JPH037724B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a molten metal by reducing a metal oxide.

(Prior art) Conventionally, methods for reducing metal oxides have generally included a blast furnace method and a method combining a direct reduction furnace and an electric furnace, but the former uses pellets or sintered ore as the metal raw material. However, it also requires strong coking coal as a carbon raw material, which imposes constraints on the raw material.Furthermore, it has the drawbacks of high equipment costs, difficult operation, and lack of flexibility in response to fluctuations in production. The latter method had the disadvantage that it required a large amount of electricity to melt the metal produced in the direct reduction furnace.

Therefore, in order to overcome the drawbacks of each of the above methods, a method that combines the smelting reduction method and the shaft furnace type direct reduction method (Japanese Patent Application Laid-open No. 120607/1983), as well as a method that combines the smelting reduction method and the fluidized bed furnace type direct reduction method, has been proposed. A method (Japanese Unexamined Patent Publication No. 174513/1983) has been proposed that combines the above methods.
In both of these methods, exhaust gas rich in CO and H ₂ (usually CO + H ₂ >80%) generated from the smelting reduction furnace is used.
is directly introduced into the reduction furnace, and the granular or powdered iron oxide in the reduction furnace is pre-reduced. The pre-reduced iron oxide is then charged into a smelting reduction furnace, where it is completely reduced and dissolved by the reducing gas generated within the furnace.

(Problems to be Solved by the Invention) By the way, in the case of a method that combines the above-mentioned smelting reduction method and shaft furnace direct reduction method, (1) the iron oxide raw material used does not have the ability to be reduced; There are various restrictions such as high price, uniform particle size, and low sulfur content, so for example, easily available and inexpensive powdered ore cannot be used.

(2) In general, in the shaft furnace method, the reduction reaction is slow and the reducing gas is not fully utilized after passing through the furnace once.Therefore, in order to increase the utilization rate of the reducing gas, a portion of the gas coming out of the shaft furnace is used. needs to be recirculated. For this reason, accessory equipment such as a device for separating CO ₂ from the circulating gas and a gas compressor is required, resulting in an enormous equipment cost.

(3) Mechanically, it is necessary to operate the shaft furnace and the melting reduction furnace continuously, which is inconvenient for work.

In addition, in the case of a method that combines the smelting reduction method and the fluidized bed furnace type direct reduction method, (1) The particle size of the iron oxide must be relatively uniform in order to fluidize the iron oxide in the fluidized bed furnace. Therefore, there are restrictions on raw materials.

(2) There is a risk that raw materials such as iron oxides may adhere to each other and form clumps in the fluidized bed furnace, and to prevent this, extremely strict temperature control is required, making operation difficult. .

(3) Mechanically, it is necessary to operate the fluidized bed furnace and the melting reduction furnace continuously, which is inconvenient for work.
This invention was made in view of the above points, and aims to provide a method for producing molten metal using a smelting reduction method that can use steam coal as a carbon raw material and can be operated with a small amount of electric power.

(Means for Solving the Problems) The metal manufacturing method of the present invention includes a first smelting reduction furnace and a second smelting reduction furnace, in which a solid metal oxide is charged into the first smelting reduction furnace, and a solid metal oxide is charged into the second smelting reduction furnace. generated in the reduction furnace
A discharge gas containing CO gas and an oxygen-containing gas are blown in to heat and melt the solid metal oxide to semi-reduce it, and then the molten semi-reduced metal is taken out from the first smelting reduction furnace and loaded into the second smelting reduction furnace. The purpose is to reduce the molten semi-reduced metal by blowing hydrocarbon fuel such as coal or petroleum or carbon raw material and oxygen-containing gas into the molten semi-reduced metal to produce molten metal. be.

