JP5971482B2 - Agglomerate production method - Google Patents

Description

  The present invention relates to a method for producing an agglomerate used as a blast furnace raw material.

  Generally, as a steelmaking raw material used in a steel factory, in addition to main raw materials such as iron ore, carbonaceous materials such as coke and auxiliary raw materials such as limestone are used in large quantities. For example, as the main raw material of the blast furnace ironmaking method, massive iron ore, sintered ore, pellets and the like are currently used, but most of them are sintered ore. The raw materials for the sintered ore include iron ore powder, sinter ore sieving powder, recovered powder such as dust and mill scale generated in steelworks, CaO-containing auxiliary raw materials such as limestone and dolomite, and quick lime. Condensation agents such as grain auxiliaries, coke powder and anthracite are used.

  Above all, for iron ore powder, high-grade iron ore with few gangues, such as hematite ore, mainly from Australia, has been used, but the fact is that such iron ore is being depleted. is there. For this reason, recently, as an alternative, the amount of high crystal hydrous ore such as pisolite ore and maramamba ore containing a large amount of crystal water is increasing. In order to use such high-crystal water-containing iron ore powder as a raw material for sintering, the use of a coagulant (powder coke or the like) serving as a heat supply source for thermal decomposition of crystal water in the iron ore powder. There was a problem that the amount had to be increased. Moreover, since water is contained as crystal water in addition to normal raw material granulation moisture, the amount of moisture brought in as raw material increases, which leads to expansion of the wet zone of the raw material packed layer in the sintering machine. There was also a problem of reducing the productivity of the sintering machine.

    Conventionally, in Patent Document 1, the iron ore containing crystallization water is reduced in advance to obtain a pre-reduced ore, and this is used as a raw material for sinter ore production. A manufacturing method is proposed. According to this conventional method, it is explained that the above-mentioned problems when using high-crystal water-containing iron ore can be solved.

Japanese Patent No. 4384698

  However, the above prior art still has the following problems. That is, in the case of the method for producing sintered ore disclosed in Patent Document 1, the calorific value due to the oxidation of the pre-reduced ore can be used as a heat source, so that the use amount of the coagulant can be reduced. However, the reaction temperature of the sintering machine itself is not lowered, and it is not possible to prevent the input of a large amount of heat and the increase in the amount of melt.

  In the technique disclosed in Patent Document 1, since iron ore is preliminarily reduced using a gas obtained by partially combusting a blast furnace gas having low reducibility, exhaust gas discharged from this process is further reduced in reducibility. Therefore, there is a big problem that it cannot be used for other purposes. That is, in the case of this prior art, it is considered that there is a big problem in using the pre-reduced ore as a raw material for producing sintered ore.

  The main object of the present invention is to propose a method capable of directly and advantageously producing an agglomerate having sufficient strength as a raw material for a blast furnace even if the iron oxide-containing raw material is fired at a low temperature.

  Another object of the present invention is to make the low oxidation degree ore as an agglomerate used as a raw material for a blast furnace, not as a raw material for producing a sintered ore, and when using this in a sintering machine, It is to wipe out the problem.

  As a result of intensive research aimed at solving the above-mentioned problems of the prior art, the inventors first reduced iron oxide ore with a high degree of oxidation to an ore with a low degree of oxidation. At this time, it was charged in a low-temperature firing furnace instead of a sintering machine and oxidized at a temperature of about 850 ° C. or lower in an oxygen-containing oxidizing atmosphere (low oxidation degree → high oxidation degree). The present invention was completed by developing a new method of producing agglomerates by a calcination reaction using the generated thermal energy.

That is, the present invention relates to a low oxidation degree iron ore having an oxidation degree xo of iron of more than 0 to 1.36, and iron composed of one or more of sintered ore, pellets, mill scale, iron dust or reduced iron powder ( and a low degree of oxidation the iron source material oxidation degree xo is greater than 0 ～1.36 of FeOxo), and mixing the formulation ingredients basicity is adjusted to 0.9 or more - shaped, then mixed - and molded The present invention proposes a method for producing agglomerated ore, characterized in that the blended raw material is calcined at a temperature of 850 ° C. or lower in a firing furnace under an oxidizing atmosphere to form agglomerated ore.

