JP2007211296A - Agglomerate including carbonaceous material to be used for vertical furnace, and production method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an agglomerate including a carbonaceous material, which is more suitable for a raw material to be charged into a vertical furnace such as a blast furnace, and further has high strength and a lower tar content, and to provide a production method therefor. <P>SOLUTION: This manufacturing method comprises the steps of: mixing a powdery charcoal wood (A) having softening and melting properties with a powdery iron-containing material (B) to prepare a mixture (C); hot-forming the mixture (C) at 250 to 550°C with a twin-roll-type forming machine 4 to produce a formed article (D); further heat-treating the formed article (D) in a heat-treatment apparatus 5 while adjusting a treatment temperature into 500 to 800°C and/or a treatment period of time into 5 to 60 min to control a reduction rate of the obtained agglomerate (E) including the carbonaceous material to be used in the vertical furnace, into a range of 3 to 17%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vertical furnace carbonaceous material-incorporated agglomerate having excellent handling strength that can be used as a raw material for vertical furnaces such as blast furnaces and cupolas, and a method for producing the same.

  For the purpose of using as a raw material for vertical furnaces such as blast furnaces and cupolas, the present inventors have formed a conventional carbon material interior by hot forming a mixture of fine ore and a soft and meltable carbon material. We have developed an agglomerate of carbonaceous materials that can provide high strength without adding a binder such as cement, such as cold pellets.

  Such a carbonaceous material agglomerated ore heats powdered iron ore to 400-800 ° C. with a rotary kiln or the like, and does not cause softening and melting of powdered carbon material having soft melting property with a rotary dryer or the like 250 After drying at a temperature of less than ℃, the powdered carbonaceous material and powdered iron ore are mixed with a biaxial mixer or the like to obtain a mixture at 250 to 550 ° C, which is the temperature at which the powdered carbonaceous material softens and melts. . Then, this mixture is hot-molded with a twin-roll molding machine or the like and briquetted to obtain a carbonaceous material-incorporated agglomerated mineral that is a high-strength molded product. And the carbon material agglomerated ore thus hot formed in the vertical furnace such as a blast furnace because the tar content contained in the carbon material is almost removed by the heating in the hot forming. This suggests that there is no problem in use (for example, see Patent Document 1).

  Thereafter, as a result of further studies, the present inventors have further carried out degassing treatment (heat treatment) by further heating the carbonized material agglomerated ore after hot forming at a forming temperature or higher for 5 minutes or more. It was suggested that the tar content could be removed more completely from the carbonaceous material agglomerated minerals, and that the crushing strength of the carbonaceous material agglomerated minerals further increased, and that pulverization in the blast furnace could be more reliably prevented. (For example, refer to Patent Document 2).

However, the optimum condition range for the above degassing treatment (heat treatment) is not clear, and it is more suitable for the charging materials of vertical furnaces such as blast furnaces. The establishment of agglomerates and their production methods has been demanded.
JP 2001-303143 A (paragraph [0025]) Japanese Patent Laying-Open No. 2003-301205 (paragraph [0025])

  Accordingly, the present invention has an object to provide a carbonaceous material-incorporated agglomerated ore for a vertical furnace that is more suitable for a raw material of a vertical furnace such as a blast furnace and has higher strength and less tar content, and a method for producing the same. And

  The invention according to claim 1 has a reduction rate of 3 to 17%, which is obtained by heat-forming a mixture of powdered iron-containing raw material and powdered carbon material having softening and melting properties. It is a charcoal-incorporated agglomerated mineral for vertical furnaces.

  Invention of Claim 2 is a carbon material interior agglomerated mineral for vertical furnaces of Claim 1 whose tar content is 0.05 mass% or less.

  The invention according to claim 3 further comprises a molded product prepared by hot forming a mixture of powdered iron-containing raw material and powdered carbon material having softening and melting properties at 250 to 550 ° C, further 500 to 800 ° C, The carbonaceous material for vertical furnaces characterized in that the carbonized material agglomerated ore according to claim 1 or 2 is obtained by performing heat treatment while adjusting the treatment temperature and / or treatment time within a range of 5 to 60 min. It is a manufacturing method of an interior agglomerate.