(Example) Hereinafter, a first example of the present invention will be described based on the drawings. FIG. 1 is a schematic diagram illustrating the apparatus and method used in the first embodiment. In the figure, 1 is a first smelting reduction furnace, 14 is a discharge port for discharge gas 8 provided at the top of the furnace 1, 12 is a charging port for iron ore 3 provided at the top of the furnace 1, and 15 is a bottom end of the furnace 1. An inlet for reducing gas 9 and pure oxygen 11 provided at , and an outlet for molten iron oxide 4 provided at the lower part of the furnace 1 are provided at 13 .
In addition, a refractory 16 protected by a water-cooled wall is fixed on the inner surface of the furnace 1, and the molten iron oxide near the furnace wall is cooled and solidified, thereby protecting the furnace wall from attack by the molten iron oxide. Protecting.

2 is a second smelting reduction furnace; 19 is a discharge port for reducing gas 9 provided at the top end of the furnace 2; 17 is a charging port for molten iron oxide 4 provided at the top of the furnace 2; and 23 is a charging port provided at the top of the furnace 2. 20 is an inlet for the coal 10 and pure oxygen gas 11 provided at the lower end of the furnace 2; 18 is an outlet for the molten pig iron 5 provided at the lower end of the furnace 2; 22 is an outlet for the molten pig iron 5; Slug 6 provided above the outlet 18
The outlet 21 is made of refractory material. 32 is a high-calorie fuel gas sent to the outside.

Next, a method for producing molten pig iron, which is an example of molten metal, will be described. In FIG. 1, a high temperature iron oxide (FexO: x≈1) molten bath of about 1600° C. (the generation process will be described later) is charged in advance into a furnace 1. Then, iron ore 3 is charged into this iron oxide molten bath. In the process in which the temperature of the iron ore 3 charged into the bath rises rapidly, Fe ₂ O ₃ , the main component of the iron ore 3, is expressed by the following formula (1).
O is dissociated by an endothermic reaction, or by CO in the reducing gas 9 blown into the furnace 1,
It is reduced to Fe ₃ O ₄ as shown in (2).

Fe ₂ O ₃ →FexO (x≒1.3) + 0 (endothermic reaction) …(1) Fe ₂ O ₃ +CO → FexO (x≒1.3) +CO ₂ (exothermic reaction) …(2) Produced by the above reaction FexO (x≒1.3)
is partly in the molten state and the rest in the solid state,
It is further reduced by the CO gas in the discharge gas 9 blown into the furnace 1, and becomes a molten iron oxide (FexO) through the reaction shown by the following equation (3).

FexO (x≒1.3) + CO → FexO (x≒1) + CO ₂ (endothermic reaction) ...(3) On the other hand, a part of the CO gas in the discharge gas 9 is expressed by the following formula
As shown in (4), it reacts with oxygen (oxygen generated in the furnace according to the above formula (1) and oxygen 11 blown into the furnace) and changes into CO ₂ .

CO+1/2・O ₂ → CO ₂ (exothermic reaction) ...(4) This reaction is an exothermic reaction, and the amount of heat required for heating the above formulas (1) and (2) and iron ore 3 is provided. .

By the way, since FexO (x≈1.3) is present in the bath, even if CO gas is blown into the bath, the reaction below (formula (5) below) hardly progresses.

FexO (x≒1) + CO → Fe + CO ₂ ... (5) Therefore, the ratio of CO to CO + CO ₂ in the discharge gas 9 exhausted from the discharge port 14 of the furnace 1 (CO/
CO + CO ₂ ) is a value approximately close to the value defined by the curve in the Fe-O-C gas equilibrium diagram (Figure 2) (for example, 20% when the discharge gas temperature is 1400°C)
become. In other words, since solids, liquids, and gases coexist in the furnace 1, complex reactions occur.
The CO/CO+CO ₂ ratio in the discharged gas 8 is the same as the Fe-O-
Point b is close to point a, which is the theoretical equilibrium point at 1400°C in the equilibrium diagram of C-based gas.

Further, the H ₂ gas blown into the furnace 1 undergoes the reactions of the following formulas (6) to (8) and turns into H ₂ O, similarly to the case of CO gas.

