EP4624600A1

EP4624600A1 - Sintered ore production method

Info

Publication number: EP4624600A1
Application number: EP23918527.5A
Authority: EP
Inventors: Wataru Miyamura; Takahide Higuchi; Yuji Iwami
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2023-01-26
Filing date: 2023-11-09
Publication date: 2025-10-01
Also published as: JPWO2024157572A1; CN120530211A; KR20250126081A; JP7460041B1; EP4624600A4

Abstract

A method for producing sintered ore is provided that enables a production rate for the production of sintered ore to be maintained even in instances in which a Marra Mamba ore is included in sintering raw materials as a substitute for a pisolite ore.

The method for producing sintered ore includes including, in total iron ores, an iron ore in an amount of 30.0 mass% or greater based on a mass of the total iron ores, the iron ore having an iron content of 58.0 mass% or greater, a combined water content of 4.00 mass% or greater and less than 9.00 mass%, an Al₂O₃ content of 2.00 mass% or greater, and a SiO₂ content of less than 5.0 mass%; and producing sintered ore from sintering raw materials including the total iron ores, wherein the method includes adjusting a blending of the sintering raw materials in a manner that enables the sintered ore to have a SiO₂ content of 5.50 to 6.00 mass% and a CaO content of 11.0 to 12.0 mass%.

Description

Technical Field

The present invention relates to a method for producing sintered ore; the method produces sintered ore from sintering raw materials including iron ores.

Background Art

Sintered ore, which is a feed material for blast furnace ironmaking methods, is produced by the sintering of sintering raw materials, which include powder-containing iron ore, an auxiliary material, such as limestone, a carbonaceous material, such as coke, and the like. The raw material iron ore comes in various brands that differ in components and particle size, and the sintering raw materials include blended multiple brands of iron ores.

The iron ores used in Japan are generally classified into South American hematite ores and magnetite ores and Australian hematite ores, pisolite ores, and Marra Mamba ores. South American ores have a high Fe content and are of a high grade, but they present problems in terms of transportation costs because their place of origin is a remote location. Regarding Australian ores, as their production volume has greatly increased since the 1980s, they have been used as main source materials of iron ores in our country. Since the 2000s, as Australian hematite ores have gradually become depleted, the use of Australian pisolite ores has expanded. Since then, Australian pisolite ores have been widely used as iron ores in our country. In recent years, Australian pisolite ores have also gradually become depleted, and, accordingly, Marra Mamba ores are attracting attention as they may become main iron ores in the future. It is anticipated that the Australian pisolite ores that are used in our country will be progressively replaced by Marra Mamba ores. Table 1 shows the properties and compositions of various types of iron ore.

[Table 1]

Type of Iron Ore	Representative Brand	Place of Origin	Fines Content [mass%]	Al₂O₃ Content [mass%]	SiO₂ Content [mass%]	Iron Content [mass%]	Combined Water Content [mass%]
Pisolite	Yandi	Australia	1	1.66	6.42	56.8	10.5
Marra Mamba	Mac	Australia	18	2.35	4.60	59.2	6.9
Hematite	Newman	Australia	10	2.33	4.22	62.3	3.7
	Carajás	South America	21	1.42	1.50	65.1	3.5
	Itabira	South America	55	0.41	6.61	64.4	0.8

As shown in Table 1, the Marra Mamba ore has a higher content of fines having a diameter of 0.15 mm or less than the pisolite ore. The Marra Mamba ore has a higher alumina content (Al₂O₃ content) and a lower silica content (SiO₂ content) than the pisolite ore. Thus, regarding the sintering of sintering raw materials that include a Marra Mamba ore, in order to address the increase in the fines content due to the use of a Marra Mamba ore, a development has been performed for improving the gas permeability of the sintering raw materials for the sintering process.
Patent Literature 1 discloses a method for preventing a problem associated with the particle size of a Marra Mamba ore, by specifying a blending ratio of the Marra Mamba ore to total iron ores of 70 % or less. Patent Literature 1 states that limiting the blending ratio of the Marra Mamba ore can limit the ratio of fine ore particles having a particle size of 0.25 mm or less, thereby suppressing an influence on productivity.
Patent Literature 2 discloses a method for producing sintered ore in which a blending amount of sintering raw materials that include no Marra Mamba ores is used as a reference and in which, based on a rate of increase in a blending ratio of a Marra Mamba ore with respect to the reference blending amount of the sintering raw materials, the blending ratio of Brazilian pellet feed is reduced by 30% or more. Patent Literature 2 states that in the instance where a Marra Mamba ore is used, by reducing the blending ratio of Brazilian pellet feed, which has poor granulability, it is possible to improve granulability, thereby maintaining good finished product yield, sintered ore quality, and productivity.
Patent Literature 3 discloses a method for producing sintered ore in which sintering is performed as follows: blended materials are prepared by adding a pisolite ore to a Marra Mamba ore, the blended materials containing 3.0 to 5.0 mass% SiO₂ and having a content of fines with a size of 0.5 mm or less of less than 30 mass%; 5 to 10 mass% water is added to the blended materials, which are then mixed and granulated in a high-speed stirring mixer; a solid fuel and other ores are added, and the resultant is mixed and granulated again; and thereafter, the resultant is sintered. According to the disclosure, the addition of a pisolite ore, which is porous, to a Marra Mamba ore, the addition of an appropriate amount of water, and the mixing and granulation of the resultant in a high-speed stirring mixer result in the sticking of a portion of the fines of the Marra Mamba ore to the interior of open pores of the pisolite ore, and, consequently, a mixed and granulated product having a low fines content can be obtained; as a result, a pseudo particle size and a pseudo particle strength are improved, which in turn improves gas permeability for the sintering process, thereby improving a production rate and a finished product yield.

