JP6992644B2 - Method for producing uncalcined agglomerate for blast furnace and method for producing pozzolan-reactive iron-containing raw material - Google Patents

Description

The present invention relates to a method for producing a non-calcined lump ore for a blast furnace. The present invention relates to a method for producing a non-calcination mass ore for a blast furnace. The present invention also relates to a method for producing a pozzolan-reactive iron-containing raw material for producing a pozzolan-reactive iron-containing raw material from powdered iron ore containing kaolin.

Sintered ore is mainly used as the raw material for iron for blast furnaces in the Japanese steelmaking process. The main iron-containing raw material for the sinter is powdered iron ore having an average particle size of about 2 to 3 mm. Auxiliary raw materials such as limestone and silica stone are mixed with carbonaceous materials such as coke breeze and smokeless charcoal, mixed and granulated while adjusting the water content, and simulated particles (0.5 mm on the surface of nuclear particles of 1 mm or more). It is manufactured by forming a granulated product to which the following fine powder particles are attached) and sintering it with a sintering machine.

On the other hand, fine iron ore such as miscellaneous raw materials (iron-containing dust collector dust, sludge, scale powder, etc. collected from a large amount of sintered dust and blast furnace dust generated in the iron making process) and pellet feed (raw material for pellets). Is also used as an iron raw material for blast furnaces. Since these raw materials are in the form of fine powder in which fine powder particles having a particle size of 0.25 mm or less occupy 80% or more of the whole, when used in the above-mentioned sinter manufacturing process, the granules collapse during sintering. Since the air permeability of the raw material packing layer deteriorates, the productivity of sintering decreases.

Therefore, for the fine iron-containing raw material, a non-calcined agglomeration process is applied in which water is added together with cement, granulated to form agglomerates such as pellets, and then cured to increase the strength. For example, see Patent Documents 1 and 2). The cement bond lump ore produced in this way (hereinafter referred to as non-calcined lump ore) needs to have a certain strength to withstand transportation to the blast furnace and pulverization at the time of loading into the blast furnace. As described above, the required strength is secured by hardening using cement as a hydraulic binder. However, if the amount of cement blended is increased, the amount of slag generated when the obtained uncalcined agglomerate is used in a blast furnace may increase, or the adverse effects of dehydration endothermic of cement in the blast furnace may become apparent. There is. Therefore, in the production of non-calcination agglomerates for blast furnaces, it is desired to reduce the amount of cement added from the viewpoint of reducing the amount of slag and the production cost.

Further, a method has been proposed in which a mass is obtained by using fly ash together with cement as a binder, and fly ash is used as a part of a raw material (see Patent Document 3). Fly ash has pozzolan reactivity, and Ca (OH) ₂ produced by the cement hydration reaction reacts with SiO ₂ , and calcium silicate hydrate (CSH) contributes to the development of strength in cement hydrate. ) Is generated. As a result, if the strength development of the non-calcined agglomerate can be promoted, the amount of cement added can be reduced. However, it cannot be said that the crushing strength (also called crushing strength) after curing when fly ash is used is still sufficient. In addition, the addition of a pozzolan-reactive substance such as fly ash causes an increase in manufacturing cost and also increases the amount of slag generated in the blast furnace.

An oxygen-containing gas is blown into the raw material obtained by heating the raw material obtained by mixing the powdered coal material and the powdered iron ore to 300 ° C. or higher, and the volatile matter generated from the powdered coal material is burned to form the powder in the heated raw material. A method has been proposed in which the temperature rise rate of the charcoal material is increased to sufficiently soften the powdered charcoal material, and then hot forming is performed by a twin roll type molding machine or the like to form a briquette (see Patent Document 4). However, this method is related to hot forming in which powdered coal is softened and used as a binder, and is a so-called cold bond pellet that is cured by using cement like the above-mentioned non-calcination agglomerate. It is a technology different from the manufacturing method.