The present invention
(1) wherein a low degree of oxidation of iron ore, the use of which a high water of crystallization-containing iron ore was pre-reduced,
(2) The low-oxidation degree iron source material is a raw material having an oxidation degree of 0.5 ≦ xo ≦ 1.10 containing wustite,
(3) The firing temperature is 250 ° C. or higher.
(4) The high crystal water containing iron ore is iron ore containing crystal water of 3 mass% or more and 15 mass% or less,
(5) The high crystal water-containing iron ore is pisolite ore or maramamba ore,
Is considered to be a more preferable solution.

According to the present invention configured as described above, the following effects can be expected. For example, even if iron ore containing a lot of crystal water, if it is first reduced to an ore with a certain low oxidation degree, it is directly used for blast furnace without any treatment by a sintering machine. It can be agglomerated minerals. Therefore, even a low-quality iron ore can be used as a raw material for a blast furnace without affecting the productivity of the sintering machine. In addition, in the present invention, for the production of blast furnace raw materials, heat generated by oxidizing and generating low-oxidized iron ore and low-oxidized iron source raw materials is used, so even at a relatively low temperature, that is, low thermal energy. Since it can be fired even if it is supplied, heat energy consumption is reduced, and a high-strength blast furnace raw material can be manufactured at low cost.

It is a schematic diagram for demonstrating the outline | summary of this invention manufacturing process. It is a cross-sectional photograph of the agglomerated when fired at 900 ° C. for 30 minutes. It is a cross-sectional photograph which shows the combined state of the low oxidation degree ore before and behind baking. It is a figure which shows the relationship between the calcination temperature of an agglomerated mineral, and crushing strength. It is a graph which shows the relationship between the gas reducibility given to the oxidation degree of iron, and a calcination temperature.

Details of the configuration of the present invention will be described below. In the production method of mass Naruko according to the present invention, as a main raw material is a starting material, except that the degree of oxidation is used mainly a certain level or lower oxidation degree of iron ore, oxidation degree or less the same level sinter and pellets and mill scale, iron dust, one or more such reduced iron powder using low oxidation degree of iron source material comprising engages mixed. In particular, the use of low-oxidized iron ore is effective in that a constant quality can be stably supplied.

  For example, as an example of the low oxidation iron ore, there is a high crystal water-containing iron ore containing a large amount (3 to 15 mass%) of crystal water such as pisolite ore or maramamba ore. By charging these iron ores into a pre-reduction furnace and pre-reducing them using reducing gases such as converter gas, blast furnace gas, coke oven gas, natural gas, and liquefied petroleum gas generated at steelworks Low iron oxide ore with low crystal water content.

Next, in the present invention, the basicity (CaO / SiO ₂ ) becomes 0.9 or more by adding a CaO source such as limestone or quicklime to the low-oxidized iron ore or low-oxidized iron source material. Adjust to. In this case, if necessary, other raw materials, coke powder and the like are added and then mixed and formed (granulated). Then, a mixed material consisting of a low oxidation degree of iron ore and low oxidation degree of iron source material, etc. was prepared as described above was charged into a firing furnace at 850 ° C. below the temperature under oxidizing atmosphere Bake. After firing, sieving is performed as necessary to obtain an agglomerated ore that is a raw material ore for a blast furnace.

  What is characteristic in the present invention is that at least the low-oxidized iron ore is used as a starting material when producing agglomerated ore as a blast furnace raw material. This is because when a low-oxidized iron ore obtained by pre-reducing normal iron ore and high-crystal-water-containing iron ore at the time of firing is placed in an oxidizing atmosphere, it has a low degree of oxidation and generates oxidation heat during the reaction. This is because firing can be sufficiently performed at a relatively low temperature as compared with the conventional sintering process described below. Hereinafter, the method of the present invention will be described in more detail with reference to the drawings.

