JPH05287340A - Iron-making method - Google Patents

Abstract

PURPOSE:To produce a high purity molten iron having small content of impurities by using a pre-reduced iron ore as a molten state, separating gangue content, transferring it to a reduction vessel, reducing the iron oxide and producing the molten iron. CONSTITUTION:The iron ore is pre-reduced to about 15-30% reduction ratio by exhaust gas from the reduction vessel, and from the pre-reduced iron ore, the iron content is extracted at <=1400 deg.C as the molten body containing CaO-FeO as the main component. Successively, the extracted molten body is shifted to the reduction vessel and then, the gangue content is separated from the molten body. The molten body after separating the gangue content is brought into contact with the carbon-containing molten iron or is added with the carbonaceous material, and the iron-oxide in the molten body is reduced to produce the molten iron, and the obtd. molten iron is taken out from the reduction vessel, By this method, the iron-making process is eliminated and the refining process is simplified to obtain a high purity molten iron.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing molten iron of high purity by reducing iron ore.

[0002]

2. Description of the Related Art Conventionally, as a method for obtaining iron, a method of producing carbon-saturated pig iron by reduction in a blast furnace or a method of producing iron sponge by reducing iron ore in a solid state has been carried out. In the former blast furnace method, carbon in the hot metal,
Since a large amount of unnecessary and harmful impurities such as silicon and phosphorus dissolve in iron, refining becomes complicated and large-scale.

In the latter method for obtaining sponge iron, since impurities such as gangue intervening in iron ore have not been separated, it is necessary to separate impurities during molten steelmaking. Raw materials containing many impurities are practically unusable because melting steelmaking is difficult.

On the other hand, there is an invention of US Pat. No. 3,264,096 as a method of dissolving pre-reduced iron ore and then reducing it. However, since this method does not perform the operation of separating the gangue in the iron ore when the pre-reduced iron ore is melted, it cannot be reduced at a low temperature as a melt containing CaO-FeO as a main component, and many impurities are contained. As a result, there is a drawback that heat loss and melting loss of refractory material increase.

[0005]

DISCLOSURE OF THE INVENTION An object of the present invention is to use iron ore as a raw material, to which gangue separation has been applied and which has an impurity content without causing the above-mentioned theoretical problems of the conventional iron making method. It is to provide a method for producing less molten iron.

[0006]

The gist of the present invention is to provide a first step of pre-reducing iron ore with exhaust gas from a reducing container, and an iron content of 1400 from the iron ore pre-reduced in the first step. A second step of extracting as a melt containing CaO-FeO as a main component at a temperature of ℃ or less, and the melt extracted in the second step is transferred to a reducing container, at which time, gangue is separated from the melt. And a third step of bringing the melt obtained in the third step into contact with molten iron containing carbon or / and adding a carbon material to reduce iron oxide in the melt to obtain molten iron, The iron making method is characterized by comprising a fifth step of taking out the molten iron produced in the four steps from the reduction container.

[0007]

According to the conventional method, since the gangue is reduced without being separated, it has a drawback that harmful impurities such as silicon and phosphorus are excessively reduced and that impurities such as sulfur are insufficiently removed. On the other hand, the technical idea of the present invention is that by melting and extracting only the iron content in the ore, the gangue content is first separated, and reduced at a low temperature and in the state of a high refining capacity melt, It is in a place where impurities such as phosphorus and silicon are not introduced into iron by preventing reduction. The first step is a step of pre-reducing iron ore. The iron ore may be powdery or lumpy. The preliminary reduction reaction vessel is selected according to the form of the iron ore. That is, a fluidized bed or a rotary kiln is used in the case of powdery iron ore, and a rotary kiln or a shaft furnace is used in the case of lumps.

The gas generated from the reducing container is used as the reducing agent. The reduction rate is 15% or more and 30% or less. As minerals, pre-reduction up to wustite is sufficient and no higher reduction rate is required. The gas discharged from this preliminary reduction step can be recovered and used as fuel or power generation.

The second step is a step of extracting iron from the pre-reduced iron ore at a temperature of 1400 ° C. or lower as a melt containing CaO--FeO as a main component. The composition of the melt is C
aO is 15 to 50% FeO is composed mainly of 50-80%, other SiO _2, Al ₂ O _3, MgO, or the like each 10%
The following may be included.

It is advantageous to add Na ₂ O in an amount of 15% or less because the reaction can be performed at a lower temperature. Na ₂ O
The addition of is also advantageous for removing phosphorus and sulfur. Add Na ₂
It is convenient to use CO ₃ . This melt melts at a lower temperature than conventional iron-making slag, has a low viscosity, and is easy to handle. Moreover, since the reduction reaction rate is extremely high and the refining ability is large, the subsequent steps can be advantageously operated.

The CaO content used in this melt is obtained by recycling the CaO recovered from the reduction step described later. However, the shortfall will be newly added. On the other hand, the gangue component in the iron ore is separated when the melt containing CaO-FeO as the main component is produced from the pre-reduced ore. That is, as compared with wustite in the pre-reduced ore, the gangue component SiO ₂ , Al ₂ O ₃ dissolves in the melt containing CaO—FeO as the main component at a slower rate, so that it can be separated.

