JP2007270260A - Non-calcined agglomerate for iron making - Google Patents

Abstract

An unfired agglomerated ore for iron making having a crushing strength of 390 N / p or more at room temperature and 100 N / p or more in a temperature range up to 1000 ° C.
SOLUTION: A non-fired agglomerated mineral obtained by solidifying a raw material of iron oxide with a phenol resin as a binder, and a crushing strength of 390 N / p or more is ensured by a cured phenol resin at a normal temperature. Carbon generated by carbonization of the phenol resin functions effectively as a binder, and a crushing strength of 100 N / p or more can be secured in a temperature range up to 1000 ° C.
[Selection figure] None

Description

  The present invention relates to an unfired agglomerated ore for iron making used as an iron raw material in an iron making furnace such as a blast furnace.

  In a pig iron manufacturing process performed using a solid iron furnace such as a blast furnace (hereinafter described as an example of a blast furnace), the porosity in the raw material packed bed is used to distribute the reducing gas in the raw material packed bed in the furnace. It is important to keep the above a certain value. For this reason, it is desirable that the furnace interior inclusions such as iron raw materials have a large particle size distribution, and it is necessary to increase the strength of the charges that may be pulverized after charging to suppress pulverization. For this reason, especially in large blast furnaces, sintered ore obtained by baking powdered ore with the heat of combustion of carbonaceous materials, or fired pellets obtained by forming powdered ore into a spherical shape with a pelletizer and then heat-hardening at 1000 ° C or higher Is widely used.

On the other hand, studies on non-fired agglomerated minerals that are not heat-treated at high temperatures have been promoted, particularly for the purpose of energy saving. This unfired agglomerated mineral is cured for a certain period of time at a relatively low temperature of several hundred degrees C or less using normal or waste heat, etc., using iron ore powder, iron dust, etc. as a binder with a hydraulic binder such as cement. Manufactured.
In Non-Patent Document 1, iron ore pellets need a crushing strength of about 100 N / p in the blast furnace, and a crushing strength of about 390 N / p is necessary to prevent generation of powder in the yard. It has been shown.

Patent Document 1 discloses a method for producing a non-baked agglomerated mineral using molasses as a binder, and according to this method, a high cold crushing strength can be obtained with a relatively short curing time. However, saccharides are pyrolyzed at 300 ° C to 350 ° C, and only about 10% of carbon remains by mass after pyrolysis. Therefore, when charged in a blast furnace, in a region where the temperature exceeds 350 ° C in the furnace. It is considered that the shape cannot be maintained.
If hydraulic binders such as cement are used, the crushing strength at room temperature can be sufficiently secured, so that it can be easily transferred from the production site to the blast furnace, and up to several hundred degrees Celsius above the blast furnace. In the temperature region, the shape can be maintained. However, it has been pointed out for a long time that the strength of the cement hydrate is significantly degraded at higher temperatures, resulting in a significant decrease in strength, resulting in pulverization in the middle and lower parts of the blast furnace and associated deterioration in air permeability. .

  In order to solve such a problem, Patent Document 2 discloses a non-fired agglomerated mineral (molded) obtained by adding and mixing an adhesive hydrocarbon mixture such as asphalt or pitch as a binder to iron ore powder, and then compressing and curing the mixture. Body) is shown. According to this document, the baked agglomerated volatile matter in the binder evaporates from about 200 ° C., and the viscosity of the binder increases, so the strength of the compact increases, and the volatile matter evaporates at about 800 ° C. Almost finished, glassy carbon binds iron ore particles, and the strength of the compact is further increased.

However, this method requires a step of heating and melting the sticky hydrocarbon mixture, and also when charged in a blast furnace, the temperature range from the melting point of the hydrocarbon mixture to the initial carbonization range, that is, hundreds of degrees Celsius to 5 ° C. In the region of about 100 ° C., the hydrocarbon mixture is melted, so that sufficient crushing strength of the agglomerate cannot be expected.
Kojima et al .; Iron and Steel, 72 (1986), S98 Japanese Patent Laid-Open No. 7-157827 JP 60-248831 A

  Accordingly, an object of the present invention is to have a crushing strength of 390 N / p or more at room temperature and a crushing of 100 N / p or more sufficient to be used in a vertical iron furnace in a temperature range up to 1000 ° C. even when heated. An object of the present invention is to provide an unfired agglomerated ore for iron making that has strength and can be agglomerated at room temperature from the viewpoint of energy saving.

