JP4356932B2 - Method for producing carbon steel interior agglomerates for iron making - Google Patents

Description

  The present invention relates to a method for producing an agglomerated carbonaceous material for iron making, and in particular, a steel material for iron making that has a high strength and promotes a reduction reaction even when a carbon material with low softening fluidity is used. The present invention relates to a method capable of producing an interior agglomerated product.

  In a steelmaking reduction furnace, a powdered ironmaking raw material previously agglomerated in the form of particles or pellets is used from the viewpoints of handleability and operability. In order to produce reduced iron by directly reducing iron ore, iron oxide raw materials such as iron ore are used as the main raw material, and carbonaceous materials and the like are blended as a reducing agent.

  As a method for producing an agglomerate mainly composed of iron ore (iron oxide raw material) and carbonaceous material, Patent Document 1 discloses a method for producing a high-strength agglomerate without adding a binder or the like. Has been. Specifically, coke powder is mixed with iron-containing fine powder generated from a steel mill or the like to make a certain amount of moisture, the mixture is agglomerated by extrusion molding, and corners of the agglomerate are removed with a drum machine, A method of charging in a mold furnace and heating and firing is shown. However, in this method, the operation becomes complicated, for example, it is necessary to adjust moisture and keep the temperature inside the vertical furnace constant.

  Patent Document 2 is obtained by using ferric oxide and a carbon-containing powder as a compacted compact that is used in a solid reduction firing reduction furnace such as a rotary hearth type reduction furnace. Thus, it has been shown to produce those having a porosity of 40% or more. Specifically, a method of extruding a raw material mixture containing moisture from a through-hole mold installed on a metal plate with a pushing roller is shown. Further, Patent Document 3 includes a mixture of powdered iron and carbon as an agglomerated material that can reduce the reduction time of the fine ore in the agglomerated material and further reduce the melting time of the reduced iron after the reduction. In this case, the bulk density is a certain value or more.

  However, agglomerates with high bulk density and high porosity like the techniques shown in Patent Document 2 and Patent Document 3 are considered difficult to apply when high strength is required such as in a blast furnace. .

In Patent Document 4, when producing a high-strength agglomerate by mixing and pressing the powdered iron ore and the carbonaceous material, if the thermoplasticity of the carbonaceous material is used, the density and reducibility are high. It has been shown that greatly improved carbonaceous agglomerates can be obtained. However, in this technique, the carbon material is limited to caking coal with high softening fluidity, and the type of carbon material to be used is limited.
Japanese Patent Laid-Open No. 9-41047 JP 2003-89813 A JP 11-92833 A JP 2001-294944 A

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an iron-making carbonaceous material-incorporated lump that has a high strength and promotes a reduction reaction at the time of ironmaking, even when using a carbonized material with low softening fluidity. The object is to provide a method by which chemical compounds can be produced.

The method for producing an agglomerate for a carbonaceous material for iron making according to the present invention is a composition for agglomeration including an iron oxide raw material and a carbonaceous material, wherein the ratio (mass ratio) of the iron oxide raw material and the carbonaceous material is expressed by the following formula: After mixing the agglomeration composition adjusted to the range of (1), it is characterized in that it is extruded while being deaerated under heating. For production, it is preferable that the atmospheric pressure during extrusion molding is 0.02 to 0.2 atm.
Iron oxide raw material: Carbonaceous material = 85-75: 15-25 (1)

  According to the present invention, by such a production method, the plasticity of the carbon material is sufficiently expressed during extrusion molding, and the carbon material is molded well, and a high-strength agglomerated product is obtained. In order to effectively develop the plasticity of the carbon material, the carbon material at a temperature lower than the softening start temperature (hereinafter, “softening start temperature” means the softening start temperature of the carbon material) and the maximum fluidity temperature of the carbon material ( In the following, “the maximum fluidity temperature” means the maximum fluidity temperature of the carbonaceous material) and the iron oxide raw material at a temperature equal to or higher than that is mixed, and the mixture (the agglomerating composition) is above the maximum fluidity temperature. And then extruding while degassing under heating as described above.

  In order to sufficiently mix the agglomeration composition in a solid or semi-solid state, the carbonaceous material at a temperature lower than the maximum fluidity temperature and the iron oxide raw material are mixed, and the mixture (agglomerated composition) Is effective when the mixture is mixed in a state where the temperature is less than the maximum fluidity temperature, and then the mixture is heated to a temperature higher than the maximum fluidity temperature by a screw type extruder having a heating mechanism and deaerated. It is.