Invention of Claim 4 is a manufacturing method of the carbonaceous material interior agglomerated for vertical furnace of Claim 3 which performs the said heat processing in inert gas atmosphere.

  The “powdered carbon material having softening and melting properties” means coal, SRC, tire chips, plastics, asphalt, tar, log MF (where MF is Giesera maximum fluidity) of 1.0 or more. It is a generic term for powdery substances containing at least one kind of carbonaceous material having softening and melting properties such as ASP and hypercoal. 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. “Powdered iron-containing raw material” is a raw material mainly containing iron oxide such as iron ore, iron-making dust (blast furnace dust, converter dust, electric furnace dust, mill scale, etc.), miscellaneous or pellet sieving, or It is a mixture of two or more of these raw materials, and is a generic term for powdered materials.

  The “reduction rate” is based on the assumption (total reduction rate 0%) when it is assumed that the total iron content in the carbonaceous material agglomerate is hematite.

  According to the present invention, the reduction rate of the vertical furnace carbonaceous material agglomerated ore (hereinafter also simply referred to as “carbonaceous material agglomerated ore” or “agglomerated ore”) is defined as 3% or more. In addition to achieving more complete removal of tar from the carbonaceous agglomerated minerals, the reduction rate of the carbonaceous agglomerated minerals is regulated to 17% or less, and the porosity of the carbonaceous agglomerated minerals The increase in strength is suppressed, the effect of increasing the strength due to solidification of the carbonaceous material is sufficiently exhibited, and the carbonaceous material-incorporated agglomerate for vertical furnaces with higher crushing strength is obtained.

(Embodiment)
The conceptual diagram of the manufacturing flow of the carbonaceous material interior agglomerate for vertical furnaces which concerns on FIG. 1 at one Embodiment of this invention is shown. Hereinafter, powder iron ore will be described as a representative example as a powder iron-containing raw material. Among the carbon materials, a carbon material having soft melting property (for example, caking coal, SRC, etc.) is 1 mm in order to maintain a good mixed state with the powdered iron ore and the carbon material substantially not having soft melting property. It is desirable to grind to the following extent. Moreover, in order to improve the filling property with the above-mentioned softening and melting carbonaceous material, iron ore and a carbonaceous material that does not substantially have softening and melting property (for example, coke powder, general coal, anthracite, oil coke). Etc.) should be crushed and used if necessary. Although the upper limit of the pulverized particle size is a particle size that can be molded, the lower limit is not particularly limited, but it is preferably about the same as that of a carbon material having softening and melting properties.

[Carbon material drying heating process]
The powdery carbon material A thus adjusted in particle size is dried and heated at a temperature of, for example, 350 ° C. or less at which the carbon material A does not substantially soften and melt in the carbon material drying and heating equipment (for example, rotary dryer) 1. , Remove adhering moisture. Here, the drying heating temperature of the powdered carbon material was set to “less than 250 ° C.” in which the carbon material is not softened and melted in the prior art (see Patent Document 1), but it was reduced to “350 ° C.” by the inventors' subsequent examination. Since it was found that there is also a carbon material that does not soften and melt even when the drying heating temperature is raised, it was set to “for example, 350 ° C. or less”.

[Raw material heating process]
On the other hand, the powdered iron ore B is preheated to 400 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 carbon material A. As fuel injected from the burner of the rotary kiln 2, pulverized coal that is solid fuel, heavy oil that is liquid fuel, natural gas that is gaseous fuel, COG, or the like can be used.

[Mixing process]
The mixing of the dried powdered carbon material A and the preheated powdered iron ore B is short as a mixing facility in order to suppress unnecessary granulation due to mineralization and / or softening of the carbonaceous material. For example, a bowl-shaped mixing tank 3 that is commonly used in this type of industry that can be mixed with time is used. In addition, this bowl-shaped mixing tank 3 is insulated and / or kept warm in order to ensure the molding temperature.

