JP7265158B2 - Method for producing non-fired coal-containing agglomerate ore for blast furnace - Google Patents

Description

TECHNICAL FIELD The present invention relates to a technique for producing non-calcined coal-containing agglomerate ore, which is used as a raw material for ironmaking furnaces such as blast furnaces and rigid melting furnaces.

Normally, in a blast furnace, raw materials such as sintered ore and lumped coke are charged from the upper part of the furnace, and air is blown from the lower part of the furnace, and the reducing gas generated from the lumped coke and blown air is circulated from the lower part of the furnace to the upper part of the furnace. Meanwhile, pig iron is obtained by reducing and dissolving the iron oxide in the raw material. Blast furnace raw materials are required to have strength so that they do not pulverize in the furnace in order to ensure the ventilation of the reducing gas in the furnace. In addition, since the blast furnace raw material is exposed to a high temperature of 1500° C. or more in the lower part of the furnace, strength at high temperature is also required. For this reason, raw materials for blast furnaces, such as sintered ore and fired pellets, are mainly fired at a high temperature of 1000° C. or higher in advance.

Further, non-calcined agglomerate ore, which is obtained by mixing a finely powdered raw material with a hydraulic binder, adding water to granulate the granules, and curing the granules to increase the strength of the granules, has also been known for a long time. Since this non-fired agglomerate ore can be charged into the blast furnace as it is without being fired, this technology can reduce the energy consumption required for heating and firing while also reducing _CO2 emissions. As a raw material for unfired agglomerate ore, it is possible to use low-grade iron ore, which has low sinterability and is difficult to sinter into a lump. It is also significant to expand the types of iron sources used in blast furnaces, conserve high-quality iron ore, which is feared to be depleted, and effectively utilize the entire earth's resources.

On the other hand, in recent years, as a technology that can achieve both the need to reduce the amount of coke used in blast furnaces and the need to reduce CO ₂ , "unburned coal-bearing agglomerate" technology has been proposed (Patent Documents 1 and 2, non-patent Reference 1, etc.). By adding a carbon-containing raw material to the fine powder raw material of the non-fired agglomerate ore, that is, when the agglomerate ore contains carbon material, the relationship between the reducing gas temperature and the gas composition (ηCO = CO ₂ /(CO + CO ₂ ) ), even in the heat preservation zone and the reduction reaction equilibrium zone of the blast furnace shaft where the progress of the reduction reaction of iron oxide is restricted, the reduction reaction occurs due to the internal carbon in the unburned agglomerate ore in the temperature range of 900 to 1100 ° C. As a result, the reduction rate is improved, so the effect of reducing the reducing agent ratio during blast furnace operation can be expected.

For the above reasons, it is desired that the non-fired coal-containing agglomerate ore for blast furnace has a high carbon content and a high strength so as not to be pulverized in a blast furnace. For example, in Patent Literature 1, which is representative of conventional non-calcined coal-containing agglomerate ore technology for blast furnaces, the proper value of the carbon content of the non-calcined carbon-containing agglomerate ore is 15% by mass or more and 25% by mass or less. However, in response to the problem that the strength decreases when the carbon content in the non-calcined coal-containing agglomerate ore is increased to exceed 15% by mass, the first method is to mix the fine powder iron-containing raw material and fine powder coke, and then add moisture. is added and kneaded, and then high-early-strength cement is added to the kneaded product to prevent the strength from decreasing. As a result, in place of conventional high-early-strength cement, which was buried in the pores on the surface of fine coke and was unable to exert its effect as an adhesive, by filling the pores of the coke with a raw material containing finely powdered iron, It is possible to efficiently exhibit the strength development effect of strong cement.

However, with this method, it was found that the non-calcined coal-bearing agglomerate ore (crushing strength>980N/piece) does not pulverize even when charged into the blast furnace. ), 10% by mass or more of high-early-strength cement is blended. When the amount of this non-calcined coal-containing agglomerate ore used in the blast furnace is increased, the dehydration reaction (endothermic reaction) of the high-early-strength cement proceeds at 400 to 500°C, so 10% by mass of the high-early-strength cement was added. Excessive use of coal-bearing agglomerate ore lowers the temperature in the blast furnace, causing a delay in the reduction of the blast furnace contents, making it impossible to obtain the effect of reducing the reducing agent ratio. In addition, since the high-early-strength cement component becomes slag in the blast furnace, there is a problem that the amount of slag increases.

In addition, in Non-Patent Document 1, by blending 3% by mass of a carbon-containing agglomerate ore having a carbon content (TC) of about 20% by mass as a blast furnace raw material, the effect of reducing the reducing agent ratio during blast furnace operation is the highest, but when blended at 6% by mass, the effect of reducing the reducing agent ratio did not appear.
The reason for this is that 10 to 11% by mass of cement must be blended in order to ensure the crushing strength to withstand charging into a blast furnace in a carbon-containing agglomerate ore with a carbon content (TC) of about 20% by mass. It is said that the increase in water of crystallization derived from cement contained in the coal-bearing agglomerate ore causes dehydration endothermic reaction in the blast furnace, lowering the temperature of the blast furnace shaft and delaying the reduction.

Therefore, in order to maximize the effect of reducing the reducing agent ratio of the blast furnace, it is necessary to increase the charging ratio of the coal-containing agglomerate ore into the blast furnace. Here, in order to increase the amount of coal-containing agglomerate ore charged to the blast furnace at 3% by mass or more, the carbon content (T.C.) must be increased while avoiding a temperature drop in the blast furnace and increasing the amount of coal-containing agglomerate ore In order to improve the crushing strength, it is necessary to develop a manufacturing method to increase the strength of the coal-bearing agglomerate ore so that it does not pulverize when it is charged into the blast furnace even if the blending ratio of cement and other hydraulic binders is 9% by mass or less. necessary.

Therefore, in Patent Document 2, as a method for increasing the room temperature crushing strength of non-fired carbon-containing pellets for blast furnaces, as a "binder", "at least one of a hydraulic binder and a starch binder or a clay binder" is added. , Even if 10 to 30% by mass of carbonaceous material-containing raw materials are blended, even if the blending ratio of hydraulic binder is 3 to 10% by mass, even if it is charged into a blast furnace, it will not powder even if it is charged into a blast furnace. It is said that it can produce agglomerate ore.