Citation List

Patent Literature

PTL 1: Japanese Patent No. 5004421
PTL 2: Japanese Patent No. 4786022
PTL 3: Japanese Unexamined Patent Application Publication No. 2004-137575

Summary of Invention

Technical Problem

Marra Mamba ores have a lower SiO₂ content, a higher Al₂O₃ content, and a higher fines content than pisolite ores. In the blast furnace process, which uses sintered ore, it is necessary to control a basicity of the slag that is produced, and, therefore it is also necessary to maintain the basicity of the sintered ore to be within a specified range. Accordingly, in sintering raw materials, in instances where the SiO₂ content is reduced, a CaO content is also reduced. Thus, as more and more pisolite ores are replaced by Marra Mamba ores, the SiO₂ content and the CaO content are further reduced, and the Al₂O₃ content and the fines content are further increased, in the sintering raw materials. In the instance where the fines content is increased, the gas permeability of the sintering raw materials for the sintering process decreases, which results in a reduction in a sintering speed and a reduction in the production rate. Accordingly, as disclosed in Patent Literature 1 to 3, methods have been developed which involve the strengthening of granulation and the limitation of the amount of use of a Marra Mamba ore, thereby achieving good gas permeability and productivity while using a Marra Mamba ore.
Patent Literature 1 to 3, however, do not discuss an influence of the difference between a chemical composition of the Marra Mamba ore and the chemical composition of the pisolite ore on the sintering process and the sintered ore. In particular, no discussions are disclosed on the SiO₂ content, the CaO content, and the Al₂O₃ content that should be employed to obtain high-strength sintered ore with good productivity, in the instance where a Marra Mamba ore is used.
The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a method for producing sintered ore that can maintain a production rate for the production of sintered ore even in instances in which a Marra Mamba ore is included in sintering raw materials as a substitute for a pisolite ore.

Solution to Problem

Primary features of the present invention for achieving the above object are as follows.

[1] A method for producing sintered ore including: including, in total iron ores, an iron ore in an amount of 30.0 mass% or greater based on a mass of the total iron ores, the iron ore having an iron content of 58.0 mass% or greater, a combined water content of 4.00 mass% or greater and less than 9.00 mass%, an Al₂O₃ content of 2.00 mass% or greater, and a SiO₂ content of less than 5.0 mass%; and producing sintered ore from sintering raw materials including the total iron ores, wherein the method includes adjusting a blending of the sintering raw materials in a manner that enables the sintered ore to have a SiO₂ content of 5.50 to 6.00 mass% and a CaO content of 11.0 to 12.0 mass%.
[2] The method for producing sintered ore according to [1], wherein, regarding the adjusting of the blending of the sintering raw materials, the blending is adjusted to include silica in the sintering raw materials.
[3] The method for producing sintered ore according to [1] or [2], wherein, regarding the adjusting of the blending of the sintering raw materials, the blending is adjusted in a manner that enables the sintered ore to have an Al₂O₃ content of 1.9 mass% or less.
[4] The method for producing sintered ore according to [3], wherein, regarding the adjusting of the blending of the sintering raw materials, the blending is adjusted to include an iron ore in an amount of 5.0 mass% or greater based on the mass of the total iron ores, the iron ore having an iron content of 64.0 mass% or greater, a combined water content of less than 1.00 mass%, and an Al₂O₃ content of less than 0.50 mass%.
[5] The method for producing sintered ore according to [3], wherein, regarding the adjusting of the blending of the sintering raw materials, the blending is adjusted to include an iron ore in an amount of 55.0 mass% or greater based on the mass of the total iron ores, the iron ore having an iron content of 60.0 mass% or greater, a combined water content of less than 4.00 mass%, an Al₂O₃ content of less than 1.50 mass%, and a SiO₂ content of 4.5 mass% or greater and less than 5.0 mass%.
[6] The method for producing sintered ore according to [5], wherein, regarding the adjusting of the blending of the sintering raw materials, the blending is adjusted in a manner that enables a ratio of particles having a size of less than 0.5 mm to be 40.0 mass% or less based on the mass of the total iron ores.