Fe ₂ O ₃ +H ₂ →FexO (x≒1) +H ₂ O (exothermic reaction) …(6) FexO (x≒1.3) +H ₂ →FexO (x≒1) +H ₂ O (endothermic reaction) …(7) H ₂ +1/2O ₂ →H ₂ O (exothermic reaction)...(8) By the way, in the discharge gas 8 discharged from the furnace 1,
For H ₂ + H ₂ O gas, as in the case of CO gas, FexO (x≒1.3) is present in the bath, so
It almost never progresses to the reaction shown below (formula (9) below).

Therefore, the H ₂ /H ₂ +H ₂ O ratio in the discharged gas 8 is
In the case of solid-gas, the value is approximately close to the value defined by the curve in the Fe-O-H gas equilibrium diagram (Figure 3) (for example, 20% when the discharge gas is 1400°C)
become. In the equilibrium diagram, point c indicates the equilibrium point, and point d indicates the actual value.

Thus, it was recognized that CO+H ₂ in the discharged gas 8 was extremely low, and compared to the conventional method, CO+
The chemical energy utilization efficiency of H ₂ is considerably increased. Here, to specifically describe a conventional example in which a shaft furnace is used instead of the first smelting reduction furnace 1, in the conventional method, CO+H ₂ gas discharged from the smelting reduction furnace and blown into the shaft furnace is Approximately 50% of the gas in the shaft furnace is used for reduction, and the remainder is discharged outside the furnace unused, but in the above embodiment of the present invention, the utilization rate of CO + H ₂ gas is approximately 84%. .

Next, the second smelting reduction furnace 2 is charged with the molten iron oxide 4 produced in the first furnace 1, as well as auxiliary raw materials 7 such as limestone, coal 10 and pure oxygen gas 11. is blown into it.

Here, the reaction inside the furnace 2 will be explained.

The molten iron oxide 4 in the furnace 2 is combined with CO gas (the generation process will be described later) generated in the furnace by the reactions of the following equations 9 and 10 and carbon C (present in the coal) dissolved in the bath. reduced to pure iron, i.e. pig iron5
It is taken out from the outlet 18 in a molten state.

FexO+CO→Fe+CO ₂ (exothermic reaction)...(9) FexO+C→Fe+CO&CO ₂ (endothermic reaction)...(10) Carbon C in coal 10 blown into the bath
is dissolved in the bath, a part is consumed in the reduction of iron oxide as shown in the above equation (10), and the rest is consumed in the pure oxygen gas 11 blown into the bath or in the reaction as shown in the following equation and Reacts with CO ₂ generated in equation (9) to produce CO and
Becomes _CO2 .

C+O ₂ →CO&CO ₂ (exothermic reaction)...(11) C+CO ₂ →2CO...(12) Thus, the gas generated in the furnace 2 is the discharged gas 9
and is discharged from the furnace through the discharge port 19.

By the way, CO/CO+CO ₂ in this discharged gas 9
The ratio is 0.95 or more, indicating that the proportion of CO is extremely high. The reason for this is that 4-5% of carbon C is always present in the bath of the furnace 2.

In other words, when there is only a small amount of carbon C in the bath, the CO/CO + CO ₂ ratio in the discharged gas is close to point e, as shown in the solid-gas system equilibrium diagram (Figure 4). Presumably, in the case of the present invention, the amount of carbon C in the bath is quite large, so the CO/CO + CO ₂ ratio in the discharged gas 9 is determined by the Bourdois curve (represented by the broken line) shown in the solid-gas system equilibrium diagram. The reaction occurs at point g (0.95), which is close to point f determined by C+CO ₂ →2CO).

In addition, the hydrogen H contained in the coal 10 blown into the furnace 2 reacts with FexO, C, and CO, becoming H ₂ gas and H ₂ O gas and forming part of the discharge gas 9. However, H ₂ /H ₂ + of this discharged gas 9
The H ₂ O ratio also becomes a value of 0.9 or more.

The auxiliary raw material 7 charged into the furnace 2 combines with the gangue content in the molten iron oxide 4 and the ash content and S content in the coal, becomes slag 6, and is taken out from the slag discharge port 22.