Japanese Unexamined Patent Publication No. 6-184653 Japanese Unexamined Patent Publication No. 2012-188678 Japanese Unexamined Patent Publication No. 2016-77965 Japanese Unexamined Patent Publication No. 2010-11917

Therefore, the present inventors develop sufficient post-curing strength in order to obtain a non-calcined lump ore for a blast furnace, instead of separately adding a pozzolan-reactive substance as a compounding raw material while reducing the amount of cement added. We made a diligent study on how we could do it. As a result, by heat-treating the iron ore containing kaolin and dehydrating the kaolin, it is possible to obtain an iron-containing raw material having pozzolan reactivity, which is used for at least a part of the iron-containing raw material. We have found that the strength after curing can be enhanced by producing uncalcined agglomerates for blast furnaces, and completed the present invention.

Therefore, an object of the present invention is to use an iron-containing raw material that exhibits pozzolan reactivity instead of separately adding a pozzolan-reactive substance as a compounding raw material, so that sufficient post-curing strength can be obtained. The present invention is to provide a method for producing a calcined agglomerate ore.

Another object of the present invention is to provide a method for producing a pozzolan-reactive iron-containing raw material capable of obtaining an iron-containing raw material having pozzolan reactivity from powdered iron ore containing kaolin.

That is, the gist of the present invention is as follows.
(1) A method for producing a non-calcined agglomerate for a blast furnace by forming an agglomerate into an agglomerate after adjusting the moisture content of an iron-containing raw material and a compounding raw material containing a binder and curing the agglomerate for a predetermined period.
Using cement as the binder and powdered iron ore containing kaolin as at least a part of the iron-containing raw material, the powdered iron ore is heat-treated and the kaolin is dehydrated to prepare a compounding raw material. A method for producing unfired agglomerate ore for a blast furnace.
(2) The method for producing a non-calcined lump ore for a blast furnace according to (1), wherein the powdered iron ore is pulverized to a particle size of 0.125 mm or less and then subjected to the heat treatment.
(3) The method for producing a non-fired lump ore for a blast furnace according to (1) or (2), wherein the powdered iron ore comprises any one or more selected from the group consisting of limonite, hematite, and magnetite. ..
(4) The method for producing a non-calcined agglomerate for a blast furnace according to any one of (1) to (3), wherein the compounding raw material further contains fine powdered coal material.
(5) A method for producing a pozzolan-reactive iron-containing raw material, which comprises heat-treating powdered iron ore containing kaolin and dehydrating the kaolin to obtain an iron-containing raw material having pozzolan reactivity. ..

According to the method for producing a non-calcined agglomerate for a blast furnace of the present invention, instead of separately adding a pozzolan-reactive substance as a compounding raw material, an iron-containing raw material exhibiting pozzolan-reactivity is used, after sufficient curing. Strength will be obtained. Therefore, it becomes possible to reduce the amount of cement added within the range of maintaining the required strength.

Further, according to the method for producing a pozolan-reactive iron-containing raw material of the present invention, an iron-containing raw material having pozolan-reactivity can be obtained from powdered iron ore containing kaolin, and thus the above-mentioned non-calcination for a blast furnace is performed. In addition to the production of lump ore, there are various new iron-containing raw materials having pozolan reactivity, such as being used as an iron-containing raw material for obtaining sinter ore and as an iron-containing raw material for obtaining calcined pellets. It can also be used for various purposes.

FIG. 1 is a graph showing a change in weight when a kaolin reagent is thermally analyzed. FIG. 2 is a graph showing the weight change when the iron ore used in the examples is thermally analyzed.

Hereinafter, the present invention will be described in detail.
In the present invention, a compounded raw material containing an iron-containing raw material and a binder is molded into a lump after adjusting the water content, and cured for a predetermined period to form a non-fired lump ore for a blast furnace (hereinafter, simply "non-fired lump ore"). In producing (referred to as), cement is used as a binder, and powdered iron ore containing kaolin is used as at least a part of the iron-containing raw material, and this powdered iron ore is heat-treated to dehydrate the kaolin. It is used as a compounding raw material.