Advantageous Effects of Invention

With the present invention, a production rate for the production of sintered ore can be maintained even in instances in which a Marra Mamba ore is included in sintering raw materials as a substitute for a pisolite ore. Brief Description of Drawings

[Fig. 1] Fig. 1 is a graph showing the results of a production rate, a yield, and a sintering speed obtained in Tests 1 and 2.
[Fig. 2] Fig. 2 is a graph showing the results of the production rate, the yield, and the sintering speed obtained in Tests 3 and 4.
[Fig. 3] Fig. 3 is a graph showing the results of the production rate, the yield, and the sintering speed obtained in Tests 5 and 6.
[Fig. 4] Fig. 4 is a graph showing the results of the production rate, the yield, the sintering speed, and a strength obtained in Tests 3, 4, 7, and 8.

Description of Embodiments

The present invention will be described below with reference to embodiments of the present invention.
In the present embodiment, regarding sintering raw materials used in the production of sintered ore, a Marra Mamba ore is used as a substitute for a pisolite ore, which has been used in the related art as an iron ore that is included in the sintering raw materials. The Marra Mamba ore is included in an amount of 30.0 mass% or greater, which is a sufficient amount for substitution for a pisolite ore, based on a mass of total iron ores that are included in the sintering raw materials.

Regarding the Marra Mamba ore that is used in the production of sintered ore, a content of each of the components, a fines content, and a combined water content will be described with reference to Table 2. Table 2 also shows the content of each of the components, the fines content, and the combined water content, of various iron ores that are used in the production of sintered ore.

[Table 2]

Type of Iron Ore	Notes (Place of Origin and Others)	Iron Content [mass%]	SiO₂ Content [mass%]	Al₂O₃ Content [mass%]	Fines Content [mass%]	Combined Water Content [mass%]
Ore A	Australian Pisolite	57.1	6.2	1.85	4	9.40
Ore B	Australian Marra Mamba	59.2	4.6	2.35	18	6.89
Ore G	Low-Alumina Fines	65.9	4.2	0.20	40	0.57
Ore D	Australian Pisolite	56.1	6.0	3.34	3	8.89
Ore E	South America	63.0	4.6	1.17	30	2.76
Ore F	South America	63.3	6.0	0.81	50	1.99
Ore C	South America	63.0	5.6	1.45	46	2.06

