JPH0987728A - Method for simultaneously executing production of alloy iron in electric furnace and melting treatment of incineration ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To treat incineration ash simultaneously with refining of metal (including alloy) by using incineration ash of various kinds of waste as a part of raw materials for metal refining at the time of refining the metal in an electric furnace. SOLUTION: A three-phase submerged arc type hermetic electric furnace is used in, for example, the melting treatment of in the electric furnace for producing silicon manganese and the incineration ash from municipal refuse are used by previously compounding the incineration ash with raw materials for refining. As a result, the silicon manganese and recyclable slag are obtd. The component compsns. of these products are substantially the same as the component compsns. of the products obtd. by ordinary refining. Although harmful components, such as As and Hg, are included in the incineration ash, the amts. thereof are small and, therefore, these components do not adversely affect the refining metal. On the other hand, the results of tests indicate that the harmful components are confined into the slag and problem, such as elution, does not arise. Then, the incineration ash is made pollution-free and reduced in volume by melting while the refining of the metal is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing the volume and detoxifying the incineration ash of general waste, industrial waste, sewer sludge, shredder dust and other wastes by melting. More specifically, the present invention relates to a method for refining metals (including alloys) in an electric furnace and treating incinerated ash at the same time.

[0002]

2. Description of the Related Art Conventionally, various kinds of waste such as general waste, industrial waste, sewer sludge, shredder dust, etc.
It is incinerated, and its ash (incinerated ash) is often disposed of in landfills. However, securing landfills is becoming more difficult each year, and it is necessary to extend the life of those landfills. In addition, since the incinerated ash contains various harmful substances such as heavy metals, when discarded, problems such as the outflow of such harmful substances due to rainwater and the elution into groundwater may occur. Therefore, conventionally, so-called volume reduction treatment for reducing the volume of incinerated ash and detoxification treatment of incinerated ash for preventing outflow of harmful substances such as heavy metals and elution into groundwater have been studied. . Furthermore, there is a long-awaited need to go one step further and to reuse incineration ash by recycling it and to develop recycling technology. By the way, a method has been proposed in which ash, sludge, and the like are treated in an electric resistance furnace to produce an artificial mineral and a metal in which heavy metals are detoxified from these ash and sludge (Japanese Patent Publication No. 60-56963). ). However, in this method, it is difficult to adjust the electric resistance of the incineration ash or its melt, or to remove harmful components because it is not a technique involving refining of metal but a technique of simply melting the ash by electric resistance heat. In order to fix the slag, it is necessary to add silicic acid and lime to adjust the composition. As a result, there has been a problem that the silicic acid content and lime content added to adjust the components reduce the volume reduction effect of the incinerated ash. Generally, since the composition and properties of incinerated ash are various and vary greatly, it is difficult to control the obtained slag and metal components and their properties, and there is also a problem that they are not reused. Furthermore, when the waste containing a large amount of carbon in the unburned residue is treated, it is necessary to burn it on the furnace or outside the furnace, which increases the amount of gas generated, so the operation cannot be stabilized and heavy metals, etc. It causes problems such as the volatilization of harmful substances, or the need for large-scale equipment for processing exhaust gas.

[0003]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for attaining detoxification and volume reduction by melting incineration ash while refining metal. Further, the present invention produces a reusable slag and recovers a metal content without particularly considering the component adjustment of incineration ash, and reduces the carbon content as an unburned residue (fuel residue) to reduce the metal component. It is an object of the present invention to provide a method for effectively utilizing energy by utilizing the generated gas containing carbon monoxide and hydrogen as a fuel for power generation and the like.

[0004]

Means for Solving the Problems As a result of earnest studies on a method for achieving the above object, the present inventor uses incinerated ash as a part of a raw material for metal refining when refining metal in an electric furnace. By doing so, they have found that the above problems can be achieved, and have reached the present invention.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The incineration ash treated in the present invention is incineration ash of general waste, industrial waste, sewer sludge, shredder dust, and other wastes. For example, incineration ash from municipal waste usually has the following composition.

