JP4797388B2 - Method for producing semi-reduced sintered ore - Google Patents

Description

  The present invention relates to a method for producing a semi-reduced sintered ore obtained by reducing a part of iron oxide used as a blast furnace raw material by using a sintering process.

  Conventionally, as a blast furnace raw material, a sintered ore obtained by sintering after mixing granulated iron ore which is a sintering raw material, a solvent medium (subsidiary raw material), a powdered coal material, etc., is used. .

  With regard to such sintered ore, conventionally, adjusting the raw material blending and granulation process to improve air permeability, adhering powder coke to the surface of the pseudo particles to improve combustibility, Various attempts have been made to improve the fuel efficiency by adjusting the structure of the pseudo particles.

  In particular, semi-reduced sintered ore that can compensate for part of the reduction reaction conventionally performed in the blast furnace by the sintering reaction process and can reduce the carbon intensity in the sintering and the total blast furnace is attracting attention. For example, in Patent Document 1, powdered coke and anthracite are blended and granulated into powdered ore to form an inner layer, and powdered ore, auxiliary materials, powdered coal and anthracite are mixed and coated, and two-layered pseudo particles are formed as an outer layer. A technology is disclosed in which the pseudo particles are mixed and granulated as a part of the sintering raw material, and then sintered with a sintering machine to produce a sintered ore. A portion of the sintered ore is reduced by direct reduction of the melt produced from the slag and the solid carbon in the inner layer of pulverized coal or anthracite. In this technique, after the temperature reaches 1100 ° C., the first produced melt and C of powdered coke and anthracite cause a direct reduction reaction, and metallic iron is generated in a part of the sintered ore.

  In such a semi-reduced sintered ore, the higher the reduction rate is, and at the same reduction rate, the higher the metallization rate, that is, the metal iron content rate, the greater the effect of reducing the carbon intensity.

However, in the technique of Patent Document 1, contact between iron ore and powdered coke as a carbon source may be insufficient, and a high reduction rate and metalization rate may not be obtained.
JP-A-4-210432

  The present invention has been made in view of such circumstances, and provides a method for producing a semi-reduced sintered ore that can stabilize a reaction in a sintering process and achieve a high reduction rate and a high content of metallic iron. The purpose is to do.

  In order to solve the above-mentioned problems, the present inventors have made basic studies on the reducibility of iron ore by changing the particle size of the carbon source. As a result, it was found that the particle size of the carbon source has a great influence on the reducibility of the iron ore, and there are particle size ranges suitable for the reduction of iron ore and particle sizes not suitable for the reduction of iron ore. Specifically, the particle size of the carbon source suitable for the reduction of iron ore is 45 μm or more and 125 μm or less, and in actual operation, it is sufficient that the carbon source in this particle size range is 50% by mass or more. The particle size of the carbon source that is not suitable for the reduction is less than 45 μm, and in actual operation, it was found that the carbon source in this particle size range is preferably 30% by mass or less.

This invention is made | formed based on such knowledge, and provides the following (1) and (2) .

( 1 ) Of iron ore as a sintering raw material, carbon source and secondary raw material, part of iron ore and part of carbon source, or part of iron ore, part of carbon source and part of secondary raw material A pressure-molded body is preliminarily molded by pressure, and the remainder is granulated into pseudo-particles. A carbon source as a fuel is further coated on the pseudo-particles and mixed with the above-mentioned pressure-molded body. When producing a semi-reduced sintered ore by reducing a part of iron ore with a carbon source by putting it into a kneading machine and firing it, each of the pressure-molded body and the pseudo-particles constitutes carbon. A method for producing a semi-reduced sintered ore, characterized in that, in the source, the proportion in the range of particle size of 45 μm or more and 125 μm or less is 50 mass% or more.

( 2 ) In the above ( 1 ), the ratio of particles having a particle size of less than 45 μm is 30% by mass or less in the carbon source constituting each of the pressure-molded body and the pseudo particle. A method for producing sintered ore.

  According to the present invention, the ratio of the particle size in the range of 45 μm or more and 125 μm or less suitable for the reduction of iron ore among the carbon sources constituting the pseudo particles is 50% by mass or more. The rate can be increased. In particular, with the particle size of the carbon source in the above range, among the iron ore as a sintering raw material, the carbon source and the auxiliary raw material, part of the iron ore and part of the carbonaceous material, or part of the iron ore, A part of the carbon source and a part of the auxiliary material are pre-pressed to form a pressure-molded body, and the remaining part is granulated to form a pseudo particle, and a carbon source as a fuel is further coated on the pseudo particle. Then, by adopting a method of mixing with the above-mentioned pressure-molded body, putting it into a sintering machine and firing it, the contact area between the iron ore and the carbon source is increased, and the reduction rate during the sintering process is further increased. Moreover, since the pressure-molded body is densified, it is blocked from the outside air, and oxidation of metallic iron is suppressed, so that a higher metallic iron content can be obtained.

