WO2022264549A1 - Agglomerated ore assessing method and agglomerated ore - Google Patents

Abstract

Provided is an agglomerated ore assessing method that enables assessment of clustering of reduced iron while taking into consideration the thermal compensation attributed to sensible heat in blown air when reduction is performed at a high hydrogen concentration. The present invention involves: producing a post-reduction aggregate by reducing an agglomerated ore at 1000-1200°C while applying a predetermined load thereon; performing a rotation process on the post-reduction aggregate by using a rotation testing machine; measuring a cluster strength CS of the post-reduction aggregate as calculated by formula (1); and assessing the clustering characteristics of the agglomerated ore by using the cluster strength CS. (1): CS=(W'/W)×100, wherein CS represents the cluster strength (mass %), W represents the mass (g) of the post-reduction aggregate having a particle size equal to or more than the maximum particle size of the agglomerated ore, and W' represents the mass (g) of the post-reduction aggregate obtained after the rotation process using the rotation testing machine and having a particle size equal to or more than the maximum particle size of the agglomerated ore.

Description

Evaluation method of agglomerate ore and agglomerate ore

The present invention relates to an agglomerate evaluation method and an agglomerate ore for evaluating clustering of agglomerate ore.

Global warming due to an increase in CO ₂ has been taken up as an international problem, and reducing its emission has become a global issue. About 1.4 billion tons of the world crude steel production of about 1.9 billion tons is produced by the blast furnace-converter process. Since the blast furnace-converter process uses coal, it emits a large amount of CO ₂ of 2t-CO ₂ /t-Fe. The remaining approximately 500 million tons are produced by direct reduction processes other than the blast furnace-converter process. If the shaft furnace solid reduction + electric furnace method represented by MIDREX (registered trademark), which accounts for more than 60% of the direct reduction process, the CO ₂ emission is about 1.1 to 1.2 t-CO ₂ /t-Fe. can be reduced. In order to reduce CO ₂ emissions from the steel industry, it is necessary to shift from the blast furnace-converter process to the direct reduction process and further increase the reduction rate with hydrogen.

The raw material used in the direct reduction process tends to have a higher iron grade than the blast furnace-converter method. In particular, in reduction using a shaft furnace, pellets of uniform particle size are used as raw materials in order to ensure air permeability in the furnace. It is known that as the reduction progresses and the raw material descends in the furnace, the reduced iron particles adhere to each other due to the load from the raw material accumulated in the high-temperature part in front of the tuyere at the bottom of the shaft furnace, causing clustering. It is If clustering occurs, it becomes a problem that the reduced iron cannot be discharged from the shaft furnace. In order to prevent clustering, it is important to control the properties of the raw material charged into the shaft furnace.

Conventionally, in the MIDREX hot load test described in Non-Patent Document 1, an evaluation is performed to what extent the agglomerated raw material sticks during reduction. According to Non-Patent Document 1, a 2000 g sample is filled in a furnace, and an air flow of 40 L/min with a composition of 45% H ₂ + 30% CO + 15% CO ₂ + 10% N ₂ in an isothermal environment of 850 ° C. The reduction rate is 95. % is returned. 60 minutes after the start of reduction, a load of 147 kPa is applied to the surface of the packed layer of the sample. After the clusters formed by reduction after cooling were rotated 10 times in a 1 m tumbler tester, +25 mm particles were defined as clusters, and the ratio thereof was evaluated as a cluster index.

In the cluster evaluation method described in Non-Patent Document 1, since CO and CO ₂ are contained in the gas, the cohesiveness of the charge when reduced in pure hydrogen cannot be sufficiently evaluated. If hydrogen accelerates the reduction reaction and completes the reduction early, increasing the amount of metallic iron and causing severe clustering of the in-furnace filling, there is a possibility that the crushability cannot be evaluated. If CO or _CO2 is contained in the gas component, carburization of the reduced iron occurs and clustering becomes difficult (Fig. 6 of Non-Patent Document 2). It is possible that the clustering phenomenon in

Also, in the reduction of iron oxide, CO reduction is an exothermic reaction, whereas _H2 reduction is an _endothermic reaction. becomes. As a method for this heat compensation, it is conceivable to raise the air temperature and the air flow rate. In this case, it is conceivable that particles that have undergone reduction are present in front of the tuyere, and particles whose particle temperature has risen close to the temperature of the blowing gas are present. Therefore, at the point of 95% reduction in the conventional method, heat is absorbed during hydrogen reduction, the temperature of the particles decreases, and the test temperature is as low as 850° C., making it difficult for clustering to occur. For this reason, the conventional evaluation method may not be able to correctly evaluate the clustering in the hydrogen reduction _shaft furnace when the ratio of H2 reduction is high and thermal compensation is performed with the sensible heat of blown air.