  The softening start temperature and the maximum fluidity temperature are temperatures measured with a Gieseler plastometer based on the method of JIS M8801.

  The method of the present invention is also a method capable of producing a high-strength carbonaceous material-incorporated agglomerate for iron making using coal having a maximum fluidity of 2.5 or less as the carbon material.

  According to the present invention, not only caking coal with high softening fluidity but also low softening fluidity as a carbon material, high strength and reduction reaction can be performed without adding a reducing agent separately during iron making. An agglomerated carbonaceous material agglomerated material for iron making can be produced. In addition, when a carbon material having softening fluidity is used, an agglomerate having a high iron content can be produced by reducing the amount of carbon material to be blended for strength improvement. Iron can be produced efficiently.

  In the production of a conventional carbonized material agglomerated product based on the use of caking coal with a high softening fluidity, the present inventors use a charcoal material with a low softening fluidity instead of the caking coal. However, earnest research on how to obtain an agglomerated carbonaceous material agglomerate for iron making that shows high strength and high adhesion between the iron oxide raw material and the carbonaceous material, and promotes the reduction reaction without adding a separate reducing agent during iron making. Went. As a result, the inventors have found that it is only necessary to mix an agglomeration composition containing an iron oxide raw material and a carbonaceous material and then extrude while degassing under heating, and arrived at the present invention.

  In this way, even when using a carbon material with low softening fluidity or reducing the blending rate of the carbon material, the reason why a high-strength agglomerate is obtained is to reduce the pressure of the chamber of the extruder, The melting point of the carbon material is lowered, the softening fluidity of the carbon material is increased, and it effectively acts as a plastic material. In addition, degassing results in a reduced pressure state and the voids in the molded body are reduced, and an agglomerated material with high adhesion is obtained. This is probably because of this.

  As a specific means for realizing the above method, an agglomeration composition containing an iron oxide raw material and a carbonaceous material is charged into, for example, a single-screw or twin-screw extruder, and extrusion molding is performed. There is a method in which a heating medium is heated through a chamber outer cylinder and an extrusion screw of the machine, and molding is performed while deaeration.

  The present invention is not particularly limited to the atmospheric pressure (chamber internal pressure) at the time of extrusion molding by degassing, and is molded at normal pressure by reducing the pressure from normal pressure (1 atm) as shown in FIG. An agglomerate having a higher strength than the case can be obtained, but if the atmospheric pressure of the extruder is reduced to 0.2 atm or less, more preferably 0.1 atm or less, and even more preferably 0.06 atm or less (degassing). It is preferable because the strength is remarkably increased.

  On the other hand, if the deaeration is excessive and the atmospheric pressure of the extruder is too low, the strength of the agglomerated material decreases. The reason is that the degree of vacuum is very high and the carbonaceous material is easily decomposed in a heated atmosphere, and low molecular hydrocarbons generated by the decomposition are easily released as volatile components. As a result, it is considered that the time during which the carbon material is in a softened and melted state is shortened, the carbon material acting as a plastic material is reduced, and the adhesion between the carbon material and iron oxide is reduced. In order to suppress such a phenomenon, the atmospheric pressure at the time of extrusion is preferably 0.02 atm or more, more preferably 0.03 atm or more, regardless of the type of carbonaceous material. The heating temperature at the time of molding is preferably (maximum fluidity temperature-30 ° C) to (maximum fluidity temperature + 30 ° C).

  As described above, the present invention is characterized in that a high strength agglomerate can be obtained by using a carbonaceous material as a plastic material regardless of the degree of softening fluidity. In order to express it more effectively, it is effective to raise the agglomeration composition containing the carbonaceous material to the maximum fluidity temperature or higher during molding.

  Specifically, a carbon material at a temperature lower than the softening start temperature and an iron oxide raw material at a temperature equal to or higher than the maximum fluidity temperature are mixed, and the mixture becomes equal to or higher than the maximum fluidity temperature (preferably [maximum fluidity temperature + 30 ° C.] or less), and then extrusion molding while degassing under heating as described above.

  If the carbonaceous material to be mixed is less than the softening start temperature, the generation of spatter can be suppressed when mixed with the iron oxide raw material, and the carbonaceous material is sufficiently spread over the entire iron oxide raw material, and high strength agglomeration with high adhesion. This is because a chemical compound is easily obtained. Therefore, it is preferable to suppress the carbonaceous material to be mixed below the softening start temperature even when preheating, and more preferably (softening start temperature−50 ° C.) or lower. In addition, since the temperature in a mixture becomes difficult to become uniform when the temperature of the carbon | charcoal material before mixing is too low, it is preferable to heat to about 200 degreeC or more.