However, both the starch binder and the clay-based binder are very viscous, and at the water addition rate (7% by mass) as shown in Patent Document 2, the roll briquette method with a very large compressive force is optimal. . Molding by the roll briquette method generally generates a large amount of powder and fragments, and has the disadvantage of a low product yield (generally 70% or less). Molding is also possible by the disk pelletizer method, but the disk pelletizer device is only a small device and is not suitable for industrial mass production.

On the other hand, if a large amount of water is added to the raw material to lower the viscosity of the raw material, it will be possible to use other molding methods (extrusion molding method, pan pelletizer granulation method, etc.). When the water contained in the granules dries, it forms voids that reduce the crushing strength, resulting in the generation of a large amount of powder when charged into the blast furnace, and the compacts sticking together during curing after molding to form large lumps. There is also a problem that the productivity is low in that the yield of the molded body is lowered because the crushing treatment is required before the molding.

Further, as shown in Patent Document 3, as a method for improving the cold strength of non-fired agglomerate ore without increasing cement, a mixture of agglomerate raw material and water is vibrated to separate air in the mixture. A method for producing a non-fired agglomerate ore has been proposed in which the strength of the agglomerate ore is improved by removing it. According to this production method, since the air in the mixed raw material is separated and removed, it is possible to improve the strength of the agglomerate ore without increasing the amount of cement.

However, the method for producing non-calcined agglomerate ore disclosed in Patent Document 3 is a batch type, and thus has a problem that it is not possible to continuously produce non-calcined agglomerate ore, resulting in poor productivity.

In this way, conventionally, in order to set the carbon content ratio (TC) contained in the raw material (in the raw material of the carbon-containing agglomerate ore) after removing moisture in the non-fired agglomerate ore to 15% by mass or more, A method for producing a coal-containing agglomerate ore having a high reducing agent ratio reduction effect by blending a carbon-containing raw material or the like has been proposed. However, since the addition of a large amount of carbon-containing raw materials reduces the strength of the molded body, in order to avoid this, in the conventional manufacturing method, about 10% by mass of a hydraulic binder is added to ensure the required strength of the molded body. rice field.

Hydrates derived from hydraulic binders undergo a dehydration reaction (large endothermic decomposition reaction) in the blast furnace. An endothermic decomposition reaction causes temperature stagnation in the furnace. For this reason, it was difficult to use 3% by mass or more of non-calcined coal-containing agglomerate ore containing about 10% by mass of hydraulic binder in a blast furnace.

In addition, although a plurality of production methods have been proposed as measures for reducing the blending ratio of the hydraulic binder, they are not suitable for mass production.

From the above, T. in the coal-bearing agglomerate ore raw material C. is 15% by mass or more, and high strength can be achieved even when the blending ratio of the hydraulic binder is 9% by mass or less. Therefore, it was desired to expand the use of unfired coal-bearing agglomerates in blast furnaces.

JP 2012-82501 A JP 2012-211363 A JP 2014-136818 A JP-A-60-187631

Yokoyama, Higuchi et al.: Tetsu to Hagané (100) 2014, 601)

The present invention provides a method for removing T. in a coal-bearing agglomerate ore raw material. C. is 15% by mass or more, and even when the mixing ratio of a hydraulic binder is small, a method for producing a high-strength non-calcined coal-containing agglomerate ore for a blast furnace can be stably and mass-produced.
In the method for producing a non-fired coal-containing agglomerate ore for blast furnace of the present invention, raw materials for the coal-containing agglomerate ore are
- A carbon-containing raw material that is a reducing agent,
・ Iron-containing raw materials that are iron sources,
・And other raw materials,
using these three raw materials,
- A hydraulic binder (adhesive, hereinafter referred to as a hydraulic binder) such as cement,
It is assumed that the coal-containing agglomerate ore is produced by adding a fine-grained silica source, and then adding water and mixing, followed by molding.

As mentioned above, T. C. is 15% by mass or more, and high strength even with a low hydraulic binder content is stably and mass-produced by the inventors. By adopting a vacuum extrusion molding method, the porosity is reduced.In addition, by controlling the particle size of the raw material and adding a fine silica source as an additive, the filling rate of the raw material particles is increased, and high strength is achieved even if the hydraulic binder is reduced. succeeded in producing non-calcined coal-bearing agglomerate ore. Namely
(1) A method for producing a non-calcined coal-containing agglomerate ore for blast furnace used as a raw material for a blast furnace in steelmaking, comprising a hydraulic binder content of 2.0 to 9.0% by mass in terms of zero water content. , an iron-containing raw material, a carbon The amount of water when the total of the raw material and water is 100% by mass to the coal-containing agglomerated ore raw material, which is blended with a total of 87.0 to 97.5% by mass by adjusting the blending ratio of the raw material and other raw materials. The mixed raw material is added at a mass ratio of 9.0 to 14.0% by mass and transferred while being continuously mixed, and the mixed raw material is pushed into a weir formed of a perforated plate installed in front of the transfer direction to the first A first extrusion section (kneading section) that forms a material seal, and a connection section (vacuum chamber) that deaerates the mixed raw material continuously supplied from the exit side of the weir and transfers it to the second extrusion section. Then, the vacuum degassed mixed raw material supplied from the connection portion (vacuum chamber) is pushed into the molding portion having a large number of holes, thereby forming a second material seal and continuously extruding to form a molded body. and a second extrusion section for producing a carbon-containing agglomerate ore, wherein the filling rate of the mixed raw material in the second extrusion section is 50 to 95% by volume. A method for producing a non-burning coal-containing agglomerate ore for a blast furnace characterized by continuous molding in the range of
(2) The non-calcined coal-containing agglomerate ore for blast furnace according to (1), characterized in that the pressure in the connecting portion (vacuum chamber) of the apparatus for producing non-calcined carbon-containing agglomerate ore for blast furnace is -50 kPaG or less. This is a method for producing an agglomerate ore.
(3) In addition, the average particle size of the fine silica source is 15% or less of the average particle size of the mixed raw material of the non-calcined coal-containing lump ore excluding the fine silica source. A method for producing a non-fired coal-containing agglomerate ore for blast furnace according to (1) or (2).