(1) Preparation of raw materials The raw materials used in the agglomerated ore production process include hematite ores of about 8 mm or less, pisolite ores (crystal water 8 mass%) that are iron ore powders containing a large amount of crystal water, and maramamba ores ( It is possible to use iron ore containing high crystal water such as crystal water (3 mass%) (hereinafter, iron ore is simply abbreviated as “ore”). However, these ores need to be pre-reduced to low-oxidation ores (pre-reduced ores) in advance.

  As described above, when the high crystal water-containing ore powder is used as a raw material for a conventional sinter ore production process, heat is required to thermally decompose the crystal water in the iron ore powder. There was a problem that the amount of the coagulant used as a source increased. In this regard, when ordinary iron ore or iron ore containing high crystal water is preliminarily reduced using a reducing gas, the iron oxide is reduced to a low-oxidized iron ore at a temperature suitable for the reduction. The present invention is a method for producing an agglomerate suitable as a raw material for a blast furnace by utilizing the oxidation heat generated when the low oxidation degree ore thus obtained is oxidized and fired.

  In addition, as a preliminary reduction furnace for reducing ore powder, a shaft furnace, a rotary kiln, a fluidized bed reduction furnace, or the like can be used. A reducing gas is introduced into the prereduction furnace to reduce the high crystalline hydrous ore powder.

  As the reducing gas, one or more gases such as converter gas, blast furnace gas, coke oven gas, natural gas, and liquefied petroleum gas can be used. These reducing gases need to be heated to a temperature required for the reduction of iron ore (usually 500 ° C. or higher), but if a high-temperature converter gas is used, the sensible heat of the gas is effectively used. This is particularly preferable. Usually, the converter gas is once used after dust removal and cooling, but in the preliminary reduction furnace, the converter dust at the time of dust removal from the converter gas can also be used as a raw material for producing low-oxidation ores. There is no need for cooling. Furthermore, since the crystal water contained in the pisolite ore or maramamba ore starts to be decomposed at around 350 ° C., the crystal water can be decomposed and removed at the same time by performing a reduction treatment at a temperature of 500 ° C. or higher. When iron ore is heated to 1200 ° C. or higher in a reducing atmosphere, it may partially melt and the particles may be fused together. Therefore, it is preferable to perform the reduction treatment at a temperature of 1200 ° C. or lower in the preliminary reduction furnace.

Meanwhile, converter gas and blast furnace gas, although CO ₂ gas concentration for CO gas concentration higher, typically, is capable of reducing the extent wustite (FeO). Therefore, when iron ore containing a large amount of crystal water, such as pisolite ore or maramamba ore, is reduced in a prereduction furnace using converter gas or blast furnace gas, the crystal water is removed, and at the same time, depending on the production conditions, some metals Although it may contain iron, it can be a low-oxidized iron ore reduced mainly to magnetite (Fe ₃ O ₄ ) and wustite.

In the present invention, the prereduction gas used in the prereduction furnace includes H ₂ concentration (H ₂ : vol.%), H ₂ O concentration (H ₂ O: vol.%), CO concentration ( . CO: vol%), and CO ₂ concentration _(CO 2:. vol When%) to, the following (1) oxidation degree is represented by the formula Xg (- used ones) is 0.8 or less. If the oxidation degree Xg (−) of the reducing gas is larger than 0.8, as shown in FIG. 5, the reduction driving force of the gas for generating at least Fe ₃ O ₄ at a firing temperature of 800 ° C. is small. Therefore, the progress of the reduction in the preliminary reduction furnace is delayed, and the productivity of the low oxidation degree ore is lowered. For this reason, the oxidation degree Xg of the reducing gas is preferably smaller than 0.8. The degree of oxidation Xg of the converter gas and blast furnace gas is usually about 0.1 to 0.6, and it can be seen that the converter gas and blast furnace gas can be suitably used as the reducing gas for the preliminary reduction furnace.
Xg (vol.%) = [(H ₂ O + CO ₂ ) / (H ₂ + H ₂ O + CO + CO ₂ )] (1)

