AGGLOMERATED ORE ASSESSING METHOD AND AGGLOMERATED ORE

Abstract

An agglomerated ore is reduced while being subjected to a predetermined load at 1000? C. to 1200? C., both inclusive, to produce a reduced aggregate; a tumble treatment is performed on the reduced aggregate using a tumble tester; cluster strength CS of the reduced aggregate calculated by Formula (1) below is measured; and a clustering property of the agglomerated ore is assessed using the cluster strength CS: CS=(W/W)?100 . . . (1), where CS is cluster strength (mass %); W is the mass (g) of a reduced aggregate that is equal to or larger than a maximum particle diameter of the agglomerated ore; and W is the mass (g) of a reduced aggregate after a tumble treatment in the tumble tester that is equal to or larger than the maximum particle diameter of the agglomerated ore.

Claims

1. An agglomerated ore assessing method wherein: agglomerated ore is reduced while being subjected to a predetermined load at 1000? C. to 1200? C., both inclusive, to produce a reduced aggregate; a tumble treatment is performed on the reduced aggregate using a tumble tester; cluster strength CS of the reduced aggregate calculated by Formula (1) below is measured; and a clustering property of the agglomerated ore is assessed using the cluster strength CS: $\begin{array}{cc}\mathrm{CS}=\left(W^{}/W\right)?100,& \left(1\right)\end{array}$ where CS is cluster strength (mass %); W is the mass (g) of a reduced aggregate that is equal to or larger than a maximum particle diameter of the agglomerated ore; and W is the mass (g) of a reduced aggregate after a tumble treatment in the tumble tester that is equal to or larger than the maximum particle diameter of the agglomerated ore.

2. The agglomerated ore assessing method according to claim 1, wherein the reduced aggregate is produced using a reducing gas that does not contain a compound having a C atom.

3. The agglomerated ore assessing method according to claim 1, wherein the reduced aggregate is produced using a reducing gas containing 70 vol % or more H.sub.2.

4. Agglomerated ore wherein cluster strength CS.sub.30 is 0 mass % as measured in the agglomerated ore assessing method according to claim 1 using the reduced aggregate having been reduced at 1000? C. and a reduced aggregate after the tumble treatment obtained by rotating the reduced aggregate 30 times at 30 rpm.

5. The agglomerated ore according to claim 4, wherein a particle diameter is 8 mm or larger.

6. The agglomerated ore according to claim 4, wherein total Fe is 64.5 mass % or less.

7. The agglomerated ore according to claim 4, wherein Formula (2) below is met: $\begin{array}{cc}{\mathrm{Al}}_2{O}_3+{\mathrm{SiO}}_2?3.5\mathrm{mass}\%,& \left(2\right)\end{array}$ where Al.sub.2O.sub.3 is a component concentration (mass %) of Al.sub.2O.sub.3 in the agglomerated ore, and SiO.sub.2 is a component concentration (mass %) of SiO.sub.2 in the agglomerated ore.

8. The agglomerated ore assessing method according to claim 2, wherein the reduced aggregate is produced using a reducing gas containing 70 vol % or more H.sub.2.

9. Agglomerated ore wherein cluster strength CS.sub.30 is 0 mass % as measured in the agglomerated ore assessing method according to claim 2 using the reduced aggregate having been reduced at 1000? C. and a reduced aggregate after the tumble treatment obtained by rotating the reduced aggregate 30 times at 30 rpm.

10. Agglomerated ore wherein cluster strength CS.sub.30 is 0 mass % as measured in the agglomerated ore assessing method according to claim 3 using the reduced aggregate having been reduced at 1000? C. and a reduced aggregate after the tumble treatment obtained by rotating the reduced aggregate 30 times at 30 rpm.