  On the other hand, in order to make the temperature of the composition for agglomeration (mixture) after mixing equal to or higher than the maximum fluidity temperature, the iron oxide raw material mixed with the carbonaceous material is heated to a temperature equal to or higher than the maximum fluidity temperature. It is good to leave. The specific heating temperature depends on the preheating temperature of the carbonaceous material and the ratio of the carbonaceous material and the iron oxide raw material, but when the carbonaceous material is less than (maximum fluidity temperature −100 ° C.), the iron oxide raw material is selected. It is preferable to heat to (maximum fluidity temperature + 150 ° C.) or higher, and when the carbonaceous material is (maximum fluidity temperature−200 ° C.) or less, the iron oxide raw material is increased to (maximum fluidity temperature + 300 ° C.) or more It is preferable to heat.

  In this way, the iron oxide raw material and charcoal material that have been heated in advance are mixed, and the mixture is brought to the maximum fluidity temperature or more, and the mixture at the temperature is charged into the extruder, and the temperature above the maximum fluidity temperature is introduced. It is only necessary to perform extrusion forming under deaeration while maintaining the temperature.

  As described above, when the carbonaceous material and the iron oxide raw material having a temperature higher than the maximum fluidity temperature are mixed, a phenomenon may occur in which the carbonaceous material locally melts and further rises in temperature and resolidifies. If it does so, the carbonaceous material which acts as a plastic material may reduce.

  In order to suppress such a phenomenon and to make the carbonaceous material sufficiently act as a plastic material, the carbonaceous material at a temperature lower than the maximum fluidity temperature and the iron oxide raw material are mixed, and the mixture (the agglomerating composition) is mixed. ) Is below the maximum fluidity temperature, and during the subsequent molding process, the temperature of the carbonaceous material is increased to the maximum fluidity temperature or higher (preferably the maximum fluidity temperature + 30 ° C. or less). Is recommended. In particular, if the extruder is of the screw type and has a heating mechanism such as passing through the chamber outer cylinder of the extruder and the extrusion screw, it will be heated by the strong kneading action of the screw. Since the efficiency is improved, the temperature can be sufficiently increased even at the molding stage.

  The temperature of the iron oxide raw material before mixing with the carbonaceous material is not particularly limited, and is preheated in a range where the temperature of the mixture (composition composition) is less than the maximum fluidity temperature when mixed with the carbonaceous material. May be.

  If such a method is adopted, the carbonaceous material is mixed at a temperature lower than the maximum fluidity temperature, so that the carbonaceous material is easily dispersed uniformly in a solid state or a semi-solid state. As a result, as shown in FIG. Even if the blending ratio is reduced, a high-strength agglomerated product can be obtained.

  The method of the present invention is more effective when producing a coal agglomerate for iron making using coal having a maximum fluidity of 2.5 or less as the carbon material, and the maximum fluidity is This is more effective when coal is used that is 1.5 or less, and that does not exhibit fluidity and cannot measure the maximum fluidity. As described above, in the method of the present invention, coal having low softening fluidity or not shown can also be used as the carbon material, so that the range of usable carbon material types is expanded.

  As the carbon material, those in a solid state at room temperature to 250 ° C. are used, but as described above, various kinds of materials can be used regardless of the presence or absence of fluidity, and powder having a size of about 0.01 to 0.50 mm. Can be used.

As the iron oxide raw material, blast furnace dust, converter dust, mill scale, etc. containing iron oxide as a main component can be used in addition to iron ore generally used as a raw material for iron making. Various types of iron ores can be used. For example, hematite (hematite: Fe ₂ O ₃ ), magnetite (magnetite: Fe ₃ O ₄ ), goethite (Fe ₂ O ₃ .H ₂ O), etc. Dolomite ore may be used as a limonite-based ore containing a large amount of Mg or a MgO-containing substance. Also, maramamba ore with low sinterability can be used. As these iron oxide raw materials, powdery ones having a size of 0.01 to 0.50 mm are preferably used from the viewpoint of ensuring strength and easy mixing.