Hereinafter, the present invention will be described in detail.
In the production of semi-reduced sintered ore, the iron ore reduction reaction is the same as in the blast furnace. The iron oxide in the iron ore reacts with carbon in carbonaceous materials such as coke represented by the formula (1) (direct reduction). And the reaction (indirect reduction) with the CO gas represented by the formula (2). Note that the CO ₂ gas generated by indirect reduction becomes CO gas by a reaction represented by the formula (3) called a solution loss reaction.
Fe ₂ O ₃ + 3 / 2C = 2Fe + 3 / 2CO ₂ (1)
Fe ₂ O ₃ + 3CO = 2Fe + 3CO ₂ (2)
CO ₂ + C = 2CO
(3)

  In these reduction reactions, indirect reduction is dominant when the temperature is 900 to 1100 ° C., and direct reduction is dominant when the temperature is 1200 ° C. or higher. In the production of the semi-reduced sintered ore, the raw material layer temperature reaches 1400 ° C., and the residence time of 1200 ° C. or more is longer than the residence time at 900 to 1100 ° C. Therefore, direct reduction is dominant. Therefore, the reduction of the sintered ore is promoted by increasing the contact area between the iron ore and the carbon source as the reducing material.

  Therefore, in the present invention, iron ore as a sintering raw material, a carbon source, and an auxiliary raw material are granulated into pseudo particles, and a carbon source as a fuel is further coated on the pseudo particles, and the resultant is put into a sintering machine. When producing a semi-reduced sintered ore by reducing a part of iron ore with a carbon source by firing, the proportion of the particle size in the range of 45 μm to 125 μm in the carbon source constituting the pseudo particles is 50 mass. % Or more.

  Such a carbon source having a particle size of 45 μm or more and 125 μm or less is suitable for reduction of iron ore. Therefore, by using 50% by mass or more of this range of carbon source, high reduction rate semi-reduction sintering is performed. It becomes possible to obtain ore. Preferably, it is 80 mass% or more.

  On the contrary, since the carbon sources constituting the pseudo particles having a particle size of less than 45 μm are not suitable for the reduction of iron ore, the carbon source in this range is preferably 30% by mass or less. More preferably, it is 20 mass% or less.

  Moreover, as long as the carbon source contains particles having a particle size of 45 μm or more and 125 μm or less in an amount of 50% by mass or more, those having a particle size of 125 μm or more may be included, and the content is inevitably 50% by mass or less. Become.

  In the present invention, the iron ore is preferably a fine iron ore having a particle size of 8 mm or less and 80% or more from the viewpoint of maintaining good reactivity. Moreover, although powder coke is suitable as a carbon source, other carbon sources, such as anthracite or dust collection powder of coke cooling equipment, can also be used. As auxiliary materials, lime-based auxiliary materials such as limestone and quicklime are used.

  The composition of the pseudo particles obtained by granulation is preferably 10 to 20 parts by mass of a carbon source as a reducing material with respect to 100 parts by mass of iron ore and auxiliary materials. The content of the auxiliary material is preferably 4 to 10 parts by mass. The pseudo particles may be a single layer or a composite layer of two or more layers. For example, it may have a two-layer structure in which an outer layer made of iron ore is formed on the outer side of an inner layer made of iron ore, auxiliary materials and carbonaceous material. Furthermore, an outermost layer made of auxiliary materials may be formed to form a three-layer structure. A carbon source as a fuel (coagulant) is coated on the outside of the pseudo particles.

  Here, if the carbon source amount of the pseudo particles is 10 to 20 parts by mass with respect to 100 parts by mass of the iron ore and the auxiliary raw material, the iron ore in the pseudo particles can be effectively reduced within this range. In addition, it is difficult to leave an unreacted carbon source. Moreover, sintering of iron ore can be appropriately advanced by setting the amount of carbon source to be covered by the pseudo particles to 1 to 4% by mass with respect to 100% by mass of iron ore and auxiliary raw materials in total.

  As the granulation method, it is preferable to use rolling granulation with a drum mixer or a disk pelletizer that has been conventionally known as a method for producing pseudo-particles that are sintering raw materials. When granulating, it is preferable to perform rolling granulation after adding an appropriate amount of water and / or binder to the raw materials and mixing them.

  As the sintering machine, it is preferable to use a downward suction type endless moving type sintering machine. The lower suction type endless moving type sintering machine has an endless moving type moving grate, and pseudo particles obtained by granulating the sintering raw material are supplied onto the moving grate so that a raw material layer is formed. It has become. An ignition furnace is provided in the moving path of the moving great, and the raw material layer is ignited and sintered when passing through the ignition furnace. A plurality of wind boxes are arranged immediately below the moving grate, and the gas above the raw material layer is sucked downward through each wind box during sintering.

