JP2006322058A - Method for manufacturing non-fired agglomerated ore - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a high-strength non-fired agglomerated ore at a good efficiency. <P>SOLUTION: The method for manufacturing a non-fired agglomerated ore includes extrusion-molding an agglomerated ore composition containing an iron oxide raw material, a hydraulic binder, clay, and water under reduced pressure, wherein the iron oxide raw material contains a fine powder-like iron oxide raw material having a grain size of 0.125 mm or smaller in an amount of 20 mass% or less based on the total weight of the iron oxide raw material. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a non-fired agglomerated mineral, and particularly relates to a method for efficiently producing a high-strength non-fired agglomerated ore.

  In the blast furnace for iron making, from the viewpoints of handleability and operability, a raw material for iron making in a granular or pellet form is usually used instead of a powder form. An example of such a raw material for iron making is sintered ore. The sintered ore is generally obtained by sintering an iron oxide raw material such as iron ore as a main raw material, and powdered limestone or silica as a secondary raw material.

However, production of such sintered ore has problems such as requiring a large amount of energy and a large amount of CO ₂ emission. Furthermore, in recent years, various ores having different qualities may be used as raw materials for iron making as the yield of high-quality ores decreases. Therefore, when an ore with low sinterability is used, there may be a problem that it is difficult to obtain an intended raw material for iron making even if it is simply sintered.

  On the other hand, it has also been proposed to use a non-fired agglomerated mineral obtained by binding an iron oxide raw material or an auxiliary raw material with a binder such as cement, for example, as a steelmaking raw material for a blast furnace. However, unfired agglomerated minerals have low strength because they are not fired. Therefore, in Patent Document 1, in order to increase the strength of the non-fired agglomerated mineral, iron-containing fine powder (dust) having a relatively finer particle size than this is blended with the iron raw material (sintered ore or sintered sieve powder). Has been proposed for use in the production of unfired agglomerates. This patent document 1 shows that the crushing strength of the non-fired agglomerated mineral is higher as the fine powder content is larger (see particularly FIG. 2 of patent document 1).

Moreover, in the manufacturing method of a non-baking agglomerated mineral, the curing process which hardens a cement etc. by leaving the shape | molded raw agglomerated mineral in the air (in the wet air) is required. However, simply leaving the green agglomerate takes a long time for curing. In such a case, it is necessary to occupy a curing yard where raw agglomerates are left for a long time. Therefore, in order to shorten the curing time, it has been proposed to perform curing in a carbon dioxide gas atmosphere or a heated gas atmosphere containing water vapor and carbon dioxide (for example, Patent Documents 2 and 3). However, in these methods, equipment for generating a gas atmosphere is essential.
JP-A-7-278687 JP-A-9-71824 JP 2000-11960 A

This invention is made | formed in view of the said situation, The objective provides the method which can manufacture a high intensity | strength non-baking agglomerate efficiently, specifically in a shorter curing time. That is.
Furthermore, in order to produce a non-fired agglomerated mineral, a binder such as cement is required, but such a binder is an impurity for steel produced from the non-fired agglomerated mineral, and it is preferable that it be as small as possible. . Moreover, in order to raise the efficiency at the time of iron-making from a non-baking agglomerated mineral, it is preferable that there are few things other than iron oxide raw materials, such as a binder, in a non-baking agglomerated mineral. Accordingly, a further object of the present invention is to provide a method capable of efficiently producing a high-quality, high-strength non-fired agglomerated mineral with a smaller amount of binder or the like.

  The present invention capable of achieving the above object is a method for producing an unfired agglomerated ore, which comprises an iron oxide raw material, a hydraulic binder, clay and water. The iron oxide raw material includes a finely divided iron oxide raw material having a particle size of 0.125 mm or less, and extrusion molding (hereinafter, may be abbreviated as “reduced pressure extrusion”) while reducing the pressure. It is characterized by being contained in a total amount of 20% by mass or less. Cement and / or blast furnace slag can be used as the hydraulic binder.

