JP6880951B2 - Manufacturing method of coal-containing agglomerate and coal-containing agglomerate - Google Patents

Description

The present invention relates to a method for producing a coal-containing agglomerate ore and a coal-containing agglomerate ore.

In the blast furnace, iron-based raw materials (raw materials containing iron oxide, mainly sintered ore) and coke are charged in layers from the top of the furnace, and hot air is blown from the tuyere at the bottom of the blast furnace. As a result, the iron oxide descending in the blast furnace is heated and reduced by the reducing gas mainly composed of CO. That is, pig iron is manufactured.

In such blast furnace operation, studies are being conducted on techniques for reducing the ratio of reducing agents from the viewpoint of energy saving and the like. Here, the reducing agent ratio is shown as, for example, the sum of the basic units of all the reducing materials introduced into the blast furnace, typically the basic unit of coke and the basic unit of pulverized coal blown from the tuyere.

Patent Documents 1 to 3 disclose a coal-containing agglomerate ore as an example of such a technique. The coal-containing lump ore is produced by granulating a compounding raw material containing an iron-containing substance, a carbonaceous material, and a hydraulic binder together with water, and then curing the granulated product. The hydraulic binder hydrates and solidifies during curing. Therefore, the hydraulic binder functions as a binder for coal-containing agglomerate ore. That is, if the coal-containing lump ore is pulverized during transportation to the blast furnace or when it is put into the blast furnace, the fluidity of the gas in the blast furnace may decrease. This is because the pulverized coal-containing agglomerate ore may cause clogging in the blast furnace. Therefore, a hydraulic binder is used to maintain the strength of the coal-containing agglomerate ore (specifically, the strength after curing) and suppress pulverization.

Japanese Unexamined Patent Publication No. 2008-95177 Japanese Unexamined Patent Publication No. 2012-21163 Japanese Unexamined Patent Publication No. 2014-25135

By the way, such a hydraulic binder is discharged from the blast furnace as slag. Therefore, from the viewpoint of reducing the amount of slag and the cost of producing coal-containing agglomerates, it has been required to reduce the amount of hydraulic binder in the coal-containing agglomerates.

In this respect, there is a problem that simply reducing the amount of hydraulic binder in the coal-containing agglomerate ore lowers the strength of the coal-containing agglomerate after curing. If the post-curing strength of the coal-containing agglomerate ore decreases, the possibility that the coal-containing agglomerate ore will be pulverized during transfer to the blast furnace or when it is put into the blast furnace increases.

On the other hand, it is known that reducing the amount of carbonaceous material contained in the coal-containing lump ore increases the post-curing strength of the coal-containing lump ore. Therefore, it is conceivable to reduce the amount of carbonaceous material in the coal-containing lump ore, but this method cannot sufficiently achieve the purpose of reducing the reducing agent ratio, which is the original purpose of the coal-containing lump ore.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to reduce the amount of water-hard binder while maintaining the amount of carbonaceous material and the post-curing strength of the coal-containing agglomerate ore. It is an object of the present invention to provide a new and improved method for producing a coal-containing agglomerate ore and a coal-containing agglomerate which can be produced.

In order to solve the above problems, according to a certain viewpoint of the present invention, it is a single-structured coal-containing agglomerate ore containing an iron-containing substance, a carbonaceous material, and a hydrate of a hydraulic binder, and the carbonaceous material is a particle. Provided is a coal-containing agglomerate ore characterized in that the diameter is less than 1 mm and the proportion of carbonaceous particles having a diameter of 150 μm or less is 8% by mass or less.
According to another aspect of the present invention, it is a method for producing a coal-containing agglomerate ore, wherein a carbonaceous material having a particle size of less than 1 mm and a carbonaceous material having a particle size of a median diameter or more are used. It is classified into two categories, a coarse-grained part containing particles and a fine-grained part containing carbon dioxide particles having a particle size smaller than the median size, and is carbon-containing using a compounding raw material containing a coarse-grained part, an iron-containing substance, and a water-hard binder. A method for producing a coal-containing agglomerate ore is provided, wherein the agglomerate ore is produced, and the coarse-grained portion has a proportion of carbonaceous particles having a particle size of 150 μm or less of 8% by mass or less.

Further, the iron-containing substance may contain particles having a particle size of 44 μm or less in a proportion of 60% by mass or more.