In addition, the excess fuel gas 32 taken out to the outside
Because of its extremely high CO content, it can be effectively used not only as a fuel but also as a chemical raw material.

Next, FIG. 5 is a schematic diagram showing an apparatus and method in a second embodiment of the present invention.

The difference between this second embodiment and the first embodiment is that coal 10 is also injected into the first melting reduction furnace 1 from an inlet 15.

That is, this embodiment is for a case where the heat quantity of the discharged gas 9 alone is insufficient to continue the reaction inside the furnace 1 (the amount of gas 32 taken out to the outside may be large).

Since the oxygen content in the bath in furnace 1 is extremely high,
In this example, the carbon content in the bath is close to O because the carbon C in the coal blown into the bath immediately reacts with oxygen and becomes mostly _CO2 . Therefore, the CO/CO+CO ₂ ratio in the discharged gas 8 becomes approximately the same value as in the first embodiment.

Next, FIG. 6 is a schematic diagram showing an apparatus and method in a third embodiment of the present invention.

The third embodiment differs from the second embodiment in that air 24 is used instead of pure oxygen 11 as the oxygen-containing gas blown into the first reducing and melting furnace 1. However, all the reactions in the furnace 1 are the same as in the second embodiment.

That is, the nitrogen N ₂ gas contained in the blown air 24 is heated without any reaction and then discharged as the discharge gas 8, so it is necessary to provide extra heat, and the flow rate of the discharge gas 8 is Since this increases by the amount of the nitrogen gas flow rate, there are drawbacks such as the need to increase the size of the processing equipment for the discharged gas 8. However, it has the advantage that the amount of expensive pure oxygen used is significantly reduced (1/2 to 1/4) compared to the above embodiment.

Next, FIG. 7 is a schematic diagram showing an apparatus and method according to a fourth embodiment of the present invention.

This fourth embodiment differs from the second embodiment in that the following equipment is added. That is, after the discharge gas 9 from the second melting reduction furnace 2 is passed through the heat exchanger 25, it is put into the boiler 26, cooled, and introduced into the dust remover 27. After dust is removed from the gas by a dust remover 27, the gas is pressurized by a compressor 28, passed through the heat exchanger 25 again, heated, and then blown into the first smelting reduction furnace 1 from the blowing port 15. . On the other hand, after the discharge gas 8 from the furnace 1 is introduced into the combustion chamber of the boiler 26 together with combustion air and combusted, the exhaust gas is passed through a dust remover 29, an induced blower 30, and a chimney 31 in this order into the atmosphere. I try to dissipate it into

By the way, when comparing this embodiment with each of the embodiments described above, in the embodiment described above, the discharge gas 9 from the second furnace 2 is directly blown into the first furnace 1, but in this embodiment, the discharge gas 9 is cooled, dust removed, and After applying pressure, heat the first
The air is blown into Furnace 1. Therefore, although this embodiment requires additional equipment such as a heat exchanger, it has the following advantages.

a Since the discharge gas 9 blown into the first furnace 1 contains almost no dust, various troubles caused by dust, such as the discharge port 1
Accumulation or adhesion of dust in the piping from the air outlet 9 to the air outlet 15, or blockage or wear and tear of the air outlet 15 can be prevented.

b In the above embodiment, the discharge gas 9 is not pressurized and the first
Since the gas is blown into the furnace 1, the pressure of the discharge gas 9 discharged from the second furnace 2 is kept quite high (for example, 3
Kg/cm ² G). For this reason, the second furnace becomes a type of pressure vessel, which increases the cost not only of the furnace itself but also of its ancillary equipment, and requires advanced technology to operate the furnace 2. However, in the case of this embodiment, since the discharge gas 9 is pressurized by the compressor 28, there is no need to increase the internal pressure of the second furnace 2, so that the above-mentioned drawback can be overcome.

c In this embodiment, since steam can be obtained from the boiler 26, the steam can be used to generate electric power necessary for operation, and also to drive turbines for air compressors, gas compressors, etc. for pure oxygen generators. It can be used as a driving source.

