JP2007077484A - Method for manufacturing carbonaceous material-containing agglomerate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method in which powdery blended iron-containing raw materials prepared by blending a plurality of iron-containing raw materials are mixed with a powdery carbonaceous material having softening and melting properties and the resultant mixture is hot formed to manufacture carbonaceous material-containing agglomerates and by which both of the strength and reducibility of the carbonaceous material-containing agglomerates can be maintained or improved even in the case where low-quality ores, such as maramanba ore and pisolite ore, are used as the raw materials to be blended for the powdery blended iron-containing raw materials. <P>SOLUTION: The respective blending amounts of a porous ore (e.g. maramanba ore) B1 and a dense ore (e.g. undersize of sintered pellets) B2 are regulated in such a way that the specific surface area of the powdery blended iron-containing raw materials B after blending measured by the BET method becomes a previously set desired value (e.g. 0.6 to 10 m<SP>2</SP>/g). A mixture C of the powdery blended iron-containing raw materials B blended as above and the powdery carbonaceous material A having softening and melting properties is hot formed at 250 to 550°C to manufacture the carbonaceous material-containing agglomerates E. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing an agglomerated carbonaceous material agglomerated as a raw material for a blast furnace, and more particularly to a method for producing an agglomerated carbonaceous material agglomerated material using an inferior ore such as maramanba ore or pisolite ore.

  Inferior ores such as maramamba ore and pisolite ore (porous or highly crystalline water ore [= ore containing 3% by mass or more of crystal water]) have a higher content of crystal water than ordinary iron ore. It has features such as high fine powder and high water absorption. For this reason, when these inferior ores are used as raw materials for blast furnaces in the production of sintered ores, the sintering bed is accompanied by a lack of heat due to the decomposition of crystal water and a decrease in granulation due to an increase in fines and water absorption. It is known that productivity and product yield decrease due to deterioration in air permeability of the product.

  In addition, when the above-mentioned inferior ore is used in the production of fired pellets, the productivity and product are also increased due to the increase in bursting due to the decomposition of crystal water and the decrease in preheating strength due to the decrease in granulation due to the increase in water absorption. It is known that the yield decreases.

  Therefore, the present condition is that only a small amount of the above-mentioned inferior ore can be used as the raw material for blast furnace.

  However, the above-mentioned inferior ores tend to be further purchased in the future, and since these inferior ores are cheaper than ordinary iron ores, they can be used in large quantities as raw materials for blast furnaces from the viewpoint of cost reduction. Development of chemical conversion technology is desired.

  On the other hand, the present applicant, as a charging raw material of a vertical furnace such as a blast furnace, is hot-molded with a mixture of fine ore and caking coal, and then heat-treated without adding a binder such as cement. A method that can produce an agglomerated carbonaceous material was developed (see Patent Document 1).

  Furthermore, the present inventors worked on improving the method for producing the above-mentioned agglomerated carbonaceous material agglomerated material, and reduced the amount of expensive caking coal by specifying the maximum flow rate and volume mixing ratio of powdery carbonaceous material. Method (see Patent Document 2), a method in which the agglomerated carbonaceous material agglomerated material can be reliably increased in strength by hot molding after applying vibration to the mixture of fine ore and powdered carbonaceous material ( (See Patent Document 3) and filed patent applications.

  Then, the present inventors considered that the above-mentioned problem could be solved if the above-mentioned inferior ore was used to produce the above-mentioned agglomerated carbonaceous material agglomerate and used it in a blast furnace.

However, the effect on the strength, reducibility, etc. of the carbonaceous agglomerates when using the above-mentioned inferior ore is unknown, and there is room for study on the optimum production conditions when using the above-mentioned inferior ore. was there.
JP-A-11-092833 (claims, etc.) Japanese Patent No. 3502008 (Claims) Japanese Patent No. 3502011 (Claims)

  Therefore, the present invention hot-molds a mixture of a powdered iron-containing raw material obtained by blending a plurality of types of iron-containing raw materials (iron ore) and a powdered carbonaceous material (powdered coal) having soft melting properties. A method for producing an agglomerated carbonaceous material agglomerate, and even if inferior ores such as maramamba ore and pisolite ore are used as a blended raw material for powdered mixed iron-containing raw materials, It aims at providing the manufacturing method which can maintain or improve both property.