  As a result of intensive studies by the present inventor, in the method for producing a non-fired agglomerated ore by reduced pressure extrusion, the non-fired agglomeration is reduced as the amount of finely divided iron oxide raw material having a particle size of 0.125 mm or less in the iron oxide raw material is reduced. It has been found that the compressive strength of the ore can be improved. The configuration of the present invention based on such knowledge and its effects are surprising. This is because in normal production of non-fired agglomerated minerals, as disclosed in Patent Document 1, it is considered that the more the fine iron raw material is, the higher the compressive strength is. The mechanism by which the effect of the present invention is achieved is unknown, but can be estimated as follows. However, the present invention is not limited to the following estimation.

  In normal non-fired agglomerate molding that does not rely on reduced pressure extrusion, the compressive strength is considered to increase as the amount of fine powder in the iron raw material increases. This is because the contact area increases as the amount of fine powder in the iron raw material increases, which is considered to lead to an improvement in compressive strength. On the other hand, in the reduced pressure extrusion of the present invention, the smaller the amount of fine powder in the iron raw material, the better the compressive strength. This is considered to be due to the fact that the iron raw materials are strongly bonded to each other in the reduced pressure extrusion as compared with the normal extrusion molding. If the iron raw materials are strongly joined to each other in this way, the strength of the iron raw material itself is likely to be reflected in the unfired agglomerated ore. Therefore, the smaller the amount of fine powder, that is, the greater the amount of iron raw material with a larger particle size, the greater the effect that the strength of the iron raw material itself, which seems to be stronger than the joint between the iron raw materials, is reflected. It is thought that the compressive strength of is improved.

  Furthermore, according to the method of the present invention, a high-strength non-fired agglomerated ore can be obtained even when the agglomerated ore formed by vacuum extrusion is cured for a short time. Further, as shown in the examples, according to the method of the present invention, high-grade agglomerates with high compressive strength can be obtained even when the blending amounts of cement and clay are 10 parts by mass and 100 parts by mass respectively in 100 parts by mass of the agglomerate composition. Can be manufactured.

BEST MODE FOR CARRYING OUT THE INVENTION

  One feature of the method for producing a non-fired agglomerated mineral of the present invention is to extrude the agglomerated mineral composition while reducing the pressure. Here, the reduced pressure in the present invention means to reduce the pressure in the extrusion molding apparatus to less than atmospheric pressure, and the pressure is usually reduced to 0.085 MPa or less on the absolute basis of MPa. In the present invention, a preferable degree of reduced pressure is 0.020 MPa or less, more preferably 0.016 MPa or less, and still more preferably 0.005 MPa or less on the absolute basis of MPa.

  For extrusion molding, a screw-type twin-screw extruder, a single-screw extruder, a roller-type extruder, or the like can be used. Further, in the following examples, the extruded continuous molded product is cut to obtain a cylindrical agglomerate, but the shape of the agglomerated mineral is not limited to this, and after the continuous molded product is cut, further press molding is performed. For example, it can be formed into various shapes such as a spherical shape.

The production method of the present invention is also characterized by using an agglomerated composition in which the content of finely divided iron oxide raw material having a particle size of 0.125 mm or less is 20% by mass or less in the total amount of the iron oxide raw material. . As the iron oxide raw material, blast furnace dust, converter dust, mill scale and the like containing iron oxide as a main component can be used in addition to iron ore generally used as a raw material for iron making. Various types of iron ores can be used, such as hematite (hematite, Fe ₂ O ₃ ), magnetite (magnetite, Fe ₃ O ₄ ), goethite (Fe ₂ O ₃ .H ₂ O). Dolomite ore may be used as a limonite-based ore containing a large amount of Mg or a MgO-containing substance. Also, maramba ore with low sinterability can be used.

  The fine powder content with a particle size of 0.125 mm or less can be adjusted, for example, by passing the iron oxide raw material through a sieve having a sieve mesh size of 0.125 mm. In this case, for example, an iron oxide raw material that has been sieved until the fine iron oxide raw material does not fall under a 0.125 mm sieve can be used. In addition, the iron oxide raw material applied to the sieve is sampled, and the particle size distribution of the sample is measured by an optical particle size distribution measuring instrument or a small sieve machine. You can also use In addition, in order to use fine powder effectively, the fine powder content of 0.125 mm or less is added to the iron oxide raw material whose fine powder content is less than 20 mass% and the fine powder content does not exceed 20 mass%. Can be used.