Here, the process values of the main raw materials, products, etc. used in this example will be explained in detail. In addition, graphite (C:
The main process values (values per ton of Fe in pig iron) in the simplest example using 100%) are:

(1) Raw materials charged into the first furnace and blown gas Iron oxide (Fe ₂ O ₃ ): 1505Kg, temperature 25℃ Pure oxygen gas: 186Nm ³ , temperature 25℃ Reducing gas (CO + CO ₂ ): 749Nm ³ , temperature 750℃ (2) Discharge gas from the first furnace (CO20%, CO ₂ 80
(%): 749Nm ³ , temperature 1400℃ (3) Charged raw materials and blowing gas into the second furnace Molten iron oxide: 1370Kg, temperature 1600℃ Carbon C: 764Kg, temperature 25℃ Pure oxygen gas: 480Nm ³ , temperature 25 °C (4) Amount of fuel gas sent to the outside (CO95%):
522Nm ³ , temperature 1500°C (5) Content of Fe in molten pig iron: 1000Kg Next, embodiments other than the above embodiments will be described.

B. Temperature control inside the furnace is performed by adjusting the amount of carbon and oxygen gas injected into the furnace, but if water vapor and carbon dioxide gas CO ₂ are also blown in, temperature control can be done precisely and quickly. It can be done.

(b) When pulverized coal is injected into the discharge gas 8 from the second furnace, the pulverized coal is gasified, the chemical heat content of the discharge gas 8 increases, and the temperature of the gas decreases, causing the gas to be blown into the first furnace 1. Gas at the optimum temperature can be obtained.

C. The reaction rate in the furnace can be increased by blowing a small amount of inert gas into the furnace to stir the bath.

(d) Iron oxide or coal is heated in the first furnace 1 or the second furnace 2.
Thermal efficiency can be improved by preheating with the discharge gas 8 or 9 before charging the fuel.

(e) If the oxygen gas, air, etc. blown into the furnace are preheated by the discharge gases 8 and 9, thermal efficiency will be improved.

F. By charging and adding scrap into the second furnace 2, the amount of iron tapped can be increased.

G. If oxygen gas is blown into the upper space of the first furnace 1 and the unburned gas generated from the bath is combusted, the charge in the furnace can be heated with the heat generated during the combustion.

H. An electromagnetic pump is installed in the flow path of molten iron oxide from the first furnace 1 to the second furnace 2, and the flow rate can be controlled by this pump.

In the above embodiment, oxygen gas, reducing gas, coal, etc. are blown in from the bottom of the furnace, but they may be blown in from the top of the furnace.

FIG. 8 is a schematic sectional view showing an embodiment in which the first furnace 1 and the second furnace 2 are integrally combined, and the same reference numerals are used to indicate the same constituent members as in the previous embodiment.

In the example, the auxiliary raw material is placed at the charging port 2 in the upper part of the second furnace.
3, but it may also be pulverized and blown into the furnace bottom from the inlet 15 or 20.

E. The example shows the case of continuous operation, but when batch operation is performed, the second
It is possible to decarburize hot metal and produce molten steel by injecting only pure oxygen into the furnace without injecting coal.

In the embodiment, the second furnace outlet gas is blown into the first furnace as it is, but it is also possible to preliminarily reduce the iron oxide with the discharge gas 9 of the second furnace and then introduce it into the first furnace.

Although the above example illustrates a method for producing molten pig iron from iron oxide as a raw material, the present invention can also be applied to the production of molten metal (pure chromium) from other metal oxides (for example, chromium oxide). It is applicable.

(Effects) Since the present invention has the above-described configuration, it has the following effects.

(1) Since the present invention reduces the metal oxide in a molten state also in the first furnace, there are fewer restrictions on the raw material and the cost is significantly reduced. In other words, it can be used with both powdered ore and lump ore, and there are no particular problems with the ability of the raw materials to be reduced or the adhesion of the raw materials to each other during reduction.
There are relatively few restrictions on impurities such as S content.