11. The agglomerated ore according to claim 9, wherein a particle diameter is 8 mm or larger.

12. The agglomerated ore according to claim 10, wherein a particle diameter is 8 mm or larger.

13. The agglomerated ore according to claim 9, wherein total Fe is 64.5 mass % or less.

14. The agglomerated ore according to claim 10, wherein total Fe is 64.5 mass % or less.

15. The agglomerated ore according to claim 5, wherein total Fe is 64.5 mass % or less.

16. The agglomerated ore according to claim 12, wherein total Fe is 64.5 mass % or less.

17. The agglomerated ore according to claim 9, wherein Formula (2) below is met: $\begin{array}{cc}{\mathrm{Al}}_2{O}_3+{\mathrm{SiO}}_2?3.5\mathrm{mass}\%,& \left(2\right)\end{array}$ where Al.sub.2O.sub.3 is a component concentration (mass %) of Al.sub.2O.sub.3 in the agglomerated ore, and SiO.sub.2 is a component concentration (mass %) of SiO.sub.2 in the agglomerated ore.

18. The agglomerated ore according to claim 5, wherein Formula (2) below is met: $\begin{array}{cc}{\mathrm{Al}}_2{O}_3+{\mathrm{SiO}}_2?3.5\mathrm{mass}\%,& \left(2\right)\end{array}$ where Al.sub.2O.sub.3 is a component concentration (mass %) of Al.sub.2O.sub.3 in the agglomerated ore, and SiO.sub.2 is a component concentration (mass %) of SiO.sub.2 in the agglomerated ore.

19. The agglomerated ore according to claim 11, wherein Formula (2) below is met: $\begin{array}{cc}{\mathrm{Al}}_2{O}_3+{\mathrm{SiO}}_2?3.5\mathrm{mass}\%,& \left(2\right)\end{array}$ where Al.sub.2O.sub.3 is a component concentration (mass %) of Al.sub.2O.sub.3 in the agglomerated ore, and SiO.sub.2 is a component concentration (mass %) of SiO.sub.2 in the agglomerated ore.

20. The agglomerated ore according to claim 6, wherein Formula (2) below is met: $\begin{array}{cc}{\mathrm{Al}}_2{O}_3+{\mathrm{SiO}}_2?3.5\mathrm{mass}\%,& \left(2\right)\end{array}$ where Al.sub.2O.sub.3 is a component concentration (mass %) of Al.sub.2O.sub.3 in the agglomerated ore, and SiO.sub.2 is a component concentration (mass %) of SiO.sub.2 in the agglomerated ore.

Description

BRIEF DESCRIPTION OF DRAWING

[0022] FIG. 1 is a graph showing cluster strengths CS.sub.0 (mass %) and CS.sub.30 (mass %) of Examples 1 to 6 and Comparative Example 1.

DESCRIPTION OF EMBODIMENT

[0023] An embodiment of the present invention will be specifically described below. The following embodiment illustrates a device and a method for embodying the technical idea of the present invention, and is not intended to restrict the configuration to the one described below. Thus, various changes can be made to the technical idea of the present invention within the technical scope described in the claims.

<Agglomerated Ore Assessing Method of Embodiment>

[0024] Regarding an agglomerated ore assessing method of this embodiment, a specific assessment method will be described below.

[0025] First, 500 g?5 g of an agglomerated ironmaking raw material (agglomerated ore) is put through a sieve to measure a particle size distribution and determine the maximum particle size of the agglomerated ore. Then, the agglomerated ore is placed in an N.sub.2 atmosphere and heated to a temperature of 1000? C. at 5? C./min. (This temperature is a predetermined temperature between 1000? C. and 1200? C., which is 1000? C. here.) Meanwhile, a load is gradually applied such that a load of 1 kg/cm.sup.2 is applied when 1000? C. is reached. Then, while a load of 1 kg/cm.sup.2 is still applied at 1000? C., the gas is switched to an N.sub.2-20 vol % H.sub.2 gas, and the agglomerated ore is held for three hours with this gas flowing at a flow rate of 24 L/min. Then, the atmosphere is switched to an N.sub.2 atmosphere and the agglomerated ore is cooled to room temperature. Thus, a reduced aggregate is produced.

