JPH05214414A - Method for reducing ore or metal oxide at high speed - Google Patents

Abstract

PURPOSE:To provide a high speed reduction method capable of performing stable operation while preventing the local temp. lowering in the reaction space by executing high speed reduction from ore and metal oxide to molten metal in gas flow in a reaction space. CONSTITUTION:By preforming the high temp. reaction space or while forming the space in a solid packing layer in a furnace, the ore or metal oxide particles coated with carbon on the whole surface or a part, are continuously supplied into the reaction space to form the stream of the particles and in this stream, the particles are reduced while smelting to make molten metal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for smelt-reducing various ores or metal oxides at a high speed to take out a molten metal, and particularly to achieve a smelt-reduction at a high speed while preventing a temperature drop in a reaction space. It's about how you can do it. The metal in the ore or metal oxide targeted by the present invention is one that can be reduced by carbon.
Starting with e, Mn, Cr, Ni, Si, Cu and the like can be mentioned. In the following, the description will be made mainly on the technology of producing pig iron from iron ore by a blast furnace, that is, the blast furnace operation, but the present invention is not limited to such a blast furnace system reduction technology, and is provided with a device for supplying particles. Any equipment that uses a reduction facility is subject to the application technology of the present invention.

[0002]

2. Description of the Related Art In recent years, in the operation of a blast furnace, the development of technology for blowing iron oxide such as powdered ore and scale from the tuyere of the blast furnace has been promoted for the purpose of effectively utilizing an inexpensive iron source and adjusting the composition of the hot metal. There is. For example, Japanese Patent Application Laid-Open No. 1-168802 proposes a technique of blowing a mixture of mill scale and flux in pulverized coal through tuyeres for the purpose of reducing Si in the hot metal. In addition, there is a technology to blow powdery ore that is thermally crackable and difficult to reduce into the furnace from the tuyere of the blast furnace (JP-A-62-224606),
A technique for maintaining a constant charge ratio of ore and coke in the shaft portion of a blast furnace and adjusting the amount of a powdered iron source or pulverized coal blown from a tuyere according to the target amount of tapping (JP-A-64) -3
No. 6713) is also proposed.

On the other hand, it is reported that the mixed injection of fine ore and pulverized coal is advantageous for maintaining the core temperature and ensuring the air permeability in the furnace ("Iron and Steel", Vol 77, No. 1, p1609). It is called super composite injection of powdered ore and pulverized coal, and it is reported that simultaneous injection of powdered ore and pulverized coal promotes gas reduction of powdered ore in the raceway (“Materials and Process”). ， Vol.
4,1991, p1920) and so on.

[0004]

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

The present invention has been made to solve these technical problems, and its purpose is to achieve a rapid reduction of powdered ore or metal oxide particles to molten metal in an air stream in a reaction space, It is an object of the present invention to provide a high-speed reduction method capable of performing stable operation while preventing a local temperature drop in the reaction space.

[0006]

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

[0007]

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

The above-mentioned function (1) surrounds and forms the reaction space required for the particles of the supplied powdered ore or the like to be finally reduced in the flow, and the function (2) is It plays the role of a heat transfer medium for maintaining the high temperature necessary for promoting the reduction of the fine ore in the reaction space and for directly transmitting high heat to the ore by its radiation. The function (3) is a ventilation function for releasing the gas supplied into the reaction space and the exhaust gas generated in the reaction space to the outside of the system, and the function (4) is for dropping the reduced and liquefied metal product. It is a liquid passing function that is taken out from the reaction space.

Therefore, as long as each of the above functions is satisfied, the type of the material forming the solid packing layer is not limited, but, 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 can sufficiently withstand the atmospheric temperature (described later) of the reaction space.
The shape of the material is not particularly limited, but when using a lump-shaped material, it is preferable to adjust the particle size to about 40 to 100 mm in view of the functions of (3) and (4) above.

By the way, when coke is used as the packed bed, the above-mentioned functions are stably achieved, and in addition to the advantage that the service life is long despite the low material cost, the partial combustion thereof causes the reaction space to enter the reaction space. At the same time as supplying heat, maintaining the same space in a reducing atmosphere to suppress the burning of the carbon coated on the powdered ore and facilitate the rapid reduction by the coated carbon.
Even if there is molten oxide that has fallen partially unreduced, contact with coke during the dropping process has the advantage that the reduction reaction progresses further and the melt reduction efficiency of the entire process is kept high. It is the preferred material.

