JP2990925B2 - Method for rapid reduction of ore or metal oxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for extracting molten metal by smelting and reducing various ores or metal oxides at high speed, and more particularly to achieving smelting reduction at high speed while preventing a temperature drop in a reaction space. It is about how you can do it. The metal in the ore or metal oxide targeted in the present invention can be reduced by carbon,
e, Mn, Cr, Ni, Si, Cu and the like. In the following, description will be made mainly on a technique for producing pig iron from iron ore by a blast furnace, that is, blast furnace operation, but the present invention is not necessarily limited to such a blast furnace type reduction technique, and includes a device for supplying particles. Any equipment that uses the reduced equipment is an application technical object of the present invention.

[0002]

2. Description of the Related Art In recent blast furnace operations, there has been developed a technique of injecting iron oxide such as fine ore or scale from a blast furnace tuyere for the purpose of effectively using an inexpensive iron source and adjusting the composition of hot metal. I have. For example, Japanese Patent Application Laid-Open No. 1-168802 proposes a technique in which a mixture of pulverized coal containing mill scale and flux is blown from a tuyere for the purpose of reducing Si in hot metal. In addition, technology to inject hot or cracking fine ore from the blast furnace tuyere into the furnace (JP-A-62-224606),
Technology for maintaining a constant charging ratio of ore and coke in the shaft portion of a blast furnace and adjusting the amount of powdered iron source and pulverized coal blown from tuyeres in accordance with the target tapping amount (Japanese Patent Laid-Open No. Sho64) -3
No. 6713) has also been proposed.

[0003] On the other hand, there is a report that the mixed injection of fine ore and pulverized coal is advantageous for maintaining the core temperature and ensuring air permeability in the furnace ("Iron and Steel", Vol 77, No. 1, p1609). And reports that super-combined injection of fine ore and pulverized coal promotes gas reduction of fine ore in the raceway by simultaneously injecting fine ore and pulverized coal ("Materials and Processes"). , Vol.
4,1991, p1920).

[0004]

When fine ore is blown from a tuyere of a blast furnace, iron oxide, which is a main component of the fine ore, melts in the raceway region (reaction space) formed in front of the tuyere. An endothermic reaction of the following formula (1) proceeds with coke. FeO + C = Fe + CO-37880 kcal / kmol (1) However, when a large amount of fine ore is blown, the above
Due to the progress of the reaction of equation (1), a local temperature drop occurs at the outer periphery of the raceway (boundary with the furnace core coke layer), and the slag solidifies, and as a result, the ventilation resistance increases. This causes a phenomenon that the gas flow to the core is deteriorated.

The present invention has been made to solve such technical problems, and an object of the present invention is to achieve high-speed reduction of fine ore or metal oxide particles to molten metal in a gas stream in a reaction space. An object of the present invention is to provide a high-speed reduction method capable of performing a stable operation while preventing a local temperature decrease in a reaction space.

[0006]

The high-speed reduction method of the present invention, which has achieved the above-mentioned object, comprises forming a high-temperature reaction space in a solid packed bed in a furnace in advance or while forming the high-temperature reaction space. Ore or metal oxide particles, the entire surface or a part of which is coated with carbon, are continuously supplied into the reaction space to form a flow of the particles, and the particles are melted in this flow. The gist is that this is reduced to form a molten metal.

[0007]

FIG. 1 is a diagram for conceptually explaining the rapid reduction method according to the present invention. The solid packed bed in FIG. 1 assumes a coke layer in a blast furnace, but in the present invention, the solid packed bed is not limited to a coke bed,
Other materials may be used. That is, the packed bed in the present invention mainly has four functions: (1) formation of a reaction space, (2) heat transfer to fine ore, (3) discharge of gas, and (4) dropping of molten metal or slag. It is provided with.

The function (1) is to form a reaction space necessary for the particles of the supplied fine ore and the like to be finally reduced in the flow, and the function (2) is The ore serves as a heat transfer medium for maintaining the high temperature required to promote the reduction of the fine ore in the reaction space and for directly transmitting high heat to the ore by radiation. The function of (3) is a ventilation function for discharging the gas supplied into the reaction space and the exhaust gas generated therein to the outside of the system, and the function of (4) is to drop the reduced and liquefied product metal. This is a function of passing liquid out of the reaction space.