As shown in Table 2, the Marra Mamba ore has a composition with an iron content (T. Fe) of 58.0 mass% or greater, an Al₂O₃ content of 2.00 mass% or greater, and a SiO₂ content of less than 5.0 mass%. The combined water content (LOI) of the Marra Mamba ore is 4.00 mass% or greater and less than 9.00 mass%.
The total iron ores including the Marra Mamba ore in an amount of 30.0 mass% or greater are included in the sintering raw materials, and, regarding the composition of the sintered ore resulting from sintering, the sintering raw materials are adjusted in a manner that enables the sintered ore to have a SiO₂ content of 5.50 to 6.00 mass% and a CaO content of 11.0 to 12.0 mass%. Specifically, regarding the adjustment of the sintering raw materials, the blending of the sintering raw materials is adjusted as follows: an auxiliary material having a high SiO₂ content is included in the sintering raw materials; or an auxiliary material having a high SiO₂ content is included in the sintering raw materials, and in addition, an iron ore having a higher SiO₂ content than the Marra Mamba ore or a pisolite ore is used in combination with the Marra Mamba ore.
The iron ore having a higher SiO₂ content than the Marra Mamba ore or a pisolite ore may be, for example, Ore F, which is among the various iron ores shown in Table 2 and has a high SiO₂ content. The auxiliary material having a high SiO₂ content may be, for example, silica or the like. That is, regarding the adjustment of the sintering raw materials, the blending of the sintering raw materials may be adjusted as follows: an auxiliary material having a high SiO₂ content, such as silica, is included in the sintering raw materials; or an auxiliary material having a high SiO₂ content is included in the sintering raw materials, and in addition, an ore having a higher SiO₂ content than the Marra Mamba ore or a pisolite ore is used in combination with the Marra Mamba ore.
Accordingly, the reduction in the SiO₂ content of the sintering raw materials due to the use of a Marra Mamba ore can be compensated for, which makes it possible to maintain a basicity at a constant level without having to reduce the CaO content, and, therefore, a reduction in the CaO content is inhibited. As a result, a sufficient melt is produced in the sintering raw materials during sintering, and, consequently, a reduction in a yield of the sintered ore is inhibited, which results in a good production rate of 1.5 t/h·m² or greater.
Regarding the composition of the sintered ore, after the sintering raw materials have been adjusted in a manner that enables the sintered ore to have a SiO₂ content of 5.50 to 6.00 mass% and a CaO content of 11.0 to 12.0 mass%, the blending of the sintering raw materials may be further adjusted in a manner that enables the sintered ore to have an Al₂O₃ content of 1.9 mass% or less.
Specifically, regarding the adjustment of the sintering raw materials, an iron ore having a lower Al₂O₃ content than the Marra Mamba ore or a pisolite ore may be used in combination with the Marra Mamba ore. In this instance, a further adjustment may be made to include the iron ore having a lower Al₂O₃ content than the Marra Mamba ore or a pisolite ore, in an amount of 5.0 mass% or greater based on the mass of the total iron ores.
The iron ore having a lower Al₂O₃ content than the Marra Mamba ore or a pisolite ore and being able to be used in combination with the Marra Mamba ore may be, for example, Ore G, which is a low-alumina fine ore; Ore G is among the various iron ores shown in Table 2 and has a low Al₂O₃ content. That is, regarding the adjustment of the sintering raw materials, low-alumina fine Ore G, which has a lower Al₂O₃ content than the Marra Mamba ore or a pisolite ore, may be used in combination with the Marra Mamba ore. In addition, a further adjustment may be made to include low-alumina fine Ore G, which has a lower Al₂O₃ content than the Marra Mamba ore or a pisolite ore, in an amount of 5.0 mass% or greater based on the mass of the total iron ores. As shown in Table 2, low-alumina fine Ore G has a composition with an iron content of 64.0 mass% or greater, a combined water content of less than 1.00 mass%, and an Al₂O₃ content of less than 0.50 mass%.
Regarding the adjustment of the sintering raw materials, it is also possible to increase a proportion of the iron ore having a lower Al₂O₃ content than the Marra Mamba ore or a pisolite ore, by increasing a blending ratio of the iron ore based on the mass of the total iron ores. In this instance, an adjustment may be made to include the iron ore having a lower Al₂O₃ content than the Marra Mamba ore or a pisolite ore in an amount of 55.0 mass% or greater based on the mass of the total iron ores.
The iron ore that has a lower Al₂O₃ content than the Marra Mamba ore or a pisolite ore and whose blending ratio based on the mass of the total iron ores can be increased may be, for example, Ore E, which is among the various iron ores shown in Table 2 and has a low Al₂O₃ content. That is, regarding the adjustment of the sintering raw materials, it is possible to increase the proportion of Ore E, which has a lower Al₂O₃ content than the Marra Mamba ore or a pisolite ore, by increasing the blending ratio of Ore E based on the mass of the total iron ores. In addition, a further adjustment may be made to include Ore E, which has a lower Al₂O₃ content than the Marra Mamba ore or a pisolite ore, in an amount of 55.0 mass% or greater based on the mass of the total iron ores. As shown in Table 2, Ore E has a composition with an iron content of 60.0 mass% or greater, a combined water content of less than 4.00 mass%, an Al₂O₃ content of less than 1.50 mass%, and a SiO₂ content of 4.5 mass% or greater and less than 5.0 mass%.
Thus, the increase in the Al₂O₃ content in the sintering raw materials due to the use of a Marra Mamba ore can be inhibited by additionally using an iron ore having a lower Al₂O₃ content than the Marra Mamba ore or a pisolite ore or by increasing the proportion of such an iron ore. As a result, an increase in the melting point of the melt produced in the sintering raw materials during sintering is inhibited, which increases a fluidity of the sintering raw materials and, therefore, promotes the coalescence of the solid particles, and, consequently, the sintered ore has improved strength. Specifically, the sintered ore can have a shatter strength of 75% or greater.
Regarding the composition of the sintered ore, the sintering raw materials may be adjusted in a manner that enables the sintered ore to have a SiO₂ content of 5.50 to 6.00 mass%, a CaO content of 11.0 to 12.0 mass%, and an Al₂O₃ content of 1.9 mass% or less; and in addition, the total iron ores in the sintering raw materials may be adjusted in a manner that enables a ratio of particles having a size of less than 0.5 mm to be 40.0 mass% or less based on the mass of the total iron ores.
Thus, in the sintering raw materials, the adjustment that enables the ratio of particles having a size of less than 0.5 mm to be 40.0 mass% or less based on the mass of the total iron ores improves the gas permeability of a sintering raw material layer for the sintering, and, therefore, an effect of promoting the sintering process is produced, which further improves the sintered ore production rate. Specifically, the sintered ore production rate can be 1.7 t/(h·m²) or greater.