In the present invention, in the raw material (mixed raw material) for agglomerated mineral production, a low oxidation degree ore showing an oxidation degree of iron xo (FeOxo) of more than 0 to 1.36 is, for example, 10 mass% or more, preferably 30 mass. % Or more, more preferably 40 mass% or more. Other than this low-oxidation ore, as mentioned above, low-oxidation iron source materials (0 <xo ≦ 1.36) such as sintered ore , pellets , mill scale, iron-making dust (converter dust, OG dust, etc.) the use engaged mixed. However, the mixed material is the degree of oxidation (xo): 0 <needs to be formulated to satisfy xo ≦ 1.36, is a preferred material as a raw material for low-temperature firing process to be described later. More preferably, the blended raw material is a raw material mainly composed of, for example, wustite, having an oxidation degree of 0.5 ≦ xo ≦ 1.10.

Wherein according to the present invention a low oxidation degree of iron ore and low oxidation degree of iron MinamotoGen fee further, by adding a CaO source such as limestone or burnt lime, basicity (CaO / SiO ₂₎ is 0.9 or more ingredients The blended raw material is adjusted to The reason is that the iron ore is generally not contain the CaO, the basicity of the mass Naruko manufacturing raw materials, is less than 0.9. Agglomerates produced using raw materials with such low basicity, when used as raw materials for vertical furnaces such as blast furnaces, melt at a relatively low temperature, leading to an increase in pressure loss. May occur. On the other hand, if the basicity of the raw material is increased to 0.9 or more by adding a CaO source, the influence on the melting temperature when used as a raw material of a vertical furnace is reduced, and an increase in pressure loss can be suppressed. it can. Here, as the CaO source, limestone, quicklime, converter slag containing CaO, or the like can be suitably used.

(2) Low-temperature calcination treatment Next, the low-oxidation degree iron source raw material having an oxidation degree (xo) composed of the above-described low-oxidation degree ore, iron-making dust, mill scale, etc., of 0 <FeOxo ≦ 1.36 is included in CaO source or the like quicklime, optionally further, other materials (low crystal water iron ore fines and sintered ore undersize powder recovered powder, auxiliary materials and condensed material) were mixed, which pan pelletizer or a drum mixer And then transferred to a baking facility such as a rotary kiln and baked at a temperature of 850 ° C. or lower to obtain an agglomerate having a high degree of oxidation.

  The agglomerated mineral thus obtained is sieved, and the material on the sieve is made into a product agglomerated with a particle size suitable as a blast furnace raw material, while the material under the sieve is fractionated as undersieving powder. Since this sieving powder is already in a state in which water of crystallization has been removed, it may be used as a raw material for this firing treatment process, or may be used by mixing with the sinter ore sieving powder during the production of sinter. May be.

Thus, the degree of oxidation (xo) is granulated mixture molded to the mixed material of a low degree of oxidation of iron ore and other low oxidation degree of iron source material indicating 0 super ～1.36, after which the material The agglomerates are charged and oxidized in a kiln such as a rotary kiln and heated. In this treatment, the advantage of using low-oxidation iron ore having an oxidation degree (xo) of more than 0 to 1.36 is exposed to an oxidizing high-temperature gas atmosphere in the firing facility, so Fe ₃ in the raw material O ₄ and FeO are oxidized to generate heat. The temperature of the raw material particles themselves is increased by the heat generation energy at this time, and the particles are appropriately bonded and agglomerated. In this regard, in the processing of the conventional sintering process, the sintering reaction proceeds by maintaining the temperature in the raw material layer at 1200 ° C. or higher. In the present invention, the oxidation heat generation of the low-oxidation iron source raw material particles themselves As a result, the particle temperature increases spontaneously, so that the reaction proceeds even if the ambient temperature is as low as 850 ° C. or lower.