As a result of examining the non-calcined agglomerated minerals that can solve the above problems, the present inventors solidified the iron oxide raw material in a lump form using a phenol resin as a binder, thereby achieving desired temperatures in the room temperature and in the furnace high temperature region. It was found that crushing strength can be obtained.
The present invention has been made based on such findings, and the gist thereof is as follows.
[1] An unfired agglomerate for iron making, characterized in that an iron oxide raw material is solidified into a lump using a phenol resin as a binder.
[2] A non-fired agglomerate for iron making according to [1], wherein the non-fired agglomerate for iron making is any one of a granulated product, a molded product, and a crushed product of the molded product.
[3] The non-fired agglomerate for iron making according to [1] or [2], wherein the iron oxide raw material is fine-grained sintered ore and / or fine-grain iron ore. Mining.

  The non-calcined agglomerated mineral of the present invention can maintain a crushing strength of 390 N / p or more by the binder function of the cured phenol resin itself at room temperature, and carbon produced by carbonization of the phenol resin in the high temperature range in the furnace is a binder. In order to exhibit the function, it is possible to maintain a crushing strength of 100 N / p or more in a temperature range of at least 1000 ° C. Therefore, there is little pulverization in a yard and a vertical iron furnace, and it has excellent performance as an unfired agglomerated ore.

The unfired agglomerated ore for iron making of the present invention is obtained by solidifying an iron oxide raw material into a lump using a phenol resin as a binder.
The unfired agglomerated ore of the present invention is used as an iron raw material in a vertical iron-making furnace represented by a blast furnace (hereinafter, a blast furnace will be described as an example).
Examples of the iron oxide raw material include fine-grained sintered ore and fine-grained iron ore. However, the iron oxide raw material is not limited to this, and can be used as an iron raw material for an iron making furnace. Any fine granular material that cannot be inserted is acceptable.

A typical example of the fine-grained sintered ore is a sintered ore called return ore generated in the iron ore sintering process. In the conventional general sintering process, this sintered ore is a sintering step. To be used as a sintering raw material. Most of the sintered ore powder is generated in the particle size selection process when obtaining the product sintered ore, but there are also those generated in the transport process to the blast furnace and around the blast furnace. In the conventional sintering process, the product yield is about 70 to 80%, and the remaining 20 to 30% is returned to the sintering process as a return mineral (sintered ore powder) (that is, the product sintered ore). Circulates within the process without becoming). Therefore, by using such sintered ore powder as an iron oxide raw material of the non-fired agglomerated mineral of the present invention, the total yield of agglomerated minerals including the sintered ore can be greatly improved.
The fine-grained iron ore includes iron ore powder. Moreover, any of iron ore having a small particle size and iron ore having a small particle size generated in the sizing process may be used.
Two or more different types of iron oxide raw materials may be used. The particle size of this iron oxide raw material is generally less than 5 mm.

The phenol resin itself functions as a binder at room temperature, and carbon generated by carbonization functions as a binder in a high temperature range in the furnace.
The phenol resin present as a binder in the unfired agglomerated mineral of the present invention is a resin obtained by thermosetting a phenol resin precursor. Phenol resin precursors include phenol, o-cresol, m-cresol, p-cresol, resorcinol, catechol, pyrogallol, bisphenol A, p-tert-butylphenol, p-octylphenol, p-phenylphenol, 2,5-xylenol , 3,5-xylenol, a phenolic raw material in which a hydroxyl group is added to an aromatic ring, and an aldehyde-based raw material such as formaldehyde, acetaldehyde, benzaldehyde, glyoxal, furfural, and hexamethylenetetramine are reacted. Of these, a combination of phenol and formaldehyde is common.

  When the phenolic raw material and the aldehyde raw material are reacted, an acid or alkali catalyst is usually added. The one using an acid catalyst is called a novolak type, and the one using an alkali catalyst is called a resol type. In the case of a combination of phenol and formaldehyde, the novolac type phenolic resin precursor is a variety of condensates having a molecular weight of about 2000 or less in which phenol is mainly linked in a straight chain by methylene bonds. In the case of the resol type, trimethylol is used. It is a mixture of methylolphenols centered on phenol and their dimers, trimers and the like. In the present invention, both a resol type and a novolac type can be used.

The phenol resin precursor has various forms such as an aqueous solution, an organic solvent solution, and a powder. Any of them can be used in the present invention, and a phenol resin precursor in a form suitable for each agglomeration method can be selected. .
In general, the resol type self-crosslinks by heating to 150 ° C. or higher, but the novolac type requires a curing agent such as hexamethylenetetramine. What is necessary is just to add a hardening | curing agent by the method suitable for each agglomeration method.
The phenol resin used in the present invention also includes a phenol-urea resin in which a part of phenols is substituted with urea.