The reaction space is assumed to be a raceway in a blast furnace, but it is meant that the reaction space includes either a continuously formed by blowing or a preformed one. There is no particular limitation on the method of supplying the powdered ore, and a method of forming a flow of particles from the side wall of the furnace toward the core like blowing from the tuyere of the blast furnace may be used. When applying to a reduction furnace with a low height, the supply device was installed at the upper part of the furnace regardless of the supply from the side wall, and the supply was performed from above or obliquely above to below or obliquely below, and the drop due to the weight of the particles was used. It does not matter if the flow is formed.

It can be said that the ambient temperature of the reaction space is preferably as high as possible in order to carry out the preheating and smelting reduction reaction of the powder ore in a short time, but considering the heat load on the solid packed bed and the main body of the reduction furnace, etc. For example, 1300 ℃ or higher, preferably 150
The object of the present invention can be sufficiently achieved under the condition of 0 ° C or higher. Further, in the present invention, the raw material coated with carbon and supplied is
Not only the ore is meant to include not only ores but also metal oxides (for example, pre-reduced ones), but in the following, the case of ores will be taken up as a typical example for the explanation.

According to the research conducted by the inventors of the present invention, as shown in FIG. 1, the powdered ore suspended in the air stream of the high temperature atmosphere first has Fe ₂ O ₃ and Fe on its surface.
_As the reduction to _1-x O progresses, it becomes a molten state, and subsequently, the reduction proceeds at high speed by contact with the coated carbon.
Furthermore, molten iron on the surface reduced from Fe _1-X O to metallic iron may aggregate in the center one after another, and the center may be composed of molten iron and the surface may be 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 in stages the molten iron produced by being reduced on the surface of the particles and moving to the central part to form a state of being covered with iron oxide. ) Is a state in which molten iron is present on the surface of molten iron oxide (slag) (step 1), and FIG. 2 (b) is a state in which molten iron is embedded and infiltrated into molten iron oxide (step 2), FIG. 2 (c). ) Indicates the state where molten iron is incorporated into iron oxide (stage 3). The energy state (energy difference ΔF) from step 1 to step 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
The relation of ( _MS ) is as shown in the following equation (2). ΔF = γ _S + γ _MS −γ _M (2)

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

From the above, the surface of the molten powdered ore is always covered with the metal oxide even if the reduction reaction proceeds, and the reduction reaction rapidly progresses by contact with the reducing gas or solid carbon. There is expected. On the other hand, as shown in the prior art, it is also reported that the reduction is promoted by simultaneously blowing the fine ore and the pulverized coal from the tuyere, but this is due to the generation of CO and H ₂ by the pulverized coal injection. It is presumed that the position was closer to the tuyere side. On the other hand, in the present invention, since the carbon-coated powdered ore in which carbon is coated on the powdered ore is supplied, the rapid reduction of the powdered ore has been achieved more efficiently than the technique of simultaneously blowing the powdered ore and the pulverized coal. I got it.
In addition, since the reduction reaction (endothermic reaction) of the metal oxide is carried out in a distributed manner within the raceway due to the achievement of high-speed reduction, the reduction reaction takes place after reaching the inner part of the raceway as in the conventional case. It is also possible to prevent local temperature drop compared to when it was open. The method of coating the powder ore with carbon is not particularly limited, but for example, a method of contacting gas generated by carbonization of coal, gas generated by decomposition of heavy oil, etc. with powdered ore (fluidized bed Method) can be adopted. When using this method, the temperature at which the powdered ore and the gas are contacted is 4
About 100 to 800 ° C is suitable.

In the present invention, by coating an appropriate amount of carbon on the powdered ore, the carbon-coated ore is heated while flying in the space inside the raceway, and the molten iron oxide comes into contact with the solid carbon. Then, the reaction of the above formula (1) proceeds rapidly,
Fine ore is reduced to metallic iron. Although a part of the coated carbon is burned and gasified in front of the tuyere, the powdered ore can be surely 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 the furnace. As shown in FIG. 1, only carbon-coated ore is supplied at high speed. Of course, in some cases, the following supply modes as described below are also included in the technical scope of the present invention. (1) The carbon-coated ore and pulverized coal are supplied while being mixed or premixed. (2) A carbon-coated ore and an ore not coated with carbon are supplied separately or in a premixed state.

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

In the case of supplying the carbon-coated ore and the pulverized coal at high speed while mixing them, it 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 pulverized coal may be concentrically and simultaneously supplied by the lance of the structure. In this case, it is preferable to supply pulverized coal from the outside. Further, the carbon-coated ore and the pulverized coal may be separately supplied by providing a supply pipe in which the ore and the pulverized coal are alternately or grouped in the circumferential direction or the height direction of the furnace. By supplying pulverized coal at the same time (including the case of premixing), oxygen in the blast reacts with the pulverized coal and the combustion heat becomes a heat source, and at the same time, the carbon coated on the ore melts and reduces the ore. It is possible to prevent consumption other than the above. Further, the supply method shown in the above (2) is, for example, a case where a hardly reducible ore is coated with carbon and a normal (relatively easily reduced) ore is supplied without carbon coating.