By adopting the method for producing a non-calcined coal-containing agglomerate ore for blast furnace in which extrusion molding is performed while vacuum degassing according to the present invention, and by blending a fine silica source with a mixed raw material, T.E. C. It is possible to produce a non-calcined coal-containing agglomerate ore with high strength at a blending ratio of 9.0% by mass or less of a hydraulic binder such as cement even if it is blended in a large amount of 15% by mass or more. became. As a result, up to 9% by mass of coal-containing agglomerate ore, which could conventionally be used only up to 3% by mass due to the endothermic decomposition reaction, can be used in the blast furnace, contributing to operation with a low reducing agent ratio.

T. in coal-bearing agglomerates C. and a reduction amount of reducing agent ratio. 1 is an example of a vacuum extruder according to the present invention; 4 is a graph showing the relationship between the vacuum pressure between the connection and the molded portion and the crushing strength. It is a figure which shows determination of the filling rate of a raw material, and the upper-lower limit image of a filling rate.

As described above, raw materials for non-calcined coal-containing agglomerate ore are generally composed of three types of raw materials: carbon-containing raw materials that are reducing agents, iron-containing raw materials that are iron sources, and other raw materials. These three kinds of raw materials are blended with a hydraulic binder and a fine silica source to obtain a raw material for carbon-containing agglomerate ore, which is further mixed with water and molded to obtain a carbon-containing agglomerate ore.

The carbon-containing raw material is preferably fine powder of carbonized coal such as coke fines obtained by crushing coke to a predetermined particle size, dust collected from coke ovens, etc., but contains a large amount of carbon content generated from anthracite, coal, and blast furnaces. Dust or the like may be used.

The iron-containing raw materials include iron ore crushed to a predetermined particle size, iron ore fine powder (pellet feed), and dust, sludge, and scale containing relatively low carbon content and high iron content generated in large amounts in the iron manufacturing process. etc. can also be used. In addition, it is also possible to use grinding scraps of rolling rolls, and especially iron ore and sintered ore that have fallen during the transportation process of the ironmaking process. Iron-bearing raw materials also include iron-containing raw materials.

The above-mentioned other raw materials refer to sludge, slag, etc., which contain little iron component (30% by mass or less as iron content) or do not contain iron component, which are generated in the iron manufacturing process. Due to the low iron content, it may contain carbon.

In addition, coal-containing agglomerate ore also contributes to the zero emission of ironworks. Currently, most of the by-products generated in steelworks are either recycled within the steelworks or commercialized as by-products for sale, but some of them are difficult to recycle or commercialize. Sludge and some types of slag are typical examples of materials that are difficult to recycle in-house. The above-mentioned other raw materials refer to raw materials that are difficult to recycle in steelworks, and by actively recycling them as raw materials for coal-containing agglomerates, it is possible to contribute to zero emissions at steelworks. , the addition of which has the advantage of being able to actively adjust the particle size of the raw material and control the fluidity of the raw material when water is added (advantage in using the extrusion molding method described later).

As shown in Table 1, dust and sludge may contain more or less carbon content. In the present invention, as will be described later, the T. C. Because the physical properties are determined by the T.D. in the coal-containing agglomerated ore raw materials including these, without classifying the compounding ratios of generally used carbon-containing raw materials, iron-containing raw materials, and other raw materials. C. Define the range of In addition, the mass % of Table 1 is an example, and is not limited to this range.

The hydraulic binder is sometimes simply called cement, and means a binder having a function of increasing the cold crushing strength of granules by hardening due to hydration reaction with water contained in the raw material or added water. do. Hydraulic binders include calcium silicate-containing Portland cement (defined by JIS R 5210), mixed cement (blast furnace cement (defined by JIS R 5211)), silica cement (defined by JIS R 5212), fly ash cement (defined in JIS R 5213)), ultra-rapid hardening cement, blast furnace slag, etc., but not limited thereto.

The fine silica source includes not only silica fume and microsilica but also fly ash.

As shown in Table 1, the hydraulic binder and the fine silica source also contain a small amount of T.I. C. However, since the fraction of the hydraulic binder and the fine silica source itself is small and the effect is considered to be small, the T.O. C. does not count to

The conditions required for the coal-containing agglomerate ore and the manufacturing conditions for achieving them are as follows.

coal-bearing agglomerate ore raw materials and T.I. C. ;
Conventionally, the T.C. C. is defined as the "carbon equivalent" and is used as a measure of the degree of reduction of iron oxide by carbon.
The T.C. C. The lower limit of 15% by mass corresponds to a carbon equivalent of 1.2 or more. When iron oxide particles and carbon particles are adjacent to each other in the non-fired coal-bearing agglomerate ore when used in a blast furnace, a solid reduction reaction occurs inside the coal-bearing agglomerate ore during the gradual temperature rise inside the blast furnace. progresses. Furthermore, surplus carbon that is not adjacent to iron oxide particles is gasified by a solution loss reaction, and gas reduction promotes the reduction of iron-containing raw materials for blast furnaces such as sintered ore and iron ore around the unburned coal-bearing agglomerate ore. You can also expect to

Fig. 1 shows T. C. and the reduction amount of the reducing agent ratio. A reduction test apparatus (BIS furnace) capable of simulating the reduction reaction in the blast furnace under load was used, and the unburned coal-containing agglomerate ore was used in the blast furnace by replacing 10% by mass of ordinary sintered ore. It is the result of evaluating the reducing agent ratio reduction effect at time. T. in coal-bearing agglomerates C. is less than 15 mass, the effect of reducing the reducing agent ratio is 0.2 kg/kg-C or less. C. is 15% by mass or more, the effect of reducing the reducing agent ratio is about 0.4 kg/kg-C. For this reason, in order to maximize the effect of reducing the reducing agent ratio by charging into the blast furnace, the T.C. C. = 15% by mass or more is a prerequisite of the present invention. Regarding the above-mentioned unit: kg/kg-C, the numerator kg is the total amount of reduced weight of the reducing material, and the numerator kg-C is the amount of carbon contained in the coal-containing agglomerate charged into the blast furnace. It is an index showing how much the carbon content contained in the coal-containing agglomerate ore has the effect of reducing the reducing agent ratio.