  When the present inventors use inferior ores such as maramamba ore and pisolite ore as a blending raw material for powdered blended iron-containing raw materials, they are abbreviated as carbonaceous agglomerates (hereinafter simply referred to as “agglomerated products”). The following lab experiment was conducted to clarify the effect on the strength.

  That is, using various types of single-grade powdered iron ore and powdered coal with log MF = 2.0, a mixture of these in a volume ratio of 55:45 to 30:70 was hot at 420 ° C. A tablet-like agglomerated material was formed by molding, and the tensile strength of the tablet was measured (for the method of measuring the tensile strength of the tablet, refer to Examples below). In addition, maramamba ore, which is originally a powdered iron ore, and sinter-returned ore are used by sieving to 1.4 mm or less. What was 4 mm or less was used. The measurement results are shown in FIG. As shown in the figure, agglomerates using maramamba ore (Australian ores A, B and C) or pisolite ore (Australian ores D and E) in a simple manner are obtained from ordinary sinter feed (South American ore F , G) and pellet feed (South American ore H), or sintered agglomerated (Ore I) and calcined pellet sieving (Ore J) once subjected to heat treatment, tensile strength compared to agglomerates Was found to be lower. In order to clarify the reason why the strength of the agglomerates changes depending on the ore brand, the relationship between various properties of the ore and the tensile strength of the agglomerates was investigated. As shown in FIG. It was found that there was a strong correlation with the measured specific surface area of the ore (hereinafter also referred to as “BET specific surface area”), and the tensile strength increased as the BET specific surface area decreased. The reason why the specific surface area of the ore has a strong influence on the tensile strength of the agglomerated material will be described with reference to the schematic diagram of FIG. Porous iron ores, such as maramamba ore and pisolite ore, have many fine open pores on the particle surface, but molten carbon material with higher viscosity than water does not easily penetrate into these fine open pores. The contact area with the carbon material is reduced, and the bonding force is reduced (see FIG. 1A). On the other hand, fine ores such as ordinary sinter feed and pellet feed, and fine ore on the surface of sintered ore and sinter pellets that have been heat-treated once densified. Since it is in a smooth state, it is assumed that the contact area with the molten carbon material is increased and a strong bonding force can be obtained (see FIG. 5B).

  Therefore, it is thought that the strength of agglomerates can be improved by adding ores with a large BET specific surface area to iron ores with a small BET specific surface area, and maramamba ore (Australian ore A) and sinter feed (South American ore F). The agglomerates were prepared using various blending ratios as the powdered iron-containing raw material, and the influence on the tensile strength was investigated. As a result, as shown in FIG. 5, it was found that the blending ratio and the tensile strength of the agglomerated material were in a substantially linear relationship. In addition, the BET specific surface area of the powdered iron-containing raw material containing two types of iron ore is a weighted average of the BET specific surface areas of each iron ore. The relationship with the tensile strength of the agglomerated material is also almost linear, and it has been found that the effect of the BET specific surface area of each iron ore on the tensile strength of the agglomerated material holds additivity. Based on the above findings, the present inventors have found that the tensile strength of the agglomerated material can be controlled by adjusting the BET specific surface area of the powdered iron-containing raw material. As a result of further studies, the following invention has been completed. I came to let you.

  Invention of Claim 1 hot-molds the mixture of the powdered iron-containing raw material which mix | blends multiple types of iron-containing raw materials, and the powdered carbonaceous material which has soft melting property at 250-550 degreeC. A method for producing an agglomerated carbonaceous material, wherein the powdered iron-containing raw material is blended with the plurality of types of powdered iron-containing raw material so that the specific surface area according to the BET method is a preset target value. It is a manufacturing method of the carbonaceous material agglomerated material characterized by adjusting a ratio.