As described above, according to the present invention, a carbonaceous material is classified into a coarse-grained portion and a fine-grained portion, and a coal-containing agglomerate ore is produced using the coarse-grained portion. Therefore, the surface area of the coal material in the coal-containing agglomerate ore, in other words, the area of the interface area of the hydrate of the carbon material / hydraulic binder having a weak bond strength can be reduced. Therefore, the post-curing strength of the coal-containing agglomerate ore can be increased. Therefore, the amount of hydraulic binder required to set the post-curing strength of the coal-containing agglomerate ore to a certain target value can be reduced. Further, it is not necessary to reduce the amount of carbonaceous material in the coal-containing lump ore in order to set the post-curing strength of the coal-containing lump ore to the target value. Therefore, it is possible to reduce the amount of hydraulic binder while maintaining the amount of carbonaceous material and the strength after curing of the coal-containing lump ore.

It is a flowchart which shows the processing procedure of the manufacturing method of the coal-containing agglomerate ore which concerns on embodiment of this invention. It is a graph which shows the particle size distribution of each material.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, so that duplicate description will be omitted.

<1. Examination by the present inventor>
The present inventor diligently studied the characteristics of each component contained in the coal-containing lump ore, and as a result, came up with the method for producing the coal-containing lump ore according to the present embodiment. Hereinafter, the contents of the study by the present inventor will be described.

The coal-containing agglomerate has a structure in which hydraulic binder hydrate is filled between the iron-containing material and the particles of the carbonaceous material. Therefore, the post-curing strength of the charcoal-containing agglomerate is the strength of the hydrate itself of the hydraulic binder (that is, the substrate strength), the binding force of the hydrate / iron-containing material interface of the hydraulic binder, and the strength of the hydraulic binder. It is considered to depend on the binding force of the hydrate / carbonaceous material interface.

By the way, carbonaceous materials often show hydrophobicity. Therefore, when a compounding raw material containing an iron-containing substance, a carbonaceous material, and a water-hard binder is granulated together with water, the water existing on the surface of the carbonaceous material particles in the granulated product is the water existing on the surface of the iron-containing substance particles. Is considered to be less than. Then, the hydration reaction of the hydraulic binder occurs at the place where the hydraulic binder and water are present. Therefore, it is considered that the amount of hydraulic binder hydrate formed on the surface of carbon is smaller than the amount of hydraulic binder hydrate formed on the surface of the iron-containing substance. Therefore, it is considered that the binding force of the hydrate / carbonaceous material interface of the hydraulic binder is weaker than the binding force of the hydrate / iron-containing substance interface of the hydraulic binder. For this reason, it is considered that reducing the amount of carbonaceous material contained in the coal-containing agglomerate increases the post-curing strength of the coal-containing agglomerate.

Therefore, the present inventor considered that if the surface area of the carbonaceous material particles in the coal-containing agglomerate can be reduced, the post-curing strength of the coal-containing agglomerate can be increased. Then, the present inventor has come up with the idea of producing a coal-containing agglomerate ore using a charcoal material from which fine particles have been removed in advance as a means for reducing the surface area of the carbonaceous material particles in the coal-containing agglomerate. The present inventor has completed the present invention based on such findings.

<2. Manufacturing method of coal-containing agglomerate>
Next, a method for producing a coal-containing agglomerate ore according to the present embodiment will be described with reference to FIG. In step S10, the carbonaceous material is classified into two categories: a coarse-grained portion containing carbonaceous material particles having a particle size of the median diameter or more and a fine-grained portion containing carbonaceous material particles having a particle size smaller than the median diameter.

Here, the type of carbonaceous material used as a raw material for the coal-containing agglomerate is not particularly limited, and the carbonaceous material used for the conventional coal-containing agglomerate can be preferably used in the present embodiment. For example, examples of the coal material include coke, coal, anthracite, coke dust (dust generated in the process of producing coke), coal char, and the like.

The method for classifying the carbonaceous material is not particularly limited, and any method for classifying fine powder can be preferably used in the present embodiment. Examples of the method for classifying the carbonaceous material include wet sieve, dry sieve, wind power classification, liquid cyclone classification and the like. Wet sieving is a method of sieving a carbonaceous material while flowing it using a liquid (for example, water). The dry sieve is a method of sieving a charcoal material without using such a fluid. Examples of dry sieves include electric heating sieves, low tap sieves and the like. The electric heating sieve is a method of sieving a carbonaceous material while heating it with electric energy. In this method, the charcoal material is classified while heating the charcoal material to remove the water content in the charcoal material, so that clogging of the sieve can be prevented. In the low-tap type sieve, the carbonaceous material is sieved while tapping the sieve with a hammer. Wind power classification is a method of classifying coal particles using wind power. In this method, coal particles are classified according to the difference in specific gravity of the coal particles. The liquid cyclone classification is a wind power classification using a liquid (for example, water).