EXAMPLES

Examples carried out with the method of the present embodiment for producing sintered ore will be described below.
A pseudo-granulated sintering raw material was prepared by adding a few percent water to sintering raw materials that included various iron ores, an auxiliary material including limestone, silica, or the like, and a carbonaceous material, such as coke, and then mixing and granulating the sintering raw materials. The pseudo-granulated sintering raw material was subjected to a sintering test, which was conducted with a cylindrical laboratory sintering pan having a diameter of 300 mm and a height of 400 mm. 20 mm of sintered ore, which served as a hearth layer, was charged onto grate within the cylindrical laboratory sintering pan, and then, the pseudo-granulated sintering raw material was charged onto the hearth layer to serve as a sintering raw material layer. In the charged sintering raw material layer, the carbonaceous material present in an upper region was ignited, and air was suctioned downward, to allow the combustion of the carbonaceous material to proceed downward. Accordingly, the sintering raw material layer was sintered with the heat of combustion of the carbonaceous material, to give a sinter cake.

In the Examples, a sintering time was defined as the time that it took for the temperature of the combustion exhaust gas to exhibit a maximum value, from the beginning of the sintering. Furthermore, a sintering speed (mm/min) was defined as the value obtained by dividing the height of the cylindrical laboratory sintering pan by the sintering time. After completion of the sintering, the sinter cake was removed from the cylindrical laboratory sintering pan and was dropped four times from a height of 2 m. Subsequently, the weight of the sinter cake retained on a 5-mm sieve was measured, and a yield (mass%) was determined as a ratio of the weight of the sinter cake retained on the 5-mm sieve to the weight of the sinter cake determined prior to the dropping. In addition, a production rate (t/(h·m²)) was determined as the value obtained by dividing the determined weight of the sinter cake retained on the 5-mm sieve by the sintering time and a base area of the laboratory pan. A strength (%) of the sintered ore was measured based on a shatter index (SI), described in "JIS M8711 Iron ore sinter-Determination of shatter strength". Table 3 shows the sintering raw materials that were subjected to the sintering test.

[Table 3]

		Test 1 (Comparative Example)	Test 2 (Comparative Example)	Test 3 (Comparative Example)	Test 4 (Invention Example)	Test 5 (Comparative Example)	Test 6 (Invention Example)	Test 7 (Invention Example)	Test 8 (Invention Example)
	Ore A	32.5	0.0	33.0	0.0	33.3	0.0	0.0	0.0
	Ore B	0.0	33.5	0.0	32.6	0.0	19.7	26.1	19.6
	Ore G	0.0	0.0	0.0	0.0	0.0	0.0	6.5	0.0
	Ore D	0.0	0.0	6.6	6.5	6.7	6.6	6.5	6.5
	Ore E	0.0	0.0	26.4	26.1	26.6	26.3	26.1	39.1
	Ore F	0.0	0.0	0.0	0.0	0.0	13.1	0.0	0.0
Raw Material Blending Ratio [mass%]	Ore C	32.5	33.5	0.0	0.0	0.0	0.0	0.0	0.0
	Silica	0.0	0.0	0.0	0.8	0.0	0.4	0.7	0.7
	Quicklime	0.0	0.0	0.0	0.0	1.0	1.0	0.0	0.0
	Return Fines	20.0	20.0	20.0	20.0	20.0	20.0	20.0	20.0
	Limestone	15.0	13.0	14.0	14.0	12.5	13.0	14.2	14.3
	Coke Breeze	4.5	4.5	4.5	4.5	4.5	4.5	4.5	4.5
Composition of Sintered Ore [mass%]	Fe	56.1	57.5	55.8	55.5	55.5	55.8	55.7	55.7
	SiO₂	5.99	5.27	5.80	5.80	5.60	5.59	5.80	5.80
	CaO	11.4	9.9	11.0	11.0	11.2	11.2	11.0	11.0
	Al₂O₃	1.78	1.99	1.91	2.06	1.77	1.82	1.90	1.88
	MgO	0.40	0.33	0.30	0.30	0.34	0.32	0.33	0.31
Basicity of Sintered Ore (-)		1.9	1.9	1.9	1.9	2.0	2.0	1.9	1.9
Suction Pressure (kPa)		7.00	7.00	10.00	10.00	7.70	7.70	10.00	10.00
Iron Ore Blending Ratio [mass%]	Ore A	50.0	0.0	50.0	0.0	50.0	0.0	0.0	0.0
	Ore B	0.0	50.0	0.0	50.0	0.0	30.0	40.0	30.0
	Ore G	0.0	0.0	0.0	0.0	0.0	0.0	10.0	0.0
	Ore D	0.0	0.0	10.0	10.0	10.0	10.0	10.0	10.0
	Ore E	0.0	0.0	40.0	40.0	40.0	40.0	40.0	60.0
	Ore F	0.0	0.0	0.0	0.0	0.0	20.0	0.0	0.0
	Ore C	50.0	50.0	0.0	0.0	0.0	0.0	0.0	0.0
Ratio of Fines [mass%]		35.0	47.5	24.8	37.3	24.8	43.9	42.9	38.5