In general, when the amount of cement added as a binder is reduced, it becomes difficult to maintain sufficient post-cure strength. In order to improve the strength after curing, it is important to promote the production of calcium silicate hydrate (CSH) that contributes to the development of strength in cement hydrate, and the pozzolan reaction represented by the following formula 1 occurs. Let me. That is, Ca (OH) ₂ produced by the cement hydration reaction represented by the following formula 2 is reacted with SiO ₂ so that calcium silicate hydrate (CSH) is produced [Kasai: Concrete Engineering, 21. , (1983) 100.].

In iron ore, SiO ₂ is contained as a gangue component as quartz or kaolin [Al ₂ Si ₂ O ₅ (OH) ₄ ]. However, they usually show little pozzolan reactivity. In addition, it is known that glassy minerals are generally relatively reactive and crystalline minerals such as quartz are difficult to react [Fukaya, Rouki: Cement / Concrete Materials Science, Technical Institute. (2003).]. Therefore, the present inventors have found that pozzolan reactivity is imparted by heat-treating powdered iron ore containing kaolin to dehydrate kaolin and change the crystal structure. That is, by heat-treating the kaolin at a temperature higher than the temperature at which the pyrolysis starts to dehydrate the kaolin and using it as an iron-containing raw material having pozzolan reactivity, the hardening of the cement is promoted and the uncalcined agglomerate is formed. Improves post-curing strength. Although kaolin is referred to as kaolinite as a mineral, it is referred to as kaolin in the present specification as having a common composition (basic chemical formula).

Here, FIG. 1 shows the weight change when 10 mg of the reagent kaolin (Kaolin reagent manufactured by SIGMA-ALDRICH) is subjected to thermal analysis under a 200 mL / min airflow atmosphere of Ar at a heating rate of 20 ° C./min. A graph is shown. As can be seen, kaolin starts dehydration at around 380 ° C and ends at around 600 ° C. Therefore, the heat treatment for dehydrating the kaolin in the powdered iron ore needs to be at a temperature higher than the temperature at which the kaolin is contained in this temperature range (380 to 600 ° C) and starts thermal decomposition, preferably 400 ° C or higher. It is more preferable to carry out at 600 ° C. or higher at which kaolin is completely dehydrated. The upper limit of the temperature of the heat treatment is not particularly limited, but from the viewpoint of saturation of the effect and economic efficiency, the upper limit can be 800 ° C. Further, when performing the heat treatment, it is not necessary to adjust the atmosphere in particular, and the heat treatment can be performed in the atmospheric atmosphere. The heating means is also not particularly limited, and for example, it can be heated by electric furnace heating, infrared heating, or the like. Further, as the heat treatment time, the time when the weight change of the powdered iron ore disappears can be used as a guide, but in general, about 5 minutes or more and 30 minutes or less is sufficient.

Further, as the powdered iron ore containing kaolin, it is preferable to use one pulverized to a particle size of 0.125 mm or less. By using the one adjusted to such a particle size (particle size adjusted), the specific surface area is large and the reactivity is high, so that the strength after curing can be further improved. Here, there is no particular limitation on the particle size adjustment method. For example, as a crushing method, ball mill crushing, roller press crushing, and the like can be mentioned, and as a classification method, sieving, wind power classification, and the like can be mentioned, and these may be performed in combination. Further, the particle size of the powdered iron ore may be adjusted before the heat treatment or after the heat treatment, but it is preferable from the viewpoint of making the dehydration reaction of kaolin more efficient. It is preferable to grind the powdered iron ore containing kaolin to a particle size of 0.125 mm or less and then heat-treat it.

The powdered iron ore containing kaolin may be any one containing kaolin as a gangue, and examples of the type of iron ore include limonite, hematite, magnetite, and the like, and one or two of these. It may contain more than a seed. In general, iron ore having a high Al ₂ O ₃ component often contains kaolin, so that the presence or absence of kaolin can be conveniently determined from the chemical component value. However, since the Al ₂ O ₃ component may exist as gibbsite [Al (OH) ₃ ] or the like, the weight is reduced by dehydration in the temperature range of 380 ° C to 600 ° C by thermogravimetric measurement as shown in FIG. It is desirable to select what is observed.