  For low-oxidation ores, the higher the reduction rate, the greater the calorific value per unit mass during oxidation, so if the amount of low-oxidation ore used is constant, the higher the reduction rate of the low-oxidation ore, It can be said that it is preferable because the oxidation reaction proceeds rapidly. Furthermore, since the crystal water in the iron ore has been removed in the process of producing the low oxidation degree ore, it is not necessary to add heat necessary for the decomposition of the crystal water during firing (at the time of agglomeration).

On the other hand, as shown in FIG. 2, when firing a blended raw material such as the low-oxidation iron ore having an oxidation degree of 0 <xo ≦ 0.5, if the ambient temperature is raised to 900 ° C., As a result of the rapid progress of the oxidation reaction and the formation of a dense shell on the surface of the pseudoparticle, oxygen does not diffuse into the pseudoparticle, and the agglomeration reaction does not proceed sufficiently. Therefore, in the present invention, it is necessary to perform the firing of the blended raw materials such as low-oxidized iron ore at a temperature of 850 ° C. or lower, preferably 250 to 800 ° C.

  As is clear from the above description, for example, once a low-oxidation ore containing a crystallite-containing pisolite ore or maramanba ore can be agglomerated except by a sintering machine, the amount of raw material used in the blast furnace is constant. Then, it becomes possible to reduce the use ratio of the pisolite ore or maramamba ore in the sintering machine. As a result, in the operation of the sintering machine, the amount of water vapor generated from crystal water is reduced and the high temperature formed by the combustion of the coagulation material as the amount of coagulation material used for thermal decomposition of crystal water decreases. The combustion region is reduced, the formation of excessive melt is suppressed, and the pressure loss in the sintered layer is reduced. Therefore, if the suction negative pressure of the main exhaust gas suction blower of the sintering machine is kept constant, the amount of suction gas per unit time increases, and the pallet speed of the sintering machine body can be increased, resulting in the productivity of sintered ore. There is also an accompanying effect that can be improved.

In this example, first, iron ores A and B shown in Table 1 were reduced in a multistage fluidized bed. That is, 2.10 kg of iron ore A and B containing 5.0 mass% of adhering moisture was supplied to the multistage fluidized bed, and a blast furnace gas at 900 ° C. and a converter gas of 2.51 Nm ^{3 were} used as the reducing gas. The oxidation degree Xg of the reducing gas used at this time was 0.51. The composition of the reducing gas used is shown in Table 2. In addition, in order to maintain the atmospheric temperature in the fluid bed for preliminary reduction at 900 ° C. ± 50 ° C., the reducing gas was partially burned using 0.69 Nm ³ of air. The gas discharged from the fluidized bed is 3.41 Nm ³ , and CO in the exhaust gas is 4.3 vol. % Included. At this time, the obtained low oxidation degree ore, ie, the pre-reduction ores C and D, was 1.69 kg, and the reduction rate was about 30%.

(2) Analytical values of low-reduction degree pre-reduction ores C and D having different reduction ratios produced by pre-reducing iron ores A and B in a multi-stage fluidized bed and changing the number of stages and the oxidation degree Xg of the reducing gas. Is also shown in Table 1. Table 1 shows the calorific value when the low oxidation degree ore is oxidized to hematite and the calorific value of the powder coke used in the firing experiment.

(3) Next, Table 3 shows iron ore A, B, pre-reduced ore C, D, mill scale, OG dust, RHF generation powder and powder coke so that the calorific value per mixed powder weight is constant. Mix as shown (No. 1-5), create pellets with a size of 10-15 mm with a pelletizer, and perform low-temperature firing for 30 minutes at 500 ° C. in an air atmosphere in an electric furnace. I did it. The crushing strength of the agglomerated mineral obtained at this time is shown in the same table. In the example using iron ore A, at this temperature (500 ° C.), although the coke was added, it was not fired and no agglomerate was obtained. On the other hand, in the example in which the pre-reduced ores C and D, the converter dust and the OG dust were blended, high strength agglomerates were obtained even with low-temperature firing for any sample. In addition, as shown in Table 3, the strength of the agglomerate was higher when the average reduction rate of the ore containing the low oxidation degree ore was higher.