Invention of Claim 2 is a manufacturing method of the carbonaceous material agglomerate of Claim 1 which uses a maramamba ore and / or a pisolite ore as a part of said multiple types of iron containing raw material.

The invention according to claim 3 is the carbonaceous material interior according to claim 2, wherein the iron ore, such as sintered ore and calcined pellet sieve, is used as another part of the plurality of types of iron-containing raw materials. It is a manufacturing method of an agglomerated material.

Invention of Claim 4 is a manufacturing method of the carbonaceous material agglomerated material of any one of Claims 1-3 which sets the target value of the said specific surface area to 0.6-10 m < ² > / g. .

  "Iron-containing raw materials" mainly include iron ore, ironworks miscellaneous materials (sintered ore, calcined pellet sieve, etc.), ironmaking dust (blast furnace dust, converter dust, electric furnace dust, mill scale, etc.) A raw material containing iron oxide. “Powdered carbon material having softening and melting property” means coal, SRC, tire chip, plastic having a log MF (here, MF is Giesera maximum fluidity [see JIS M8801]) of 1.0 or more. It is a generic name for powdery substances containing at least one carbonaceous material having softening and melting properties such as asphalt and tar. This “powdered carbonaceous material having softening and melting properties” includes carbon having substantially no softening and melting properties, such as coke, steaming coal, anthracite, and oil coke, in addition to the carbonaceous material having softening and melting properties. It may be a mixture of one or more substances.

  According to the present invention, by adjusting the specific surface area of the powdered mixed iron-containing raw material, even if inferior ores such as maramamba ore and pisolite ore are used as the mixed raw material of the powdered mixed iron-containing raw material, Both the strength and reducibility of the compound can be maintained or improved, and a carbonaceous agglomerate suitable for a raw material charged into the blast furnace can be produced at a low cost. Furthermore, by using the above-mentioned inferior ore preferentially in the production of a carbonaceous agglomerate, it is possible to reduce the blending ratio of the inferior ore into the conventional raw materials for blast furnaces such as sintered ores and pellets. The effect of improving the productivity and product yield of the raw materials for blast furnaces can be obtained.

  The conceptual diagram of the manufacture flow of the carbonaceous material interior agglomerate which concerns on FIG. 1 at one Embodiment of this invention is shown. Hereinafter, two types of iron ore, a marine mamba ore which is an inferior ore (porous and high crystal water ore) and a normal sinter feed as a plurality of types of iron-containing raw materials, and log MF ≧ 1.0 as a carbonaceous material having soft melting property Each of these coals will be described as a representative example.

First, in advance, the BET specific surface area is measured for each of the maramamba ore B1 and the normal sinter feed B2, and the tablet-like carbonaceous material agglomerates are prepared for each ore and the tensile strength is measured in advance. . Next, based on these BET specific surface area and agglomerate tensile strength data, the relational expression σ = a−bS between the BET specific surface area S of the powdered iron-containing raw material B and the agglomerate tensile strength σ Constants a and b are determined. Then, using this relational expression, a BET specific surface area S (for example, 5 m ² / g) at which a predetermined tensile strength σ (for example, 6 kgf / cm ² ≈0.6 MPa) suitable for the blast furnace charging raw material is obtained can be obtained. Is set as a target value for the BET specific surface area of the iron-containing raw material B. Then, the blending ratio of the maramamba ore B1 and the normal sinter feed B2 is determined so that the BET specific surface area of the powdered ore (raw powdered iron-containing raw material) B after blending becomes the above target value. Here, the BET specific surface area of the powdered ore after blending (powdered iron-containing raw material) B can be obtained by weighted averaging the BET specific surface areas of the ores B1 and B2 at a blending ratio based on mass.

The target value of the BET specific surface area of the powdered iron-containing raw material is such that the tensile strength (5 kg / cm ² [about 0.5 MPa] or more) of the agglomerate suitable for the raw material charged into the blast furnace can be obtained. It is preferably 10 m ² / g or less. On the other hand, if the BET specific surface area is too small, the reducibility of the agglomerated material is deteriorated, so that it is preferably 0.6 m ² / g or more.