The coarse-grained portion contains carbonaceous particles having a particle size of the median diameter or more, and the fine-grained portion contains carbonaceous particles having a particle size of less than the median diameter. The median diameter of the carbonaceous material can be calculated from the particle size distribution of the carbonaceous material. The particle size distribution of the carbonaceous material can be measured by, for example, a laser diffraction / scattering method. For example, when the carbonaceous material is sieved, the carbonaceous material particles remaining on the sieve become coarse-grained portions, and the carbonaceous material particles dropped from the sieve become fine-grained portions. The mesh size of the sieve may be smaller than the maximum particle size of the carbonaceous particles before classification. When the mesh size of the sieve satisfies this condition, coal having a particle size equal to or larger than the median diameter always remains in the sieve, and carbonaceous material particles having a particle size smaller than the median diameter are always contained in the fine grain portion. Further, in the present embodiment, the particle size means a so-called sphere-equivalent diameter. The maximum particle size of the coarse particle portion is not particularly limited, but may be less than 1 mm. The mesh opening of the sieve at this time may be in the range of 0.1 mm to 0.5 mm.

Here, the coarse grain portion preferably contains carbonaceous particles having a particle size of 150 μm or less (hereinafter, “150 μm or less” is also referred to as “−150 μm”) in a proportion of 42% by mass or less. More preferably, the coarse-grained portion contains −150 μm of carbonaceous particles in a proportion of 36% by mass or less. As shown in Examples described later, when this condition is satisfied, the post-curing strength of the coal-containing agglomerate ore is further improved. The particle size distribution of the coarse grain portion can be adjusted by adjusting the mesh opening of the sieve, the setting conditions of the wind power classification, and the like. Here, due to the characteristics of the classification operation, the smaller the mesh size of the sieve used and the larger the processing amount per hour, the larger the particle size on the sieve (coarse grain portion) after classification.

In step S20, the compounding raw material containing the iron-containing substance, the coarse-grained portion, and the hydraulic binder is mixed with water and kneaded. As described above, in the present embodiment, the carbonaceous material is classified into a coarse-grained portion and a fine-grained portion, and a coal-containing agglomerate ore is produced using the coarse-grained portion. Therefore, the surface area of the coal material in the coal-containing agglomerate ore, in other words, the area of the interface area of the hydrate of the carbon material / hydraulic binder having a weak bond strength can be reduced. Therefore, the post-curing strength of the coal-containing agglomerate ore can be increased. Therefore, the amount of hydraulic binder required to set the post-curing strength of the coal-containing agglomerate ore to a certain target value can be reduced. Further, it is not necessary to reduce the amount of carbonaceous material in the coal-containing lump ore in order to set the post-curing strength of the coal-containing lump ore to the target value. Therefore, it is possible to reduce the amount of hydraulic binder while maintaining the amount of carbonaceous material and the strength after curing of the coal-containing lump ore.

The type of iron-containing substance is not particularly limited, and the iron-containing substance used in the conventional coal-containing agglomerate ore can be preferably used in this embodiment as well. Examples of such iron-containing substances include iron ore, blast furnace dust, iron-containing dust generated in the process of steelmaking, sludge, scale and the like. Further, the particle size of the iron-containing substance is not particularly limited, and may be appropriately adjusted according to the characteristics required for the coal-containing agglomerate ore. For example, the particle size of the iron-containing substance may be less than 0.1 mm.

Here, the iron-containing substance preferably contains particles having a particle size of 44 μm or less in a proportion of 60% by mass or more with respect to the total mass of the iron-containing substance. The particle size distribution of the iron-containing substance can be measured by, for example, a laser diffraction / scattering method. When the particle ratio of the iron-containing substance to be used is 44 μm or less is less than 60% by mass, the iron-containing substance may be pulverized in advance using a ball mill or the like to a desired particle size. By adjusting the particle size distribution of the iron-containing material in this way, the post-reduction strength of the coal-containing agglomerate can be further improved. This is because the post-reduction strength of the coal-containing agglomerate depends on the bonding state of the metallic iron produced during the reduction and the metallic iron contained in the compounding raw material, and the finer the metallic iron is dispersed, the higher the post-reduction strength is. caused by.

The type of hydraulic binder is not particularly limited, and the hydraulic binder used in the conventional coal-containing agglomerate ore can be preferably used in this embodiment as well. For example, the hydraulic binder may be Portland cement, early-strength Portland cement, alumina cement, blast furnace cement, or the like. The hydraulic binder may contain powder of blast furnace slag.