  In order to further increase the reduction rate and metallization rate of iron ore, in addition to defining the particle size of the carbon source as described above, among the iron ore as the sintering raw material, the carbon source and the auxiliary raw material, iron ore Part of the stone and part of the carbonaceous material, or part of the iron ore, part of the carbon source, and part of the auxiliary material are pre-press-molded into a pressure-molded body, and the rest of these are as described above. It is preferable to granulate into pseudo particles, coat a carbon source as a fuel on the pseudo particles, mix with the pressure-molded body, and put into a sintering machine to fire. In this case, both the carbon source constituting the pseudo particles and the carbon source constituting the pressure-molded body satisfying the particle size range are used.

  In this way, iron ore and carbon source can be obtained by pressure molding part of iron ore and part of carbon source, or part of iron ore, part of carbon source carbonaceous material and part of auxiliary material. Since the contact area becomes larger due to the compaction, it is possible to further promote the reduction of the iron ore by inserting such a pressure-molded body into the sintering machine as a part of the raw material.

  In addition, since the raw material of the pressure-molded body is densified by pressurization, even when it becomes a sintered ore, the raw material is present more densely than the pseudo-particles, which is blocked from the outside air and directly reduced. Oxidation of the generated metallic iron is suppressed.

  Therefore, a higher reduction ratio and metallic iron content can be realized by introducing such a pressure-molded body together with pseudo particles into a sintering machine to produce a semi-reduced sintered ore.

  In the present invention, the pressure-molded product refers to a material that has been agglomerated by an appropriate pressure-molding means and that has a single particle crushing strength of 4 kg or more. Although the pressure molding method is not particularly limited, a method of briquetting with a briquette machine is suitable.

The composition of the pressure-molded body is preferably 10 to 20 parts by mass of the carbon source as the reducing material with respect to 100 parts by mass of the iron ore and the auxiliary raw material, similarly to the pseudo particles. The content of the auxiliary material is preferably 4 to 10 parts by mass. In addition, the pressure-molded body preferably has a width of the thinnest portion of 8 mm or more and 20 mm or less and a volume of 10 cm ³ or less. By setting it within this range, optimum air permeability can be obtained. If the size is larger than this, the air permeability tends to be excessive, and unfired portions are likely to be generated.

  Moreover, you may coat | cover the carbon source as a fuel on the outer side of a pressure molding body. In this case, the carbon source coated as the fuel is preferably 1 to 4 parts by mass with respect to 100 parts by mass in total of the iron ore and the auxiliary raw materials.

  In this case, the charging of the sintering raw material to the sintering machine may be performed after mixing the pressure-molded body and the granulated material, or when both are charged separately and the raw material layer is formed. You may make it mix. As will be described below, it is preferable that the pressure-molded body is charged separately when it is distributed. For example, as shown in FIG. 1, pseudo particles 1 that are granulated products are supplied from above by a conveying means such as a belt conveyor 9, and a charging position from a pressure molded body hopper 7 to an appropriate position of the raw material layer 2 is provided. What is necessary is just to supply the press-molding body 4 through the chute | shoot 3 which can adjust this. In addition, the code | symbol 5 is a bedding ore, 6 is a sintering pallet, 8 is the fixed_quantity | quantitative_quantity cutting device for press-molding bodies, 10 is a segregation charging wire.

  When the pressure-molded body is charged into the sintering machine, it is preferably charged into the region of the lower part 3/4 of the raw material layer of the sintering machine. In the region close to the surface of the raw material layer, the temperature during sintering is relatively low and the high temperature holding time is short. Moreover, since the air permeability is improved by inserting the pressure-molded body into this region, this tendency becomes more remarkable. As a result, the reduction reaction of the molded body ends in an insufficient state as compared with the lower layer of the packed bed.

  When using a pressure-molded body, it is preferable to make the mixing ratio of the pressure-molded body with respect to the pseudo particles charged into the sintering machine smaller than 1. When the mixing ratio is 1 or more, that is, when the pressure-molded product has the same ratio as the granulated product or a higher ratio than the granulated product, the air permeability tends to be excessive, and an unfired portion tends to occur.

The results of tests conducted to confirm the effects of the present invention will be described below.
Here, pellet feed was used as iron ore, limestone and quicklime as CaO sources were used as auxiliary materials, and powdered coke was used as a carbon source. These compositions are shown in Table 1.

