JP2001323275A - Reductant for metal refining and method for refining metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a reductant for metal refining, having reducing capability equivalent to conventional coke powder, from municipal refuse i.e., domestic refuse at a lower cost than the coke powder. SOLUTION: The characteristic of this reductant is to produce it by heating and corboniging at 500-900 deg.C a refuse solid fuel which is obtained by pressure- molding crushed, dried and nonflammables-removed municipal refuse.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reducing agent for metal refining and a method for refining metal, and more particularly to a so-called "zero emission" in which waste from one industry is used as a raw material for another industry. A metal refining reducing agent that is manufactured by carbonizing garbage solid fuel and has the same performance as coke powder that has been used as a reducing agent in metal refining. .

[0002]

2. Description of the Related Art In recent years, in electric furnace steelmaking using iron scrap as a main raw material, it has become common to increase the refining efficiency by using a large amount of oxygen, to improve the productivity of molten steel, and to reduce the unit power consumption. I have. However, the use of a large amount of oxygen puts the steel in a peroxidized state, causing a problem of deterioration in quality and an increase in cost. In order to solve this deterioration in quality, a technique of adding a reducing agent (mainly carbon-based) to the steel bath during the refining period to suppress the peroxidation state of the steel bath has been developed and has achieved results. The reducing agent used in this technology is usually a product obtained by pulverizing coke obtained by carbonizing coal, and the addition to the steel bath is performed by blowing nitrogen, argon, etc. into the steel bath as a carrier gas, Alternatively, it is performed by spraying on the surface of a steel bath. However, even with this technique, even if the deterioration of steel quality can be solved, if coke powder is used, the problem of high raw material costs and an increase in the refining costs still remains.

On the other hand, in Japan, the amount of waste generated continues to increase, and disposal of the waste has become a current social problem. Therefore, in order to reduce the amount of waste generated, it is considered necessary to circulate the waste in society, and the development of a recycling technique for various types of waste has been progressing for quite some time. Urban waste (including garbage) that the general public discharges in their daily lives
In the past, the volume was reduced by incineration, and the ash was landfilled for final disposal. Also, 8370
Focusing on thermal energy of about kJ / kg (2000 kcal / kg), the heat generated when incinerating municipal garbage may be recovered as electricity through a waste heat boiler-steam turbine process. became. That is, about 25% by mass of carbon contained in the municipal waste is reused as fuel.

The applicant of the present invention has also been interested in the recycling of municipal waste, and crushes, dries, separates incombustibles, and press-molds the municipal waste to obtain a refuse solid fuel having a predetermined shape and size. He proposes many technologies. As a result, it was expected that not only the moisture and heat per one garbage would become constant, but also the municipal garbage would be transformed into garbage solid fuel convenient for handling and transport, and its use would increase.

[0005]

However, such solid waste fuel is used only as a fuel. Therefore, it competes with other fuels, not only solid fuels such as coal and coke, but also liquid fuels such as heavy oil and kerosene, and gaseous fuels such as natural gas and city gas, to stabilize the reuse of waste at an early stage. It ’s clear that you ca n’t,
The development of applications other than fuel is eagerly awaited. In view of the above, the present applicant disclosed in Japanese Patent Application Laid-Open No. Hei 9-53085, in order to prevent the odor of the refuse solid fuel, a part of the produced refuse solid fuel was carbonized to generate carbide and carbonized gas. In addition, a technique has been proposed in which the carbonized gas is used as a fuel in a refuse drying step in the production of a solid fuel, and the carbide is added to a forming raw material as a deodorant and preservative.

The present invention uses municipal solid waste as a raw material in order to develop a further use of solid fuel for garbage, but it is cheaper than conventional coke powder and has the same reducing ability. It is an object of the present invention to provide a reducing agent and a method for refining a metal using the same.