  The phenol resin charged into the blast furnace as part of the agglomerated ore is decomposed by heat and partly gasified, and carbon (thermal decomposition residue) is generated in the agglomerated ore. The amount of carbon generated from the resin can be represented by the residual carbon ratio. When the mass after mass heating of the resin after mass x (g) is sufficiently heated at 500 ° C. in a non-oxidizing atmosphere and carbonized is y (g), the residual carbon ratio b = (y / x) × 100. The proportion of carbon remaining when heated to 500 ° C. or higher in a non-oxidizing atmosphere (residual carbon ratio) is almost 0% for many resins such as acrylic and polyolefin, whereas phenol resin is usually as high as 40% by mass or higher. . Therefore, the non-fired agglomerated mineral of the present invention agglomerated using a phenol resin as a binder maintains the crushing strength by the binder function of the phenol resin itself from the time of blast furnace charging to about 350 ° C., and 350 ° C. to 500 ° C. During this period, the phenol resin gradually decomposes and carbonizes, and at 500 ° C. or higher, the carbon generated by the carbonization of the phenol resin functions as a binder, thereby exhibiting hot crushing strength.

  The amount of the phenol resin added is required to allow the agglomerated mineral to develop a crushing strength of 390 N / p or more at room temperature. The specific amount of addition differs depending on conditions such as the particle size distribution of the iron oxide raw material, so it cannot be uniquely defined, but in general, in terms of the required crushing strength and the cost of the binder, agglomerated ore About 3 to 10% by mass in the (product) is appropriate. An agglomerated mineral having a crushing strength of 390 N / p or more at normal temperature using a phenol resin as a binder can maintain a hot crushing strength of 100 N / p or more in a temperature range up to 1000 ° C.

The non-calcined agglomerated mineral of the present invention is mainly composed of an iron oxide raw material (A), a binder (B), and a powdery pitch (C), but other components such as various types are included as necessary. One or more of a dispersant, a curing accelerator, limestone fine powder, fly ash, silica fine powder, and the like can be blended in an appropriate amount as long as the effects of the present invention are not impaired. The total blending amount of these other components in the non-fired agglomerated ore is preferably about 10 mass%, particularly preferably about 5 mass%. However, about reducing materials, such as coke powder, you may mix | blend about 20 mass% separately as an upper limit according to the use purpose.
The particle size of the unfired agglomerated mineral of the present invention (spherical equivalent particle size in a normal temperature atmosphere) is preferably about 8 to 30 mm. If the particle size of the unfired agglomerated mineral is less than 8 mm, the air permeability of the raw material packed layer when charged in the furnace may be deteriorated. On the other hand, if the particle size exceeds 30 mm, the reducibility may be reduced. .

As a material agglomeration method for obtaining the unfired agglomerated mineral of the present invention, a known agglomeration method can be used, but it is necessary to select a method suitable for the form of the phenol resin precursor to be used. For example, a solution-like phenol resin precursor can be easily mixed with an iron oxide raw material, but in the case of a powdered phenol resin precursor, mixing with an iron oxide raw material while heating to the melting point or higher is more effective. There is a tendency that a higher crushing strength is obtained than when the body is granulated.
Specific examples of agglomeration methods that can be industrially mass-produced include methods such as granulation, molding, and crushing of molded products. Non-fired agglomerates obtained by these agglomeration methods are granulated products. It becomes a crushed body of a molded product and a molded product.

A rotary granulator can be used for granulation, and a briquetting machine or the like can be used for molding. However, the present invention is not limited to these, and any equipment can be used as long as granulation and molding are possible. For example, in a granulation method or a molding method, a raw material and a resin solution are mixed and stirred (kneaded), and then granulated or molded. The molding method may be a method of casting by casting into a mold.
The granulated and molded iron oxide raw material (agglomerated product) becomes a product of agglomerated ore by heat treatment and thermosetting the phenol resin precursor. In general, the phenol resin precursor can be cured by heating to 150 ° C. or higher to obtain a three-dimensionally crosslinked phenol resin. However, the optimum conditions such as the heating temperature and the heating time are the phenol resin precursor to be used. Therefore, it is only necessary to select conditions suitable for each.
Moreover, even if it is not fully heat-cured, as long as a crushing strength of 390 N / p or more is developed, it may be a product of agglomerate.