  These iron ores B1 and B2 are ground, if necessary, after blending, for example, the most frequent particle size (the most frequent particle size obtained from the particle size distribution measured with a laser scattering / diffraction type particle size distribution meter, the same applies hereinafter) 50 μm A powdery mixed iron ore (a raw material containing powdered mixed iron) B is used. The pulverization may be performed for each brand or may be pulverized together after blending.

  Coal is pulverized as necessary so that it is evenly arranged in the gaps when mixed with the above-mentioned powdered iron ore, and is a little finer than powdered iron ore B (for example, the modest particle size is powdered iron ore) Powdered coal (powdered carbonaceous material) A having a mode diameter of B of 0.2 to 0.8 times, more preferably about 0.3 to 0.7 times.

[Carbon material drying heating process]
The powdery coal A thus adjusted in particle size is dried and heated at a temperature of 350 ° C. or less at which the coal A does not substantially soften and melt in the carbonaceous material drying and heating equipment (for example, rotary dryer) 1, Remove. Here, the drying heating temperature of the powdered coal was set to “less than 250 ° C.” in which the coal is not softened and melted in the prior art (see Patent Documents 2 and 3). Since it was found that the coal was not substantially softened and melted even when the drying heating temperature was raised, it was set to “350 ° C. or lower”.

[Raw material heating process]
On the other hand, the powdered blended iron ore B is preheated to 500 to 800 ° C. with the raw material heating equipment (for example, rotary kiln) 2 so that the target temperature becomes 250 to 550 ° C. when mixed with the powdered coal A. By preheating at 500 ° C. or higher, the crystal water in the maramamba ore is dissociated and removed. Therefore, when the agglomerated material is charged into the blast furnace, the crystallization water is already removed, so that a temperature rise delay due to dissociation of the crystallization water as in the conventional cold bond pellet is prevented.

[Mixing process]
For mixing the dried powdered coal A and the preheated powdered mixed iron ore B, as mixing equipment, in order to suppress unnecessary granulation due to mineralization and / or coal softening of the powdered coal A, it takes a short time. For example, a bowl-shaped mixing tank 3 that is commonly used in this type of industry that can be mixed is used. This bowl-shaped mixing tank 3 is preferably insulated and / or kept warm in order to ensure the molding temperature.

  Here, by adjusting the BET specific surface area of the powdered ore B after blending to the above target value, a sufficient contact area of the molten coal to the iron ore particle surface is obtained, and a strong binding force is expressed after the coal solidification Therefore, it becomes difficult to peel off and high tensile strength is obtained.

  In addition, the blending ratio of the powdered coal is the volume ratio with respect to the mixture C composed of the powdered coal A and the powdered blended iron ore B in order to fill the gap between the powdered blended iron ore B without excess or deficiency. It is preferable to set it as 45 to 65%. Here, the volume of the powdered coal A and the powdered blended iron ore B means an apparent volume including the pore volume inside, and the volume of the mixture C is the powdered coal A and the powdered blended iron ore B. It is assumed that the apparent volume of each of the above is simply summed (that is, the volume change due to melting of coal A by heating is not considered).

[Hot forming process]
The mixture C composed of the powdered coal A and the powdered blended iron ore B is pressure-molded by using, for example, a hot-roll twin roll molding machine 4 as a molding facility to obtain a molded product D. The pressure molding has a strength sufficient for the agglomerate E obtained by heat-treating the molding D to withstand handling from the molding machine 4 to the vertical furnace (for example, blast furnace). The molding pressure is set to 10 kN / cm or more so that 5 kN / piece or more is obtained.

In the molded product D thus molded, the molten coal A uniformly enters the gaps of the powdered mixed iron ore B, and the molten coal A acts as a lubricant, and the surface of the molded product D Since the molding pressure applied to the inside of the molding D is almost evenly distributed, only the vicinity of the surface is prevented from being consolidated, the porosity distribution in the molding D is averaged, and explosion occurs during heating. An agglomerate E that does not occur is obtained.