[0007]

Means for Solving the Problems In order to achieve the above object, the inventor has already crushed, dried, and crushed municipal waste.
The intense research was carried out on the carbonization of refuse solid fuel produced by pressure molding after removing incombustibles. As a result, only by heating the refuse solid fuel at a relatively low temperature and carbonizing, it was found that the carbide was excellent in the reducing ability of the metal oxide, and that the carbide itself and the metal using the carbide were used. The refining method is the present invention.

[0008] That is, according to the present invention, 50 solid waste fuels are used.
A reducing agent for metal smelting characterized by being heated and carbonized at 0 to 900 ° C. This metal refining reducing agent preferably uses the metal as molten steel. Further, the present invention is a method for refining a metal, wherein the reducing agent for metal refining is charged into a furnace holding the molten metal during a period of refining the molten metal.

According to the present invention, even when a coke powder is used together with a large amount of oxygen in a refining furnace such as an electric furnace, it is possible to prevent the metal bath from being over-oxidized as in the case of using coke powder. As a result, the operation cost is not only lower than when coke flour is used, but also a large amount of municipal waste can be treated, thereby contributing to society.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the circumstances that led to the invention.

The reducing agent for metal refining according to the present invention uses solid waste fuel as a raw material. First, a method for producing the solid waste fuel will be described.

As shown in FIG. 1, the municipal garbage 1 discharged from homes and the like (containing about 50% by mass
Start with the water). The stored municipal garbage 1 is supplied to a hopper 10 and then crushed and removed by a crusher 2 and irons are removed by a magnetic separator 3, and then the primary crusher 4 removes the iron garbage to a length of 20 c.
m and a width of about 2 to 3 cm. After that, the water is dried to 10% by mass or less by the drier 5 and the non-combustible materials such as glass and metal are removed by using the wind separator 6.
It is crushed by the secondary crusher 7 into a size of about m square. This crushed material is continuously supplied to a molding machine 8, which is pressed into a cylinder having a size of 1.5 cm in diameter × 3 to 4 cm in length, cooled to a normal temperature by a cooling machine 9, and solidified as garbage of the product. Fuel 9
Usually, the refuse solid fuel is measured by the measuring device 10 and packed in a bag. In addition, lime (CaO) 11 may be added to the secondary crushed material for sterilization and deodorization and mixed. Further, the method for producing the solid refuse fuel is not limited to the above-described method, and may be a method of crushing refuse, removing incombustible substances, adding quicklime, causing a chemical reaction, and then forming and drying. Absent.

[0013] The solid fuel 9 can uniformly obtain municipal solid waste 1 having various components, sizes and shapes, and the content and the amount of heat and the amount of heat are kept constant. Becomes We have been studying that carbonization is performed at a high temperature (100 to 1300 ° C) such as a coke oven and without using large-scale equipment.
The present inventors have found that a heating agent at a low temperature of 00 to 900 ° C. can be used as a reducing agent that can withstand practical use in refining, and completed the present invention. In other words, by processing at a low temperature, an inexpensive reducing agent can be obtained. The device used for carbonization is shown in FIG.
As shown in FIG. 1, a rotary or swing type carbonization furnace 12 and
Fuel supply port 17 for supplying combustion fuel, air 15
It is only necessary to have a blower 13 for supplying air and a cooler 18 for cooling the obtained carbide 16. Exhaust gas generated in the carbonization furnace 12 may be introduced into a combustion furnace 14, supplied with air 15 to the combustion furnace 14, burned, and then processed by an exhaust gas treatment device (not shown) or the like.

The heating temperature of the solid waste fuel during carbonization is 50
It is 0-900 degreeC, Preferably it is 600-800 degreeC. When the heating temperature at the time of carbonization is less than 500 ° C., the carbonization of the refuse solid fuel is insufficient, so that decomposition products such as plastics and rubber are likely to remain in the carbide, and when used as a metal refining reducing agent, The amount of dust increases. Further, since the carbonization of the refuse solid fuel proceeds sufficiently at a heating temperature of 800 to 900 ° C., it is not necessary to heat at a temperature exceeding 900 ° C.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to confirm the effect of the present invention, a solid fuel produced by using the solid fuel produced by the apparatus shown in FIG. (Reducing agent for metal refining) was manufactured, and the obtained carbide was used for refining steel in an electric furnace.