[Hot forming process]
The mixture C composed of the powdered carbon material A and the powdered iron ore B is pressure-molded by using, for example, a hot-rolling twin-roll molding machine 4 as a molding facility to obtain a molded product D. The pressure molding has a strength sufficient to allow the agglomerate E obtained by heat-treating the molded product D to withstand handling from the molding machine 4 to charging into a vertical furnace (for example, a 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 melted softening and melting carbon material A enters the voids of the powdered iron ore B, and this carbon material A acts as a lubricant to form the molded product D. Since the molding pressure applied to the surface of the material extends almost uniformly to the inside of the molded product D, it is prevented that only the vicinity of the surface is consolidated, the porosity distribution in the molded product D is averaged, and during heating, An agglomerate E in which no explosion occurs is obtained.

  In addition, the carbonized material A after solidification firmly connects the particles of the powdered iron ore B and has a large contact area with the powdered iron ore B, and the agglomerates obtained in this way. E has high strength and excellent reducibility.

[Heat treatment process]
The molded product D is charged into a heat treatment facility (for example, a shaft furnace) 5 and subjected to heat treatment so that the reduction rate of the agglomerated E obtained in the range of 3 to 17% is 500 to 800 ° C., 5 Heat treatment is performed by adjusting the treatment temperature and / or treatment time within a range of ˜60 min. That is, the reduction rate of the agglomerate E may be adjusted by changing the treatment time while keeping the treatment temperature in the heat treatment equipment 5 constant, or conversely, changing the treatment temperature while keeping the treatment time constant. It may be performed by changing the processing temperature and the processing time.

  As described above, the reason why the reduction rate of the agglomerated mineral is specified in the range of 3 to 17% is as follows. That is, the volatile matter and tar content remaining in the molded product D are removed by the heat treatment, and the resulting agglomerate E shrinks and becomes dense, and the carbonaceous material cokes and solidifies. On the other hand, the powdered iron ore B in the molded product D is reduced with the carbon material A, and the porosity of the obtained agglomerated ore E increases. The densification of the agglomerate E and the solidification of the carbonaceous material act in the direction of increasing the strength of the agglomerate E, but the increase in porosity acts in the direction of decreasing the strength of the agglomerate E. . Therefore, as the heat treatment progresses, the crushing strength of the agglomerate E increases at the beginning because the effect of densification of the molded product by removing volatiles and the like and the strength improvement effect by solidifying the carbonaceous material are more prevalent. Since the strength reduction effect due to the increase in the porosity becomes dominant, the removal of the metal has almost reached the maximum value and then tends to decrease. Moreover, the reduction rate of the agglomerate E can be used as an index representing the progress degree of the heat treatment, and a certain relationship is recognized between the reduction rate and the crushing strength, as shown in Examples below. When the reduction rate of the agglomerated E is less than 3%, the heat treatment is insufficient and the volatile matter and the tar content remaining in the molded product D after hot forming cannot be sufficiently removed. The solidification of the carbon material becomes insufficient, and the effect of increasing the crushing strength is small. On the other hand, when the reduction rate of the agglomerated mineral exceeds 17%, the removal of volatile components and tars is substantially completed, and the effect of improving the strength due to densification of the agglomerated mineral and solidification of the carbonaceous material is saturated. The strength reduction effect due to the increase in rate becomes dominant. Therefore, the range of the reduction rate of the agglomerated ore is 3 to 17%. In addition, a preferable range is 5 to 15%, and a more preferable range is 7 to 13%.

  As described above, the agglomerate E having a reduction rate of 3 to 17% obtained by further heat treatment after hot forming is no longer carbonaceous even when charged in a vertical furnace and heated. The strength is maintained because it is not softened and the increase in porosity is suppressed during heat treatment.

  Further, the tar content remaining in the agglomerated ore E after heat treatment is preferably as small as possible, but it is sufficient if it is 0.05% by mass or less, and this generates tar content in the vertical furnace. The occurrence of troubles such as sticking of tar to the exhaust gas system of the vertical furnace can be prevented.

  The reason why the heat treatment temperature is set to 500 to 800 ° C. is that when the temperature is lower than 500 ° C., the removal rate of volatile components and tars is slow, and it is very difficult to remove them. This is because it is remarkably increased and it becomes difficult to control the reduction rate within the specified range (3 to 17%). In addition, the preferable range of heat processing temperature is 550-700 degreeC, and especially preferable temperature is about 600 degreeC.