The temperature in this step is preferably low in order to complete the separation. If it is higher than 1400 ° C, the gangue will be dissolved at the same time. Therefore, 1400 ° C. or lower is required. If possible, the temperature is preferably 1200 ° C. or lower.
If an alkali metal carbonate such as Na ₂ CO ₃ or K ₂ CO ₃ or an alkali metal chloride such as NaCl or KCl is added as a flux in an amount of 15% or less in order to lower the operation temperature, the temperature can be further lowered. ..

The reaction vessel is a trough type or a pot type, and is provided with a heating device, a preliminary reduction ore charging port, and a melt discharge port. The container wall may be made of cast iron or a refractory material and may be cooled by water cooling or the like. Since this melt has a high erosion resistance to the refractory material, the container wall is protected by the cell lining in which the portion in contact with the container wall is solidified.

The third step is a step of transferring the melt extracted in the second step to the reduction container. At that time, undissolved iron ore gangue is separated. As an example of the separation method, there is a method in which a weir is provided in the flow path and the separation is performed by the difference in specific gravity. The gangue floats above and is dammed by the weir. On the other hand, CaO-FeO
The melt containing as a main component passes under the weir and is transferred to the reduction container.

In order to carry out the present invention efficiently,
It is important to perform the process from the second step of dissolving the pre-reduced ore to the transfer separation of this step as quickly as possible, and the time required from dissolution to separation is preferably within 1 minute. Further, the FeO content extraction in the second step and the melt transfer in this step are continuously performed. The device is gutter type, and cell-lining is used as in the second step.

The fourth step is a step of bringing the melt obtained in the third step into contact with molten iron containing carbon and adding a carbon material to reduce the iron oxide in the melt. The temperature is 1150 ° C. or higher, which is the temperature at which molten iron containing carbon serving as a reducing agent melts, 1400 ° C.
℃ or less. At high temperatures above 1400 ° C, silicon,
It is not good because excessive reduction of harmful unnecessary impurities such as phosphorus is caused, and refractory consumption and thermal loss increase.

The reducing container is charged with the melt from the transfer container through the charging port provided in the container. As a heat source, there are a type using fossil fuel and a type using electricity. FIG. 1 shows the former Example 1 using an upper-bottom blown converter type container.
2 shows Example 2 of the latter using a self-burning electrode (Zederberg electrode) arc furnace.

As the former fuel, carbon type such as coal and coke, hydrocarbon type such as petroleum and natural gas, or hydrogen type is used. The combustion improver is oxygen or oxygen enriched air. For the latter electric heating, existing heating techniques such as arc, plasma, induction heating, and direct current heating can be applied. Example 2 in FIG. 2 shows the case of three-phase AC arc heating employing a self-baking electrode.

Since the present invention has a high refining ability of a melt containing CaO-FeO as a main component and is reduced at a low temperature, it has a remarkable feature that molten iron of extremely high purity can be obtained. That is, dephosphorization and desulfurization proceed extremely, and molten iron containing almost no silicon can be obtained.

As an example, the composition of the molten iron obtained by the method of Example 1 is C3.5%, Si0.01% or less, Mn0.0.
2%, P 0.003% or less, and S 0.003% or less. Since carbon in molten iron has a high reduction rate and a sufficiently high productivity, a certain concentration or more is required, and at least 2
% Or more is required. On the other hand, the upper limit may be the saturation concentration. Within this carbon range, the carbon concentration is adjusted to a temperature required for the temperature control and the heat source for melting the additional alloy in the subsequent steel making process.

The generated gas is used as a reducing agent and fuel in the preliminary reduction process and the dissolution process. Furthermore, the surplus gas is supplied to the outside of the system for heating and power generation. The refractory material of the container shall be cell lining, like the containers used for other processes. Since it is operated at a low temperature of 1400 ° C or less, heat loss is small, and the material can be cast iron or refractory. This process is a low temperature operation, but since it is liquid phase reduction, it has high productivity.
Therefore, pretreatment such as agglomeration of iron ore is unnecessary. On the other hand, CaO that precipitates with the progress of reduction is recovered and returned to the FeO melting step.

The fifth step is a step of taking out the molten iron produced in the fourth step from the reduction container. In this case, a batch process employing the same method as a normal steelmaking furnace is easy. It may be tilted like a converter or may be taken out from the bottom like an electric furnace. In addition, as a continuous type, an openable / closable hole provided in the vessel wall like a blast furnace may be used.

[0023]

According to the present invention, there is an advantage that the iron making process can be omitted and the refining process can be simplified. as a result,
Energy saving can be realized.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of the whole of the present invention when an upper bottom blowing converter type container is used in the fourth step of the present invention.

FIG. 2 is an explanatory view showing an embodiment of the entire present invention when a self-burning electrode arc furnace type container is used in the fourth step of the present invention.

[Explanation of symbols]

 1 Top-bottom blow converter type container 2 Lance 3,23 Taphole 4 Bottom blow tuyer 5,25 Slag 6,26 Hot metal 21 Self-burning electrode Arc furnace type container 22 Self-burning electrode

Claims (1)

[Claims] 1. A first step of pre-reducing iron ore with exhaust gas from a reduction vessel, and iron content of the iron ore pre-reduced in the first step at 1400 ° C.
Second step of extracting as a melt containing CaO-FeO as a main component at the following temperature, and transferring the melt extracted in the second step to a reducing container, at which time, gangue is separated from the melt. A third step, a fourth step of bringing the melt obtained in the third step into contact with molten iron containing carbon and / or adding a carbon material to reduce iron oxide in the melt to obtain molten iron, And a fifth step of taking out the molten iron produced in the step from the reduction container.