In the present invention, it is assumed that the ratio (mass ratio) of the carbonaceous material and the iron oxide raw material contained in the agglomeration composition satisfies the following range. This is because if the ratio of the iron oxide raw material is too small, the iron content in the agglomerated material is reduced, which causes a decrease in the productivity of the blast furnace, and also causes problems such as insufficient strength of the agglomerated material. On the other hand, if the iron oxide raw material becomes excessive and the amount of the carbon material is too small, not only the effect of the carbon material is not sufficiently exhibited, but also the reduction reaction at the time of iron making is hardly promoted.
Iron oxide raw material: Carbonaceous material = 85-75: 15-25 (1)

  As a forming method, in the following example, the extruded continuous molded product is cut to obtain a cylindrical agglomerate, but the shape of the agglomerated mineral is not limited to this, and after the continuous molded product is cut Further, it can be formed into various shapes such as a spherical shape and a gravel shape by further press molding. In addition, when manufacturing an agglomerated material, you may add limestone etc. as needed.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. It is also possible to implement, and they are all included in the technical scope of the present invention.

<Example 1>
Powdered iron ore heated to about 750 ° C (pulverized to a particle size of about 0.5 mm or less) into powdered coal of the properties shown in Table 1 preheated to about 200 ° C (pulverized to a particle size of about 0.5 mm or less) Are mixed in a mass ratio of coal (charcoal material): iron ore = 20: 80, put into a high-speed mixer kept at 250 ° C., and stirred and mixed (the temperature of the mixture is 450). C), the mixture was charged into a screw-type twin-screw extruder, and a circular shape with a diameter of 30 mm under conditions of a molding temperature: 450 ° C. and a molding pressure (linear pressure): 2.0 to 2.9 t / cm. Is continuously extruded using a molding die (cutting die), and a cylindrical continuous molded body having a diameter of 30 mm is cut at a length of 30 mm to obtain a cylindrical agglomerate having a diameter of 30 mm and a height of 30 mm. It was. As shown in Table 1, the molding temperature 450 ° C. is a temperature close to the maximum fluidity temperature between the softening start temperature and the solidification temperature of the caking coal A and caking coal B, and it is easy to mold at that temperature. Can be formed into a high-strength agglomerated material.

  And as shown in Table 2, the agglomerate was manufactured by changing the kind of coal and the atmospheric pressure (chamber internal pressure) at the time of extrusion molding, and the strength of the obtained agglomerate was measured.

  The strength of the agglomerated material was evaluated by the crushing strength measured according to ISO 4700. Specifically, the crushing strength was measured by applying a load to the central part of the circular surface of the cylindrical molded body. The measured values are shown in Table 2. In addition, the numerical value in Table 2 shows crushing strength (unit: N).

  Table 1 shows the maximum fluidity, the softening start temperature, the maximum fluidity temperature, and the solidification temperature measured with a Gieseler plastometer by the method of JIS M8801 as an index of the softening fluidity of each coal. The higher the maximum fluidity, the higher the softening fluidity, and the caking coal A is a coal having a high softening fluidity that has been used conventionally. In the present Example, the intensity | strength of the agglomerate using this caking coal A is made into the reference value of intensity | strength (FIGS. 1-3 mentioned later). As shown in Table 1, the caking coal B has a softening fluidity smaller than that of the caking coal A, and the general coal C has softening fluidity even at high temperatures, unlike the caking coal A and caking coal B. It is not shown and remains in a powder form and is regarded as a coal that is not preferable for the production of agglomerates. “A + C” shown in Table 2 below is a mixture of the caking coal A and steaming coal C at 60:40 (mass ratio).

  FIG. 1 is a graph showing the relationship between the type of coal, the atmospheric pressure at the time of extrusion molding, and the strength of the agglomerated material. The data in Table 2 is organized. The strength of each agglomerated material is a relative value based on the strength of the agglomerated material obtained by mixing caking coal A and iron ore at a ratio of 20:80 (mass ratio) (◯ shown in FIG. 1). (Hereinafter, the same applies to FIGS. 2 and 3).

  From FIG. 1, when the molding pressure (mechanical pressure) at the time of extrusion molding is constant, if the atmospheric pressure at the time of extrusion molding is lowered, the molding is carried out at normal pressure when any kind of coal is used. It can be seen that a higher strength can be obtained.

  In particular, if the atmospheric pressure at the time of extrusion molding is degassed to 0.2 atm or less, and further to 0.08 atm or less, caking coal B having a low softening fluidity and the caking coal A and softening fluidity are provided. It can be seen that an agglomerate having a strength level almost equal to that obtained when molded at normal pressure using caking coal A with good softening fluidity can be obtained even when a mixture of non-general coal C is used.

  However, as is apparent from FIG. 1, when any type of coal is used, when the atmospheric pressure is less than about 0.03 atm, the strength of the agglomerates tends to decrease. It was confirmed that the strength reduction of the agglomerated material was remarkable when caking coal B was used and when (A + C) was used.