The present invention has been made in view of such circumstances, and its purpose is to evaluate the clustering of reduced iron in consideration of the heat compensation due to the sensible heat of blown air when reducing at a high hydrogen concentration. It is to provide a lump ore evaluation method and to provide agglomerate ore based on the evaluation method.

In the present invention, agglomerates are reduced at 1000° C. or higher and 1200° C. or lower while applying a predetermined load to prepare post-reduction aggregates, and the post-reduction aggregates are subjected to rotation treatment using a rotation tester, and the following ( 1) A method for evaluating an agglomerate ore, characterized in that the cluster strength CS of the post-reduction agglomerate calculated by the formula is measured, and the clustering property of the agglomerate ore is evaluated using the cluster strength CS. be.
CS=(W′/W)×100 (1)
Here, CS is the cluster strength (% by mass), W is the mass (g) of the post-reduction agglomerate that is equal to or larger than the maximum particle size of the agglomerate ore, and W′ is the maximum particle size of the agglomerate ore. It is the mass (g) of the post-reduction agglomerate after the rotation treatment with the rotation tester described above.

In addition, in the method for evaluating agglomerate ore according to the present invention configured as described above,
(1) using a reducing gas that does not contain a compound having a C atom to prepare the post-reduction aggregate;
( ₂ ) using a reducing gas containing 70% by volume or more of H2 to prepare the post-reduction aggregates;
is considered to be a more preferable solution.

Further, in the method for evaluating agglomerate ore described above, the present invention provides the post-reduction aggregate reduced at 1000° C. and the post-reduction aggregate after the rotation treatment in which the post-reduction aggregate is rotated 30 times at 30 rpm. and a cluster strength _CS30 of 0% by mass.

In addition, in the agglomerate ore according to the present invention configured as described above,
(1) having a particle size of 8 mm or more;
(2) Total Fe is 64.5% by mass or less,
(3) satisfy the following formula (2);
Al ₂ O ₃ +SiO ₂ ≧3.5% by mass (2)
Here, Al ₂ O ₃ is the component concentration (% by mass) of Al ₂ O ₃ in the agglomerate ore, and SiO ₂ is the component concentration (% by mass) of SiO ₂ in the agglomerate ore.
is considered to be a more preferable solution.

According to the present invention configured as described above, the clustering evaluation is performed at a higher temperature than conventionally, so the evaluation of the agglomerate ore can evaluate the clustering of the agglomerate ore in consideration of the heat compensation due to the sensible heat of the blown air in the hydrogen reduction. You can get a way. As a result, clustering in the shaft furnace can be correctly evaluated, and an agglomerate with good properties can be obtained based on the evaluation method of the present invention.

4 is a graph showing cluster strength CS ₀ (mass %) and CS ₃₀ (mass %) of Examples 1 to 6 and Comparative Example 1. FIG.

Hereinafter, embodiments of the present invention will be specifically described. It should be noted that the following embodiments are intended to exemplify apparatuses and methods for embodying the technical idea of the present invention, and are not intended to limit the configurations to those described below. That is, the technical idea of the present invention can be modified in various ways within the technical scope described in the claims.

<Method for evaluating agglomerate ore according to the present embodiment>
Concerning the evaluation method of the agglomerate ore of the present embodiment, a specific evaluation method will be described below.
First, 500 g±5 g of the agglomerated iron-making raw material (agglomerate ore) is sieved and the particle size distribution is measured to determine the maximum particle size of the agglomerate ore. Next, the agglomerate ore is heated to 1000° C. (this temperature is a predetermined temperature between 1000° C. and 1200° C., here 1000° C.) at a rate of 5° C./min in an N ₂ atmosphere. At that time, a load is gradually applied so that a load of 1 kg/cm ² is applied when the temperature reaches 1000°C. Next, the gas is switched to N ₂ -20% by volume H ₂ at 1000° C. with a load of 1 kg/cm ² applied, and this gas is flowed at a flow rate of 24 L/min and held for 3 hours. Then switch to _N2 atmosphere and cool to room temperature. Thus, a post-reduction aggregate is produced.