On the other hand, it has been believed that if the carbon-containing raw material of the coal-containing agglomerate ore raw material is further increased, the required blast furnace strength of the non-fired coal-containing agglomerate ore cannot be maintained. As a result of verifying the upper limit value in the present invention, T.I. C. = When it exceeded 40 mass %, molding became difficult.

For the above reasons, the T.C. C. is blended so as to be 15 to 40% by mass. Although the upper and lower limits of each of the carbon-containing raw material, the iron-containing raw material, and other raw materials are not particularly defined, the carbon-containing agglomerated ore raw material includes T.I. C. In addition, it is preferable that the content of the iron component is large. Because T. C. This is because components other than iron and iron will become slag, which will increase the amount of unnecessary input heat.

Therefore, the blending ratio of the coal-containing agglomerated ore raw material is 2.0 to 9.0% by mass for the hydraulic binder and 0.5 to 4.0% by mass for the fine silica source, as will be described later. Coal agglomeration raw material T. C. = 15 to 40%, the total of the carbon-containing raw material, the iron-containing raw material, and the other raw materials is made 87.0 to 97.5% by mass.

Here, for example, when coke breeze is used as the carbon-containing raw material, the carbon content of coke breeze is about 75 to 85% by mass. C. is 15 to 40%, the minimum = 15 ÷ 0.85 × 0.87 ≒ 15.3 mass%, the maximum = 40 ÷ 0.75 × 0.975 ≒ 52.0 mass%, carbon content The raw material is blended with the carbon-containing agglomerate ore so that the amount is 15.3 to 52.0% by mass, and the difference between the above three raw materials is 87.0 to 97.5% by mass, and iron that does not contain carbon. Add ingredients and other ingredients.

Also, for example, when using blast furnace dust with a high carbon content (carbon content = about 30 to 40%) as the carbon-containing raw material, in order to satisfy the minimum content of carbon content in the coal-containing agglomerate ore = 15 mass, 15 ÷ 0.40 × 0.87 ≈ 32.6% by mass, and 40 ÷ 0.30 × 0.975 > 100% to satisfy the maximum content = 40% by mass. The blending ratio of the contained raw material is 32.6 to 97.5% by mass.

hydraulic binder;
A hydraulic binder is added to the coal-containing agglomerated ore raw material in order to develop strength (>1100 N/piece) that does not pulverize even when charged into a blast furnace. The hydraulic binder in the coal-bearing agglomerate ore changes into a connective tissue such as calcium silicate hydrate during the curing period, thereby improving the strength of the agglomerate ore. However, part of this connective tissue decomposes due to an endothermic reaction when the temperature rises above 400 to 500° C. inside the blast furnace. This endothermic reaction lowers the temperature in the furnace, lowers the temperature range of 400 to 500° C. toward the lower part of the furnace, and delays the gas reduction reaction in the upper part. For this reason, if more than a certain amount of cement is charged into the blast furnace, insufficient reduction occurs in the furnace. become unable. Therefore, the smaller the amount of the hydraulic binder, the better.

When the ratio of the carbon-containing raw material in the coal-containing agglomerate ore raw material increases, the strength of the agglomerate ore decreases inversely. C. = 15 to 40% by mass of non-calcined coal-containing agglomerate ore, it is necessary to increase the blending amount of the hydraulic binder in the conventional production method. This is because there is a proportional relationship between the strength of the coal-containing agglomerate ore and the blending amount of the hydraulic binder. Here, if the hydraulic binder is less than 2.0% by mass, the strength-improving action and effect of the binder cannot be sufficiently exhibited. Even if the content exceeds 9.0% by mass, the effect of improving the strength is sufficiently exhibited. The crushing strength of compacts of 1100 N/piece or more can be greatly cleared, and the addition of more than that may cause the temperature in the blast furnace to decrease and hinder reduction, increase costs, increase the amount of blast furnace slag, and reduce the above-mentioned silicon It is useless because it leads to promotion of cooling of the blast furnace due to decomposition of calcium acid hydrate. For the above reasons, the amount of the hydraulic binder to be added is set to 2.0 to 9.0% by mass.

particulate silica source;
As the production method of the coal-containing agglomerate ore, we adopted the method of extruding while vacuum degassing, which will be described later. The score can be increased, and the strength of the molded body can be improved. On the other hand, raw materials suitable for the extrusion molding method are relatively fluid plastic raw materials ( clay, paste, etc.). In general, a method of adding more water is used as a method for improving the fluidity of the raw material. The number of interparticle points cannot be increased, and the strength of the produced coal-bearing agglomerate ore is lowered.

Therefore, in the present invention, as a method of increasing the fluidity without increasing the water content, it was decided to add fine particles sufficiently smaller than the average particle size of the mixed raw material. When the fine-grained substance is added to the raw material mixture, it penetrates between the raw material particles and coats the particles, exerting an effect like a bearing that lubricates the particles to improve the fluidity of the mixed raw material. In addition, part of the fine-grained substances that coat the surface of the raw material particles increases the number of contact points by becoming contact points between particles, and partly enters the gaps between the raw material particles and fills them (by replacing with water). By improving the rate, the strength of the coal-bearing agglomerate ore can be improved. The main component of the fine-grained substance is fine-grained silica because it is stable at room temperature, and as typified by silica fume and fly ash, it is commercially available as a by-product and can be easily obtained in relatively abundant amounts. Also, it has the following three advantages: it accelerates the hardening reaction of cement during curing after molding, and can be expected to improve the strength of the molded product.

In addition, when the particles have a close-packed structure (from geometric calculations), the minimum diameter of the inter-particle gaps is 15% of the particle diameter. It is preferably 15% or less of the particle size. With this particle diameter, it can enter between the raw material particles without resistance, contributing to increasing the strength of the non-burned carbon-containing agglomerate ore. At present, the average particle size of mixed raw materials is about 60 to 100 μm, but the average particle size of silica fume, which is a representative fine silica source, is 0.1 to 0.2 μm, and the average particle size of fly ash is 10 to 20 μm. and the above conditions can be substantially satisfied. By selecting the type of the fine silica source or adjusting the particle size by pulverization in accordance with the average particle size of the mixed raw material in this way, the effect of improving the strength can be exhibited, which is preferable.