The carbonization furnace is a horizontal swing type carbonization furnace 12 having a diameter of 2 m and a length of 6 m, the inner wall of which is lined with a refractory. The refuse solid fuel 9 produced by the apparatus shown in FIG. 1 using municipal refuse was continuously supplied to the furnace at a rate of 1 ton / hour, discharged for a residence time of 30 minutes, and cooled to room temperature. The heating temperature was set at three levels of 400 ° C. (Comparative Example 1), 600 ° C. (Inventive Example 1), and 800 ° C. (Inventive Example 2).

An electric furnace (not shown) used for refining
Is a direct current type having a capacity of 60 tons / batch and equipped with an oxygen gas blowing device. In the operation, iron scrap was used as the main raw material for melting, and oxygen gas was injected during the refining period from the burnt-down of scrap to tapping to promote decarburization. The amount of oxygen gas used is 10 Nm ³ /
Tons of molten steel. The operation time is 65 minutes per charge. In the operation of the electric furnace, the reducing agent produced by the above-mentioned method is added to molten steel at a rate of 6 kg / kg in the refining period.
Injected with tons of molten steel. As the carrier gas,
Nitrogen is used.

Table 1 shows the composition of the molten iron and slag obtained in these operations and the amount of dust in the exhaust gas. From Table 1, it is clear that even when the reducing agent according to the present invention is used, the composition of molten iron and slag is the same as when coke is used, the amount of dust in the exhaust gas is small, and there is no inferiority as a reducing agent. It is. That is, it can be said that the reducing agent according to the present invention is excellent as far as it can be produced at low cost. However, waste solid fuel 4
Those carbonized at 00 ° C. have a larger amount of dust in the exhaust gas than those of the conventional example and invention examples 1 and 2, indicating that they are unsuitable as a reducing agent.

[0019]

[Table 1]

In the above embodiment, the metal is molten steel and the refining furnace is an electric furnace. However, the present invention is not limited to these, and the present invention is also effective when the metal is a non-ferrous metal or the refining furnace is a converter. Needless to say.

[0021]

As described above, according to the present invention, a metal refining reducing agent which is less expensive than conventional coke powder and exhibits the same reducing ability even when using municipal waste as domestic waste as a raw material can be obtained. . Therefore, it is expected that the recycling of urban waste can be achieved at an early stage.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a process of manufacturing solid waste fuel using municipal waste as a main raw material.

FIG. 2 is a view showing an apparatus for carbonizing the refuse solid fuel of FIG. 1;

[Description of Signs] 1 Municipal waste 2 Crusher 3 Magnetic separator 4 Primary crusher 5 Dryer 6 Wind separator 7 Secondary crusher 8 Molding machine 9 Solid fuel 10 Metering machine 11 Lime (CaO) 12 Carbonization furnace 13 Blower 14 Combustion furnace 15 Air 16 Carbide (reducing agent for metal refining) 17 Fuel supply port 18 Cooler

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22B 9/10 101 C22B 9/10 101 4K014 102 102 // C21B 11/10 C21B 11/10 13/12 13 / 12 C21C 7/00 C21C 7/00 F (72) Inventor Tetsuo Yoshida 2-3-2 Uchisaiwai-cho, Chiyoda-ku, Tokyo F-term in Kawasaki Steel Corporation (reference) 4H012 HA00 KA02 4H015 AA01 AB01 BA09 BA13 BB05 CA03 CB01 4K001 DA05 FA10 HA01 4K012 CA04 CA09 4K013 EA30 4K014 CB05

Claims (3)

[Claims] 1. A reducing agent for metal refining, comprising heating and carbonizing refuse solid fuel at 500 to 900 ° C. 2. The metal refining reducing agent according to claim 1, wherein the metal is molten steel. 3. A method for refining a metal, comprising: introducing the reducing agent for metal refining according to claim 1 or 2 into a furnace holding the molten metal during a period of refining the molten metal.