[0006]

[Table 1] Table 1 Chemical analysis values of incinerated ash Component SiO ₂ CaO MgO Al ₂ O ₃ Fe ₂ O ₃ Na ₂ OK ₂ OP concentration (%) 37.1 18.5 2.6 17.9 3.0 3.0 1.6 0.9 Component Hg Pb As Cd Cr concentration (ppm ) 0.3 860 20 12 150 As the electric furnace for refining metals used in the present invention, various electric furnaces can be used without particular limitation as long as they are used for refining metals (including alloys). be able to. As such an electric furnace, generally, a resistance furnace that generates heat by resistance, an arc furnace that uses heat generation of an arc, an induction furnace that uses induction heating, and the like are listed according to the difference in heat generation method. From the viewpoint of thermal efficiency and prevention of scattering of harmful substances such as heavy metals, a resistance furnace is preferable.
A cross-sectional view of a typical example used as an electric furnace is outlined in FIG. The electric furnace 1 is of a closed type and is in the form of a substantially cylindrical container. The electric furnace 1 is provided with three electrodes 2 and three or more raw material charging devices 3 through the upper wall. During the refining process, each of the electrodes 2 is held with its tip fitted in a coke layer 11 charged on a slag layer 8 formed on a refined metal layer 9. On the other hand, the raw material charging device 3 is composed of a hopper 3a provided at the upper end and a chute 3b provided below the hopper 3a so that the raw material 12 is sequentially charged onto the coke layer 11 during the refining process. ing. Further, in FIG. 1, the side wall 4 a of the electric furnace 1
A metal outlet 5 is provided in the lower part of the, and a slag outlet 6 is provided at a position higher than the metal outlet 5 on the side wall on the opposite side. Furthermore, at the upper wall end of the electric furnace 1,
A gas outlet 7 is provided for taking out the gas generated in the refining process.

In the present invention, the kind of metal to be refined is not particularly limited. Even when refining a metal with high purity, the amount of impure metal can be suppressed by adjusting the amount of incinerated ash to be added, so that no problem usually occurs. Also, for the metal to be refined,
Alloys are included. Typically, as the metal, for example,
Pig iron is an example. Also, as an alloy, typically,
An alloy with iron, such as silicomanganese, may be used.
In metal refining, there are usually various combinations of raw materials depending on the metal to be refined. For example, raw materials ores such as iron ore, manganese ore, chromium ore and nickel ore, limestone or silica stone for adjusting slag basicity, and coke or coal as a reducing material are used as raw materials for refining ferroalloys and pig iron. In the present invention, the incineration ash is used as a part of a raw material for refining metal. Specifically, it varies depending on the metal to be refined, but it is 2 with
When used in an amount of 0% by weight or less, preferably 1 to 10% by weight, more preferably 2 to 5% by weight, the volume of impurities in the refined metal is not significantly changed, and the volume of incinerated ash can be reduced. Enough to achieve. Silicic acid content in incineration ash,
Since the basic components of CaO and MgO and the unburned carbon content act as raw materials, the silicic acid content, basic components, and
The raw material equivalent to carbon content can be reduced. Further, if the incineration ash containing a relatively large amount of the metal is selected according to the metal to be refined and used as a part of the raw material, it is also effective in improving the yield of the refined metal.

The incinerated ash may be added to the raw material for refining the metal in advance, or may be added to the molten metal or the slag on the molten metal during the refining operation. In the present invention, the temperature of molten slag in ferroalloy and pig iron refining is 1400 to 1500.
The temperature is extremely high (° C), the incineration ash is completely melted, and harmful components such as heavy metals are transferred to the network structure of silicic acid (SiO ₂ ) in the slag and become a stable vitreous substance after solidification. Secondary pollution such as runoff by water and elution into groundwater will be prevented. Further, iron and other metal components in the incinerated ash are recovered as alloy iron and pig iron, the unburned carbon content is used as a reducing agent, and the generated gas containing carbon monoxide and hydrogen is used for power generation. It is used as fuel. Furthermore,
The generated slag can be used as a road base and a construction material as in the conventional case, is the same as the standardized alloy iron and slag, and is excellent in versatility such as intended use.