In this example, the appropriate addition rate of the fine silica source is about 0.5 to 4.0% by mass, and the optimum addition rate is 0.5 to 2.0% by mass. The reason for this is that at 0.5% by mass or less, the amount of the fine silica source covering the surface of the raw material particles is too small, and the effect of the bearing cannot be sufficiently exhibited, so it is necessary to add excess moisture, and the produced carbon-containing The strength of the agglomerate ore decreases. Conversely, if it exceeds 4.0% by mass, the fluidity increases and there is no need to increase the water content, but the cost of the fine silica source becomes too high, resulting in a negative cost-effectiveness. For this reason, the smaller the addition rate of the fine silica source, the better, 0.5 to 4.0% by mass is appropriate, and 0.5 to 2.0% by mass is optimal. The appropriate addition rate has a range of 0.5 to 4.0% by mass because the amount of effect varies depending on the type of fine silica source, and the return on investment fluctuates due to market price fluctuations. However, this does not apply to the appropriate addition rate when there is a large price fluctuation in the future.

moisture;
The blending ratio of the coal-containing agglomerate ore raw material is a mass ratio in terms of zero water content (=the raw material is completely dried = the state of only raw material solids with 0% moisture). Water is added, but the water content is adjusted to 9.0 to 14.0% by mass as a percentage of the total 100% by mass, including the mass ratio in terms of zero moisture.

Production method;
<Adoption of vacuum extrusion molding method>
In the present invention, by adopting a vacuum extrusion molding method as a production method, the number of contact points between the raw material particles can be increased, that is, the voids can be reduced, and the strength of the molded body can be increased. As a result of evaluating the quality of the molded body obtained by changing the pressure in the vacuum chamber, it was found that the quality of the molded body obtained varies depending on the degree of vacuum in the vacuum chamber (vacuum chamber pressure).

<Example of vacuum extruder used in the present invention, extrusion molding method, and formation of material seal>
An example of a vacuum extruder used in the present invention is shown in FIG. Using the vacuum extruder, it is necessary to stably maintain a high negative pressure in the vacuum chamber while continuously and stably supplying and discharging raw materials. Therefore, it is important to stably maintain a high negative pressure (high degree of vacuum) in the vacuum chamber by filling the gaps in the equipment structure before and after the vacuum chamber with materials, that is, by continuously forming a material seal. Become.

A coal-containing agglomerated ore manufacturing apparatus 10 has a mixer 1 , an inlet 2 , a first extrusion section 3 , a connecting pipe 4 , a second extrusion section 5 , a molding section 6 and a vacuum pump 7 .
The first extrusion section 3 (also referred to as a kneading section) is a uniaxial screw feeder having a cylindrical casing 3a and a screw 3b that is rotatably disposed inside the casing 3a and continuously formed vertically. is. The screw 3b is rotated by driving means (not shown). The upper portion of the base of the casing 3a is connected to the inlet 2 by a connecting pipe 8. As shown in FIG. A weir 3c formed of a perforated plate is disposed at the tip of the casing 3a. In this embodiment, the weir 3c formed of a perforated plate has a structure in which a large number of holes are opened in a thick circular plate.

A second extrusion portion 5 is arranged below the first extrusion portion 3 . The tip of the first extruded portion 3 and the base of the second extruded portion 5 are connected by a connecting pipe 4 (also referred to as a vacuum chamber). The connection pipe 4 is connected to the vacuum pump 7 by a vacuum pump connection pipe 9 .
The second extrusion part 5 (also referred to as an extrusion molding part) is a uniaxial type having a cylindrical casing 5a and a screw 5b that is rotatably disposed inside the casing 5a and continuously formed vertically. It is a screw feeder. The screw 5b is rotated by driving means (not shown). A molded part 6 is attached to the tip of the casing 5a. In this embodiment, the molded portion 6 has a structure in which a large number of holes are formed in a thick disc.

The raw materials of the coal-containing agglomerate ore are each supplied to the mixer 1 so as to have a predetermined mixing ratio, and water is added and mixed to produce a mixed raw material. The mixed raw material is continuously or intermittently charged into the charging port 2 . The mixed raw material introduced into the inlet 2 is supplied through the connecting pipe 8 into the first extruding section 3, is gradually compressed by the screw 3b, and reaches the weir 3c formed of a perforated plate. At this time, by adjusting the rotation speed of the screw 3b and the supply speed of the mixed raw material so that all the holes of the weir 3c formed of the perforated plate are filled with the mixed raw material, the weir 3c formed of the perforated plate A material seal is formed. Since the mixed raw material is continuously supplied by the screw 3b, the mixed raw material is continuously discharged and supplied into the connecting pipe 4 while always forming a material seal on the back surface of the weir 3c formed of a perforated plate. will be The shape of the holes in the perforated plate (weir c) is not particularly defined, but it is important to adjust and determine the hole diameter and opening ratio according to the physical properties of the mixed raw material so that the material seal can be easily formed. is.

Since the inside of the connection pipe 4 is evacuated by the operation of the vacuum pump 7 connected by the vacuum pump connection pipe 9, the mixed raw material supplied to the connection pipe 4 is degassed, and the raw material particles in the raw materials are reliably separated. Contacting and densifying can increase the strength of the produced non-calcined carbon-containing agglomerate ore.

The mixed raw material densified in the connecting pipe 4 is supplied to the second extrusion section 5 . The mixed raw material supplied to the second extrusion section 5 is extruded to the molding section 6 by the screw 5b.
As described above, in the example of the apparatus for producing a coal-containing agglomerate ore according to the present invention, the material seal is used to continuously perform extrusion molding while vacuum degassing, so that the productivity can be improved. It is possible. In this embodiment, if the particle size of each raw material is 8 mm or less (maximum particle size is 8 mm, average particle size is about 60 to 100 μm), the mixed raw material is extruded by the screws 3b and 5b. , the casings 3a and 5a, the weir 3c formed of a perforated plate, and the molded portion 6, so that they do not mesh with each other, which is preferable. The mixed raw material is molded into the cross-sectional shape of the molding section 6 when passing through the molding section 6 . The raw material mixture extruded from the molding section 6 is broken by its own weight and molded into a molding of a predetermined length.