  Moreover, the coal A after solidification has a sufficiently large contact area with the particle surface of the powdered iron ore B, and a high-strength agglomerate E is obtained. Moreover, since it contains a porous maramamba ore, the reducibility is further improved.

[Heat treatment process]
The molded product D was charged into a heat treatment facility (for example, a shaft furnace) 5 adjusted to a temperature of the hot molding temperature (250 to 550 ° C.) or higher and 800 ° C. or lower, and the volatile matter remaining in the molded product D and Tar content is removed and coal is solidified. Thereby, when the agglomerate E obtained by heat-treating the molded product D is charged into the vertical furnace and heated, the coal is no longer softened and the strength of the agglomerate E is maintained. In addition, a large amount of tar is not generated, and troubles such as tar sticking to the exhaust gas system of the vertical furnace can be prevented. The lower limit of the temperature in the shaft furnace 5 is set as the molding temperature because if the temperature is lower than the molding temperature, it is very difficult to remove volatile components and tar components. The upper limit is set to 800 ° C. The iron content in the molded product D This is to prevent the strength of the agglomerated material H from being reduced unnecessarily in the shaft furnace 5. Further, in order to promote the removal of volatile matter and tar content, it is one of effective means to control the inside of the shaft furnace 5 to a negative pressure.

  The agglomerate E heat-treated in the shaft furnace 5 may be ignited, burned or reoxidized if discharged into the atmosphere while being hot. Therefore, the lower part of the shaft furnace 5 is heated to 400 ° C. or less by an inert gas such as nitrogen gas. It is desirable to discharge after cooling.

The rotary dryer 1, the vertical mixing tank 3, the molding machine 4 and the shaft furnace 5 are structured to prevent the intrusion of air (oxygen) from the outside, and the pyrolytic gas (volatilization) of the carbonaceous material A generated in these facilities. Since the main component is hydrocarbon, the gas is sucked and recovered using an ejector or the like, and the recovered gas is used as a heating fuel for the rotary kiln 2 or the like. In addition, since harmful components such as dust and high boiling point tar are contained in this gas, it is desirable to use it after dust removal and cleaning by an exhaust gas treatment facility (for example, a water-resistant scrubber) 9.

(Modification)
In the above embodiment, an example using two types of iron ore of maramamba ore and sinter feed as a plurality of types of powdered iron-containing raw materials has been shown, but pisolite ore may be used instead of or in addition to maramamba ore, Further, instead of or in addition to the sinter feed, at least one of pellet feed, sintered reverse sinter, calcined pellet sieving, and iron-making dust may be used. Among them, since the BET specific surface area is particularly small in the sintered sinter and the calcined pellet sieving, a small amount may be used to set the BET specific surface area of the powdered mixed iron-containing raw material as the target value. The effect that can be blended in a large amount is obtained. In addition, it is possible to effectively use ironworks miscellaneous materials such as sintered ore and fired pellets.

In order to confirm the effect of the present invention, the following laboratory experiment was conducted.
In the following Comparative Examples 1 and 2 and Invention Examples, powdered coal (log MF = 2.0) obtained by pulverizing blended coal (log MF = 2.0) to 300 μm or less with a ball mill (moderate particle size 20 μm) was used in common.

(Comparative Example 1)
As powdered iron ore, Australian ore A, which is a kind of maramamba ore, was calcined at 700 ° C. and sieved to 1.4 mm or less (mode particle size 50 μm) as a plain. It was 13.7 m < ² > / g as a result of measuring the BET specific surface area of this ore A with the BET specific surface area measuring apparatus (SHIMADZU micrometrics make, model: Gemini 2375).

(Comparative Example 2)
As powdered iron ore, sinter pellets (ore J), which is a kind of ironworks miscellaneous material, is pulverized and then fired at 700 ° C. and sieved to 1.4 mm or less (moderate particle size 300 μm). Used in. The BET specific surface area of this calcined pellet sieve (Ore J) was measured by the same BET specific surface area measuring apparatus as in Comparative Example 1 and found to be 0.5 m ² / g.