Therefore, as long as it fulfills each of the above functions, it does not matter what kind of material constitutes the solid packed bed. For example, in addition to coke, coal, MgO, Al ₂ O ₃ , Zr ₂
It can be said that it is preferable that O ₃ , dolomite, Mg—C, and the like also sufficiently withstand the atmospheric temperature (described later) of the reaction space.
Although there is no particular limitation on the shape of the material, when a lump-shaped material is used, it is desirable to adjust the particle size to about 40 to 100 mm from the functions of (3) and (4) above.

By the way, when coke is used as this packed bed, the above-mentioned function is stably achieved, and in addition to the advantage that the material cost is inexpensive and the service life is long, the partial combustion of the coke in the reaction space. In addition to supplying heat, the space is maintained in a reducing atmosphere to suppress burnout of the carbon coated on the fine ore, facilitating high-speed reduction with the coated carbon,
Even if there is a molten oxide that has fallen partially unreduced, it comes into contact with coke in the dropping process, so that there is the merit that the smelting reduction efficiency of the entire process is kept high, such as further progress of the reduction reaction. Preferred material.

Although the reaction space is assumed to be a raceway in a blast furnace, the reaction space includes a space continuously formed by blowing or a space formed in advance. There is no particular limitation on the method of supplying the fine ore, and a method of forming a flow of particles from the side wall of the furnace toward the core as in blowing from the tuyere of the blast furnace may be used. When applied to a reduction furnace with a low height, a supply device is installed at the furnace upper part and supplied from above or diagonally upward to downward or diagonally downward without using the supply from the side wall, and the particles fall by their own weight. The flow may be formed.

The temperature of the atmosphere in the reaction space is preferably as high as possible in order to perform the preheating and the smelting reduction reaction of the fine ore in a short time, but it is necessary to consider the heat load on the solid packed bed and the reduction furnace body. 1300 ° C or more, preferably 150
The object of the present invention can be sufficiently achieved at a temperature of 0 ° C. or higher. Further, in the present invention, the raw material coated and supplied with carbon is:
This is intended to include not only ores but also metal oxides (for example, pre-reduced ones), but in the following, the case of ores is representatively described.

According to the research conducted by the inventors of the present invention, as shown in FIG. 1, fine ore suspended in a high-temperature atmosphere is firstly changed from Fe ₂ O ₃ to Fe ₂ O ₃ around its surface.
_As the reduction to _1-xO progresses, it becomes a molten state, and subsequently, the reduction proceeds at high speed by contact with the coated carbon.
Furthermore, the molten iron on the surface reduced from Fe _1-X O to metallic iron agglomerates one after another at the center, and the center is composed of molten iron and the surface is covered with iron oxide. I understand.

The mechanism by which the above phenomenon occurs can be considered as follows. FIG. 2 is a schematic diagram showing step by step until molten iron produced by reduction at the surface portion of the particles migrates to the center and forms a state covered with iron oxide. ) Shows the state in which the molten iron exists on the surface of the molten iron oxide (slag) (step 1), and FIG. 2 (b) shows the state in which the molten iron is immersed and infiltrated into the molten iron oxide (step 2). ) Indicates the state in which the molten iron is taken into the iron oxide (step 3). The energy state (energy difference ΔF) from stage 1 to stage 3 is determined by the surface tension of molten iron (γ _M ), the surface tension of iron oxide (γ _S ), and the interfacial tension between molten iron and iron oxide ( γ
_MS ), the following equation (2) is obtained. ΔF = γ _S + γ _MS −γ _M (2)

Here, γ _S ≒ 500 dyne / cm, γ _MS ≒ 30
Since it is known that 0 dynes / cm and γ _M ≒ 1200 dynes / cm, the energy difference ΔF is clearly a negative value. Therefore, it can be seen that the state of stage 3 in which the molten iron particles are covered with the molten iron oxide is the most stable. In addition, in Step 3, the molten iron taken into the iron oxide is aggregated and spheroidized to be in a more stable state. Step 2 can also be regarded as the flow of the molten iron oxide to the surface of the molten iron, which is movement by surface tension (the so-called Marangoni effect), and the movement speed is very high.