The shape of the molded product is determined by the cross-sectional shape of the molded part 6, and the hole can be formed in the shape of a prism such as a square prism, a hexagonal prism, etc. in addition to the shape of a cylinder. The reason is described below.

When comparing the pressure loss in blast furnace packed bed ventilation for various tendencies of coal-bearing agglomerates, the columnar shape exhibits the lowest pressure loss. In addition, as compared with a prism, the columnar carbon-containing agglomerate ore has the characteristic that it is less likely to pulverize when the walls of the packed bed or the coal-containing agglomerate ore rub against each other or drop impact. Agglomerates with a diameter of 30 mm to 40 mm have the highest crushing strength, while the raw material charging mechanism into the blast furnace has a structure suitable for transporting raw materials with a diameter of 20 mm or less in accordance with the existing sintered ore. Therefore, it is desirable to form a cylinder with a diameter of about 10 to 20 mm.

The molded products are piled up in a curing yard with a roof and cured in the curing yard for a predetermined period. During the curing period, the molding is solidified, and water is gradually removed by natural drying to complete the production of the coal-containing agglomerate ore.

<Conditions for continuous stable production>
In the embodiment of the present invention, in order to continue stably producing a dense and strong molded body, the inside of the vacuum chamber is maintained at a high negative pressure while continuously supplying raw materials into the connecting pipe 4 (a reduced pressure chamber called a vacuum chamber). At the same time, it is necessary to extrude the mixed raw material supplied into the vacuum chamber to the extruder 6 . That is, in order to prevent air from entering from the perforated plate 3c or the holes of the molding portion 6, all the holes of the weir 3c formed of the perforated plate and all the holes of the molding portion 6 are always filled with the raw material mixture, It is important to maintain a material seal and maintain a high negative pressure between the connecting pipe 4 and the molded portion 6 . Therefore, we investigated the conditions under which the material seal can be maintained using a continuous vacuum extrusion molding device.

As the test conditions, the iron-containing raw material, the carbon-containing raw material, the hydraulic binder, and the fine-particle silica source are weighed so that the raw materials have a predetermined composition, and they are put into a single-shaft paddle type continuous mixer, and a predetermined amount of water is added. was added and mixed for 2 minutes to 2 minutes and 30 seconds. The mixed raw material is put into an extrusion molding device composed of a single-screw kneader and a single-screw extrusion molding unit, and the extrusion speed (the speed at which the raw material passes through the holes of the molding unit 6) is set to 40 to 40. A molding test was performed by adjusting the speed to 100 mm/s.

Here, by changing the supply amount of the mixed raw material to the kneading unit, the rotation speed of the screws (3b, 5b), and the filling rate of the raw material in each casing (3a, 5a), the effects of these factors on the material seal investigated.

A weir 3c formed of a perforated plate is installed on the inlet side of the vacuum chamber, and the mixed raw material is continuously pushed by the screw 3b toward the weir 3c formed of a perforated plate to form the first material seal. In order to continuously form this first material seal, the mixed raw material is pushed into the weir 3c formed of a perforated plate and the mechanical resistance when passing through each hole is adjusted. We found that it is effective to adjust the pore size, total aperture ratio, and thickness of the perforated plate.

The forming part 6 installed at the tip of the extruding part 5 is a porous thick plate, and has a structure very similar to the weir 3c formed of the porous plate on the side of the entrance of the vacuum chamber. In order to form a material seal, it was found to be effective to adjust the number of holes and plate thickness in the same way as the vacuum chamber entrance side.

<Optimal vacuum conditions>
The test results of the coal-containing agglomerate ore agglomerated by changing the negative pressure between the connecting pipe 4 and the molding section 6 by the extrusion molding method described above are shown below. The iron-containing raw material, the carbon-containing raw material, the hydraulic binder, and the fine silica source are weighed so that the raw materials have a predetermined composition. The mixture was mixed for a minute to obtain a mixed raw material. The mixed raw material was put into an extrusion molding device, and a molding test was carried out by setting the extrusion speed (the speed at which the raw material passes through the holes of the molding section 6) to 10 mm/s.

The agglomerated coal-containing agglomerate ore was air-cured at room temperature for 1 day, then placed in a thermo-hygrostat at 80°C for 2 days for curing, air-cooled to 30°C, and a crushing strength test was conducted. The crushing strength was measured according to JIS M8718 "Iron ore pellet crushing strength test method", a load was applied to one sample at a specified pressurization speed, and the load when the sample broke was taken as the crushing strength. .

Table 2 shows the blending conditions of the raw materials.

When the pressure value between the connecting pipe 4 and the molding portion 6 during molding is -50 kPaG, the variation in crushing strength changes greatly. In particular, as shown in FIG. 3, it is found that the closer the pressure between the connecting pipe 4 and the molding section 6 is to the vacuum pressure, the higher the quality (higher strength), and the vacuum chamber pressure is in the range of -60 kPaG to -50 kPaG. Although the room-temperature crushing strength of the molded bodies is 1100 N/unit or more, which is the target value, the crushing strength of the molded bodies varies greatly and is on the low strength side. The crushing strength that varies toward the low strength side has not reached the target. By shifting the pressure between the connecting pipe 4 and the molding section 6 to a lower level, that is, to the vacuum side, the variation in bulk density and crushing strength is reduced, and the crushing strength at room temperature of the molded body is the target value of 1100 N/piece. was confirmed to exceed

In order to ensure ventilation of the reducing gas in the blast furnace, the blast furnace raw material must be strong enough not to pulverize during transportation to the blast furnace and charging into the furnace. As a result of a blast furnace operation test of non-fired coal-containing agglomerate ore, if the room-temperature crushing strength per molded body is 1100 N/piece or more, pulverization in the blast furnace can be suppressed and reducing gas permeability can be improved. It turns out that it can be secured, and this is the target strength of the coal-bearing agglomerate ore.

The reason for this is presumed as follows. If the pressure between the connecting pipe 4 and the molding section 6 is high, the air in the raw material to be molded cannot be discharged sufficiently, so that the mixed raw material is molded with a large amount of air trapped therein. This molding has a low bulk density and low strength. On the other hand, the portion that does not entrain much air also becomes a molded body, and this molded body has a high bulk density and high strength. The difference in the amount of air entrained in the molded body causes variations in strength. Conversely, when the pressure between the connecting pipe 4 and the molding section 6 is lowered, the amount of air remaining in the mixed material is reduced, which is considered to reduce the strength variation.

