061 NB01 NB06 NB20 4D004 AA36 AA43 AB10 BA02 CA29 CB33 CB34 DA01 DA03 DA10 4G012 JL03 JM04 4K001 AA10 BA12 4K002 AE05

Claims (3)

[Claims] 1. A method for melting incineration ash, comprising mixing converter slag generated in a steel making process when melting incineration ash to reduce its volume, and melting the converter slag together with the incineration ash. . 2. The incineration according to claim 1, wherein the blending amount of the converter slag is 100 to 150 kg per 1 ton of molten slag generated by melting the incineration ash and the converter slag. Ash melting method. 3. The method for melting incinerated ash according to claim 1, wherein the incinerated ash is incinerated ash of combustible waste separated and collected.