Eight types of sintering raw materials in total were subjected to the sintering test; Tests 1 to 3 and 5 are Comparative Examples, and Tests 4 and 6 to 8 are Invention Examples, as shown in Table 3. The sintering raw materials were adjusted based on the raw material blending ratios shown in Table 3 so that, after sintering, the composition of the sintered ore could have the values shown in Table 3. Thereafter, the pseudo-granulated sintering raw material obtained by performing mixing, controlling moisture, and granulation was charged as a sintering raw material layer, which was then sintered with the heat of combustion of the carbonaceous material to give sintered ore. Regarding the sintering raw materials of Tests 1 to 8, the sintering was performed by suctioning air from below the sintering raw material layer with the suction pressure (kPa) shown in Table 3.
<Example 1> Fig. 1 shows the results of the implementation of Test 1 and Test 2, which are Comparative Examples. Test 1 is a Comparative Example in which a pisolite ore was used as an iron ore of the sintering raw materials. In Test 2, a Marra Mamba ore was used as an iron ore of the sintering raw materials. That is, Test 2 is a Comparative Example in which a Marra Mamba ore was used as a substitute for a pisolite ore, which was used in Test 1.
As shown in Table 3, the SiO₂ content of Test 2 was 5.27 mass%, in a comparison with the SiO₂ content (5.99 mass%) of Test 1. Furthermore, the CaO content of Test 2 was 9.9 mass%, in a comparison with the CaO content (11.4 mass%) of Test 1. Accordingly, in Test 2, the yield was reduced, and the production rate was also reduced, compared to Test 1 as shown in Fig. 1. Specifically, the production rate of Test 2 was 1.28 t/(h·m²), in a comparison with the production rate (1.36 t/(h·m²)) of Test 1. A reason for this is that because of the lower SiO₂ content and the lower CaO content of the sintering raw materials, the melt produced during sintering was reduced, which led to the reduction in the yield.
<Example 2> Fig. 2 shows the results of the implementation of Test 3, which is a Comparative Example, and of Test 4, which is an Invention Example. In Test 3, a pisolite ore was used as an iron ore of the sintering raw materials. The results of the implementation are shown. In Test 4, a Marra Mamba ore was used as an iron ore of the sintering raw materials. The results of the implementation are shown. In Test 4, silica, which has a high SiO₂ content, was additionally included as an auxiliary material in the sintering raw materials, to inhibit the reduction in the SiO₂ content of the sintering raw materials due to the use of a Marra Mamba ore. That is, Test 4 is an Invention Example in which a Marra Mamba ore was used as an iron ore of the sintering raw materials and in which the sintering raw materials were adjusted to achieve a SiO₂ content of 5.80 mass% and a CaO content of 11.0 mass% in the composition of the sintered ore resulting from the sintering. In Test 3, the test was conducted under the same conditions as those of Test 4, except for the adjustment regarding the use of a Marra Mamba ore and silica in Test 4.
As shown in Table 3, the SiO₂ content of Test 4 was 5.80 mass%, in a comparison with the SiO₂ content (5.80 mass%) of Test 3. Furthermore, the CaO content of Test 4 was 11.0 mass%, in a comparison with the CaO content (11.0 mass%) of Test 3. As a result, in Test 4, as shown in Fig. 2, a good production rate of 1.62 t/(h·m²) was achieved without causing a reduction in the yield with respect to Test 3, while such a reduction was observed in the results of the implementation of Test 2.
<Example 3> Fig. 3 shows the results of the implementation of Test 5, which is a Comparative Example, and of Test 6, which is an Invention Example. In Test 5, a pisolite ore was used as an iron ore of the sintering raw materials. The results of the implementation are shown. In Test 6, a Marra Mamba ore was used as an iron ore of the sintering raw materials. The results of the implementation are shown. In Test 6, silica, which has a high SiO₂ content, was additionally included as an auxiliary material in the sintering raw materials, and in addition, Ore F (see Table 2), which has a high SiO₂ content, was used in combination with the Marra Mamba ore, to inhibit the reduction in the SiO₂ content of the sintering raw materials due to the use of a Marra Mamba ore. The results of the implementation are shown. That is, Test 6 is an Invention Example in which a Marra Mamba ore was used as an iron ore of the sintering raw materials and in which the sintering raw materials were adjusted to achieve a SiO₂ content of 5.59 mass% and a CaO content of 11.2 mass% in the composition of the sintered ore resulting from the sintering. In Test 5, the test was conducted under the same conditions as those of Test 6, except for the adjustment regarding the use of a Marra Mamba ore, silica, and Ore F in Test 6. The results of the implementation are shown.
As shown in Table 3, the SiO₂ content of Test 6 was 5.59 mass%, in a comparison with the SiO₂ content (5.60 mass%) of Test 5. Furthermore, the CaO content of Test 6 was 11.2 mass%, in a comparison with the CaO content (11.2 mass%) of Test 5. As a result, in Test 6, as shown in Fig. 3, a good production rate of 1.54 t/(h·m²) was achieved without causing a reduction in the yield with respect to Test 5.
<Example 4> Regarding the strength (shatter strength, hereinafter simply referred to as a "strength") of the sintered ore, Fig. 4 shows the results of the implementation, which includes Test 3 and Invention Examples: Test 4, Test 7 and Test 8. Referring to Fig. 4, Test 3 and Test 4 are tests conducted by using the same sintering raw materials as those of Test 3 and Test 4 shown in Fig. 2.