As described above, the feature of the vacuum extruder used in the present invention is that a high negative pressure of -50 kPaG or less is applied between the connection pipe 4 and the molding section 6 while continuously supplying the raw material to a decompression chamber called a vacuum chamber. While maintaining (high degree of vacuum), the raw material supplied between the connecting pipe 4 and the molding section 6 is extruded to the extrusion molding section and molded.

Next, other conditions necessary for stable extrusion were investigated. Table 3 shows the contents and results of this investigation.

The second material seal can be formed by installing the molded portion 6 of the perforated plate adjusted to the extruded portion 5 as described above. However, in actual production, the raw material supply speed to the molding unit 6 changes due to changes in raw material flow resistance (operational fluctuations) or changes in the screw rotation speed (operational actions).

For example, if the moisture content of the raw material becomes excessive, the flow resistance of the raw material is lowered, the raw material is discharged before the second material seal is formed, and the pressure in the vacuum chamber cannot be stably maintained. A similar change occurs with respect to the rotational speed UP of the screw 5b. As a result of investigating these phenomena, it was found that when the mixed raw material filling rate of the second extruding section 5 is less than 50% by volume, the second material seal tends to collapse when the supply speed to the molding section 6 increases. Do you get it.

On the other hand, if the flow resistance of the raw material increases or the rotation speed of the screw 5b is reduced, the raw material supply speed to the molding unit 6 decreases, and from the second extrusion unit 5 to the connecting pipe 4 (vacuum chamber) It was found that the raw material accumulated excessively and the screw 5b in the second extruder 5 was overloaded and easily stopped. As a result of the investigation, it was found that when the filling rate of the second extruding section 5 exceeds 95% by volume, the discharge failure of the molded body tends to occur when the supply speed to the molding section is lowered.

Therefore, the rotation speed of the screw 5b of the second extrusion section 5 and the rotation speed of the screw 3b of the first extrusion section 3 upstream of the connection pipe 4 (vacuum chamber) and the raw material properties are adjusted as needed, and the second extrusion section 5 By continuing to control the raw material filling rate of 50% by volume or more and 95% by volume or less (essential condition), it was found that stable and continuous production of molded bodies is possible even if there are fluctuations in operation.

The raw material filling rate of the second extrusion section 5 is the ratio of the raw material to the volume of the cylindrical space in which the screw 5b of the second extrusion section 5 rotates (excluding the volume of the screw). say. Stable and continuous molding is possible by controlling the raw material filling rate to 50% by volume or more and 95% by volume or less by increasing or decreasing the number of revolutions of the screw 5b of the second extruder 5 and by increasing or decreasing the amount of raw material supplied.

The determination of the raw material filling rate is generally made by visual determination, for example, by observing the extruded part through an observation window attached to the upper part of the vacuum chamber, as shown in FIG. This time, in order to determine the raw material filling rate from the range of the screw that can be seen through the observation window, for example, the relationship between the range where the screw blades are hidden by the raw material and the raw material filling rate is investigated in advance. However, for example, you can install a level meter (microwave level meter, proximity sensor, various level switches, etc.) at each part of the extrusion molding section and calculate the filling rate from the level measurement value. good.

As described above, regarding the control range of the raw material filling rate, if it is 50% by volume or more and 95% by volume or less, continuous stable molding is possible. A content of 60% by volume or more is optimal. The reason for this is that by controlling the filling rate to be constant, the force with which the screw of the extrusion molding unit presses against the perforated plate is stabilized, so that variations in the ejected moldings are reduced.

As described above, as a method for producing a non-calcined carbon-containing agglomerate ore for a blast furnace, an iron-containing raw material containing iron oxide, a carbon-containing raw material, a hydraulic binder, and a small amount of a fine silica source are mixed, and water is added. After mixing, the vacuum chamber pressure is set to -50 kPaG or less and extrusion molding is performed while vacuum degassing, so that even if the amount of hydraulic binder in the raw material is 2 to 9% by mass, when charging into the blast furnace It is possible to produce a coal-containing agglomerate ore having a crushing strength of 1100 N/piece or more required for.

In the present embodiment, the screw 3b is of a uniaxial type and the screw 5b is of a uniaxial type, but the screw 3b may be of a biaxial type, or the screw 5b may be of a biaxial type.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, the invention is not limited to the embodiments disclosed herein. , can be appropriately changed within the scope not contrary to the gist or idea of the invention that can be read from the scope of claims and the entire specification, and the method for producing the coal-containing agglomerate ore and the coal-containing agglomerate ore that involve such changes are also technically should be understood as being included in the scope.

EXAMPLES Next, examples of the present invention will be described, but the present invention is not limited to these. The coal-containing agglomerate ore raw material is obtained by using a carbon-containing raw material, an iron-containing raw material and other raw materials, C. = 15 to 40%. As carbon-containing raw materials, coke fine (TC=84%) and ironmaking dust (TC=23%) with a high carbon content were sieved through a 5 mm sieve, and the under-sieves were used. Ore M (Australian ore fine) and ore C (Canadian ore fine) were mixed as iron-containing raw materials, pulverized in a ball mill, sieved through a 5 mm sieve, and the under-sieves were used. Also, as the hydraulic binder, high-speed cement and ultra-rapid-hardening cement were used.
Silica fume and fly ash were used as fine silica sources.