[0026] Next, the reduced aggregate is sifted using a sieve with an opening size corresponding to the maximum particle diameter of the agglomerated ore before reduction, and the reduced aggregate on the sieve and the reduced aggregate under the sieve are weighed. Here, the mass of the reduced aggregate on the sieve is denoted by W (g). Then, the reduced aggregate on the sieve is transferred to an I-type tumble tester (132 mm??700 mm) and rotated 30 times at 30 rpm. Then, the reduced aggregate taken out is put through the same sieve, and the reduced aggregate on the sieve and the reduced aggregate under the sieve are weighed. Here, the mass of the reduced aggregate on the sieve is denoted by W.sub.30 (g). Thereafter, using the obtained W and W.sub.30, cluster strength CS.sub.30 (mass %) is measured from Formula (3) below:

[00003]$\begin{array}{cc}{\mathrm{CS}}_{30}=\left(W_{30}^{}/W\right)?100& \left(3\right)\end{array}$

[0027] The rpm and the number of times of rotation of the I-type tumble tester may be adjusted as necessary according to the impact applied to the sintered ore in the shaft furnace used for reduction. When cluster strength in the case where treatment is performed at the rpm and the number of times of rotation corresponding to the impact is denoted by CS, cluster strength CS (mass %) can be measured from Formula (1) below using the aforementioned W and the mass W of the reduced aggregate on the sieve having undergone the tumble treatment in the I-type tumble tester:

[00004]$\begin{array}{cc}\mathrm{CS}=\left(W^{}/W\right)?100& \left(1\right)\end{array}$

[0028] Thus, producing a reduced aggregate at 1000? C. to 1200? C., both inclusive, allows an accurate assessment of clustering in the case where hydrogen reduction is performed while thermal compensation using blowing sensible heat is made.

[0029] As mentioned above, when the gas components include a compound having a C atom, such as CO, CO.sub.2, and methane, reduced iron becomes carburized and less prone to clustering. In the case of reduction using a reducing gas of which the gas concentration of a compound having a C atom is low and the H.sub.2 concentration is increased, clustering cannot always be accurately assessed. In this embodiment, on the other hand, clustering is assessed using a reducing gas that is an N.sub.2-20 vol % H.sub.2 gas and does not contain a compound having a C atom. Thus, it is possible to accurately assess clustering in the case where a reducing gas that does not contain a compound having a C atom is used. Moreover, when such a reducing gas is used, as the number of types of gases used is fewer than in the conventional method, the assessment can be conducted in a simplified manner. From this viewpoint, in the agglomerated ore assessing method of this embodiment, it is preferable that a reduced aggregate be produced using a reducing gas that does not contain a compound having a C atom. Further, it is preferable that a reduced aggregate be produced using a reducing gas containing 70 vol % or more H.sub.2. Thus, reduction of agglomerated ore using a reducing gas with the H.sub.2 concentration increased to 70 vol % or more can be simulated to assess clustering in this reduction.

<Agglomerated Ore of Embodiment>

[0030] Agglomerated ore of this embodiment is characterized in that cluster strength CS.sub.30 measured by the above-described agglomerated ore assessing method according to the present invention is 0 mass %. When the cluster strength CS.sub.30 is 0 mass %, the agglomerated ore is found to have favorable disintegratability at high temperatures. Therefore, if this agglomerated ore is used to produce reduced iron in a shaft furnace etc., clustering can be appropriately reduced even when a reducing gas with an increased H.sub.2 concentration is used.

[0031] In the agglomerated ore of this embodiment, it is preferable that the particle diameter of the agglomerated ore be 8 mm or larger. When the particle diameter is 8 mm or larger, the area of contact between the particles can be made smaller to further reduce clustering. Here, a particle diameter of 8 mm or larger means a particle diameter of agglomerated ore that remains on a sieve with a mesh size of 8 mm. It is preferable that total Fe in the agglomerated ore be 64.5 mass % or less. Here, the total Fe refers to the component concentration (mass %) of Fe contained in metal Fe and Fe compounds (iron oxide, calcium ferrite, iron sulfide, etc.). Using an ironmaking raw material in which the total Fe is 64.5 mass % or less can further reduce clustering. In addition, it is preferable that the agglomerated ore meet Formula (2) below:

[00005]$\begin{array}{cc}{\mathrm{Al}}_2{O}_3+{\mathrm{SiO}}_2?3.5\mathrm{mass}\%,& \left(2\right)\end{array}$

[0032] where Al.sub.2O.sub.3 is the component concentration (mass %) of Al.sub.2O.sub.3 in the agglomerated ore, and SiO.sub.2 is the component concentration (mass %) of SiO.sub.2 in the agglomerated ore.