As shown in Fig. 4, the strength of the sintered ore of Test 4 was 71.2 %, which was lower than the strength (74.4%) of the sintered ore of Test 3, in which a pisolite ore was used as an iron ore. It can be said that this was due to the Al₂O₃ content (2.06 mass%) of Test 4 that was higher than the Al₂O₃ content (1.91 mass%) of Test 3. Specifically, it can be said that because of the higher Al₂O₃ content of the sintering raw materials, the melting point of the melt produced during the sintering process increased, which reduced fluidity, thereby inhibiting the coalescence of the solid particles, and, consequently, caused the reduction in the strength. It is, therefore, apparent that limiting the Al₂O₃ content is preferable in order to obtain high-strength sintered ore while using a Marra Mamba ore as an iron ore that is included in the sintering raw materials.
In Test 7, low-alumina fine Ore G (see Table 2), which has a low Al₂O₃ content, was used in combination with the Marra Mamba ore, to inhibit an increase in the Al₂O₃ content of the sintering raw materials due to the use of a Marra Mamba ore. That is, Test 7 is an Invention Example in which a Marra Mamba ore was used as an iron ore of the sintering raw materials with silica being used in combination therewith as an auxiliary material and in which the sintering raw materials were adjusted to achieve a SiO₂ content of 5.80 mass%, a CaO content of 11.0 mass%, and an Al₂O₃ content of 1.90 mass% in the composition of the sintered ore resulting from the sintering.
In Test 8, the proportion of Ore E (see Table 2), which has a low Al₂O₃ content, was increased by increasing its blending amount in the sintering raw materials, to inhibit an increase in the Al₂O₃ content of the sintering raw materials due to the use of a Marra Mamba ore. That is, Test 8 is an Invention Example in which a Marra Mamba ore was used as an iron ore of the sintering raw materials with silica being used in combination therewith as an auxiliary material and in which the sintering raw materials were adjusted to achieve a SiO₂ content of 5.80 mass%, a CaO content of 11.0 mass%, and an Al₂O₃ content of 1.88 mass% in the composition of the sintered ore resulting from the sintering.
In Test 7 and Test 8, the tests were conducted under the same conditions as those of Test 3 and Test 4, except for the adjustments regarding the use of low-alumina fine Ore G for Test 7 and the increase in the proportion of Ore E for Test 8. The results of the implementation are shown in Fig. 4. In Test 7 and Test 8, a good result was achieved with the strength of the sintered ore being 75% or greater, as shown in Fig. 4. Furthermore, in Test 7 and Test 8, another good result was achieved with the yield being 75% or greater.
In particular, in Test 7, the strength of the sintered ore was 80% or greater, and thus, a high strength was achieved. It can be said that this was due to the limitation of the amount of Al₂O₃ and, in addition, to the reduction in the sintering speed resulting from an influence of the inhibition of gas permeation in the sintering raw material layer caused by the fine ore. In Test 8, a good result was achieved with the strength of the sintered ore being 75% or greater. It can be said that the improvement in the strength of the sintered ore was due to the limitation of the Al₂O₃ content, which inhibited an increase in the melting point of the melt produced during sintering, which in turn resulted in strong binding of the particles.
Note that in Test 7, as shown in Fig. 4, the sintering speed was lower than in Test 3 and Test 4, in which the test was conducted under the same conditions. It can be said that this was due to the fact that in Test 7, the ratio of particles having a size of less than 0.5 mm (hereinafter also simply referred to as "fines") in the iron ores was high, that is, the ratio was 40 mass% or greater (see Table 3). That is, when the ratio of fines in the total iron ores of the sintering raw materials is 40 mass% or greater, the gas permeability for sintering is significantly reduced, which reduces the sintering speed. This result indicates that it is preferable to make an adjustment in a manner that enables the ratio of fines in the total iron ores of the sintering raw materials to be less than 40 mass%. Consequently, the gas permeability for sintering is improved, and, therefore, high-strength sintered ore can be produced at a high production rate.
Accordingly, in Test 8, an adjustment was made in a manner that enables the ratio of fines in the total iron ores of the sintering raw materials to be less than 40 mass%, as shown in Table 3. As a result, the sintering speed in Test 8 was higher than that in Test 7. In Test 8, since the Al₂O₃ content was 1.90 mass% or less, a good result of the strength of the sintered ore was also achieved. Furthermore, in Test 8, since the SiO₂ content was 5.80 mass%, and the CaO content was 11.0 mass%, a good result of the yield was also achieved. In addition, an increase in the amount of the melt in the sintering raw material during sintering resulted in strong binding of the solid particles, and also, the reduced amount of fines in the total iron ores resulted in an increase in the sintering speed; consequently, high-strength sintered ore was produced at a good sintering speed, and thus, the production rate was significantly improved. Specifically, in Test 8, sintered ore with a high strength of 75% or greater was produced at a high production rate of 1.7 t/(h·m²) or greater.