Non-fired agglomerated minerals of Invention Examples 1 to 3 and Comparative Examples 1 and 2 were produced under the conditions shown below using a return mineral (sintered ore powder) having a particle size of less than 4 mm as an iron oxide raw material.
[Invention Example 1]
“Resitop PL-5601” (trade name, 50 mass% solid content aqueous solution) manufactured by Gunei Chemical Co., Ltd. was used as the phenol resin precursor. The residual carbon ratio of the phenol resin precursor at 500 ° C. in a nitrogen atmosphere of the thermoset at 180 ° C. is 59 mass%.
In the agglomeration of raw materials, an iron oxide raw material and a phenol resin precursor are mixed and granulated at room temperature using a rotary granulator, and the resulting granulated product is heated at 180 ° C. using an electric oven. The phenolic resin was heat-cured by heating for 30 minutes to produce an agglomerate.

[Invention Example 2]
Agglomerate was produced under the same conditions as Invention Example 1 except that Gunei Chemical Co., Ltd. “Resitop PL-4804” (trade name, solid content: 70 mass% aqueous solution) was used as the phenol resin precursor. The residual carbon ratio of the used phenolic resin precursor at 500 ° C. in a nitrogen atmosphere of the thermoset at 180 ° C. is 59 mass%.
[Invention Example 3]
Gunei Chemical Co., Ltd. “Resitop PGA-2165” (trade name, powder) was used as the phenol resin precursor. The residual carbon ratio of the phenol resin precursor at 500 ° C. in a nitrogen atmosphere of the thermoset at 180 ° C. is 73 mass%.
In agglomeration of raw materials, an iron oxide raw material and a phenol resin precursor are mixed, and 10 mass% (outer) water is added to this mixture at room temperature using a rotary granulator. Granulated. The obtained granulated product was heated at 180 ° C. for 30 minutes using an electric oven to thermally cure the phenol resin, thereby producing an agglomerate.

[Comparative Example 1]
In accordance with Invention Example 1, a styrene / acrylic emulsion (“Muvinyl 940” (trade name) manufactured by Nichigo Movinyl Co., Ltd.) was used as a binder, and this binder was mixed with an iron oxide raw material. The mixture was granulated at room temperature using a rotary granulator, and the granulated product was heated at 180 ° C. for 30 minutes to produce an agglomerate. The residual carbon ratio of the resin component of the used styrene / acrylic emulsion at 500 ° C. in a nitrogen atmosphere is 0.9 mass%.
[Comparative Example 2]
Boltland cement was used instead of phenolic resin as the binder. The iron oxide raw material and Portland cement were mixed, water having the same mass as the cement was added, granulated at room temperature using a rotary granulator, and the granulated material was cured at room temperature for 3 days.

About the non-baking agglomerated minerals of the inventive example and the comparative example obtained as described above, the crushing strength directly or after heat treatment was measured at a temperature of 6 levels for those having a particle size of about 15 mm.
In measurement of crushing strength at normal temperature (23 ° C), 200 ° C, and 400 ° C, after standing at each measurement temperature for 1 hour or more in a nitrogen atmosphere, one agglomerated ore is crushed by a compression test using a universal testing machine. The load to be measured was measured. Each of the 5 grains was measured under the same conditions, and the average value thereof was taken as the crushing strength.
On the other hand, in the measurement of the crushing strength at 600 ° C., 800 ° C., and 1000 ° C., the crushing strength of the agglomerated heat-treated at each temperature in a nitrogen atmosphere was measured at room temperature. The heating rate during the heat treatment was 5 ° C./min, and the holding time at the target temperature was 10 minutes. After completion of the holding time, the sample was left in a nitrogen atmosphere until the temperature reached 100 ° C. or lower. The load at which one agglomerate crushes was measured by a compression test using a universal testing machine, and 5 grains were measured under the same conditions, and the average value thereof was taken as the crushing strength.

Table 1 shows the compositions of the agglomerates of the invention examples and comparative examples and the crushing strength at each temperature.
According to this, the agglomerate of the present invention has a crushing strength of 390 N / p or more at room temperature and 100 N / p or more at each temperature other than room temperature. On the other hand, in Comparative Example 1 using a styrene / acrylic emulsion as a binder, the crushing strength exceeds 390 N / p at room temperature, but is less than 100 N / p at 400 ° C., and the shape cannot be maintained at 600 ° C. or higher. It was pulverized. Further, in Comparative Example 2 using cement as the binder, the crushing strength is still below 100 N / p at 800 ° C. or higher.

Claims (3)

  A non-fired agglomerated mineral for iron making, characterized in that an iron oxide raw material is solidified into a lump using a phenol resin as a binder.   The non-baked agglomerate for iron making according to claim 1, wherein the non-fired agglomerated mineral for iron making is any one of a granulated product, a molded product, and a crushed product of the molded product.   The non-fired agglomerated mineral for iron making according to claim 1 or 2, wherein the iron oxide raw material is fine-grained sintered ore and / or fine-grained iron ore.