By the way, as the carbon coating amount on the ore, the amount of carbon required for the metal oxide in the ore to become a molten metal entirely by the reduction reaction with carbon, and the amount of carbon gasified by the combustion reaction and the like are given. It is most preferable not to fall below the total amount in order to increase the reaction rate and reaction efficiency. Therefore, when oxygen and water vapor are supplied at the same time, the amount of carbon coating needs to take into consideration the amount consumed in the reaction with them. In the present invention, the term “coating” is meant to include both “overall coating” and “partial coating”. The particle size of the ore coated with carbon is preferably 1 mm or less, more preferably 0.1 mm or less, in consideration of reaction efficiency and the like.

In applying the method of the present invention to the operation of a blast furnace, as in the prior art, massive ores and coke are charged in layers from above the blast furnace, the carbon-coated ore blown from the raceway is smelt-reduced, and the coke is burned. The CO produced by is used for the reduction of massive ores from above the blast furnace. On the other hand, when applied to a furnace other than the blast furnace, for example, the ore is not charged into the furnace, the solid packed bed is composed only of coke, and the ore supplied at a high speed is mainly subjected to smelting reduction. In this case, effective use of CO gas generated by consumption of coke becomes a problem. This CO gas can be used as a fuel or a raw material for chemical products, but as a specific example for increasing the energy efficiency in the process, for example, the CO gas is used as a gas for preliminary reduction of powdered ore to be used as a preliminary gas. Advantageously, a reduced ore is produced and this pre-reduced ore is coated with carbon as a feedstock. In this way, the scale of the furnace itself used for smelting reduction can be made comparatively small, and the strength of the coke to be filled can also be lowered. In the future, a method that replaces the current blast furnace method or smelting reduction process. It can be expected that it can become.

[0023]

【Example】

Example 1 In order to investigate how the morphology of powdered ore blown from the tuyere of a blast furnace affects the reduction rate, a reduction test was conducted using a small electric furnace. The temperature inside the core tube of the electric furnace is 1550 ℃
Maintained at the same temperature, and mixed with reducing gas, untreated ore, carbon ore (carbon content: 14% by weight) ore and pulverized coal mixed (carbon content: 14% by weight). After dropping, the temperature was raised at high speed for reduction, and the reduction rate in each case was investigated. The relationship between the composition of the reducing gas and the reduction rate in each case is shown in FIG. 3. From these results, the following considerations were possible. (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 carbon-coated ore is about three times higher when the degree of oxidation is high and about twice higher when the degree of oxidation is lower than that of plain untreated ore. In addition, it is about 1.5 to 2 times larger than when mixed with pulverized coal. (3) The reduction rate in the case of mixed injection with pulverized coal (conventional method) is about twice as large as that of untreated ore alone when the oxidation degree of gas is large, but as the oxidation degree becomes smaller The difference decreases and becomes almost equal in pure CO gas. From the above results, it is expected that the carbon-coated ore blown into the raceway of the actual furnace will undergo a rapid reduction reaction in the air flow.

Example 2 FIG. 4 is a graph showing a comparison of the pressure loss in the lower part of the blast furnace when injecting untreated ore or carbon-coated ore, respectively.
As is clear from this result, blowing carbon ore-treated powdered ore facilitates melting of slag in the raceway area, which can suppress pressure loss increase in the lower part of the furnace and enable stable operation of the blast furnace. It was

[0025]

EFFECTS OF THE INVENTION The present invention is configured as described above, and can rapidly reduce from ores and metal oxides to molten metal in a gas stream in the reaction space, and reduce local temperature drop in the reaction space. It became possible to operate stably while preventing it.

[Brief description of 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 stepwise a process until molten iron produced by reduction is coated with iron oxide.

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

FIG. 4 is a graph showing a comparison of lower blast furnace pressure drops when untreated ore and carbon-coated ore were blown in respectively.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuya Miyagawa 1-3-1-710 Uozaki-nakacho, Higashinada-ku, Kobe (72) Inventor Isao Kobayashi 4-4-5, Midorigaoka-cho, Miki-shi (72) Inventor Inaba Shinichi 513-162 Ishimori, Kamino-cho, Kakogawa-shi

Claims (1)

[Claims] 1. A high-temperature reaction space is previously formed in a solid packed bed in a furnace, or while forming a high-temperature reaction space, particles of ore or metal oxide whose entire surface or a part is coated with carbon, The ore or metal oxide is characterized in that it is continuously supplied into the reaction space to form a stream of the particles, and the particles are melted in the stream to reduce the particles to form a molten metal. Fast reduction method.