  The heat treatment time is set to 5 to 60 minutes because if less than 5 minutes, the volatile matter and tar content cannot be sufficiently removed, or the quality of the agglomerate tends to vary. This is because the equipment becomes excessive and the equipment cost increases. In addition, the preferable range of heat processing time is 10 to 50 min, and a more preferable range is 20 to 40 min.

  Further, since the strength decreases when the agglomerated mineral reduced during the heat treatment is re-oxidized with an oxidizing gas such as air, the shaft furnace 5 is preferably kept in an inert gas atmosphere with nitrogen gas or the like.

  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.

  Since the agglomerate H heat-treated in the shaft furnace 5 may be ignited or burned if discharged into the atmosphere while being hot, it is cooled to 400 ° C. or lower with an inert gas such as nitrogen gas at the bottom of the shaft furnace 5. It is desirable to discharge from.

  Since the pyrolysis gas (volatile matter) of the carbonaceous material A generated in the shaft furnace 5 is mainly composed of hydrocarbons, this gas is sucked and recovered using an ejector or the like, and the recovered gas is the rotary kiln 2 or the like. It can be used as a heated fuel.

(Modification)
In the above embodiment, an example in which a rotary dryer is used for the carbonaceous material drying and heating process has been shown, but a fluidized bed dryer, a tube dryer, an externally heated multi-cylinder rotary dryer, an airflow dryer, a fluidized bed dryer, etc. Alternatively, a combination of these may be used.

  Moreover, in the said embodiment, although the example which uses a rotary kiln for the raw material heating process was shown, using a fluidized bed type heating furnace, a tube type heating furnace, an external heating type multi-cylinder kiln, an indirect heating furnace by heating solid, etc. Alternatively, a combination of these may be used.

  Moreover, although the example which uses a vertical mixing tank for a mixing process was shown in the said embodiment, a container rotation type mixing tank, a horizontal type mixing tank, etc. may be used and you may use combining these two or more. In addition to the continuous mixing method, a batch type mixing method in which a hopper is installed upstream of the mixing tank and operated intermittently may be adopted. Also good.

  Moreover, although the example which uses a twin roll type | mold molding machine for the hot forming process was shown in the said embodiment, you may use an extrusion molding machine, a tableting machine, etc.

  Moreover, in the said embodiment, although the example which uses a shaft furnace for the heat treatment process was shown, you may use a rotary kiln, a rotary hearth furnace, an external heating type multi-cylinder kiln, a batch furnace, etc., combining these two or more. It may be used.

  Moreover, although the example which provided the cooling part in the lower part of the shaft furnace was shown in the said embodiment, you may provide cooling equipment separately from a shaft furnace.

[Relationship between reduction rate and crushing strength of agglomerates]
In order to investigate the effect of the reduction rate on the crushing strength of agglomerates, the following hot forming experiments and heat treatment experiments were conducted.

  FIG. 2 shows an outline of the hot forming machine used in this hot forming experiment. As raw materials, two types of powdered coal shown in Table 1 and four types of powdered iron ore shown in Table 2 were used in various combinations. In addition, the particle size of the powdered coal was 74 μm or less and about 60 to 80% by mass, and the particle size of the powdered iron ore was −1 mm and 100% by mass.

Then, after preheating the powdered coal and the powdered iron ore at a mass ratio of 18:82 to 22:78, only the powdered iron ore at 600 to 800 ° C. in an electric furnace (not shown), the oil heater is heated to about 200 ° C. The mixture was charged into a heat-insulated mixer and mixed to 400 to 550 ° C., and this mixture was supplied to a twin roll molding machine while being hot, and 30 mm × under conditions of a roll rotation speed of 4 to 8 rpm and a molding pressure of 10 to 50 kN / cm. Molded into a 25 mm × 17 mm egg-shaped briquette (molded product). And this briquette was heat-processed by changing process temperature and process time variously in the range of 500-800 degreeC and 30-90min by nitrogen atmosphere.

  For each briquette (agglomerated ore) after heat treatment, the reduction rate and crushing strength were measured, and the results are shown in FIGS. 3 and 4 (however, for the combination of ore C / coal B, only crushing strength was measured and reduced) Since the rate was not measured, it is shown in FIG. 3 only by the plot of ■ [black square]. In these figures, the crushing strength is expressed as a relative crushing strength (= crushing strength of the briquette after heat treatment / crushing strength of the briquette before heat treatment) based on the crushing strength of the briquette (molded product) before the heat treatment.