Next, the post-reduction agglomerates are sieved using a sieve having the maximum particle size of the agglomerate ore before reduction, and the post-reduction agglomerates on the sieve and the post-reduction agglomerates under the sieve are weighed. At this time, the mass of the post-reduction aggregates on the sieve is W (g). Next, the reduced aggregate on the sieve is subjected to an I-type rotation tester (132 mmφ×700 mm) and rotated 30 times at 30 rpm. Next, the collected post-reduction aggregates are passed through the same sieve, and the post-reduction aggregates on the sieve and the post-reduction aggregates under the sieve are weighed. At this time, the mass of the post-reduction aggregate on the sieve is W′ ₃₀ (g). After that, using the obtained W and W' ₃₀ , the cluster strength CS ₃₀ (% by mass) is measured from the following equation (3).
CS30 = _{( W'30} /W) x 100 (3)

The number of revolutions and the number of revolutions of the I-type rotation tester may be appropriately adjusted according to the impact applied to the calcined ore in the shaft furnace used for reduction. Let CS be the cluster strength when processed at the number of rotations and the number of times corresponding to the impact, and the mass W 'of the post-reduction aggregates on the sieve after rotation processing with the above W and the I-type rotation tester. , the cluster strength CS (% by mass) can be measured from the following formula (1).
CS=(W′/W)×100 (1)
Thus, by producing post-reduction aggregates at 1000° C. or higher and 1200° C. or lower, it is possible to correctly evaluate clustering when hydrogen reduction is performed while heat compensation is performed by air sensible heat.

As described above, if the gas component contains a compound having a C atom such as CO, CO ₂ , or methane, carburization of the reduced iron occurs, making clustering difficult. Therefore, the gas concentration of the compound having C atoms is low, and clustering in reduction using a reducing gas with an increased H ₂ concentration may not be correctly evaluated. In contrast, in the present embodiment, clustering is evaluated using a reducing gas that is N ₂ -20% by volume H ₂ gas and does not contain a compound having a C atom. This makes it possible to correctly evaluate clustering when using a reducing gas that does not contain a compound having a C atom. Furthermore, by using such a reducing gas, fewer types of gases are used than in the past, and evaluation can be performed easily. From the above point of view, in the method for evaluating agglomerate ore of the present embodiment, it is preferable to prepare the post-reduction agglomerate using a reducing gas that does not contain a compound having a C atom. Furthermore, it is preferable to prepare the post-reduction agglomerate using a reducing gas containing 70% by volume or more of H ₂ . This makes it possible to simulate the reduction of agglomerate ore using a reducing gas with an H ₂ concentration increased to 70% by volume or more, and to evaluate the clustering in the reduction.

<Regarding agglomerate ore of the present embodiment>
The agglomerate ore of the present embodiment is characterized in that the cluster strength _CS30 measured by the agglomerate ore evaluation method according to the present invention is 0% by mass. It can be seen that when the cluster strength _CS30 is 0% by mass, the agglomerate ore has good crushability at high temperatures. Therefore, if reduced iron is produced in a shaft furnace or the like using this agglomerate ore, clustering can be suitably suppressed even if a reducing gas with an increased H ₂ concentration is used.

In addition, in the agglomerate ore of the present embodiment, the particle size of the agglomerate ore is preferably 8 mm or more. By setting the particle size to 8 mm or more, the contact area between particles can be reduced, so clustering can be further suppressed. Here, the particle size of 8 mm or more is the particle size of the agglomerate ore that passes through a sieve with an opening of 8 mm. Further, the total Fe content of the agglomerate ore is preferably 64.5% by mass or less. Here, total Fe is the component concentration (% by mass) of Fe contained in metal Fe and Fe compounds (iron oxide, calcium ferrite, iron sulfide, etc.). Clustering can be further suppressed by using ironmaking raw materials having a total Fe content of 64.5% by mass or less. Furthermore, the agglomerate ore preferably satisfies the following formula (2).
Al ₂ O ₃ +SiO ₂ ≧3.5% by mass (2)
Here, Al ₂ O ₃ is the component concentration (% by mass) of Al ₂ O ₃ in the agglomerate ore, and SiO ₂ is the component concentration (% by mass) of SiO ₂ in the agglomerate ore.