  The sintering pot test was done using the said sintering raw material. As shown in Table 3, pseudo particles having a raw material composition as shown in Table 2 were prepared by changing the particle size of the powder coke (interior coke) as shown in Table 2. Each quasi-particle was coated with powdered coke on the outside so as to be 3% by mass of the charged raw material as a coagulant (exterior coke). In addition, the interior coke was sieved in advance with a particle size of less than 45 μm, 45 to 125 μm, 125 to 1000 μm, and blended at a predetermined ratio. In addition, the exterior coke was blended 1/3 of the above three particle sizes. In the sintering pot test, the raw material was pretreated under the same mixing and granulation conditions, and the raw material packed layer was 270 mm in diameter and 300 mm in height, and the suction negative pressure was 6 kPa. The test results are shown in Table 3.

  In Table 3, Comparative Example 1 is a case where all of the interior coke has a particle size of 45 μm or less, and is outside the scope of the present invention. In this case, pseudo particles were melted during firing, an unburned region was generated, and stable firing could not be performed, so that both the production rate and the reduction rate of the sintered ore were low.

  Invention Example 1 is a case where all of the interior coke has a particle size of 45 to 125 μm and is within the scope of the present invention. In this case, a relatively high production rate and reduction rate were obtained by stable firing, and it was confirmed that this range was suitable for the reduction reaction.

  Inventive Example 2 is a case where the inner coke having a mass of 45 μm or less is 20% by mass and 45 to 125 μm is 80% by mass, and is within the scope of the present invention. In this case, the firing was relatively stable, and both the productivity and the reduction rate of the sintered ore were high.

  The comparative example 2 is a case where 45 to 125 μm is 40 mass% and 125 to 1000 μm is 60 mass% as the interior coke, which is outside the scope of the present invention. In this case, since the ratio of 45 to 125 μm is low, the production rate is high, but the reduction rate is low.

  Inventive Example 3 is a case in which 45 to 125 μm is 50 mass% and 125 to 1000 μm is 50 mass% as the interior coke, and is within the scope of the present invention. In this case, firing was more stable than in Comparative Example 2, and both the production rate and the reduction rate of the sintered ore were high.

  Next, pseudo particles and a pressure-molded body were produced using the same sintering raw material, and a similar sintering pot test was performed. The compounding of the pseudo particles was the same as that of the above-mentioned Invention Example 3. As the pressure-molded body, the raw material composition shown in Table 4 was used, and the powder coke was prepared by changing the particle size of the coke as shown in Table 5. In addition, the compounding ratio of the pressure-molded body was 15% by mass in the total amount of the pseudo particles and the pressure-molded body. The test results are shown in Table 5.

  In Table 5, Comparative Example 3 is a case where all the coke in the pressure-molded product has a particle size of 45 μm or less, which is outside the scope of the present invention. In this case, the pressure molded body melted and disappeared.

  Invention Example 4 is a case where all the cokes in the pressure-molded product have a particle size of 45 to 125 μm, and are within the scope of the present invention. In this case, it was found that a relatively high reduction rate was obtained by stable firing, and that this particle size range was suitable for the reduction reaction in the same manner as the pseudo particles.

  Invention Example 5 is a case where the coke in the pressure-molded product is less than 45 μm and 20% by mass and 45 to 125 μm is 80% by mass, and is within the scope of the present invention. In this case, the reduction was relatively stable and the reduction rate was high.

  The comparative example 4 is a case where 45 to 125 μm is 40% by mass and 125 to 1000 μm is 60% by mass as coke in the press-molded body, which is outside the scope of the present invention. In this case, since the ratio of 45 to 125 μm was low, the reduction rate was low.

  Invention Example 6 is a case where the coke in the pressure-molded body is 45 to 125 μm having 50 mass% and 125 to 1000 μm having 50 mass%, and is within the scope of the present invention. In this case, the reduction rate was higher than that of Comparative Example 4.

The figure for demonstrating an example of the charging method of a sintering raw material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pseudo-particle 2 Raw material layer 3 Chute 4 Press-molded body 5 Floor covering 6 Sinter pallet 7 Press-molded body hopper 8 Press-molded body quantitative cutting device 9 Belt conveyor 10 Segregation charging wire

Claims (2)

  Among iron ore and carbon source and auxiliary materials as sintering raw materials, pressurize part of iron ore and part of carbon source, or part of iron ore, part of carbon source and part of auxiliary material in advance Molded into a pressure-molded body, the remainder of these is granulated into pseudo particles, and the pseudo-particles are further coated with a carbon source as fuel and mixed with the pressure-molded body. In producing a semi-reduced sintered ore by reducing a portion of iron ore with a carbon source by charging and firing, in each of the pressure molded body and the pseudo particle, A method for producing a semi-reduced sintered ore, characterized in that the proportion of the particle size in the range of 45 μm or more and 125 μm or less is 50 mass% or more. 2. The semi-reduced sintered ore according to claim 1 , wherein a ratio of a particle size of less than 45 μm is set to 30% by mass or less among the carbon sources constituting each of the pressure-molded body and the pseudo particles. Manufacturing method.

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