Claims

A method for producing sintered ore comprising:
including, in total iron ores, an iron ore in an amount of 30.0 mass% or greater based on a mass of the total iron ores, the iron ore having an iron content of 58.0 mass% or greater, a combined water content of 4.00 mass% or greater and less than 9.00 mass%, an Al₂O₃ content of 2.00 mass% or greater, and a SiO₂ content of less than 5.0 mass%; and

producing sintered ore from sintering raw materials including the total iron ores, wherein

the method comprises adjusting a blending of the sintering raw materials in a manner that enables the sintered ore to have a SiO₂ content of 5.50 to 6.00 mass% and a CaO content of 11.0 to 12.0 mass%.
The method for producing sintered ore according to Claim 1, wherein, regarding the adjusting of the blending of the sintering raw materials, the blending is adjusted to include silica in the sintering raw materials.
The method for producing sintered ore according to Claim 1 or 2, wherein, regarding the adjusting of the blending of the sintering raw materials, the blending is adjusted in a manner that enables the sintered ore to have an Al₂O₃ content of 1.9 mass% or less.
The method for producing sintered ore according to Claim 3, wherein, regarding the adjusting of the blending of the sintering raw materials, the blending is adjusted to include an iron ore in an amount of 5.0 mass% or greater based on the mass of the total iron ores, the iron ore having an iron content of 64.0 mass% or greater, a combined water content of less than 1.00 mass%, and an Al₂O₃ content of less than 0.50 mass%.
The method for producing sintered ore according to Claim 3, wherein, regarding the adjusting of the blending of the sintering raw materials, the blending is adjusted to include an iron ore in an amount of 55.0 mass% or greater based on the mass of the total iron ores, the iron ore having an iron content of 60.0 mass% or greater, a combined water content of less than 4.00 mass%, an Al₂O₃ content of less than 1.50 mass%, and a SiO₂ content of 4.5 mass% or greater and less than 5.0 mass%.
The method for producing sintered ore according to Claim 5, wherein, regarding the adjusting of the blending of the sintering raw materials, the blending is adjusted in a manner that enables a ratio of particles having a size of less than 0.5 mm to be 40.0 mass% or less based on the mass of the total iron ores.