  The blending amount of the iron oxide raw material is preferably 60 parts by mass or more in terms of the proportion occupied in 100 parts by mass of the solid content of the agglomerated mineral composition. This is because agglomerates with a high blending amount of the iron oxide raw material can efficiently produce a large amount of steel in iron making. A more preferable blending amount of the iron oxide raw material is 70 parts by mass or more in terms of the ratio occupied in 100 parts by mass of the solid content of the agglomerated mineral composition. In addition, the upper limit of the compounding amount of the iron oxide raw material may be determined in consideration of the compounding amount of clay to be blended for improving moldability and the hydraulic binder to be blended for curing.

  In the present invention, the upper limit of the particle size of the iron oxide raw material is not particularly limited as an invention, and may be appropriately determined from the viewpoint of implementation such as the structure or availability of an actually used extruder. In view of availability, it is desirable to use one having an upper limit of particle size of about 5 mm or less.

  In the present invention, clay is used as a component of the agglomerated mineral composition. It is because the plasticity at the time of shaping | molding can be ensured by mix | blending clay, and it can shape | mold favorably. The clay in the present invention is a highly plastic soil material mainly composed of a fine hydrous aluminum silicate material, and mainly contains kaolin, halloy stone, diaspore, quartz, sericite, phyllite, and the like. Although it says a thing, it does not specifically limit about the kind of concrete clay, A quarrying waste soil, the waste soil for ceramics, etc. can be used.

  The blending amount of clay is preferably in the range of 5 to 30 parts by mass in the proportion of 100 mass parts of the solid content of the agglomerated mineral composition. The proper blending amount of clay depends on the amount and size of the iron oxide raw material to be used, but if it is too small, the kneaded material becomes insufficiently plastic and cannot be molded well, so the solid content of the agglomerated mineral composition is 100 mass. It is good to mix | blend so that it may become 5 mass parts or more in a part. A more preferable blending amount of clay is 10 parts by mass or more. On the other hand, if the amount of clay is too large, the iron content in the agglomerated ore will be reduced, which may cause a decrease in productivity of the blast furnace, as well as problems such as insufficient agglomerate strength. It is preferable to set it as 30 mass parts or less in 100 mass parts of solid content of an agglomerated mineral composition. More preferably, it is 25 parts by mass or less.

  In the present invention, a hydraulic binder that is cured with time by adding water is used. As the hydraulic binder, for example, cement, bentonite, blast furnace slag, or the like can be used. In addition to the usual so-called Portland cement, commercially available Portland cement, super early Portland cement, moderately hot Portland cement, blast furnace cement containing blast furnace slag, silica cement containing silica in Portland cement, fly Fly ash cement containing ash or alumina cement mixed with alumina can be used.

Examples of hydraulic binders include blast furnace slag and converter slag containing SiO ₂ , CaO, and Al ₂ O ₃ as main components. Further, bentonite may be used as a hydraulic binder, and sodium-based and calcium-based ones can be used without particularly limiting the brand.

  These hydraulic binders are mainly used alone, but two or more kinds can be used in combination if necessary. Cement and / or blast furnace slag is preferably used as the hydraulic binder in the process of the present invention. The blending amount of the hydraulic binder may be appropriately determined in consideration of the strength, formability, curing time, etc. required for the agglomerate, but in that case, the blending amount of the iron oxide raw material and clay is also considered. It is good to do.

  The agglomerated mineral composition of the present invention contains water for the hardening of the hydraulic binder. The amount of water to be blended is preferably adjusted so that the moisture content of the agglomerated composition is 14% by mass ± 5% by mass based on the total mass of the agglomerated mineral composition.