From the above, the molten fine ore is in a state where the surface is always covered with the metal oxide even if the reduction reaction proceeds, and the reduction reaction proceeds rapidly by contact with the reducing gas or solid carbon. There is expected. On the other hand as shown in the conventional art, although reports have also been made that reduction by writing simultaneously blow the fine ore and pulverized coal from the tuyere is promoted, which is the included pulverized coal injection, CO of or H ₂ occurs It is estimated that the position was closer to the tuyere side. On the other hand, in the present invention, since the carbon-coated powder ore obtained by coating the powder ore with carbon is supplied, the high-speed reduction of the powder ore has been succeeded more efficiently compared to the technique of simultaneously injecting the powder ore and the pulverized coal. I got it.
Also, by achieving high-speed reduction, the reduction reaction (endothermic reaction) of the metal oxide is performed in a dispersed manner in the raceway, so that the reduction reaction is performed after reaching the inner part of the raceway as in the conventional case. Local temperature decrease can be prevented as compared with the case where the temperature is low. The method of coating the fine ore with carbon is not particularly limited. For example, a method of contacting the fine ore with a gas generated by dry distillation of coal or a gas generated by the decomposition of heavy oil (fluidized bed) Using a method). When this method is employed, the temperature at which the fine ore is brought into contact with the gas is 4 ° C.
About 00 to 800 ° C. is appropriate.

In the present invention, by coating the fine ore with an appropriate amount of carbon, the carbon-coated ore is heated while flying in the space in the raceway, and the molten iron oxide contacts the solid carbon. As a result, the reaction of the formula (1) proceeds rapidly,
Fine ore is reduced to metallic iron. Part of the coated carbon is burned and gasified in front of the tuyere, but fine ore can be reliably reduced by adjusting the carbon coating amount.

The present invention is characterized in that carbon-coated ore (or carbon-coated metal oxide) is supplied into a furnace, and only carbon-coated ore is supplied at high speed as shown in FIG. Needless to say, other supply modes as described below are also included in the technical scope of the present invention. (1) Carbon-coated ore and pulverized coal are supplied while being mixed or mixed in advance. (2) The carbon-coated ore and the ore not coated with carbon are supplied separately or mixed in advance.

In addition to the methods described in the above (1) and (2), oxygen and steam may be supplied simultaneously for the purpose of controlling the temperature in the reaction space. In order to smoothly drop molten metal and slag, flux (CaO, M
nO, MgO, etc.) may be mixed or supplied separately.

When the carbon-coated ore and the pulverized coal are supplied at high speed while being mixed, this can be achieved by adopting an apparatus configuration in which an independent lance for supplying the pulverized coal is separately arranged. The carbon-coated ore and the pulverized coal may be concentrically supplied simultaneously by the lance of the structure. In this case, pulverized coal is preferably supplied from the outside. Alternatively, the supply of the carbon-coated ore and the pulverized coal may be performed separately by providing a supply pipe in which the furnace is arranged alternately or in groups in the circumferential direction or the height direction. By supplying pulverized coal at the same time (including the case of premixing), the oxygen in the blast reacts with the pulverized coal, and the combustion heat serves as a heat source, and at the same time, the carbon coated on the ore melts and reduces the ore. Can be prevented. The supply method shown in the above (2) is, for example, a case where a hardly reducible ore is coated with carbon, and an ordinary (relatively easily reduced) ore is supplied without carbon coating.

The amount of carbon coating on the ore includes the amount of carbon necessary for the metal oxide in the ore to become a molten metal by a reduction reaction with carbon and the amount of carbon gasified by a combustion reaction or the like. Is most preferably not lower than the total amount in order to increase the reaction rate and the reaction efficiency. Therefore, when oxygen and water vapor are supplied at the same time, it is necessary to consider the amount consumed for the reaction with the carbon coating amount. In the present invention, the term “coating” is intended to include both “overall coating” and “partial coating”. The particle size of the ore coating the carbon is preferably 1 mm or less, and more preferably 0.1 mm or less in consideration of reaction efficiency and the like.