[0033] Clustering occurs as metallic iron particles bind to one another in a solid phase. When the component concentration of gangue components, such as Al.sub.2O.sub.3 and SiO.sub.2, contained in the agglomerated ore increases, the iron concentration in the surfaces of reduced iron particles decreases, so that solid-phase binding of metallic iron particles is reduced and clustering is thereby reduced. Thus, agglomerated ore containing a large amount of gangue components that meets Al.sub.2O.sub.3+SiO.sub.2?3.5 mass % is reduced in clustering compared with conventional agglomerated ore in which Al.sub.2O.sub.3+SiO.sub.2<3.5 mass % applies, and is therefore preferably used to produce hydrogen-reduced iron.

Examples

[0034] Examples of the present invention will be described in detail below.

[0035] Agglomerated ores of Examples 1 to 6 and pellets of Comparative Example 1 were assessed for clustering in accordance with the above-described agglomerated ore assessing method. Table 1 below shows the sintering temperatures and the component compositions of the agglomerated ores of Examples 1 to 6 and the pellets of Comparative Example 1. As Comparative Example 1, pellets produced from a raw material that has been conventionally used was used.

TABLE-US-00001 TABLE 1 Sintering Total Fe CaO/SiO.sub.2 SiO.sub.2 + Al.sub.2O.sub.3 temperature ? C. mass % mass % mass % Example 1 1150 63.94 0.38 5.84 Example 2 1250 64.12 0.37 5.87 Example 3 1350 64.00 0.37 5.82 Example 4 1150 63.40 0.75 5.72 Example 5 1250 63.45 0.76 5.72 Example 6 1350 63.47 0.77 5.68 Comparative 1350 65.22 0.27 2.72 Example 1

[0036] For assessment of clustering, cluster strength CS.sub.0 before the assessment and cluster strength CS.sub.30 after 30 rotations were obtained. CS.sub.0, which is before the tumble treatment, is 100.0 mass %. The assessment result is shown in Table 2 below and FIG. 1. The reduction temperatures and the reducing gas compositions are shown in Table 2 below.

TABLE-US-00002 TABLE 2 Reducing Reduction gas temperature composition CS.sub.0 CS.sub.30 ? C. (vol %) (mass %) (mass %) Example 1 1000 N.sub.220%H.sub.2 100.0 0 Example 2 1000 N.sub.220%H.sub.2 100.0 0 Example 3 1000 N.sub.220%H.sub.2 100.0 0 Example 4 1000 N.sub.220%H.sub.2 100.0 0 Example 5 1000 N.sub.220%H.sub.2 100.0 0 Example 6 1000 N.sub.220%H.sub.2 100.0 0 Comparative 1000 N.sub.220%H.sub.2 100.0 57.0 Example 1

[0037] As shown in FIG. 1 and Table 2, compared with Comparative Example 1 in which cluster strength CS.sub.30 is as high as 57.0 mass %, all the agglomerated ores of Examples 1 to 6 that meet Al.sub.2O.sub.3+SiO.sub.2?3.5 mass % have cluster strength CS.sub.30 of 0 mass % and thus have proven to have favorable disintegratability. From this result, the agglomerated ores of Examples 1 to 6 that meet Al.sub.2O.sub.3+SiO.sub.2?3.5 mass % can be said to be agglomerated ores that are less prone to clustering, and these agglomerated ores have been confirmed to be preferably used for hydrogen reduction using a shaft furnace.

INDUSTRIAL APPLICABILITY

[0038] The agglomerated ore assessing method of the present invention assesses clustering at a higher temperature than the conventional method, and can thereby assess clustering of agglomerated ore taking into account thermal compensation that is made using blowing sensible heat in hydrogen reduction, which makes the present invention industrially useful. Further, clustering inside a shaft furnace can be thus accurately assessed and agglomerated ore having favorable characteristics can be obtained based on the assessment method of the present invention, which also makes the present invention industrially useful.