  There are no particular limitations on the method of mixing or kneading the components and the order of adding the components in producing the agglomerated composition. Mixing or kneading may be performed by a generally used method, and a mixer, a kneader, or a twin-screw or single-screw kneader can be used. However, in order to mix the components of the agglomerated composition satisfactorily, it is preferable to first mix the iron oxide raw material, clay, and hydraulic binder, and add water to the mixture to knead. The agglomerated mineral composition thus obtained is subjected to the aforementioned vacuum extrusion.

  The agglomerated mineral composition of the present invention may contain other additives in addition to the iron oxide raw material, clay, hydraulic binder and water. For example, in order to adjust the curing time, the agglomerated mineral composition mainly comprises an inorganic metal element. It may contain a curing agent.

  The molded product (green agglomerate) obtained by the reduced pressure extrusion according to the present invention needs to be cured. Here, the term “curing” as used in the present invention means that the raw agglomerated ore is hardened by the reaction of water and a hydraulic binder (this also includes a hydraulic component present in the iron oxide raw material in some cases). It means leaving the agglomerate for a certain period of time. Curing is performed by leaving the green agglomerate in a curing yard, preferably an indoor curing yard. While leaving the green agglomerate, the green agglomerate may be heated or carbon dioxide and / or steam may be supplied. In addition, it is included in the curing as used in the present invention to cure the green agglomerated mineral obtained by the reduced pressure extrusion molding over a period of time during transportation to another place. When leaving the green agglomerates for curing, they may be arranged regularly, but from the viewpoint of productivity, they may be stacked somewhat messy.

  According to the method of the present invention, there is little tendency for the molded products to coalesce immediately after extrusion or during curing. For this reason, it is not necessary to provide sufficient intervals between the individual molded products, and the space for the curing yard can be saved. Moreover, even if the molded products are stacked and cured, the handling workability after curing is extremely good.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, and may be implemented with appropriate modifications within a scope that can meet the gist of the present invention. These are all included in the technical scope of the present invention.

  As schematically shown in FIG. 1, 80 parts by mass of iron ore 1 (under-sieving powder of product pellets) having a composition shown in Table 1 as an iron oxide raw material, 10 parts by mass of cement 2 (ordinary Portland cement), and clay 3 (quarry waste) Sat) A mixture containing 10 parts by mass was conveyed to the kneader 5 by the conveyor 4, and 10 parts by mass of water 6 was added by the kneader 5 and kneaded to obtain an agglomerated composition. Then, the agglomerated composition was charged into a reduced pressure extrusion molding machine 7 and extruded while reducing pressure (0.016 MPa in absolute terms), and the resulting continuous molded product 8 was cut with a cutter 9 to obtain a diameter. A cylindrical shaped product (green agglomerate) 10 having a height of about 50 mm and a height of about 130 mm was obtained. The raw agglomerated mineral 10 was moved to an indoor curing yard 11 and allowed to stand at room temperature for 1, 2, and 7 days to obtain agglomerated minerals. The average compressive strength of the agglomerate thus obtained was measured. These results are also shown in Table 1.

  From the results shown in Table 1, the present invention using a fine iron ore content having a particle size of 0.125 mm or less and 20 mass% or less in any case where iron ores having an upper particle size upper limit of 1 mm and 3 mm are used. It is shown that a non-fired agglomerated mineral having a high average compressive strength was produced as compared with a comparative example using a fine powder content of 40% by mass.

1 is a process diagram schematically illustrating one embodiment of the present invention.

Explanation of symbols

1 Iron oxide raw material (Ore)
2 Cement 3 Clay 4 Conveyor 5 Kneading machine 6 Water 7 Vacuum extrusion molding machine 8 Continuous molded product 9 Cutter 10 Molded product (green agglomerate)
11 Curing Yard

Claims (2)

A method for producing a non-fired agglomerated mineral,
The production method includes extruding an agglomerated mineral composition containing an iron oxide raw material, a hydraulic binder, clay and water while reducing the pressure,
The iron oxide raw material contains finely divided iron oxide raw material having a particle size of 0.125 mm or less in a total amount of the iron oxide raw material of 20% by mass or less.   The method according to claim 1, wherein cement and / or blast furnace slag is used as the hydraulic binder.

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