(Invention example)
As the powdered mixed iron ore, two kinds of ores of maramamba ore (Ore A) and calcined pellet sieve (Ore J) adjusted in particle size in Comparative Examples 1 and 2 above are blended, and the BET specific surface area after blending is 7 What was adjusted so that it might be set to 0.0 m < ² > / g (target value) was used.

Each simple powdered iron ore and the powdered mixed iron ore prepared by blending these are heated to a predetermined temperature in a small heating furnace, and the powdered coal is added to the mixture at a volume ratio of 55%. A mixture of 420 ° C. (target) was prepared by mixing, and this was immediately tableted in a crushing strength tester with a pressure of 800 kgf / cm ² (≈78.5 MPa) and a diameter d = 20 mm and a height h = 20 mm. Molded into an agglomerate of carbonaceous material.

And after cooling this tablet to room temperature, according to the tensile strength test method (JIS-A1113) of concrete, the fracture load P is measured by applying a compressive load in the diameter direction of the tablet with the above crushing strength tester, This was converted into a tensile strength σ in the tablet height direction using a relational expression of σ = 2P / (πdh).

In addition, a reduction test was performed under the condition that the tablet was held at 900 ° C. × 1 h in an atmosphere of CO: 50 vol% + N ₂ : 50 vol%, and the reduction rate of the tablet after the reduction test was determined. did.

Table 3 shows the measurement results. As shown in the table, Comparative Example 1 has excellent reducibility but low tensile strength, and Comparative Example 2 has high tensile strength but poor reducibility, and an agglomerated material satisfying both characteristics at the same time is obtained. It is not done. On the other hand, in the invention examples, high levels of both tensile strength and reducibility were obtained, and it was confirmed that an agglomerated material satisfying both characteristics was obtained.

It is a conceptual diagram of the manufacture flow of the carbonaceous material interior agglomerate which concerns on implementation of this invention. It is a schematic diagram explaining the contact state of a molten carbon material and an iron ore surface, (a) is a porous iron ore and (b) shows the case of a dense ore as an iron ore. It is a graph which shows the BET specific surface area of the iron ore of various single brands. It is a graph which shows the relationship between the BET specific surface area of an iron ore, and the tensile strength of a carbonaceous material interior agglomerate. It is a graph which shows the relationship between the mixture ratio of the dense ore to a powdery mix iron ore, and the tensile strength of a carbonaceous material agglomerated material.

Explanation of symbols

1: Carbon material drying and heating equipment (rotary dryer)
2: Raw material heating equipment (rotary kiln)
3: Mixing equipment (vertical mixing tank)
4: Molding equipment (double roll type molding machine)
5: Heat treatment equipment (shaft furnace)
9: Exhaust gas treatment facility (Ansui scrubber)
A: Powdered carbon material (powdered coal)
B: Powdered mixed iron-containing raw material (powdered mixed iron ore)
B1, B2: Iron-containing raw material (iron ore)
C: Mixture D: Molded product E: Carbon material interior agglomerate

Claims (4)

  A mixture of a powdered iron-containing raw material containing a plurality of types of iron-containing raw materials and a soft powdered carbonaceous material is hot-molded at 250 to 550 ° C. to produce a carbonaceous material agglomerated material. It is a method, Comprising: The blending ratio of the said multiple types of powder iron containing raw material is adjusted so that the specific surface area by the BET method of the said powder iron blend raw material may become a preset target value, It is characterized by the above-mentioned. A method for producing a carbonized material agglomerated material.   The method for producing an agglomerated carbonaceous material agglomerated product according to claim 1, wherein maramamba ore and / or pisolite ore are used as part of the plurality of types of iron-containing raw materials.   The method for producing an agglomerated carbonaceous material agglomerated product according to claim 2, wherein one or more of the plurality of types of iron-containing raw materials used are those obtained by firing iron ore such as sintered ore and calcined pellet sieve. The method for producing an agglomerated carbonaceous material agglomerated product according to any one of claims 1 to 3, wherein a target value of the specific surface area is 0.6 to 10 m ² / g.

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