[0009]

EXAMPLES The present invention will be described in more detail below with reference to examples. Example 1 Hereinafter, an example of the melting process in the electric furnace for producing silicomanganese of the present invention will be described. This example is an example of producing silicomanganese by using a three-phase submerged arc type closed electric furnace having a structure basically shown in FIG. The production capacity of this electric furnace is 65,000t / year, and the specifications of the main part are that the transformer capacity is 50,000KVA (maximum load, 28,000).
0 kw), furnace diameter, 15 m, furnace height, 6 m electrode diameter, 1.
It was 7 m. In addition, in this embodiment, the above-mentioned Table 1 is previously set.
The incineration ash having the composition shown in (1) was used as a raw material for refining. The raw materials for refining were as follows. Raw material composition Kg manganese ore 2285 silica stone 435 iron ore 145 dolomite 30 coke 400 incineration ash 100 Next, refining work was performed. The conditions for the refining work were as follows. Electric furnace load 5000-28000 KW voltage 100-200 V resistance 500-600 MΩ The quality of silico manganese and slag obtained by the refining process was examined and compared with the products obtained by normal refining. The results are shown in Tables 2 and 3 below.

[0010]

[Table 2] Table 2: Components of silicomanganese
Change in quality (%) Mn C Si P S Remaining Fe Normal product 61.4 2.15 14.2 0.067 0.009 Example 1 61.1 2.17 14.1 0.085 0.010

[0011]

[Table 3] Table 3: Change in component quality in slag Mn SiO ₂ CaO MgO Al ₂ O ₃ (%) Normal product 12.7 37.7 16.9 5.64 15.9 Example 1 12.8 37. 7 16.4 5.42 16.5 As can be seen from Tables 2 and 3 above, there was substantially no change in the component composition of the silicomanganese and slag produced in Example 1. The incinerated ash contains harmful components such as As and Hg, but since it is originally contained in a small amount, it does not adversely affect the refined metal. On the other hand, a dissolution test was carried out in order to test whether harmful components were fixed in the slag and there was no problem such as dissolution. The elution operation was carried out according to the Environmental Agency Notification No. 13 (Showa 48), and the analysis was carried out according to JIS K0102. The results of the analysis are shown in Table 4 below.

[0012]

[Table 4] Table 4: Dissolution test of slag (ppm) Hg Pb As Cd Cr CNP Not detected Not detected Not detected Not detected Not detected Not detected Not detected Note) Not detected: Indicates below the lower limit of quantification. From Table 4 above, it can be seen that harmful substances are contained in the generated slag and there is substantially no risk of problems such as elution. Therefore, when the incinerated ash is mixed and the silicomanganese is smelted, the obtained slag can be used as a construction material such as a roadbed material, a caisson material, a concrete aggregate and the like, as in a usual silicomanganese slag. Although the volume reduction effect is expected to some extent in the conventional melting treatment using only incinerated ash, the components in the incinerated ash are not effectively used. Is often required. Therefore, the effect of weight loss can hardly be expected in practice. On the other hand, in the method of the present invention, since the silicic acid component and the basic component in the incinerated ash are also used as raw materials for refining, a weight reduction effect is produced. Moreover, the volume reduction rate is 20 to 20% of the volume of the incineration ash to be treated in the simple incineration ash melting process.
On the other hand, in the method of the present invention, the volume reduction rate is about 70%, and the weight reduction rate is 60%, while the amount is about 30%.

[0013]

EFFECTS OF THE INVENTION By refining metal in an electric furnace and treating incinerated ash at the same time, the volume of incinerated ash and the volume of the incinerated ash can be reduced without substantially affecting the components of the produced metal. At the same time, the harmful substances contained in the incinerated ash can be effectively rendered harmless. Further, the components contained in the incinerated ash can be effectively used as a resource, which is excellent in economical efficiency such as operability and operating cost in the refining process.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an electric furnace that can be used to carry out the present invention.

[Explanation of symbols]

 1: Electric furnace 2: Electrode 3: Raw material charging device 5: Metal outlet port 6: Slag outlet port 7: Gas outlet port

Front Page Continuation (72) Inventor Fumio Yoshida 4 Hikari, Kashima City, Ibaraki Prefecture, inside Kashima Plant Co., Ltd. (72) Inventor Takashi Furukawa 4 Hikari, Kashima City, Ibaraki Plant, Kashima Plant

Claims (1)

[Claims] 1. A method for refining metal in an electric furnace and treating incinerated ash at the same time, wherein the incinerated ash is used as a part of a raw material used for refining metal.