Here, the weight loss in the temperature range of 380 ° C. to 600 ° C. is taken as the dehydration weight, and from the reaction formula (1) of Al ₂ Si ₂ O ₅ (OH) ₄ → Al ₂ Si ₂ O ₇ + 2H ₂ O, it is powdery. The kaolin content in iron ore can be determined. Therefore, the kaolin content may be used as an index to determine the blending ratio of the powdered iron ore containing kaolin in the blending raw material. For example, it is preferable that the cement used as a binder and the kaolin content in the powdered iron ore have a mass ratio of 1: 0.4 to 1: 1.1, whereby the pozzolan reaction can be efficiently carried out. Can be made to be. Although it depends on the type of iron ore, the kaolin content is generally about 0.1 to 8% by mass.

In the present invention, as the iron-containing raw material, a material other than powdered iron ore containing kaolin may be used in combination. Generally, as a compounding raw material for non-calcined agglomerates, a fine iron-containing raw material in which fine powder particles having a particle size of 0.25 mm or less occupy 80% or more of the whole is used, but in the present invention, these are mixed. You may do it. Examples of such fine powder iron-containing raw materials include iron-containing dust such as sintered dust and blast furnace dust generated in the iron making process, fine powder iron ore used as pellet feed (raw material for pellets), sludge, and scale. Examples thereof include powder and powdered iron ore crushed in advance with a crusher.

Further, the cement used as a binder is not particularly limited, and examples thereof include Portland cement such as ordinary Portland cement and early-strength Portland cement (early-strength cement), as well as blast furnace cement and alumina cement.

Further, in the present invention, powdered charcoal material may be included as a compounding raw material. By adding the powdered coal material necessary for reducing the reduced oxygen in the iron-containing raw material to form metallic iron to form a charcoal-containing non-calcined agglomerate, the ratio of reducing material during blast furnace operation can be reduced. Can be planned. As such a powdery coal material, a material having a particle size of 1 mm or less is generally used, and specific examples thereof include blast furnace primary ash, coke dust, coke powder, and coal.

In the present invention, since kaolin is dehydrated by heat treatment and powdered iron ore having pozzolan reactivity is used as an iron-containing raw material, it is not necessary to separately add a pozzolan-reactive substance such as fly ash. Therefore, in the case of containing powdered carbonaceous material, although it depends on the required post-curing strength, when all the iron-containing raw materials are made into powdered iron ore having pozolan reactivity, iron in the compounding raw material is used. As an example, the blending ratio is shown such that the contained raw material is 60% by mass or more and 87% by mass or less, the cement as a binder is 3% by mass or more and 10% by mass or less, and the powdered iron material is 10% by mass or more and 30% by mass or less. Can be done. Needless to say, the present invention does not exclude the addition of a pozzolan-reactive substance such as fly ash.

Then, in the present invention, a non-calcined agglomerate is produced in the same manner as a known method except that the powdered iron ore having pozzolan reactivity is used as at least a part of the iron-containing raw material as described above. Can be done. That is, for example, the compounding raw material is cut out from the hopper so as to have a predetermined compounding amount, crushed with a crusher such as a ball mill as necessary, and water is used with a kneader such as a Reidge mixer or an Erich mixer. And knead while adjusting the water content. At that time, the water content is generally set to about 9 to 14% by mass when made into pellets (lumps). Then, for example, granulation is performed with a granulator such as a pan pelletizer, and further sieved with a vibrating sieve or the like to obtain granulated pellets (lumps). At this time, each raw material constituting the blended raw material may be crushed and then blended to form a blended raw material. In addition, instead of granulating the compounded raw material that has been kneaded by adjusting the water content into agglomerates by a granulator, for example, it is made into a briquette by using a compression molding machine or extruded by an extrusion molding machine. You may try to obtain a mass.

Then, the agglomerates obtained as described above can be cured for a predetermined period to obtain uncalcined agglomerates. At that time, by dehydrating the kaolin contained in the powdered iron ore to impart pozzolan reactivity, it is possible to increase the production of CSH by the pozzolan reaction in the curing process.