As for the blending conditions of the coal-containing agglomerate ore, the carbon-containing raw material, the iron-containing raw material, the hydraulic binder, and the fine-grained silica source were weighed so as to obtain the composition shown in Table 4, and the entire amount was added to the uniaxial paddle-type continuous type. After being put into a mixer and mixed for 1 minute, a predetermined amount of water was added and mixed for 3 minutes to obtain a mixed raw material. The mixed raw material is put into an extrusion molding device composed of a uniaxial screw type kneader and a uniaxial screw type extrusion molding unit, and the extrusion speed (the speed at which the raw material passes through the holes of the molding unit 6) is 10 mm / A molding test was carried out by adjusting to s. The diameter of the holes (multiple holes) of the extruded portion was φ16 mm.
The agglomerated coal-containing agglomerate ore was air-cured at room temperature for 1 day, then placed in a thermo-hygrostat at 80°C for 2 days for curing, air-cooled to 30°C, and a crushing strength test was conducted. The crushing strength was measured according to JIS M8718 "Iron ore pellet crushing strength test method", a load was applied to one sample at a specified pressurization speed, and the load when the sample broke was taken as the crushing strength. . In addition, passing is 1100 N / piece or more, which is the target crushing strength, and it is impossible to release the vacuum or extrude during molding, there is no powder generation in the molded product, the molded product does not become large, and reduction when using a blast furnace. It was assumed that the material reduction effect was not bad. Table 4 shows examples, and Table 5 shows comparative examples.

In Table 4, Examples 1 to 17 are T.I. C. = 20 to 40% by mass, hydraulic binder = 2.0 to 9.0% by mass, fine silica source = 0.5 to 4.0% by mass, molded product moisture = 9.0 to 14.0% by mass %, and molded with a filling rate of 50 to 95% by volume in the second extrusion part of the vacuum extruder.

Comparative Example 1 is T.I. C. is an example of being outside the upper limit. T. C. was increased to more than 40% by mass, the fluidity of the mixed raw material was lowered and vacuum escape began to occur, and finally the vacuum extrusion molding itself became impossible. Comparative Example 2 is an example in which the blending ratio of the hydraulic binder is off the lower limit, and Comparative Example 3 is an example in which the blending ratio of the particulate silica source is off the lower limit. The hydraulic binder hardens through a chemical reaction with water, and the fine silica source increases the strength by increasing the number of contact points with the raw material particles. Comparative Example 4 is an example of extruding without applying a vacuum. The strength of the molding did not reach the target value.

Comparative Example 5 and Comparative Example 6 are examples of the moisture content of the molding being out of the lower limit and out of the upper limit, respectively. If the water content is too low, the fluidity of the raw material will be significantly reduced, and the extrusion resistance of the screw will increase, making extrusion (molding) impossible. Conversely, if the water content is excessive, extrusion can be performed without problems, but the target strength is not reached, and as shown in Table 5, when the molded products are piled up after molding and cured, the molded products adhere to each other and form large lumps. , there is a problem of pre-crushing when used in a blast furnace.

Comparative Examples 7 and 8 are examples in which the filling rate of the second extruded portion during vacuum extrusion molding is outside the lower limit and the upper limit, respectively. If the filling rate falls below the lower limit, it becomes difficult to continuously form a material seal at the tip of the extruded part, and vacuum breaks occur intermittently, and the raw material of the molded product is discharged in the form of powder. This causes a phenomenon that causes a decrease in the yield of molded products. Further, if the filling rate is excessive, the extrusion load increases and the raw material stays in the extrusion molding section, making continuous molding difficult.

Example 16 is an example in which the average particle size of the fine silica source exceeded 15% of the average particle size of the mixed raw material of non-calcined coal-containing lump ore excluding the fine silica source. Example 17 is an example in which the degree of vacuum of the extruder exceeded -50 kPaG. Although both reached the target value of strength, they were close to the lower limit and cannot be said to be a favorable example.

Table 5 shows comparative examples of deviations from the upper and lower limits of the water content of the molded product. As shown in Table 6, when the carbon-containing agglomerate ore is produced under the above conditions by the vacuum extrusion molding method, molding becomes difficult when the moisture content of the molded body is less than 9% by mass, and when it exceeds 14%, the molded bodies separate from each other. The problem of sticking and clumping was revealed. Therefore, the appropriate moisture content is set to 9 to 14% by mass.

1 mixer 2 inlet 3 first extrusion section (kneading section)
3a casing 3b screw 3c weir formed of perforated plate 4 connecting pipe (vacuum chamber)
5 Second extruded part (extruded part)
5a Casing 5b Screw 6 Molding Unit 7 Vacuum Pump 8 Connection Pipe 9 Vacuum Pump Connection Pipe 10 Production Apparatus for Carbon-containing Agglomerate Ore

Claims (3)

A method for producing a non-calcined carbon-containing agglomerate ore for blast furnace having a carbon content (T.C.) of 15% by mass or more, which is used as a raw material for a blast furnace in steelmaking, comprising:
In terms of the mass ratio of zero water content, the hydraulic binder is 2.0 to 9.0% by mass, the fine silica source is 0.5 to 4.0% by mass, and the ratio of carbon contained in the carbon-containing agglomerate ore raw material ( A coal-containing mass containing 87.0 to 97.5% by mass of iron-containing raw material, carbon-containing raw material, and other raw materials by adjusting the blending ratio of the iron-containing raw material, the carbon-containing raw material, and other raw materials so that the T.C.) is 15 to 40% by mass. For ore raw materials,
Water is added at a mass ratio of 9.0 to 14.0% by mass when the total of the raw material and water is 100% by mass, and is continuously mixed and transferred, and a perforated plate installed in front of the transfer direction. A first extrusion section (kneading section) that forms a first material seal by pushing the mixed raw material into the weir formed by
A connecting portion (vacuum chamber) for vacuum degassing the mixed raw material continuously supplied from the exit side of the weir and transferring it to the second extruding portion;
By pushing the vacuum degassed mixed raw material supplied from the connection part (vacuum chamber) into the molding part equipped with a large number of holes, it is continuously extruded while forming the second material seal to manufacture the molded body. a second extruded portion to
A method for producing a coal-containing agglomerate ore using a production apparatus comprising
A method for producing a non-calcined coal-containing agglomerate ore for a blast furnace, characterized in that the second extruded portion is continuously molded so that the filling rate of the mixed raw material is in the range of 50 to 95% by volume. 2. Production of non-fired coal-containing agglomerate ore for blast furnace according to claim 1, characterized in that the pressure in the connecting part (vacuum chamber) of the manufacturing apparatus for non-fired coal-containing agglomerate ore for blast furnace is -50 kPaG or less. Method. The average particle size of the fine silica source is 15% or less of the average particle size of the mixed raw material of the non-calcined coal-containing lump ore excluding the fine silica source. Item 3. A method for producing a non-fired coal-containing agglomerate ore for blast furnace according to item 1 or 2.

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