  About the compounding example (3), the cross-sectional photograph of the pellet before and behind baking is shown in FIG. Before firing, low-oxidation ores and other low-oxidation iron source materials (OG dust) do not appear to be bound, but after firing, low-oxidation ores and other materials are bound together. Recognize.

For the pellets prepared from the raw materials of the above blending examples, the influence of the firing temperature was examined. The above-described pellets having a size of 10 to 15 mm were prepared and baked for 30 minutes at a predetermined atmospheric temperature in an air atmosphere in an electric furnace. FIG. 4 shows the relationship between the firing temperature and the crushing strength of the agglomerate. As shown in this figure, at a firing temperature of 200 ° C. to 900 ° C., it was agglomerated under any conditions, but at 900 ° C., a dense shell was formed on the pellet surface, and the inside of the pellet was not fired. Further, at 200 ° C., the strength of the agglomerated ore was low, but the strength was improved under the condition that the reaction time was extended. Therefore, it is considered that the reaction time of 30 minutes was not sufficient under the condition of 200 ° C. On the other hand, at 900 ° C., the strength was not improved even if the reaction time was increased. Therefore, it was confirmed that the temperature for firing the blended raw material containing the low-oxidized iron ore is preferably 250 ° C to 850 ° C, more preferably 250 ° C to 800 ° C.

Next, pellets having a size of 10 to 15 mm were prepared with a pelletizer using the raw materials of the blending examples (6) to (9) obtained by adding the CaO reagent to the conditions of the blending example (3). In the air atmosphere, low temperature baking was performed at an atmospheric temperature of 500 ° C. for 30 minutes. Using this agglomerate, the behavior of the agglomerate when heated and reduced at a temperature and gas composition simulating the inside of a blast furnace was investigated by a load softening test.
As a result, as shown in Table 4, by adding CaO to increase the basicity, the dropping temperature of the melt was increased, and the pressure loss was greatly reduced as compared with the case where CaO was not added. In addition, the pressure loss here was shown by the relative value when the sintered ore used in the blast furnace is 1.0. Since the raw material used in the blast furnace is 1.1 or less, it was found that the basicity of the raw material is preferably 0.9 or more.

  The technique of the present invention can be used not only as a technique for producing agglomerated ore used as a raw material for blast furnaces but also as a technique for agglomerating other steelmaking raw materials.

Claims (6)

Oxidation degree xo of iron (FeOxo) composed of one or more of low-oxidation degree iron ore whose oxidation degree xo of iron is more than 0 to 1.36 and sintered ore, pellets, mill scale, iron-making dust or reduced iron powder There and a low degree of oxidation the iron source material of greater than 0 ～1.36, and mixed formulations materials basicity is adjusted to 0.9 or more - shaped, then mixed - oxidizing a molded their mixed material A method for producing an agglomerated mineral, characterized in that the agglomerated mineral is calcined at a temperature of 850 ° C. or lower in a firing furnace under an atmosphere.   The method for producing an agglomerated ore according to claim 1, wherein the low-oxidation iron ore is a pre-reduced iron ore containing high crystal water.   The method for producing agglomerated minerals according to claim 1 or 2, wherein the low-oxidation-degree iron source material is a material having an oxidation degree of 0.5≤xo≤1.10.   The method for producing agglomerated minerals according to any one of claims 1 to 3, wherein the firing temperature is 250 ° C or higher.   5. The method for producing an agglomerated ore according to claim 2, wherein the high crystal water-containing iron ore is iron ore containing crystal mass of 3 mass% or more and 15 mass% or less.   The method for producing an agglomerated ore according to any one of claims 2 to 5, wherein the high crystal water-containing iron ore is pisolite ore or maramanba ore.