Here, in the production of non-calcined agglomerates, it is generally performed in two stages of primary curing and secondary curing. The primary curing is strong enough to withstand normal handling without pulverization of the agglomerates, and until strong bonds between the particles of the agglomerates proceed and a large number of agglomerates agglomerate. It develops strength in a range that does not reach. The curing time (duration) of this primary curing is generally about 2 to 3 days.

After the primary curing, the agglomerates are crushed and the secondary curing is performed until the strength that can withstand the use in the blast furnace is developed. For example, after the primary curing, by breaking the pile of agglomerates (pile such as pellets), the agglomerates are moved from the primary curing yard to the secondary curing yard while separating the individual agglomerates. .. At that time, the agglomerates after the primary curing may be crushed when they are loaded in the secondary curing yard or the like. The curing time (duration) of this secondary curing is generally about 2 weeks. Further, as the strength finally required by the secondary curing (post-curing strength), it is generally desirable that the crushing strength per agglomerate is 980 N / p or more.
In this way, by including the crushing operation (crushing process) at the time of slight mutual adhesion (primary curing), adhesion does not occur after that, so curing by direct loading in the yard etc. (secondary curing) ) Is possible.

Further, the iron-containing raw material having pozzolan reactivity obtained in the present invention can be used for other than the production of the non-calcined agglomerate for blast furnace as described above. That is, by heat-treating powdered iron ore containing slaked iron and dehydrating the slaked iron, it is possible to impart pozzolan reactivity while being an iron-containing raw material. Therefore, for example, when obtaining a sinter. By using it as an iron-containing raw material and adding quicklime or slaked lime at the same time, it becomes possible to increase the cold strength of the simulated particles in the manufacturing process. In addition, by using it in combination with quicklime or slaked lime in the process of producing calcined pellets, the cold strength of the calcined pellets before calcining can be increased.

The present invention will be specifically described with reference to Examples. The present invention is not limited to these contents.

(Example 1)
Experiment I (Experiment No. 1) to produce uncalcined agglomerates using Australian limonite as the kaolin-containing iron ore, coke powder as the carbonaceous material, and early-strength cement as the binder as follows. ~ 9) was performed. These raw materials have the chemical components shown in Table 1. In Experiment Nos. 1 to 8, the raw material compounding ratio was 75 mass% for limonite produced in Australia, 20 mass% for coke powder, and 5 mass% for early-strength cement (hereinafter referred to as compounding ratio 1). Australian limonite was 72 mass%, coke powder was 20 mass%, and early-strength cement was 8 mass% (hereinafter referred to as compounding ratio 2). As shown in Table 2, for limonite produced in Australia, the particle size is adjusted under four conditions of 1 mm or less, 0.25 mm or less, 0.125 mm or less, and 0.045 mm or less by pulverization and sieving. did. The particle size of coke powder is 1 mm or less.

Among these compounded raw materials, Australian limonite (hereinafter, simply referred to as iron ore) of Experiment Nos. 5 to 8 was heat-treated at 600 ° C. for 30 minutes in an air atmosphere after adjusting the particle size. FIG. 2 shows the results when the weight change (TG) of this iron ore was confirmed in advance, and the weight change in the case of the kaolin reagent (Kaolin reagent manufactured by SIGMA-ALDRICH) and the temperature at the time of these thermal analyzes. The profile is also shown. As can be seen from FIG. 1 above, kaolin starts dehydration at around 380 ° C and ends at around 600 ° C. Therefore, the weight decrease between 380 ° C and 600 ° C is defined as the dehydration weight, and the above-mentioned reaction formula is used. The kaolin content can be determined from (1). That is, the weight change of the iron ore in this temperature range is 0.99%, and the kaolin content of the iron ore used in this example is assumed to correspond to the desorption of the water of crystallization of the reaction formula (1). Is 7.0 mass%. The thermogravimetric analysis in FIG. 2 was performed by thermal analysis in an atmosphere of 200 mL / min airflow of Ar using 10 mg as a measurement sample.