The compounding raw material containing the iron-containing substance, the coarse grain portion, and the hydraulic binder is mixed with water and kneaded. Here, the compounding ratio of the iron-containing substance, the coarse-grained portion, the hydraulic binder, and the water is not particularly limited, and may be appropriately determined according to the characteristics required for the coal-containing agglomerate ore. For example, the blending ratio of the coarse-grained portion may be 5 to 30% by mass with respect to the total mass of the iron-containing substance, the coarse-grained portion, and the hydraulic binder. Further, the hydraulic binder may be 5 to 10% by mass with respect to the total mass of the iron-containing substance, the coarse grain portion, and the hydraulic binder. The rest of the compounding raw material (parts other than the coarse grain portion and the hydraulic binder) may be all iron-containing substances. Water may be about 10% by mass with respect to the total mass of the compounding raw materials.

In step S30, the granulated product of the compounded raw material is produced by granulating the kneaded product of the compounded raw material. Here, the granulation method is not particularly limited, and any method used for granulation of a conventional carbon-containing agglomerate ore is preferably used in the present embodiment. For example, the granulated product may be a pan pelletizer, a drum pelletizer, a pair of molding rolls having a recess for molding, or the like. The granulated product produced by the pelletizer is a so-called pellet, and the granulated product produced by the molding roll is a so-called briquette.

In step S40, the granulated product is cured. As a result, the hydraulic binder undergoes a hydration reaction and solidifies. By the above steps, a coal-containing agglomerate ore is produced.

As described above, in the present embodiment, since the coal-containing agglomerate ore is produced using the charcoal material excluding the fine-grained portion, the surface area of the charcoal material in the coal-containing agglomerate can be reduced. Therefore, the post-curing strength of the coal-containing agglomerate ore can be increased. In other words, the amount of hydraulic binder required to bring the post-curing strength of the coal-containing agglomerate ore to a certain target value can be reduced. Further, it is not necessary to reduce the amount of carbonaceous material in the coal-containing lump ore in order to set the post-curing strength of the coal-containing lump ore to the target value. Therefore, it is possible to reduce the amount of hydraulic binder while maintaining the amount of carbonaceous material and the strength after curing of the coal-containing lump ore.

<3. Composition of coal-containing lump ore>
The coal-containing agglomerate ore obtained as a result of the above steps contains an iron-containing substance, a carbonaceous material (specifically, the coarse-grained portion described above), and a hydrate of a hydraulic binder. The carbonaceous material preferably contains carbonaceous material particles having a particle size of 150 μm or less in a proportion of 42% by mass or less. More preferably, the carbonaceous material contains carbonaceous material particles having a particle size of 150 μm or less in a proportion of 36% by mass or less.

(Experiment 1)
Next, an embodiment of the present embodiment will be described. In Experiment 1, first, the raw materials shown in Table 1 were prepared. Specifically, five types of coke powder having different particle size distributions were prepared by drying coke powder for 20 minutes with a low-tap type sieve shaker (rotation speed 300 rpm, hammer stroke number 150 tpm). The coke powder A is under the sieve when the sieve is sieved with a mesh opening of 106 μm, and the coke powder D is on the sieve. The particle size of coke powder B has not been adjusted. The coke powder C is a mixture of coke powders A and D in a mass ratio of 1: 9. The coke powder E is on a sieve when sieved with a sieve mesh opening of 125 μm. FIG. 2 shows data obtained by measuring the particle size distribution of each raw material by the laser diffraction / scattering method. The horizontal axis shows the particle size, and the vertical axis shows the integrated distribution (mass%).

Then, a compounding raw material was prepared by mixing early-strength Portland cement: charcoal material (any of coke powders A to E): iron-containing substance at a mass ratio of 7:10:83. Here, as the iron-containing substance, a mixture of Canadian ore A and Brazilian ore B in a mass ratio of 3: 1 was used.

Then, after adding 8% by mass of water to the compounding raw material, the mixture was kneaded with a mixing stirrer to obtain a kneaded product. Then, the kneaded product was granulated with a pan pelletizer to produce raw pellets. The raw pellets were placed in a closed container and cured at 50 ° C. for 2 days. As a result, a coal-containing agglomerate ore was prepared.

The obtained coal-containing agglomerate ore was screened into a coal-containing agglomerate having a particle size of 9.5 to 11.2 mm (9.5 mm or more and less than 11.2 mm). Then, 10 coal-containing agglomerates having a particle size within this range were obtained, and their crushing strengths were measured. Then, the average value of the measured values was adopted as the strength after curing. The crushing strength test method conformed to JIS M8718. That is, a compressive load was applied to one coal-containing agglomerate ore at a specified pressure plate speed, and the maximum value of the compressive load at the time when the pellets broke was defined as the crushing strength. The pressurizing board speed was 12 mm / min. In addition, T.I. Fe (mass% of total iron) was analyzed by X-ray fluorescence, T.I. C (mass% of carbon atom) was measured by the combustion infrared absorption method. Table 2 shows the evaluation results of the coal-containing agglomerate ore.