Clustering is caused by the solid state bonding of metallic irons. When the concentration of gangue components such as Al ₂ O ₃ and SiO ₂ contained in the agglomerate ore increases, the iron concentration on the surface of the reduced iron particles decreases, thereby suppressing the solid phase bonding between metallic irons, thereby preventing clustering. Suppressed. Thus, the agglomerate containing a large amount of gangue that satisfies Al ₂ O ₃ + SiO ₂ ≥ 3.5% by mass is higher than the conventional agglomerate that satisfies Al ₂ O ₃ + SiO ₂ < 3.5% by mass. Since the clustering is also suppressed, it is preferable to use the agglomerate ore for the production of hydrogen-reduced iron.

Examples of the invention are described in detail below.
The clustering of the agglomerates of Examples 1 to 6 and the pellets of Comparative Example 1 was evaluated according to the method for evaluating agglomerates described above. Table 1 below shows the sintering temperatures and component compositions of the agglomerates of Examples 1 to 6 and the pellets of Comparative Example 1. In Comparative Example 1, pellets made from conventionally used raw materials were used.

As an evaluation of clustering, a cluster strength CS of ₀ before evaluation and a cluster strength CS of ₃₀ after 30 rotations were obtained. CS ₀ is 100.0% by mass because it is before the rotation treatment. The evaluation results are shown in Table 2 below and FIG. Also, the reduction temperature and the reduction gas composition are shown in Table 2 below.

As shown in FIG. 1 and Table 2, all of the agglomerates of Examples 1 to 6 satisfying Al ₂ O ₃ +SiO ₂ ≧3.5% by mass had a cluster strength CS ₃₀ of 0% by mass, and the cluster strength CS Compared to Comparative Example 1 in which ₃₀ was as high as 57.0% by mass, it was found that the crushability was good. From this result, it can be said that the agglomerates of Examples 1 to 6 satisfying Al ₂ O ₃ +SiO ₂ ≧3.5% by mass are agglomerates capable of suppressing clustering, and the agglomerates can be treated in a shaft furnace. It was confirmed that it is preferable to use for the hydrogen reduction used.

According to the method for evaluating agglomerate ore of the present invention, clustering is evaluated at a higher temperature than before, so it is possible to evaluate clustering of agglomerate ore in consideration of thermal compensation due to sensible heat of air blowing in hydrogen reduction, which is industrially useful. is. In addition, this is industrially useful in that clustering in the shaft furnace can be correctly evaluated, and agglomerates with good properties can be obtained based on the evaluation method of the present invention.

Claims (7)

1. Agglomerate ore is reduced at 1000° C. or higher and 1200° C. or lower while applying a predetermined load to prepare a post-reduction aggregate, and the post-reduction aggregate is subjected to rotation treatment using a rotation tester, and is subjected to the following formula (1). A method for evaluating an agglomerate ore, comprising measuring the calculated cluster strength CS of the post-reduction agglomerate, and evaluating the clustering property of the agglomerate ore using the cluster strength CS.
   CS=(W′/W)×100 (1)
   Here, CS is the cluster strength (% by mass), W is the mass (g) of the post-reduction agglomerate that is equal to or larger than the maximum particle size of the agglomerate ore, and W′ is the maximum particle size of the agglomerate ore. It is the mass (g) of the post-reduction agglomerate after the rotation treatment with the rotation tester described above.
2. The method for evaluating agglomerate ore according to claim 1, wherein the post-reduction aggregate is produced using a reducing gas that does not contain a compound having a C atom.
3. The method for evaluating agglomerate ore according to claim 1 or 2, wherein the post-reduction agglomerate is produced using a reducing gas containing 70% by volume or _more of H2.
4. The method for evaluating agglomerate ore according to any one of claims 1 to 3, wherein the post-reduction aggregate reduced at 1000 ° C. and the post-reduction aggregate rotated 30 times at 30 rpm Aggregate ore characterized by having a cluster strength _CS30 of 0% by weight, measured using post-reduction agglomerates after treatment.
5. The agglomerate ore according to claim 4, characterized by having a particle size of 8 mm or more.
6. The agglomerate ore according to claim 4 or 5, characterized in that the total Fe is 64.5% by mass or less.
7. 7. The agglomerate ore according to any one of claims 4 to 6, which satisfies the following formula (2).
   Al ₂ O ₃ +SiO ₂ ≧3.5% by mass (2)
   Here, Al ₂ O ₃ is the component concentration (% by mass) of Al ₂ O ₃ in the agglomerate ore, and SiO ₂ is the component concentration (% by mass) of SiO ₂ in the agglomerate ore.
   
   

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