In applying the method of the present invention to blast furnace operation, a lump ore and coke are charged in a layered manner from above the blast furnace as in the past, and the carbon-coated ore blown from the raceway is melted and reduced, and the coke is burned. The CO generated by the blast furnace is used to reduce massive ore from above the blast furnace. On the other hand, when applied to a furnace other than a blast furnace, for example, the solid packed bed is made of only coke without charging the ore into the furnace, and mainly performs smelting reduction of ore supplied at high speed. In this case, effective utilization of CO gas generated by coke consumption becomes a problem. This CO gas can be used as a raw material for fuels and chemical products. As a specific example of increasing the energy efficiency in the process, for example, the above-mentioned CO gas is used as a gas for preliminary reduction of fine ore. Advantageously, the reduced ore is produced, and the prereduced ore is coated with carbon to provide a feedstock. In this way, the scale of the furnace itself used for smelting reduction can be made relatively small, and the strength of coke to be filled can be reduced, and in the future, a method that can replace the current blast furnace method or smelting reduction process Can be expected.

[0023]

【Example】

Example 1 A reduction test was performed using a small electric furnace in order to investigate how the form of fine ore injected from a blast furnace tuyere affects the reduction rate. The temperature inside the furnace core tube of the electric furnace is 1550 ° C
And the untreated ore, carbon-coated (carbon content: 14% by weight) fine ore, and pulverized coal mixed (carbon content: 14% by weight) together with the reducing gas. It was dropped, heated at a high speed and reduced, and the reduction rate in each case was investigated. FIG. 3 shows the relationship between the composition of the reducing gas and the reduction ratio in each case. From the results, the following can be considered. (1) The reduction rate of fine ore increases in the order of untreated ore, mixed injection with pulverized coal, and carbon-coated ore. (2) The reduction rate of the carbon-coated ore is about three times larger when the degree of oxidation is large and about twice as large when the degree of oxidation is smaller than that of the untreated ore. Also, it is about 1.5 to 2 times as large as when mixed with pulverized coal. (3) In the case of mixed injection with pulverized coal (conventional method), the reduction rate is about twice as large as that of untreated ore when the degree of oxidation of the gas is high, but as the degree of oxidation decreases, the reduction rate decreases. The difference decreases and becomes almost equal in pure CO gas. From the above results, it is expected that the carbon-coated ore injected into the raceway of the actual furnace will undergo a rapid reduction reaction in the gas stream.

Example 2 FIG. 4 is a graph showing a comparison of the blast furnace lower pressure loss when untreated ore or carbon-coated ore was injected.
As is evident from the results, the injection of carbon-coated fine ore facilitates melting of slag in the raceway area, thereby suppressing the rise in pressure loss at the lower part of the furnace and enabling stable operation of the blast furnace. Was.

[0025]

According to the present invention, the ore or metal oxide can be rapidly reduced to a molten metal in an air stream in the reaction space, and the local temperature decrease in the reaction space can be reduced. Prevention and stable operation became possible.

[Brief description of the drawings]

FIG. 1 is a diagram for conceptually explaining a rapid reduction method according to the present invention.

FIG. 2 is a schematic diagram showing step by step until molten iron produced by reduction is coated with iron oxide.

FIG. 3 is a graph showing the relationship between the composition of a reducing gas and the reduction rate in each form of fine ore.

FIG. 4 is a graph showing a comparison of the blast furnace lower pressure loss when an untreated ore and a carbon-coated ore are respectively injected.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Isao Kobayashi 4-4-5, Midorigaoka-cho, Miki-shi (72) Inventor Shinichi Inaba 513-162, Ishinomari, Kaminocho, Kakogawa-shi (56) References JP-A-63-45312 (JP) , A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C21B 5/00 C21B 11/00 C21B 13/00

Claims (1)

(57) [Claims] A high-temperature reaction space is previously formed in a solid packed bed in a furnace, or while forming the high-temperature reaction space, particles of ore or metal oxide coated with carbon on the entire surface or a part thereof, Ore or metal oxide, characterized in that the particles are continuously supplied into the reaction space to form a flow of the particles, and the particles are reduced while melting the particles in the flow to form a molten metal. Fast reduction method.