In Comparative Example 1, coke powder A (removing the coarse grain portion in the charcoal material) was used, and the strength after curing was very low. In Comparative Example 2, the carbonaceous material was used as it was without adjusting the particle size, and although the post-curing strength was improved as compared with Comparative Example 1, the post-cured strength was still low. In Example 1, the ratio of the carbonaceous material particles in which the fine particles were removed and the particle size was −150 μm was 36% by mass or less. Therefore, the strength after curing became very high. In Example 2, the ratio of carbonaceous particles having a particle size of −150 μm was further reduced as compared with Example 1. Therefore, the strength after curing was further increased. In Example 3, the ratio of the carbonaceous material particles having a particle size of −150 μm was 42% by mass or less. In Example 3, since the fine-grained portion was removed, the strength after curing was higher than that in Comparative Examples 1 and 2. However, since the ratio of the carbonaceous particle having a value of −150 μm exceeds 36% by mass, the post-curing strength was lower than that of Examples 1 and 2.

(Experiment 2)
Next, in Example 1, the particle size of the iron-containing substance was adjusted in order to improve the post-reduction strength of the coal-containing agglomerate ore. The particle size of the iron-containing material was adjusted by changing the mixing ratio of Canadian ore A and Brazilian ore B. The particle size distribution was measured by the laser diffraction scattering method. The post-reduction strength was measured according to the load softening test method for ore described in Patent Document 3, and was evaluated by the post-reduction crushing strength at 900 ° C. The crushing strength was measured by the same method as described above. The results are shown in Table 3.

Example 1 uses an iron-containing substance in which Canadian ore A and Brazilian ore B are blended in a mass ratio of 3: 1 and is the same as in Example 1 of (Experiment 1) described above. The ratio of particles having a size of −44 μm (44 μm or less) in the iron-containing substance of Example 1 was approximately 21% by mass.

In Example 4, an iron-containing substance in which Canadian ore A and Brazilian ore B were mixed at a mass ratio of 1: 2 was used, and the ratio of particles having a mass ratio of −44 μm in the iron-containing substance was approximately 54% by mass. It was. The post-reduction strength was slightly improved from 3.9 daN in Example 1 to 4.4 daN.

In Example 5, an iron-containing substance in which Canadian ore A and Brazilian ore B were mixed at a mass ratio of 1: 3 was used, and the ratio of particles having a mass ratio of −44 μm in the iron-containing substance was approximately 60% by mass. It was. The post-reduction strength was significantly improved from 4.4 daN in Example 4 to reach 7.9 daN.

In Example 6, only Brazilian ore B was used as the iron-containing substance, and the ratio of particles having a size of −44 μm in the iron-containing substance was further increased as compared with Example 5. Therefore, the strength after reduction was further improved. In Experiment 2, the strength after curing tended to improve with the miniaturization of the iron-containing substance.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person having ordinary knowledge in the field of technology to which the present invention belongs can come up with various modifications or modifications within the scope of the technical idea described in the claims. , These are also naturally understood to belong to the technical scope of the present invention.

Claims (3)

A single- layer coal-containing agglomerate containing iron-containing substances, carbonaceous materials, and hydraulic binder hydrate.
The carbonaceous material is less than the particle diameter 1 mm, wherein the proportion of less carbonaceous material particles 150μm is equal to or less than 8 wt%, carbonaceous mass Naruko. A method for producing a coal-containing agglomerate ore according to claim 1, wherein the coal-containing agglomerate ore is produced.
A carbonaceous material having a particle size of less than 1 mm is classified into two categories: a coarse-grained portion containing carbonaceous particles having a particle size of less than the median diameter and a fine-grained portion containing carbonaceous particles having a particle size of less than the median diameter.
A coal-containing agglomerate ore was prepared using the compounding raw material containing the coarse-grained portion, the iron-containing substance, and the hydraulic binder .
The coarse-grained portion is a method for producing a coal-containing agglomerate ore , characterized in that the proportion of carbonaceous particles having a particle size of 150 μm or less is 8% by mass or less. The method for producing a coal-containing agglomerate ore according to claim 2 , wherein the iron-containing substance contains particles having a particle size of 44 μm or less in a proportion of 60% by mass or more.

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