The compounding raw materials of Experiments No. 1 to 9 were kneaded while adjusting the water content by adding water using a kneader, and pellets (lumps) were prepared by a disc pelletizer. The obtained pellets had an average particle size of 15 mm, and the water content in the pellets was in the range of 10 to 13 mass%. Then, the prepared pellets were naturally cured for 14 days, and the crushing strength after curing was measured. Here, the crushing strength after curing was measured according to JIS M8718. That is, a compressive load was applied to one sample (pellet) at a specified pressurizing board speed (12 mm / min), and the maximum value of the compressive load at the time when the pellet broke was taken as the crushing strength. This measurement was carried out with 60 samples for each experiment number, and the average value of each was calculated. The results are shown in Table 2.

In Table 2, the particle size of iron ore is shown for the post-curing pellets of Experiment Nos. 1 to 4 in which the iron ore in the compounding raw material is not heat-treated and the post-curing pellets of Experiment Nos. 5 to 8 which are heat-treated. The crushing strengths are compared with the same ones, and the strength improvement effect cost is described. According to this, by using the heat-treated iron ore as a compounding raw material, the strength after curing is increased in all of the iron ores as compared with those having the same particle size, and the iron ore is imparted with pozzolan reactivity by the heat treatment. It is thought that it was a result. Among them, when the particle size of iron ore is 0.125 mm or less (Experiment No. 7) and 0.045 mm or less (Experiment No. 8), the effect of improving the strength is remarkable, and the cement addition amount is 8%. It was possible to develop the same strength as the No. 9 post-curing pellet. That is, according to the present invention, the strength after curing can be ensured even if the amount of cement added is reduced.

(Example 2)
Experiment No. 1 was carried out in the same manner as in Example 1 except that the iron ore (brown iron ore produced in Australia) whose particle size was adjusted to 0.045 mm or less was heat-treated at each temperature shown in Table 3 for 30 minutes. The crushing strength of the pellets after curing according to 10 to 14 was measured. The results are shown in Table 3. In addition, here, each strength improvement effect margin is described as compared with the case of Experiment No. 4 in Example 1.

As can be seen from the results shown in Table 3, when the iron ore in the compounding raw material was heat-treated at 300 ° C. (Experiment No. 10), after curing when it was not heat-treated (Experiment No. 4). There was no difference from the strength. It is considered that this is because kaolin in iron ore did not cause dehydration reaction. In addition, when the iron ore was heat-treated at 400 ° C or higher (Experiment Nos. 11 to 14), the strength after curing was increased as compared with the case where the heat treatment was not performed (Experiment No. 4). It is probable that the iron ore was imparted with pozzolan reactivity by heat treatment. Above all, as the temperature of the heat treatment increased, the cost of improving the strength increased. However, when the temperature of the heat treatment was 600 ° C. or higher, the strength improving effect tended to be saturated.

Claims (5)

It is a method of producing a non-calcined agglomerate for a blast furnace by molding an iron-containing raw material and a compounding raw material containing a binder into agglomerates after adjusting the water content and curing them for a predetermined period.
Using cement as the binder and powdered iron ore containing kaolin as at least a part of the iron-containing raw material, the powdered iron ore is heat-treated and the kaolin is dehydrated to prepare a compounding raw material. A method for producing unfired agglomerate ore for a blast furnace. The method for producing a non-calcined agglomerate for a blast furnace according to claim 1, wherein the powdered iron ore is pulverized to a particle size of 0.125 mm or less and then heat-treated. The method for producing a non-fired lump ore for a blast furnace according to claim 1 or 2, wherein the powdered iron ore comprises any one or more selected from the group consisting of limonite, hematite, and magnetite. The method for producing a non-calcined agglomerate for a blast furnace according to any one of claims 1 to 3, wherein the compounding raw material further contains fine powdered coal material. A method for producing a pozzolan-reactive iron-containing raw material, which comprises heat-treating powdered iron ore containing kaolin and dehydrating the kaolin to obtain an iron-containing raw material having pozzolan-reactivity.

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