  From FIG. 3, the crushing strength of the agglomerates initially increases when the heat treatment temperature is increased from 500 ° C., but shows a maximum value near 600 ° C., and shows a tendency to decrease when the heat treatment temperature is exceeded, at 800 ° C. It can be seen that the level returns to almost the same level as before the heat treatment. In this example, since the heat treatment time was set to 30 min or more, at 800 ° C., the reduction of the agglomerate was excessive and the crushing strength was reduced to the level before the heat treatment. It is considered possible to limit the reduction of the ore and to make the crushing strength higher than the value before the heat treatment.

  In addition, from FIG. 4, the crushing strength of the agglomerated ore increases initially when the agglomerated ore reduction rate increases, but the reduction rate varies depending on the combination of the coal type and the ore type. In this range, the maximum value is reached, and after that, it shows a tendency to decrease. When the reduction rate is about 20% or more, it can be seen that the level returns to a level almost equal to that before the heat treatment.

[Tar content of agglomerated ore]
Next, in order to measure the tar content of the agglomerated ore, each heated briquette (agglomerated ore) is heated and heated under conditions simulating the heat pattern in the blast furnace, and the generated gas, moisture, and volatilization Experiments were conducted to recover the minute and tar. Then, the benzene-soluble component in the recovered material was weighed and used as the tar amount.

  FIG. 5 shows the relationship between the heat treatment temperature and the agglomerated tar content. For comparison, the tar content of a briquette (molded product) before heat treatment and the tar content of a waste tire subjected to a charging experiment in an actual blast furnace are also shown.

  As is clear from FIG. 5, the tar content of the briquette (molded product) before heat treatment is in the range of about 0.2 to 0.025% by mass although it varies depending on the coal type, compared with about 35% by mass of the waste tire. The order of 1/100 to 1/1000 is much less, and it is considered that there is almost no trouble due to the generation of tar even if a large amount is charged into the actual blast furnace. However, by further heat-treating this molded product, the tar content of the agglomerated mineral can always be 0.05% by mass or less regardless of the type of coal, and troubles due to tar generation in the vertical furnace can be avoided. It was confirmed that it could be prevented more reliably.

It is a conceptual diagram of the manufacturing flow of the carbon material interior agglomerate for vertical furnaces concerning implementation of this invention. It is a flowchart which shows the outline | summary of the hot forming machine used in the Example. It is a graph which shows the relationship between heat processing temperature and the crushing strength of a carbonaceous material interior agglomerate for vertical furnaces. It is a graph which shows the relationship between the reduction rate and crush strength of a vertical furnace carbonaceous material agglomerate. It is a graph which shows the relationship between heat processing temperature and tar content of the carbonaceous material interior agglomerate for vertical furnaces.

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 (twin roll molding machine)
5: Heat treatment equipment (shaft furnace)
A: Powdered carbon material (powdered coal)
B: Powdered iron-containing raw material (powdered iron ore)
C: Mixture D: Molded product (briquet before heat treatment)
E: Carbonaceous agglomerate (briquet after heat treatment)

Claims (4)

  A vertical furnace charcoal characterized by a reduction rate of 3 to 17% obtained by further heat-treating a mixture of a powdered iron-containing raw material and a powdered carbon material having softening and melting properties. Material interior agglomeration.   The coal internal agglomerate for vertical furnace according to claim 1, wherein the tar content is 0.05 mass% or less.   A molded product prepared by hot forming a mixture of powdered iron-containing raw material and powdered carbon material having soft melting property at 250 to 550 ° C., and further processed at a processing temperature in the range of 500 to 800 ° C. and 5 to 60 min. A method for producing a carbonaceous material-incorporated agglomerated mineral for vertical furnaces according to claim 1 or 2, wherein heat treatment is carried out by adjusting the treatment time.   The manufacturing method of the carbonaceous material interior agglomerate for vertical furnaces of Claim 3 which performs the said heat processing in inert gas atmosphere.

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