<Example 2>
Using caking coal B as a carbon material, changing the addition rate of caking coal B (mass% of caking coal B with respect to the sum of caking coal B and iron ore) and the atmospheric pressure during extrusion molding, An agglomerated material was produced in the same manner as in Example 1, and the strength of the obtained agglomerated material was measured. For comparison, the same experiment was performed when caking coal A was used as the charcoal material. The results are shown in Table 3. “Pressurization” in Table 3 is formed by mixing at 400 ° C. and then heating to 450 ° C. as shown in FIG. 3 of Example 3 described later. Numerical values in Table 3 indicate crushing strength (unit: N).

  FIG. 2 is a graph showing the relationship between the carbon material addition rate, the atmospheric pressure during extrusion molding, and the strength of the agglomerated material, and the data shown in Table 3 is organized. From FIG. 2, it can be seen that by molding while degassing, a product having almost the same level of strength as that obtained by molding with caking coal A at normal pressure can be obtained. Moreover, when using the same kind of carbonaceous material (caking coal B), by molding while degassing, the same level of strength as when molding at normal pressure can be produced with less carbonaceous material. And there is no need to increase the amount of charcoal to ensure strength.

<Example 3>
Using caking coal B having a maximum fluidity temperature of 450 ° C., the blending ratio of caking coal B is changed, and the agglomerates are produced by changing the production conditions as shown in (A) or (B) below. Then, the strength of the obtained agglomerated material was measured. The results are shown in FIG. 3 as the relationship between the coal addition rate and production conditions, and the strength of the agglomerated material.
(A) Manufacture under the same conditions as in Example 1.
(However, chamber internal pressure is 0.06 atm)
(B) The caking coal B is heated to about 200 ° C. regardless of the addition rate, while the iron ore is heated to 750 ° C. so that the mixing instrument temperature becomes 400 ° C. after mixing with the caking coal. After mixing these at 400 ° C., extrusion molding is performed at 450 ° C. (instrument temperature) while deaeration so that the atmospheric pressure is 0.06 atm.

  As shown in FIG. 3, when the mixing ratio of coal is the same, if iron ore and coal are mixed at a temperature lower than the maximum fluidity temperature, a lump with a higher strength than when mixing and forming at or above the maximum fluidity temperature. An obtained compound is obtained, and it is understood that this tendency becomes clear as the blending ratio of caking coal B decreases. Moreover, when obtaining the agglomerate of the same level, if the coal is mixed at a temperature lower than the molding temperature, the blending ratio of coal can be suppressed.

It is the graph which showed the influence which the kind of coal and the atmospheric pressure at the time of extrusion molding (chamber internal pressure) exert on the intensity | strength of an agglomerate. It is the graph which showed the influence which the coal compounding rate and the atmospheric pressure at the time of extrusion molding (chamber internal pressure) exert on the intensity | strength of an agglomerate. It is the graph which showed the influence which a coal compounding rate and manufacturing conditions have on the intensity | strength of an agglomerate.

Claims (5)

A composition for agglomeration comprising one or more iron oxide raw materials and carbon materials selected from the group consisting of iron ore, blast furnace dust, converter dust and mill scale , wherein the ratio of the iron oxide raw materials and carbon materials ( A method for producing an agglomerated carbonaceous material-incorporated agglomerate for iron making, comprising mixing an agglomeration composition having a mass ratio adjusted to the range of the following formula (1) and then extruding while degassing under heating: .
Iron oxide raw material: Carbonaceous material = 85-75: 15-25 (1)   The manufacturing method of Claim 1 which makes atmospheric pressure at the time of the said extrusion molding 0.02-0.2atm.   A carbon material at a temperature lower than a softening start temperature and an iron oxide raw material at a temperature equal to or higher than the maximum fluidity temperature of the carbon material are mixed, and the mixture is mixed in a state where the mixture is equal to or higher than the maximum fluidity temperature. Or the manufacturing method of 2.   The carbonaceous material at a temperature lower than the maximum fluidity temperature and the iron oxide raw material are mixed and mixed in a state where the mixture is lower than the maximum fluidity temperature, and thereafter, a screw type extruder having a heating mechanism is used. The production method according to claim 1 or 2, wherein the mixture is extruded while being heated to the maximum fluidity temperature or higher and deaerated.   The manufacturing method according to any one of claims 1 to 4, wherein coal having a maximum fluidity of 2.5 or less is used as the carbon material.

Images