(2) Since the metal oxide is reduced in the molten state in the first furnace as well, the reduction reaction is much faster than in the conventional pre-reduction method in the solid state, and therefore the capacity of the furnace is small, which reduces equipment costs. is cheap.

(3) In the present invention, the reduction step is divided into two stages, in which only the preliminary reduction reaction of Fe ₂ O ₃ → Fe ₃ O ₄ → FeO occurs in the first furnace, and only the final reduction of FeO → Fe occurs in the second furnace. I'm making it happen.

Therefore, in the first reactor, the outlet gas composition is mostly CO ₂ gas based on the reaction equilibrium theory, so CO gas can be used effectively. There is no need to provide facilities for use. In addition, even if sufficient stirring is performed, the components of the outlet gas do not change, making it possible to carry out vigorous stirring and rapid dissolution and reduction reactions, making it possible to make the equipment more compact and reduce equipment costs.

(4) Since the semi-reduced metal oxide in the first furnace is also in a molten state, the first and second furnaces can be operated not only continuously but also in batches, and can also be used in emergencies and regular intervals. (5) Not only pure oxygen but also air can be used as the oxygen-containing gas.

(6) Fuel (coal, etc.) consumption is low, so running costs are low.

(7) There are few restrictions on fuel, and in addition to inexpensive steam coal, petroleum-based fuels (heavy oil, residue, etc.) can be used.

(8) Extremely low power consumption.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the apparatus and method of the first embodiment of the present invention, Fig. 2 is an equilibrium composition diagram of the gas phase of the Fe-O-C system, and Fig. 3 is a diagram of the equilibrium composition of the gas phase of the Fe-O-H system. Equilibrium composition diagram of the gas phase, FIG. 4 is an equilibrium composition and Bourdois equilibrium curve diagram of the Fe-O-C system gas phase, FIG. 5 is a schematic diagram showing the apparatus and method of the second embodiment of the present invention, FIG. 6 is a schematic diagram showing an apparatus and method according to a third embodiment of the present invention, FIG. 7 is a schematic diagram showing an apparatus and method according to a fourth embodiment of the present invention, and FIG. 8 is a schematic diagram showing an apparatus and method according to a fourth embodiment of the present invention. FIG. 5 is a schematic cross-sectional view showing a device according to a fifth embodiment. 1... First smelting reduction furnace, 2... Second smelting reduction furnace, 8, 9... Discharge gas, 10... Coal, 11...
...Oxygen gas.

Claims (1)

[Claims] 1. In the first melting reduction furnace and the second melting reduction furnace,
A solid metal oxide is charged into a first smelting reduction furnace, and a discharge gas containing CO gas and an oxygen-containing gas generated in a second smelting reduction furnace are blown into the first smelting reduction furnace, and the solid metal oxide is heated and melted to be semi-reduced. Next, the molten semi-reduced metal is taken out from the first smelting reduction furnace and charged into the second smelting reduction furnace, and a hydrocarbon fuel such as coal or petroleum or a carbon raw material and an oxygen-containing gas are added to the molten semi-reduced metal. A method for producing molten metal by smelting reduction, characterized by reducing molten semi-reduced metal by blowing in molten metal to produce molten metal. 2. The method for producing molten metal by smelting reduction according to claim 1, wherein an inert gas is appropriately blown into the first smelting reduction furnace and the second smelting reduction furnace to stir the molten contents. . 3. The melting method according to claim 1, wherein in the first or second smelting reduction furnace, an oxygen-containing gas is blown into the upper space of the furnace to cause secondary combustion of the gas generated from the bath. A method of producing molten metal by reduction. 4. Claim 1, wherein the oxygen-containing gas blown into the first smelting reduction furnace and the second smelting reduction furnace is preheated by the gas discharged from the first smelting reduction furnace or the second smelting reduction furnace. A method for producing molten metal by smelting reduction as described in .